Adjustable damping shock absorber and pressure control valve

Abstract

To provide an attenuation force adjustment type shock absorber which can suppress the vibration of a valve body, and can reduce the pulsation of hydraulic pressure (discharge pressure), and a pressure control valve.SOLUTION: A pressure control valve 33 has a pilot valve body 32 as a valve body seated on a seat face 26E, a shaft part 49 arranged at a pilot valve body 32 integrally therewith, a plunger 48 inserted with the shaft part 49, energizing the pilot valve body 32 to the seat face 26E side, and adjusting valve-opening pressure, a solenoid 35A for adjusting the thrust of the plunger 48, and a first bearing 38 and a second bearing 43 for supporting one side and the other side of the shaft part 49. By this constitution, when the pilot valve body 32 is separated from the seat face 26E, a length in an axial direction (distance in the axial direction) up to the seat face 26E is differentiated by a position of the pilot valve body 32 in a circumferential direction.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to, for example, a damping force adjustable shock absorber and a pressure control valve. [Background technology]

[0002] Vehicles such as four-wheeled automobiles are provided with shock absorbers (dampers) between the vehicle body (sprung part) and each wheel (unsprung part). One known shock absorber for such vehicles is a damping force adjustable hydraulic shock absorber that variably adjusts the damping force according to the driving conditions, vehicle behavior, etc. The damping force adjustable hydraulic shock absorber constitutes a semi-active suspension for the vehicle.

[0003] In a damping force adjustable hydraulic shock absorber, the generated damping force is variably adjusted by adjusting the valve opening pressure of a damping force adjustment valve using a damping force variable actuator, for example, a solenoid actuator.

[0004] Patent Document 1 describes a damping force control shock absorber in which the valve opening pressure of a damping force control valve (main valve) is controlled by a pressure control valve. The pressure control valve has a valve body integrally provided with a rod (shaft) of a solenoid actuator. The rod (shaft) is supported by two bearings. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-281584 Summary of the Invention [Problem to be solved by the invention]

[0006] In the case of the prior art, when the valve element of the pressure control valve opens, the pressure applied to the valve element changes suddenly, which can cause the valve element to vibrate and result in pulsation of the oil pressure (discharge pressure).

[0007] An object of one embodiment of the present invention is to provide a damping force adjustable shock absorber and a pressure control valve that can suppress vibration of the valve body and reduce pulsation of the hydraulic pressure (discharge pressure). [Means for solving the problem]

[0008] One embodiment of the present invention is a damping force adjustable shock absorber comprising: a cylinder filled with working fluid; a piston slidably fitted within the cylinder; a piston rod having one end connected to the piston and the other end extending out of the cylinder; and a pressure control valve that controls the flow of fluid generated by the sliding of the piston within the cylinder to generate a damping force and adjust a valve-opening pressure, wherein the pressure control valve comprises: a valve body that seats on a seat surface; a shaft portion that is provided integrally with the valve body; a plunger into which the shaft portion is inserted and that urges the valve body toward the seat surface to adjust the valve-opening pressure; a solenoid that adjusts the thrust of the plunger; and first and second bearings that support one and the other sides of the shaft portion. a clearance between the first bearing on the side farther from the valve body and the shaft portion is larger than a clearance between the second bearing on the side closer to the valve body and the shaft portion; When the valve body is spaced from the seat surface, the axial length to the seat surface varies depending on the circumferential position of the valve body.

[0009] Moreover, one embodiment of the present invention is a pressure control valve provided in a damping force control shock absorber, the pressure control valve including: a valve body that seats on a seat surface; a shaft portion that is provided integrally with the valve body; a plunger into which the shaft portion is inserted and that biases the valve body toward the seat surface to adjust a valve-opening pressure; a solenoid that adjusts the thrust of the plunger; and a first bearing and a second bearing that support one side and the other side of the shaft portion, a clearance between the first bearing on the side farther from the valve body and the shaft portion is larger than a clearance between the second bearing on the side closer to the valve body and the shaft portion; When the valve body is spaced from the seat surface, the axial length to the seat surface varies depending on the circumferential position of the valve body. [Effects of the Invention]

[0010] According to one embodiment of the present invention, vibration of the valve body can be suppressed, and pulsation of the hydraulic pressure (discharge pressure) can be reduced. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a vertical cross-sectional view showing a damping force control shock absorber incorporating a pressure control valve according to an embodiment. [Figure 2] 2 is an enlarged cross-sectional view showing the damping force adjusting mechanism in FIG. 1. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing the pressure control valve in FIG. 2. [Figure 4] FIG. 2 is an enlarged cross-sectional view showing a valve body, a part of a shaft portion, and a pilot body (seat surface) of the pressure control valve. [Figure 5] 1 is an explanatory diagram (cross-sectional view) showing the "open state" and "state in transition from closed to open" of a pressure control valve, with the gap between the shaft and the bearing, the inclination of the shaft, etc. exaggerated. [Figure 6] FIG. 4 is a characteristic diagram showing a change in discharge pressure of a pressure control valve over time. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a pressure control valve and a damping force adjustable shock absorber according to an embodiment will be described with reference to the accompanying drawings, taking as an example a case where the pressure control valve and the damping force adjustable shock absorber are used in a damping force adjustable hydraulic shock absorber.

[0013] 1, a damping force adjustable hydraulic shock absorber 1 (hereinafter referred to as shock absorber 1) is provided with a damping force adjustment mechanism 17 that uses a solenoid actuator 34 as a drive source. That is, the shock absorber 1 as a damping force adjustable shock absorber is configured to include an outer cylinder 2 and an inner cylinder 4 as cylinders, a piston 5, a piston rod 8, and the damping force adjustment mechanism 17.

[0014] The shock absorber 1, which is a hydraulic shock absorber, has a cylindrical outer cylinder 2 with a bottom that forms an outer shell. The lower end of the outer cylinder 2 is closed by a bottom cap 3 using welding or the like. The upper end of the outer cylinder 2 forms a crimped portion 2A that is bent radially inward. A rod guide 9 and a seal member 10 are provided between the crimped portion 2A and the inner cylinder 4. Meanwhile, an opening 2B is formed at the lower side of the outer cylinder 2, concentric with a connection port 12C of the intermediate cylinder 12. A damping force adjustment mechanism 17 is attached to the lower side of the outer cylinder 2, facing the opening 2B. The bottom cap 3 is provided with a mounting eye 3A that is attached, for example, to the wheel side of a vehicle.

[0015] An inner cylinder 4 is provided coaxially with the outer cylinder 2 within the outer cylinder 2. The lower end of the inner cylinder 4 is fitted into and attached to a bottom valve 13. The upper end of the inner cylinder 4 is fitted into and attached to a rod guide 9. Oil as a working fluid is sealed within the outer cylinder 2 and inner cylinder 4 as cylinders. The working fluid is not limited to oil, and may be, for example, water mixed with an additive.

[0016] An annular reservoir chamber A is formed between the inner cylinder 4 and the outer cylinder 2. Gas is sealed in the reservoir chamber A along with oil. This gas may be air at atmospheric pressure, or a gas such as compressed nitrogen gas may also be used. The reservoir chamber A compensates for the advancement and retreat of the piston rod 8. An oil hole 4A is drilled radially at a position midway along the length (axial direction) of the inner cylinder 4, which constantly connects the rod-side oil chamber B with the annular oil chamber D.

[0017] The piston 5 is slidably fitted in the inner cylinder 4. The piston 5 is inserted into the inner cylinder 4, and divides (partitions) the interior of the inner cylinder 4 into two chambers: a rod-side oil chamber B (rod-side chamber) and a bottom-side oil chamber C (bottom-side chamber). The piston 5 is formed with a plurality of oil passages 5A, 5B spaced apart in the circumferential direction, which allow communication between the rod-side oil chamber B and the bottom-side oil chamber C.

[0018] Here, an extension-side disc valve 6 is provided on the lower end surface of the piston 5. The extension-side disc valve 6 opens when the pressure in the rod-side oil chamber B exceeds a set relief pressure as the piston 5 slides upward during the extension stroke of the piston rod 8, and relieves the pressure at this time to the bottom-side oil chamber C via each oil passage 5A. The set relief pressure is set to a pressure higher than the valve-opening pressure when the damping force adjusting mechanism 17 is set to hard.

