JP3865271B2 - Hydraulic shock absorber - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a hydraulic shock absorber that is suitable for use of a suspension device interposed between a vehicle body and an axle of a motorcycle, an automobile, or the like, and in particular, is in contact with a hydraulic oil chamber and an oil level of the hydraulic oil chamber. The present invention relates to a gas-liquid mixed type single cylinder hydraulic shock absorber provided with a gas chamber made of air, gas or the like.
[0002]
[Prior art]
In this type of hydraulic shock absorber, a piston rod is generally movably inserted into a cylinder via a piston, and the piston defines an upper hydraulic oil chamber and a lower hydraulic oil chamber in the cylinder, and an upper operation in the cylinder. It has a gas chamber made of air or gas that comes into contact with the oil level of the oil chamber, and the piston is provided with an extension port and a pressure port that communicate the two upper and lower oil chambers, and at the outlet end of each port the extension side A damping valve and a compression side damping valve are provided so as to be freely opened and closed.
[0003]
In the hydraulic shock absorber described above, the hydraulic fluid flows from one hydraulic fluid chamber to the other hydraulic fluid chamber through the damping valve provided in the piston in accordance with the expansion and contraction operation, and the hydraulic fluid flows through the damping valve. A predetermined damping force corresponding to the expansion / contraction speed is generated by resistance. Therefore, if bubbles are included in the hydraulic oil that is the damping force generation medium during the expansion and contraction operation of the hydraulic shock absorber, the hydraulic oil is compressed first and then the hydraulic oil passes through the piston damping valve to the other hydraulic oil chamber. Begins to flow. As a result, a delay occurs in the rise of the initial damping force during the expansion / contraction operation of the hydraulic shock absorber, and the damping performance deteriorates due to the delay, so it is necessary to prevent air bubbles from being mixed into the hydraulic oil.
[0004]
Therefore, in a gas-liquid mixing type single cylinder hydraulic shock absorber that does not have a moving wall that divides the hydraulic oil and gas chamber, the piston rod should be directed downward to ensure stable gas sealing. In general, it is used in an inverted state. Therefore, the gas chamber that is a gas chamber for compensating for the volume change in the cylinder due to the withdrawal and intrusion of the piston rod is provided in contact with the free surface of the hydraulic fluid in the upper hydraulic fluid chamber in the cylinder.
[0005]
Therefore, during the extension operation of the hydraulic shock absorber, the hydraulic oil in the lower hydraulic oil chamber is jetted into the upper hydraulic oil chamber while being squeezed by the extension side damping valve of the piston, and is moved upward from the upper hydraulic oil chamber. The gas in the gas chamber is entrained in the hydraulic oil because it is sprayed toward the gas chamber.
[0006]
As a result, there is a response delay in the rise of the expansion side and compression side damping characteristics of the hydraulic shock absorber, and the initial damping characteristics sag, or depending on the progress of gas mixing into the hydraulic oil, the damping characteristics themselves may be As a result, the vibration of the vehicle cannot be sufficiently absorbed.
[0007]
Therefore, in this type of hydraulic shock absorber, for example, a device described in US Pat. No. 2,823,915 has already been proposed as means for preventing gas from entering the hydraulic oil.
[0008]
That is, in this technology, a large number of oil holes are located near the hydraulic oil level in the upper hydraulic oil chamber, and a plate-like partition board is submerged and fixed in the hydraulic oil. An oil storage chamber leading to the oil chamber and an upper gas chamber are provided.
[0009]
And even if the gas in the gas chamber is trapped and mixed in the hydraulic oil while shielding the flow of the hydraulic oil accompanying the extension operation of the hydraulic shock absorber and reducing the momentum of the jet to prevent entrainment of bubbles due to the jet, When the hydraulic oil entrained with this gas returns to the upper hydraulic oil chamber through the oil hole at the bottom of the partition board, the flow resistance of these oil holes is used to promote the separation of the gas trapped in the hydraulic oil, The gas in the gas chamber is prevented from being mixed into the hydraulic oil in the oil chamber.
