JP3781818B2 - Hydraulic shock absorber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic shock absorber suitable for use in a suspension device for automobiles, motorcycles, industrial vehicles and the like.
[0002]
[Prior art]
As a conventional damping adjustment type hydraulic shock absorber, for example, there is one described in Japanese Patent Laid-Open No. 4-54339. This has a piston that slidably fits into the cylinder and divides the cylinder into two chambers.
[0003]
In addition, a communication passage that connects the two chambers to each other is provided in the axial center portion of the piston rod that is fitted and fixed to the piston, and valve means for opening and closing the communication passage is provided in the communication passage. Is provided.
[0004]
Another conventional damping force adjustment type hydraulic shock absorber is described in Japanese Patent Application Laid-Open No. 62-220728. This is called a triple pipe uniflow adjustable damper, and is configured to share one bypass (soft) valve for both the extension stroke and the pressure stroke.
[0005]
[Problems to be solved by the invention]
However, since the hydraulic shock absorber described in Japanese Patent Laid-Open No. 4-54339 has a structure in which a pressure side variable mechanism is provided on the piston, hydraulic fluid from the piston lower chamber to the piston upper chamber during the pressure stroke is provided. In order to prevent poor running around, there is a problem that the variable range of the compression side damping force is limited by the compression side throttle and the sealed gas pressure arranged in series with the piston rod diameter, the cylinder diameter, and the damping force variable mechanism.
[0006]
In addition, since each of the expansion side and compression side variable damping force mechanisms is installed in the piston, there is a problem in that the piston valve length increases and the piston rod operating stroke decreases.
[0007]
Further, when the hydraulic shock absorber is applied to an electronically controlled suspension, the mounting position or the mounting mechanism of the control actuator is in series in the axial direction with respect to the main body of the hydraulic shock absorber. In some cases, there is a problem that the operation stroke of the piston rod is reduced.
[0008]
On the other hand, in the hydraulic shock absorber described in Japanese Patent Laid-Open No. 62-220728, the variable range of the damping force on the expansion side and the compression side is affected by the piston rod diameter and the cylinder diameter. There was a problem that could not be done.
[0009]
The present invention solves the conventional problems as described above, and it is possible to obtain a large damping force variable range for both the extension stroke and the pressure stroke with one adjusting means, and to make the damping force adjusting mechanism compact. An object of the present invention is to provide a hydraulic shock absorber capable of sufficiently ensuring the operation stroke of the piston rod.
[0010]
[Means for Solving the Problems]
    In order to achieve the above object, one means of the present invention is that a piston rod is movably inserted into a cylinder via a piston, and the piston partitions a piston upper chamber and a piston lower chamber into the cylinder. The piston upper chamber and the piston lower chamber are opened and closed via a first extension side valve provided on the piston, and the piston lower chamber is opened outside the cylinder via a first pressure side valve provided on a base valve member below the cylinder. Open and close to the reservoir chamber,A first bypass that bypasses the first extension valve and connects the piston upper chamber and the piston lower chamber, and a second bypass that bypasses the first pressure valve and connects the piston lower chamber and the reservoir chamber The opening area of the first bypass and the second bypass is continuously adjusted by a common switching valve.In the hydraulic shock absorber, the second expansion side valve is provided to be opened and closed during the first bypass, and the second pressure side valve is provided to be opened and closed during the second bypass.The switching valve has a second position that is opened simultaneously with a first position in which the first bypass and the second bypass are simultaneously closed, and the opening areas of the first bypass and the second bypass are simultaneously increased or decreased. Is what.
[0011]
  in this case, The opening areas of the first bypass and the second bypass are preferably adjusted in three stages so that the expansion-side damping force and the compression-side damping force are switched to soft, medium, and hard, respectively.