[0019] A compression-side check valve 7 is provided on the upper end surface of the piston 5. The check valve 7 opens when the piston 5 slides downward during the compression stroke of the piston rod 8 and closes at other times. The check valve 7 allows oil in the bottom-side oil chamber C to flow through each oil passage 5B toward the rod-side oil chamber B and prevents oil from flowing in the opposite direction. The opening pressure of the check valve 7 is set lower than the opening pressure when the damping force adjustment mechanism 17 is set to soft, so that it generates virtually no damping force. This means that the force is below the friction of the piston 5 and seal member 10 and does not affect the movement of the vehicle.

[0020] The piston rod 8 extends axially (vertically in FIG. 1 ) within the inner cylinder 4. The lower end of the piston rod 8 is inserted into the inner cylinder 4. The piston rod 8 is fixed to the piston 5 with a nut 8A or the like. The upper end of the piston rod 8 protrudes outside the outer cylinder 2 and the inner cylinder 4 via a rod guide 9. That is, the lower end of the piston rod 8 is connected to the piston 5, and the upper end of the piston rod 8 extends outside the inner cylinder 4 and the outer cylinder 2. The lower end of the piston rod 8 may be further extended to protrude outward from the bottom portion (for example, the bottom cap 3) to form a so-called double rod.

[0021] A stepped cylindrical rod guide 9 is provided at the upper end of the inner cylinder 4. The rod guide 9 positions the upper part of the inner cylinder 4 at the center of the outer cylinder 2 and guides the piston rod 8 axially slidably on its inner periphery. An annular seal member 10 is provided between the rod guide 9 and the crimped portion 2A of the outer cylinder 2. The seal member 10 is formed, for example, by baking an elastic material such as rubber onto a metal circular plate having a hole in the center through which the piston rod 8 is inserted. The inner periphery of the elastic material of the seal member 10 slides against the outer periphery of the piston rod 8, thereby providing a seal between the piston rod 8 and the rod guide 9.

[0022] The seal member 10 has a lip seal 10A formed on its underside as a check valve that extends so as to come into contact with the rod guide 9. The lip seal 10A is disposed between the oil sump chamber 11 and the reservoir chamber A. The lip seal 10A allows oil and liquid in the oil sump chamber 11 to flow toward the reservoir chamber A through the return passage 9A of the rod guide 9, and prevents reverse flow.

[0023] An intermediate cylinder 12 made of a cylindrical body is disposed between the outer cylinder 2 and the inner cylinder 4. The intermediate cylinder 12 is attached, for example, to the outer periphery of the inner cylinder 4 via upper and lower cylindrical seals 12A and 12B. The intermediate cylinder 12 defines an annular oil chamber D therein that extends to surround the entire outer periphery of the inner cylinder 4. The annular oil chamber D is an oil chamber independent of the reservoir chamber A. The annular oil chamber D is constantly in communication with the rod-side oil chamber B via a radial oil hole 4A formed in the inner cylinder 4. The annular oil chamber D forms a flow path through which a flow of hydraulic fluid occurs as the piston rod 8 moves. A connection port 12C is provided at the lower end of the intermediate cylinder 12 to which a connection pipe 20 of a damping force control valve 18 is attached.

[0024] The bottom valve 13 is located at the lower end of the inner cylinder 4 and is provided between the bottom cap 3 and the inner cylinder 4. The bottom valve 13 is composed of a valve body 14 that separates (divides) the reservoir chamber A and the bottom-side oil chamber C between the bottom cap 3 and the inner cylinder 4, a contraction-side disc valve 15 provided on the underside of the valve body 14, and an extension-side check valve 16 provided on the upper side of the valve body 14. The valve body 14 has oil passages 14A and 14B formed at intervals in the circumferential direction, which allow communication between the reservoir chamber A and the bottom-side oil chamber C.

[0025] The compression-side disc valve 15 opens when the pressure in the bottom-side oil chamber C exceeds a set relief pressure as the piston 5 slides downward during the compression stroke of the piston rod 8, and relieves the pressure at this time via each oil passage 14A to the reservoir chamber A. The set relief pressure is set to a pressure higher than the valve-opening pressure when the damping force adjusting mechanism 17 is set to hard.

[0026] The extension-side check valve 16 opens when the piston 5 slides upward during the extension stroke of the piston rod 8, and closes at other times. The check valve 16 allows oil in the reservoir chamber A to flow through each oil passage 14B toward the bottom-side oil chamber C, and prevents oil from flowing in the opposite direction. The opening pressure of the check valve 16 is set to a pressure lower than the opening pressure when the damping force adjustment mechanism 17 is set to soft, and therefore generates virtually no damping force.

[0027] Next, the damping force adjusting mechanism 17 for variably adjusting the damping force generated by the shock absorber 1 will be described with reference to FIG. 2 in addition to FIG.

[0028] The damping force adjustment mechanism 17 generates a damping force by controlling the flow of hydraulic fluid generated by the sliding of the piston 5 inside the cylinder (inner tube 4), and variably adjusts the damping force generated by the shock absorber 1. Note that the damping force adjustment mechanism 17 in Fig. 2 shows a state in which the plunger 48, shaft 49, and pilot valve element 32 have moved to the left in Fig. 2 by externally energizing the solenoid 35A of the solenoid actuator 34 (for example, control to generate a hard damping force). In other words, the damping force adjustment mechanism 17 in Fig. 2 shows a closed valve state in which the pilot valve element 32, which is the valve element of the pressure control valve 33, is seated on the seat surface 26E of the pilot body 26.

[0029] As shown in Fig. 1, the damping force adjustment mechanism 17 is disposed such that its base end (the left end in Fig. 1) is interposed between the reservoir chamber A and the annular oil chamber D, and its tip end (the right end in Fig. 1) protrudes radially outward from the lower part of the outer cylinder 2. The damping force adjustment mechanism 17 generates a damping force by controlling the flow of oil from the annular oil chamber D to the reservoir chamber A using a damping force adjustment valve 18 (main valve 23, pilot valve body 32). The valve opening pressure of the damping force adjustment valve 18 (main valve 23, pilot valve body 32) is adjusted using a pressure control valve 33 driven by a solenoid actuator 34, thereby variably adjusting the generated damping force.

[0030] In this way, the damping force adjustment mechanism 17 generates a damping force by controlling the flow of hydraulic fluid (oil) generated by the sliding of the piston 5 inside the inner cylinder 4. To this end, the damping force adjustment mechanism 17 is configured to include a damping force adjustment valve 18 and a solenoid actuator 34. The damping force adjustment valve 18 generates a damping force with hard or soft characteristics by variably controlling the flow of hydraulic fluid from the annular oil chamber D to the reservoir chamber A. The damping force adjustment valve 18 is driven by the solenoid actuator 34. That is, the damping force adjustment valve 18 is a valve whose opening and closing operation is adjusted by the solenoid actuator 34, and is provided in a flow path (for example, between the annular oil chamber D and the reservoir chamber A) where a flow of hydraulic fluid occurs due to the movement (extension and contraction) of the piston rod 8.

[0031] The damping force control valve 18 includes a main valve 23 and a pilot valve element 32. The pilot valve element 32, together with a solenoid actuator 34, constitutes a pressure control valve 33. That is, the pilot valve element 32 corresponds to the valve element of the pressure control valve 33. The solenoid actuator 34 adjusts the opening and closing operation of the damping force control valve 18 (pilot valve element 32, and therefore the main valve 23). In this case, the valve opening pressure of the damping force control valve 18 (pilot valve element 32, and therefore the main valve 23) is adjusted by the solenoid actuator 34, which is used as a damping force variable actuator, and thereby the generated damping force is variably controlled to have hard or soft characteristics.

[0032] Here, the damping force control valve 18 is configured to include a valve case 19, a connecting pipe body 20, and a valve member 21. The valve case 19 is formed in a substantially cylindrical shape, with its base end fixed to the periphery of the opening 2B of the outer cylinder 2 and its tip end protruding radially outward from the outer cylinder 2. The connecting pipe body 20 has its base end fixed to the connection port 12C of the intermediate cylinder 12 and its tip end forming an annular flange portion 20A that is disposed inside the valve case 19 with a gap. The valve member 21 abuts against the flange portion 20A of the connecting pipe body 20.

