ELECTRIC BRAKE DEVICE

Abstract

A connecting member 29 is arranged between a nut 26 of a linear motion conversion mechanism 20, which converts the rotation of an electric motor 18 into linear motion, and a piston 21. This connecting member 29 transmits the compressive force between the nut and the piston. The nut 26 is pivotable with respect to the connecting member 29, and the connecting member 29 is arranged for radial movement with respect to the piston.

Description

TECHNICAL FIELD

[0001] The present invention relates to an electric braking device. BACKGROUND ART

[0002] As an electric brake device, a device described in Patent Literature 1 is known. The electric brake device in Patent Literature 1 includes an electric motor, a linear motion conversion mechanism, and a piston. The linear motion conversion mechanism includes a rotary member rotated by the electric motor and a linear motion member that moves linearly in accordance with the rotation of the rotary member. A pressing member is provided between the linear motion member of the linear motion conversion mechanism and the piston. The piston and / or the pressing member are formed in an arc shape. The piston and the pressing member contact each other at the arc-shaped portion. In such an electric brake device, the pivoting of the pressing member with respect to the piston is possible.By pivoting, the bending deformation of the components and the increase in the sliding resistance of the piston against the cylinder due to the deflection of the cylinder or the like at the time of generation of the braking force are suppressed. CITATION LISTPATENT LITERATURE

[0003] Patent Literature 1: Japanese Patent Application Laid-Open No. 2020-193641 SUMMARY OF THE INVENTION TECHNICAL PROBLEMS

[0004] Depending on how the cylinder or similar is deformed at the time the braking force is generated, bending deformations and a deformation-related increase in sliding resistance cannot be sufficiently suppressed by pivoting the pressure element relative to the piston alone. SOLUTIONS TO PROBLEMS

[0005] An electric brake device for solving the above problem includes a piston linearly movably housed in a cylinder and configured to generate a braking force of a wheel according to the linear motion of the piston using the rotation of an electric motor as power. Furthermore, the electric brake device includes a linear motion conversion mechanism including a rotary member configured to rotate upon receiving the rotation of the electric motor and a linear motion member configured to move linearly according to the rotation of the rotary member; and a connecting member disposed between the linear motion member and the piston to effect transmission of a thrust force in an axial direction of the cylinder between the linear motion member and the piston.The linear motion member in the electric brake device is installed to be pivotable with respect to the link member, and the link member is installed to be movable in a radial direction of the cylinder with respect to the piston.

[0006] There is a case where the cylinder center axis is tilted relative to the piston center axis due to deflection of components of the electric braking device and a machining error or assembly error at the time of manufacturing. In addition to the cylinder center axis, the rotation axis of the rotary component of the linear motion conversion mechanism may also be tilted relative to the piston center axis, and an unbalanced load may be generated in the components of the electric braking device. Such unbalanced load leads to uneven wear and bending deformation of the component.

[0007] In the electric braking device, the pivoting of the linear motion member with respect to the link member and the radial movement of the link member with respect to the piston are permitted. In such an electric braking device, it is possible to maintain a state where the cylinder center axis, which is inclined with respect to the piston center axis, and the rotation axis of the rotary member are consistent with each other regardless of the position of the piston in the cylinder. Therefore, the electric braking device has the effect of suppressing the generation of an unbalanced load on the member due to the inclination of the piston center axis with respect to the cylinder. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view of an electric braking device as an embodiment. Fig. 2 is a cross-sectional view of a piston, a connecting member, and a linear motion conversion mechanism of the electric brake device. Fig. 3 is a diagram showing the perspective structure of the connecting member and a linear motion member of the electric brake device. Fig. 4 is a cross-sectional view showing a state at the time of generation of a braking force of the piston, the connecting member, and the linear motion conversion mechanism of the electric braking device. Fig. 5 is a cross-sectional view illustrating a state at the time of generation of a braking force of the piston, the connecting member, and the linear motion conversion mechanism of the electric brake device when the wear of a friction member is more advanced than in the case of Fig. 4. Fig. 6 is a side view of a connecting member and a nut in a modified example of the electric brake device. Fig. 7 is a cross-sectional view of the connecting member and the nut in the modified example of the electric brake device. DESCRIPTION OF THE EMBODIMENTS

