JP5180023B2 - Electric linear actuator - Google Patents

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. ing. 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.

  For example, as a parking lock device that engages and locks a parking pole on a parking gear provided on an output shaft of a mission when the vehicle is stopped, an electric parking lock device that engages the parking gear with an electric linear actuator is used. It is known (for example, refer to Patent Document 1).

  As shown in FIG. 5, the electric linear actuator includes an electric motor 51 attached to a housing 50, a screw shaft 52 supported so as to be rotatable with respect to the housing 50 and not movable in the axial direction, and the screw shaft. A ball screw 54 including a nut 53 which is extrapolated through a number of balls (not shown) 52 and supported so as not to rotate and to be movable in the axial direction is disposed in parallel with the screw shaft 52. On the other hand, a rod shaft 55 supported so as to be movable in the axial direction, and a connecting member 56 having a base end portion 56a fixed to a substantially middle portion of the rod shaft 55 and a tip end portion 56b engaged with the outer periphery of the nut 53, The rotational movement of the electric motor 51 is converted into the axial movement of the rod shaft 55 via the ball screw 54.

  The distal end portion 56 b of the connecting member 56 connected to the rod shaft 55 is engaged in a concave portion 57 formed in the nut 53, and for example, the nut 53 is rotated by the positive rotation of the screw shaft 52 driven by the electric motor 51. Is linearly moved in the right direction in the figure, the distal end portion 56b of the connecting member 56 is pressed against one wall surface 57a of the concave portion 57, so that the connecting member 56 is connected in accordance with the linear movement in the right direction. The rod shaft 55 that is moving linearly moves to the right (when parking is locked).

  On the other hand, when the nut 53 moves linearly in the left direction in the drawing due to the reverse rotation of the screw shaft 52 driven by the electric motor 51, the leading end portion 56b of the connecting member 56 is pressed against the other wall surface 57b of the concave portion 57. The rod shaft 55 linearly moves in the left direction in accordance with the linear movement of the connecting member 56 in the left direction (when the parking lock is released).

  When the nut 53 is not energized to the electric motor 51, the ball accommodated between the screw shaft 52 and the nut 53 circulates infinitely, so that the screw shaft 52 rotates while the screw shaft 52 rotates. Smooth linear movement is possible along the direction. That is, the parking lock ON and OFF can be operated manually.

In these conventional electric linear actuators, the actuators used for parking lock mechanisms, transmissions, engines, etc. of the conventional patents are mechanically forced when the ball screw moves directly beyond the normal operating range without using the sensors. Since it needs to be stopped, a stopper mechanism is often provided to prevent ball screw overrun.
As a stopper mechanism, for example, Patent Document 2 discloses a cylinder device that uses a ball screw mechanism for pushing out brake fluid during braking of a vehicle or the like. In this cylinder device, in the unlikely event that the nut overruns, the leaf spring provided between the bearing that supports the screw shaft and the nut reduces the collision energy of the nut by elastic deformation and suppresses damage to the nut and case. doing.

In addition, the ball screw overrun prevention mechanism disclosed in Patent Document 3 uses a coil spring and a plate-like stopper to reduce the collision force of the nut, so that an excessive force is not applied to the ball screw or the motor. Yes.
JP 2006-322490 A JP 2007-40397 A JP 59-196152

  However, when trying to restrict the movement of the nut with these conventional stopper mechanisms, a stopper mechanism including an elastic member such as a leaf spring and a coil spring that alleviates the impact, and an attaching means for attaching the stopper mechanism to the housing The size in the axial direction is increased, and a desired stroke cannot be obtained with a compact structure. Conversely, if a desired stroke is to be obtained, the size must be increased. Further, the conventional stopper mechanism has a large number of parts, increases the number of assembly steps, and increases the cost.

  An object of the present invention is to provide an electric linear actuator provided with a stopper mechanism that eliminates such conventional problems, reduces the number of parts such as a stopper member, and does not increase the axial size. .

