JP2006038173A - Motor driven brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor driven brake device inexpensively incorporating a wear compensation mechanism for a brake member without impairing a design required for compact and light construction. <P>SOLUTION: A nut 8 for a ball screw as a screw mechanism is internally fitted to a rotor 6 of an electric motor, and a thrust member 11 is mounted on the front end side of a screw shaft 9 as a linear motion member for thrusting a brake pad 3 against a disc rotor 2. A retaining ring 17 as a linear motion one-way clutch is mounted on a stepped portion 16a of a bolt 16 threaded to the rear end of the screw shaft 9 has contact with the inner diameter face of the rotor 6 in tensile inclination to the the opposite side to the forward direction of the screw shaft 9 to allow the linear motion of the screw shaft 9 in the forward direction but prevent it in the backward direction. Thus, the wear compensation mechanism for the brake member is inexpensively incorporated without impairing a design for compact and light construction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric brake device that converts a rotational driving force of an electric motor into a linear driving force and presses a brake member against a member to be braked.

  Although many hydraulic brake devices have been adopted as a vehicle brake device, in recent years, with the introduction of advanced brake control such as ABS (Antilock Brake System), these controls can be performed without complicated hydraulic circuits. Electric brake devices that can be designed compactly are drawing attention. The electric brake device operates the electric motor in response to a brake pedal depression signal, etc., and transmits the linear driving force to the linear motion member by a driving force conversion mechanism that converts the rotational driving force of the electric motor into a linear driving force. The brake member is pressed against the member to be braked by the linear motion of the member.

  Usually, since an electric brake device is attached under the spring of a vehicle, it is desired that a compact and lightweight design is possible. In order to make such a design possible, a screw mechanism in which a linear member is screwed to a rotating body that is rotationally driven by an electric motor is often used as a driving force conversion mechanism of an electric brake device. In many cases, ball screws with low frictional resistance and low conversion loss of driving force are used (see, for example, Patent Documents 1 and 2). Some employ a cam mechanism in which a plurality of rolling elements that engage with the cam surface are arranged between the cam surfaces of two cam members that are opposed in the axial direction.

  In these electric brake devices, as the brake member wears, the pressing position of the brake member by the linear motion member changes so as to move forward. For this reason, in order to ensure the responsiveness of the brake effect, it is necessary to gradually change the standby position of the linear motion member forward in accordance with the change of the pressing position accompanying the wear of the brake member.

  In the one described in Patent Document 1, the screw shaft of a ball screw as a linear motion member that has been rotated forward by the electric motor during braking and advanced toward the brake member pressing side is reversely rotated by rotating the electric motor reversely when releasing the brake. After retracting from the member, the electric motor is rotated forward again to return the screw shaft to the standby position, but the standby position is not changed to compensate for the wear of the brake member.

  In addition, in Patent Document 2, an adjustment screw is provided between the driving force conversion mechanism and the piston as the linear motion member, and the predetermined range of the rotor is exceeded between the adjustment screw and the rotor of the electric motor. A limiter that transmits only rotational displacement and a one-way clutch are provided, and when the rotational displacement during braking of the rotor exceeds a predetermined range, the reverse rotational displacement when the rotor is released is transmitted to the adjustment screw via the one-way clutch. Thus, the piston is advanced toward the disk rotor that is the member to be braked to compensate for wear of the brake pad that is the brake member.

JP 2002-213505 A (page 2-4, FIG. 1-2) JP 2000-283195 A (page 2-5, Fig. 1-4)

  In order to compensate for the wear of the brake member with the electric brake device described in Patent Document 1, the amount of wear of the brake member is detected, and after the brake is released, the electric motor is rotated forward again to return the screw shaft to the standby position. In addition, the standby position may be changed according to the detected amount of wear of the brake member, but a separate sensor and an extra control algorithm are required, and the apparatus becomes complicated.

  On the other hand, what is described in Patent Document 2 can compensate for brake pad wear without requiring a separate sensor or control algorithm, but the pad wear compensation mechanism is complex and has a large number of parts. There is a problem that a compact and lightweight design imposed on the electric brake device is difficult and the manufacturing cost is high.

