JP2526553Y2 - Hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a hydraulic shock absorber applied to a vehicle suspension, and in particular, an inverted hydraulic shock absorber in which a piston rod side is connected to an axle and a cylinder tube side is connected to a vehicle body. With regard to type.

(Prior Art) Conventionally, as an inverted type hydraulic buffer, for example,
The one described in JP-A-58-97334 is known.

The inside of the hydraulic shock absorber c and the cylinder tube were defined by a piston into an upper chamber and a lower chamber, and a reservoir chamber was defined by a base above the upper chamber. The seal structure of the rod guide portion is such that the gap between the piston rod and the rod insertion hole is sealed with one seal member.

(Problems to be Solved by the Invention) However, such a conventional hydraulic shock absorber has a structure in which the gap between the piston rod and the rod insertion hole is sealed with a single seal, In order to prevent leakage, it is necessary to increase the contact pressure of the seal, which increases the friction and lowers the durability of the seal, and the stroke of the piston rod is not smoothed. There was a problem of feeling uncomfortable.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a hydraulic buffer capable of reliably preventing liquid leakage while having low friction.

(Means for Solving the Problems) In order to achieve the above-mentioned object, in the hydraulic shock absorber according to the present invention, a guide tube having a rod insertion hole is provided at a lower end, and a cylinder tube having a base provided at an upper end; A piston connected to a piston rod inserted through the rod insertion hole into the cylinder tube, and a piston provided around the cylinder tube, and a lower connection passage formed around the cylinder tube; Forming an outer chamber that communicates with the lower chamber through the outer tube, and an outer tube that forms a reservoir chamber defined by the base as the outer chamber and the upper chamber above the cylinder tube; and a reservoir chamber that is formed in the base. Check flow provided with a check valve that communicates with the upper chamber and allows flow from the reservoir chamber to the upper chamber, but prohibits reverse flow. A pressure reducing seal provided in the rod insertion hole in contact with the outer peripheral surface of the piston rod, and a seal housing formed between the pressure reducing seal and the oil seal provided outside the pressure reducing seal; A pressure relief check flow path provided with a check valve which communicates the seal housing with the outer chamber and permits flow from the seal housing to the outer chamber while prohibiting reverse flow is provided.

(Operation) The operation of the hydraulic shock absorber according to the present invention will be described with reference to the fluid circuit diagram of FIG. FIG. 1 shows the flow path of the fluid in the configuration of the present invention (the flow path when the fluid in the outer chamber is made to flow to the reservoir chamber side via the damping force generating means during the expansion stroke as the expansion side communication path). A) is an upper chamber, b is a lower chamber, c is an outer chamber, d is a reservoir chamber, e is a lower communication path, f is a compression side communication path, g is a compression side damping force generating means, h is the extension side damping force generating means, j is the extension side communication path, and n is the check channel.

First, during the extension stroke, the lower chamber b is reduced in the cylinder tube, and the upper chamber a is expanded.

In accordance with this volume change, the fluid in the lower chamber b flows into the outer chamber c via the lower communication path e, then passes through the expansion-side communication path j of the base, and on the way through the expansion-side damping force generating means h to the reservoir. Flow into chamber d. Then, when flowing into the reservoir chamber d, it further flows into the upper chamber a through the check channel n.

Accordingly, a damping force is generated in the extension-side damping force generating means h.

In this case, an amount of fluid corresponding to the volume of the piston rod retreated from the cylinder tube is supplied to the upper chamber a from the reservoir chamber d via the base check flow path n. Therefore, the upper chamber a does not have a negative pressure and cavitation does not occur.

Next, in the compression stroke, the lower chamber b is enlarged and the upper chamber a is reduced.

In accordance with this volume change, a part of the fluid in the upper chamber a passes through the pressure-side communication path f, flows into the outer chamber c through the pressure-side damping force generating means g on the way, and then flows through the lower communication path e. And flows into the lower chamber b. Further, the remaining fluid (fluid of an amount corresponding to the volume of the piston rod that has entered the cylinder tube) passes through the compression-side damping force generating means g, and further passes through the expansion-side damping force generating means h to the reservoir. Room d
Flows into.

