JP2009156415A - Electric linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric linear actuator having a deceleration mechanism with a function which efficiently transmits input torque from an electric motor side to a ball screw mechanism, and cuts off reverse input torque from the ball screw mechanism to prevent the recirculation of the reverse input torque to the electric motor side. <P>SOLUTION: In the electric linear actuator having the deceleration mechanism 5 arranged between the electric motor 3 and the ball screw mechanism 4, the deceleration mechanism 5 is constituted of a combined planetary gear mechanism having a first planetary gear mechanism 51 and a second planetary gear mechanism 52 constituting a hypocycloid gear mechanism. Even if reverse input torque is applied from the ball screw mechanism 4 side, since internal gears 51a, 52a of the first and second planetary gear mechanisms 51, 52 are integrally constituted and a first planetary external gear 51b is fixed to a housing 2, the reverse input torque can be completely locked. Rotation in both directions is enabled from the electric motor 3 side, thus preventing the deterioration of high efficiency and the low friction of the ball screw mechanism 4 from being impaired. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric linear actuator used in a drive unit of a vehicle such as an automobile, and more particularly to an electric linear actuator used by converting rotation of an electric motor into linear motion via a ball screw mechanism.

In electric linear actuators used in various drive parts of vehicles such as automobiles, a gear mechanism such as a trapezoidal screw or a rack and pinion is generally used as a mechanism for converting the rotational movement of the electric motor into an axial linear movement. (For example, refer to Patent Document 1). Since these conversion mechanisms involve a sliding contact portion, the power loss is large, and it is necessary to increase the size of the electric motor and increase the power consumption. Therefore, a ball screw mechanism has been adopted as a more efficient actuator.
JP 2001-336597 A

  However, when a ball screw is applied to the rear wheel steering mechanism or the power transmission control friction clutch mechanism, a reverse input torque is not generated in the electric motor even if an axial load is applied from the outside in the conversion mechanism using a trapezoidal screw or the like. On the other hand, since this ball screw is highly efficient regardless of the direction of operation, there is a possibility that reverse input torque may be applied to the electric motor due to the axial load. New problems have arisen.

  In order to solve these problems and to hold the position mechanically without performing complicated electric control such as electromagnetic brakes, it is conceivable to use a worm gear as a speed reducer, but the efficiency is low and a ball screw mechanism is adopted. The meaning disappears.

  The present invention eliminates such conventional problems and efficiently transmits input torque from the electric motor side to the ball screw mechanism, while preventing reverse input torque from the ball screw mechanism side from flowing back to the electric motor side. It aims at providing the electric linear actuator provided with the deceleration mechanism which has this.

In order to achieve such an object, the invention according to claim 1 of the present invention includes an electric motor attached to a housing, a ball screw mechanism for converting the rotational motion of the electric motor into a linear motion, and the electric motor. An electric linear actuator including a speed reduction mechanism disposed between ball screw mechanisms, wherein the speed reduction mechanism includes a first planetary gear mechanism and a second planetary gear mechanism constituting a hypocycloid mechanism. Consists of a gear mechanism, and the external gears of the first planetary gear mechanism and the second planetary gear mechanism rotate integrally with an eccentric shaft portion provided on an input side member connected to the motor shaft of the electric motor. The internal gear of the first planetary gear mechanism is provided so as not to rotate relative to the housing, and the internal gear of the second planetary gear mechanism is rotatable relative to the housing. Characterized in that it is relatively non-rotatably connected to the rotary portion of the ball screw mechanism via the output-side member together is provided.
Here, the external gears of the first planetary gear mechanism and the second planetary gear mechanism are supported rotatably on an eccentric shaft portion provided on an input side member connected to the motor shaft of the electric motor. Not only is the external gear of the first planetary gear mechanism and the second planetary gear mechanism made of the same member to be able to rotate integrally, but it is made of a separate member so that they cannot rotate relative to each other. The case where it can be connected and rotated integrally is also included.

