Disc brake device

Abstract

To provide a disc brake device which can prevent a piston from excessively displacing to the axial direction inside with respect to a caliper body when releasing a parking brake also under an extremely low temperature environment.SOLUTION: A rotary-linear motion conversion mechanism 49 includes a recessed-groove shaped nut communication passage 75a on an inner peripheral surface of a nut 53 as a communication section 74 which communicates with an inside internal space 72 existing around an axial direction inside section of a spindle 52 and an outside internal space 73 existing between an end face at the axial direction outside of the spindle 52 and a bottom section 25 of a shared piston 7.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to a disc brake device. [Background technology]

[0002] Disc brake devices are increasingly being used not only on the front wheels of automobiles but also on the rear wheels, due to their excellent heat dissipation properties and the ability to finely adjust the braking force while driving.

[0003] Disc brake devices can be broadly classified into hydraulic disc brake devices, which use hydraulic fluid to generate braking force, and electric disc brake devices, which use an electrically driven actuator to generate braking force.

[0004] A known electric disc brake device has an electric parking brake structure in which the braking force of the service brake is generated by pumping pressurized oil (brake oil) into a cylinder, and the braking force of the parking brake is generated by driving an electric actuator such as a rotary-linear conversion mechanism with an electric motor.

[0005] 22 and 23 show an electric parking brake type disc brake device 100 described in U.S. Patent Application Publication No. 2022 / 0090641 (Patent Document 1).

[0006] The disc brake device 100 has a configuration in which a hydraulic opposed piston type brake mechanism unit 101 that functions as a service brake is combined with an electric floating type brake mechanism unit 102 that functions as a parking brake.

[0007] The disc brake device 100 comprises an opposed-piston caliper body 103 fixed to the suspension device, a clamp member 104 supported on the caliper body 103 to allow axial displacement, a pair of pads 105a, 105b (inner pad 105a, outer pad 105b), and multiple pistons 106, 107 (one dual-purpose piston 106 and three service-only pistons 107). It should be noted that, with respect to the disc brake device 100, the terms "axial direction," "radial direction," and "circumferential direction" refer to the axial direction, radial direction, and circumferential direction of a rotor that rotates together with the wheel, unless otherwise specified.

[0008] The caliper body 103 has two inner cylinders 108a, 108b axially inwardly of the rotor, and two outer cylinders 109a, 109b axially outwardly of the rotor.

[0009] Of the two inner cylinders 108a, 108b, a dual-purpose piston 106 is fitted into the inner cylinder 108a so as to be movable in the axial direction, and a service-only piston 107 is fitted into the other inner cylinder 108b so as to be movable in the axial direction. On the other hand, a service-only piston 107 is fitted into each of the two outer cylinders 109a, 109b.

[0010] The disc brake device 100 generates braking force from the service brake by sending pressurized oil, which is the hydraulic fluid, to all of the cylinders 108a, 108b, 109a, and 109b provided in the caliper body 103, and pressing one dual-purpose piston 106 and three service-only pistons 107 against a pair of pads 105a, 105b.

[0011] In contrast, the disc brake device 100 obtains the braking force from the parking brake without using hydraulic oil, by driving the rotary-linear motion conversion mechanism 110 that constitutes the floating type brake mechanism section 102, and displacing the clamp member 104 in the axial direction relative to the caliper body 103.

[0012] Specifically, the spindle 111 constituting the rotary-to-linear motion conversion mechanism 110 is rotated by energizing the electric motor, and the nut 112 is displaced axially outward. Then, the tip of the nut 112 is pressed against the bottom 113 of the dual-purpose piston 106, and the dual-purpose piston 106 is extended toward the rotor, thereby pressing the inner pad 105a against the axially inner surface of the rotor. Also, the reaction force caused by the pressing is transmitted to the clamp member 104 via the spindle 111, thereby displacing the clamp member 104 axially inward relative to the caliper body 103. Then, the pressing portion 114 provided on the axially outer portion of the clamp member 104 presses the outer pad 105b against the axially outer surface of the rotor. As a result, the rotor is strongly pressed from both axial sides, and braking is performed.

[0013] To release the parking brake, the spindle 111 is rotated by the electric motor in the opposite direction to that during braking. This displaces the nut 112 inward in the axial direction relative to the caliper body 103. Also, by displacing the spindle 111 outward in the axial direction relative to the caliper body 103, the clamp member 104 is displaced outward in the axial direction relative to the caliper body 103. Also, when the nut 112 is displaced inward in the axial direction, the piston seal 115 that seals between the dual-purpose piston 106 and the inner cylinder 108a elastically restores its original shape, displacing the dual-purpose piston 106 inward in the axial direction. This ensures clearance between the pair of pads 105a, 105b and both axial side surfaces of the rotor. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] US Patent Application Publication No. 2022 / 0090641 [Patent Document 2] Patent Publication No. 2021-21423 Summary of the Invention [Problem to be solved by the invention]

[0015] In the conventional electric disc brake device 100, a lubricating liquid such as brake fluid is filled in a space accommodating a plurality of mechanical parts, including the rotary-linear motion conversion mechanism 110, in order to lubricate the plurality of mechanical parts. Specifically, in the conventional electric disc brake device 100, an inner internal space 116 existing around the axially inner part of the spindle 111, and an outer internal space 117 existing between the axially outer end face of the spindle 111 and a bottom part 113 of the dual-purpose piston 106 are filled with lubricating liquid 118.

[0016] In order to prevent the lubricating liquid 118 from leaking out, an outer seal 119 seals between the dual-purpose piston 106 and the nut 112, and an inner seal 120 seals between the axially inner portion of the inner cylinder 108a and the portion of the nut 112 exposed from the dual-purpose piston 106. For this reason, in the electric disc brake device 100 having the conventional structure, the inner internal space 116 and the outer internal space 117 communicate only through a screwed portion 121 between the spindle 111 and the nut 112. Specifically, the inner internal space 116 and the outer internal space 117 communicate through a minute gap present in the screwed portion 121.

[0017] Incidentally, when the parking brake is released, the nut 112 is displaced axially inward relative to the caliper body 103, and the spindle 111 is displaced axially outward relative to the caliper body 103. Therefore, when the parking brake is released, the volume of the inner internal space 116 decreases, and the volume of the outer internal space 117 increases. Then, the lubricating liquid 118 moves from the inner internal space 116 to the outer internal space 117 through the screw-fitting portion 121 between the spindle 111 and the nut 112.

[0018] On the other hand, it is known that the viscosity of the lubricating fluid 118 such as brake oil increases with a decrease in temperature, and increases rapidly in an extremely low temperature environment of, for example, -30°C or lower.

[0019] For this reason, when the disc brake device 100 with the conventional structure is used in an extremely low temperature environment, when the parking brake is released, there is a shortage of lubricating liquid 118 that moves from the inner internal space 116 to the outer internal space 117, and negative pressure is likely to occur in the outer internal space 117. As a result, the dual-purpose piston 106 tends to move axially inward together with the nut 112, and there is a possibility that the amount of displacement of the dual-purpose piston 106 axially inward will become excessive.

[0020] In addition, JP 2021-21423 A (Patent Document 2) is a prior art document related to the present invention. JP 2021-21423 A discloses a technology for forming a hole inside a spindle constituting a rotary-linear conversion mechanism. However, the invention described in JP 2021-21423 A forms a hole inside the spindle to suppress air retention at the meshing portion between the spindle and the nut. In addition, in the invention described in JP 2021-21423 A, the inner internal space existing around the axial inner part of the spindle and the outer internal space existing between the axial outer end face of the spindle and the bottom of the piston are connected not only through the screwing portion between the spindle and the nut, but also through the gap between the inner peripheral surface of the piston and the outer peripheral surface of the nut, and the above-mentioned problem of the piston being excessively displaced inward in the axial direction when the parking brake is released does not occur. The invention described in JP 2021-21423 A requires forming a hole inside the spindle, and therefore the shaft diameter of the spindle needs to be increased to ensure the strength of the spindle, which creates another problem of the entire device becoming larger.

