JPS5997338A - Hydraulic buffer - Google Patents

Abstract

PURPOSE:To cause a damping force in prescribed resonance regions near the primary and secondary resonance points of a suspension spring but reduce the damping force except in said regions, by providing a rotary member horizontally rotatable in contact with the peripheral surface of a piston rod. CONSTITUTION:When a large rotation is caused due to a prescribed resonance, one of the communication holes 41a, 41b of a rotary member 40 is opposed to the horizontal oil passage 9 of a piston rod 2 so that an upper chamber 4 and a lower chamber 5 communicate with each other. At that time, oil from the upper chamber 4 flows to an oil passage 6 through the communication hole 41a or 41b and a horizontal oil passage 9 and goes down to the lower chamber 6 through an oil passage 16 in a clamping metal 14, which communicates with the lower end, and an annular opening 17. Much of the oil in the upper chamber 4 flows to the lower chamber 6, as mentioned above, but does not flow to a damping mechanism, so that a damping force is reduced. The damping mechanism and the rotary member 40 are provided together to cause the damping force and reduce it only in desired regions, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic shock absorber, and particularly to a hydraulic shock absorber that is used in combination with a suspension and a shock absorber in a specific resonance region such as near the primary resonance point and near the secondary resonance point of a suspension spring. It relates to a hydraulic shock absorber that generates damping force but otherwise reduces damping force.

Hydraulic shock absorbers used as shock absorbers for automobiles and cushion units for motorcycles, as shown in Figure 1, have a vibration frequency (X-axis in the figure) of the suspension spring near the -order resonance point and the secondary resonance point. The amount of sprung displacement of the suspension spring (Y-axis in the figure) becomes significantly large in certain vibration frequency ranges (0 ''-, Z'/ and x2 to 3:3 in the figure), so α), damping force is generated by a damper and suppressed to a small level overall (dotted chain line 6) in the figure, in order to stabilize the maneuverability of the vehicle and improve the ride comfort.However, in a specific vibration frequency range At locations other than the above (in the figure, from Z'/~2 and x3), the amount of sprung mass displacement increases due to the damper action, which deteriorates the maneuverability and ride comfort of the vehicle.Therefore, 1. Outside of a specific vibration frequency range, it is sufficient to eliminate or reduce the damping force generated by the damper (solid line C in the figure).However,
For example, if a damping force is generated near the primary resonance point up to 0''-DCl in the figure, but the damping force is decreased after X/ in the figure, it will also be damped near the secondary resonance points x2 to x3 in the figure. This is inconvenient because no force is generated.Also, if the damping force is reduced only after x3 in the figure, Zl ''-jC2 in the figure
There is a disadvantage that the damping force cannot be reduced within the range of .

Therefore, the present invention provides a hydraulic damper that generates a damping force within a specific resonance region such as near the primary resonance point and the secondary resonance point of the suspension spring, but reduces the damping force in other ranges. The purpose is to provide equipment. In order to achieve this objective, the structure of the present invention is such that the inside of the cylinder is divided into an upper chamber and a lower chamber, and a piston is formed by drilling an oil passage in the axial direction communicating from the upper chamber, and the piston is fixedly attached. a piston rod having an oil passage bored therein which communicates with the upper chamber on one side and communicates with the lower chamber on the other hand, and a lower end of the piston rod communicates with the oil passage of the piston. In a hydraulic shock absorber equipped with a damping force mechanism that generates a damping force within a predetermined vibration frequency range and reduces the damping force in a range that exceeds a predetermined vibration frequency range, the outer periphery of the piston rod is A rotary body is attached to it that slides into contact with it so that it can rotate freely in the horizontal direction,
The rotary body has a through hole formed through the thick part in the radial direction, and the outer peripheral wall surface thereof has a plurality of inclined concave grooves formed by cutting out the through hole. be.

The present invention will be explained below based on the illustrated embodiments.

