Attenuation force adjustment-type damper

Abstract

To provide an attenuation force adjustment-type damper which can improve an insufficient attenuation force at a minor low piston speed.SOLUTION: An attenuation force adjustment-type damper 1 includes: a first attenuation force valve mechanism 15 having a first valve 18 for adjusting a flow of work fluid L in a flow path 95, a solenoid 21 for adjusting an operation of the first valve 18, and a first orifice 18D that communicates an upstream side and a downstream side of the first valve 18 at all times; and a second attenuation force valve mechanism 51 aligned with the first attenuation force valve mechanism 15 in the flow path 95 in series, having a second valve 50 for adjusting a flow of the work fluid L that moves inside the flow path 95, and a second orifice 50A that communicates an upstream side and a downstream side of the second valve 50 at all times. The first orifice 18D is formed to have a flow path cross sectional area larger than that of the second orifice 50A, and a movement speed of a piston 5 of the second valve 50 operates at a speed slower than that of an operation of the first valve 18.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a damping force adjustable shock absorber. [Background technology]

[0002] There are shock absorbers that have two damping force valve mechanisms that open in the same stroke, and among them there is a damping force adjustable shock absorber in which the opening and closing operation of the valve of one of the damping force valve mechanisms can be adjusted by a solenoid (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 195264 Summary of the Invention [Problem to be solved by the invention]

[0004] In the damping force adjustable shock absorber, it is desired to improve the insufficient damping force when the piston speed is very low.

[0005] An object of the present invention is to provide a damping force adjustable shock absorber that can improve the insufficient damping force when the piston speed is extremely low. [Means for solving the problem]

[0006] In order to achieve the above object, one aspect of the present invention provides a first damping force valve mechanism including: a cylinder in which a working fluid is sealed; a piston slidably inserted into the cylinder and dividing the interior of the cylinder into two chambers; a piston rod having a first end connected to the piston and a second end extending outward from an end of the cylinder; a flow path through which the working fluid moves between the two chambers as the piston rod moves; a first valve provided in the flow path and regulating the flow of the working fluid moving within the flow path; a solenoid adjusting the operation of the first valve; and a first orifice constantly communicating between the upstream side and the downstream side of the first valve; and a second damping force valve mechanism having a second valve that adjusts the flow of the working fluid moving within the flow path and a second orifice that constantly communicates between the upstream and downstream sides of the second valve, wherein the first orifice is formed so that the flow path cross-sectional area is larger than the flow path cross-sectional area of ​​the second orifice, and the second valve operates at a piston moving speed that is slower than that at which the first valve operates, and the second damping force valve mechanism has a case member that has a cylindrical portion that covers the radial outside of the second valve and a bottom portion that supports the radial inside of the second valve, and a pin member that is inserted through the second valve and a hole formed in the bottom portion of the case member and fastened to the second valve by crimping. [Effects of the Invention]

[0007] According to the present invention, it is possible to improve the lack of damping force when the piston speed is extremely low. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a damping force adjustable shock absorber according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing a main part of a damping force control shock absorber according to an embodiment of the present invention. [Figure 3] 1 is a hydraulic circuit diagram showing a main part of a damping force adjustable shock absorber according to an embodiment of the present invention. [Figure 4]4 is a characteristic diagram of damping force versus piston speed during an extension stroke of the damping force control shock absorber according to the embodiment of the present invention; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] The embodiments will be described with reference to the drawings. For the sake of convenience, the upper side in Figures 1 and 2 will be referred to as "top" and the lower side in the figures will be referred to as "bottom."

[0010] <Configuration> The damping force adjustable shock absorber 1 of the embodiment shown in Fig. 1 is a damping force adjustable shock absorber used in suspension devices for railway vehicles and automobiles such as two-wheeled and four-wheeled vehicles, and more specifically, it is a damping force adjustable shock absorber used in suspension devices for four-wheeled automobiles. The damping force adjustable shock absorber 1 is configured to include an outer cylinder 2, an inner cylinder 4, a piston 5, a piston rod 6, a rod guide 9, a bottom valve 11, a first damping force valve mechanism 15 including a first valve 18, and a second damping force valve mechanism 51 including a second valve 50. The damping force generated by the damping force adjustable shock absorber 1 is variably adjusted by the first damping force valve mechanism 15 including the first valve 18 in response to an external control command.

[0011] The outer cylinder 2, which is a cylindrical cylinder with a bottom that forms the outer shell of the damping force adjustable shock absorber 1, has one end (lower end) closed by a bottom cap 3 using welding or the like, and the other end (upper end) forms a crimped portion 2A that is bent radially inward. The bottom cap 3 is provided with a mounting eye 3A that is attached to, for example, the wheel side of a vehicle.

[0012] The inner cylinder 4 is located radially inside the outer cylinder 2 and is provided coaxially with the outer cylinder 2. The inner cylinder 4 and the outer cylinder 2 form a cylinder 40. The bottom (lower end) side of the inner cylinder 4 is fitted and attached to the valve body 12 of the bottom valve 11, and the upper end side is fitted and attached to the rod guide 9. A working fluid L is sealed inside the inner cylinder 4 of the cylinder 40 as a working fluid. The working fluid L is not limited to oil, but may be, for example, water mixed with an additive.

[0013] An annular reservoir chamber A is formed between the outer cylinder 2 and the inner cylinder 4, and gas G is sealed in this reservoir chamber A together with the working fluid L. This gas G may be air at atmospheric pressure, or a gas such as compressed nitrogen gas may also be used. The gas G sealed in the reservoir chamber A has the function of compensating for the ingress (egress) volume of the piston rod 6 entering or exiting the inner cylinder 4 by being compressed or expanded.

[0014] The piston 5 is slidably inserted into the inner cylinder 4. The piston 5 divides the inner cylinder 4 into two chambers: a bottom-side chamber B on one side and a rod-side chamber C on the other side. The bottom-side chamber B is formed between the piston 5 and a bottom valve 11, and the rod-side chamber C is formed between the piston 5 and a rod guide 9.

[0015] 2, the lower side of the piston 5 is provided with an annular step 5A that protrudes radially inward, and a cylindrical extension portion 5B that extends downward from the position of the annular step 5A, i.e., toward the bottom-side chamber B. The cylindrical extension portion 5B is formed so that its outer diameter is smaller than the inner diameter of the inner cylinder 4, and a second damping force valve mechanism 51, which will be described later, is provided inside the cylindrical extension portion 5B.

[0016] A cylindrical valve seat member 17, which will be described later, is disposed radially inward of the piston 5, and an intermediate chamber 5C is provided radially inward of this valve seat member 17 as a flow path that allows communication between a bottom-side chamber B and a rod-side chamber C via a valve case 8, which will be described later. A second damping force valve mechanism 51, which is disposed in series with a damping force adjustment valve 16 of a first damping force valve mechanism 15, which will be described later, is provided on the bottom-side chamber B side of this intermediate chamber 5C. The damping force adjustment valve 16 of the first damping force valve mechanism 15 is provided in the inner cylinder 4 at a position above the piston 5, and the second damping force valve mechanism 51 is provided in the inner cylinder 4 at a position below the piston 5. The unitized second damping force valve mechanism 51, which will be described later, is fixed to the piston 5 by laser welding so as to form a welded portion 5D. Alternatively, a female thread may be formed on the radially inner side of the cylindrical extension portion 5B of the piston 5, and a unitized second damping force valve mechanism 51, which will be described later, may be screwed and fixed to this female thread.