[0021] The present invention has been made to solve the above-mentioned problems, and aims to provide a disc brake device that can prevent the piston from displacing excessively axially inward relative to the caliper body when the parking brake is released, even in an extremely low temperature environment. [Means for solving the problem]

[0022] A disc brake device according to one aspect of the present invention includes a caliper body, a pair of pads, a clamp member, a piston, a rotary-linear motion conversion mechanism, an outer seal and an inner seal, an inner internal space and an outer internal space, and a lubricating fluid. The caliper body has a cylinder axially inwardly of the rotor. The pair of pads are disposed on both axial sides of the rotor. The clamp member has a pressing portion on an axially outer portion and a clamp base portion on an axially inner portion that supports an electric drive unit, and is supported so as to straddle the pair of pads from the radial outside and be capable of axial displacement relative to the caliper body. The piston has a cylindrical portion and a bottom portion that closes the axially outer end opening of the cylindrical portion, and is configured as a bottomed cylinder, and is fitted into the axially outer portion of the cylinder to allow axial displacement. The rotary-to-linear motion conversion mechanism includes a spindle rotatably supported on the clamp base, and a cylindrical nut that threadably engages with the spindle and has an axially outer portion inserted inside the piston. The outer seal provides a seal between the piston and the nut. The inner seal provides a seal between an axially inner portion of the cylinder and a portion of the nut exposed from the piston. The inner interior space exists around an axially inner portion of the spindle. The outer internal space exists between an axially outer end face of the spindle and the bottom of the piston. The lubricating liquid is filled in each of the inner and outer internal spaces.

[0023] In one embodiment of the disc brake device of the present invention, the rotary-linear motion conversion mechanism has at least one communication portion that communicates the inner internal space with the outer internal space, and the lubricating liquid can move between the inner internal space and the outer internal space only through the threaded engagement portion between the spindle and the nut and the communication portion. The communication portion is either a nut communication hole that penetrates the nut in the axial direction, a nut communication passage formed on the inner surface of the nut, or a spindle communication passage formed on the outer surface of the spindle.

[0024] In a disc brake device according to one aspect of the present invention, the communication portion may include the nut communication passage, and the nut communication passage may be configured by a groove recessed radially outward from the inner surface of the nut and extending in the axial direction. In this case, the groove depth of the nut communication passage can be made larger than the tooth height dimension of the female thread portion provided on the inner peripheral surface of the nut. Furthermore, the nut communicating passage can be formed by forging, and the surface of the nut communicating passage can be formed from a forged surface. Furthermore, when the nut communicating passage is formed by forging, the nut communicating passage can be provided at two locations on diametrically opposite sides of the nut. Furthermore, when the nut communicating passage is formed by forging, the female thread portion provided on the inner surface of the nut and the nut communicating passage can be smoothly connected at the intersection between the female thread portion and the nut communicating passage. When the nut communicating passage is constituted by the recessed groove, the female thread portion provided on the inner peripheral surface of the nut can be formed by forging (rolling) or by cutting.

[0025] In a disc brake device according to one aspect of the present invention, the communication portion may include the spindle communication passage, and the spindle communication passage may be configured by a groove that is recessed radially inward from the outer peripheral surface of the spindle and extends in the axial direction.

[0026] In the disc brake device according to one aspect of the present invention, the spindle communication passage may be formed by a notch formed by removing a portion of the outer circumferential surface of the spindle in the circumferential direction.

[0027] The disc brake device according to one aspect of the present invention may further include a piston seal that seals between an axially outer portion of the cylinder and the piston.

[0028] In a disc brake device according to one aspect of the present invention, the cylinder can be a stepped hole having a large diameter hole portion on the axially outer side and a small diameter hole portion on the axially inner side, and a hydraulic chamber can be provided between a bottom surface of the large diameter hole portion and an axially inner end face of the cylindrical portion.

[0029] In a disc brake device according to one embodiment of the present invention, the inner diameter of the nut communicating hole, the groove width and / or groove depth of the nut communicating passage, and the groove width and / or groove depth of the spindle communicating passage can be constant in the axial direction or can vary depending on the axial position. Effect of the Invention

[0030] According to the disc brake device according to one aspect of the present invention, even in an extremely low temperature environment, when the parking brake is released, the piston can be prevented from being excessively displaced axially inward relative to the caliper body. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a front view of a disc brake device according to a first embodiment, as viewed from the outside in the axial direction. [Diagram 2] FIG. 2 is a rear view of the disc brake device according to the first embodiment, as viewed from the axially inner side. [Diagram 3] FIG. 3 is a side view of the disc brake device according to the first embodiment, as viewed from the rotation side. [Figure 4] FIG. 4 is a plan view of the disc brake device according to the first embodiment, as viewed from the radial outside. [Diagram 5] FIG. 5 is a bottom view of the disc brake device according to the first embodiment, as viewed from the radially inner side. [Figure 6]FIG. 6 is a perspective view of the disc brake device according to the first embodiment, as viewed from the radial outside and the axial outside. [Figure 7] FIG. 7 is a cross-sectional view taken along line AA in FIG. [Figure 8] FIG. 8 is a partially enlarged view of FIG. [Figure 9] FIG. 9 is a perspective view showing a nut constituting the rotary-linear motion conversion mechanism taken out from the disc brake device according to the first example of the embodiment. [Figure 10] Figure 10 shows a nut that constitutes the rotary-linear motion conversion mechanism from a disc brake device of a first example of an embodiment, where (A) is a cross-sectional view, (B) is an end view seen from the axially inner side, and (C) is an end view seen from the axially outer side. [Figure 11] FIG. 11 is a graph showing the results of an experiment conducted to confirm the effect of providing a communication portion in the rotary motion conversion mechanism according to the first embodiment. [Figure 12] FIG. 12 is a diagram showing a second example of the embodiment, and corresponds to FIG. [Figure 13] FIG. 13 is a diagram showing a second example of the embodiment, and corresponds to FIG. [Figure 14] FIG. 14 is a diagram showing a second example of the embodiment, and corresponds to FIG. [Figure 15] FIG. 15 is a diagram showing a third example of the embodiment, and corresponds to FIG. [Figure 16] FIG. 16 is a diagram showing a third example of the embodiment, and corresponds to FIG. [Figure 17] FIG. 17 is a diagram showing a fourth example of the embodiment, and corresponds to FIG. [Figure 18] FIG. 18 is a perspective view showing a spindle constituting the rotary-linear motion conversion mechanism taken out from a disc brake device according to a fourth example of the embodiment. [Figure 19]Figure 19 is a diagram showing a spindle constituting a rotary-linear motion conversion mechanism from a disc brake device according to a fourth example of an embodiment, in which (A) is a plan view seen from the radial outside, (B) is an end view seen from the axial outside, and (C) is a cross-sectional view along line BB of (A). [Figure 20] FIG. 20 is a diagram showing a fifth example of the embodiment, and corresponds to FIG. [Figure 21] FIG. 21 is a diagram showing a fifth example of the embodiment, and corresponds to FIG. [Figure 22] FIG. 22 is a cross-sectional view showing a disk brake device of a conventional structure. [Diagram 23] FIG. 23 is a cross-sectional view taken along line CC in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] [First Example of Implementation] A first example of the embodiment will be described with reference to FIGS. 1 to 11. FIG.

