JP2018017335A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorber that can tune damp force property in a minute low-speed range.SOLUTION: A shock absorber includes: a cylinder 1; an outer tube 2 disposed on an outer peripheral side of the cylinder 1 so as to be slidable relative to the cylinder 1; and a plurality of bushing 3, 4 disposed in an axial direction in an inner periphery of the outer tube 2 and coming into slide contact with an outer periphery of the cylinder 1, where slide property of a first bushing 3 that is at least one of the plurality of bushing 3, 4 is different from that of a second bushing 4 that is at least one of the other bushing.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a shock absorber.

  A strut-type shock absorber used as a vehicle wheel positioning column is usually interposed in an inclined posture between a wheel and a vehicle body. Therefore, a bending moment is always applied to the strut type shock absorber, and the strut type shock absorber tends to increase the diameter of the rod so as to counter the bending moment.

  However, when the rod diameter is increased in this manner, the pressure receiving area on the side of the extension side chamber of the piston is reduced. When the rigidity against the bending moment is increased, it is difficult to increase the damping force during the extension stroke of the strut type shock absorber.

  Therefore, the shock absorber body equipped with a cylinder and a rod that can be projected and retracted in the cylinder is placed upside down, and is slidably inserted into the outer tube connected to the axle so that the bending moment is also received by the cylinder and the outer tube. An inverted strut type shock absorber has been developed. In this way, the bending rigidity can be ensured without increasing the rod diameter, the pressure receiving area in the piston is ensured, and the generation of a high damping force and the increase in the outer diameter can be avoided.

  Further, in this inverted strut type shock absorber, a pair of cylindrical bushes are attached to the inner periphery of the outer tube, and the inner peripheral surface of the bush is slidably contacted with the outer periphery of the cylinder to guide the axial movement of the outer tube. doing. (For example, refer to Patent Document 1).

  Here, the shock absorber body includes a cylinder, a rod inserted in the cylinder so as to be movable in the axial direction, a piston connected to a tip of the rod and partitioning the inside of the cylinder into two chambers, and the two A passage that communicates with the chamber and a valve that provides resistance to the flow of liquid that passes through the passage are configured.

  Such a shock absorber body exerts a damping force by applying a resistance to the flow of liquid flowing between the two chambers through the passage when expanding and contracting, creating a differential pressure between the two chambers, Suppresses shaking.

  However, when the shock absorber expands and contracts in a very low speed region, the amount of liquid flowing back and forth between the two chambers is small, and the shock absorber exerts a damping force by the valve, and is provided on the inner periphery of the outer tube. A damping force is also exerted by a frictional force generated between the inner periphery of the pair of bushes and the outer periphery of the cylinder. When the shock absorber expands and contracts in a very low speed region, the damping force due to the valve becomes very small, so that the damping force due to the friction force occupies most of the total damping force.

JP 2004-301161 A

  However, in the conventional shock absorber, the frictional force generated between the inner periphery of the pair of bushes provided on the inner periphery of the outer tube and the outer periphery of the cylinder could not be tuned. Was not allowed to have a width.

  Therefore, an object of the present invention is to provide a shock absorber that can tune damping force characteristics in a very low speed region by a bush provided on the inner periphery of the outer tube.

  Means for solving the problem includes an inner cylinder, an outer cylinder disposed on the outer peripheral side of the inner cylinder so as to be slidable with respect to the inner cylinder, and an axially disposed inner periphery of the outer cylinder. A plurality of bushes slidably in contact with the outer periphery of the inner cylinder, wherein a sliding characteristic of a first bush that is at least one bush of the plurality of bushes is different from a second bush that is at least one bush of the other bushes; Features.

  The material of at least the inner peripheral surface of the first bush may be different from the material of at least the inner peripheral surface of the second bush. According to this configuration, bushes having different inner peripheral surfaces that are in sliding contact with the inner cylinder are arranged in the axial direction, so that the sliding characteristics of the bushes can be tuned by selecting the material.