As shown in Figure 2, the hydraulic shock absorber according to the present invention has an upper chamber (4) and a lower chamber (5) formed inside a cylinder (1) by a piston (3) fixed to the tip of a piston rod (2).
The interior of the piston rod (2) has an oil passage (6) bored in its axial direction, and the piston (3) has an upper chamber (4) and a lower chamber ( 5)
It has an inner oil passage (8) and an outer oil passage (8) bored in the axial direction so as to communicate with the piston rod (2). The passage (6) is connected to a horizontal oil passage (9) bored on one side, that is, upwardly.
) formed so as to be able to communicate with the upper chamber (4) via the upper chamber (4);
Moreover, the other side, ie, the lower part, can communicate with the lower chamber (5). In addition, the outer oil passage (8) of the piston (3)
communicates with the lower chamber (5) at its lower end, but at its upper end there is a non-return valve α0) that abuts thereon, and a stopper (1) that fixes a spring (l]) that presses this non-return valve (10) downward.
It communicates with the upper chamber (4) via the notch (i3) of 12).

Note that the force is applied to the inner oil passage of the piston (3) via the oil passage (15) drilled in the tightening fitting α that fixes the piston (3) to the tip of the piston rod (2). In addition, the lower part of the piston rod (2) is connected to the cylinder (1) via an oil passage (16) which is also bored in the tightening fitting 04). It communicates with the lower chamber (5) via an annular gap (17) formed between the two.

Further, this hydraulic shock absorber has a damping force mechanism consisting of a disc (20) held slidably up and down and a pressure chamber (30) arranged below the disc (20), which is held so as to be slidable up and down. A rotating body (40) is slidably contacted with the outer periphery of the piston rod (2) so as to be freely rotatable in the horizontal direction.

That is, the disk (20) branches the flow of oil flowing into it into at least two parts, one of which causes the damping force to be generated and the damping force to be reduced, and the other stream causes the damping force to be reduced. , which attempts to induce the effects of generating and decreasing the damping force. For this reason,
In this embodiment, a main valve (22) is attached to the center of the disk main body (22), and an oil passage (23) is bored in the peripheral part, and the upper part of the main valve I22 is connected to the peripheral oil passage (23).
), and the lower part of the main valve n is formed so as to communicate with a pressure chamber (30), which will be described later, and the lower end of the peripheral oil passage (c) is connected to a leaf valve (24). ) shall be attached.

In addition, there is an orifice (22) in the center of the main valve (22).
) is formed. In addition, in this embodiment, the oil chamber (251
It has an oil passage (26) drilled around it so as to branch from this oil chamber (25), and the oil passage (26) and the lower end of the central oil chamber (251) are closed off. It has an inner leaf valve (27) attached to the lower surface of the disk body (2I).An orifice (2'v) is also formed in the center of this inner leaf valve (27).

The disk (20) configured as described above is slidably held within the tightening fitting aa, but due to the relationship with the pressure chamber (30) described later, the disk (20) is held on the tightening fitting side. In particular, when the upper surface of the disk (20) is in an unpressurized state, the lower surface of the disk (20), that is, the lower surface of the inner leaf valve 0'7 in this embodiment, is brought into close contact with the upper surface between the lower pressure chambers. Spring α8 at the upper end of the disk eO)
) is pressed downwards. Note that the spring 08) does not prevent the disk (20) from rising as the oil pressure in the lower chamber (5) rises during the pressure stroke in which the piston (3) descends.

Further, the pressure chamber (30) has an oil passage (32) bored in the periphery of the main body 011 fixed to the lower end of the tightening fitting α, and has a casing (33) in the center. And at the upper end of the casing (33),
It has an oil chamber 04) that communicates with the central oil chamber (25) of the upper disk (20) via an orifice 07), and a lower oil chamber (35) that communicates with this oil chamber t34). This lower oil chamber G9 has a free piston (S6) and a free piston (a spring C7 that slidably supports the ceramic from below), which locks the lower end of the spring (37) and locks the lower oil chamber ( A cap (support) that forms three parts is fitted.In addition, a through hole (39
), and an orifice (38) is formed in the cap (38).