[0010]
[Problems to be solved by the invention]
However, the gas mixture prevention means that stimulates the flow of jets and promotes the separation of the gas in the hydraulic oil using the plate-shaped partition board having the oil holes as described above is a contradictory contradiction as described below. It has a duality. In order to reduce the momentum of the jet and to sufficiently separate the gas mixed in the hydraulic oil, the area of the oil holes in the partition board formed in the shape of a plate is made as small as possible. It is necessary to increase the flow resistance.
[0011]
On the other hand, as described above, when the hydraulic oil in the oil storage chamber above the partition wall returns to the upper hydraulic oil chamber as the piston rod retracts during the extension operation, the flow resistance of the oil hole becomes an obstacle. Thus, there is a time delay in the return of the hydraulic oil, and this delay creates a vacuum in the upper hydraulic oil chamber and sucks the gas in the gas chamber to produce a mixture of gas and hydraulic oil.
[0012]
The gas portion of this mixture is compressed and filled with hydraulic oil at the beginning of the transition to the next compression operation, and then the hydraulic oil in the upper hydraulic oil chamber is pushed out to the lower hydraulic oil chamber through the compression damping valve of the piston. The hydraulic shock absorber enters normal compression operation. For this reason, the damping action is reduced by delaying the rise of the compression side damping force during the compression operation of the hydraulic shock absorber.
[0013]
Moreover, after the hydraulic shock absorber has entered the normal compression operation as described above, the hydraulic oil that does not enter the lower hydraulic oil chamber with the penetration of the piston rod compresses the gas chamber through the oil hole, It tries to flow into the oil storage chamber above. At this time, the larger the flow resistance due to the oil holes in the shielding board, the more the hydraulic oil flows into the oil storage chamber, and the hydraulic oil pressure in the upper hydraulic chamber becomes abnormally high, impeding its function as a hydraulic shock absorber. Will do.
[0014]
Furthermore, when the hydraulic oil that has flowed into the oil storage chamber returns to the upper hydraulic oil chamber by the gas working pressure during the next expansion operation, the flow resistance pressure of the oil holes in the shielding plate is higher than the gas pressure. If it is large, the flow into the upper hydraulic oil chamber is hindered, the hydraulic oil remains in the oil storage chamber, the amount of hydraulic oil in the upper hydraulic oil chamber decreases, and a damping force cannot be generated in the next compression operation. You can lose your job as well.
[0015]
From the above, it is impossible to determine the oil hole passage area in the partition wall in consideration of the jet flow suppression and gas separation action, and the expansion and compression of the gas chamber as the piston rod retreats and enters. In consideration of the follow-up performance, it must be determined to a certain size.
[0016]
As a result, the suppression of the jet flow by the oil holes in the partition wall and the gas separation action are sacrificed, and it is impossible to sufficiently prevent the gas from being mixed into the hydraulic oil and to separate the gas from the hydraulic oil. .
[0017]
Accordingly, the object of the present invention is to suppress the expelling of the working oil during the extension operation and to prevent the gas from flowing into the working oil so as not to impair the followability of the expansion and compression of the gas chamber due to the withdrawal and entry of the piston rod. The object is to provide a gas-liquid mixed type single cylinder hydraulic shock absorber capable of preventing gas entrainment in the room.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, according to the means of the present invention, a piston rod is movably inserted into a cylinder via a piston, and the piston partitions an upper hydraulic oil chamber and a lower hydraulic oil chamber in the cylinder. The cylinder is provided with a gas chamber in contact with the oil level of the upper hydraulic oil chamber, and the piston is provided with an extension side port and a pressure side port communicating with the upper hydraulic oil chamber and the lower hydraulic oil chamber. In the hydraulic shock absorber in which an expansion side damping valve is provided at the outlet end of the pressure side so that it can be opened and closed, and at the outlet end of the pressure side port, a compression side damping valve is provided at the opening side. A jet flow suppression mechanism that suppresses the jet flow that has passed through the side damping valve is provided, and the jet flow suppression mechanism is sandwiched between the upper support plate, the lower support plate having a smaller diameter than the upper support plate, and the upper support plate and the lower support plate. And with these upper supports A shielding plate that can bend up and down with the outer end of the support plate as a fulcrum, and an annular gap that is formed between the outer circumference of the shielding plate and the inner circumference of the cylinder to generate flow resistance. it is characterized in that there.
