JP2007002915A - Motor driven parking brake driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor driven parking brake driving device which is compact and can inexpensively be designed while surely retaining the effectiveness of the parking brake and capable of sufficiently extending the life span of a ball screw mechanism. <P>SOLUTION: A rotary drive force of an electric-powered motor 1 is transmitted to a nut 3 of a ball screw mechanism 2 for converting to a linear drive force of a screw axis 4 and so that a return linear movement of a brake power transfer member 10 which transmits the brake power is locked on a connecting part with the brake power transfer member 10 connected to the screw axis 4, a direct acting one way clutch which engages a ball 14 to a sloping cam surface 16 is provided, by which the return linear movement of the brake power transfer member 10 of an amount of play of the ball screw mechanism 2 is prevented and at the same time, caution is paid so that a load of the brake operating part is not reversely transmitted to the ball screw mechanism 2 and the effectiveness of the parking brake is surely maintained and the life span of the ball screw mechanism 2 is so designed as to be lengthened. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric parking brake driving device that operates a parking brake with an electric motor.

  In general, parking brake devices for automobiles operate levers and pedals with hands and feet, and transmit braking force to the brake operating part with wires and rods connected to them. An electric parking brake drive device that operates a parking brake with an electric motor has been proposed from the viewpoint of effective use of the interior space. This electric parking brake driving device is expected to be highly functional by providing a reverse prevention function on an uphill road. An electric parking brake drive device mounted on a vehicle is required to be smaller, lighter, and lower in power by using a smaller motor, and further to be reduced in cost.

  In order to satisfy such a requirement, the electric parking brake driving device converts the rotational driving force of the electric motor into the linear driving force of the brake force transmitting member connected to the wire or the rod. Many proposals using a few ball screw mechanisms have been made. However, unlike a general slide screw, a ball screw with low frictional resistance cannot hold the relative position of the screw shaft and nut, so the brake force transmission member that transmits the brake force with a wire or rod is operated as a parking brake. It cannot be held in the state position.

  Since it is not realistic to continue to drive the electric motor while the parking brake is operating for a long time, the electric parking brake drive device using the ball screw mechanism is provided with a clutch mechanism in the brake force transmission path, Some brake force transmission members that have transmitted force are prevented from moving back in a straight line. Preventing the return linear movement of the brake force transmission member is connected to preventing the load of the brake operating unit from being transmitted back to the electric motor (see, for example, Patent Document 1).

  The electric parking brake driving device described in Patent Document 1 is intended to prevent the load of the brake operating unit from being transmitted back to the electric motor, and the rotational driving force of the electric motor is applied to the screw shaft of the ball screw mechanism. Is converted into a linear driving force of the nut, a brake force transmitting member is connected to the nut, a rotating one-way clutch is provided at the connecting portion of the electric motor and the screw shaft, and the load of the brake operating portion is used. The reverse rotation of the screw shaft is prevented from being transmitted back to the electric motor.

Japanese Patent Laid-Open No. 2003-232390 (FIG. 5)

  In the electric parking brake drive device described in Patent Document 1, a rotating one-way clutch is provided at the connecting portion between the electric motor and the screw shaft, and the reverse rotation of the screw shaft due to the load of the brake operating portion is transmitted back to the electric motor. Therefore, the return linear movement of the brake force transmitting member is indirectly prevented by the rotating one-way clutch through the ball screw mechanism. For this reason, there is a problem that the linear force of the ball screw mechanism returns to the brake force transmission member and linear movement occurs, and the effectiveness of the parking brake is reduced.

  In addition, since the load of the brake operating part is interrupted by the connecting part of the electric motor and the screw shaft, the load of the brake operating part is transmitted back to the ball screw mechanism, and a thrust load of about 3000 N is transmitted by this reverse transmission. There is also a problem that the life of the ball screw mechanism is shortened due to the load. If the screw diameter is increased in order to extend the life of the ball screw mechanism, the overall size and weight of the apparatus are hindered. Further, since a rotating one-way clutch is used for the clutch mechanism, a bearing for holding the rotation and a space for the arrangement are required, and there is a problem that compactness and cost reduction are hindered.

  Accordingly, an object of the present invention is to provide an electric parking brake drive device that can reliably maintain the effectiveness of the parking brake and that can sufficiently extend the life of the ball screw mechanism and that can be designed in a compact and inexpensive manner. is there.

