U.S. patent application number 10/646737 was filed with the patent office on 2004-02-26 for solenoid and hydraulic control valve.
Invention is credited to Takahashi, Tamami, Yamashina, Chishiro.
Application Number | 20040036567 10/646737 |
Document ID | / |
Family ID | 17184285 |
Filed Date | 2004-02-26 |
United States Patent
Application |
20040036567 |
Kind Code |
A1 |
Takahashi, Tamami ; et
al. |
February 26, 2004 |
Solenoid and hydraulic control valve
Abstract
A solenoid has a cylindrical excitation coil and a plunger
movable in the excitation coil and generates electromagnetic force
to move the plunger when an electric current is supplied to the
excitation coil. A cover for closing a side of a plunger
compartment accommodating the plunger is provided with upper and
lower through-holes communicatively extending through the cover
from the outside of the solenoid to the plunger compartment. The
uppermost part of the upper through-hole is above or level with the
uppermost part of the plunger compartment. The lowermost part of
the lower through-hole is below or level with the lowermost part of
the plunger compartment.
Inventors: |
Takahashi, Tamami; (Tokyo,
JP) ; Yamashina, Chishiro; (Kanagawa, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
17184285 |
Appl. No.: |
10/646737 |
Filed: |
August 25, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10646737 |
Aug 25, 2003 |
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10069998 |
Mar 1, 2002 |
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6659121 |
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10069998 |
Mar 1, 2002 |
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PCT/JP00/05821 |
Aug 29, 2000 |
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Current U.S.
Class: |
336/188 |
Current CPC
Class: |
Y10T 137/4245 20150401;
F16K 31/0689 20130101; F16K 31/0613 20130101; Y10T 137/86622
20150401; Y10T 137/8013 20150401 |
Class at
Publication: |
336/188 |
International
Class: |
H01F 027/28 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 2, 1999 |
JP |
248845/1999 |
Claims
1. A solenoid having a cylindrical excitation coil and a plunger
movable in the excitation coil, said solenoid being adapted to
generate electromagnetic force to move the plunger when an electric
current is supplied to the excitation coil, wherein a cover for
closing a side of a plunger compartment accommodating the plunger
is provided with upper and lower through-holes communicatively
extending through said cover from an outside of the solenoid to the
plunger compartment, wherein an uppermost part of the upper
through-hole is above or level with an uppermost part of the
plunger compartment, and a lowermost part of the lower through-hole
is below or level with a lowermost part of the plunger
compartment.
2. A hydraulic control valve including a hydraulic control valve
body having a spool sliding in a sleeve, and a solenoid having a
plunger and an excitation coil for generating magnetic force to
move the plunger, said solenoid being attached to the hydraulic
control valve body to apply moving force to the spool by movement
of the plunger, wherein a cover for a side of said solenoid at
which said solenoid is attached to the hydraulic control valve body
is provided with upper and lower through-holes communicating with a
plunger compartment accommodating the plunger, wherein an uppermost
part of the upper through-hole is above or level with an uppermost
part of the plunger compartment, and a lowermost part of the lower
through-hole is below or level with a lowermost part of the plunger
compartment, and wherein said hydraulic control valve body has
upper and lower vertical holes, said upper vertical hole being
provided at a position above the upper through-hole provided in the
cover of said solenoid in communication with said upper
through-hole, said lower vertical hole being provided at a position
below the lower through-hole provided in the cover of said solenoid
in communication with said through-hole, and said upper vertical
hole being in communication with a tank port.
Description
TECHNICAL FIELD
[0001] The present invention relates to a proportional solenoid for
driving a spool of a hydraulic control valve and also pertains to a
hydraulic control valve using the solenoid.
BACKGROUND ART
[0002] (Prior Art)
[0003] FIG. 1 is a sectional view showing a structural example of a
conventional solenoid of the type described above. The solenoid is
a proportional solenoid that generates electromagnetic force
proportional to the electric current supplied to an excitation
coil. The solenoid 100 has a cylindrical casing 101. An axially
movable plunger 102 is placed in the casing 101, together with an
excitation coil 104 wound around a bobbin 103. The excitation coil
104 is disposed to surround the outer periphery of the plunger 102.