In order to achieve such an object, the invention according to claim 1 of the present invention is an electric motor attached to a housing, and is coaxially coupled to a main shaft of the electric motor, and is rotatable with respect to the housing. A screw shaft that is supported so as not to move in the axial direction, and a ball screw that includes a nut that is extrapolated to the screw shaft via a large number of balls and is supported so as not to rotate and that can move in the axial direction. A rod shaft that is disposed in parallel with the housing and supported so as to be axially movable with respect to the housing, and a connecting member that connects a substantially intermediate portion of the rod shaft and a support shaft that projects to the outer periphery of the nut, In the electric linear actuator in which the rotational movement of the electric motor is converted into the axial movement of the rod shaft via the nut, the nut is connected to a nut-side connecting portion that engages with the support shaft of the connecting member. The section provided, the stopper portion on both end surfaces of the nut width direction of the nut-side connecting portion of the connecting member is constituted by a convex portion slightly partially protrudes from the nut width stopper of the housing side the stopper portion Abutting on the abutting portion to restrict axial movement of the nut, the support shaft is disposed symmetrically and orthogonally with respect to the axis of the screw shaft, and includes a plane including the rod shaft and the screw shaft. And the direction perpendicular to both axes is the height direction, the support shaft is in contact with the connecting member at the same height as the axis of the screw shaft, and the stopper portion and the stopper contact portion are in contact with each other. The contact position is provided at the same height as the axis of the screw shaft.

As described above, the electric motor attached to the housing, the screw shaft that is coaxially coupled to the main shaft of the electric motor, and is supported so as to be rotatable with respect to the housing and not movable in the axial direction, and the screw shaft A ball screw consisting of a nut that is extrapolated via a large number of balls and supported so as to be non-rotatable and axially movable, and is arranged in parallel to the screw shaft and is axially movable with respect to the housing And a connecting member that connects a substantially intermediate portion of the rod shaft and a support shaft projecting to the outer periphery of the nut, and the rotational movement of the electric motor is caused by the rotation of the rod shaft via the nut. In the electric linear actuator that is converted into the axial movement, a stopper is provided on the nut-side connecting portion that engages the support shaft of the connecting member, and the stopper is connected to the nut-side link of the connecting member. On both end surfaces of the nut width direction of the parts is constituted by a convex portion slightly partially protrudes from the nut width, the stopper portion is brought into contact with the stopper contact portion of the housing-side restricting the axial movement of the nut At the same time, the support shaft is arranged symmetrically and orthogonally to the axis of the screw shaft, and when the height direction is parallel to the plane including the rod shaft and the screw shaft and perpendicular to both axes, the support shaft is The structure is in contact with the connecting member at the same height as the axis of the screw shaft, and the contact position between the stopper part and the stopper contact part is provided at the same height as the axis of the screw shaft. No space is required for the stopper portion in the moving direction, and a desired stroke can be obtained without increasing the size in the axial direction. In addition, the reaction line of the reaction force when the stopper part comes into contact with the mating member on the housing side is the axial direction of the screw shaft, so that moment load does not act on the nut. Thus, no bending load is applied to the rod shaft.

Further, as in the invention described in claim 2 , if the stopper portion is integrally formed with the connecting member, an increase in the number of parts and assembly man-hours can be prevented, and an increase in cost can be avoided. Further, by integrating the stopper portion with the connecting member, the stopper portion need not be fixed and a highly reliable stopper structure is obtained.

Further, as in the third aspect of the invention, a compact design is possible by using the inner wall of the housing as the stopper contact portion on the housing side.

If the stopper portion is longer in the radial direction than the support shaft of the nut as in the invention described in claim 4 , the distance between the contact surface between the stopper portion and the stopper abutting portion from the axis of the screw shaft Can be expanded as much as possible. Therefore, when the stopper part collides, even if rotational force acts on the connecting member from the nut side, the distance from the axis of the screw shaft is large, so the contact friction force between the stopper part and the stopper contact part is increased. It can be suppressed, and the return after overrun is easy without the stopper part self-locking.

