JPH1061710A - Damping force adjusting hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen an adjusting range of damping force also obtain stable damping force, in a damping force adjusting hydraulic shock absorber. SOLUTION: In accordance with a current carried in an actuator, a spool is moved, by changing a flow path area of an extension/contraction side variable orifice B1 , B2 , an orifice characteristic is directly adjusted, also in accordance with a pressure loss thereof, a pilot pressure is changed, a valve opening characteristic of an extension/contraction side main damping valve A1 , A2 is changed, a valve characteristic is adjusted. At contraction stroke time, a check valve 12 is closed, a check valve 10 is opened, cylinder upper/lower chambers 2a, 2b are both pressurized, an oil fluid flows in a reservoir 4, so as to prevent a negative pressure in a cylinder 2, stable damping force is obtained. At extension stroke time, a pressure of a cylinder upper chamber 2a is introduced to the contraction side main damping valve A2 by a subpilot passage P, so as to prevent a response delay of damping force just after a transfer to a contraction stroke, stable damping force is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 ride 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 so as to divide the cylinder into two chambers.
The piston section is provided with a main oil passage and a bypass passage for communicating the two chambers in the cylinder. The main oil passage is provided with a damping force generating mechanism comprising an orifice and a disc valve. The damping force adjusting valve for adjustment is provided. A reservoir for compensating for a volume change in the cylinder due to expansion and contraction of the piston rod by compression and expansion of gas is connected to one chamber in the cylinder via a base valve.

The damping force adjusting valve opens the bypass passage to reduce the flow resistance of the oil between the two chambers in the cylinder, thereby reducing the damping force, and closing the bypass passage to reduce the damping force between the two chambers. , The damping force can be increased. As described above, the damping force characteristic 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 changes the damping force characteristic in a low piston speed range because the damping force depends on the orifice of the oil passage. However, in the middle and high speed range of the piston speed, the damping force characteristic cannot be largely changed because the damping force depends on the damping force generation mechanism (disk valve) of the main oil liquid passage.

Therefore, conventionally, for example, Japanese Utility Model Laid-Open No. Sho 62-155
As described in Japanese Patent Publication No. 242, a pressure chamber is formed at the back of a disk valve, which is a mechanism for generating a damping force of a main oil liquid passage provided in a piston portion, and this pressure chamber is connected to a disk valve via a fixed orifice. Is connected to a cylinder chamber on the upstream side of the disk valve and to a cylinder chamber on the downstream side of the disk valve via a variable orifice.

According to this damping force adjusting type hydraulic shock absorber, by opening and closing the variable orifice, the passage area between the two chambers in the cylinder is adjusted, and the pressure in the pressure chamber is changed to open the disk valve. The initial pressure can be changed. In this manner, the orifice characteristics (the damping force is approximately proportional to the square of the piston speed) and the valve characteristics (the damping force is approximately proportional to the piston speed) can be adjusted, and the adjustment range of the damping force characteristics can be widened. can do.

[0008]

However, in the above-described conventional damping force adjusting type hydraulic shock absorber in which a damping force generating mechanism and a damping force adjusting valve are provided in a piston portion, the damping force is interposed between a cylinder chamber and a reservoir. If the flow resistance of the piston part with respect to the base valve becomes large, the outflow of the oil liquid from the cylinder chamber to the reservoir during the contraction stroke of the piston rod becomes excessive, and one cylinder chamber becomes negative pressure, and a stable damping force is obtained. It is difficult to obtain. For this reason, in the high-speed range of the piston speed, the cylinder chamber is liable to become negative pressure during the contraction stroke, and it is difficult to obtain a stable damping force. As described above, since the contraction-side damping force characteristic depends on the flow resistance of the base valve, there is a problem that the setting range of the contraction-side damping force characteristic is limited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a damping force-adjustable hydraulic shock absorber which has a wide damping force adjustment range and can obtain a stable damping force. Aim.

