JPH06103053B2 - Hydraulic shock absorber - Google Patents

Description

The present invention relates to a hydraulic shock absorber, and more particularly to a hydraulic shock absorber suitable for use as a vehicle shock absorber.

[Prior Art and Problems] Generally, in shock absorbers used for suspensions for passengers, trucks, etc., a cylinder is coaxially arranged inside a cylindrical outer shell, and the cylinder operates inside the cylinder and between the cylinder and the outer shell. Oil is stored. The piston rod extending in and out of the cylinder is guided slidably in the axial direction by a rod guide provided at one end of the cylinder, and the piston that is in sliding contact with the inner peripheral surface of the cylinder is provided at the inner end of the piston rod. To be The piston defines the interior of the cylinder into two liquid chambers. A base valve is provided in the liquid chamber on the other end side of the cylinder.

The piston is provided with an orifice that connects the two liquid chambers in the cylinder. When the piston rod vibrates in the axial direction with respect to the cylinder, the vibration is damped by the flow resistance of the hydraulic oil passing through the orifice of the piston, the resistance when the base valve is pushed open, and the like.

In such a conventional shock absorber, the frictional heat generated on the sliding surface due to the sliding frictional resistance between the outer peripheral portion of the piston and the inner surface of the cylinder has various adverse effects. For example, this frictional heat causes expansion of the piston, eliminating the gap between the outer peripheral surface of the piston and the inner surface of the cylinder,
It was causing galling and damage. Further, when the piston is provided with a piston band, this frictional heat may cause deterioration of the material of the piston band. Therefore, in order to eliminate the defect due to the expansion of the piston, an attempt has been made to increase the gap between the outer peripheral portion of the piston and the inner surface of the cylinder, but the hydraulic oil that should pass through the orifice of the piston to attenuate the vibration is This causes leakage from this gap, which causes a drawback that sufficient damping force cannot be obtained.

Moreover, when the magnitude of the vibration to be absorbed changes like the shock absorber for automobiles, the friction heat also changes, and the size of the gap changes accordingly. For this reason, the amount of hydraulic oil leaking from this gap also fluctuates, resulting in the disadvantage that only an unstable damping force can be obtained.

On the other hand, in the conventional shock absorber, the piston and the inner surface of the cylinder partially contact and slide, but there is not enough oil in the vicinity of this contact surface and the frictional force is high.
In such a shock absorber having a high friction at the sliding portion, the frictional heat is increased and the delicate damping force control cannot be performed at the orifice in some cases. Further, since there is not enough oil, the frictional force is likely to change due to long-term use, and the damping force changes.

Therefore, the damping force is stable even during long use, and
There has been a demand for a hydraulic shock absorber that can be controlled by an orifice.

[Means for solving problems]

As a means for solving the above problems, the present invention guides a piston rod extending inside and outside a cylinder so as to be slidable in an axial direction by a rod guide provided at one end of the cylinder, and In a hydraulic shock absorber provided with a piston at an end portion in sliding contact with an inner peripheral surface of the cylinder, the sliding surface of the piston with respect to the cylinder and / or the sliding surface of the rod guide with respect to the piston rod is A hydraulic shock absorber provided with a groove extending axially from one or both ends of a moving surface and terminating at an axially intermediate position of the sliding surface.

Further, according to the present invention, a piston rod extending inside and outside the cylinder is guided slidably in an axial direction by a rod guide provided at one end of the cylinder, and an inner peripheral surface of the cylinder is provided at an inner end portion of the piston rod. In a hydraulic shock absorber provided with a piston in sliding contact with the sliding surface of the piston with respect to the cylinder and / or the sliding surface of the rod guide with respect to the piston rod, axial direction from one or both ends of the sliding surface. And a chamfered portion is provided at the axial end of the sliding surface, and a hydraulic shock absorber is provided.

[Work]

According to the above-mentioned means according to the present invention, since the groove extends axially from one end or both ends of the sliding surface to the axially intermediate position of the sliding surface, the working oil in the cylinder passes through the groove and slides on the sliding surface. To be easily replenished. Therefore, sufficient lubrication can be performed, and the heat generated on the sliding surface can easily escape to the outside of the sliding surface in the axial direction by the hydraulic fluid in the groove. Moreover,
Since the piston reciprocates, new hydraulic fluid is always supplied into the concave groove. Therefore, the thermal expansion of the piston or the piston band is suppressed, so that the gap between the outer peripheral portion of the piston and the inner surface of the cylinder can be reduced.

In this way, it is possible to achieve low friction heat and stable damping force by sufficient lubrication.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a shock absorber for a suspension of an automobile.
Referring to this figure, the shock absorber includes a cylindrical outer shell 11, and a cylinder 12 is coaxially arranged inside the outer shell 11. Hydraulic oil is contained inside the cylinder 12 and between the cylinder 12 and the outer shell 11.

The piston rod 13 extending in and out of the cylinder 12 is slidably guided in the axial direction of a rod guide 14 provided at one end of the cylinder 12. An oil seal member 15 is provided on the axially outer side of the rod guide 14. A base valve 16 is provided in the other end of the cylinder 12.

