JP2015187474A - hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic shock absorber capable of always stably generating required attenuating force.SOLUTION: In a hydraulic shock absorber 1 equipped with a check valve device 25, a cylinder 2 is made to have a triple pipe structure by an inner cylinder 2a, an intermediate cylinder 2b, and an outer cylinder 2c coaxially disposed. A space between the intermediate cylinder 2b and the outer cylinder 2c is made to be a reservoir chamber S3, and a piston 9 is slidably fitted in the inner cylinder 2a to divide a space in the inner cylinder 2a into a rod side oil chamber S1 and a piston side oil chamber S2. The check valve device 25 is provided with a pressure side check valve 29 which prevents an oil flow from the piston side oil chamber S2 to the reservoir chamber S3 during a compression stroke, and accepts an oil flow from the reservoir chamber S3 to the piston side oil chamber S2 during an expansion stroke; and an expansion side check valve 31 which prevents an oil flow from the rod side oil chamber S1 to the reservoir chamber S3 during the expansion stroke, and accepts an oil flow from the rod side oil chamber S1 to the reservoir chamber S3 during the compression stroke.

Description

  The present invention relates to a hydraulic shock absorber that suspends a wheel of a motorcycle or the like from a vehicle body.

  For example, in a hydraulic shock absorber that suspends the wheel of a motorcycle from the vehicle body, a cylinder is attached to one of the vehicle body side or the axle side, a piston rod is attached to the other side, and a part of the piston rod is inserted inside the cylinder. A piston bound to an end of the piston rod facing the cylinder is brought into sliding contact with the inner periphery of the cylinder, and a damping force generating means is provided on the piston, so that the piston rod enters and moves into the cylinder. There is a type in which a check valve device for switching a flow path of oil corresponding to the exit volume is provided in the cylinder (for example, see Patent Document 1). An example of this type of hydraulic shock absorber is shown in FIG.

  That is, FIG. 5 is a half-sectional view of a conventional hydraulic shock absorber. The illustrated hydraulic shock absorber 101 includes a cylinder 102 having a double tube structure formed by a concentric inner cylinder 102a and an outer cylinder 102b. It is attached to the axle side by the side attachment member 103, the piston rod 104 is attached to the vehicle body side by the vehicle body side attachment member 105, and the lower spring attached to the outer periphery of the cylinder 102 and the upper spring receiver 106 attached to the vehicle body side attachment member 105. A suspension spring 108 is interposed between the spring receiver 107 and the spring receiver 107.

  In the illustrated hydraulic shock absorber 101, a part of the piston rod 104 is inserted into the inner cylinder 102a of the cylinder 102 from above, and at the lower end of the piston rod 104 inserted into the inner cylinder 102a, A piston 109 is attached to the inner cylinder 102a of the cylinder 102 so as to be slidable in the vertical direction. Here, the space in the inner cylinder 102a of the cylinder 102 is partitioned into the rod-side oil chamber S1 and the piston-side oil chamber S2 by the piston 109, and the rod-side oil chamber S1 and the piston-side oil chamber S2 are separated from each other. Is filled with oil which is a working fluid. A reservoir chamber S3 is formed between the inner cylinder 102a and the outer cylinder 102b of the cylinder 102. Oil and air are enclosed in the reservoir chamber S3, and the upper portion of the reservoir chamber S3 is occupied by air. ing.

  Incidentally, a compression side damping valve 110 and an extension side damping valve 111 constituting damping force generating means are provided on the upper and lower surfaces of the piston 109, and a check valve device 112 is provided at the bottom of the inner cylinder 102a of the cylinder 102. Is provided. Here, details of the configuration of the check valve device 112 will be described with reference to FIGS. 6 and 7.

  That is, FIG. 6 is a half-cut sectional view showing the action during the compression stroke of the check valve device, FIG. 7 is a half cut-away view showing the action during the extension stroke of the check valve device, and the check valve device 112 shown in FIG. 102, a disc-shaped base plate 113 and a bottomed cylindrical valve case 114 fitted to the bottom of the inner cylinder 102a, a valve seat 115 accommodated in the valve case 114 so as to be vertically movable, and the valve seat 115 A check valve 116 that selectively opens and closes the orifice 115a formed in the above, a spring 117 that urges the valve seat 115 downward, and the like. A plurality of cutout oil grooves (only one is shown in FIGS. 6 and 7) are formed in the outer peripheral portion, and the inside of the valve case and the reservoir chamber communicate with each other by these oil grooves.

  In the hydraulic shock absorber 101 configured as described above, for example, when the wheel moves up and down following the road surface unevenness while the motorcycle is running, the cylinder 102 and the piston rod 104 expand and contract and are attached to the piston rod 104. The piston 109 slides up and down in the inner cylinder 102a of the cylinder 102.