The pressure chamber configured as described above (in other words, the free piston (36)
) is lowered and the oil in the lower chamber G5) flows out into the lower chamber (5) through the through hole (39) and orifice (34), but the width of the piston (3) is extremely large, so the free piston The descent of (g) becomes larger and the through hole (
30 is closed, care is taken to allow oil to continue flowing out through the orifice G8) so that the damping force within the disk Cω does not rise suddenly, as will be described later.

The damping force mechanism consisting of the above-mentioned disk (20) and the above-mentioned pressure chamber (30) generates a damping force until the vibration frequency applied to the cylinder (1) falls within a predetermined range. When this value is exceeded, on the contrary, a significant reduction in damping force appears. In this example, the damping force decreases significantly when the x3 point in the fang 1 figure is exceeded.
．． It is set to be. This set value is the main valve (22) on the disc (20).
It is determined by the selection of the diameter of the orifice (22), the bending rigidity of the leaf valve (24), the bending stiffness of the inner leaf valve Cη, the orifice (2h diameter, etc.).

It is also possible to omit the inner leaf valve (27) in the disk (20), but as in this embodiment, an inner leaf valve (27) is attached in addition to the leaf valve f24+, and the leaf When the oil flow from the inner peripheral end of the valve (24) and the oil flow from the outer peripheral end of the inner leaf valve (27) are made to collide,
There is an advantage in that a stronger damping force can be generated than the damping force produced simply by the flow of oil from the inner circumferential end of the leaf valve seat 4). In addition, the above set value is the pressure receiving area of the free piston 06) of the pressure chamber (30) - the spring c37)
It can be made arbitrary by selecting the spring constant.

Furthermore, the rotating body (40) rotates in the horizontal direction when there is a flow of oil in the upper chamber (4) of the cylinder (1), and when the rotating body (40) rotates due to a specific resonance. Except for the horizontal oil passage (9) bored in the piston rod (2).
) is closed, and the upper chamber (4) and lower chamber (5) are pistoned so that they do not communicate through the oil passage (6) of the rod (2). For this reason, in this embodiment, the rotary body (40) has through holes (41α) (41A) formed horizontally and radially through the thick part thereof, and (40) and the lower valve stopper a are interposed with four rotation springs so that the valve stopper a can freely rotate in the horizontal direction.

Concave grooves (431 (see Figure 4) that slope from the upper end to the lower end are cut out at a plurality of locations at appropriate intervals on the outer circumferential wall surface of the rotating body (40).

As shown in Figure 4, this concave groove (431) is formed so that the groove width on the oil outflow side (lower in the figure) is smaller than the groove width on the oil inflow side (upper in the figure). rotational torque can be obtained.

Furthermore, in this embodiment, the rotation is made with a gentle curve so that the rotation is smooth.

Alternatively, as shown by the dotted line in the figure, it may be composed of a straight line.

If oil flows in the concave groove (4) in the direction shown by arrow A in Fig. 4, this rotating body (40)
It will rotate horizontally in the direction shown.

The rotating body (40) is secured at its upper and lower ends with snap rings (44) so that it does not slide vertically on the outer circumferential surface of the piston rod (2).

In addition, this rotating body (40), as shown in Figure 3,
It has a fan-shaped cutout (45), and the cutout (45) has a fan-shaped cutout (45).
5) The through hole (41α) or (41b ), one of the through holes (1υ) faces the horizontal oil passage (9) of the piston rod (2), and the upper chamber (4)
and the oil passage (6), that is, the lower chamber (5). In addition, considering the role of this rotating body (40), although it is not shown in the figure, instead of the embodiment shown in Fig. 3t'3,
Two horizontal oil passages (9) are bored horizontally in the radial direction in the piston rod (2), and one through hole (9) is bored in the rotating body (40).
Of course, it is also possible to drill the holes horizontally and radially.

