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Patent Abstract
A coil assembly for a solenoid valve includes a bobbin formed from
an electrically insulative material. A bore extends axially through
the bobbin. A first flux ring having a sleeve extending axially
from an annular base is mounted upon a first end of the bobbin with
the sleeve extending into the bobbin bore. Similarly, a second flux
ring also having a sleeve extending from an annular base is mounted
upon a second end of the bobbin that is opposite from the first
flux ring with its sleeve extending into the bobbin bore. The flux
rings are formed from a magnetically permeable material that has
a high heat conductivity. Magnet wire is wound upon the assembled
bobbin and flux rings to form the coil assembly.
Patent Claims
What is claimed is:
1. A bobbin assembly for a solenoid valve comprising: a bobbin
formed from an electrically insulative material and having pair
of flanges formed upon the ends thereof, each of said flanges extending
in a radial outward direction from said bobbin, said bobbin also
having an axial bore formed therethrough, said bore being stepped
with the inside diameter of one end of said bore being less than
the inside diameter of the other end of said bore with the two inside
diameters defining an axial shoulder within said bore; and a first
flux ring formed from a magnetically permeable material having a
high heat conductivity, said flux ring having an annular base portion
and a tubular sleeve extending axially into an end of said bobbin
bore; and a second flux ring formed from a magnetically permeable
material having a high heat conductivity, said second flux axially
into the other end of said bobbin bore and contacting said shoulder
formed within said bobbin bore.
2. A bobbin assembly according to claim 1 further including a winding
wound upon said bobbin between said flanges.
3. A bobbin assembly according to claim 2 wherein said bobbin includes
a third flange formed upon an end thereof, said third flange spaced
axially apart from one of said pair of flanges, said third flange
having an arcuate slot formed therein, said arcuate slot defining
a spring having a free end, said free end being movable in an axial
direction, and further wherein at least one coil lead support tower
extends in an axial direction from said free end of said spring
whereby said spring allows axial movement of said support tower
to accommodate component stack up tolerances.
4. A bobbin assembly according to claim 3 wherein said coil support
tower has at least one axial slot formed therein, said axial slot
receiving a coil lead wire.
5. A bobbin assembly according to claim 2 wherein said first flux
ring has an inside diameter and sleeve length selected to correspond
to a particular solenoid valve.
6. A bobbin assembly according to claim 5 wherein said second flux
ring also has an inside diameter and sleeve length selected to correspond
to said particular solenoid valve.
7. A bobbin assembly according to claim 6 wherein at least one
of said flux rings includes an annular recess formed in an inner
surface whereby magnetic flux is concentrated in a portion of said
bobbin bore.
8. A bobbin assembly according to claim 2 wherein said second flux
ring includes an annular base portion and a tubular sleeve that
extends axially into said bobbin bore
9. A coil assembly for a solenoid valve comprising: a bobbin formed
from an electrically insulative material, said bobbin having a stepped
axial bore formed therethrough; a first flux ring formed from a
magnetically permeable material having a high heat conductivity,
said flux ring having an annular base portion and a tubular sleeve,
said tubular sleeve extending axially into an end of said bobbin
bore; a second flux ring formed from a magnetically permeable material
having a high heat conductivity, said second flux ring having generally
tubular shape, said second flux ring extending axially into an end
of said bobbin bore and into contact with said bore step; a winding
wound upon said bobbin to form a winding assembly; and a generally
cup-shaped flux casing having an open end, said flux casing receiving
said winding assembly and being secured to the circumference of
said flux ring.
10. A coil assembly for a solenoid valve comprising: a bobbin formed
from an electrically insulative material, said bobbin having an
axial bore formed therethrough, said bore being stepped with the
inside diameter of one end of said bore being less than the inside
diameter of the other end of the bore with the two inside diameters
defining an axial shoulder within said bore; a first flux ring formed
from a magnetically permeable material having a high heat conductivity,
said flux ring having an annular base portion and a tubular sleeve,
said tubular sleeve extending axially into an end of said bobbin
bore; a second flux ring formed from a magnetically permeable material
having a high heat conductivity, said second flux ring having an
annular base portion and a tubular sleeve extending axially into
an end of said bobbin bore that is opposite from said first flux
ring and contacting said bore step; a winding wound upon said bobbin
to form a winding assembly; and a tubular flux casing, said winding
assembly disposed within said flux casing with at least one of said
flux rings secured to said flux casing.
11. A method for fabricating a solenoid coil comprising the steps
of: (a) forming a bobbin from an electrically insulative material,
the bobbin having an axial bore extending therethrough, the axial
bore being stepped with the inside diameter of one end of the bore
being less than the inside diameter of the other end of the bore
with the two inside diameters defining an axial shoulder within
said bore; (b) providing a flux ring formed from a magnetically
permeable material that has a high heat conductivity, the flux ring
having a generally tubular shape, and pressing the flux ring into
an end of the bobbin bore with the end of the sleeve portion contacting
the shoulder formed within the bore; (c) winding a coil upon the
bobbin to form a coil assembly; (d) inserting the coil assembly
into a flux casing; and (e) securing the flux casing to the coil
assembly.