Therefore, the damping force is generated in series in the compression side damping force generation unit g and the extension side damping force generation unit h.

Also, during the extension stroke of the piston, if the fluid pressure in the lower chamber b rises and a differential pressure is generated between the piston and the outside of the cylinder tube, the fluid in the lower chamber b passes through the pressure reducing seal by this differential pressure. The oil flows into the seal housing in a reduced pressure state, and is prevented from flowing out of the cylinder tube by the oil seal. During the pressure side stroke, the fluid pressure in the outer chamber c also increases, and a differential pressure is generated between the outer chamber c and the seal housing. However, in the check passage for depressurizing, the check valve is closed. By keeping the flow, the flow of the fluid in the direction of the seal housing is prevented, so that the fluid pressure in the seal housing does not increase.

On the other hand, during the pressure side stroke of the piston, since the fluid pressure in the outer chamber c decreases, when the fluid pressure in the seal housing is higher than the fluid pressure in the outer chamber c,
The fluid in the seal housing opens the check valve and flows out to the outer chamber c through the check flow path for depressurization, whereby the pressure in the seal housing is reduced.

As described above, the accumulated pressure in the seal housing is absorbed into the outer chamber c every time the pressure stroke of the hydraulic shock absorber is performed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

 First, the configuration of the first embodiment will be described.

FIG. 2 is a sectional view showing the hydraulic shock absorber according to the first embodiment of the present invention, wherein 1 is a cylinder tube.

The cylinder tube 1 has a cylindrical shape, a guide member 2 having a rod insertion hole 2a formed at a lower end portion, and a base 3 provided at an upper end portion. The inside of the cylinder tube 1 is filled with a fluid such as oil, and a piston 5 is slidably provided to define an upper chamber A and a lower chamber B.

The piston 5 is provided with a rod insertion hole of the guide member 2.
The piston rod 6 inserted from 2a into the cylinder tube 1 is fastened by a nut 6a to the tip of the piston rod 6, and a compression-side damping valve 5a and an extension-side damping valve 5b are provided. Is caused to occur. In addition, 5c is a compression-side communication passage, and 5d is an extension-side communication passage.

The lower end of the piston rod 6 is fastened to the bottom 7a of the strut tube 7 by a nut 7b.

The strut tube 7 has a lower end fitted and fixed to a knuckle spindle 8 and a spring seat 9 for supporting a lower end of a spring (not shown) provided at an upper end. At the bottom of the strut tube 7, a bound stopper 10 is provided.

As shown in detail in FIG. 3, the rod insertion hole 2a of the guide member 2 has a pressure reducing seal 2b slidably in contact with the outer peripheral surface of the piston rod 6, and a piston rod 6
Guide bush that slides with a small gap
2c is provided.

At the outer end of the guide member 2, there is provided a seal member 4 having an oil jewel 4a slidably in contact with the outer peripheral surface of the piston rod 6. The oil seal 4a and the guide bush 2c A seal housing 4b is formed between them.

Referring back to FIG. 2, the outer tube 11 is provided on the outer periphery of the cylinder tube 1 so as to extend above the cylinder tube 1. The outer periphery of the outer tube 11 is fitted to the guide member 2 at the lower end and screwed to the sealing member 4, and the inner periphery of the upper portion of the middle part is fitted to the base 3. Upper lid member 11c fitted and fixed in the upper end opening.
Is provided with a mounting portion 11e having a screw portion 11d for mounting the upper end of the outer tube 11 to the vehicle body. The outer tube 11 has two bearings, upper and lower.
The strut tube 7 is provided so as to be relatively slidable in the vertical direction via 11a and 11b.

The outer tube 11 forms an outer chamber C on the outer periphery of the cylinder tube 1 through the lower communication passage 2d formed at the lower end of the cylinder tube 1 and communicates with the lower chamber B. On the upper side of the base 3, a reservoir chamber D filled with a desired amount of fluid under the pressure of the sealed gas is formed.