The hydraulic shock absorber configured as described above operates as follows.

First, during the extension stroke of the piston (3), the oil in the upper chamber (4) enters the stopper (12) through the notch α3) of the stopper α2), and then the piston (3)
passes through the inner oil passage (7) and reaches the oil passage (1■) of the tightening fitting I, which communicates therewith.
From there it branches into two streams.

One is the oil passage (23) drilled around the piston (3).
) and the leaf valve (2
This is a flow that pushes down the inner circumferential end of 4), reaches the peripheral oil passage C32 of the lower pressure chamber (to), and flows into the lower chamber (5). Incidentally, when this flow pushes down the leaf valve (24) and reaches the peripheral oil passage (32) below, a damping force is generated.

The other of the branched flows flows into the central oil chamber (2) of the disc (20) via the orifice (22) of the main valve (22), and is further branched into two streams here. One is the inner leaf valve (2℃
The outer peripheral end of the inner leaf valve (27) is pressed down, and the flow merges with the flow from the above-mentioned first leaf valve (24) and flows into the lower peripheral oil passage (32). 17 enters the upper end oil chamber (34) of the lower pressure chamber (30) via the lower free piston (3
6). Of these two streams,
The outer peripheral end of the inner leaf valve (2'?) is pressed down and the oil flow flowing into the lower peripheral oil passage (321) generates a damping force, and the pressure chamber (30
) upper end oil chamber! 34) The other flow flowing into the damping force causes the above-mentioned two damping force generation effects or the damping force reduction effect.

That is, the orifice (27) of the inner leaf valve (5) is inserted from above into the upper end oil chamber G4) of the pressure chamber (30).
Reduced pressure oil flows in through the upper central oil chamber (20), and the larger the oil pressure difference with the upper central oil chamber (20), the more oil flows into this upper end oil chamber (34). When the amplitude is small and the vibration frequency is small, the pressure difference becomes small, and as a result, the amount of oil passing through the inner peripheral end of the leaf valve 24) and the outer peripheral end of the inner leaf valve 127) increases, and therefore the damping force generation effect is reduced. will appear. Furthermore, when the vibration frequency increases, for example, when it reaches the point x3 in FIG. The amount of oil flowing through the inner circumferential end of 4) and the outer circumferential end of the inner leaf pallet 7 (27) decreases, resulting in a reduction in damping force (see the solid line C on the right side of Fig. 1).

As described above, until a predetermined vibration frequency is reached - for example, in Figure 1, the damping force is generated by the damping force mechanism until the 13th point in the figure is reached, and when it exceeds the 23rd point in the figure, the damping force is generated. Similarly, a damping force mechanism is used to reduce the damping force.

In a specific vibration frequency range before that, for example, in the range of X/ to x2 in Fig. 1, the damping force is reduced by the rotary body (4σ).

That is, when a large rotation occurs due to a specific resonance, either the through hole (41a) or (41b) of the rotating body (40) is connected to the horizontal oil passage (9) of the piston rod (2).
The upper chamber (4) and the lower chamber (5) are communicated with each other. In other words, the oil from the upper chamber (4) passes through the through hole (4υ) and the horizontal oil passage (9), reaches the oil passage (6) ν, and enters the oil passage α6 in the tightening fitting α4 that communicates with the lower end. through the annular gap α
It reaches the force and flows out into the lower chamber (6). And at this time,
Most of the oil in the upper chamber (4) flows into the lower chamber (5) as described above.
As a result, not much flows into the damping force mechanism, and as a result, the damping force decreases (see solid line C on the left in Figure 1).

In addition, if the amplitude of the piston (4) is extremely large and therefore the descent of the free piston (30) is forcibly stopped by the cap 08, an extremely large damping force may be generated within the disk (20). In order to prevent the toninal from rising rapidly, a hole (39) is bored in the side wall of the casing (33), and the hole (39) gradually closes as the free piston 09 descends. After the closure is completed, the oil continues to be discharged through the orifice.

