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Patent Abstract
To provide a small-sized and low-cost proportional solenoid valve
which is capable of controlling a bidirectional fluid flow. A core
is fixed in a pipe, and a hollow shaft having an extreme end thereof
closed by a valve seat and a portion adjacent thereto formed with
valve holes is fixed in the core. Within the pipe, there are arranged
a hollow cylindrical valve element axially movable using the shaft
as a guide and urged in a direction away from the core by a spring,
for opening and closing the valve holes, and a plunger, while outside
the pipe, there is arranged a solenoid coil. The proportional solenoid
valve has a body formed by the pipe, and the component parts for
opening and closing the valve are arranged within the pipe, so that
it is possible to reduce the size of the proportional solenoid valve,
the number of component parts, and machining costs and material
costs, which contributes to reduction of costs of the valve. Further,
since the operation of the hollow cylindrical valve element for
opening and closing the valve holes is not adversely affected by
the direction of the fluid flow, it is possible to control a bidirectional
flow of fluid.
Patent Claims
What is claimed is:
1. A proportional solenoid valve for changing a valve lift continuously
according to a value of an electric current supplied to a solenoid
coil, characterized by comprising: a core fixed in a hollow cylindrical
pipe; a partially hollow shaft having one end thereof fixed in the
core axially of the pipe and another end thereof bored with a plurality
of valve holes on a circumference thereof such that the bores communicate
with a fluid passage extending axially of the pipe; a hollow cylindrical
valve element arranged in a manner axially movable using the shaft
as a guide so as to open and close the valve holes; a first spring
arranged between the core and the hollow cylindrical valve element,
for urging the hollow cylindrical valve element in a direction away
from the core; a hollow cylindrical plunger fixedly fitted on the
hollow cylindrical valve element; and a solenoid coil circumferentially
provided on an outside of the pipe.
2. The proportional solenoid valve according to claim 1, wherein
the pipe is a straight pipe, and the fluid passage within the shaft,
which communicates with the valve holes, extends to a core-side
extreme end of the shaft and further communicates with a passage
formed through the core axially thereof.
3. The proportional solenoid valve according to claim 1, wherein
the pipe has a shape formed by joining a second pipe perpendicularly
to a straight first pipe, the first pipe having one end thereof
closed by the core, and the fluid passage within the shaft, which
communicates with the valve holes, extending to an extreme end of
the another end of the shaft, an outer peripheral surface of the
shaft close to the extreme end of the another end being in intimate
contact with an inner wall surface of the first pipe.
4. The proportional solenoid valve according to claim 3, wherein
the solenoid coil is removable from the first pipe and the core.
5. The proportional solenoid valve according to claim 1, wherein
the shaft has a communication groove formed along a whole circumference
thereof in an outer peripheral surface of a portion thereof formed
with the valve holes.
6. The proportional solenoid valve according to claim 1, wherein
a portion of the shaft with which the hollow cylindrical valve element
is brought into abutment by being urged by the first spring is formed
into a conical shape to provide a tapered valve seat.
7. The proportional solenoid valve according to claim 1, wherein
a portion of the shaft with which the hollow cylindrical valve element
is brought into abutment by being urged by the first spring is formed
as a flange projecting radially outward.
8. The proportional solenoid valve according to claim 7, wherein
the hollow cylindrical valve element has a plurality of cutout portions
formed in a flange-side end thereof, the cutout portions fully closing
the valve holes when the hollow cylindrical valve element is in
contact with the flange, and communicating with the valve holes
when the hollow cylindrical valve element is moved toward the core
by energization of the solenoid coil.
9. The proportional solenoid valve according to claim 1, comprising
a second spring for urging the hollow cylindrical valve element
and the plunger toward the core.
10. The proportional solenoid valve according to claim 9, wherein
the hollow cylindrical valve element is formed with a circumferentially
elongated slot which fully closes the valve holes when the first
spring and the second spring are balanced with each other, and communicates
with the valve holes when the hollow cylindrical valve element is
moved toward the core by energization of the solenoid coil.
11. The proportional solenoid valve according to claim 9, wherein
the hollow cylindrical valve element has an end portion thereof
formed to have a reduced thickness, the end portion including a
portion formed with the slot.
12. The proportional solenoid valve according to claim 11, wherein
a ratio of a sum of a spring constant of the first spring and a
spring constant of the second spring to an outer-diametric cross-sectional
area of a valve seat-side end portion of the hollow cylindrical
valve element is equal to or larger than 0.05.
13. The proportional solenoid valve according to claim 1, wherein
the plunger has an outer diameter which produces a predetermined
gap between an inner wall of the pipe and the plunger itself.
14. The proportional solenoid valve according to claim 1, wherein
the core and the plunger have respective end faces opposed to each
other, the end faces being formed to have respective tapered surfaces
sloped with identical gradients.
15. The proportional solenoid valve according to claim 1, wherein
the hollow cylindrical valve element is made of a non-magnetic material.
16. The proportional solenoid valve according to claim 1, wherein
the shaft has at least one groove circumferentially formed in a
sliding surface thereof on which the hollow cylindrical valve element
slides.
17. The proportional solenoid valve according to claim 1, wherein
the pipe has open ends thereof each drawn in a manner adapted to
a diameter of a mating pipe for welding.
18. The proportional solenoid valve according to claim 1, wherein
the hollow cylindrical valve element is integrally formed with the
plunger.
19. The proportional solenoid valve according to claim 1, wherein
the shaft is fixed to the core by press-fitting, and a flow characteristic
is adjusted by changing an amount of press-fitting.
20. The proportional solenoid valve according to claim 1, wherein
the pipe has piping joints attached to open ends thereof.
Patent Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] This invention relates to a proportional solenoid valve,
and more particularly to a proportional solenoid valve having a
valve lift thereof continuously changed in accordance with a value
of an electric current supplied thereto.
[0003] (2) Description of the Related Art
[0004] In general, a proportional solenoid valve which has a valve
lift thereof continuously changed by a solenoid force is comprised
of a valve section for opening and closing a fluid passage by a
valve seat and a valve element arranged in a manner opposed to the
valve seat, and a solenoid section for actuating the valve element
such that the valve element is moved to and moved away from the
valve seat.