[0012]
  Further, according to another means of the present invention, a piston rod is movably inserted into a cylinder via a piston, and the piston defines a piston upper chamber and a piston lower chamber in the cylinder, and these piston upper chamber and piston The lower chamber is opened and closed via a first extension valve provided on the piston, and the piston lower chamber is opened and closed to a reservoir chamber outside the cylinder via a first pressure valve provided on a base valve member below the cylinder. A first bypass that bypasses the first extension valve and connects the piston upper chamber and the piston lower chamber, and a second bypass that bypasses the first pressure valve and connects the piston lower chamber and the reservoir chamber. In the hydraulic shock absorber in which the opening area is continuously adjusted by one common switching valve, the first bypass and the second bypass are in a stepless manner. And the second pressure side valve is openable and closable during the second bypass. The switching valve has a first position in which the second bypass is opened and the first bypass is closed; A second position where the second bypass closes and a third position where the first bypass and the second bypass open simultaneously, and when the opening area of one bypass increases, the other The opening area of the bypass is reduced.
[0013]
  In the above means, the switching valve is preferably constituted by a solenoid switching valve controlled by current or voltage.
[0014]
  Similarly, The stroke may be controlled by hydraulic pressure or pneumatic pressure of the switching valve.
[0015]
  Similarly, The stroke of the switching valve may be controlled by screwing operation.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
1 is a conceptual diagram showing a basic configuration of a hydraulic shock absorber, and FIG. 2 is a longitudinal sectional view showing a specific configuration of the hydraulic shock absorber. 1 is a piston rod, and 11 is a piston that is attached to the lower end of the piston rod 1 and slides into the cylinder 2. 2a and 2b are oil holes formed in the upper and lower portions of the cylinder 2, respectively.
[0018]
Reference numerals 7 and 14 denote an upper plate and a base valve member for closing the upper end and the lower end of the cylinder 2, and the piston 11 is located above the piston in the cylinder 2 closed by the upper plate 7 and the base valve member 14. It is divided into a chamber 4 and a piston lower chamber 5. The piston rod 1 passes through the upper plate 7, the seal member 10, and a central hole at the outer shell end described later.
[0019]
3 is an outer shell that divides the reservoir chamber 6 of the hydraulic oil on the outer periphery of the inner tube 21 that is suspended from the upper plate 7. The gap 8 between the outer shell 3 and the base valve member 14, the reservoir chamber 6, Are communicated via an oil passage 9.
[0020]
Reference numeral 12 denotes an extension side hard valve as a first extension side valve provided in the piston 11, and 13 denotes a flow of hydraulic oil from the piston lower chamber 5 to the piston upper chamber 4 provided in the piston 11. It is a check valve that permits
[0021]
Further, 15 is a pressure side hard valve as a first pressure side valve provided in the base valve member 14, and 16 is provided in the base valve member 14 and supplies hydraulic oil from the reservoir chamber 6 to the piston lower chamber 5. This is a check valve that allows flow.
[0022]
Reference numeral 21 denotes a predetermined length of an inner tube attached to the upper plate 7 via a seal ring 7 a, which is interposed between the cylinder 2 and the outer shell 3. Reference numeral 22 denotes a substantially cylindrical joint that is oil-tightly inserted between the lower end portion of the inner tube 21 and the base valve member 16, and an oil hole 22a is formed in the upper portion of the joint 22. .
[0023]
Further, a partition wall projection 22b that is in close contact with the outer periphery of the cylinder 2 is provided on the inner peripheral side of the joint 22, and an upper gap 22c that communicates between the cylinder 2 and the joint 22 with the oil hole 2a and a lower portion that communicates with the oil hole 2b. It is partitioned into a gap 22d.
[0024]
A cylindrical inner disk member 32 includes a small diameter portion 32 d and a large diameter portion 32 e, of which the small diameter portion 32 d is mounted at a position communicating with the lower gap 22 d of the joint 22.
[0025]
The inner disk member 32 has an oil hole 32a at the center and an oil passage 32b penetrating from the annular vertical surface portion to the ring-shaped valve seat surface portion 32f within the thickness of the large diameter portion 32e.
