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Patent Abstract
In a proportional solenoid valve, a valve drive portion that includes
a coil, a core that is excited by application of a current to the
coil, a plunger that is displaced by a magnetic attraction force
generated by the excited core, and a spring that biases the plunger
in a direction in which a distance to the core is increased. The
spring is set so that a space is maintained between the plunger
and an attraction surface of the core when the spring is fully compressed.
Patent Claims
What is claimed is:
1. A proportional solenoid valve comprising: a seat portion; a
valve element that is brought into and out of contact with the seat
portion; and a valve drive portion that (i) includes a coil, a core
that is excited by application of a current to the coil, a plunger
that is displaced by a magnetic attraction force generated by the
excited core, and a spring that biases the plunger in a direction
in which a distance to the core is increased, and (ii) displaces
the valve element in accordance with the current applied to the
coil, wherein the spring is set so that a space is maintained between
the plunger and an attraction surface of the core when the spring
is fully compressed.
2. A proportional solenoid valve comprising: a seat portion; a
valve element that is brought into and out of contact with the seat
portion; and a valve drive portion that (i) includes a coil, a core
that is excited by application of a current to the coil, a plunger
that is displaced by a magnetic attraction force generated by the
excited core, a rod that is abutted against the valve element and
is displaced integrally with the plunger, a bearing that holds the
rod in a slidable manner, and a spring that is provided between
the bearing and the plunger and biases the plunger in a direction
in which a distance to the core is increased, and (ii) displaces
the valve element in accordance with the current applied to the
coil, wherein the bearing is provided with an extension portion
that extends along an axial direction of the rod and regulates the
displacement of the plunger toward a core side, so that when the
plunger is abutted against an end surface of the extension portion,
a space is maintained between the plunger and an attraction surface
of the core.
3. A proportional solenoid valve comprising: a seat portion; a
valve element that is brought into and out of contact with the seat
portion; and a valve drive portion that (i) includes a coil, a core
that is excited by application of a current to the coil, a plunger
that is displaced by a magnetic attraction force generated by the
excited core, a rod that is abutted against the valve element and
is displaced integrally with the plunger, a spring that biases the
plunger in a direction in which a distance to the core is increased,
and a load adjustment member that is displaced with reference to
the core in an axial direction of the rod to thereby adjust a compressive
load of the spring, and (ii) displaces the valve element in accordance
with the current applied to the coil, wherein the load adjustment
member is provided with an abutment portion which an end surface
of the rod is abutted against and regulates the displacement of
the plunger toward a core side, so that when the end surface of
the rod is abutted against the abutment portion, a space is maintained
between the plunger and an attraction surface of the core.
Patent Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a proportional solenoid
valve that displaces a valve element by applying a current to a
solenoid coil and obtains an output pressure proportional to the
value of the applied current, and a control method for the proportional
solenoid valve.
[0003] 2. Description of the Related Art
[0004] In a conventional proportional solenoid valve, when a high
current exceeding an ordinary working current range is applied to
a solenoid coil or when a high pressure is temporarily exerted on
a valve element due to pulsation of an input pressure, for instance,
a plunger is displaced to exceed an ordinary operating range. In
this case, if an end surface of the plunger is attracted so as to
directly contact an end surface of a core, there occurs a malfunction
of the plunger and output pressure becomes unstable. In view of
this problem, a stopper made of a non-magnetic material is arranged
between the end surface of the plunger and the end surface of the
core (see JP 61-63088 A, for instance).
[0005] In the conventional proportional solenoid valve described
above, however, the stopper is arranged between the plunger and
the core, so that the number of components and the number of assembly
steps are increased, which leads to an increase in cost. In addition,
there is a problem that variations occur in magnetic attraction
force characteristics.
SUMMARY OF THE INVENTION
[0006] The present invention has been made in order to solve the
problems described above, and provides a proportional solenoid valve
with which it is possible to reduce the number of components and
to stabilize magnetic attraction force characteristics.
[0007] In a proportional solenoid valve according to the present
invention, a spring is set so that a space is maintained between
the plunger and an attraction surface of a core when the spring
is fully compressed. With this construction, the spring is fully
compressed before the plunger is abutted against the attraction
surface. The plunger does not directly contact an attraction surface.
