JP3484488B2 - Damping force adjustable hydraulic shock absorber - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force-adjustable hydraulic shock absorber mounted on a suspension system of a vehicle such as an automobile. 2. Description of the Related Art A hydraulic shock absorber mounted on a suspension system of a vehicle such as an automobile has a damping device capable of appropriately adjusting a damping force in order to improve riding comfort and steering stability according to road surface conditions, running conditions, and the like. There is a power adjustable hydraulic shock absorber. [0003] In general, a damping force adjusting type hydraulic shock absorber slidably fits a piston having a piston rod connected to a cylinder filled with an oil liquid, thereby defining the inside of the cylinder as two chambers.
A main oil liquid passage and a bypass passage for communicating the two chambers in the cylinder with the piston portion are provided, and a damping force generating mechanism including an orifice and a disc valve is provided in the main oil liquid passage,
The bypass passage is provided with a damping force adjusting valve for adjusting the passage area. The damping force is reduced by opening the bypass passage by the damping force adjusting valve to reduce the flow resistance of the oil fluid between the two chambers in the cylinder (soft characteristic), and by closing the bypass passage to reduce the oil flow. By increasing the flow resistance between the chambers, the damping force can be increased (hard characteristic). As described above, the damping force characteristics can be appropriately adjusted by opening and closing the damping force adjustment valve. However, when the damping force is adjusted by the passage area of the bypass passage as described above, the damping force greatly varies in the low-speed region of the piston speed because the damping force depends on the orifice characteristics of the oil passage. However, in the medium and high speed range of the piston speed,
Since the damping force depends on the damping force generation mechanism (disk valve) of the main oil liquid passage, the damping force characteristics cannot be changed significantly. Therefore, conventionally, for example, Japanese Utility Model Laid-Open No. Sho 62-155
No. 242, a back pressure chamber is formed at the back of a valve body of a damping force adjusting valve such as a disc valve for adjusting a passage area of a main oil liquid passage communicating between cylinder chambers. A damping force-adjustable hydraulic shock absorber is known in which a pressure chamber communicates with a cylinder chamber on the upstream side of a valve body via a fixed orifice, and communicates with a cylinder chamber on the downstream side of the valve body via a variable orifice. Have been. According to this damping force adjusting type hydraulic shock absorber, by opening and closing the variable orifice, the communication passage area between the cylinder chambers is adjusted, and the pressure in the pressure chamber is changed to open the damping force adjusting valve. The pressure can be varied.
In this way, the orifice characteristics and the valve characteristics can be adjusted, and the adjustment range of the damping force characteristics can be widened. [0008] Generally, in a damping force-adjustable hydraulic shock absorber mounted on a suspension system of a vehicle, orifice characteristics and valve characteristics are required in terms of both steering stability and ride comfort. And can be adjusted,
The opening pressure of the damping force adjustment valve at the time of hardware characteristics is sufficiently increased,
Further, it is desired to reduce the inclination of the valve characteristics, that is, the tendency of the damping force to increase with the increase in the piston speed when the valve is opened. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is possible to adjust an orifice characteristic and a valve characteristic, and to sufficiently increase a valve opening pressure of a damping force adjusting valve in a hard characteristic, and It is an object of the present invention to provide a damping force-adjustable hydraulic shock absorber that can reduce the inclination of the damper. [0010] In order to solve the above-mentioned problems, the present invention provides a communication path between two chambers in accordance with expansion and contraction of an operating rod inserted into a cylinder filled with an oil liquid. in the damping force adjustable hydraulic shock absorber which controls the flow of hydraulic fluid occurring within the damping force adjusting mechanism, the damping force adjusting mechanism, the inner
Peripheral portion is fixed, a disk valve for adjusting the passage area of the communication passage between the outer peripheral portion and the valve seat, and a back pressure chamber for applying a pressure in the closing direction to the disk valve <br/>, wherein disk
Liquid-tight contact with the outer periphery of the valve to define the back pressure chamber
Movable member, the valve seat of the disc valve and the
Provided near the inner periphery side of the contact portion between the movable member, the upstream passage for communicating the upstream side of the chamber of said two chambers and the back pressure chamber with a flow resistance, wherein said back pressure chamber equipped with downstream passage for communicating the downstream chamber of the two chambers, and the variable orifice for adjusting the passage area of the downstream side passage, the