Next, during the pressure stroke in which the piston (3) descends, the lower chamber (
The oil in 5) passes through the annular gap (17) and reaches the peripheral oil passage (8) of the piston (3), pushes up the non-discharge valve α0), reaches the stopper (12), and enters the notch (t3). ) into the upper chamber (4), but at that time, pressurized oil also enters into the peripheral oil passage (32) of the pressure chamber (30), and this oil pressure pushes up the disk (20). becomes.

The rise of this disk (20) is caused by the upper oil chamber C on the pressure chamber side.
, J) 4) The lower surface of the inner leaf valve (2'/) of the disk (20) will be separated from the upper surface, and the reduced pressure oil in the upper end oil chamber t34) will flow out to the outside.

In other words, during the extension stroke of the piston (3), the upper end oil chamber 04)
The reduced pressure oil that has entered the piston (3) flows out to the outside during the compression stroke of the piston (3), and as a result, during the next extension stroke of the piston (3), new reduced pressure oil is allowed to flow in without accumulating pressure. This makes it possible to obtain the desired oil pressure difference.

In addition, during the pressure stroke of the piston (3), when the rotary body (4@) has its through hole facing the horizontal oil passage (9) of the piston rod (2), the annular gap is opened from inside the lower chamber (5). residence η
A part of the oil passing through the oil passage Q6 is drilled on the fastening fitting side.
) and reaches the oil passage (6) of the piston rod (2), and passes through the horizontal oil passage (9) and the through hole (4υ) to the upper chamber (4
) flows also occur.

As described above, by using the damping force mechanism in combination with the rotating body (40), it is possible to generate the damping force and reduce the damping force only within the desired range. This can also be done with the rotating body (40) according to the example.

That is, in the embodiment shown in Figure 5, the piston (
3) The damping force mechanism installed below the disc (
A) and the configuration of the pressure chamber (30) are designed so that when a predetermined vibration frequency is reached, for example after point X1 in the oni diagram, a damping force reduction effect appears. When a specific vibration frequency is reached in a range exceeding this predetermined vibration frequency, for example, Z', 2-' in FIG.
When the ratio reaches the 3:3 range, the damping force is generated by the operation of the rotor (4).For this reason, the rotor (4o) differs from the above embodiment in that the rotor (4o) does not penetrate through its wall thickness. It has one through hole (11) formed by
Furthermore, an oil chamber (41) of an appropriate size is formed at the inner end of this through hole (4υ). For example, when the vibration frequency ranges from the middle phrase to x3 in Fig. 1, the oil passage (6) of the piston rod (2)
), and the oil from the upper chamber (4) is allowed to flow exclusively into the lower damping force mechanism to generate the desired damping force. .

Therefore, when the piston (3) rises with a small amplitude such as extension, the imaging frequency is a predetermined vibration frequency (the first vibration frequency).
The oil in the upper chamber (4) reaches the through hole (x1 point in the figure).
41), oil chamber (41), horizontal oil passage (9), oil passage (6),
The oil reaches the lower chamber (5) through the oil passage aO and the annular gap αn, and no damping force is generated. However, on the other hand, a part of the oil in the upper chamber (4) flows into the lower damping force mechanism and this oil is The desired damping force can be generated by the inflow.

When the vibration frequency becomes equal to or higher than a predetermined vibration frequency (point x1 or higher in FIG. 1), a damping force reduction effect appears by the lower damping force mechanism (see solid line C on the left side of FIG. 1). At this time, the through hole (·1υ) of the rotating body (40) is communicated with the oil passage (6) of the piston rod (2). ~x
3), the rotating body (40) undergoes a large rotation due to resonance, which causes the oil chamber (4υ, that is, the through hole (,1]) and the horizontal oil passage (
9) will be cut off. Therefore, all the oil in the upper chamber (4) flows into the lower damping force mechanism to obtain the desired damping force. However, after that, the rotation of the rotating body (40) deviated from the specific resonance, and the rotation of the rotating body (40)
In other words, when returning to the range where the oil chamber (4I) communicates with the horizontal oil passage (9) (after x3 in Figure 1), the oil from the upper chamber (4) flows through the through hole (4υ, oil chamber (4I)). , horizontal oilway (9),
The flow rate increases as it reaches the lower chamber (5) through the oil passage (6), the oil passage ([6), and the annular gap α force, and the flow rate to the lower damping force mechanism decreases, resulting in further damping. A force reduction effect will appear.