The sides of the casing 101 are covered with covers 105 and
106.
[0004] A push pin 107 projects through the center of the cover 106
to transmit force generated from the plunger 102 and the
displacement thereof to the outside of the solenoid 100. The cover
106 has a disk-shaped cover portion 106a made of a magnetic
material and a cylindrical portion 106b projecting from the cover
portion 106a in such a manner as to surround a part of the outer
periphery of the plunger 102. The cylindrical portion 106b has a
tapered portion at the distal end thereof. The tapered portion is
engaged with a tapered portion of a non-magnetic cylindrical member
108. A magnetic cylindrical member 109 is engaged with an end of
the non-magnetic cylindrical member 108 on the side thereof remote
from the cover 106. The cylindrical portion 106b of the cover 106,
together with the non-magnetic cylindrical member 108 and the
magnetic cylindrical member 109, surrounds the plunger 102.
[0005] The tapered portion of the cylindrical portion 106b and the
tapered portion of the non-magnetic cylindrical member 108 allow a
part of the axial magnetic flux produced from the excitation coil
104 to escape to the outer peripheral side, whereby the axial
attraction force acting on the plunger 102 is kept constant
independently of the position of the plunger. The cover 106 is
provided with a through-hole 111 communicating with a compartment
110 accommodating the plunger 102. The through-hole 111 is a hole
for allowing fluid to come in and out of the compartment 110
therethrough in an amount corresponding to a change in the volume
of fluid in the compartment 110 due to displacement of the plunger
102.
[0006] In FIG. 1, if the plunger 102 moves rightward from the
solid-line position by dx to the broken-line position, an amount of
fluid corresponding to A.sub.PLdx flows in the space at the
left-hand side of the plunger 102 from the right-hand space.
Meanwhile, an amount of fluid corresponding to
(A.sub.PL-A.sub.PIN)dx is discharged from the right-hand space. An
amount of fluid corresponding to the volume difference A.sub.PINdx
is sucked into the solenoid 100 through the through-hole 111 from
the outside of the solenoid 100. Here, A.sub.PL denotes the
sectional area of the plunger, and A.sub.PIN denotes the sectional
area of the push pin 107.
[0007] In the above-described conventional solenoid 100, the
through-hole 111 formed in the cover 106 is at a position below the
top of the cylindrical compartment 110 accommodating the plunger
102. Therefore, an air reservoir 112 is undesirably formed in the
compartment 110. That is, in FIG. 1, the distance Dh from the axis
of the plunger 102 to the uppermost part of the through-hole 111 is
smaller than the distance Di from the axis of the plunger 102 to
the uppermost part of the compartment 110. Consequently, the
conventional solenoid 100 has a structure in which air stays in the
upper part of the compartment 110 without being exhausted therefrom
(i.e. the air reservoir 112 is formed).
[0008] In a case where the air reservoir 112 is not present, when
the plunger 102 moves rightward in the figure, for example, the
fluid at the right-hand side of the plunger 102 flows leftward, and
at this time, a moderate damping action is applied to the plunger
102 by the viscosity of the fluid flowing from the right to the
left. However, if there is air in the compartment 110, because the
viscosity of the air is extremely smaller than that of a liquid
used as a working fluid, the damping action applied to the plunger
102 is reduced, and hence vibrations occur unfavorably.
[0009] If the air reservoir 112 is present in the solenoid 100 as
used in a hydraulic control valve having a damping orifice
(described later), a change in the volume of the solenoid-side
space due to the displacement of the spool is undesirably absorbed
by the compressibility of the air. Consequently, the damping effect
cannot be obtained, and hence the spool vibrates unfavorably.
Accordingly, the operation of the hydraulic control valve cannot be
stabilized.
[0010] Further, when water is used as a working fluid, if there is
air in the compartment 110, the air oxidizes the plunger 102 and
the surrounding members. This causes friction to increase and
degrades performance unfavorably.
DISCLOSURE OF THE INVENTION
[0011] (Problem to be Solved by the Invention)
[0012] The present invention was made in view of the
above-described circumstances. An object of the present invention
is to provide a solenoid wherein air cannot be collected in the
space inside the solenoid, and hence the plunger or the spool
operates stably without vibrating, and there is no possibility of
an increase in friction or performance degradation which would
otherwise be caused by oxidation of the plunger and the surrounding
members, and also provide a hydraulic control valve using the
solenoid.