Further, the guide member 2 is provided with a check flow path 2e for depressurization that allows only the flow from the seal housing 4b in the direction of the outer chamber C. That is, on the upper surface of the guide member 2 facing the outer chamber C, an annular groove 2f communicating with the check channel 2e for depressurization is formed, and an inner upper end surface of the annular groove 2f and a lower end of the cylinder tube 1 are formed. A check valve 2g is provided so as to sandwich the inner peripheral portion thereof and abut on the upper end surface of the annular groove 2f.

Next, referring to FIG. 4, the structure of the base 3 will be described in detail.

As shown, the base 3 is
Washer 14, second damping valve 15, second body 16, second check valve 17, washer 18, retainer 19, washer 20, first damping valve 21, first body 22, first check valve 23,
Attach washer 24 and retainer 25 in order, and finally nut 2
It is configured by fastening at 6.

The first body 22 is fitted to the second body 16 and an intermediate chamber E is formed between the first and second bodies 22 and 16.

The first body 22 has a first communication hole 22a that communicates the upper chamber A with the intermediate chamber E, a first check channel 22b that communicates the reservoir chamber D with the upper chamber A, an intermediate chamber E and an outer chamber C. And a base communication passage 22c that communicates with the base.

The inner surface of the first body 22 has a double annular groove 22.
d and 22e are formed, and inner and outer seat surfaces 22f and 22g with which the first damping valve 21 contacts are formed on the outer periphery thereof, and a constant orifice 22h is formed on the inner seat surface 22f. . And the inner annular groove 22d is the first
It communicates with the communication hole 22a.

That is, the first communication hole 22a is throttled by the first damping valve 21, and the first check channel 22b is allowed to flow only from the reservoir chamber D to the upper chamber A by the first check valve 23. Has become.

The second body 16 is formed with a second communication hole 16a that communicates the intermediate chamber E with the reservoir chamber D, and a second check channel 16b that communicates the reservoir chamber D with the intermediate chamber E.

In addition, an inner and outer double annular groove 16 is provided on the upper surface of the second body 16.
d and 16e are formed, and the inner and outer seal surfaces 1
6f and 16g are formed, and a constant orifice 16h is formed on the inner sheet surface 16f. And
The inner annular groove 16d communicates with the second communication hole 16a.

That is, the second communication hole 16a is throttled by the second damping valve 15, and the second check flow path 16b is allowed to flow only from the reservoir chamber D to the intermediate chamber E by the second check valve 17. Has become.

As described above, in the first embodiment of the present invention, the upper chamber A, the outer chamber C, and the reservoir chamber D are defined by the base 3, and each chamber A is formed by the passage formed in the base 3. , C, and D, that is, as shown in FIG. 4, that is, the first communication passage 22a, the inner annular groove 22d, the constant orifice 22h, the outer annular groove 22e, and the intermediate chamber E
The base communication passage 22c and the base communication passage 22c constitute a pressure side communication passage I according to the claims.

Further, the base communication passage 22c, the intermediate chamber E, the second communication hole 16a, the inner annular groove 16d, the constant orifice 16h, and the outer annular groove 16e constitute an extension side communication passage according to the claims.

Further, the reservoir chamber D is communicated with the upper chamber A by a first check channel 22b.
This constitutes the check flow channel in the claims.

Next, the operation of the embodiment will be described with reference to the circuit diagram of FIG.

(A) During Stretch Side Stroke During the stretch side stroke, the volume of the lower chamber B in the cylinder tube 1 is reduced, and the upper chamber A is enlarged.

In accordance with this volume change, the fluid in the lower chamber B flows into the outer chamber C through the lower communication path 2d of the guide member 2, and from the outer chamber C passes through the extension side communication path II, and passes through the second damping valve 15. It flows into the reservoir D.

Accordingly, a damping force having a speed 2/3 power characteristic is generated in the second damping valve 15.

In addition, corresponding to the volume change of the upper chamber A, of the fluid in the reservoir chamber D, an amount of fluid corresponding to the inflow from the outer chamber C and the volume of the piston rod 6 withdrawn from the cylinder tube 1 as described above. , First check channel 22 of base 3
supplied via b.