  The first bush is disposed closer to the atmosphere of the outer cylinder than the second bush, and the material of at least the inner peripheral surface of the first bush is more excellent in wear resistance than the material of the second bush. The material of at least the inner peripheral surface of the second bush may be a material having a lower friction coefficient than the material of the first bush. According to this configuration, when a bending moment acts on the outer cylinder and the inner cylinder, the first bush made of a material having excellent wear resistance is provided on the atmosphere side of the outer cylinder that receives a larger radial load. A second bushing having a low coefficient of friction is provided on the bottom side of the outer cylinder that is not subjected to a radial load. Thereby, since the improvement of the slidability at the time of expansion / contraction of the shock absorber and the wear resistance of the bush can be achieved, the ride quality of the vehicle can be improved while improving the product life of the shock absorber.

  Further, the axial length of the first bush may be longer than the axial length of the second bush. According to this configuration, when the bending moment acts on the outer cylinder and the inner cylinder, the axial length of the first bush disposed on the atmosphere side of the outer cylinder that receives a larger radial load becomes longer. Surface pressure acting between the cylinders can be reduced, and deterioration of the first bush can be suppressed.

  According to the shock absorber of the present invention, the damping force characteristic in the very low speed region of the shock absorber can be obtained by combining the sliding characteristics of a plurality of bushes that are arranged in the axial direction on the inner periphery of the outer cylinder and are in sliding contact with the outer periphery of the inner cylinder. Can be tuned.

It is a longitudinal cross-sectional view of the buffer which concerns on this Embodiment.

  Hereinafter, an embodiment in which the present invention is embodied in an automobile strut type shock absorber will be described with reference to the drawings.

  As shown in FIG. 1, the shock absorber D according to the present embodiment includes a cylinder 1 that is an inner cylinder and an outer tube 2 that is an outer cylinder that is slidably disposed with respect to the cylinder 1 on the outer peripheral side of the cylinder 1. And a plurality of bushes 3 and 4 that are arranged in the axial direction on the inner periphery of the outer tube 2 and are in sliding contact with the outer periphery of the cylinder 1.

  The configuration of the shock absorber D will be described in detail. As shown in FIG. 1, the shock absorber D is inserted into the outer tube 2 with a bottomed cylindrical outer tube 2 connected to the vehicle axle side. An inverted shock absorber body 10 is provided. The shock absorber main body 10 includes a cylinder 1 connected to the vehicle body side, and a rod 5 having one end movably inserted in the cylinder 1 in the axial direction and the other end connected to the bottom of the outer tube. Is connected to the vehicle body.

  A free piston 11 is movably inserted into the cylinder 1, and the free piston 11 partitions the inside of the cylinder 1 into a liquid chamber R and a gas chamber G.

  Further, a piston 6 slidably contacting the inner peripheral surface of the cylinder 1 is connected to one end, which is the upper end of the rod 5 in FIG. 1, and the piston 6 is divided into two chambers, an expansion chamber R1 and a pressure chamber R2. It is divided into.

  The liquid chamber R is filled with a liquid such as hydraulic oil, and the gas chamber G is filled with an inert gas such as nitrogen at a predetermined pressure.

  In addition, the piston 6 according to the present embodiment is provided with a plurality of passages 6a communicating the extension side chamber R1 and the compression side chamber R2. Further, an extension side leaf valve 6b is laminated on the extension side chamber R1 side of the piston 6, and a pressure side leaf valve 6c is laminated on the pressure side chamber R2 side of the piston 6.

  As shown in FIG. 1, the pressure side leaf valve 6c is a plurality of annular plates stacked on the extension side chamber R1 side of the piston 6, and closes the outlet end of the pressure side passage which is the inner half of the plurality of passages 6a. To do. When the pressure difference between the pressure side chamber R2 and the expansion side chamber R1 exceeds the valve opening pressure of the pressure side leaf valve 6c when the shock absorber D is contracted, the pressure side leaf valve 6c is bent and opened on the outer peripheral side, and the pressure side chamber R2 is opened. Is communicated with the extension side chamber R1. Thereby, the pressure side leaf valve 6c allows the flow of the liquid from the pressure side chamber R2 to the extension side chamber R1 when the shock absorber D contracts, and gives resistance to this flow.