[0008] An embodiment of an electric braking device is described below with reference to the Fig. 1 to 5. <Gesamtkonfiguration der elektrischen Bremsvorrichtung>

[0009] First, an overall configuration of an electric brake device 10 of the present embodiment will be described with reference to Fig. 1. The electric brake device 10 of the present embodiment is configured as a caliper-type disc brake device that brakes the rotation of a disc rotor 12 by clamping the disc rotor 12 with two friction members 11A and 11B.

[0010] The electric brake device 10 includes a brake caliper 13. The brake caliper 13 includes a cylinder body 14, a bridge portion 15, and a claw portion 16. The cylinder body 14 and the claw portion 16 are arranged to sandwich the disc rotor 12. The bridge portion 15 is a portion connecting the cylinder body 14 and the claw portion 16 in the brake caliper 13 and is arranged on the radially outer side of the disc rotor 12. One (11A) of the two friction members 11A and 11B is connected to the claw portion 16, and the other (11B) is connected to the cylinder body 14. Furthermore, the cylinder body 14 is provided with a cylinder 17. The cylinder 17 is a bottomed cylindrical hole opened on the side where the disc rotor 12 is located as viewed from the cylinder body 14.

[0011] Furthermore, 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 connected to the cylinder body 14. The speed reduction mechanism 19 is housed in a gear case 19A mounted on the cylinder body 14. The linear motion conversion mechanism 20 and the piston 21 are housed in the cylinder 17 of the cylinder body 14.

[0012] The speed reduction mechanism 19 is a mechanism that brakes the rotation of the electric motor 18 and transmits the rotation to the linear motion conversion mechanism 20. In the electric braking device 10 of the present embodiment, a speed reduction mechanism having a plurality of gears is used as the speed reduction mechanism 19. The Fig. The speed reduction mechanism 19 shown in Fig. 1 comprises 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 arranged between the first gear 22 and the third gear 24.

[0013] The linear motion conversion mechanism 20 is a mechanism that converts the rotational motion transmitted from the speed reduction mechanism 19 into linear motion. In the electric brake device 10 of the present embodiment, a screw shaft 25 serving as a rotary member that rotates in accordance with the rotation of the electric motor 18 and a nut 26 serving as a linear motion member that moves linearly in accordance with the rotation of the screw shaft 25 are provided. The screw shaft 25 is connected to the third gear 24 of the speed reduction mechanism 19 so that it rotates integrally. Note that the linear motion conversion mechanism 20 is installed so that the rotation axis of the screw shaft 25 is coaxial with the central axis L of the cylinder 17.

[0014] The piston 21 is installed in the cylinder 17 so as to be linearly movable in the axial direction. In the following description, the side in the axial direction of the cylinder 17 on which the friction component 11B is located, as viewed from the piston 21, is referred to as the axial front side F, and the opposite side is referred to as the axial rear side R.

[0015] As in Fig. 2, the piston 21 has a cylindrical bottom shape opened toward the axial rear side R, and includes a side peripheral wall 21A in the shape of a circular tube and a bottom wall 21B in the shape of a disc. In a portion that has become a space surrounded by the side peripheral wall 21A of the piston 21, a connecting member 29 is installed in a state of being in contact with the bottom wall 21B. The connecting member 29 is a member that is interposed between the nut 26 and the piston 21 and causes the thrust force in the axial direction of the cylinder 17 to be transmitted therebetween. Details of the connecting structure between the piston 21 and the nut 26 via the connecting member 29 will be described later.