12. The method according to claim 11 wherein the bobbin includes
pair of flanges formed upon the ends thereof, each of the flanges
extending in a radial outward direction from the bobbin ends and
further wherein in step (d) the coil is wound upon the bobbin between
the flanges.
13. The method according to claim 12 wherein the flux ring is a
first flux ring and step (b) also includes providing a second flux
ring formed from a magnetically permeable material that has a high
heat conductivity, the second flux ring having a sleeve portion
extending axially from an annular base portion, step (b) further
including pressing the sleeve portion of the second flux ring into
an end of the bobbin bore that is opposite from the first flux ring.
14. A bobbin assembly for a solenoid valve comprising: a first
portion formed from an electrically insulative material, said first
portion having an annular base portion with a first cylindrical
portion extending in an axial direction therefrom, said first cylindrical
portion terminating in a first end portion; a second portion formed
from a magnetically permeable material having a high heat conductivity,
said second portion having an annular base portion with a second
cylindrical portion extending in an axial direction therefrom, said
second cylindrical portion terminating in a second end portion,
said second end portion of said second cylindrical portion cooperating
with said first end portion of said first cylindrical portion to
form a bobbin; and a plurality of wire coils wound upon said bobbin.
15. A bobbin assembly according to claim 14 wherein one of said
first and second end portions has a first annular notch formed in
an inside surface thereof and said other of said first and second
end portions has a second annular notch formed in outside surface
thereof that is complementary to said first annular notch, said
first and second annular notches extending over one another to form
said bobbin.
16. A bobbin assembly according to claim 15 wherein a press fit
exists between said first and second notches.
17. A bobbin assembly according to claim 14 wherein one of said
first and second ends of said first and second cylindrical portions
has an annular barb formed upon an inside surface thereof and said
other of said first and second ends of said first and second cylindrical
portions has an annular groove formed in outside surface thereof,
said barb engaging said groove to secure one of said first and second
bobbin portions to the other of said first and second bobbin portions
to form said bobbin.
Patent Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending International
Patent Application No. PCT/US02/14428 filed May 8, 2002 claiming
priority to U.S. patent application Ser. No. 09/850,701 filed May
8, 2001. International Patent Application PCT/US02/14428 was published
as WO 02/091403 on Nov. 14, 2002 in English under PCT Article 21(2).
BACKGROUND OF INVENTION
[0002] This invention relates in general to solenoid valves for
electronic brake control systems and in particular to a solenoid
valve coil wound upon an integrated bobbin and flux ring assembly.
[0003] An Electronic Brake Control System (EBCS) is often included
as standard equipment on new vehicles. When actuated, the EBCS is
operative to modulate the pressure applied to the vehicle wheel
brakes. A typical EBCS includes a plurality of solenoid valves mounted
within a control valve body and connected to the vehicle hydraulic
brake system between the brake master cylinder and the individual
wheel brake cylinders. The solenoid valves usually are normally
open, or isolation, valves and normally closed, or dump, valves.
Proportional solenoid valves also can be included. The valve body
further includes one or more accumulators for the temporary storage
of brake fluid during an operating cycle of the EBCS.
[0004] A separate hydraulic source, such as a motor driven pump,
is usually included in the EBCS. The pump supplies pressurized brake
fluid for reapplying the controlled wheel brakes during an EBCS
operational cycle. The pump is typically included within the control
valve body while the pump motor is mounted upon the exterior of
the control valve body. The pump motor is usually a direct current
motor which operates from the vehicle power supply. Typically, the
motor runs continuously during an EBCS braking cycle.
[0005] An EBCS further includes an electronic control module which
has a microprocessor. The microprocessor is electrically connected
to the pump motor, a plurality of solenoid coils associated with
the solenoid valves, and wheel speed sensors for monitoring the
speed and deceleration of the vehicle wheels. The microprocessor
also is typically electrically connected to the brake light switch
and receives a signal from the switch when the vehicle brakes are
applied. Additionally, the EBCS may include one or more accelerometers
which also are connected to the microprocessor. The microprocessor
includes a memory portion which stores control algorithms for each
mode of operation of the EBCS. The control algorithms comprise a
set of instructions for the microprocessor which control the operation
of the EBCS. The control module is usually mounted upon the valve
body. The assembled valve body, motor and control module form a
compact unit which is often referred to as an electro-hydraulic
control unit.
[0006] During vehicle operation, the microprocessor in the EBCS
control module continuously receives speed signals from the wheel
speed sensors. Depending upon the received signals, the microprocessor
can select one of several modes for operation of the EBCS. For example,
if the microprocessor detects a potential wheel lock-up condition
while the vehicle brakes are applied, the microprocessor will select
an Anti-Lock Brake System (ABS) mode of operation and activate an
ABS braking cycle. During an ABS braking cycle, the microprocessor
actuates the pump motor and selectively operates the solenoid valves
in the control valve to cyclically relieve and reapply hydraulic
pressure to the wheel brakes. The hydraulic pressure applied to
the wheel brakes is adjusted by the operation of the solenoid valves
to limit wheel slippage to a safe level while continuing to produce
adequate brake torque to decelerate the vehicle as desired by the
vehicle operator.
