JP4117673B2 - Actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an actuator, for example, a power window of an automobile, a wire winding mechanism of an electric parking brake device, a caliper pushing mechanism of an electric disc brake device, a cam phase conversion mechanism in an engine valve timing variable device, and a belt CVT pulley drive mechanism. The present invention relates to an actuator using an electric motor as a power source, which can be used for other industrial winches, hoists, cranes, various positioning devices and the like.
[0002]
[Prior art]
For example, a linear actuator such as an electric parking brake driving device that reduces the burden on the driver by performing an operation of a parking brake of a vehicle using the power of an electric motor is known. As such a linear actuator, an actuator that rotates a pulley with an electric motor to wind up a cable to operate a parking brake and rewinds the cable to release the parking brake has been proposed (see JP 2001-106060).
[0003]
[Problems to be solved by the invention]
The linear actuator disclosed in the above publication uses a worm gear and a worm hole to decelerate the power from the electric motor and transmit it to the parking brake. When power is transmitted using the worm gear and worm wheel, the reduction ratio can be increased, and the power from the parking brake can be prevented from being transmitted to the electric motor side by designing the worm twist angle appropriately. There is. Accordingly, the operation state of the parking brake can be maintained without energizing the electric motor all the time, and inadvertent release can be prevented.
[0004]
However, if the above advantages are reversed, the worm gear and the worm hole have the disadvantage that the transmission efficiency is low. Therefore, in order to operate the parking brake, the output of the electric motor must be increased, and thereby the electric motor However, there is a problem that the size of the battery is increased and power saving cannot be achieved. On the other hand, if an electromagnetic brake device or the like that can electromagnetically transmit and shut off power can be used, power transmission can be interrupted as necessary while maintaining high transmission efficiency, but the configuration is complicated. There is a problem that the manufacturing cost increases.
[0005]
The present invention has been made in view of the problems of the prior art, and while maintaining a simple configuration, the transmission efficiency from the electric motor to the driven member is kept high, and the power from the driven member to the electric motor is maintained. An object is to provide an actuator capable of interrupting transmission.
[0006]
[Means for Solving the Problems]
The actuator of the present invention is an actuator for driving a driven member,
A housing;
An electric motor attached to the housing;
A power transmission mechanism that transmits the power of the electric motor to the driven member;
The power transmission mechanism is
A driven shaft coupled to the driven member;
A coil spring connecting the output shaft of the electric motor and the driven shaft;
An inner ring surrounding the coil spring;
One-way clutch means that is positioned between the housing and the inner ring and that allows the housing to rotate in the permitted direction of the inner ring, but prevents rotation in a blocking direction different from the permitted direction. And
When the output shaft of the electric motor rotates in the first direction, the winding diameter of the coil spring expands and comes into contact with the inner peripheral surface of the inner ring, and the inner ring is moved in the permission direction by the friction force generated between them. The one-way clutch means allows the inner ring to rotate, so that the coil spring transmits the rotational force in the first direction to the driven shaft.
When the output shaft of the electric motor rotates in a second direction different from the first direction, the winding diameter of the coil spring is reduced and separated from the inner peripheral surface of the inner ring. Regardless, the coil spring transmits the rotational force in the second direction to the driven shaft.
[0007]
[Action]
According to the actuator of the present invention, when the output shaft of the electric motor rotates in the first direction, the winding diameter of the coil spring expands and comes into contact with the inner peripheral surface of the inner ring, and is generated between them. In this case, the inner ring is allowed to rotate by the one-way clutch means, whereby the first direction is applied to the driven shaft via the coil spring. The rotational force is transmitted with high efficiency. On the other hand, when the output shaft of the electric motor rotates in a second direction different from the first direction, the coil spring is reduced in winding diameter and separated from the inner peripheral surface of the inner ring. The clutch means does not block the rotation of the coil spring that transmits power between the output shaft and the driven shaft, so that the rotational force in the second direction is applied to the driven shaft with high efficiency. Will be transmitted.