[0026]
Further, a ring-shaped flange portion 32g protrudes vertically on the outer periphery of the large-diameter portion 32e of the disk member 32, and an oil hole 32c is drilled through the ring-shaped flange portion 32g. A pressure side soft valve 36 as a ring-shaped second pressure side valve fitted into the outer peripheral base portion of the small diameter portion 32d is located at a position (valve seat portion) facing the annular vertical end surface of the oil hole 32b. It is in contact.
[0027]
Reference numeral 33 denotes a housing in which a disk portion 33c is tightly fitted on the outer periphery of the small diameter portion 32d between an outer disk member 31 and an inner disk member 32, which will be described later, and the outer peripheral ring portion 33d is a large diameter portion 31c of the outer disk member 31 The outer periphery is held oil-tight, and the inner ring portion 33e holds the outer periphery of the large-diameter portion 32e of the inner disk member 32 in an oil-tight manner.
[0028]
Reference numeral 31 denotes the outer disk member attached to the outer periphery of the small diameter portion 32d of the inner disk member 32. The joint 23 is oiltight between the outer periphery of the end of the small diameter portion 31b and a part of the joint 22. It is attached to.
[0029]
An oil passage 23 a communicating with the oil hole 22 a is formed between the outer disk member 31 and the joint 23 and the small diameter portion 32 d of the inner disk member 32 and the joint 22.
[0030]
The outer disk member 31 is provided with an oil hole 31a communicating with the oil passage 23a so as to penetrate from the inner peripheral surface toward the vertical end surface of the large-diameter portion 31c. An extension side soft valve 35 as a second extension side valve fitted into the outer periphery of the small diameter portion 32d of the inner disk member 32 is in contact with the end of the oil hole 31a (valve seat portion) that faces.
[0031]
The housing 33 is formed with oil holes 33a having both ends opened in the oil holes 32c of the extension side soft valve 35 and the inner disk member 32, and both ends on the reservoir chamber 6 and the pressure side soft valve 36 side. Is formed with an oil hole 33b.
[0032]
A spool valve 34 is slidable in the axial direction along the annular valve seat surface portion 32f of the inner disk member 32, and has an oil hole 34a penetrating inward and outward.
[0033]
On the other hand, 37 is a cylindrical case that oil-tightly covers an opening formed in a part of the outer periphery of the outer shell 3, and the case 37 projects in a direction perpendicular to the axial direction of the outer shell 3. The outer periphery of the flange portion 32g of the inner disk member 32 and the outer periphery of the housing 33 are supported on the inner peripheral surface thereof.
[0034]
Reference numeral 38 denotes a cover that is screwed into the open end of the case 37 to close the open end. A ring-shaped exciting coil 39 is disposed on the open side of the case 37 so as to cover the spool valve 34. ing. In addition, a normal oil-tight (sealing) process is applied between the exciting coil 39 and the case 37 and the cover 38.
[0035]
Reference numeral 40 denotes a spring interposed between the cover 38 and the spool valve 34, and the spring 40 has a predetermined elastic force corresponding to an electrode suction force of a coil 39 to be described later. Therefore, the spool valve 34 is normally urged in the direction in which the cylinder 2 is located.
[0036]
The upper plate 7 is provided with an oil hole 41 between the seal plate 10 and the seal member 10 for collecting the hydraulic oil leaked by the pressure increasing operation of the piston rod 1 into the reservoir chamber 6. Reference numeral 42 denotes a spring that urges the seal member 10 so as to be in close contact with the outer periphery of the piston rod 1 via the spring receivers 43 and 44.
[0037]
The spool valve 34 selectively switches and connects the oil hole 32a to either the oil hole 32b or the oil hole 32c through the oil hole 34a by energizing and deactivating the coil 39. A common switching valve is configured.
[0038]
The spool valve 34 has two types of switching positions, a first position P1 and a second position P2, as shown in FIG. In FIG. 2, parts corresponding to those in FIG.
[0039]
Therefore, according to the above configuration, the oil passage A as shown in FIG. 1 is formed which communicates with the piston lower chamber 5 -the oil hole 2b of the cylinder 2, the oil hole 32a of the inner disk member 32, and the oil hole 34a of the spool valve 34. Is done.
