Disc brake device

Abstract

To facilitate air bleeding of a hydraulic circuit in a disc brake device in which a ball screw is disposed in a cylinder.SOLUTION: A disc brake device includes: a piston which presses a brake pad to a rotor; a caliper body having a cylinder in which the piston slides; and a ball screw which is disposed in the cylinder filled with brake fluid and may presses the piston. The ball screw includes: a cylindrical body in which a spiral screw groove is formed in a first area of an inner peripheral surface; a screw shaft which is inserted into the cylindrical body through balls and in which a spiral screw groove corresponding to the screw groove of the cylindrical body is formed on an outer peripheral surface; and a first air bleeding path which is formed in a penetrating manner at the first area provided with the screw groove of the cylindrical body so as to allow communication between the inner peripheral surface and an outer peripheral surface of the cylindrical body.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] In recent years, automobile braking devices have been proposed that use an electric parking brake mechanism, such as that disclosed in Patent Document 1. In addition, actuators used in electric parking brake mechanisms include those that use a linear ball screw, such as those disclosed in Patent Documents 2 and 3. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-19473 A [Patent Document 2] JP 2008-169983 A [Patent Document 3] JP 2011-190926 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of a disk brake device that uses hydraulic pressure to operate a piston, it is necessary to properly bleed the air from the hydraulic circuit in order to exert braking force. However, when the ball screw of the parking brake mechanism is arranged inside the cylinder of the hydraulic circuit, air tends to remain in the ball screw, making it difficult to bleed the air from the hydraulic circuit.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to facilitate bleeding of air from a hydraulic circuit in a disc brake device in which a ball screw is disposed inside a cylinder. [Means for solving the problem]

[0006] In order to solve the above problem, in the present invention, an air bleed path that connects the inner and outer surfaces of the cylindrical body that forms the ball screw is provided in the area where the screw groove is formed.

[0007] In detail, the present invention is a disc brake device comprising: a piston that presses a brake pad against a rotor; a caliper body having a cylinder in which the piston slides; and a ball screw arranged in the cylinder filled with brake fluid and capable of pressing the piston, wherein the ball screw has a cylindrical body having a helical thread groove formed in a first region of its inner surface, a screw shaft that is inserted into the cylindrical body via a plurality of balls and has a helical thread groove formed on its outer surface that corresponds to the thread groove of the cylindrical body, and a first air bleed path formed through the cylindrical body in the first region where the thread groove of the cylindrical body is formed so as to communicate between the inner and outer surfaces of the cylindrical body.

[0008] Here, the cylindrical body is a hollow member that is open at both ends in the axial direction, and the first region is a portion of the cylindrical body in which a screw groove is formed for screwing onto the screw shaft via a ball.

[0009] In such a disc brake device, when the cylinder is filled with brake fluid, the air near the ball moves to the outside of the cylindrical body through the air bleeding path, and therefore, with such a disc brake device, it is possible to minimize the possibility that air will remain inside the cylindrical body, particularly near the first region.

[0010] The cylindrical body may have a ball return path connecting both ends of the predetermined section of the thread groove in the first region, and the predetermined section of the thread groove in the first region and the ball return path may form a ball circulation path. With such a disc brake device, it is possible to continuously move the cylindrical body with the screw shaft.

[0011] The cylindrical body may have a second air bleed path formed through the cylindrical body so as to communicate between the inner circumferential surface and the outer circumferential surface in a second region other than the first region in which the thread groove is formed. With such a disc brake device, it is possible to minimize the possibility of air remaining inside the cylindrical body, particularly near the second region.

[0012] In addition, the cylindrical body may have ball return paths at multiple locations, thereby forming ball circulation paths at multiple locations, and the ball screw may have a first air bleed path at an adjacent location among the multiple ball circulation paths. With such a disc brake device, it is possible to minimize the possibility of air remaining inside the cylindrical body, particularly near the first region.

