JP2006071008A - Actuator - Google Patents

Abstract

【Task】
A compact actuator with less vibration and the like is provided.
[Solution]
The sleeve 9 fitted with the nut 11 is disposed so as to be enclosed in the hollow rotor 2b. Therefore, the nut 11 can be moved to the radially inner position of the stator 2a. The axial length can be suppressed, and a compact configuration can be provided.
[Selection] Figure 1

Description

  The present invention relates to an actuator, for example, a general-purpose elevator, a jack, an electric parking brake for a vehicle, an electric disc brake, a pulley drive mechanism for a belt CVT, a 4WD 2WD, a 4WD switching mechanism, a transmission switching mechanism, a clutch switching mechanism, a door The present invention relates to an electric actuator that can be used in a switchgear or the like.

  In recent years, labor saving of vehicles and the like has progressed, and for example, a system has been developed in which a transmission, a parking brake, and the like of an automobile are performed not by hand but by the power of an electric motor. An electric actuator used for such an application may use a ball screw mechanism in order to convert the rotational motion transmitted from the electric motor into the axial motion with high efficiency.

Here, Patent Document 1 discloses a linear actuator that transmits power from a motor to an output rod via a ball screw mechanism to cause linear motion.
JP 2000-220715 A

  Here, in the linear actuator disclosed in Patent Document 1, the nut of the ball screw mechanism is provided away from the stator of the motor in the axial direction, as is apparent from the figure. Therefore, there is a problem that the dimension in the axial direction of the linear actuator becomes large and the installation place is limited. Moreover, in the structure of patent document 1, since the rotor and nut of a motor are connected and the screw shaft moves to an axial direction, when rotating a nut at high speed, the rotation balance accuracy is ensured. There is a need to.

  The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a compact actuator with less vibration and the like.

The actuator of the present invention is
A housing;
A motor having a stator and a rotor;
A screw shaft connected to the rotor of the motor and having a male screw groove formed on an outer peripheral surface thereof, and a nut connected to a driven member and disposed so as to surround the screw shaft and having a female screw groove formed on the inner peripheral surface thereof. A ball screw mechanism that converts a rotational movement of the screw shaft into an axial movement of the nut, and a plurality of balls that are arranged to freely roll along a rolling path formed between the two screw grooves. In the actuator
The nut is movable to a radially inner position of the stator.

  According to the actuator of the present invention, the nut can move to a position radially inward of the stator, so that the axial length of the actuator can be suppressed, and a compact configuration can be provided. Further, by rotating a screw shaft that is generally higher in rotation balance accuracy than a nut, vibrations and the like during high-speed rotation can be suppressed.

  It is preferable to provide a detector for detecting the rotation angle of the rotor or the screw shaft. Needless to say, the axial amount of the nut can be calculated from the conversion ratio of the ball screw mechanism from the rotation angle of the nut.

  It is preferable that the nut is fitted in a sleeve, and a groove extending in the longitudinal direction is formed in the sleeve, and a member (for example, a pin) protruding from the housing is engaged with the groove. However, a groove may be formed in the nut itself.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of an actuator having a ball screw mechanism according to the first embodiment.

  In FIG. 1, a stator 2 a is fixed to the inner periphery of a hollow cylindrical housing 1. Furthermore, a rotor 2b is rotatably arranged with respect to the housing 1 via bearings 3 and 4. The rotor 2b has a hollow cylindrical portion 2c included in the stator 2a, and a shaft portion 2d connected to the cylindrical portion 2c. A resolver 2f that is a detector that detects the rotation angle of the rotor 2b is disposed between the shaft portion 2d and the housing 1. An encoder or the like can be used instead of the resolver 2f. However, the resolver 2f has an advantage that it can output a stable signal from a low temperature to a high temperature and can be used even in oil.

  A round shaft portion 5a formed in the right half portion of the screw shaft 5 is fitted in a through hole 2e formed in the shaft portion 2d, and the rotor 2b is screwed by a nut 6 screwed into the end portion thereof. The screw shaft 5 is fixed and rotated integrally. The rotor 2b can move relative to the bearing 3 in the axial direction. Further, the outer ring of the bearing 4 that supports the shaft portion 2 d is fixed to the housing 1 by a bearing retainer 7. Therefore, the rotor 2b and the screw shaft 5 are fixed so as not to move in the axial direction via the bearing 4, and can only rotate. The stator 2a, the rotor 2b, and the resolver 5f constitute the electric motor 2.