A piston 17 is provided at the inner end of the piston rod 13 and is in sliding contact with the inner peripheral surface of the cylinder 12. A piston 17 defines two liquid chambers inside the cylinder 12.

Referring to FIG. 2 and FIG. 3, in this embodiment, the piston 17 is provided with a metal piston body 18 and a resin exterior member 19 mounted on the outer periphery of the piston body 18, The outer peripheral surface of the outer cover member 19 is formed so as to slide on the inner peripheral surface of the cylinder 12. Piston body 18
Is an orifice 20 that connects the two liquid chambers in the cylinder 12.
Is provided. When the piston 17 and the piston rod 13 vibrate in the axial direction with respect to the cylinder 12, the piston
The vibration is attenuated by the flow resistance of the hydraulic oil passing through the orifice 20 of 17 and the resistance when the base valve 16 is pushed open.

On the outer peripheral surface of the outer cover member 19 of the piston 17, that is, on the sliding surface, a plurality of (in this case, eight) concave grooves 21, 22 are provided extending from one end and the other end in the axial direction, respectively. The concave grooves 21 and 22 are terminated at the axially intermediate position of the sliding surface. FIG. 4 is a partially developed view of the sliding surface of the jacket member 19 of the piston 17. As is clear from FIG. 4, the concave groove 21 opening at one end of the sliding surface and the concave groove 22 opening at the other end are located at positions facing each other in the axial direction.
No. 2 terminates at the axially intermediate position of the sliding surface and does not communicate with each other, so the sealing performance of the sliding surface is not impaired.

5 and 6 are partially developed views showing another mode of the concave grooves 21, 22 provided on the sliding surface of the piston 17.

In the example of FIG. 5, the concave grooves 21 opening at one end in the axial direction and the concave grooves 22 opening at the other end are alternately arranged in the circumferential direction. In the case of this example, the grooves 21 and 22 do not communicate with each other even if the grooves 21 and 22 have a length of more than half the axial width of the piston 17, so that the grooves 21 and 22 can be made longer than in the example of FIG. .

In the example of FIG. 6, concave grooves 21 and 22 having substantially sinusoidal contours are alternately arranged continuously in the circumferential direction on one end side and the other end side of the sliding surface of the piston 17, respectively. In the case of this example, it is possible to increase the axial length of the concave grooves 21 and 22 as in the example of FIG. Moreover, since the areas of the concave grooves 21 and 22 are increased, the contact area between the piston 17 and the cylinder 12 is reduced, the sliding resistance is reduced, and the heat dissipation of the heat generated on the sliding surface is improved.

The cross-sectional shape of the concave grooves 21 and 22 may be formed in a gentle taper shape from the end of the sliding surface toward the intermediate position in the axial direction as shown in FIG. Especially, the bottom of the groove 21
When it is formed substantially parallel to the axial direction of, the concave grooves 21 and 22 and the sliding surface of the piston 17 can be smoothly connected by the arcuate convex surface 23 as shown in an enlarged view in FIG. preferable.
With this configuration, the oil drawing effect is extremely high,
The low friction property and the decrease in the temperature of the sliding surface are achieved, and the extremely stable damping force is obtained in combination with the suppression of the thermal expansion. Moreover, the depth of the groove can be reduced, and the above effect can be obtained with less oil.

Although not particularly limited, the depth of the concave grooves 21 and 22 is 0.001 at maximum.
˜0.5 mm, preferably 0.01 to 0.2 mm.

Referring again to FIG. 1, the rod guide 14 is a cylinder.
The guide body 24 is fixed to the outer shell 12 and the outer shell 11, and the bush 25 fixed to the inner surface of the guide body 24.The piston rod 13 is slidably guided to the inner peripheral surface of the bush 25. There is.

On the inner peripheral surface of the bush 25, that is, on the sliding surface, a plurality of recessed grooves extending in the axial direction from one end and the other end in the axial direction, respectively.
26,27 are provided. Each groove 26, 27 terminates at an axially intermediate position of the sliding surface. The recessed grooves 26, 27 provided in the bush 25 may have the same form as the recessed grooves 21, 22 of the piston 17.

In the shock absorber having the above structure, the wear heat generated on the inner peripheral surface of the cylinder 12 is the inner peripheral surface of the rod guide 14, and the wear heat generated in the concave grooves 21 and 22 formed on the sliding surface of the piston 17 and the bush 25. The oil taken into the recessed grooves 26 and 27 respectively removed quickly and suppresses thermal expansion.

On the other hand, concave grooves 21,22,26,2 that function as a kind of oil sump
Since 7 extends in the axial direction from one end and the other end of the sliding surface to the axially intermediate position of the sliding surface, the working oil in the cylinder 12 is easily replenished to the sliding surface through these concave grooves. Therefore, in addition to preventing damage to the sliding surface, the frictional force can be made small and stable over long-term use.
Therefore, the damping force of the hydraulic shock absorber can be made extremely stable.