[0007] Another mode of operation provides Traction Control (TC).
If the microprocessors detect excessive slip of a driven wheel when
the wheel brakes are not applied, the EBCS will apply the brakes
to the slipping wheel and thereby transfer more engine torque to
the non-slipping wheel.
[0008] The EBCS can also include Vehicle Stability Control (VSC)
mode of operation. The VSC mode is entered when the microprocessor
detects a potential loss of directional control, such as, for example,
a spin-out of the vehicle. In the VSC mode of operation, selected
wheel brakes are applied to restore directional control of the vehicle.
[0009] Referring now to FIG. 1, there is shown a partial sectional
view of a typical EBCS solenoid valve 10 mounted upon an EBCS control
valve body 11. The control valve body includes a plurality of internal
passages (not shown) that communicate with the valve 10. The valve
10 is a digital valve, that is, it is either open or closed. The
particular valve 10 shown in FIG. 1 is a normally open valve, however,
the following discussion also applies to normally closed valves.
The valve 10 includes an axially shiftable armature (not shown)
which is biased in an upward direction by a spring (not shown) such
that a ball valve (not shown) is maintained in a normally open position.
The ball valve cooperates with a valve seat member 15 which is mounted
in the valve body 11. The armature and ball valve are slideably
disposed within a valve sleeve 16 having a closed end.
[0010] A solenoid coil 20 is carried by the valve sleeve 16 and
surrounds the armature 12. The coil 20 is enclosed by a cup shaped
metal flux casing 21. The valve sleeve 16 extends through an aperture
22 formed in the upper end of the flux casing 21. An annular flux
ring 23 is disposed in the open lower end of the flux casing 21.
The flux casing 21 and flux ring 23 complete a magnetic flux path
which passes through the armature and the valve seat member 15.
[0011] The solenoid coil 20 is of conventional design, comprising
a winding 24 formed from multiple turns of an insulated magnet wire
having a round cross section, such as #28 1/2 magnet wire. The magnet
wire is helically wound upon a plastic bobbin 26. The bobbin 26
has a cylindrical center portion 28 that terminates in upper and
lower flanges, 30 and 32, respectively. A pair of terminal pin supports
34 extend in an axial direction from the top of the bobbin 26. Each
of the supports 34 is molded over a terminal pin 36. An end 38 of
the coil winding wire is wound around the base of each of the terminal
pins 36 and soldered thereto. The pins 36 are electrically coupled
to via a printed circuit board (not shown) to the EBCS microprocessor.
[0012] When it is necessary to actuate the valve 10 during an anti-lock
braking cycle, an electric current is supplied through the terminal
pins 36 to the solenoid coil 20. The current establishes a magnetic
field in the armature which pulls the armature in a downward direction,
closing the ball valve. When the current is interrupted, the magnetic
field collapses, allowing the spring to return the armature to its
original position, thereby reopening the ball valve. An EBCS control
unit also typically includes other digital solenoid valves, such
as normally closed solenoid valves (not shown), which have structures
similar to the normally open valve 10 described above. Additionally,
an EBCS control unit can include proportional solenoid valves.
SUMMARY OF INVENTION
[0013] This invention relates to a solenoid valve coil wound upon
an integrated bobbin and flux ring assembly.
[0014] For electronic brake control systems being currently developed,
vehicular solenoid valves can be energized for long periods of time.
The energized coils generate heat that must be conducted away from
the coils to avoid overheating. Conventional coil bobbins typically
have air gaps and low-pressure contacts between the bobbins and
the metal parts of the other components of the control system. Accordingly,
current units have poor heat conduction properties. Therefore, a
coil assembly having improved heat conduction properties would be
desirable.
[0015] The present invention contemplates a bobbin assembly for
a solenoid valve coil that includes a bobbin formed from an electrically
insulative material with a stepped bore extending axially therethrough.
The bobbin assembly further includes a flux ring formed from a magnetically
permeable material having a high heat conductivity. The flux ring
has an annular base portion and a tubular sleeve extending axially
into an end of the bobbin bore. The bobbin has a pair of flanges
formed upon the ends thereof. A winding is wound upon the bobbin
between said flanges.
[0016] The bobbin assembly can include a second flux ring that
also is formed from a magnetically permeable material having a high
heat conductivity. The second flux ring has an annular base portion
and a tubular sleeve extending into an end of the bobbin bore opposite
from the other flux ring.
[0017] The bobbin can include an annular ring formed upon an inner
surface of the bore and spaced from the ends of the bore. The annular
ring forms a stepped bore within the sleeve with the steps positioning
at least one of the first and second flux rings within the bore.
Alternately, the bobbin can include an least one axially extending
rib formed upon an inner surface of the bore and spaced from the
ends of the bore. The rib positions at least one of the first and
second flux rings within the bore.
[0018] The invention further contemplates that the coil and flux
rings are received within a flux casing with at least one of the
flux rings secured to the flux casing. In the preferred embodiment,
the flux rings are pressed into the ends of the flux casing to retain
the coil and flux rings within the flux casing.
[0019] The invention also contemplates a bobbin assembly having
a first portion formed from an electrically insulative material.