[0013] The ball screw may have a first air bleed path in a portion of the ball return path in the first region where the thread groove of the cylindrical body is formed. With such a disc brake device, it is possible to minimize the possibility of air remaining inside the cylindrical body, particularly near the first region. Effect of the Invention

[0014] With the above-described disc brake device, air can be easily bled from the hydraulic circuit. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is an overall configuration diagram of a disc brake device. [Diagram 2] FIG. 2 is the first diagram showing in detail the structure inside the cylinder. [Diagram 3] FIG. 3 is a second diagram showing the internal structure of the cylinder in detail. [Figure 4] FIG. 4 is an external perspective view of the nut. [Diagram 5] FIG. 5 shows the circulation path of the balls inside the nut. [Figure 6]FIG. 6 is a diagram showing a deflector used in a disc brake device according to a modified example. [Figure 7] FIG. 7 shows the circulation paths of balls within a nut of a disk brake device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described. The embodiment described below is one aspect of the present invention, and does not limit the technical scope of the present invention. Each embodiment and modified example described below is suitable for automobiles, for example, but may be applied to other vehicles.

[0017] Fig. 1 is an overall configuration diagram of a disc brake device 1. The disc brake device 1 is a device that brakes a vehicle by clamping a brake rotor fixed to an axle with brake pads. The disc brake device 1 has a function of a service brake used to brake a moving vehicle and a function of a parking brake used to brake a parked vehicle.

[0018] In this embodiment, a floating type disc brake device 1 is illustrated, but the disc brake device disclosed in this application is not limited to this. The disc brake device disclosed in this application may be a disc brake device other than a floating type. Furthermore, with regard to the disc brake device 1, 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.

[0019] The disc brake device 1 includes a brake device main body 2. The brake device main body 2 is a core part of the disc brake device 1, and includes a caliper body 21, a support 22, brake pads 23, 24, pad clips 25, 26 for fastening the brake pads 23, 24 to the support 22, and a piston 2F for pressing the brake pad 24. The piston 2F disposed in the cylinder 2G of the caliper body 21 presses the brake pad 24 axially outward. Then, as a reaction to this pressing force, the caliper body 21 is displaced based on the sliding between both guide pins and the guide hole of the support 22, and the claws of the caliper body 21 press the brake pad 23 on the outer side (axially outer side) axially inward. As a result, the rotor is tightly clamped from both inner and outer side surfaces by both brake pads 23, 24, and braking is performed.

[0020] 1, only one piston 2F is illustrated, but the disc brake device 1 is a two-pod disc brake device having two pistons 2F. However, the disc brake device disclosed in the present application may be a one-pod disc brake device, or a three or more-pod disc brake device.

[0021] The disc brake device 1 has both a service brake function and a parking brake function, and therefore has two types of means for operating the piston 2F. That is, the disc brake device 1 is provided with a hydraulic circuit for moving the piston 2F with the hydraulic pressure of the brake fluid, and an electric motor unit 3 for moving the piston 2F with the force of an electric motor. The hydraulic circuit is responsible for the service brake function. On the other hand, the electric motor unit 3 is responsible for the parking brake function.

[0022] The hydraulic circuit provided in the disc brake device 1 for hydraulically moving the piston 2F is mainly formed by a cylinder 2G communicating with a brake hose connected to the caliper body 21, and a piston 2F disposed in the cylinder 2G. When hydraulic pressure is applied from a master cylinder to the inside of the cylinder 2G through a brake hose connected to the caliper body 21, a pressing force is applied to the piston 2F toward the outside in the axial direction. This causes the brake pad 24 to be pressed by the piston 2F.

[0023] 1 shows a state in which the nut 2N (an example of the "cylindrical body" referred to in the present application) is fitted into the piston 2F, but the piston 2F is able to slide relative to the nut 2N in the pressing direction. The nut 2N is also provided with slits and the like for passing brake fluid. Therefore, when hydraulic pressure is applied from the master cylinder to the inside of the cylinder 2G through a brake hose connected to the caliper body 21, the piston 2F can move axially outward from the cylinder 2G.

[0024] In addition, a boot 27 is provided at the opening of the cylinder 2G where the piston 2F is exposed to prevent foreign matter from entering the gap between the piston 2F and the cylinder 2G. In addition, a seal 29 is provided on the inner circumferential surface near the opening of the cylinder 2G to prevent brake fluid from leaking from the gap between the cylinder 2G and the nut 2N.