[0033] 2, the base end side of the valve case 19 forms an annular inner flange portion 19A extending radially inward. The tip end side of the valve case 19 forms an externally threaded portion 19B onto which a lock nut 53 is threadedly attached, connecting the valve case 19 to a yoke 39 (one side cylindrical portion 39G) of the solenoid actuator 34. An annular oil chamber 19C that is constantly in communication with the reservoir chamber A is formed between the inner circumferential surface of the valve case 19 and the outer circumferential surface of the valve member 21, and further between the inner circumferential surface of the valve case 19 and the outer circumferential surfaces of the pilot body 26, etc. Note that instead of connecting the valve case 19 to the solenoid actuator 34 with the lock nut 53, for example, the tip end side of the valve case may be crimped to the yoke of the solenoid (a configuration without using a lock nut).

[0034] The inside of the connecting pipe body 20 has an oil passage 20B, one side of which is connected to the annular oil chamber D and the other side of which extends to the position of the valve member 21. An annular spacer 22 is sandwiched between the flange portion 20A of the connecting pipe body 20 and the inner flange portion 19A of the valve case 19. The spacer 22 has a plurality of radially extending notches 22A that serve as radial oil passages for communicating between the oil chamber 19C and the reservoir chamber A. In this embodiment, the spacer 22 is configured to have the notches 22A for forming the oil passages. However, instead of the spacer 22, notches (grooves) for forming the oil passages may be radially provided in the inner flange portion 19A of the valve case 19.

[0035] The valve member 21 is provided with a central hole 21A located at the radial center and extending in the axial direction. The valve member 21 also has a plurality of oil passages 21B spaced apart circumferentially around the central hole 21A. One side (the left side in FIGS. 1 and 2) of each oil passage 21B is constantly connected to an oil passage 20B of the connecting pipe body 20. The other end face (the right side in FIGS. 1 and 2) of the valve member 21 is provided with an annular recess 21C formed to surround the other opening of the oil passage 21B, and an annular valve seat 21D located radially outward of the annular recess 21C and on which the main valve 23 is seated and released. Each oil passage 21B of the valve member 21 serves as a flow path through which pressurized oil flows at a flow rate corresponding to the aperture of the main valve 23 between the oil passage 20B of the connecting pipe body 20, which is connected to the annular oil chamber D, and the oil chamber 19C of the valve case 19, which is connected to the reservoir chamber A.

[0036] The main valve 23 is configured as a disc valve. The inner peripheral side of the main valve 23 is sandwiched between the valve member 21 and the large diameter portion 24A of the pilot pin 24. The outer peripheral side of the main valve 23 is seated and released from the annular valve seat 21D of the valve member 21. An elastic seal member 23A is fixed to the outer peripheral portion of the back side of the main valve 23 by means of baking or the like. The main valve 23 opens when it receives pressure from the oil passage 21B side (annular oil chamber D side) of the valve member 21 and releases itself from the annular valve seat 21D. As a result, the oil passage 21B (annular oil chamber D side) of the valve member 21 is connected to the oil chamber 19C (reservoir chamber A side) via the main valve 23. The amount (flow rate) of pressurized oil flowing in the direction of arrow Y at this time is variably adjusted according to the opening of the main valve 23.

[0037] The pilot pin 24 is formed in a stepped cylindrical shape and has an annular large-diameter portion 24A provided in the axially intermediate portion. The pilot pin 24 has a central hole 24B extending axially on its inner circumferential side. A small-diameter hole (orifice 24C) is formed in one end (the end on the connecting pipe body 20 side) of the central hole 24B. One end (the left end in Figures 1 and 2) of the pilot pin 24 is press-fitted into the central hole 21A of the valve member 21. In this state, the large-diameter portion 24A of the pilot pin 24 clamps the main valve 23 between itself and the valve member 21.

[0038] The other end side (the right end side in FIGS. 1 and 2) of the pilot pin 24 is fitted into a central hole 26C of the pilot body 26. An oil passage 25 extending in the axial direction is formed between the central hole 26C of the pilot body 26 and the other end side of the pilot pin 24. This oil passage 25 communicates with a back pressure chamber 27 formed between the main valve 23 and the pilot body 26. In other words, a plurality of oil passages 25 extending in the axial direction are provided in the circumferential direction on the side surface of the other end side of the pilot pin 24, and other circumferential positions are press-fitted into the central hole 26C of the pilot body 26.

[0039] The pilot body 26 is formed as a generally bottomed cylindrical body and includes a cylindrical portion 26A with a stepped hole formed on the inside and a bottom portion 26B that closes the cylindrical portion 26A. The bottom portion 26B of the pilot body 26 has a central hole 26C into which the other end of the pilot pin 24 fits. A protruding cylindrical portion 26D is integrally formed on one end (the left end in FIGS. 1 and 2 ) of the bottom portion 26B of the pilot body 26, located on the outer diameter side and protruding along its entire circumference toward the valve member 21. The elastic seal member 23A of the main valve 23 is fluid-tightly fitted to the inner circumferential surface of the protruding cylindrical portion 26D, thereby forming a backpressure chamber 27 between the main valve 23 and the pilot body 26. The backpressure chamber 27 generates pressure (internal pressure, pilot pressure) that presses the main valve 23 in a valve-closing direction, i.e., in a direction that seats the main valve 23 against the annular valve seat 21D of the valve member 21.

[0040] A seat surface 26E on which the pilot valve element 32 seats and leaves is provided so as to surround the central hole 26C at the other end side (the right end side in FIGS. 1 and 2) of the bottom portion 26B of the pilot body 26. Inside the cylindrical portion 26A of the pilot body 26, there are disposed a return spring 28 that urges the pilot valve element 32 in a direction away from the seat surface 26E of the pilot body 26, a disk valve 29 that constitutes a fail-safe valve when the solenoid actuator 34 is in a de-energized state (when the pilot valve element 32 is farthest from the seat surface 26E), a retaining plate 30 in which an oil passage 30A is formed on the central side, and the like.

[0041] A cap 31 is fitted and fixed to the open end of the cylindrical portion 26A of the pilot body 26, with the return spring 28, disc valve 29, retaining plate 30, etc., arranged inside the cylindrical portion 26A. Notches 31A are formed in the cap 31, for example, at four positions spaced apart in the circumferential direction. As indicated by arrows X in Fig. 2, the notches 31A serve as flow paths that allow oil that has flowed through the oil passage 30A of the retaining plate 30 to the solenoid actuator 34 side to circulate to the oil chamber 19C (reservoir chamber A side).

[0042] The pilot valve element 32, together with the pilot body 26, constitutes a pilot valve (pilot control valve). The pilot valve element 32, together with the solenoid actuator 34, constitutes a pressure control valve 33. The pilot valve element 32 is formed in a stepped cylindrical shape. The tip of the pilot valve element 32, i.e., the tip that seats on and separates from the seat surface 26E of the pilot body 26, is tapered. A shaft 49 of the solenoid actuator 34 is fitted and fixed inside the pilot valve element 32, and the valve opening pressure of the pilot valve element 32, and therefore the valve opening pressure of the main valve 23, is adjusted in response to the supply of electricity to the solenoid actuator 34.

[0043] That is, the pilot valve element 32 is controlled by the axial movement of a shaft 49 of the solenoid actuator 34 (more specifically, a plunger 48 fixed to the shaft 49). A flange 32A that serves as a spring bearing is formed around the entire circumference on the base end side of the pilot valve element 32. When the solenoid actuator 34 is not energized, that is, when the pilot valve element 32 is displaced to the fully open position where it is farthest from the seat surface 26E, the flange 32A comes into contact with the inner periphery of the disc valve 29, thereby forming a fail-safe valve.

[0044] Next, the solenoid actuator 34 will be described with reference to Fig. 3 in addition to Fig. 1 and Fig. 2. Note that in Fig. 3, reference numerals are assigned with the right side in the left-right direction of Fig. 2 facing up.

[0045] The solenoid actuator 34 is incorporated into the damping force adjustment mechanism 17 as a variable damping force actuator of the damping force adjustment mechanism 17. That is, the solenoid actuator 34 is used in a damping force adjustable shock absorber to adjust the opening and closing operation of the damping force adjustment valve 18. The solenoid actuator 34, together with the pilot valve element 32, constitutes the pressure control valve 33. The solenoid actuator 34 includes a molded coil 35, a housing 36 as a magnetic member (storing member), a yoke 39, an anchor 41 as a fixed core (stator), a cylinder 44 as a joining member (non-magnetic ring), a plunger 48 as a movable core (mover), a shaft portion 49 as an operating pin, and a cover member 51.