  In order to solve the above-mentioned problems, the present invention converts the rotational driving force of an electric motor into a linear driving force by a ball screw mechanism, and brake operation as a braking force by a brake force transmission member that linearly moves the linear driving force. In the electric parking brake driving device for transmitting to the part, the rotational driving force of the electric motor is transmitted to the nut of the ball screw mechanism and converted into a linear driving force of the screw shaft, and the brake force transmitting member is transmitted to the screw shaft. And a direct-acting one-way clutch that locks the return linear movement of the brake force transmission member that has transmitted the brake force to the brake operating portion. did.

  That is, the rotational driving force of the electric motor is transmitted to the nut of the ball screw mechanism and converted into the linear driving force of the screw shaft, and the brake force transmission member is connected to the screw shaft, and the screw shaft and the brake force transmission By providing a linear motion one-way clutch that locks the return linear movement of the brake force transmitting member that transmitted the braking force to the brake operating portion at the connecting portion of the member, the return of the brake force transmitting member corresponding to the backlash of the ball screw mechanism In addition to preventing linear movement, the load of the brake operating part is not transmitted back to the ball screw mechanism, so that the effectiveness of the parking brake can be reliably maintained and the life of the ball screw mechanism can be extended sufficiently.

  The linear motion one-way clutch, between the outer diameter surface of the brake force transmission member connected to the screw shaft and the inner diameter surface of the fixed outer ring provided on the outer peripheral side of the outer diameter surface of the brake force transmission member, A plurality of engaging elements that can roll in the axial direction of the fixed outer ring are arranged in the circumferential direction, and the axial direction in which each engaging element engages with the outer diameter surface of the brake force transmitting member or the inner diameter surface of the fixed outer ring. By providing an inclined cam surface to each other and urging each of the engaging elements with an elastic member in an axial direction engaging with the cam surfaces, a compact and inexpensive design can be realized.

  By engaging at least one of the outer diameter surface of the brake force transmitting member and the inner diameter surface of the fixed outer ring with the respective engagement elements arranged between them in a cross-sectional shape in which the respective engagement elements are in line contact with each other, The mating pressure can be reduced to extend the clutch life, and the effectiveness of the clutch can be further ensured.

  The engaging member that can roll in the axial direction of the screw shaft can be a roller or a barrel roller.

  The electric parking brake driving device of the present invention transmits the rotational driving force of the electric motor to the nut of the ball screw mechanism, converts it into a linear driving force of the screw shaft, and connects the brake force transmitting member to the screw shaft. By providing a linear motion one-way clutch for locking the return linear movement of the brake force transmission member that has transmitted the brake force to the brake operating portion at the connecting portion between the screw shaft and the brake force transmission member, the backlash of the ball screw mechanism is increased. The brake force transmission member is prevented from moving back in a straight line and the load on the brake operating part is not transmitted back to the ball screw mechanism, so that the effectiveness of the parking brake can be reliably maintained and the life of the ball screw mechanism can be maintained. Can also be extended sufficiently.

  The linear motion one-way clutch, between the outer diameter surface of the brake force transmission member connected to the screw shaft and the inner diameter surface of the fixed outer ring provided on the outer peripheral side of the outer diameter surface of the brake force transmission member, A plurality of engaging elements that can roll in the axial direction of the fixed outer ring are arranged in the circumferential direction, and the axial direction in which each engaging element engages with the outer diameter surface of the brake force transmitting member or the inner diameter surface of the fixed outer ring. By providing an inclined cam surface to each other and urging each of the engaging elements with an elastic member in an axial direction engaging with the cam surfaces, a compact and inexpensive design can be realized.

  By engaging at least one of the outer diameter surface of the brake force transmitting member and the inner diameter surface of the fixed outer ring, in which the respective engagement elements are arranged in between, with a cross-sectional shape in which each engagement element makes a line contact, the engagement of the engagement elements It is possible to extend the clutch life by reducing the surface pressure, and to further ensure the effectiveness of the clutch.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 3 show a first embodiment. As shown in FIG. 1, this electric parking brake driving device transmits the rotational driving force of the electric motor 1 to the nut 3 of the ball screw mechanism 2 and converts it into the linear driving force of the screw shaft 4. The brake force transmission member 10 connected to the straight line is moved linearly, and the brake force is transmitted to the brake operating portion by a wire (not shown) connected to the brake force transmission member 10. Thus, the return linear movement of the brake force transmitting member 10 that has transmitted the brake force is locked.

