JPH10238576A - Rubber bush and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a remarkably increased life for a product by reducing the occurrence of a local strain to a corner part between a cylinder part and a flange, in a rubber bush with a flange. SOLUTION: A rubber bush is formed in a manner to apply radial contraction on an outer cylinder 13 to effect preliminary compression of a rubbery elastic substance 14. The of the outer cylinder 13 before contraction is formed in a recessed part 25 in a way that a base end part is dented by curving further radially internally than other part. The contraction rate of the rubbery elastic substance 14 at the base end part of the outer cylinder 13 after contraction is reduced to a value approximately equalized to zero as much as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber bush used for a connecting portion of a vehicle suspension or the like.

[0002]

2. Description of the Related Art There are various types of anti-vibration rubbers used for automobiles. In particular, as anti-vibration rubbers used for connecting portions such as suspension arms, cylindrical rubber bushes as shown in FIG. There is. The rubber bush 1 includes an inner cylinder 2 into which a bolt can be inserted, and an outer cylinder 3 disposed around the inner cylinder 2 and externally connecting a suspension arm.
And a rubber-like elastic body 4 interposed between the inner cylinder 2 and the outer cylinder 3. In addition, the rubber-like elastic body 4 is connected to the inner cylinder flange 5 and the outer cylinder flange 6 continuously with the cylinder elastic portion 4a between the inner and outer cylinders 2 and 3 in order to buffer a torsional force in the rotation direction of the outer cylinder. Flange side elastic part 4 between
b is formed by filling.

Further, the rubber-like elastic body 4 is pre-compressed in the radial direction in order to improve its durability, and is completed as a product. This preliminary compression is performed by drawing the outer cylinder 3 in the radial direction using a split-die drawing jig (not shown).

[0004]

When the rubber bush 1 is used for a connection portion with a suspension arm, the rising angle of the outer cylinder flange 6 is set substantially in consideration of the mounting accuracy with the arm. Set at right angles,
The cylindrical portion 3a of the outer cylinder 3 is also set to be substantially straight tubular. Therefore, due to the outer cylinder shape, stress is easily concentrated on the rubber-like elastic body 4 at the corner 7 between the straight tubular cylinder 3 a and the outer cylinder flange 6, and a crack is easily generated from the corner 7.

[0005] Further, cracks are likely to be generated from the corners 7 due to the non-uniform pre-compression of the rubber-like elastic body 4. That is, in the above-mentioned rubber bush 1 with a flange, drawing of the outer cylinder 3 cannot be performed at the flange 6 due to the peculiarity of the outer cylinder shape, but can be performed only at the straight tubular cylinder 3a. For this reason, the rubber-like elastic body 4 after drawing is not subjected to the pre-compression and the pre-compressed cylinder-side elastic portion 4a. The flange-side elastic portion 4b under stress is present.

Since the boundary portion A between the elastic portion 4a to be subjected to the preliminary compression and the elastic portion 4b not to be present coincides with the corner portion 7 where cracks are likely to occur, the rubber bush 1 is removed. When a fatigue test is carried out using a vibration fatigue tester, cracks occur at the corners of the rubber-like elastic body due to the above-mentioned shape of the rubber-like elastic body and non-uniformity of preliminary compression, and the product life is shortened. There was a problem that it became.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a rubber bush which can minimize local distortion generated at a corner portion between a cylindrical portion and a flange and can greatly improve product life. is there

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventor has conducted intensive studies. As a result, the boundary between the portion to which the pre-compression is applied and the portion to which the pre-compression is not applied is set to the flange-side elastic portion where distortion easily occurs. The focus was on shifting from the corner with the cylinder-side elastic part. As a measure, if the base end of the cylindrical portion of the outer cylinder before drawing is curved and depressed radially inward from other parts, it is known that drawing will not be applied to that part during drawing. was gotten.

Therefore, in the present invention, a concave portion is formed in the outer cylinder as a shape before drawing, the base end of which is curved inward in the radial direction with respect to the other portions so as to be depressed. A configuration is adopted in which the drawing ratio of the rubber-like elastic body at the flange rising portion of the outer cylinder is made as close to zero as possible.

Therefore, according to the present invention, the pre-compressed part and the non-pre-compressed part are present in the cylindrical part of the outer cylinder. Since it is displaced from the corner portion with the elastic portion, it is possible to minimize the influence of residual strain due to the diaphragm. For this reason, the local distortion of the corner portion where cracks easily occur is reduced, and even if a force is applied to the rubber bush in the axial direction, the direction perpendicular to the axis, and the torsion direction around the axis, the crack is prevented from entering the corner portion. It can be avoided as much as possible, and the product life can be greatly extended.

