JPH09242805A - Damping force adjustable hydraulic shock absorber - Google Patents

Abstract

(57) Abstract: In a damping force adjustable hydraulic shock absorber, the degree of freedom in setting damping force characteristics is increased by changing the damping force characteristics on the extension side and the contraction side. A cylinder (3) is fitted with a piston (3) and a reservoir chamber (6) is connected. Cylinder upper chamber 2a and reservoir chamber 6
And the main passage 11 provided with a main damping valve 12 are communicated with each other. The pilot line 13 of the main damping valve 12 is connected to the first and second upstream side passages 16 and 17
The main passage 11 communicates with the upstream side of the main damping valve 12, and the downstream passage 20 communicates with the downstream side. On both the expansion and contraction sides, the oil liquid flows from the cylinder upper chamber 2a to the reservoir chamber 6 through the first and second upstream passages 14 and 15, the downstream passage 20 and the main passage 11. The flow control valve 21 adjusts the flow passage area of the downstream passage 20, and the pressure introduced from the upstream pilot pipe 13 is changed to adjust the valve opening pressure of the main damping valve 12. Switching valve using the pressure in the cylinder lower chamber 2b as the pilot pressure between the extension side and the contraction side
At 18, the second upstream passage 15 is opened and closed to change the damping force characteristic.

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.

As an example of the damping force adjusting hydraulic shock absorber, a cylinder filled with oil liquid, a reservoir chamber filled with oil liquid and gas, and a cylinder upper chamber fitted inside the cylinder are provided. A piston that is defined by two chambers, a cylinder lower chamber, a piston rod that has one end connected to the piston and the other end that extends through the cylinder upper chamber to the outside, and a communication passage that communicates between the cylinder upper chamber and the lower chamber. A check valve that allows the oil liquid to flow from the cylinder lower chamber side to the cylinder upper chamber side of this communication passage, a communication passage that communicates the cylinder lower chamber and the reservoir chamber, and a cylinder from the reservoir chamber side of this communication passage. A non-return valve that allows the oil liquid to flow to the lower chamber side, a main passage that connects the cylinder upper chamber and the reservoir chamber, and the flow of the oil liquid in the main passage can be controlled, and the flow resistance can be adjusted appropriately. And the damping force control valve Made a the Japanese 62-22
No. 0728.

According to this structure, the check valve between the cylinder upper chamber and the lower chamber is closed during the extension stroke of the piston rod to pressurize the oil liquid in the cylinder upper chamber, and during the compression stroke, the cylinder lower chamber and the reservoir chamber. Since the check valve between and closes, the cylinder upper and lower chambers are pressurized by the piston rod penetrating, so that the oil flows through the main passage from the cylinder upper chamber side to the reservoir chamber side during the expansion and contraction stroke, and the damping force A damping force is generated by the adjusting valve. Thus, by adjusting the flow resistance of the damping force adjusting valve, the extension side and the contraction side damping force can be adjusted.

[0005]

However, in the above conventional damping force adjusting type hydraulic shock absorber, the main passage in which the oil liquid is common is directed in the same direction from the cylinder upper chamber side to the reservoir side during the expansion and contraction strokes of the piston rod. Since the damping force is generated by the damping force adjusting valve after being circulated, the damping force on the extension side and the compression side has a constant relationship determined by the pressure receiving area ratio on the extension side and the compression side of the piston rod. There is a problem that the degree of freedom of setting of is limited.

For example, when the pressure receiving area S _E on the extension side of the piston rod and the pressure receiving area S _C on the compression side are defined as the piston speed V _{E at} the extension side opening point of the pressure reducing valve of the damping force adjusting valve, the compression side The piston speed V _{C at} the valve opening point of is V _C = V _E · S _E / S _C , and is determined only by the ratio of the pressure receiving area S _E on the extension side and the pressure receiving area S _C on the contraction side of the piston rod. As a result, the damping force characteristics on the extension side and the contraction side cannot be set independently.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a damping force adjustable hydraulic shock absorber capable of increasing the degree of freedom in setting damping force characteristics on the extension side and the contraction side. To aim.