[0008]
Furthermore, when the rotational force in the second direction is transmitted from the driven member to the driven shaft, the winding diameter of the coil spring increases if the output shaft of the electric motor is stationary. The inner ring comes into contact with the inner peripheral surface of the inner ring and tries to rotate the inner ring in the blocking direction by the friction force generated between them, but in this case, the rotation of the inner ring is blocked by the one-way clutch means. As a result, the drive shaft does not rotate, that is, transmission of power from the driven member to the electric motor is interrupted. Therefore, for example, when the driving member of the parking brake device as the driven member is driven by the power of the electric motor to be in a desired brake state, after the supply of power to the electric motor is stopped, The parking brake device is not released.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the actuator according to the first embodiment. In FIG. 1, a cylindrical stator 2b is fixed to an inner peripheral surface 1a of a tubular housing 1, and the stator 2b includes a rotor 2c. The left end of the housing 1 in FIG. 1 is closed by a lid 4. An output shaft 3 rotatably supported by a bearing 5 (prestressed to the outer ring by a spring washer 7) disposed in the central opening 4a of the lid 4 and a bearing 6 disposed in the housing 1. A rotor 2c is attached to the outer peripheral surface of the two, and both rotate integrally. The electric motor 2 includes a stator 2b, a rotor 2c, and an output shaft 3.
[0010]
A hole 3b parallel to the axis is formed in the vicinity of the outer periphery of the diameter-reduced portion 3a at the right end in FIG. A driven shaft 8 connected to a driven member (not shown) is rotatably supported by a bearing 9 inside the right side of the housing 1 in FIG. 1, and in the vicinity of the outer periphery of the left end surface in FIG. A hole 8a parallel to the axis is formed. The ends of the coil spring 10 are inserted into the holes 3b and 8a, respectively.
[0011]
An inner ring 11 is rotatably supported by a bearing 12 with respect to the housing 1 so as to include a part of the reduced diameter portion 3 a of the output shaft 3, the coil spring 10, and the driven shaft 8. A wedge member 14 is disposed between the outer peripheral surface of the inner ring 11 and the outer ring 13 attached to the inner peripheral surface of the housing 1. The wedge member 14 has a higher height when it is upright than a height when it is tilted, and constitutes a one-way clutch means. In the present embodiment, the outer ring 13 is separated from the housing 1, but may be integrated. In either case, the outer ring forms part of the housing.
[0012]
Next, the operation of the present embodiment will be described. It is assumed that electric power is supplied to the electric motor 2 and the output shaft 3 is rotated in the first direction (the direction in which the output shaft 3 rolls to the back side when the output shaft 3 is free in FIG. 1). At this time, the end portion of the coil spring 10 engaged with the hole 3b of the output shaft 3 is rotated with the rotation of the output shaft 3, thereby increasing the winding diameter of the coil spring 10. In such a case, the circumferential surface of the coil spring 10 comes into contact with the inner circumferential surface of the inner ring 11 and tries to rotate the inner ring 11 in the same direction by the frictional force generated between them.
[0013]
At this time, since the inner ring 11 rotates in the first direction (permitted direction) with respect to the stationary outer ring 13, the wedge member 14 receives a force to tilt, and thus receives almost resistance from the wedge member 14. The inner ring 11 can rotate without any problem. Further, in a state where the winding diameter is enlarged and the outer periphery of the coil spring 10 is in contact with the inner peripheral surface of the inner ring 11, the relative rotation of both ends of the coil spring 10 is further suppressed. Accordingly, power transmission from the output shaft 3 to the driven shaft 8 can be performed without delay through the coil spring 10 which is a rigid body.
[0014]
On the other hand, it is assumed that electric power having a different polarity is supplied to the electric motor 2 and the output shaft 3 rotates in the second direction (the direction that rolls forward if the output shaft 3 is free in FIG. 1). At this time, the end portion of the coil spring 10 engaged with the hole 3b of the output shaft 3 rotates with the rotation of the output shaft 3, thereby reducing the winding diameter of the coil spring 10. In this case, since the peripheral surface of the coil spring 10 is separated from the inner peripheral surface of the inner ring 11, the coil spring 10 can be rotated without being affected by the wedge member 14, that is, driven from the output shaft 3 via the coil spring 10. Power can be transmitted to the shaft 8 without delay. It is more preferable that a cylindrical portion that suppresses the reduction of the winding diameter is extended from the driven shaft 8 inside the coil spring 10.
[0015]
On the other hand, when a rotational force is transmitted from a driven member (not shown) to the driven shaft 8 in the second direction (the direction in which the driven shaft 8 rolls forward if the driven shaft 8 is free in FIG. 1). If the output shaft 3 of the electric motor 2 is stationary, the winding diameter of the coil spring 10 expands and comes into contact with the inner peripheral surface of the inner ring 11, and the inner ring 11 is moved in the second direction (with the frictional force generated between them). Try to rotate in the blocking direction. In such a case, however, the inner ring 11 rotates with respect to the stationary outer ring 13, whereby the wedge member 14 receives a force in the vertical direction, and the inner ring 11 is locked by the wedge member 14 whose posture has changed. It becomes like this. Therefore, power transmission from the driven member to the electric motor 2 can be prevented.