Here, the term "axial direction" refers to the axial direction of a bolt or a shaft (hereinafter referred to as "bolt or the like") fitted to the inner cylinder.
The direction perpendicular to the axis refers to the direction orthogonal to the axis of the bolt or the like, and the torsion direction refers to the direction of rotation about the central axis of the bolt or the like. In addition, the corner portion is an inner surface of the flange rising portion of the outer cylinder, and refers to a bent portion between the cylinder-side elastic portion and the flange-side elastic portion of the rubber-like elastic body.

The material, diameter, thickness and the like of the outer cylinder can be appropriately selected. That is, a material that can be easily drawn, for example, a hot-rolled steel (SPH) or a cold-rolled steel (SPC) can be used as the outer cylinder. The thickness of the outer cylinder is not limited as long as it is a plate thickness that enables drawing, but when the above-described SPH or SPC is used, its workability is taken into consideration, and the thickness is about 1.2 mm to 3 mm. Things are desirable. The diameter of the outer cylinder can be appropriately selected depending on the place of use, the damping performance of the rubber-like elastic body, and the like. The shape of the cylindrical portion of the outer cylinder is not limited to a cylinder, and the present invention can be applied to a square cylinder or an elliptical cylinder.

The concave portion formed in the outer cylinder may be formed by pressing the base end side of the cylindrical portion over the entire circumference by press working or the like before drawing, so as to be depressed. The tube base end is a concept that includes not only a case where the tube is formed from the rising portion of the outer tube but also a case where the tube is shifted from the flange rising portion to the tube portion front end side. However, considering that the portion to be pre-compressed is increased as much as possible, it is desirable to form the recess from the flange rising portion.

The shape of the recess may be any shape as long as it can be deformed by drawing. FIG.
FIG. FIG. 2A shows a tapered recess in which a tapered surface having an upward slope is formed from the arc portion of the rising portion to the distal end side. FIG. 2B shows a tapered recess in which an arc portion is also formed on the flange side. Figure (c)
Indicates a semicircular concave portion, (d) indicates a V-shaped concave portion, and (e) indicates a U-shaped concave portion.

The present invention can be applied to any of these concave portions. However, in consideration of a shape in which preliminary compression is applied to the base end of the cylindrical portion and drawing is relatively easy,
The tapered concave portions shown in FIGS. In the case of the tapered recess shown in FIG. 4 (a), the rubber-like elastic body gradually transitions from a portion that is not pre-compressed to a portion that is pre-compressed, which is advantageous in that concentrated distortion is reduced. is there.

Further, in order to prevent stress from concentrating, the concave portion of the concave portion closest to the inner cylinder side has an arc shape rather than a pointed shape even in the case of a V-shaped concave portion as shown in FIG. It is desirable that Note that the depth of the concave portion may be determined by the drawing ratio of the rubber-like elastic body, and even if the concave portion depth is larger than the drawing amount, there is no problem in achieving the object of the present invention.

Next, the inner cylinder will be described.
As with the outer cylinder, various materials, diameters, thicknesses, and the like can be appropriately selected. In particular, in the material of the inner cylinder, unlike the outer cylinder, the bolts etc. that penetrate are securely tightened with nuts,
Buckling strength that can withstand this is required. Therefore, the inner cylinder is preferably a thick cylindrical cast or forged product.

Further, in the present invention, since the draw ratio at the base end of the cylindrical portion of the outer cylinder is a problem, the present invention can be applied regardless of the presence or absence of the end flange on the inner cylinder side. However, in a rubber bush in which the flange-side elastic portion is formed between the inner and outer cylinders in order to perform a buffering action against the torsional force in the rotation direction of the outer cylinder, the flange-side elastic portion is provided on the outer cylinder tube side. Since the tensile stress is easily applied by the pre-compression, it is particularly significant to adopt the present invention in such a form.

Further, since the present invention is concerned with the draw ratio at the base end of the cylindrical portion, the rubber-like elastic body is not limited to a straight tubular type in order to obtain an optimum spring constant for the rubber-like elastic body. The present invention can be applied to a type in which a protruding portion is formed on the outer surface of the cylindrical portion. In addition, the present invention can be applied not only to the case where the inner and outer cylinders are arranged concentrically but also to the case where the inner and outer cylinders are arranged non-concentrically.