[0008]

In order to solve the above-mentioned problems, a damping force adjusting hydraulic shock absorber of the present invention comprises a cylinder in which an oil liquid is sealed, and a reservoir chamber in which the oil liquid and a gas are sealed. A piston slidably fitted in the cylinder to define a first chamber and a second chamber in the cylinder; a cylinder having one end connected to the piston and the other end passing through the first chamber Of the piston rod, the first communication passage that communicates between the first and second chambers, and the oil liquid flowing from the second chamber side to the first chamber side of the first communication passage. A first check valve that allows circulation, a second communication passage that communicates the second chamber with the reservoir chamber, and an oil liquid from the reservoir chamber side of the second communication passage to the second chamber side. A second check valve that allows circulation, a main passage that communicates the first chamber with the reservoir chamber, and the main passage The pilot type main damping valve for controlling the flow of the oil liquid to generate the damping force and adjusting the damping force according to the pilot pressure, and the pilot pressure introducing portion of the pilot type main damping valve are connected to the pilot type main valve in the main passage. First and second upstream passages that are arranged in parallel with each other and communicate with the upstream side of the damping valve, first and second fixed orifices respectively provided in the first and second upstream passages, and the pilot pressure introduction A downstream passage for communicating a portion of the main passage with a downstream side of the pilot type main damping valve, a variable orifice for adjusting a flow passage area of the downstream passage, and a pilot type switching for opening and closing the second upstream passage. A valve and a pilot passage for connecting a pilot pressure introducing portion of the pilot type switching valve to the second chamber are provided.

With this configuration, the first check valve is closed and the hydraulic fluid in the first chamber is pressurized during the extension stroke of the piston rod, and the first check valve is opened during the contraction stroke. Since the second check valve is closed and the piston rod intrudes into the cylinder, the oil liquid in the first and second chambers is pressurized.
During the expansion and contraction stroke, the oil liquid flows from the cylinder upper chamber side to the reservoir chamber side through the first and second upstream side passages, the downstream side passage and the main passage, and the first and second fixed orifices, the variable orifice and the main damping valve. A damping force is generated by. Then, by changing the flow area of the variable orifice, the flow resistance of the downstream passage is directly adjusted and the pilot pressure of the pilot type main damping valve is changed to adjust the valve opening characteristics, and the expansion side and the contraction side are adjusted. Adjust the damping force characteristics of.
At this time, the second movement is caused by the movement of the piston during the extension stroke.
Since the chamber is decompressed and pressurized during the compression stroke, the pilot pressure in the pilot pressure introducing part changes between the expansion side and the compression side, and the pilot type switching valve opens and closes the second upstream side passage to reduce the damping force characteristic. Changes.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

A hydraulic circuit showing an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, in a damping force adjustable hydraulic shock absorber 1, a piston 3 is slidably fitted in a cylinder 2 in which an oil liquid is sealed. Cylinder upper chamber 2a (first
Chamber) and a cylinder lower chamber 2b (second chamber). One end of a piston rod 4 is connected to the piston 3, and the other end of the piston rod 4 extends outside the cylinder 2 through the cylinder upper chamber 2a. A reservoir chamber 6 in which an oil liquid and a gas are sealed is connected to the lower cylinder chamber 2b via a base valve 5 provided at the bottom of the cylinder 2.

The piston 3 has an oil passage 7 (first communication passage) for communicating between the cylinder upper and lower chambers 2a and 2b, and an oil liquid flowing through the oil passage 7 from the cylinder lower chamber 2b side to the cylinder upper chamber 2a side. A check valve 8 (first check valve) that allows only the above is provided. Further, the base valve 5 has an oil passage 9 (second communication passage) for communicating the cylinder lower chamber 2b and the reservoir chamber 6 and oil liquid from the reservoir chamber 6 side of the oil passage 9 to the cylinder lower chamber 2b side. A check valve 10 (second check valve) that allows only circulation is provided.

