JPH05270287A - Rubber bush for automobile - Google Patents

Abstract

PURPOSE:To improve durability against bending fatigue by distributing short fibers in the circumferential direction in an elastic member inserted between an inner circumferential member and an outer circumferential member, and setting specified values for length, diameter, and a mixed quantity of the short fibers. CONSTITUTION:In the rubber bush 1, an elastic member 4 is inserted between an inner cylindrical metal fitting 2 and an outer cylindrical metal fitting 3, and the inner cylindrical metal fitting 2 is fitted to a center bearing and the outer cylindrical metal fitting 3 is fitted to a body or a frame. The elastic member 4 is vulcanizingly stuck to the inner cylindrical metal fitting 2 and the outer cylindrical metal fitting 3, and short fibers are distributed in the circumferential direction of the bush in the elastic member 4. The length of the short fiber is set 0.1-2mm, the diameter is set 0. 3-50mum, and the mixed quantity is set 0.5-5 volume %. Hereby, even if crack is generated in the elastic member, propagation of the crack in the bush axial direction and the bush radial direction is restrained. Because the short fibers are arranged in the circumferential direction, the modulus of elasticity in strain direction applied on the elastic member is almost equal to that before reinforcement and flexibility is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical rubber bush for an automobile, which is attached to a center bearing which supports an intermediate portion of an automobile propeller shaft.

[0002]

2. Description of the Related Art Conventionally, in order to support an intermediate portion of a propeller shaft of an automobile, a propeller shaft is supported by a center bearing (ball bearing) and is supported by a vehicle body or a frame through an elastic body such as rubber. A bearing support structure is known (for example, actual Kaihei 2-127).
819).

This support structure is required to have a function of interrupting transmission of vibrations due to the propeller shaft to the vehicle interior, and therefore various improvements have been made to the shape of the elastic body such as rubber. In general, this support structure utilizes the elastic characteristics of an elastic body such as rubber to support the propeller shaft in a vibration-proof manner.

That is, when the vehicle starts moving, the relative position between the engine and the differential shifts, so that the propeller shaft is twisted and a large-amplitude vibration occurs at a low frequency (so-called flapping phenomenon). Therefore, a vibration-damping rubber used for automobiles is required to have a function of suppressing vibration of an engine or a propeller shaft. Further, when the vehicle is running, minute vibrations of high frequency are generated as the engine rotates at high speed, and therefore a function of not transmitting the vibrations of the engine and the propeller shaft to the vehicle body is required. Therefore,
In order to exert such a function, it is necessary that the static spring constant is large and the dynamic spring constant is small, that is, the dynamic magnification is small.

However, like the elastic body of the above-mentioned support structure, in the case where it is attached to the inner peripheral portion and the outer peripheral portion in a state where it is thinly formed and greatly curved in the axial direction, the dynamic magnification is It has not been able to adequately meet the demand for a smaller size.

[0006] Therefore, the applicant presupposes a rubber bush for an automobile, which is attached to a center bearing that supports an intermediate portion of a propeller shaft of the automobile, and an inner peripheral member attached to the center bearing. An outer peripheral member attached to the vehicle body or the frame,
A rubber bush for automobiles, which is provided between the inner peripheral member and the outer peripheral member and has a rectangular cross-section or a drum-shaped elastic member recessed inward in the axial direction, has been developed and filed (Practical application 3). -94347).

[0007]

However, since such a device supports a propeller shaft that constantly rotates when the automobile is running, it suffers repeated bending fatigue.
A crack is generated in the elastic member, the elastic member easily propagates, and there is a risk of breakage due to bending fatigue.

An object of the present invention is to provide a rubber bush for automobiles having an improved bending fatigue life.

[0009]

The invention of claim 1 is premised on a cylindrical rubber bush for an automobile, which is attached to a center bearing that supports an intermediate portion of a propeller shaft of the automobile, and is attached to the center bearing. An inner peripheral member, an outer peripheral member attached to a vehicle body or a frame, and an elastic member intervening between the inner peripheral member and the outer peripheral member and having a rectangular cross section or an hourglass-shaped elastic member recessed inward in the axial direction, Short fibers are orientated and mixed in the elastic member in the circumferential direction of the propeller shaft, and the short fibers have a length of 0.1 to 2 m.
m, diameter 0.3 to 50 μm, mixed amount 0.5 to 5% by volume
The configuration is

According to the second aspect of the present invention, the inner peripheral member is an inner cylindrical metal member, and the outer peripheral member is an outer cylindrical metal member. The both metal members are vulcanized and bonded to the elastic member.

