JP2001012534A - Damping force adjustable type hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To directly control damping force regardless of piston velocity and slow a rise of damping force in a damping force adjustable type hydraulic shock absorber. SOLUTION: Damping force is generated by controlling fluid flow generated by sliding of a piston in a cylinder 2 with using a main disc valve 34 and a disc valve 49 attached to a plunger 46. The damping force is directly controlled regardless of piston velocity by adjusting opening pressure of the disc valve 49 according to a carried electric current to a coil 59, and simultaneously changes pressure in a back pressure chamber 40 to adjust opening pressure of the main disc valve 34. A rise of the damping force is made slow and hysteresis of the damping force against expansion and contraction of a piston rod is made small to improve comfortabless of a vehicle by providing a variable orifice B for opening a channel to bypass the disc valve 49 when the opening pressure thereof is set to be low and by circulating an oil before opening the disc valve 49.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on a suspension system of a vehicle such as an automobile, and the damping force can be appropriately adjusted according to road surface conditions, running conditions, etc., in order to improve ride comfort and steering stability. The present invention relates to a damping force adjustable hydraulic shock absorber.

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 so as to divide the cylinder into two chambers.
A damping force adjusting valve (flow rate control valve) is provided in an oil passage communicating between these cylinder chambers, and a damping force is generated by controlling the flow of the oil liquid caused by the movement of the piston by the damping force adjusting valve. The damping force can be appropriately adjusted by adjusting the flow path area of the above. During normal running of the vehicle, the damping force is reduced to absorb the vibration caused by the unevenness of the road surface to improve the riding comfort. Also, at the time of turning, accelerating, braking, high-speed running, etc., the damping force is reduced. , The change in the attitude of the vehicle body can be suppressed, and the steering stability can be improved.

In addition, an actuator for switching the damping force of the damping force adjusting type hydraulic shock absorber, various sensors such as an acceleration sensor for detecting a running condition of the vehicle, and a controller for controlling the actuator based on the detection of these sensors are used. There is known a suspension control device that controls a damping force in real time in accordance with a road surface condition, a running condition, and the like to improve riding comfort and steering stability.

In the above damping force adjusting type hydraulic shock absorber using a flow control valve as the damping force adjusting valve, the damping force is adjusted by determining the flow path area. Will change. Therefore, the adjustment of the damping force is to adjust the damping coefficient using the piston speed as a variable. Therefore, in order to control the damping force in the suspension control device, the piston speed is detected, and a damping coefficient (a flow area of the damping force adjusting valve) at which a desired damping force is generated with respect to the input of the piston speed is calculated. In addition, it is necessary to take a procedure of driving the actuator so that the damping coefficient is obtained, which increases the load on the controller.

Therefore, conventionally, a pressure control valve is used as a damping force adjusting valve, and the opening of the pressure control valve is adjusted by adjusting the opening of the pressure control valve by the pressure of the oil generated by the movement of the piston and the thrust of the proportional solenoid. Damping force-adjustable hydraulic shock absorber capable of directly controlling the damping force has been proposed (JP-A-6-330977, JP-A-10-19678).
No. 3 etc.). As described above, by applying the damping force-adjustable hydraulic shock absorber capable of directly controlling the damping force to the suspension device, the load on the controller can be reduced and an appropriate damping force can be obtained quickly. .

[0006]