  Thus, an electric motor attached to the housing, a ball screw mechanism that converts the rotational motion of the electric motor into a linear motion, and a speed reduction mechanism disposed between the electric motor and the ball screw mechanism. In the electric linear actuator, the speed reduction mechanism is constituted by a compound planetary gear mechanism including a first planetary gear mechanism and a second planetary gear mechanism constituting a hypocycloid mechanism, and the first planetary gear mechanism and the second planetary gear mechanism. Each external gear of the gear mechanism is rotatably supported integrally on an eccentric shaft provided on an input side member connected to the motor shaft of the electric motor, and the internal gear of the first planetary gear mechanism is The internal gear of the second planetary gear mechanism is provided so as to be relatively rotatable with respect to the housing, and the ball screw via the output side member. Since it is connected to the rotating portion of the mechanism so as not to be relatively rotatable, even if a reverse input torque acts on the output side member of the speed reduction mechanism from the ball screw mechanism side, the first gear integral with the external gear of the second planetary gear mechanism. Since the external gear of the planetary gear mechanism is engaged with the internal gear fixed to the housing, the rotation is prevented and the reverse input to the electric motor can be locked. Moreover, the electric motor can be rotated in both directions, and the high efficiency and low friction of the ball screw mechanism are not impaired.

In the invention according to claim 2, since the rotating portion of the ball screw mechanism is a screw shaft, and the screw shaft rotates to linearly move the nut, space-saving and good assemblability can be obtained. It is done.
Further, as in the invention described in claim 3, the rotating portion of the ball screw mechanism may be a nut, and the nut may rotate to linearly move the screw shaft.

  In the invention according to claim 4, since the counter balance is provided on the input side member, the dynamic balance of the eccentric shaft is good when rotating at a high speed, and the vibration of the speed reducer can be prevented. .

  Preferably, as in the invention described in claim 5, if the reduction ratio of the reduction mechanism is set to 1:70 or more and the lead angle of the thread groove of the ball screw mechanism is set to 7 degrees or more, the efficiency of the actuator can be improved. There is an advantage not to slow down.

  An electric linear actuator according to the present invention includes an electric motor attached to a housing, a ball screw mechanism that converts a rotational motion of the electric motor into a linear motion, and a speed reducer disposed between the electric motor and the ball screw mechanism. An electric linear actuator comprising: a first planetary gear mechanism including a first planetary gear mechanism and a second planetary gear mechanism constituting a hypocycloid mechanism; The external gears of the mechanism and the second planetary gear mechanism are rotatably supported integrally on an eccentric shaft portion provided on an input side member connected to the motor shaft of the electric motor, and the first planetary gear mechanism The internal gear of the second planetary gear mechanism is provided so as not to rotate relative to the housing, and the internal gear of the second planetary gear mechanism is provided so as to be rotatable relative to the housing. Since it is connected to the rotating part of the ball screw mechanism through the output side member so as not to be relatively rotatable, even if a reverse input torque acts on the output side member of the speed reduction mechanism from the ball screw mechanism side, the second planetary gear mechanism Since the external gear of the first planetary gear mechanism integrated with the external gear is engaged with the internal gear fixed to the housing, the external gear is prevented from rotating and can lock the reverse input to the electric motor. it can. Moreover, the electric motor can be rotated in both directions, and the high efficiency and low friction of the ball screw mechanism are not impaired.

  An electric linear actuator comprising: an electric motor attached to a housing; a ball screw mechanism that converts the rotational movement of the electric motor into a linear movement; and a speed reduction mechanism disposed between the electric motor and the ball screw mechanism. The speed reduction mechanism is configured by a compound planetary gear mechanism including a first planetary gear mechanism and a second planetary gear mechanism that constitute a hypocycloid mechanism, and each of the first planetary gear mechanism and the second planetary gear mechanism. An external gear is rotatably supported integrally on an eccentric shaft portion provided on an input side member connected to the motor shaft of the electric motor, and the internal gear of the first planetary gear mechanism is relative to the housing. The internal gear of the second planetary gear mechanism is provided so as to be relatively non-rotatable, and is provided so as to be relatively rotatable with respect to the housing. Was relatively rotate linked configuration.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a longitudinal sectional view showing a rod extension state of an electric linear actuator according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view showing a rod contraction state of FIG. 1, and FIG. 3 (a) is a deceleration of FIG. FIG. 3B is an enlarged sectional view of the mechanism, and FIG. 3B is a sectional view taken along line III-III in FIG.