A main passage 11 is provided outside the cylinder 2 for connecting the cylinder upper chamber 2a and the reservoir chamber 6 to each other.
The main passage 11 is provided with a pilot type main damping valve 12 (hereinafter referred to as the main damping valve 12). The pilot pipe line 13 (pilot pressure introducing portion) of the main damping valve 12 has a first upstream side passage 14 and a second upstream side passage 15 arranged in parallel with each other, so that the main passage 11 is upstream of the main damping valve 12 (cylinder). Upper chamber 2a
Side). First and second fixed orifices 16 and 17 are provided in the first and second upstream passages 14 and 15, respectively. A normally open pilot type switching valve 18 (hereinafter referred to as switching valve 18) is provided in the second upstream side passage 15, and a pilot passage 19 for introducing pilot pressure into the switching valve 18 has a cylinder lower chamber 2b. Is in communication with. Further, the pilot conduit 13 of the main damping valve 12 is connected to the downstream side (the reservoir chamber 6 side) of the main damping valve 12 of the main passage 11 by the downstream passage 20. The downstream passage 20 is provided with a flow control valve 21 (variable orifice) for adjusting the flow passage area.

The main damping valve 12 is a pilot type pressure control valve, and is opened by a predetermined pressure of the oil liquid on the cylinder upper chamber 2a side of the main passage 11 to generate a damping force according to the opening degree of the pilot damping pressure control valve. The pressure of the oil liquid between the first and second upstream side passages 14 and 15 and the downstream side passage 20 is introduced from the pipe line 13, and the valve opening pressure is changed according to this pilot pressure to increase the pilot pressure. Along with this, the valve opening pressure becomes higher. The switching valve 18 introduces the pressure of the oil liquid in the lower cylinder chamber 2b from the pilot passage 19 and operates according to this pilot pressure, and when the lower cylinder chamber 2b is depressurized, the switching valve 18 opens in the second upstream passage. It opens and closes when pressurized. Further, the flow rate control valve 21 acts as a variable orifice according to the current supplied to the solenoid to adjust the flow passage area of the downstream passage 20.

The operation of the present embodiment configured as described above will be described below.

During the extension stroke of the piston rod 4, the check valve 8 of the piston 3 is closed along with the movement of the piston 3 to pressurize the oil liquid on the cylinder upper chamber 2a side, and the first and second upstream side passages. Flows to the reservoir chamber 6 side through 14, 15 and the downstream side passage 20 and the main passage 11. At this time, piston rod 4
The oil liquid that has withdrawn from the inside of the cylinder 2 flows from the reservoir chamber 6 to the check valve 10 of the base valve 5 and flows into the lower cylinder chamber 2b. Also, during the compression stroke, the check valve 8 in the oil passage 7 opens as the piston 3 moves, and the oil liquid in the cylinder lower chamber 2b directly flows into the cylinder upper chamber 2a, and the cylinder upper and lower chamber 2
A and 2b have almost the same pressure, the check valve 10 of the base valve 5 is closed, and the piston rod 4 enters the cylinder 2 to the extent that the oil liquid in the cylinder 2 is pressurized, resulting in the same extension stroke as above. Similarly, it flows from the cylinder upper chamber 2a side to the reservoir chamber 6 side through the cylinder first and second upstream passages 14 and 15, the downstream passage 20 and the main passage 11.

As a result, the piston speed is low during the expansion and contraction strokes, and before the main damping valve 12 is opened, the flow passage areas of the fixed orifices 16 and 17 of the first and second upstream passages 14 and 15 and the flow control valve. According to the flow passage area of the downstream passage 20, which is determined by 21, the orifice characteristic (the damping force is approximately 2
A damping force (proportional to the power) is generated. Then, when the piston speed increases, the pressure on the cylinder upper chamber 2a side rises, and the main damping valve 12 opens, the damping force of the valve characteristic (the damping force is almost proportional to the piston speed) is changed according to the opening degree. Occurs and suppresses an excessive increase in damping force.

