JPH0835531A - Wheel cylinder - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a wheel cylinder that can simplify the structure of a piston and can easily attach a dust seal. [Structure] A piston 4 is slidably mounted in a cylinder body 3, and a fitting step portion 30 formed toward the piston 4 is provided inside an opening end 31 of the cylinder body 3. A ring-shaped dust seal 2 is fitted between and the fitting step portion 30. The fitting step 3
Reference numeral 0 has a protrusion 33 that protrudes toward the outer periphery of the piston 4. The dust seal 2 has an annular recess 21 that does not come into contact with the protrusion 33 on the outer peripheral side thereof, and has a pair of outer peripheral contact portions 201 and 202 on both sides thereof, and the pair of outer peripheral contact portions 201 and 202 on the inner peripheral side of the dust seal 2. Outer peripheral contact portion 20
A pair of inner peripheral contact portions 203 and 204 are provided in a portion located outside of 1,202.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel cylinder of a brake, and more particularly to a seal structure thereof.

[0002]

2. Description of the Related Art Wheel cylinders 90 for automobile brakes
As shown in FIGS. 7 and 8, the cylinder body 8 has a cylinder body 8, two pistons 7 slidably mounted therein, and a dust boot 9. As shown in FIG. 7, when the wheel cylinder 90 is used for the drum brake 99, the left and right pistons 7 are installed so as to expand the two left and right brake shoes 98, respectively. Further, the piston 7 is operated by the hydraulic pressure sent from a master cylinder (not shown). Reference numeral 96 is a spring coil and 97 is a seal cup.

Since the wheel cylinder 90 is installed in the drum of an automobile, it is exposed to an atmosphere that is easily contaminated with dust such as mud, water, and abrasion powder of brake shoes. Particularly, when such dust enters the cylinder body 8, it hinders the smooth movement of the piston.

Therefore, in the wheel cylinder 90,
A dust boot 9 is attached to prevent the dust from entering the cylinder body 8. This dust boot 9
Has an outer diameter portion 91 fitted to the cylinder body 8 and an inner diameter portion 92 fitted to the piston 7, and a retainer 911 is bonded to the outer diameter portion 91.

That is, the outer peripheral surface of the cylinder body 8 is provided with a fitting groove 80 into which the outer diameter portion 91 of the boot is fitted. A fitting groove 70 into which the inner diameter portion 92 of the boot 9 is fitted is provided on the outer peripheral surface of the piston 7.

[0006]

However, the conventional wheel cylinder 90 has the following problems. That is, since it is necessary to provide the fitting grooves 80 and 70 in the cylinder body 8 and the piston 7, respectively,
Each requires cutting. Particularly, the piston 7 needs to have a complicated structure. Further, when the dust boot 9 is mounted, it is necessary to press the dust boot 9 into the opening end of the cylinder body 8 or the piston 7 using the retainer 911 or the like in order to improve the adhesion thereof. The installation method is not easy.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a wheel cylinder in which the structure of the piston can be simplified and the dust seal can be easily attached.

[0008]

According to the present invention, a piston is slidably mounted in a cylinder body, and a fitting step portion formed toward the piston is provided inside an opening end of the cylinder body. A wheel cylinder having a ring-shaped dust seal fitted between the dust seal and the fitting step portion, wherein the fitting step portion has a protrusion protruding toward the outer periphery of the piston, while the dust seal is provided. On the outer peripheral side,
It has an annular recess that does not contact the protrusion of the fitting step, a pair of outer peripheral contact parts that contact the fitting step on both sides of the annular recess, and an inner peripheral side of the dust seal. A wheel cylinder is characterized in that it has a pair of inner peripheral contact portions that come into contact with the outer periphery of the piston, at portions that are located outside the pair of outer peripheral contact portions.

What is most noticeable in the present invention is that the fitting step portion is provided with the projecting portion, while the dust seal is provided with the annular concave portion and a pair of outer peripheral contact portions on the outer peripheral side thereof, and the inner peripheral portion thereof. Is provided with a pair of inner peripheral contact portions positioned outside the pair of outer peripheral contact portions.

The inner diameter of the dust seal is slightly smaller than the outer diameter of the piston to which it is mounted, and the outer diameter of the dust seal is slightly larger than the inner diameter of the fitting step portion. Also,
The material is, for example, synthetic rubber, thermoplastic elastomer,
An elastic body such as natural rubber is used. Further, it is preferable that the dust seal is provided with annular concave grooves on both sides thereof.
As a result, the effect of reducing the resistance when the piston slides can be obtained.