[0033] Throughout this specification and claims, unless otherwise specified, the terms "axial direction," "radial direction," and "circumferential direction" refer to the axial, radial, and circumferential directions of a disk-shaped rotor that rotates with the wheel. Furthermore, when the disc brake device is attached to a vehicle body, the outer side in the width direction of the vehicle body is referred to as the axial outer side, and the center side in the width direction of the vehicle body is referred to as the axial inner side. Furthermore, the center side in the circumferential direction of the disc brake device is referred to as the circumferential inner side, and both circumferential sides of the disc brake device are referred to as the circumferential outer side. Furthermore, the rotation-in side refers to the side of the circumferential outer side where the rotor enters the caliper body when the vehicle moves forward, and the rotation-out side refers to the side of the circumferential outer side where the rotor exits the caliper body when the vehicle moves forward.

[0034] The disc brake device 1 of this embodiment has a configuration in which a hydraulic disc brake device and an electric disc brake device are combined. Specifically, the disc brake device 1 has a configuration in which a hydraulic opposed piston type brake mechanism unit 2 that functions as a service brake is combined with an electric floating type brake mechanism unit 3 that functions as a parking brake.

[0035] The disc brake device 1 comprises an opposed-piston caliper body 4 fixed to a suspension device such as a knuckle, a clamp member 5 supported on the caliper body 4 so as to be able to move axially, a pair of pads 6a, 6b (inner pad 6a, outer pad 6b), and a total of four pistons 7, 8 (one dual-purpose piston 7 and three service-only pistons 8).

[0036] The disc brake device 1 obtains braking force from the service brake by supplying pressurized oil, which is the hydraulic oil, to all (four in the illustrated example) cylinders 10a, 10b, 11a, and 11b provided in the caliper body 4 that constitutes the opposed piston type brake mechanism section 2.

[0037] In contrast, the disc brake device 1 obtains the braking force from the parking brake without using hydraulic oil, by driving an electric actuator 12 that constitutes a floating type brake mechanism unit 3 and displacing a clamp member 5 in the axial direction relative to the caliper body 4.

[0038] The opposed piston type brake mechanism 2 and the floating type brake mechanism 3 share a pair of pads 6a, 6b and one dual-purpose piston 7.

[0039] [Structural explanation of opposed piston type brake mechanism part 2] The caliper body 4 constituting the opposed piston type brake mechanism 2 has a generally arched shape when viewed in the axial direction, is fixed to the vehicle body, and supports the inner pad 6a and the outer pad 6b so that they can move in the axial direction. The caliper body 4 is disposed so as to cover a portion of the circumferential direction of the rotor 9 from the radial outside, and is supported and fixed to a knuckle constituting the suspension device. The caliper body 4 in this example is a casting (including a die-cast molding) of a light alloy such as an aluminum alloy.

[0040] The caliper body 4 has an inner body 13, an outer body 14, a pair of connecting portions 15a, 15b, and an intermediate connecting portion 16.

[0041] The inner body 13 is disposed axially inside the radially outer portion of the rotor 9. The inner body 13 has two cylinders 10a, 10b that open axially outward. Specifically, the inner body 13 has a rotation-in side inner cylinder 10a on the rotation-in side (right side in Figs. 1, 4, 7, left side in Figs. 2, 5) and a rotation-out side inner cylinder 10b on the rotation-out side (left side in Figs. 1, 4, 7, right side in Figs. 2, 5). Therefore, the rotation-in side inner cylinder 10a and the rotation-out side inner cylinder 10b are disposed axially inside the rotor 9. The inner body 13 also has a pair of mounting seats 17 at both circumferentially outer ends. The caliper body 4 is fixed to the suspension device using the pair of mounting seats 17.

[0042] The outer body 14 is disposed axially outward of the radially outer portion of the rotor 9. The outer body 14 has two cylinders 11a, 11b that open axially inward. Specifically, the outer body 14 has the inlet side outer cylinder 11a at the inlet side portion and the outlet side outer cylinder 11b at the outlet side portion. Therefore, the inlet side outer cylinder 11a and the outlet side outer cylinder 11b are disposed axially outward of the rotor 9. The inlet side outer cylinder 11a and the inlet side inner cylinder 10a are disposed axially opposite each other with the rotor 9 in between, and the outlet side outer cylinder 11b and the outlet side inner cylinder 10b are disposed axially opposite each other with the rotor 9 in between.

[0043] A pair of guide walls 18a, 18b are provided on both circumferential outer portions of the axially outer surface of the inner body 13 and both circumferential outer portions of the axially inner surface of the outer body 14, and protrude in the axial direction so as to approach the rotor 9. Each of the guide walls 18a, 18b is provided with a guide groove 19 extending in the circumferential direction.

[0044] In the illustrated example, the inner body 13 and the outer body 14 are formed separately from each other and connected by a plurality of connecting bolts 30. However, the inner body and the outer body can also be formed integrally with each other.

[0045] The pair of connecting portions 15a, 15b and the intermediate connecting portion 16 are each disposed radially outside the rotor 9, and connect the inner body 13 and the outer body 14 in the axial direction. Of the pair of connecting portions 15a, 15b, one connecting portion 15a connects an end portion of the outer body 14 on the rotation side to an end portion of the inner body 13 on the rotation side in the axial direction, and the other connecting portion 15b connects an end portion of the outer body 14 on the rotation side to an end portion of the inner body 13 on the rotation side in the axial direction. The intermediate connecting portion 16 is disposed between the pair of connecting portions 15a, 15b in the circumferential direction, and connects a circumferential middle portion of the outer body 14 to a circumferential middle portion of the inner body 13 in the axial direction.

[0046] Of the two inner cylinders 10a, 10b provided in the inner body 13, a dual-purpose piston 7 used for both the service brake and the parking brake is fitted into the inlet inner cylinder 10a so as to be movable in the axial direction. A service-only piston 8 used only for the service brake is fitted into the outlet inner cylinder 10b so as to be movable in the axial direction. In contrast, a service-only piston 8 used only for the service brake is fitted into each of the two outer cylinders 11a, 11b provided in the outer body 14 so as to be movable in the axial direction.

[0047] 7 and 8, the rotation-in side inner cylinder 10a is open not only to the axially outer side surface of the inner body 13, but also to the axially inner side surface of the inner body 13. In other words, the rotation-in side inner cylinder 10a is formed so as to penetrate the inner body 13 in the axial direction.

[0048] The rotation-inlet inner cylinder 10a is a stepped hole, and has a hollow cylindrical large-diameter hole portion 20 in its axially outer half, and a hollow cylindrical small-diameter hole portion 21 in its axially inner half. A bottom surface 22 of the large-diameter hole portion 20 is provided between the large-diameter hole portion 20 and the small-diameter hole portion 21. The bottom surface 22 faces axially outward and is a circular ring-shaped flat surface perpendicular to the central axis of the rotation-inlet inner cylinder 10a.

[0049] The small diameter hole portion 21 is disposed coaxially with the large diameter hole portion 20, and is provided inside a cylindrical insertion tube 23 that protrudes axially inward from the axially inner surface of the inner body 13. The axial length of the insertion tube 23 is greater than the amount of displacement of the clamp member 5 that is displaced in the axial direction when the parking brake is activated.

[0050] The dual-purpose piston 7 corresponds to the piston described in the claims, and is made of, for example, an aluminum alloy and has a cylindrical shape with a bottom. The dual-purpose piston 7 is fitted into the large diameter hole 20 of the rotating-side inner cylinder 10a so as to be movable in the axial direction.

[0051] The dual-purpose piston 7 comprises a tubular portion 24 having a substantially cylindrical shape, and a bottom portion 25 that closes the axially outer end opening of the tubular portion 24 .

[0052] The tubular portion 24 has a non-circular hole portion 26 at the axially outer end (rear portion) of its inner circumferential surface, and a circular hole portion 27 from the axially middle portion to the axially inner end. In the illustrated example, the non-circular hole portion 26 has a substantially rectangular inner surface shape. The circular hole portion 27 has a cylindrical inner surface shape and has an inner diameter substantially the same as that of the small diameter hole portion 21 constituting the rotation-inlet inner cylinder 10a.