[0008] Further, in a proportional solenoid valve according to the
present invention: a bearing is provided with an extension portion
that extends along an axial direction of the rod and regulates the
displacement of a plunger toward a core side, and when the plunger
is abutted against an end surface of the extension portion, a space
is maintained between the plunger and an attraction surface of the
core. With this construction, even when the plunger is displaced
to exceed an ordinary operating range. The plunger does not directly
contact an attraction surface.
[0009] Furthermore, in a proportional solenoid valve according
to the present invention, a load adjust member is provided with
an abutment portion which an end surface of the rod is abutted against
and regulates the displacement of the plunger toward a core side,
and when the end surface of the rod is abutted against the abutment
portion, a space is maintained between the plunger and an attraction
surface of the core. With this construction, even when the plunger
is displaced to exceed an ordinary operating range. The plunger
does not directly contact an attraction surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Preferred embodiments of the present invention will be described
in detail based on the following figures, wherein:
[0011] FIG. 1 is a cross-sectional view of a proportional solenoid
valve according to a first embodiment of the present invention;
[0012] FIG. 2 is a magnified cross-sectional view of portion 11
shown in FIG. 1;
[0013] FIG. 3 is a cross-sectional view of a proportional solenoid
valve according to a second embodiment of the present invention;
[0014] FIG. 4 is a magnified cross-sectional view of portion IV
shown in FIG. 3;
[0015] FIG. 5 is a cross-sectional view of a proportional solenoid
valve according to a third embodiment of the present invention;
and
[0016] FIG. 6 is a magnified cross-sectional view of portion VI
shown in FIG. 5;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Embodiments of the present invention will now be described
based on the accompanying drawings.
[0018] First Embodiment
[0019] A proportional solenoid valve according to a first embodiment
of the present invention is a hydraulic circuit for an electronically
controlled automatic transmission for an automobile (hereinafter
simply referred to as an "automatic transmission"), and
is used to change the operating oil pressure in an operating portion
of the automatic transmission.
[0020] FIG. 1 is a cross-sectional view of the proportional solenoid
valve according to the first embodiment of the present invention.
Note that in this drawing, there is illustrated a proportional solenoid
valve of a normally high type. Also, a coil 1 is accommodated in
a cylindrical case 2 made of metal and a terminal 3 for connecting
the coil 1 to a power supply is arranged outside of the case 2.
Further, the coil 1 and the terminal 3 are molded by a resin portion
4 and a plunger accommodating hole 4a that passes through the hollow
portion of the coil 1 while extending in the axial direction of
the coil 1 is provided in the resin portion 4.
[0021] To one end portion of the resin portion 4, there is coupled
a core 5 made of metal. This core 5 includes a cylinder portion
5a inserted into one end portion of the plunger accommodating hole
4a and a flange portion 5b that is abutted against an end surface
of the resin portion 4. The flange portion 5b is welded to the case
2 at the outer periphery of its joining surface with the case 2.
[0022] Into the cylinder portion 5a, there is inserted a first
plain bearing 6. Also, a cylindrical load adjustment member (spring
pin) 7 is press-fitted into the cylinder portion 5a.
[0023] To the other end portion of the resin portion 4, there is
coupled a guide member 8 made of metal. This guide member 8 includes
an annular-shaped flange portion 8a abutted against an end surface
of the resin portion 4, a cylindrical fitting portion 8b that protrudes
from the flange portion 8a, and a cylindrical valve guide portion
8c that extends from one end portion of the fitting portion 8b.
The flange portion 8a is welded to the case 2 at the outer periphery
of its joining surface with the case 2. The diameter of the valve
guide portion 8c is made smaller than the diameter of the fitting
portion 8b.
[0024] In the valve guide portion 8c, there is fixed a second plain
bearing 9. Into the first plain bearing 6 and the second plain bearing
9, a rod 10 is inserted so as to be slidable. This rod 10 is arranged
inside of the core 5, the plunger accommodating hole 4a, and the
guide member 8 so as to be capable of reciprocating in the axial
direction of the coil 1.
[0025] To the middle portion of the rod 10, there is fixed a cylindrical
plunger 11. That is, the rod 10 is press-fitted into the plunger
11. A spring 12 is arranged between the plunger 11 and the first
plain bearing 6. The plunger 11 is made capable of reciprocating
integrally with the rod 10 inside of the plunger accommodating hole
4a. In the cylinder portion 5a of the core 5, an attraction surface
5c is provided opposite to the end surface of the plunger 11.