  Thus, in the compression stroke in which the piston rod 104 and the piston 109 move downward relative to the cylinder 102, the oil in the piston-side oil chamber S2 is compressed by the piston 109 to increase its pressure. The portion passes through a pressure-side oil passage (not shown) formed in the piston 109 and pushes the pressure-side damping valve 110 to flow into the rod-side oil chamber S1, and the oil flows due to the flow resistance when the oil passes through the pressure-side damping valve 110. The hydraulic shock absorber 101 generates a required compression side damping force.

  In the compression stroke, as shown in FIG. 6, the valve seat 115 of the check valve device 112 is pressed downward by the oil pressure in the piston-side oil chamber S <b> 2 and the urging force of the spring 117. Seated and closed. Accordingly, in the compression stroke, a volume amount of oil that the piston rod 104 enters into the inner cylinder 102a of the cylinder 102 passes through the plurality of orifices 115a of the valve seat 115 from the piston-side oil chamber S2 as indicated by arrows in FIG. The air passes through and flows into the reservoir chamber S3 (see FIG. 5) while expanding the check valve 116 with the pressure, so that the air in the reservoir chamber S3 is compressed, and the compression of the air causes the inner cylinder 102a due to the piston rod 104 to enter. The volume change of the oil inside is compensated.

  On the other hand, in the extension stroke in which the piston rod 104 and the piston 109 move up relatively with respect to the cylinder 102, the oil in the rod side oil chamber S1 is compressed by the piston 109, and the pressure becomes high, and a part of the pressure is increased. The extension side damping valve 111 is pushed open through the extension side oil passage 118 formed in 109 and flows into the piston side oil chamber S2, and the hydraulic pressure is generated by the flow resistance when this oil passes through the extension side damping valve 111. A required extension side damping force is generated in the shock absorber 101.

  In the extension stroke, the pressure of the oil in the piston-side oil chamber S2 decreases, and the valve seat 115 of the check valve device 112 moves up against the urging force of the spring 117. As shown in FIG. The valve seat 115 is opened apart from the base plate 113 together with the check valve 116. Accordingly, the oil corresponding to the volume of the piston rod 104 withdrawing from the inner cylinder 102a of the cylinder 102 during the extension stroke passes through the check valve device 112 from the reservoir chamber S3 (see FIG. 5) as indicated by an arrow in FIG. Then, the piston side oil chamber S2 is replenished. For this reason, the air in the reservoir chamber S3 expands, and the expansion of the air compensates for the volume change of the oil in the inner cylinder 102a due to the withdrawal of the piston rod 104. In this extension stroke, the oil in the reservoir chamber S3 passes through the check valve device 112 with almost no resistance, so that the damping force generated in the check valve device 112 is smaller than the damping force generated in the compression stroke. Become.

Japanese Utility Model Publication No. 58-116841

  However, in the hydraulic shock absorber 101 shown in FIG. 5, the flow of high-pressure oil in the piston-side oil chamber S2 is divided into two directions, that is, the pressure-side damping valve 110 side and the check valve device 112 side of the piston 109 in the compression stroke. The pressure in the rod side oil chamber S1 fluctuates in the range from positive pressure to negative pressure depending on the balance of the flow resistance of the oil passing through the pressure side damping valve 110 and the check valve device 112 (orifice 115a of the valve seat 115). When the flow resistance of the oil passing through the damping valve 110 is excessive, the rod side oil chamber S1 is in a negative pressure state. When the rod-side oil chamber S1 is in a negative pressure state in this way, the pressure in the rod-side oil chamber S1 does not increase immediately at the time of transition from the compression stroke to the extension stroke, so that the required damping force is not normally generated. The phenomenon of “throwing power” occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a hydraulic shock absorber that can always stably generate a required damping force.

In order to achieve the above object, according to the first aspect of the present invention, a part of a piston rod is inserted into a cylinder, and a piston bound to an end of the piston rod facing the cylinder is disposed inside the cylinder. The cylinder is provided with a check valve device that is slidably contacted with the circumference, and provided with a damping force generating means for the piston, and switches the flow path of the oil corresponding to the volume of the piston rod entering and leaving the cylinder. In hydraulic shock absorber,
The cylinder is a triple pipe structure with an inner cylinder and an intermediate cylinder and an outer cylinder arranged concentrically, and a space between the intermediate cylinder and the outer cylinder serves as a reservoir chamber,
The piston is slidably fitted into the inner cylinder, and the space in the inner cylinder is divided into a piston-side oil chamber and a rod-side oil chamber,
In the check valve device,
A pressure-side check valve that prevents the flow of oil from the piston-side oil chamber to the reservoir during the compression stroke, and permits the flow of oil from the reservoir chamber to the piston-side oil chamber during the extension stroke;
An extension check valve is provided that prevents the flow of oil from the rod side oil chamber to the reservoir chamber during the extension stroke and allows the oil flow from the rod side oil chamber to the reservoir chamber during the compression stroke. Features.