[0053] An axially inner end face of the cylindrical portion 24 faces axially a bottom surface 22 of the large diameter hole portion 20 constituting the inlet side inner cylinder 10a. Between the axially inner end face of the cylindrical portion 24 and the bottom surface 22 of the large diameter hole portion 20, a ring-shaped hydraulic chamber 28 for introducing pressure oil is formed.

[0054] The gap between the dual-purpose piston 7 and the large diameter hole portion 20 of the rotation-inlet inner cylinder 10a is sealed by a ring-shaped piston seal 29. The piston seal 29 is fitted in a seal groove having a rectangular cross section formed in the axial middle portion of the inner peripheral surface of the large diameter hole portion 20, and is in contact with the outer peripheral surface of the cylindrical portion 24.

[0055] A dust cover 31 is fitted between the portion of the outer peripheral surface of the dual-purpose piston 7 that is exposed axially outward from the inlet side inner cylinder 10a and the axially outer opening edge of the inlet side inner cylinder 10a.

[0056] The service piston 8 is made of, for example, an aluminum alloy and has a cylindrical shape with a bottom. A hydraulic chamber 32 for introducing pressurized oil is provided between the bottom surface of the service piston 8 and the innermost portion of each of the cylinders 10b, 11a, and 11b into which the service piston 8 is fitted. A piston seal 33 seals between the service piston 8 and each of the cylinders 10b, 11a, and 11b. A dust cover 34 is hung between the outer circumferential surface of the service piston 8 and the opening edge of each of the cylinders 10b, 11a, and 11b.

[0057] In this example, the area (pressure receiving area) of the axially inner end face of the cylindrical portion 24 constituting the dual-purpose piston 7 is equal to the area (pressure receiving area) of the bottom face of the service piston 8. Therefore, during service braking, the dual-purpose piston 7 and the service piston 8 axially opposed to the dual-purpose piston 7 (and other service pistons 8) press both axial side faces of the rotor 9 with equal force.

[0058] The inner pad 6a and the outer pad 6b are disposed on both axial sides of the rotor 9. Specifically, the inner pad 6a is disposed between the rotor 9 and the inner body 13 in the axial direction, and the outer pad 6b is disposed between the rotor 9 and the outer body 14 in the axial direction.

[0059] Each of the inner pad 6a and the outer pad 6b includes a lining (friction material) 35, a metal back plate (pressure plate) 36 that supports the back surface of the lining 35, and a shim plate 78 attached to the back surface of the back plate 36.

[0060] The back plate 36 has ears 37 at both circumferentially outer ends. The pair of ears 37 on the inner pad 6a are loosely engaged with the guide grooves 19 on the guide walls 18a, 18b of the inner body 13 via pad clips 38 so as to allow axial movement. The pair of ears 37 on the outer pad 6b are loosely engaged with the guide grooves 19 on the guide walls 18a, 18b of the outer body 14 via pad clips 38 so as to allow axial movement. As a result, the inner pad 6a and the outer pad 6b are supported relative to the caliper body 4 so as to allow axial movement but not to allow circumferential or radial movement.

[0061] [Structural explanation of floating type brake mechanism part 3] The clamp member 5 constituting the floating type brake mechanism 3 is made of an aluminum alloy or an iron alloy and has an inverted U shape. The clamp member 5 is disposed between the connecting part 15a on the rotation side and the intermediate connecting part 16 in the circumferential direction, and straddles the pair of pads 6a, 6b and the inner body 13 from the radially outer side. In other words, the clamp member 5 is supported so as to be mounted on the caliper body 4.

[0062] The clamp member 5 has a bifurcated pressing portion 39 on the axially outer side, and a clamp base portion 40 on the axially inner side. The clamp member 5 further has a bridge portion 41 that is disposed radially outside the rotor 9 and axially connects the pressing portion 39 and the clamp base portion 40.

[0063] The pressing portion 39 is inserted from the radially outer side between the axially inner surface of the outer body 14 and the axially outer surface of the outer pad 6b, straddling the rotation-in side outer cylinder 11a in the circumferential direction. For this reason, the outer body 14 has accommodation recesses 42 for inserting parts of the pressing portion 39 on both circumferential outer portions of the rotation-in side outer cylinder 11a.

[0064] The clamp base 40 is disposed axially inside the inner body 13 and supports an electric drive unit 48, which will be described later. A support hole 43 is provided inside the clamp base 40. The support hole 43 is a substantially cylindrical space and has an inner diameter slightly larger than the outer diameter of the insertion tube 23 provided in the inner body 13. The support hole 43 opens axially outward. A through hole 45 is provided in the center of a bottom plate portion 44 that constitutes the bottom of the support hole 43.

[0065] The clamp member 5 is supported so as to be displaceable in the axial direction relative to the caliper body 4. For this purpose, the insertion tube 23 provided in the inner body 13 is fitted into the support hole 43 provided in the clamp base 40 so as to allow relative displacement in the axial direction.

[0066] The gap between the support hole 43 and the insertion tube 23 is sealed by a circular annular first seal member 46. A dust cover 47 is provided between the axially outer opening edge of the support hole 43 and the axially outer portion of the outer circumferential surface of the insertion tube 23.

[0067] In this example, since the insertion tube 23 is inserted into the support hole 43, the support hole 43 and the rotation-in side inner cylinder 10a communicate with each other in the axial direction.

[0068] The electric actuator 12 that constitutes the floating type brake mechanism part 3 includes an electric drive unit (MGU) 48 arranged axially inside the clamp base 40, and a rotary-linear conversion mechanism 49 arranged in the support hole 43 and the inlet side inner cylinder 10a.

[0069] The electric drive unit 48 includes a casing 50 and an electric motor as a drive source and a reduction mechanism such as a gear-type reducer, both of which are housed inside the casing 50. An output shaft 51 to which a final gear constituting the reduction mechanism is fixed is inserted into a through hole 45 formed in the bottom plate portion 44 of the clamp base 40.

[0070] As shown in Figures 7 and 8, the rotary-to-linear motion conversion mechanism 49 is a feed screw mechanism that converts rotary motion into linear motion and changes its overall axial length when activated, and is equipped with a spindle 52 and a cylindrical nut 53.

[0071] The spindle 52 is rotatably supported by the clamp base 40 constituting the clamp member 5. Specifically, the spindle 52 is arranged coaxially with the support hole 43. An axially inner half of the spindle 52 is arranged inside the support hole 43.

[0072] The spindle 52 has a shaft portion 54, a flange portion 55, and a connection base portion 56. The shaft portion 54, the flange portion 55, and the connection base portion 56 are arranged coaxially with each other.

[0073] The shaft portion 54 is provided in a range from the axially outer end (tip portion) of the spindle 52 to the axially middle portion, and has a male thread portion 57 on its outer circumferential surface. The axially outer portion of the shaft portion 54 is inserted into the inside of the dual-purpose piston 7, and the axially inner portion of the shaft portion 54 is inserted into the inside (small diameter hole portion 21) of the insertion tube 23 inserted into the support hole 43.

[0074] The connection base 56 is provided at the axially inner end of the spindle 52, and is inserted from the axially outer side into a through hole 45 formed in the bottom plate portion 44 of the clamp base 40. The connection base 56 is connected to the tip end of the output shaft 51 so as not to rotate relative to the output shaft 51. Therefore, the spindle 52 is driven to rotate by the electric motor. The gap between the connection base 56 and the through hole 45 is sealed by a second seal member 58 having an annular shape.