  A ring-shaped member 8 is fitted to the inner periphery of the left end of the housing 1 in FIG. A hollow cylindrical sleeve 9 is movably supported on the ring-shaped member 8 via a bush 10. The sleeve 9 is fitted and fixed to a nut 11 so that both move together. The sleeve 9 has a linear groove 9a on the outer periphery, and the tip of a pin 12 that is implanted in the housing 1 and extends through the opening 8a of the ring-shaped member 8 engages with the groove 9a. ing. Therefore, the sleeve 9 and the nut 11 can move only in the axial direction with respect to the housing 1 by the function of preventing the pin 12 from rotating.

  A female thread groove 11 a is formed on the inner peripheral surface of the nut 11. A male screw groove 5b (only a part of which is shown) is formed on the outer peripheral surface of the left half of the screw shaft 5. A plurality of balls 13 are arranged so as to be able to roll in a spiral rolling path formed between the opposing screw grooves 11a and 5b. The nut 11 is provided with a top (not shown) for circulating the ball 13. The screw shaft 5, the nut 11, and the ball 13 constitute a ball screw mechanism (transmission means).

  The operation of the present embodiment will be described. When electric power is supplied from a power source (not shown) and the rotor 2b of the electric motor 2 rotates, the screw shaft 5 rotates with it. When the screw shaft 5 rotates, the rotational motion is efficiently converted into the axial motion of the nut 11 by the ball 13 that rolls on the rolling path and circulates through the top, so that the driven body connected to the nut 11 is driven. A member (not shown) can be moved in the axial direction. At this time, by detecting a signal from the resolver 5f, the rotation angle of the screw shaft 5 can be obtained, whereby the nut 11 can be stopped at an appropriate position.

  According to the actuator of the present embodiment, the sleeve 9 fitted with the nut 11 is arranged so as to be enclosed in the hollow rotor 2b, and therefore the nut 11 reaches a position radially inward of the stator 2a. Since it is movable, the axial length of the actuator can be suppressed, and a compact configuration can be provided. Further, by rotating the screw shaft 5 that is generally higher in rotation balance accuracy than the nut 11, vibration and the like during high-speed rotation can be suppressed. In addition, although the diameter of the stator 2a becomes large by having made the structure which can move the nut 11 to the position inside radial direction of the stator 2a, there exists an advantage that the electric motor 2 of high torque can be provided by it.

  Even if the specifications of the actuator change, it can be dealt with by changing the lead and diameter of the screw shaft 5 and nut 11 without changing the size and shape of the electric motor 2. Manufacturing cost can be reduced. The electric motor 2 may be a normal DC motor, but can be used even in oil by being a brushless motor.

  FIG. 2 is a sectional view of an actuator having a ball screw mechanism according to the second embodiment. The actuator shown in FIG. 2 differs from the embodiment shown in FIG. 1 in that a composite nut 11 ′ is formed by integrating a sleeve 9 and a nut 11. Since the other configuration is the same as the configuration of FIG. 1, the same components are denoted by the same reference numerals and the description thereof is omitted.

  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.

It is sectional drawing of the actuator provided with the ball screw mechanism which is 1st Embodiment. It is sectional drawing of the actuator provided with the ball screw mechanism which is 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Electric motor 2a Stator 2b Rotor 2c Cylindrical part 2d Shaft part 2e Through hole 2f Resolver 3 Bearing 4 Bearing 5 Screw shaft 5a Round shaft part 5b Screw groove 6 Nut 7 Bearing restraint 8 Ring-shaped member 8a Opening 9 Sleeve 9a Groove 10 Bush 11 Nut 11 'Compound nut 11a Groove 12 Pin 13 Ball

Claims (3)

A housing;
A motor having a stator and a rotor;
A screw shaft connected to the rotor of the motor and having a male screw groove formed on an outer peripheral surface thereof, and a nut connected to a driven member and disposed so as to surround the screw shaft and having a female screw groove formed on the inner peripheral surface thereof. A ball screw mechanism that converts a rotational movement of the screw shaft into an axial movement of the nut, and a plurality of balls that are arranged to freely roll along a rolling path formed between the two screw grooves. In the actuator
The actuator according to claim 1, wherein the nut is movable to a radially inward position of the stator.   The actuator according to claim 1, further comprising a detector that detects a rotation angle of the rotor or the screw shaft. The nut is fitted to a sleeve, and a groove extending in a longitudinal direction is formed in the sleeve, and a member protruding from the housing is engaged with the groove. Or the actuator of 2.

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