Then, the downstream passage 20 by the flow control valve 21
The smaller the flow passage area of, the larger the pressure loss due to it and the higher the pressure on the upstream side, so the pilot pressure introduced from the pilot conduit 13 becomes higher and the valve opening pressure of the main damping valve 12 becomes higher. Become. Further, the larger the flow passage area of the flow control valve 21, the smaller the pressure loss due to it and the lower the pressure on the upstream side thereof.
The pilot pressure introduced from 13 becomes low and the main damping valve
12 Valve opening pressure becomes low. In this way, the flow control valve
By adjusting the flow passage area of the downstream passage 20 by 21, the orifice characteristics and valve characteristics on the extension side and the contraction side change, so the damping force characteristics on the extension side and the contraction side from the low speed region to the high speed region of the piston speed. Can be adjusted.

At this time, during the expansion stroke of the piston rod 4, the cylinder lower chamber 2b is decompressed by the movement of the piston 3 and the pilot pressure introduced from the pilot passage 19 into the switching valve 18 is lowered, so that the second upstream side The passage 15 is open. Therefore, the first and second upstream passages 14,
The flow passage area of 15 becomes the total area of the first and second fixed orifices 16 and 17, and the pressure loss due to this becomes small, and the pilot pressure introduced from the pilot pipe line 13 on the downstream side to the main damping valve 12 becomes As a result, the valve opening pressure of the main damping valve 12 increases.

On the other hand, during the compression stroke, the piston rod 4
The cylinder lower chamber 2b is pressurized by the entry into the cylinder 2 and the pilot pressure introduced from the pilot passage 19 to the switching valve 18 becomes high, so that the second upstream passage 15 is closed. Therefore, the flow passage areas of the first and second upstream side passages 14 and 15 are the area of only the first fixed orifice 16, and the pressure loss due to this increases, and the pilot line 13 from the downstream side to the main damping valve 12 is increased. The pilot pressure introduced into the main damping valve 12 becomes low and the valve opening pressure of the main damping valve 12 becomes low.

Incidentally, both during the expansion stroke and the contraction stroke,
When the flow control valve 21 is fully closed, the damping force becomes maximum without being affected by the first and second fixed orifices 16 and 17.

In this way, by opening and closing one of the first and second upstream side passages 14 and 15 during the expansion stroke and the contraction stroke of the piston rod 4, the flow passage area is switched,
Since the valve opening pressure of the main damping valve 12 can be changed,
The degree of freedom in setting the damping force characteristics on the extension side and the contraction side can be increased.

The damping force characteristics of the damping force adjustable hydraulic shock absorber 1 are shown in FIG. The broken line in FIG. 4 indicates the opening point of the main damping valve 12.

Next, one embodiment showing a more specific structure of the present invention will be described with reference to FIGS.

As shown in FIGS. 2 and 3, the damping force adjusting hydraulic shock absorber 22 has a double cylinder structure in which an outer cylinder 24 is provided outside the cylinder 23. A reservoir chamber 25 is formed between them. A piston 26 is slidably fitted in the cylinder 23.
The inside of the cylinder 23 is divided into two chambers, that is, a cylinder upper chamber 23a (first chamber) and a cylinder lower chamber 23b (second chamber).
One end of a piston rod 27 is connected to the piston 26 by a nut 28, and the other end of the piston rod 27 is
It passes through the cylinder upper chamber 23 a, is inserted into a rod guide 29 and a seal member 30 mounted on the upper ends of the cylinder 23 and the outer cylinder 25, and extends to the outside of the cylinder 23. At the lower end of the cylinder 23, a base valve 31 that partitions the cylinder lower chamber 23b and the reservoir chamber 25 is provided. And
Oil liquid is sealed in the cylinder 23,
Oil liquid and gas are enclosed inside.

The piston 26 includes a cylinder upper and lower chambers 23a and 23a.
Oil passage 32 (first communication passage) for communicating between b and this oil passage
A check valve 33 (first check valve) that allows only the flow of oil liquid from the cylinder lower chamber 23b side to the cylinder upper chamber 23a side of 32 is provided. In addition, the base valve 31 has a cylinder lower chamber.
An oil passage 34 (second communication passage) for communicating the 23b with the reservoir chamber 25 and a check valve 35 (the second passage for allowing only oil liquid to flow from the reservoir chamber 25 side of the oil passage 34 to the cylinder lower chamber 23b side). Two
Check valve) is provided.