  In addition, both of those described in Patent Documents 1 and 2 have a problem that the timing of releasing the brake is delayed and the driver feels uncomfortable because it is necessary to reversely rotate the electric motor when releasing the brake.

  Accordingly, an object of the present invention is to incorporate a brake member wear compensation mechanism at a low cost without impairing the compact and light weight design imposed on the electric brake device.

  In order to solve the above-described problems, the present invention includes a driving force conversion mechanism that converts a rotational driving force of an electric motor into a linear driving force, and a linear motion member to which the linear driving force is transmitted by the driving force conversion mechanism. In the electric brake device that presses the brake member against the member to be braked by linear motion, the linear motion of the linear motion member is allowed in the forward direction of pressing the brake member, but is prevented from moving in the reverse direction. A configuration with a directional clutch was adopted.

  In other words, by providing a linear motion one-way clutch that allows linear motion of the linear motion member in the forward direction that presses the brake member but prevents it in the backward direction, the brake member wears out with the addition of a small number of parts. However, the linear motion member after braking can always be held near the pressing position of the brake member, and the wear compensation mechanism of the brake member can be incorporated at low cost without impairing the compact and lightweight design.

  The driving force conversion mechanism is a screw mechanism provided on the inner diameter side of a cylindrical rotating member that is rotated by the rotational driving force of the electric motor, and the linear motion member to which a linear driving force is transmitted by the screw mechanism is the cylinder. A linear motion in the axial direction on the inner diameter side of the cylindrical rotating member, the linear motion one-way clutch is rotatably mounted on the linear motion member side, and engages with the inner diameter surface of the cylindrical rotating member; Thus, a screw mechanism suitable for a compact design can be adopted as the driving force conversion mechanism, and a wear compensation mechanism for the brake member can be incorporated.

  By mounting the linear motion one-way clutch with a backlash gap in the axial direction of the linear motion member, the linear motion member after braking is released from the brake member by the backlash gap in the axial direction, and when not braked The brake member can be prevented from dragging.

  The linear one-way clutch is annularly cut at one place on the circumference, the inner diameter edge is not in contact with the linear motion member side, the outer diameter edge is the inner diameter surface of the cylindrical rotating member, and the linear motion By using a retaining ring member that contacts at an inclined angle so as to stretch in the direction opposite to the forward direction of the member, the linear motion one-way clutch can be made simple and lightweight.

  By forming the retaining ring member from spring steel, the effectiveness of the linear motion one-way clutch can be provided with buffering properties.

  By making the inner surface of the cylindrical rotating member engaged with the linear motion one-way clutch rough, the effectiveness of the linear motion one-way clutch can be ensured satisfactorily.

  The surface roughness Ra of the inner surface of the cylindrical rotating member having the rough surface is preferably 6.3 to 50 μm. This is because if the surface roughness Ra is less than 6.3 μm, the effect of the linear motion one-way clutch cannot be sufficiently secured, and if it exceeds 50 μm, the frictional resistance when the linear motion member moves forward increases.

  By using a ball screw as the screw mechanism, the conversion loss of the driving force in the driving force conversion mechanism can be reduced.

  The electric brake device of the present invention is provided with a linear motion one-way clutch that allows linear motion of the linear motion member in the forward direction that presses the brake member, but prevents it in the backward direction. Therefore, even if the brake member is worn, the linear motion member after braking can always be held near the pressing position of the brake member, and the wear compensation mechanism of the brake member is incorporated at a low cost without impairing the compact and lightweight design. Can do.

  The driving force conversion mechanism is a screw mechanism provided on the inner diameter side of a cylindrical rotating member that is rotated by the rotational driving force of the electric motor, and the linearly acting member to which the linear driving force is transmitted by the screw mechanism is a cylindrical rotating member. The linear movement one-way clutch is rotatably attached to the linear motion member side and is engaged with the internal diameter surface of the cylindrical rotary member. A brake mechanism wear compensation mechanism can be incorporated by adopting a screw mechanism suitable for the design as the driving force conversion mechanism.