[0017] As shown in FIG. 1 , the piston rod 6 has a first end on one axial side that is connected to the piston 5 via a solenoid case 7 and a valve case 8, and is configured as an integral unit. The piston rod 6 has a second end on the other axial side that extends to the outside of the cylinder 40 from an end of the cylinder 40 opposite the bottom cap 3 in the axial direction. A wiring hole 6A extending in the axial direction is formed in the center of the piston rod 6, and a harness 30, which is an electrical wiring described below, is inserted into this wiring hole 6A. The piston rod 6 extends axially inside the inner cylinder 4, and a cylindrical solenoid case 7 and a valve case 8 are provided integrally at one end side (lower end side) of the piston rod 6. The solenoid case 7 and the valve case 8 are also configured to form part of the piston rod 6.

[0018] In this case, the piston 5 is screwed and fastened to one end (lower end) of the valve case 8. The other end (upper end) of the piston rod 6 protrudes so as to extend outside the outer cylinder 2 and the inner cylinder 4 via a rod guide 9 or the like. A cylindrical solenoid case 7 is used as a connecting member for connecting (integrating) the lower end of the piston rod 6 to the valve case 8.

[0019] 2, the valve case 8, together with a stator core 23 described later, constitutes the fixed iron core of the solenoid 21. The valve case 8 is formed as a stepped cylindrical body from a magnetic material (for example, an iron-based material), and a plunger 25 described later is inserted and fitted into the inner periphery thereof so as to be able to slide and displace. On one side (lower side) of the valve case 8, a valve seat member 17 described later and a first valve 18 of a variable set pressure type are fitted inside and located below the plunger 25. On one side (lower side) of the valve case 8, a throttle passage 8A is provided at a position that connects the rod-side chamber C with a bottomed hole 18A described later. In addition, on one side (lower side) of the valve case 8, a plurality of radial holes 8B are provided at positions (i.e., positions radially opposite the annular valve portion 18C and the annular valve seat 17A) that connect the rod-side chamber C to the intermediate chamber 5C in the valve seat member 17 via a passage between the first valve 18 (annular valve portion 18C) described below and the valve seat member 17 (annular valve seat 17A) described below.

[0020] As shown in Fig. 1, a stepped cylindrical rod guide 9 is provided on the upper end side of the inner cylinder 4. This rod guide 9 positions the upper end portion of the inner cylinder 4 in the center of the outer cylinder 2, and has the function of guiding the piston rod 6 on its inner circumferential side so that it can slide in the axial direction. An annular seal member 10 is provided between the crimped portion 2A of the outer cylinder 2 and the rod guide 9. The inner circumferential side of this seal member 10 slides against the outer circumferential side of the piston rod 6, thereby sealing the gap with the piston rod 6 and preventing the working fluid L and gas G in the outer cylinder 2 and inner cylinder 4 from leaking to the outside.

[0021] The bottom valve 11 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 11 is composed of a valve body 12 that is located between the bottom cap 3 and the inner cylinder 4 and defines a reservoir chamber A and a bottom-side chamber B, a compression-side disc valve 13 that is provided on the lower surface (one axial side) of the valve body 12, and an extension-side check valve 14 that is provided on the upper surface (the other axial side) of the valve body 12. The valve body 12 is formed with passages 12A and 12B that are spaced apart circumferentially. These passages 12A and 12B allow communication between the reservoir chamber A and the bottom-side oil chamber B.

[0022] Here, when the piston 5 slides downward during the compression stroke in which the piston rod 6 enters the cylinder 40, the compression-side disc valve 13 opens if the pressure in the bottom-side chamber B exceeds a set relief pressure, thereby relieving the hydraulic fluid L (pressure) in the bottom-side chamber B through each passage 12A to the reservoir chamber A. This set relief pressure is set as a valve opening pressure in relation to the pressure when the first damping force valve mechanism 15, which will be described later, is set to hard, etc.

[0023] The extension-side check valve 14 opens when the piston 5 slides upward during the extension stroke in which the piston rod 6 extends from the cylinder 40, and closes at other times. This extension-side check valve 14 allows hydraulic fluid L in the reservoir chamber A to flow through each passage 12B toward the bottom-side oil chamber B, and prevents hydraulic fluid L from flowing in the opposite direction. The opening pressure of the extension-side check valve 14 is set to a lower pressure than the pressure when the first damping force valve mechanism 15, described below, is set to the soft setting, and therefore does not actually generate any damping force.

[0024] Next, the first damping force valve mechanism 15 serving as a damping force adjusting mechanism for variably adjusting the damping force generated by the damping force adjustable shock absorber 1 will be described.

[0025] As shown in FIG. 2, the first damping force valve mechanism 15 is disposed between the piston 5 and the piston rod 6 inside the inner cylinder 4. That is, one end of the first damping force valve mechanism 15 (the lower end of the valve case 8 shown in FIG. 2) is fixed to the upper end of the piston 5, and the other end (the upper end of the solenoid case 7 shown in FIG. 2) is fixed to the lower end of the piston rod 6. The first damping force valve mechanism 15 controls the flow of hydraulic fluid L between the bottom-side chamber B and the rod-side chamber C of the inner cylinder 4 using a damping force adjustment valve 16, and variably adjusts the damping force generated thereby. That is, the damping force adjustment valve 16 variably controls the generated damping force by adjusting the valve opening pressure of a variable set pressure first valve 18, which will be described later, using a solenoid 21, which is a variable damping force actuator.

[0026] Here, the damping force control valve 16 is configured to include a valve case 8 having one end (lower end) fixed to the upper end side of the piston 5 and the other end (upper end) protruding axially upward into the solenoid case 7, a valve seat member 17 fixedly provided on the inner periphery of the lower end side of the valve case 8 and having an annular valve seat 17A at its upper end, a covered, cylindrical first valve 18 positioned above the valve seat member 17 and slidably inserted into the valve case 8, an annular back pressure chamber 19 formed and extending circumferentially between the valve case 8 and the first valve 18 so that the first valve 18 is pressed toward the lower valve seat member 17 by pilot pressure, and a poppet valve element 20 serving as a pilot valve member that variably sets the pilot pressure (back pressure) in the back pressure chamber 19 in accordance with the current (current value) supplied to the solenoid 21, thereby adjusting the valve opening pressure of the first valve 18.

[0027] The first valve 18 of the damping force control valve 16 is a variable-pressure valve element whose valve opening pressure is adjusted according to the opening degree of the poppet valve element 20. The first valve 18 includes a bottomed hole 18A through which the poppet valve element 20 is seated and released to open and close the valve, a through-hole 18B positioned radially apart from the bottomed hole 18A and extending in the axial direction of the first valve 18, and an annular valve portion 18C consisting of an annular protrusion formed on the lower surface (one surface) of the first valve 18. When the first valve 18 is displaced in the up-down direction (axial direction), the annular valve portion 18C seats and releases from the annular valve seat 17A of the valve seat member 17. This allows the first valve 18 to establish and block communication between the intermediate chamber 5C and the hole portion 8B, i.e., open and close. The through-hole 18B connects the intermediate chamber 5C below the first valve 18 with the chamber 5E above it.

