JP2007002934A - Clutch mechanism and electric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily reduce the releasing torque of each engagement element at a same timing without damaging a plurality of engagement elements of a clutch mechanism. <P>SOLUTION: This clutch mechanism comprises a piezoelectric element 7 imparting high-frequency vibration for imparting vibration to the outer ring 2 of the clutch mechanism 1. When a lock to prevent the relative rotation of an inner ring to an outer ring is released, a frictional force caused by the engagement of rollers 5 being the engagement elements with cam faces 2a and 3a is reduced to easily reduce the releasing torque at the same timing without damaging the rollers 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a clutch mechanism and an electric actuator including the clutch mechanism.

  In automobiles, various types of operation devices such as brake devices and power windows are moving toward BY-WIRE, which allows various operation controls, and electric actuators that use electric motors as drive sources are applied. Is going on. Many of the electric actuators convert the rotational driving force of the electric motor into a linear driving force and output it, and many of these driving force conversion mechanisms employ a ball screw mechanism with little conversion loss.

  In this way, an electric actuator that uses a ball screw mechanism for the drive force conversion mechanism is different from a general slide screw in that the ball screw has a very small frictional resistance between the screw shaft and the nut and blocks reverse input to the electric motor. In many cases, a clutch mechanism for preventing reverse input is provided in the rotational drive force transmission portion (see, for example, Patent Documents 1 and 2).

  In the one described in Patent Literature 1, a clutch mechanism that transmits a rotational driving force of an electric motor to a nut of a ball screw mechanism and converts it into a linear driving force of a screw shaft to prevent reverse input to the electric motor. The rotation driving force is transmitted from the electric motor to the nut. Moreover, in what is described in Patent Document 2, the rotational driving force of the electric motor is transmitted to the screw shaft of the ball screw mechanism and converted into the linear driving force of the nut, and the clutch mechanism is transmitted to the screw shaft. Provided in the department.

  In the clutch mechanism provided in the rotational driving force transmission unit as described above, a plurality of engaging members such as rollers and sprags held by a cage are interposed between the inner ring and the outer ring, and these engaging elements are connected to the inner ring and the outer ring. In many cases, the inner ring and the outer ring are engaged with each other by a frictional force to lock the relative rotation of the inner ring and the outer ring. In this type of clutch mechanism, once an engagement element is engaged with a cam surface, it is generally necessary to release a torque about 1.5 to 2 times the torque at the time of engagement to release the engagement. It is. For this reason, conventionally, an electric motor capable of applying a sufficiently large release torque is employed, and there is a problem that it is difficult to reduce the size and cost of the electric actuator.

JP 2004-144124 A (FIGS. 1-4) Japanese Patent Laid-Open No. 2003-232390 (FIG. 5)

  In the clutch mechanism of the electric actuator described in Patent Document 1, in order to reduce the release torque, the outer peripheral surface of the roller is attached to the pocket end surface of the cage that is in contact with the engagement release side of the roller that is the engagement element. A protrusion that presses radially outward from the center position is formed, and a moment load is applied to the roller that is pressed to the disengagement side.

  In this clutch mechanism, in order to reduce the release torque of the roller that is the engaging element, a sharp protruding part that presses the outer peripheral surface of the roller is formed on the pocket end surface of the cage, so that the engaging element and the protruding part are damaged. There is a problem that is easy to do. In addition, since a plurality of engagement elements are individually pressed by the protrusions, if there is a variation in dimensions between the protrusions, the timing of pressing the engagement elements is shifted, and the pressing force is concentrated on some of the engagement elements. Therefore, there is a problem that damage is more likely to occur. Furthermore, there is also a problem that it takes time to mold each protrusion with high accuracy.

  Accordingly, an object of the present invention is to easily reduce the release torque of each engagement element at the same timing without damaging a plurality of engagement elements of the clutch mechanism.

  In order to solve the above-described problem, the clutch mechanism of the present invention has a plurality of engagement elements held by a cage between an inner ring and an outer ring, and these engagement elements are provided on a cam surface provided on the inner ring and the outer ring. In the clutch mechanism that engages with frictional force and locks the relative rotation of the inner ring and the outer ring, a vibration applying means that applies vibration to at least one of the inner ring, the outer ring, and the cage is provided, and the relative relationship between the inner ring and the outer ring is provided. A configuration is adopted that reduces the frictional force with which the engaging element engages with the cam surface when unlocking rotation.

  That is, a vibration applying means for applying vibration to at least one of the inner ring, the outer ring and the cage is provided to reduce the frictional force with which the engagement element engages with the cam surface when unlocking the relative rotation of the inner ring and the outer ring. By doing so, the release torque of each engagement element can be easily reduced at the same timing without damaging the plurality of engagement elements.

  By applying high-frequency vibration to the vibration applying means using a piezoelectric element, vibration can be applied with excellent responsiveness.