According to a second aspect of the present invention, in the first aspect of the present invention, in the first aspect of the invention, the partition member fixed in the cylinder communicates the reservoir chamber with both the piston-side oil chamber and the rod-side oil chamber. Form the
The pressure side check valve is provided at a communication port of the communication passage to the piston side oil chamber, and the extension side check valve is provided at a communication port to the rod side oil chamber.

  The invention according to claim 3 is the invention according to claim 1, wherein the partition member is provided between the piston-side oil chamber and the reservoir chamber in the cylinder, and the communication passage formed in the partition member is provided. The outer oil passage formed between the inner cylinder and the intermediate cylinder of the cylinder is communicated with the rod-side oil chamber via a lateral hole formed in the inner cylinder.

The invention according to claim 4 is the invention according to claim 2 or 3, wherein the compression side check valve and the extension side check valve are combined and integrated, and both are held movably on the partition member.
The pressure side check valve faces the piston side oil chamber, and the extension side check valve faces the rod side oil chamber.

  According to a fifth aspect of the present invention, in the fourth aspect of the invention, the extension check valve and a spring that biases in the opening direction are provided.

  The invention according to claim 6 is characterized in that, in the invention according to claim 4 or 5, the pressure receiving area of the pressure side check valve is set larger than the pressure receiving area of the extension side check valve.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, characterized in that air at atmospheric pressure is sealed in the reservoir chamber.

  According to the first aspect of the present invention, in the compression stroke, the pressure side check valve of the check valve device prevents the flow of oil from the piston side oil chamber to the reservoir, and the extension side check valve moves from the rod side oil chamber to the reservoir chamber. In order to allow oil to flow into the cylinder, oil corresponding to the volume of the piston rod entering the cylinder passes through the expansion check valve without resistance, and almost no damping force is generated in the expansion check valve. For this reason, the compression side damping force is generated by the flow resistance when all of the pressurized oil in the piston side oil chamber passes through the piston damping force generation means and flows into the rod side oil chamber.

  In the extension stroke, the extension side check valve of the check valve device prevents the flow of oil from the rod side oil chamber to the reservoir, and the pressure side check valve allows the oil flow from the reservoir chamber to the piston oil chamber. The oil corresponding to the retraction volume of the piston rod from the cylinder passes through the pressure side check valve without resistance, and almost no damping force is generated in the pressure side check valve. For this reason, the extension side damping force is generated by the flow resistance when all of the pressurized oil in the rod side oil chamber passes through the piston damping force generating means and flows into the piston side oil chamber. Therefore, it is not necessary to balance the pressures of the three chambers of the piston-side oil chamber, the rod-side oil chamber, and the reservoir chamber, and a required pressure-side damping force can be always generated stably. In this extension stroke, since the flow resistance of the oil passing through the pressure side check valve is very small, the pressure in the piston side oil chamber almost depends only on the pressure of the air that pressurizes the reservoir chamber, and means for generating the damping force of the piston It does not fluctuate due to the flow resistance of the oil passing through. Therefore, the rod-side oil chamber is not in a vacuum state, and the required damping force is not normally generated because the pressure in the rod-side oil chamber does not increase immediately at the transition from the compression stroke to the extension stroke. The phenomenon of “squirting” does not occur.

  According to the second aspect of the present invention, the partition member fixed in the cylinder is formed with a communication path that allows the reservoir chamber to communicate with both the piston-side oil chamber and the rod-side oil chamber, and the piston side of the communication path Since the pressure side check valve is provided at the communication port to the oil chamber and the expansion side check valve is provided at the communication port to the rod side oil chamber, the structure of the check valve device provided in the cylinder can be simplified.

  According to the third aspect of the present invention, the partition member is provided between the piston-side oil chamber and the reservoir chamber in the cylinder, and the communication passage formed in the partition member is provided between the inner cylinder and the intermediate cylinder of the cylinder. Since the outer oil passage is formed in communication with the rod-side oil chamber via a lateral hole formed in the inner cylinder, the structure of the check valve device can be further simplified.

  According to the invention described in claim 4, since the pressure side check valve and the extension side check valve of the check valve device are coupled and integrated, and the both are movably held by the partition member, the check valve device is provided with the piston rod in the cylinder. It functions as an ON / OFF valve for switching the flow path of oil corresponding to the volume of entry and exit, and hardly generates damping force. For this reason, the compression side and extension side damping forces are generated only by the piston damping force generating means, and as a result, there is no need to balance the pressure in the three chambers, the piston side oil chamber, the rod side oil chamber, and the reservoir chamber. The required compression side damping force can always be generated stably. Further, by combining and integrating the pressure side check valve and the extension side check valve, the configuration of the check valve device can be further simplified.

  According to the fifth aspect of the present invention, since the extension side check valve of the check valve device is biased in the opening direction by the spring, the extension side check valve is surely opened in the compression stroke, and is integrated with the extension side check valve. The compressed pressure side check valve can be closed reliably, and the response and stability of the damping force are improved. In addition, during the extension stroke, even if the pressure in the piston-side oil chamber and the pressure in the rod-side oil chamber are in a balanced state, the pressure-side check valve is securely closed and the extension-side check valve is reliably opened. , Responsiveness and stability of damping force is enhanced.