An electric linear actuator according to the present invention includes an electric motor attached to a housing, and a screw shaft that is coaxially coupled to the main shaft of the electric motor and is rotatably supported with respect to the housing and not axially movable. And a ball screw composed of a nut that is extrapolated to the screw shaft through a number of balls and is supported so as to be non-rotatable and movable in the axial direction, and disposed parallel to the screw shaft, And a connecting member that connects a substantially intermediate portion of the rod shaft and a support shaft projecting to the outer periphery of the nut, and the rotational movement of the electric motor is performed via the nut. In the electric linear actuator that is converted into the axial movement of the rod shaft, a stopper is provided on the nut-side coupling portion that engages with the support shaft of the coupling member. Tsu path section on both end surfaces of the nut width direction of the nut-side connecting portion of the connecting member is constituted by a convex portion slightly partially protrudes from the nut width, the stopper portion to the stopper abutting portion of the housing side The support shaft is arranged symmetrically and orthogonally to the axis of the screw shaft, and is parallel to a plane including the rod shaft and the screw shaft. When the direction perpendicular to the axis is the height direction, the support shaft is in contact with the connecting member at the same height as the axis of the screw shaft, and the contact position between the stopper portion and the stopper contact portion is Since it is configured to be provided at the same height as the axis of the screw shaft, there is no need for a space for the stopper portion in the nut moving direction, and a desired stroke can be obtained without increasing the size in the axial direction. it can. In addition, the reaction line of the reaction force when the stopper part comes into contact with the mating member on the housing side is the axial direction of the screw shaft, so that moment load does not act on the nut. Thus, no bending load is applied to the rod shaft.

An electric motor attached to the housing, a screw shaft that is coaxially coupled to the main shaft of the electric motor, is supported so as to be rotatable with respect to the housing and is not movable in the axial direction, and a number of balls on the screw shaft A ball screw made of a nut that is extrapolated through the shaft and is supported so as to be non-rotatable and movable in the axial direction, and is arranged in parallel with the screw shaft and supported so as to be movable in the axial direction with respect to the housing. A rod shaft, and a connecting member that connects a substantially intermediate portion of the rod shaft and a support shaft protruding to the outer periphery of the nut, and the rotational motion of the electric motor is caused to move in the axial direction of the rod shaft via the ball screw. In the electric linear actuator that is converted into a stopper, a stopper portion is provided on the nut side connecting portion that engages with the support shaft of the connecting member, and the stopper portion is connected to the nut side link of the connecting member. On both end surfaces of the nut width direction of the parts is constituted by a convex portion slightly partially protrudes from the nut width, the stopper portion is brought into contact with the stopper contact portion of the housing-side restricting the axial movement of the nut In addition, the support shaft is disposed symmetrically and orthogonally to the axis of the screw shaft, and a direction perpendicular to both axes in parallel to a plane including the rod shaft and the screw shaft is defined as a height direction. The support shaft is in contact with the connecting member at the same height as the axis of the screw shaft, and the contact position between the stopper portion and the stopper contact portion is provided at the same height as the axis of the screw shaft.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a front cross-sectional view showing an embodiment of an electric linear actuator according to the present invention, and FIG. 2 is a main cross-sectional view when the stopper portion of the actuator in FIG. 1 is provided at a position shifted from the axis. .

  The electric linear actuator 1 includes an electric motor 3 attached to a housing 2, a screw shaft 4 supported so as to be rotatable with respect to the housing 2 and not movable in the axial direction, and a number of unillustrated screw shafts 4. A ball screw 7 including a nut 5 that is extrapolated through the ball and supported so as to be non-rotatable and axially movable, and a rod shaft 8 provided in parallel with the screw shaft 4 of the ball screw 7; A connecting member 9 that connects a substantially intermediate portion of the rod shaft 8 and a pair of support shafts 12 projecting opposite to each other to the outer periphery of the nut 5 is provided, and the rotational movement of the electric motor 3 is connected to the rod shaft via the ball screw 7. It is configured to be converted into 8 axial movements.

  The housing 2 includes a motor-side end wall 21 to which the electric motor 3 is attached, a counter-motor-side end wall 22 opposite to the electric motor 3, and a connecting wall 23 that connects the motor-side end wall 21 and the counter-motor-side end wall 22. The screw shaft 4 is configured to be bridged between the motor side end wall 21 and the non-motor side end wall 22.

  One shaft end 4a of the screw shaft 4 can be transmitted to the main shaft 3a of the electric motor 3 via a serration or the like in the shaft hole 21a provided in the motor side end wall 21 and can be attached and detached in the axial direction. Is bound to. The inner diameter of the shaft hole 21a is larger than the screw shaft 4 and the main shaft 3a, and does not interfere with the screw shaft 4 and the main shaft 3a. Further, the other shaft end portion 4 b of the screw shaft 4 is not movable in the axial direction through the rolling bearing 10 in the shaft hole 22 a provided in the non-motor side end wall 22 of the housing 2, and is attached to the housing 2. On the other hand, it is rotatably supported. The shaft hole 22a has a larger diameter than the screw shaft 4, and the rolling bearing 10 is mounted in a bearing hole 22b formed on the outer opening side of the shaft hole 22a.

