Cup seal

Abstract

To provide a cup seal that is able to reduce sliding friction resistance to a piston and to an inner bottom surface of a seal groove while preventing damage to a specific part of the cup seal and that is able to avoid influence on sealing performance.SOLUTION: A cup seal has an annular rotational force applying member 19 provided at a center-side end part of a base portion 16 and extending in the same direction as an inner seal lip 17 and an outer seal lip 18. The rotational force applying member is composed of a plurality of wing-like portions 22 dividedly formed at almost equal intervals in a circumferential direction. A first projecting portion 24 and a second projecting portion 25 are provided on a tip surface of each wing-like portion. A first pressure receiving surface 24a formed in an inclined shape in one direction, with a twist angle with respect to an axial direction of the cup seal, is provided on an inner-side surface of the first projecting portion. A second pressure receiving surface 25a formed in an inclined shape in the other direction, with a twist angle with respect to the axial direction of the cup seal, is provided on an outer-side surface of the second projecting portion.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an improvement in a cup seal that is incorporated into a master cylinder in a brake system of, for example, an automobile. [Background technology]

[0002] As is well known, the cup seal in the master cylinder is generally a seal member with a substantially U-shaped cross section, and slides between the cylinder body and the piston inserted in the cylinder body to perform a sealing function and a checking function for isolating and forming a hydraulic chamber. Therefore, a phenomenon called "eating" has been a problem. This phenomenon is a phenomenon in which a part of the cup seal gets caught between the cylinder body and the piston, and is torn off and locally damaged as the sliding action is repeated. This phenomenon is particularly noticeable when the anti-lock brake system is activated, in which the hydraulic pressure on the wheel cylinder side is kicked back to the master cylinder side.

[0003] Therefore, there are cup seals that generate rotational force in the cup seal by utilizing the change in hydraulic pressure that accompanies the movement of the piston inside the cylinder body, such as the cup seal described in the following Patent Document 1, which was previously applied for by the same applicant.

[0004] FIG. 12 is an enlarged cross-sectional view of a main portion of a master cylinder to which a conventional cup seal is applied, and FIG. 13 is a perspective view of an inner diameter sliding type primary cup seal of the same cup seal.

[0005] 12 and 13, this conventional cup seal 30 is housed and held in an annular seal groove 2a formed in the inner circumferential surface of the cylinder body 2 of the master cylinder 1, and is a so-called inner diameter sliding type with a substantially U-shaped cross section. This cup seal 30 includes an annular base portion 31, an inner seal lip 32 that slides against the primary piston 3, and an outer seal lip 33. The base portion 31, the inner seal lip 32, and the outer seal lip 33 form a substantially U-shaped cross section.

[0006] The inner seal lip 32 is provided with a plurality of protrusions 34 having wing-like surfaces inclined at a twist angle relative to the axial direction of the cup seal 30 on the inner peripheral surface of the root portion, and a guide groove portion 35 is formed adjacent to the root portion on the wing-like surface 34a side of each of the protrusions 34.

[0007] Then, hydraulic pressure M when hydraulic fluid is supplied to the hydraulic chamber is applied directly as dynamic pressure to the blade surface 34a from a reservoir tank (not shown) through the supply hole 36 and via the guide grooves 35 of each protrusion 34. This actively rotates the cup seal 30 in one circumferential direction. This prevents a specific portion of the cup seal 30 from being repeatedly bitten, reducing the phenomenon of wear and tear, thereby improving durability. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2011-99516 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the conventional cup seal 30 described in the above publication, a plurality of protrusions 34 that slide against the outer peripheral surface 3a of the primary piston 3 are provided on the inner peripheral surface of the root portion of the inner seal lip 32, which may increase the sliding friction resistance between the inner peripheral surface 3a of the primary piston 3.

[0010] In addition, the inner seal lip 32 of the cup seal 30 is an important sealing surface between it and the outer peripheral surface 3a of the primary piston 3, and the presence of each protrusion 34 may disrupt the balance of surface pressure on the circumference, which may affect the sealing performance.

[0011] As another example, the protrusions 34 may be provided at the base of the outer seal lip 33. However, in this case as well, the sliding friction resistance with the inner bottom surface 2b of the seal groove 2a increases, and the balance of surface pressure is disrupted, which may affect the sealing performance with the inner bottom surface 2b of the seal groove 2a.

