Solenoid valve and shock absorber

Abstract

This solenoid valve (V) comprises: a valve seat member (13); an annular first spool (14) which is separated from and seated on an annular valve seat (13d) and can open and close a port (13c); a second spool (15) which can move in the axial direction with respect to the valve seat member (13) and the first spool (14), and which can open and close the port (13c) by being separated from and seated on the first spool (14); and a solenoid (S) capable of applying pressing thrust to the second spool (15) toward the valve seat member side. The first spool (14) and the second spool (15) are biased in a direction away from the valve seat member (13) by pressure on one side of the port (13c), and are biased in a direction away from each other by pressure on the other side of the port (13c). In the second spool (15), the area of a front-side pressure receiving part is greater than the area of a back surface-side pressure receiving part.

Description

Solenoid valves and shock absorbers

[0001] The present invention relates to a solenoid valve and a shock absorber.

[0002] Solenoid valves are used as variable damping valves in shock absorbers that are installed between the vehicle body and wheels, and adjust the damping force generated by the shock absorber to suitably suppress vibrations in the vehicle body, thereby improving the ride comfort of the vehicle.

[0003] Such a solenoid valve, as disclosed in JP2019-160994A, for example, is installed in a piston portion of a shock absorber, and includes a main passage that communicates between an expansion-side chamber and a compression-side chamber, an annular valve seat member through the inner periphery of which the main passage passes, a main valve body that seats on and releases from the valve seat member to provide resistance to the flow of liquid passing through the main passage, an expansion-side pressure introduction passage that has a throttle provided midway and reduces and introduces the pressure in the expansion-side chamber to a back pressure chamber on the back side of the main valve body, and a pressure introduction passage that reduces and introduces the pressure in the compression-side chamber to the back pressure chamber. The main valve body has a compression-side pressure introduction passage that introduces pressure into the back pressure chamber, a control valve that controls the pressure in the back pressure chamber, and a solenoid that applies thrust to the control valve. The main valve body has an annular first spool that seats and releases from the valve seat member, and a second spool that is stacked on the side of the first spool opposite the valve seat member and seats and releases from the first spool. The first and second spools are urged in a direction away from the valve seat member by the pressure in the expansion-side chamber, and the second spool is urged in a direction away from the first spool by the pressure on the inner peripheral side of the first spool.

[0004] In the solenoid valve configured as described above, when hydraulic oil moves from the expansion-side chamber to the compression-side chamber, the pressure in the expansion-side chamber causes both the first spool and the second spool to move away from the valve seat member to open the valve, but the valve-opening pressure can be adjusted by adjusting the pressure in the back pressure chamber depending on the amount of current applied to the solenoid, and the damping force can be changed by adjusting the valve-opening pressure. Also, in the solenoid valve, when hydraulic oil moves from the compression-side chamber to the expansion-side chamber, the pressure in the compression-side chamber causes the first spool and the second spool to move away from each other to open the main passage, but the thrust force pressing the second spool can be adjusted depending on the amount of current applied to the solenoid, and the valve-opening pressure can be adjusted to change the damping force.

[0005] JP2019-160994A

[0006] In such a solenoid valve, when hydraulic oil flows through the main passage from the compression side chamber to the expansion side chamber, the pressure in the compression side chamber presses the first spool against the valve seat member, while the pressure in the compression side chamber presses the second spool in a direction away from the valve seat member.

[0007] Therefore, when the force pressing the second spool in a direction away from the valve seat member exceeds the resultant force of the solenoid thrust and the force pressing the second spool against the valve seat member, the solenoid valve opens to open the main passage.

[0008] However, in conventional solenoid valves, the seat diameter of the seat portion of the second spool that abuts against the first spool is small, and the pressure-receiving area on the back side, where the pressure in the compression side chamber acts to press the second spool in a direction to move it closer to the valve seat member, is much larger than the pressure-receiving area on the front side, where the pressure in the compression side chamber acts to press the second spool in a direction to move it away from the valve seat member.

[0009] Therefore, when the hydraulic oil flows through the main passage from the compression-side chamber to the extension-side chamber, the force pressing the second spool against the first spool becomes too large, making it difficult for the second spool to separate from the first spool. Therefore, with conventional solenoid valves, even when it is desired to minimize the thrust of the solenoid to generate a soft damping force, the damping force becomes too large, which can impair the ride comfort of the vehicle.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a solenoid valve and a shock absorber that can reduce the damping force generated during soft driving and improve the ride comfort of a vehicle.

[0011] In order to solve the above problems, the solenoid valve of the present invention comprises a valve seat member having an annular valve seat surrounding a flow path, an annular first spool that is movable in the axial direction relative to the valve seat member and can be seated on and removed from the annular valve seat to open and close the flow path, a second spool that is movable in the axial direction relative to the valve seat member and the first spool, stacked on the side opposite the valve seat member of the first spool, and can be seated on and removed from the first spool to open and close the flow path, and a solenoid that can apply a thrust to the second spool toward the valve seat member, The first spool and the second spool are both urged in a direction away from the valve seat member by the pressure on one side of the flow path and are urged in directions away from each other by the pressure on the other side of the flow path, and the second spool has a front pressure receiving portion that faces the valve seat member and causes the pressure in the flow path to act as a force in a direction away from the valve seat member, a back pressure receiving portion that faces the opposite valve seat member and causes the pressure acting as a force in a direction approaching the valve seat member, and a passage that guides the pressure in the flow path to the back pressure receiving portion, and the area of ​​the front pressure receiving portion is larger than the area of ​​the back pressure receiving portion.

[0012] With a solenoid valve configured in this manner, the area of ​​the front pressure receiving portion of the second spool is larger than the area of ​​the rear pressure receiving portion, so that during contraction, the pressure acting on the second spool through the flow path urges the second spool in a direction away from the first spool.Therefore, by reducing the thrust of the solenoid and reducing the opening pressure of the solenoid valve, the damping force generated during soft settings can be reduced, improving the ride comfort of the vehicle.

[0013] Fig. 1 is a longitudinal sectional view of a shock absorber equipped with a solenoid valve of one embodiment. Fig. 2 is a longitudinal sectional view showing an enlarged piston portion of a shock absorber equipped with a solenoid valve of one embodiment. Fig. 3 is an enlarged sectional view of a solenoid valve of one embodiment. Fig. 4 is a characteristics diagram showing the relationship between the amount of current supplied to the solenoid and thrust in a solenoid valve of one embodiment. Fig. 5 is a diagram showing the damping force characteristics of a shock absorber equipped with a solenoid valve of one embodiment.

[0014] An embodiment of the present invention will be described below with reference to the drawings. As shown in Fig. 1, a shock absorber D in one embodiment of the present invention is configured to include a cylinder 1 as an outer shell, a piston rod 2 inserted into the cylinder 1 so as to be axially movable, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movable, and a solenoid valve V housed in the cylinder 1 and disposed between two working chambers, an extension-side chamber R1 and a compression-side chamber R2, which are provided in the cylinder 1. The shock absorber D is installed between the body and wheels of a vehicle (not shown) to suppress vibrations of the body and wheels.

[0015] Hereinafter, each part of the shock absorber D will be described in detail. As shown in Fig. 1 , the shock absorber D includes a cylindrical cylinder 1 with a bottom as an outer tube, a piston rod 2 movably inserted into the cylinder 1, and a piston 3 connected to the piston rod 2 and movably inserted into the cylinder 1, which divides the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2 as working chambers.

[0016] A bracket (not shown) is provided at the base end of the piston rod 2, which is the upper end in Fig. 1, and the piston rod 2 is connected to a vehicle body (not shown) of a vehicle via the bracket (not shown). A bracket (not shown) is also provided at the bottom 1a of the cylinder 1, and the cylinder 1 is connected to a wheel (not shown) of the vehicle via the bracket (not shown).

[0017] In this way, shock absorber D is interposed between the vehicle body and the wheels of the vehicle. When the vehicle travels on an uneven road surface and the wheels vibrate up and down relative to the vehicle body, piston rod 2 moves in and out of cylinder 1, expanding and contracting shock absorber D, and piston 3 moves up and down (axially) within cylinder 1.

[0018] The shock absorber D also includes an annular rod guide 10 that closes the upper end of the cylinder 1 and through which the piston rod 2 is slidably inserted, forming an enclosed space inside the cylinder 1. A free piston 11 is slidably inserted into the cylinder 1 on the opposite side of the piston 3 from the piston rod 2.

[0019] A liquid chamber L is formed above the free piston 11 in the cylinder 1, and an air chamber G is formed below it. The liquid chamber L is further divided by the piston 3 into an extension-side chamber R1 on the piston rod 2 side and a compression-side chamber R2 on the piston 3 side, and the extension-side chamber R1 and the compression-side chamber R2 are each filled with a liquid. The liquid filled in the shock absorber D may be hydraulic oil, water, an aqueous solution, or other liquid. On the other hand, compressed air or a gas such as nitrogen gas is sealed in the air chamber G.

[0020] When the shock absorber D is extended, the piston rod 2 retracts from the cylinder 1, and the internal volume of the cylinder increases by the volume of the retracted piston rod 2, so the free piston 11 moves upward within the cylinder 1, expanding the air chamber G. Conversely, when the shock absorber D is retracted, the piston rod 2 advances into the cylinder 1, and the internal volume of the cylinder decreases by the volume of the advanced piston rod 2, so the free piston 11 moves downward within the cylinder 1, reducing the air chamber G.

[0021] Instead of the free piston 11, a bladder or bellows or the like may be used to separate the liquid chamber L and the air chamber G, and the configuration of the movable partition that separates the liquid chamber L and the air chamber G may be changed as appropriate.

[0022] Furthermore, in this embodiment, the shock absorber D is a single-rod, single-cylinder shock absorber, and when the shock absorber D expands or contracts, the air chamber G is expanded or contracted by the free piston 11 to compensate for the volume of the piston rod 2 moving in and out of the cylinder 1. However, the configuration for this volume compensation can also be changed as appropriate.

[0023] For example, in the case where the free piston 11 and the air chamber G are eliminated and an outer tube is provided around the cylinder 1, and a reservoir for storing liquid is formed between the cylinder 1 and the outer tube, making the shock absorber a twin-cylinder shock absorber, the reservoir may be used to compensate for the volume of the piston rod 2 moving in and out of the cylinder 1. The reservoir may be formed in a tank that is separate from the cylinder 1. The shock absorber D may also be configured as a double-rod shock absorber in which the piston 3 is attached to the center of the piston rod 2 and the ends of the piston rod 2 protrude outside the cylinder 1 from both ends of the cylinder 1.