[0025] The components of the hydraulic circuit for moving the piston 2F with the hydraulic pressure of the brake fluid have been described above. Next, components for moving the piston 2F with an electric motor will be described.

[0026] In addition to the electric motor unit 3, the components for moving the piston 2F with an electric motor include a nut 2N and a spindle 2A (an example of a "screw shaft" as used in this application), but we will first explain the electric motor unit 3.

[0027] The electric motor unit 3 has a motor housing 31 that houses a drive mechanism such as a motor and gears. The motor housing 31 is fixed to the caliper body 21 by a set screw 32. A boss 34, a gear 35, and other parts such as gears (not shown) are arranged in an internal space 33 of the motor housing 31. The motor of the electric motor unit 3 is controlled by an ECU (Electronic Control Unit) of the vehicle. The ECU of the vehicle controls the operation of the parking brake. The motor of the electric motor unit 3 is operated in response to a switch operation, a shift lever operation, or in conjunction with an auto brake hold function for maintaining the brake state even when the driver releases his / her foot from the brake pedal. When the motor of the electric motor unit 3 is operated, the boss 34 rotates via gears such as the gear 35. Then, the spindle 2A, which is fitted to the boss 34 at the spline shaft 2L, rotates.

[0028] The spindle 2A is a rotating part having a helical ball screw groove 2B on its outer circumferential surface. The spindle 2A is rotatably screwed through balls 2D to a nut 2N, which is a cylindrical part having a helical ball screw groove 2M formed in a predetermined region (an example of the "first region" in the present application) on its inner circumferential surface. Therefore, when the spindle 2A is rotated by the electric motor unit 3, the nut 2N screwed through the balls 2D moves along the axial direction of the spindle 2A. Therefore, by rotating the spindle 2A in an appropriate direction by the motor of the electric motor unit 3, the nut 2N can be moved closer to the brake pad 24 or farther away from the brake pad 24. When the nut 2N approaches the brake pad 24 and presses the piston 2F, the brake pad 24 is pressed against the nut 2N through the piston 2F. Furthermore, when the nut 2N moves away from the brake pad 24 and no longer presses the piston 2F, the pressure on the brake pad 24 is released and the piston 2F becomes capable of moving due to the hydraulic pressure of the hydraulic circuit.

[0029] The predetermined area on the inner peripheral surface of the nut 2N refers to a portion of the nut 2N, which is a cylindrical member, where a ball screw groove 2M for screwing with the spindle 2A via a ball 2D is formed. In the disc brake device 1 of this embodiment, the portion indicated by the symbol A in FIG. 1 corresponds to the predetermined area. As can be seen from FIG. 1, the ball screw groove 2M is formed in a portion of the inner peripheral surface of the nut 2N, which is a cylindrical body, far from the brake pad 24. This is in accordance with the designed movement amount of the piston 2F in the disc brake device 1. That is, as the wear of the brake pads 23, 24 and the brake rotor progresses, the position of the piston 2F relative to the cylinder 2G gradually moves toward the brake pad 24 side. And the position of the nut 2N in a state where the parking brake is activated also gradually moves toward the brake pad 24 side according to the progress of the wear of the brake pads 23, 24 and the brake rotor. For this reason, the area of ​​the ball screw groove 2M of the nut 2N is set so that the ball 2D circulates within a range where the ball 2D does not come off the ball screw groove 2B even when wear of the brake pads 23, 24 and the brake rotor progresses and the piston 2F reaches the maximum design movement amount of the disc brake device 1.

[0030] In addition, a flange 2I and a thrust bearing 2J are attached to the spindle 2A to receive a thrust load generated when the nut 2N presses the brake pad 24 via the piston 2F. This allows the spindle 2A to withstand the reaction force from the nut 2N when the parking brake is applied. In addition, a seal ring 2K is provided near the thrust bearing 2J to prevent brake fluid from leaking from a gap between the spindle 2A and the caliper body 21.

[0031] The nut 2N is provided with a deflector 2C for repeatedly circulating the balls 2D within a predetermined section of the ball screw groove 2M. The deflector 2C forms a ball 2D return path (an example of the "ball return path" in the present application) connecting both ends of the predetermined section of the nut 2N. Therefore, the deflector 2C and the ball screw groove 2M form a ball 2D circulation path (an example of the "ball circulation path" in the present application) and the balls 2D can be moved along the axial direction without interruption even if the spindle 2A is rotated continuously. The deflector 2C is fitted into a deflector hole 2H formed so as to penetrate the peripheral surface of the nut 2N.