  According to the invention described in claim 6, since the pressure receiving area of the pressure side check valve of the check valve device is set larger than the pressure receiving area of the expansion side chuck valve, the expansion side check valve is surely opened during the compression stroke, The pressure side check valve integrated with the valve can be reliably closed, and the response and stability of the damping force are improved. Also, during the extension stroke, even if the pressure in the piston-side oil chamber and the pressure in the rod-side oil chamber are in a balanced state, the pressure-side check valve is securely closed and the extension-side check valve is reliably opened. Damping force response and stability are improved.

  According to the seventh aspect of the present invention, since air at atmospheric pressure is enclosed in the reservoir chamber instead of compressed air, equipment for enclosing the compressed air in the reservoir chamber becomes unnecessary, and the equipment cost can be kept low.

It is a longitudinal cross-sectional view which shows the state at the time of the compression stroke of the hydraulic shock absorber which concerns on this invention. It is a longitudinal cross-sectional view of the check valve apparatus of FIG. It is a longitudinal cross-sectional view which shows the state at the time of the expansion stroke of the hydraulic shock absorber which concerns on this invention. It is a longitudinal cross-sectional view of the check valve apparatus of FIG. It is a half cut sectional view of the conventional hydraulic shock absorber. FIG. 6 is a half-cut sectional view showing an operation during a compression stroke of the check valve device of the hydraulic shock absorber shown in FIG. 5. FIG. 6 is a half-cut sectional view showing an operation during an extension stroke of the check valve device of the hydraulic shock absorber shown in FIG. 5.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
[Hydraulic] Shock absorber configuration]
1 is a longitudinal sectional view showing a state of a hydraulic shock absorber according to the present invention during a compression stroke, FIG. 2 is a longitudinal sectional view of the check valve device of FIG. 1, and FIG. 3 is a state of the hydraulic shock absorber during an expansion stroke. FIG. 4 is a longitudinal sectional view of the check valve device of FIG.

  A hydraulic shock absorber 1 according to the present embodiment is an upright rear cushion that suspends a rear wheel of a motorcycle (not shown) from a vehicle body, and a piston rod on the vehicle body side inside a cylinder 2 on the axle side. 3 is inserted from above, and a suspension spring 4 is interposed between the cylinder 2 and the piston rod 3.

  The cylinder 2 is configured as a triple pipe structure by an inner cylinder 2a, an intermediate cylinder 2b, and an outer cylinder 2c arranged concentrically, and a bifurcated axle-side mounting member 5 is bound to the lower end thereof. . The lower end of the cylinder 2 is attached to the rear wheel support member of the motorcycle via an axle (not shown) that is inserted into a shaft hole 5a that is provided in the axle side attachment member 5 in a lateral direction.

  A vehicle body side mounting member 6 is attached to the upper end of the piston rod 3, and a cylindrical rubber bush 7 is inserted and held in the vehicle body side mounting member 6 in the lateral direction (left and right direction in FIG. 1). Inside, a cylindrical collar 8 is also inserted and held in the horizontal direction. The upper end portion of the piston rod 3 is attached to the motorcycle body by a shaft (not shown) that is inserted into the collar 8 that is inserted and held in the vehicle body side attachment member 6.

  A part of the piston rod 3 is inserted into the inner cylinder 2 a of the cylinder 2 from above, and a piston 9 is bound to the lower end of the piston rod 3 facing the inner cylinder 2 a by a nut 10. The suspension spring 4 is interposed between an upper spring receiver 11 attached to the vehicle body side mounting member and a lower spring receiver 12 attached to the outer periphery of the cylinder 2 (outer cylinder 2c). Around the upper portion of the piston rod 3 that extends outside the cylinder 2, a cylindrical dust cover 13 having an upper end clamped by the upper spring receiver 11 and the suspension spring 4 is disposed. A bump rubber 14 is inserted and held at the upper end of the piston rod 3.

  By the way, a cap 15, an oil seal 16, and a rod guide 17 are sequentially fitted on the inner periphery of the upper end opening of the cylinder 2 from above, and the piston rod 3 includes the cap 15, the oil seal 16, and the rod guide. The center part of 17 is slidably penetrated. Here, the rod guide 17 is fitted to the inner periphery of each upper end of the inner cylinder 2a, the intermediate cylinder 2b, and the outer cylinder 2c of the cylinder 2, and the space inside the inner cylinder 2a is rod-side oil chamber S1 by the piston 9. And the rod-side oil chamber S1 and the piston-side oil chamber S2 are filled with oil as a working fluid. A rebound spring 18 is accommodated in the rod side oil chamber S1.