A damping force generating mechanism 36 is attached to the side surface of the outer cylinder 24. The damping force generating mechanism 36 has an outer cylinder at one end.
A proportional solenoid 38 is fitted to the other end of a cylindrical case 37 fixed to the side wall of 24 and fixed by a retainer 39. Inside the case 37, one end has a proportional solenoid 38
A substantially cylindrical guide member 40 that is screwed into the is inserted. An annular fixing member 41 and a valve member 42 are fitted to the outer periphery of the guide member 40 and fixed by a union nut 43 having an oil passage 43a screwed to the other end of the guide member 40. The tip of the union nut 43 is
It is fitted to the side wall of a substantially cylindrical passage member 44 fitted to the outside of 23. A large-diameter side end of a substantially taper-shaped housing member 45 is fitted to the outer peripheral portion of the valve member 42, and a small-diameter side end is fitted to the side wall of the passage member 44. An oil chamber 46 is formed inside. In addition, an oil chamber 47 communicating with the reservoir chamber 25 is formed in the case 37.

At the upper part of the cylinder 23, an upper tube 48
Is externally fitted and coupled to the passage member 44, and the cylinder 23
An annular oil passage 48a is formed between and. Ring oil passage 48a
Is an oil passage 49 provided on the side wall near the upper end of the cylinder 23.
Is communicated with the cylinder upper chamber 23a via an oil passage 46, and is also communicated with an oil chamber 46 via an oil passage 50 provided in the passage member 44. A lower tube 51 is externally fitted to the lower portion of the cylinder 23 and is coupled to the passage member 44, and an annular oil passage 52 is formed between the lower tube 51 and the cylinder 23. The annular oil passage 52 is a cylinder
It is communicated with the cylinder lower chamber 23b via an oil passage 53 provided on the side wall near the lower end of 23, and is also connected to the oil passage 43a of the union nut 43 via an oil passage 54 provided in the passage member 44. It is in communication.

The valve member 42 is provided with a plurality of oil passages 55 penetrating in the axial direction, and annular valve seats 56, 57 are provided around the oil passage 55.
Is protruding. The inner valve seat 56 has an orifice 58a.
A sub valve 58 composed of a notch valve 58b having a (notch) and a disc valve 58c laminated thereon is seated.

A substantially cylindrical movable member 59 is slidably fitted around the outer periphery of the fixed member 41. The movable member 59 is seated on the valve seat 57 on the outer side of the valve member 42 through the floating valve 60 having an annular end portion, and the outer peripheral portion of the disc-shaped leaf spring 61 is attached to the flange portion formed inside the one end portion. It is liquid-tightly contacted and urged in the valve closing direction, that is, toward the valve seat 57 side.
An oil chamber 62 is formed between the valve member 42 and the leaf spring 61, and the back pressure chamber 63 is formed by the fixed member 41, the movable member 59 and the leaf spring 61.
(Pilot pressure introducing part) is formed. Leaf spring 61
Is composed of a notch valve 64a and a disc valve 64b that form an orifice 64 (first upstream passage, first fixed orifice) that connects the oil chamber 62 and the back pressure chamber 63 to each other.
The fixed member 41, the valve seat 57, the movable member 59, the floating valve 60 and the leaf spring 62 constitute a pilot type main damping valve A (hereinafter referred to as the main damping valve A).
The movable member 59, the floating valve 60, and the leaf spring 61 receive the pressure on the oil chamber 62 side to open the valve, generate a damping force according to the opening, and use the pressure in the back pressure chamber 63 as the pilot pressure to close the valve. The valve opening pressure is adjusted by acting in the direction. The valve opening pressure of the sub valve 58 is set lower than the valve opening pressure of the main damping valve A.