Therefore, even if the extension-side damping force characteristic is set high, the upper chamber A
Does not become negative pressure and cavitation does not occur.

During the extension stroke, the extension damping valve 5b of the piston 5 is also opened to generate a damping force.

(B) During the compression stroke During the compression stroke, the lower chamber B in the cylinder tube 1 is enlarged and the upper chamber A is reduced.

According to this volume change, a part of the fluid in the upper chamber A flows through the pressure side communication passage I, flows into the outer chamber C through the first damping valve, and flows therefrom into the lower chamber B through the lower communication passage 2d. I do. The remaining fluid (integral volume of the piston rod 6 entering the cylinder tube 1) flows from the first communication hole 22a to the first communication hole 22a.
The damping valve 21 is opened to flow into the intermediate chamber E, from which the second communication hole 16a, the inner annular groove 16d, the constant orifice
After passing through 16h and the outer annular groove 16e, the second damping valve 15 is opened and flows into the reservoir chamber D.

Therefore, a damping force having a speed 2/3 power characteristic is obtained in series in both damping valves 21 and 15.

During the compression stroke, the compression-side damping valve 5a is opened even in the piston 5, and a damping force is generated.

In addition, since the fluid flows to the reservoir chamber D only through the first damping valve 21 provided in the flow path from the upper chamber A to the lower chamber B, the fluid always flows when the piston 3 operates. The fluid in the upper chamber A is supplied to the lower chamber B, so that the lower chamber B does not become a negative pressure during this compression stroke, and cavitation does not occur. Further, if the lower chamber B is likely to be under a negative pressure due to the influence of the piston speed or the like, the second check valve 17 is opened and the fluid is supplied from the second check channel 16b. , The lower chamber B never becomes negative pressure.

(C) When a lateral load is input When a lateral load is input to the hydraulic shock absorber, this load is supported by the strut tube 7 and the outer tube 11.

The strut tube 7 and the outer tube 11
As shown in the drawing, the diameter is larger than the cylinder tube 1, which is advantageous in terms of strength. Further, unlike the cylinder tube 1, the piston 5, etc., accuracy is not required. It has the feature of being able to.

(D) Sealing action of rod insertion hole 2a.

When the extension stroke of the piston is performed, the fluid pressure in the lower chamber B rises and a pressure difference is generated between the piston and the outside of the cylinder tube 1. However, the pressure between the rod insertion hole 2a and the piston rod 6 is reduced. Sealed by seal 2b, pressure reducing seal 2b
The leaked fluid that has passed through the pressure-reducing seal 2b flows into the seal housing 4b through a minute gap between the guide bush 2c and the piston rod 6 in a state where the pressure is reduced by the pressure-reducing seal 2b, and then flows out of the cylinder tube 1 with the oil seal 4a. Outflow is prevented.

During the pressure side stroke, the fluid pressure in the outer chamber C also increases, and a differential pressure is generated between the outer chamber C and the seal housing 4b. However, a check valve provided in the check passage 2e for depressurizing is provided. Since 2g prevents the flow of fluid in the direction of the seal housing 4b, the fluid pressure in the seal housing 4b does not increase.

On the other hand, during the pressure side stroke of the piston, the lower chamber B side expands and the fluid pressure in the outer chamber C decreases, so that the fluid pressure in the seal housing 4b is higher than the fluid pressure in the outer chamber C. In this case, the check valve 2g is opened by the differential pressure, and the fluid in the seal housing 4b flows out to the outer chamber C through the check channel 2e for depressurization, whereby the pressure in the seal housing 4b is reduced. State.

FIG. 6 is a graph showing the relationship between the generated damping force, the fluid pressure in the lower chamber B, and the fluid pressure in the seal housing 4b. The slightly increased fluid pressure in the seal housing 4b is also reduced in the pressure side stroke.

As described above, in the present embodiment, the pressure inside the seal housing 4b is reduced every time the pressure side stroke is performed, so that it is possible to reliably prevent the fluid from leaking while having a low friction. It has the feature that durability can be improved.