[0012] The present invention was devised in consideration of the technical problems with the conventional cup seals described above, and aims to provide a cup seal that can reduce sliding friction resistance with the piston and the inner bottom surface of the seal groove while suppressing damage to specific parts of the cup seal, and can avoid any impact on sealing performance. [Means for solving the problem]

[0013] The invention according to claim 1 of the present application is a cup seal comprising: an annular base portion; an annular inner seal lip extending in the axial direction from an inner peripheral end portion of the base portion and capable of sliding on an outer peripheral surface of a piston; and an annular outer seal lip extending from an outer peripheral end portion of the base portion in the same direction as the inner seal lip, the cup seal being housed and held in an annular seal groove formed on an inner peripheral surface of a cylinder body in which the piston slides, a rotational force applying member provided at a center end between the inner peripheral end and the outer peripheral end of the base portion and extending in the same direction as the inner seal lip and the outer seal lip, The rotational force imparting member has a first pressure-receiving surface formed in a unidirectional inclined shape with a twist angle relative to the axial direction of the cup seal, and is characterized in that a unidirectional rotational force is imparted to the cup seal by hydraulic pressure acting on the first pressure-receiving surface. Effect of the Invention

[0014] According to the present invention, it is possible to suppress deterioration of the sealing function due to damage to a specific portion of the cup seal, and to reduce sliding friction resistance. [Brief description of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view showing a schematic structure of a master cylinder to which a cup seal according to the present invention is applied; [Diagram 2] FIG. 1 is a perspective view showing a first embodiment of a cup seal according to the present invention. [Diagram 3] 3 is a partially enlarged perspective view of the cup seal shown in FIG. 2. FIG. [Figure 4] FIG. 2 is a front view of the cup seal of the first embodiment. [Diagram 5] 5 is a partially enlarged front view of the cup seal shown in FIG. 4. [Figure 6] 2 is an enlarged view of a portion A in FIG. 1, illustrating a state in which hydraulic pressure acts on a cup seal from a hydraulic pressure chamber used in the present embodiment. [Figure 7] 7 is a schematic diagram showing a direction in which a liquid pressure acts on the cup seal shown in FIG. 6. [Figure 8] 2 is an enlarged view of a portion A in FIG. 1, illustrating a state in which hydraulic pressure supplied from a master cylinder of the embodiment acts on a cup seal. [Figure 9] 9 is a schematic diagram showing a direction in which a hydraulic pressure acts on the cup seal shown in FIG. 8. [Figure 10] FIG. 4 is a perspective view showing a second embodiment of a cup seal according to the present invention. [Figure 11] FIG. 11 is a perspective view showing a third embodiment of a cup seal according to the present invention. [Figure 12]1 is a cross-sectional view of a main portion of a master cylinder to which a conventional cup seal is applied. [Figure 13] FIG. 13 is a perspective view of the inner diameter sliding type primary cup seal shown in FIG. 12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a cup seal according to the present invention will be described with reference to the drawings.

[0017] Fig. 1 is a cross-sectional view showing an outline of a master cylinder 1 of an automobile brake device to which the cup seal of this embodiment is applied, showing a state in which each of pistons 3, 4 has moved in the advancing direction. Figs. 2 to 5 are views showing the details of the cup seal.

[0018] 1, the master cylinder 1 includes a cylindrical cylinder body 2 with a bottom, and a primary piston 3 and a secondary piston 4 that are arranged in series and slidably within the cylinder body 2. The cylinder body 2 includes a reservoir tank 5 that stores hydraulic fluid (brake fluid) therein.

[0019] When the brake pedal is depressed, the primary piston 3 is pushed to the left in FIG. 1 by a push rod (not shown) or the like.

[0020] A first hydraulic pressure chamber 6 is formed between the two pistons 3, 4, and a second hydraulic pressure chamber 7 is formed between the inner bottom of the cylinder body 2 and the secondary piston 4. The first and second hydraulic pressure chambers 6, 7 also serve as spring accommodating sections, with a first return spring 8, which is a compression coil spring, being accommodated in the first hydraulic pressure chamber 6, and a second return spring 9, which is also a compression coil spring, being accommodated in the second hydraulic pressure chamber 7. The primary piston 3 and secondary piston 4 are urged to the right in FIG. 1 by the first and second return springs 8, 9.

