Electric brake device

Abstract

The invention relates to an electric brake device. A connection member (29) for transferring pressing force between a nut (26) and a piston (21) of a linear motion conversion mechanism (20) for converting rotation of an electric motor (18) into linear motion is interposed between the nut (26) and the piston (21). Furthermore, the nut (26) is provided so as to be swingable with respect to the connecting member (29), and the connecting member (29) is provided so as to be movable in the radial direction with respect to the piston.

Description

Technical Field

[0001] The invention relates to an electric braking device. Background Art

[0002] As an electric brake device, there is a device described in Patent Document 1. The electric brake device of this document includes an electric motor, a linear motion conversion mechanism, and a piston. The linear motion conversion mechanism includes a rotating part that is rotated by the electric motor, and a linear motion part that moves linearly according to the rotation of the rotating part. A pressing piece is sandwiched between the linear motion part of the linear motion conversion mechanism and the piston. An arc shape is formed on at least one of the piston and the pressing piece. Moreover, the piston and the pressing piece are in contact at the arc-shaped portion. In such an electric brake device, the pressing piece is allowed to swing relative to the piston. Moreover, by this swinging, the bending deformation of the components caused by the bending of the cylinder and the like when the braking force is generated and the increase in the sliding resistance of the piston relative to the cylinder are suppressed.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2020-193641

[0004] Depending on how the cylinder or the like deforms when the braking force is generated, there may be a case where the bending strain or increase in sliding resistance due to the deformation cannot be sufficiently suppressed simply by the swinging of the pusher relative to the piston. Summary of the invention

[0005] The electric brake device for solving the above-mentioned problems has a piston that can be accommodated in a cylinder so as to move linearly, and generates a braking force for the wheel according to the linear motion of the piston powered by the rotation of an electric motor. In addition, the electric brake device has: a linear motion conversion mechanism, which has a rotating component that rotates by receiving the rotation of the electric motor, and a linear motion component that moves linearly according to the rotation of the rotating component; and a connecting component that is sandwiched between the linear motion component and the piston and mediates the transmission of axial pressure of the cylinder between the linear motion component and the piston. Moreover, the linear motion component on the electric brake device is configured to be able to swing relative to the connecting component, and the connecting component is configured to be able to move radially relative to the piston in the cylinder.

[0006] There are cases where the central axis of the cylinder is tilted relative to the central axis of the piston due to bending of the components of the electric brake device, processing errors during manufacturing, and assembly errors. In addition, there are cases where the rotating axis of the rotating component of the linear motion conversion mechanism is also tilted from the central axis of the piston together with the central axis of the cylinder, and an eccentric load is generated on the components of the electric brake device. Such an eccentric load causes eccentric wear and bending deformation of the components.

[0007] In the above electric brake device, the linear motion component is allowed to swing relative to the connecting component, and the connecting component is allowed to move radially relative to the piston. In such an electric brake device, regardless of the position of the piston in the cylinder, the central axis of the cylinder tilted relative to the central axis of the piston and the rotating axis of the rotating component can be maintained in a state of being consistent. Therefore, the above electric brake device has the following effect, that is, the generation of eccentric loads on the components caused by the tilt of the piston relative to the central axis of the cylinder is suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a diagram schematically showing a cross-sectional structure of an embodiment of an electric brake device.

[0009] Figure 2 It is a cross-sectional view of the piston, connecting component, and linear motion conversion mechanism of the electric brake device.

[0010] Figure 3 It is a diagram showing a three-dimensional structure of a connecting member and a linear motion member of the electric brake device.

[0011] Figure 4 This is a cross-sectional view showing a state when a braking force is generated by a piston, a connecting member, and a linear motion conversion mechanism of the electric brake device.

[0012] Figure 5 It means Figure 4 A cross-sectional view of the state of the piston, the connecting member, and the linear motion conversion mechanism of the electric brake device when the braking force is generated when the wear of the friction member is more severe than in the case of .

[0013] Figure 6 It is a side view of a connecting member and a nut in a modified example of the electric brake device.