  The rod shaft 8 is inserted into insertion holes 21c and 22c formed in the motor-side end wall 21 and the non-motor-side end wall 22 of the housing 2, and is supported through the bearings 11 and 11 so as to be axially movable. The intermediate part is fixed to the connecting member 9. At both ends of the rod shaft 8, connecting portions 8a and 8b made of yokes connected to a push-pull cable or the like are provided.

The support shafts 12 projecting from the outer periphery of the nut 5 are cylindrical and are provided in pairs on both sides of the nut 5, and are arranged orthogonally to the axis of the screw shaft 4 symmetrically by 180 °.
The connecting member 9 has a shape including an arm portion 9a connected to the rod shaft 8 and a gate-shaped nut-side connecting portion 9b connected to the support shaft 12 of the nut. The support shaft 12 is a nut. It interlock | cooperates in the state fitted in the recessed part 9c of the side connection part 9b. Assuming that the direction parallel to the plane including the rod shaft 8 and the screw shaft 4 and perpendicular to both the shafts is the height direction, the support shaft 12 is recessed at the nut-side connecting portion 9b at the same height as the axis of the screw shaft 4. The structure is in contact with the left and right inner surfaces of 9c.

  On the other hand, a stopper portion 13 is provided on the nut-side connecting portion 9b that engages with the support shaft 12 of the connecting member 9, and when the overrun is caused by an abnormal operation, the stopper portion 13 is opposite to the motor-side end wall 21 on the housing 2 side. It is configured to abut against the inner wall of the motor side end wall 22 to restrict the axial movement of the nut 5. The stopper portion 13 is formed by convex portions slightly protruding from the nut width on the left and right side surfaces of the nut-side connecting portion 9 b of the connecting member 9, and the motor-side end wall 21 and the counter-motor-side end wall 22 of the housing 2. It collides with the inner wall of and acts as a stopper. The stopper portion 13 abuts on the left and right side edge portions of the shaft holes 21a and 22a of the motor side end wall 21 and the counter motor side end wall 22, and is the same as the shaft center of the support shaft 12 of the nut 5 and the screw shaft 4. It is set to height.

In the present embodiment, the housing 2 is made of an aluminum casting, and as it is, the inner walls of the motor side end wall 21 and the counter motor side end wall 22 with which the stopper portion 13 abuts are cast and have a draft angle. There is a risk of twisting when the stopper portion 13 collides. In order to prevent this twist, the gradient portion is removed by machining, and the inner walls of the motor-side end wall 21 and the non-motor-side end wall 22 of the housing 2 are parallel surfaces. Further, the connecting member 9 has a surface hardness increased by heat treatment, whereas the housing 2 side is made of an aluminum material and a soft material, so that the impact force at the time of collision is reduced.
The stopper portion 13 of the connecting member 9 is longer in the radial direction than the support shaft 12 of the nut 5, and one end of the connecting member 9 is connected to the rod shaft 8 that is supported so as to be movable in the axial direction. Thus, when the stopper portion 13 comes into contact with the inner wall of the housing 2, the screw portion does not self-lock due to the bending generated in the connecting member 9 with the ball screw shaft core as a fulcrum, and the return after overrun is facilitated. .
In addition, since the connecting member 9 has an uneven shape having the convex stopper portion 13, it becomes a costly part in machining, but it can be manufactured at a relatively low cost by employing a lost wax manufacturing method or the like. is there.

  In the electric linear actuator having the above configuration, when the electric motor 3 is energized, for example, when the nut 5 linearly moves in the right direction in the drawing due to the normal rotation of the main shaft 3a driven by the electric motor 3, the support shaft 12 The connecting member 9 to be connected linearly moves in the right direction, and the rod shaft 8 linearly moves in the right direction as the connecting member 9 moves. On the other hand, when the nut 5 moves linearly in the left direction in the figure due to the reverse rotation of the main shaft 3a driven by the electric motor 3, the connecting member 9 moves linearly in the left direction. As the connecting member 9 moves, the rod shaft 8 moves to the left. Move straight in the direction.