Further, it is preferable that the piston has a flange portion having a larger outer diameter than the outer diameter of the fitting step portion at the tip end portion thereof. As a result, it is possible to prevent the dust seal from coming off from the piston during assembly.

[0012]

In the wheel cylinder of the present invention, when the piston is stationary, the pair of outer peripheral contact portions and the pair of inner peripheral contact portions of the dust seal are subjected to tensioning forces in opposite directions. There is. Further, in this stationary state, the tightening force of one outer peripheral contact portion and the other outer peripheral contact portion are substantially equal. In addition, the tightening force of one inner peripheral contact portion and the other inner peripheral contact portion are almost equal.

Next, when the piston moves in the contracting direction, that is, when moving to the cylinder side, the dust seal receives a force that moves in the same direction as the piston moving direction due to the action of the frictional force on the sliding surface. At this time, the action of the protruding portion of the cylinder body changes the distribution of the tightening force. That is, the distance between the one outer peripheral contact portion and the one inner peripheral contact portion on the transfer direction side of the piston, that is, in the cylinder inward direction with respect to the protruding portion is wider than that at the stationary state. As a result, the tension force at those positions becomes smaller than that at rest.

Further, the distance between the other outer peripheral contact portion and the other inner peripheral contact portion outside the protruding portion is narrowed. As a result, the tension force at those positions becomes larger than that at rest. Therefore, the tension on the outer side of the dust seal is increased. Therefore, it is possible to improve the sealing force that prevents dust attached to the outer peripheral surface of the piston from entering the cylinder body. In addition, the total sum of the tightening forces has almost no increase or decrease compared to when stationary, so there is no effect on the sliding resistance of the piston.

Next, when the piston moves in the extension direction, that is, in the outward direction, the same operation as in the above-described contraction direction transition occurs when the transition direction is used as a reference. That is, the tightening force at one outer peripheral contact portion and one inner peripheral contact portion located inward of the cylinder with respect to the protruding portion is greater than that at rest. On the other hand, the tightening force at the other outer peripheral contact portion and the other inner peripheral contact portion is smaller than that at the time of rest, but sufficient tightening force is retained to prevent dust from entering.

Further, since the tightening force of the inner portion of the dust seal is increased in this manner, it is possible to prevent the lubricating oil in the cylinder body from flowing out due to the movement of the piston in the extension direction. Also in this case, the total sum of the tensioning forces does not increase or decrease as compared with that at rest, so that the sliding resistance of the piston is not affected. Further, even when the piston moves in the extension direction or the contraction direction, the inner peripheral contact portion of the dust seal is located outside of the outer peripheral contact portion as in the stationary state, so that the sliding resistance during the piston transfer can be reduced.

The fitting of the dust seal can be easily performed by pushing the dust seal between the fitting step portion and the gap portion of the piston. Further, in the fitted dust seal, the pair of outer peripheral contact portions are positioned so as to sandwich the projecting portion of the fitting step portion, and the respective contact portions are pressed against each other in the sliding direction of the piston. Therefore, the fitted dust seal does not come off.

That is, the dust seal can be easily mounted without using auxiliary components such as a retainer as in the conventional example. Moreover, since such a fitting means is used,
There is no need to perform complicated processing for fitting the dust seal to the piston, and the piston structure can be simplified.

Therefore, according to the present invention, it is possible to provide a wheel cylinder in which the structure of the piston can be simplified and the dust seal can be easily attached.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A wheel cylinder according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 to 4, the wheel cylinder 10 of this example has a piston 4 slidably mounted in a cylinder body 3, and the piston 4 is fitted inside the opening end 31 of the cylinder body 3. A fitting stepped portion 30 formed facing toward is provided, and a ring-shaped dust seal 2 is fitted between the piston 4 and the fitting stepped portion 30.

Then, as shown in FIG. 2, the fitting stepped portion 30 has a protruding portion 33 protruding toward the outer periphery of the piston 4. On the other hand, the dust seal 2 has, on the outer peripheral side thereof, an annular recess 21 that does not come into contact with the protrusion 33 of the fitting step 30.
And a pair of outer peripheral contact portions 201 and 202 that contact the fitting step portion 30 on both sides of the annular recess 21. Further, on the inner peripheral side of the dust seal 2, there are provided a pair of inner peripheral contact portions 203 and 204, which are in contact with the outer periphery of the piston 4, at portions located outside the pair of outer peripheral contact portions 201 and 202. In addition, the inner peripheral contact portion 20
An annular inner peripheral concave portion 205 is provided between 3, 204.