[0021] Furthermore, if there are two brake systems operated by the master cylinder 1, the first hydraulic chamber 6 is connected to the wheel cylinder of one brake system via an output port not shown, and the second hydraulic chamber 7 is connected to the wheel cylinder of the other brake system via an output port not shown.

[0022] A first supply hole 10 and a second supply hole 11 are formed in the inner peripheral surface of the cylinder body 2, and these first and second supply holes 10, 11 can communicate with the reservoir tank 5. The first supply hole 10 is set to communicate with the first hydraulic pressure chamber 6, and the second supply hole 11 is set to communicate with the second hydraulic pressure chamber 7 when the pistons 3, 4 have moved backward from the state shown in FIG. 1 to the non-braking state, i.e., when the pistons 3, 4 are at their backward limit positions.

[0023] Additionally, a primary cup seal 12 or 13 and a secondary cup seal 14 or 15 are attached to the front and rear of the first supply hole 10 and the second supply hole 11, respectively. Each of the primary cup seals 12, 13 and each of the secondary cup seals 14, 15 are made of solid rubber such as EPDM and have a substantially E-shaped cross section. The primary cup seal 12 and the secondary cup seal 14 are in pressure contact with the primary piston 3, while the primary cup seal 13 and the secondary cup seal 15 are in pressure contact with the secondary piston 4, and these sealing functions isolate the first hydraulic chamber 6 and the second hydraulic chamber 7, ensuring their independence.

[0024] Then, as shown in FIG. 1, when the brake pedal is depressed and the primary piston 3 is pressed leftward against the biasing force of the first and second return springs 8, 9, the communication between the first hydraulic pressure chamber 6 and the first supply hole 10 is blocked, the first hydraulic pressure chamber 6 becomes an enclosed space and the internal pressure rises. As a result, the hydraulic pressure in the first hydraulic pressure chamber 6 is supplied to the wheel cylinder of one of the brake systems, generating a braking force.

[0025] At the same time, the increase in pressure in the first hydraulic pressure chamber 6 also presses the secondary cup seal 14 to the left in the figure, blocking communication between the second hydraulic pressure chamber 7 and the second supply hole 11. The second hydraulic pressure chamber 7 then becomes an enclosed space and the internal pressure increases. As a result, the hydraulic pressure in the second hydraulic pressure chamber 7 is supplied to the wheel cylinder of the other brake system, generating a braking force.

[0026] On the other hand, when the brake pedal force is released, the primary piston 3 and the secondary piston 4 move to the right in Fig. 1 due to the spring forces of the first and second return springs 8, 9 in order to return the master cylinder 1 from the braking state in Fig. 1 to the non-braking state. During this return movement of the primary piston 3 and the secondary piston 4, if the pressure in the first and second hydraulic chambers 6, 7 isolated and formed by the primary piston 3 temporarily becomes lower than the atmospheric pressure (pressure in the reservoir tank 5) and a pressure difference occurs, the primary cup seals 12, 13 are deflected in a direction away from the primary piston 3 and the secondary piston 4, performing a so-called valve opening operation, and the hydraulic fluid from the reservoir tank 5 is supplied to the first and second hydraulic chambers 6, 7 through the gaps between the primary piston 3 and the secondary piston 4 and the primary cup seals 12, 13.

[0027] Figure 2 is an oblique view showing a first embodiment of a cup seal according to the present invention, Figure 3 is an oblique view showing a partially enlarged portion of the cup seal shown in Figure 2, Figure 4 is a front view of the cup seal of the first embodiment, Figure 5 is a partially enlarged front view of the cup seal shown in Figure 4, and Figure 6 is an enlarged view of part A in Figure 1 showing the state in which hydraulic pressure acts on the cup seal from the hydraulic pressure chamber used in this embodiment.

[0028] In the following, the primary cup seal 12 on the primary piston 3 side will be mainly described.

