JP2012180859A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic shock absorber that effectively prevents bubbles from being formed in oil that flows from a communication passage formed in a cylinder or an outer cylinder to a reservoir, without increasing the cost of manufacture or reducing productivity.SOLUTION: An extension 25 is formed by extending a rod guide 7 in an axial direction so as to allow oil flowing from a communication passage 23 to a reservoir 4 to collide with the extension 25 to be diffused. The flow velocity of the oil flowing from the communication passage 23 to the reservoir 4 is moderately decreased, there by preventing a vortex to be caused by a jet flow and effectively preventing air bubbles from being formed due to the vortex. A component (collision member) such as a baffle plate can be eliminated to reduce manufacturing cost. Moreover, assemblability of a hydraulic shock absorber 1 is improved, and productivity is increased.

Description

  The present invention relates to a hydraulic shock absorber.

  For example, in a suspension in which a damping force generating mechanism is disposed outside a cylinder, in a uniflow type hydraulic shock absorber, the amount of oil liquid that has entered a piston rod into the cylinder during the contracting stroke is supplied from the second cylinder to the damping force generating mechanism. It is known that flows through a reservoir to a reservoir formed between the cylinder and the outer cylinder. In such a hydraulic shock absorber, the oil liquid that has passed through the damping force generation mechanism during the contraction stroke flows into the reservoir from the communication path formed in the outer cylinder, but the piston speed increases and flows into the reservoir from the communication path. When the flow rate of the oil liquid becomes high, the flow is separated from the wall surface and becomes a jet flow. As a result, bubbles are generated in the oil liquid in the reservoir, and a stable damping force may not be obtained due to cavitation.

JP-A-9-264364

  Therefore, in the invention described in Patent Document 1, the baffle plate provided above the communication path in the reservoir gradually reduces the flow rate of the oil liquid flowing into the reservoir from the communication path to prevent the generation of a jet. Thus, the generation of bubbles in the oil liquid in the reservoir is suppressed. However, since the baffle plate is an independent part (part separate from the cylinder and the outer cylinder), the manufacturing cost increases. Moreover, since assembly property deteriorates by adding a baffle plate, a man-hour increases and productivity falls.

  Therefore, the present invention has been made in view of the above circumstances, and bubbles are generated in the oil liquid flowing into the reservoir from the communication path formed in the cylinder or the outer cylinder without causing an increase in manufacturing cost and a decrease in productivity. It is an object of the present invention to provide a hydraulic shock absorber capable of effectively suppressing the operation.

  In order to solve the above-described problems, a hydraulic shock absorber according to the present invention is formed between a cylinder filled with an oil liquid, an outer cylinder provided on an outer periphery of the cylinder, and the cylinder and the outer cylinder. A reservoir that is slidably fitted into the cylinder and divides the inside of the cylinder into two cylinder chambers, one end connected to the piston and the other end outside the cylinder and the outer cylinder A hydraulic shock absorber provided with a piston rod projecting to the cylinder and a rod guide provided at one end of the cylinder and the outer cylinder, for flowing an oil liquid to the cylinder or the outer cylinder toward the reservoir A communicating path is provided, and the rod guide has an extending portion that extends in the axial direction to a position facing an opening on the reservoir side of the communicating path.

  According to the present invention, it is possible to effectively suppress the generation of bubbles in the oil liquid flowing into the reservoir from the communication path formed in the cylinder or the outer cylinder without causing an increase in manufacturing cost and a decrease in productivity. It is possible to provide a hydraulic shock absorber capable of.

It is an axial plane sectional view of the hydraulic shock absorber according to the first embodiment. It is AA sectional drawing in FIG. It is an axial plane sectional view of a hydraulic shock absorber according to a second embodiment. It is BB sectional drawing in FIG. It is an axial plane sectional view of a hydraulic shock absorber according to a third embodiment. It is CC sectional drawing in FIG. It is an axial plane sectional view of a hydraulic shock absorber according to a fourth embodiment. It is DD sectional drawing in FIG.