[0016]
FIG. 2 is a cross-sectional view of the actuator according to the second embodiment. The actuator shown in FIG. 2 is obtained by applying the actuator shown in FIG. 1 to an electric parking brake driving device. Since the basic configuration is the same as that of the actuator shown in FIG. 1, the description of the common main configuration is omitted by giving the same reference numerals.
[0017]
In FIG. 2, a cylindrical sub housing 1 </ b> A that is connected to the housing 1 and is a part of the housing 1 is coupled to the chassis F by bolts 1 </ b> B. The joint between the housing 1 and the sub-housing 1A can secure a high degree of coaxiality because the outer peripheral surface of the bearing 9 serves as a guide.
[0018]
In the present embodiment, the driven shaft 8 ′ has an enlarged diameter portion 8 b ′ on the right side in the drawing, and a nut 16 is fitted on the inner peripheral surface thereof by press-fitting. The driven shaft 8 ′ is rotatably supported by a bearing 9 and the nut 16 is rotatably supported by a bearing 15 inside the sub-housing 1 </ b> A so that both rotate integrally.
[0019]
A screw shaft 17 passes through the nut 16. The screw shaft 17 has a round shaft portion 17a on the left side in the drawing, a round shaft portion 17c on the right side in the drawing, and a screw portion 17b in the center. The left round shaft portion 17 a is inserted into the bag hole 8 c ′ of the driven shaft 8 ′ and is rotatably supported by the bush 18. On the other hand, the right round shaft portion 17c protrudes rightward from the central opening 1b of the sub-housing 1A, and the outer peripheral surface thereof is sealed with a seal 19 disposed in the sub-housing 1A. Further, the front end of the guide bolt 20 screwed and fixed to the sub-housing 1A is engaged with the linear groove 17d formed on the outer periphery of the round shaft portion 17c so as to prevent the screw shaft 17 from rotating. The other end of the wire W having one end connected to a parking brake (not shown) is attached to the protruding end of the round shaft 17c. The wire W constitutes a driven member.
[0020]
A screw groove (not shown) is formed on the inner peripheral surface of the hollow nut 16, and a large number of balls (not shown) are formed in the spiral space formed by the screw groove of the screw portion 17 b of the screw shaft 17. ) Are arranged so as to roll freely. A passage 16 a for returning the ball from one end of the nut 16 to the other end during operation is provided outside the nut 16. A nut screw, a screw shaft 17 and a ball (not shown) constitute a ball screw mechanism.
[0021]
The operation of the present embodiment will be described with reference to FIG. When the driver performs a predetermined operation to operate the parking brake, electric power is supplied from a power source (not shown) to the electric motor 2, and the output shaft 3 rotates in the first direction. At this time, the end portion of the coil spring 10 engaged with the hole 3b of the output shaft 3 is rotated with the rotation of the output shaft 3, thereby increasing the winding diameter of the coil spring 10. In such a case, the circumferential surface of the coil spring 10 comes into contact with the inner circumferential surface of the inner ring 11 and tries to rotate the inner ring in the same direction by the frictional force generated between them.
[0022]
At this time, since the inner ring 11 rotates in the first direction (permitted direction) with respect to the stationary outer ring 13, the wedge member 14 receives a force to tilt, and thus receives almost resistance from the wedge member 14. The inner ring 11 can rotate without any problem. Further, in a state where the winding diameter is enlarged and the outer periphery of the coil spring 10 is in contact with the inner peripheral surface of the inner ring 11, the relative rotation of both ends of the coil spring 10 is further suppressed. Therefore, power transmission from the output shaft 3 to the driven shaft 8 ′ can be performed without delay through the coil spring 10 which is a rigid body.
[0023]
When the driven shaft 8 ′ rotates, the nut 16 also rotates integrally. At this time, due to the principle of the ball screw mechanism, the rotational displacement of the nut 16 is smoothly converted into the axial displacement of the screw shaft 17. Accordingly, the screw shaft 17 performs an operation of drawing into the sub-housing 1A and pulls the wire W, so that a parking brake device (not shown) can be maintained in an operating state and a wheel (not shown) can be put in a braking state. In this state, power supply to the electric motor 2 is interrupted.