[0016] As in Fig. 1, a flange portion 25A having an enlarged diameter is provided at a portion on the axial rear side R that is not coincident with the portion where the nut 26 engages the screw shaft 25. A thrust bearing 27 and the pressure sensor 28 are installed inside the cylinder 17 while being sandwiched between the bottom wall 17A of the cylinder 17 and the flange portion 25A of the screw shaft 25.

[0017] When the electric motor 18 rotates, the rotation is decelerated by the speed reduction mechanism 19 and transmitted to the screw shaft 25 of the linear motion conversion mechanism 20. The linear motion conversion mechanism 20 then converts the rotation of the screw shaft 25 into linear motion of the nut 26. When the nut 26 moves toward the axial front side F until it comes into contact with the connecting member 29, a pressing force is applied to the piston 21 in the direction of the axial front side F via the connecting member 29. Subsequently, the pressing force is transmitted to the friction member 11B via the piston 21. Thus, the electric brake device 10 generates the braking force through the friction members 11A and 11B clamping the disc rotor 12.Note that when the piston 21 applies the pushing force to the friction member 11B via the flange portion 25A of the screw shaft 25, a reaction force against the pushing force is applied to the pressure sensor 28. Therefore, the output signal of the pressure sensor 28 is a signal corresponding to the braking force generated by the electric brake device 10. <Verbindungsstruktur von Kolben 21 und Mutter 26>

[0018] Next, a connecting structure of the piston 21 and the nut 26 will be described with reference to Fig. 2 and Fig. 3 described. Fig. 2 shows a cross-sectional structure of the piston 21, the connecting member 29 and the linear motion conversion mechanism 20 of the electric brake device 10. Fig. 3 also shows a perspective exploded view of the connecting component 29 and the nut 26.

[0019] The connecting member 29 has an annular columnar shape. Furthermore, the connecting member 29 has a tapered portion 29A, which is a conically tapered recessed portion, at one end portion on the axial rear side R. On the other hand, the nut 26 has a spherically curved surface portion 26A, the center of which is located on the rotational axis of the screw shaft 25, at one end portion on the axial front side F. The connecting member 29 and the nut 26 are in contact by line contact of the curved surface portion 26A with respect to the tapered portion 29A. Therefore, the connecting member 29 can pivot with two degrees of freedom with respect to the nut 26 in a state where the pressing force is applied from the nut 26 at the time of generating the braking force.

[0020] Furthermore, an elastic member 30, such as an O-ring, is inserted in a portion 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 in the radial direction of the piston 21 by the elastic deformation of the elastic member 30 with respect to the piston 21.

[0021] In the present embodiment, the material of the piston 21 is a material with lower strength but lower specific gravity than the material of the connecting member 29. An example of the material of the piston 21 is an aluminum material, and an example of the material of the connecting member 29 is a steel material. <Operationen und Auswirkungen des Ausführungsbeispiels>

[0022] The operation and effects of the present embodiment are described.

[0023] The electric brake device 10 generates the braking force by clamping the disc rotor 12 by the friction member 11A mounted on the claw portion 16 and the friction member 11B mounted on the cylinder body 14. At the time of generating such a braking force, a reaction force against the pressing force of the friction members 11A and 11B is exerted on the claw portion 16 and the cylinder body 14. On the other hand, the claw portion 16 and the cylinder body 14 are connected by a bridge portion 15 located in a portion on the radially outer side of the disc rotor 12. Therefore, when a reaction force against the pressing force is applied by the friction members 11A and 11B, the brake caliper 13 deflects. Due to such deflection, the center axis L of the cylinder 17 is inclined from the position before the deflection occurred. Fig. 1, a state of deflection of the brake caliper 13 at the time of generation of the braking force is exaggeratedly shown with a dashed line.