Characterized in that that. [0011] [act] By having such a configuration, with the expansion and contraction of the rod, the damping force adjusting mechanism, the variable orifice and the disk valve hydraulic fluid to flow through the upstream passage, the back pressure chamber and the downstream passage As a result, a damping force is generated. By changing the passage area of the variable orifice, the orifice characteristics can be directly adjusted, the internal pressure of the back pressure chamber can be changed, and the valve opening characteristics of the disc valve can be changed to adjust the valve characteristics. In addition, disk server
The aperture of the flow path to be formed when the valve is opened between the lube valve seat, although the flow rate of the hydraulic fluid is reduced increases and the pressure valve body of the flow channel around is drawn in the closing direction, and this reduction
Pressure is applied to the valve seat of the disc valve and the
Since it is transmitted to the back pressure chamber via the upstream passage provided near the inner peripheral side , the disc valve is easily opened, and as a result, the disc valve is opened and closed in the valve closing direction and the valve opening direction caused by the flow of the oil liquid. it especially forces acting is canceled
You . Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 3 shows a hydraulic circuit of the damping force adjusting type hydraulic shock absorber 1 of the present embodiment. As shown in FIG. 3, in the damping force-adjustable hydraulic shock absorber 1, a piston 3 is slidably fitted in a cylinder 2 filled with an oil liquid, and the piston 3 moves the inside of the cylinder 2 on the cylinder. Chamber 2a and cylinder lower chamber 2b
Are defined in two rooms. One end of a piston rod 4 (operating rod) is connected to the piston 3, and the other end of the piston rod 4 is inserted through a rod guide and an oil seal (not shown) mounted on the upper end of the cylinder 2. And extends outside the cylinder 2. In an outer peripheral portion of the cylinder 2, a reservoir chamber 5 filled with an oil liquid and a gas is provided.
And is connected to the cylinder lower chamber 2b via a base valve 6 provided at the bottom of the cylinder 2. The piston 3 has a check valve 7 which allows only the flow of the oil liquid from the cylinder lower chamber 2b side to the cylinder upper chamber 2a side.
Is provided. The base valve 6 has a reservoir chamber 5
A check valve 8 that allows only the flow of the oil liquid from the side to the cylinder lower chamber 2b side is provided. The two chambers of the cylinder upper chamber 2a and the reservoir chamber 5 are communicated by a communication passage 9 (consisting of 9a and 9b), and a damping force adjusting mechanism 10 is provided in the communication passage 9. The damping force adjusting mechanism 10 is provided with a damping valve A for opening the valve under the pressure of the oil liquid in the cylinder upper chamber 2a to adjust the passage area of the communication passage 9. The damping valve A is a pilot pressure control relief valve, and the passage area is determined by the pilot pressure from the pilot pressure passage B. The pilot pressure passage B communicates with the cylinder upper chamber 2a on the upstream side of the communication passage 9a via an upstream passage having a flow path resistance by the fixed orifice C, and a downstream side having a pilot valve D (variable orifice). It is connected to the reservoir chamber 5 downstream of the communication passage 9b via the passage. The pilot valve D acts as a variable orifice, and adjusts the pilot pressure by a passage area ratio with the fixed orifice C on the upstream side. Next, a more specific structure of the damping force adjusting mechanism 10 will be described with reference to FIGS. As shown in FIG. 1, the damping force adjusting mechanism 10
A valve member 12 and a plug member 13 are fitted into a cylindrical housing 11 to form an oil chamber 11a inside the housing 11. An oil chamber 11a is connected to the valve member 12 through the communication passage 9a.
An inlet port 14 is provided for communication with the cylinder upper chamber 2a. An oil chamber 11a communicates with a side wall of the housing 11.
An outlet port 15 is provided for communication with the reservoir chamber 5 side of 9b. The plug member 13 is integrally provided with a cylindrical guide portion 16. The guide portion 16 extends along the axial direction of the housing 11, and its tip is inserted through the valve member 12. ing. A valve member 12 is provided on the outer periphery of the guide portion 16.
Disc valve 17 which is a valve body facing the inlet port 14 of
(Corresponding to the damping valve A in FIG. 3) and a bottomed cylindrical fixing member 18 forming an annular space facing the back side of the disk valve 17 and fitted and fixed. On the end face of the valve member 12 on the side of the oil chamber 11a, an annular holding portion 19 is provided on the inner peripheral portion with the inlet port 14 therebetween, and an annular valve seat 20 is provided on the outer peripheral portion. I have. The disk valve 17 has an inner peripheral portion sandwiched and fixed between the holding portion 19 and the retainer 21, and an outer peripheral portion in contact with the valve seat 20. Here, the valve seat 20 has a predetermined dimension L with respect to the holding portion 19.