[First Embodiment]
A first embodiment of the present invention will be described with reference to the accompanying drawings. In addition, although 1st Embodiment demonstrates the case where it applies to the uniflow type hydraulic shock absorber 1A used for the semi-active suspension of a railway vehicle, it does not intend limiting application to this.
As shown in FIGS. 1 and 2, the hydraulic shock absorber 1 </ b> A has a double cylinder structure in which an outer cylinder 3 is provided outside the cylinder 2, and a reservoir is provided between the cylinder 2 and the outer cylinder 3. 4 is formed. A piston 5 is slidably inserted into the cylinder 2, and the piston 5 is formed between the first cylinder chamber 2 </ b> A on the left side in FIG. 1 and the second cylinder chamber 2 </ b> B on the right side in FIG. 1. It is divided into two cylinder chambers.

  As shown in FIG. 1, one end of a piston rod 6 (right end in FIG. 1) is connected to the piston 5, and the other end (left end in FIG. 1) side of the piston rod 6 is Through the first cylinder chamber 2A, the cylinder 2 and the outer cylinder 3 are inserted into a rod guide 7 attached to an end (one end) on the opening side (left side in FIG. 1) and extend to the outside of the cylinder 2. . A base valve 8 for separating the second cylinder chamber 2B and the reservoir 4 is provided at the other end of the cylinder 2 (the right end in FIG. 1). An oil liquid is sealed in the cylinder 2, and an oil liquid and a gas are sealed in the reservoir 4.

  The piston 5 has an oil passage 9 that allows the cylinder chambers 2A and 2B to communicate with each other, and a check valve 10 that allows only fluid flow from the second cylinder chamber 2B side of the oil passage 9 to the first cylinder chamber 2A side. Is provided. In addition, the base valve 8 has an oil passage 11 that allows the second cylinder chamber 2B and the reservoir 4 to communicate with each other, and a reverse flow that allows only the fluid flow from the reservoir 4 side of the oil passage 11 to the second cylinder chamber 2B side. A stop valve 12 is provided.

  A substantially cylindrical passage member 13 is fitted on the outer periphery of the cylinder 2. On the inner peripheral surface 13b of the passage member 13, there are formed two annular grooves (reference numerals omitted) that extend in the circumferential direction and are spaced apart in the axial direction (left-right direction in FIG. 1). Thereby, an annular oil passage 15 is formed between the left annular groove in FIG. 1 and the outer peripheral surface 2 a of the cylinder 2. An annular oil passage 18 is formed between the right annular groove in FIG. 1 and the outer peripheral surface 2 a of the cylinder 2. The annular oil passage 15 communicates with the first cylinder chamber 2 </ b> A via an oil passage 16 provided on the side wall of the cylinder 2. The annular oil passage 18 communicates with the second cylinder chamber 2B via an oil passage 19 provided on the side wall of the cylinder 2.

  The outer cylinder 3 and the passage member 13 are connected by connecting pipes 21 and 22 communicated with the annular oil passages 15 and 18, respectively. A damping force generating mechanism 24 is attached to the outer peripheral surface 3 a of the outer cylinder 3. In addition, the outer cylinder 3 is provided with a communication path 23 that allows the reservoir 4 and the damping force generation mechanism 24 to communicate with each other on the side where the rod guide 7 is attached (left side in FIG. 1). The first cylinder chamber 2A and the second cylinder chamber 2B are communicated with each other by the oil passage 16, the annular oil passage 15, the connection pipe 21, the damping force generation mechanism 24, the connection pipe 22, the annular oil passage 18 and the oil passage 19. A first oil / liquid passage is formed. Further, the oil passage 19, the annular oil passage 18, the connecting pipe 22, the damping force generation mechanism 24, and the communication passage 23 constitute a second oil / liquid passage through which the second cylinder chamber 2 </ b> B and the reservoir 4 are communicated. Note that the damping force generation mechanism 24 is applied as it is with the prior art (see, for example, the above-mentioned Patent Document 1) in which an expansion-side damping valve and a contraction-side damping valve are incorporated. A detailed description of the force generation mechanism 24 is omitted.

  Normally, the length of the rod guide 7 in the axial direction is L0 shown in FIG. 1, but in the hydraulic shock absorber 1A of the first embodiment, the rod guide 7 moves toward the axial base (right direction in FIG. 1). Lengthened by L1. In other words, the rod guide 7 extends in the axial direction to a position facing the opening on the reservoir 4 side of the communication path 23 formed in the outer cylinder 3. 1, the portion with the axial length L1 in FIG. 1 extended in the axial direction of the rod guide 7 is the extended portion 25, and the portion with the axial length L0 in FIG. 1 (the original portion) is the rod. Each is defined as the main part of the guide.