However, in the above-described damping force adjusting type hydraulic shock absorber using the conventional pressure control valve,
There are the following problems. Before the pressure control valve, which is the damping force adjusting valve, is opened, the oil passage is blocked by the pressure control valve even when the damping force is adjusted low, and the pressure of the oil liquid reaches the valve opening pressure. At this time, since the oil passage is suddenly communicated, the damping force rises sharply, and the ride quality deteriorates. Also, when the stroke direction of the piston rod is switched (piston speed is 0), the pressure fluctuation becomes large due to the compression of the oil liquid, deformation of the seal, etc., so that the switching from the extension side to the contraction side and the contraction side to the extension side. There is a problem that the difference in the damping force that occurs between the switching and the hysteresis increases, and it is difficult to obtain a stable damping force.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to directly control a damping force irrespective of a piston speed and to make the rise of the damping force gentle to reduce the hysteresis of the damping force. It is an object of the present invention to provide a damping force-adjustable hydraulic shock absorber that can perform pressure reduction.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a cylinder filled with an oil liquid, a piston slidably fitted in the cylinder,
A piston rod having one end connected to the piston and the other end extending to the outside of the cylinder, a main oil passage and an auxiliary oil passage connected to the cylinder and allowing oil to flow by sliding of the piston, A pilot-type damping valve provided in the main oil passage, a fixed orifice and a pressure control valve provided in the sub-oil passage, and the fixed orifice of the sub-oil passage and the pressure control valve. A damping force-adjusting hydraulic shock absorber wherein the pressure between the pilot-type damping valve and the pilot-type damping valve is a pilot pressure, wherein the pressure control valve adjusts a valve opening pressure by balancing with a thrust of a solenoid; It is characterized in that a variable orifice is provided to open the sub oil passage when the pressure is adjusted low and bypass the pressure control valve and close the sub oil passage when the pressure is adjusted high. To.

With this configuration, when the opening pressure of the pressure control valve is adjusted to a low value, the pressure control valve is bypassed by the variable orifice, so that the rise of the damping force becomes gentle, and the piston rod has Fluctuations in the pressure of the oil liquid when the stroke is switched are reduced.

A second aspect of the present invention is characterized in that, in the configuration of the first aspect, the pressure control valve is a disc valve.

With this configuration, it is possible to relieve a sudden increase in the pressure of the oil liquid due to the bending of the disk valve.

According to a third aspect of the present invention, in the configuration of the second aspect, the variable orifice forms a flow path by a gap between the disk valve and a seat member disposed on the back of the variable orifice, and the pressure control is performed. The flow path area is adjusted by bending the disc valve pressed against the valve seat of the valve.

With this configuration, when the pressure of the disc valve on the valve seat is increased to increase the valve opening pressure, the disc valve is bent and the gap between the disc member and the seat member is reduced, and the flow of the variable orifice is reduced. The road closes.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 2, the damping force-adjusting hydraulic shock absorber 1 of the present embodiment has a double cylinder structure in which an outer cylinder 3 is provided outside a cylinder 2.
A reservoir 4 is formed between the outer cylinder 3 and the outer cylinder 3. A piston 5 is slidably fitted in the cylinder 2.
This piston 5 causes the cylinder 2 to move inside
And a lower chamber 2b. One end of a piston rod 6 is connected to the piston 5 by a nut 7, and the other end of the piston rod 6 passes through the cylinder upper chamber 2 a and is mounted on the upper end of the cylinder 2 and the outer cylinder 3. 8 and the oil seal 9, and extend outside the cylinder 2. At the lower end of the cylinder 2, a base valve 10 that partitions the cylinder lower chamber 2b and the reservoir 4 is provided.

The piston 5 has an oil passage 11 communicating between the cylinder upper and lower chambers 2a and 2b, and a cylinder lower chamber 2b of the oil passage 11.
A check valve 12 that allows only the flow of the oil liquid from the side to the cylinder upper chamber 2a side is provided. The base valve 10 has an oil passage 13 for communicating the cylinder lower chamber 2b with the reservoir 4.
Further, a check valve 14 is provided which allows only the flow of the oil liquid from the reservoir 4 side of the oil passage 13 to the cylinder lower chamber 2b side. An oil liquid is sealed in the cylinder 2,
The reservoir 4 is filled with an oil liquid and a gas of a predetermined pressure.

An outer tube 15 is externally fitted to the cylinder 2, and an annular oil passage is provided between the cylinder 2 and the outer tube 15.
16 are formed. The annular oil passage 16 is formed in an upper chamber of the cylinder by an oil passage 17 provided on a side wall near the upper end of the cylinder 2.
Communicated with 2a. An opening 18 is formed in a side wall of the outer tube 15. A damping force generating mechanism 19 is attached to a side surface of the outer cylinder 3.

