JP3051004B2 - Tubular elastic bush - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a tubular elastic bush which is incorporated in a suspension mechanism of an automobile and used to reduce vibration propagation.

[0002]

2. Description of the Related Art Conventionally, in a suspension mechanism of an automobile, a tubular elastic bush as a suspension bush is swingably attached to a connecting portion between a vehicle body and a suspension so as to reduce vibration of the vehicle body.

In this type of suspension bush, generally, in order to increase the lateral rigidity of the vehicle and secure steering stability, the spring constant in the direction perpendicular to the bush axis and the spring constant in the twisting direction are reduced. It is an important requirement to secure the swingability of the suspension arm and obtain a good ride quality.

Therefore, recently, as a cylindrical elastic bush that can satisfy such requirements, an axially intermediate portion of the inner cylinder is protruded in a spherical shape, and is interposed and fixed between the inner cylinder and the cylindrical outer cylinder. By reducing the thickness of the rubber-like elastic body in the axial middle portion toward the center in the axial direction, the spring constant in the direction perpendicular to the axis is increased while securing a low spring constant in the twisting direction. A bulge-type elastic bush has been proposed, and is preferably used for each connecting portion of the suspension mechanism.

[0005]

As described above, this type of elastic bush has a soft spring characteristic in the twisting direction, can effectively absorb the input in the twisting direction, has a good ride comfort, and has a right angle direction. The spring characteristics are set to be hard and the steering stability is excellent, and the structure is relatively simple, it is easy to make, and it is advantageous in terms of cost. The rubber-like elastic body is vulcanized and adhered to the outer peripheral surface of the inner cylindrical fitting having the spherical convex portion at the portion by an appropriate method such as vulcanization bonding or using an adhesive, and then the outer peripheral surface of the rubber-like elastic body is further A method has been adopted in which cylindrical metal fittings are press-fitted and externally inserted, and these inner and outer cylindrical metal fittings are concentrically connected and integrated by the rubber-like elastic body.

In this case, the outer peripheral surface of the rubber-like elastic body into which the outer cylindrical metal fitting is press-fitted / externally inserted is formed into a straight surface shape, and the straight surface has an axial end. The outer peripheral surface of the rubber-like elastic body located in the portion is provided with a constricted portion and is formed to have a smaller diameter than the other portion. The reduction rate of the thickness of the rubber-like elastic body when the metal fittings were extrapolated) was the largest at the axial center portion where the thickness in the radial direction was thin, and gradually decreased at both sides thereof. .

[0007] In the case of an outer cylinder press-fit type elastic bush, generally,
When the drawing ratio of the rubber-like elastic body is 20 to 28%, the press-fitting is very easy to be stabilized. However, when the drawing ratio is lower than 20%, a margin is insufficient, and when the drawing ratio is higher than 28%, the axial displacement of the rubber-like elastic body is increased. It is well-known that the size of the rubber becomes large and ears are formed, and that the rubber is apt to come off and the axial pull-out force is reduced. In the conventional bulge-type elastic bush having the above-described structure, when the squeezing rate of the rubber-like elastic body portion adjacent to the axial side of the spherical convex region is set in the range of 20 to 28%, In fact, the draw ratio at the axially central portion, which is thinner, is 1.5 times or more. When an external force in the axial direction is applied to the cylindrical elastic bush in such a press-fit state , the rubber-like elastic body becomes inadequate for the above-mentioned reason.
A stable state may occur and the axial pullout force may decrease.
The problem arises .

SUMMARY OF THE INVENTION The present invention has been made in order to cope with the above-described circumstances. It is an object of the present invention to provide a bulge-type tubular elastic bush in which a radial drawing ratio of a rubber-like elastic body is reduced in an axial middle portion. The cylindrical elastic bushing which is averaged to a substantially constant value in a predetermined region including, and preferably in the range of 20 to 28% to obtain a stable press-fitted state and thereby has improved resistance to pullout in the axial direction of the bush. To provide.