[0046] The molded coil 35 is formed into a substantially cylindrical shape by integrally covering (molding) the solenoid 35A with a resin member 35B such as a thermosetting resin. The solenoid 35A includes a coil bobbin 35A1 and a coil 35A2. The coil 35A2 is wound around the coil bobbin 35A1. A cable outlet 35C (FIG. 3) that protrudes axially or radially outward is provided at a portion of the circumference of the molded coil 35. An electric cable (not shown) is connected to the cable outlet 35C. The solenoid 35A becomes an electromagnet and generates a magnetic field (magnetic force) when power is supplied (energized) to the coil 35A2, which is wound in a circular shape around the coil bobbin 35A1, via an external cable.

[0047] The housing 36 constitutes a magnetic member (storage member) disposed on the inner periphery of the solenoid 35A. The housing 36 is formed as a covered cylindrical body using a magnetic material (magnetic substance), such as low-carbon steel or carbon steel for mechanical structures (S10C). The housing 36 includes a cylindrical storage portion 36A serving as a storage portion, a lid portion 36B, and a small-diameter cylindrical portion 36C. The cylindrical storage portion 36A extends in the direction of the winding axis of the solenoid 35A (coil 35A2) and is open at one end (left side in FIG. 2, bottom side in FIG. 3). The lid portion 36B closes the other end (right side in FIG. 2, top side in FIG. 3) of the cylindrical storage portion 36A. The small-diameter cylindrical portion 36C is located on the open side (one side) of the cylindrical storage portion 36A and is formed to reduce the outer diameter of the cylindrical storage portion 36A.

[0048] The inner periphery of the cylinder 44 is joined to the outer periphery of the small diameter cylindrical portion 36C of the housing 36 by brazing. The inner diameter of the cylindrical storage portion 36A of the housing 36 is formed to be slightly larger than the outer diameter of the plunger 48. The plunger 48 is housed within the cylindrical storage portion 36A so as to be movable in the axial direction. That is, one end of the housing 36 in the axial direction is open, and the plunger 48 is housed therein. The housing 36 and the cylinder 44 form a pressure vessel by press-fitting the housing 36 (small diameter cylindrical portion 36C) into the inside of the cylinder 44 and brazing them together.

[0049] Meanwhile, the lid portion 36B of the housing 36 is integrally formed with the cylindrical storage portion 36A as a covered cylinder that closes the other axial side of the cylindrical storage portion 36A. The lid portion 36B has a stepped shape with an outer diameter smaller than that of the cylindrical storage portion 36A. A fitting cylindrical portion 51A of a cover member 51 is fitted onto the outer periphery of the lid portion 36B. The housing 36 also has a bottomed stepped hole 37 formed inside the lid portion 36B. The stepped hole 37 has a bearing mounting hole portion 37A and a small-diameter hole portion 37B located deeper than the bearing mounting hole portion 37A and formed with a smaller diameter. A first bearing 38 is provided within the bearing mounting hole portion 37A to slidably support a shaft portion 49 that serves as an actuation pin. The first bearing 38 is formed, for example, by a cylindrical bushing (bearing cylinder).

[0050] The lid portion 36B of the housing 36 is disposed such that its other end surface faces the lid plate 51B of the cover member 51, with an axial gap therebetween. This axial gap serves to prevent axial force from being directly applied to the housing 36 from the lid plate 51B side of the cover member 51 via the lid portion 36B. The lid portion 36B of the housing 36 does not necessarily have to be formed integrally with the cylindrical storage portion 36A from the same material (magnetic material). In this case, the lid portion 36B can be formed from a rigid metal material, ceramic material, or fiber-reinforced resin material, instead of a magnetic material. The joint between the cylindrical storage portion 36A and the lid portion 36B of the housing 36 is positioned in consideration of the transfer of magnetic flux.

[0051] The yoke 39 is provided on one side of the plunger 48 in the direction of movement. The yoke 39 is a magnetic member that, together with the housing 36, forms a magnetic circuit (magnetic path) across the inner and outer peripheries of the solenoid 35A. That is, the yoke 39 is formed of the same magnetic material as the housing 36. The yoke 39 includes an annular portion 39B that extends radially from one axial side of the solenoid 35A (one side in the winding axis direction of the coil 35A2) and whose inner periphery forms a stepped fixing hole 39A, and a cylindrical protrusion 39C that protrudes cylindrically from the inner periphery of the annular portion 39B toward the other axial side (the solenoid 35A side) along the axial direction of the fixing hole 39A. The cylindrical protrusion 39C forms a protrusion (cylindrical portion) for joining with the cylinder 44, and the cylinder 44 is inserted into the inner diameter side of the cylindrical protrusion 39C.

[0052] In other words, yoke 39 has a fixing hole 39A, and anchor 41 is disposed within fixing hole 39A. An inward flange 39D that protrudes radially inward along the entire circumference is provided within fixing hole 39A. One axial end face (one end face) of cylinder 44 abuts against the side face (the side face on the solenoid 35A side) of inward flange 39D. The outer periphery of one axial end of cylinder 44 is fitted into the inner periphery of yoke 39, i.e., the inner surface of fixing hole 39A (in other words, the inner circumferential surface of cylindrical protrusion 39C).

[0053] The yoke 39 is formed as a single unit including a cylindrical one-side tube portion 39G extending from the outer periphery of the annular portion 39B toward one axial side (the main valve 23 side), an other-side tube portion 39H extending from the outer periphery of the annular portion 39B toward the other axial side (the cover member 51 side) and formed to surround the molded coil 35 from the radial outside, and a crimped portion 39J provided at the tip of the other-side tube portion 39H and holding the flange 51C of the cover member 51 in a non-removable state. The other-side tube portion 39H of the yoke 39 is provided with a notch 39K for exposing the cable outlet portion 35C of the molded coil 35 to the outside of the other-side tube portion 39H.

[0054] Between one side cylindrical portion 39G and the other side cylindrical portion 39H of the yoke 39, engagement recesses 39L having a semicircular cross section are provided (along the entire circumference or at multiple locations spaced apart in the circumferential direction) so as to open onto the outer circumferential surface of the yoke 39. A lock nut 53 threadedly attached to the valve case 19 is engaged with the engagement recesses 39L via a retaining ring 54 (see FIG. 2).

[0055] The anchor 41 is provided on one side of the plunger 48 in the moving direction. The anchor 41 is disposed axially opposite the plunger 48. The anchor 41 is a fixed core (stator) fixed in the fixing hole 39A of the yoke 39 by press-fitting or other means. The anchor 41, like the housing 36 and the yoke 39, is made of a magnetic material (magnetic substance) such as low-carbon steel or carbon steel for mechanical structures (S10C) and is shaped to fill the fixing hole 39A of the yoke 39 from the inside. The anchor 41 is formed as a short cylindrical annular body with a through-hole 41A extending axially at its center. One axial side surface of the anchor 41 (the surface axially facing the cap 31 shown in FIG. 2 ) is formed to be flat, similar to one side surface of the annular portion 39B of the yoke 39.

[0056] A circular recessed portion 41B is recessed on the other axial side of the anchor 41 (the other side axially facing the plunger 48) so as to be coaxial with the cylindrical storage portion 36A of the housing 36. The recessed portion 41B is formed as a circular groove with a diameter slightly larger than that of the plunger 48 so that the plunger 48 can be inserted therein and retracted by magnetic force. For this purpose, a cylindrical outer peripheral protrusion 41C is provided on the other side of the anchor 41. The outer peripheral surface on the opening side of the outer peripheral protrusion 41C is formed as a conical surface so that the magnetic characteristics between the anchor 41 and the plunger 48 are linear. In other words, the outer peripheral protrusion 41C, also called a corner portion, protrudes cylindrically from the outer peripheral side of the anchor 41 toward the other axial side. The outer peripheral surface (the outer peripheral surface on the opening side) of the outer peripheral protrusion 41C is a tapered conical surface so that the outer diameter gradually decreases toward the other axial side (the opening side).