(For example, about 0.2 mm) (see FIG. 2), whereby the disk valve 17 is bent and pressed against the valve seat 20 with a predetermined initial load. Further, the plate thickness of the disk valve 17 is, for example, 0.4 mm or less so that the flexural rigidity is sufficiently low. A cylindrical movable member 22 is slidably fitted in the fixed member 18, and one end of the movable member 22 is in liquid-tight contact with the back surface of the disk valve 17. A compression spring 23 is interposed between the inner flange portion at one end of the fixing member 22 and the bottom of the fixing member 18, and the fixing member is pressed against the disk valve 17 by the elastic force of the spring 23,
A back pressure chamber 24 (corresponding to the pilot pressure passage B in FIG. 3) is formed on the back side of the disc valve by the disc valve 17, the fixed member 18, and the movable member 22. The back pressure chamber 24 is connected to the inlet port 14 via a fixed orifice 25 (corresponding to the fixed orifice C in FIG. 3) as an upstream passage provided in the disc valve 17, that is, upstream of the communication passage 9 a. Is communicated with the cylinder upper chamber 2a side. The fixed orifice 25 is for the valve seat 20 of the disc valve 17.
The disk valve 17 is opened near the inner peripheral side of the contact portion with the movable member 22 , that is, near the valve seat of the flow path formed when the disk valve 17 is opened. The back pressure chamber 24 is provided on the outlet port 15 side via guide ports 26 and 27 as downstream passages provided on the side wall of the guide portion 16, a flow path 29 of a spool 28 described later, and an oil chamber 11 a. That is, it is communicated with the reservoir chamber 5 side on the downstream side of the communication passage 9b. A spool 28 is slidably fitted in the guide portion 16 of the plug member 13, and the movement of the spool 28 adjusts the area of the communication passage between the guide port 26 and the flow path 29. (The guide port 26 and the flow path 29 correspond to the pilot valve D as the variable orifice in FIG. 3). The guide port 27 and the flow path 29 are always in communication with a constant passage area. And the spool 28 has a spring
30 is biased to one side, and an operating rod 31 of a proportional solenoid actuator (not shown) moves the spool 28 against the biasing force of the spring 30 and positions the spool 28 according to the thrust. By the guide port
The area of the communication passage between the passage 26 and the flow passage 29 can be adjusted. The operation of the embodiment constructed as described above will now be described. During the extension stroke of the piston rod 4, the check valve 7 is closed by the movement of the piston 3, the oil liquid in the cylinder upper chamber 2 a side is pressurized, and the oil liquid moved by the piston 3 flows through the communication passage 9. Through the damping force adjusting mechanism 10 and the reservoir chamber 5
Flows to At the same time, the oil liquid corresponding to the movement of the piston 3 due to the opening of the check valve 8 flows from the reservoir chamber 5 to the cylinder lower chamber 2b due to the expansion of the gas. In the damping force adjusting mechanism 10, the oil liquid flowing into the inlet port 14 from the cylinder upper chamber 2a is supplied to the fixed orifice 25 (the fixed orifice C in FIG. 3) of the disk valve 17 and the back pressure chamber.
The gas flows from the outlet port 15 to the reservoir chamber 5 through the guide port 26 and the flow path 29 (pilot valve in FIG. 3), the guide port 27 and the oil chamber 11a. At this time, when the pressure on the cylinder upper chamber 2a side reaches the valve opening pressure and the disk valve 17 (the damping valve A in FIG. 3) opens, the oil liquid flows directly from the inlet port 14 to the oil chamber 11a. Therefore, before the piston speed is low and the disc valve 17 (damping valve A) is opened, the guide port
26, the orifice characteristic damping force is generated according to the area of the communication passage between the flow passages 29 (the communication passage area of the pilot valve D). When the piston speed increases and the pressure on the cylinder upper chamber side 2a increases to open the disc valve 17 (damping valve A), a damping force having valve characteristics is generated according to the opening degree. And
The damping force characteristic can be adjusted by moving the spool 28 by the proportional solenoid actuator to change the area of the communication path between the guide port 26 and the flow path 29 (the area of the communication path of the pilot valve D). In this case, the smaller the area of the communication passage between the guide port 26 and the flow passage 29 (the area of the communication passage of the pilot valve D), the greater the pressure loss and the greater the back pressure chamber 24.
