JPH0665902B2 - shock absorber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a shock absorber, and more particularly to a shock absorber for vehicles such as automobiles.

"Prior art" Conventionally, the large diameter part of the stepped rod guide is fitted in the outer shell, and the small diameter part of the rod guide is fitted in the cylinder provided in the outer shell and is slidable on the cylinder. The piston rod of the piston fitted to
A shock absorber slidably inserted into the hole of the rod guide shaft portion is known.

[Problems to be Solved by the Invention] Since this type of shock absorber is usually installed in a tilted state, the piston rod is tilted relative to the cylinder while the vehicle is running. When the rod guide bends or bends, the end of the rod guide comes into one-sided contact due to the axial misalignment between the piston rod and the rod guide. If the piston rod and the rod guide make one-sided contact, the lubrication state between the two deteriorates and the durability of the rod guide deteriorates.Furthermore, the frictional resistance of the rod guide, especially the static frictional resistance increases, and the damping force of the shock absorber increases. There is also a drawback that it becomes unstable. This drawback is remarkable especially when the wheel rides on uneven road surface.

[Means for Solving the Problems] In view of such circumstances, the present invention forms the inner peripheral surface of the hole of the rod guide shaft portion into a drum shape having a small inner diameter at the central portion and a large inner diameter at both ends. At the same time, at least on the large-diameter portion side of the rod guide, an annular protruding portion that surrounds the hole is formed to protrude, and the outer peripheral surface thereof is separated from the outside, and the annular protruding portion of the rod guide is elastically deformed outward in the radial direction. It was possible.

[Operation] According to such a configuration, even if the piston rod swings with respect to the rod guide to cause axial misalignment, the inner peripheral surface of the hole is formed in a drum shape. The degree of partial contact between the outer peripheral surface of the piston rod and the end of the rod guide is reduced.

At the same time, if the outer peripheral surface of the piston rod and the end of the rod guide on the large diameter portion side are strongly pressed against each other in spite of forming the inner peripheral surface of the hole in a drum shape, Due to the pressure contact force, the annular protrusion is elastically deformed outward and the pressure contact force with the piston rod is reduced.Therefore, due to the fact that the inner peripheral surface of the hole is formed in a drum shape, wear due to one-sided contact Can be significantly reduced.

"Embodiment" The present invention will be described below with reference to the illustrated embodiment. In Fig. 2, an outer shell 2 having a cylinder 1 housed therein is provided.
Has a lower end connected to a wheel (not shown), and a piston rod 4 of a piston 3 slidably fitted in the cylinder 1 has an upper end connected to the vehicle body.

A stepped rod guide 5 is provided on the upper end of the outer shell 2.
The large diameter portion 5a of the rod guide 5 is fitted in, and the small diameter portion 5b of the rod guide 5 is fitted in the upper end opening portion of the cylinder 1 (see FIG. 1). Then, a guide bush 7 is fitted into a hole 6 formed in the shaft portion of the rod guide 5, and the piston rod 4 is slidably passed through the guide bush 7, and at the same time, the upper end opening of the outer shell 2 is closed. The packing 8 for sealing is slidably penetrated and protruded to the outside. An outer cylinder 9 for covering the packing 8 portion is provided on the upper end of the piston rod 4.
Is installed.

A valve 10 is provided inside the piston 3, and the inside of the cylinder 1 is filled with oil.
The space between the outer shell 2 and the outer shell 2 serves as a reservoir 11.
Such a structure is basically the same as the conventionally known one, and when the cylinder 1 is moved back and forth, the oil in the cylinder 1 passes through the valve 10 inside the piston to move the piston rod and the cylinder 1 together. The relative movement of the oil is allowed, and a damping action is performed based on the viscous resistance of this oil.

However, as shown in an enlarged scale in FIG. 1, the inner peripheral surface of the hole 6 formed in the rod guide 5 is formed in a drum shape having a small inner diameter at the central portion and a large inner diameter at both ends, and The guide bush 7 is also formed in a drum shape corresponding to the inner peripheral surface of the hole 6 so that the inner diameter of the central portion is small and the inner diameters of both end portions are large. The sliding surface of the hourglass-shaped guide bush 7 is
Even when the piston rod 4 slides on the guide bush 7, it always comes into smooth sliding contact with the outer peripheral surface of the piston rod 4.