[0029] As shown in Figures 2 to 6, the primary cup seal 12 comprises a relatively thick annular base portion 16, an annular inner seal lip 17 extending in the axial direction from the inner peripheral end of the base portion 16 and capable of sliding on the outer peripheral surface of the primary piston 3, an annular outer seal lip 18 extending from the outer peripheral end of the base portion 16 in the same direction as the inner seal lip 17, and a rotational force imparting member 19 extending from a central end between the inner peripheral end and outer peripheral end of the base portion 16 in the same direction as the inner seal lip 17 and the outer seal lip 18, and is formed into a substantially E-shaped cross section by the base portion 16, the two seal lips 17, 18, and the rotational force imparting member 19.

[0030] The primary cup seal 12 is fitted and held in an annular first seal groove 20 formed in the inner circumferential surface of the cylinder body 2 adjacent to the first supply hole 10. The secondary cup seal 14 is also fitted and held in an annular second seal groove 21 formed in the inner circumferential surface of the cylinder body 2.

[0031] 6, a protrusion 17b formed at approximately the center in the axial direction of the inside inner circumferential surface 17a of the inner seal lip 17 abuts against the outer circumferential surface 3a of the primary piston 3 to exert a sealing function, and a tip end 17c is out of contact with one axial end face 20a of the first seal groove 20 to form a first gap C1 between the tip end face 17c and the one axial end face 20a. A wave-shaped abutment portion 17d is provided at a position on the base portion 16 side of the protrusion 17b of the inner circumferential surface 17a, which flexibly abuts against the outer circumferential surface 3a of the primary piston 3 when the inner seal lip 17 is flexibly deformed to ensure sealing performance.

[0032] The outer seal lip 18 is formed to protrude slightly outward, with the outer peripheral surface of the tip portion 18a abutting against the inner bottom surface 20b of the first seal groove 20 to perform a checking function, while the tip edge 18b is in a non-contact state with the axial end face 20a of the first seal groove 20, forming a second gap C2 between it and the axial end face 20a.

[0033] As shown in Figs. 2 to 5, the rotational force applying member 19 is composed of a plurality of (ten in this embodiment) wing-like portions 22 divided and formed at approximately equal intervals in the circumferential direction, and are continuously arranged in the circumferential direction with gaps 23 provided between each pair of wing-like portions 22, 22 adjacent in the circumferential direction. Each wing-like portion 22 is formed in an approximately trapezoidal shape when viewed from the radial side, and has a flared base portion 22a integrally joined to the base portion 16, and a tip portion 22b rising from the base portion 22a and extending toward one axial end face 20a of the first seal groove 20. The shape of each wing-like portion 22 viewed from the side is not limited to a trapezoidal shape, and may be a rectangular shape or other shapes.

[0034] The tip surface of the tip portion 22b of each wing-shaped portion 22 is provided with a first protrusion 24 and a second protrusion 25 protruding toward the axial end face 20a of the first seal groove 20, and these two protrusions 24, 25 are circumferentially spaced apart from each other at a constant circumferential pitch P.

[0035] The first protrusion portion 24 has a first pressure-receiving surface 24a formed on its inner surface facing the inner seal lip 17, which is inclined in one direction at a twist angle with respect to the axial direction of the primary cup seal 12, and the hydraulic pressure M of the working fluid acts on this first pressure-receiving surface 24a.

[0036] The second protrusion 25 has a second pressure-receiving surface 25a formed on its outer surface on the outer seal lip 18 side, the second pressure-receiving surface 25a being inclined in the other direction at a twist angle with respect to the axial direction of the primary cup seal 12. In other words, the second pressure-receiving surface 25a is formed inclined in the same direction as the first pressure-receiving surface 24a, and as a pressure-receiving surface, it is adapted to receive the hydraulic pressure M in the opposite direction to the first pressure-receiving surface 24a.

[0037] In other words, with regard to the hydraulic pressure in the first hydraulic pressure chamber 6, the hydraulic pressure M flowing in from the inner seal lip 17 side of the primary cup seal 12 acts on the first pressure-receiving surface 24a of the first protrusion 24, while the hydraulic pressure M flowing in from the outer seal lip 18 side acts on the second pressure-receiving surface 25a of the second protrusion 25.