[0040]
Also, the piston upper chamber 4 -the oil hole 2a of the cylinder 2, the inside of the inner tube 21, the oil hole 22a above the joint 22, the oil passage 23a, the oil hole 31a of the outer disk member 31, the extension side soft valve 35, and the oil in the housing 33. An oil passage B as a first bypass as shown in FIG. 1 is formed through the hole 33a, the oil hole 32c of the inner disk member 32, and the oil passage 37a on the outer periphery of the spool valve 34.
[0041]
Further, the second bypass oil passage as shown in FIG. 1 passes through the reservoir chamber 6-the oil hole 33b of the housing 33-the pressure side soft valve 36-the oil hole 32b of the inner disk member 32-the other outer peripheral portion of the spool valve 34. C is formed.
[0042]
Next, the operation will be described. First, in the extending stroke, the oil hole 34a of the spool valve 34 as the switching valve is closed by the valve seat surface portion 32f of the inner disk member 32 as shown in FIG. If so, as shown in FIG. 1, since the spool valve 34 is in the first position, the oil passage B and the oil passage C do not communicate with the oil passage A.
[0043]
For this reason, the hydraulic oil does not flow into the expansion side soft valve 35, and the hydraulic oil in the piston upper chamber 4 flows to the piston lower chamber 5 through the expansion side hard valve 12, and here, a large flow resistance is generated, The chamber 4 becomes a high pressure and generates a high damping force (the damping force during the extension stroke is hard).
[0044]
On the other hand, when a small current of a predetermined value is passed through the coil 39, the spool valve 34 moves slightly to the right, and the oil hole 34a slightly passes into the oil passage 37a on the oil hole 32c side of the inner disk member 32. Open.
[0045]
Therefore, the hydraulic oil in the piston upper chamber 4 is the oil hole 2a of the cylinder 2, the upper gap 22c, the oil hole 22a, the oil passage 23a, the oil hole 31a, the extension side soft valve 35, the oil hole 33a, the oil hole 32c, and the oil. It flows into the piston lower chamber 5 through the path 37a-oil hole 34a-oil hole 32a-lower gap 22d-oil hole 2b of the cylinder 2.
[0046]
At the same time, the expansion side hard valve 12 is slightly opened by the flow resistance, and the hydraulic oil flows from the piston upper chamber 4 to the piston lower chamber 5 through them, so that the flow resistance of the hydraulic oil as a whole decreases, and the piston upper chamber 4 Pressure and extension side damping force will be lower than in the case of the above-mentioned extension side damping force hard (the damping force during the extension side stroke is medium).
[0047]
Next, when a larger current is passed through the coil 39, the spool valve 34 moves greatly to the right. That is, in FIG. 1, the spool valve 34 shifts from the first position P1 to the second position P2. As a result, the oil hole 34a opens greatly into the oil passage 37a on the oil hole 32c side, and the flow resistance of the hydraulic oil in the oil passage 37a becomes so small that it almost disappears.
[0048]
For this reason, the flow of the working oil through the extension side soft valve 35 increases, and the flow resistance in the oil passage B which is the first bypass is reduced. Therefore, the damping force during the extension side stroke is further smaller than the medium. Thus, the pressure of the piston upper chamber 4 and the extension side damping force are further greatly reduced (the damping force during the extension side stroke is soft).
[0049]
On the other hand, in the pressure stroke, when the oil hole 34a of the spool valve 34 as the switching valve is closed by the valve seat surface portion 32f of the inner disk member 32 as shown in FIG. Therefore, the oil passage C does not communicate with the oil chamber A because it is in the first position.
[0050]
For this reason, the hydraulic oil does not flow into the pressure side soft valve 36, and the hydraulic oil in the piston lower chamber 5 flows to the reservoir 6 via the pressure side hard valve 15 as the first pressure side valve of the base valve member 14. This produces a large flow resistance, and the piston lower chamber 5 becomes a high pressure, and a high compression side damping force is generated (the damping force during the compression side stroke is hard).