The electric linear actuator 1 includes an electric motor 3 attached to a housing 2, and
The configuration includes a ball screw mechanism 4 that converts the rotational motion of the electric motor 3 into linear motion, and a speed reduction mechanism 5 disposed between the electric motor 3 and the ball screw mechanism 4. The electric motor 3, the speed reduction mechanism 5, and the ball screw mechanism 4 are arranged in series on a straight line.

The ball screw mechanism 4 includes a nut 6, a screw shaft 7 inserted in the nut 6 via a number of balls (not shown), and a hollow rod 8 whose base end is fixed to the nut 6. The rod 8 protrudes and retracts from a rod hole provided at one end of the housing 2.
The screw shaft 7 has a connecting shaft 7 b provided at one end thereof connected to the connecting hole 54 d of the output side member 54 of the speed reduction mechanism 5 in a relatively non-rotatable manner, and a base end portion adjacent to the connecting portion through the rolling bearing 9. 2 is rotatably supported.

  A fixed end 8 a provided at the base of the rod 8 is fixed to the outer periphery of the nut 6 via a rod connecting pin 10. The rod connecting pin 10 is press-fitted into a pin hole formed in the nut 6. The rod 8 is supported so as to be slidable in the axial direction by a sliding bearing 2 a provided on the inner periphery of the rod hole of the housing 2. Further, a groove 11 extending in the axial direction is provided on the outer periphery of the rod 8, and a tip end portion of the rotation preventing member 12 screwed into the housing 2 is engaged with the groove 11, so that the rod 8 cannot rotate and is axially Is supported so as to be relatively movable.

Although not particularly illustrated, a spiral thread groove is formed on the inner periphery of the nut 6, while a spiral thread groove corresponding to the thread groove provided on the inner periphery of the nut 6 is also formed on the outer periphery of the screw shaft 7. The ball screw mechanism 4 is formed by rolling and accommodating a large number of balls between the nut 6 and the screw groove of the screw shaft 7. In the illustrated example, a piece system is used as a circulation mechanism for circulating the ball, and a piece member 13 is attached to the nut 6. However, the circulation mechanism is not limited to the piece system, and may be another system such as a return tube or an end plate.
A spring 14 is interposed between the nut 6 and the outer ring of the rolling bearing 9 in a contracted state in the axial direction to absorb axial backlash. The end of the spring 14 on the nut 6 side is engaged with the nut 6 via the spring seat 15.

  The speed reduction mechanism 5 is configured by a compound planetary gear mechanism including a first planetary gear mechanism 51 and a second planetary gear mechanism 52 that constitute a hypocycloid mechanism. The first planetary gear mechanism 51 and the second planetary gear mechanism 52 are arranged in series in the axial direction, the first planetary gear mechanism 51 is arranged on the electric motor 3 side, and the second planetary gear mechanism 52 is arranged on the ball screw mechanism 4 side. ing. The external gears 51 a and 52 a of the first planetary gear mechanism 51 and the second planetary gear mechanism 52 are an integral structure formed on one cylindrical body, and the inner periphery is connected to the motor shaft 3 a of the electric motor 3. The side member 53 is rotatably supported via a rolling bearing 58 using needle rollers.

  The input side member 53 includes an eccentric shaft portion 53a that is eccentric by a predetermined dimension with respect to the central axis, a connecting shaft portion 53b that protrudes along the central axis from the electric motor side end of the eccentric shaft portion 53a, And a central shaft portion 53c extending from the end of the eccentric shaft portion 53a on the ball screw mechanism 4 side along the central axis to the ball screw mechanism 4 side. The connecting shaft portion 53b is connected to the motor shaft 3a of the electric motor 3 in a relatively non-rotatable manner, and the external gears 51a and 52a of the first planetary gear mechanism 51 and the second planetary gear mechanism 52 are rolling bearings on the eccentric shaft portion 53a. It is fitted via 58 so as to be relatively rotatable.