[0038] In this way, when hydraulic pressure M acts on each first pressure surface 24a, a rotational force is applied to the primary cup seal 12, causing it to rotate in the right direction (forward direction) as indicated by the black arrow in Figure 7, and when hydraulic pressure acts on each second pressure surface 25a, it causes it to rotate in the left direction (reverse direction) as indicated by the black arrow in Figure 8.

[0039] 6, when the primary cup seal 12 is housed and held in the first seal groove 20, the leading edges 24b, 25b of the first protrusion 24 and the second protrusion 25 abut against one axial end face 20a of the first seal groove 20. As shown in FIG. 3, the protrusions 24, 25 have first and second inclined cut surfaces 24c, 25c formed at the leading ends of the opposing sides.

[0040] The respective structures and shapes of the first and second protrusions 24, 25 and the first and second pressure receiving surfaces 24a, 25a are the same as those of the primary cup seal 13 on the secondary piston 4 side in FIG.

[0041] [Functions and Effects of the Primary Cup Seal According to this Embodiment] Figure 7 is a schematic diagram showing the direction in which hydraulic pressure acts on the cup seal shown in Figure 6, Figure 8 is an enlarged view of part A in Figure 1 showing the state in which hydraulic pressure supplied from the master cylinder of this embodiment acts on the cup seal, and Figure 9 is a schematic diagram showing the direction in which hydraulic pressure acts on the cup seal shown in Figure 8.

[0042] The effects of the primary cup seal 12 according to this embodiment will be described below.

[0043] First, as described above, when the primary piston 3 is pressed leftward in Fig. 1, the internal pressure of the first hydraulic pressure chamber 6 rises, and the hydraulic pressure M in the first hydraulic pressure chamber 6 is supplied to the wheel cylinder of one of the brake systems to generate a braking force. At this time, the hydraulic pressure M in the first hydraulic pressure chamber 6 flows toward the tips of the wing-like portions 22 (the protrusions 24, 25) through the first gap C1 between the tip 17c of the inner seal lip 17 of the primary cup seal 12 and one axial end face 20a of the first seal groove 20, as shown by the arrow in Fig. 6.

[0044] The hydraulic pressure M flowing in the direction of each protrusion 24, 25 of each wing-like portion 22 passes through the gaps 23 between each wing-like portion 22 and flows toward the outer seal lip 18, as shown by the arrows in Figure 6, causing the outer seal lip 18 to flex and deform toward the inner bottom surface 20b of the first seal groove 20, i.e., in the opening direction, thereby performing a checking function.

[0045] On the other hand, the hydraulic pressure M flowing in the direction of each of the protrusions 24, 25 of each of the wing-like portions 22 acts directly as dynamic pressure on each of the first pressure-receiving surfaces 24a of each of the first protrusions 24, as shown by the white arrows in Figures 6 and 7. When the dynamic pressure acts on each of the first pressure-receiving surfaces 24a, a component force in the circumferential direction is generated, and in response to this component force, the primary cup seal 12 rotates in one direction, that is, to the right in the figure, as shown by the black arrow in Figure 7.

[0046] This rightward rotation of the primary cup seal 12 changes the relative positional relationship in the circumferential direction of the primary cup seal 12 with respect to the cylinder body 2 and the primary piston 3, and as a result, specific parts of the base portion 16 and the inner seal lip 17 of the primary cup seal 12 are no longer repeatedly caught between the cylinder body 2 and the primary piston 3. This reduces the occurrence of the erosion phenomenon in the inner seal lip 17, improving durability (erosion resistance).

[0047] Next, when returning from the braking state to the non-braking state, that is, when the primary piston 3 moves rightward from the position shown in Fig. 1, the pressure in the first hydraulic pressure chamber 6 temporarily becomes lower than the atmospheric pressure (pressure in the reservoir tank 5), causing a pressure difference. Then, as shown by the arrow in Fig. 8, part of the hydraulic fluid in the reservoir tank 5 passes through the first supply hole 10 from between the outer circumferential surface 3a of the primary piston 3 and the inner circumferential surface of the cylinder body 2, pushing the inner seal lip 17 of the primary cup seal 12 outward and opening it, and is supplied to the first hydraulic pressure chamber 6.