Next, the rubber-like elastic body will be described.
The rubber-like elastic body depends on the required use purpose, characteristics, etc.
Alternatively, natural rubber, synthetic rubber, or a mixture thereof can be appropriately selected depending on the difficulty of the processing step. Also,
In order to obtain different dynamic characteristics in the two axial directions of the rubber bush, the present invention can be applied to a rubber-like elastic body having a hole formed therein or a liquid-filled rubber bush.

Further, the present invention is based on the premise that the rubber-like elastic body is subjected to drawing in order to give a pre-compression, so that the rubber-like elastic body is originally vulcanized and bonded to the inner and outer cylinders. It is targeted. However, even if the rubber-like elastic body is bonded to the inner cylinder and the outer cylinder is press-fitted from above, or the inner and outer cylinders are both non-bonded and press-fitted, in order to further obtain a predetermined drawing ratio, The present invention can be applied to any type in which drawing is performed. Note that the rubber-like elastic body can be naturally applied to the present invention not only by vulcanization bonding but also by simply bonding with an adhesive.

The squeezing rate of the rubber-like elastic body can be appropriately selected depending on the material, thickness, etc. of the outer cylinder. In consideration of the durability of the rubber-like elastic body, the area of the inner peripheral surface of the outer cylinder to be bonded to the rubber-like elastic body is considered. Comes into question. The inner peripheral surface of the outer cylinder is subjected to a chemical treatment before applying the adhesive in consideration of adhesion with the rubber-like elastic body, but it is important that the treated film is not broken by drawing. To achieve this, it is desirable to set the aperture ratio to less than 7%.

In the rubber bush described above, an outer cylinder with an outer cylinder flange is disposed around the inner cylinder, and the rubber bush is formed between the inner cylinder and the outer cylinder and the outer surface of the outer cylinder flange in the axial direction. A rubber-like elastic body is pre-compressed by subjecting the outer cylinder to radial drawing in the presence of an elastic body. At this time, the base end of the outer cylinder before drawing is subjected to drawing using a concave portion curved inward in the radial direction from the other portions, and the flange at the flange rising portion of the outer cylinder after drawing is processed. A method is adopted in which the drawing ratio of the rubber-like elastic body is made as close to zero as possible.

Therefore, no drawing is applied to the rising portion of the outer cylinder flange after drawing, and the internal strain due to drawing is close to zero, so that the pre-compressed part and the part which is not pre-compressed are separated. The boundary portion A is displaced from the corner portion of the rubber-like elastic body where cracks are likely to occur, so that stress concentration at this corner portion is eased and the product life is extended as compared with the conventional rubber bush.

[0025]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a manufacturing process of a rubber bush showing an embodiment of the present invention, FIG. 2 is a side view of the rubber bush, and FIG. 3 is an example in which a pair of rubber bushes are used to face a suspension arm connecting portion. FIG. 4 shows an example of a concave shape of the outer cylinder.

As shown in the figure, the rubber bush 11 in the present embodiment is interposed between an inner cylinder 12, an outer cylinder 13 disposed around the inner cylinder, and the inner cylinder 12 and the outer cylinder 13. And a rubber-like elastic body 14.

As shown in FIG. 3, the inner cylinder 12 is a thick-walled cylindrical casting having a central hole 17 that penetrates a bolt 16 for connecting to a bracket 15 on the body frame side.
An inner cylinder flange 19 is formed at its base end so that the connecting cylinder 18a of the suspension arm 18 does not fall off even when the rubber-like elastic body 14 is broken. Also, the inner cylinder 12
2 has a serration 20 formed on the end face thereof as shown in FIG. 2, and the bracket 15 on the vehicle body frame side is fastened and fixed by a nut 21.

The outer cylinder 13 is made of an SPH having a thickness of 1.2 to 3 mm.
A cylindrical portion 13a formed of a material and having a cylindrical shape
And an outer cylinder flange 13b bent at a right angle on the base end side. The outer cylinder 13 is drawn by interposing a rubber-like elastic body 14 between the outer cylinder 13 and the inner cylinder 12 to complete the product.
As shown in (1), the entire periphery of the cylindrical portion 13a on the proximal end side is bent radially inward from the other portions to be depressed by press working or the like, so that the concave portion 25 is formed.

As shown in FIG. 4A, the shape of the concave portion 25 is an arc portion 25a whose tangential direction coincides with the outer surface of the outer cylinder flange 13b, and the arc portion 25a is continuous with the arc portion 25a. And an upwardly inclined tapered portion 25b formed at
The tip of the tapered portion 25b and the straight portion 13c of the tip of the cylindrical portion 13a
A gentle arcuate surface 25c is formed at the boundary between the two.