[0051]
On the other hand, when a small current of a predetermined value is passed through the coil 39, the spool valve 34 moves slightly to the right, and the oil hole 34a slightly passes into the oil passage 37a on the oil hole 32c side of the inner disk member 32. Open.
[0052]
Therefore, the hydraulic oil in the piston lower chamber 5 flows into the reservoir chamber 6 via the pressure side hard valve 15 of the base valve member 14, and separately, the hydraulic oil in the piston lower chamber 5 Oil hole 2b, lower gap 22d, oil hole 32a, left end side of spool valve 34, oil hole 32b of inner disk member 32, pressure side soft valve 36, oil hole 33b of housing 33, outer ring portion 33d of housing 33 It flows into the reservoir chamber 6 through a path on the outer peripheral side.
[0053]
For this reason, the flow resistance of the hydraulic fluid as a whole is lowered, and the pressure and compression side damping force of the piston lower chamber 5 are reduced as compared with the case of the hard damping force (the damping force during the compression side stroke is medium). .
[0054]
Next, when a larger current is passed through the coil 39 during the pressure stroke, the spool valve 34 is greatly moved to the right. As a result, the opening end of the oil hole 32b of the inner disk member 32 is greatly opened to the oil hole 32a, the flow resistance of the hydraulic oil in the oil hole 32b is almost eliminated, and the flow of hydraulic oil to the compression side soft valve 36 increases. To do.
[0055]
For this reason, the flow resistance of the hydraulic oil in this path is further reduced, and the pressure and compression side damping force of the piston lower chamber 5 are greatly reduced (the damping force during the compression side stroke is soft).
[0056]
In this way, since the expansion side soft valve 35 and the compression side soft valve 36 are connected in parallel to the expansion side hard valve 12 and the compression side hard valve 15 via the spool valve 34, respectively, the compression side damping of the piston 11 is performed when the compression side damping force is hard. It is possible to avoid increasing the force load, thereby preventing the hydraulic oil from flowing around from the piston lower chamber 5 to the piston upper chamber 4 during the pressure stroke and eliminating the restriction of the variable range of the compression side damping force. can do.
[0057]
Further, the extension side soft valve 35 and the pressure side soft valve 36 are coaxially arranged together with the spool valve 34 as a switching valve, so that the soft valve portion can be made compact, and the piston 11 is configured independently of the damping force adjusting mechanism. Therefore, the structure of the piston 11 can be used as it is, and the piston rod can be reciprocated with the same stroke as a normal hydraulic shock absorber without changing the piston valve length. The degree of freedom of the place can be increased. Further, the oil passages B and C as bypasses are independently set in the extension stroke and the pressure stroke, and the extension side soft valve 35 and the pressure side soft valve 36 are coaxially installed in the valve unit, so that each soft valve is extended to the extension side. , The pressure side can be adjusted separately, and the variable range of the damping force on the expansion side and the compression side can be set freely.
[0058]
FIG. 3 is a cross-sectional view showing another form of the valve unit V according to the present invention. Here, the configuration of the spool valve 34A is different from FIG. It is provided at a position overlapping with the hole 34a.
[0059]
That is, as shown in FIG. 4, the first position P3 where the oil passage C opens and the oil passage B closes to the spool valve 34A, the second position P4 where the oil passage B opens and the oil passage C closes, and the oil passage B , C open at the same time, and a third position P5.
[0060]
In addition to this, by adjusting each of the above positions so that when the opening area of one of the oil passages B and C increases, the other opening area is reduced, the semi-active control for an arbitrary damping force is performed. It can be used as a damper.
[0061]
FIG. 5 is a cross-sectional view showing another valve unit V according to the present invention. In FIG. 1, the position of the spool valve 34 is adjusted within the relationship between the electrode suction force of the coil 39 and the spring force of the spring 40. On the other hand, in this embodiment, fluid pressure such as air pressure or hydraulic pressure, which is press-fitted from the hub-shaped center hole 38 a formed in the cover 38, is oil-tight against the spring 46 at the inner periphery of the case 37. The position of the spool valve 34B is adjusted in accordance with the movement of the operation plate 47 against the side surface of the operation plate 47 that slides on the side.