[0005] A conventional proportional solenoid valve has the component
parts of a valve section and a solenoid section formed or mounted
in a body formed by machining a block body. The valve section includes
two ports bored in the block body, a valve seat integrally formed
with the body at a location between the two ports, and a valve element
opened and closed by the solenoid section. On the other hand, the
solenoid section includes a solenoid coil to which an electric current
is supplied from the outside, a core fixedly arranged on the same
axis as the valve element and the valve seat and a plunger arranged
such that it can move to and from the core in the axial direction
to actuate the valve element, and a spring arranged between the
plunger and the valve element, for urging the plunger in a direction
away from the core.
[0006] In general, in the proportional solenoid valve constructed
as above, since the valve element is arranged upstream or downstream
of the valve seat with respect to flow of a fluid, and pressure
applied to the valve element acts in the valve closing or valve
opening direction, the characteristic of the valve lift with respect
to a solenoid force is quite different depending on the direction
of the fluid flow. For this reason, the proportional solenoid valve
is given a directional property related to the fluid, and designed
in a manner adapted to the direction of the fluid flow.
[0007] In the conventional proportional solenoid valve, however,
the body in the form of a block is formed with the two ports, and
has the component parts of the valve section and the solenoid section
for opening and closing the valve element of the valve section,
mounted therein, which causes an increase in the size of the proportional
solenoid valve.
[0008] Further, when the proportional solenoid valve is applied
to a location where the direction of the fluid flow is reversed,
two pairs of a proportional solenoid valve and a check valve are
required to be arranged in parallel such that the two pairs allow
fluid to flow in respective directions opposite to each other, which
causes an increase in the size of the proportional solenoid valve.
SUMMARY OF THE INVENTION
[0009] The present invention has been made in view of the above
circumstances, and an object thereof is to provide a small-sized
and low-cost proportional solenoid valve which is capable of controlling
bidirectional fluid flow.
[0010] To achieve the object, there is provided a proportional
solenoid valve for changing a valve lift continuously according
to a value of an electric current supplied to a solenoid coil. The
proportional solenoid valve comprises a core fixed in a hollow cylindrical
pipe, a partially hollow shaft having one end thereof fixed in the
core axially of the pipe and another end thereof bored with a plurality
of valve holes on a circumference thereof such that the bores communicate
with a fluid passage extending axially of the pipe, a hollow cylindrical
valve element arranged in a manner axially movable using the shaft
as a guide so as to open and close the valve holes, a first spring
arranged between the core and the hollow cylindrical valve element,
for urging the hollow cylindrical valve element in a direction away
from the core, a hollow cylindrical plunger fixedly fitted on the
hollow cylindrical valve element, and a solenoid coil circumferentially
provided on an outside of the pipe.
[0011] The above and other objects, features and advantages of
the present invention will become apparent from the following description
when taken in conjunction with the accompanying drawings which illustrate
preferred embodiments of the present invention by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a central longitudinal cross-sectional view showing
a proportional solenoid valve according to a first embodiment, in
a non-energized state;
[0013] FIG. 2 is a central longitudinal cross-sectional view showing
the proportional solenoid valve according to the first embodiment,
in an energized state;
[0014] FIG. 3 is a graph showing a current-lift characteristic
of the proportional solenoid valve;
[0015] FIG. 4 is a graph showing an example of a current-lift characteristic
of a conventional proportional solenoid valve;
[0016] FIG. 5 is a diagram useful in explaining a refrigeration
cycle for cooling, in which the proportional solenoid valve is integrated;
[0017] FIG. 6 is a diagram useful in explaining a refrigeration
cycle for cooling and heating, in which the proportional solenoid
valve is integrated;
[0018] FIG. 7 is a central longitudinal cross-sectional view showing
a proportional solenoid valve according to a second embodiment,
in a non-energized state;
[0019] FIG. 8 is a central longitudinal cross-sectional view showing
the proportional solenoid valve according to the second embodiment,
in an energized state;
[0020] FIG. 9 is a central longitudinal cross-sectional view showing
a proportional solenoid valve according to a third embodiment, in
a non-energized state;
[0021] FIG. 10 is a plan view of the proportional solenoid valve
according to the third embodiment;
[0022] FIG. 11 is a central longitudinal cross-sectional view showing
a proportional solenoid valve according to a fourth embodiment,
in a non-energized state;
[0023] FIG. 12 is a central longitudinal cross-sectional view showing
the FIG. 11 proportional solenoid valve as viewed from a position
rotated through 90 degrees from the FIG. 11 position about an axis
thereof;
[0024] FIG. 13 is a central longitudinal cross-sectional view showing
the proportional solenoid valve according to the fourth embodiment,
in an energized state;
[0025] FIG. 14 is a central longitudinal cross-sectional view showing
the FIG. 13 proportional solenoid valve as viewed from a position
rotated through 90 degrees from the FIG. 13 position about an axis
thereof;
[0026] FIG. 15 is a perspective view showing a state of the inside
of the proportional solenoid valve according to the fourth embodiment,
in the non-energized state;
[0027] FIG. 16 is a cross-sectional view taken on line A-A of FIG.
15;
[0028] FIG. 17 is a perspective view showing a state of the inside
of the proportional solenoid valve according to the fourth embodiment,
in the energized state;
[0029] FIG. 18 is a cross-sectional view taken on line B-B of FIG.
17;
[0030] FIG. 19 is a central longitudinal cross-sectional view showing
a proportional solenoid valve according to a fifth embodiment;
[0031] FIG. 20 is a central longitudinal cross-sectional view showing
a proportional solenoid valve according to a sixth embodiment, in
a non-energized state;
[0032] FIG. 21 is a perspective view showing a state of the inside
of the proportional solenoid valve according to the sixth embodiment,
in the non-energized state;
[0033] FIG. 22 is a central longitudinal cross-sectional view showing
the proportional solenoid valve according to the sixth embodiment,
in an energized state;
[0034] FIG. 23 is a perspective view showing a state of the inside
of the proportional solenoid valve according to the sixth embodiment,
in the energized state;
[0035] FIG. 24 is a graph showing the relationship between an outer-diametric
cross-sectional area of an end of a hollow cylindrical valve element
and plunger and a spring constant; and
[0036] FIG. 25 is a diagram schematically showing a current-lift
characteristic of the proportional solenoid valve according to the
sixth embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] Hereinafter, embodiments of the present invention will be
described with reference to drawings.
[0038] First, a first embodiment will be described. FIG. 1 is a
central longitudinal cross-sectional view showing a proportional
solenoid valve of the first embodiment in a non-energized state,
while FIG. 2 is a central longitudinal cross-sectional view showing
the same in an energized state.
[0039] The proportional solenoid valve of the first embodiment
has a body formed by a straight hollow cylindrical pipe 1 which
both ends are opening. Within the pipe 1, there is arranged a hollow
cylindrical core 2 formed therethrough with a fluid passage extending
axially.