The damping force generating mechanism 19 will be described with reference to FIG. As shown in FIG. 1, one end opening having a flange portion 21 of a cylindrical case 20 is welded to a side wall of the outer cylinder 3. The passage member 22, the valve member 23, the cylindrical member 24, and the pilot valve member 25 are inserted into the case 20 in order from the flange portion 21 side so as to abut each other. Then, a proportional solenoid control unit 26 is attached to the other end of the case 20 by a nut 27, and a pilot valve member is provided.
25, the passage member 22, the valve member 23, and the cylindrical member 24.
And the pilot valve member 25 are fixed. Passage member 2
2, valve member 23, cylindrical member 24 and pilot valve member 2
An annular oil chamber 28 is formed between the outer peripheral portion of 5 and the case 20. The annular oil chamber 28 is connected to the reservoir 4 by an oil passage 29 provided in the flange 21 of the case 20.

The valve member 23 includes a passage member 22 and an annular oil chamber.
Oil passages 30, 31 and an annular groove 32 are provided for communication with the passage 28. The valve member 23 has a main disc valve 34.
(Pilot type damping valve), spacer disk 35, seal ring 36 and disc-shaped leaf spring 37 are pin 38 and nut
Installed by 39. The main disk valve 34 is
The outer peripheral part lifts and opens the valve, and the oil passage
The flow of the oil liquid from the 30 side to the annular groove 32 side is controlled to generate a damping force. Also, spacer disk
35 and the seal ring 36 are pressed against the back of the main disc valve 34 by a leaf spring 37, and form a back pressure chamber 40 between the pilot valve member 25 and the inner pressure of the back pressure chamber 40. It acts on the valve 34 in the valve closing direction. The main disk valve 34 is provided with a fixed orifice 34a, and the fixed orifice 34a communicates with the back pressure chamber 40 through an oil passage 35a of the spacer disk 35 and a notch 37a formed on the outer periphery of the leaf spring 37. Have been.

The pilot valve member 25 is provided with an oil passage 42 for communicating the back pressure chamber 40 with an oil chamber 41 formed between the back pressure chamber 40 and the proportional solenoid control unit 26. The oil chamber 41 is connected to the annular oil chamber 28 by an oil passage 43. Pilot valve member 25
Has an annular valve seat 45 protruding around the oil passage 42,
A plunger 46 of the proportional solenoid control unit 26 is guided by a guide 47 so as to move forward and backward, facing the valve seat 45. A disc valve 49, a sub disc valve 50, a retainer 51, and a washer 52 (seat member) are slidably fitted along the axial direction of the projection 48 at the tip of the plunger 46 in this order from the tip side. I have.

As shown in FIG. 3, the disc valve 49 is
The seat is seated on the valve seat 45, receives the pressure of the oil liquid on the back pressure chamber 40 side, bends, and its outer peripheral portion is lifted from the valve seat 45. A notch is provided at the periphery of the opening of the disc valve 49 through which the projection 48 is inserted, and an oil passage 53 is provided between the projection 48 and the projection 48.
Are formed. The auxiliary disk valve 50 has a smaller diameter than the disk valve 49, and is provided with a notch 54 abutting on the back of the disk valve 49 and communicating with the oil passage 53. The retainer 51 has a smaller diameter than the notch 54 of the sub-disc valve 50, communicates the notch 54 with the oil chamber 41, and bends the disc valve 49 and the sub-disc valve 50 with the outer peripheral portion serving as a fulcrum. The washer 52 has a larger diameter than the auxiliary disk valve 50, and forms a variable orifice B together with the auxiliary disk valve 50. The washer 52 is brought into contact with the auxiliary disk valve 50 to cut off the communication of the notch 54 with the oil chamber 41. With
The maximum deflection amount of the disc valve 49 and the sub disc valve 50 is regulated.