[0075] The flange portion 55 has an outer diameter larger than the through hole 45 formed in the bottom plate portion 44 of the clamp base 40 and has a disk shape. The flange portion 55 is provided on the axially inner side of the spindle 52. In other words, the flange portion 55 is provided between the shaft portion 54 and the connection base portion 56 in the axial direction. A thrust bearing 59 is disposed between the axially inner side surface of the flange portion 55 and the axially outer side surface of the bottom plate portion 44. This allows the axial load acting on the spindle 52 to be supported by the bottom plate portion 44, and allows the flange portion 55 to rotate relative to the bottom plate portion 44.

[0076] The nut 53 has a hollow cylindrical shape and is screwed onto the shaft portion 54 constituting the spindle 52. For this reason, as shown in Figures 9 and 10, a female thread portion 60 that screws into a male thread portion 57 provided on the outer peripheral surface of the shaft portion 54 is provided at an axially intermediate portion (small diameter surface portion 64 described later) of the inner peripheral surface of the nut 53. The male thread portion 57 and the female thread portion 60 form a screw-engagement portion 61 (see Figure 10(C)). In this example, the female thread portion 60 is formed by forging (rolling), but it may also be formed by cutting.

[0077] The outer axial half of the nut 53 is inserted into the inside of the cylindrical portion 24 constituting the dual-purpose piston 7 so as to allow relative axial displacement but not relative rotation. The inner axial half of the nut 53 is inserted into the inside of the insertion tube 23 (small diameter hole portion 21) provided in the caliper body 4 so as to allow relative axial displacement.

[0078] The nut 53 has a non-circular cylindrical portion 62 having a non-circular outer surface shape at its axially outer end. In the illustrated example, the non-circular cylindrical portion 62 has a substantially rectangular outer surface shape. The nut 53 has a cylindrical portion 63 having a cylindrical outer surface shape in a range from the axially inner end to the axially intermediate portion. The cylindrical portion 63 has an outer diameter larger than the diameter of a circumscribed circle passing through the outer surface of the non-circular cylindrical portion 62.

[0079] The non-circular cylindrical portion 62 of the nut 53 is engaged (non-circularly fitted) with the non-circular hole portion 26 provided at the axially outer end of the cylindrical portion 24 constituting the dual-purpose piston 7 so as to allow relative displacement in the axial direction but not to rotate relatively. Therefore, the nut 53 can move in the axial direction by rotating the spindle 52. In addition, the axially outer end face of the non-circular cylindrical portion 62 can press the bottom portion 25 constituting the dual-purpose piston 7 outward in the axial direction.

[0080] The nut 53 has a small diameter surface portion 64 on which the female thread portion 60 is formed, at an axially intermediate portion of the inner circumferential surface. The nut 53 has a medium diameter surface portion 65 on the axially outer portion of the inner circumferential surface, the medium diameter surface portion 65 having an inner diameter larger than the circumscribed circle diameter of the male thread portion 57 of the spindle 52, and a large diameter surface portion 66 on the axially inner end portion of the inner circumferential surface.

[0081] 7 and 8, the gap between the dual-purpose piston 7 and the nut 53 is sealed by an outer seal 68 having an annular shape. Specifically, the outer seal 68 seals the gap between the axially inner end of the circular hole portion 27 of the dual-purpose piston 7 and the axially middle portion of the outer circumferential surface of the cylindrical portion 63 constituting the nut 53.

[0082] The gap between the small diameter hole 21 of the rotation-in side inner cylinder 10a and the portion of the nut 53 exposed axially inward from the dual-purpose piston 7 is sealed by an inner seal 69 that is disposed axially inward of the outer seal 68 and has an annular shape. Specifically, the inner seal 69 seals between the axially outer end of the small diameter hole 21 of the rotation-in side inner cylinder 10a and the axially middle part of the outer circumferential surface of the cylindrical part 63 that constitutes the nut 53. The inner seal 69 and the outer seal 68 have the same diameter.

[0083] In this example, the threaded portion 61 between the spindle 52 and nut 53 that constitute the rotary-linear motion conversion mechanism 49, the engagement portion 70 between the non-circular hole portion 26 of the dual-purpose piston 7 and the non-circular cylindrical portion 62 of the nut 53, and the rolling contact portion of the thrust bearing 59 are lubricated with a lubricating liquid 71 such as brake fluid.

[0084] For this reason, in this example, lubricating liquid 71 is filled in an inner internal space 72 that exists around the flange portion 55 provided on the axially inner portion of the spindle 52 and is formed by the support hole 43 of the clamp base 40, and an outer internal space 73 that exists between the axially outer end face of the spindle 52 and the bottom 25 of the dual-purpose piston 7.

[0085] The lubricating liquid 71 filled in the inner internal space 72 lubricates the rolling contact parts of the thrust bearing 59. The first seal member 46 and the second seal member 58 prevent the lubricating liquid 71 filled in the inner internal space 72 from leaking out to the outside, and the inner seal 69 prevents the lubricating liquid 71 from communicating with the hydraulic chamber 28.

[0086] The lubricating liquid 71 filled in the outer internal space 73 lubricates the engagement portion 70 between the dual-purpose piston 7 and the nut 53. The lubricating liquid 71 filled in the outer internal space 73 is prevented from communicating with the hydraulic chamber 28 by the outer seal 68.

[0087] The inner internal space 72 and the outer internal space 73 communicate with each other through a screw thread portion 61 between the male thread portion 57 of the spindle 52 and the female thread portion 60 of the nut 53. Specifically, the communication occurs through a minute gap that exists in the screw thread portion 61. Therefore, the screw thread portion 61 is lubricated by the lubricating liquid 71. Furthermore, the lubricating liquid 71 can move between the inner internal space 72 and the outer internal space 73 through the screw thread portion 61.

[0088] In the disc brake device 1 of this example, the lubricating liquid 71 can move between the inner internal space 72 and the outer internal space 73 not only through the screwing portion 61 but also through the communicating portion 74 provided in the rotary-linear motion conversion mechanism 49. In other words, the lubricating liquid 71 can move between the inner internal space 72 and the outer internal space 73 only through the screwing portion 61 and the communicating portion 74. In this example, since the cross-sectional area of ​​the communicating portion 74 is sufficiently larger than the cross-sectional area of ​​the gap present in the screwing portion 61, most of the lubricating liquid 71 moves between the inner internal space 72 and the outer internal space 73 through the communicating portion 74.

[0089] 9 and 10, a nut communication passage 75 that functions as the communication part 74 is provided on the inner peripheral surface of the nut 53 that constitutes the rotary-to-linear motion conversion mechanism 49. In this example, the communication part 74 is constituted by the nut communication passage 75 alone.

[0090] A plurality of nut communicating passages 75 are provided on the inner peripheral surface of the nut 53. In this example, the nut communicating passages 75 are provided at two positions on diametrically opposite sides of the nut 53. Only one nut communicating passage may be provided on the inner peripheral surface of the nut, or three or more nut communicating passages may be provided. When a plurality of nut communicating passages are provided, the plurality of nut communicating passages may be disposed at equal intervals in the circumferential direction. There is no particular limit to the position at which the nut communicating passages 75 are formed. For example, the nut communicating passages 75 may be formed in a portion of the nut 53 that is located on the vertically lower side (not in a portion that is located on the vertically upper side) with the caliper body 4 fixed to the suspension device.

[0091] The nut communicating passage 75 is formed by a groove that is recessed radially outward from the inner circumferential surface of the nut 53 and extends linearly in the axial direction. However, the nut communicating passage may also be provided in a curved (spiral) shape.

[0092] In this example, the nut communicating passages 75 are formed in the small diameter surface portion 64 of the inner circumferential surface of the nut 53. Therefore, the nut communicating passages 75 axially cross the female threaded portion 60 formed in the small diameter surface portion 64, and open to both end faces in the axial direction of the female threaded portion 60. Furthermore, the nut communicating passages 75 and the portion of the female threaded portion 60 that screws into the male threaded portion 57 are alternately arranged in the circumferential direction of the nut 53.