[0040] A hollow shaft 3 is arranged in the fluid passage of the
core 2. The hollow shaft 3 has one end thereof fitted in the fluid
passage of the core 2 in a manner communicating with the fluid passage.
The shaft 3 has the other end thereof integrally formed with a valve
seat 4 forming a conical tapered valve seat having a diameter thereof
increasing toward the extremity of the other end of the shaft 3.
Further, the shaft 3 is formed with a plurality of valve holes 5
on the circumference thereof at respective locations adjacent to
the valve seat 4. On the outer peripheral surface of a portion formed
with the valve holes 5, there is formed a communication groove 5a
along the whole circumference of the shaft 3.
[0041] A hollow cylindrical valve element 6 made of a non-magnetic
material is arranged between the core 2 and the valve seat 4 in
a manner axially movable using the shaft 3 as a guide. The shaft
3 that guides the hollow cylindrical valve element 6 has the outer
peripheral surface thereof formed with a plurality of grooves 3a
along the circumference which form a fluid seal on the sliding surface.
A spring 7 is arranged between the hollow cylindrical valve element
6 and the core 2, for urging the hollow cylindrical valve element
6 in a direction for seating the same on the valve seat 4. Further,
a hollow cylindrical plunger 8 is fixedly fitted on the hollow cylindrical
valve element 6 to perform axial motion together with the valve
element 6. The plunger 8 is formed to have such an outer diameter
that a predetermined gap is produced between the pipe 1 and the
plunger 8, so that equal fluid pressures can be applied to the axial
both end faces of the plunger 8 through the gap.
[0042] The core 2 and the plunger 8 has respective end faces 2a,
8a opposed to each other, and the end faces 2a, 8a are formed to
have respective tapered surfaces sloped with identical gradients
so as to improve linearity of attraction characteristics with respect
to an applied electric current. The end face 2a of the core 2 has
a washer 9 of a non-magnetic material arranged thereon so as to
suppress attraction of the plunger 8 to the core 2 by residual magnetism
when the end face 8a of the plunger 8 is demagnetized in a state
of being in contact with the washer 9.
[0043] Fitted on the outer peripheral surface of the pipe 1 is
a bobbin 11 having a solenoid coil 10 wound therearound. The bobbin
11 is surrounded by a first yoke 12. The first yoke 12 has an upper
end portion thereof mounted on the pipe 1 in a manner covering the
outside of the bobbin 11. On the other hand, the lower end of the
first yoke 12 is closed by a second yoke 13 from below the bobbin
11 to form a continuous magnetic circuit.
[0044] The pipe 1 has opposite open both ends thereof each drawn
in a manner adapted to the diameter of a mating pipe to which the
pipe 1 is to be welded for integrating the proportional solenoid
valve in a system.
[0045] In the proportional solenoid valve, the core 2, the plunger
8, and the first yoke 12 and the second yoke 13 form a magnetic
circuit including the solenoid coil 10, with the core 2 functioning
as a fixed iron core and the plunger 8 as a movable iron core.
[0046] According to the proportional solenoid valve constructed
as above, when it is not energized, the hollow cylindrical valve
element 6 and the plunger 8 are moved downward, as viewed in the
figure, by the spring 7, as shown in FIG. 1, whereby the hollow
cylindrical valve element 6 is seated on the valve seat 4. As a
result, the valve holes 5 and the communication groove 5a adjacent
to the valve seat 4 are closed by the side wall of the hollow cylindrical
valve element 6, whereby the fluid passage is blocked. When a fluid
flows into the pipe 1 via the upper open end thereof as viewed in
the figure in this state, the fluid is introduced into the hollow
of the shaft 3. However, since the valve holes 5 and the communication
groove 5a are closed by the hollow cylindrical valve element 6,
the fluid is prevented from flowing out via the lower open end of
the pipe 1. On the other hand, when the fluid flows into the pipe
1 via the lower open end thereof as viewed in the figure, the fluid
flows through the gap between the pipe 1 and the plunger 8 and is
introduced into a space 14 formed between the end face 2a of the
core 2 and the end face 8a of the plunger 8. This causes equal fluid
pressures to act on the respective axially opposite sides of the
plunger 8 and those of the hollow cylindrical valve element 6, which
prevents valve opening/closing operations from being adversely affected
by the pressure of the fluid, thereby making it possible to maintain
the valve closed state only by the urging force of the spring 7.
[0047] On the other hand, when the proportional solenoid valve
is energized with the maximum current, the plunger 8 is attracted
toward the core 2 against the urging force of the spring 7, as shown
in FIG. 2, and the end face 8a of the plunger 8 comes into contact
with the washer 9. At this time, the hollow cylindrical valve element
6 moves together with the plunger 8 to stop closing of the valve
holes 5 and the communication groove 5a and thereby allow communication
between the open both ends of the pipe 1 via the valve holes 5 and
the communication groove 5a. Consequently, when fluid flows into
the pipe 1 via the upper open end thereof as viewed in the figure,
the fluid passes through the fluid passage in the shaft 3 to enter
the communication groove 5a via the valve holes 5. Then, after filling
the whole communication groove 5a, the fluid flows toward the lower
open end as viewed in the figure, via a space between the conical
tapered surface of the valve seat 4 and the end face of the hollow
cylindrical valve element 6. Similarly, when fluid flows in via
the lower open end as viewed in the figure, the fluid enters the
communication groove 5a via the space between the conical tapered
surface of the valve seat 4 and the end face of the hollow cylindrical
valve element 6. Then, the fluid enters the fluid passage in the
shaft 3 via the valve holes 5, followed by flowing toward the upper
open end, as viewed in the figure, of the pipe 1.
[0048] Now, when the value of electric current to be supplied to
the solenoid coil 10 is changed, the plunger 8 is stopped at an
axial position where the attractive force of the core 2 and the
urging force of the spring 7 are balanced with each other, depending
on the current value. Thus, the proportional solenoid valve can
be set to a valve lift corresponding to the current value.
[0049] As described above, according to the proportional solenoid
valve of the first embodiment, it is possible to control the flow
rate of fluid in either direction of fluid flow. Further, since
the opening degree of the valve holes 5 and that of the communication
groove 5a in the energized state of the proportional solenoid valve
can be changed by changing the amount of press-fitting of the shaft
3, which is press-inserted into the fluid passage of the core 2
and fitted in the inner wall of the same, into the core 2, it is
possible to adjust the flow rate characteristics in the fully-opened
state of the proportional solenoid valve.