Next, a second embodiment shown in FIG. 7 will be described.
In describing this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and only the differences will be described.

This embodiment is an example in which a variable damping force structure is added to the decompression shock absorber of the first embodiment. A support rod 120 is used instead of the fastening bolt 12 in the first embodiment. A variable damping force structure is incorporated therein.

That is, an annular groove 220 communicating with the first communication hole 22a is formed on the upper surface of the first body 22 (see FIG. 10), and an annular groove 160 is formed on the upper surface of the second body 16. (See FIG. 9).

The support rod 120 has a through hole 121 formed in the upper liquid chamber A at the axis thereof, and has a first port 122 communicating with the reservoir chamber D in the radial direction, and an annular groove 161 through a communication groove 161. A second port 123 communicating with the groove 160 and a third port 124 communicating with the annular groove 220 via the communication groove 221 are formed.

In the through hole 121, a cylindrical adjuster 270 having a hollow portion 271 is provided so as to be rotatable in the circumferential direction while being supported vertically by thrust bushes 28 and 29. In addition, this through hole
The lower end opening of 121 is closed by the thrust bush 29 below.

This adjuster 270 has a first port through an annular space 125.
A communication hole 272 that communicates with 122, an upper orifice hole 273 and a lower orifice hole 274 that form a variable orifice are formed.

8 is a sectional view taken along the line VIII-VIII of FIG. 7, FIG. 9 is a sectional view taken along the line IX-IX of FIG. 7, and FIG.
It is a sectional view, and as shown in each figure, a first port 122, a second port 123, and a third port 124 are formed at two locations facing each other. The communication groove 161 communicating the port 123 and the annular groove 220 and the third
Communication grooves 221 communicating the ports 124 are also formed at two locations. Therefore, the cross-sectional views of FIG.
The cutting state is shown corresponding to each of the lines VII-VII in the figure.

The upper orifice hole 273 and the lower orifice hole 274
Is provided with a phase shift of about 45 degrees in the drilling direction, so that when one orifice hole is opened as shown in FIGS. 9 and 10, the other orifice hole is closed. ing.

Further, the adjuster 270 is connected via a control rod 30 to a motor actuator (not shown) attached to the upper end of the reservoir chamber D, and is rotated by drive control of the motor actuator. Opening and closing of the upper orifice hole 273 and the lower orifice hole 274 is switched.

In the figure, reference numeral 32 denotes a seal ring.

As described above, in the second embodiment, the first communication hole 22a, the annular groove 220, the intermediate chamber E, and the base communication passage 22c constitute the pressure side communication passage I in the claims.

In addition, the base communication passage 22c, the intermediate chamber E, the second communication hole 16a, and the annular groove 160 constitute an extension-side communication passage II according to the present invention.

Further, the first damping valve 21 is formed by the first communication hole 22a, the annular groove 220, the communication groove 221, the third port 124, the lower orifice hole 274, the intermediate portion 271, the communication hole 272, the annular space 125, and the first port 122. To form a pressure side bypass passage III which communicates between the upper chamber A and the reservoir chamber D.

The base communication passage 22c, the intermediate chamber E, the second communication hole 16a, the annular groove
160, the communication groove 161, the second port 123, the upper orifice hole 273, the hollow portion 271, the communication hole 272, the annular space 125, and the first port 122 bypass the second damping valve 15 and the outer chamber C and the reservoir chamber D. The extension side bypass path IV which connects between them is constituted.

Next, the operation of the embodiment will be described with reference to the circuit diagram of FIG.

(A) During Stretch Side Stroke During the stretch side stroke, the volume of the lower chamber B in the cylinder tube 1 is reduced, and the upper chamber A is enlarged.

In accordance with this volume change, the fluid in the lower chamber B flows into the outer chamber C via the lower communication passage 2d of the guide member 2, and then flows into the upper chamber A through the following two paths.

That is, the first path passes through the extension side communication path II, flows into the reservoir chamber D via the second damping valve 15, passes therethrough, passes through the first check flow path 22b, and opens the first check valve 23. The second path passes through the extension side bypass path IV in parallel with the upper chamber A, and flows into the reservoir chamber D via the upper orifice hole 273 constituting a variable throttle.
From there, it passes through the first check flow path 22b, opens the first check valve 23, and flows into the upper chamber A.