  The nut 3 of the ball screw mechanism 2 is rotatably supported by the bearings 8 on the housings 6 and 7, and rotates by meshing between a gear 9 a attached to the output shaft 1 a of the electric motor 1 and a gear 9 b attached to the nut 3. The driving force is transmitted, and the rotational driving force of the nut 3 is converted into a linear driving force of the screw shaft 4 that is prevented from rotating and screwed through the ball 5. In this embodiment, when the screw shaft 4 is linearly driven to the cylindrical portion 7a side of the housing 7 in the cylindrical portions 6a and 7a of the respective housings 6 and 7, the brake force transmitting member 10 linearly moves to the left. The brake force is transmitted to the brake operating portion by pulling the wire connected to the brake force transmitting member 10.

  The distal end portion of the brake force transmitting member 10 is inserted into a hole 4 a provided on the right end side of the screw shaft 4, and a connecting pin 11 attached in the hole 4 a is provided at the distal end portion of the brake force transmitting member 10. The brake force transmitting member 10 is connected to the screw shaft 4 by being inserted into the through hole 12 formed. The through-hole 12 is formed to have a larger diameter than the connecting pin 11, and the brake force transmitting member 10 and the screw shaft 4 are allowed to move relative to each other.

  As shown in FIGS. 2A and 2B, a fixed outer ring 13 is fitted to the right end side of the cylindrical portion 6 a of the housing 6, and an inner diameter surface of the fixed outer ring 13 and a brake inserted into the fixed outer ring 13. A plurality of engaging balls 14 that can roll in the axial direction of the fixed outer ring 13 between the outer diameter surface of the force transmission member 10 and the circumferential direction so as to open in the hole 4 a portion of the screw shaft 4. Are arranged one by one in each pocket 15 provided at equal intervals. On the outer diameter surface of the brake force transmitting member 10, an inclined cam surface 16 is provided in the axial direction in which each of these balls 14 is engaged, and the balls 14 arranged in each pocket 15 are engaged with the inclined cam surface 16. It is urged by a coil spring 17 in the axial direction, and a linear motion one-way clutch is formed by engagement of these balls 14 and the inclined cam surface 16. Further, the inclined cam surface 16 of the outer diameter surface of the brake force transmission member 10 and the inner diameter surface of the fixed outer ring 13 in which the balls 14 are arranged in between, respectively, so that the balls 14 are in line contact with these surfaces, respectively. Grooves 10a and 13a having an arcuate cross section extending in the axial direction are formed.

  Hereinafter, the operation of the linear motion one-way clutch will be described. When the electric motor 1 is driven in the state shown in FIG. 2A, the screw shaft 4 is linearly driven to the left as shown in FIG. 3A, and the front left side of the connecting pin 11 transmits the braking force. The brake force transmitting member 10 linearly moves to the left together with the screw shaft 4 by hitting the left front surface of the through hole 12 of the member 10, and pulls the wire connected to the brake force transmitting member 10 to the left to increase the braking force. Transmit to the brake actuator. At this time, each ball 14 urged to the left by the coil spring 17 does not engage with the inclined cam surface 16 because the brake force transmitting member 10 moves linearly to the left and the inclined cam surface 16 escapes.

  Next, when the electric motor 1 is stopped in the parking brake operating state where the braking force is transmitted to the brake operating unit, the wire is pulled rightward by the reaction force of the braking force. As described above, since the ball screw mechanism 2 cannot hold the relative position between the screw shaft 4 and the nut 3, the screw shaft 4 is pulled by the wire and returned to the right to try to move linearly. However, at this time, as shown in FIG. 3 (b), each ball 14 is engaged with the inclined cam surface 16 of the brake force transmitting member 10 which returns to the right and tries to move linearly. The return linear movement of the transmission member 10 is locked.

  4 (a) and 4 (b) show a second embodiment. This electric parking brake drive device has the same basic configuration as that of the first embodiment, except that the linear motion one-way clutch has a roller 18 as an engaging element. Each roller 18 is laterally arranged in each pocket 15 of the screw shaft 4 so that it can roll in the axial direction of the fixed outer ring 13. In addition, the inclined cam surface 16 of the outer diameter surface of the brake force transmission member 10 in which the rollers 18 are arranged therebetween and the inner diameter surface of the fixed outer ring 13 are respectively large so that the rollers 18 are in line contact with these surfaces. It is formed in a square cross section.