[0013] (Means for Solving the Problem)
[0014] To solve the above-described problem, a first feature of the
present invention resides in a solenoid having a cylindrical
excitation coil and a plunger movable in the excitation coil and
adapted to generate electromagnetic force to move the plunger when
an electric current is supplied to the excitation coil. A cover for
closing a side of a plunger compartment accommodating the plunger
is provided with upper and lower through-holes extending through
the cover from the outside of the solenoid to the plunger
compartment. The uppermost part of the upper through-hole is above
or level with the uppermost part of the plunger compartment. The
lowermost part of the lower through-hole is below or level with the
lowermost part of the plunger compartment.
[0015] A second feature of the present invention resides in a
hydraulic control valve including a hydraulic control valve body
having a spool sliding in a sleeve, and a solenoid having a plunger
and an excitation coil for generating magnetic force to move the
plunger. The solenoid is attached to the hydraulic control valve
body to apply moving force to the spool by the movement of the
plunger. A cover for a side of the solenoid at which the solenoid
is attached to the hydraulic control valve body is provided with
upper and lower through-holes communicating with a plunger
compartment accommodating the plunger. The uppermost part of the
upper through-hole is above or level with the uppermost part of the
plunger compartment. The lowermost part of the lower through-hole
is below or level with the lowermost part of the plunger
compartment. The hydraulic control valve body has upper and lower
vertical holes. The upper vertical hole is provided at a position
above the upper through-hole provided in the cover of the solenoid
in communication with the upper through-hole. The lower vertical
hole is provided at a position below the lower through-hole
provided in the cover of the solenoid in communication with the
lower through-hole. The upper vertical hole is in communication
with a tank port.
[0016] As stated above, the cover of the solenoid is provided with
upper and lower through-holes extending through the cover to the
plunger compartment. The uppermost part of the upper through-hole
is above or level with the uppermost part of the plunger
compartment. The lowermost part of the lower through-hole is below
or level with the lowermost part of the plunger compartment. Thus,
the air in the solenoid can be exhausted to the outside. Therefore,
it is possible to stabilize the operation of the plunger of the
solenoid and the operation of the spool of the hydraulic control
valve.
[0017] Further, because wear particles generated in the solenoid
are discharged through the lower through-hole, it is possible to
prevent the plunger from sliding in wear particles, which would
otherwise accelerate wear, and hence possible to improve
durability.
[0018] When water is used as a working fluid for the hydraulic
control valve, because the air in the solenoid is exhausted, it is
possible to prevent oxidation of portions of constituent members
that are in contact with water.
[0019] Because a vertical hole is provided in the hydraulic control
valve body at a position above the upper through-hole in the cover
of the solenoid in communication with the tank port, the air in the
solenoid can be exhausted to the outside of the hydraulic control
valve.
[0020] Because a vertical hole is provided in the hydraulic control
valve body at a position below the lower through-hole in the cover
of the solenoid, wear particles generated by the sliding movement
of the plunger can be accumulated in the vertical hole. Moreover,
there is no possibility that the wear particles accumulated in the
vertical hole may be scattered or caused to flow backward by the
operation of the hydraulic control valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a sectional view showing a structural example of a
conventional solenoid.
[0022] FIG. 2 is a sectional view showing a structural example of a
solenoid according to the present invention.
[0023] FIG. 3 is a sectional view showing a structural example of a
hydraulic control valve according to the present invention.
[0024] FIG. 4 is a view seen from the arrow A-A in FIG. 3.
EXPLANATION OF REFERENCE SYMBOLS
[0025] 10: solenoid, 11: casing, 12: plunger, 13: bobbin, 14:
excitation coil, 15: cover, 16: cover, 17: push pin, 18:
non-magnetic cylindrical member, 19: magnetic cylindrical member,
20: compartment, 21: through-hole, 22: through-hole, 30: hydraulic
control valve body, 31: hydrostatic bearing, 32: hydrostatic
bearing, 33: spool, 35: sleeve, 36: spring, 37: pump port, 38:
bearing orifice, 39: control port, 40: control port, 50:
intermediate plate, 51: through-hole, 52: through-hole, 53: damping
orifice, 54: horizontal hole, 55: vertical hole, 56: plug, 57:
horizontal hole, 58: plug, 60: displacement sensor, 70: controller,
71: input terminal, P: reference position signal, Q: deviation
signal, S: spool position signal.
