JP2008069862A - Electric linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric linear actuator to be able to obtain high reduction rate, and to make a device compact. <P>SOLUTION: A small gear 5b and a large gear 5a are formed in the right hand in a figure, and in the left hand in the figure in the outer peripheral surface of an intermediate gear 5 respectively. A cylindrical spot facing 5c is formed in a left hand end in a figure of the intermediate gear 5. A shaft end 5d left not drilled through is formed in the middle of the spot facing 5c. A roll bearing 12 is fitted in the shaft end 5d. The roll bearing 12 is arranged in the spot facing 5c. The roll bearing 12 is arranged in a cylindrical bearing case 13 having one end in the left hand of the figure blocked by a wall surface. A hole 13a is drilled through the almost middle of the wall surface of the bearing case 13. The hole 13a is press-fitted into a projection 2c formed in a housing 2a. <P>COPYRIGHT: (C)2008,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. 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.

  This ball screw mechanism includes a nut rotatably supported with respect to a housing, a screw shaft that is fitted in the nut and is movable in the axial direction, and a plurality of screw grooves formed in the nut and the screw shaft. Made up of balls. When the nut rotates, the ball rolls in the thread groove and the screw shaft moves in the axial direction.

An actuator using this ball screw mechanism includes an electric motor attached to a housing, a spur gear fixed to a motor shaft of the electric motor, and a nut integrally formed with a flange formed with teeth meshing with the spur gear. And a screw shaft inserted into the nut via a large number of balls, and a linear clutch connected to one end of the screw shaft. And the housing which installs them is divided into 2 so that a nut and a spur gear may be pinched | interposed.
JP 2005-83474 A

  When it is desired to increase the reduction ratio of the conventional actuator, it is necessary to increase the number of teeth of the spur gear on the nut side and decrease the number of teeth on the motor side. However, in this case, since the diameter of the flange portion of the nut increases, the apparatus becomes large.

  Therefore, there is a method of obtaining a large reduction ratio by arranging an intermediate gear between a spur gear on the nut side and a spur gear on the motor side and making the gear a two-stage structure. However, in order to make the device compact, it is necessary to reduce the distance between the center of the motor shaft and the screw shaft. In this case, the support bearing of the intermediate gear interferes with the support bearing of the nut. Also, even if the distance between the center of the motor shaft and the screw shaft is made slightly large so as not to interfere, a part of the mounting hole of the bearing of the intermediate gear is missing, so that a so-called oval state is formed, and the mounting error of the bearing Problems such as an increase in temperature, deformation of the housing, and early wear. Furthermore, there is a method of preventing interference by lowering the model number of the nut-side support bearing, but the load capacity is insufficient, which may cause a problem of early breakage. In the end, in order to obtain a large reduction ratio, the distance between the center of the motor shaft and the screw shaft must be increased.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electric linear actuator capable of obtaining a large reduction ratio and reducing the size of the apparatus.

  In order to achieve such an object, the present invention provides an electric motor attached to a housing and a motor shaft of the electric motor, which is disposed in parallel to the housing and is supported so as to be rotatable and non-movable in the axial direction with respect to the housing. And a nut that is inserted into the nut via a large number of balls and is supported so as to be non-rotatable and freely movable in the axial direction, and converts the rotational motion of the electric motor into axial motion. A screw mechanism and a reduction gear disposed between the nut of the ball screw mechanism and the motor shaft, and an output shaft is connected coaxially with the screw shaft, and a linear portion is connected in the vicinity of the connecting portion of the output shaft. In the electric linear actuator provided with the clutch, the reduction gear is configured, and a first gear formed on a flange provided on an outer periphery of the nut, and a second gear fixed to the motor shaft. An intermediate gear disposed between the vehicle and having a third gear meshing with the first gear and a fourth gear meshing with the second gear is fixed to the housing via two bearings. Thus, a configuration is adopted in which one of the bearings is disposed in a separate bearing case fixed to the housing.

  Thus, by providing the reduction gear with the intermediate gear having the third gear and the fourth gear, the gear can have a two-stage structure, so that a large reduction ratio can be obtained. In addition, by arranging one of the bearings that supports the intermediate gear in the bearing case, the bearing mounting portion is not in a missing circle state as in the past, and the bearing can be suitably supported on the housing. The apparatus can be made compact without causing problems such as increased bearing mounting errors, housing deformation, and early wear.