Therefore, the upper orifice hole 273 (extension side bypass passage IV)
7 can flow through (the state shown in FIG. 7), a damping force is generated in parallel in the second damping valve 15 and the upper orifice hole 273. In this case, the flow rate of the fluid is large and the Characteristics. Then, the speed 2/3 power characteristic of the second damping valve 15 and the speed square characteristic of the upper orifice hole 273 are combined in parallel, and become a characteristic linearly proportional to the speed.

Also, based on the rotation of the adjuster 270, the upper orifice hole 2
If 73 is closed, only the characteristic of the second damping valve 15 is obtained. In this case, the flow rate of the fluid is small, and the speed of the high damping force range is reduced.
2/3 power characteristic.

The opening area of the upper orifice hole 273 is
By rotating the 70, it can be changed arbitrarily in the range from the fully closed state to the fully open state, and thereby the damping force range can be changed to any range within the range from the low damping force range to the high damping force range. It has the characteristic that it can be changed to

(B) During the compression side stroke During the compression side stroke, the volume of the lower chamber B is increased and the upper chamber A is reduced in the cylinder tube 1.

According to this volume change, the fluid in the upper chamber A becomes the following 2
The fluid flows into the outer chamber C through the two paths and flows into the lower chamber B via the lower communication passage 2d.

That is, the first path is a path that passes through the compression-side communication path I and flows into the outer chamber C via the second damping valve 21, and the second path is a path that passes through the compression-side bypass path III that is parallel to the first path, and The fluid flows into the reservoir chamber D through the side orifice hole 274, passes through the second check flow path 16b from the reservoir chamber D, opens the second check valve 17, flows into the intermediate chamber E, and further flows into the base communication path. This is a path that flows into the outer chamber C through 22c.

Further, during the compression stroke, there is a third path through which the fluid in the upper chamber A flows into the reservoir chamber D. That is, the third path extends from the upper chamber A through the first communication hole 22a and the annular groove 220 to the intermediate chamber E via the first damping valve 21, and further from this position, the second communication hole 16a and the annular Groove 160
This is a path that flows into the reservoir D via the second damping valve 15.

Therefore, the lower orifice hole 274 (pressure side bypass passage III)
When the fluid can flow (the state shown in FIG. 7), a damping force is generated in the first damping valve 21, the second damping valve 15, and the lower orifice hole 274. In this case, the flow rate of the fluid is large. , Low damping force range characteristics.

Further, if the third port 124 is closed based on the rotation of the adjuster 270, a damping force is generated in series between the first damping valve 21 and the second damping valve. In this case, the flow rate of the fluid decreases. As a result, a speed 2/3 power characteristic of a high damping force range is obtained. still,
In this embodiment, the opening area of the lower orifice hole 274 can be arbitrarily changed in a range from the fully closed state to the fully opened state by the rotation of the adjuster 270. It has the characteristic that it can be changed to any range within the range from the reduction force range to the high damping force range.

Further, by providing the upper orifice hole 273 and the lower orifice hole 274 with the phase in the drilling direction shifted by about 45 degrees, when one of the two orifice holes 27b and 27c is opened, the other is closed. Therefore, the modes of the damping force characteristics include the first mode in which the extension side has a high damping force range and the compression side has a low damping force range, and the second mode in which the extension side has a low damping force range and the compression side has a high damping force range. There are modes and adjusters
Switching between the two modes is performed by the rotation of 270. still,
9 and 10 show the state of the second mode.

In the shock absorber of the embodiment having such a damping force characteristic, when the damping force in the stroke direction is controlled as hard, the characteristic on the opposite side becomes soft, so that the damping force in the direction opposite to the stroke direction is soft. It is characterized by absorbing high-frequency input, preventing transmission to the vehicle body, and improving ride comfort.

The embodiment of the present invention has been described in detail with reference to the drawings.
The specific configuration is not limited to this embodiment, and any change in the design without departing from the gist of the present invention is included in the present invention.