[0019]
In this case, it is preferable that through holes are provided along the circumferential direction at positions where the shielding plate is closed by the upper support plate.
[0020]
Similarly, it is preferable that the lower support plate is formed to have the same diameter or smaller than the spacer that supports the expansion-side damping valve.
[0021]
Alternatively, the lower support plate may also serve as a spacer that supports the extension side damping valve.
[0022]
According to the above means, when the hydraulic shock absorber is extended , the hydraulic oil pushed out from the lower hydraulic oil chamber to the upper hydraulic oil chamber through the piston extension port pushes and extends the extension side damping valve that closes the piston. While being throttled by the flow resistance, it generates an extension side damping force and becomes a jet and flows into the upper hydraulic oil chamber side.
[0023]
Then, the flow of hydraulic oil tends to flow into the upper hydraulic oil chamber through the gap between the cylinder and the shielding board. For this reason, the hydraulic fluid that flows into the upper hydraulic fluid chamber generates flow path resistance due to the gap relationship between the cylinder and the shielding board. Furthermore, the hydraulic oil flows along the cylinder wall.
[0024]
As a result, the hydraulic oil flowing into the upper hydraulic oil chamber as a jet flow is shielded, and the flow of the jet flow is gathered by the flow path resistance or the like, the flow direction is made constant, and the upper hydraulic oil is made uniform. Further, the flow velocity is reduced by friction with the cylinder wall surface, and the protrusion from the oil surface is eliminated to prevent the gas in the gas chamber from getting into the hydraulic oil.
[0025]
Moreover, even if the operating speed of the piston rises and the amount of hydraulic oil flowing in increases, the shielding board bends toward the upper hydraulic oil chamber with the outer diameter of the upper support board as a fulcrum, and excessive flow resistance increases. In addition to ensuring operation as a shock absorber, it is possible to allow the jet to flow above the upper hydraulic oil chamber at an appropriate flow rate, and to stably prevent gas entrainment in the hydraulic oil. Become. Furthermore, since the pressure state when the damping force is generated is successively reduced with the expansion side damping valve part and the shielding board part, generation of gas from the hydraulic oil can be prevented.
[0026]
On the other hand, during the compression operation of the hydraulic shock absorber, contrary to the extension operation, the piston pushes up the hydraulic oil in the upper hydraulic oil chamber to the gas chamber side and passes through the pressure side port to the lower hydraulic oil chamber. Hydraulic oil will flow in.
[0027]
The amount of hydraulic fluid in the upper hydraulic fluid chamber is large compared to when it is extended , and further, it only pushes up the entire cross section with respect to the oil level. Stable, the gas pressure in the gas chamber acts evenly, pushes open the pressure side damping valve that closes the pressure port from the upper working oil chamber, and pushes the working oil into the lower working oil chamber while generating the pressure side damping force.
[0028]
The shielding panel is largely deflected to the piston side with the small outer diameter of the lower support panel as a fulcrum, reducing the inflow resistance from the upper hydraulic oil chamber to the pressure side port, facilitating inflow, and operating in the upper hydraulic oil chamber above the shielding board Prevent oil stagnation and stabilize the oil level. The lower hydraulic oil chamber is filled with hydraulic oil, and the gas pressure in the gas chamber acts on the upper and lower hydraulic oil chambers to suppress the separation of gas from the hydraulic oil. No abnormalities will occur.
[0029]
Thus, the gas in the gas chamber is caught in the hydraulic oil or the generation of the gas is prevented, thereby preventing the gas from being mixed into the hydraulic buffer hydraulic oil. Further, since no hydraulic oil stays in the upper hydraulic oil chamber above the shielding board, the expansion and compression followability of the gas chamber is not impaired.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0031]
1, 2 and 3 show an embodiment of the present invention.