[0093] The nut communicating passage 75 in this example is formed by forging. Therefore, the surface of the nut communicating passage 75 is composed of a forged surface (forged skin). The nut communicating passage 75 has a substantially semicircular opening shape when viewed in the axial direction, and has an inner surface (surface) in the shape of a concave cylindrical surface. In addition, at the intersection between the nut communicating passage 75 and the female thread portion 60, the nut communicating passage 75 and the female thread portion 60 are smoothly connected. That is, in this example, the nut communicating passage 75 is formed by forging, and then the female thread portion 60 is formed by forging (rolling), so that there is no corner (ridge) at the intersection between the nut communicating passage 75 and the female thread portion 60, and the nut communicating passage 75 and the female thread portion 60 are smoothly connected with a rounded shape.

[0094] In the illustrated example, the groove depth (radial dimension) of the nut communicating passage 75 is slightly smaller than the tooth height dimension of the female thread portion 60. However, the groove depth of the nut communicating passage may be larger than the tooth height dimension of the female thread portion, or may be the same as the tooth height dimension of the female thread portion. From the viewpoint of increasing the amount of lubricating liquid 71 passing through the nut communicating passage 75, it is more advantageous to increase the groove depth rather than the groove width (circumferential dimension) because this can efficiently increase the fluidity of the lubricating liquid 71.

[0095] [Operation of disc brake device 1] When the service brake is operated by the disc brake device 1 of this embodiment, pressure oil is sent to the hydraulic chambers 28, 32 of all the cylinders 10a, 10b, 11a, 11b provided in the caliper body 4 through the oil passages. This pushes all the pistons 7, 8 (one dual-purpose piston 7 and three service-only pistons 8) out of the cylinders 10a, 10b, 11a, 11b, respectively, and presses the pair of pads 6a, 6b against both axial sides of the rotor 9. As a result, the rotor 9 is pressed strongly from both axial sides to apply braking. In this way, the disc brake device 1 obtains the braking force of the service brake by pushing out all the pistons 7, 8 through the introduction of hydraulic oil.

[0096] On the other hand, when the parking brake is operated by the disc brake device 1, the electric motor constituting the electric drive device 48 is energized to rotate the spindle 52 constituting the rotary-linear conversion mechanism 49. This displaces the nut 53 axially outward relative to the inner body 13. Then, the tip of the nut 53 is pressed against the bottom 25 of the dual-purpose piston 7, and the dual-purpose piston 7 is extended toward the rotor 9, thereby pressing the inner pad 6a against the axially inner surface of the rotor 9. In addition, the reaction force caused by this pressing is transmitted from the spindle 52 to the clamp member 5 via the thrust bearing 59. This displaces the spindle 52 and the clamp member 5 axially inward relative to the caliper body 4. At this time, the insertion tube 23 and the support hole 43 slide in the axial direction. Then, the pressing portion 39 of the clamp member 5 presses the outer pad 6b against the axially outer surface of the rotor 9. As a result, the rotor 9 is strongly pressed from both axial sides, thereby performing braking. In this way, the disc brake device 1 obtains the braking force by the parking brake by pushing out the dual-purpose piston 7 using the electric actuator 12 and displacing the clamp member 5 inward in the axial direction relative to the caliper body 4.

[0097] To release the parking brake, the spindle 52 is rotated by the electric motor constituting the electric drive device 48 in the opposite direction to that during braking. This displaces the nut 53 axially inward relative to the inner body 13. Also, by displacing the spindle 52 axially outward relative to the inner body 13, the clamp member 5 is displaced axially outward relative to the inner body 13. At this time, the insertion tube 23 and the support hole 43 slide in the axial direction.

[0098] Furthermore, when the nut 53 is displaced inward in the axial direction, the piston seal 29 elastically restores its original shape, displacing the dual-purpose piston 7 inward in the axial direction, that is, toward the side opposite the rotor 9 .

[0099] According to the disc brake device 1 of this embodiment as described above, even in an extremely low temperature environment, it is possible to prevent the dual-purpose piston 7 from being excessively displaced axially inwardly with respect to the caliper body 4 when the parking brake is released.

[0100] That is, in the disc brake device 1 of this embodiment, the rotary-linear motion conversion mechanism 49 is provided with a communication part 74 that communicates the inner internal space 72 and the outer internal space 73. Therefore, the lubricating liquid 71 can be moved between the inner internal space 72 and the outer internal space 73 not only through the screw part 61 but also through the communication part 74. Therefore, even if the viscosity of the lubricating liquid 71 increases by using the disc brake device 1 in an extremely low temperature environment, the lubricating liquid 71 can be quickly moved from the inner internal space 72 to the outer internal space 73 through the communication part 74 when the parking brake is released. This makes it possible to suppress the generation of negative pressure in the outer internal space 73, and to suppress the dual-purpose piston 7 from moving axially inward together with the nut 53. As a result, according to the disc brake device 1 of this embodiment, even if the viscosity of the lubricating liquid 71 increases in an extremely low temperature environment, it is possible to suppress the dual-purpose piston 7 from being displaced excessively axially inward. And, it is possible to prevent an increase in the amount of pressure oil required for braking by the service brake.

[0101] In this example, the communication portion 74 is configured by a nut communication passage 75 formed on the inner peripheral surface of the nut 53. Therefore, the temperature of the lubricating liquid 71 present in the nut communication passage 75 can be efficiently increased by the sliding friction generated between the male thread portion 57 and the female thread portion 60. This can reduce the viscosity of the lubricating liquid 71, so that the lubricating liquid 71 can be quickly moved from the inner internal space 72 to the outer internal space 73.

[0102] In addition, in this example, since the communication portion 74 is configured by the nut communication passage 75 formed on the inner circumferential surface of the nut 53, the degree of reduction in strength of the nut 53 due to the provision of the communication portion 74 can be suppressed. Therefore, since the outer diameter of the nut 53 does not need to be made larger than necessary, the size of the rotary-to-linear motion conversion mechanism 49 can be suppressed. Note that, as in the invention described in JP 2021-21423 A described above, when a hole is formed inside the spindle, it is necessary to increase the outer diameter of the spindle in order to ensure the rigidity of the spindle, which makes the rotary-to-linear motion conversion mechanism larger. However, in this example, the size of the rotary-to-linear motion conversion mechanism 49 can be suppressed.

[0103] Furthermore, in this example, since the nut communicating passage 75 is formed by forging, the nut communicating passage 75 and the female thread portion 60 can be smoothly connected at the intersection of the nut communicating passage 75 and the female thread portion 60. Therefore, when the spindle 52 is rotated relative to the nut 53, the male thread portion 57 and the intersection (connection portion) of the female thread portion 60 and the nut communicating passage 75 rub against each other, and the generation of wear powder can be suppressed.

[0104] Furthermore, since the nut communicating passages 75 are disposed at two positions on diametrically opposite sides of the nut 53, the two nut communicating passages 75 are simultaneously formed by forging, thereby making it possible to balance the forces applied to the nut 53. Furthermore, since the nut communicating passages 75 are formed by forging, it is possible to prevent burrs from being generated in the nut communicating passages 75, and also to prevent the generation of cutting chips.

[0105] In order to confirm how the amount of axial inward displacement of the dual-purpose piston changes depending on the presence or absence of a nut communication passage, a disc brake device of this example having one nut communication passage (groove depth 4 mm (depth from the thread), groove width 2 mm) on the inner peripheral surface of the nut and a disc brake device having the same configuration as the disc brake device of this example except that the nut communication passage is not provided were prepared, and an experiment (simulation) was performed in an extremely low temperature environment of -40°C. In the experiment, a common lubricant (product name: BASF DOT 4 type) was used, and the return amount (about 1 mm) and return speed (maximum speed expected in the usage environment) of the nut when releasing the parking brake were each constant. As shown in Figure 11, it was confirmed that when a nut communication passage (communication part) was provided in the nut, the amount of axial inward displacement of the dual-purpose piston could be suppressed to about 1 / 10 compared to when the nut communication passage was not provided.