The first portion has an annular base portion with a first cylindrical
portion extending in an axial direction therefrom that terminates
in a first end portion. The bobbin assembly also includes a second
portion formed from a magnetically permeable material having a high
heat conductivity. The second portion has an annular base portion
with a second cylindrical portion extending in an axial direction
therefrom that terminates in a second end portion. The second end
portion of the second cylindrical portion cooperates with said first
end portion of the first cylindrical portion to form a bobbin. A
plurality of wire are coils wound upon the bobbin.
[0020] The invention also contemplates a method for fabricating
a solenoid coil assembly that includes forming a bobbin having a
generally tubular shape with a stepped axial bore extending therethrough.
A flux ring having a sleeve portion extending axially from an annular
base portion is provided and the sleeve portion of the flux ring
is pressed into an end of the bobbin bore. A coil is then wound
upon the bobbin to form a coil assembly. The coil assembly is inserted
into a flux casing and the flux casing is secured to the coil assembly.
The invention further contemplates that the step of mounting a flux
ring upon the bobbin center portion also can include providing a
second flux ring having a sleeve portion extending axially from
an annular base portion and pressing the sleeve portion of the flux
ring into the end of the bobbin bore that is opposite from the first
flux ring.
[0021] Various objects and advantages of this invention will become
apparent to those skilled in the art from the following detailed
description of the preferred embodiment, when read in light of the
accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0022] FIG. 1 is partial sectional view of a prior art EBCS solenoid
valve.
[0023] FIG. 2 is a partial sectional view of an EBCS solenoid valve
in accordance with the invention.
[0024] FIG. 3 is an isometric view of the solenoid coil included
in the valve shown in FIG. 2.
[0025] FIG. 4 is a cross-sectional view of the bobbin included
in the valve shown in FIG. 2.
[0026] FIG. 5 is a cross-sectional view of an alternate embodiment
of the bobbin included in the valve shown in FIG. 2.
[0027] FIG. 6 is a partial sectional view of an alternate embodiment
of the valve shown in FIG. 2.
[0028] FIG. 7 is a partial sectional view of another alternate
embodiment of the valve shown in FIG. 2.
[0029] FIG. 8 is a partial sectional view of another alternate
embodiment of the valve shown in FIG. 2.
[0030] FIG. 9 a partial sectional view of another alternate embodiment
of the valve shown in FIG. 2.
[0031] FIG. 10 a partial sectional view of another alternate embodiment
of the valve shown in FIG. 2.
[0032] FIG. 11 is a flow chart for assembling the solenoid coil
shown in FIG. 2.
[0033] FIG. 12 is a sectional view of an alternate embodiment of
the coil assembly shown in FIG. 2.
[0034] FIG. 13 is a sectional view of another alternate embodiment
of the coil assembly shown in FIG. 2.
[0035] FIG. 14 is a sectional view of an alternate embodiment of
the solenoid valve shown in FIG. 2.
[0036] FIG. 15 is an enlarged sectional view of a portion of the
solenoid valve shown in FIG. 14.
[0037] FIG. 16 is a sectional view of an alternate embodiment of
the solenoid valve shown in FIG. 2.
[0038] FIG. 17 is an enlarged sectional view of a portion of the
solenoid valve shown in FIG. 16.
DETAILED DESCRIPTION
[0039] Referring again to the drawings, there is illustrated in
FIG. 2 a partial sectional view of an improved normally open proportional
solenoid valve 40 for an electronic brake control system that is
in accordance with the invention. Components in FIG. 2 that are
similar to components shown in FIG. 1 have the same numerical identifiers.
Also, for clarity, the components of the valve 40 disposed within
the valve sleeve 16 are not shown in FIG. 2. The valve 40 includes
an improved three piece bobbin assembly 42 that has a center bobbin
44 molded from an electrically insulative material, such as a plastic.
The bobbin 44 has a tubular center portion 45 with a double upper
flange 46 and a lower flange 48 extending in an outward radial direction
from the ends thereof.
[0040] The upper flange 46 includes a first flange 50 that is axially
separated from a second flange 52. The first and second flanges
50 and 52 define a circumferential channel 54 therebetween. Additionally,
a coil lead tower 56 is formed upon the circumference of the first
flange 50 and extends in an upward axial direction in FIG. 2. As
best seen in FIG. 3, an arcuate slot 57 is formed in the first flange
50. The slot 57 extends from the lower end of lead tower 56 and
separates the lead tower 56 from the remainder of the bobbin 44
while forming an arcuate leaf spring 58. While the slot 57 is shown
as extending through an arc of approximately 90 degrees in FIG.
3, it will be appreciated that the slot 57 also can extend through
an arc that is greater or less than 90 degrees. The resilient nature
of the plastic forming the bobbin 44 permits the leaf spring 58
to flex and thus allows movement of the lead tower 56 in an axial
direction. The movement of the lead tower 56 accommodates stack
up tolerances during assembly of electronic control units. As also
best seen in FIG. 3, a pair of axial slots 60 are formed in the
coil lead tower 56.