[0028] The back pressure chamber 19 of the damping force control valve 16 is constantly in communication with the rod-side chamber C via the throttle passage 8A of the valve case 8, and is also constantly in communication with the bottomed hole 18A of the first valve 18. Therefore, while the poppet valve element 20 closes the bottomed hole 18A, the pressure (pilot pressure) within the back pressure chamber 19 is basically the same as the pressure within the rod-side chamber C. On the other hand, when the poppet valve element 20 opens the bottomed hole 18A, the pressure (pilot pressure) within the back pressure chamber 19 is variably adjusted so as to be reduced to a pressure corresponding to the opening degree of the poppet valve element 20.

[0029] The first valve 18 of the damping force control valve 16 receives pressure in a direction in which the annular valve portion 18C seats on the annular valve seat 17A (i.e., in the valve closing direction) due to the pilot pressure (back pressure) from the back pressure chamber 19. That is, the first valve 18 receives the pressure of the rod-side chamber C through the hole 8B of the valve case 8, and when this pressure exceeds the pilot pressure (back pressure) on the back pressure chamber 19 side, the annular valve portion 18C of the first valve 18 lifts off (displaces upward) from the annular valve seat 17A and opens.

[0030] In this case, the valve opening pressure of the first valve 18 is set to be variable by adjusting the pilot pressure (back pressure) in the back pressure chamber 19 via the poppet valve element 20. When the annular valve portion 18C of the first valve 18 leaves the annular valve seat 17A of the valve seat member 17 (opens), working fluid L from the rod-side chamber C flows from each hole portion 8B into the intermediate chamber 5C of the piston 5 through a passage between the annular valve portion 18C of the first valve 18 and the annular valve seat 17A of the valve seat member 17. Then, the working fluid L flows into the bottom-side chamber B via a second damping force valve mechanism 51, which will be described later.

[0031] Here, for example, a first orifice 18D is provided between the annular valve portion 18C of the first valve 18 and the annular valve seat 17A of the valve seat member 17, which allows the working fluid L to circulate between the rod-side chamber C and the intermediate chamber 5C via a passage in the hole portion 8B even when these are in a seated (closed) state. The first orifice 18D functions as a throttle while the damping force control valve 16 is closed, and does not function as a throttle after the damping force control valve 16 is opened, and therefore is provided in parallel with the damping force control valve 16 in the flow path of the working fluid L.

[0032] The solenoid 21, together with the damping force control valve 16, constitutes the first damping force valve mechanism 15 and is used as a variable damping force actuator. The solenoid 21 is configured to include a cylindrical coil 22 that generates a magnetic force when energized from the outside, a stator core 23 serving as a first fixed iron core that is located on the inner circumferential side of the coil 22 and spaced apart in the axial direction from the upper end of the valve case 8, and a cylindrical non-magnetic portion 24 that is interposed between the upper end of the valve case 8 (second fixed iron core) that is located on the inner circumferential side of the coil 22 and the lower end of the stator core 23 (first fixed iron core) and magnetically isolates them from each other.

[0033] The solenoid 21 is also composed of a plunger 25 as a movable iron core that is arranged on the inner periphery of the valve case 8 so as to be movable in the axial direction, a spring bearing member 26 that is arranged on the central side of the plunger 25 and is movable following the plunger 25, a biasing spring 27 that is arranged inside the plunger 25 so as to constantly bias the spring bearing member 26 in one direction (downward), an adjustment rod 28 that is threadedly engaged with the central side of the stator core 23 and adjusts the biasing force of the biasing spring 27, a movable spring bearing 29 that is located inside the plunger 25 and is arranged between the adjustment rod 28 and the biasing spring 27, and the solenoid case 7 that serves as a cover member that covers the outer periphery of the coil 22.

[0034] Here, the upper end of valve case 8 constitutes another stator core (second fixed iron core) that faces the lower end of stator core 23 across non-magnetic portion 24. Non-magnetic portion 24 is arranged on the inner circumferential side of coil 22, between the upper side of valve case 8 and stator core 23 (i.e., between the first and second fixed iron cores), so as to increase the magnetic flux density of the magnetic circuit for movable iron core (plunger 25).

[0035] The solenoid case 7 constitutes a yoke made of a magnetic material and forms a magnetic circuit on the outer periphery of the coil 22. The solenoid case 7 surrounds the coil 22 of the solenoid 21, the stator core 23, the upper side of the valve case 8, etc. from the outside, and constitutes the outer shell of the solenoid 21.

[0036] The shaft portion 20A of the poppet valve body 20 is inserted into the inside of the spring receiving member . The biasing spring 27 biases the poppet valve element 20 together with the spring receiving member 26 toward the bottomed hole 18A of the first valve 18. The biasing force of the biasing spring 27 is variably adjusted by changing the screw engagement position of the adjustment rod 28 with respect to the stator core 23. The first valve 18 is also biased in the axial direction by the biasing spring 27 via the poppet valve element 20 toward the annular valve seat 17A of the valve seat member 17.

[0037] A wiring hole 6A extending in the axial direction is provided on the inner peripheral side of the piston rod 6, and a harness 30, which is an electric wiring, is inserted into the wiring hole 6A from the end of the piston rod 6 protruding from the cylinder 40. An end of the harness 30 is connected to a controller (not shown) serving as a control device outside the piston rod 6 (for example, on the vehicle body side). The coil 22 of the solenoid 21 is excited by controlling the supply of electricity from the controller via the harness 30, and the solenoid 21 is placed in a demagnetized state when the supply of electricity is stopped.

[0038] When the coil 22 is excited, the solenoid 21 generates a magnetic force that attracts the plunger 25 toward the stator core 23. This magnetic force causes the spring receiving member 26 to displace together with the plunger 25 in a direction that compresses the biasing spring 27. As a result, the force acting on the poppet valve element 20 in the direction that seats it in the bottomed hole 18A of the first valve 18 is weakened.

[0039] That is, an axial thrust proportional to the current flowing through the coil 22 is generated in the plunger 25 of the solenoid 21, which weakens the force of the poppet valve element 20 in the direction of contact with the bottomed hole 18A of the first valve 18, causing the poppet valve element 20 to open using the pilot pressure (back pressure) in the back pressure chamber 19 and the bottomed hole 18A. Therefore, the pilot pressure (back pressure) in the back pressure chamber 19 is set variably in accordance with the displacement of the poppet valve element 20 in response to the thrust of the plunger 25. As a result, the valve opening pressure of the first valve 18, which opens against the pressure in the back pressure chamber 19, is variably adjusted by displacing the poppet valve element 20 in the axial direction in response to the current flowing through the solenoid 21.

[0040] In other words, the valve opening pressure of the first valve 18 is increased or decreased by using the controller to control the value of the current passed through the coil 22 of the solenoid 21 to displace the poppet valve element 20 in the axial direction. Therefore, the damping force generated by the damping force control shock absorber 1 can be variably adjusted according to the valve opening pressure of the first valve 18, which is proportional to the current passed through the solenoid 21. The poppet valve element 20 of the damping force control valve 16 is configured as a normally closed valve that is normally closed in a demagnetized state and opens when the solenoid 21 is excited. Note that the poppet valve element 20 of the damping force control valve 16 may also be configured as a normally open valve that is normally open in a demagnetized state and closes when the solenoid 21 is excited.