  A cylindrical outer oil passage 19 is formed between the inner cylinder 2a and the intermediate cylinder 2b of the cylinder 2, and a cylindrical reservoir chamber S3 is also formed between the intermediate cylinder 2b and the outer cylinder 2c. Yes. The outer oil passage is filled with oil, and the reservoir chamber is filled with oil and air. Here, the upper portion of the reservoir chamber S3 is occupied by air, and when the hydraulic shock absorber 1 is assembled, air at atmospheric pressure is sealed in the reservoir chamber S3. Further, a plurality of lateral holes 20 (only two are shown in FIGS. 1 and 3) for communicating the rod-side oil chamber S1 and the outer oil passage 19 are formed at the upper end of the inner cylinder 2a of the cylinder 2. Yes. Note that leakage of oil from the cylinder 2 is prevented by the sealing action of the oil seal 16.

  By the way, the piston 9 is provided with a plurality of pressure side passages 21 and an extension side oil passage 22 (only one is shown in each of FIGS. 1 and 3) extending vertically. Are provided with a pressure-side damping valve 23 for selectively opening and closing the pressure-side oil passage 21 and an extension-side damping valve 24 for selectively opening and closing the extension-side oil passage 22. The compression side damping valve 23 and the extension side damping valve 24 constitute damping force generating means for generating a compression side damping force and an extension side damping force, respectively, as will be described later. Here, the pressure side oil passage 21 is always open to the piston side oil chamber S2, and the extension side oil passage 22 is always open to the rod side oil passage S1.

  Thus, in the hydraulic shock absorber 1 according to the present embodiment, when the piston rod 3 moves up and down relatively with respect to the cylinder 2 as the cylinder 2 and the piston rod 3 expand and contract, the piston rod 3 The amount of oil that enters into the cylinder 2 and the volume that exits the cylinder 2 flows into and out of the reservoir chamber S3. A check valve device 25 for switching the flow path of the oil is provided in the cylinder 2. Is provided between the piston side oil chamber S2 and the reservoir chamber S3. Here, details of the configuration of the check valve device 25 will be described with reference to FIGS. 1 and 2.

  The check valve device 25 includes a partition wall member 26 fixed to the bottom of the cylinder 2. The partition wall member 26 has a bottomed cylindrical shape whose upper outer periphery is fitted to the lower inner periphery of the inner cylinder 2a. The first member 26A and the upper inner periphery are configured by a second member 26B having the same bottomed cylindrical shape that is fitted and integrated with the outer periphery of the first member 26A. The lower outer periphery of the two member 26B is fitted to the lower inner periphery of the intermediate cylinder 2b.

  The partition member 26 is formed with a communication passage 27 that allows the reservoir chamber S3 to communicate with both the rod-side oil chamber S1 and the piston-side oil chamber S2, and is formed at the center of the first member 26A. A cylindrical valve shaft 28 is inserted and supported so as to be movable up and down. Here, the communication passage 27 includes a first space 27c, a first space 27c defined by a horizontal hole 27a and a vertical hole 27b formed in the second member 26B of the partition wall member 26, a first member 26A and a second member 26B, and a first space 27c. A communication port 27d formed around the valve shaft 28 below the member 26A, a vertical hole 27e and a second space 27f formed in the first member 26A, and around the valve shaft 28 above the first member 26A. The communication port 27g is formed. The lateral hole 27a formed in the second member 26B of the partition wall member 26 opens into the first space 27c of the outer oil passage 19 and the communication passage 27 and is formed in the second member 26B. The vertical hole 27b allows the reservoir chamber S3 and the second space 27f to communicate with each other. The communication ports 27d and 27g formed on the upper and lower portions of the first member 26A of the partition wall member 26 communicate with each other by the second space 27f and the vertical hole 27e formed in the first member 26A. . Here, the upper communication port 27g opens to the piston-side oil chamber S2, and the lower communication port 27d includes the first space 27c and the lateral hole 27a of the communication passage 27, the outer oil passage 19, and the inner oil passage 19. It opens to the rod side oil chamber S1 through a lateral hole 20 formed in the upper part of the cylinder 2a.

  By the way, a disc-shaped pressure side check valve 29 for selectively opening and closing a communication port 27g opened at the upper part of the first member 26A of the partition wall member 26 is attached to the upper end portion of the valve shaft 28 by a bolt 30. A disc-shaped extension side check valve 31 that selectively opens and closes the communication port 27d that opens at the lower portion of the first member 16A is attached to the lower end of the valve shaft 28 by a bolt 32. In this way, the pressure side check valve 29 and the extension side check valve 31 are coupled and integrated by the valve shaft 28. The pressure side check valve 29 and the extension side chuck valve 31 are moved up and down integrally to form a communication port 27d. , 27g are selectively opened and closed, and when the pressure side check valve 29 closes the upper communication port 27g, the lower communication port 27d is opened by the expansion side check valve 31, and conversely, the expansion side check valve 31 is When the lower communication port 29 d is closed, the upper communication port 27 g is opened by the compression side check valve 29.