[0010]

In order to solve the above-mentioned problems, a damping force-adjustable hydraulic shock absorber according to the present invention comprises: a cylinder filled with an oil liquid; a reservoir filled with an oil liquid and a gas; A piston slidably fitted in the cylinder and defining the inside of the cylinder as a first chamber and a second chamber, one end of which is connected to the piston and the other end of which passes through the first chamber; A first piston rod extending to the outside of the first chamber and a first rod provided in the piston for communicating between the first and second chambers;
A communication passage, a first check valve provided in the first communication passage, which allows a flow of the oil liquid from the second chamber side to the first chamber side, and communicates the second chamber with the reservoir. A second communication passage;
A second check valve provided in the second communication passage for permitting the flow of the oil liquid from the reservoir side to the second chamber side;
An extension-side main passage communicating between the second chambers, and an extension-side pilot-type main damping valve that controls a flow of an oil liquid in the extension-side main passage to generate a damping force and adjusts the damping force according to a pilot pressure. An extension-side sub-passage connected to the extension-side main passage and bypassing the extension-side pilot-type main damping valve; an extension-side orifice provided on the upstream side of the extension-side sub-passage; and provided on the downstream side. An expansion side variable orifice, and the pressure of the oil liquid between the expansion side orifice and the expansion side variable orifice of the expansion side auxiliary passage is introduced as pilot pressure to the expansion side pilot type main damping valve, and A contraction-side main passage that communicates the second chamber with the reservoir; a contraction-side pilot that controls a flow of an oil liquid in the contraction-side main passage to generate a damping force and adjusts the damping force according to pilot pressure; A compression main damping valve, a compression sub-passage connected to the compression main passage and bypassing the compression pilot main damping valve, a compression orifice provided upstream of the compression sub-passage, and a downstream. A contraction-side variable orifice provided on the side, and the pressure of the oil liquid between the contraction-side orifice of the contraction-side auxiliary passage and the contraction-side variable orifice is introduced as pilot pressure to the contraction-side pilot-type main damping valve. Further, a communication path is provided for connecting the first chamber and a pilot pressure introduction section of the contraction-side pilot type main damping valve, and the communication path includes at least oil from the pilot pressure introduction section to the first chamber. It is characterized by giving resistance to the flow of the liquid.

With this configuration, during the extension stroke of the piston rod, the first check valve closes, and the oil liquid flows from the first chamber through the extension main passage and the extension sub passage to the second chamber. Oil flows to the side and the second check valve opens the second check valve from the reservoir and flows to the second chamber from the reservoir. Before the opening of the extension-side main damping valve, the piston speed is small, and a damping force is generated according to the flow area of the extension-side orifice and the extension-side variable orifice of the extension-side sub-passage,
When the piston speed increases and the extension-side main damping valve opens, a damping force is generated according to the degree of opening. By adjusting the passage area of the extension-side variable orifice, the passage area of the extension-side sub-passage can be directly adjusted, and the pilot pressure can be changed to adjust the valve opening characteristics of the extension-side main damping valve.

Also, during the contraction stroke of the piston rod,
The first check valve is opened, the second check valve is closed, and the hydraulic fluid in the cylinder is pressurized by an amount corresponding to the piston rod having entered the cylinder. Flows through reservoir to reservoir. Before the compression-side main damping valve is opened, damping force is generated according to the flow path area of the compression-side orifice and compression-side variable orifice of the compression-side sub-passage, and the piston speed increases. When the side main damping valve is opened, a damping force is generated according to the degree of opening. By adjusting the passage area of the contraction-side variable orifice, the passage area of the contraction-side auxiliary passage can be directly adjusted, and the pilot pressure can be changed to adjust the valve opening characteristics of the contraction-side main damping valve.

At this time, during the contraction stroke of the piston rod, the flow of the oil liquid between the cylinder chamber and the reservoir is controlled to generate a damping force, so that the contraction-side orifice, the contraction-side variable orifice and the contraction-side main orifice are formed. There is no negative pressure in the cylinder chamber due to the flow resistance of the damping valve.