  Although not shown, the expansion side leaf valve 6b is a plurality of annular plates stacked on the pressure side chamber R2 side of the piston 6, and is the expansion side that is the remaining half of the plurality of passages 6a excluding the internal pressure side passage. Close the exit end of the passage. If the differential pressure between the expansion side chamber R1 and the compression side chamber R2 exceeds the valve opening pressure of the expansion side leaf valve 6b when the shock absorber D is extended, the expansion side leaf valve 6b is bent and opened on the outer peripheral side. The side chamber R1 communicates with the compression side chamber R2. Thereby, the extension side leaf valve 6b allows the flow of the liquid from the extension side chamber R1 to the compression side chamber R2 when the shock absorber D is extended, and provides resistance to this flow.

  Therefore, when the shock absorber D expands or contracts, resistance is given to the liquid that moves back and forth between the expansion side chamber R1 and the compression side chamber R2 via the passage 6a by the expansion side leaf valve 6b or the compression side leaf valve 6c. To do. In addition, you may employ | adopt valves other than leaf valve 6b, 6c as a valve which gives resistance to the flow of the liquid which passes the channel | path 6a.

  In the present embodiment, since the free piston 11 moves up and down in the cylinder 1, the volume of the gas chamber G changes as the free piston 11 moves. Therefore, the volume change in the cylinder 1 due to the rod 5 entering and leaving the cylinder 1 can be compensated by the volume change of the gas chamber G.

  Therefore, in the case of the present embodiment, the shock absorber body 10 is a single cylinder type that compensates for the volume change in the cylinder 1 due to the rod 5 entering and exiting the cylinder 1 by the change in the volume of the gas chamber G. Yes. However, the shock absorber body 10 includes an inner tube into which the piston 6 is slidably inserted into the cylinder 1, and forms a reservoir that compensates for a volume change in the cylinder 1 between the cylinder 1 and the inner tube. It may be a double cylinder type.

  A spring seat 17 on which a suspension spring (not shown) is seated is fixed to the upper outer periphery of the outer tube 2 according to the present embodiment, and a bracket 12 that can be connected to an axle is fixed to the outer periphery of the lower end. In addition, an annular first bush 3 and a second bush 4 are aligned and fixed in the axial direction on the inner periphery of the outer tube 2.

  The first bush 3 is disposed at the upper side in FIG. 1 that is the atmosphere side, and the second bush 4 is disposed at the lower side in FIG. 1 that is the bottom side of the outer tube 2. These bushes 3 and 4 are in sliding contact with the outer periphery of the cylinder 1 inserted into the outer tube 2 to guide the axial movement of the outer tube 2 when the shock absorber D is expanded and contracted.

  In addition, a lubricant L such as grease is filled in the annular gap between the outer tube 2 and the cylinder 1 and between the first bush 3 and the second bush 4. Lubricating between 3 and 4 and the cylinder 1.

  Further, an O-ring 13 is mounted as a seal directly below the second bush 4 disposed on the inner circumference of the outer tube 2 on the lower side, and the axial direction of the O-ring 13 is directly below the O-ring 13. A cylindrical fixing ring 14 that restricts the downward movement is attached. Thereby, the lubricant L filled between the first bush 3 and the second bush 4 leaks to the bottom side of the outer tube 2 through the sliding gap between the inner periphery of the second bush 4 and the outer periphery of the cylinder 1. It can be sealed off by the O-ring 13.

  Further, a seal case 16 having a seal member 15 slidably contacting the outer periphery of the cylinder 1 is provided at the upper end opening in FIG. 1 of the outer tube 2, and seals the annular gap and the outer tube 2.

  Moreover, the 1st bush 3 and the 2nd bush 4 which concern on this Embodiment are formed with the material from which a sliding characteristic differs, respectively. Here, the sliding characteristics refer to both friction characteristics and wear characteristics when the bush moves in the axial direction in contact with the cylinder.