[0024] 2, the piston rod 2 is cylindrical and includes a rod main body 2a whose upper end protrudes outward from the cylinder 1 via the rod guide 10, and a topped cylindrical housing 2b that is connected to the lower end of the rod main body 2a and houses a solenoid S of the solenoid valve V. The housing 2b is made of a soft magnetic material, and as shown in FIG. 2, includes an annular top portion 2b1 whose inner periphery is connected to the lower end of the rod main body 2a, and a cylindrical portion 2b2 that hangs down from the outer periphery of the top portion 2b1.

[0025] A spool holder 12 is threadedly connected to the inner periphery of the cylindrical portion 2b2 of the piston rod 2, and the piston 3 is connected to the spool holder 12. The spool holder 12 accommodates all of the components constituting the solenoid valve V, except for the solenoid S.

[0026] 2, the solenoid valve V includes a valve seat member 13, a first spool 14, a second spool 15, and a solenoid S. As described above, the solenoid S is housed in the housing 2b at the lower end of the piston rod 2, and the valve seat member 13, the first spool 14, and the second spool 15 are housed in the spool holder 12.

[0027] 3, the spool holder 12 is cylindrical, and its upper end is threadedly connected to the inner periphery of the cylindrical portion 2b2 of the piston rod 2, thereby connecting the spool holder 12 to the piston rod 2. Specifically, the inner diameter of the spool holder 12 increases in stages from the upper end, and the inner periphery of the spool holder 12 is provided with an uppermost small inner diameter portion 12a, a medium inner diameter portion 12b that is connected to the lower side of the small inner diameter portion 12a and has a larger inner diameter than the small inner diameter portion 12a, a large inner diameter portion 12c that is connected to the lower side of the medium inner diameter portion 12b and has a larger inner diameter than the medium inner diameter portion 12b, and a protrusion 12d that protrudes inward in the axial direction from the large inner diameter portion 12c. A threaded portion 12e is formed on the large inner diameter portion 12c of the spool holder 12 below the protrusion 12d.

[0028] The spool holder 12 has an outer diameter that is largest at its center, and the spool holder 12 has an outer periphery that is provided with a fitting portion 12f having a small outer diameter at its top and that is inserted into the cylindrical portion 2b2 of the housing 2b and threadedly engaged therewith, a large outer diameter portion 12g that is continuous with the fitting portion 12f and has the largest outer diameter, and a piston fitting portion 12h that is continuous with the large outer diameter portion 12g and has a smaller outer diameter than the large outer diameter portion 12g and fits onto the piston 3. The spool holder 12 also has a pilot passage 12i that opens from the outer periphery of the lower end of the fitting portion 12f and communicates with the medium inner diameter portion 12b, and a communication hole 12j that opens from the outer periphery of the large outer diameter portion 12g and communicates above the protrusion 12d of the large inner diameter portion 12c. The pilot passage 12i has a restriction O1 that functions as an orifice and provides resistance to the flow of liquid passing through the pilot passage 12i.

[0029] 3, the valve seat member 13 is annular and fitted below the protrusion 12d of the large inner diameter portion 12c. Specifically, the valve seat member 13 includes a cylindrical fitting portion 13a that fits onto the inner periphery of the protrusion 12d of the spool holder 12, a flange 13b that protrudes radially from the outer periphery of the lower end of the cylindrical fitting portion 13a and abuts against the lower end of the protrusion 12d in FIG. 2, a port 13c formed by a gap inside the cylindrical fitting portion 13a, the annular valve seat 13d that protrudes axially from the upper end of the cylindrical fitting portion 13a and surrounds the port 13c, a step 13e formed by making the inner diameter of the cylindrical fitting portion 13a larger on the lower side than on the upper side, and a thread portion 13f formed on the inner periphery of the cylindrical fitting portion 13a below the step 13e.

[0030] The valve seat member 13 configured in this manner is fixed within the spool holder 12 by being clamped between the protrusion 12d and the piston holder 17, with the fitting cylindrical portion 13a fitted into the protrusion 12d of the large inner diameter portion 12c of the spool holder 12 and the piston holder 17 screwed to the threaded portion 12e on the lower side of the large inner diameter portion 12c of the spool holder 12 with the flange 13b abutting against the lower end of the protrusion 12d.

[0031] A guide member 16 that guides the first spool 14 is screwed to a threaded portion 13f that is located on the inner periphery of the cylindrical fitting portion 13a of the valve seat member 13 and below the stepped portion 13e. The guide member 16 is annular and includes a fixed portion 16a that is inserted into the lower end of the cylindrical fitting portion 13a and has its outer periphery screwed to the threaded portion 13f of the valve seat member 13, a guide tube 16b that rises from the inner periphery side of the fixed portion 16a and is inserted into the inner periphery of the cylindrical fitting portion 13a of the valve seat member 13 with an annular gap between them, and a plurality of holes 16c that radially penetrate the guide tube 16b and communicate between the inside and outside of the guide tube 16b.

[0032] 3, the guide member 16 is fixed to the valve seat member 13 by screwing the fixing portion 16a to the threaded portion 13f of the valve seat member 13, and the upper end thereof protrudes upward beyond the hole 16c of the guide cylinder 16b and beyond the annular valve seat 13d. Note that the guide member 16 may be integrated with the valve seat member 13 and configured as a single component together with the valve seat member 13.

[0033] 3, the piston holder 17 is disk-shaped and includes a disk portion 17a that is threadedly coupled to the threaded portion 12e on the inner periphery of the lower end of the spool holder 12, a piston holder shaft 17b that extends axially downward from the lower end of the axial center of the disk portion 17a and has a threaded portion formed on the outer periphery of its tip, and a hole 17c that passes through the disk portion 17a in the axial direction and communicates with the space inside the guide member 16. As described above, when the piston holder 17 is threadedly coupled to and fixed to the inner periphery of the lower end of the large inner diameter portion 12c of the spool holder 12, it cooperates with the protrusion 12d of the spool holder 12 to fix the valve seat member 13 and the guide member 16 that is fixed to the valve seat member 13.

[0034] An extension side soft valve 18 and a compression side soft valve 19 are attached to the outer periphery of the piston holder shaft 17b of the piston holder 17, together with the piston 3. Specifically, the piston 3, the extension side soft valve 18, and the compression side soft valve 19 are annular, and after being fitted onto the outer periphery of the piston holder shaft 17b, are fixed to the piston holder shaft 17b by a piston nut 23 that is screwed onto the tip of the piston holder shaft 17b.

[0035] The piston 3 includes an annular main body portion 3a that fits onto the outer periphery of the piston retaining shaft 17b, a cylindrical portion 3b on which a piston ring 3c that is provided on the outer periphery of the main body portion 3a and slides against the inner periphery of the cylinder 1 is attached, and an extension side passage 3e and a compression side passage 3d that pass through the main body portion 3a in the axial direction.

[0036] When the piston 3 is attached to the piston holder 17, the inner periphery of the cylindrical portion 3b is fitted onto the outer periphery of the lower end of the spool holder 12, and a piston ring 3c attached to the outer periphery of the cylindrical portion 3b is brought into sliding contact with the inner periphery of the cylinder 1, thereby dividing the interior of the cylinder 1 into an expansion-side chamber R1 on the upper side in Fig. 1 and a compression-side chamber R2 on the lower side. Note that a seal ring 12k attached to the outer periphery of the piston fitting portion 12h on the outer periphery of the spool holder 12 and a seal between the outer periphery of the piston fitting portion 12h and the cylindrical portion 3b of the piston 3 are provided to prevent liquid from bypassing the solenoid valve V and moving back and forth between the expansion-side chamber R1 and the compression-side chamber R2.

[0037] Further, the expansion-side passage 3e and the compression-side passage 3d provided in the piston 3 communicate the expansion-side chamber R2 with the space between the piston 3 and the piston holder 17 in the spool holder 12. The interior of the spool holder 12 is communicated with the expansion-side chamber R1 through a communication hole 12j that opens from the large outer diameter portion 12g and leads to the large inner diameter portion 12c. Further, a port 13c formed inside the valve seat member 13 communicates with the space between the piston 3 and the piston holder 17 via a hole 16c of the guide member 16, the interior of the guide member 16, and a hole 17c, and also opens into the spool holder 12. A flow path F in the solenoid valve V is formed by the communication hole 12j, the interior of the spool holder 12, the port 13c, the hole 16c, and the interior of the guide member 16, and the expansion-side chamber R1 and the compression-side chamber R2 are communicated with the flow path F, the hole 17c, the expansion-side passage 3e, and the compression-side passage 3d.

[0038] The expansion-side soft valve 18 is an annular leaf valve stacked below the main body 3a of the piston 3, and its inner periphery is fixed to the outer periphery of the piston holder shaft 17b together with the piston 3. The expansion-side soft valve 18 is allowed to flex on its outer periphery to open and close the expansion-side passage 3e. The expansion-side soft valve 18 flexes the outer periphery of the expansion-side passage 3e against the flow of liquid from the expansion-side chamber R1 to the compression-side chamber R2, thereby allowing the flow and providing resistance to the flow. Conversely, the expansion-side soft valve 18 blocks the flow of liquid from the compression-side chamber R2 to the expansion-side chamber R1 by closing the lower end of the expansion-side passage 3e.

[0039] The compression-side soft valve 19 is an annular leaf valve stacked above the main body 3a of the piston 3, and has an inner periphery fixed to the outer periphery of the piston holder shaft 17b together with the piston 3. The compression-side soft valve 19 is allowed to deflect on the outer periphery to open and close the compression-side passage 3d. The compression-side soft valve 19 deflects the outer periphery of the compression-side passage 3d against the flow of liquid from the compression-side chamber R2 to the expansion-side chamber R1, thereby allowing the flow and providing resistance to the flow. Conversely, the compression-side soft valve 19 blocks the flow of liquid from the expansion-side chamber R1 to the compression-side chamber R2 by closing the upper end of the compression-side passage 3d.

[0040] The first spool 14 is annular and is attached to the outer periphery of the upper end of the guide tube 16b of the guide member 16 in Fig. 3 so as to be movable in the up-down direction in Fig. 3, which is the axial direction, and faces the annular valve seat 13d of the valve seat member 13 in the axial direction. The outer diameter of the first spool 14 is larger than the outer diameter of the annular valve seat 13d, and the inner diameter of the first spool 14 is smaller than the inner diameter of the annular valve seat 13d, so that the inner periphery of the first spool 14 is in sliding contact with the outer periphery of the guide tube 16b, and the first spool 14 can move toward and away from the valve seat member 13 in the axial direction and can be seated on and removed from the annular valve seat 13d. Because the first spool 14 is in sliding contact with the outer periphery of the guide tube 16b of the guide member 16, which is fixed to the valve seat member 13, the first spool 14 is positioned radially and can be seated on and removed from the annular valve seat 13d of the valve seat member 13 without axial wobble.