Further, during the extension stroke of the piston rod, the pressurized oil in the first chamber is introduced into the pilot pressure introduction portion of the contraction-side main damping valve through the communication passage, and is transmitted from the pilot pressure introduction portion of the communication passage. Due to the resistance of the oil liquid to the first chamber,
Even during the extension stroke of the piston rod, the pressure of the pilot pressure introduction portion of the contraction-side main damping valve can be increased to a predetermined pressure and held, so that the pilot pressure of the contraction-side main damping valve does not excessively decrease. .

[0015]

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 FIGS. 1 and 2, the damping force-adjustable hydraulic shock absorber 1 has a double cylinder structure in which an outer cylinder 3 is provided outside a cylinder 2. Is formed between them. In the cylinder 2,
A piston 5 is slidably fitted, and the piston 5 defines the inside of the cylinder 2 into two cylinder chambers, an upper cylinder chamber 2a (first chamber) and a lower cylinder chamber 2b (second chamber). ing. One end of a piston rod 6 is connected to the piston 5 by a nut 7.
Is extended through the cylinder upper chamber 2a, through the rod guide 6a and the oil seal 6b attached to the upper end of the cylinder 2 and the outer cylinder 3, and to the outside of the cylinder 2. At the lower end of the cylinder 2, a base valve 8 that partitions the cylinder lower chamber 2b and the reservoir 4 is provided.
An oil liquid is sealed in the cylinder 2, and an oil liquid and a gas are sealed in the reservoir 4.

The piston 5 has an oil passage 9 (first communication passage) for communicating between the cylinder upper and lower chambers 2a and 2b, and the flow of oil from the cylinder lower chamber 2b of the oil passage 9 to the cylinder upper chamber 2a. Check valve 10 (first check valve) is provided.
The base valve 8 has an oil passage 11 (second communication passage) for communicating the cylinder lower chamber 2b with the reservoir 4, and the oil passage 11
A check valve 12 (second check valve) that allows the flow of the oil liquid from the reservoir 4 side to the cylinder lower chamber 2b side is provided.

A substantially cylindrical passage member 13 is fitted around the center of the cylinder 2. An upper tube 14 is fitted on the upper outer periphery of the cylinder 2 and connected to the passage member 13 to form an annular oil passage 15 with the cylinder 2. The annular oil passage 15 communicates with the cylinder upper chamber 2a via an oil passage 16 provided on a side wall near the upper end of the cylinder 2. A lower tube 17 is provided on the outer periphery of the lower part of the cylinder 2.
Are fitted and connected to the passage member 13, and the cylinder 2
To form an annular oil passage 18. The annular oil passage 18 communicates with the cylinder lower chamber 2b via an oil passage 19 provided on a side wall near the lower end of the cylinder 2.

A connection plate 20 is attached to the outer cylinder 3 so as to face the passage member 13. Connection pipes 21 and 22 communicating with the annular oil passages 15 and 18 are inserted and fitted into the connection plate 20 and the passage member 13, respectively. In addition, the connection plate 20 is provided with a connection hole 23 communicating with the reservoir 4. The connecting plate 20 has a damping force generating mechanism 24
Is installed.

As shown in FIG. 2, the damping force generating mechanism 24 includes:
Two valve members 26 and 27 are fitted into a substantially cylindrical case 25 having a bottom, and a proportional solenoid actuator 29 (hereinafter, referred to as an actuator 29) is screwed into an opening through a retainer 28. The inside is partitioned into three oil chambers 25a, 25b and 25c by valve members 26 and 27. The valve members 26 and 27 are inserted with annular fixing members 30 and 31 disposed in the oil chambers 25b and 25c, respectively, and a substantially cylindrical guide member 32 whose one end is screwed to the actuator 29.
A nut 33 is screwed to the other end, and fixed to the case 25 integrally therewith. And three oil chambers 25a, 25
b and 25c are connected to the connection pipe 21, the connection pipe 22 and the connection hole 23 through connection holes 34, 35 and 36 provided in the side wall of the case 25, respectively.