[0062]
Accordingly, when the fluid pressure to be pressed into the center hole 38a is, for example, air pressure, the pressure of the air suspension (hydropneumatic) is fed back to the center hole 38a, and the spool valve 34B slides according to the air pressure. By adjusting the moving position, the damping force can be adjusted. As a result, it is possible to realize a mechanical damping force adjustment that is linked to the loaded load or the like.
[0063]
FIG. 6 is a cross-sectional view showing a valve unit V according to still another embodiment of the present invention, which is formed with a screw hole portion 48 in the center portion of the cover 38, and a screw-shaped spool valve 34C in the screw hole portion 48. Is screwed so that the amount of movement in the axial direction can be adjusted.
[0064]
In such a valve unit V, by manually rotating the spool valve 34C using a jig, the opening amount of the oil hole 34a with respect to the oil hole 32b and the oil passage 37a is adjusted to adjust the attenuation amount. This can be implemented arbitrarily and can be realized with a simple and inexpensive configuration.
[0065]
In FIG. 5 and FIG. 6, other operations are the same as those described with reference to FIG. 1 and FIG.
[0066]
【The invention's effect】
    As aboveClaims 1, 2, 3According to the invention, the piston rod is movably inserted into the cylinder via the piston, the piston partitions the piston upper chamber and the piston lower chamber in the cylinder, and the piston upper chamber and the piston lower chamber are defined as The piston is opened and closed via a first extension valve provided on the piston, and the piston lower chamber is opened and closed to a reservoir chamber outside the cylinder via a first pressure side valve provided on a base valve member below the cylinder.A first bypass that bypasses the first extension valve and connects the piston upper chamber and the piston lower chamber, and a second bypass that bypasses the first pressure valve and connects the piston lower chamber and the reservoir chamber Since the first bypass and the second bypass are configured to adjust the opening area steplessly by a common switching valve.In addition, it is possible to suppress an increase in the pressure side damping force load of the piston when the compression side damping force is hard, thereby preventing the occurrence of poor circulation of hydraulic oil from the piston lower chamber to the piston upper chamber, An effect is obtained that there is no restriction on the adjustment range of the compression damping force.
  Further claims 1 According to the invention, the switching valve includes the second position opened simultaneously with the first position where the first bypass and the second bypass are simultaneously closed, and the opening areas of the first bypass and the second bypass are simultaneously set. Since it is configured to increase or decrease, the effect that two damping force adjustments on the extension side and the compression side can be performed simultaneously is obtained.
[0068]
According to a third aspect of the present invention, the switching valve has a first position in which the second bypass is opened and the first bypass is closed, and a second position in which the first bypass is opened and the second bypass is closed. Since the first bypass and the third bypass are configured to open at the same time and the opening area of one bypass increases, the opening area of the other bypass decreases. The damping force can be set such that the compression side damping force is soft when the force is hard, and the compression side damping force is hard when the extension side damping force is soft. For example, it can be applied as a damper for semi-active control. Is obtained.
[0069]
  Also,Claim 2According to the invention, the opening areas of the first bypass and the second bypass are configured to be adjusted in three stages so that the expansion side damping force and the compression side damping force are switched to soft, medium, and hard, respectively. As a result, it is possible to freely select the optimum expansion side damping force and compression side damping force having a magnitude corresponding to the operation amount of the switching valve.
[0070]
  Also,Claim 4According to the present invention, since the switching valve is constituted by a solenoid switching valve controlled by current or voltage, an effect is obtained that the damping force can be accurately and continuously adjusted from a remote commanded current command value. It is done.