[0014] Figure 7 It is a cross-sectional view of a connecting member and a nut in a modified example of the electric brake device. DETAILED DESCRIPTION

[0015] Below, according to Figure 1 to Figure 5 , an embodiment of the electric brake device is described.

[0016] <Overall structure of electric brake device>

[0017] First, refer to Figure 1 The overall structure of the electric brake device 10 of this embodiment will be described. The electric brake device 10 of this embodiment is configured as a caliper type disc brake device that brakes the rotation of the disc rotor 12 by clamping the disc rotor 12 with two friction members 11A and 11B.

[0018] The electric brake device 10 includes a brake caliper 13. The brake caliper 13 includes a cylinder 14, a bridge 15, and a claw 16. The cylinder 14 and the claw 16 are arranged so as to sandwich the disc rotor 12 therebetween. The bridge 15 is a portion located in the brake caliper 13 and connecting the cylinder 14 and the claw 16, and is arranged radially outward of the disc rotor 12. In addition, one (11A) of the two friction members 11A and 11B is assembled to the claw 16, and the other (11B) is assembled to the cylinder 14. In addition, a cylinder 17 is provided in the cylinder 14. The cylinder 17 is a bottomed cylindrical hole that is open on the side where the disc rotor 12 is located when viewed from the cylinder 14.

[0019] In addition, the electric brake device 10 includes an electric motor 18, a speed reduction mechanism 19, a linear motion conversion mechanism 20, and a piston 21. The electric motor 18 is assembled to the cylinder 14. The speed reduction mechanism 19 is accommodated in a transmission case 19A assembled to the cylinder 14. The linear motion conversion mechanism 20 and the piston 21 are accommodated in the cylinder 17 of the cylinder 14.

[0020] The speed reduction mechanism 19 is a mechanism for reducing the speed of the rotation of the electric motor 18 and transmitting the reduced speed to the linear motion conversion mechanism 20. In the case of the electric brake device 10 of the present embodiment, a speed reduction gear mechanism having a plurality of gears is used as the speed reduction mechanism 19. Figure 1 The speed reduction mechanism 19 shown includes a first gear 22 connected to the electric motor 18 , a third gear 24 connected to the linear motion conversion mechanism 20 , and a second gear 23 interposed between the first gear 22 and the third gear 24 .

[0021] The linear motion conversion mechanism 20 is a mechanism that converts the rotation transmitted from the reduction mechanism 19 into a linear motion. In the case of the electric brake device 10 of this embodiment, it is provided with a threaded shaft 25 as a rotating member that receives the rotation of the electric motor 18 and rotates, and a nut 26 as a linear motion member that linearly moves according to the rotation of the threaded shaft 25. The threaded shaft 25 is connected to the third gear 24 of the reduction mechanism 19 so as to rotate integrally with the third gear 24. In addition, the linear motion conversion mechanism 20 is configured so that the rotation axis of the threaded shaft 25 is coaxial with the central axis L of the cylinder 17.

[0022] The piston 21 is provided to be linearly movable in the axial direction in the cylinder 17. In the following description, the side of the cylinder 17 where the friction member 11B is located as viewed from the piston 21 in the axial direction is referred to as the axial front side F, and the opposite side is referred to as the axial rear side R.

[0023] like Figure 2As shown in FIG. 1 , the piston 21 is in the shape of a bottomed cylindrical body opened in the axial rear R, and has a tubular side wall 21A and a disc-shaped bottom wall 21B. A connecting member 29 is provided in a portion of the space surrounded by the side wall 21A of the piston 21 in a state of contact with the bottom wall 21B. The connecting member 29 is a member that is sandwiched between the nut 26 and the piston 21 and mediates the transmission of the axial pressure of the cylinder 17 therebetween. The details of the connection structure of the piston 21 and the nut 26 via the connecting member 29 will be described later.