The valve members 26 and 27 have oil chambers 25 respectively.
a and 25b, oil passages 37 and 38 communicating between oil chambers 25b and 25c
Is provided. Annular valve seats 39, 40 are protrudingly provided on the outer peripheral side of the oil passages 37, 38 of the valve members 26, 27, and are provided on the outer peripheral side thereof. Four
1,42 are protruding. Sub disc valves 43 and 44 are seated on the inner valve seats 39 and 40, respectively. The sub disk valves 43 and 44 have their inner peripheral portions fixed to the valve members 26 and 27, and the outer peripheral portions are bent by receiving the pressure of the oil liquid on the oil chambers 25a and 25b side of the oil passages 37 and 38, and are opened. Thus, a damping force is generated according to the degree of opening. Also, orifices 43a, 44a (notches) are provided on the outer peripheral portions of the sub-disk valves 43, 44, which always allow the oil passages 37, 38 to flow therethrough.

On the outer peripheral portions of the fixing members 30 and 31, respectively,
Cylindrical movable members 45 and 46 are slidably fitted.
One end of each of the movable members 45 and 46 has a floating disk 4
It is seated on the valve seats 41, 42 outside the valve members 26, 27 via 7, 48, and the inner peripheral part is fixed to the valve members 26, 27 side on the flange formed inside one end, and a plurality of layers are laminated. The outer peripheral portions of the disc-shaped leaf springs 49 and 50 are abutted in a liquid-tight manner and urged in the valve closing direction, that is, in the valve seats 41 and 42 side. Fixing member
30, 31, movable members 45, 46 and leaf springs 49, 50,
Pilot chambers 51 and 52 are formed. Fixed orifices 49a and 50a (notches) are provided on the outer peripheral portions of the leaf springs 49 and 50 as extension or contraction orifices for communicating the oil passages 37 and 38 with the pilot chambers 51 and 52.

The valve seat 41 and the floating disk
47, the fixed member 30, the movable member 45, the leaf spring 49, and the pilot chamber 51, the extension side pilot type main damping valve A ₁ (hereinafter, referred to as
It is configuration) that extension-side main damping valve A _1, the extension-side main damping valve A ₁ is opened under the pressure of the hydraulic fluid from the oil passage 37 side, the damping force according to the degree of opening Is generated, and the internal pressure of the pilot chamber 51, which is the pilot pressure introduction section, is adjusted as the pilot pressure acting in the valve closing direction, and the valve opening pressure is adjusted. Also, valve seat 42, floating disk 4
8, the contraction-side pilot-type main damping valve A ₂ (hereinafter, referred to as the fixed member 31, the movable member 46, the leaf spring 50, and the pilot chamber 52)
Are called compression-side main damping valve A ₂₎ is configured, the compression-side main damping valve A _2, and open under the pressure of the hydraulic fluid from the oil passage 38 side, the damping force according to the degree of opening Is generated, and the internal pressure of the pilot chamber 52, which is the pilot pressure introduction section, is adjusted as the pilot pressure acting in the valve closing direction, and the valve opening pressure is adjusted. Incidentally, the valve opening pressure of the secondary disk valve 43 and 44, respectively, the extension-side main damping valve A ₁ and compression-side main damping valve
It is set sufficiently lower than the opening pressure of A _2.

The pilot chamber 5 is provided on the side wall of the guide member 32.
Ports 53 and 55 and oil chamber 25b communicating with 1 and 52, respectively
, 25c are provided with ports 54 and 56, respectively. A spool 57 is slidably fitted in the guide member 32. The outer peripheral portion of the spool 57 is provided with two annular grooves 58 and 59 facing the ports 53 and 54 and the ports 55 and 56 of the guide member 32, respectively. Annular groove
The port 58 communicates with the port 54 at a constant flow area, and communicates with the port 53 with a flow area corresponding to the axial position of the spool 57. Is adjusted. In addition, the annular groove 59
Communicates with the port 55 on the pilot chamber 52 side with a constant flow area at all times, and communicates with the port 56 on the oil chamber 25c side with a flow area according to the axial position of the spool 57. By doing so, the flow path area between the ports 55 and 56 is adjusted.