BEST MODE FOR CARRYING OUT THE INVENTION
[0026] Embodiments of the present invention will be described below
on the basis of the drawings. FIG. 2 is a sectional view showing a
structural example of a solenoid according to the present
invention. This solenoid is also a solenoid that generates
electromagnetic force proportional to the electric current supplied
to an excitation coil in the same way as the conventional
proportional solenoid shown in FIG. 1. The solenoid 10 has a
cylindrical casing 11. An axially movable plunger 12 is placed in
the casing 11, together with an excitation coil 14 wound around a
bobbin 13. The excitation coil 14 is disposed to surround the outer
periphery of the plunger 12. The sides of the casing 11 are covered
with covers 15 and 16.
[0027] A push pin 17 projects through the center of the cover 16 to
transmit force generated from the plunger 12 and the displacement
thereof to the outside of the solenoid 10. The cover 16 has a
disk-shaped cover portion 16a made of a magnetic material and a
cylindrical portion 16b projecting from the cover portion 16a in
such a manner as to surround a part of the outer periphery of the
plunger 12. The cylindrical portion 16b has a tapered portion at
the distal end thereof. The tapered portion is engaged with a
tapered portion of a non-magnetic cylindrical member 18. A magnetic
cylindrical member 19 is engaged with an end of the non-magnetic
cylindrical member 18 on the side thereof remote from the cover 16.
The cylindrical portion 16b of the cover 16, together with the
non-magnetic cylindrical member 18 and the magnetic cylindrical
member 19, surrounds the plunger 12.
[0028] The tapered portion of the cylindrical portion 16b and the
tapered portion of the non-magnetic cylindrical member 18 allow a
part of the axial magnetic flux produced from the excitation coil
14 to escape to the outer peripheral side, whereby the axial
attraction force acting on the plunger 12 is kept constant
independently of the position of the plunger. The above-described
arrangement and the function of the solenoid 10 are the same as
those of the conventional proportional solenoid.
[0029] The solenoid 10 has two through-holes 21 and 22 provided in
the cover 16 at upper and lower positions, respectively. The
through-holes 21 and 22 communicate with a cylindrical compartment
20 accommodating the plunger 12. The respective end surfaces of the
through-holes 21 and 22 are located at positions remote from the
axis of the compartment 20. More specifically, the distance Dh from
the axis of the compartment 20 to the uppermost part of the upper
through-hole 21 is set greater than the distance (the radius of the
section of the compartment 20) Di from the axis to the uppermost
part of the compartment 20. The distance Dh from the axis of the
compartment 20 to the lowermost part of the lower through-hole 22
is set greater than the distance Di from the axis to the lowermost
part of the compartment 20. It should be noted that the distance Dh
and the distance Di may be set equal to each other (Dh=Di).
[0030] Providing the upper and lower through-holes 21 and 22 in the
cover 16 as stated above allows the air remaining in the
compartment 20 accommodating the plunger 12 to be exhausted to the
outside of the solenoid 10 through the upper through-hole 21.
Meanwhile, an amount of fluid corresponding to the amount of
exhausted air is sucked into the solenoid 10 through the lower
through-hole 22.
[0031] When the plunger 12 slides in the compartment 20, the outer
surface of the plunger 12 and the inner peripheral surface of the
compartment 20 rub against each other. If the use of the solenoid
10 is continued for a long period of time, wear particles are
generated. The lower through-hole 22 performs the function of
discharging the wear particles to the outside. If wear particles
accumulate in the compartment 20 where the plunger 12 is
accommodated, the plunger 12 slides in the wear particles. This
accelerates the wear of the inner surface of the compartment 20.
Therefore, by discharging the generated wear particles through the
lower through-hole 22, it is possible to increase the usable life
of the solenoid, that is, durability thereof.