[0057] Additionally, a side surface portion 41D is formed on the outer periphery of the anchor 41, extending in a direction away from the opening of the cylindrical storage portion 36A of the housing 36 along the outer periphery of the outer periphery protrusion 41C. The end of this side surface portion 41D away from the opening forms an annular flange portion 41E that protrudes radially outward. The annular flange portion 41E is located at a position significantly spaced apart from the open end of the cylindrical storage portion 36A of the housing 36 to one side in the axial direction (i.e., the end opposite the recessed portion 41B).

[0058] The annular flange portion 41E is fixed, for example, by press-fitting or other means into the fixing hole 39A of the yoke 39. The annular flange portion 41E serves as a fixing portion for the anchor 41 (side surface portion 41D) to the fixing hole 39A of the yoke 39, and is also the portion where the flange portion 41E and the fixing hole 39A face each other in the radial direction. The side surface 41D of the anchor 41 (excluding the annular flange portion 41E) faces the inner circumferential surface of the cylinder 44 and the inner surface of the inward flange portion 39D of the yoke 39 via a gap (radial gap).

[0059] As shown in Fig. 3, a second bearing 43 for slidably supporting the shaft portion 49 is fitted into a stepped through hole 41A formed on the center (inner periphery) side of the anchor 41. The second bearing 43 is formed, for example, by a cylindrical bushing (bearing sleeve). Meanwhile, as shown in Fig. 2, the pilot body 26, return spring 28, disc valve 29, retaining plate 30, cap 31, etc. are inserted into the inner periphery side of one side cylindrical portion 39G of the yoke 39. In addition, the valve case 19 is fitted (externally attached) onto the outer periphery side of the one side cylindrical portion 39G.

[0060] The cylinder 44 is disposed between the yoke 39 and the anchor 41 in the radial direction. The cylinder 44 is also disposed between the yoke 39 and the housing 36 in the axial and radial directions. That is, the cylinder 44 is a non-magnetic connecting member (joint member) located between the small-diameter cylindrical portion 36C of the housing 36 and the cylindrical protrusion portion 39C of the yoke 39 and disposed on the inner periphery of the solenoid 35A. The cylinder 44 is made of a non-magnetic material. More specifically, the cylinder 44 is formed as a cylindrical body (simple cylindrical body) using a non-magnetic material such as austenitic stainless steel.

[0061] The outer periphery of the cylinder 44 at one end (yoke 39 side) in the winding axis direction of the solenoid 35A (coil 35A2) is joined to the inner periphery of the yoke 39 (fixing hole 39A, cylindrical protrusion 39C). As a result, one axial side of the cylinder 44 is fixed to the yoke 39, which serves as the stator. Also, the inner periphery of the cylinder 44 at the other end (housing 36 side) in the winding axis direction of the molded coil 35 (solenoid 35A) is joined to the outer periphery of the housing 36 (small diameter cylindrical portion 36C). That is, the cylinder 44 is fitted (press-fitted) onto the outside (outer periphery side) of the small diameter cylindrical portion 36C of the housing 36, and the two are joined by brazing. In this embodiment, the housing 36 and the cylinder 44, and the cylinder 44 and the yoke 39 are joined via brazing material. That is, the cylinder 44 is joined to the small diameter cylindrical portion 36C of the housing 36 and the cylindrical protrusion portion 39C of the yoke 39 by brazing.

[0062] The plunger 48, also called an armature, is disposed between the cylindrical storage portion 36A of the housing 36 and the recessed portion 41B of the anchor 41. The plunger 48 is a movable iron core (mover) made of a magnetic material that is disposed so as to be movable in the winding axis direction of the solenoid 35A (coil 35A2). That is, the plunger 48 is disposed on the inner periphery of the solenoid 35A so as to be movable in the axial direction. The plunger 48 is disposed on the inner periphery of the cylindrical storage portion 36A of the housing 36, the recessed portion 41B of the anchor 41, the cylindrical protrusion 39C of the yoke 39, and the cylinder 44, and is movable in the axial direction between the cylindrical storage portion 36A of the housing 36 and the recessed portion 41B of the anchor 41. That is, the plunger 48 is arranged on the inner circumferential side of the storage cylindrical portion 36A of the housing 36 and the recessed portion 41B of the anchor 41, and is movable in the axial direction via the first and second bearings 38, 43 and the shaft portion 49 by the magnetic force generated in the solenoid 35A.

[0063] Plunger 48 is fixed (integrated) to shaft 49 that extends through the center of plunger 48 and moves together with shaft 49. Shaft 49 is supported by cover 36B of housing 36 and anchor 41 via first and second bearings 38, 43 so as to be slidable in the axial direction. Here, plunger 48 is formed in a substantially cylindrical shape using an iron-based magnetic material, similar to housing 36, yoke 39, and anchor 41, for example. A magnetic force generated in solenoid 35A generates a thrust (attraction force) on plunger 48 in a direction that attracts it toward recess 41B of anchor 41.

[0064] The shaft portion 49 is an operating pin that transmits the thrust of the plunger 48 to the pilot valve element 32, and is formed from a hollow rod. The shaft portion 49 moves integrally with the plunger 48. That is, the plunger 48 is fixed integrally to the axially middle portion of the shaft portion 49 by means of press fitting or the like, thereby forming the plunger 48 and the shaft portion 49 into a sub-assembly. Both axial ends of the shaft portion 49 are slidably supported by the cover portion 36B on the housing 36 side and the yoke 39 (anchor 41) via first and second bearings 38, 43.

[0065] One end of the shaft 49 (the left end in FIG. 2 and the lower end in FIG. 3) protrudes axially from the anchor 41 (yoke 39), and the pilot valve element 32 of the pressure control valve 33 is fixed to the protruding end. Therefore, the pilot valve element 32 moves axially together with the plunger 48 and the shaft 49. In other words, the set valve-opening pressure of the pilot valve element 32 is a pressure value corresponding to the thrust of the plunger 48 based on the energization of the solenoid 35A. The plunger 48 moves axially due to the magnetic force from the solenoid 35A (coil 35A2), thereby opening and closing the pilot valve element 32 relative to the pilot body 26.

[0066] The cover member 51 is a magnetic cover that covers the molded coil 35 from the outside together with the other-side cylindrical portion 39H of the yoke 39. The cover member 51 is made of a magnetic material (magnetic substance) and serves as a lid that covers the molded coil 35 from the other axial side, and forms a magnetic circuit (magnetic path) outside the molded coil 35 (solenoid 35A) together with the other-side cylindrical portion 39H of the yoke 39. The cover member 51 is formed in a covered cylindrical shape as a whole, and is generally composed of a cylindrical fitting cylindrical portion 51A and a disk-shaped cover plate 51B that closes the other end side of the fitting cylindrical portion 51A (the right end portion in FIG. 2, the upper end portion in FIG. 3).

[0067] Here, the fitting cylindrical portion 51A of the cover member 51 is inserted onto the outer periphery of the lid portion 36B of the housing 36, and in this state, the lid portion 36B of the housing 36 is accommodated inside. Meanwhile, the outer periphery of the lid plate 51B of the cover member 51 forms an annular flange 51C extending radially outward from the fitting cylindrical portion 51A, and the outer periphery of the flange 51C is fixed to a crimped portion 39J provided on the other-side cylindrical portion 39H of the yoke 39. As a result, the other-side cylindrical portion 39H of the yoke 39 and the lid plate 51B of the cover member 51 are pre-assembled (sub-assembled) with the molded coil 35 housed inside, as shown in FIG. In this manner, with the molded coil 35 housed inside the other-side cylindrical portion 39H of the yoke 39 and the lid plate 51B of the cover member 51, the lid portion 36B of the housing 36 is fitted into the fitting cylindrical portion 51A of the cover member 51. This allows magnetic flux to be transferred between the fitting cylindrical portion 51A of the cover member 51, the lid plate 51B, and the yoke 39.

[0068] The yoke 39 and cover member 51, with the molded coil 35 housed inside as shown in Fig. 3, are fastened to the valve case 19 of the damping force control valve 18 using a lock nut 53 and a retaining ring 54 as fastening members as shown in Fig. 2. In this case, the retaining ring 54 is attached to the engagement recess 39L of the yoke 39 prior to the lock nut 53. The retaining ring 54 partially protrudes radially outward from the engagement recess 39L of the yoke 39 and transmits the fastening force of the lock nut 53 to one side cylindrical portion 39G of the yoke 39.