[0041] While a single lead tower 56 is shown in FIG. 3, it will
be appreciated that the invention also can be practiced with a pair
of lead towers (not shown) spaced apart upon the circumference of
the first flange 50. Additionally, a second arcuate slot (not shown)
would be formed in the first flange 50 to define a second leaf spring
(not shown). The second tower would extend from the end of the second
leaf spring and be movable in an axial direction to accommodate
tolerance stack up.
[0042] The bobbin 44 also includes a plurality of radially extending
ribs 61 formed upon the inside surface of the bobbin center portion
45, as best seen in FIG. 4. Alternately, the bobbin 44 can include
a thickened annular portion 62 formed upon its inner surface, as
shown in FIG. 5. The thickened portion 62 forms a pair of annular
steps 63A and 63B within the bobbin center portion 45.
[0043] The bobbin assembly 42 also includes an upper flux ring
64 that has a sleeve 66 extending in a downward axial direction
in FIG. 2 from an annular base portion 68. The upper flux ring 64
is formed from a material having a high heat conductivity and a
high magnetic permeability. In the preferred embodiment, the upper
flux ring 64 is formed from AISI 1215 steel. The flux ring sleeve
66 is pressed into the upper end of the bobbin center portion 45
and surrounds the upper end of the valve sleeve 16. The sleeve 66
has a bore 69 formed therethrough that has an inside diameter to
match the corresponding valve sleeve 16 that extends into the bore
69 upon assembly. Additionally, as illustrated in FIG. 2, the flux
ring bore 69 can be stepped to match the shape of flux ring sleeve
16 to reduce any air gap between the flux ring 64 and the valve
sleeve 16.
[0044] The three piece bobbin assembly 42 also includes a lower
flux ring 70. Similar to the upper flux ring 64, the lower flux
ring 70 that has a sleeve 72 extending in an upward axial direction
in FIG. 2 from an annular base portion 74. The lower flux ring 70
also is formed from a material having a high heat conductivity and
a high magnetic permeability. In the preferred embodiment, the lower
flux ring 70 is formed from AISI 1215 steel. The sleeve 74 is pressed
into the lower end of the bobbin center portion 45. Similar to the
upper flux ring sleeve 66, the lower flux ring sleeve 72 has an
inside diameter that is selected to minimize any air gaps between
the flux ring 70 and the valve sleeve 16.
[0045] The upper and lower flux ring sleeves 66 and 72 co-operate
with the ribs 61 to position the flux rings 64 and 70 with respect
to the bobbin 44. However, in the preferred embodiment, the ribs
61 position the upper flux ring 64 while the lower flux ring 70
is positioned by the bobbin lower flange 48. The flux ring positioning
provides a first small axial gap between the upper flux ring base
portion 68 and the bobbin first flange 50 and a second small axial
gap between the upper end of the lower flux ring sleeve 72 and the
lower ends of the ribs 61, as illustrated in FIG. 2. The small axial
air gaps accommodate stack up tolerances of valve components. Alternately,
the thickened annular portion 62 formed upon the inner surface of
the bobbin 44 and the corresponding pair of annular steps 63A and
63B can axially position the upper and lower flux rings 64 and 70
within the bore 68.
[0046] As shown in FIG. 2, magnet wire is wound about the bobbin
44 between the flanges 52 and 48 to form a winding 76. A pair of
coil leads 78 extend from the winding 76 and through the channel
56. The coil leads 78 are received in the lead tower slots 58 and
extend in an upward axial direction from the upper end of the lead
tower 56.
[0047] The bobbin assembly 42 is disposed within a tubular flux
casing 80 that is also formed from a material having a high heat
conductivity and a high magnetic permeability, such as, for example,
Steel AISI 1215. As shown in FIG. 2, the lower end 82 of the flux
casing 80 has a reduced diameter. In the preferred embodiment, the
lower flux ring base 74 has the same diameter as the bobbin lower
flange 48 while the upper flux ring base 68 has a greater diameter.
Accordingly, the bobbin assembly 42 can be easily inserted into
the flux sleeve 80 and then the lower flux ring base 74 is pressed
into the lower end 82 of the flux sleeve 80 while the upper flux
ring base 68 is pressed into the upper end of the flux sleeve 80
to retain the bobbin assembly 42 within the sleeve 80. It will be
appreciated that the flux casing 80 also can be attached to the
bobbin assembly 42 by other conventional methods, such as crimping,
spot welding or an adhesive bond. The upper end of the flux casing
80 includes a plurality of axial slits 84 (two shown) formed in
its upper end. The coil support towers 56 and the coil leads 78
pass through the slits 84.
[0048] The support towers 56 are optional and it will be understood
that other conventional structures can be incorporated for coil
leads 78. For example, the coil leads 78 could extend axially through
apertures or slits formed through the upper flux ring base 68 (not
shown) similar in structure to the prior art valve 10 shown in FIG.
1. Additionally, with the coil leads extending through the upper
flux ring base 68, a single upper flange could be formed upon the
bobbin (not shown) in place of the double flange 46. A bore 86 extends
through the bobbin 44 and receives the portion of the solenoid valve
extending from the EBCS control valve body 11.