[0106] [Second Example of the Implementation Form] The second embodiment will be described with reference to FIGS.

[0107] In this example, only the structure of a nut communicating passage 75a provided on the inner circumferential surface of a nut 53 is different from that of the first example of the embodiment.

[0108] In this example, the nut communicating passage 75a is also configured as a groove that is recessed radially outward from the inner peripheral surface of the nut 53 and extends linearly in the axial direction. In this example, the nut communicating passage 75a is formed over the entire axial length of the inner peripheral surface of the nut 53. Therefore, the nut communicating passage 75a axially crosses the female thread portion 60 formed in the small diameter surface portion 64. The nut communicating passage 75a also opens to both end faces of the nut 53 in the axial direction. The groove depth of the nut communicating passage 75a is greater than the tooth height dimension of the female thread portion 60.

[0109] The nut communication passage 75a of this example is not formed by forging as in the first example of the embodiment, but is formed by cutting. Therefore, the surface of the nut communication passage 75a is composed of a cutting surface (machined surface). The nut communication passage 75a has a substantially rectangular opening shape when viewed in the axial direction. The nut communication passage 75a is provided at only one location in the circumferential direction on the inner peripheral surface of the nut 53.

[0110] In the case of this example as described above, the lubricating liquid 71 can be moved between the inner internal space 72 and the outer internal space 73 not only through the screw portion 61 but also through the nut communicating passage 75a. Therefore, even if the viscosity of the lubricating liquid 71 increases in an extremely low temperature environment, the lubricating liquid 71 can be quickly moved from the inner internal space 72 to the outer internal space 73 through the nut communicating passage 75a (communicating portion 74) when the parking brake is released.

[0111] In addition, in this example, since the nut communicating passage 75a is formed by cutting, the nut communicating passage 75a can be easily provided in an existing nut 53. Furthermore, the groove depth and groove width of the nut communicating passage 75a can be easily changed according to the operating temperature of the disc brake device 1 and the type of lubricating fluid 71. The other configurations and effects are the same as those of the first embodiment.

[0112] [Third Example of the Implementation Form] The third embodiment will be described with reference to FIGS.

[0113] In this example, only the structure of a communication portion 74a provided in a nut 53 is different from that of the first and second examples of the embodiment.

[0114] In this example, a nut communication hole 76 that functions as the communication portion 74a is provided in the nut 53. In this example, the communication portion 74a is formed only by the nut communication hole 76.

[0115] The nut communicating hole 76 is a through hole that axially passes through a radially intermediate portion of the nut 53. In this example, the nut communicating hole 76 is provided at only one location in the circumferential direction of the nut 53. However, a plurality of nut communicating holes may be provided in the nut.

[0116] The nut communicating hole 76 has a circular cross-sectional shape and a constant inner diameter along the axial direction. The nut communicating hole 76 opens to an end face on the inner side in the axial direction of the nut 53 and also opens to an end face on the outer side in the axial direction of the nut 53. The inner diameter of the nut communicating passage can be made to vary depending on the axial position of the nut.

[0117] In the case of this example as described above, the lubricating liquid 71 can be moved between the inner internal space 72 and the outer internal space 73 not only through the screw portion 61 but also through the nut communicating hole 76. Therefore, even if the viscosity of the lubricating liquid 71 increases in an extremely low temperature environment, the lubricating liquid 71 can be quickly moved from the inner internal space 72 to the outer internal space 73 through the nut communicating hole 76 (communicating portion 74a) when the parking brake is released.

[0118] In addition, in this example, since the communicating portion 74a is configured from the nut communicating hole 76 that penetrates the nut 53 in the axial direction, the nut communicating hole 76 can be easily provided in an existing nut 53. Also, the inner diameter and number of the nut communicating holes 76 can be easily changed depending on the operating temperature of the disc brake device 1 and the type of lubricating fluid 71. The other configurations and effects are the same as those of the first embodiment.

[0119] [Fourth Example of the Implementation Form] The fourth embodiment will be described with reference to FIGS.

[0120] In this example, a spindle communication passage 77 that functions as the communication portion 74b is provided in the spindle 52 that constitutes the rotary-to-linear motion conversion mechanism 49. In this example, the communication portion 74b is constituted only by the spindle communication passage 77.

[0121] The spindle communicating passage 77 is provided on the outer circumferential surface of the shaft portion 54 that constitutes the spindle 52. In this example, the spindle communicating passage 77 is provided at one location in the circumferential direction on the outer circumferential surface of the shaft portion 54. In other words, the spindle 52 has one spindle communicating passage 77. However, a plurality of spindle communicating passages may be provided on the outer circumferential surface of the shaft portion that constitutes the spindle.

[0122] The spindle communication passage 77 is formed by a groove that is recessed radially inward from the outer circumferential surface of the shaft portion 54 and extends linearly in the axial direction. However, the spindle communication passage may also be provided in a curved (spiral) shape.

[0123] In this example, the spindle communication passage 77 is formed over the entire axial length of the outer circumferential surface of the shaft portion 54. Therefore, the spindle communication passage 77 axially crosses the male thread portion 57 formed on the outer axial surface of the shaft portion 54. The spindle communication passage 77 also opens to the end face of the shaft portion 54 on the outer side in the axial direction.

[0124] The spindle communicating passage 77 is formed by cutting. Therefore, the surface of the spindle communicating passage 77 is composed of a cut surface (cutting surface). Moreover, the spindle communicating passage 77 has a substantially rectangular opening shape when viewed in the axial direction.

[0125] In the illustrated example, the groove depth of the spindle communicating passage 77 is greater than the tooth height dimension of the male thread portion 57. However, the groove depth of the spindle communicating passage may be less than the tooth height dimension of the male thread portion, or may be the same as the tooth height dimension of the female thread portion.

[0126] In the case of this example as described above, the lubricating liquid 71 can be moved between the inner internal space 72 and the outer internal space 73 not only through the screw portion 61 but also through the spindle communication passage 77. Therefore, even if the viscosity of the lubricating liquid 71 increases in an extremely low temperature environment, the lubricating liquid 71 can be quickly moved from the inner internal space 72 to the outer internal space 73 through the spindle communication passage 77 (communication portion 74b) when the parking brake is released.

[0127] In addition, in this example, since the communication portion 74b is configured from the spindle communication passage 77 formed on the outer peripheral surface of the shaft portion 54 that constitutes the spindle 52, the spindle communication passage 77 can be easily provided in the existing spindle 52. In addition, the groove depth and groove width of the spindle communication passage 77 can also be easily changed depending on the operating temperature of the disc brake device 1 and the type of lubricating fluid 71.

[0128] Moreover, the communication portion 74b is configured by a spindle communication passage 77 formed on the outer circumferential surface of the spindle 52. Therefore, the temperature of the lubricating liquid 71 present in the spindle communication passage 77 can be efficiently increased by the sliding friction generated between the male thread portion 57 and the female thread portion 60. This can reduce the viscosity of the lubricating liquid 71, so that the lubricating liquid 71 can be quickly moved from the inner internal space 72 to the outer internal space 73. The other configurations and effects are the same as those of the first embodiment.

[0129] [Fifth Example of the Implementation Form] The fifth embodiment will be described with reference to FIGS.

[0130] In this example, only the structure of a spindle communication passage 77a provided in the shaft portion 54 of the spindle 52 differs from that of the fourth example of the embodiment.

[0131] The spindle communicating passage 77a in this example is not a groove recessed radially inward from the outer circumferential surface of the shaft portion 54, but is formed by a notch formed by removing a portion of the outer circumferential surface of the shaft portion 54 in the circumferential direction.