[0069] The lock nut 53 is formed as a stepped cylindrical body and is provided with: a female threaded portion 53A located on one axial side thereof and threadedly engaging the male threaded portion 19B of the valve case 19 on its inner peripheral side; and an engaging cylindrical portion 53B bent radially inward so that its inner diameter is smaller than the outer diameter of the retaining ring 54 and engaging with the retaining ring 54 from the outside. The lock nut 53 is a fastening member that integrally connects the damping force control valve 18 and the solenoid actuator 34 by threading the female threaded portion 53A into the male threaded portion 19B of the valve case 19 with the inner surface of the engaging cylindrical portion 53B abutting against the retaining ring 54 attached to the engaging recess 39L of the yoke 39.

[0070] The damping force adjustable shock absorber of the aforementioned Patent Document 1 variably controls the damping force by directly adjusting the hydraulic fluid flow resistance using the valve element of the pressure control valve and by adjusting the internal pressure of the backpressure chamber of the main valve to adjust the valve opening pressure of the main valve. According to the prior art, when the pressure control valve is in a closed state where the valve element and the seating surface are in contact with each other, a hollow circular contact surface with uniform surface pressure is formed between the valve element and the seating surface. With this structure, when the valve is opened, the pressure within the contact surface decreases, and the differential pressure between the pressure within the contact surface and the pressure downstream of the valve element acts as a resistance force against the valve opening movement of the valve element. As a result, the valve element opens over the entire contact surface when the combined force of the resistance force and the thrust force of the solenoid actuator is exceeded. After the valve is opened, the resistance force disappears, causing the valve element to vibrate due to a sudden large acceleration. This can result in a sudden change in oil flow rate and pulsation of the hydraulic pressure (discharge pressure), potentially generating unwanted noise (rattling noise, 100-500 Hz). In other words, in the case of conventional technology, when the pressure control valve opens (when the valve body moves away from the seat surface), the pressure applied to the valve body changes suddenly, which can cause an unwanted noise (a rattling sound).

[0071] Therefore, in this embodiment, the tip of the pilot valve element 32 serving as a valve element is inclined. This suppresses vibration of the pilot valve element 32 when the pilot valve element 32 opens, i.e., when the pilot valve element 32 separates from the seat surface 26E of the pilot body 26, thereby reducing pulsation of the hydraulic pressure (discharge pressure). These points will be described below.

[0072] First, as shown in FIG. 1, the shock absorber 1 includes an inner cylinder 4 and an outer cylinder 2 serving as cylinders, a piston 5, a piston rod 8, and a pressure control valve 33. The pressure control valve 33 controls the flow of fluid generated by the sliding of the piston 5 inside the inner cylinder 4 to generate a damping force and adjust the valve opening pressure. The pressure control valve 33 is provided in the shock absorber 1. As shown in FIG. 3, the pressure control valve 33 includes a pilot valve element 32 serving as a valve element, a shaft portion 49 serving as an actuating pin, a plunger 48, a solenoid 35A, a first bearing 38, and a second bearing 43. As shown in FIGS. 2 and 5A, the pilot valve element 32 is seated on a seat surface 26E. The seat surface 26E corresponds to a valve seat portion (valve seat surface) provided on the bottom portion 26B of the pilot body 26.

[0073] As shown in FIG. 3, the shaft portion 49 is provided integrally with the pilot valve element 32. The shaft portion 49 is inserted into the plunger 48. The plunger 48 biases the pilot valve element 32 toward the seat surface 26E to adjust the valve-opening pressure. The solenoid 35A adjusts the thrust of the plunger 48. The solenoid 35A includes a coil bobbin 35A1 and a coil 35A2. The first bearing 38 and the second bearing 43 support one side and the other side of the shaft portion 49. The first bearing 38 is provided on one side (upper side in FIG. 3) that is away from the pilot valve element 32, and the second bearing 43 is provided on the other side (lower side in FIG. 3) that is closer to the pilot valve element 32.

[0074] As shown in Fig. 4, in this embodiment, the shape of the pilot valve element 32 of the pressure control valve 33 is devised. Specifically, a contact surface 61 of the pilot valve element 32 that contacts the seat surface 26E is inclined at an inclination angle β with respect to a plane CC that is perpendicular to the central axis DD of the pilot valve element 32 (and the shaft portion 49). This makes it possible to vary the axial length to the seat surface 26E depending on the circumferential position of the pilot valve element 32 when the pilot valve element 32 is separated from the seat surface 26E. In other words, when the pilot valve element 32 and the seat surface 26E are separated with the central axis DD of the pilot valve element 32 perpendicular to the seat surface 26E, the axial length from the pilot valve element 32 (contact surface 61) to the seat surface 26E (the axial distance between the contact surface 61 and the seat surface 26E) varies depending on the circumferential position of the pilot valve element 32.

[0075] More specifically, the portion of the pilot valve element 32 that contacts the seat surface 26E is referred to as a contact portion 62, and the plane defined by the contact portion 62 is referred to as a contact surface 61. In this case, the contact surface 61 is inclined. That is, when the contact surface 61 is referred to as plane AA, the seat surface 26E is referred to as plane BB, and a plane parallel to the seat surface 26E (plane BB) is referred to as plane CC, an inclination angle β is formed between the plane AA and the plane CC. In other words, the central axis of the shaft portion 46 formed integrally with the pilot valve element 32 is referred to as plane DD, and the central axis DD of the shaft portion 49 is perpendicular to the plane BB (plane BB) that is the seat surface 26E (the central axis DD is perpendicular to the plane CC). In this state, the plane AA that forms the contact surface 61 does not coincide with the plane CC that is perpendicular to the central axis DD, but is inclined relative to the plane CC.

[0076] 5, clearances (gaps) are provided between the two bearings 38, 43 supporting the shaft portion 49 and the shaft portion 49. In this case, the respective clearance amounts e1, e2 are determined from the distances between the bearings 38, 43 and the pilot valve element 32 (e.g., the distance h1 between the upper end of the first bearing 38 and the seat surface 26E, and the distance h2 between the upper end of the second bearing 43 and the seat surface 26E) and the inclination angle β. Specifically, the clearance amounts e1, e2 are set so that, when the pilot valve element 32 is closed, the shaft portion 49 of the pilot valve element 32 receives normal forces F1, F2 from the bearings 38, 43 as the shaft portion 49 inclines based on contact between the surface AA, which is the contact surface 61, and the surface BB, which is the seat surface 26E.

[0077] FIG. 5 shows the pressure control valve 33 in (A) an open state and in (B) a state in transition from a closed state to an open state. In FIG. 5, the gaps (clearance amounts e1 and e2) between the shaft portion 49 and the bearings 38 and 43, the inclination of the shaft portion 49, and other details are exaggerated. As shown in FIG. 5(A), when the clearance of the first bearing farther from the pilot valve element 32 is e1 and the clearance of the second bearing closer to the pilot valve element 32 is e2, e1 > e2. As a result, as shown in FIG. 5(B), in the closed state where the pilot valve element 32 is in contact with the seat surface 26E, the shaft portion 49 inclines based on the inclination angle β of the contact surface 61 and the clearance amounts e1 and e2. Then, when ... Open When the pilot valve element 32 is operated, the shaft portion 49 moves in a direction away from the seat surface 26E while in contact with the bearings 38 and 43 at an angle relative to the moving direction of the pilot valve element 32. As a result, the shaft portion 49 receives normal forces F1 and F2 from the bearings 38 and 43.

[0078] In this manner, in the embodiment, the axial distance to the seat surface 26E varies depending on the circumferential position of the pilot valve element 32. As a result, the plane formed by the contact portion 62 of the pilot valve element 32, i.e., the contact surface 61 of the pilot valve element 32, has an inclination angle β with respect to the seat surface 26E. The center hole 26C side of the pilot body 26 is located upstream of the pressure control valve 33, and the oil chamber into which the pilot valve element 32 is displaced is located downstream of the pressure control valve 33.