[0048] On the other hand, another portion of the working fluid that has passed between the outer peripheral surface 3a of the primary piston 3 and the inner peripheral surface of the cylinder body 2 flows around to the back side of the base portion 16 and into the first seal groove 20, passes between the other axial end face 20c of this first seal groove 20 and the back side of the base portion 16, causes the outer seal lip 18 to flex inwardly and deform, flows in the direction of each of the protrusions 24, 25 of each wing-like portion 22, and is supplied to the first hydraulic pressure chamber 6 through between the tip portion 17c of the inner seal lip 17 and one axial end face 20a.

[0049] Then, the working fluid (hydraulic pressure M) that flows from the tip 18a side of the outer seal lip 18 in the direction of each of the protrusions 24, 25 of each of the wing-like portions 22 acts directly as dynamic pressure on the second pressure-receiving surfaces 25a of each of the second protrusions 25, as shown in Fig. 9. When the dynamic pressure acts on each of the second pressure-receiving surfaces 25a, a component force in the circumferential direction is generated, and in response to this component force, the primary cup seal 12 rotates in the other direction, that is, the leftward direction in the figure, as indicated by the black arrow in Fig. 9.

[0050] Therefore, as described above, the relative positional relationship in the circumferential direction of the primary cup seal 12 with respect to the cylinder body 2 and the primary piston 3 changes due to the rotation of the primary cup seal 12 in the other direction, and as a result, specific parts of the base portion 16 and the inner seal lip 17 of the primary cup seal 12 are not repeatedly caught between the cylinder body 2 and the primary piston 3. This reduces the occurrence of the erosion phenomenon in specific parts of the inner seal lip 17, improving durability (erosion resistance).

[0051] Incidentally, such a function is also exhibited in the primary cup seal 13 on the secondary piston 4 side.

[0052] Furthermore, in this embodiment, the first and second protrusions 24, 25 are not provided on the inner surface of the inner seal lip 17 or the outer surface of the outer seal lip 18, as in the conventional cup seals described in the above-mentioned publication, but are provided on the rotational force applying member 19 (each wing-like portion 22).Therefore, the sealing function provided by the inner seal lip 17 of the primary cup seal 12 is not affected and an increase in sliding friction resistance can be suppressed.

[0053] That is, in this embodiment, no protrusions are provided on the inner seal lip 17 or the outer seal lip 18, and instead, the protrusions 24, 25 are provided on the tip end surface of the rotational force applying member 19 (each wing-like portion 22) that is not in contact with the inner bottom surface 20b of the first seal groove 20 or the outer peripheral surface 3a of the primary piston 3, so that the surface pressure balance between the outer peripheral surface 3a of the primary piston 3 against which the inner peripheral surface 17a of the inner seal lip 17 slides is properly maintained. This prevents the inner seal lip 17 from affecting the sealing performance. As a result, good sealing performance of the primary cup seal 12 can be ensured, and durability can be improved.

[0054] Also, the sliding friction resistance between the protrusion 17b formed on the inner peripheral surface 17a of the inner seal lip 17 and the outer peripheral surface 3a of the primary piston 3 can be reduced.

[0055] Furthermore, according to this embodiment, first protrusions 24 and second protrusions 25 are provided on multiple wing-like portions 22, and hydraulic pressures with different inflow directions are received by multiple first pressure-receiving surfaces 24a and multiple second pressure-receiving surfaces 25a, respectively. As a result, the overall component force applied to the primary cup seal 12 is increased, and the rotational force in one direction or the other on the primary cup seal 12 can be increased.

[0056] As described above, the hydraulic pressure M generated by the sliding of each primary piston 3 in the advancing and retracting directions within the cylinder body 2 acts on either the first pressure-receiving surface 24a of the first protrusion 24 or the second pressure-receiving surface 25a of the second protrusion 25, so that a rotational force in two directions, one direction (rightward) or the other direction (leftward), is applied to the primary cup seal 12 when the primary piston 3 slides in either the advancing or retracting direction. This makes it possible to more effectively prevent damage to specific portions of the primary cup seal 12.