A port 65 communicating with the back pressure chamber 63 and a throttle port 66 (second upstream passage, second fixed orifice) communicating with the oil chamber 62 are provided on the side wall of the guide member 40. A plunger 67 for opening and closing the throttle port 66 is slidably fitted in the guide member 40, and the plunger 67 allows the inside of the guide member 40 to communicate with the port 65 by connecting the oil chamber 40a and the union nut 43. Oil chamber communicating with oil passage 43a
It is defined by 40b. The plunger 67 has a guide member 40.
The range of movement is restricted by cylindrical stoppers 68, 69 fitted to both ends of the. Then, the guide member 40
And plunger 67 form a pilot type switching valve
53, annular oil passage 52, oil passage 54 and union nut 43 oil passage
43a composes the pilot passage, usually
The plunger 67 is biased by the compression spring 70 provided on the oil chamber 40a side, contacts the stopper 69 on the union nut 43 side, and opens the throttle port 66 (see the upper side of the one-dot chain line in FIG. 3). Further, when a predetermined pressure or more acts on the oil chamber 40b side, it moves until it contacts the stopper 68 on the proportional solenoid 38 side to close the throttle port 66 (see the lower side of the one-dot chain line in FIG. 3). There is.

The proportional solenoid 38 is provided with a bore 71 communicating with the inside of the guide member 40. An annular groove 72 is formed in the inner peripheral portion of the bore 71, and the annular groove 72 is formed in the oil passage 73.
It communicates with the oil chamber 47 via the (downstream passage). Boa
A spool 74 is slidably fitted to the 71. A flow control valve B (variable orifice) is formed by the bore 71 and the spool 74, and the spool 74 moves against the biasing force of the spring 76 in response to the energizing current to the solenoid 75, and the annular groove 72 is formed. By opening and closing, the flow passage area between the inside of the guide member 40 and the oil passage 73 is adjusted. A filter 77 is provided between the guide member 40 and the bore 71.

In the above structure, the oil passage 49, the annular oil passage 48a, the oil passage 50, the oil chamber 46, the oil passage 55, the oil chamber 62 and the oil chamber
47 forms a main passage that connects the cylinder upper chamber 23a and the reservoir chamber 25.

The operation of the present embodiment configured as described above will be described below.

During the extension stroke of the piston rod 27, as the piston 26 moves, the check valve 33 of the piston 26 closes and the oil liquid in the cylinder upper chamber 23a side is pressurized, and the cylinder lower chamber
The inside of 23b is decompressed. The pressure in the lower cylinder chamber 23b is
3, the damping force generating mechanism 36 through the annular oil passage 52 and the oil passage 54
Is transmitted to the oil passage 43a of the union nut 43, is transmitted from the oil passage 43a to the oil chamber 40b in the guide member 40, and acts on the plunger 67. This depressurizes the oil chamber 40b, so that the plunger 67 remains in contact with the stopper 69 and the throttle port 66
Is opened.

The oil liquid pressurized on the cylinder upper chamber 23a side is
Flows through the oil passage 49, the annular oil passage 48a, and the oil passage 50 to the oil chamber 46 of the damping force generating mechanism 36, and further, the oil passage 55 and the sub valve.
It flows into the oil chamber 62 through the orifice 58a of 58. here,
Since the throttle passage 66 is open, the oil liquid is guided from the oil chamber 62 through the orifice 64 of the leaf spring 61, the back pressure chamber 63 and the port 65, and from the oil chamber 62 through the throttle port 66.
It flows to the oil chamber 40a in 40. Then, it flows from the oil chamber 40a to the reservoir 25 through the filter 77, the bore 71, the annular groove 72, the oil passage 73 and the oil chamber 47. At this time, when the pressure on the cylinder upper chamber 23a side reaches the opening pressure of the main damping valve A, the main damping valve A
Is opened and the oil liquid flows directly from the oil chamber 62 to the oil chamber 47. on the other hand,
The oil liquid corresponding to the piston rod 27 withdrawing from the inside of the cylinder 23 flows from the reservoir chamber 25 to the check valve 35 of the base valve 31 and flows into the cylinder lower chamber 23b.