A plug 60 is mounted on an end of the guide member 32 on the oil chamber 25a side, and a return spring 61 is interposed between the plug 60 and one end of the spool 57. A plunger 62 of the actuator 29 is in contact with the other end of the spool 57. The guide extension side variable orifice B ₁ with an annular groove 58 of the port 53 and the spool 57 of the member 32 is configured, the compression-side variable orifice between the port 56 and the annular groove 59 of the guide member 32
B ₂ is configured, and the solenoid 63 of the actuator 29 is
The spool 57 moves against the spring force of the return spring 61 in response to the current supplied to the
The flow path area between them is adjusted.

The spool 57 is provided along its axis with a passage 64 communicating between the chambers 32a and 32b at both ends of the spool 57 in the guide member 32, and the oil liquid is supplied between the chambers 32a and 32b. By causing the guide member 32 to circulate,
It can move smoothly inside. The spool 57 is provided with an oil passage 65 that connects the annular groove 59 and the passage 64. The plug 60 has a chamber 32a in the guide member 32.
An oil passage 66 is provided for communicating the oil passage 25 with the oil chamber 25a. The oil passage 66 is provided with an orifice 67.

In the above configuration, the oil passage 16, the annular oil passage 1
5, connection pipe 21, connection hole 34, oil chamber 25a, oil path 37, oil chamber 25b
Connection hole 35, the connecting tube 22, the annular oil passage 18 and the oil passage 19, the cylinder upper and lower chambers 2a, extension-side main passage C ₁ to communicate is formed between 2b, fixed orifice 49a, the pilot chamber 51, the port 53, by annular groove 58 and port 54,
Extension-side sub-passage D ₁ bypassing the extension-side main damping valve A ₁ is formed. Oil passage 19, annular oil passage 18, connection pipe 22, connection hole 3
5, the oil chamber 25b, the oil passage 38, the oil chamber 25c, the connecting hole 36 and the connection hole 23, the compression-side main passage C ₂ to communicate is formed between the cylinder lower chamber 2b and the reservoir 4, the fixed orifice 50a, the pilot chamber 52, port 55, by an annular groove 59 and the port 56, the contraction-side passage D ₂ bypassing the compression-side main damping valve a ₂ are formed. Further, the oil passage 65 and the passage 64 of the spool 57, the oil chamber 32a, and the orifice 67 of the plug 60 are provided.
A sub-pilot passage P (communication passage) is formed by the oil passage 66 having the orifice 67, and the pilot chamber 52 and the cylinder upper chamber 2a are communicated via the sub-pilot passage P having the orifice 67.

FIG. 3 shows a hydraulic circuit of the damping force-adjustable hydraulic shock absorber 1 configured as described above. In FIG. 3,
1 and FIG. 2 are denoted by the same reference numerals as those in FIG. 1 and FIG.

Next, the operation of the embodiment constructed as described above will be described.

[0030] During the extension stroke of the piston rod 6, with the movement of the piston 5, close the check valve 10 of the piston 5, the hydraulic fluid in the upper chamber 2a cylinder is pressurized, the extension-side main passage C ₁ and elongation through the collateral passage D ₁ flows into the cylinder lower chamber 2b. In addition, the oil liquid corresponding to the piston rod 6 having withdrawn from the cylinder 2 flows from the reservoir 4 to the cylinder lower chamber 2b by opening the check valve 12.