For example, in the embodiment, the extension side communication path is configured to allow the fluid in the outer chamber to flow only to the reservoir chamber during the extension side stroke. However, the communication path that allows the outer chamber to flow to the upper chamber bypassing the first damping valve. Alternatively, the outer chamber may be configured to communicate with both the reservoir chamber and the upper chamber.

Also, the piston is provided with a damping valve,
The upper chamber and the lower chamber may not be connected at all on the piston side.

(Effects of the Invention) As described above, in the decompression shock absorber of the present invention,
Since the seal housing formed between the double seal structures is communicated only in the outer chamber direction with the check passage for depressurizing, the accumulated pressure in the seal housing forms a pressure-side stroke. Each time, when the hydraulic shock absorber of the present invention is applied to a suspension, it is possible to improve the durability of the seal because the leakage of the fluid can be reliably prevented while having low friction. The effect that the riding comfort of the vehicle can be improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a fluid flow path of a hydraulic shock absorber according to a first embodiment of the present invention, FIG. 2 is a sectional view showing the entire hydraulic shock absorber according to the first embodiment, and FIG. FIG. 4 is an enlarged sectional view showing a rod guide part which is a main part of the embodiment, FIG. 4 is an enlarged sectional view showing a base part which is a main part of the first embodiment, and FIG. FIG. 6 is a graph showing the relationship between the generated damping force, the fluid pressure in the lower chamber, and the fluid pressure in the seal housing. FIG. 6 (a) is a graph showing a change in damping force. FIG. 6 (b) is a graph showing a change in fluid pressure in the lower chamber, FIG. 6 (c) is a graph showing a change in fluid pressure in the seal housing, and FIG. 7 is a base part which is a main part of the second embodiment of the present invention. FIG. 8 is a sectional view taken along the line VIII-VII of FIG.
FIG. 9 is a sectional view taken along the line IX-IX of FIG. 7, and FIG.
FIG. 11 is a circuit diagram showing the fluid flow path of the second embodiment. 1… Cylinder tube 2… Guide member 2a… Rod insertion port 2b …… Pressure reduction seal 2d …… Lower communication path 2e …… Check flow path for pressure release 3 …… Base 4a …… Oil seal 4b …… Seal Housing 5 Piston 6 Piston rod 11 Outer tube 15 Second damping valve (damping force generating means) 21 First damping valve (damping force generating means) 22b First check channel ( Check channel) 22c Base communication path (extension side / pressure side communication path) A ... Upper chamber B ... Lower chamber C ... Outside chamber D ... Reservoir chamber I ... Pressure communication path II ... Extension side communication aisle

Claims (1)

(57) [Scope of request for utility model registration] A guide member having a rod insertion hole is provided at a lower end, a cylinder tube having a base provided at an upper end, and an upper chamber and a lower chamber which define the inside of the cylinder tube. A piston connected to a piston rod inserted into the cylinder tube, and an outer chamber provided around the cylinder tube and communicating with the lower chamber through a lower communication passage on the outer periphery of the cylinder tube, and a base above the cylinder tube by a base. An outer tube that forms a reservoir chamber defined as the outer chamber and the upper chamber, a pressure-side communication passage formed in the base, and that allows the fluid in the upper chamber to flow to the outer chamber via the damping force generating means during the pressure-side stroke;
And an extension communication path for allowing fluid in the outer chamber to flow through the damping force generating means to the upper chamber or the reservoir chamber during the extension stroke, and communicating the reservoir chamber with the upper chamber formed in the base, A check flow passage provided with a check valve for permitting the flow from the upper chamber to the upper chamber while prohibiting the flow in the opposite direction; a pressure reducing seal provided in the rod insertion hole in contact with the outer peripheral surface of the piston rod; An oil seal formed outside the pressure reducing seal by forming a seal housing between the seal and the seal housing, and communicating the seal housing with the outer chamber to allow the flow from the seal housing to the outer chamber, and vice versa And a check flow path for depressurization provided with a check valve for inhibiting the pressure.