[0050] It is possible to change the valve lift of the proportional
solenoid valve continuously according to the value of electric current
supplied thereto for energization. Next, an example of the characteristic
of the proportional solenoid valve is shown.
[0051] FIG. 3 is a graph showing the current-lift characteristic
of the proportional solenoid valve. Further, FIG. 4 shows an example
of the current-lift characteristic of a conventional proportional
solenoid valve for comparison. In each of FIGS. 3 and 4, the abscissa
represents electric current supplied to the solenoid coil, while
the ordinate represents the amount of valve lift of the hollow cylindrical
valve element toward the core. Changes in the valve lift amount
with an increase in the value of electric current supplied for energization
are indicated by a solid line, and changes in the valve lift amount
with a decrease in the value of electric current supplied for energization
are indicated by a dotted line.
[0052] When the proportional solenoid valve is not energized, the
end face 8a of the plunger 8 is held in a state completely separated
from the washer 9 arranged on the end face 2a of the core 2, as
shown in FIG. 1. As the current value is progressively increased,
the end face 8a of the plunger 8 is gradually brought closer to
the washer 9. Then, when the electric current reaches a predetermined
current value, the end face 8a is brought into contact with the
washer 9 as shown in FIG. 2. Thereafter, as the value of electric
current supplied for energization is progressively decreased from
this state, the end face 8a gradually moves away from the washer
9, and when the supply of electric current is stopped, the end face
8a is completely separated from the washer 9 again, as shown in
FIG. 1.
[0053] In the proportional solenoid valve that operates as above,
the relationship between the value of electric current supplied
for energization and the valve lift amount of the hollow cylindrical
valve element 6 in the case of the current value being progressively
increased to the predetermined value as shown in FIG. 3 is represented
by an S-shaped curve of the solid line in the figure. On the other
hand, in the case of the current value being progressively decreased
after having reached the predetermined value, the relationship between
the current value and the valve lift amount of the hollow cylindrical
valve element 6 is represented by an S-shaped curve of the dotted
line in the figure. The curves in the respective cases differ from
each other, which means that the relationship between the current
value and the valve lift amount of the hollow cylindrical valve
element 6 has a hysteresis characteristic. As shown in FIG. 4, the
conventional proportional solenoid valve also has the current-lift
characteristic with hysteresis.
[0054] However, in the proportional solenoid valve of the present
invention, the difference between each valve lift amount in the
process of increasing electric current and the corresponding valve
lift amount in the process of decreasing electric current is smaller
than in the prior art, which means that a maximum hysteresis error
is reduced. The reason for this is that pressures which the plunger
8 receives on the respective axially both ends thereof are equal
to each other, and hence the plunger 8 is prevented from being adversely
affected by fluid pressure when moving in the valve-closing direction
or in the valve-opening direction, and that a sliding area between
the hollow cylindrical valve element 6 and the shaft 3 for axial
motion of the hollow cylindrical valve element 6 using the shaft
3 as a guide is small.
[0055] The proportional solenoid valve described above can be utilized
e.g. as an electrically controlled expansion valve for adiabatically
expanding refrigerant within a refrigeration cycle used in an air
conditioning system for an automotive vehicle.
[0056] FIG. 5 is a diagram useful in explaining a refrigeration
cycle for cooling in which the proportional solenoid valve is integrated.
In this refrigeration cycle for cooling, first, gaseous refrigerant
compressed by a compressor 20 is condensed by heat exchange with
outside air in a condenser 21, and the resulting liquid refrigerant
flows into the proportional solenoid valve 22 functioning as an
expansion valve. In the proportional solenoid valve 22, the supplied
liquid refrigerant is adiabatically expanded into low-temperature
and low-pressure refrigerant. This refrigerant is supplied to an
evaporator 23 to exchange heat with air within a vehicle compartment,
whereby the air is cooled. The refrigerant evaporated by the heat
exchange in the evaporator 23 is delivered to an accumulator 24
to be separated into gas and liquid, followed by gaseous refrigerant
alone being returned to the compressor 20.
[0057] Further, this proportional solenoid valve can be applied
to a refrigeration cycle for both cooling and heating based on the
heat pump method, by making use of its characteristic of allowing
bidirectional flow of fluid. FIG. 6 is a diagram useful in explaining
the refrigeration cycle for cooling and heating in which the proportional
solenoid valve is integrated.
[0058] First, when this refrigeration cycle is operating for cooling,
gaseous refrigerant compressed by a compressor 30 is guided to an
outdoor heat exchanger 32 operating as a condenser, via a path in
a four-way valve 31 represented by a solid line in the figure, and
condensed by the outdoor heat exchanger 32. The resulting liquid
refrigerant is delivered to the proportional solenoid valve 33 which
functions as the expansion valve, where it is adiabatically expanded.
Then, the adiabatically expanded refrigerant is supplied to an indoor
heat exchanger 34 operating as an evaporator, to exchange heat with
air in a vehicle compartment. The refrigerant having passed through
the indoor heat exchanger 34 flows via a path in the four-way valve
31 represented by a solid line in the figure, into an accumulator
35, where it is separated into gas and liquid, followed by gaseous
refrigerant alone being returned to the compressor 30.
[0059] On the other hand, when the refrigeration cycle is operating
for heating, high-temperature and high-pressure gaseous refrigerant
compressed by the compressor 30 is guided to the indoor heat exchanger
34 via the four-way valve 31 switched to open a path represented
by a dotted line in the figure. The gaseous refrigerant supplied
to the indoor heat exchanger 34 exchanges heat with air in the vehicle
compartment to heat the air. The liquid refrigerant formed by condensation
due to the heat exchange in the indoor heat exchanger 34 is adiabatically
expanded by the proportional solenoid valve 33 and then delivered
to the outdoor heat exchanger 32. In the outdoor heat exchanger
32, the supplied refrigerant is evaporated by heat exchange with
the outside air and delivered to the accumulator 35 via a path in
the four-way valve 31 represented by a dotted line in the figure.
Then, the refrigerant is separated into gas and liquid by the accumulator
35, followed by gaseous refrigerant alone being returned to the
compressor 30.
[0060] As described above, from whichever of the open both ends
of the pipe 1 a liquid may flow in, the proportional solenoid valve
of the invention is capable of controlling the flow rate of the
liquid. Therefore, it is possible to apply the proportional solenoid
valve not only to the refrigeration cycle for cooling, in which
refrigerant flow is unidirectional, but also the refrigeration cycle
for both cooling and heating, in which refrigerant flow is reversed.