[0079] 5A shows the pilot valve element 32 in an open state. From this state, the pilot valve element 32 receives a thrust force in response to the supply of current to the solenoid 35A via the plunger 48 and the shaft portion 49, and is pressed against the seat surface 26E of the pilot body 26. As a result, the pilot valve element 32 closes, as shown in FIG. 5B. When the pilot valve element 32 closes, the pilot valve element 32 tilts relative to the direction of travel of the pilot valve element 32 based on the tilt angle β, and portions of the outer circumferential surface of the shaft portion 49 come into contact with portions of the inner circumferential surfaces of the bearings 38 and 43. As a result, the shaft portion 49 receives normal forces F1 and F2 from both bearings 38 and 43, causing uneven contact pressure between the contact surface 61 of the pilot valve element 32 and the seat surface 26E.

[0080] As a result, when the pilot valve element 32 first opens, the frictional force between the outer peripheral surface of the shaft portion 49 and the inner peripheral surfaces of the bearings 38 and 43 allows the shaft portion to move slowly in the up and down direction. Furthermore, because the contact pressure between the contact surface 61 of the pilot valve element 32 and the seat surface 26E is uneven, the pilot valve element 32 opens slowly from the portion with the lowest contact pressure when the valve opens. As a result, when the pilot valve element 32 opens, the oil flow rate rises slowly and hydraulic pressure pulsation can be reduced.

[0081] Here, the smaller the inner diameter of the bearings 38, 43, the greater the normal force during valve closing. Therefore, adjusting the inner diameter of the bearings 38, 43 allows adjustment of the normal forces F1, F2. Adjusting the normal forces F1, F2 allows adjustment of the frictional force between the outer peripheral surface of the shaft portion 49 and the inner peripheral surface of the bearings 38, 43, and the contact pressure (degree of non-uniformity) between the contact surface 61 of the pilot valve element 32 and the seat surface 26E. Furthermore, increasing the inclination angle β of the contact surface 61 allows adjustment of the normal forces F1, F2 during valve closing. Therefore, adjusting the inclination angle β of the contact surface 61 allows adjustment of the normal forces F1, F2. This also allows adjustment of the frictional force between the outer peripheral surface of the shaft portion 49 and the inner peripheral surface of the bearings 38, 43, and the contact pressure (degree of non-uniformity) between the contact surface 61 of the pilot valve element 32 and the seat surface 26E. By adjusting the friction force and contact surface pressure (degree of unevenness), the oil flow rate can be made to rise more gradually, thereby reducing hydraulic pressure pulsation.

[0082] The pressure control valve 33 and shock absorber 1 according to this embodiment have the above-described configuration, and their operation will now be described.

[0083] First, when the shock absorber 1 is mounted on a vehicle such as an automobile, for example, the upper end (protruding end) of the piston rod 8 is attached to the vehicle body, and the mounting eye 3A provided on the bottom cap 3 is attached to the wheel. In addition, the solenoid actuator 34 of the damping force adjusting mechanism 17 is connected to a control device (controller) provided on the vehicle body via an electrical wiring cable (neither is shown) or the like.

[0084] When the vehicle is traveling and vibrations in the vertical direction occur due to unevenness of the road surface or the like, the piston rod 8 is displaced so as to extend or contract from the outer cylinder 2, and a damping force can be generated by the damping force adjustment mechanism 17 or the like, thereby cushioning the vibrations of the vehicle. At this time, the controller controls the current value to the solenoid 35A (coil 35A2) and adjusts the valve opening pressure of the pilot valve body 32, thereby variably adjusting the damping force generated by the shock absorber 1.

[0085] For example, during the extension stroke of the piston rod 8, the movement of the piston 5 inside the inner cylinder 4 closes the compression-side check valve 7 of the piston 5. Before the disc valve 6 of the piston 5 opens, the oil in the rod-side oil chamber B is pressurized and flows into the oil passage 20B of the connecting pipe body 20 of the damping force control valve 18 through the oil hole 4A of the inner cylinder 4, the annular oil chamber D, and the connection port 12C of the intermediate cylinder 12. At this time, the oil equivalent to the movement of the piston 5 flows from the reservoir chamber A into the bottom-side oil chamber C, opening the extension-side check valve 16 of the bottom valve 13. When the pressure in the rod-side oil chamber B reaches the opening pressure of the disc valve 6, the disc valve 6 opens, relieving the pressure in the rod-side oil chamber B to the bottom-side oil chamber C.

[0086] In the damping force adjusting mechanism 17, before the main valve 23 opens (when the piston speed is in the low speed range), the oil that has flowed into the oil passage 20B of the connecting pipe body 20 passes through the center hole 21A of the valve member 21, the center hole 24B of the pilot pin 24, and the center hole 26C of the pilot body 26, as shown by arrow X in Fig. 2, pushes open the pilot valve element 32, and flows into the inside of the pilot body 26. The oil that has flowed into the inside of the pilot body 26 then flows between the flange portion 32A of the pilot valve element 32 and the disc valve 29, through the oil passage 30A of the retaining plate 30, the notch 31A of the cap 31, and the oil chamber 19C of the valve case 19, to the reservoir chamber A. As the piston speed increases, the pressure in the oil passage 20B of the connecting pipe body 20, i.e., the pressure in the rod-side oil chamber B, reaches the valve-opening pressure of the main valve 23. As shown by arrow Y in Figure 2, the oil that has flowed into the oil passage 20B of the connecting pipe body 20 passes through the oil passage 21B of the valve member 21, pushes open the main valve 23, and flows into the reservoir chamber A through the oil chamber 19C of the valve case 19.

[0087] On the other hand, during the compression stroke of the piston rod 8, the movement of the piston 5 inside the inner cylinder 4 opens the compression-side check valve 7 of the piston 5, and the extension-side check valve 16 of the bottom valve 13 closes. Before the bottom valve 13 (disc valve 15) opens, oil in the bottom-side oil chamber C flows into the rod-side oil chamber B. At the same time, oil equivalent to the amount of oil that the piston rod 8 has penetrated into the inner cylinder 4 flows from the rod-side oil chamber B via the damping force control valve 18 to the reservoir chamber A, following the same path as during the extension stroke. When the pressure in the bottom-side oil chamber C reaches the opening pressure of the bottom valve 13 (disc valve 15), the bottom valve 13 (disc valve 15) opens, relieving the pressure in the bottom-side oil chamber C to the reservoir chamber A.

[0088] As a result, during the extension stroke and compression stroke of the piston rod 8, before the main valve 23 of the damping force control valve 18 opens, a damping force is generated by the orifice 24C of the pilot pin 24 and the valve-opening pressure of the pilot valve element 32, and after the main valve 23 opens, a damping force is generated according to the opening degree of the main valve 23. In this case, by adjusting the valve-opening pressure of the pilot valve element 32 by energizing the solenoid 35A of the solenoid actuator 34, it is possible to directly control the damping force regardless of the piston speed.

[0089] Specifically, when the current flowing through solenoid 35A is reduced to reduce the thrust of plunger 48, the valve-opening pressure of pilot valve element 32 decreases, generating a soft damping force. On the other hand, when the current flowing through solenoid 35A is increased to increase the thrust of plunger 48, the valve-opening pressure of pilot valve element 32 increases, generating a hard damping force. At this time, the internal pressure of back pressure chamber 27, which communicates with pilot valve element 32 via oil passage 25 upstream of pilot valve element 32, changes depending on the valve-opening pressure of pilot valve element 32. As a result, by controlling the valve-opening pressure of pilot valve element 32, the valve-opening pressure of main valve 23 can be adjusted at the same time, thereby widening the adjustment range of damping force characteristics.

[0090] If the thrust of the plunger 48 is lost due to a break in the solenoid 35A or the like, the pilot valve element 32 will move backward (displaced in a direction away from the seat surface 26E) due to the return spring 28, and the flange portion 32A of the pilot valve element 32 will come into contact with the disc valve 29. In this state, a damping force can be generated by the valve-opening pressure of the disc valve 29, and the necessary damping force can be obtained even in the event of a malfunction such as a break in the coil.