  Further, the input side member 53 is provided with a counter balance weight 60 in order to eliminate the unbalance of the weight of the eccentric shaft portion 53a. In the example of illustration, it is provided in two places, the boundary part of the eccentric shaft part 53a and the connection shaft part 53b, and the boundary part of the eccentric shaft part 53a and the center shaft part 53. Although the counter balance weight is provided in this example, the counter balance with respect to the eccentric shaft portion 53a may be obtained by another method.

  Further, the outer periphery of the internal gear 51 b that meshes with the external gear 51 a of the first planetary gear mechanism 51 is fitted and fixed to the inner periphery of the housing 2 so as not to be relatively rotatable. On the other hand, the outer periphery of the internal gear 52b meshed with the external gear 52a of the second planetary gear mechanism 52 is supported so as to be relatively rotatable with respect to the housing 2 via a rolling bearing 55 using needle rollers, and a pin 56, the output side member 54 is connected to the output side member 54 so as not to be relatively rotatable, and the output side member 54 is connected to the screw shaft 7 which is a rotating portion of the ball screw mechanism 4 so as not to be relatively rotatable.

  The output side member 54 has a stepped cylindrical shape with a large diameter on the electric motor side and a small diameter on the ball screw mechanism 4 side, and the large diameter portion 54a uses needle rollers on the outer periphery of the central shaft portion 53c of the input side member 53. The ball screw mechanism 4 has a shape in which the end portion on the side of the ball screw mechanism 4 is closed by an end plate portion 54c having a connection hole 54d. Further, the inner periphery of the end of the internal gear 52 b of the second planetary gear mechanism 52 is fitted to the outer periphery of the large-diameter portion 54 a of the output side member 54, and is fixed by a pin 56 so as not to be relatively rotatable. Further, the outer periphery of the small diameter portion 54 b of the output side member 54 is supported by the inner periphery of the housing 2 through a rolling bearing 59 so as to be relatively rotatable. The outer ring of the rolling bearing 59 is fitted and fixed to the inner periphery of the housing 2 via a cylindrical spacer 59a.

  In the electric linear actuator having the above-described configuration, when the electric motor 3 is energized and rotated, the rotational motion of the electric motor 3 is decelerated via the speed reduction mechanism 5 and transmitted to the screw shaft 7. The nut 6 is moved in the axial direction (left-right direction in the figure) by the rotation.

  In the speed reduction mechanism 5, the eccentric shaft portion 53a is eccentrically rotated by the rotation of the input side member 53, and the external gear 51a of the first planetary gear mechanism 51 supported by the eccentric shaft portion 53a is the internal gear 51b. Revolves around the central axis while rotating in a meshed state. In synchronization with the external gear 51a of the first planetary gear mechanism 51, the external gear 52a of the second planetary gear mechanism 52 rotates as a unit while revolving, and the second planetary gear mechanism is driven by the movement of the external gear 52a. The internal gear 52b of 52 rotates. This rotation is transmitted to the screw shaft 7 via the output side member 54, and the screw shaft 7 rotates.

  Here, the number of teeth of the external gear 51a of the first planetary gear mechanism 51 is Z1, the number of teeth of the internal gear 51b is Z2, the number of teeth of the external gear 52a of the second planetary gear mechanism 52 is Z3, and the internal gear. If the number of teeth of 52b is Z4, the reduction gear ratio is 1−Z1 · Z4 / Z2 · Z3. The reduction ratio can be increased by reducing the difference in the number of teeth. If the reduction ratio is 1:70 or more and the lead angle of the thread groove of the ball screw mechanism 4 is set to 7 degrees or more, it is possible to increase the efficiency and not reduce the speed of the actuator.

  Next, when the electric motor 3 is stopped, even if a reverse input torque acts on the output side member 54 of the speed reduction mechanism 5 from the ball screw mechanism 4 side due to the reverse input load from the rod 8, the second planetary gear mechanism 52 Since the external gear 51a of the first planetary gear mechanism 51 integrated with the external gear 52a is engaged with the internal gear 51b fixed to the housing 2, the rotation is prevented, and the reverse rotation to the electric motor 3 is performed. The input can be locked.