[0011]

[Function] Since the short fibers are oriented in the rubber bush circumferential direction, even if cracks occur in the elastic member, cracks in the bush axial direction and the bush radial direction corresponding to the propeller shaft axial direction and the propeller shaft radial direction are not generated. Progress is suppressed. This is because the short fibers have higher mechanical strength than the base material of the elastic member, and the short fibers have a reinforcing effect.

Generally, when an elastic body is reinforced with short fibers, the elastic modulus increases, and when a certain amount of strain is applied, the strain energy becomes larger than that before the reinforcement, and the bending resistance decreases. Since the short fibers are oriented in the circumferential direction,
The elastic modulus in the strain direction acting on the rubber bush is almost the same as that before mixing the short fibers, and the bending resistance is maintained.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

In FIG. 1 and FIG. 2 showing the overall structure, 1
Is a rubber bush for an automobile, which is attached to a center bearing (not shown) that supports an intermediate portion of an automobile propeller shaft.

The rubber bush 1 includes an inner cylindrical metal member 2 which is a cylindrical inner peripheral member attached to the center bearing and an outer cylindrical metal member which is a cylindrical outer peripheral member attached to a vehicle body or a frame (not shown). 3 and an elastic member 4 made of a short fiber composite rubber interposed between the inner tubular metal member 2 and the outer tubular metal member 3. The short fibers have a length of 0.1 to 2 mm, a diameter of 0.3 to 50 μm, and a mixed amount of 0.5 to 5% by volume.

The inner tubular metal fitting 2 is formed longer than the outer tubular metal fitting 3 in the axial direction, and is formed in a stepped shape whose radius gradually decreases from one end 2a to the other end 2b. There is. On the other hand, the outer tubular metal fitting 3 is curved so that the end portion 3a corresponding to the smaller radius of the inner tubular metal fitting 2 expands outward in the radial direction. The inner tubular metal fitting 2 and the outer tubular metal fitting 3 are eccentric with the center of the inner tubular metal fitting 2 slightly displaced upward with respect to the outer tubular metal fitting 3.

In the elastic member 4, the short fibers 5 are oriented in the circumferential direction (circumferential direction of the propeller shaft) with respect to the base material 6 (see FIG. 3), and the cross section is curved so as to be recessed inward in the axial direction. It has a so-called drum shape (see Fig. 2). That is, the elastic member 4 of the rubber bush 1 for an automobile starts from the portion 4a which is vulcanized and bonded to the outer tubular metal fitting 3,
The thickness gradually decreases toward the radial middle portion 4b, then gradually increases, and is vulcanized and adhered to the axial middle portion of the inner tubular member 2, and the elastic member 4 is slightly inclined in the axial direction. It is in the state of having done. The thickness of the portion 4c vulcanized and bonded to the inner tubular metal fitting 2 is thicker than the thickness of the portion 4a vulcanized and bonded to the outer tubular metal fitting 3. The length, diameter, and amount of the short fibers are limited to the above range. When the length exceeds the above range, the short fibers become foreign substances in the rubber member, and the elastic modulus of the rubber member increases.
This is because the bending fatigue resistance is lowered due to the fact that the strain energy received becomes large.

An example of specific dimensions will be shown. In FIG. 2, H1 = 7 mm, H2 = 12.5 mm, H3 = 20 mm, H
4 = 38.5mm, H5 = 13.5mm, H6 == 24.5
mm, R1 = 16 mm, R2 = 12.8 mm, φ1 = 58 m
m, φ2 = 90 mm, φ3 = 101.2 mm, φ4 = 55 m
m, φ5 = 63 mm.

Next, an elastic member was formed by the composition shown in Table 1 below, and an example of the present invention (see FIG. 3), a comparative example 1 containing pure rubber, and a short fiber composite rubber were used as the elastic member. Comparative Examples 2 and 3 (Fig.
And FIG. 5). In the present invention example, the short fibers 5 are in the bush circumferential direction on the base material 6, in Comparative Example 2 the short fibers 5A are in the bush axial direction in the base material 6A, and in Comparative Example 3, the short fibers 5B are in the bush radial direction on the base material 6B. It is oriented. The above-mentioned short fibers are nylon short fibers, and have a length of 0.5 mm, a diameter of 0.3 μm, and a mixing amount of 2 vol%.