The plunger 46 is urged toward the valve seat 45 by a coil spring 55.
49 is pressed against the valve seat 45 with a predetermined initial load by the elastic force of the spring 55, and the disk valve 49 and the auxiliary disk valve 50 bend with the retainer 51 as a fulcrum so that the auxiliary disk valve 50 contacts the washer 52 and the notch 54 The communication with the oil chamber 41 is cut off (see FIG. 4). The plunger 46 is formed with a throttle passage 57 that connects an oil chamber 56 formed at the back of the plunger 46 with the oil passage 42.
In addition to balancing the pressures acting on both ends of the plunger 46, an appropriate damping force is applied to the movement of the plunger 46. A pressure control valve A is constituted by the valve seat 45, the plunger 46, and the disc valve 49.
When a coil 59 (solenoid) is energized by the lead wire 58, a thrust is generated in the plunger 46 in a direction to separate the disc valve 49 from the valve seat 45, and the thrust and the initial load by the spring 55 balance the disc valve 49. The valve opening pressure is determined, whereby the control pressure (relief pressure) of the pressure control valve A can be adjusted according to the current supplied to the coil 59.

In the above configuration, the oil passage 17, the annular oil passage 16, the opening 18, the passage member 22, the oil passage 30, the annular groove 32, the oil passage
31, the annular oil chamber 28 and the oil passage 29, the cylinder upper chamber 2a
And a main oil liquid passage which communicates with the reservoir 4, and has a fixed orifice 34a, an oil passage 35a, a notch 37a,
The back pressure chamber 40, the oil passage 42, the oil chamber 41, and the oil passage 43 constitute a sub oil passage that bypasses the main disk valve 34 that is a pilot damping valve.

The operation of the present embodiment having the above configuration will be described below. During the extension stroke of the piston rod 6, the check valve of the oil passage 11 of the piston 5 is moved by the movement of the piston 5.
12 is closed, the oil liquid in the cylinder upper chamber 2a side is pressurized, and the oil passage
17, damping force generating mechanism 19 through annular oil passage 16 and opening 18
Through the oil passage 30, the fixed orifice 34a of the main disk valve 34, the oil passage 35a of the spacer disk 35, and the notch 37a of the leaf spring 37 to the back pressure chamber 40, and further, the pressure control valve A Oil chamber 41, oil passage 43, annular oil chamber 28
And flows to the reservoir 4 through the oil passage 29. Also, the oilway
When the pressure reaches the valve opening pressure of the main disk valve 34, the oil liquid flowing through 30 opens the main disk valve 34, flows into the annular groove 32, and flows into the annular oil chamber 28 through the oil passage 31. Inflow directly. At this time, the oil liquid corresponding to the movement of the piston 5 opens the check valve 14 of the oil passage 13 of the base valve 10 from the reservoir 4 and flows into the cylinder lower chamber 2b.

During the contraction stroke of the piston rod 6, the movement of the piston 5 causes the check valve 12 in the oil passage 11 of the piston 5 to move.
Opens, the check valve 14 of the oil passage 13 of the base valve 10 closes,
The oil liquid in the lower piston chamber 2b flows into the upper cylinder chamber 2a, and the oil liquid that has entered the cylinder 2 from the piston rod 6 flows from the upper cylinder chamber 2a through the same path as in the above-described extension stroke. Flows to

Therefore, before the main disk valve 34 is opened (low-speed region of the piston speed) during both the extension and retraction strokes of the piston rod 6, a damping force is generated by the fixed orifice 34a and the pressure control valve A, and the proportional solenoid control is performed. Department
By controlling the control pressure (relief pressure) of the pressure control valve A according to the current supplied to the coil 59 of the 26, the pressure of the back pressure chamber 40, that is, the damping force, is directly controlled regardless of the piston speed. Can be. At this time, since the internal pressure of the back pressure chamber 40 acts in the valve closing direction of the main disc valve 34,
The opening pressure of the main disk valve 34 is adjusted together with the control pressure of the pressure control valve A, and the main disk valve 34
The damping force (damping force in the high-speed range of the piston speed) due to the valve opening characteristics of the above can be adjusted at the same time.