[0024] In addition, if Figure 1 As shown, a flange portion 25A having an enlarged diameter is provided on the threaded shaft 25 at a portion axially rearward R of a portion engaged with the nut 26. Furthermore, a thrust bearing 27 and a pressure sensor 28 are provided inside the cylinder 17 in a state of being sandwiched between the bottom wall 17A of the cylinder 17 and the flange portion 25A of the threaded shaft 25.

[0025] When the electric motor 18 rotates, the rotation is decelerated by the speed reduction mechanism 19 and transmitted to the threaded shaft 25 of the linear motion conversion mechanism 20. Then, the linear motion conversion mechanism 20 converts the rotation of the threaded shaft 25 into the linear motion of the nut 26. When the nut 26 moves axially forward F until it contacts the connecting member 29, the piston 21 is pressed toward the axial front F via the connecting member 29. Then, the pressing is transmitted to the friction member 11B via the piston 21. As a result, in the electric brake device 10, the two friction members 11A and 11B clamp the disc rotor 12, thereby generating a braking force. In addition, when the piston 21 applies pressure to the friction member 11B, the reaction force to the pressing is applied to the pressure sensor 28 via the flange portion 25A of the threaded shaft 25. Therefore, the output signal of the pressure sensor 28 is a signal corresponding to the braking force generated by the electric brake device 10.

[0026] <Connection Structure between Piston 21 and Nut 26>

[0027] Next, refer to Figure 2 and Figure 3 , the connection structure between the piston 21 and the nut 26 will be described. Figure 2 The cross-sectional structure of the piston 21, the connecting member 29, and the linear motion conversion mechanism 20 of the electric brake device 10 is shown. Figure 3 An exploded perspective structure of the connection member 29 and the nut 26 is shown.

[0028] The connecting member 29 is in the shape of an annular column. Furthermore, the connecting member 29 has a tapered portion 29A at the end portion on the axially rearward R side thereof, and the tapered portion 29A is a concave portion in the shape of a cone. On the other hand, the nut 26 has a spherical curved portion 26A having its center on the rotation axis of the threaded shaft 25 at the end portion on the axially forward F thereof. Furthermore, the connecting member 29 and the nut 26 are in contact with each other through the line contact of the curved portion 26A relative to the tapered portion 29A. Therefore, the connecting member 29 can swing with two degrees of freedom relative to the nut 26 when the pressure from the nut 26 is applied when the braking force is generated.

[0029] An elastic member 30 such as an O-ring is interposed between the connecting member 29 and the side peripheral wall 21A of the piston 21 in the radial direction of the cylinder 17. Therefore, the connecting member 29 can move relative to the piston 21 in the radial direction of the piston 21 by elastic deformation of the elastic member 30.

[0030] In this embodiment, the piston 21 is made of a material that is lower in strength but lighter in specific gravity than the material of the connecting member 29. For example, an example of the material of the piston 21 is aluminum, and an example of the material of the connecting member 29 is steel.

[0031] <Functions and effects of implementation methods>

[0032] The operation and effects of this embodiment will be described.

[0033] The electric brake device 10 generates a braking force by clamping the disc rotor 12 using the friction member 11A assembled to the claw 16 and the friction member 11B assembled to the cylinder 14. When such a braking force is generated, a reaction force to the pressure of the friction members 11A and 11B is applied to the claw 16 and the cylinder 14. On the other hand, the claw 16 and the cylinder 14 are connected by a bridge portion 15 located radially outside the disc rotor 12. Therefore, when a reaction force to the pressure is applied from the friction members 11A and 11B, bending occurs in the brake caliper 13. Then, the center axis L of the cylinder 17 is tilted from the position before the bending occurs due to this bending. In addition, Figure 1 In FIG. 1 , the bending state of the brake caliper 13 when the braking force is generated is exaggeratedly shown by the dotted line.