[0026] In the valve guide portion 8c, there is inserted a ball-shaped
(spherical) valve element 14 against which a tip portion of the
rod 10 is abutted. The load of the spring 12 that biases the plunger
11 toward the valve element 14 is adjusted by changing the position
of the load adjustment member 7. To the fitting portion 8b, there
is fitted a housing 16 defining a flow path for oil. The housing
16 is welded to the flange portion 8a at the outer periphery of
its joining surface with the flange portion 8a.
[0027] Also, the housing 16 includes an input port 16a through
which the oil is supplied, an output port 16b that communicates
with the input port 16a, and a drain port 16c from which a portion
of the oil supplied through the input port 16a is discharged. Further,
between the input port 16a and the drain port 16c and between the
output port 16b and the drain port 16c, there is provided a seat
portion 16d which the valve element 14 is brought into and out of
contact with.
[0028] Also, the case 2, the core 5, the guide member 8, and the
plunger 11 collectively constitute a magnetic circuit. The core
5 functions as a magnetic attraction portion for the plunger 11.
A valve drive portion 20 in this first embodiment includes the coil
1, the case 2, the terminal 3, the resin portion 4, the core 5,
the first plain bearing 6, the load adjustment member 7, the guide
member 8, the second plain bearing 9, the rod 10, the plunger 11,
and the spring 12.
[0029] FIG. 2 is a magnified cross-sectional view of portion II
shown in FIG. 1. The spring 12 is set so that a space is maintained
between the plunger 11 and the attraction surface 5c of the core
5 when the spring 12 is fully compressed. Note that FIGS. 1 and
2 each show a state where the spring 12 is fully compressed, and
an opening degree of the valve element 14 is changed within a range
smaller than that shown in the drawings during an ordinary operation.
[0030] Next, there will be described an operation in this embodiment.
Under a state where the coil 1 is not excited, the plunger 11 is
pressed to the valve element 14 side by the spring force of the
spring 12. Consequently, the valve element 14 is pressed against
the seat portion 16d by the rod 10, and the oil flow path to the
drain port 16c is closed. As a result, a high-pressure output is
obtained from the output port 16b.
[0031] When the coil 1 is excited and an electromagnetic force
attracting the plunger 11 exceeds a predetermined degree, the plunger
11 and the rod 10 are displaced in opposition to the spring force
of the spring 12 in a direction in which their distances to the
seat portion 16d are increased. When doing so, a pressing force
exerted through the rod 10 (force obtained by subtracting the electromagnetic
force generated in proportion to the value of a current applied
to the coil 1 from the compressive load of the spring 12) and a
fluid force resulting from a pressure output from the output port
16b are exerted on the valve element 14, so that the valve element
14 is displaced to a position at which there is struck a balance
between the pressing force and the fluid force. As a result, an
output pressure proportional to the current value is obtained from
the output port 16b. Note that in an ordinary working range, the
plunger 11 does not contact the attraction surface 5c of the core
5.
[0032] In the hydraulic circuit for an automatic transmission in
which this proportional solenoid valve is arranged, the oil accumulated
in an oil pan, that is, an automatic transmission fluid is pumped
by an oil pump. The oil pump is driven in synchronization with an
engine. The automatic transmission fluid pumped by the oil pump
is adjusted to a predetermined pressure by a regulator or the like
and then is sent to the input port 16a under pressure.
[0033] Then, by the output pressure from the output port 16b, the
opening/closing of a control valve is controlled and a clutch is
controlled, thereby performing a shifting operation. Also, the automatic
transmission fluid discharged from the drain port 16c is recovered
by the oil pan.
[0034] Here, when a high current exceeding an ordinary working
current range is applied to the coil 1 or when a high pressure is
temporarily exerted on the valve element 14 due to pulsation of
an input pressure, for instance, the plunger 11 is displaced to
exceed an ordinary operating range. However, the spring 12 is fully
compressed before the plunger 11 is abutted against the attraction
surface 5c, so that a situation where the plunger 11 is attracted
so as to directly contact the attraction surface 5c is prevented.
As a result, it becomes possible to obtain a stabilized output pressure.