In this way, the damping force can be adjusted from a low piston speed range to a high piston speed range, and the adjustment range can be widened. With the pressure control valve A, an appropriate damping force due to the valve characteristics can be obtained even in a low piston speed range, so that a shortage of the damping force in a low piston speed range and an excessive increase in the damping force in a high speed range are prevented. be able to. Pressure control valve A
Since the influence on the flow resistance due to the viscosity change of the oil liquid is smaller than that of the flow control valve, it is possible to obtain a stable damping force with respect to the temperature change. Also, when the pressure in the back pressure chamber 40 rises sharply due to a sudden input such as a thrust from the road surface, the disk valve 49 of the pressure control valve A is bent and its outer peripheral portion is lifted from the valve seat 45. , Back pressure chamber 40
Can be quickly relieved to the oil chamber 41, so that a sharp increase in the damping force can be suppressed, and the riding comfort of the vehicle can be improved. Disc valve 49
As compared with the conventional poppet valve, since the opening area for the lift amount is large, the amount of movement of the plunger 46 can be small, so that the responsiveness is excellent, and it is hardly affected by frictional resistance. Disc valve 49 and secondary disc valve 50
By superimposing, the vibration caused by the pressure fluctuation can be buffered by the friction therebetween, and the generation of noise can be suppressed. Further, the disc valve 49 and the sub disc valve 50 are fitted slidably in the axial direction on the projection 48 of the plunger 46, and the inner peripheral side thereof is not fixed by a nut or the like. valve seat
As shown in FIG. 4, it is possible to easily incline (low rigidity) the pressing force to 45, so that the diameter of the disc valve 49 can be reduced, and the radial size of the damping force generating mechanism 19 can be reduced. Can be achieved.

To adjust the damping force to the soft side, the current supplied to the coil 59 is increased, and the plunger 46 is
Of the disc valve 49 by retracting against the spring force of
Reduce the pressing force to 45 to lower the valve opening pressure. At this time, as shown in FIG. 3, since the back pressure chamber 40 is always in communication with the oil chamber 41 via the oil passage 53 and the notch 54, the flow of the oil liquid occurs instantaneously at the same time as the movement of the piston 5. So
The damping force can be raised smoothly and the disc valve
It is possible to improve the ride comfort by relaxing the pressure fluctuation before and after opening the 49 valve. Further, a stable damping force can be obtained by reducing the hysteresis of the damping force due to the expansion and contraction of the piston rod 6.

When the damping force is adjusted to the hard side, the current supplied to the coil 59 is reduced, and the plunger 46 is
Of the disc valve 49 by the spring force of
Increase the pressing force to 45 to increase the valve opening pressure.
At this time, as shown in FIG. 4, the disk valve 49 and the auxiliary disk valve 50 bend with the retainer 51 as a fulcrum,
The auxiliary disk valve 50 abuts against the washer 52 to cut off the communication of the notch 54 with the oil chamber 41. With this, the disc valve
Until 49 reaches the valve opening pressure and opens, the pressure of the oil liquid will increase and the damping force will rise sharply, so it is possible to generate a sufficiently large damping force even in the low speed range of the piston speed. Thus, the posture control of the vehicle body can be effectively performed.

FIG. 5 shows the damping force characteristics of the damping force adjusting type hydraulic shock absorber 1. As shown in FIG. 5, when it is adjusted damping force to the soft side (current I ₁ ~I _2), the rise of the damping force becomes gentle exhibit an orifice characteristics, when adjusted to the hard side In (currents I _{3 to} I ₅ ), the rise of the damping force sharply rises with almost no orifice characteristics. FIGS. 6 and 7 show damping force characteristics when the piston rod 6 is expanded and contracted at a constant cycle. FIG.
This shows the case where the damping force is adjusted to the soft side, and almost the same damping force is generated when the stroke shifts from the extension side to the contraction side and when the stroke shifts from the contraction side to the extension side. Has a small hysteresis. On the other hand, FIG. 7 shows a case where the damping force is adjusted to the hard side, and occurs when the stroke shifts from the extension side to the contraction side and when the stroke shifts from the contraction side to the extension side. The damping force is different and the hysteresis is large.