[0061] Next, a second embodiment will be described. FIG. 7 is a
central longitudinal cross-sectional view showing a proportional
solenoid valve of the second embodiment in a non-energized state,
while FIG. 8 is a central longitudinal cross-sectional view showing
the proportional solenoid valve of the second embodiment in an energized
state. Component parts and elements in FIGS. 7 and 8 corresponding
to those in FIGS. 1 and 2 are designated by identical reference
numerals.
[0062] The proportional solenoid valve of the second embodiment
has a T-shaped body formed by a hollow cylindrical first pipe 101a
which both ends are opening and a second pipe 101b joined perpendicularly
to the first pipe 101a. A core 102 is fixedly fitted in the first
pipe 101a in a manner closing one end of the first pipe 101a.
[0063] Within the core 102, there is arranged a shaft 103 axially
of the first pipe 101a, with one end thereof fitted in the core
102. The shaft 103 has the outer peripheral surface thereof formed
with a plurality of grooves 103a along the circumference, which
form a fluid seal with a hollow cylindrical valve element 6.
[0064] A valve seat 104 and a fixed portion 104a are integrally
formed with the other end of the shaft 103 which is not fitted in
the core 102. Bored at a location between the shaft 103 and the
valve seat 104 are valve holes 105 communicating with a fluid passage
extending axially, and a communication groove 105a is formed along
the whole circumference of the shaft 103 at the location where the
valve holes 105 are bored. The fixed portion 104a in the form of
a large diameter hollow cylinder is fixed in the first pipe 101a
in a state in which the outer peripheral surface of the fixed portion
104a is held in intimate contact with the inner peripheral surface
of the first pipe 101a.
[0065] The hollow cylindrical valve element 6 formed of a non-magnetic
material is arranged between the core 102 and the valve seat 104
in a manner axially movable using the shaft 103 as a guide. A spring
7 is arranged between the hollow cylindrical valve element 6 and
the core 102, for urging the hollow cylindrical valve element 6
in a direction for seating the same on a tapered face of the valve
seat 104. Further, a hollow cylindrical plunger 8 is fixedly fitted
on the hollow cylindrical valve element 6 in a state a predetermined
gap is formed between the inner peripheral surface of the first
pipe 101a and the plunger 8 to perform axial motion together with
the valve element 6. Further, an end face 8a of the plunger 8 and
an end face 102a of the core 102 opposed to the end face 8a are
formed to have respective tapered surface sloped with identical
gradients. The end face 102a of the core 102 has a washer 9 of a
non-magnetic material arranged thereon, and the end face 8a of the
plunger 8 is brought into contact with the washer 9.
[0066] An open end of the first pipe 101a opposite to the open
end in which the core 102 is fitted is drawn in a manner adapted
to the diameter of a mating pipe for welding.
[0067] According to the proportional solenoid valve constructed
as above, when it is not energized, the hollow cylindrical valve
element 6 and the plunger 8 are moved downward, as viewed in FIG.
7, by the spring 7, as shown in FIG. 7, and the hollow cylindrical
valve element 6 is seated on the valve seat 104. As a result, the
valve holes 105 bored in the valve seat 104 and the communication
groove 105a are closed by the side wall of the hollow cylindrical
valve element 6, whereby the fluid passage is blocked. When fluid
flows in via the lower open end, as viewed in the figure, of the
first pipe 101a in this state, the fluid reaches the valve holes
105, but since the valve holes 105 are closed by the hollow cylindrical
valve element 6, the fluid is prevented from flowing out toward
an open end of the second pipe 101b, shown on a right-hand side.
On the other hand, when fluid flows in via the open end of the second
pipe 101b, the fluid is introduced into a space 14 formed between
the end face 102a of the core 102 and the end face 8a of the plunger
8, via a gap between the first pipe 101a and the plunger 8. As a
result, fluid pressures equal to each other act on the respective
axially both sides of the plunger 8 and those of the hollow cylindrical
valve element 6, which prevents valve opening/closing operations
from being adversely affected by the fluid pressure, thereby making
it possible to maintain the valve closed state by the urging force
of the spring 7.
[0068] On the other hand, when the maximum current is supplied
to a solenoid coil 10, the plunger 8 is attracted toward the core
102 against the urging force of the spring 7, as shown in FIG. 8,
and the end face 8a of the plunger 8 is brought into contact with
the washer 9. At this time, the hollow cylindrical valve element
6 moves together with the plunger 8, whereby the valve holes 105
and the communication groove 105a are fully opened, and the open
ends of the respective first and second pipes 101a, 101b communicate
with each other via the valve holes 105 and the communication groove
105a. Consequently, the proportional solenoid valve allows bidirectional
flow of fluid, i.e. allows a fluid to flow in both of a case of
the fluid flowing in via the upper open end, as viewed in the figure,
of the first pipe 101a and a case of the fluid flowing in via the
open end of the second pipe 101b.
[0069] Now, when the value of electric current supplied to the
solenoid coil 10 is changed, the plunger 8 and the hollow cylindrical
valve element 6 are controlled to a valve lifting position dependent
on the current value.
[0070] According to the above proportional solenoid valve, before
the open ends of the first and second pipes 101a, 101b are joined
to mating pipes, respectively, e.g. by welding, it is possible to
remove a bobbin 11 having the solenoid coil 10 wound therearound
and first and second yokes 12 and 13, all of which are arranged
outside the first pipe 101a and the core 102, so as to prevent effects
of heat generated by the welding. This makes it possible to prevent
the solenoid coil 10 and others from interfering with pipe welding
work, thereby improving workability in mounting the proportional
solenoid valve as well as to avoid adverse affects, such as distortion,
caused by welding heat.
[0071] Next, a third embodiment will be described. FIG. 9 is a
central longitudinal cross-sectional view showing a proportional
solenoid valve of the third embodiment in a non-energized state,
and FIG. 10 is a plan view of the proportional solenoid valve of
the third embodiment. In FIG. 10, a core, a valve element, a valve
seat and a plunger are omitted from illustration.
[0072] The proportional solenoid valve of the third embodiment
is constructed, as shown in FIGS. 9 and 10, by fitting a piping
joint 200 for use in connection to a mating pipe on each of the
open both ends of the proportional solenoid valve of the first embodiment.