[0132] In this example, the spindle communication passage 77a is provided at only one location in the circumferential direction on the outer circumferential surface of the shaft portion 54. However, it is also possible to provide a plurality of spindle communication passages in the spindle.

[0133] The spindle communication passage 77a has a generally arch-shaped cross section and is formed over the entire axial length of the outer circumferential surface of the shaft portion 54. Therefore, the spindle communication passage 77a opens to the end face of the shaft portion 54 on the outer side in the axial direction.

[0134] In the illustrated example, the groove depth (maximum groove depth) of the spindle communicating passage 77a is slightly smaller than the tooth height dimension of the male thread portion 57. However, the groove depth of the spindle communicating passage may be larger than the tooth height dimension of the male thread portion, or may be the same as the tooth height dimension of the female thread portion.

[0135] In the case of this example as described above, the lubricating liquid 71 can be moved between the inner internal space 72 and the outer internal space 73 not only through the screw portion 61 but also through the spindle communication passage 77a. Therefore, even if the viscosity of the lubricating liquid 71 increases in an extremely low temperature environment, the lubricating liquid 71 can be quickly moved from the inner internal space 72 to the outer internal space 73 through the spindle communication passage 77a (communication portion 74b) when the parking brake is released.

[0136] In this embodiment, since the communication portion 74b is formed from the spindle communication passage 77a formed by a cutout, the workability of machining the spindle communication passage 77a can be improved. Also, since it is easy to ensure a large cross-sectional area of ​​the spindle communication passage 77a, the amount of lubricating liquid 71 moving through the spindle communication passage 77a can be increased. The other configurations and effects are the same as those of the first embodiment.

[0137] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. Furthermore, the structures of the examples of the embodiment can be combined as appropriate.

[0138] Specifically, when carrying out the present invention, a nut communication passage, a nut communication hole, a groove-shaped spindle communication passage, and a notch-shaped spindle communication passage, which function as communication parts, can be appropriately combined and provided in one rotary-to-linear motion conversion mechanism. For example, a nut communication passage can be formed on the inner peripheral surface of the nut, and a groove-shaped spindle communication passage can be formed on the outer peripheral surface of the spindle. [Explanation of symbols]

[0139] 1 Disc brake device 2 Opposed piston type brake mechanism 3. Floating type brake mechanism 4 Caliper body 5 Clamping member 6a Inner Pad 6b Outer pad 7 Dual-purpose piston 8 Service-only piston 9 Rotor 10a Inner cylinder on the rotating side 10b Outlet side inner cylinder 11a Rotating outer cylinder 11b Outer cylinder 12 Actuator 13 Inner Body 14 Outer Body 15a, 15b connection part 16 Intermediate connection 17 Mounting seat 18a, 18b Guide wall 19 Guide groove 20 Large diameter hole 21 Small diameter hole 22 Bottom 23 Insertion tube 24 Cylinder part 25 Bottom 26 Non-circular hole 27 Circular hole 28 Hydraulic chamber 29 Piston seal 30 Connecting bolt 31 Dust cover 32 Hydraulic chamber 33 Piston seal 34 Dust cover 35 Lining 36 Back plate 37 Ears 38 Pad Clip 39 Pressing section 40 Clamp base 41 Bridge section 42 Recessed portion 43 Support hole 44 Bottom plate part 45 Through hole 46 First seal member 47 Dust cover 48 Electric Drive Unit 49 Rotational-linear conversion mechanism 50 Casing 51 Output shaft 52 Spindle 53 Nut 54 Shaft 55 Flange part 56 Connection base 57 Male thread 58 Second seal member 59 Thrust bearing 60 Female thread 61 Threaded joint 62 Non-circular cylindrical section 63 Cylindrical section 64 Small diameter surface section 65 Medium diameter surface section 66 Large diameter surface section 68 Outer seal 69 Inner seal 70 Engagement part 71 Lubricants 72 Inner interior space 73 Outside interior space 74, 74a, 74b communication part 75, 75a Nut connecting passage 76 Nut connecting hole 77, 77a Spindle connecting passage 78 Shim plate 100 Disc brake device 101 Opposed piston type brake mechanism 102 Floating type brake mechanism 103 Caliper body 104 Clamping member 105a Inner Pad 105b Outer pad 106 Dual-purpose piston 107 Service dedicated piston 108a, 108b Inner cylinder 109a, 109b Outer cylinder 110 Rotary-linear conversion mechanism 111 Spindle 112 Nut 113 Bottom 114 Pressing part 115 Piston seal 116 Inner interior space 117 Outside interior space 118 Lubricating Fluid 119 Outer seal 120 Inner seal 121 Threaded part

Claims

1. a caliper body having a cylinder axially inwardly of the rotor; A pair of pads arranged on both axial sides of the rotor; a clamp member having a pressing portion on an axially outer side and a clamp base portion for supporting an electric drive device on an axially inner side, the clamp member being supported so as to straddle the pair of pads from the radially outer side and be capable of being displaced in the axial direction with respect to the caliper body; a cylindrical piston having a bottom and a bottom portion closing an axially outer end opening of the cylindrical portion, the piston being fitted in the axially outer portion of the cylinder so as to be displaceable in the axial direction; a rotary-to-linear motion conversion mechanism including a spindle rotatably supported on the clamp base and a cylindrical nut screwed with the spindle and having an axially outer portion inserted inside the piston; an outer seal that seals between the piston and the nut, and an inner seal that seals between an axially inner portion of the cylinder and a portion of the nut that is exposed from the piston; an inner internal space existing around an axially inner portion of the spindle, and an outer internal space existing between an axially outer end face of the spindle and the bottom of the piston; a lubricating liquid filled in each of the inner and outer internal spaces, the rotary-to-linear motion conversion mechanism has at least one communication part that communicates the inner internal space and the outer internal space, and the lubricating liquid can move between the inner internal space and the outer internal space only through a screw-threaded portion between the spindle and the nut and the communication part; The communication portion is any one of a nut communication hole penetrating the nut in the axial direction, a nut communication passage formed on the inner peripheral surface of the nut, and a spindle communication passage formed on the outer peripheral surface of the spindle. Disc brake device.

2. The communication portion includes the nut communication passage, The nut communication passage is formed by a groove recessed radially outward from the inner circumferential surface of the nut and extending in the axial direction.

2. A disc brake device according to claim 1.

3. 3. The disc brake device according to claim 2, wherein a groove depth of the nut communication passage is greater than a tooth height dimension of a female thread portion provided on an inner peripheral surface of the nut.

4. 3. The disc brake device according to claim 2, wherein a surface of the nut communication passage is a forged surface.

5. 5. The disc brake device according to claim 4, wherein the nut communication passages are provided at two positions on diametrically opposite sides of the nut.

6. 5. The disc brake device according to claim 4, wherein the female thread portion provided on the inner peripheral surface of the nut and the nut communicating passage are smoothly connected to each other at an intersection between the female thread portion and the nut communicating passage.

7. the communication portion includes the spindle communication passage, The spindle communication passage is formed by a groove recessed radially inward from the outer circumferential surface of the spindle and extending in the axial direction.

2. A disc brake device according to claim 1.

8. 2. The disk brake device according to claim 1, wherein the spindle communication passage is formed by a cutout formed by removing a portion of the outer circumferential surface of the spindle in the circumferential direction.

9. 2. The disc brake device according to claim 1, further comprising a piston seal for sealing between an axially outer portion of the cylinder and the piston.

10. the cylinder is a stepped hole having a large diameter hole portion on an axially outer side and a small diameter hole portion on an axially inner side, a hydraulic chamber is provided between a bottom surface of the large diameter hole portion and an axially inner end surface of the cylindrical portion of the piston.

2. A disc brake device according to claim 1.

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