  By attaching the linear motion one-way clutch with a backlash gap in the axial direction of the linear motion member, the linear motion member after braking is released from the brake member by the backlash gap in the axial direction, and when the brake is not braked. The drag of the brake member can be prevented.

  The linear motion one-way clutch is annularly cut at one place on the circumference, the inner diameter edge is not in contact with the linear motion member side, the outer diameter edge is the inner diameter surface of the cylindrical rotating member, and the linear motion member is advanced. By using a retaining ring member that contacts at an inclined angle so as to stretch in the direction opposite to the direction, the linear motion one-way clutch can be made simple and lightweight.

  By forming the retaining ring member from spring steel, the effectiveness of the linear motion one-way clutch can be provided with buffering properties.

  By making the inner surface of the cylindrical rotating member engaged with the linear motion one-way clutch rough, the effectiveness of the linear motion one-way clutch can be ensured satisfactorily.

  By using a ball screw as the screw mechanism, the conversion loss of the driving force in the driving force conversion mechanism can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, this electric brake device is a disc brake in which brake pads 3 as brake members are arranged oppositely on both sides of a disc rotor 2 as a braked member inside the caliper 1. A stator 5 of an electric motor is fixed to an inner diameter surface of the integrally formed casing 4 and a rotor 6 as a cylindrical rotating member is rotatably supported by bearings 7a and 7b. A ball screw nut 8 as a screw mechanism, which is a driving force conversion mechanism, is fitted into the axially front end side of the rotor 6, and a screw shaft 9 as a linear motion member is screwed into the nut 8 via the ball 10. A separate pressing member 11 that presses the brake pad 3 against the disc rotor 2 is attached to the front end side of the screw shaft 9, and the screw shaft 9 and the pressing member 11 coupled by the bolt 12 are connected to the rotation key 13. It is locked. The front end side of the casing 4 is sealed with a boot 14 attached between the caliper 1 and the pressing member 11, and the rear end side is closed with a lid 15.

  As shown in FIG. 2A, a bolt 16 is screwed onto the rear end of the screw shaft 9 of the ball screw, and a stepped portion 16a provided on the bolt 16 is stopped as a linear motion one-way clutch. A ring member 17 is attached. The retaining ring member 17 is made of spring steel, and as shown in FIG. 3, is a ring and is provided with a cutting portion 17a at one place on the circumference. In addition, holes 17b are provided on both sides of the cutting portion 17a to reduce the diameter and remove it from the inner diameter surface of the rotor 6 when replacing the brake pad 3 described later.

  As shown in FIGS. 2 (a) and 2 (b), the retaining ring member 17 has an inner diameter edge that is not in contact with the stepped portion 16a of the bolt 16 and can rotate around the stepped portion 16a, and bends to the outer periphery. A portion 17c is provided so that the outer diameter edge comes into contact with the inner diameter surface of the rotor 6 at an angle inclined so as to protrude toward the opposite side of the forward direction of the screw shaft 9. Allow movement in the forward direction but prevent it in the backward direction. The inner surface of the rotor 6 that contacts the outer diameter edge of the retaining ring member 17 has a surface roughness Ra of 6.3 to 50 μm in order to ensure adequate frictional resistance with the outer diameter edge of the retaining ring member 17. The rough surface.

  At the time of braking in which the screw shaft 9 moves forward, as shown in FIG. 2A, the retaining ring member 17 abuts against the head of the bolt 16 together with the screw shaft 9 while rotating following the rotor 6. Move in the forward direction. At the time of brake release when the rotation of the electric motor stops, as shown in FIG. 2 (b), when the screw shaft 9 moves backward by the amount of play of the ball screw, the retaining ring member 17 moves along the stepped portion 16a. 9 moves relative to the rear end side and is locked to the rear end surface of the screw shaft 9 to prevent further retreat of the screw shaft 9. For this reason, since the screw shaft 9 after braking is allowed to be slightly retracted by a gap in the axial direction of the attachment of the retaining ring member 17 corresponding to the length of the stepped portion 16a, the brake at the time of non-braking is performed. There is no dragging of the pad 3.