[0049] The lower flux ring 70 contacts the valve body 11, the valve
seat member 15 and the valve sleeve 16. Similarly, the upper flux
ring sleeve 66 contacts the valve sleeve 16. The contact between
the upper and lower flux rings 64 and 70 with the valve components
provides a path for heat conduction to the valve body 11 and enhances
cooling of the coil 24. Additionally, the outer circumferences of
the upper and lower flux ring bases 68 and 74 contact the flux casing
80, providing another path for conducting heat away from the coil
76 and to the flux casing 80. The coil winding stresses on prior
art bobbins require that the bobbins have a typical thickness of
1.00 mm. Because the improved bobbin assembly 42 has steel flux
ring sleeves 66 and 72 reinforcing the bobbin center portion 45,
the center portion 45 can have a much thinner wall, perhaps as thin
as 0.20 mm. The thinner wall further improves heat conduction away
from the coil 76. The inventors have found, during testing, that
the improved bobbin assembly 42 provides significant improvement
in heat conduction over prior art bobbins.
[0050] Another alternate embodiment of the invention as applied
to a normally open digital valve 90 is illustrated in FIG. 6. As
before, components in FIG. 6 that are similar to components shown
in the previous figures have the same numerical designators. The
valve 90 includes a modified bobbin assembly 92 that includes upper
and lower flux rings 94 and 96 that are shaped to accommodate the
valve sleeve 97. As shown in FIG. 6, the valve sleeve 97 has a shape
that differs from the valve sleeve shapes shown in FIGS. 1 and 2.
Accordingly, the inside diameters and the lengths of the sleeves
of the flux rings 94 and 96 are selected to provide close magnetic
coupling with the valve sleeve 97 and the valve armature (not shown)
that is contained within the sleeve 97. Additionally, the lower
flux ring 96 includes an annular recess 98 formed in the upper end
of the sleeve bore that concentrates the flux at the lower end of
the valve sleeve 97 adjacent to the valve armature (not shown).
However, the bobbin assembly 92 utilizes the same bobbin 44 and
winding 76 as described above for the valve 40 shown in FIG. 2.
Similarly, the same flux casing 80 as described above is used with
the valve 90. Thus, the number of component variations is reduced
and the manufacturing of the valve is significantly simplified with
associated time and cost savings.
[0051] Similarly, another alternate embodiment of the invention
as applied to a normally closed proportional solenoid valve 100
is illustrated in FIG. 7. As before, components in FIG. 7 that are
similar to components shown in the previous figures have the same
numerical designators. Similar to the valve 90 described above,
the valve 100 includes a modified bobbin assembly 101 having upper
and lower flux rings 102 and 104 that are shaped to accommodate
the valve sleeve 106 and the valve armature (not shown) that is
contained within the sleeve. Again, the same bobbin 44 and winding
76 are used. Also the flux casing 80 is identical the that used
on the valves 40 and 90 described above. Therefore, the manufacturing
of the valve is significantly simplified with associated time and
cost savings.
[0052] Another alternate embodiment of the invention is illustrated
in FIG. 8, where another normally open digital valve 110 is illustrated.
As before, components in FIG. 87 that are similar to components
shown in the previous figures have the same numerical designators.
The valve 110 has a modified bobbin assembly 112 that includes a
bobbin 114 that does not have internal spacing ribs or a stepped
bore as described for the preceding valves 40, 90 and 100. Accordingly,
the upper flux ring 116 is positioned relative to the bobbin 114
by the first bobbin flange 50. Additionally, the upper and lower
flux rings 116 and 118 have different shapes and the lower flux
ring sleeve does not extend as far into the bobbin bore as shown
above in FIG. 6. Because the lower flux ring sleeve supports less
of the bobbin bore, the wall of the bobbin bore is thicker than
the wall of the bobbin 45 utilized in the preceding embodiments
of the invention. However, the flux casing 80 described above is
again utilized with the valve 110.
[0053] For the valve 110, the bobbin upper and lower flanges, 46
and 48, align the upper and lower flux rings 116 and 118 with respect
to axial distance and angular positions as the upper flux ring base
bottoms on the first upper bobbin flange 50 and the lower flux ring
base bottoms on the lower bobbin flange 48. This is important, especially
when the bobbin assembly 82 is installed into lateral-gap proportional
valves.
[0054] Another alternate embodiment of the solenoid valve is shown
generally at 120 in FIG. 9. As before, components in FIG. 9 that
are similar to components shown in the previous figures have the
same numerical designators. The valve 120 has a two piece bobbin
assembly 122 that includes bobbin 124 and a single upper flux ring
126 having a downwardly extending sleeve 127 that is pressed into
the bobbin bore as described above. A coil 76 is wound upon the
bobbin 124 and the resulting bobbin assembly 122 is pressed into
the flux casing 80. A conventional flux ring 23 is then pressed
into the open lower end of the flux casing 80. Similar to the coil
assembly 112 shown in FIG. 8, the wall of the bobbin bore is thicker
than the wall of the bobbin 45 utilized in the earlier illustrated
embodiments of the invention.
[0055] Another embodiment of a valve having a two piece coil assembly
is shown generally at 130 in FIG. 10. Again, components shown in
FIG. 10 that are similar to components shown in previous figures
have the same numerical designators. The valve 130 includes a bobbin
132 molded from an electrically insulative material, such as plastic.