The piston speed is small, and the main damping valve A ₁ on the extension side is provided.
Before the opening, by bypassing the extension-side main damping valve A ₁ through the extension-side sub-passage D ₁ is the hydraulic fluid, the sub disk valve 43
And damping force is generated by the orifice 43a and the fixed orifice 49a and the extension-side variable orifice B _1. At this time, the damping force of the orifice characteristics is generated by the orifice 43a before the secondary disk valve 43 is opened, and the damping force of the valve characteristics is generated according to the opening degree after the secondary disk valve 43 is opened. Thereby, an appropriate damping force can be obtained in a low-speed range of the piston speed.

As the piston speed increases, the upper chamber of the cylinder
When the pressure in the 2a side is opened is extension-side main damping valve A ₁ rises,
A damping force is generated according to the opening. The smaller the flow area of the extension-side variable orifice B _1, large pressure loss, the higher the upstream pilot pressure in the pilot chamber 51 of the valve opening pressure of the extension-side main damping valve A ₁ is increased.
Thus, the current supplied to the solenoid 63 of the actuator 29, by adjusting the flow passage area of the extension-side variable orifice B _1, with adjusting the direct orifice characteristics, by changing the pilot pressure of the extension-side main damping valve A ₁ Thus, the valve characteristics can be adjusted, and the adjustment range of the damping force characteristics can be widened.

During the contraction stroke of the piston rod 6, the check valve 10 of the piston 5 is opened with the movement of the piston 5, and the oil liquid in the cylinder lower chamber 2b passes through the oil passage 9 and the cylinder upper chamber.
Since the cylinder upper and lower chambers 2a and 2b have almost the same pressure by flowing directly into the cylinder 2a, the connection holes 34 and
No oil flow occurs between 35. On the other hand, the check valve 21 of the base valve 17 is closed by the penetration of the piston rod 6 into the cylinder 2, and the oil liquid that has entered the cylinder 2 by the piston rod 6 is pressurized and contracts from the cylinder lower chamber 2 b. It flows to the reservoir 4 through the side main passage C ₂ and the contraction side sub passage D ₂ . Incidentally, a small amount of hydraulic fluid through the auxiliary pilot passage P from the upper chamber 2a side cylinder, an annular groove 59 of the spool 57, i.e., between the contraction side fixed orifice 50a and the compression-side variable orifice B ₂ of the secondary passage D ₂ But the sub pilot passage P
Since the flow path area is sufficiently narrowed by the orifice 67, the effect is sufficiently small.

The piston speed is low and the contraction side main damping valve A ₂
Before the opening, by bypassing the compression-side main damping valve A ₂ through the contraction-side passage D ₂ is the hydraulic fluid, the sub disk valve 44
And damping force is generated by the orifice 44a and the fixed orifice 50a and the compression-side variable orifice B _2. At this time, the damping force of the orifice characteristic is generated by the orifice 44a before the secondary disk valve 44 is opened, and the damping force of the valve characteristic is generated according to the opening degree after the secondary disk valve 44 is opened. Thereby, an appropriate damping force can be obtained in a low-speed range of the piston speed.

The piston speed increases, the pressure of the cylinder 2 side is opened is compression-side main damping valve A ₂ rises, the damping force is generated according to the degree of opening thereof. The shrinkage as side flow area of the variable orifice B ₂ is small, large pressure loss, the pilot pressure in the pilot chamber 52 on the upstream side becomes high, the valve opening pressure of the compression-side main damping valve A ₂ is increased. Therefore, by adjusting the flow passage area of the compression-side variable orifice B ₂ by flowing current to the solenoid 63 of the actuator 29, in addition to adjusting the direct orifice characteristics, by changing the pilot pressure of the compression-side main damping valve A ₂ The valve characteristics can be adjusted, and the adjustment range of the damping force characteristics can be widened.

As described above, by moving the spool 57 in accordance with the current supplied to the solenoid 63 of the actuator 29, the spool 57 is moved between the ports 53 and 54 (extended variable orifice B ₁ ) and between the ports 55 and 56 (compressed variable orifice). By changing the flow passage area of B ₂ ), it is possible to adjust the damping force characteristics on the extension side and the contraction side, respectively. In this case, for example, the port on the extension side according to the position of the spool 57
Each of the ports 53, 54, 55, 56 is such that the flow path area between the ports 53, 54 and the ports 55, 56 on the contraction side is large when one is large and the other is large when one is small. By arranging the annular grooves 58 and 59 of the spool 57, a combination of damping force characteristics of different sizes on the extension side and the contraction side (for example, the extension side is hard and the contraction side is soft or the extension side is soft and the contraction side is hard) Combination) can be selected at the same time.