The curvature and the taper angle of the arc portion 25a, the taper portion 25b, and the arc surface 25c can be appropriately selected depending on the drawing ratio, the diameter of the rubber bush 11, and the like. Specifically, when the outer diameter of the outer cylinder portion 13a is 34 mm, the arc portion 25a
Can be set to 1.5 mm, the taper angle of the tapered portion 25b to 10 degrees, and the radius of curvature of the arc surface 25c at the boundary with the straight cylindrical portion 13a can be set to 10 mm.

The shape of the concave portion 25 is not limited to the above-described embodiment, and a configuration in which a part of the arc portion 25a is also formed on the flange side at the flange rising portion as shown in FIG. You can also. Further, FIG.
The shapes shown in (c), (d), and (e) may be used. FIG. 3C shows a semicircular concave portion, FIG. 4D shows a V-shaped concave portion, and FIG. 4E shows a U-shaped concave portion.

The present invention can be applied to the recess 25 having any of these shapes.
5b is relatively easy to perform drawing processing,
In addition, the rubber-like elastic body 14 has an advantage that the portion gradually changes from a portion that is not pre-compressed to a portion that is pre-compressed, and there is no portion where the distortion is extremely changed.

The concave portion 25 of the outer cylinder 13 is narrowed down by being pressed radially inward from the periphery of the outer cylinder by a known split die 28. In FIG. 4A, when pressure is applied inward in the radial direction by the split die 28, the outer cylinder 13 is pressed.
The cylindrical portion 13a of the circular arc portion 2 of the concave portion 25 is reduced in diameter.
Since a force is applied from 5a in the direction of the distal end of the outer cylinder 13, the cylindrical portion 13a expands in the axial direction, and reduces its diameter to the state shown by the two-dot chain line in FIG.

At this time, the squeezing rate is set to less than 7% in consideration of prevention of destruction of the chemically treated film on the inner peripheral surface of the outer cylinder 13 before the application of the adhesive. Specifically, the outer cylinder diameter is 34 m
When the outer cylinder 13 having a diameter of 32 m is used, the diameter after drawing is 32.2.
15 mm (average diameter).

The rubber-like elastic body 14 is provided on the cylindrical portion 13 of the outer cylinder 13.
a-side elastic portion 1 interposed between a and the cylindrical portion of the inner cylinder 12
4a and a flange elastic portion 14b interposed between the inner and outer flanges 13b and 19 successively. A contact portion between the end of the rubber-like elastic body 14 and the inner and outer cylinders 12 and 13 is adhered in a state where a fillet is formed in consideration of stress displacement.

The material of the rubber-like elastic body 14 is generally a natural rubber used for a vibration-proof rubber or a synthetic rubber, for example, SBR (styrene butadiene rubber), BR
(Butadiene rubber), IR (isoprene rubber), NBR
(Acrylonitrile butadiene rubber), CR (chloroprene rubber), IIR (butyl rubber), EPDM (ethylene propylene rubber), urethane elastomer, or the like. A compounding agent such as a vulcanizing agent, a vulcanization accelerator, an antioxidant, a reinforcing agent, a filler, and a softening agent is added to these raw rubbers, and a predetermined elastic modulus, mechanical strength, dynamic characteristics, fatigue characteristics, etc. So that you can get

The rubber bush 11 is formed by setting an inner cylinder 12 with a flange 19, an outer cylinder 13 before drawing, and a rubber-like elastic body 14 in a mold, and vulcanizing and molding by pressing. At this time, the rubber-bonded surfaces of the inner and outer cylinders 12 and 13 are subjected to a chemical treatment with a zinc-based phosphate or the like to form a treated film, and then an adhesive is applied and vulcanized and adhered.

Thereafter, the outer cylinder 13 is subjected to drawing by a drawing jig using the split die 28. At this time, when the outer cylinder 13 is squeezed inward in the radial direction by a die, the taper portion 25b of the concave portion 25 of the outer cylinder 13 receives a force in the diameter reducing direction, and shifts to the tip of the outer cylinder by the component force. And
Since the straight pipe portion 13c is similarly squeezed, the tapered portion 25b and the straight pipe portion 13c are finally squeezed until they become straight,
Preliminary compression is applied to the rubber-like elastic body 14 to complete the product.

In the state of this finished product, the recess 2
5, the drawing ratio of the portion B closest to the inner cylinder side corresponding to the flange rising portion 13d is close to zero, and as a result, no residual distortion remains in the corner portion 14c of the rubber-like elastic body. ing. Therefore, the fatigue of the corner portion 14c of the rubber-like elastic body where stress tends to concentrate can be minimized, and the product life can be greatly extended.