[0020]

[Table 1] The results of the bending fatigue test for these are shown in FIG.
The bending fatigue test is ± 10 mm, 7H in the bush axis direction.
Sine wave distortion of z was applied, and the measurement was performed in an environment of an ambient temperature of 24 ± 1 ° C.

From the results shown in FIG. 6, the example of the present invention has a longer life than the comparative example. It is considered that this is because the short fibers are oriented in the bush circumferential direction, and therefore the short fibers suppress crack propagation of bending cracks generated in the elastic member in the bush axis direction and the bush radial direction.

On the other hand, in Comparative Example 2 in which the short fibers are oriented in the bush axial direction, the crack of the elastic member propagates in the bush axial direction, the crack penetrates early, and the bending fatigue life is shortened. In Comparative Example 3 in which the short fibers are oriented in the radial direction of the bush, the elastic modulus in the strain direction applied to the rubber bush is increased, and the energy applied to the elastic member is increased, so that it is destroyed early.

The bending fatigue life is defined as the number of times of bending when the total crack length is 100 mm, and the effect on the bending fatigue life is investigated by varying the length of the short fibers and the mixing amount.
This is shown in FIGS. 8 and 9. From this result, it is found that the length of the short fibers is preferably in the range of 0.1 to 2 mm and the mixing amount is preferably in the range of 0.5 to 5% by volume.

[0024]

As described above, according to the invention of claims 1 to 3, short fibers are oriented in the bush circumferential direction with respect to the elastic member interposed between the inner peripheral member and the outer peripheral member. Since the short fibers have a length of 0.1 to 2 mm, a diameter of 0.3 to 50 μm, and the mixing amount is 0.5 to 5% by volume, even if a crack occurs in the elastic member, the short fibers By the reinforcing effect of, the crack propagation in the bush axial direction and the bush radial direction is suppressed. Moreover, since the short fibers are oriented in the circumferential direction, the elastic modulus in the strain direction acting on the elastic member is almost the same as that before the reinforcement, and the bending resistance is maintained.

[Brief description of drawings]

FIG. 1 is a front view of a rubber bush for an automobile.

FIG. 2 is a cross-sectional view of the same center.

FIG. 3 is an explanatory diagram of an elastic member.

FIG. 4 is an explanatory diagram of an elastic member of Comparative Example 2.

FIG. 5 is an explanatory diagram of an elastic member of Comparative Example 3.

FIG. 6 is a diagram showing test results.

FIG. 7 is a diagram showing the relationship between short fiber length and flexural fatigue life.

FIG. 8 is a diagram showing a relationship between a mixed amount of short fibers and a bending fatigue life.

[Explanation of symbols]

 1 Rubber bushes for automobiles 2 Inner tube fitting (inner peripheral member) 3 Outer tube fitting (outer member) 4 Elastic member 5 Short fiber

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[Procedure amendment]

[Submission date] April 8, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

The bending fatigue life is defined as the number of times of bending when the total crack length is 100 mm, and the effect on the bending fatigue life is investigated by varying the length of the short fibers and the mixing amount.
This is shown in FIGS. 7 and 8 . From this result, it is understood that the length of the short fibers is preferably in the range of 0.1 to 2 mm and the mixing amount is preferably in the range of 0.5 to 5% by volume.

Claims (3)

[Claims] 1. A cylindrical rubber bush for an automobile, which is attached to a center bearing supporting an intermediate portion of a propeller shaft of the automobile, wherein an inner peripheral member attached to the center bearing and an outer peripheral member attached to a vehicle body or a frame. And an elastic member interposed between the inner peripheral member and the outer peripheral member, wherein short fibers are circumferentially oriented in the elastic member, and the short fibers have a length of 0.1 to 2 mm and a diameter of 0. A rubber bush for automobiles, characterized in that the content is from 3 to 50 μm and the content is from 0.5 to 5% by volume. 2. The rubber bush for an automobile according to claim 1, wherein the elastic member has a rectangular cross section or a drum shape recessed inward in the axial direction. 3. The rubber bush for an automobile according to claim 1, wherein the inner peripheral member is formed of an inner cylindrical metal member and the outer peripheral member is formed of an outer cylindrical metal member, and the both metal members are vulcanized and bonded to the elastic member.