  In the rod guide 7, the radius of the extending portion 25 is set to be smaller by R1 than the radius of the main body portion. In other words, in the rod guide 7, the outer peripheral surface 25a of the extending portion 25, the inner peripheral surface 3b of the outer cylinder 3, and the opening on the reservoir 4 side of the communication passage 23 are R1 in the radial direction (vertical direction in FIG. 1). It is formed to face each other with a gap. Thereby, the rod guide 7 is provided with an annular step portion 26 formed by denting (reducing the diameter of) the extending portion 25 in the radial direction toward the axis.

Next, the operation of the first embodiment will be described.
During the extension stroke of the hydraulic shock absorber 1, the check valve 10 of the piston 5 is closed and the hydraulic fluid in the first cylinder chamber 2 </ b> A is pressurized as the piston 5 moves. Thus, the oil liquid flows through the oil passage 16, the annular oil passage 15, and the connection pipe 21 to the damping force generation mechanism 24, and further passes through the connection pipe 22, the annular oil passage 18, and the oil passage 19 to the second cylinder. Flows to chamber 2B. Then, the amount of oil that the piston rod 6 has withdrawn from the cylinder 2 flows from the reservoir 4 through the check valve 12 of the base valve 8 to the second cylinder chamber 2B.

  Further, during the contraction stroke of the hydraulic shock absorber 1, the check valve 10 of the piston 5 opens as the piston 5 moves, and the oil in the second cylinder chamber 2B passes through the oil passage 9 to the first cylinder chamber 2A. It flows directly. As a result, the pressure between the two cylinder chambers 2A and 2B becomes substantially the same, and no fluid flows between the connecting pipes 21 and 22 (inside the damping force generation mechanism 24). On the other hand, when the piston rod 6 enters the cylinder 2, the check valve 12 of the base valve 8 is closed and the hydraulic fluid in the cylinder 2 is pressurized. As a result, the amount of oil that has entered the piston rod 6 flows from the second cylinder chamber 2B to the damping force generation mechanism 24 through the oil passage 19, the annular oil passage 18 and the connecting pipe 22, and further through the communication passage 23. Pass through to the reservoir 4.

  In the first embodiment, the rod guide 7 is extended in the axial direction to form the extending portion 25, and the opening on the reservoir 4 side of the communication path 23 is connected to the outer peripheral surface 25 a of the extending portion 25 of the rod guide 7. By facing each other at an interval, the extending portion 25 acts in the same manner as a baffle wall (or baffle plate) that diffuses the jet flow. That is, the oil liquid flowing into the reservoir 4 from the communication path 23 in the contraction stroke collides with the front wall of the opening on the reservoir 4 side of the communication path 23 (also referred to as the outer peripheral surface 25a of the extension 25 and the wall of the step 26). However, as shown in FIG. 1 and FIG. 2, roughly divided, a flow along the outer peripheral surface 25a of the extending portion 25 and a flow wrapping around the end surface 25b side of the extending portion 25 are generated, and the speed decreases due to diffusion. . Further, the flow FL1 along the outer peripheral surface 25a of the extending portion 25 and the flow FL2 that goes around to the end surface 25b side of the extending portion 25 are roughly divided into a clockwise direction (leftward direction) and a counterclockwise direction in FIG. It occurs in the direction toward the turning direction (right direction).

Therefore, according to the hydraulic shock absorber 1A of the first embodiment, by diffusing the jet flow, the flow rate of the oil liquid flowing into the reservoir 4 from the communication path 23 is gently reduced, and the oil liquid flow is hardly separated from the wall surface. And the generation of vortices due to the jet is suppressed. As a result, the generation of bubbles due to the generation of vortices, the generation of bubbles due to the entrainment of the gas in the reservoir 4, and the dissolution of gas into the oil liquid are suppressed, and cavitation and aeration are prevented to obtain a stable damping force Is possible.
Moreover, parts (collision member) such as a baffle plate for colliding the oil liquid flowing into the reservoir 4 from the communication path 23 can be eliminated. Thereby, the manufacturing cost and the man-hour for attaching the said part can be reduced. Moreover, the assembly | attachment property of the hydraulic shock absorber 1 improves and productivity can be improved. In addition, problems caused by damage or dropout of components (collision members) are eliminated, and the reliability of the apparatus can be improved.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to the accompanying drawings. In addition, the same name and code | symbol are provided to the structure which is the same as that of 1st Embodiment mentioned above, or equivalent. In addition, for the sake of brevity, descriptions overlapping with the first embodiment are omitted.
As described above, in the first embodiment, the rod guide 7 is extended in the axial direction to form the extended portion 25, and the extended portion 25 is uniformly recessed in the radial direction toward the axial line (reduced diameter). By forming the annular step portion 26 and causing the oil liquid flowing into the reservoir 4 from the communication passage 23 to collide with the outer peripheral surface 25a (the wall of the step portion 26) of the extension portion 25 during the contraction stroke, The hydraulic shock absorber 1 </ b> A is configured to reduce the flow rate of the oil liquid flowing into the reservoir 4 from 23. On the other hand, in the hydraulic shock absorber 1B of the second embodiment, instead of forming the annular step portion 26 in the rod guide 7, as shown in FIG. 3 and FIG. A groove 28 facing the opening on the reservoir 4 side is provided.