[0032] Next, a hydraulic control valve according to the present
invention that uses the solenoid 10 arranged as stated above will
be described. FIG. 3 is a sectional view showing the arrangement of
the hydraulic control valve according to the present invention. The
hydraulic control valve has a structure in which a solenoid 10 is
attached to a hydraulic control valve body 30 through an
intermediate plate 50. It should be noted that reference numeral 60
denotes a displacement sensor.
[0033] As has been stated above, the solenoid 10 has two
through-holes 21 and 22 provided in the cover 16 at upper and lower
positions, respectively. The through-holes 21 and 22 communicate
with the compartment 20 accommodating the plunger 12. The
through-holes 21 and 22 are positioned so that the uppermost part
of the through-hole 21 is above the compartment 20 and the
lowermost part of the through-hole 22 is below the compartment 20.
The intermediate plate 50 has through-holes 51 and 52 formed to
extend therethrough at positions that are above and below the two
through-holes 21 and 22, respectively, which are formed in the
cover 16 of the solenoid 10. More specifically, the distance Dp
from the axis to the uppermost part of the upper through-hole 51 is
greater than the distance Dh from the axis to the uppermost part of
the through-hole 21 in the solenoid 10 (Dp.gtoreq.Dh), and the
distance Dp from the axis to the lowermost part of the lower
through-hole 52 is greater than the distance Dh from the axis to
the lowermost part of the through-hole 22 in the solenoid 10
(Dp.gtoreq.Dh).
[0034] The intermediate plate 50 is provided with a horizontal hole
54 at a position above the upper through-hole 51. The horizontal
hole 54 has a damping orifice 53 and extends through the
intermediate plate 50 as far as an intermediate position in the
intermediate plate 50. In addition, the intermediate plate 50 is
provided with a vertical hole 55 extending from the lower surface
of the intermediate plate 50 to a depth where the vertical hole 55
communicates with the horizontal hole 54. The vertical hole 55
communicates with three holes formed in the intermediate plate 50,
i.e. the through-holes 51 and 52 and the horizontal hole 54. The
vertical hole 55 is sealed with a plug 56 or the like from below
after being machined.
[0035] When air is present in the solenoid 10, the air is exhausted
to the outside through the upper through-hole 21 provided in the
solenoid 10. Then, the air flows into the vertical hole 55 through
the through-hole 51 in the intermediate plate. Then, the air is
discharged through the damping orifice 53 in the horizontal hole
54. Once the air has been discharged to the downstream side of the
damping orifice 53, even if the air remains in the flow passage in
the upper part of the hydraulic control valve body 30, it has no
effect on the operation and function of the valve. In addition, the
hydraulic control valve body 30 in this embodiment has hydrostatic
bearings 31 and 32 provided at both ends of a spool 33. Therefore,
such a flow is induced that the fluid at the left- and right-hand
sides of the spool 33 is always removed and led to a tank port (not
shown). Accordingly, the discharge of air is facilitated.
[0036] Wear particles generated by the sliding movement of the
plunger 12 in the solenoid 10 are discharged to the outside through
the lower through-hole 22 and enter the vertical hole 55 through
the lower through-hole 52 in the intermediate plate 50. Because
they have already entered the vertical hole 55, the wear particles
accumulate in the bottom of the vertical hole 55 without being
stirred or flowing backward even when the spool 33 operates or the
fluid in the intermediate plate 50 moves.
[0037] FIG. 4 is a diagram showing a side of the intermediate plate
50, which is a view seen from the arrow A-A in FIG. 3. The amount
of wear particles generated by the solenoid 10 is very small.
Therefore, there will be no problem even if the wear particles
accumulated in the vertical hole 55 are left as they are. However,
the arrangement may be as shown in FIG. 4. That is, the
intermediate plate is provided with a horizontal hole 57, and the
horizontal hole 57 is sealed with a plug 58 or the like during use.
When the valve is not in an operative state, the accumulated wear
particles are discharged. Even if air enters the hydraulic control
valve body 30 when the plug 58 is installed, the air is discharged
from the vertical hole 55 above. By discharging wear particles to
the outside of the solenoid 10 in this way, the durability of the
solenoid 10 is improved markedly.