[0041] In addition, a hole 16c is provided on the guide tube 16b closer to the valve seat member than the first spool 14, so that even when the lower end of the first spool 14 is seated at its upper end on the annular valve seat 13d, the space on the outer periphery of the guide tube 16b on the valve seat member side of the first spool 14, i.e., the space between the mating tube portion 13a of the valve seat member 13 and the guide tube 16b, is connected to the inside of the guide tube 16b.

[0042] As shown in FIG. 3 , the second spool 15 includes a cylindrical main body 15 a, an annular flange 15 b provided on the outer periphery of the main body 15 a and protruding radially outward, an annular protrusion 15 c protruding from the lower end of the flange 15 b, which is the end closest to the valve seat member, a valve hole 15 d opening axially downward from the axial center of the upper end of the main body 15 a, which is the end closest to the valve seat member, a control valve seat 15 e located at the upper end of the main body 15 a and surrounding the valve hole 15 d, a main body passage 15 f opening from the lower end of the main body 15 a, extending linearly in the axial direction and leading to the upper end of the main body 15 a, a flange passage 15 g opening from the inside of the annular protrusion 15 c at the lower end of the flange 15 b, extending linearly in the axial direction and leading to the upper end of the flange 15 b, and a pressure control passage 15 h opening from the side of the main body 15 a and leading to the valve hole 15 d.

[0043] The second spool 15 is inserted into the inner circumference of the spool holder 12 so that the outer periphery of the main body 15a is in sliding contact with the small inner diameter portion 12a of the inner circumference of the spool holder 12, and the outer periphery of the flange portion 15b is in sliding contact with the medium inner diameter portion 12b of the inner circumference of the spool holder 12, and is movable up and down in the axial direction.

[0044] When the second spool 15 is inserted into the spool holder 12, a back pressure chamber P is formed between the second spool 15 and the spool holder 12. The back pressure chamber P is partitioned by the back surface end of the flange portion 15b, which is the end opposite to the valve seat, the outer periphery of the main body portion 15a, the medium inner diameter portion 12b of the spool holder 12, and a step portion at the boundary between the medium inner diameter portion 12b and the small inner diameter portion 12a. The back pressure chamber P is connected to the expansion-side chamber R1 by a pilot passage 12i that passes radially through the spool holder 12, and is also connected to the valve hole 15d via a pressure control passage 15h provided in the second spool 15 and to the flow path F via the flange portion passage 15g.

[0045] The main body passage 15f opens from the lower end of the main body 15a, is provided in a straight line parallel to the axis of the second spool 15, and communicates with the upper end of the main body 15a. The flange passage 15g opens from the lower end of the flange 15b, inside the annular protrusion 15c, and is provided in a straight line parallel to the axis of the second spool 15, and communicates with the upper end of the flange 15b.

[0046] In addition, an annular protrusion 15i rises from the outer periphery of the end portion on the back surface side of the main body 15a of the second spool 15, opposite the valve seat member side, and the fitting length of the second spool 15 with respect to the small inner diameter portion 12a of the spool holder 12 is ensured, allowing the second spool 15 to stably move in the axial direction, which is the up and down direction in Figure 3, relative to the spool holder 12.

[0047] A check valve 20 that opens and closes the flange passage 15g is attached to the outer periphery of the main body 15a of the second spool 15. The check valve 20 includes an annular valve element 20a that is stacked on the back surface end of the flange 15b of the second spool 15, which is the end opposite the valve seat member, and that is slidably attached to the outer periphery of the main body 15a, an annular spring retainer 20b that is located on the opposite side of the flange of the valve element 20a, is fixedly attached to the outer periphery of the main body 15a, and faces the valve element 20a in the axial direction, and a wave washer 20c that serves as a spring that is interposed between the valve element 20a and the spring retainer 20b.

[0048] The wave washer 20c biases the valve element 20a toward the back surface of the flange portion 15b, which is the upper end in FIG. 3 . The valve element 20a is guided by the main body portion 15a and can move axially. When it contacts the flange portion 15b, it closes the flange portion passage 15g. When it moves away from the flange portion 15b, it opens the flange portion passage 15g. Therefore, in the check valve 20, when liquid flows through the flange portion passage 15g from the valve seat member side toward the back pressure chamber P, the valve element 20a retracts from the flange portion 15b, opening the flange portion passage 15g and allowing the liquid to flow. Conversely, when liquid flows through the flange portion passage 15g from the back pressure chamber P toward the valve seat member side, the valve element 20a contacts the flange portion 15b, closing the flange portion passage 15g and preventing the liquid from flowing. Therefore, the flange portion passage 15g is configured as a one-way passage that allows liquid to flow only from the valve seat member side toward the back pressure chamber P. The spring in the check valve 20 may be an elastic body other than the wave washer 20c as long as it is capable of biasing the valve body 20a to close the valve.

[0049] The annular protrusion 15c includes an annular base 15c1 that protrudes downward in the axial direction from the lower end of the flange portion 15b in Figure 3 and has an outer diameter at its lower end, which is its tip, that is expanded so that the outer diameter is larger than the outer diameter of the flange portion 15b, and an annular protrusion 15c2 that protrudes downward from the outer periphery at the lower end of the base 15c1 and has at its lower end a flat surface that can abut against the back surface, which is the anti-valve seat side of the first spool 14.

[0050] After the first spool 14 and second spool 15 configured as described above are inserted into the spool holder 12, the valve seat member 13 and the guide member 16 are fixed to the spool holder 12 using the piston holder 17. The first spool 14 is attached to the outer periphery of the guide member 16 so as to be movable in the axial direction, and is movable in the vertical direction in FIG. 3 , which is the axial direction relative to the valve seat member 13 and the spool holder 12, so as to be seated on and removed from the valve seat member 13. The second spool 15 is in sliding contact with the inner periphery of the spool holder 12, forming a back pressure chamber P between itself and the spool holder 12. It is therefore movable in the vertical direction, which is the axial direction relative to the spool holder 12 and the valve seat member 13, while being guided by the spool holder 12, and the lower end surface of the annular protrusion 15c can be seated on and removed from the back surface of the first spool 14. Furthermore, even if the pressure acting on the first spool 14 becomes uneven due to reasons such as the flow of liquid passing through the solenoid valve V becoming uneven around the first spool 14 and a lateral force acting to move it radially, the axial movement does not occur because the first spool 14 is supported by the guide member 16, and the lateral force is not transmitted to the second spool 15. Therefore, the lateral force acting on the first spool 14 does not press the second spool 15 against the spool holder 12, increasing the sliding resistance and making it difficult to move in the axial direction.

[0051] When the first spool 14 moves away from the annular valve seat 13d of the valve seat member 13, the port 13c of the valve seat member 13 communicates with the communication hole 12j of the spool holder 12 to open the flow path F, thereby communicating between the expansion-side chamber R1 and the compression-side chamber R2. When the second spool 15 moves away from the first spool 14 with the first spool 14 seated on the annular valve seat 13d, the port 13c of the valve seat member 13 communicates with the communication hole 12j of the spool holder 12 to open the flow path F, thereby communicating between the expansion-side chamber R1 and the compression-side chamber R2.

[0052] Furthermore, when the first spool 14 is seated on the annular valve seat 13d of the valve seat member 13 and the second spool 15 is seated on the first spool 14, the solenoid valve V closes to block the flow path F. An orifice (not shown) is provided in the annular valve seat 13d or the annular protrusion 15c, and when the solenoid valve V closes, the port 13c of the valve seat member 13 and the communication hole 12j in the spool holder 12 are communicated only through the orifice.

[0053] In this manner, when the first spool 14 moves away from the annular valve seat 13d or when the first spool 14 seats on the annular valve seat 13d and the second spool 15 moves away from the first spool 14, the solenoid valve V opens to communicate between the expansion-side chamber R1 and the compression-side chamber R2 via the flow path F. On the other hand, when the first spool 14 seats on the annular valve seat 13d and the second spool 15 seats on the first spool 14, the solenoid valve V closes the flow path F but blocks communication between the expansion-side chamber R1 and the compression-side chamber R2 only through the orifice.

[0054] Here, when the shock absorber D performs an expansion operation and the liquid attempts to move through the flow path F in a direction from the expansion-side chamber R1, which is one side of the flow path F, to the contraction-side chamber R2, which is the other side of the flow path F, the pressure in the expansion-side chamber R1 acts on the front surface (lower surface in FIG. 3 ), which is the valve seat member side surface of the first spool 14, from the portion abutting against the annular valve seat 13d to the outer periphery side. Therefore, if the diameter of the first spool 14 is φa and the outer diameter of the upper end surface of the annular valve seat 13d abutting against the first spool 14 is φb, the magnitude of the force pushing the first spool 14 upward in FIG. 3 toward the side opposite the valve seat member is equal to the area obtained by subtracting the area of ​​the circle with diameter φb from the area of ​​the circle with diameter φa, multiplied by the pressure in the expansion-side chamber R1.

[0055] On the other hand, the pressure in the expansion-side chamber R1 acts on the back surface (upper surface in FIG. 3 ) of the first spool 14, which is the surface opposite the valve seat member, and on the back surface (upper surface in FIG. 3 ) of the annular protrusion 15c of the second spool 15, which is the surface opposite the valve seat member. Therefore, if the diameter of the flange portion 15b is φc, the magnitude of the force pressing the first spool 14 and the second spool 15 toward the valve seat member, which is the lower part in FIG. 3 , is the area obtained by subtracting the area of ​​the circle with diameter φc from the area of ​​the circle with diameter φa, and multiplying this area by the pressure in the expansion-side chamber R1. Furthermore, since the pressure in the extension-side chamber R1 also acts on the back surface of the annular protrusion 15c of the second spool 15, the second spool 15 is pressed toward the first spool 14 by the pressure in the extension-side chamber R1, so that when the shock absorber D is extended and liquid attempts to flow from the extension-side chamber R1 toward the compression-side chamber R2, the annular protrusion 15c remains in contact with the first spool 14 and does not move away.