  Here, in the very low speed region of the shock absorber D, since the flow rate of the liquid flowing back and forth between the expansion side chamber R1 and the compression side chamber R2 is small, the damping force by the expansion side leaf valve 6b and the compression side leaf valve 6c is very small. The damping force due to the friction force occupies most of the total damping force.

  Therefore, if the frictional force generated between the first bush 3 and the second bush 4 is tuned to an arbitrary magnitude by selecting the material of the first bush 3 and the second bush 4, the damping characteristics of the shock absorber D in the very low speed range will be described. The targeted damping force can be obtained.

  Thus, depending on the combination of the materials of the first bush 3 and the second bush 4, the durability of the bushes 3 and 4 and the frictional force generated between the bushes 3 and 4 and the cylinder 1 when the shock absorber D is expanded and contracted. Can be tuned.

  In the present embodiment, the wear characteristics of the bushes 3 and 4 can also be changed for each bush 3 and 4, so that the durability required for each bush 3 and 4 depends on the arrangement and use of the bushes 3 and 4. Even in different cases, only one bushing that requires durability can be formed of a material having excellent wear resistance. Therefore, the other bush is not constrained by the wear characteristics required for one bush.

  Therefore, in the present embodiment, the degree of freedom in selecting the material of the bush is improved as compared with the case where all the bushes are formed of the same material.

  In the present embodiment, the first bush 3 and the second bush 4 are different in the overall material of the bushes 3, 4, but the material of the inner peripheral surface that is the sliding contact surface with the outer periphery of the cylinder 1. Only may be different.

  Next, a specific example of a combination of materials of the first bush 3 and the second bush 4 will be described.

  In general, when the frictional force generated between the bush and the cylinder provided on the inner circumference of the outer tube when the shock absorber expands and contracts is high, friction resistance acts at the beginning of rod movement in the very low speed region of the shock absorber. And since the riding comfort of a vehicle will deteriorate, it is preferable that the bush has a low friction coefficient. In addition, in a shock absorber in which a bending moment acts on the outer tube and the cylinder, such as a strut type shock absorber, since a large radial load acts on the bush, the bush should have better wear resistance. preferable.

  However, when the first bush 3 and the second bush 4 are formed of the same sliding characteristic material as in the prior art, the first bushing 3 is attempted to achieve both low friction and excellent sliding characteristics. The second bush 4 must be formed of a material having a low friction coefficient and excellent wear resistance, and the degree of freedom in selecting the material is low.

  Therefore, the first bush 3 disposed on the atmosphere side that receives a larger radial load when a bending moment acts on the cylinder 1 and the outer tube 2 is formed of a material having higher wear resistance than the second bush 4. It is conceivable to form the second bush 4 disposed on the bottom side where the radial load is less likely to act than the atmosphere side with a material having a lower friction coefficient than the first bush 3.

  In this case, a material having excellent wear resistance may be selected for the first bush 3 and a material having a low friction coefficient may be selected for the second bush 4. The degree of freedom is high, and it is possible to easily improve the slidability of the outer tube 2 and the wear resistance of the bush.

  Therefore, according to the selection of the material, the product life of the shock absorber D and the ride comfort of the vehicle are improved.

  Moreover, in this Embodiment, the axial direction length of the 1st bush 3 arrange | positioned in the upper direction in FIG. 1 used as the atmosphere side is the axis | shaft of the 2nd bush 4 arrange | positioned in FIG. It is longer than the direction length.

  Thereby, when a bending moment acts on the cylinder 1 and the outer tube 2, the surface pressure with the cylinder 1 can be reduced by increasing the total length of the first bush 3 on the atmosphere side that receives a larger radial load. Therefore, it is possible to suppress the deformation and deterioration of the first bush 3 and further improve the product life of the shock absorber D.