Also, it is not required to provide an additional component between
the plunger 11 and the attraction surface 5c, so that it becomes
possible to reduce the number of components and the number of assembly
steps, contributing to cost reduction. Further, it becomes possible
to stabilize magnetic attraction force characteristics.
[0035] Second Embodiment
[0036] Next, there will be described a second embodiment of the
present invention. FIG. 3 is a cross-sectional view of a proportional
solenoid valve according to the second embodiment, while FIG. 4
is a magnified cross-sectional view of portion IV shown in FIG.
3. In these drawings, the first plain bearing 6 serving as a bearing
is provided with a cylindrical extension portion 6a that extends
along the axial direction of the rod 10 and regulates the displacement
of the plunger 11 toward the core 5 side. With this extension portion
6a, when the plunger 11 is abutted against an end surface of the
extension portion 6a, a space is maintained between the plunger
11 and the attraction surface 5c of the core 5. Here, the first
plain bearing 6 is made of a non-magnetic material. Also, the inside
diameter of the extension portion 6a is made larger than the inside
diameter of the main body portion of the first plain bearing 6.
Further, even when the plunger 11 is abutted against the end surface
of the extension portion 6a, the spring 12 is not fully compressed.
Other constructions are the same as those in the first embodiment.
[0037] As described above, the first plain bearing 6 is provided
with the extension portion 6a, so that even if the plunger 11 is
displaced to exceed the ordinary operating range, a situation where
the plunger 11 is attracted so as to directly contact the attraction
surface 5c is prevented. As a result, it becomes possible to obtain
a stabilized output pressure. Also, it is not required to provide
an additional component between the plunger 11 and the attraction
surface 5c, so that it becomes possible to reduce the number of
components and the number of assembly steps, contributing to cost
reduction. Further, it becomes possible to stabilize magnetic attraction
force characteristics.
[0038] It should be noted here that in the second embodiment, there
has been described a case where one cylindrical extension portion
6a is provided, although multiple rod-shaped extension portions
may be provided at regular intervals in the circumferential direction
of the first plain bearing 6.
[0039] Also, in FIG. 4, the extension portion 6a is arranged inside
of the spring 12, although this portion 6a may also be arranged
outside of the spring 12.
[0040] Third Embodiment
[0041] Next, there will be described a third embodiment of the
present invention. FIG. 5 is a cross-sectional view of a proportional
solenoid valve according to the third embodiment of the present
invention. FIG. 6 is a magnified cross-sectional view showing a
portion VI of FIG. 5. In these drawings, the load adjustment member
7 is provided with the abutment portion 7a that regulates the displacement
of the plunger 11 toward the core 5 side by the abutment with the
end surface of the rod 10. When the abutment portion 7a abuts the
end surface of the rod 10, a space is maintained between the plunger
11 and an attraction surface of the core 05. Also when the abutment
portion 7a abuts the rod 10, the spring 12 is not completely compressed.
Other constructions are the same as those in the first embodiment.
[0042] As described above, the load adjustment member 7 is provided
with the abutment portion 7a, so that even if the plunger 11 is
displaced to exceed an ordinary operating range, a situation is
prevented where the plunger 11 is attracted so as to directly contact
the attraction surface 5c. As a result, it becomes possible to obtain
a stabilized output pressure. Also, it is not required to provide
an additional component between the plunger 11 and the attraction
surface 5c, so that it becomes possible to reduce the number of
components and the number of assembly steps, contributing to cost
reduction. Further, it becomes possible to stabilize magnetic attraction
force characteristics.
[0043] It should be noted here that in the third embodiment, although
the abutment portion 7a is provided so that one end portion of the
cylindrical load adjustment member 7 is completely closed, as long
as displacement of the rod 10 can be regulated it only a step portion
need be provided on the inner surface of the load adjustment member
7.
[0044] Also, in the first to third embodiments, there has been
described a proportional solenoid valve of a normally high type
whose output pressure is high at the time of non-energization and
is decreased in accordance with an increase in applied current.
However, the present invention is also applicable to a proportional
solenoid valve of a normally low type whose output pressure is low
at the time of non-energization and is increased in accordance with
an increase in applied current.
[0045] Further, although in the first to third embodiments a proportional
solenoid valve arranged in the hydraulic circuit for an automatic
transmission has been described, the present invention can be applied
to a proportional solenoid valve for any intended use.
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