[0032]
In this hydraulic shock absorber, a piston rod 5 is movably inserted into a cylinder 2 via a piston 3 in the same manner as a general hydraulic shock absorber, and the piston 3 is inserted into the cylinder 2 in an upper hydraulic oil chamber B and a lower hydraulic oil chamber A. And a gas chamber comprising an air chamber or a gas chamber G in contact with the oil level P of the upper hydraulic oil chamber B is provided in the cylinder 2, and the upper hydraulic oil chamber B and the lower operation are provided in the piston 3. An extension side port 20 and a pressure side port 21 that communicate with the oil chamber A are provided, and an extension side damping valve 10 is provided at the outlet end of the extension side port 20 so as to be openable and closable. The valve 11 is provided so as to be freely opened and closed.
[0033]
In the present invention, the shielding board 13 is further held above the extension side damping valve 10 by the upper support board 14 and the lower support board 15 having a smaller diameter than the upper support board 14 and the outer peripheral end thereof can be bent vertically. And an annular gap 13b is formed between the outer periphery of the shielding board 13 and the inner periphery of the cylinder.
[0034]
In the shielding plate 13, through holes 13 a are provided along the circumferential direction at positions closed by the upper support plate 14. The details will be described below.
[0035]
FIG. 1 shows an example in which the present invention is applied to a gas-liquid mixing type single cylinder hydraulic shock absorber 1 used in a suspension device for a rear wheel of a motorcycle. The hydraulic shock absorber 1 includes a piston as shown in FIG. It is used in an inverted state with the rod 5 facing downward.
[0036]
The hydraulic shock absorber 1 includes a cylinder 2 formed of a sealed cylinder, a piston 3 slidably inserted into the cylinder 2, and a piston rod extending downward from the piston 3 through a lower end sealing member 4 of the cylinder 2. 5 and a suspension spring 6 interposed between the cylinder 2 and the piston rod 5. Mounting brackets 7 and 8 are provided at the upper end of the cylinder 2 and the protruding end of the piston rod 5, respectively. The hydraulic shock absorber 1 is interposed between the vehicle body of the motorcycle and the rear fork via these mounting brackets 7 and 8. It is attached to.
[0037]
Inside the upper end of the cylinder 2, a space portion is formed as a gas chamber G that compensates for the intrusion and withdrawal volume of the piston rod 5 with the hydraulic oil surface of the hydraulic oil chamber B as a free surface. In addition, the piston 3 is fixed by a piston nut 9 in a state where the piston 3 is fitted to the upper end of the piston rod 5. The piston 3 partitions the inside of the cylinder 2 into a lower hydraulic oil chamber A and an upper hydraulic oil chamber B. A known expansion side damping valve 10 and a compression side damping valve 11 are provided on both end faces of the piston 3, and the lower hydraulic oil chamber A and the upper operation are passed through ports 20, 21 corresponding to these expansion side and compression side damping valves 10 , 11. The oil chambers B communicate with each other. Although not shown, the damping valve seat portion of the piston 3 has a fan-shaped partial seat shape.
[0038]
Further, a jet flow suppressing mechanism 12 for hydraulic oil that forms a characteristic portion of the present invention adjacent to the upper side of the expansion side damping valve 10 is coupled to the tip of the piston rod by a piston nut 9. In this embodiment, the above-described jet flow suppressing mechanism 12 includes a shielding plate 13 and support plates 14 and 15 provided outside the expansion-side damping valve 10, as can be seen from the detailed view shown in FIG. . The shielding board 13 is a thin disk disk having flexibility. The shielding board 13 has a plurality of through holes 13a in the center of the board, and forms a small annular gap 13b between the cylinder 2 and the inner diameter. The support plates 14 and 15 have a structure in which the shielding plate 13 is sandwiched by a disk. The support plate 14 on one side is disposed above the shielding plate 13 to close the through hole 13a of the shielding plate 13 and the support plate 15 on the other side. Is arranged on the extension side damping valve side.
