JP4731395B2 - Electric linear actuator - Google Patents

Description

  The present invention relates to an electric linear actuator using a ball screw mechanism, and more particularly to an axial fixing structure of a bearing that supports a rotating nut of a ball screw mechanism in a housing.

2. Description of the Related Art An electric linear actuator that is used in a driving unit of a vehicle such as an automobile by converting the rotational force of an electric motor into a linear motion via a ball screw mechanism is known (for example, FIG. 1 and FIG. 6 of Patent Document 1). In the electric linear actuator disclosed in Patent Document 1, a rotating nut of a ball screw mechanism is rotatably supported by a rolling bearing with respect to a housing. Further, a screw shaft is fitted into the rotary nut through a large number of balls so as to be movable in the axial direction, and these are housed in a split housing. And when the axial load from the outside is loaded from the rod part of the ball screw shaft end, the load is cut off by the clutch, and the reverse input torque is not transmitted to the motor.

By the way, in the above electric linear actuator, since it receives an axial load from the rod portion at the ball screw shaft end, at least one of the bearings on both sides supporting the rotating nut can receive the axial load. A bearing or an angular bearing is selected and adopted. Further, in the electric linear actuator of Patent Document 1, bearings on both sides of the rotating nut are arranged separately in each of the divided housings for assembly considerations. However, when both loads that push and pull the screw shaft are generated, in such a housing structure, if the distance between the two shoulders of the bearing is wider than the distance between the two shoulders of the bearing, a positive gap will be generated and play will occur in the axial direction. . On the other hand, if the negative clearance is too large, the clearance in the bearing may be reduced or deformed, resulting in an increase in rotational torque or heat generation during rotation. Therefore, it is desirable that there is no dimension between the two bearing shoulders and the housing mounting shoulder, or an appropriate negative clearance state, but it is very difficult to manage the dimensions to adjust to the appropriate dimension.
JP 2005-83474 A

  Therefore, the present inventors eliminate the axial backlash of the bearing by tightening the axial fixation on the bearing side that receives the axial load to the housing using a tightening nut having an external thread on the outer peripheral surface, and troublesome dimensional control. I tried to make it unnecessary. FIG. 6 is a longitudinal sectional view of the electric linear actuator of the prototype.

  The electric linear actuator B shown in FIG. 6 includes an electric motor 2 attached to the housing 1, a power transmission gear 3 fixed to the output shaft 2 a of the electric motor 2, and a power transmission that meshes with the power transmission gear 3. A rotary nut 5 formed with a gear 4, a screw shaft 7 fitted and inserted into the rotary nut 5 via a number of balls 6, and a linear clutch 8 connected to one end of the screw shaft 7 are provided. Yes. The power transmission gear 3 and the driven transmission gear 4 constitute a power transmission means for the rotating nut 5.

The rotating nut 5 is rotatably supported by a pair of rolling bearings 9 and 10 on both sides of the gear 4, and a helical thread groove 5 a is formed on the inner periphery thereof. On the other hand, on the outer periphery of the screw shaft 7, a spiral screw groove 7a is formed corresponding to the screw groove 5a, and a large number of balls 6 are accommodated in a freely rollable manner between these screw grooves 5a, 7a. The rotating nut 5, the ball 6 and the screw shaft 7 constitute a ball screw mechanism. When the electric motor 2 is operated, the rotating nut 5 is rotated through the power transmission gear 3 and the driven transmission gear 4 along with the rotation of the output shaft 2 a, and the screw shaft 7 is rotated by the rotation of the rotating nut 5. Instead, it moves in the axial direction (left and right in the figure). That is, this ball screw mechanism converts the rotational motion of the output shaft 2 a into the axial motion of the screw shaft 7.

  The housing 1 is composed of two divided housings 11 and 12, and a nut arrangement space 1 a is formed by the divided housings 11 and 12, and a ball screw mechanism is accommodated in the nut arrangement space 1 a. In addition, the rotating nut 5 is rotatably supported by the rolling bearings 9 and 10 that are fitted to the inner peripheral surfaces of the circular recesses 11a and 12a formed in the divided housings 11 and 12, respectively. Further, the bearing 10 is axially faced in the circular recess 12a by screwing and tightening a tightening nut 13 having an external thread formed on the outer peripheral surface to an internal thread 12b formed on the inner peripheral surface of one circular recess 12a. The axial backlash of the bearings 9 and 10 is eliminated. FIG. 6 shows a state in which the tightening nut 13 is loosened. In this state, there is a difference (L1-L2) between the bearing shoulder dimension L1 and the housing shoulder dimension L2. This difference becomes the axial backlash of the bearings 9 and 10, but by tightening the tightening nut 13, this difference (L1-L2) becomes zero and there is no backlash.