[0041] The first damping force valve mechanism 15 communicates between the rod-side chamber C and the intermediate chamber 5C via the hole portion 8B and the passage between the first valve 18 in the open state and the valve seat member 17 or the first orifice 18D, and when the poppet valve element 20 is open, the rod-side chamber C and the intermediate chamber 5C are further communicated with each other via the passage 8A, the passage in the bottomed hole 18A, the chamber 5E between the first valve 18 and the plunger 25, and the through-hole 18B. When the first damping force valve mechanism 15 is open during the extension stroke, the damping force adjustment valve 16 serves as the extension-side damping force adjustment valve 16(a), and when it is open during the compression stroke, the damping force adjustment valve 16 serves as the compression-side damping force adjustment valve 16(b).

[0042] Here, the first orifice 18D functions as a throttle that throttles and allows the hydraulic fluid L to flow between the rod-side chamber C and the intermediate chamber 5C when the damping force control valves 16(a), 16(b) are in a closed state, and does not function as a throttle when the damping force control valves 16(a), 16(b) are in an open state. Therefore, the first orifice 18D is provided in parallel on the flow path of the hydraulic fluid L to the damping force control valves 16(a), 16(b), which allow the hydraulic fluid L to flow between the rod-side chamber C and the intermediate chamber 5C in an open state, as shown in the hydraulic circuit diagram of FIG.

[0043] As shown in FIG. 2, the second damping force valve mechanism 51 has a second valve 50, a case member 52, a pin member 53, and a spring member 54, which are integrated into a unit.

[0044] The case member 52 has a disk-shaped bottom portion 61 and a cylindrical tube portion 62 that extends from the outer peripheral edge of the bottom portion 61 to one side along the axial direction of the bottom portion 61 . The bottom 61 has a hole 65 at its radial center that penetrates the bottom 61 in the axial direction. The bottom 61 has a passage hole 66 that penetrates the bottom 61 in the axial direction of the bottom 61, outside the radial hole 65. A plurality of passage holes 66 are formed in the bottom 61 at intervals in the circumferential direction. The cylindrical portion 62 has an annular protrusion 69 that protrudes radially inward from the edge portion opposite the bottom portion 61 in the axial direction. The case member 52 has an outer periphery 70 which fits onto the cylindrical extension 5B of the piston 5.

[0045] The second valve 50 is configured by stacking multiple discs 71. Each of the multiple discs 71 is a flexible, circular, flat plate with holes. The multiple discs 71 are arranged on the axial side of the bottom 61 of the case member 52, toward the cylindrical portion 62. The central disc 71 in the stacking direction has the largest outer diameter, and the discs 71 further away from this disc 71 in the axial direction have smaller outer diameters.

[0046] In the second valve 50, the outer diameter of the largest-diameter disk 71, which is the outer diameter of the second valve 50, is slightly smaller than the inner diameter of the protruding portion 69, which is the inner diameter of the cylindrical portion 62 of the case member 52. When the second valve 50 is stacked on the bottom portion 61, the disk 71 with the largest outer diameter overlaps and faces the protruding portion 69 of the cylindrical portion 62 of the case member 52 in the radial direction.

[0047] The multiple discs 71 each have the same inner diameter, which is larger than the diameter of the hole 65 in the bottom 61 of the case member 52. Therefore, the inner diameter of the second valve 50 is formed to be larger than the diameter of the hole 65 in the bottom 61.

[0048] The spring member 54 is a flexible, perforated disc spring that curves so that its radially outer edge is positioned toward one axial side. The spring member 54 is provided on the axially opposite side of the bottom 61 of the case member 52 from the second valve 50, with its inner diameter side abutting the bottom 61 and its outer diameter side spaced axially from the bottom 61. The disc spring has a passage hole (not shown) that penetrates through it in the thickness direction at a position other than the radial center.

[0049] The pin member 53 has a base portion 81 , a shaft portion 82 , and a head portion 83 . The base 81 is disk-shaped. The shaft portion 82 is cylindrical with an outer diameter smaller than that of the base portion 81, and extends from the center of the base portion 81 in the radial direction to one side of the base portion 81 in the axial direction. The head 83 is disk-shaped with an outer diameter larger than that of the shaft 82, and spreads outward in the radial direction from the end of the shaft 82 opposite the base 81 in the axial direction.

[0050] The head 83 of the pin member 53 is formed by plastic deformation due to crimping. That is, before the head 83 of the pin member 53 is formed by crimping, the axial length of the shaft portion 82 is longer by the volume of the head 83. Then, in the second damping force valve mechanism 51, the shaft portion 82 is inserted into the radially inner side of the base portion 81 of the pin member 53 before the head 83 is formed, and then the multiple discs 71, the bottom portion 61 of the case member 52, and the spring member 54 are stacked in this order. At this time, the case member 52 is in a state where the cylindrical portion 62 protrudes from the bottom portion 61 toward the base portion 81 in the axial direction. At this time, the spring member 54 is in a state where the inner diameter side is in contact with the bottom portion 61.

[0051] At this time, that is, before the head 83 is formed by crimping, the difference between the outer diameter of the shaft portion 82 of the pin member 53 and the inner diameter of the second valve 50 is greater than the radial length of the gap between the outer diameter of the largest-diameter disc 71, which is the outer diameter of the second valve 50, and the inner diameter of the protruding portion 69, which is the inner diameter of the cylindrical portion 62. The head 83 is then formed by crimping and plastically deforming the portion of the shaft portion 82 of the pin member 53 that protrudes beyond the spring member 54. The base 81 and the head 83 then clamp and fix at least the inner peripheries of the second valve 50, which is made up of multiple discs 71, the bottom portion 61 of the case member 52, and the spring member 54 in an axially pressurized state.

[0052] The second damping force valve mechanism 51 integrated in this manner comprises a case member 52 having a cylindrical portion 62 that covers the radial outside of the second valve 50 and a bottom portion 61 that supports the radial inside of the second valve 50, and a pin member 53 that is inserted through the second valve 50 and a hole 65 formed in the bottom portion 61 of the case member 52 and fastened to the second valve 50 by crimping. Here, as described above, the inner diameter of the second valve 50 is formed to be larger than the diameter of the hole 65 in the bottom portion 61. Furthermore, the difference between the outer diameter of the shaft portion 82 of the pin member 53 and the inner diameter of the second valve 50 is formed to be larger than the radial length of the gap between the outer diameter portion of the largest-diameter disc 71, which is the outer diameter portion of the second valve 50, and the inner diameter portion of the protrusion 69, which is the inner diameter portion of the cylindrical portion 62, before the pin member 53 is crimped.

[0053] The second damping force valve mechanism 51 is fitted to the cylindrical extension portion 5B of the piston 5 at the outer circumferential portion 70 of the case member 52 so that the second valve 50 is exposed to the bottom-side chamber B. At this time, the case member 52 of the second damping force valve mechanism 51 is butted against the piston 5 in the axial direction. In this state, the case member 52 is laser-welded to the piston 5 so as to form a welded portion 5D on the underside. As a result, the second damping force valve mechanism 51 is provided integrally with the piston 5. At this time, the outer diameter side of the spring member 54 of the second damping force valve mechanism 51 is in contact with the end of the valve seat member 17 on the opposite side in the axial direction from the annular valve seat 17A. As a result, the spring member 54 biases the valve seat member 17 toward the first valve 18.