[0073] The piping joint 200 is formed to have a generally oval
shape, and fitted on each open end of a pipe 201 of the proportional
solenoid valve. The diameter of the end 201a of the pipe 201 is
expanded after the piping joint 200 having been fitted on the pipe
201, so as to prevent the piping joint 200 from falling off. Further,
the piping joint 200 is formed with a through hole 200a through
which a bolt extends at a location outward of the pipe 201.
[0074] When the proportional solenoid valve having the piping joint
200 fitted thereon is to be connected to a mating pipe, a piping
joint identical in structure to the piping joint 200 is fitted on
the mating pipe, and the two piping joints are faced to each other
via an O ring, and then fixed to each other by inserting a bolt
through the through holes thereof and fastening with a nut.
[0075] According to the proportional solenoid valve constructed
as above, it is possible to connect the pipe 201 to mating pipes
via respective O rings, which enhances durability against vibration,
compared with a case where the pipe 201 is joined to mating pipes
by welding. Particularly, the proportional solenoid valve can be
effectively applied to cases of use thereof at locations where violent
vibration occur, such as in an automotive vehicle.
[0076] Although in the third embodiment, the piping joints are
fitted on the open both ends of the proportional solenoid valve
of the first embodiment, a single piping joint may be fitted only
on either of the open ends. Further, the piping joints can be fitted
on the open ends of the proportional solenoid valve having the T-shaped
body described in the second embodiment.
[0077] Next, a fourth embodiment will be described. FIG. 11 is
a central longitudinal cross-sectional view showing a proportional
solenoid valve of the fourth embodiment in a non-energized state,
and FIG. 12 is a central longitudinal cross-sectional view of the
FIG. 11 proportional solenoid valve as viewed from a position rotated
through 90 degrees from the FIG. 11 position about its axis. FIG.
13 is a central longitudinal cross-sectional view showing the proportional
solenoid valve of the fourth embodiment in an energized state, and
FIG. 14 is a central longitudinal cross-sectional view of the FIG.
13 proportional solenoid valve as viewed from a position rotated
through 90 degrees from the FIG. 13 position about its axis. Component
parts and elements in FIGS. 11 to 14 corresponding to those in FIGS.
1 and 2 are designated by identical reference numerals.
[0078] The proportional solenoid valve of the fourth embodiment
has a hollow shaft 303 arranged in a fluid passage extending through
a core 2 fixed in a pipe 1. The shaft 303 has one end thereof fitted
in the fluid passage in the core 2. A solid stopper 304 having a
flange projecting radially outwardly from the whole periphery of
an extreme end thereof is integrally formed with the other end of
the shaft 303, which is not fitted in the core 2. The shaft 303
has two valve holes 305 bored in a portion thereof adjacent to the
stopper 304 such that the valve holes 305 communicate with a fluid
passage extending axially. On the outer peripheral surface of the
portion formed with the valve holes 305, there is formed a communication
groove 305a along the whole circumference of the shaft 303.
[0079] A hollow cylindrical valve element 306 made of a non-magnetic
material is arranged between the core 2 and the stopper 304 in a
manner axially movable using the shaft 303 as a guide. A hollow
cylindrical plunger 8 is fixedly fitted on the hollow cylindrical
valve element 306 to perform axial motion together with the same.
The hollow cylindrical valve element 306 has cutout portions 306a
formed in an end thereof. When the proportional solenoid valve is
not energized, the extreme end of the hollow cylindrical valve element
306 comes into contact with the flange of the stopper 304 to fully
close the valve holes 305 and the communication groove 305a, whereas
when the proportional solenoid valve is energized, the cutout portions
306a communicate with the communication groove 305. In short, the
cutout portions 306a of the hollow cylindrical valve element 306
and the communication groove 305a of the shaft 303 form a mechanism
similar to a spool valve.
[0080] Next, the operation of the proportional solenoid valve of
the fourth embodiment will be described with reference to FIGS.
15 to 18.
[0081] FIG. 15 is a perspective view showing essential parts of
the proportional solenoid valve of the fourth embodiment in the
non-energized state, and FIG. 16 is a cross-sectional view taken
on line A-A of FIG. 15. FIG. 17 is a perspective view showing the
essential parts of the proportional solenoid valve of the fourth
embodiment in the energized state, and FIG. 18 is a cross-sectional
view taken on line B-B of FIG. 17. In FIGS. 15 to 18, a washer and
a spring are omitted from illustration.
[0082] In the non-energized state, as shown in FIGS. 15 and 16,
the extreme end of the hollow cylindrical valve element 306 is held
in contact with the flange of the stopper 304. In this state, the
whole of each cutout portion 306a is positioned on a portion of
the outer peripheral surface of the shaft 303, which is not formed
with the communication groove 305a, and hence the valve holes 305
and the communication groove 305a are covered and fully closed by
the inner wall of the hollow cylindrical valve element 306.
[0083] On the other hand, in the energized state, the hollow cylindrical
valve element 306 and the plunger 8 are attracted by the core 2
and moved toward the same, as shown in FIGS. 17 and 18, whereby
each of the cutout portions 306a partially overlaps the communication
groove 305a, and hence the respective fluid passages from the both
ends of the pipe 1 communicate with each other via the cutout portion
306a, the communication groove 305a and the valve holes 305.
[0084] The proportional solenoid valve of the fourth embodiment
is suitable for controlling the flow rate of a high-pressure working
fluid. Speaking of its application to the expansion valve of a refrigeration
cycle, the proportional solenoid valve of the fourth embodiment
is applicable to a system in which carbon dioxide whose operating
pressure is high is used as refrigerant. On the other hand, the
proportional solenoid valves of the first, second, and third embodiments
are each applicable to a system in which an alternative fluorocarbon
(HFC-134a) whose operating pressure is low is used as refrigerant.
[0085] The reason for this is that when refrigerant pressure is
high, the difference between pressure of refrigerant from the communication
groove before passing through a gap between the end face of the
hollow cylindrical valve element and the tapered surface of the
valve seat and pressure of the refrigerant after passing through
the gap is increased to increase the velocity of refrigerant flow.
This causes negative pressure to be generated around a flow of the
refrigerant having passed through the space, and the negative pressure
acts on the end face of the hollow cylindrical valve element to
cause the movable hollow cylindrical valve element to be attracted
toward the tapered surface of the fixed valve seat. Particularly
when the valve lift is small, the velocity of the refrigerant flow
is high, and hence the force attracting the hollow cylindrical valve
element is large, which makes it difficult to control the valve
lift. It should be noted that when refrigerant is flowing toward
the communication groove and the valve holes through the gap between
the end face of the hollow cylindrical valve element and the tapered
surface of the valve seat, no such attractive force is generated,
so that each of the proportional solenoid valves of the first to
third embodiments can be applied to a cooling system which allows
only unidirectional flow of refrigerant, even if the cooling system
uses a refrigerant whose operating pressure is high.