  As shown in FIG. 4, the groove 28 has a length L1 in the axial direction (left-right direction in FIG. 3) with respect to the end face 25 b of the extension 25. Further, the groove 28 has a surface facing the opening on the reservoir 4 side of the communication passage 23 formed by a semi-inner cylindrical surface. And in 2nd Embodiment, this groove part 28 acts equivalent to a baffle wall (or baffle plate). That is, the oil liquid that flows into the reservoir 4 from the communication path 23 in the contraction stroke collides with the wall of the groove 28 on the front surface of the opening on the reservoir 4 side of the communication path 23, and the flow direction is changed as shown in FIG. The direction is changed to the axial direction (right direction in FIG. 3).

  As a result, the speed of the oil liquid flowing into the reservoir 4 from the communication path 23 decreases, and the flow of the oil liquid becomes difficult to separate from the wall surface, and the generation of vortices due to the jet flow is suppressed. As a result, the generation of bubbles due to the generation of vortices and the dissolution of gas into the oil liquid are suppressed, and cavitation and aeration can be prevented and a stable damping force can be obtained. And in the hydraulic shock absorber 1B of 2nd Embodiment, the effect equivalent to 1 A of hydraulic shock absorbers of 1st Embodiment mentioned above can be acquired. In the second embodiment, the extension portion 25 is provided with the groove portion 28 facing the opening on the reservoir 4 side of the communication passage 23. However, the configuration is not limited thereto, and the side surface of the extension portion of the rod guide 7 is directed toward the center side. Then, the first hole may be opened, and the second hole may be opened in the axial direction of the rod guide 7 so as to penetrate the center side of the first hole. Further, a passage may be formed by machining obliquely from the side surface of the extended portion of the rod guide 7 toward the surface of the rod guide 7 facing the reservoir 4.

[Third Embodiment]
A third embodiment of the present invention will be described with reference to the accompanying drawings. In addition, the same name and code | symbol are provided to the structure same as the 1st and 2nd embodiment mentioned above or an equivalent. Further, for the sake of brevity, the description overlapping with the first and second embodiments is omitted.
As described above, in the first embodiment, the outer cylinder 3 is provided with the communication passage 23 that allows the reservoir 4 and the damping force generation mechanism 24 to communicate with each other, and the rod guide 7 extends in the axial direction to extend the extension portion 25. And an annular stepped portion 26 is formed by uniformly denting (reducing the diameter of) the extending portion 25 in the radial direction toward the axis, and flows into the reservoir 4 from the communication path 23 during the contraction stroke. The hydraulic shock absorber 1A is configured to reduce the flow velocity of the oil flowing into the reservoir 4 from the communication path 23 by colliding the oil with the outer peripheral surface 25a of the extending portion 25 (the wall of the step portion 26). Yes.

  On the other hand, in the third embodiment, the cylinder 2 is provided with a communication passage 23 that allows the first cylinder chamber 2A and the reservoir 4 to communicate with each other, and only the outer peripheral portion of the rod guide 7 is axially moved (rightward in FIG. 5). The hydraulic shock absorber 1 </ b> C is configured to extend in the direction) to form an annular extending portion 25. In other words, in 3rd Embodiment, the extension part 25 is provided in the part (annular space part) in which the step part 26 in 1st Embodiment is provided, and the extension part 25 in 1st Embodiment. The part where is formed is a space. And the cyclic | annular extension part 25 in 3rd Embodiment acts equivalent to the baffle wall (or baffle plate) which diffuses a jet flow.