The bobbin 132 has a generally tubular shape with a pair a flanges
extending in a radial outward direction from the ends. A single
flux ring 132 is pressed into the lower end of the bobbin bore.
As before, the flux ring 132 is formed from a material having a
high heat conductivity and a high magnetic permeabiltiy, such as,
for example ANSI 1215 steel and includes an a sleeve 133 extending
in an upward axial direction from an annular base 134. Magnet wire
is wound about the bobbin 134 between the flanges to form the coil
24. The bobbin 132 with winding 24 and the flux ring 132 form a
two piece coil assembly 135.
[0056] The valve 130 also includes a generally cup-shaped flux
casing 136 having an open end that receives the coil two piece assembly
135. As shown in FIG. 10, the flux casing 136 has a central aperture
137 formed through the end opposite from the open end. The central
aperture 137 receives the upper end of the valve sleeve 138; however,
it will be appreciated that the flux casing 136 can have other shapes
than that shown in FIG. 10. Also, the upper end of the flux casing
136 includes a portion 139 that extends axially into the upper end
of the bobbin bore to position the bobbin 132 relative to the upper
end of the valve sleeve 138. The lower end of the flux casing 136
is secured to the circumference of the flux ring base 134 by a conventional
method, such as, for example, crimping, spot welding, press fitting
or adhesive bonding. As before, the flux ring sleeve 133 and the
base 134 provide a conduction path for heat from the coil 24 to
the valve body 11 and the flux casing 136 where the coil heat can
be absorbed and dissipated or radiated.
[0057] It will be appreciated that the structure of the coil assembly
described above is adaptable to solenoid valve sleeves having different
axial lengths and diameters by using different shaped flux rings
but the same bobbin and flux casing, as illustrated in FIGS. 6 and
7.
[0058] The invention also contemplates a method of fabricating
the improved bobbin, as illustrated by the flow chart in FIG. 11.
In functional block 140 the bobbin is formed by a conventional method,
such as injection molding. The upper flux ring sleeve is pressed
into the center portion in functional block 142 and the lower flux
ring sleeve is pressed into the center portion in functional block
144. The bobbin assembly is placed upon a winding mandrel in functional
block 146 and the coil is wound upon the bobbin from magnet wire.
[0059] The winding tension of the magnet wire helps retain the
sleeves of the flux rings within the bobbin. Additionally, the hoop
stress of the windings establishes a high contact stress between
the windings and the bobbin center portion and between the bobbin
center portion and the flux ring sleeves. The high contact stress
provides a much lower thermal resistance path between the coil windings
and the flux casing and valve body, where the heat generated by
the coil can be absorbed and dissipated. Also, as described above,
the steel flux ring sleeves reinforce the bobbin center portion,
permitting use of a much thinner wall that further improves heat
conduction.
[0060] In functional block 147, the bobbin assembly is removed
from the winding machine and inserted into a flux casing. In the
preferred embodiment, the bobbin assembly is secured within the
flux casing by pressing the assembly the rest of the way into the
casing in functional block 148. The flux casing can alternately
be secured to the bobbin assembly in functional block 148 by other
conventional methods, such as crimping, spot welding or adhesive
bonding. While the coil assembly is completed in functional block
148, an additional step is shown in functional block 150 where the
coil assembly is installed in the electronic brake control system.
Typically, the coil leads are electrically connected to a printed
circuit board or lead frame carried by a housing that is then attached
to the valve body with the coil bores receiving corresponding valve
sleeves. Functional block 150 is included for completeness and is
not required for fabrication of the improved bobbin.
[0061] An alternate embodiment 154 of the coil assembly shown in
FIG. 2 is illustrated in FIG. 12 where components that are similar
to components shown in FIG. 2 have the same numerical designators.
For simplicity, only the coil assembly 154 is shown in FIG. 12.
The coil assembly 154 includes a stepped bobbin 156 that has a upper
portion 158 and lower portion 160 with the upper portion 158 having
a smaller diameter than the lower portion 160. A bobbin shoulder
162 is defined between the upper and lower portions 158 and 160.
The lower flux ring sleeve 72 extends into the lower end of the
bobbin bore and rests against the bobbin shoulder 162. An upper
flux ring sleeve 164, having a reduced diameter from the upper flux
ring sleeve 66 shown in FIG. 2, extends into the upper end of the
bobbin bore. The stepped bobbin 156 allows winding more turns of
the coil 166 upon the upper portion of the bobbin156. Thus, a stronger
magnetic field is produced when the coil 166 is energized. Alternately,
the same number of turns may be used, with the stepped bobbin providing
a reduced outside diameter for the coil 166. Accordingly, the size
of the coil assembly 154 is correspondingly reduced.
[0062] Another alternate embodiment 170 of the coil assembly shown
in FIG. 2 is illustrated in FIG. 13. Again, components that are
similar to components shown in previous drawings have the same numerical
designators. The coil assembly 170 includes a stepped bobbin as
described above. However, the lower flux ring and sleeve shown above
has been replaced by a separate flux sleeve 172 that extends through
an aperture 174 formed an end of a flux casing 176 and into the
lower portion of the bobbin bore. Thus, the flux casing 176 replaces
the tubular flux casing 80 shown in the previous drawings.