  In normal operation, the nut 5, the connecting member 9, and the rod shaft 8 repeat reciprocating motion in the axial direction without interference between the inner space of the housing 2, that is, between the motor side end wall 21 and the non-motor side end wall 22. In the case of overrun due to abnormal operation, the nut 2 on the screw shaft 4 continues to move to the right or left within the movable range, but the stopper portion 13 provided on the nut side connecting portion 9b of the connecting member 9 The movement of the rod shaft 8 can be restricted by mechanically colliding with the inner wall of the motor side end wall 21 or the non-motor side end wall 22.

  Since the convex stopper portion 13 is provided on the connecting member 9 in this way, a space for the stopper portion is unnecessary in the moving direction of the nut 5, and a desired stroke can be obtained without increasing the size in the axial direction. it can. Further, since the stopper portion 13 is provided at the same height as the axis of the screw shaft 4, no bending load is applied to the rod shaft 8 via the connecting member 9 when the stopper is in contact.

Here, for comparison, FIG. 2 shows a schematic diagram when the stopper position is provided at a position deviated from the axis.
2, the stopper portion 13 ′ in FIG. 2 is an end portion on the rod shaft side of the nut side connecting portion 9 b of the connecting member 9, and the shafts of the motor side end wall 21 and the counter motor side end wall 22 of the housing 2. Upper edge portions of the holes 21a and 22a serve as stopper contact portions.
Thus, when the position of the stopper portion 13 ′ is deviated from the shaft center, a reaction force acts to mechanically stop the right movement at the stopper position, and a moment load with the stopper position as a fulcrum is applied to the rod shaft 8. Will be loaded. On the other hand, in the example shown in FIG. 1, since the stopper portion 13 of the connecting member 9 is provided at the same height as the axis of the screw shaft 4, the connecting member 9 is configured so that the thrust of the ball screw and the stopper at the time of collision. The bending force is not applied to the rod shaft 8 connected to the connecting member 9 because the bending is not caused by the moment generated by the difference in the height of the reaction force in the portion 13.

On the other hand, in the example shown in FIG. 1, when the stopper portion 13 collides with the motor side end wall 21 and the non-motor side end wall 22 of the housing 2, a rotational force acts on the connecting member 9 from the nut 5 side. Is bent in the rotation direction of the nut 5. While the impact is mitigated by this bending, the stopper portion 13 bites into the motor side end wall 21 or the counter motor side end wall 22 of the housing 2, and the contact frictional force of the stopper portion 13 increases, so that the self locking at the stopper portion 13 is prevented. May occur.
3 and 4 show a modification of the first embodiment configured to prevent the occurrence of self-locking.
When compared with FIG. 1, in the example shown in FIG. 1, although not particularly illustrated, the stopper portion 13 is set to be the same length or short in the radial direction with respect to the support shaft 12 of the nut 5. Furthermore, the width of the stopper portion 13 in the height direction (the direction parallel to the plane including the rod shaft 8 and the screw shaft 4 and perpendicular to both axes) is about half of the diameter of the screw shaft 4.
In contrast, in the modification shown in FIGS. 3 and 4, the stopper portion 13 is longer in the radial direction than the support shaft 12 of the nut 5, and the distance from the axis of the stopper portion 13 is as large as possible. I'm taking it. Further, the width of the stopper portion 13 in the height direction (the direction parallel to the plane including the rod shaft 8 and the screw shaft 4 and perpendicular to both axes) is expanded to substantially the same width as the diameter of the screw shaft 4.

In this way, the distance from the axial center of the screw shaft 4 on the contact surface S of the stopper portion 13 is the longest at the corner of the rectangular contact surface S as shown in FIG. On the other hand, the contact area can be increased as much as possible. Therefore, when the stopper portion 13 collides, a rotational force acts on the connecting member 9 from the nut 5 side, and even if the arm portion 9a of the connecting member 9 is bent as shown by a two-dot chain line in FIG. Since the distance from the shaft center of the shaft 4 is large and the contact area is large, an increase in the contact friction force of the contact surface S of the stopper portion 13 can be suppressed, and the occurrence of self-locking of the stopper portion 13 can be prevented. Can be easily restored after overrun. In FIG. 4, the arc-shaped arrow drawn concentrically about the axis of the screw shaft 4 described on the contact surface S indicates the direction of the friction torque acting upon return after overrun. .
Further, when the width in the height direction of the stopper portion 13 is larger than the diameter of the screw shaft 4, for example, when the corner portion of the stopper portion 13 comes into contact with one side, the axial force acting on the nut 5 from the screw shaft 4. Then, since the direction of the reaction force from the stopper portion 13 is shifted in the height direction in the same manner as in FIG.