[0054] In the second damping force valve mechanism 51, when the second valve 50 is not deformed and the outer diameter portion of the largest-diameter disc 71, which is the outer diameter portion of the second valve 50, is axially aligned with the inner diameter portion of the protruding portion 69, which is the inner diameter portion of the cylindrical portion 62, and the gap between the cylindrical portion 62 of the case member 52, i.e., the gap with the protruding portion 69, is minimized, this gap becomes the second orifice 50A. In other words, the second orifice 50A is formed by the gap between the outer diameter portion of the second valve 50 and the inner diameter portion of the cylindrical portion 62. The second orifice 50A communicates between the intermediate chamber 5C and the bottom-side chamber B via a passage within the passage hole 66 and a passage within a passage hole (not shown) of the spring member 54.

[0055] When the second valve 50 deforms, the second damping force valve mechanism 51 widens the gap between the second valve 50 and the cylindrical portion 62 of the case member 52, i.e., the gap between the second valve 50 and the protrusion 69. The second valve 50 and the cylindrical portion 62 of the case member 52 constitute a damping valve 91. The second orifice 50A functions as a throttle when the damping valve 91 is closed, and does not function as a throttle after the damping valve 91 is opened, and therefore is provided in parallel with the damping valve 91 in the flow path.

[0056] The second damping force valve mechanism 51 connects the intermediate chamber 5C and the bottom side chamber B via a passage in the passage hole (not shown) of the spring member 54, a passage in the passage hole 66 of the case member 52, and a passage between the second valve 50 in the open state and the cylindrical portion 62 or the second orifice 50A.

[0057] When the damping valve 91 opens during the extension stroke, the second valve 50 deforms opposite to the bottom portion 61 to expand the gap with the cylindrical portion 62, and the working fluid L flows from the intermediate chamber 5C to the bottom-side chamber B through a passage in a passage hole (not shown) of the spring member 54, a passage in a passage hole 66 of the case member 52, and the gap with the cylindrical portion 62. At this time, the damping valve 91 functions as an extension-side damping valve 91(a) that suppresses the flow of the working fluid L and generates a damping force.

[0058] When the damping valve 91 opens during the compression stroke, the second valve 50 deforms toward the bottom 61 to expand the gap with the cylindrical portion 62, and the working fluid L flows from the bottom-side chamber B to the intermediate chamber 5C through this gap, the passage in the passage hole 66 of the case member 52, and the passage in the passage hole (not shown) of the spring member 54. At this time, the damping valve 91 functions as a compression-side damping valve 91(b) that suppresses the flow of the working fluid L and generates a damping force.

[0059] Here, when the damping valves 91(a), 91(b) are in a closed state, the second orifice 50A functions as a throttle that throttles and flows the hydraulic fluid L between the intermediate chamber 5C and the bottom-side chamber B via the passage in the passage hole 66 of the case member 52 and the passage in the passage hole (not shown) of the spring member 54, and does not function as a throttle when the damping valves 91(a), 91(b) are in an open state. Therefore, the second orifice 50A is provided in parallel on the flow path of the hydraulic fluid L to the damping valves 91(a), 91(b) that, in an open state, allow the hydraulic fluid L to flow between the intermediate chamber 5C and the bottom-side chamber B, as shown in the hydraulic circuit diagram of FIG.

[0060] 2, the passage within the hole portion 8B of the valve case 8 and the passage 8A, the back pressure chamber 19, the passage within the bottomed hole 18A of the first valve 18, the chamber 5E, the passage within the through hole 18B of the first valve 18, the passage between the first valve 18 and the valve seat member 17 in the open state or the first orifice 18D between the first valve 18 and the valve seat member 17 in the closed state, the intermediate chamber 5C, the passage within the passage hole (not shown) of the spring member 54, the passage within the passage hole 66 of the case member 52, and the passage between the second valve 50 and the tubular portion 62 of the case member 52 in the open state or the second orifice 50A between the second valve 50 and the tubular portion 62 of the case member 52 in the closed state. As shown in the hydraulic circuit diagram of Figure 3, a first damping force valve mechanism 15 having a first orifice 18D and damping force adjustment valves 16(a), 16(b) arranged in parallel is provided between the rod side chamber C of this flow path 95 and the intermediate chamber 5C, and a second damping force valve mechanism 51 having a second orifice 50A and damping valves 91(a), 91(b) arranged in parallel is provided between the bottom side chamber B of the flow path 95 and the intermediate chamber 5C.

[0061] In the flow path 95, the movement of the piston rod 6 shown in Fig. 2 causes the working fluid L to move between the bottom-side chamber B and the rod-side chamber C. The first damping force valve mechanism 15 is provided in the flow path 95 and has a first valve 18 that adjusts the flow of the working fluid L moving within the flow path 95, a solenoid 21 that adjusts the operation of the first valve 18, and a first orifice 18D that constantly communicates between the upstream side and downstream side of the first valve 18.

[0062] The second damping force valve mechanism 51 is provided in the flow path 95 and arranged in series with the first damping force valve mechanism 15, and has a second valve 50 that adjusts the flow of the working fluid L moving within the flow path 95, and a second orifice 50A that constantly connects the upstream side and downstream side of the second valve 50.

[0063] Here, the first orifice 18D is formed so that the flow path cross-sectional area is larger than the flow path cross-sectional area of ​​the second orifice 50A. Also, the second valve 50 is set so that the axial movement speed of the piston 5 (hereinafter referred to as the piston speed) is slower than the piston speed at which the first valve 18 operates.

[0064] <Activation> The damping force control shock absorber 1 of this embodiment has the above-described configuration, and its operation will now be described.

[0065] When the damping force adjustable shock absorber 1 is mounted on a vehicle, the upper end of the piston rod 6 is attached to the vehicle body, and the mounting eye 3A of the bottom cap 3 side of the outer cylinder 2 is attached to the wheel side. When the vehicle is traveling and vertical vibrations occur due to unevenness in the road surface or the like, the piston rod 6 is displaced so as to extend and contract from the inner cylinder 4, and a damping force can be generated by the first damping force valve mechanism 15 (damping force adjustment valve 16 and solenoid 21), the second damping force valve mechanism 51, etc., and the vehicle vibrations can be absorbed.

[0066] First, we will explain the extension stroke when the solenoid 21 of the first damping force valve mechanism 15 is in a demagnetized state. When the solenoid 21 of the first damping force valve mechanism 15 is in a demagnetized state, the poppet valve element 20 of the damping force control valve 16 closes the bottomed hole 18A of the first valve 18.

[0067] During the extension stroke, the piston 5 moves toward the rod-side chamber C, thereby increasing the pressure in the rod-side chamber C and decreasing the pressure in the bottom-side chamber B. During the extension stroke in an extremely low speed region where the piston speed is equal to or less than a first predetermined value X1, the damping force adjustment valve 16 of the first damping force valve mechanism 15 and the damping valve 91 of the second damping force valve mechanism 51 are both in a closed state, and the working fluid L in the rod-side chamber C flows into the bottom-side chamber B via, within the flow path 95, the passage within the hole portion 8B of the valve case 8, the first orifice 18D between the first valve 18 in the closed state and the valve seat member 17, the intermediate chamber 5C, the passage within a passage hole (not shown) of the spring member 54, the passage within the passage hole 66 of the case member 52, and the second orifice 50A between the second valve 50 in the closed state and the cylindrical portion 62 of the case member 52. This generates a damping force with orifice characteristics (damping force is approximately proportional to the square of the piston speed) determined by the flow path cross-sectional area of ​​the second orifice 50A. Therefore, as shown by the solid line Y1 in Fig. 4, in the extension stroke in the extremely low speed region where the piston speed is equal to or less than the first predetermined value X1, the damping force characteristic with respect to the piston speed is such that the rate of increase in the damping force is relatively high as the piston speed increases.