[0056] As described above, during an extension operation of the shock absorber D in which the liquid attempts to flow from the expansion-side chamber R1 to the compression-side chamber R2, the force pushing up the first spool 14 is equal to the area obtained by subtracting the area of ​​the circle with diameter φb from the area of ​​the circle with diameter φc, multiplied by the pressure in the expansion-side chamber R1. Here, because the outer diameter φc of the flange portion 15b is larger than the outer diameter φb of the annular valve seat 13d, during an extension operation of the shock absorber D in which the liquid attempts to flow from the expansion-side chamber R1 to the compression-side chamber R2, a force equal to the area obtained by subtracting the area of ​​the circle with diameter φc from the area of ​​the circle with diameter φb, multiplied by the pressure in the expansion-side chamber R1, acts in a direction separating both the first spool 14 and the second spool 15 from the valve seat member 13.

[0057] Furthermore, since the expansion-side chamber R1 communicates with the back pressure chamber P via the pilot passage 12i of the spool holder 12, the second spool 15 is urged toward the valve seat member 13 by the pressure in the back pressure chamber P. If the diameter of the main body 15a of the second spool 15 is φd, the magnitude of the force that presses down the second spool 15 due to the action of the pressure in the back pressure chamber P is a value obtained by subtracting the area of ​​a circle with diameter φd from the area of ​​a circle with diameter φc, and multiplying this value by the pressure in the back pressure chamber P.

[0058] The pressure in the back pressure chamber P is adjusted by a control valve 21, which will be described later. Therefore, during an extension operation of the shock absorber D in which fluid attempts to flow from the extension-side chamber R1 to the compression-side chamber R2, if the force pushing up the first spool 14 due to the pressure in the extension-side chamber R1 exceeds the resultant force of the force pushing down the first spool 14 and the second spool 15 due to the pressure in the extension-side chamber R1 and the force pushing down the second spool 15 due to the pressure in the back pressure chamber P, the first spool 14 and the second spool 15 move in a direction away from the valve seat member 13, and the solenoid valve V opens. In this way, with the solenoid valve V of this embodiment, the valve opening pressure can be adjusted by adjusting the pressure in the back pressure chamber P during an extension operation of the shock absorber D.

[0059] Next, when the shock absorber D contracts and the liquid attempts to move through the flow path F in the direction from the compression-side chamber R2 to the expansion-side chamber R1, the pressure in the port 13c of the valve seat member 13 acts on the front surface (lower surface in FIG. 3 ), which is the valve seat member side surface of the first spool 14, and on a portion of the first spool 14 that is inward from the portion abutting against the annular valve seat 13d, via the hole 16c of the guide member 16. On the other hand, the pressure in the port 13c of the valve seat member 13 also acts on the back surface (upper surface in FIG. 3 ), which is the anti-valve seat side surface of the first spool 14, and on a portion of the first spool 14 that is inward from the flat surface of the protrusion 15c2 of the annular protrusion 15c that abuts against the first spool 14. Here, the inner diameter of the portion of the annular valve seat 13d that abuts against the first spool 14 is smaller than the inner diameter of the flat surface of the protrusion 15c2 that abuts against the first spool 14, so the area over which the pressure in the port 13c acts on the back surface of the first spool 14 is larger than the area over which it acts on the front surface of the first spool 14, and the first spool 14 is pressed toward the valve seat member 13 and does not move away from the annular valve seat 13d.

[0060] On the other hand, since the flow path F is in communication with the inside of the spool holder 12 even when the solenoid valve V is in a closed state, the pressure in the flow path F also acts on the second spool 15 .

[0061] Specifically, the pressure in flow path F acts on the front surface (lower surface in FIG. 3 ) of the main body 15 a and flange 15 b of the second spool 15, which is the valve seat member side surface, and on the inner peripheral side of the annular protrusion 15 c that abuts against the first spool 14, as a front pressure-receiving portion, and urges the second spool 15 toward the side away from the valve seat member. Therefore, if the inner diameter of the flat surface of the protrusion 15 c 2 of the second spool 15 that abuts against the first spool 14 is φe, the magnitude of the force pushing the second spool 15 toward the side away from the valve seat member, which is the upper part in FIG. 3 , is the area of ​​a circle with diameter φe multiplied by the pressure in flow path F.

[0062] The pressure in flow path F acts on the back surface (upper surface in FIG. 3 ) of the main body portion 15a, which is the side opposite the valve seat member, through the main body portion passage 15f, and also acts on the back surface (upper surface in FIG. 3 ) of the flange portion 15b, which is the side opposite the valve seat member, through the flange portion passage 15g. The main body portion passage 15f and the flange portion passage 15g form a passage that guides the pressure in flow path F to the back surface pressure receiving portion. In this way, the pressure in flow path F acts on the back surface of the main body portion 15a and the back surface of the flange portion 15b, which serve as back surface pressure receiving portions, and urges the second spool 15 toward the valve seat member. Therefore, since the diameter of the flange portion 15b is φc, the magnitude of the force pressing the second spool 15 toward the valve seat member, which is the lower part in FIG. 3 , is calculated by multiplying the area of ​​a circle with a diameter φc by the pressure in flow path F.

[0063] The protruding portion 15c2 of the annular projection 15c protrudes from the lower end of the base portion 15c1, which has a diameter larger than the outer diameter of the flange portion 15b, and therefore the inner diameter φe of the flat surface of the protruding portion 15c2 of the second spool 15 that abuts against the first spool 14 is larger than the outer diameter φc of the flange portion 15b of the second spool 15. Therefore, the pressure in the flow path F constantly presses the second spool 15 upward, away from the valve seat member 13 and the first spool 14.

[0064] Therefore, when no force other than the pressure in the flow path F acts on the second spool 15, the second spool 15 moves away from the valve seat member 13 and the first spool 14, but receives a downward thrust from the solenoid S described below.

[0065] As described above, when the shock absorber D is contracting and the liquid is attempting to flow from the compression-side chamber R2 to the expansion-side chamber R1, if the force pushing up the second spool 15 due to the action of the pressure in the flow path F exceeds the thrust pushing down the second spool 15 by the solenoid S, the second spool 15 moves in a direction away from the first spool 14, and the solenoid valve V opens. In this way, with the solenoid valve V of this embodiment, the valve opening pressure can be adjusted by adjusting the thrust in the downward direction that the solenoid S applies to the second spool 15 when the shock absorber D is contracting.

[0066] Next, the control valve 21 that adjusts the pressure of the back pressure chamber P includes a control valve element 22 that is axially movably inserted into the valve hole 15d of the second spool 15, and a control valve seat 15e that is formed at the rear end of the main body 15a, which is the upper end, surrounding the periphery of the valve hole 15d. The control valve element 22 of the control valve 21 is pressed against the control valve seat 15e by thrust from the solenoid S, and the valve opening pressure can be changed by adjusting the thrust of the solenoid S.

[0067] Specifically, the control valve body 22 is cylindrical and includes a flange-shaped valve portion 22a provided at the upper end in Figure 3, which is the base end, a tip portion 22b inserted into the valve hole 15d in the second spool 15 and in sliding contact with the inner periphery of the valve hole 15d, an annular groove 22c provided on the outer periphery between the valve portion 22a and the tip portion 22b, and an orifice 22d provided on the inner periphery.

[0068] 3 faces the control valve seat 15e of the second spool 15 in the vertical direction, which is the axial direction. When the control valve element 22 is inserted into the valve hole 15d, the outer periphery of the tip end 22b comes into sliding contact with the inner periphery of the valve hole 15d, allowing it to move in the vertical direction, which is the axial direction, relative to the second spool 15 in FIG. 3, and the annular groove 22c faces the opening of the pressure control passage 15h that communicates with the back pressure chamber P.

[0069] Therefore, the control valve 21 closes when the control valve valve element 22 abuts the lower end of the valve portion 22 a in FIG. 3 against the control valve seat 15 e to close the open end of the valve hole 15 d, thereby cutting off communication between the back pressure chamber P and the space above the second spool 15 in FIG. 3 , and opens when the control valve valve element 22 moves upward within the valve hole 15 d and separates the lower end of the valve portion 22 a in FIG. 3 from the control valve seat 15 e, thereby connecting the back pressure chamber P to the space above the second spool 15 in FIG. 3 via the annular groove 22 c.

[0070] The space above the second spool 15 in FIG. 3 is in communication with the flow path F through the main body passage 15f, so that when the control valve 21 opens, the back pressure chamber P is in communication with the contraction side chamber R2.

[0071] The back pressure chamber P is connected to the expansion-side chamber R1 through the pilot passage 12i, and the flange portion passage 15g is provided with a check valve 20, so that the pressure in the expansion-side chamber R1, which rises when the shock absorber D is expanded, is reduced through the pilot passage 12i and introduced into the back pressure chamber P. When the pressure in the back pressure chamber P reaches the valve opening pressure of the control valve 21, the control valve 21 opens to connect the back pressure chamber P to the compression-side chamber R2, so that the pressure in the back pressure chamber P is controlled to be equal to the valve opening pressure of the control valve 21. The valve opening pressure of the control valve 21 is adjusted by the solenoid S, and therefore the pressure in the back pressure chamber P is also controlled by the solenoid S.

[0072] On the other hand, when the shock absorber D is contracting, the check valve 20 opens, and the pressure inside the spool holder 12 acts on the back pressure chamber P via the flange passage 15g. Also, the pressure inside the spool holder 12 acts on the space above the second spool 15 in Figure 3 via the main body passage 15f of the second spool 15, and the pressure inside the spool holder 12 also acts on the upper end of the control valve disc 22 in Figure 3. Therefore, when the shock absorber D is contracting, the control valve 21 seats the valve portion 22a on the control valve seat 15e, maintaining the closed state.

[0073] An orifice 22d is provided on the inner periphery of the control valve element 22, and the space below the tip 22b of the valve hole 15d is in communication with the outside of the valve hole 15d through the orifice 22d, so that the control valve element 22 is movable within the valve hole 15d and is prevented from sudden axial movement relative to the second spool 15. Therefore, in the shock absorber D of this embodiment, it is possible to prevent the pressure in the back pressure chamber P from vibrating due to repeated small opening and closing of the control valve 21.

[0074] Next, the solenoid S in this embodiment is configured to include a coil 40 accommodated axially within the housing 2b of the piston rod 2, a first fixed iron core 41 arranged above the coil 40, a second fixed iron core 42 arranged below the coil 40 with a gap between it and the first fixed iron core 41, a first movable iron core 43 arranged between the first fixed iron core 41 and the second fixed iron core 42 and attracted to the first fixed iron core 41 when current is passed through the coil 40, a second movable iron core 44 arranged between the first fixed iron core 41 and the second fixed iron core 42 and attracted to the second fixed iron core 42 when current is passed through the coil 40, and a spring 45 that urges the first movable iron core 43 toward the second fixed iron core 42.