To install the guide bush 7 in the hole 6, the guide bush 7 may be inserted into the hole 6 and then sized so that the outer peripheral surface of the guide bush 7 is in close contact with the inner wall surface of the hole 6. In the above, the guide bush 7 is plastically deformed so that the outer peripheral surface and the inner peripheral sliding surface thereof are formed in a shape corresponding to the inner wall surface of the hole 6, that is, in a drum shape having an arcuate cross section.

In this case, the outer diameter of the guide bush 7 before insertion is preferably set to be equal to or slightly larger than the diameter of the central portion of the inner diameter of the hole 6, and the outer diameter of the guide bush 7 is set to the above-mentioned hole 6 If the inner diameter of the central portion is set to be larger than the inner diameter by a predetermined amount, the guide bush 7 can be made to follow the drum shape of the inner peripheral surface of the hole 6 simply by press-fitting the guide bush 7 into the hole 6 without sizing. It is possible.

The amount of swelling of the central portion of the hole 6 with respect to both ends is
When the axial length of the guide bush 7 is 20 mm, 10 to 100
It is desirable to set so as to bulge inward by about μm. Alternatively, the rod guide 5 may be aluminum die cast (for example ADC-12), aluminum casting (for example AC8A), aluminum casting, mechanical cutting from an aluminum drawing bar, iron sintering or forging, zinc or magnesium alloy, or The guide bush 7 can be made of plastic or the like. On the other hand, the guide bush 7 is made of polytetrafluoroethylene (PTF) on a copper-based sintered layer sintered on the back metal.
It is desirable to manufacture by impregnating E).

Further, in this embodiment, an annular protrusion 5c surrounding the hole 6 is formed on the large diameter portion 5a side of the rod guide 5 so as to separate the outer peripheral surface thereof from the outside.
5c is elastically deformable relatively easily. The wall thickness of the annular protruding portion 5c naturally varies depending on the material of the rod guide 5. For example, 2 mm is suitable in the case of ferrous sintered metal, but it is thicker in the case of manufacturing with aluminum or FRP. There is a need to. Such thickness is
It can be determined by a simple preliminary experiment.

According to the above configuration, even when the piston rod 4 swings with respect to the guide bush 7 and the axial center shift occurs, the inner peripheral surface of the hole 6 has a drum shape.
One-sided contact between the outer peripheral surface of the and the end portion of the guide bush 7 can be effectively prevented. In addition, when the outer peripheral surface of the piston rod 4 and the upper end portion of the guide bush 7 are strongly pressed against each other even though the inner peripheral surface of the hole 6 is formed in a drum shape, the annular protrusion is caused by the pressure contact force. Since the portion 5c elastically deforms outward to reduce the pressure contact force with the piston rod 4, it is possible to greatly reduce the abrasion due to one-sided contact.

Further, the drum-shaped inner peripheral surface of the hole 6 is the piston rod 4
A wedge shape is formed between and, and an oil film is easily formed due to the wedge effect, so that the lubrication state becomes very good. Therefore, the static friction resistance and the dynamic friction resistance between them can be reduced and the piston rod 4 can be operated smoothly, so that the feeling during traveling is improved and the damping force of the shock absorber can be stabilized. it can.

Furthermore, since the guide bush 7 has an hourglass shape that is in close contact with the inner wall surface of the hourglass-shaped hole 6, the force with which the rod guide 5 holds the guide bush 7 is the same as in the conventional case in the cylindrical hole. Compared with the case where the cylindrical guide bush is press-fitted and fixed, the load of the guide bush 7 is increased, the durability of the guide bush 7 is improved, and the durability and safety of the shock absorber are improved. You will be able to improve.

By the way, the one-sided contact phenomenon of the piston rod 4 also occurs at the lower end portion of the guide bush 7, but is more remarkable at the upper end portion of the guide bush 7 than that. This is because the lower part of the piston rod 4 is supported by the guide bush 7 and the piston 3 so that the position in the axial direction is relatively easy to hold, but the upper part of the piston rod 4 is substantially free. This is because it is easy to bend.