  Further, the electric actuator of the present invention converts the rotational driving force of the electric motor into a linear driving force by a ball screw mechanism and outputs it, and a clutch mechanism for preventing reverse input to the electric motor is provided in the rotational driving force transmitting portion. By adopting one of the clutch mechanisms described above as the clutch mechanism, the release torque of each engagement element can be easily set at the same timing without damaging the plurality of engagement elements of the clutch mechanism. I was able to reduce.

  The clutch mechanism of the present invention is provided with vibration applying means for applying vibration to at least one of the inner ring, the outer ring, and the cage, and the engagement element engages with the cam surface when unlocking the relative rotation of the inner ring and the outer ring. Since the frictional force is reduced, the release torque of each engagement element can be easily reduced at the same timing without damaging the plurality of engagement elements.

  By applying high-frequency vibration to the vibration applying means using a piezoelectric element, vibration can be applied with excellent responsiveness.

  In addition, the electric actuator of the present invention is provided with a clutch mechanism for converting the rotational driving force of the electric motor into a linear driving force by a ball screw mechanism and outputting it, and preventing reverse input to the electric motor in the rotational driving force transmission portion. In the electric actuator, any one of the clutch mechanisms described above is adopted as the clutch mechanism, so that the release torque of each engagement element can be easily reduced at the same timing without damaging the plurality of engagement elements of the clutch mechanism. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIGS. 1A and 1B show a torque diode employing the clutch mechanism 1 of the first embodiment. In this torque diode, the input shaft 11 and the output shaft 12 are coaxially supported by ball bearings 16 and 17, respectively, and two pins 13 provided on the end surface of the output shaft 12 are provided on the end surface of the input shaft 11. The long hole 14 is inserted with a gap, and the rotation of the input shaft 11 is transmitted to the output shaft 12 by the engagement of the pin 13 and the long hole 14, and the outer ring 2 provided in the housing 15, the output A clutch that locks the rotation of the output shaft 12 to the outer ring 2 by an inner ring 3 provided on the shaft 12 and a plurality of rollers 5 as an engaging member held by a cage 4 provided between the input shaft 11 and the inner ring 3. A mechanism 1 is formed.

  The inner surface of the outer ring 2 of the clutch mechanism 1 is a cylindrical surface, and the outer surface of the inner ring 3 is a hexagonal cylinder surface. It is stored in each pocket 4a of the cage 4 at a position corresponding to each cam surface 3a of the hexagonal cylinder surface. In addition, on the outer ring 2, piezoelectric elements 7 that impart high-frequency vibration to reduce the release torque of each roller 5 are attached at three positions with a phase of 120 °.

  The operation of the clutch mechanism 1 will be described below. When the input shaft 11 is not driven and is stopped, as shown in FIG. 2A, the two rollers 5 are pressed in a direction away from each other by the spring 6, and the outer ring 2 and the inner ring are respectively pressed. 3 is engaged with the cam surfaces 2a and 3a, and the output shaft 12 is locked in both forward and reverse directions.

  As shown in FIG. 2 (b), when the input shaft 11 rotates, for example, in the forward direction (clockwise), the retainer 4 formed integrally with the output shaft 12 causes the left roller 5 to move to the cam surfaces 2a, 3a. Press in the direction to leave. At this time, the piezoelectric element 7 is actuated to apply high-frequency vibration to the outer ring 2, and the engagement of the left roller 5 with the cam surfaces 2a and 3a is easily released at the same timing. The right roller 5 does not engage with the cam surfaces 2a and 3a when rotating in the forward direction.

  As shown in FIG. 2 (c), when the input shaft 11 further rotates in the forward direction, the pin 13 provided on the output shaft 12 engages with the elongated hole 14 provided on the input shaft 11, and the input shaft 11 Is transmitted to the output shaft 12. Although illustration is omitted, when the input shaft 11 rotates in the reverse direction, the reverse rotation is transmitted to the output shaft 12 by the same action. In this case, the right roller 5 is caused by high-frequency vibration applied by the piezoelectric element 7. Are easily released from the cam surfaces 2a and 3a at the same timing.

  FIG. 3 shows a modification in which high-frequency vibration is applied to the cam surface of the clutch mechanism of the first embodiment. In this modified example, the piezoelectric element 7 is attached to the end face of the output shaft 12 via a thrust needle roller bearing 18, and high-frequency vibration is applied to the inner ring 3 from the end face of the output shaft 12. The engagement with each cam surface 2a, 3a is released.

  4 and 5 show an electric actuator employing the clutch mechanism of the second embodiment. As shown in FIG. 4, the electric actuator includes an electric motor 32, a planetary gear reduction mechanism 33, and a ball screw mechanism 34 incorporated in a housing 31, and the rotation of the rotor 32 b of the electric motor 32 is caused by the planetary gear reduction mechanism 33. Is transmitted to the nut 34a of the ball screw mechanism 34, and the rotation of the nut 34a is converted into a linear motion of the screw shaft 34c via the ball 34b. A front lid 31a having an opening through which the tip of the screw shaft 34c protrudes and a rear lid 31b to which a detent pin 35 of the screw shaft 34c is attached are attached to the housing 31.