]・In the embodiment shown in Figure 5, O-, 2 in Figure 1
Even if oil flows from the upper chamber (4) to the lower chamber (5) through the oil passage (6) in the piston rod (2) within the range of In order to generate a damping force by the damping force mechanism, the deflection rigidity of the leaf valve <24) of the disc (2o) and the inner leaf valve η in the damping force mechanism, and the main valve (
2) Orifice (droplet diameter and inner leaf valve (27)
Of course, this depends on the selection of the diameter of the orifice (5), etc., and also on the selection of the free piston (3) of the pressure chamber (30).
Of course, this can be achieved by selecting the pressure-receiving area and the spring constant of the spring Gη in 6).

As described above, according to the present invention, damping force is generated within a specific resonance region such as near the primary resonance point and the secondary resonance point of the suspension spring, but the damping force is reduced in other ranges. As a result, if this hydraulic shock absorber is used as a shock absorber for an automobile or a 5-nit shock absorber for a motorcycle, it will stabilize the maneuverability of the automobile, etc. Riding comfort can be improved.

Furthermore, as in the present invention, when the damping force is generated or reduced by a rotating body that rotates in the horizontal direction, a resonator that slides in the vertical direction is installed to perform the same action. There is also the advantage that the cylinder length can be kept small in comparison.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the vibration frequency and the amount of displacement of the sprung mass, Figure 2 is a longitudinal sectional view partially showing a hydraulic shock absorber according to an embodiment of the present invention, and Figure 3 is a line I in Figure 2. -4 is a cross-sectional view of the piston rod and the rotating body, Figure 4 is a developed view partially showing the outer peripheral wall surface of the rotating body, and Figure 5 is a cross-sectional view of the rotating body according to another embodiment together with the piston rod. It is a diagram. (1)...Cylinder (2)...Piston rod,
(3)... Piston, (4)... Upper chamber - (6).
・・Oil passage, (20) damping force mechanism disc, (30)・
...Pressure chamber of the damping force mechanism, (4■...Rotating body. Figure 3 Figure 4 Procedural amendment (voluntary) March 1983 / Japan Patent Office Commissioner Kazuo Wakasugi 1, Incident Display Patent application filed in 1982, No. 8206936 2, Name of the invention Hydraulic shock absorber 3, Relationship with the amended youth case Patent applicant address 4 ゛°°Pa ``sx*a''i = i ?f4, Agent Address: Yaesu Building, No. 8, Yaesu 2-chome, Chuo-ku, Tokyo Name (z73) Patent Attorney Izumi Amano 5,
Target of amendment 1) Column for detailed description of the invention 2) Column for brief explanation of drawings 1) EA specification page 3, lines 3 to 4 and line 10 K "Spring mass displacement amount" has been replaced with "Spring mass door speed" ” and corrected each other. 2) In the specification, page 6, line 16, K "Rotating body floor 01, J" is corrected to read "between resonant rotating bodies." 3) On page 8, line 5 of the specification, the phrase ``at the time of,'' is replaced with ``noto volume,'' and from line 19 to line 20 of the same description, it says ``111~-free piston (86) connected to.'' is corrected to ``The upper end of the free piston (86) housed in the lower oil chamber is seen, and the above is inside this lower oil chamber.'' 4) On page 10 of the specification, lines 5 and 19, the words ``setting value'' are replaced with ``damping force reduction characteristics,'' and on line 18 of the same page, ``obtainable.''