[0075] Each component of the solenoid S according to this embodiment will be described in detail below. As shown in FIG. 2, the coil 40 is housed in a resin case 50. The resin case 50 includes a cylindrical portion 50a that houses the coil 40, and a bridge 50b that spans two locations on the upper end of the cylindrical portion 50a and houses wiring 51 that is connected to the coil 40. The resin case 50 is formed by housing the coil 40 in a mold and then injecting molding resin into the mold, and houses the coil 40 and the wiring 51 that is connected to both ends of the coil 40.

[0076] The wiring 51 extends upward from the center of the bridge 50b, and although not shown, passes through the rod body 2a of the piston rod 2, is pulled out from the upper end of the rod body 2a to the outside of the shock absorber D, and is connected to an external power source (not shown) via an externally installed drive circuit (not shown).

[0077] The first fixed core 41 is composed of two parts: a stopper 41a made of a soft magnetic material that is fitted onto the inner circumference of the upper end side of the cylindrical portion 50a in the resin case 50, and a disk-shaped base 41b made of a soft magnetic material that is stacked on the upper end of the cylindrical portion 50a and abuts against the stopper 41a.

[0078] The stopper 41a is disk-shaped and includes a flange 41a1 provided at the upper end of its outer periphery, an annular groove 41a2 provided on the outer periphery, and a recess 41a3 provided in the center of its lower end. The outer periphery of the flange 41a1 of the stopper 41a is fitted into the inner periphery of the cylindrical portion 50a of the resin case 50, and the stopper 41a is positioned radially by the resin case 50 so as to be concentric with the coil 40.

[0079] The stopper 41a is inserted into the cylindrical portion 50a together with a guide pipe 46 made of a non-magnetic material that fits into the inner periphery of the cylindrical portion 50a on the inner periphery side of the coil 40, and the lower side of the flange 41a1 fits into the inner periphery of the upper end of the guide pipe 46 in Figure 2. A seal ring 47 is housed in the annular groove 41a2 of the stopper 41a, and the seal ring 47 fits tightly against the inner periphery of the guide pipe 46, thereby sealing the gap between the stopper 41a and the guide pipe 46.

[0080] The base 41b is disk-shaped and has notches 41b1 that open from the side and accommodate the bridges 50b of the resin case 50. The base 41b is attached to the resin case 50 by inserting the bridges 50b into the notches 41b1 from the side of the resin case 50 and then stacking the base 41b on the upper end of the cylindrical portion 50a. When stacked on the upper end of the cylindrical portion 50a, the base 41b abuts against the upper end surface of a stopper 41a housed in the cylindrical portion 50a, and cooperates with the stopper 41a to form the first stationary core 41. When attached to the resin case 50, the first stationary core 41 is positioned upward in the axial direction of the coil 40. When housed in the housing 2b, the upper end of the base 41b abuts against the top portion 2b1 of the housing 2b.

[0081] The second fixed iron core 42 is formed of a soft magnetic material and is annular overall, and includes an engaging portion 42a that is inserted into the inner circumference of a cylindrical portion 50a that contains the coil 40 of the resin case 50 and fits into the guide pipe 46, a flange portion 42b that is connected to the engaging portion 42a and abuts the lower end of the cylindrical portion 50a, an annular groove 42c formed on the outer circumference of the flange portion 42b, and an annular socket 42d that protrudes from the inner circumference side of the engaging portion 42a toward the first fixed iron core side.

[0082] The fitting portion 42a is fitted onto the inner periphery of the lower end of a guide pipe 46, which is fitted onto the inner periphery of the cylindrical portion 50a. In this way, the second stationary core 42 is positioned radially by the resin case 50 via the guide pipe 46 so as to be concentric with the coil 40. A seal ring 48 is installed between the outer periphery of the socket 42d and the guide pipe 46, and the seal ring 48 is in close contact with the outer periphery of the socket 42d and the inner periphery of the guide pipe 46, thereby sealing the gap between the second stationary core 42 and the guide pipe 46. An annular protrusion 46a is provided on the inner periphery of the guide pipe 46 to prevent the seal ring 48 from falling out from between the socket 42d and the guide pipe 46.

[0083] The flange portion 42b is fitted into the tubular portion 2b2 of the housing 2b while abutting against the lower end of the cylindrical portion 50a of the resin case 50. A seal ring 49 is housed in the annular groove 42c of the flange portion 42b and is in close contact with the inner periphery of the tubular portion 2b2, thereby sealing the gap between the second stationary core 42 and the housing 2b. A push rod 55 is inserted into the inner periphery of the second stationary core 42 so as to be axially movable. The push rod 55 is fitted into the inner periphery of the upper end of the control valve element 22 of the control valve 21 in FIG. 2 .

[0084] As shown in Figure 2, the first movable iron core 43 comprises an outer tube 43a made of a soft magnetic material and having a cylindrical guide portion 43a1 that slides against the inner circumference of the guide pipe 46 and an annular bottom portion 43a2 that extends radially inward from the inner circumference of the guide portion 43a1, and a cup-shaped inner tube 43b made of a non-magnetic material that is fitted onto the inner circumference of the bottom portion 43a2 of the outer tube 43a.

[0085] The inner cylinder 43b has a flange 43b1 on the outer periphery of its upper end and a hole 43b2 in its bottom that connects the inside and outside of the inner cylinder 43b, and is fitted to the inner periphery of the bottom 43a2 of the outer cylinder 43a. The inner periphery of the upper end of the bottom 43a2 of the outer cylinder 43a is provided with an annular recess 43a3 into which the flange 43b1 fits, and when the inner cylinder 43b is attached to the outer cylinder 43a, the upper end of the flange 43b1 and the upper end of the bottom 43a2 are flush with each other.

[0086] Furthermore, when the first movable core 43 is inserted into the guide pipe 46, the interior of the inner tube 43b of the first movable core 43 and the recess 41a3 of the stopper 41a of the first fixed core 41 face each other in the axial direction. A spring 45 is housed between the bottom of the inner tube 43b and the bottom surface of the recess 41a3 of the stopper 41a. The spring 45 is interposed in a compressed state between the first movable core 43 and the first fixed core 41, and constantly biases the first movable core 43 toward the second fixed core 42.

[0087] Although the first movable core 43 is in sliding contact with the guide pipe 46, the hole 43b2 of the inner cylinder 43b connects the space between the first fixed core 41 and the first movable core 43 to the space below the first movable core 43. Therefore, when the first movable core 43 moves axially inside the guide pipe 46, the liquid filled in the cylinder 1 passes through the hole 43b2 and flows in and out of the space between the first fixed core 41 and the first movable core 43. As a result, the space between the first fixed core 41 and the first movable core 43 is not sealed, and the first movable core 43 can move smoothly inside the coil 40. The cross-sectional area of ​​the hole 43b2 is set so as to provide resistance to the flow of liquid passing through it. This resistance provides resistance to the flow of liquid passing through it when the first movable core 43 moves up and down in the axial direction, thereby suppressing sudden movement of the first movable core 43.

[0088] 2, the second movable core 44 is formed of a soft magnetic material and has a cylindrical shape with a bottom, and includes a sliding contact cylinder 44a that slides against the inner periphery of the guide portion 43a1 of the first movable core 43, and a lid portion 44b that closes the lower end of the sliding contact cylinder 44a, with the outer periphery of the lower end being slidably inserted into the inner periphery of the socket 42d of the second stationary core 42, allowing the second movable core 44 to move in the axial direction between the first stationary core 41 and the second stationary core 42 within the coil 40. The lower end of the lid portion 44b of the second movable core 44 abuts against the upper end of a push rod 55 that is axially movably inserted into the inner periphery of the second stationary core 42, and when current is applied to the coil 40 to apply thrust to the second movable core 44, the thrust acts on the control valve element 22 of the control valve 21 via the push rod 55.

[0089] The second movable iron core 44 is radially aligned by the guide portion 43a1 of the first movable iron core 43, and the first movable iron core 43 is radially aligned by the guide pipe 46, and the guide pipe 46 is fitted into the cylindrical portion 50a that contains the coil 40, so that the second movable iron core 44 and the first movable iron core 43 can move axially while maintaining coaxiality with the coil 40.

[0090] The second movable core 44 has a communication hole 44c in the cover portion 44b that communicates the inside and outside of the second movable core 44, and the space between the second movable core 44 and the first movable core 43 is connected to the space below the second movable core 44. Therefore, when the second movable core 44 moves axially relative to the first fixed core 41, the liquid filled in the cylinder 1 passes through the communication hole 44c and flows in and out of the space between the first movable core 43 and the second movable core 44. As a result, the space between the first movable core 43 and the second movable core 44 is not sealed, and the second movable core 44 can move smoothly within the coil 40. The cross-sectional area of ​​the communication hole 44c is set so as to provide resistance to the flow of liquid passing through it. Since the communication hole 44c provides resistance to the flow of liquid passing through it when the second movable core 44 moves up and down in the axial direction, sudden movement of the second movable core 44 is suppressed.

[0091] Furthermore, in shock absorber D of this embodiment, the inner periphery of second fixed core 42 is expanded in diameter on the upper side in Fig. 2, and a step 42e is provided on the inner periphery of second fixed core 42, and a coil spring 52 is provided between step 42e and cover 44b of second movable core 44. Coil spring 52 always biases second movable core 44 toward first fixed core 41, and when current is not applied to coil 40, second movable core 44 is compressed by the biasing force of spring 45. When current is not applied to coil 40, first movable core 43 and second movable core 44 are sandwiched between spring 45 and coil spring 52 and are brought into the closest position to each other.

[0092] An annular restricting member 53 is provided between the bottom 43a2 of the first movable core 43 and the sliding contact tube 44a of the second movable core 44 to prevent them from attracting each other. Even when the second movable core 44 and the first movable core 43 are closest to each other, the restricting member 53 prevents direct surface contact between the bottom 43a2 and the sliding contact tube 44a. The restricting member 53 may be attached to either the first movable core 43 or the second movable core 44. An annular restricting member 54 is provided on the inner periphery of the upper end of the fitting portion 42a of the second stationary core 42, and the restricting member 54 prevents the second stationary core 42 and the second movable core 44 from attracting each other. The restricting member 54 may be attached to the second movable core 44. The restricting members 53, 54 may be made of a non-magnetic material, such as rubber, to function as a cushion.

[0093] The coil 40, first fixed iron core 41, second fixed iron core 42, first movable iron core 43, second movable iron core 44 and spring 45 that constitute the solenoid S configured as described above are housed within the housing 2b of the piston rod 2, and when the spool holder 12 is screwed to the threaded portion 2b3 provided on the inner circumference of the lower end of the cylindrical portion 2b2 of the housing 2b, it is clamped between the top portion 2b1 and the spool holder 12 and fixed within the housing 2b.