Since the pressure in the inside increases, and this pressure acts on the back side of the disc valve 17 in the valve closing direction, the valve opening pressure of the disc valve 17 (damping valve A) also increases. Therefore, the spool
The orifice characteristic and the valve characteristic change simultaneously by moving the 28 to change the communication passage area between the guide port 26 and the flow passage 29 (the communication passage area of the pilot valve D). The damping force characteristics can be largely changed over the range, and the adjustment range of the damping force characteristics can be widened. On the other hand, during the contraction stroke of the piston rod 4, the check valve 8 of the base valve 6 is closed by the movement of the piston 3, the check valve 7 of the piston 3 is opened, and the piston rod 4 intrudes into the cylinder 2. Is pressurized,
That amount of oil flows from the upper cylinder chamber 2a through the communication passage 9a to the reservoir chamber 5 via the damping force adjusting mechanism 10, and compresses the gas. Therefore, as in the case of the extension stroke, a damping force is generated by the damping force adjusting mechanism 10, and the orifice characteristics and the valve characteristics can be adjusted by moving the spool. During the contraction stroke, the piston rod 4
As a result, the damping force is generated by the flow of the oil liquid that enters the cylinder 2 due to the shortening of the piston rod 4, so that the flow rate of the oil liquid of the damping force adjusting mechanism 10 with respect to the stroke of the piston rod 4 becomes smaller than that during the extension stroke. Since the flow rate of the oil liquid is reduced, the flow resistance of the oil liquid is also reduced, so that a smaller damping force is generated than during the extension stroke. In the above case, as shown in FIG.
When the disc valve 17 is opened, the oil liquid at the inlet port 14 flows toward the oil chamber 11a through the gap E between the valve seat 20 and the disc valve 17 (a flow path formed when the disc valve 17 is opened). At this time, in the gap portion E, the flow path of the oil liquid is narrowed to increase the flow velocity, so that the pressure decreases. Then, the disc valve 17 is drawn toward the valve seat 20 due to a decrease in the pressure in the gap E, and it becomes difficult to open the valve. On the other hand, since the fixed orifice 25 is provided in the vicinity of the seat of the disc valve 17 on the valve seat 20,
The pressure in the gap E is transmitted through the fixed orifice 25 to the back pressure chamber 24.
And the pressure in the downstream portion F near the fixed orifice 25 also decreases. When the pressure in the downstream portion F decreases, the disk valve 17 is drawn in the valve opening direction near the outer periphery, so that the disk valve 17 is easily opened. As described above, since the pressures in both the gap portion E and the downstream portion F are reduced, the forces acting in the valve opening direction and the valve closing direction are offset, thereby preventing the disk valve 17 from becoming difficult to open. Can be. Therefore, as shown by the solid line in FIG. 5 , the damping force characteristic of the damping force adjustable hydraulic shock absorber 1 indicates the slope of the valve characteristic, that is, the disc valve 17.
The tendency of the damping force to increase with an increase in the piston speed when the valve is opened decreases. Further, the valve seat 20 is projected from the holding portion 19 by a predetermined dimension L (for example, about 0.2 mm) so that
In addition to increasing the initial load of
The thickness of the disk valve 17 is, for example, 0.4 mm or less, and the flexural rigidity is sufficiently low, so that the valve opening pressure of the disk valve 17 is sufficiently high, and the inclination of the valve characteristic at the time of valve opening is small. Here, for example, as shown in FIG. 4, when the fixed orifice 25 is arranged at a position from the center of the disk valve 17, as shown in FIG. In the gap E with the valve 17,
The flow path of the oil liquid is narrowed, the flow velocity is increased, and the pressure is reduced. Also, in the downstream portion G of the fixed orifice 25, the throttle of the fixed orifice 25 increases the flow velocity of the oil liquid, and the pressure decreases. On the other hand, in the vicinity H of the outer peripheral portion on the back side of the disk valve, the pressure becomes high because almost no flow of the oil liquid occurs. For this reason, a force in the valve closing direction acts on the disc valve 17 due to a pressure difference between the gap E and the vicinity H of the outer periphery, so that the disc valve 17 becomes difficult to open. The downstream part G is
Since the disc valve 17 is located away from the seat on the valve seat 20, the pressure drop hardly affects the valve opening pressure. As a result, the apparent rigidity after opening of the disk valve 17 is increased (the disk valve 17 becomes difficult to open), and the damping force characteristic is as shown by the broken line in FIG.