[0009]

SUMMARY OF THE INVENTION To achieve the above object, a cylindrical elastic bush according to the present invention comprises a rubber elastic elastic member provided on the outer peripheral surface of an inner cylindrical metal fitting having a spherical convex portion at an axially intermediate portion. The rubber-like elastic body is externally fitted with a cylindrical outer cylinder fitting, and the inner and outer cylinder fittings are concentrically connected by the rubber-like elastic body to be integrated, and the axial direction of the elastic body is fixed. Depress the middle part
To form a concave surface.
Of the rubber-like elastic part with the
Approximately equal to the drawing ratio of the rubber-like elastic part adjacent to the opposite side
Value.
The concave surface is preferably an arc shape, and the concave surface
Constriction on the outer peripheral surface of the side end separated by a predetermined distance on both sides in the axial direction of
Is preferable.

In the present invention, a rubber-like elastic body conventionally formed on a straight cylindrical surface is depressed at an outer peripheral surface at an intermediate portion in the axial direction, and the outer diameter at the central portion in the axial direction is minimized. A circular arc-shaped concave surface whose diameter gradually expands outward from the center in the direction is made smaller, so that the smaller the thickness of the rubber-like elastic body when the outer cylindrical bracket is extrapolated, the smaller the thickness in the center in the radial direction. Thereby, the drawing ratio of the rubber-like elastic body portion interposed between the spherical projection provided on the inner cylinder and the inner surface of the outer cylinder is set to a substantially constant value, preferably 20 to 28%.
Set to a value in the range. At the same time, a small-diameter constriction is formed on the outer peripheral surface of the rubber-like elastic body separated from the arc-shaped concave surface by a predetermined distance in the axial direction to absorb the axial displacement of the rubber-like elastic body and to form the constriction. And a straight surface is left between the arc-shaped concave surface and the outer diameter thereof is selected to a desired value, and the drawing ratio of the rubber-like elastic body in this region is substantially equal to the drawing ratio of the intermediate portion in the axial direction. Configure so that they have the same value. The aperture ratio can be set relatively easily by appropriately selecting the shapes and dimensions of the arc-shaped concave surface and the constricted portion in conjunction with the shapes and dimensions of the inner and outer cylindrical fittings and the spherical convex portions.

[0011] The shape of the rubber-like elastic body fixed to the outer peripheral surface of the inner cylindrical metal member, particularly, the surface shape is configured as described above, so that the rubber-like elastic body is formed despite the bulge type bush. It is possible to obtain a cylindrical elastic bush in which the radial reduction ratio of the rubber-like elastic body is set to be substantially the same over the entire region relating to the axial pull-out resistance.

[0012]

[Action] rather each of the above, in the cylindrical elastic bushing outer cylinder pressure Irigata bulge type, recessed outer peripheral surface of the axially intermediate portion of the rubber-like elastic body outer tubular member is extrapolated to form a concave surface
By press-fitting the outer metal fitting, the radial drawing rate of the rubber-like elastic body in the area involved in the axial pull-out resistance,
It is possible to set the average value to a desired value, a stable press-fit state is secured, and the pull-out resistance in the axial direction of the bush is remarkably improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the embodiments shown in the accompanying drawings. FIG. 1 is a longitudinal sectional view showing an example of a tubular elastic bush according to the present invention. In the figure, reference numeral 1 denotes an inner cylindrical fitting, and a spherical convex portion 4 is provided on an outer peripheral surface of an intermediate portion in the axial direction. Numeral 2 is a cylindrical outer cylindrical fitting concentrically arranged radially outward of the inner cylindrical fitting 1,
Reference numeral 3 denotes a rubber-like elastic body that connects and integrates the inner and outer cylindrical fittings 1 and 2. The radial reduction ratio of the rubber-like elastic body 3 in this embodiment is set within a range of 20 to 28% over the entire region related to the axial pull-out resistance.