[0094] When no current is applied to the coil 40, the coil spring 52 contracts due to the biasing force of the spring 45, and the first movable iron core 43 and the second movable iron core 44 are positioned at the lowest position closest to the second fixed iron core 42.

[0095] On the other hand, when current is passed through coil 40, magnetic flux passes through a magnetic path formed by first fixed core 41, first movable core 43, second movable core 44, second fixed core 42, and housing 2b, generating a magnetic force that attracts first movable core 43 and first fixed core 41 to each other, thereby applying a thrust that moves first movable core 43 upward, and also generating a magnetic force that attracts second movable core 44 and second fixed core 42 to each other, thereby applying a thrust that moves second movable core 44 downward. The magnitude of the thrust that moves first movable core 43 upward and the magnitude of the thrust that moves second movable core 44 downward can be adjusted depending on the amount of current passed through coil 40. Furthermore, since the lower end of the outer periphery of the second movable iron core 44 is in sliding contact with the inside of the annular socket 42d provided on the second fixed iron core 42, when current is applied to the coil 40, the second movable iron core 44 is attracted to the second fixed iron core 42 without moving toward the first fixed iron core 41 together with the first movable iron core 43.

[0096] The restricting member 53 prevents the bottom 43a2 of the first movable core 43 from coming into direct contact with the sliding contact cylinder 44a of the second movable core 44, preventing the first movable core 43 and the second movable core 44 from attracting to each other when current begins to flow through the coil 40. Therefore, when current is passed through the coil 40, the first movable core 43 and the second movable core 44 can quickly move in a direction separating them from each other. The restricting member 54 prevents the upper end of the fitting portion 42a of the second fixed core 42 from coming into direct contact with the lower end of the second movable core 44 when current is passed through the coil 40 and the second movable core 44 is attracted to the second fixed core 42, preventing the second fixed core 42 and the second movable core 44 from attracting to each other. Therefore, when the amount of current flowing through the coil 40 is reduced, the second movable core 44 can quickly move in a direction separating from the second fixed core 42. The contact length of the coil spring 52 is shorter than the axial length from the upper end of the regulating member 54 to the step 42e, and therefore does not fully contract even when the coil 40 is energized and the second movable core 44 is attracted to the second fixed core 42, sandwiching the regulating member 54 between them. Although the coil spring 52 can be eliminated, providing the coil spring 52 prevents the second movable core 44 from suddenly displacing toward the second fixed core 42 when the coil 40 is energized and the first movable core 43 is attracted to the first fixed core 41, thereby preventing the opening and closing of the solenoid valve V from becoming oscillatory due to the sudden movement of the second movable core 44.

[0097] Next, the operation of the solenoid S will be described. Fig. 4 shows the relationship between the amount of current supplied to the solenoid S and the force that the solenoid S applies to the control valve element 22. In Fig. 4, Ia is the minimum amount of current required to attract the first movable core 43 to the first fixed core 41 by passing current through the coil 40 from a state in which the first movable core 43 and the second movable core 44 are closest to each other and are at a position furthest from the first fixed core 41 without passing current through the coil 40, and Ib is the minimum amount of current required to maintain the attracted state between the first fixed core 41 and the first movable core 43 after passing current through the coil 40 and attracting the first movable core 43 to the first fixed core 41. Ic will be described later.

[0098] First, when the amount of current supplied to the coil 40 is zero, that is, when the solenoid S is not energized, the first movable iron core 43 is pushed down by the biasing force of the spring 45 and hits the second movable iron core 44 via the regulating member 53, and the second movable iron core 44 is pushed down together with the push rod 55, so that the solenoid S applies a thrust in the valve closing direction to the control valve element 22. In this way, when the solenoid S is not energized, a downward thrust is applied to the control valve element 22 by the biasing force of the spring 45 via the push rod 55, the second movable iron core 44, the regulating member 53, and the first movable iron core 43. In the shock absorber D of this embodiment, the force pushing the control valve element 22 downward is in a direction to close the control valve element 22, so when the solenoid S is not energized, the biasing force of the spring 45 applies a thrust to the control valve element 22 in a direction to close the control valve element 22.

[0099] Next, when the amount of current supplied to the coil 40 is increased, the upward force attracting the first movable core 43 toward the first fixed core 41 increases, and the downward force attracting the second movable core 44 toward the second fixed core 42 also increases. In such a case, in the region where the amount of current supplied to the solenoid S is less than Ia, the biasing force of the spring 45 is transmitted to the control valve element 22, but part of the biasing force of the spring 45 that biases the first movable core 43 downward is offset by the force attracting the first movable core 43 upward (toward the first fixed core 41). For this reason, in the region where the amount of current is less than Ia, the downward thrust that the solenoid S applies to the control valve element 22 decreases as the amount of current supplied to the solenoid S increases.

[0100] On the other hand, when the amount of current supplied to the coil 40 is increased and the amount of current is equal to or greater than Ia, the first movable core 43 is attracted to and attracted to the first fixed core 41 against the biasing force of the spring 45. In this state, the biasing force of the spring 45 is not transmitted to the second movable core 44, and only the force attracting the second movable core 44 to the second fixed core 42 acts as a thrust to press the control valve element 22 downward. This downward force attracting the second movable core 44 increases in proportion to the amount of current supplied to the coil 40, so in the range where the amount of current supplied to the coil 40 is equal to or greater than Ia, the more the amount of current supplied to the coil 40 is increased, the greater the downward thrust applied by the solenoid S to the control valve element 22 in proportion to the amount of current.

[0101] Conversely, when the amount of current supplied to the coil 40 is reduced, the upward force attracting the first movable core 43 to the first fixed core 41 decreases, and the downward force attracting the second movable core 44 to the second fixed core 42 also decreases. Even in such a case, in the region where the amount of current supplied to the coil 40 is Ib or more, the first movable core 43 is attracted to the first fixed core 41, and a state is maintained in which the biasing force of the spring 45 is not transmitted to the second movable core 44. Therefore, in the region where the amount of current supplied to the coil 40 is Ib or more, the more the amount of current supplied to the coil 40 is reduced, the smaller the downward thrust applied by the solenoid S to the control valve element 22 becomes in proportion to the amount of current.

[0102] On the other hand, when the amount of current supplied to the coil 40 is reduced and the amount of current is less than Ib, the attracting state between the first movable iron core 43 and the first fixed iron core 41 is released by the biasing force of the spring 45, and the biasing force of the spring 45 is transmitted to the second movable iron core 44. Therefore, in the area where the amount of current is less than Ib, the downward thrust applied to the control valve body 22 by the solenoid S increases as the amount of current supplied to the coil 40 is reduced.

[0103] As can be seen from Fig. 4, Ib, which is the minimum amount of current required to maintain attraction between the first movable core 43 and the first fixed core 41, is smaller than Ia, which is the minimum amount of current required to attract the separated first movable core 43 to the first fixed core 41 (Ia > Ib). Therefore, the characteristic of the force that the solenoid S applies to the control valve element 22 relative to the amount of current supplied to the coil 40 exhibits hysteresis. Note that in Fig. 4, the region where the amount of current supplied to the solenoid S is small is exaggerated for ease of understanding.

[0104] In this embodiment, when controlling the thrust applied by the solenoid S to the control valve element 22 by controlling the amount of current supplied to the coil 40, a current of Ia or more is first supplied to attract the first movable core 43 to the first fixed core 41, and then the amount of current supplied to the coil 40 is controlled within a range of Ic or more, which is larger than Ib. As a result, during normal operation when the amount of current supplied to the solenoid S is controlled, the first movable core 43 is maintained in a state of being attracted to the first fixed core 41, so that the amount of current supplied to the solenoid S and the downward thrust applied by the solenoid S to the control valve element 22 are proportional to each other, and the thrust increases as the amount of current supplied to the coil 40 increases.

[0105] In this way, in the shock absorber D of this embodiment, the amount of current supplied to the coil 40 and the thrust force applied by the solenoid S to the control valve body 22 are proportional to each other, and the thrust force increases as the amount of current supplied increases, and decreases as the amount of current supplied decreases.

[0106] On the other hand, in the event of a failure where the solenoid S is de-energized, the control valve element 22 is urged downward by the spring 45 of the solenoid S, and the urging force is determined in advance according to the specifications of the spring 45, such as the spring constant. Furthermore, the direction of the urging force of the spring 45 that urges the control valve element 22 in the event of a failure (when not energized) is the same as the direction of the thrust that the solenoid S applies to the control valve element 22 in normal operation.

[0107] Next, an operation of the shock absorber D of this embodiment will be described. When the shock absorber D is extended and the piston 3 moves upward in FIG. 1 relative to the cylinder 1, the movement of the piston 3 relative to the cylinder 1 causes the liquid in the expansion-side chamber R1, which is compressed, to move through the flow path F to the expansion-side chamber R2.

[0108] The solenoid valve V opens when the pressure in the expansion-side chamber R1 during the expansion operation of the shock absorber D reaches a valve-opening pressure, separating the first spool 14 and the second spool 15 from the valve seat member 13 and connecting the communication hole 12j to the port 13c. As described above, the valve-opening pressure of the solenoid valve V is changed according to the pressure in the backpressure chamber P controlled by the control valve 21. More specifically, the solenoid S can change the thrust that urges the control valve element 22 in the valve-closing direction according to the amount of current supplied to the coil 40. Therefore, when the amount of current supplied to the solenoid S is set to Ib, the solenoid valve V minimizes the valve-opening pressure of the control valve 21 to the extent that the pressure in the backpressure chamber P can be controlled, thereby minimizing the valve-opening pressure when separating the first spool 14 from the valve seat member 13.

[0109] In this state, the liquid in the expansion-side chamber R1 passes through the communication hole 12j, the solenoid valve V, and the port 13c, and then pushes open the expansion-side soft valve 18, passes through the expansion-side passage 3e of the piston 3, and moves to the compression-side chamber R2. Therefore, when the shock absorber D is expanding and the solenoid valve V minimizes the valve opening pressure, the expansion-side soft valve 18 mainly applies flow resistance to the liquid from the expansion-side chamber R1 to the compression-side chamber R2, thereby generating a soft damping force that obstructs the expansion operation of the shock absorber D.