A torsional fatigue test was performed to compare the above embodiment with the conventional product shown in FIG. The torsional fatigue test is
Similarly to the case shown in FIG. 3, in a state where the pair of the present embodiment is assembled, the connecting cylinder of the arm is fitted over the outer cylinder portion, and a load of 1.1 KN is applied by the arm in a direction perpendicular to the axis, and this is applied. The test is performed at a test temperature of 23 ± 2 ° C., a torsion angle of 15 to 25 deg, and a frequency of 3 Hz.

As a result of this test, no abnormality was observed even after 500,000 times of twisting in this example, whereas cracks occurred in the corners of the rubber-like elastic body after 50,000 times in the conventional product. did.

FIG. 5 is a sectional view of a rubber bush showing another embodiment of the present invention. In the above embodiment, the rubber-like elastic body 14b is filled and bonded between the inner and outer flanges, but in this embodiment, the flange-side elastic portion 14b of the rubber-like elastic body 14 is bonded only to the outer cylinder flange 13b. The flange-side elastic portion 14b and the inner cylinder flange 19
The figure shows a rubber bush in which a gap 29 is formed between the rubber bush. In this case, the flange-side elastic portion 14b functions more as a buffering stopper in the axial direction than as a vibration-proof function in the torsional direction.

[0043]

As is apparent from the above description, according to the present invention, in order to pre-compress the rubber-like elastic body, in the rubber bush in which the flanged outer cylinder is drawn in the radial direction, the outer periphery before drawing is used. The shape of the cylinder is such that the base end is curved more radially inward than the other parts and is depressed, so that the drawing ratio of the rubber-like elastic body on the base end side of the outer cylinder after drawing can be reduced as much as possible. Since it is close to zero, there is an excellent effect that the residual strain at the corners of the rubber-like elastic body where cracks easily occur can be reduced as much as possible, and the product life can be greatly extended.

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing process of a rubber bush according to an embodiment of the present invention.

FIG. 2 is a side view of the rubber bush as viewed from the axial direction.

FIG. 3 is a cross-sectional view showing an example in which the rubber bushes of the present invention are arranged symmetrically in a pair and applied to a connection portion of a suspension arm.

4A and 4B are cross-sectional views showing a form of a concave portion according to the present invention, wherein FIG. 4A shows a tapered concave portion, FIG. 4B shows a modified example of FIG. 4A, and FIG. (D) shows a V-shaped concave portion, and (e) shows a U-shaped concave portion.

FIG. 5 is a cross-sectional view showing another embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional rubber bush.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Rubber bush 12 Inner cylinder 13 Outer cylinder 13a Cylindrical part 13b Outer cylinder flange 13c Straight pipe part 14 Rubber-like elastic body 19 Inner cylinder flange 25 Depression 25a Arc part 25b Tapered part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Eiichi Kusama 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yoshiyuki Mori 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (4)

[Claims] 1. An inner cylinder, an outer cylinder disposed around the inner cylinder, an outer cylinder flange formed radially outward at an axial base end of the outer cylinder, and the inner cylinder and the outer cylinder. And a rubber-like elastic body interposed between the outer cylinder flange side and the outer cylinder flange side, in order to pre-compress the rubber-like elastic body, in a rubber bush in which the outer cylinder is drawn radially inward, In the outer cylinder, as a shape before the drawing, a concave portion is formed by curving the base end thereof inward in the radial direction than the other portions, and a rubber at a flange rising portion of the outer cylinder after the drawing is formed. A rubber bush characterized in that the drawing ratio of the elastic body is made as close to zero as possible. 2. An inner cylinder flange, which protrudes radially outward, is formed at an axial end of the inner cylinder corresponding to the outer cylinder flange, and the rubber-like member is provided between the inner cylinder flange and the outer cylinder flange. The rubber bush according to claim 1, wherein the rubber bush is filled with an elastic body. 3. The rubber bush according to claim 1, wherein the squeezing ratio of the rubber-like elastic body is set to less than 7%. 4. An outer cylinder having an outer cylinder flange at a base end is disposed around the inner cylinder, and a rubber-like elastic body is provided between the inner cylinder and the outer cylinder and up to the outer surface of the outer cylinder flange. Filling, by drawing the outer cylinder radially inward, in a method of manufacturing a rubber bush by pre-compressing the rubber-like elastic body,
Before drawing, the base end of the outer cylinder is bent radially inward from the other parts and subjected to drawing using
A method for producing a rubber bush in which a drawing ratio of a rubber-like elastic body at a flange rising portion of an outer cylinder after drawing is as close to zero as possible.