  In the example of FIG. 6, since the axial play of the bearing is substantially eliminated, it is effective for suppressing an increase in rotational torque and heat generation at the time of rotation, but when the tightening nut 13 is loosened by a vibration load. The components of the bearing and ball screw mechanism are swung in the axial direction by the vibration load, and the components collide with each other. Although it is possible to reinforce and fix the tightening nut 13 with an adhesive such as Loctite, it is not sufficient in terms of reliability and assembly workability, and there is still room for improvement.

  An object of the present invention is to provide an electric linear actuator that stably eliminates axial play of a bearing that supports a rotating nut.

The electric linear actuator according to the present invention transmits the rotation of the electric motor installed in the housing to the rotating nut of the ball screw mechanism through the power transmission means, and converts it into a linear motion of the screw shaft of the ball screw mechanism. in the actuator, the rotation nut of the ball screw mechanism, rotatably supported by a pair of rolling rising bearing that match fitted to the inner peripheral surface of the circular recess provided in the housing, of the pair of bearings, the rolling the output end side of the screw shaft is bearing receiving the axial load, the pre-Symbol circular recess rolling rising bearing of the output end side of the inner circumferential surface before Symbol screw shaft is screwed into the female screw portion formed in the A clamping nut that presses against the axially facing surface in the circular recess is provided, and a crimping piece is provided on the open edge of the circular recess of the housing, and this clamping piece is provided on the width surface of the clamping nut. The caulked characterized in was in the recess.

  According to this configuration, the rotation of the electric motor is transmitted via the power transmission means to the rotating nut supported by the rolling bearing that is fitted to the inner peripheral surface of the circular recess provided in the housing. The nut rotates. The rotation of the rotary nut is converted into a linear motion of the screw shaft of the ball screw mechanism. The rolling bearing that supports the rotating nut is pressed against the axially facing surface in the circular recess by a tightening nut that is screwed into the female thread formed on the inner peripheral surface of the circular recess of the housing. . And this clamping nut is caulked by the vibration load accompanying the rotation of the bearing because the crimping piece provided at the opening edge of the circular recess of the housing is caulked in the recess provided in the width surface of the clamping nut. And the above-mentioned play prevention is stably maintained.

In this invention, the rotating nut has a gear that constitutes the power transmission means projecting to the outer periphery in the middle of the width direction on the outer peripheral surface, and the housing is formed by a pair of circular recesses that are opposed to both sides of the gear. A nut arrangement space is formed, and the rotating nut is rotatably supported on both sides of the gear by a plurality of rolling bearings that are fitted into the pair of circular recesses, respectively, You may make it provide in one circular recessed part of said pair of circular recessed parts.
According to this configuration, the axial direction of the rolling bearing that rotatably supports the portions on both sides of the gear of the rotating nut by the tightening nut and the crimping piece provided in one of the pair of circular recesses of the housing. The backlash is eliminated, and the tightening nut is not loosened.

  The electric linear actuator of the present invention can be used for driving a clutch of a vehicle such as an automobile. As described above, when used for driving a clutch of a vehicle such as an automobile, the axial load is cut off by the clutch, and the reverse input torque is not transmitted to the motor, thereby increasing the size of the electric motor and increasing the power consumption. Instead, an efficient actuator is constructed.

The electric linear actuator according to the present invention transmits the rotation of the electric motor installed in the housing to the rotating nut of the ball screw mechanism through the power transmission means, and converts it into a linear motion of the screw shaft of the ball screw mechanism. in the actuator, the rotation nut of the ball screw mechanism, rotatably supported by a pair of rolling rising bearing that match fitted to the inner peripheral surface of the circular recess provided in the housing, of the pair of bearings, the rolling the output end side of the screw shaft is bearing receiving the axial load, the pre-Symbol circular recess rolling rising bearing of the output end side of the inner circumferential surface before Symbol screw shaft is screwed into the female screw portion formed in the A clamping nut that presses against the axially facing surface in the circular recess is provided, a crimping piece is provided at the opening edge of the circular recess of the housing, and this clamping piece is provided on the width surface of the clamping nut. Because it as crimping the resulting recess, without increasing the number of parts is made possible relatively inexpensive construction with reliable clamping nut and axial fixation of the bearing. This eliminates the need to strictly manage the dimensional difference between the bearing shoulder dimension and the housing mounting shoulder dimension, which improves actuator productivity and increases the axial load of pushing and pulling on the actuator shaft end. Even in a loaded situation, there is no mounting play, and it is possible to prevent loosening of parts. For this reason, the generation of sound and vibration due to an increase in looseness is prevented, the component parts are not damaged, and the reliability as an actuator is improved.