  Further, according to the present invention, the bearing case has a cylindrical shape whose one end is closed by a wall surface, a hole is formed in a substantially central portion of the wall surface, and the hole is formed in a convex portion provided in the housing. The bearing case can be fixed to the housing by press-fitting. Thereby, since a bearing case is fixed to a housing simply and firmly, the rolling bearing arrange | positioned in a bearing case can be supported suitably.

  Further, the present invention may be configured such that a counterbore portion that is wound in a cylindrical shape is provided at an end portion of the intermediate gear, and one of the bearings is accommodated in the counterbore portion. Thereby, since a bearing can be arrange | positioned inside a counterbore part, an apparatus can be made compact.

  Further, the present invention is configured such that one of the bearings for fixing the nut is housed in a circular hole provided in the housing, and the bearing is disposed on the back side of the wall surface of the bearing case. It is preferable to do. Thereby, the bearing which fixes a nut does not interfere with a bearing case, and a device can be made compact.

  An electric linear actuator according to the present invention includes an electric motor attached to a housing, and a nut that is arranged in parallel to the motor shaft of the electric motor and is rotatably supported with respect to the housing and not axially movable. A ball screw mechanism that has a screw shaft that is inserted into the nut via a large number of balls and that is non-rotatable and supported so as to be axially movable, and that converts the rotational motion of the electric motor into axial motion And a reduction gear disposed between the nut of the ball screw mechanism and the motor shaft, an output shaft is connected coaxially with the screw shaft, and a linear clutch is provided near the connecting portion of the output shaft. In the arranged electric linear actuator, the reduction gear is configured and fixed to the motor shaft and a first gear formed on a flange provided on an outer periphery of the nut. An intermediate gear that is disposed between the second gear and has a third gear that meshes with the first gear and a fourth gear that meshes with the second gear. Since it is fixed to the housing and one of the bearings is disposed in a separate bearing case fixed to the housing, the gear can be a two-stage structure and a large reduction ratio can be obtained. . Further, by disposing one of the bearings for supporting the intermediate gear in the bearing case, the conventional broken circle state is not caused, and the bearing can be favorably supported on the housing, and the device can be made compact.

  An electric motor attached to the housing, a nut that is arranged in parallel to the motor shaft of the electric motor, is supported so as to be rotatable with respect to the housing and not movable in the axial direction, and a number of balls are attached to the nut. A ball screw mechanism having a screw shaft that is inserted through the shaft and supported so as to be non-rotatable and movable in the axial direction, and that converts the rotational motion of the electric motor into axial motion, and a nut of the ball screw mechanism; An electric linear actuator comprising a speed reducer disposed between the motor shaft, an output shaft connected coaxially with the screw shaft, and a linear clutch disposed near a connecting portion of the output shaft. The first reduction gear is disposed between a first gear formed on a flange provided on an outer periphery of the nut and a second gear fixed to the motor shaft, and An intermediate gear having a third gear meshing with a vehicle and a fourth gear meshing with the second gear is fixed to the housing via two bearings, and one of the bearings is fixed to the housing. It is arranged in a separate bearing case to be fixed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing an embodiment of an electric linear actuator according to the present invention. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is an exploded perspective view of the housing and the bearing case.

  The electric linear actuator 1 includes an electric motor 3 attached to a housing 2, a spur gear 4 fixed to a motor shaft 3 a of the electric motor 3, and a gear 5 a that meshes with teeth 4 a of the spur gear 4. And a nut 6 integrally having a flange 6b provided with a gear 6a meshing with a gear 5b formed on the intermediate gear 5, and a plurality of balls 7 inserted thereinto. A screw shaft 8 and a linear clutch 9 connected to one end of the screw shaft 8 are provided.

  The tip of the motor shaft 3 a of the electric motor 3 is rotatably supported by the housing 2 b via the rolling bearing 10.

  As shown in FIG. 2, a small gear 5b is formed on the right side of the drawing and a large gear 5a is formed on the left side of the drawing. A right end of the intermediate gear 5 in the drawing is rotatably supported by the housing 2b via a rolling bearing 11.

  A counterbore portion 5c that is wound in a cylindrical shape is formed at the left end of the intermediate gear 5 in the drawing. The counterbore part 5c is arrange | positioned in the position used as the inner side of the gearwheel 5a. In the center of the spot facing portion 5c, a shaft end portion 5d that remains without being punched is provided. A rolling bearing 12 is fitted to the shaft end 5d. The rolling bearing 12 is disposed in the spot facing portion 5c. The rolling bearing 12 is disposed in a cylindrical bearing case 13 whose one end on the left side of the figure is closed by a wall surface. The outer peripheral surface of the bearing case 13 is provided with a certain distance without being in contact with the spot facing portion 5c.