[0024] The piston 21 exerts a compressive force on the friction member 11B at the time of generating the braking force. Therefore, even if the brake caliper 13 is deflected, the posture of the piston 21 remains on the pressure surface of the friction member 11B. On the other hand, if the center axis L of the cylinder 17 is inclined due to the deflection of the brake caliper 13, the posture of the linear motion conversion mechanism 20 changes accordingly. Therefore, at the time of generating the braking force, the rotation axis of the screw shaft 25 may be inclined with respect to the center axis of the piston 21. If the piston 21 and the nut 26 are rigidly fixed at this time, an unbalanced load is applied to the piston 21, the linear motion conversion mechanism 20, and the like. Such an unbalanced load leads to uneven wear of the cylinder 17 and the piston 21, as well as bending deformation of the screw shaft 25.

[0025] Fig. 4 shows a state at the time of generation of the braking force of the piston 21, the connecting member 29 and the linear motion conversion mechanism 20. In the case of Fig. 4, a central axis L2 of the cylinder 17 is inclined with respect to a central axis L1 of the piston 21. Even in such a case, when the linear motion conversion mechanism 20 is pivoted with respect to the piston 21 around the intersection point P of the two central axes L1 and L2, a state in which the rotational axis of the screw shaft 25 is coaxial with the central axis L2 of the cylinder 17 can be maintained, and thus the generation of an unbalanced load is suppressed. In the present embodiment, the linear motion conversion mechanism 20 is installed in the cylinder 17 in a state in which the nut 26 is pivotable with respect to the connecting member 29. The position of the pivot point O of the nut 26 with respect to the connecting member 29 is the center of a sphere of the spherically curved surface forming the curved surface portion 26A.Therefore, when the position of the pivot point O is consistent with the position of the intersection point P between the two center axes L1 and L2, the generation of an unbalanced load at the time of generating the braking force is suppressed.

[0026] Fig. 5 shows a state at the time of occurrence of braking when the wear of the friction member 11B is more advanced than in the case of Fig. 4. When the friction member 11B is worn, the position of the piston 21 at the time of generating the braking force accordingly approaches the disc rotor 12. The position of the connecting member 29 changes together with the piston 21. Therefore, the position of the pivot point O of the nut 26 in the case of Fig. 5 closer to the disc rotor 12 than in the case of Fig. 4. Therefore, in this case, the position of the fulcrum O of the nut 26 becomes a position shifted in the axial direction of the cylinder 17 with respect to the intersection point P of the two center axes L1 and L2. Therefore, if the linear motion conversion mechanism 20 is merely pivotable with respect to the piston 21, the generation of an unbalanced load at the time of generating the braking force due to the wear of the friction member 11B cannot be sufficiently suppressed.

[0027] On the other hand, in the electric brake device 10 of the present embodiment, the connecting member 29 is installed in a state in which it can move in the radial direction with respect to the piston 21. Therefore, the position of the fulcrum O of the nut 26 can be moved in the radial direction of the piston 21. Therefore, even in the case of Fig. 5, by the radial movement of the connecting member 29 with respect to the piston 21 and the pivoting of the nut 26 with respect to the connecting member 29, a state can be maintained in which the rotational axis of the screw shaft 25 is coaxial with the central axis L2 of the cylinder 17. As described above, the electric brake device 10 of the present embodiment has the effect of suppressing the generation of an unbalanced load on the components when the central axes L1 and L2 of the piston 21 and the cylinder 17 are inclined.

[0028] Furthermore, the electric brake device 10 of the present embodiment includes an elastic member 30 disposed in a portion 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 with respect to the piston 21 through 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, the connecting member 29 is less likely to tilt or move in the axial direction within the piston 21.

[0029] The connecting member 29 has a tapered portion 29A having a tapered shape at a portion facing the nut 26. Furthermore, the nut 26 has a spherically curved surface portion 26A in line contact with the tapered portion 29A. Therefore, the pivoting of the nut 26 with respect to the connecting member 29 at the time of generating the braking force can be realized with a simple structure. Incidentally, since the nut 26 and the connecting member 29 are not always coupled to each other, such a connecting structure can be easily applied to a device that uses both electric power and hydraulic pressure.