The statement has been corrected to ``can be obtained without increasing the rigidity of the leaf valve.'' 5) In the second line of page 11 of the specification, the phrase ``the above-mentioned rotating body (g)'' has been replaced with ``the above-mentioned resonant rotary body 1401 "The relative flow of oil according to the movement", line 4 K "specific resonance" is replaced by "resonance caused by a specific piston motion", and line 9 "between rotating bodies" is replaced by "resonance". ``Rotating body (equipment)'' and ``large rotation'' on the same line 20 are corrected to ``effectively large rotation.'' 6) On page 12, line 13 of the specification, the phrase ``drilled'' should be corrected to ``projected,'' and on the 15th line of the same specification, the phrase ``at the time of that'' should be corrected to ``only at the time of that.'' 7) On page 16 of the specification, lines 1 to 2, the phrase "when a large rotation occurs," is corrected to "when a large rotation occurs." 8) In the 1st line of page 17 of the specification, the word "Yoshi" is changed to "only", and in the 11th line of the specification, the word "of Disk (company)" is changed to "with Disk (branch)", and in the same line 13 , instead of "the decompression oil inside" is changed to "the oil that was flowing into the inside" and the same line 16 says "
Correct the phrase ``to be easily leaked to'' to ``to be easily leaked to,'' respectively. 9) “Rotating body (g))” in line 7 and 10 of statement 18
" has been corrected to read "between resonant rotating bodies." 14. Pressure-receiving area of free piston (86) and spring (37)
"obtained by appropriately selecting the strength, etc. of" is added. 10) In the 1st line of page 19 of the specification, "rotating body (G)" is replaced with "resonant rotating body (G)", and in lines 5 to 7 of the same specification, "forming 11111, for example," Until a predetermined resonance frequency is reached, the oil holes (9) communicate with each other and allow the oil to flow through the oil holes (6) of the piston rod (2) to generate a damping force. However, when the resonant rotating body 4α rotates greatly due to a specific resonant frequency, for example, the phrase ``generation of desired damping force'' in the same line 11 is changed to ``generation of a desired high damping force'' in the same line 18. ``To! In line 19, the phrase ``inflow into'' was corrected to ``flow into'', and in line 20, ``desired by'' was corrected to ``also desired by''. do. 11) On page 20, line 18 of the Book of Ill., it says, ``The flow rate will not increase,'' but it is replaced with ``Because the flow rate will occur again,'' Ill. 19.
In line 20, the word ``further'' is changed to ``first'', and in the same line 20, ``is further''.
Correct the phrase "to appear" to "to be reproduced." 12) On page 22, line 10 of the specification, the phrase "spring mass displacement amount" is corrected to "spring mass door speed."

Claims (3)

[Claims] (1) A piston that divides the inside of the cylinder into an upper chamber and a lower chamber and is formed by drilling an oil passage in the axial direction that communicates with the upper chamber, fixes the piston, and communicates with the upper chamber. On the other hand, the piston rod has an oil passage bored therein which communicates with the lower chamber, and the lower end of the piston rod communicates with the oil passage of the piston and is damped within a predetermined vibration frequency range. A hydraulic shock absorber is equipped with a damping force mechanism that generates force and reduces damping force in a range exceeding a predetermined vibration frequency range. A rotary body is attached to the rotary body that slides into contact with the movable body, and a through hole is formed in the thick part of the rotary body to penetrate in the radial direction, and a plurality of slopes are formed by cutting out the through hole in the outer peripheral wall surface of the rotary body. A hydraulic shock absorber having a concave groove. (2) When the rotary body rotates due to a specific resonance, its through hole faces one of the oil passages of the piston rod to communicate the upper chamber and the lower chamber to reduce the damping force. A hydraulic shock absorber according to claim 1. (3) When the rotating body rotates due to a specific resonance, communication between one of the oil passages of the piston rod and its through hole is cut off to generate a damping force. Hydraulic shock absorber as described in section.