  More specifically, during the compression stroke, the pressure side check valve 29 closes the upper communication port 27g to prevent the oil flow from the piston side oil chamber S2 to the reservoir chamber S3, as shown in FIG. During the stroke, as shown in FIG. 4, the upper communication port 27g is opened to allow the oil flow from the reservoir chamber S3 to the piston-side oil chamber S2. Further, the extension side check valve 31 closes the lower communication port 27d as shown in FIG. 4 during the extension stroke to block the flow of oil from the rod side oil chamber S1 to the reservoir chamber S3, and during the compression stroke, As shown in FIG. 2, the lower communication port 2d is opened to allow oil to flow from the rod side oil chamber S1 to the reservoir chamber S3.

Thus, the pressure-side check valve 29 faces the piston-side oil chamber S2, and the extension-side check valve 31 includes the first space 27c, the lateral hole 27a, the outer oil passage 19, and the communication passage 27 of the partition wall member 26. Although it faces the rod side oil chamber S1 through the lateral hole 20 formed in the upper part of the inner cylinder 2a, the pressure receiving area (outer diameter) of the pressure side check valve 29 is the pressure receiving area (outer diameter) of the extension side check valve 31. ) Is set larger than. The extension check valve 31 is always biased to the open side (downward) by a spring 33.
Action of “hydraulic” shock absorber]
Next, the operation of the hydraulic shock absorber 1 configured as described above will be described for the compression stroke and the expansion stroke.

1) Compression process:
When the rear wheel moves up and down following the road surface unevenness while the motorcycle is running, the cylinder 2 and the piston rod 3 of the hydraulic shock absorber 1 that suspends the rear wheel are expanded and contracted. In the relatively downward compression stroke, the oil in the piston-side oil chamber S2 is compressed by the piston 9 to increase its pressure, and the oil in the piston-side oil chamber S2 is indicated by an arrow in FIG. In this way, the pressure side damping valve 23 is pushed open through the pressure side oil passage 21 of the piston 9 and flows into the rod side oil chamber S1. At this time, a required compression side damping force is generated in the hydraulic shock absorber 1 due to the flow resistance when the oil passes through the compression side damping valve 23.

  Further, in the check valve device 25, the pressure check valve 29 closes the upper communication port 27g of the partition wall member 26 by the pressure in the piston side oil chamber S2 to block the flow of oil from the piston side oil chamber S2 to the reservoir chamber S3. Then, the extension side check valve 31 opens the lower communication port 27d of the partition wall member 26. Therefore, an amount of oil corresponding to the volume of the piston rod 3 entering the cylinder 2 flows from the rod side oil chamber S1 to the reservoir chamber S3 as indicated by an arrow in FIG. More specifically, the amount of oil corresponding to the volume of entry of the piston rod 3 passes through the lateral hole 20 formed in the upper portion of the inner cylinder 2a and flows downward in the outer oil passage 19 to the check valve device 25. And so on. In the check valve device 25, as indicated by arrows in FIG. 2, the horizontal space 27a constituting the communication passage 27 of the partition wall member 26 is connected to the first space 27c, the first space 27c is connected to the communication port 27d, and the vertical hole 27e. Then, it flows through the second space 27f and the vertical hole 27b to the reservoir chamber S3. For this reason, the air occupying the upper part of the reservoir chamber S is compressed, and the compression of the air compensates for the volume change in the inner cylinder 2a as the piston rod 3 enters the inner cylinder 2a.

  Thus, in the compression stroke, the oil corresponding to the volume of the piston rod 3 entering the cylinder 2 (inner cylinder 2a) passes through the extension side check valve 31 of the check valve device 25 without resistance, and the extension side check is performed. In the valve 31, almost no damping force is generated. For this reason, the pressure side damping force is generated by the flow resistance when all of the pressurized oil in the piston side oil chamber S2 passes through the pressure side damping valve 23 of the piston 9 and flows into the rod side oil chamber S1. Therefore, it is not necessary to balance the pressures of the three chambers of the rod-side oil chamber S1, the piston-side oil chamber S2, and the reservoir chamber S3, and the required compression-side damping force is always generated stably.

2) Extension process:
In the extension stroke in which the piston rod 3 moves up relative to the cylinder 2, the piston 9 moves up in the inner cylinder 2a of the cylinder 2 together with the piston rod 3, so that the oil in the rod side oil chamber S1 is moved to the piston. The oil in the rod side oil chamber S1 pushes the extension side damping valve 24 through the extension side oil passage 22 of the piston 9 as shown by an arrow in FIG. It opens and flows into the piston side oil chamber S2. At this time, a required extension side damping force is generated in the hydraulic shock absorber 1 due to the flow resistance when the oil passes through the extension side damping valve 24.