[0034] When the braking force is generated, the piston 21 applies pressure to the friction member 11B. Therefore, even if the brake caliper 13 is bent, the posture of the piston 21 is maintained along the pressed surface of the friction member 11B. On the other hand, when the center axis L of the cylinder 17 is tilted due to the bending of the brake caliper 13, the posture of the linear motion conversion mechanism 20 changes accordingly. Therefore, when the braking force is generated, there is a situation where the rotation axis of the threaded shaft 25 is tilted relative to the center axis of the piston 21. At this time, if the piston 21 and the nut 26 are rigidly fixed, an eccentric load is applied to the piston 21, the linear motion conversion mechanism 20, etc. Such an eccentric load is the cause of eccentric wear of the cylinder 17 and the piston 21 and bending deformation of the threaded shaft 25.

[0035] exist Figure 4 2 shows the state of the piston 21, the connecting member 29 and the linear motion conversion mechanism 20 when the braking force is generated. Figure 4 In the case of , the center axis L2 of the cylinder 17 is tilted relative to the center axis L1 of the piston 21. In such a case, if the linear motion conversion mechanism 20 swings relative to the piston 21 with the intersection P of the two center axes L1 and L2 as the center, the rotation axis of the threaded shaft 25 can be maintained coaxial with the center axis L2 of the cylinder 17, thereby suppressing the generation of eccentric load. In the case of the present embodiment, the linear motion conversion mechanism 20 is arranged in the cylinder 17 in a state that allows the nut 26 to swing relative to the connecting part 29. The position of the swing center O of the nut 26 relative to the connecting part 29 is the center of the ball of the spherical curved surface constituting the curved portion 26A. Therefore, when the position of such a swing center O coincides with the position of the intersection P of the two center axes L1 and L2, the generation of eccentric load when the braking force is generated is suppressed.

[0036] exist Figure 5 Shown in Figure 4 The state of braking when the friction member 11B is worn more than the state of braking when the friction member 11B is worn. When the friction member 11B is worn, the position of the piston 21 when the braking force is generated is close to the disc rotor 12 according to the amount of wear. The position of the connecting member 29 also changes with the piston 21. Therefore, Figure 5 The position of the swing center O of the nut 26 in the case of Figure 4 . Therefore, in this case, the position of the swing center O of the nut 26 is offset from the intersection point P of the two center axes L1 and L2 in the axial direction of the cylinder 17. Therefore, only by enabling the linear motion conversion mechanism 20 to swing relative to the piston 21, it is impossible to fully suppress the generation of an eccentric load when a braking force is generated due to the wear of the friction member 11B.

[0037] In contrast, in the electric brake device 10 of the present embodiment, the connecting member 29 is provided in a state that allows movement in the radial direction relative to the piston 21. Therefore, the position of the swing center O of the nut 26 can be moved in the radial direction of the piston 21. Figure 5 Even in the case of the piston 21, the rotation axis of the threaded shaft 25 can be maintained coaxial with the center axis L2 of the cylinder 17 by the radial movement of the connecting member 29 relative to the piston 21 and the swing of the nut 26 relative to the connecting member 29. In this way, the electric brake device 10 of this embodiment has the following effect, that is, when the center axes L1 and L2 of the piston 21 and the cylinder 17 are tilted, the generation of eccentric loads on the components is suppressed.

[0038] In addition, the electric brake device 10 of the present embodiment includes an elastic member 30 that is sandwiched between the connecting member 29 and the piston 21 in the radial direction of the cylinder 17. The elastic member 30 allows the connecting member 29 to move in the radial direction relative to the piston 21 by its elastic deformation. On the other hand, the elastic member 30 holds the connecting member 29 to the side peripheral wall 21A of the piston 21. Therefore, it is difficult for the connecting member 29 in the piston 21 to tilt or move in the axial direction.

[0039] The connecting member 29 has a tapered portion 29A in a tapered shape at a portion facing the nut 26. In addition, the nut 26 has a spherical curved surface portion 26A in line contact with the tapered portion 29A. Therefore, the nut 26 can swing relative to the connecting member 29 when the braking force is generated with a simple structure. In addition, since the nut 26 and the connecting member 29 are not always connected, such a connection structure can also be easily applied to a brake device that uses both electric and hydraulic pressure.