As described above, during the contraction stroke of the piston rod 6, the check valve 10 of the piston 5 opens, the check valve 12 of the base valve 8 closes, and the piston rod 6 enters the cylinder 2. The oil in the cylinder upper and lower chambers 2a and 2b is pressurized together by the cylinder lower chamber 2b, and the contraction side main passage C ₂
It flows into the reservoir 4 through and contraction-side passage D _2, since the damping force by the flow resistance occurs, even at the time of compression stroke, without the cylinder 2 becomes negative pressure, to obtain a stable damping force be able to. FIG. 4 shows the relationship between the stroke of the piston rod 6 and the pressure of the oil liquid in the cylinder upper chamber 2a and the cylinder lower chamber 2b.

As shown in FIG. 4, during the extension stroke of the piston rod 6, the pressure in the cylinder lower chamber 2b is in an equilibrium state due to the slight flow resistance of the oil passage 11 of the base valve 8 and the check valve 12. Slightly lower than the pressure P ₀ (determined by the gas pressure sealed in the reservoir 4). Cylinder lower chamber 2b, so communicates with the pilot chamber 52 of the compression-side main damping valve A _2, the pressure in the cylinder lower chamber 2b is reduced, the internal pressure in the pilot chamber 52 also decreases, and thus, the piston rod 6 Immediately after the stroke shifts to the contraction side, it takes time for the internal pressure (pilot pressure) of the pilot chamber 52 to rise to the predetermined pressure, so that a response delay tends to occur in the generation of the damping force.

On the other hand, in the damping force adjusting type hydraulic shock absorber 1 of the present embodiment, since the cylinder upper chamber 2a and the pilot chamber 52 communicate with each other through the auxiliary pilot passage P having the orifice 67, the piston The oil liquid on the side of the cylinder upper chamber 2a that is pressurized during the extension stroke of the rod 6 is supplied to the sub pilot passage P
Introduced into the pilot room 52 by the
Due to 67, even during the extension stroke of the piston rod 6, the internal pressure of the pilot chamber 52 can be increased and maintained at a predetermined pressure, and the response delay of the generation of the damping force immediately after the stroke of the piston rod 6 shifts to the contraction side. And a stable damping force can be obtained.

The sub-pilot passage P (communication passage) in the above embodiment is connected to the pilot chamber 52 (the pilot pressure introducing portion of the contraction-side pilot type main damping valve) and the cylinder upper chamber 2a (the first chamber) by the orifice 67. )), A check valve that allows only the flow of the oil liquid from the pilot chamber 52 to the cylinder upper chamber 2a is provided instead of the orifice 67. It may be provided to provide resistance to the flow of the oil liquid. In this case, the response delay of the generation of the damping force immediately after the stroke of the piston rod 6 shifts from the extension side to the contraction side can be more reliably prevented.

Further, in the above-described embodiment, the fixed orifices 49a, 50a are used as the extension side and the contraction side orifice.
Although a notch is shown, a variable-type orifice whose opening changes according to the flow rate of the oil liquid may be provided instead. In this case, it is possible to set the damping force characteristics more finely.

[0042]

As described above in detail, according to the damping force-adjustable hydraulic shock absorber of the present invention, by changing the flow path areas of the extension side and the contraction side variable orifice, respectively, the orifice having the extension side is changed. In addition to directly adjusting the characteristics, the pilot pressure can be changed to change the valve opening characteristics of the expansion-side and contraction-side pilot-type main damping valves, thereby adjusting the valve characteristics. be able to.