[0068] At this time, the pressure in the rod-side chamber C shown in Figure 2 is introduced into the back pressure chamber 19 through the passage 8A of the valve case 8, but because the poppet valve body 20 of the damping force control valve 16 is in a state in which the bottomed hole 18A of the first valve 18 is closed, the back pressure chamber 19 has the same pressure as the rod-side chamber C, and there is no pressure difference with the passage side in the hole portion 8B.

[0069] During the extension stroke in the extremely low speed region where the piston speed is greater than a first predetermined value X1 and less than a second predetermined value X2 that is greater than the first predetermined value X1, the pressure in the intermediate chamber 5C introduced through the passage in the hole portion 8B of the valve case 8 and the first orifice 18D between the first valve 18 in the closed state and the valve seat member 17 becomes high. As a result, the damping valve 91(a) of the second damping force valve mechanism 51 opens, and while the damping force adjustment valve 16 of the first damping force valve mechanism 15 remains in a closed state, the working fluid L in the rod side chamber C flows to the bottom side chamber B via the passage within the hole portion 8B of the valve case 8, the first orifice 18D between the first valve 18 in a closed state and the valve seat member 17, the intermediate chamber 5C, the passage within the passage hole (not shown) of the spring member 54, the passage within the passage hole 66 of the case member 52, and the passage between the second valve 50 in an open state of the damping valve 91(a) and the tubular portion 62 of the case member 52. As a result, during the extension stroke in the extremely low speed region where the piston speed is less than the second predetermined value X2, a damping force with valve characteristics (characteristics in which the damping force is approximately proportional to the piston speed) determined by the valve opening characteristics of the damping valve 91(a) is obtained, and as shown by the solid line Y1 in Figure 4, the rate of increase in the damping force relative to an increase in piston speed is lower than during the extension stroke in the extremely low speed region where the piston speed is equal to or less than the first predetermined value X1.

[0070] During the extension stroke in the low-speed region where the piston speed is greater than the second predetermined value X2 and less than a third predetermined value X3 that is greater than the second predetermined value X2, the damping force adjustment valve 16 of the first damping force valve mechanism 15 shown in FIG. 2 remains closed, and the damping valve 91(a) of the second damping force valve mechanism 51 remains open, so that the flow rate of hydraulic fluid L in the rod-side chamber C through the passage in the hole portion 8B of the valve case 8, the first orifice 18D between the closed first valve 18 and the valve seat member 17, the intermediate chamber 5C, the passage in the passage hole (not shown) of the spring member 54, the passage in the passage hole 66 of the case member 52, and the passage between the open second valve 50 of the damping valve 91(a) and the cylindrical portion 62 of the case member 52 increases and is throttled by the first orifice 18D. As a result, a damping force with orifice characteristics defined by the flow path cross-sectional area of ​​the first orifice 18D is generated. Therefore, as shown by the solid line Y1 in Figure 4, in the extension stroke in the low-speed region where the piston speed is less than the third predetermined value X3, the characteristic of the damping force relative to the piston speed is such that the rate of increase of the damping force with respect to an increase in piston speed is lower than in the extension stroke in the extremely low-speed region where the piston speed is equal to or less than the first predetermined value X1, and higher than in the extension stroke in the extremely low-speed region where the piston speed is less than the second predetermined value X2.

[0071] During the extension stroke in the normal speed range where the piston speed is equal to or greater than the third predetermined value X3, the damping force control valve 16(a) of the first damping force valve mechanism 15 opens while the damping valve 91(a) of the second damping force valve mechanism 51 shown in FIG. 2 remains open. That is, the pressure in the rod-side chamber C increases and is introduced into the passage within the hole 8B of the valve case 8, and into the backpressure chamber 19 via passage 8A of the valve case 8. However, the pressure introduced into the backpressure chamber 19 is restricted by passage 8A, and as a result, the differential pressure in the valve-opening direction applied to the first valve 18 of the damping force control valve 16 from the passage within the hole 8B toward the backpressure chamber 19 increases, and the first valve 18 moves upward together with the poppet valve element 20 and the spring receiving member 26, compressing the biasing spring 27. Then, the annular valve portion 18C of the first valve 18 moves away from the annular valve seat 17A of the valve seat member 17. Therefore, the working fluid L in the rod-side chamber C flows into the bottom-side chamber B via the passage within the hole 8B of the valve case 8, the passage between the first valve 18 of the damping force control valve 16(a) in the open state and the valve seat member 17, the intermediate chamber 5C, the passage within a passage hole (not shown) of the spring member 54, the passage within the passage hole 66 of the case member 52, and the passage between the second valve 50 of the damping valve 91(a) in the open state and the cylindrical portion 62 of the case member 52. As a result, during the extension stroke in the normal speed range where the piston speed is equal to or greater than the third predetermined value X3, a damping force with valve characteristics defined by the valve opening characteristics of the damping valve 91(a) and the damping force control valve 16(a) is obtained, and as shown by the solid line Y1 in FIG. 4, the rate of increase of the damping force relative to an increase in piston speed is lower than during the extension stroke in the low speed range where the piston speed is less than the third predetermined value X3.

[0072] Here, during the extension stroke, when the coil 22 of the first damping force valve mechanism 15 is energized from the outside (i.e., the controller) and the solenoid 21 changes from a demagnetized state to an excited state, a magnetic force is generated that attracts the plunger 25 toward the stator core 23. As a result, the spring receiving member 26 is displaced together with the plunger 25 in a direction that compresses the biasing spring 27, and the poppet valve element 20 moves in the valve-opening direction so as to be lifted off the bottomed hole 18A of the first valve 18 due to the pressure in the bottomed hole 18A introduced from the backpressure chamber 19. At this time, the poppet valve element 20 opens the bottomed hole 18A of the first valve 18, and the pilot pressure (back pressure) in the backpressure chamber 19 is introduced into chamber 5E from the passage in the bottomed hole 18A and becomes lower. At this time, the pressure in the rod side chamber C is introduced into the passage inside the hole portion 8B of the valve case 8 and into the back pressure chamber 19 via the passage 8A of the valve case 8, but the pressure introduced into the back pressure chamber 19 is restricted by being throttled in the passage 8A and is therefore suppressed. As a result, the differential pressure in the valve opening direction applied to the first valve 18 of the damping force control valve 16 from the passage inside the hole portion 8B in the direction of the back pressure chamber 19 increases, and the annular valve portion 18C of the first valve 18 moves away from the annular valve seat 17A of the valve seat member 17. Therefore, the hydraulic fluid L in the rod-side chamber C flows to the bottom-side chamber B through the flow path 95, including the passage within the hole 8B of the valve case 8, the passage between the first valve 18 and the valve seat member 17 when the damping force control valve 16(a) is in the open state, the intermediate chamber 5C, the passage within the passage hole (not shown) of the spring member 54, the passage within the passage hole 66 of the case member 52, and the passage between the second valve 50 and the cylindrical portion 62 of the case member 52 when the damping valve 91(a) is in the open state. This results in a softer damping force than when the solenoid 21 is in the demagnetized state. At this time, the valve-opening characteristic of the first valve 18 is variably set in response to the thrust of the plunger 25 (the opening degree of the poppet valve element 20) due to the displacement of the poppet valve element 20. In this way, during the extension stroke, the controller controls the value of the current applied to the coil 22 of the solenoid 21 to displace the poppet valve element 20 in the axial direction, thereby increasing or decreasing the valve-opening pressure of the first valve 18. Therefore, the damping force generated by the damping force control shock absorber 1 during the extension stroke can be variably adjusted according to the valve opening pressure of the first valve 18, which is proportional to the current supplied to the solenoid 21 (current value).That is, during the extension stroke, the damping force generated by the damping force control valve 16 can be switched from a hard characteristic to a soft characteristic by externally energizing the coil 22 of the first damping force valve mechanism 15 to excite the solenoid 21.