FIG. 9 shows another embodiment of the present invention. In this embodiment, the piston 17 is provided with a piston body 18 made of metal and a cylindrical portion 32 extending in the axial direction on the outer periphery of the piston body 18, and the cylindrical portion 32 has a plurality of (here, four). The annular grooves 33 are provided at equal intervals in the axial direction.

A resin jacket member 19 is attached to the cylindrical portion 32 of the piston body 18. The material of the outer cover member 19 is not particularly limited, but polytetrafluoroethylene (PTFE) or a resin containing PTFE is preferable in terms of slidability. Jacket material
An annular protrusion 31 that engages with the annular groove 33 of the piston body 18 is provided inside the piston 19. The tip of each protrusion 31 is an annular groove 33.
Has a semi-circular cross section whose diameter is the width. Jacket member 19
On the outer peripheral surface, that is, the sliding surface, a plurality of concave grooves 21, 22 extending in the axial direction thereof are provided. Each groove 21, 22 terminates at an axially intermediate position on the sliding surface. Furthermore, the jacket member
An engaging portion 30 is deeply engaged with the piston body 18 at an end portion of the axial direction 19 where the piston rod 13 is not provided.

Although the illustrated embodiments have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the invention described in the claims. In the above embodiment, the sliding surfaces of the piston 17 and the bush 25 are provided with the recessed grooves 21 and 26 respectively opened at one end of the sliding surface and the recessed grooves 22 and 27 opened at the other end of the sliding surface. Although it is provided, only the concave groove that opens at one end of the sliding surface may be formed. Further, in the above embodiment, the piston 17 is made of a metal piston body 18
Although the outer jacket member 19 is provided on the outer periphery of the piston and the resinous outer jacket member 19, the piston 17 may be entirely formed of a resin body.
Further, the sliding surface of the piston 17 may be composed of a sintered layer of copper alloy. The sliding surface of the rod guide 14 can also be made of various materials known per se. Furthermore, the hydraulic shock absorber according to the present invention can be applied to applications other than shock absorbers for automobiles.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the oil is supplied by the groove, so that the heat of the sliding surface can be taken and the thermal expansion of the piston can be suppressed. Therefore, the gap between the outer circumference of the piston and the inner surface of the cylinder can be reduced, and a stable damping force can be obtained.

Moreover, at the same time, the sliding surface can be sufficiently lubricated, and low friction can be maintained for a long period of time. Therefore, it is possible to prevent the seizure caused by performing the delicate control of the damping force for a long period of time.

Therefore, it is possible to provide a highly durable hydraulic shock absorber capable of preventing an increase in sliding friction resistance even during long-term use.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway vertical sectional view of a shock absorber showing an embodiment of the present invention, and FIG. 2 is a piston in the shock absorber shown in FIG. Fig. 3 is a sectional view taken along line III, Fig. 3 is an end view of the piston in the shock absorber shown in Fig. 1, and Fig. 4 is an arrangement form of concave grooves with respect to the sliding surface of the piston shown in Figs. 2 and 3. FIG. 5 and FIG. 6 are partial developed views showing modified examples of the arrangement form of the concave groove with respect to the sliding surface of the piston, and FIG. 7 and FIG. 8 are the concave groove provided in the piston, respectively. FIG. 9 is a partially enlarged sectional view showing a modified example of the sectional shape of FIG. 9, and FIG. 9 is an enlarged partial sectional view of the essential parts of a hydraulic shock absorber showing still another embodiment of the present invention. 11 …… Outer shell, 12 …… Cylinder, 13 …… Piston rod, 14 …… Rod guide, 17 …… Piston, 19 …… Coating member, 20 …… Orifice, 21,22 …… Concave groove, 25 …… Bush, 26,27 …… Concave groove.

Claims (6)

[Claims] 1. A piston rod extending inward and outward of a cylinder is slidably guided in an axial direction by a rod guide provided at one end of the cylinder, and an inner peripheral surface of the cylinder is formed at an inner end portion of the piston rod. In a hydraulic shock absorber provided with a piston in sliding contact, a sliding surface of the piston with respect to the cylinder and / or a sliding surface of the rod guide with respect to the piston rod is axially extended from one or both ends of the sliding surface. A hydraulic shock absorber, comprising a recessed groove extending and terminating at an axially intermediate position of the sliding surface. 2. The hydraulic shock absorber according to claim 1, wherein the concave groove and the sliding surface are connected by a slow contact surface in the axial direction of the sliding surface. 3. The hydraulic shock absorber according to claim 2, wherein the loose contact surface is a rounded surface. 4. The hydraulic shock absorber according to claim 2, wherein the loose contact surface is a tapered surface. 5. The hydraulic shock absorber according to claim 4, wherein the loose contact surface is a taper surface that is integral with the bottom surface of the concave groove. 6. The hydraulic shock absorber according to claim 1, wherein a chamfered portion is provided at an end of the sliding surface in the axial direction. .