Also, during the contraction stroke, the first
The damping force is generated by controlling the flow of the oil liquid in the contraction-side main passage and the contraction-side sub-passage which communicate the chamber and the second chamber with the reservoir. A stable damping force can be obtained without becoming.

Further, during the extension stroke of the piston rod,
Since the pressurized oil liquid in the first chamber is introduced into the pilot pressure introduction portion of the contraction-side main damping valve via the communication passage, the pilot pressure of the contraction-side main damping valve is introduced even during the extension stroke of the piston rod. The pressure of the part does not drop excessively,
It is possible to prevent a response delay of the generation of the damping force immediately after the stroke of the piston rod shifts to the contraction side, and to obtain a stable damping force.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a damping force generating mechanism of the device of FIG.

FIG. 3 is a hydraulic circuit diagram of the apparatus of FIG.

FIG. 4 is a diagram showing a relationship between a stroke of a piston rod and pressures in an upper cylinder chamber and a lower cylinder chamber of the apparatus of FIG. 1;

[Explanation of symbols]

Reference Signs List 1 damping force adjustable hydraulic shock absorber 2 cylinder 2a upper cylinder chamber (first chamber) 2b lower cylinder chamber (second chamber) 4 reservoir 5 piston 6 piston rod 9 oil passage (first communication passage) 10 check valve (first 1 Check valve) 11 Oil passage (2nd communication passage) 12 Check valve (2nd check valve) 49a Fixed orifice (expansion side orifice) 50a Fixed orifice (compression side orifice) 52 Pilot chamber (pilot pressure introduction section) 67 Orifice A ₁ Extension side pilot type main damping valve A ₂ Retraction side pilot type main damping valve B ₁ Extension side variable orifice B ₂ Retraction side variable orifice C ₁ Extension side main passage C ₂ Retraction side main passage D ₁ Extension side auxiliary passage D ₂ contraction side auxiliary passage P auxiliary pilot passage (communication passage)

Claims (1)

[Claims] 1. A cylinder filled with an oil liquid, a reservoir filled with an oil liquid and a gas, and a first chamber and a second chamber which are slidably fitted in the cylinder and slidably fit in the cylinder. A piston defining a piston, a piston rod having one end connected to the piston and the other end extending to the outside of the cylinder through the first chamber;
A first communication passage communicating between the second chambers, a first check valve provided in the first communication passage for permitting an oil liquid to flow from the second chamber to the first chamber; A second communication passage for communicating the two chambers with the reservoir, a second check valve provided in the second communication passage for permitting the flow of the oil liquid from the reservoir side to the second chamber side; An extension-side main passage that communicates between the first and second chambers, and an extension-side pilot-type main that controls a flow of oil in the extension-side main passage to generate a damping force and adjusts the damping force according to a pilot pressure. A damping valve, an extension sub-passage connected to the extension main passage and bypassing the extension pilot main damping valve, an extension orifice provided upstream of the extension sub passage, and a downstream An extension side variable orifice provided, and an extension side orifice of the extension side sub-passage. The pressure of the oil liquid between the expansion side pilot type main damping valve and the contraction side main passage for communicating the second chamber with the reservoir; A contraction-side pilot-type main damping valve that controls the flow of oil in the main passage to generate a damping force and adjusts the damping force according to the pilot pressure; and the contraction-side pilot type connected to the contraction-side main passage. A contraction-side sub-passage that bypasses the main damping valve, a contraction-side orifice provided upstream of the contraction-side sub-passage, and a contraction-side variable orifice provided downstream. The pressure of the oil liquid between the contraction side orifice and the contraction side variable orifice is introduced as pilot pressure to the contraction side pilot type main damping valve, and further, the first chamber and the contraction side pilot type main reduction valve are introduced. A communication path connecting the pilot pressure introduction section of the valve to the pilot pressure introduction section is provided, and the communication path is configured to provide resistance to at least the flow of the oil liquid from the pilot pressure introduction section to the first chamber. Damping force adjustable hydraulic shock absorber.