More specifically, as shown in FIG. 1 and FIG. 2, the inner cylindrical fitting 1 is a cylinder made of a straight pipe, and a spherical convex part 4 made of synthetic resin is provided on the outer peripheral surface of the axial middle part. Is provided. A rubber-like elastic body 3 is vulcanized and fixed to the outer peripheral surface of the inner cylinder 1. The outer diameter of the rubber-like elastic body 3 is formed to be larger than the inner diameter of the outer cylindrical metal fitting 2 to be extrapolated. ₂ is obtained.
In addition, an arc-shaped concave surface 5 having the deepest shape at the axial center is formed by recessing the outer peripheral surface of the rubber-like elastic body 3 in the axial middle part. The arc-shaped concave surface 5 is first positioned at the center (the deepest position) so that the squeezing ratio ε ₁ of the rubber-like elastic body at the center in the axial direction becomes substantially the same as the above-mentioned ε ₂ when the outer cylinder 2 is press-fitted. Portion), and the squeezing rate of not only the central portion but also the entire rubber-like elastic body interposed between the arc-shaped concave surface portion 5 and the spherical convex portion 4 becomes substantially equal to ε _2. It is formed in such a shape.

The aperture ratios ε ₁ and ε ₂ are values obtained by the following equations (1) and (2), respectively.

(Equation 1)

(Equation 2) However, the outer diameter of the rubber-like elastic body 3 on the outer peripheral surface of the inner sleeve 1 is pressurized硫固wearing phi _A in the formula in FIG. 2, phi _B is the inner diameter of the outer sleeve 2, phi _C is the inner cylindrical member 1 outer diameter of, the phi _D the outer diameter of the axially central portion of the concave arc surface 5, .phi.d have the same outer diameter of the spherical protruding portion 4. In this embodiment, both ε ₁ and ε ₂ are configured to be 22%.

Further, a pair of left and right constricted portions 6 and 6 are formed on the outer peripheral surface of the axial side end portion which is separated from the arcuate concave surface 5 by a predetermined distance. The constricted portions 6, 6 absorb and limit the displacement of the rubber-like elastic body 3 extending outward in the axial direction when the outer cylindrical fitting 2 is press-fitted. Is formed as an inverted truncated triangle,
The depth is made substantially equal to the diameter reduction (φA−φB) of the rubber-like elastic body. The positions of the outer ends 7, 7 of the constricted portion are displaced in the axial direction with the press fitting of the outer tube fitting 2,
The positions are set such that the mutual distance is equal to the axial length L of the outer tube fitting 2.

On the other hand, the outer cylinder fitting 2 comprises an inner cylinder fitting 1.
To a straight tubular cylinder having a pressurized硫固wearing rubber-like elastic body 3 of the outer diameter phi _A smaller inner diameter phi _B, the axial length L is shorter than the axial length of the rubber-like elastic body 3 in FIG. 2 Having a dimension larger than the distance between the outer ends 7, 7 of the constriction,
The rubber-like elastic body 3 is configured to cover the elongation.

When the outer metal fitting 2 is press-fitted onto the outer peripheral surface of the rubber-like elastic body 3 using a normal press-fitting machine, a rubber-like elastic body portion A having the arc-shaped concave surface 5 as the outer peripheral surface is formed.
However, the diameter of the rubber elastic body portion B adjacent to the axial side portion is reduced at a drawing ratio substantially the same as that of the rubber elastic body portion B, thereby obtaining a target cylindrical elastic bush.

Next, the cylindrical elastic bush obtained as described above was evaluated for its axial pull-out resistance. This is because, as shown in FIG. 3, the outer cylindrical metal fitting 2 of the cylindrical elastic bush is fixed on the sample support 8 of the pull-out tester, and the inner cylindrical metal fitting 1 is pulled out in the direction of the arrow ↓. Evaluated by finding the maximum of the curve. FIG. 4 shows the results. In the figure, (a) is a stress-deflection curve according to the embodiment, and (b) is a stress-deflection curve relating to a conventional bulge-type elastic bush as a comparative example. As is clear from this, the pull-out resistance of the elastic bush of the example is larger than that of the comparative example by 500 kg or more, and the radial drawing ratio of the rubber-like elastic body interposed between the inner cylinder and the outer cylinder is set to the above value. And stabilize the press-fit state by averaging to almost constant value,
It can be seen that the pull-out resistance in the axial direction of the bush is remarkably improved.