[0057] Furthermore, since the first and second protrusions 25 are provided together on one wing-like portion 22, the structure is simplified compared to when they are provided individually on separate wing-like portions 22. [Second embodiment] FIG. 10 shows a second embodiment of the present invention, which differs from the first embodiment in that the structure of each wing portion 26 of the rotational force applying member 19 of the primary cup seal 12 is changed.

[0058] That is, each wing-like portion 26 is divided intermittently along the circumferential direction, and in this embodiment, is divided into 20 pieces, and each wing-like portion 26 is formed into a triangular prism shape. Also, each wing-like portion 26 is arranged continuously with a constant gap 23 between adjacent wing-like portions 26 in the circumferential direction, so that the entire wing-like portion 26 is formed into an annular shape, and each tip portion 26a in the circumferential direction is oriented in the same direction.

[0059] Each wing-like portion 26 has an outer surface 26b facing the outer seal lip 18, which is formed as a curved surface along the circumferential direction, while an inner surface facing the inner seal lip 17 is formed as a first pressure-receiving surface 26c that is linearly inclined in one direction at a twist angle relative to the axial direction of the primary cup seal 12.

[0060] Therefore, as described above, when the primary piston 3 is pressed leftward in FIG. 1, the hydraulic pressure in the first hydraulic chamber 6, whose internal pressure has increased, passes through the first gap C1 between the tip end 17c of the inner seal lip 17 of the primary cup seal 12 and the axial end face 20a of the first seal groove 20, and flows toward each of the wing-like portions 26. The hydraulic pressure flowing toward each of the wing-like portions 26 acts directly as dynamic pressure on each of the pressure-receiving surfaces 26c of the inner surfaces. When dynamic pressure acts on each of the pressure-receiving surfaces 26c, a circumferential component force is generated, and the primary cup seal 12 rotates in one circumferential direction (to the right in the figure) in response to this component force.

[0061] Therefore, similarly to the first embodiment, the base portion 16 of the primary cup seal 12 and specific portions of the inner seal lip 17 are prevented from being repeatedly caught between the cylinder body 2 and the primary piston 3. This reduces the occurrence of the erosion phenomenon on the inner seal lip 17, improving durability (erosion resistance).

[0062] Furthermore, since the inner surface of each wing-like portion 26 of the rotational force applying member 19 is formed as the pressure-receiving surface 26c, the sealing function provided by the inner seal lip 17 and the outer seal lip 18 of the primary cup seal 12 is not affected, and an increase in sliding friction resistance can be suppressed.

[0063] That is, in the primary cup seal 12 of this embodiment, no pressure receiving surfaces are provided on the inner seal lip 17 or the outer seal lip 18, and instead, the pressure receiving surfaces 26c are provided on the wing-like portions 26 of the rotational force applying member 19, which is not in contact with the cylinder body 2 or the primary piston 3, so that the balance of surface pressure between the inner seal lip 17 and the outer peripheral surface of the primary piston 3 on which it slides is properly maintained. This prevents the inner seal lip 17 from affecting the sealing performance. As a result, good sealing performance of the primary cup seal 12 can be ensured, and durability can be improved.

[0064] Also, the sliding friction resistance between the protrusion 17b of the inner seal lip 17 and the outer circumferential surface 3a of the primary piston 3 can be reduced, as in the first embodiment. [Third embodiment] FIG. 11 shows a third embodiment of a cup seal of the present invention, the basic structure of which is the same as that of the second embodiment except that the base 26d sides of the wing-like portions 26 of the rotational force imparting member 19 are connected in the circumferential direction by connecting portions 27 provided between adjacent gaps 23.

[0065] Therefore, according to this embodiment, the base portions 26d of adjacent wing-like portions 26 are connected by the connecting portions 27, which increases the connecting force of each wing-like portion 26 to the base portion 16 and the connecting force between each wing-like portion 26 in the circumferential direction, thereby increasing the rigidity of the entire rotational force imparting member 19. This prevents excessive radial bending deformation of each wing-like portion 26 due to hydraulic pressure acting on each pressure-receiving surface 26c in particular, thereby increasing the efficiency of transmission of rotational force from the rotational force imparting member 19 to the primary cup seal 12 and improving the durability of the rotational force imparting member 19. [Fourth embodiment] Although not specifically shown, the fourth embodiment has the basic structure of the second embodiment, and further includes a second pressure receiving surface on the outer surface of each wing-like portion 26. That is, in the second embodiment, the first pressure receiving surface 26c is provided on the inner surface of each wing-like portion 26, but a second pressure receiving surface is further formed on each outer surface. In this case, the second pressure receiving surface is formed inclined in the other direction with a twist angle with respect to the axial direction of the cup seal, so that a rotational force in the other direction is applied to the primary cup seal 12 by the hydraulic pressure acting on the second pressure receiving surface.