  Moreover, as a material provided with the material excellent in abrasion resistance used for the 1st bush 3, if it is a material excellent in abrasion resistance with respect to the cylinder 1 rather than the 2nd bush 4, it will not specifically limit, For example, metal etc. It may be formed.

  The material having a low friction coefficient used for the second bush 4 is not particularly limited as long as the material has a lower friction coefficient than that of the first bush 4. For example, fluororesin such as PTFE, polyacetal, polyphenylene sulfide, super A solid lubricant excellent in self-lubricating property such as a synthetic resin such as high molecular weight polyethylene is particularly preferable. When the second bush 4 is formed of a material having excellent self-lubricating properties, the outer tube 2 slides smoothly even when the lubricant L is not sufficiently supplied between the second bush 4 and the cylinder 1. To do.

  As described above, the first bush 3 is formed of a material having excellent wear resistance, and the second bush 4 is formed of a material having a low friction coefficient, which is an example of the present embodiment. The material of the bush 3 and the second bush 4 is not limited to this.

  For example, the material of at least the inner peripheral surface of the first bush 3 may be formed of a material that has better wear resistance than the second bush 4. In this case, the first bush 3 that receives a larger radial load when a bending moment acts on the cylinder 1 and the outer tube 2 is formed of a material having excellent wear resistance. Will improve.

  Alternatively, at least the inner peripheral surface of the second bush 4 may be formed of a material having a lower friction coefficient than that of the first bush 3. In this way, the sliding performance of the outer tube 2 during expansion / contraction of the shock absorber D is improved, so that the riding comfort of the vehicle is improved.

  In the present embodiment, the number of bushes is two, but the number of bushes may be three or more. When the number of bushes is three or more, the combination of bush materials increases as the number of bushes increases, so that friction generated between the bushes 3 and 4 and the cylinder 1 during expansion and contraction of the shock absorber D is increased. The degree of freedom of force tuning is further improved.

  Even if the number of bushes is three or more, it is not necessary that the materials of the bushes are all different. For example, if at least one bush of a plurality of bushes is a first bush and the other bushes excluding the first bush are second bushes, the material of the first bush and the second bush may be different from each other. Good. Specifically, when the number of bushes is three or more, bushes of different materials may be provided alternately, or only one of the plurality of bushes may be a bush of different materials.

  However, when the number of bushes is two, the number of parts is small as compared with the case where there are three or more bushes, so that the labor for assembling is reduced.

  In the present embodiment, the shock absorber D has been described as an automobile strut-type shock absorber. However, the shock absorber D has an inner tube 1 as an inner cylinder 1 and an outer tube 2 as an outer cylinder 2 for straddle-type vehicles. The front fork may be used.

  Although the preferred embodiments of the present invention have been described in detail above, it is obvious that modifications, changes and modifications can be made without departing from the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Cylinder (inner cylinder), 2 ... Outer tube (outer cylinder), 3 ... 1st bush, 4 ... 2nd bush, D ... Shock absorber

Claims (4)

A shock absorber that includes an inner cylinder and an outer cylinder that is slidably disposed with respect to the inner cylinder on the outer peripheral side of the inner cylinder, and that exhibits a damping force during expansion and contraction.
A plurality of bushes arranged in the axial direction on the inner periphery of the outer cylinder and in sliding contact with the outer periphery of the inner cylinder;
The shock absorber according to claim 1, wherein a sliding characteristic of a first bush which is at least one bush of the plurality of bushes is different from that of a second bush which is at least one bush of another bush.   The shock absorber according to claim 1, wherein a material of at least an inner peripheral surface of the first bush is different from a material of at least an inner peripheral surface of the second bush. The first bush is disposed closer to the atmosphere of the outer cylinder than the second bush,
The material of at least the inner peripheral surface of the first bushing is a material having higher wear resistance than the material of the second bushing, and the material of at least the inner peripheral surface of the second bushing is made of the material of the first bushing. The shock absorber according to claim 2, wherein the shock absorber is made of a material having a low friction coefficient. The shock absorber according to claim 3, wherein an axial length of the first bush is longer than an axial length of the second bush.