[0030]

As described above in detail, according to the damping force adjusting type hydraulic shock absorber according to the first aspect, when the opening pressure of the pressure control valve is adjusted to be low, the pressure control valve is bypassed by the variable orifice. Therefore, the rise of the damping force becomes gentle, and the fluctuation of the pressure of the oil liquid when the stroke of the piston rod is switched is reduced. As a result, the response of the damping force is improved, the hysteresis is reduced, and the riding comfort of the vehicle can be improved.

According to the damping force-adjusting hydraulic shock absorber according to the second aspect, the sudden rise in the pressure of the oil liquid can be relieved by the bending of the disc valve, so that a sudden input due to a thrust from the road surface or the like can be prevented. By absorbing it, the riding comfort of the vehicle can be improved.

Further, according to the damping force adjusting type hydraulic shock absorber according to the third aspect, the gap between the disc valve and the seat member changes in accordance with the pressing force of the solenoid on the valve seat of the disc valve. The flow passage area of the variable orifice is adjusted.

[Brief description of the drawings]

FIG. 1 is an enlarged longitudinal sectional view of a damping force generating mechanism of a damping force adjusting type hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a damping force adjusting type hydraulic shock absorber according to one embodiment of the present invention.

FIG. 3 is an enlarged view showing a state where a variable orifice of a pressure control valve of the damping force generating mechanism of FIG. 1 is opened.

FIG. 4 is an enlarged view showing a state where a variable orifice of a pressure control valve of the damping force generating mechanism of FIG. 1 is closed.

FIG. 5 is a diagram showing a damping force characteristic of the damping force adjustable hydraulic shock absorber shown in FIG. 2;

6 is a damping force-adjustable hydraulic shock absorber shown in FIG. 2;
It is a figure which shows the damping force characteristic at the time of adjusting a damping force low and making a piston rod expand and contract at a fixed period.

7 is a diagram illustrating a damping force adjusting type hydraulic shock absorber shown in FIG. 2;
It is a figure which shows the damping force characteristic at the time of adjusting a damping force high and making a piston rod expand and contract at a fixed period.

[Description of Signs] 1 Hydraulic shock absorber with damping force adjustment 2 Cylinder 5 Piston 6 Piston rod 34 Main disc valve (pilot type damping valve) 34a Fixed orifice 45 Valve seat 49 Disc valve 50 Secondary disc valve (variable orifice) 52 Washer ( Seat member, variable orifice) 59 Coil (solenoid) A Pressure control valve B Variable orifice

Claims (3)

[Claims] 1. A cylinder filled with oil, a piston slidably fitted in the cylinder, and a piston rod having one end connected to the piston and the other end extending outside the cylinder. A main oil passage and a sub oil passage connected to the cylinder and through which the oil flows by sliding the piston; a pilot damping valve provided in the main oil passage; and a sub oil passage. A damping force-adjustable hydraulic shock absorber having a fixed orifice and a pressure control valve provided, wherein a pressure between the fixed orifice and the pressure control valve in the auxiliary oil passage is used as a pilot pressure of the pilot damping valve. The pressure control valve adjusts the valve opening pressure in accordance with the balance with the thrust of a solenoid, and when the valve opening pressure is adjusted low, opens the sub-oil passage and closes the pressure control valve. Path to higher closing the auxiliary hydraulic fluid passage when the adjusted damping force adjustable hydraulic shock absorber, characterized in that the variable orifice is provided. 2. The hydraulic shock absorber according to claim 1, wherein the pressure control valve is a disc valve. 3. The variable orifice forms a flow path by a gap between the disk valve and a seat member disposed on the back of the variable orifice, and the variable orifice flows by a deflection of the disk valve pressed by a valve seat of the pressure control valve. The damping force-adjustable hydraulic shock absorber according to claim 2, wherein the road area is adjusted.