  An embodiment of the present invention will be described with reference to FIGS. The electric linear actuator A shown in FIG. 1 has the same basic configuration as the electric linear actuator B shown in FIG. That is, the electric linear actuator A of this embodiment includes an electric motor 2 attached to the housing 1, a power transmission gear 3 fixed to the output shaft 2 a of the electric motor 2, and a gear engaged with the power transmission gear 3. A rotary nut 5 in which a power transmission gear 4 is formed, a screw shaft 7 fitted into the rotary nut 5 via a number of balls 6, and a linear clutch 8 connected to one end of the screw shaft 7. I have. The tip end side of the output shaft 2a is rotatably supported by the housing 1 by a rolling bearing 2b. The driven transmission gear 4 is formed so as to project in the middle in the width direction on the outer peripheral surface of the rotary nut 5, and the power transmission gear 34 and the driven transmission gear 4 constitute a power transmission means 34 of the rotary nut 5. .

  The rotary nut 5 is rotatably supported by a pair of rolling bearings 9 and 10 on both sides of the gear 4 and has a thread groove 5a formed on the inner periphery thereof. On the other hand, a screw groove 7a is formed on the outer periphery of the screw shaft 7 so as to correspond to the screw groove 5a, and a large number of balls 6 are rotatably accommodated between these screw grooves 5a, 7a. The rotating nut 5, the ball 6 and the screw shaft 7 constitute a ball screw mechanism 50. When the electric motor 2 is actuated, the rotation nut 5 rotates through the power transmission gear 3 and the driven transmission gear 4 as the output shaft 2a rotates, and the rotation of the rotation nut 5 causes the ball 6 to become thread grooves 5a, 7a. The screw shaft 7 moves in the axial direction (left-right direction in the figure) without rotating the shaft. That is, the ball screw mechanism 50 converts the rotational motion of the output shaft 2 a into the axial motion of the screw shaft 7.

  The housing 1 is composed of two divided housings 11 and 12. The split housings 11 and 12 are provided with a pair of circular recesses 11a and 12a that are opposed to both sides of the gear 4, and a nut arrangement space 1a is formed by the pair of circular recesses 11a and 12a. The ball screw mechanism 50 is housed in the nut arrangement space 1a. Rolling bearings 9 and 10 are fitted to the inner peripheral surfaces of the circular recesses 11a and 12a, and the rotating nut 5 is rotatably supported by the rolling bearings 9 and 10. Furthermore, by tightening and tightening a tightening nut 13 having a male threaded portion 13a formed on the outer peripheral surface of the female threaded portion 12b formed on the inner peripheral surface of one circular concave portion 12a, the rolling bearing 10 is moved into the circular recessed portion 12a. The axial backlash of the pressing bearing 10 is eliminated from the axially facing surface.

  On the opening edge of the circular recess 12a of the divided housing 12, a large number of crimping pieces 12c are projected in the axial direction at equal intervals along the circumferential direction. A pocket 12d as a crimping allowance for the crimping piece 12c is formed behind each crimping piece 12c, that is, on the outer diameter side. In addition, a large number of recesses 13b corresponding to the respective crimping pieces 12c are formed radially on the outer peripheral side width surface of the tightening nut 13.

  A procedure for positioning and fixing the rolling bearing 10 in the axial direction in the circular recess 12a of one divided housing 12 will be described. As shown in FIG. 3, the rolling bearing 10 is fitted into the circular recess 12a, and the tightening nut 13 is formed from the opening side of the circular recess 12a, and the male screw portion 13a is formed on the inner peripheral surface of the circular recess 12a. The screw 10 is screwed into the female screw portion 12b, and the bearing 10 is pressed against the axially facing surface in the circular recess 12a. Next, the crimping piece 12 c is refracted in the inner diameter direction and is crimped into the recess 13 b of the tightening nut 13. 5, 3 and 2 show the state before caulking, and the solid line portion in FIGS. 1 and 2 shows the state where the caulking piece 12c is caulked in the recess 13b of the clamping nut 13. Is shown. Thus, without using set screws or the like, loosening of the tightening nut 13 can be prevented by tightening the tightening piece 12c to the tightening nut 13, and the axial backlash and bearing of the bearing 10 can be prevented without increasing the number of parts. The loosening of the tightening nut 13 can be suppressed.

Then, the rotating nut 5 of the ball screw mechanism 50 is fitted to the circumferential recess 11a of the other divided housing 11 via the rolling bearing 9, and is fitted and fixed to the circumferential recess 12a of the divided housing 12 as described above. The rolling bearing 10 is fitted to the part of the rotating nut 5 opposite to the above, and the two divided housings 11 and 12 are combined using a jig or the like (not shown). Thereby, as shown in FIG. 1, the electric linear actuator A in which the ball screw mechanism 50 is housed in the nut arrangement space 1a formed by the circular recesses 11a and 12a is configured. By this combination, the rolling bearings 9 and 10 are fixed in the nut arrangement space 1a via the rotary nut 5 without being loose in the axial direction.