[0066] Therefore, this fourth embodiment also provides the same effects as the first to third embodiments, but in particular, since the area of ​​the first and second pressure-receiving surfaces can be made larger than that of the first embodiment, the rotational force imparted to the primary cup seal 12 in the left-right direction is greater.

[0067] The present invention is not limited to the configuration of the above embodiment, and it is possible to further modify the structure of each wing-like portion of the rotational force applying member 19. Furthermore, the cup seal can be applied to other devices and equipment that use a master cylinder, in addition to the above-mentioned automobile brake device. [Explanation of symbols]

[0068] 1...Master cylinder 2...Cylinder body 3…Primary piston 3a...Outer surface 4…Secondary piston 5…Reservoir tank 6...First hydraulic chamber 7…Second hydraulic chamber 8…1st return spring 9…Second return spring 10・11…1st and 2nd supply hole 12·13…Primary cup seal 14·15…Secondary cup seal 16…Base section 17…Inner seal lip 17a...Inner peripheral surface 18…Outer seal lip 18a...Tip 19... Rotational force imparting member 20…First seal groove 20a...One end surface in the axial direction 20b…Inner bottom surface 20b…Other end surface in the axial direction 21…Second seal groove 22...Alar part 23...Gap 24...First protrusion 24a…First pressure surface 24b…Tip surface 25…Second protrusion 25a…Second pressure surface 25b…Tip surface 26…Alar part 26c…Pressure surface 27...Connection part M…Hydraulic pressure

Claims

1. a ring-shaped base portion; an annular inner seal lip extending in an axial direction from an inner peripheral end portion of the base portion and capable of sliding on an outer peripheral surface of a piston; and an annular outer seal lip extending from an outer peripheral end portion of the base portion in the same direction as the inner seal lip, the cup seal being accommodated and held in an annular seal groove formed on an inner peripheral surface of a cylinder body in which the piston slides, a rotational force applying member provided at a center end between the inner peripheral end and the outer peripheral end of the base portion and extending in the same direction as the inner seal lip and the outer seal lip, The rotational force imparting member has a first pressure-receiving surface formed in a unidirectional manner with a twist angle relative to the axial direction of the cup seal, and imparts a unidirectional rotational force to the cup seal by hydraulic pressure acting on the first pressure-receiving surface.

2. 2. The cup seal of claim 1, the rotational force applying member is composed of a plurality of wing-like portions formed by dividing the wing-like portions at positions approximately equally spaced in the circumferential direction, Each of the wing-like portions is provided at a tip end thereof with a first protrusion and a second protrusion spaced apart from the first protrusion in the circumferential direction, The first pressure receiving surface is provided on an inner surface of the first protrusion, and a second pressure receiving surface is provided on an outer surface of the second protrusion, The second pressure surface is formed inclined in the other direction at a twist angle relative to the axial direction of the cup seal, and a rotational force in the other direction is applied to the cup seal by hydraulic pressure acting on the second pressure surface.

3. 2. The cup seal of claim 1, The cup seal is characterized in that the rotational force imparting member is composed of a plurality of wing-like portions divided and formed at approximately equally spaced positions in the circumferential direction, and the first pressure-receiving surface is provided on the inner surface of each of the wing-like portions.

4. 4. The cup seal according to claim 3, A second pressure surface is provided on an outer surface of each of the wing-like portions, The second pressure surface is formed inclined in the other direction with a twist angle relative to the axial direction of the cup seal, and a rotational force in the other direction is applied to the cup seal by hydraulic pressure acting on the second pressure surface.

5. 4. The cup seal according to claim 3, A cup seal characterized in that each of the wing-like portions has its base portion connected to the base portion along a circumferential direction.

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