  As described above, this electric brake device rotates the electric motor in one direction at the time of braking, and only stops the electric motor at the time of releasing the brake, so that the retaining ring member 17 is engaged with the inner diameter surface of the rotor 6. The position naturally moves forward as the brake pad 3 wears during braking gradually moves, and the standby position of the screw shaft 9 after braking moves naturally. FIG. 4 shows a state in which the brake pad 3 is worn, and the screw shaft 9 and the retaining ring member 17 have moved considerably forward due to the accumulation of forward movement little by little.

  Next, a method for replacing the worn brake pad 3 will be described. As shown in FIG. 4, with the screw shaft 9 and the retaining ring member 17 moved considerably forward, as shown in FIG. 5, after removing the lid 15 from the casing 4, the retaining ring member 17 is shrunk with a tool. Remove the diameter from the inner diameter surface of the rotor 6. After that, the electric motor is reversely rotated to retract the screw shaft 9 to the initial position, and the brake pad 3 is replaced with a new one.

  In the embodiment described above, the outer peripheral portion of the retaining ring member as the linear motion one-way clutch is brought into contact with the inner diameter surface of the rotor at an inclined angle so as to stretch toward the opposite side of the forward direction of the screw shaft. However, the outer peripheral portion may be bent and contacted at an inclined angle. Further, the linear motion one-way clutch is not limited to the retaining ring member of the embodiment, and the driving force conversion mechanism is not limited to one using a ball screw.

A longitudinal sectional view showing an embodiment of an electric brake device a and b are cross-sectional views showing enlarged main parts of FIG. The top view which shows the retaining ring member of FIG. 1 is a longitudinal sectional view showing a state where the brake pad of FIG. 1 is worn FIG. 4 is a longitudinal sectional view for explaining a method of replacing the worn brake pad in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Caliper 2 Disc rotor 3 Brake pad 4 Casing 5 Stator 6 Rotor 7a, 7b Bearing 8 Nut 9 Screw shaft 10 Ball 11 Pressing member 12 Bolt 13 Non-rotating key 14 Boot 15 Lid 16 Bolt 16a Stepped portion 17 Retaining ring member 17a Cutting Part 17b hole 17c bent part

Claims (8)

  A driving force conversion mechanism that converts the rotational driving force of the electric motor into a linear driving force is provided, and the brake member is pressed against the member to be braked by the linear motion of the linear motion member to which the linear driving force is transmitted by the driving force conversion mechanism. An electric brake device comprising: a linear one-way clutch that allows a linear motion of the linear motion member in a forward direction to press the brake member, but prevents the linear motion of the linear motion member in a reverse direction. apparatus.   The driving force conversion mechanism is a screw mechanism provided on the inner diameter side of a cylindrical rotating member that is rotated by the rotational driving force of the electric motor, and the linear motion member to which a linear driving force is transmitted by the screw mechanism is the cylinder. A linear motion in the axial direction on the inner diameter side of the cylindrical rotating member, the linear motion one-way clutch is rotatably mounted on the linear motion member side, and engages with the inner diameter surface of the cylindrical rotating member; The electric brake device according to claim 1.   The electric brake device according to claim 2, wherein the linear motion one-way clutch is attached with a backlash gap in the axial direction of the linear motion member.   The linear one-way clutch is annularly cut at one place on the circumference, the inner diameter edge is not in contact with the linear motion member side, the outer diameter edge is the inner diameter surface of the cylindrical rotating member, and the linear motion The electric brake device according to claim 2 or 3, wherein the retaining ring member is brought into contact with an inclined angle so as to stretch in a direction opposite to the advancing direction of the member.   The electric brake device according to claim 4, wherein the retaining ring member is made of spring steel.   The electric brake device according to any one of claims 2 to 5, wherein an inner diameter surface of the cylindrical rotating member with which the linear motion one-way clutch is engaged is a rough surface.   The electric brake device according to claim 6, wherein a surface roughness Ra of an inner diameter surface of the cylindrical rotating member having the rough surface is set to 6.3 to 50 μm.   The electric brake device according to any one of claims 2 to 7, wherein the screw mechanism is a ball screw.

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