Therefore, most of the one-side contact phenomenon can be eliminated only by forming the elastically deformable annular protrusion 5c on the upper portion of the rod guide 5, but the one-side contact phenomenon in the lower portion of the rod guide 5 can be completely eliminated. In order to do so, as shown in FIG. 3, it is obvious that an annular protrusion 5d surrounding the hole 6 and having an outer peripheral surface spaced from the outside may be formed in a protruding manner.

Further, in the embodiment shown in FIG. 3, the guide bush 7 is omitted and the piston rod 4 is directly slidably contacted with the inner peripheral surface of the hole 6 having the hourglass shape. The surface has a drum shape in which the central portion in the axial direction bulges from both ends thereof.

Therefore, in this embodiment, the drum-shaped inner peripheral surface of the hole 6 and the upper and lower annular protrusions 5c and 5d provide the same effects as the above-described embodiment, and the drum-shaped large-diameter portion 5a.
As a result, the rod guide 5 itself can be inclined in the load direction, so that the pressure contact force with the piston rod 4 can be further reduced.

Next, the effect of reducing the wear due to one-sided contact can be achieved by forming the guide bushes 7 individually in the shape of an hourglass or by providing the annular protruding portion 5c, but by combining both. Therefore, further synergistic effect can be expected.

FIG. 4 shows the test results showing such an effect. This test uses a shock absorber with a built-in guide bush.
The load is 250 kg, the stroke is 50 mm, and the operation is performed 2 million times at a rate of 3 times per second, and the frictional force before the test and the frictional force after the test are measured to measure the increase amount of the frictional force. The frictional force was measured when the load was 250 kg, the stroke was 10 mm, and the frictional force was 0.05 times per second.

In FIG. 4, sample A is the present invention, and sample B is the one in which the annular protrusion is omitted and the guide bush is formed in a drum shape.
Sample C forms an annular protrusion to form the guide bush into a simple columnar shape, and the annular protrusion is elastically deformable outward in the radial direction. Sample D omits the annular protrusion, and at the same time, In addition to the conventional general guide bush having a simple columnar shape, Sample E further has an annular protrusion to form the guide bush into a simple cylindrical shape, and the annular protrusion is substantially outward in the radial direction. It shows that it is not elastically deformable.

As is apparent from the test results in the figure, the sample E in which the annular protrusion is not substantially elastically deformable outward in the radial direction even if the annular protrusion is formed is the same as the conventional sample D. Only the result of is obtained. On the other hand, the sample B having the hourglass shape of the guide bush and the sample C provided with the annular protrusion have also obtained better results than the conventional sample D. However, in the sample A according to the present invention which is a combination of both. Have a far superior effect to those of their own.

In addition, in the above embodiment, the axial cross section is arcuate as the hourglass shape, but in addition, for example, a shape in which the central portion is cylindrical and both ends are tapered and the cylindrical portion and the tapered portion are smoothly continuous. May be used, and in short, it may be a drum shape as a whole.

[Advantages of the Invention] As described above, according to the present invention, it is possible to significantly reduce the wear due to one-sided contact.

[Brief description of drawings]

1 is a sectional view of an essential part showing an embodiment of the present invention, FIG. 2 is a sectional view showing the whole of FIG. 1, FIG. 3 is a sectional view showing another embodiment of the present invention, and FIG. The figure is a figure which shows the test result for demonstrating the effect of this invention. DESCRIPTION OF SYMBOLS 1 ... Cylinder, 2 ... Outer shell 3 ... Piston, 4 ... Piston rod 5 ... Rod guide, 5a ... Large diameter part 5b ... Small diameter part, 5c, 5d ... Annular protrusion 6 ... Hole, 7 ... Guide bush

Claims (1)

[Claims] 1. A large diameter portion of a stepped rod guide is fitted in the outer shell, a small diameter portion of the rod guide is fitted in a cylinder provided in the outer shell, and is slidably fitted in the cylinder. In the shock absorber in which the piston rod of the fitted piston is slidably penetrated into the hole of the rod guide shaft, the inner peripheral surface of the hole of the rod guide shaft is The rod guide is formed in a drum shape having a large inner diameter, and at least on the large diameter portion side of the rod guide, an annular protruding portion surrounding the hole is formed so as to separate the outer peripheral surface thereof from the outside, and the annular protruding portion of the rod guide is formed. A shock absorber characterized in that it is elastically deformable outward in the radial direction.