Therefore, during the extension stroke, the piston speed is low and before the main damping valve A is opened, the total flow passage area and flow rate control of the orifice 58a, the disc valve 58c, the orifice 64 and the throttle port 66 arranged in parallel with each other are controlled. A damping force having an orifice characteristic is generated depending on the flow passage area of the valve B. Then, when the piston speed increases and the pressure on the cylinder upper chamber 23a side rises to open the main damping valve A, a damping force having a valve characteristic is generated according to the opening degree, and the damping force is excessively increased. Suppress.

At this time, the smaller the flow passage area of the flow control valve B, the larger the pressure loss due to it, and the higher the pressure of the back pressure chamber 63 on the upstream side thereof, so that the valve opening pressure of the main damping valve A is increased. Further, the larger the flow passage area of the flow control valve B, the smaller the pressure loss due to it, and the lower the pressure of the back pressure chamber 63 on the upstream side thereof. Therefore, the opening pressure of the main damping valve A becomes low. Become. In this way, by changing the flow passage area of the flow control valve B, the valve opening pressure of the main damping valve A is changed at the same time, and the orifice characteristic and the valve characteristic are changed. The damping force characteristic can be adjusted over the range.

During the contraction stroke, the check valve 33 of the piston 26 opens along with the movement of the piston 26, and the oil liquid in the cylinder lower chamber 23b directly flows into the cylinder upper chamber 23a through the oil passage 32, so that the base valve When the check valve 35 of 31 is closed and the piston rod 27 enters the cylinder 23,
The oil liquids 23a and 23b are pressurized. The pressure in the cylinder lower chamber 23b is transmitted to the oil passage 43a of the union nut 43 of the damping force generating mechanism 36 through the oil passage 53, the annular oil passage 52, and the oil passage 54, and the oil chamber in the guide member 40 is transmitted from the oil passage 43a. It is transmitted to 40b and acts on the plunger 67. As a result, the oil chamber 40b is pressurized, so that the plunger 67 moves and contacts the stopper 68 to close the throttle port 66.

The oil liquid pressurized in the cylinder upper and lower chambers 23a and 23b passes from the cylinder upper chamber 23a side to the reservoir through the same flow passage as in the above extension stroke, except that the throttle port 66 is closed by the plunger 67. Flows to room 25 side.

Therefore, during the compression stroke, the piston speed is small and before the main damping valve A is opened, a damping force having an orifice characteristic is generated by the flow passage areas of the orifice 58a, the disc valve 58c, the orifice 64 and the flow control valve B. . Then, when the piston speed increases and the pressure on the cylinder upper chamber 23a side rises to open the main damping valve A, a damping force having a valve characteristic is generated according to the opening degree, and the damping force is excessively increased. Suppress.

By changing the flow passage area of the flow control valve B in the same manner as in the extension stroke, the valve opening pressure of the main damping valve A is changed at the same time, and the orifice characteristic and the valve characteristic are changed. The damping force characteristics can be adjusted from the low speed region to the high speed region of the piston speed.

At this time, during the contraction stroke, the plunger 67
Because the throttle port 66 is closed by
Since the flow path area on the upstream side of the flow path becomes only the orifice 64 and becomes smaller than that at the time of the expansion stroke, the pressure loss due to it becomes large, the pressure in the back pressure chamber 63 becomes low, and the main damping valve The valve opening pressure of A becomes low. In this way,
By opening and closing the throttle port 66 during the expansion stroke and the contraction stroke of the piston rod 27, the flow passage area on the upstream side of the back pressure chamber 63 can be switched to change the valve opening pressure of the main damping valve A. Therefore, the damping force characteristics as shown in FIG. 4 can be obtained, and the degree of freedom in setting the damping force characteristics on the extension side and the contraction side can be increased.