  That is, the reverse input torque is transmitted from the output side member 54 to the internal gear 52b of the second planetary gear mechanism 52 and tries to rotate the external gear 52a meshing with the internal gear 52b. The external gear 51a of the first planetary gear mechanism 51 integrated with the gear 52a meshes with the internal gear 51b that is fixed to the housing 2 so as not to rotate. It is possible to prevent backflow of reverse input torque to the motor 3 side. Therefore, the impact on the electric motor 3 due to the reverse input torque can be reduced.

  As described above, the speed reduction mechanism 5 according to the present embodiment has a function of transmitting the input torque from the input side to the output side, and blocking the reverse input torque from the output side so as not to circulate to the input side electric motor. An electric linear actuator that is light and compact can be provided. Further, there is an advantage that a simple general-purpose motor can be used without using an electric motor having a special structure, and the specification can be easily changed even when the reduction ratio is changed.

  In the above embodiment, the nut 6 is linearly moved by rotating the screw shaft 7 of the ball screw mechanism 4. However, the screw shaft 7 may be linearly moved by rotating the nut 6. .

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  The electric linear actuator according to the present invention can be applied as an actuator such as a rear wheel steering mechanism of a vehicle such as an automobile or a friction clutch mechanism for power transmission control.

It is a longitudinal section showing a rod extension state of one embodiment of an electric linear actuator concerning the present invention. It is a longitudinal cross-sectional view which shows the rod contraction state of FIG. (A) is an expanded sectional view of the speed-reduction mechanism of FIG. 1, (b) is the III-III sectional view taken on the line of (a).

Explanation of symbols

1 ... Electric linear actuator 2 ... Housing 3 ... Electric Motor 3a ... motor shaft 4 ... ball screw mechanism 5 ... Deceleration mechanism 6 ··················································· Connection Shaft 8 ... Rod 9 ... Rolling bearing 10 ... Pin 11 ............ Groove 12 ......... Rotation stop member 13 ......... Piece member 14 ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Spring 15 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Spring seat 51 ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ First planetary gear mechanism 51a ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ External gear 51b ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Internal gear 52 ・ ・ ・... 2nd planetary gear mechanism 52a ... External gear 52b ... Internal gear 53 ... ············ Input side member 53a ····································································・ ・ ・ ・ ・ ・ ・ ・ Center shaft 54 ・ ・ ・ ・ ・ ・ ・ ・ Output side member 54a ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Large diameter portion 54b ・ ・ ・······ Small diameter portion 54c ················· End plate portion 54d ...・ ・ ・ ・ Rolling bearing 56 ・ ・ ・ ・ ・ ・ ・ ・ Pin 57 ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ Rolling bearings 58 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Rolling bearings 59 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Rolling bearings 59a ・ ・ ・ ・ ・ ・・ Spacer 60 ... Counter balance weight

Claims (5)

An electric motor attached to the housing;
A ball screw mechanism that converts the rotational motion of the electric motor into linear motion;
In the electric linear actuator comprising a reduction mechanism disposed between the electric motor and the ball screw mechanism,
The speed reduction mechanism is constituted by a compound planetary gear mechanism including a first planetary gear mechanism and a second planetary gear mechanism constituting a hypocycloid mechanism,
Each external gear of the first planetary gear mechanism and the second planetary gear mechanism is rotatably supported integrally with an eccentric shaft portion provided on an input side member connected to a motor shaft of an electric motor,
The internal gear of the first planetary gear mechanism is provided so as not to rotate relative to the housing, and the internal gear of the second planetary gear mechanism is provided so as to be rotatable relative to the housing and via an output side member. An electric linear actuator characterized by being connected to a rotating portion of a ball screw mechanism so as not to be relatively rotatable.   The electric linear actuator according to claim 1, wherein the rotating portion of the ball screw mechanism is a screw shaft, and the screw shaft rotates to linearly move the nut.   The electric linear actuator according to claim 1, wherein the rotating portion of the ball screw mechanism is a nut, and the nut rotates to linearly move the screw shaft.   The electric linear actuator according to any one of claims 1 to 3, wherein a counterbalance is provided on the input side member.   The electric linear actuator according to any one of claims 1 to 4, wherein a reduction ratio of the reduction mechanism is set to 1:70 or more, and a lead angle of a thread groove of the ball screw mechanism is set to 7 degrees or more.

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