[0039]
Next, the operation of the gas-liquid mixing type single cylinder hydraulic shock absorber 1 will be described together with the basic buffer operation.
[0040]
When the hydraulic shock absorber 1 is extended , the piston 3 compresses the lower hydraulic oil chamber A. The hydraulic oil in the lower hydraulic oil chamber A flows into the upper hydraulic oil chamber B by pushing the extension side damping valve 10 through the extension side port 20 of the piston 3.
[0041]
The extension side damping valve 10 generates an extension side damping force corresponding to the extension speed. At this time, the flow passage area that pushes the extension side damping valve 10 is extremely small, and the valve seat shape is not a whole circumference but a partial seat as described above, so that the jet flow is opened from a specific narrow portion. And flows into the upper hydraulic oil chamber B.
[0042]
Then, the higher the speed of expansion of the hydraulic shock absorber 1 at that time, the faster the jet flows toward the upper hydraulic oil chamber B, and it tends to protrude from the horizontal oil surface into the gas chamber G. However, in this case, a jet flow suppression mechanism 12 for setting the jet flow that has passed through the expansion side damping valve 10 is set behind the expansion side damping valve 10.
[0043]
Therefore, the shielding plate 13 which is a main member of the jet flow restraining mechanism 12 shields and prevents the jet flow, and the upper hydraulic oil along the inner wall of the cylinder 2 while generating a flow resistance using the annular gap 13b as an oil passage. The hydraulic oil is caused to flow upward of the chamber B. Since the flow path resistance is an annular gap flow, it has sliding walls on the inner and outer peripheries, and further the direction of movement of the shielding plate (moves downward in the same manner as the piston) and the direction of hydraulic oil flow (from the lower to the upper hydraulic oil chamber) Therefore, there is a characteristic that the resistance is larger than that of a normal hole having the same area. In other words, the flow path area can be increased for the resistance value. Accordingly, there is an effect that the jet flow is gathered when flowing through the annular gap 13b, the flow direction is made constant, the flow is made uniform, and the flow velocity can be lowered.
[0044]
Further, since the flow of the hydraulic oil follows the wall surface of the cylinder 2 even after passing through the annular gap 13b, the frictional resistance with the cylinder 2 continues, and the effect of lowering the inflow velocity is further produced.
[0045]
Moreover, even if the operating speed of the hydraulic shock absorber 1 increases and the amount of hydraulic fluid flowing in increases, the shielding plate 13 bends toward the upper hydraulic fluid chamber B with the outer end of the upper support plate 14 as a fulcrum. It is possible to suppress the increase in flow path resistance, ensure the operation as the hydraulic shock absorber 1, and allow the jet flow to flow into the upper hydraulic oil chamber B at an appropriate flow rate.
[0046]
Thus, the hydraulic oil flowing into the upper hydraulic oil chamber B does not protrude from the free oil surface, and it is possible to stably prevent the gas from being caught in the hydraulic oil. Further, since the pressure state when the damping force is generated is successively reduced with the expansion side damping valve 10 part and the shielding board 13 part, cavitation in the extension side damping valve 10 part can be prevented, and the generation of gas from the hydraulic oil Other obstacles caused by cavitation can also be prevented.
[0047]
On the other hand, during the compression operation of the hydraulic shock absorber 1, the piston 3 pushes the hydraulic oil in the upper hydraulic oil chamber B to the gas chamber G side through the pressure side port 21, contrary to the extension operation. The hydraulic oil will flow into the lower hydraulic oil chamber A.