In the above embodiment, the pilot type switching valve is a normally open switching valve, that is, the cylinder lower chamber 2b.
Although the one opened by decompressing the oil liquid inside and closed by the pressurization is shown, the invention is not limited to this and a normally closed switching valve 18A as shown in the hydraulic circuit of FIG. 5 may be used. In this case, the switching valve
18A is configured to close the second upstream passage 15 by depressurizing the oil liquid in the cylinder lower chamber 2b, while opening it by pressurizing, so that damping force characteristics as shown in FIG. 6 can be obtained. it can.

[0045]

As described in detail above, according to the damping force adjusting type hydraulic shock absorber of the present invention, the oil liquid flows from the cylinder upper chamber side to the first and second upstream side passages and the downstream side passages during the expansion and contraction strokes. And through the main passage to the reservoir chamber side, and damping force is generated by the first and second fixed orifices, the variable orifice and the main damping valve. Then, by changing the flow area of the variable orifice, the flow resistance of the downstream passage is directly adjusted and the pilot pressure of the pilot type main damping valve is changed to adjust the valve opening characteristics, and the expansion side and the contraction side are adjusted. Adjust the damping force characteristics of. At this time, the second chamber is decompressed by the movement of the piston during the extension stroke and pressurized during the contraction stroke, so the pilot pressure changes between the extension side and the contraction side, and the pilot type switching valve moves through the second upstream side passage. Since the damping force characteristics change by opening and closing, the degree of freedom in setting the damping force characteristics on the extension side and the contraction side can be increased.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.

FIG. 2 is a vertical sectional view of an embodiment of the present invention.

FIG. 3 is an enlarged vertical sectional view showing a damping force generating mechanism of the apparatus of FIG.

FIG. 4 is a diagram showing damping force characteristics of the apparatus of FIGS. 1 and 2.

FIG. 5 is a hydraulic circuit diagram showing a modified example of the embodiment of the present invention.

FIG. 6 is a diagram showing damping force characteristics of the modification shown in FIG.

[Explanation of Codes] 1 Damping force adjusting hydraulic shock absorber 2 Cylinder 2a Cylinder upper chamber (first chamber) 2b Cylinder lower chamber (second chamber) 3 Piston 4 Piston rod 6 Reservoir chamber 7 Oil passage (first communication passage) 8 Check valve (first check valve) 9 Oil passage (second communication passage) 10 Check valve (second check valve) 11 Main passage 12 Pilot type main damping valve 13 Pilot line (pilot pressure introduction part) 14 First upstream passage 15 Second upstream passage 16 First fixed orifice 17 Second fixed orifice 18 Pilot type switching valve 19 Pilot passage 20 Downstream passage 21 Flow control valve (variable orifice)

Claims (1)

[Claims] 1. A cylinder in which oil liquid is sealed, a reservoir chamber in which oil liquid and gas are sealed, and a first chamber and a second chamber which are slidably fitted in the cylinder. And a piston rod having one end side connected to the piston and the other end side extending to the outside of the cylinder through the first chamber, and a first connection for communicating between the first and second chambers. A passage, a first check valve that allows the flow of the oil liquid from the second chamber side to the first chamber side of the first communication passage, and a second check valve that connects the second chamber and the reservoir chamber A communication passage, a second check valve that allows the flow of the oil liquid from the reservoir chamber side of the second communication passage to the second chamber side, and a main passage that connects the first chamber and the reservoir chamber. And control the flow of the oil liquid in the main passage to generate a damping force and adjust the damping force according to the pilot pressure. And a first and a second upstream side passages arranged in parallel with each other for communicating a pilot type main damping valve to be regulated and a pilot pressure introducing portion of the pilot type main damping valve to the upstream side of the pilot type main damping valve in the main passage. And first and second fixed orifices respectively provided in the first and second upstream passages, and a downstream passage for communicating the pilot pressure introducing portion to the downstream side of the pilot type main damping valve of the main passage. A variable orifice that adjusts the flow passage area of the downstream passage, a pilot type switching valve that opens and closes the second upstream passage, and a pilot pressure introducing portion of the pilot type switching valve that communicates with the second chamber. A damping force adjusting hydraulic shock absorber comprising a pilot passage.