  In the check valve device 25, the extension side check valve 31 resists the urging force of the spring 33 due to the difference (differential pressure) between the pressure in the piston side oil chamber S2 and the pressure in the rod side oil chamber S1 higher than this. As shown in FIGS. 3 and 4, the pressure side check valve 29 moves upward and closes the lower communication port 27 d of the partition wall member 26, and the pressure side check valve 29 opens the upper communication port 27 g of the partition wall member 26. For this reason, the flow of oil from the rod side oil chamber S1 to the reservoir chamber S3 is blocked, and the oil corresponding to the retraction volume from the inside of the inner cylinder 2a of the piston rod 3 flows from the reservoir chamber S3 to the communication port of the check valve device 25. The oil is supplied to the piston side oil chamber S2 through 27g. More specifically, as indicated by an arrow in FIG. 4, the oil in the reservoir chamber S3 passes from the vertical hole 27b constituting the communication path 27 of the partition wall member 26 through the second space 27f and the vertical hole 27e to the communication port 27g. It flows to the piston side oil chamber S2. For this reason, the air which occupies the upper part of reservoir chamber S3 expand | swells, and the expansion of this air compensates the volume change in the inner cylinder 2a accompanying the withdrawal from the inner cylinder 2a of the piston rod 3.

  Thus, in the check valve device 25, the oil corresponding to the volume of the piston rod 3 withdrawing from the cylinder 2 passes through the pressure side check valve 29 without resistance, and almost no damping force is generated in the pressure side check valve 29. . For this reason, the expansion side damping force is generated by the flow resistance when all of the pressurized oil in the rod side oil chamber S1 passes through the expansion side damping valve 24 of the piston 9 and flows into the piston side oil chamber S2. Therefore, it is not necessary to balance the pressures of the three chambers of the rod-side oil chamber S1, the piston-side oil chamber S2, and the reservoir chamber S3, and the required compression-side damping force can always be generated stably. In this extension stroke, the flow resistance of the oil passing through the pressure side check valve 29 is very small. Therefore, the pressure in the piston side oil chamber S2 depends substantially only on the pressure of the air that pressurizes the reservoir chamber S3. It does not fluctuate due to the flow resistance of oil passing through the provided expansion side damping valve 24. Therefore, the rod-side oil chamber S1 is not in a negative pressure state, and the pressure in the rod-side oil chamber S1 does not increase immediately at the time of transition from the compression stroke to the extension stroke. The phenomenon of “damping force reduction” does not occur.

  As described above, according to the hydraulic shock absorber 1 according to the present embodiment, a required damping force can always be stably generated in both the compression stroke and the expansion stroke. That is, in the present embodiment, the pressure side check valve 29 and the extension side check valve 31 of the check valve device 25 are coupled and integrated by the valve shaft 28 and are held movably on the partition wall member 26. It functions as an ON / OFF valve for switching the flow path of oil corresponding to the volume of the piston rod 3 entering and leaving the cylinder 2 and generates almost no damping force. Therefore, the compression side and extension side damping forces are generated only by the compression side damping valve 23 and the extension side damping valve 24 provided on the piston 9, and as a result, the rod side oil chamber S1, the piston side oil chamber S2, and the reservoir It is not necessary to balance the pressure in the three chambers S3, and the required compression side damping force can always be generated stably.

  In the present embodiment, the partition member 26 fixed in the cylinder 2 is provided with a communication passage 27 that allows the reservoir chamber S3 to communicate with both the rod-side oil chamber S1 and the piston-side oil chamber S2. Since the pressure side check valve 29 is provided at the communication port 27g to the piston side oil chamber S2 of the passage 27 and the expansion side check valve 31 is provided at the communication port 27d to the rod side oil chamber S1, a check valve device provided in the cylinder 2 is provided. The structure of 25 can be simplified.

  A partition wall member 26 is provided between the piston side oil chamber S2 and the reservoir chamber S3 in the cylinder 2, and the communication passage 27 formed in the partition wall member 26 is connected to the inner cylinder 2a and the intermediate cylinder 2b of the cylinder 2. The structure of the check valve device 25 can be further simplified because the outer oil passage 19 formed therebetween and the side hole 20 formed in the inner cylinder 2a communicate with the rod-side oil chamber S1. In particular, in the present embodiment, the pressure side check valve 29 and the extension side check valve 31 of the check valve device 25 are coupled and integrated by the valve shaft 28 and are held movably on the partition wall member 26. The structure of the device 25 can be simplified.

  Further, in the present embodiment, since the extension side check valve 31 of the check valve device 25 is biased in the opening direction by the spring 33, the extension side check valve 31 is reliably opened in the compression stroke, and this extension side check valve is The pressure side check valve 29 integrated with 31 can be reliably closed, and the response and stability of the damping force are enhanced. In addition, during the extension stroke, even if the pressure in the rod side oil chamber S1 and the pressure in the piston side oil chamber S2 are balanced, the pressure side check valve 29 is securely closed and the extension side check valve 31 is surely closed. Therefore, the response and stability of the damping force are improved.