[0110] Furthermore, if the amount of current supplied to the solenoid S is increased during the extension operation of the shock absorber D, the thrust force that the solenoid S applies to the control valve 21 is increased, and the pressure in the back pressure chamber P is increased, the shock absorber D will generate a damping force that corresponds to the valve opening pressure of the solenoid valve V. That is, as shown in Fig. 5, if the amount of current supplied to the solenoid S is increased, the resistance that the solenoid valve V applies to the flow of fluid from the expansion-side chamber R1 to the compression-side chamber R2 increases, so the damping force generated by the shock absorber D can be adjusted according to the amount of current supplied to the solenoid S. In the shock absorber D of this embodiment, if the amount of current supplied to the solenoid S is increased during the extension operation of the shock absorber D, the pressure in the back pressure chamber P can be increased, and therefore, the damping force that hinders the extension operation of the shock absorber D can be increased as the amount of current supplied to the solenoid S is increased. Even when the solenoid valve V is closed, the liquid can pass through the flow path F through the orifice provided in the annular valve seat 13d or the annular protrusion 15c, and while the solenoid valve V is closed, the shock absorber D generates a damping force through the orifice.

[0111] Furthermore, if the extension speed of the shock absorber D increases while the damping force during extension of the shock absorber D is high, the flow rate of the liquid passing from the extension side chamber R1 through the communication hole 12j into the narrow gap between the first spool 14 and the annular valve seat 13d increases, and the pressure in the gap tends to decrease, so that the force separating the first spool 14 from the valve seat member 13 decreases, narrowing the gap between the first spool 14 and the annular valve seat 13d, which may result in a damping force higher than the desired damping force. To solve this problem, in the solenoid valve V of this embodiment, the area of ​​the hole 16c provided in the guide cylinder 16b of the guide member 16 is reduced so that a pressure loss occurs when the flow rate of the liquid passing through the hole 16c is high, thereby increasing the pressure in the space on the outer periphery of the guide cylinder 16b between the valve seat member 13 and the first spool 14 and increasing the force that pushes the first spool 14 in the direction away from the valve seat member 13, thereby preventing the gap between the first spool 14 and the annular valve seat 13d from becoming smaller even when the extension speed of the shock absorber D increases while the damping force during extension of the shock absorber D is high. Therefore, the ride comfort of the vehicle can be improved by preventing the damping force of the shock absorber D from becoming excessive even when the shock absorber D is extended at high speeds. 3, instead of providing the hole 16c in the guide cylinder 16b, a notch 14a may be provided axially penetrating the first spool 14 on the inner side of the portion that abuts against the annular valve seat 13d, and the notch 14a may allow the space on the outer circumferential side of the guide cylinder 16b and on the valve seat member side of the first spool 14 to communicate with the inside of the guide cylinder 16b via the space above the first spool 14. Even in this case, if the extension speed of the shock absorber D increases while the damping force during extension of the shock absorber D is increased, a pressure loss occurs when the liquid passes through the notch 14a, the pressure in the space increases, and the force that separates the first spool 14 from the valve seat member 13 increases, and the gap between the first spool 14 and the annular valve seat 13d does not need to be reduced, so that the damping force of the shock absorber D is prevented from becoming excessive even during high-speed extension, thereby improving the ride comfort of the vehicle.In the above description, the guide tube 16b is provided with a hole 16c to connect the space on the outer periphery of the guide tube 16b closer to the valve seat member than the first spool 14 to the inside of the guide tube 16b, but communication may also be achieved by a notch other than the hole 16c. Also, the first spool 14 is provided with a notch 14a to connect the space on the outer periphery of the guide tube 16b closer to the valve seat member than the first spool 14 to the inside of the guide tube 16b, but communication may also be achieved by a hole other than the notch 14a.

[0112] When the shock absorber D is extended, the piston rod 2 retreats from the cylinder 1, reducing the volume displaced by the piston rod 2 within the cylinder 1. However, the free piston 11 moves upward within the cylinder 1, expanding the air chamber G, thereby compensating for this reduction in volume.

[0113] Furthermore, when the shock absorber D contracts and the piston 3 moves downward in FIG. 1 relative to the cylinder 1, the movement of the piston 3 relative to the cylinder 1 causes the liquid in the compression-side chamber R2, which is compressed, to move through the flow path F to the expansion-side chamber R1.

[0114] When the shock absorber D is contracting, the liquid in the compression side chamber R2 passes through the compression side passage 3d of the piston 3, pushes open the compression side soft valve 19, and flows into the flow path F, so that the pressure in the compression side chamber R2 is reduced and transmitted into the flow path F.

[0115] When the shock absorber D is contracting, the pressure inside the spool holder 12 acts on the first spool 14, pressing it toward the valve seat member 13, while the pressure inside the spool holder 12 acts on both the front surface of the second spool 15 facing the valve seat member and the back surface opposite the valve seat member. Because the pressure-receiving area on the front side of the second spool 15 (area of ​​diameter φe) is larger than the pressure-receiving area on the back side of the second spool 15 (area of ​​a circle with diameter φc), the second spool 15 is urged by the pressure inside the flow path F in a direction away from the valve seat member 13 and the first spool 14 (upward in FIG. 2 ).

[0116] The solenoid S applies a thrust to the control valve element 22 toward the second spool 15, which is downward in Fig. 2, regardless of whether the coil 40 is energized or not, and when the shock absorber D is contracting, the pressure inside the spool holder 12 is transmitted to the back side of the second spool 15 via the main body passage 15f, and the control valve element 22 is pressed toward the second spool 15 by the pressure inside the spool holder 12, with the valve portion 22a coming into contact with the control valve seat 15e of the second spool 15. The solenoid S applies a thrust to the control valve element 22 downward in Fig. 3, whether energized or not, and the thrust of the solenoid S acts on the second spool 15 via the control valve element 22.

[0117] Therefore, when the force pushing up the second spool 15 in Figure 3 due to the action of the pressure inside the spool holder 12 exceeds the thrust of the solenoid S, the second spool 15 moves away from the first spool 14, the solenoid valve V opens, and the port 13c communicates with the communication hole 12j, allowing the flow of fluid from the compression-side chamber R2 to the extension-side chamber R1.

[0118] As described above, when the shock absorber D is contracting, the compression-side soft valve 19 opens, and the pressure in the flow path F, which is connected to the compression-side chamber R2, reaches the valve-opening pressure of the solenoid valve V. The solenoid valve V opens, the second spool 15 moves away from the first spool 14, and the communication hole 12j communicates with the port 13c. The valve-opening pressure of the solenoid valve V is changed according to the thrust of the solenoid S, as described above. More specifically, the solenoid S can change its thrust according to the amount of current supplied to the coil 40. Therefore, when the amount of current supplied to the solenoid S is set to Ib, the solenoid valve V minimizes its thrust and minimizes the valve-opening pressure when separating the second spool 15 from the first spool 14. Until the solenoid valve V opens, the fluid in the compression-side chamber R2 passes through the compression-side passage 3d and the compression-side soft valve 19, and then passes through the flange portion passage 15g, the check valve 20, and the pilot passage 12i to move to the expansion-side chamber R1. When the shock absorber D contracts at an extremely slow speed, the resistance that the restrictor O1 of the pilot passage 12i applies to the fluid flow is extremely small, so a damping force is generated by the compression-side soft valve 19. As the contraction speed of the shock absorber D increases, it becomes difficult for the fluid to pass through the restrictor O1, so the pressure in the flow path F increases and the solenoid valve V opens. Therefore, the pilot passage 12i has little effect on the soft damping force, and the pilot passage 12i does not have a significant effect on the damping force adjusted by the solenoid valve V.

[0119] In this state, the liquid in the compression-side chamber R2 passes through the compression-side soft valve 19, and then passes through the flow path F and the solenoid valve V to move to the expansion-side chamber R1, but the resistance that the solenoid valve V applies to the flow of liquid is small. Therefore, when the shock absorber D is contracting and the solenoid valve V has a minimum valve opening pressure, the compression-side soft valve 19 mainly applies resistance to the flow of liquid from the compression-side chamber R2 to the expansion-side chamber R1, thereby generating a soft damping force that hinders the contraction of the shock absorber D. In the solenoid valve V of this embodiment, the area of ​​the front-side pressure receiving portion of the second spool 15 is larger than the area of ​​the rear-side pressure receiving portion, so that when the shock absorber D is contracting, the second spool 15 is necessarily urged in a direction away from the first spool 14 by the pressure acting through the flow path F. Therefore, according to the solenoid valve V of this embodiment, by reducing the thrust of the solenoid S and reducing the valve opening pressure of the solenoid valve V, the damping force generated in the soft state can be reduced compared to conventional solenoid valves, thereby improving the ride comfort of the vehicle.

[0120] Furthermore, if the amount of current supplied to the solenoid S is increased during the contraction operation of the shock absorber D, and the thrust of the solenoid S is increased, the shock absorber D will generate a damping force corresponding to the valve opening pressure of the solenoid valve V. That is, as shown in FIG. 5 , if the amount of current supplied to the solenoid S is increased, the resistance that the solenoid valve V applies to the flow of liquid from the compression-side chamber R2 to the expansion-side chamber R1 increases, and the damping force generated by the shock absorber D can be adjusted according to the amount of current supplied to the solenoid S. In the shock absorber D of this embodiment, if the amount of current supplied to the solenoid S is increased during the contraction operation of the shock absorber D, the valve opening pressure of the solenoid valve V can be increased, and therefore, the damping force that hinders the contraction operation of the shock absorber D can be increased as the amount of current supplied to the solenoid S increases. Note that even when the solenoid valve V is closed, liquid can pass through the flow path F through the orifice provided in the annular valve seat 13d or the annular protrusion 15c, and the shock absorber D generates a damping force through the orifice while the solenoid valve V is closed.

[0121] When the shock absorber D is contracting, the piston rod 2 enters the cylinder 1, increasing the volume displaced by the piston rod 2 within the cylinder 1, but the free piston 11 moves downward within the cylinder 1, thereby reducing the air chamber G, thereby compensating for this increase in volume.

[0122] As described above, the solenoid valve V of this embodiment includes the valve seat member 13 having the annular valve seat 13d surrounding the flow path F, the annular first spool 14 that is movable in the axial direction relative to the valve seat member 13 and can be seated on and removed from the annular valve seat 13d to open and close the flow path F, the second spool 15 that is movable in the axial direction relative to the valve seat member 13 and the first spool 14 and is stacked on the opposite side of the first spool 14 from the valve seat member 13 and can be seated on and removed from the first spool 14 to open and close the flow path F, and the solenoid S that can apply a thrust to the second spool 15 toward the valve seat member side. The first spool 14 and the second spool 15 are connected to the expansion-side chamber R1 of the flow path F. The second spool 15 is urged in a direction away from the valve seat member 13 by the pressure on the pressure side chamber R2 of the flow path F (pressure on one side), and is urged in directions away from each other by the pressure on the compression side chamber R2 of the flow path F (pressure on the other side). The second spool 15 has a front-side pressure-receiving portion that faces the valve seat member side and acts as a force that moves the pressure in the flow path F away from the valve seat member 13, a back-side pressure-receiving portion that faces the anti-valve-seat side member side and acts as a force that moves the pressure closer to the valve seat member, and a main body passage 15 f and a flange passage 15 g that serve as passages that guide the pressure in the flow path F to the back-side pressure-receiving portion, and the area of ​​the front-side pressure-receiving portion is larger than the area of ​​the back-side pressure-receiving portion.