[0063] An alternate structure 180 for the coil assembly is shown
in FIG. 14 where components that are similar to components shown
in previous drawings again have the same numerical designators.
The coil assembly 180 is mounted upon a normally closed solenoid
valve and includes a two piece bobbin 181. The two piece bobbin
has a lower portion 182 that includes a one piece flux ring 183
and a cylindrical flux sleeve 184. The bobbin lower portion 182
is formed from a magnetic material, such as steel. As best seen
in FIG. 15, which is an enlargement of a portion of FIG. 14, an
annular notch 186 is formed on the inner surface of the upper end
of the flux sleeve 184. The bobbin sleeve 184 extends in an upward
direction to form the lower end of the bobbin bore.
[0064] The bobbin 182 also includes a one piece upper portion 186
formed from a insulative material, such as a plastic. The bobbin
upper portion 186 includes a cylindrical sleeve 188 that extends
in a downward direction to form the upper end of the bobbin bore.
An annular notch 190 is formed on the outer surface of the lower
end of the sleeve 186. As also shown in FIG. 15, the upper sleeve
annular notch 190 is complementary to the lower sleeve annular notch
186 and received therein to form the bobbin 181. In the preferred
embodiment, the upper sleeve notch 190 is pressed into the lower
sleeve notch 186. The upper end of the bobbin upper portion 186
is formed into a flange 192 for retaining a coil 194 upon the bobbin
181. Additionally, a pair of terminal supports 196 extend in an
axial direction from the flange 192. A flux casing 198 encloses
the bobbin and coil assembly.
[0065] The coil 194 is wound upon the bobbin 181 with insulated
wire. In the preferred embodiment, the wire insulation is sufficient
to preclude shorting of the coil 194 by the lower bobbin sleeve184.
However, it is also contemplated that a layer of insulative tape
(not shown), such as, for example mylar, may be wound over the lower
bobbin sleeve 184 before the coil wire is wound upon the bobbin
181.
[0066] While the preferred embodiment has been illustrated and
described with one notch 186 formed on the inner surface of the
bobbin lower portion sleeve 184 and another notch 190 formed on
the outer surface of the bobbin upper portion sleeve 188, it will
be appreciated that the invention also may be practiced with one
notch formed on the outer surface of the bobbin lower portion sleeve
and the other notch formed on the inner surface of bobbin upper
portion sleeve (not shown).
[0067] An alternate embodiment 200 of the coil assembly shown in
FIG. 14 is illustrated in FIGS. 16 and 17. Components in FIGS. 16
and 17 that are the same as components shown in previous figures
have the same numerical designators. The coil assembly includes
a two piece bobbin 201 having an upper portion 186 formed from an
insulative material, such as, for example, a plastic, and a lower
portion 182 formed from a magnetic material, such as, for example
steel. As described above, the bobbin lower portion 182 includes
a cylindrical flux sleeve 184; however, an annular notch 202 is
formed on the outer surface of the upper end of the flux sleeve.
Also, as best seen in FIG. 17, an annular groove 204 is formed in
the axially extending portion of the notch 202. The groove 204 is
offset in an axial direction from the upper end of the flux sleeve
184.
[0068] The bobbin upper portion includes a cylindrical sleeve 188
that has an annular notch 206 formed on an inner surface. The upper
sleeve notch 206 is complementary to the notch 202 formed upon the
flux sleeve 184. Furthermore, an annular barb 208 is formed upon
the lower end of the sleeve 188. When the bobbin upper and lower
portions 188 and 184 are pressed together, the upper notch 206 slides
over the lower notch 202 and the barb 208 is received in the groove
204 to lock the portions 188 and 184 together. A coil 194 is then
wound upon the bobbin.
[0069] While the preferred embodiment has been illustrated and
described with one notch 186 formed on the outer surface of the
bobbin lower portion sleeve 184 and another notch 190 formed on
the inner surface of the bobbin upper portion sleeve 188, it will
be appreciated that the invention also may be practiced with one
notch formed on the inner surface of the bobbin lower portion sleeve
and the other notch formed on the outer surface of bobbin upper
portion sleeve (not shown).
[0070] The extension or the flux ring with a sleeve increases the
area of the secondary gap between the flux ring and the valve armature.
This decreases the magnetic reluctance of this part of the magnetic
circuit. The decreased reluctance allows either a decrease in magneto
motive force with a corresponding decrease in the number of turns
of wire used to wind the coil or an increased output force for the
solenoid if the number of coil turns are kept the same. The extended
flux ring sleeve also increases the transfer of heat from the coil
windings to the valve body or hydraulic control unit. Generally,
the structures described above result in a reduction in the coil
outer diameter, current demand and power consumption.
[0071] In accordance with the provisions of the patent statutes,
the principle and mode of operation of this invention have been
explained and illustrated in its preferred embodiment. However,
it must be understood that this invention may be practiced otherwise
than as specifically explained and illustrated without departing
from its spirit or scope.
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