[0073] The compression stroke when the solenoid 21 of the first damping force valve mechanism 15 is in a demagnetized state will be described. When the solenoid 21 of the first damping force valve mechanism 15 is in a demagnetized state, the poppet valve element 20 of the damping force control valve 16 closes the bottomed hole 18A of the first valve 18.

[0074] During the compression stroke, the piston 5 moves toward the bottom-side chamber B, increasing the pressure in the bottom-side chamber B and decreasing the pressure in the rod-side chamber C. During the compression stroke in an extremely low speed region where the piston speed is equal to or less than the fifth predetermined value X5, the damping force adjustment valve 16(b) of the first damping force valve mechanism 15 and the damping valve 91(b) of the second damping force valve mechanism 51 are both in a closed state, and the working fluid L in the bottom-side chamber B flows into the rod-side chamber C via, within the flow path 95, the second orifice 50A between the second valve 50 in a closed state and the cylindrical portion 62 of the case member 52, the passage inside the passage hole 66 of the case member 52, the passage inside a passage hole (not shown) of the spring member 54, the intermediate chamber 5C, the first orifice 18D between the first valve 18 in a closed state and the valve seat member 17, and the passage inside the hole portion 8B of the valve case 8. This generates a damping force with orifice characteristics determined by the flow path cross-sectional area of ​​second orifice 50A. Therefore, during the compression stroke in the extremely low speed region where the piston speed is equal to or less than fifth predetermined value X5, the damping force increases at a relatively high rate as the piston speed increases.

[0075] At this time, the pressure in the back pressure chamber 19, which is connected to the rod side chamber C via the passage 8A of the valve case 8, also decreases in the same manner as the pressure in the rod side chamber C, so that the pressure in the back pressure chamber 19 becomes the same as that of the rod side chamber C, and there is no pressure difference with the passage side inside the hole 8B.

[0076] During the compression stroke in the extremely low speed region where the piston speed is greater than the fifth predetermined value X5 and less than a sixth predetermined value X6 that is greater than the fifth predetermined value X5, the pressure in the bottom-side chamber B becomes higher, so that the damping force adjustment valve 16(b) of the first damping force valve mechanism 15 remains closed and the damping valve 91(b) of the second damping force valve mechanism 51 opens. As a result, the working fluid L in the bottom-side chamber B flows into the rod-side chamber C via the passage in the flow path 95 between the second valve 50 in the open state of the damping valve 91(b) and the cylindrical portion 62 of the case member 52, the passage inside the passage hole 66 of the case member 52, the passage inside a passage hole (not shown) of the spring member 54, the intermediate chamber 5C, the first orifice 18D between the first valve 18 in the closed state and the valve seat member 17, and the passage inside the hole portion 8B of the valve case 8. As a result, during the extension stroke in the extremely low speed region where the piston speed is less than the sixth predetermined value X6, a damping force with valve characteristics determined by the valve opening characteristics of the damping valve 91(b) is obtained, and the rate of increase in the damping force relative to an increase in piston speed is lower than during the compression stroke in the extremely low speed region where the piston speed is equal to or less than the fifth predetermined value X5.

[0077] During the extension stroke in the low-speed region where the piston speed is greater than the sixth predetermined value X6 and less than a seventh predetermined value X7 that is greater than the sixth predetermined value X6, the damping force adjustment valve 16(b) of the first damping force valve mechanism 15 remains in a closed state, and the damping valve 91(b) of the second damping force valve mechanism 51 remains in an open state, and the flow rate of hydraulic fluid L in the bottom-side chamber B through the passage between the second valve 50 in the open state of the damping valve 91(b) and the cylindrical portion 62 of the case member 52, the passage inside the passage hole 66 of the case member 52, the passage inside a passage hole (not shown) of the spring member 54, the intermediate chamber 5C, the first orifice 18D between the first valve 18 in the closed state and the valve seat member 17, and the passage inside the hole 8B of the valve case 8 increases and is throttled by the first orifice 18D. As a result, a damping force with orifice characteristics defined by the flow path cross-sectional area of ​​the first orifice 18D is generated. Therefore, during the compression stroke in the low speed region where the piston speed is less than the seventh predetermined value X7, the damping force characteristics relative to the piston speed are such that the rate of increase of the damping force with respect to an increase in piston speed is lower than during the compression stroke in the extremely low speed region where the piston speed is equal to or less than the fifth predetermined value X5, and higher than during the compression stroke in the extremely low speed region where the piston speed is less than the sixth predetermined value X6.

[0078] During the compression stroke in the normal speed range where the piston speed is equal to or greater than the seventh predetermined value X7, the damping force control valve 16(b) of the first damping force valve mechanism 15 opens while the damping valve 91(b) of the second damping force valve mechanism 51 remains open. That is, the pressure in the intermediate chamber 5C and chamber 5E increases, and the thrust toward chamber 5E, i.e., the valve-opening direction, due to the difference in the pressure-receiving area of ​​the first valve 18 of the damping force control valve 16(b) increases. As a result, the first valve 18 moves upward together with the poppet valve element 20 and the spring receiving member 26 while compressing the biasing spring 27. Then, the annular valve portion 18C of the first valve 18 moves away from the annular valve seat 17A of the valve seat member 17. Therefore, the working fluid L in the bottom-side chamber B flows to the rod-side chamber C through the passage of the flow path 95 between the second valve 50 of the damping valve 91(a) in an open state and the cylindrical portion 62 of the case member 52, the passage inside the passage hole 66 of the case member 52, the passage inside a passage hole (not shown) of the spring member 54, the intermediate chamber 5C, the passage between the first valve 18 of the damping force control valve 16(a) in an open state and the valve seat member 17, and the passage inside the hole 8B of the valve case 8. As a result, during the compression stroke in a normal speed range where the piston speed is equal to or greater than the seventh predetermined value X7, a damping force with valve characteristics defined by the valve opening characteristics of the damping valve 91(b) and the damping force control valve 16(b) is obtained, and the rate of increase of the damping force relative to an increase in piston speed is lower than during the compression stroke in a low speed range where the piston speed is less than the seventh predetermined value X7.