[0086] Although in the proportional solenoid valve of the fourth
embodiment, the hollow cylindrical valve element 306 having the
cutout portions 306a for opening and closing the valve is arranged
in the straight pipe 1, this is not limitative but it is also possible
to arrange a hollow cylindrical valve element formed with cutout
portions in a pipe having the shape shown in the second embodiment.
[0087] Although in the above description, the hollow cylindrical
valve element made of a non-magnetic material is fixedly fitted
in the plunger to perform axial motion together with the plunger,
this is not limitative but e.g. when strainers are arranged at the
respective open both ends of a proportional solenoid valve or within
a system integrating the proportional solenoid valve, such that
dirt can be removed from magnetic elements, the hollow cylindrical
valve element can be made of a magnetic material.
[0088] Further, when the hollow cylindrical valve element is made
of a magnetic material, it can be integrally formed with a plunger.
[0089] FIG. 19 is a central longitudinal cross-sectional view showing
a proportional solenoid valve according to a fifth embodiment. The
proportional solenoid valve of the fifth embodiment has a hollow
cylindrical valve element integrally formed with a plunger. FIG.
19 shows a case in which the hollow cylindrical valve element 306
of the proportional solenoid valve of the fourth embodiment is integrally
formed with the plunger 8.
[0090] A hollow cylindrical valve element and plunger 400 shown
in FIG. 19 can axially move using a shaft 303 as a guide while maintaining
a predetermined gap between the inner wall of a pipe 1 and the hollow
cylindrical valve element and plunger 400 itself. More specifically,
when the proportional solenoid valve is not energized, the hollow
cylindrical valve element and plunger 400 is moved downward, as
viewed in the figure, by a spring 7, whereas when an electric current
is supplied, the hollow cylindrical valve element and plunger 400
is attracted toward a core 2 against the urging force of the spring
7. When the current value is changed, the hollow cylindrical valve
element and plunger 400 is stopped at an axial position where the
attractive force of the core 2 and the urging force of the spring
7 are balanced with each other depending on the current value. Thus,
the proportional solenoid valve is set to a valve lift corresponding
to the current value.
[0091] Although in the above embodiment, description has been given
of the case where the hollow cylindrical valve element and the plunger
are integrally formed with each other, by taking the proportional
solenoid valve of the fourth embodiment as an example, it goes without
saying that the construction can also be applied to the proportional
solenoid valves of the first, second, and third embodiments.
[0092] Next, a sixth embodiment will be described. FIG. 20 is a
central longitudinal cross-sectional view showing a proportional
solenoid valve of the sixth embodiment in a non-energized state,
and FIG. 21 is a side view showing essential parts of the proportional
solenoid valve of the sixth embodiment in the non-energized state.
FIG. 22 is a central longitudinal cross-sectional view showing the
proportional solenoid valve of the sixth embodiment in an energized
state, and FIG. 23 is a side view showing the essential parts of
the proportional solenoid valve of the sixth embodiment in the energized
state. Component parts and elements in FIGS. 20 to 23 corresponding
to those in FIGS. 1 and 2 are designated by identical reference
numerals.
[0093] The proportional solenoid valve of the sixth embodiment
has a hollow cylindrical valve element and plunger 500, which is
formed by integrating a hollow cylindrical valve element and a plunger
into one piece, arranged therein in a manner axially movable using
a shaft 503 as a guide. The shaft 503 has a fluid passage extending
axially therethrough, and one end of the shaft 503 is fitted in
the fluid passage in the core 2. A closing portion 504 closing the
axially extending fluid passage is integrally formed with the other
end of the shaft 503, which is not fitted in the core 2. The shaft
503 has valve holes 505 bored in a portion thereof adjacent to the
closing portion 504, such that the bores communicate with the axially
extending fluid passage. In the outer peripheral surface of the
portion formed with the valve holes 505, there is formed a communication
groove 505a along the whole circumference of the shaft 503.
[0094] The proportional solenoid valve is provided with a strainer
515a fitted in the inner wall of a pipe 1 in a manner opposed to
the closing portion 504 and a strainer 515b fitted on the core 2,
so as to prevent dirt from entering the central portion of the valve.
[0095] The proportional solenoid valve has a second spring 516
for urging the hollow cylindrical valve element and plunger 500
toward the core 2. The second spring 516 utilizes the strainer 515a
as a spring seat and prevents the hollow cylindrical valve element
and plunger 500 from falling off the shaft 503.
[0096] For a reason described hereinbelow, the hollow cylindrical
valve element and plunger 500 has an end formed to have a thinner
tube thickness than the other portions, and the end of the hollow
cylindrical valve element and plunger 500 is formed with a circumferentially
elongated slot 500a.
[0097] According to the proportional solenoid valve of the sixth
embodiment, when it is not energized, a first spring 7 and the second
spring 516 are balanced with each other. In this state, the slot
500a formed in the end of the hollow cylindrical valve element and
plunger 500 is positioned on the outer peripheral surface of the
closing portion 504, and hence the valve holes 505 and the communication
groove 505a are covered and fully closed by the inner wall of the
hollow cylindrical valve element and plunger 500.
[0098] On the other hand, when the proportional solenoid valve
is energized, the hollow cylindrical valve element and plunger 500
is attracted toward the core 2 and moved toward the same. As a result,
the slot 500a partially overlaps the communication groove 505a,
and the fluid passages from the respective both ends of the pipe
1 communicate with each other via the slot 500a, the communication
groove 505a, and the valve holes 505.
[0099] In this case, when the pressure of a working fluid is high,
negative pressure is generated around a flow of the fluid having
passed through the slot 500a of the hollow cylindrical valve element
and plunger 500 via the communication groove 505a, and an attractive
force is generated to attract the hollow cylindrical valve element
and plunger 500 toward the end of the closing portion 504. This
attractive force is stronger as the inner surface of the slot 500a
has a larger area. For this reason, in the proportional solenoid
valve of the sixth embodiment, the end of the hollow cylindrical
valve element and plunger 500 is formed to have the thin tube wall
so as to reduce the area of the inner surface of the slot 500a bored
therein, thereby suppressing the influence of the attractive force.