[0032] Incidentally, in order for the disc brake device 1 to exert an appropriate braking force, it is essential that no air remains in the brake fluid filling the cylinder 2G. However, as described above, the cylinder 2G has a complicated structure in which the spindle 2A and balls 2D for electrically moving the nut 2N are present. For this reason, the disc brake device 1 of this embodiment is provided with air bleed holes at various locations in the nut 2N so that the brake fluid flowing into the cylinder 2G can smoothly discharge the air in the cylinder 2G from the bleeder valve. This minimizes the possibility of air remaining in the brake fluid filling the cylinder 2G.

[0033] Fig. 2 is a first diagram showing the internal structure of the cylinder 2G in detail. Fig. 3 is a second diagram showing the internal structure of the cylinder 2G in detail. While Fig. 2 shows the spindle 2A, Fig. 3 omits the spindle 2A.

[0034] As can be seen from Figs. 2 and 3, the nut 2N is provided with, for example, air bleed holes 2E (an example of the "second air bleed path" in the present application) penetrating the inner and outer circumferential surfaces at multiple locations. The air bleed holes 2E are provided so as to penetrate the inner and outer circumferential surfaces of the nut 2N in an area (an example of the "second area" in the present application) other than the predetermined area in which the ball screw groove 2M is provided. The air bleed holes 2E are provided at four locations, each at 90 degrees around the axis of the nut 2N. Due to the presence of such air bleed holes 2E, when the cylinder 2G is filled with brake fluid, the air in the nut 2N moves to the outside of the nut 2N through the air bleed holes 2E and is discharged to the outside of the cylinder 2G through a bleeder valve communicating with the cylinder 2G.

[0035] Fig. 4 is an external perspective view of the nut 2N. Fig. 5 shows the circulation path of the balls 2D in the nut 2N. In Fig. 4, the slits 2P for passing the brake fluid are shown on the outer circumferential surface of the nut 2N. Fig. 5(A) shows the circulation path of the balls 2D in a see-through view so that the positional relationship with the ball screw groove 2B can be seen, and Fig. 5(B) shows a cross-sectional view of the nut 2N with the spindle 2A omitted.

[0036] As can be seen from FIG. 5, the nut 2N is provided with three deflectors 2C at 90 degrees each around the axis of the nut 2N. Therefore, three circulation paths for the balls 2D that roll while being sandwiched between the nut 2N and the spindle 2A are formed in a shape corresponding to the three deflectors 2C. The balls 2D continue to circulate in each of the three circulation paths in conjunction with the rotation of the spindle 2A. Therefore, in the predetermined region where the ball screw groove 2M of the nut 2N is formed, there are two parts sandwiched between the three circulation paths where the balls 2D do not roll. Therefore, the nut 2N is provided with air vent holes 2Q (an example of the "first air vent path" in this application) that penetrate the inner and outer peripheral surfaces of the nut 2N in such a place where the balls 2D do not roll in the predetermined region. Due to the presence of such air bleed hole 2Q, when the cylinder 2G is filled with brake fluid, air near the ball 2D moves to the outside of the nut 2N through the air bleed hole 2Q and is discharged to the outside of the cylinder 2G through a bleeder valve that communicates with the cylinder 2G. Therefore, with the disc brake device 1 of this embodiment, it is possible to minimize the possibility that air will remain inside the nut 2N, particularly near a predetermined area.

[0037] The disc brake device 1 may be modified as follows. 7A and 7B are diagrams showing a deflector 4 used in the disc brake device 1 according to the modified example. Also, Fig. 7 shows the circulation path of the balls 2D in the nut 2N of the disc brake device 1 according to the modified example. In Fig. 7A, the circulation path of the balls 2D is shown in a see-through view so that the positional relationship with the ball screw groove 2B can be seen, and in Fig. 7B, a cross-sectional view of the nut 2N is shown with the spindle 2A omitted.