[0048]
Since the hydraulic fluid chamber of the upper hydraulic fluid chamber B is larger than that at the extension side, and only pushes up in the entire cross section with respect to the free oil surface, the hydraulic fluid itself can equivalently become a partition wall. The oil level is stabilized, the gas pressure in the gas chamber G acts equally, and the pressure side damping valve 11 that closes the pressure side port 21 from the upper working oil chamber B is pushed open to generate the pressure side damping force while the lower working oil chamber A. Extrude hydraulic fluid into
[0049]
The shielding plate 13 bends to the piston side with the outer diameter of the lower support plate 15 as a fulcrum, and the through hole 13a closed by the upper support plate 14 is opened to flow into the pressure side port 21 from the upper hydraulic fluid chamber B. It is possible to reduce the resistance, facilitate the inflow, prevent the hydraulic oil from staying in the upper hydraulic oil chamber B above the shielding board 13, and stabilize the free oil level.
[0050]
At this time, the lower hydraulic oil chamber A is filled with the hydraulic oil, and the gas pressure in the gas chamber G acts on the upper hydraulic oil chamber B and the lower hydraulic oil chamber A, so that the gas from the hydraulic oil Since the separation will be suppressed, no abnormality will occur.
[0051]
Thus, the hydraulic fluid in the upper hydraulic fluid chamber B can flow into the lower hydraulic fluid chamber A while the free oil level is stable, and the gas in the gas chamber G is entrained in the hydraulic fluid or the gas is separated. Generation | occurrence | production can be blocked | prevented and it will prevent that gas mixes in the hydraulic fluid of the hydraulic buffer 1 beforehand. In addition, since the free oil level is stable and there is no stagnation of hydraulic oil in the upper hydraulic oil chamber B, the followability of expansion and compression of the gas chamber G is impaired, and the function as a hydraulic shock absorber is obstructed. There is nothing to do.
[0052]
Incidentally, in the embodiment described above, but are configured to have a hole 13a in the shield plate 13 as well as equal to the outer diameter of the spacer a outer diameter of the lower support plate 15, FIG. 4, FIG. 5 As in the other embodiment shown, the through hole 13a of the shielding board 13 is eliminated, the outer diameter of the support board 15 is made smaller than the outer periphery of the spacer a, and the piston 3 is moved from the upper hydraulic oil chamber B of the shielding board 13 to the piston 3. The structure may be such that the inward resistance to the expansion side port 20 is reduced by increasing the lateral deflection. In this case, it becomes easy to ensure the strength of the shielding board.
[0053]
Furthermore, as shown in FIG. 6, the support board 15 may be configured to be used in common with the spacer a that supports the valve of the expansion side damping valve. The operation and effect in this case are the same as those in FIG.
[0054]
【The invention's effect】
The present invention has the following effects.
[0055]
According to the invention of each claim, since the shielding board is provided above the expansion side damping valve, and the annular gap for generating the flow resistance is provided between the outer circumference of the shielding board and the inner circumference of the cylinder , the extension operation is performed. Occasionally, the jet of hydraulic oil that has passed through the expansion side damping valve from the expansion side port is suppressed by the shielding board, and then flows upward through the gap while generating flow resistance. It is possible to prevent the air or gas in the gas chamber from being mixed into the hydraulic oil without the surface suddenly protruding into the gas chamber.
Since the flow path resistance due to the gap is an annular gap flow, it must have sliding walls on the inner and outer circumferences, and the direction of movement of the shielding plate (moves downward in the same manner as the piston) and the direction of flow of hydraulic oil (from bottom to top) Since the fluid flows upward in the oil chamber), there is a feature that the resistance becomes larger than that of a normal hole having the same area. In other words, the flow path area can be increased for the resistance value. Accordingly, there is an effect that the flow of the jet is gathered when flowing through the annular gap, the flow direction is made constant, the flow is made uniform, and the flow velocity can be lowered.
Further, since the flow of the hydraulic oil follows the inner peripheral surface of the cylinder even after passing through the annular gap, the frictional resistance with the cylinder continues, and the effect of further reducing the inflow velocity is produced.
Further, even if the extension operation speed increases, the outer periphery of the shielding plate bends upward with the upper support plate as a fulcrum, and the jet flow from the extension side port can be suppressed to an appropriate flow velocity. Thus, the gas does not protrude rapidly and the gas is prevented from being mixed into the hydraulic oil. Further, since the pressure state when the damping force is generated is successively reduced by the expansion side damping valve portion and the shielding plate portion, generation of gas from the hydraulic oil can be prevented.