[0123] With the solenoid valve V configured in this manner, the area of ​​the front pressure receiving portion of the second spool 15 is larger than the area of ​​the rear pressure receiving portion, so that during the contraction operation, the pressure acting on the second spool 15 through the flow path F urges the second spool 15 in a direction away from the first spool 14. Therefore, by reducing the thrust of the solenoid S and reducing the valve opening pressure of the solenoid valve V, the damping force generated during soft setting can be reduced, improving the ride comfort of the vehicle. Furthermore, by increasing the area of ​​the front pressure receiving portion of the second spool 15, the inner diameter of the portion where the second spool 15 abuts against the first spool 14 increases, and therefore the area of ​​the gap between the first spool 14 and the second spool 15 increases when the second spool 15 is open and away from the first spool 14. Therefore, according to the solenoid valve V of this embodiment, when the second spool 15 opens and moves away from the first spool 14, the area of ​​the gap between the first spool 14 and the second spool 15 becomes larger, which effectively reduces the resistance of the liquid passing through the gap, thereby generating a softer damping force.

[0124] In the solenoid valve V of this embodiment, the second spool 15 has a main body 15a, a flange 15b provided on the outer periphery of the main body 15a, and an annular protrusion 15c that protrudes from the front side of the flange 15b and abuts against the first spool 14, the back side pressure receiving portion includes the end of the main body 15a opposite the valve seat member and the end of the flange 15b opposite the valve seat member, and the passage includes a linear main body passage 15f that connects the front side of the main body 15a with the back side of the main body 15a, and a linear flange passage 15g that is on the front side of the flange 15b and connects the inside of the annular protrusion 15c with the back side of the flange.

[0125] According to the solenoid valve V configured in this manner, by providing the linear main body passage 15f and flange passage 15g in the second spool 15, pressure is directed to the pressure-receiving portion on the back surface of the second spool 15, which makes it easier to form the passages and reduces the processing costs of the second spool 15. Furthermore, in the solenoid valve V of this embodiment, a back pressure chamber P is provided on the back surface of the flange portion 15b, and during the contraction operation of the shock absorber D, the pressure on the compression-side chamber R2 side is directed to the back pressure chamber P via the flange passage 15g, and the back pressure chamber P is connected to the expansion-side chamber R1 through the pilot passage 12i, and by making the cross-sectional area of ​​the flange passage 15g larger than the restriction O1 in the pilot passage 12i, it is possible to reduce variations in damping force due to variations in dimensions.

[0126] Furthermore, in the solenoid valve V of this embodiment, the main body passage 15f and the flange passage 15g are arranged parallel to the axis of the second spool 15, which makes it easier to drill holes to provide the main body passage 15f and the flange passage 15g in the second spool 15. In addition, compared to when the main body passage 15f and the flange passage 15g are arranged at an angle to the axis, the main body passage 15f and the flange passage 15g are shorter, which reduces the installation space occupied by the main body passage 15f and the flange passage 15g within the second spool 15, thereby enabling the second spool 15 to be made smaller.

[0127] Furthermore, the solenoid valve V of this embodiment includes a back pressure chamber P into which pressure (pressure on one side) of the expansion-side chamber R1 of the flow path F is introduced on the back side of the flange portion 15 b, and a control valve 21 that adjusts the pressure of the back pressure chamber P by receiving thrust from the solenoid S. The second spool 15 has a valve hole 15 d that opens from the back side of the main body portion 15 a and an annular control valve seat 15 e provided on the back side of the main body portion 15 a. The control valve 21 has a control valve element 22 that is inserted axially movably into the valve hole 15 d and is seated on and releasable from the control valve seat 15 e. The solenoid S applies thrust to the second spool 15 with the control valve element 22 seated on the control valve seat 15 e.

[0128] With the solenoid valve V configured in this manner, when liquid passes through the flow path F from one side to the other, in this embodiment, during the extension operation of the shock absorber D, the thrust of the solenoid S is applied to the control valve 21 to control the pressure in the back pressure chamber P, thereby making the valve opening pressure of the solenoid valve V variable, and the damping force during the extension operation of the shock absorber D can be adjusted; and when liquid passes through the flow path F from the other side to one side, in this embodiment, during the contraction operation of the shock absorber D, the thrust of the solenoid S is applied to the second spool 15 via the control valve valve body 22, making the valve opening pressure of the solenoid valve V variable, and the damping force during the contraction operation of the shock absorber D can be adjusted.

[0129] The specific shapes and structures of the valve seat member 13, first spool 14, and second spool 15 of the solenoid valve V may be modified in design as long as the effects of the invention are not lost. Also, the solenoid S of the solenoid valve V includes the first movable iron core 43 and the second movable iron core 44, but is not limited to this, and may be any other element as long as it is capable of generating thrust for adjusting the valve-opening pressure of the second spool 15. Furthermore, in the solenoid valve V of this embodiment, when liquid passes through the flow path F from one side to the other, the pressure in the back pressure chamber P acting on the second spool 15 is controlled by applying the thrust of the solenoid S to the control valve 21 to adjust the valve opening pressure, and when liquid passes through the flow path F from the other side to the one side, the thrust of the solenoid S is applied to the second spool 15 to adjust the valve opening pressure, but regardless of the flow direction of the liquid passing through the flow path F, the pressure in the back pressure chamber P acting on the second spool 15 may be controlled by applying the thrust of the solenoid S to the control valve 21 to adjust the valve opening pressure, or the thrust of the solenoid S may be applied to the second spool 15 to adjust the valve opening pressure.

[0130] In addition, since the first spool 14 in the solenoid valve V of this embodiment is formed from an annular flat plate, the axial length of the first spool 14 is shortened, which shortens the overall length of the solenoid valve V, improving the ease of installation on the shock absorber D, and reducing manufacturing costs due to the simplified shape of the first spool 14.

[0131] In addition, the shock absorber D of this embodiment includes a cylinder (outer shell) 1, a piston rod 2 inserted into the cylinder (outer shell) 1 so as to be axially movable, a piston 3 connected to the piston rod 2 and inserted into the cylinder (outer shell) 1 so as to be axially movable, and a solenoid valve V housed in the cylinder (outer shell) 1 and arranged between an extension side chamber (operating chamber) R1 and a compression side chamber (operating chamber) R2 provided in the cylinder (outer shell) 1.

[0132] The shock absorber D configured in this manner is equipped with the solenoid valve V configured as described above, so that when a soft damping force is generated, the damping force does not become excessive and the ride comfort of the vehicle is not impaired. Note that, although the shock absorber D of this embodiment is illustrated as a mono-tube shock absorber with the cylinder 1 as the outer shell, it may also be a double-tube shock absorber that has an outer shell that covers the outer periphery of the cylinder 1 and has a reservoir between the cylinder 1 and the outer shell, and the solenoid valve V may be installed between the compression-side chamber R2 and the reservoir as working chambers, other than between the expansion-side chamber R1 and the compression-side chamber R2, as long as it is housed in the outer shell.

[0133] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims.

[0134] 1... Cylinder (outer shell), 2... Piston rod, 3... Piston, 13... Valve seat member, 13d... Annular valve seat, 14... First spool, 15... Second spool, 15a... Main body portion, 15b... Flange portion, 15c... Annular protrusion, 15d... Valve hole, 15e... Control valve seat, 15f... Main body passage (passage), 15g... Flange passage (passage), 21... Control valve, 22... Control valve valve body, D... Shock absorber, F... Flow path, P... Back pressure chamber, R1... Expansion side chamber (working chamber), R2... Compression side chamber (working chamber), S... Solenoid, V... Solenoid valve

Claims

1. A solenoid valve comprising: a valve seat member having an annular valve seat surrounding a flow path; a first annular spool movable in the axial direction relative to the valve seat member and capable of opening and closing the flow path by seating on and off the annular valve seat; a second spool movable in the axial direction relative to the valve seat member and the first spool, stacked on the side opposite the valve seat member of the first spool and capable of seating on and off the first spool to open and close the flow path; and a solenoid capable of applying a thrust to the second spool toward the valve seat member, wherein the first spool and the second spool are both urged in a direction away from the valve seat member by pressure on one side of the flow path, and are urged in directions away from each other by pressure on the other side of the flow path, a front pressure receiving portion that faces the valve seat member and applies a force in a direction that moves the pressure in the flow path away from the valve seat member; a rear pressure receiving portion that faces the opposite side of the valve seat member and applies a force in a direction that moves the pressure toward the valve seat member; and a passage that introduces the pressure in the flow path to the rear pressure receiving portion, wherein the area of ​​the front pressure receiving portion is larger than the area of ​​the rear pressure receiving portion.

2. A solenoid valve as claimed in claim 1, wherein the second spool has a main body, a flange provided on the outer periphery of the main body, and an annular protrusion protruding from the front side of the flange and abutting against the first spool, the rear side pressure receiving portion includes the end of the main body opposite the valve seat member and the end of the flange opposite the valve seat member, and the passage has a linear main body passage connecting the front side of the main body with the rear side of the main body, and a linear flange passage on the front side of the flange connecting the inside of the annular protrusion with the rear side of the flange.

3. A solenoid valve as set forth in claim 2, comprising: a back pressure chamber into which pressure from one side of the flow path is introduced to the back side of the flange; and a control valve that receives thrust from the solenoid and adjusts the pressure in the back pressure chamber; the second spool has a valve hole that opens from the back side of the main body and an annular control valve seat provided on the back side of the main body; the control valve has a control valve body that is inserted axially movably into the valve hole and can be seated on and removed from the control valve seat; and the solenoid applies thrust to the second spool when the control valve seat is seated on the control valve seat.

4. A solenoid valve as set forth in claim 2, wherein the body passage and the flange passage are arranged parallel to the axis of the second spool.

5. A shock absorber comprising: an outer shell; a piston rod inserted into the outer shell so as to be axially movable; a piston connected to the piston rod and inserted into the outer shell so as to be axially movable; and a solenoid valve according to any one of claims 1 to 4 housed in the outer shell and disposed between two operating chambers provided in the outer shell.

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