[0038] Next, the structure and operation of the hydraulic control
valve arranged as stated above will be described. The hydraulic
control valve body 30 has a sleeve 35 accommodated therein. A spool
33 is slidably inserted in the sleeve 35. A spring 36 generates
force against the force for axially moving the spool 33 that is
generated from the solenoid 10. The sleeve 35 is formed with a
plurality of ports (a pump port 37, control ports 39 and 40, and a
tank port) for switching between flow passages of the fluid
supplied thereto. The spool 33 is displaced in either direction
from a neutral position by sliding in the sleeve 35, thereby
switching the flow passages from one to another (i.e. switched to
the direction of pump port 37.fwdarw.control port 39 or to the
direction of pump port 37.fwdarw.control port 40). By placing the
spool 33 at a desired position in the sleeve 35, the opening of the
flow passage (valve opening) can be changed continuously. It is
also possible to control the flow rate or pressure
continuously.
[0039] When a reference position of the spool 33 is entered from an
input terminal 71, a deviation signal Q is produced from the
reference position signal P and the actual spool position signal S
fed back from the displacement sensor 60. The deviation signal Q is
input to a controller 70 for the solenoid 10. The controller 70
amplifies the deviation signal directly and also integrates the
deviation signal to supply the solenoid 10 with an excitation
current balancing with the resilient force of the opposing spring
36, thereby placing the spool 33 at the reference position.
[0040] The hydraulic control valve has hydrostatic bearings 31 and
32 formed in the sleeve 35. A pressurized fluid is led to the
hydrostatic bearings 31 and 32 from the pump port 37 and blown off
toward the inner peripheral side through hydrostatic bearing
orifices 38, thereby supporting the spool 33 out of contact with
the sleeve 35. By providing such hydrostatic bearings 31 and 32,
the spool 33 is allowed to slide smoothly in the sleeve 35 even if
a fluid of low lubricating properties (e.g. water) is used as a
working fluid.
[0041] It should be noted that the arrangement of the hydraulic
control valve body 30 is merely an example. The arrangement of the
hydraulic control valve body is not limited to the foregoing.
Although in the above-described example the horizontal hole 54, the
through-holes 51 and 52 and the vertical hole 55 are provided in
the intermediate plate 50, these holes may be provided in the
hydraulic control valve body 30.
[0042] Effect of the Invention
[0043] As has been described above, according to the features of
the present invention, the following advantageous effects can be
obtained.
[0044] According to the first feature of the present invention, the
cover of the solenoid is provided with upper and lower
through-holes extending through the cover to the plunger
compartment. The uppermost part of the upper through-hole is above
or level with the uppermost part of the plunger compartment. The
lowermost part of the lower through-hole is below or level with the
lowermost part of the plunger compartment. Thus, the air in the
solenoid can be exhausted to the outside. Therefore, it is possible
to provide a solenoid having a stabilized plunger operation.
[0045] Further, because wear particles generated in the solenoid
are discharged to the outside through the lower through-hole, it is
possible to prevent the plunger from sliding in wear particles,
which would otherwise accelerate wear, and hence possible to
improve durability. Further, when water is used as a working fluid
for the hydraulic control valve, because the air in the solenoid is
exhausted, it is possible to prevent oxidation of portions of
constituent members that are in contact with water.
[0046] According to the second feature of the present invention,
the above-described solenoid is attached to a hydraulic control
valve body, and a vertical hole is provided in the hydraulic
control valve body at a position above the upper through-hole in
the cover of the solenoid. The vertical hole communicates with a
tank port. Therefore, the air in the solenoid can be exhausted to
the outside of the hydraulic control valve. Accordingly, the spool
does not vibrate, and the operation of the hydraulic control valve
is stabilized.
[0047] Further, because a vertical hole is provided in the
hydraulic control valve body at a position below the lower
through-hole in the cover of the solenoid, wear particles generated
by the sliding movement of the plunger can be accumulated in the
vertical hole. Moreover, there is no possibility that the wear
particles accumulated in the vertical hole may be scattered or
caused to flow backward by the operation of the hydraulic control
valve.
* * * * *