[0056]
(2) Similarly, according to the invention of each claim, since the outer periphery of the shielding board can be largely bent with the lower support board having a small diameter as a fulcrum during the compression operation, the inflow resistance to the pressure side port can be reduced and the inflow is facilitated. Therefore, the hydraulic oil can be prevented from staying in the upper hydraulic oil chamber, the oil level of the upper hydraulic oil chamber can be stabilized, cavitation can be prevented, and gas separation from the hydraulic oil can be suppressed.
[0057]
(3) According to the invention of claim 2, since the through hole is formed in the shielding board, the hydraulic oil also flows from this through hole during the compression operation, so that it operates in cooperation with the outer peripheral deflection of the shielding board. The inflow resistance of oil can be further reduced, the occurrence of cavitation can be more reliably prevented, and the occurrence of gas separation from the hydraulic oil can be prevented.
[0058]
(4) According to the invention of claim 3, since the outer diameter of the lower support plate is small, the outer periphery of the shielding plate is easily bent during the compression operation, so that the flow resistance can be reduced without providing a through hole. This eliminates the need for processing to form through holes, which is advantageous for workability and economy.
[0059]
(5) According to the invention of claim 4, since the lower support disk also serves as a spacer, the number of parts is small, the workability and assembling property are improved, and the economy is excellent.
[Brief description of the drawings]
FIG. 1 is a partially longitudinal front view of a hydraulic shock absorber according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a piston portion of FIG.
3 is a cross-sectional plan view taken along line AA in FIG. 2;
FIG. 4 is an enlarged sectional view of a piston portion of a hydraulic shock absorber according to another embodiment of the present invention.
FIG. 5 is a plan view of the shielding board in FIG. 4;
FIG. 6 is an enlarged sectional view of a piston portion of a hydraulic shock absorber according to another embodiment of the present invention.
[Explanation of symbols]
2 Cylinder 3 Piston 5 Piston rod 10 Extension side damping valve 11 Pressure side damping valve 13 Shielding board 13a Through hole 13b Gap 14 Upper support board 15 Lower support board A Lower hydraulic oil chamber B Upper hydraulic oil chamber G Gas chamber P Between oil level a seat

Claims (4)

A piston rod is movably inserted into the cylinder via a piston, and the piston defines an upper hydraulic oil chamber and a lower hydraulic oil chamber in the cylinder, and contacts the oil level of the upper hydraulic oil chamber in the cylinder. A gas chamber is provided, and the piston is provided with an extension side port and a pressure side port communicating with the upper hydraulic oil chamber and the lower hydraulic oil chamber, and an extension side damping valve is provided at the outlet end of the extension side port so as to be freely opened and closed. Similarly, in the hydraulic shock absorber in which a pressure side damping valve is provided at the outlet end of the pressure side port so as to be freely opened and closed, a jet flow suppressing mechanism for suppressing the jet flow that has passed through the extension side damping valve is provided above the extension side damping valve. The jet flow suppression mechanism is sandwiched between the upper support plate, the lower support plate having a smaller diameter than the upper support plate, the upper support plate and the lower support plate, and the outer ends of the upper support plate and the lower support plate are provided. Use the fulcrum to move the outer circumference up and down A shielding plate that may look, a hydraulic shock absorber which is characterized by being composed by an annular gap which has been generating the flow resistance formed between the outer and the cylinder inner circumference of the shielding plate.  2. The hydraulic shock absorber according to claim 1, wherein through holes are provided along the circumferential direction at positions where the shielding plate is closed by the upper support plate.  The hydraulic shock absorber according to claim 1 or 2, wherein the lower support plate is formed to have the same diameter as or smaller than the spacer that supports the expansion side damping valve.  The hydraulic shock absorber according to claim 1 or 2, wherein the lower support plate also serves as a spacer for supporting the expansion-side damping valve.

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