  The stator 32a of the electric motor 32 is fixed to the inner diameter surface of the cylindrical housing 31, and the sun gear 33a of the planetary gear reduction mechanism 33 is provided on the outer diameter surface of the forward extension of the rotor 32b. A planetary gear 33c is engaged with an internal gear 33b fixed to the surface. The planetary gear 33c is rotatably supported by the shaft pin 36 using the nut 34a of the ball screw mechanism 34 as a carrier.

  The nut 34a of the ball screw mechanism 34 is rotatably supported on the inner diameter surface of the housing 31 by a ball bearing 37, and reverse rotation is locked by the clutch mechanism 21, so that reverse input to the electric motor 32 is prevented. It has become.

  As shown in FIG. 5, the clutch mechanism 21 includes an outer ring 22 fixed to the inner surface of the housing 31, an inner ring 23 provided on the nut 34a, and an engagement member held by a cage 24 therebetween. In the same manner as in the first embodiment, a piezoelectric element 27 that applies high-frequency vibration to the outer ring 22 is attached in order to reduce the release torque of each roller 25. .

  The retainer 24 is fixed to the inner ring 23 side, and the rollers 25 housed in the pockets 24a of the retainer 24 are engaged with the cam surfaces 22a and 23a provided on the outer ring 22 and the inner ring 23. It is biased by a spring 26. Each roller 25 does not engage with each cam surface 22a, 23a when the inner ring 23 is transmitted clockwise rotation from the electric motor 32, and each cam surface when the inner ring 23 rotates counterclockwise by reverse input. 22a and 23a are engaged, and the inner ring 23, that is, the nut 34a is locked. Also in this embodiment, the engagement of the rollers 25 with the cam surfaces 22 a and 23 a is easily released at the same timing by the high-frequency vibration applied by the piezoelectric element 27.

  In each of the above-described embodiments, high frequency vibration for reducing the release torque is applied to the outer ring and the inner ring by the piezoelectric element. However, the high frequency vibration may be applied to the cage, and the vibration applying means is not limited to the piezoelectric element. Absent.

  Moreover, in each embodiment mentioned above, although the engaging element of the clutch mechanism was used as the roller, the clutch mechanism which concerns on this invention is applicable also to what uses a sprag as an engaging element.

a is a longitudinal sectional view showing a torque diode employing the clutch mechanism of the first embodiment, and b is a sectional view taken along line Ib-Ib of a. a, b, and c are sectional views for explaining the operation of the clutch mechanism of FIG. The longitudinal cross-sectional view which shows the modification which provides a high frequency vibration to the cam surface of the clutch mechanism of 1st Embodiment A longitudinal sectional view showing an electric actuator employing the clutch mechanism of the second embodiment Sectional view along line VV in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Clutch mechanism 2 Outer ring 3 Inner ring 2a, 3a Cam surface 4 Cage 4a Pocket 5 Roller 6 Spring 7 Piezoelectric element 11 Input shaft 12 Output shaft 13 Pin 14 Long hole 15 Housing 16, 17 Ball bearing 18 Thrust needle roller bearing 21 Clutch Mechanism 22 Outer ring 23 Inner ring 22a, 23a Cam surface 24 Cage 24a Pocket 25 Roller 26 Spring 27 Piezoelectric element 31 Housing 31a Front lid 31b Rear lid 32 Electric motor 32a Stator 32b Rotor 33 Planetary gear reduction mechanism 33a Sun gear 33b Internal gear 33c Planet Gear 34 Ball screw mechanism 34a Nut 34b Ball 34c Screw shaft 35 Non-rotating pin 36 Axial pin

Claims (3)

  A plurality of engagement elements held by a cage are interposed between the inner ring and the outer ring, and these engagement elements are engaged with cam surfaces provided on the inner ring and the outer ring by a frictional force so that the inner ring and the outer ring are relatively rotated. In the clutch mechanism for locking, vibration applying means for applying vibration to at least one of the inner ring, the outer ring and the cage is provided, and when the relative rotation of the inner ring and the outer ring is unlocked, the engagement element is moved to the cam surface. A clutch mechanism characterized by reducing a frictional force engaged with the clutch.   The clutch mechanism according to claim 1, wherein the vibration applying means applies high-frequency vibration by a piezoelectric element.   In the electric actuator in which the rotational driving force of the electric motor is converted into a linear driving force by a ball screw mechanism and output, and a clutch mechanism for preventing reverse input to the electric motor is provided in the rotational driving force transmitting portion, the clutch An electric actuator comprising the clutch mechanism according to claim 1 or 2 as a mechanism.

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