As a comparative example of the embodiment of FIG. 1, an example in which the stopper position is shifted from the axis of the screw shaft as shown in FIG. 2 is shown. The example shown in FIG. 2 is not excluded, but is included in the concept of the present invention in that a stopper is provided on the connecting member.
Moreover, in the said Example, although the stopper part 13 and the connection member 9 were integrated, it is good also as another components instead of integral. If the connecting member 9 and the stopper portion 13 are integrally formed, the number of parts and the number of assembling steps are not increased, and an increase in cost can be avoided. Moreover, since there is no fixed part of the stopper part by integrating, a highly reliable stopper structure can be realized.

  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 electric linear actuator such as an electric parking lock device for locking a parking lock by engaging a pawl with a parking gear of an automobile.

It is a front sectional view showing one embodiment of an electric linear actuator concerning the present invention. FIG. 2 is a cross-sectional view of a principal part when a stopper portion of the actuator of FIG. 1 is provided at a position shifted from an axis. It is front sectional drawing which shows the modification of the electric linear actuator of FIG. It is the IV-IV sectional view taken on the line of FIG. It is a schematic front view of the conventional electric linear actuator.

Explanation of symbols

1 ... Electric linear actuator 2 ... Housing 21 ... Motor side end wall 21a・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Shaft hole 21c ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Through hole 22 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Non-motor side end wall 22a ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ Shaft hole 22b ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Bearing hole 22c ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Through hole 23 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・Connecting wall 3 ... Electric motor 3a ... Main shaft 4 ... Screw shaft 4a, 4b ... Shaft end 5 ... Nut 7 ... Ball screw 8 ...・ ・ ・ ・ ・ ・ ・ ・ Rod shafts 8a, 8b ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Connector 9 ・ ・ ・ ・ ・ ・······ Connecting member 9a ······························································ Nut side connecting portion 9c ... Recess 10 ... Rolling bearing 11 ... Bearing 12 ... Support shaft 13・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Stopper part S ・ ・ ・ ・ ・ ・ ・ ・ Contact

Claims (4)

An electric motor attached to the housing, a screw shaft that is coaxially coupled to the main shaft of the electric motor, is supported so as to be rotatable with respect to the housing and is not movable in the axial direction, and a number of balls on the screw shaft A ball screw made of a nut that is extrapolated through the shaft and is supported so as to be non-rotatable and movable in the axial direction, and is arranged in parallel with the screw shaft and supported so as to be movable in the axial direction with respect to the housing. A rod shaft, and a connecting member that connects a substantially intermediate portion of the rod shaft and a support shaft protruding to the outer periphery of the nut, and the rotational motion of the electric motor is changed to the axial motion of the rod shaft via the nut. In the electric linear actuator to be converted,
A stopper portion is provided on the nut-side connecting portion that engages with the support shaft of the connecting member, and this stopper portion is slightly partially smaller than the nut width on both end surfaces of the nut-side connecting portion of the connecting member in the nut width direction. Consists of projecting convex portions, the stopper portion is brought into contact with the stopper abutting portion on the housing side to restrict the axial movement of the nut, and the support shaft is symmetrical with respect to the axis of the screw shaft The connecting member is disposed at a right angle, and when the height direction is a direction parallel to a plane including the rod axis and the screw axis and perpendicular to both axes, the support shaft is at the same height as the axis of the screw axis. An electric linear actuator characterized in that the contact position between the stopper portion and the stopper contact portion is provided at the same height as the axis of the screw shaft.   The electric linear actuator according to claim 1, wherein the connecting member is formed by integrally forming a stopper portion.   The electric linear actuator according to claim 1, wherein the stopper contact portion on the housing side is an inner wall of the housing.   The electric linear actuator according to any one of claims 1 to 3, wherein the stopper portion is longer in the radial direction than the support shaft of the nut.

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