[0071]
Also,Claim 5According to the invention, since the switching valve is configured such that the stroke is controlled by hydraulic pressure or pneumatic pressure, the stepless adjustment of the damping force can be easily performed by a mechanical method, for example, only by feeding back the pressure of the air suspension. The effect that can be implemented is obtained.
[0072]
  Also,Claim 6According to the invention, since the switching valve is configured so that the stroke is controlled by screwing operation, the stepless adjustment of the damping force can be easily realized by manual operation, and this can be realized at a low cost with an extremely simple configuration. An effect is obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a hydraulic shock absorber according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing details of the hydraulic shock absorber shown in FIG. 1;
FIG. 3 is a cross-sectional view of a main part showing another form of the valve unit in FIG. 2;
FIG. 4 is a conceptual diagram showing a hydraulic shock absorber according to another embodiment of the present invention.
FIG. 5 is a cross-sectional view showing another form of the valve unit in FIG. 1;
6 is a cross-sectional view showing another form of the valve unit in FIG. 1. FIG.
[Explanation of symbols]
1 Piston rod
2 cylinders
4 Piston upper chamber
5 Piston lower chamber
6 Reservoir chamber
11 Piston
12 Stretch side hard valve (first stretch side valve)
14 Base valve member
15 Pressure side hard valve (first pressure side valve)
34 Spool valve (switching valve)
35 Extension side soft valve (second extension side valve)
36 Pressure side soft valve (second pressure side valve)
A Oil passage
B Oil passage (first bypass)
C oil passage (second bypass)

Claims (6)

A piston rod is movably inserted into the cylinder via a piston, the piston partitions a piston upper chamber and a piston lower chamber in the cylinder, and the piston upper chamber and the piston lower chamber are provided in the piston. The piston lower chamber is opened and closed to a reservoir chamber outside the cylinder via a first pressure side valve provided in a base valve member below the cylinder , bypassing the first extension side valve. A first bypass that connects the piston upper chamber and the piston lower chamber, and a second bypass that bypasses the first pressure side valve and connects the piston lower chamber and the reservoir chamber, second bypass in the hydraulic shock absorber for adjusting the opening area steplessly by sharing one switching valve, during first bypass provided openably the second extension side valve, a second During bypass provided openably the second pressure side valve, the switching valve and a second position that opens simultaneously with the first position for closing the first bypass and a second bypass simultaneously, the first bypass And an opening area of the second bypass is increased or decreased simultaneously . The opening areas of the first bypass and the second bypass are adjusted in three stages so that the expansion side damping force and the compression side damping force are switched to soft, medium, and hard, respectively. Hydraulic shock absorber as described in. A piston rod is movably inserted into the cylinder via a piston, the piston partitions a piston upper chamber and a piston lower chamber in the cylinder, and the piston upper chamber and the piston lower chamber are provided in the piston. The piston lower chamber is opened and closed to a reservoir chamber outside the cylinder via a first pressure side valve provided in a base valve member below the cylinder, bypassing the first extension side valve. A first bypass that connects the piston upper chamber and the piston lower chamber, and a second bypass that bypasses the first pressure side valve and connects the piston lower chamber and the reservoir chamber, The second bypass is a hydraulic shock absorber in which the opening area is adjusted steplessly by a common switching valve. During the first bypass, the second extension side valve is provided to be openable and closable. During the bypass, a second pressure side valve is provided to be freely opened and closed. The switching valve has a first position in which the second bypass opens, a first bypass closes, a first bypass opens, and a second bypass opens. A second position to be closed and a third position in which the first bypass and the second bypass are simultaneously opened so that when the opening area of one bypass increases, the opening area of the other bypass decreases. A hydraulic shock absorber characterized by that. 4. The hydraulic shock absorber according to claim 1, wherein the switching valve is constituted by a solenoid switching valve controlled by current or voltage. The hydraulic shock absorber according to claim 1, 2 or 3 , wherein the stroke of the switching valve is controlled by hydraulic pressure or pneumatic pressure. The hydraulic shock absorber according to claim 1, 2, or 3 , wherein the stroke of the switching valve is controlled by screwing operation.

Images