The inner diameter of the dust seal 2 is slightly smaller than the outer diameter of the piston 4, and the outer diameter of the dust seal 2 is
It is slightly larger than the inner diameter of the fitting step portion 30. The material is synthetic rubber. Also, the dust seal 2
Has annular recessed grooves 22 on both sides thereof. Further, the piston 4 has a flange portion 40 having an outer diameter larger than the outer diameter of the fitting step portion 30.

Next, the function and effect of this example will be described. In the wheel cylinder 10 of the present example, as shown in FIG. 3, when the piston 4 is stationary, the pair of outer peripheral contact portions 201 and 202 of the dust seal 2 are provided.
And, the pair of inner peripheral contact portions 203, 204 are subjected to the tightening forces 51, 52, 53, 54 in opposite directions. Further, in this stationary state, the tightening forces 51 and 52 of the one outer peripheral contact portion 201 and the other outer peripheral contact portion 202 are substantially equal. Further, the tightening forces 53 and 54 of the one inner peripheral contact portion 203 and the other inner peripheral contact portion 204 are substantially equal.

Next, when the piston 4 moves in the contracting direction, as shown in FIG. 4, the force of the dust seal 2 moving in the same direction as the moving direction of the piston 4 is generated by the action of the frictional force on the sliding surface. receive. At this time, the distribution of the tightening forces 51, 52, 53, 54 changes due to the action of the protrusion 33 of the cylinder body 3.

That is, as can be seen from a comparison between FIG. 3 and FIG. 4, one outer peripheral contact portion 201 and one inner peripheral contact portion 203, which are located on the transitional side of the piston 4, that is, on the inner side of the protruding portion 33. The interval L becomes wider than that at the time of rest (FIG. 3). This also allows the tensioning force 5 at those positions.
5, 57 are smaller than the straining forces 51, 53 at rest, and are distributed as shown in FIG.

Further, the distance R between the other outer peripheral contact portion 202 and the other inner peripheral contact portion 204, which are outside the protruding portion 33, is narrowed. As a result, the tightening forces 56, 58 at those positions become larger than the tightening forces 52, 54 at rest, and are distributed as shown in FIG. By increasing the tightening force of the outer portion of the dust seal 2 in this way, it is possible to improve the sealing force for preventing the dust 400 adhering to the outer peripheral surface of the piston 4 from entering the cylinder body 3. . Further, the total sum of the tightening forces 55 to 58 has almost no increase or decrease as compared with the tightening forces 51 to 54 (FIG. 3) at rest, so that there is no influence on the sliding resistance of the piston 4.

Next, even when the piston 4 moves in the extension direction, the same operation as in the contraction direction transition occurs when the transition direction is used as a reference. That is, one outer peripheral contact portion 20 located inward of the cylinder with respect to the protruding portion 33.
1 and the inner peripheral contact portion 203 on one side have a greater tightening force than when stationary. On the other hand, although the tightening force at the other outer peripheral contact portion 202 and the other inner peripheral contact portion 204 is smaller than that at the time of rest, a sufficient tightening force is retained to prevent dust from entering.

Further, since the tightening force of the inner portion of the dust seal 2 is increased in this way, it is possible to prevent the lubricating oil in the cylinder body 3 from flowing out due to the movement of the piston 4 in the extension direction. Also in this case, the total sum of the tensioning forces does not increase or decrease as compared with the stationary state, so that the sliding resistance of the piston 4 is not affected. Furthermore, piston 4
Even when moving in the extension direction or the contracting direction, the inner peripheral contact portions 203 and 204 of the dust seal 2 are located outside the outer peripheral contact portions 201 and 202, as in the stationary state, so that the sliding resistance when the piston 4 moves is reduced. it can.

Further, since the piston 4 has the flange portion 40 having a diameter larger than the outer diameter of the fitting step portion 30, it is possible to prevent the dust seal 2 from coming off from the piston 4 during assembly.

The fitting of the dust seal 2 can be easily performed by pushing the dust seal 2 between the fitting step portion 30 and the gap portion of the piston 4. The fitted dust seal 2 is positioned such that the pair of outer peripheral contact portions 201 and 202 sandwich the protruding portion 33 of the fitting step portion 30, and the respective contact portions 201 and 202 slide on the piston 4. It is pressed in the opposite direction.
Therefore, the fitted dust seal 2 does not come off.