  In this embodiment, since the pressure receiving area of the pressure side chuck valve 29 of the check valve device 25 is set larger than the pressure receiving area of the expansion side chuck valve 31, the pressure side check valve 29 is securely closed during the compression stroke. The extension side check valve 31 integrated with the check valve 31 can be opened reliably, and the response and stability of the damping force are enhanced. Further, during the extension stroke, the pressure side check valve 29 is securely closed and the extension side check valve 31 is reliably opened even when the pressures of the rod side oil chamber S1 and the piston side oil chamber S2 are balanced. , Responsiveness and stability of damping force is enhanced.

  In addition, in the present embodiment, when the hydraulic shock absorber 1 is assembled, air at atmospheric pressure is enclosed in the reservoir chamber S3 instead of compressed air, so that a facility for enclosing the compressed air in the reservoir chamber S3 becomes unnecessary. Also, the effect that the equipment cost can be kept low can be obtained.

  In the above, the embodiment in which the present invention is applied to an upright hydraulic shock absorber (rear cushion) in which a cylinder is attached to the axle side and a piston rod is attached to the vehicle body side has been described. Of course, the present invention can be similarly applied to an inverted hydraulic shock absorber in which a cylinder is attached to the side and a piston rod is attached to the axle side.

  Although the present invention has been described with respect to a form in which the present invention is applied to a hydraulic shock absorber used as a rear cushion for suspending a rear wheel of a motorcycle, the present invention is not limited to a wheel of any vehicle other than a motorcycle. Needless to say, the present invention can also be applied to a hydraulic shock absorber that suspends.

DESCRIPTION OF SYMBOLS 1 Hydraulic shock absorber 2 Cylinder 2a Cylinder inner cylinder 2b Cylinder intermediate cylinder 2c Cylinder outer cylinder 3 Piston rod 4 Suspension spring 5 Axle side attachment member 6 Car body side attachment member 9 Piston 19 Outer oil path 20 Inner cylinder side hole 21 Pressure side oil passage 22 Extension side oil passage 23 Pressure side damping valve (damping force generating means)
24 Stretching side damping valve (Damping force generating means)
25 Check valve device 26 Bulkhead member 27 Communication path 27d, 27g Communication port 28 Valve shaft 29 Pressure side check valve 31 Extension side check valve 33 Spring S1 Rod side oil chamber S2 Piston side oil chamber S3 Reservoir chamber

Claims (7)

A part of the piston rod is inserted into the inside of the cylinder, the piston bound to the end of the piston rod facing the cylinder is slidably contacted with the inner periphery of the cylinder, and a damping force generating means is provided on the piston. In a hydraulic shock absorber provided with a check valve device in the cylinder for switching a flow path of oil in an amount corresponding to the volume of the piston rod entering and exiting in the cylinder,
The cylinder is a triple pipe structure with an inner cylinder and an intermediate cylinder and an outer cylinder arranged concentrically, and a space between the intermediate cylinder and the outer cylinder serves as a reservoir chamber,
The piston is slidably fitted into the inner cylinder, and the space in the inner cylinder is divided into a piston-side oil chamber and a rod-side oil chamber,
In the check valve device,
A pressure-side check valve that prevents the flow of oil from the piston-side oil chamber to the reservoir during the compression stroke, and permits the flow of oil from the reservoir chamber to the piston-side oil chamber during the extension stroke;
An extension check valve is provided that prevents the flow of oil from the rod side oil chamber to the reservoir chamber during the extension stroke and allows the oil flow from the rod side oil chamber to the reservoir chamber during the compression stroke. Features a hydraulic shock absorber. Formed in the partition member fixed in the cylinder is a communication path for communicating the reservoir chamber with both the piston-side oil chamber and the rod-side oil chamber;
2. The hydraulic pressure according to claim 1, wherein the pressure side check valve is provided at a communication port of the communication passage to the piston side oil chamber, and the extension side check valve is provided at a communication port of the rod side oil chamber. Shock absorber.   The partition member is provided between the piston-side oil chamber and the reservoir chamber in the cylinder, and the communication passage formed in the partition member is formed between the inner cylinder and the intermediate cylinder of the cylinder. 2. The hydraulic shock absorber according to claim 1, wherein the hydraulic shock absorber is communicated with the rod-side oil chamber via a formed outer oil passage and a lateral hole formed in the inner cylinder. The pressure side check valve and the extension side check valve are combined and integrated, and both are held movably on the partition member,
4. The hydraulic shock absorber according to claim 2, wherein the pressure side check valve faces the piston side oil chamber, and the extension side check valve faces the rod side oil chamber.   5. The hydraulic shock absorber according to claim 4, further comprising a spring that biases the extension side check valve in an opening direction.   6. The hydraulic shock absorber according to claim 4, wherein a pressure receiving area of the pressure side check valve is set larger than a pressure receiving area of the extension side check valve. The hydraulic shock absorber according to any one of claims 1 to 6, wherein air at atmospheric pressure is sealed in the reservoir chamber.

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