  That is, in the third embodiment, the oil liquid flowing into the reservoir 4 from the communication path 23 during the extension stroke is caused by the wall of the extension part 25 (the inner peripheral surface of the extension part 25) on the front side of the opening of the communication path 23 on the reservoir 4 side. 25c), as shown in FIG. 5 and FIG. 6, a flow FL1 along the inner peripheral surface 25c of the extension portion 25 and a flow FL2 that wraps around the end surface 25b side of the extension portion 25 are generated. The speed is reduced. Furthermore, the flow FL1 along the inner peripheral surface 25c of the extension part 25 and the flow FL2 that goes around to the end face 25b side of the extension part 25 are roughly divided from the direction toward the clockwise direction (left direction) in FIG. It occurs in a direction toward the clockwise direction (right direction). In the hydraulic shock absorber 1C of the third embodiment, the same operational effects as those of the hydraulic shock absorbers 1A and 1B of the first and second embodiments described above can be obtained.

[Fourth Embodiment]
A fourth embodiment of the present invention will be described with reference to the accompanying drawings. In addition, the same name and code | symbol are provided to the structure which is the same as that of 1st thru | or 3rd embodiment mentioned above, or equivalent. Further, for the sake of brevity, the description overlapping with the first to third embodiments is omitted.
As described above, in the third embodiment, only the outer peripheral portion of the rod guide 7 extends in the axial direction to form the annular extending portion 25, and the oil liquid flowing into the reservoir 4 from the communication path 23 during the extending stroke is extended. The hydraulic shock absorber 1 </ b> C is configured to reduce the flow rate of the oil liquid flowing into the reservoir 4 from the communication path 23 by colliding with the inner peripheral surface 25 c of the outlet portion 25. On the other hand, in the fourth embodiment, the portion of the rod guide 7 facing the reservoir 4 is extended in the axial direction to form an annular extending portion 25, and the reservoir of the communication passage 23 is formed on the inner peripheral portion of the extending portion 25. The hydraulic shock absorber 1D was configured by providing a groove 28 facing the opening on the 4 side.

  And in 4th Embodiment, this groove part 28 acts equivalent to a baffle wall (or baffle plate). That is, the oil liquid flowing into the reservoir 4 from the communication path 23 during the extension stroke collides with the wall of the groove 28 on the front surface of the opening of the communication path 23 on the reservoir 4 side, and the flow direction is an axis line as shown in FIG. The direction is changed (right direction in FIG. 7). As a result, the speed of the oil liquid flowing into the reservoir 4 from the communication path 23 decreases, and the flow of the oil liquid becomes difficult to separate from the wall surface, and the generation of vortices due to the jet flow is suppressed. As a result, in the hydraulic shock absorber 1D of the fourth embodiment, it is possible to obtain the same effects as the hydraulic shock absorbers 1A to 1C of the first to third embodiments described above.

1A, 1B, 1C, 1D Hydraulic shock absorber, 2 cylinders (2a outer peripheral surface, 2b inner peripheral surface, 2A first cylinder chamber, 2B second cylinder chamber), 3 outer cylinder (3a outer peripheral surface, 2b inner peripheral surface), 4 Reservoir, 5 Piston, 6 Piston rod, 7 Rod guide, 23 Communication path, 24 Damping force generation mechanism, 25 Extension part (25a outer peripheral surface, 25b end surface, 25c inner peripheral surface), 26 step part, 28 groove part

Claims (2)

A cylinder filled with oil, an outer cylinder provided on the outer periphery of the cylinder, a reservoir formed between the cylinder and the outer cylinder, and slidably inserted into the cylinder; A piston for dividing the inside of the cylinder into two cylinder chambers; a piston rod having one end connected to the piston and the other end protruding outside the cylinder and the outer cylinder; and one end of the cylinder and the outer cylinder A rod guide provided to the cylinder or the outer cylinder, provided with a communication path for flowing an oil liquid toward the reservoir in the cylinder or the outer cylinder, the rod guide being connected to the reservoir side of the communication path A hydraulic shock absorber having an extending portion extending in the axial direction to a position facing the opening of the hydraulic shock absorber. 2. The hydraulic shock absorber according to claim 1, wherein the extending portion has a step portion formed by being recessed in a cylinder radial direction with respect to an opening on a reservoir side of the communication path.