That is, the adhesion of the dust seal 2 can be easily secured without using auxiliary components such as a retainer as in the conventional example. Moreover, since such a fitting means is used,
It is not necessary to perform complicated processing for fitting the dust seal 2 on the piston 4, and the structure of the piston 4 can be simplified.

Therefore, according to this example, it is possible to provide the wheel cylinder 10 in which the structure of the piston 4 can be simplified and the dust seal 2 can be easily mounted.

Comparative Example A comparative example of the present invention will be described with reference to FIGS.
As shown in FIG. 5, the wheel cylinder 800 in this comparative example is such that the dust seal 82 adhered to the retainer 85 is press-fitted into the flat step portion 830 provided at the opening end portion 831 of the cylinder body 83.

The inner surface of the flat step portion 830 is flat without any protrusion. In addition, the dust seal 82
Has an annular recess 820 in its inner diameter and inner circumference contact portions 821, 822 contacting the piston 84 on both sides thereof. Others are the same as the embodiment.

In this comparative example, the dust seal 8 is used.
When the two are fitted together, the retainer 85 adhered to the dust seal 82 is indispensable, impairing the ease of mounting the dust seal and increasing the number of parts. Further, in the stationary state of the piston 84, as shown in FIG. 6, the tightening forces 851 and 852 of the inner peripheral contact portions 821 and 822 act in the contact area S downward in the drawing direction. Further, the tightening force 850 of the outer peripheral contact portion 823 has the strongest distribution in the contact area S and the weakest distribution in the area C between the contact areas S on both sides, and acts upward in the drawing direction.

That is, the tightening force is concentrated on the contact area S in the vertical direction in the figure. Therefore, the distribution of the tightening force is extremely concentrated on one of the inside and the outside of the contact area S when the piston 84 contracts or moves in the extension direction, and the sliding resistance of the piston 84 is larger than that of the embodiment. Become.

Therefore, in this comparative example, not only the ease of mounting the dust seal obtained in the example is impaired, but also extra parts are required and the sliding resistance of the piston is increased.

[Brief description of drawings]

FIG. 1 is a sectional view of a wheel cylinder according to an embodiment.

FIG. 2 is a sectional view of a dust seal portion in the wheel cylinder according to the embodiment.

FIG. 3 is an explanatory view of a tension force distribution when the piston is stationary in the wheel cylinder according to the embodiment.

FIG. 4 is an explanatory view of a tension force distribution at the time of piston transfer in the wheel cylinder according to the embodiment.

FIG. 5 is a cross-sectional view of a dust seal portion in a wheel cylinder according to a comparative example.

FIG. 6 is an explanatory view of a tension force distribution when the piston is stationary in the wheel cylinder in the comparative example.

FIG. 7 is an explanatory diagram of how a wheel cylinder according to a conventional example is attached to a drum brake.

FIG. 8 is a cross-sectional view of a dust boot portion in a wheel cylinder according to a conventional example.

[Explanation of Codes] 10. ． ． Wheel cylinder, 2. ． ． Dust seal, 21. ． ． Annular recess, 201, 202. ． ． Outer peripheral contact portion, 203, 204. ． ． Inner circumference contact part, 3. ． ． Cylinder body, 30. ． ． Mating step, 31. ． ． Open end, 33. ． ． Protruding portion, 4. ． ． Piston, 40. ． ． Flange part,

Claims (3)

[Claims] 1. A piston is slidably mounted in a cylinder body, and a fitting step formed toward the piston is provided inside an opening end of the cylinder body. A ring-shaped dust seal is fitted between the wheel cylinder and the fitting part, and the fitting step part has a protrusion protruding toward the outer circumference of the piston, while the dust seal is on the outer circumference side. Has an annular recess that does not come into contact with the protruding portion of the fitting step, a pair of outer peripheral contact portions that contact the fitting step on both sides of the annular recess, and an inner peripheral side of the dust seal. Is a wheel cylinder characterized in that it has a pair of inner peripheral contact portions that come into contact with the outer periphery of the piston, at a portion located outside the pair of outer peripheral contact portions. 2. The wheel cylinder according to claim 1, wherein the dust seal has concave grooves on both sides thereof. 3. The wheel cylinder according to claim 1, wherein the piston has a flange portion having a larger outer diameter than an outer diameter of the fitting step portion at a tip end portion thereof.