[0040] In addition, there are cases where the center axes L1 and L2 of the piston 21 and the cylinder 17 are offset or tilted due to processing errors and assembly errors during manufacturing. The offset and tilt of the center axes L1 and L2 caused by such processing errors and assembly errors are also important factors that cause eccentric loads to be generated in the components of the electric brake device 10. In the electric brake device 10 of this embodiment, the generation of eccentric loads caused by the offset and tilt of the center axes L1 and L2 caused by such processing errors and assembly errors is also suppressed.

[0041] In addition, the tapered portion 29A of the connecting member 29 is in line contact with the curved surface portion 26A of the nut 26. When the braking force is generated, a high load is locally applied to such a tapered portion 29A. In the present embodiment, since the material of the connecting member 29 is set to steel, it is possible to ensure strength that can withstand the high load applied when braking is generated. On the other hand, the piston 21 receives pressure on the connecting member 29 and the friction member 11B with its surface, so the required strength is not as high as that of the connecting member 29. In the present embodiment, since the material of the piston 21 is set to aluminum, it can contribute to the lightweighting of the device.

[0042] <Other embodiments>

[0043] The present embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within the range that there is no technical contradiction.

[0044] As the elastic member 30 , a member other than the O-ring such as a leaf spring may be used.

[0045] For example Figure 6 As shown in FIG. 1 , the curved surface portion 26A may be formed into a cylindrical shape, and the tapered portion 29A may be formed into a V-shaped valley shape. In this case, the linear motion conversion mechanism 20 can swing with one degree of freedom relative to the connecting member 29. When the bending manner of the brake caliper 13 when the braking force is generated is fixed to a certain extent, even the swing with one degree of freedom can suppress the generation of eccentric load.

[0046] In the case where the nut 26 and the connecting member 29 are always in contact with each other and the movement of the connecting member 29 in the axial direction in the piston 21 is restricted, the elastic member 30 may be omitted.

[0047] For example Figure 7 As shown, the curved surface portion 26A may be provided on the connecting member 29 , and the tapered portion 29A may be provided on the nut 26 .

[0048] The linear motion conversion mechanism 20 may be configured such that the nut is used as a rotating member and the screw shaft is used as a linear motion member. In this case, the tapered portion 29A or the curved surface portion 26A is provided on the screw shaft.

[0049] As a structure for realizing the swing of the linear motion member relative to the connecting member 29, a structure other than the contact between the tapered portion 29A and the curved surface portion 26A, such as a ball joint, may be adopted.

[0050] The electric brake device 10 can also be configured as a wet electric brake device. A wet electric brake device generates hydraulic pressure by applying pressure to the brake fluid introduced into the cylinder through the reciprocating motion of the piston in the cylinder, and uses the hydraulic pressure to generate braking force. In such a wet electric brake device, there is a situation where the center axis of the piston and the center axis of the cylinder are tilted due to external force, processing errors of the components, and assembly errors. Therefore, in a wet electric brake device, if the connection structure of the piston 21 and the linear motion component via the connecting component 29 as described above is adopted, the generation of eccentric loads on the components is also suppressed.

Claims

1. An electric brake device, comprising a piston housed in a cylinder so as to be capable of linear movement, and generating a braking force according to the linear movement of the piston driven by the rotation of an electric motor, the electric brake device comprising: a linear motion conversion mechanism including a rotating member that rotates in response to the rotation of the electric motor and a linear motion member that linearly moves in accordance with the rotation of the rotating member; and a connecting member, which is interposed between the linear motion member and the piston and mediates the transmission of the axial pressure of the cylinder between the linear motion member and the piston, The linear motion member is configured to be able to swing relative to the connecting member. The connecting member is provided to be movable relative to the piston in a radial direction of the piston.

2. The electric brake device according to claim 1, wherein: An elastic member is interposed between the connection member and the piston in a radial direction of the cylinder.

3. The electric brake device according to claim 1, wherein: One of the connecting member and the linear motion member has a tapered portion in a tapered shape at a portion facing the other. The other of the connection member and the linear motion member has a cylindrical or spherical curved surface portion that is in line contact with the tapered portion.

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