[0020]

As described above, the cylindrical elastic bush of the present invention is provided between the spherical convex portion of the inner cylindrical member and the inner surface of the outer cylindrical member, and has a rubber-like elasticity in a thin region in the radial direction. The drawing ratio of the rubber-like elastic body located in the radially thick region located on the axial side of the body and the drawing ratio of the rubber-like elastic body is set to be almost the same value, so that the press-fit state of the outer cylinder is stabilized. As a result, the pull-out resistance against external force in the axial direction of the bush is remarkably improved.
Moreover, except for the squeezing rate of the rubber-like elastic body in the thin region in the radial direction described above, there is no difference from the conventional bulge-type elastic bush in its configuration, so that the safety characteristic of the bulge-type spring is secured. A high cylindrical elastic bush can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a cylindrical elastic bush as one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a state in which a rubber elastic body constituting the cylindrical elastic bush is vulcanized and fixed to an outer peripheral surface of an inner cylindrical fitting.

FIG. 3 is an explanatory view showing a method of measuring a pull-out force of a cylindrical elastic rubber bush.

FIG. 4 is a stress-deflection curve obtained by the measurement method.

[Explanation of symbols]

 1: inner cylinder fitting 2: outer cylinder fitting 3: rubber-like elastic body 4: spherical convex part 5: arc-shaped concave surface 6: constricted part 7: axially outer end of constricted part 8: sample support

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masayuki Toriumi 3rd Ikuyama, Uchikoshi, Miyoshi-cho, Nishikamo-gun, Aichi Prefecture Inside the Toyo Tire & Rubber Co., Ltd. Automobile Parts Product Technology Center (72) Inventor Hiroshi Ono Nishikamo-gun, Aichi Prefecture No. 3 Ikayama, Uchikoshi, Miyoshi-cho, Toyo Tire & Rubber Co., Ltd. Inside the Product Technology Center (72) Inventor Toshihiro Kakimoto No. 3, Ikayama, Uchikoshi, Ooike, Miyoshi-cho, Nishikamo-gun, Aichi Pref. Within the Technical Center (72) Inventor Moriya Takeshita 3 Ikuyama, Uchigoe, Miyoshi-cho, Nishikamo-gun, Aichi Prefecture Toyo Tire & Rubber Co., Ltd. Automotive Parts Technology Center (56) References U) JitsuHiraku Akira 62-114222 (JP, U) JitsuHiraku flat 3-12029 (JP, U) (58 ) investigated the field (Int.Cl. ^7, B name) F16F 1/00 - 6/00 B60G 7/02

Claims (4)

(57) [Claims] 1. A rubber-like elastic body is fixed to an outer peripheral surface of an inner cylindrical fitting having a spherical convex portion at an axial middle part, and a cylindrical outer cylindrical fitting is extrapolated to the outer peripheral surface of the rubber-like elastic body. a the inner and outer tubular member is cylindrical elastic bushing connected to become integrated concentrically with said rubber-like elastic material, the rubber-like elastic body, by depressing the axially intermediate portion arc
A concave shape is formed, and when the outer cylinder fitting is press-fitted,
The concave surface is used to absorb the axial displacement of the elastic body.
Constriction on the outer peripheral surface of the side end separated by a predetermined distance on both sides in the axial direction of
Forming a straight line between the constricted portion and the concave surface.
When the outer cylindrical metal fitting is extrapolated while leaving the surface, the drawing ratio of the rubber-like elastic portion having the concave surface as the outer peripheral surface is the same as the drawing ratio of the rubber-like elastic portion adjacent to the axial side portion. A cylindrical elastic bush that is configured to have almost the same value. 2. The constricted portion has a surface portion having a large displacement amount.
It is formed in a wide inverted inverted triangle shape, and its depth is
2. The cylindrical elastic bush according to claim 1, wherein the diameter of the elastic body is substantially equal to the diameter of the elastic body. 3. The position of the axially outer end of the constricted portion,
When displaced in the axial direction due to the press fitting of the outer cylinder,
The cylindrical elastic bush according to claim 2 , wherein the distance is set at a position where the distance is equal to the axial length of the outer cylinder . 4. The squeezing rate of the rubber-like elastic body is 20 to 28%.
The cylindrical elastic bush according to claim 1, 2, or 3.