[0024]
In such a state, a brake reaction force is generated in the parking brake device, and a pulling force is generated toward the right of the wire W in FIG. At this time, since the screw shaft 17 tends to move to the right, the rotational force in the second direction is transmitted to the nut 16 and the driven shaft 8 ′. Here, if the output shaft 3 of the electric motor 2 is stationary, the winding diameter of the coil spring 10 expands and comes into contact with the inner peripheral surface of the inner ring 11, and the inner ring 11 is moved to the second by the frictional force generated between them. Try to rotate in the direction (blocking direction). However, in such a case, the inner ring 11 is rotated with respect to the stationary outer ring 13, so that the wedge member 14 receives a force in the vertical direction and the inner ring is locked by the wedge member 14 whose posture has changed. become. Therefore, power transmission from the driven member to the electric motor 2 can be prevented. Therefore, even after the supply of electric power to the electric motor 2 is stopped, the parking brake device is not released, and there is no need to continue energizing the electric motor 2 or provide a lock device separately.
[0025]
Further, when the driver performs a predetermined operation to release the parking brake in order to start the vehicle, electric power having a different polarity is supplied to the electric motor 2 and the output shaft 3 rotates in the second direction. . At this time, the end portion of the coil spring 10 engaged with the hole 3b of the output shaft 3 rotates with the rotation of the output shaft 3, thereby reducing the winding diameter of the coil spring 10. In this case, since the peripheral surface of the coil spring 10 is separated from the inner peripheral surface of the inner ring 11, the coil spring 10 can be rotated without being affected by the wedge member 14. That is, power transmission from the output shaft 3 to the driven shaft 8 ′ is executed without delay through the coil spring 10, so that the nut 16 is rotated and the screw shaft 17 is moved rightward in FIG. And thereby the parking brake device can be released.
[0026]
The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate.
[0027]
【The invention's effect】
According to the actuator of the present invention, when the output shaft of the electric motor rotates in the first direction, the winding diameter of the coil spring expands and comes into contact with the inner peripheral surface of the inner ring, and is generated between them. In this case, the inner ring is allowed to rotate by the one-way clutch means, whereby the first direction is applied to the driven shaft via the coil spring. The rotational force is transmitted with high efficiency. On the other hand, when the output shaft of the electric motor rotates in a second direction different from the first direction, the coil spring is reduced in winding diameter and separated from the inner peripheral surface of the inner ring. The clutch means does not block the rotation of the coil spring that transmits power between the output shaft and the driven shaft, so that the rotational force in the second direction is applied to the driven shaft with high efficiency. Will be transmitted.
[0028]
Furthermore, when the rotational force in the second direction is transmitted from the driven member to the driven shaft, the winding diameter of the coil spring increases if the output shaft of the electric motor is stationary. The inner ring comes into contact with the inner peripheral surface of the inner ring and tries to rotate the inner ring in the blocking direction by the friction force generated between them, but in this case, the rotation of the inner ring is blocked by the one-way clutch means. As a result, the drive shaft does not rotate, that is, transmission of power from the driven member to the electric motor is interrupted. Therefore, for example, when the driving member of the parking brake device as the driven member is driven by the power of the electric motor to be in a desired brake state, after the supply of power to the electric motor is stopped, The parking brake device is not released.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an actuator according to a first embodiment.
FIG. 2 is a sectional view of an actuator according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 1A Sub housing 2 Electric motor 3 Output shaft 8, 8 'Drive shaft 10 Coil spring 14 Wedge member 16 Nut 17 Screw shaft W Wire

Claims (1)

An actuator for driving a driven member,
A housing;
An electric motor attached to the housing;
A power transmission mechanism that transmits the power of the electric motor to the driven member;
The power transmission mechanism is
A driven shaft coupled to the driven member;
A coil spring connecting the output shaft of the electric motor and the driven shaft;
An inner ring surrounding the coil spring;
One-way clutch means that is positioned between the housing and the inner ring and that allows the housing to rotate in the permitted direction of the inner ring, but prevents rotation in a blocking direction different from the permitted direction. And
When the output shaft of the electric motor rotates in the first direction, the winding diameter of the coil spring expands and comes into contact with the inner peripheral surface of the inner ring, and the inner ring is moved in the permission direction by the friction force generated between them. The one-way clutch means allows the inner ring to rotate, so that the coil spring transmits the rotational force in the first direction to the driven shaft.
When the output shaft of the electric motor rotates in a second direction different from the first direction, the winding diameter of the coil spring is reduced and separated from the inner peripheral surface of the inner ring. Regardless, the coil spring transmits the rotational force in the second direction to the driven shaft.

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