  FIGS. 5A and 5B show a third embodiment. This electric parking brake driving device is also basically the same in configuration as that of the first embodiment, except that the linear roller one-way clutch has a die roller 19 as an engaging element. These barrel rollers 19 are also arranged laterally in the pockets 15 of the screw shaft 4 so as to roll in the axial direction of the fixed outer ring 13. Further, the inclined cam surface 16 of the outer diameter surface of the brake force transmission member 10 in which the respective barrel rollers 19 are arranged therebetween extend in the axial direction so that the respective barrel rollers 19 are in line contact with these surfaces. A groove 10b having a barrel-like cross section is formed. The inner diameter surface of the fixed outer ring 13 is in line contact with each barrel roller 19 as it is.

  In each of the above-described embodiments, the inclined cam surface of the linear motion one-way clutch is provided on the outer diameter surface of the brake force transmission member. However, this inclined cam surface can also be provided on the inner diameter surface of the fixed outer ring. Further, the engaging elements of the linear motion one-way clutch are not limited to the balls, rollers, and barrel rollers of each embodiment, and may be anything that can roll in one direction.

  Moreover, in each embodiment mentioned above, although it was set as the type which pulls a wire with a brake force transmission member, the electric parking brake drive device which concerns on this invention is applied also to the type which presses a rod with a brake force transmission member. be able to.

The longitudinal cross-sectional view which shows the electric parking brake drive device of 1st Embodiment a is an enlarged longitudinal sectional view showing a portion of the linear motion one-way clutch of FIG. 1, and b is a sectional view taken along line IIb-IIb of a. a and b are longitudinal sectional views for explaining the operation of the linear motion one-way clutch shown in FIG. a is a longitudinal sectional view showing an enlarged part of the linear motion one-way clutch of the electric parking brake driving device of the second embodiment, and b is a sectional view taken along line IVb-IVb of a. a is a longitudinal sectional view showing an enlarged part of the linear motion one-way clutch of the electric parking brake driving device of the third embodiment, and b is a sectional view taken along the line Vb-Vb of a.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 1a Output shaft 2 Ball screw mechanism 3 Nut 4 Screw shaft 4a Hole 5 Balls 6, 7 Housing 6a, 7a Cylindrical part 8 Bearing 9a, 9b Gear 10 Brake force transmission member 10a, 10b Groove 11 Connecting pin 12 Through-hole 13 Fixed outer ring 13a Groove 14 Ball 15 Pocket 16 Inclined cam surface 17 Coil spring 18 Roller 19 Coil roller

Claims (4)

  In the electric parking brake driving device, the rotational driving force of the electric motor is converted into a linear driving force by a ball screw mechanism, and the linear driving force is transmitted as a braking force to a brake operating unit by a brake force transmitting member that linearly moves. The rotational driving force of the motor is transmitted to the nut of the ball screw mechanism and converted into a linear driving force of the screw shaft, and the brake force transmission member is connected to the screw shaft, and the screw shaft and the brake force transmission member An electric parking brake drive device characterized in that a linear motion one-way clutch for locking a return linear movement of a brake force transmitting member that transmits a brake force to the brake operating portion is provided at the connecting portion.   The linear motion one-way clutch is between an outer diameter surface of a brake force transmission member connected to the screw shaft and an inner diameter surface of a fixed outer ring provided on the outer peripheral side of the outer diameter surface of the brake force transmission member. A plurality of engaging elements that can roll in the axial direction of the fixed outer ring are arranged in the circumferential direction, and the axial direction in which each engaging element engages with the outer diameter surface of the brake force transmitting member or the inner diameter surface of the fixed outer ring. The electric parking brake drive device according to claim 1, wherein an inclined cam surface is provided, and the engaging members are urged by an elastic member in an axial direction engaging with the cam surfaces.   The electric parking according to claim 2, wherein at least one of an outer diameter surface of the brake force transmitting member and an inner diameter surface of the fixed outer ring, in which the respective engagement elements are arranged, is formed in a cross-sectional shape in which the engagement elements are in line contact. Brake drive device.   The electric parking brake driving device according to claim 2 or 3, wherein an engaging roller capable of rolling in the axial direction of the fixed outer ring is a roller or a barrel roller.

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