[0030] Note that displacement or inclination of the center axes L1 and L2 of the piston 21 and the cylinder 17 may occur due to a machining error or assembly error at the time of manufacturing. Such displacement and inclination of the center axes L1 and L2 caused by the machining error and assembly error are also factors that cause an unbalanced load in the components of the electric brake device 10. In the electric brake device 10 of the present embodiment, the generation of an unbalanced load due to the displacement or inclination of the center axes L1 and L2 caused by the machining error or assembly error can be similarly suppressed.

[0031] Note that the tapered portion 29A of the connecting member 29 is in line contact with the curved surface portion 26A of the nut 26. A large load is locally applied to the tapered portion 29A at the time of generation of the braking force. In the present embodiment, since the material of the connecting member 29 is a steel material, the strength to absorb a large load applied at the time of generation of the braking force can be ensured. On the other hand, since the piston 21 receives a compressive force against the connecting member 29 and the friction member 11B on the surface, the required strength is not as high as that of the connecting member 29. Since the material of the piston 21 in the present embodiment is an aluminum material, contribution can be made to the weight reduction of the device. <Andere Ausführungsbeispiele>

[0032] The present embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be combined with each other within a technically consistent framework. - A component other than the O-ring, such as a leaf spring, can also be used as the elastic component 30. - For example, as in Fig. 6, the curved surface portion 26A has a cylindrical shape, and the tapered portion 29A has a V-shaped valley shape. In this case, the linear motion conversion mechanism 20 can swing with one degree of freedom with respect to the connecting member 29. In a case where the manner of deflection of the brake caliper 13 at the time of generating the braking force or the like is fixed to a certain extent, the generation of an unbalanced load can be suppressed even with the swing with one degree of freedom. - If the nut 26 is constantly in contact with the connecting member 29 to limit the movement of the connecting member 29 in the axial direction in the piston 21, the elastic member 30 can be omitted. - As in Fig. 7, for example, 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. - The linear motion conversion mechanism 20 may be configured such that the nut is a rotary member and the screw shaft is a linear motion member. In this case, the tapered portion 29A or the curved surface portion 26A is provided on the screw shaft. - As a structure that allows the linear motion member to swing with respect 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 used. The electric brake device 10 may be configured as a wet electric brake device. A wet electric brake device generates hydraulic pressure by applying a pressing force to a brake fluid introduced into the cylinder by the reciprocating motion of a piston in the cylinder, and generates braking force using the hydraulic pressure. Even in such an electric brake device, the center axis of the piston and the center axis of the cylinder may be inclined due to an external force, a machining error of a component, or an assembly error. Therefore, even in the electric brake device, if the above-described connection structure of the piston 21 and the linear motion member via the connection member 29 is adopted, the generation of unbalanced load on the components can be suppressed. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2020-193641

[0003]

Claims

[1] An electric braking device having a piston linearly movably housed in a cylinder and configured to generate a braking force according to a linear movement of the piston with a rotation of an electric motor as a power, the electric braking device comprising: a linear motion conversion mechanism having a rotary member configured to rotate upon receiving rotation of the electric motor and a linear motion member configured to move linearly in accordance with rotation of the rotary member; and a connecting member arranged between the linear movement member and the piston to transmit a compressive force in an axial direction of the cylinder between the linear movement member and the piston; wherein the linear motion component is installed to be pivotable with respect to the connecting component, and the connecting member is installed to be movable in a radial direction of the piston with respect to the piston. [2] The electric brake device according to claim 1, wherein an elastic member is arranged at a portion between the connecting member and the piston in a radial direction of the cylinder. [3] Electric braking device according to claim 1, wherein one of the connecting member and the linear movement member has a tapered portion formed in a tapered shape at a portion facing the other member, and the other of the connecting member and the linear motion member has a cylindrical or spherical curved surface portion that comes into line contact with the tapered portion.

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