[0100] Further, in the proportional solenoid valve of the sixth
embodiment, it is possible to increase the respective spring constants
of the first and second springs 7 and 516 for urging the hollow
cylindrical valve element and plunger 500 from the both sides, to
make the hollow cylindrical valve element and plunger 500 less movable,
thereby reducing the influence of the attractive force attracting
the hollow cylindrical valve element and plunger 500 toward the
end of the closing portion 504.
[0101] Thus, by setting the respective spring constants of the
first and second springs 7 and 516 properly according to the size
of the hollow cylindrical valve element and plunger 500 of the proportional
solenoid valve, it is possible to prevent the communication groove
505a and the valve holes 505 from being closed due to attraction
of the hollow cylindrical valve element and plunger 500 toward the
end of the closing portion 504.
[0102] FIG. 24 is a graph showing the relationship between the
outer-diametric cross-sectional area (in other words, the area of
the circle which makes an outer diameter a diameter) of the end
of the hollow cylindrical valve element and plunger 500 and the
spring constant. The abscissa in FIG. 24 represents the value of
the outer-diametric cross-sectional area of the end of the hollow
cylindrical valve element and plunger 500 which is proportional
to the end area of the hollow cylindrical valve element and plunger
500, while the ordinate represents the value of the spring constant
of the first and second springs 7 and 516 for urging the hollow
cylindrical valve element and plunger 500 from the respective both
sides. The spring constant here represents the sum of the spring
constant of the first spring 7 and that of the second spring 516.
[0103] In FIG. 24, points substantially free of the influence of
the attractive force of fluid which are found in the relationship
between the outer-diametric cross-sectional area of the end of the
hollow cylindrical valve element and plunger 500 and the spring
constant of the first spring 7 and the second spring 516 are plotted
as a line. This line indicates that the ratio of the spring constant
to the outer-diametric cross-sectional area of the hollow cylindrical
valve element and plunger 500 (spring constant/outer-diametric cross-sectional
area) is 0.05.
[0104] More specifically, when the ratio of the spring constant
of the first spring 7 and the second spring 516 to the outer-diametric
cross-sectional area of the hollow cylindrical valve element and
plunger 500 becomes equal to or larger than 0.05, the hollow cylindrical
valve element and plunger 500 is made less movable by an increase
in the spring constant, so that the attractive force of fluid which
passes through the slot 500a via the communication groove 505a can
be practically ignored.
[0105] On the other hand, when the ratio of the spring constant
to the outer-diametric cross-sectional area is smaller than 0.05,
the hollow cylindrical valve element and plunger 500 become more
easily movable, and hence is affected by the attractive force of
the fluid.
[0106] Therefore, by setting the ratio of the spring constant of
the first spring 7 and the second spring 516 to the outer-diametric
cross-sectional area of the hollow cylindrical valve element and
plunger 500 to 0.05 or more, it is possible to positively prevent
the hollow cylindrical valve element and plunger 500 from being
moved by the attractive force of the fluid.
[0107] FIG. 25 is a diagram schematically showing the current-lift
characteristic of the proportional solenoid valve of the sixth embodiment.
In FIG. 25, the abscissa represents electric current supplied to
the solenoid coil 10, while the ordinate represents the amount of
valve lift of the hollow cylindrical valve element and plunger 500
toward the core 2. In FIG. 25, changes in the lift amount occurring
as the value of the electric current supplied to the solenoid coil
10 is increased are schematically represented by a solid line. Further,
for comparison, the current-lift characteristic of a proportional
solenoid valve having a single spring is schematically shown by
a dotted line.
[0108] The proportional solenoid valve of the sixth embodiment
has the two springs for urging the hollow cylindrical valve element
and plunger 500 from the respective both sides, and when the proportional
solenoid valve is not energized, the communication groove 505a and
the valve holes 505 are closed by the hollow cylindrical valve element
and plunger 500 in a state of the springs being balanced with each
other, whereby the proportional solenoid valve is held in the valve
closed state.
[0109] When the solenoid coil 10 is energized in this state, the
hollow cylindrical valve element and plunger 500 is immediately
moved toward the core 2. Actually, however, since there occurs friction
between the hollow cylindrical valve element and plunger 500 and
the shaft 503 as a guide, the hollow cylindrical valve element and
plunger 500 starts moving toward the core 2 only after the electric
current supplied to the core 2 exceeds a predetermined value. Compared
with the proportional solenoid valve having the single spring, in
which a hollow cylindrical valve element and plunger requires a
magnetic attractive force stronger than the urging force of the
spring to start moving, the proportional solenoid valve of the sixth
embodiment is capable of causing the hollow cylindrical valve element
and plunger 500 to start moving with a smaller electric current.
[0110] It should be noted that the piping joints described in the
third embodiment can also be mounted to the open ends of each of
the proportional solenoid valves according to the fourth, fifth,
and sixth embodiments.
[0111] As described above, according to the present invention,
the body of the proportional solenoid valve is formed by a hollow
cylindrical pipe, and within the pipe, there are arranged the shaft
formed with the valve holes for communication between the open ends
of the pipe, and the hollow cylindrical valve element fixedly fitted
in the plunger, for axially moving using the shaft as a guide to
open and close the valve holes, while outside the pipe, there is
arranged the solenoid coil. According to this construction, since
the component parts for opening and closing the valve are arranged
within the pipe, it is possible to reduce the number of component
parts and the size of the proportional solenoid valve, which contributes
to reduction of manufacturing costs including machining costs and
material costs.
[0112] Further, since the hollow cylindrical valve element has
a construction which prevents fluid pressure from adversely affecting
the operation thereof, the proportional solenoid valve of the invention
is capable of controlling a flow rate of bidirectional flow of a
fluid, which makes it possible to widely use the proportional solenoid
valve in various systems.
[0113] Furthermore, by forming the hollow cylindrical valve element
arranged within the pipe by using a non-magnetic material, it is
possible to prevent dirt of magnetic materials from being deposited
on the hollow cylindrical valve element, thereby improving sealability
and durability of the proportional solenoid valve.
[0114] Moreover, since the springs for urging the hollow cylindrical
valve element in the valve opening direction and in the valve closing
direction, respectively, are provided, it is possible to carry out
valve opening operation with a small electric current and at the
same time maintain communication between the opposite ends of the
pipe reliably.
[0115] The foregoing is considered as illustrative only of the
principles of the present invention. Further, since numerous modifications
and changes will readily occur to those skilled in the art, it is
not desired to limit the invention to the exact construction and
applications shown and described, and accordingly, all suitable
modifications and equivalents may be regarded as falling within
the scope of the invention in the appended claims and their equivalents. |