[0079] During the compression stroke, when the coil 22 of the first damping force valve mechanism 15 is energized from the outside (i.e., the controller) and the solenoid 21 changes from a de-energized state to an energized state, a magnetic force is generated that attracts the plunger 25 toward the stator core 23. As a result, the spring bearing member 26 is displaced together with the plunger 25 in a direction that compresses the biasing spring 27. This reduces the force introduced from the poppet valve element 20 against the thrust in the valve opening direction due to the difference in pressure-receiving area of ​​the first valve 18 of the damping force control valve 16(b). As a result, the valve opening pressure of the first valve 18, which pushes up the poppet valve element 20 to open it, decreases. This results in a softer damping force than when the solenoid 21 is de-energized. At this time, the valve opening characteristic of the first valve 18 is variably set in accordance with the thrust of the plunger 25. In this way, even during the compression stroke, the controller controls the value of the current passed through the coil 22 of the solenoid 21 to displace the plunger 25 in the axial direction, thereby increasing or decreasing the valve opening pressure of the first valve 18. Therefore, the damping force generated by the damping force adjustable shock absorber 1 during the compression stroke can be variably adjusted according to the valve opening pressure of the first valve 18, which is proportional to the current passed through the solenoid 21. In other words, even during the compression stroke, the damping force generated by the damping force adjustable valve 16 can be switched from a hard characteristic to a soft characteristic by externally passing current through the coil 22 of the first damping force valve mechanism 15 to excite the solenoid 21.

[0080] The reference example shown in the above-mentioned Patent Document 1 discloses a damping force adjustable shock absorber having two damping force valve mechanisms that open in the same stroke, and in which the opening and closing operation of the valve of one of the damping force valve mechanisms can be adjusted by a solenoid. However, in a damping force adjustable shock absorber, it is desired to improve the insufficient damping force when the piston speed is very low.

[0081] The damping force control shock absorber 1 of this embodiment includes a first valve 18 that adjusts the flow of hydraulic fluid L in a flow path 95 through which hydraulic fluid L moves between the rod-side chamber C and the bottom-side chamber B as the piston rod 6 moves, a solenoid 21 that adjusts the operation of the first valve 18, a first damping force valve mechanism 15 that has a first orifice 18D that constantly communicates between the upstream and downstream sides of the first valve 18, and a second damping force valve mechanism 51 that is arranged in series with the first damping force valve mechanism 15 in the flow path 95 and adjusts the flow of hydraulic fluid L moving in the flow path 95, and a second orifice 50A that constantly communicates between the upstream and downstream sides of the second valve 50. The first orifice 18D has a flow path cross-sectional area larger than that of the second orifice 50A. The second valve 50 operates at a speed slower than the speed at which the piston 5 moves than the first valve 18. In addition, the second damping force valve mechanism 51 includes a case member 52 having a cylindrical portion 62 that covers the radially outer side of the second valve 50 and a bottom portion 61 that supports the radially inner side of the second valve 50, and a pin member 53 that passes through a hole 65 formed in the bottom portion 61 of the case member 52 and fastens the second valve 50 to the case member 52 by crimping. Therefore, the damping force control shock absorber 1 can effectively improve the insufficient damping force when the piston speed is extremely low speed and extremely low speed by using the second orifice 50A of the second damping force valve mechanism 51 and the second valve 50. That is, in the shock absorber of the reference example described in Patent Document 1, as shown by the dashed line Y2 in FIG. 4, the damping force is low, particularly in the extremely low speed and extremely low speed ranges where the piston speed is less than the second predetermined value X2. However, in the damping force control shock absorber 1 of the embodiment, the damping force can be increased in the extremely low speed and extremely low speed ranges where the piston speed is less than the second predetermined value X2. This prevents a decrease in the ride comfort of the vehicle.

[0082] Furthermore, since the second valve 50, the case member 52, and the pin member 53 of the second damping force valve mechanism 51 can be integrated in advance, the assembly work to the piston 5 can be simplified. In addition, differences in the specifications of the second damping force valve mechanism 51 can be easily accommodated by simply changing the second damping force valve mechanism 51.

[0083] Furthermore, since the second damping force valve mechanism 51 is fixed to the piston 5 by welding, the second damping force valve mechanism 51 can be reliably fixed to the piston 5.

[0084] Furthermore, since the pin member 53 that is fastened by crimping is used, the axial length of the second damping force valve mechanism 51 can be shortened, and the mechanism can be made more compact.

[0085] The inner diameter of the second valve 50 is larger than the diameter of the hole 65 in the bottom 61 of the case member 52, so that when the pin member 53 is tightened, the second valve 50 is prevented from getting caught in the case member 52.

[0086] Furthermore, the second orifice 50A is formed by the gap between the outer diameter portion of the second valve 50 and the inner diameter portion of the tubular portion 62 of the case member 52, and the difference between the outer diameter of the pin member 53 and the inner diameter of the second valve 50 is formed to be larger than the radial length of the gap between the outer diameter portion of the second valve 50 and the inner diameter portion of the tubular portion 62 of the case member 52 before the pin member 53 is crimped. Therefore, before the pin member 53 is crimped, the second valve 50 can be positioned radially by its outer diameter portion and the inner diameter portion of the tubular portion 62 of the case member 52, and by crimping the pin member 53 in this state, it is possible to prevent the second valve 50 from getting caught in the case member 52. [Explanation of symbols]

[0087] 1...damping force adjustable shock absorber, 5...piston, 6...piston rod, 15...first damping force valve mechanism, 18...first valve, 18D...first orifice, 21...solenoid, 40...cylinder, 50...second valve, 50A...second orifice, 51...second damping force valve mechanism, 52...case member, 53...pin member, 61...bottom, 62...cylindrical portion, 65...hole, 95...flow path, B...bottom side chamber (chamber), C...rod side chamber (chamber).

Claims

1. a cylinder in which a working fluid is sealed; a piston slidably inserted into the cylinder and dividing the interior of the cylinder into two chambers; a piston rod having a first end connected to the piston and a second end extending outward from an end of the cylinder; a flow path through which the working fluid moves between the two chambers as the piston rod moves; a first damping force valve mechanism including: a first valve provided in the flow path and regulating the flow of the working fluid moving within the flow path; a solenoid that regulates the operation of the first valve; and a first orifice that constantly communicates between the upstream side and the downstream side of the first valve; a second damping force valve mechanism that is provided in the flow path and arranged in series with the first damping force valve mechanism, the second valve adjusting the flow of the working fluid moving within the flow path, and a second orifice that constantly communicates between the upstream side and the downstream side of the second valve; Equipped with The first orifice is formed so that a flow path cross-sectional area is larger than a flow path cross-sectional area of ​​the second orifice, The second valve operates at a speed at which the piston moves slower than the speed at which the first valve operates; The second damping force valve mechanism is a damping force adjustable shock absorber that includes a case member having a cylindrical portion that covers the radial outside of the second valve and a bottom portion that supports the radial inside of the second valve, and a pin member that passes through the second valve and a hole formed in the bottom portion of the case member and fastens them together by crimping.

2. 2. The damping force adjustable shock absorber according to claim 1, An adjustable damping force shock absorber, wherein the inner diameter of the second valve is larger than the diameter of the hole in the bottom portion.

3. 2. The damping force adjustable shock absorber according to claim 1, the second orifice is formed by a gap between an outer diameter portion of the second valve and an inner diameter portion of the cylindrical portion, A damping force adjustable shock absorber in which the difference between the outer diameter of the pin member and the inner diameter of the second valve is formed larger than the radial length of the gap before the pin member is crimped.

4. The damping force adjustable shock absorber according to any one of claims 1 to 3, The second damping force valve mechanism is fixed to the piston by welding.

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