[0038] In this modification, a deflector 4 as shown in Fig. 6 is used instead of the above-mentioned deflector 2C. As shown in Fig. 6, the deflector 4 has a return block 41, a ball stopper 42, an air vent hole 43 (an example of the "first air vent path" in the present application), and a return groove 44. The deflector 4 is formed, for example, by a resin molding. The deflector 4 is assembled into the deflector hole 2H from the inside of the nut 2N.

[0039] The return block 41 is a portion that forms a return groove 44 for circulating the ball 2D, and is shaped to fit into the deflector hole 2H. The return groove 44 connects adjacent grooves of the ball screw groove 2M by a path that is inclined in the opposite direction to the spiral formed by the ball screw groove 2M. The ball stopper 42 plays a role in stopping the ball 2D that has entered the return groove 44 from rolling toward the ball screw groove 2M. As a result, when the ball 2D that has made about one revolution around the ball screw groove 2M formed on the inner peripheral surface of the nut 2N enters the return groove 44, it deviates from the orbit of the ball screw groove 2M and proceeds through the return groove 44, and is returned to the original position of the ball screw groove 2M before making about one revolution. As a result, the ball 2D continues to circulate in conjunction with the rotation of the spindle 2A.

[0040] The air bleed hole 43 is provided in the middle of the return groove 44 and communicates the inside and outside of the nut 2N. This allows the air that accumulates in the return groove 44 to move to the outside of the nut 2N when the cylinder 2G is filled with brake fluid. By using such a deflector 4 having the air bleed hole 43, when the cylinder 2G is filled with brake fluid, the air near the ball 2D moves to the outside of the nut 2N through the air bleed hole 43 and is discharged to the outside of the cylinder 2G through a bleeder valve that communicates with the cylinder 2G. Therefore, with the disc brake device 1 of this modified example using the deflector 4, it is possible to minimize the possibility that air will remain inside the nut 2N, especially near a predetermined area.

[0041] The disc brake device 1 may be provided with both the air bleed hole 2Q and the air bleed hole 43, or may be provided with only one of them.

[0042] Furthermore, the disc brake device 1 may include three deflectors 2C or three deflectors 4, or may include two or less deflectors 2C or two or more deflectors 2C or four or more deflectors 4. In this case, the number of air bleed holes 2Q or the number of air bleed holes 43 will be changed as appropriate.

[0043] Furthermore, the disc brake device 1 can be modified as appropriate without departing from the spirit and scope of the invention disclosed in this application. [Explanation of symbols]

[0044] 1. Disc brake device 2. Brake device body 3. Electric motor unit 4. Deflector 2A··Spindle 2B Ball screw groove 2C··Deflector 2D Ball 2E, 2Q, 43 Air vent hole 2F Piston 2G··Cylinder

Claims

1. A piston that presses the brake pad against the rotor; a caliper body having a cylinder in which the piston slides; a ball screw disposed in the cylinder filled with brake fluid and capable of pressing the piston; The ball screw is a cylindrical body having a helical thread groove formed in a first region of an inner circumferential surface; A screw shaft is inserted into the cylindrical body via a plurality of balls, and has a helical screw groove formed on its outer circumferential surface corresponding to the screw groove of the cylindrical body; a first air vent path formed through the cylindrical body in the first region where the thread groove is formed so as to communicate between the inner peripheral surface and the outer peripheral surface of the cylindrical body; Disc brake device.

2. The cylindrical body has a ball return path connecting both ends of a predetermined section of the thread groove in the first region, and a ball circulation path is formed by the predetermined section of the thread groove in the first region and the ball return path. The disc brake device according to claim 1.

3. The cylindrical body has a second air vent path formed through the cylindrical body so as to communicate between the inner peripheral surface and the outer peripheral surface in a second region other than the first region in which the screw groove is formed. The disc brake device according to claim 2.

4. The cylindrical body has the ball return paths at a plurality of locations, thereby forming the ball circulation paths at a plurality of locations, The first air vent path is provided at an adjacent portion of the plurality of ball circulation paths. The disc brake device according to claim 3.

5. the ball screw has the first air bleed path at a portion of the ball return path in the first region in which the screw groove of the cylindrical body is formed, A disc brake device according to any one of claims 2 to 4.

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