In FIG. 1, a linear clutch 8 is connected to one end of the screw shaft 7 via a transmission pin 14. The linear clutch 8 is fitted into the divided housing 12 and is slidably inserted into an outer ring 15 having a cylindrical inner peripheral surface and a cylindrical holding portion 16 formed at one end of the screw shaft 7. It is accommodated between the output shaft 17, a circumferential groove-shaped engagement recess 17 a formed on the outer periphery of the output shaft 17 and having a gently inclined surface, and the engagement recess 17 a and the inner peripheral surface 15 a of the outer ring 15. And an engagement element 18 composed of a plurality of balls. An annular space 19 is formed between the engagement concave portion 17a of the output shaft 17 and the inner peripheral surface 15a of the outer ring 15, and a plurality of engagements are provided via elastic members 20 made of compression springs in pockets of a holding portion (not shown). The joints 18 are held at equal intervals in the circumferential direction and at neutral positions in the axial direction. Here, a single-row ball is illustrated as the engagement element 18, but the present invention is not limited to this, and a double-row ball may be used. A roller may be used as the engagement element 18.
The transmission pin 14 is inserted into a pin insertion hole 17b formed in the output shaft 17 with a predetermined gap.

The linear clutch 8 having this configuration has the same effect as the linear clutch disclosed in Patent Document 1, and the axial movement of the output shaft 17 is smoothly performed. Even when a load in the direction is applied, no reverse input torque is generated in the electric motor 2 via the ball screw mechanism 50. That is, the screw shaft 7 moves in the same direction as the output shaft 17 moves in the axial direction, and the nut 5 does not rotate as the screw shaft 7 moves in the axial direction. Therefore, it is possible to reduce the impact on the electric motor 2 and to prevent the electric motor 2 from generating heat or increasing power consumption.
Thus, the electric linear actuator A in this embodiment, using the driving of the clutch of a vehicle such as an automobile, without requiring a conventional such complex electrical control, axial fixation of the rolling bearing 9 and 10 gas motor Combined with being done stably and continuously without sticking, its suitability increases.

  As the rolling bearings 9 and 10, roller bearings may be used in addition to the angular ball bearings as illustrated. In the example shown in the figure, a single row rolling bearing is used, but a double row rolling bearing may be used. In addition, the overall shape of the actuator A is not limited to the illustrated example.

1 is a longitudinal sectional view showing an embodiment of an electric linear actuator according to the present invention. It is an enlarged view of the II section in FIG. It is a longitudinal cross-sectional view which shows a part of component of the electric linear actuator. In FIG. 3, it is a top view of the clamping nut seen from arrow IV. It is an enlarged view of the V section in FIG. It is a longitudinal cross-sectional view which shows the prototype of the electric linear actuator which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Housing 1a ... Nut arrangement space 2 ... Electric motor 3 ... Power transmission gear 4 ... Power transmission gear 34 ... Power transmission means 5 ... Rotation nut 50 ... Ball screw mechanism 7 ... Screw shaft 8 ... Linear clutch 9 ... Rolling bearing 10 ... Rolling bearing 11a ... Circular recess 12a ... Circular recess 12b ... Female thread 12c ... Clamping piece 13 ... Clamping nut 13b ... Concave A ... Electric linear actuator

Claims (3)

In the electric linear actuator that transmits the rotation of the electric motor installed in the housing to the rotation nut of the ball screw mechanism through the power transmission means and converts it into the linear motion of the screw shaft of the ball screw mechanism.
Rotation nut of the ball screw mechanism, the rotatably supported by a pair of rolling rising bearing that match fitted to the inner peripheral surface of the circular recess provided in the housing, of the pair of bearings, of the screw shaft the output end of the rolling bearing is a bearing that receives the axial load, before Symbol said bearing rising rotation of the output end side of the front Symbol screw shaft is screwed into the female screw portion formed in an inner peripheral surface of the circular recess circular recess A clamping nut to be pressed against the axially facing surface is provided, a crimping piece is provided at the opening edge of the circular recess of the housing, and the crimping piece is crimped into a recess provided in the width surface of the clamping nut. A feature of the electric linear actuator.   2. The pair of circular recesses according to claim 1, wherein the rotating nut has a gear that constitutes the power transmission means protrudes to the outer periphery in the middle of the outer peripheral surface in the width direction, and the housing is positioned opposite to both sides of the gear. A nut arrangement space is formed by the rotary nut, and the rotary nut is rotatably supported at both sides of the gear by a plurality of rolling bearings respectively fitted into the pair of circular recesses. An electric linear actuator provided in one of the pair of circular recesses.   3. The electric linear actuator according to claim 1, wherein the electric linear actuator is used for driving a clutch of a vehicle such as an automobile.

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