The inclination of the valve characteristics, that is, the tendency of the damping force to increase as the piston speed increases when the disc valve 17 is opened increases. Therefore, as shown in FIGS. 1 and 2, by providing the fixed orifice 25 near the seat of the disc valve 17 on the valve seat 20, the inclination of the valve characteristic after the disc valve 17 is opened can be reduced. The inclination of the valve characteristic after the disc valve 17 is opened can be set freely by the arrangement of the fixed orifice 25. In the above embodiment, as an example, one damping force adjusting mechanism generates a damping force on both the extension side and the contraction side. Although the present invention is not limited to this, the present invention is not limited to this, and the flow of the oil liquid generated in the oil liquid passage between the two chambers according to the expansion and contraction of the operating rod inserted into the cylinder filled with the oil liquid Can be applied to other types of damping force-adjustable hydraulic shock absorbers as long as the damping force is controlled by a damping force adjusting mechanism to generate damping force. [0046] As has been described above in detail, according to the damping force adjustable hydraulic shock absorber of the present invention, with the expansion and contraction of the actuating rod, a damping force adjusting mechanism, the upstream-side passage hydraulic fluid, back variable orifice and disposition in circulation the pressure chamber and the downstream passage
The damping force is generated by the valve . By changing the passage area of the variable orifice, the orifice characteristics can be directly adjusted, the internal pressure of the back pressure chamber can be changed, and the valve opening characteristics of the disc valve can be changed to adjust the valve characteristics. Also, due to the restriction of the flow path formed when the disc valve is opened between the valve seat and the valve seat, the flow rate of the oil liquid near this flow path increases, the pressure decreases, and the valve body is drawn in the valve closing direction. This reduced pressure
Near the inner peripheral side of the contact part between the valve seat and the movable member of the valve.
Since it is transmitted to the back pressure chamber via the provided upstream passage ,
The disc valve becomes easy to open. As a result, the forces acting on the disc valve in the valve closing direction and the valve opening direction caused by the flow of the oil liquid are offset, and it is possible to prevent the disc valve from becoming difficult to open, thereby reducing the inclination of the valve characteristics. It has an excellent effect that it can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a damping force adjusting mechanism of a damping force adjusting type hydraulic shock absorber according to one embodiment of the present invention. FIG. 2 is an enlarged view of the vicinity of a disc valve showing a state of oil pressure when the damping force adjusting mechanism of FIG. 1 is opened. FIG. 3 is a circuit diagram showing a damping force adjusting type hydraulic shock absorber according to one embodiment of the present invention. FIG. 4 is an enlarged view of the periphery of the disc valve showing the state of oil pressure at the time of valve opening when the fixed orifice is arranged from the center of the disc valve in the damping force adjusting mechanism of FIG. FIG. 5 is a view showing a damping force characteristic of the damping force adjustable hydraulic shock absorber according to one embodiment of the present invention. [Description of Signs] 1 Damping force adjustable hydraulic shock absorber 2 Cylinder 2a Upper cylinder chamber 4 Piston rod (operating rod) 5 Reservoir chamber 10 Damping force adjusting mechanism 17 Disk valve (valve element) 22 Movable member 24 Back pressure chamber 25 Fixed Orifice (upstream passage) 26,27 Guide port (back pressure passage, variable orifice) 29 Flow path (back pressure passage, variable orifice)

Continuation of the front page (56) References JP-A-63-312532 (JP, A) JP-A-62-155242 (JP, U) JP-A-62-163345 (JP, U) German Patent Application Publication 3924168 (DE) , A1) German Patent Application Publication No. 4007261 (DE, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16F 9/44 F16F 9/348

Claims (1)

(57) [Claim 1] Damping force adjustment of the flow of the oil liquid generated in the communication path between the two chambers in accordance with the expansion and contraction of the operating rod inserted into the cylinder in which the oil liquid is sealed. In a damping force adjustment type hydraulic shock absorber controlled by a mechanism, the damping force adjustment mechanism may have an inner periphery.
Parts are fixed, a disk valve for adjusting the passage area of the communication passage between the outer peripheral portion and the valve seat, and a back pressure chamber for applying a pressure in the closing direction to the disc valve, the disc bar
Liquid-tightly abuts the outer periphery of the lube to define the back pressure chamber
A movable member, the valve seat of the disc valve, and the movable member;
Provided near the inner periphery side of the contact portion between rotary members, an upstream passage for communicating the upstream side of the chamber of said two chambers and the back pressure chamber with a flow resistance, wherein said back pressure chamber a downstream passage for communicating the downstream chamber of the two chambers, the damping force adjustable hydraulic pressure and a variable orifice for adjusting the passage area of the downstream side passage, wherein <br/> that it comprises a for Shock absorber.