[0091] According to the embodiment, when the pressure control valve 33 is open, that is, when the pilot valve element 32 is separated from the seat surface 26E, the axial length to the seat surface 26E (the axial distance between the contact surface 61 and the seat surface 26E) varies depending on the circumferential position of the pilot valve element 32. Therefore, as shown in FIG. 5B , when the pilot valve element 32 contacts the seat surface 26E, the central axis DD of the shaft portion 49 can be inclined with respect to the central axes of the first bearing 38 and the second bearing 43. That is, the outer peripheral surface of the shaft portion 49 can be inclined with respect to the inner peripheral surfaces of the first bearing 38 and the second bearing 43. As a result, when the pilot valve element 32 is initially open, frictional force is generated by sliding between the outer peripheral surface of the shaft portion 49 and the inner peripheral surfaces of the first bearing 38 and the second bearing 43, and the vertical movement of the shaft portion 49 can be slowed. As a result, the oil flow rate increases gradually when the pilot valve element 32 opens, and oil pressure pulsation can be reduced.

[0092] Furthermore, when the pilot valve element 32 is in the closed state, the contact between the pilot valve element 32 and the seat surface 26E causes the shaft portion 49 to tilt relative to the central axes of the first bearing 38 and the second bearing 43. As a result, normal forces F1 and F2 are applied to the shaft portion 49 due to contact between a portion of the outer circumferential surface of the shaft portion 49 and a portion of the inner circumferential surface of the first bearing 38 and a portion of the inner circumferential surface of the second bearing 43. This makes it possible to make the surface pressure between the contact surface 61 of the pilot valve element 32 and the seat surface 26E uneven. Therefore, when the pilot valve element 32 opens, the pilot valve element 32 opens gradually from the portion with the lowest surface pressure. As a result, this surface also causes the oil flow rate to rise gradually, reducing hydraulic pressure pulsation.

[0093] FIG. 6 shows the analysis results of the pressure control valve 33, i.e., the change in the discharge pressure of the pressure control valve 33 over time. The solid line 71 in FIG. 6 corresponds to the discharge pressure of the pressure control valve 33 of the embodiment in which the contact surface 61 is inclined, and the dashed line 72 in FIG. 6 corresponds to the discharge pressure of the pressure control valve of the comparative example in which the contact surface is not inclined. FIG. 6 shows the waveform (characteristics) of hydraulic pressure pulsation due to the differential pressure across the valve element (pilot valve element) (the differential pressure between the upstream and downstream sides) when a step input of a flow rate of 1 [L / min] is applied to the pressure control valve 33 of the embodiment and the pressure control valve of the comparative example. As is clear from FIG. 6, the pressure control valve 33 of the embodiment can reduce the maximum differential pressure of hydraulic pressure pulsation and suppress hydraulic pressure pulsation compared to the pressure control valve of the comparative example.

[0094] In the embodiment, a case has been described in which a normal force F1 based on contact with the first bearing 38 and a normal force F2 based on contact with the second bearing 43 are applied to the shaft portion 49. However, the present invention is not limited to this, and the clearance amount and the inclination angle may be set so that a normal force based on contact with either the first bearing or the second bearing is applied to the shaft portion.

[0095] In the embodiment, the case where the housing 36 and the cylinder 44, and the cylinder 44 and the yoke 39 are joined via brazing material has been described as an example. However, the present invention is not limited to this, and the housing 36 and the cylinder 44, and the cylinder 44 and the yoke 39 may be joined by welding, for example.

[0096] In the embodiment, the anchor 41 is fixed by press-fitting into the fixing hole 39A of the yoke 39. However, the present invention is not limited to this, and the anchor may be fixed to the yoke using, for example, a screw or other threading means, a caulking means, or the like.

[0097] In the embodiment, the anchor 41 and the yoke 39 are configured as separate bodies (separate components) as described above. However, the present invention is not limited to this, and the anchor and the yoke may be configured as one integral part (one component).

[0098] In the embodiment, an example has been described in which one side of the cylinder 44 is fixed to the yoke 39. However, the present invention is not limited to this, and for example, one side of the cylinder (joint member) may be fixed to an anchor.

[0099] In the embodiment, an example has been described in which the other-side cylindrical portion 39H is provided on the yoke 39, and the tip side (the other axial side) of the other-side cylindrical portion 39H is fixed to the outer circumferential side of the cover member 51 by the crimped portion 39J. However, the present invention is not limited to this, and for example, the annular portion of the yoke and the other-side cylindrical portion may be formed separately, and the other-side cylindrical portion may be formed integrally with the cover member.

[0100] In the embodiment, the solenoid actuator 34 is configured as a proportional solenoid, but is not limited to this, and may be configured as, for example, an ON / OFF solenoid.

[0101] In the embodiment, a description has been given of an example of a twin-tube shock absorber 1 made up of an outer tube 2 and an inner tube 4. However, the present invention is not limited to this, and may be used, for example, in a damping force adjustable shock absorber made up of a single-tube cylindrical member (cylinder).

[0102] In the embodiment, the solenoid actuator 34 is used as a variable damping force actuator for the shock absorber 1, that is, the pilot valve element 32 of the damping force adjustment mechanism 17 is used as the driven object of the solenoid actuator 34. However, the solenoid actuator is not limited to this, and can be widely used as, for example, an actuator incorporated into various mechanical devices such as a valve used in a hydraulic circuit, that is, a drive device that drives a driven object that should be driven linearly.

[0103] According to the above-described embodiment, when the valve disc is separated from the seat surface, the axial length to the seat surface varies depending on the circumferential position of the valve disc. Therefore, when the valve disc contacts the seat surface, the shaft portion can be tilted relative to the central axis of the first bearing and the second bearing. That is, the outer circumferential surface of the shaft portion can be brought into contact with the inner circumferential surface of the first bearing and / or the inner circumferential surface of the second bearing while being tilted. As a result, when the valve disc is initially opened, frictional force is generated due to sliding between the outer circumferential surface of the shaft portion and the inner circumferential surface of the first bearing and / or the inner circumferential surface of the second bearing, thereby easing the vertical movement of the shaft portion. As a result, the oil flow rate increases gradually upon valve opening, reducing hydraulic pressure pulsation. Furthermore, when the valve disc is closed, the shaft portion is tilted relative to the central axis of the first bearing and the second bearing due to contact between the valve disc and the seat surface. This causes a normal force to be applied to the shaft portion due to contact between a portion of the outer circumferential surface of the shaft portion and a portion of the inner circumferential surface of the first bearing and / or the inner circumferential surface of the second bearing. This allows the contact pressure between the valve disc and the seat surface to be uneven. As a result, when the valve opens, the valve opens gradually from the part of the valve disc with the lowest contact pressure. As a result, the oil flow rate also rises gradually, reducing hydraulic pressure pulsations. [Explanation of symbols]

[0104] 1: Buffer (damping force adjustable buffer) 2: Outer cylinder 4: Inner cylinder 5: Piston 8: Piston rod 26E: Seat surface 32: Pilot valve body (valve body) 33: Pressure control valve 35A: Solenoid 38: First bearing 43: Second bearing 48: Plunger 49: Shaft

Claims

1. a cylinder in which a working fluid is sealed; a piston slidably fitted in the cylinder; a piston rod having one end connected to the piston and the other end extending to the outside of the cylinder; a pressure control valve capable of controlling a flow of fluid generated by sliding of the piston inside the cylinder to generate a damping force and adjusting a valve opening pressure, The pressure control valve is a valve body seated on a seat surface; a shaft portion integrally formed with the valve body; a plunger into which the shaft portion is inserted and which biases the valve body toward the seat surface to adjust the valve opening pressure; a solenoid for adjusting the thrust of the plunger; a first bearing and a second bearing supporting one side and the other side of the shaft portion, a clearance between the first bearing on the side farther from the valve body and the shaft portion is larger than a clearance between the second bearing on the side closer to the valve body and the shaft portion; A damping force adjustable shock absorber, wherein when the valve body is separated from the seat surface, the axial length to the seat surface varies depending on the circumferential position of the valve body.

2. A pressure control valve provided in a damping force adjustable shock absorber, The pressure control valve is a valve body seated on a seat surface; a shaft portion integrally formed with the valve body; a plunger into which the shaft portion is inserted and which biases the valve body toward the seat surface to adjust the valve opening pressure; a solenoid for adjusting the thrust of the plunger; a first bearing and a second bearing supporting one side and the other side of the shaft portion, a clearance between the first bearing on the side farther from the valve body and the shaft portion is larger than a clearance between the second bearing on the side closer to the valve body and the shaft portion; A pressure control valve, wherein when the valve body is separated from the seat surface, the axial length to the seat surface varies depending on the circumferential position of the valve body.

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