  A part of the wall surface of the bearing case 13 is in contact with the inner surface of the housing 2a. A hole 13 a is formed in the approximate center of the wall surface of the bearing case 13. The hole 13a is press-fitted into a convex portion 2c provided in the housing 2a. Here, a part of the wall surface of the bearing case 13 is not in contact with the inner surface of the housing 2a. However, since the bearing case 13 is fixed to the convex portion 2c of the housing 2a, the bearing case 13 is firmly fixed in the housing. Since it is fixed, the rolling bearing 12 can be suitably supported even if a part thereof does not contact the inner surface of the housing 2a. In this example, the hole 13a is press-fitted into the convex portion 2c and fixed, but the present invention is not limited to this. For example, the hole 13a is fixed by a method using axial screwing or the like. Also good.

  The nut 6 is supported so as to be rotatable with respect to the housing 2 via a pair of rolling bearings 20 and 21 so as not to move in the axial direction. A spiral thread groove 6c is formed on the inner periphery. On the other hand, a helical screw groove 8a corresponding to the screw groove 6c is formed on the outer periphery of the screw shaft 8, and is supported so as to be movable in the axial direction and non-rotatable. A large number of balls 7 are slidably accommodated between these screw grooves 6c and 8a to constitute a ball screw mechanism. Here, since the rolling bearing 20 is disposed behind the wall surface of the bearing case 13, the rolling bearing 20 and the bearing case 13 do not interfere with each other.

  When the electric motor 3 is energized, the intermediate gear 5 rotates through the spur gear 4 as the motor shaft 3a rotates. When the intermediate gear 5 rotates, the nut 6 rotates, and the rotation of the nut 6 moves the screw shaft 8 in the axial direction (left-right direction in the figure). That is, by this ball screw mechanism, the rotational motion of the motor shaft 3a is converted into the axial motion of the screw shaft 8 via the ball screw mechanism.

  Here, a linear clutch 9 is connected to one end of the screw shaft 8 via a transmission pin 22. The linear clutch 9 is fitted to the housing 2b and is slidably inserted into an outer ring 23 having a cylindrical inner peripheral surface and a cylindrical holding portion 24 formed at one end of the screw shaft 8. A plurality of engagement elements (balls) 26 housed between the shaft 25, an engagement surface 25 a formed on the outer periphery of the output shaft 25 and having both end portions inclined inward, and an inner peripheral surface 23 a of the outer ring 23. And. An annular wedge-shaped space 27 is formed between the engagement surface 25 a of the output shaft 25 and the inner peripheral surface 23 a of the outer ring 23, and a plurality of pockets 24 a formed in the holding portion 24 are interposed via elastic members 28. The engagement elements 26 are held at a circumferentially even position and at a neutral position in the axial direction. Here, a single-row ball is illustrated as the engagement element 26, 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 26.

  An output shaft 25 is inserted into the holding portion 24 formed at one end of the screw shaft 8, and a transmission pin 22 is inserted in the radial direction of the holding portion 24 and the output shaft 25. A pin insertion hole 29 is formed so as to have a diameter larger than the outer diameter of the pin 22, and the output shaft 25 can move relative to the screw shaft 8 by a predetermined amount in the axial direction.

  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 cross-sectional view which shows embodiment of the electric linear actuator which concerns on this invention. It is a principal part enlarged view of FIG. It is a disassembled perspective view of a housing and a bearing case.

Explanation of symbols

1 .... Electric linear actuator 2, 2a, 2b ... Housing 2c ... ... Projection 3 ... Electric motor 3a ... Motor shaft 4 ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Spur Gear 4a ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Tooth 5 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・..Intermediate gears 5a, 5b, 6a ... Gear 5c ... Counterbore 5d ... .... Shaft end 6 ..... Nut 6b ..... Flange 6c, 8a・ ・ ・ ・ ・ ・ ・ ・ Thread groove 7 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Ball 8 ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Screw shaft 9 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Linear clutch 10, 11, 12, 20, 21... Rolling bearing 13・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Bearing case 13a ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Hole 22 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・.... Transmission pin 23 ... Outer ring 23a ... Inner peripheral surface 24 ... ... holding part 24a ... pocket 25 ... output shaft 25a ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Engagement surface 26 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ engagement element 27・ Wedge shaped space 28 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Elastic member 29 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・... pin insertion hole

Claims (4)

An electric motor attached to the housing;
A nut that is arranged in parallel to the motor shaft of the electric motor, is rotatably supported with respect to the housing and is supported so as not to move in the axial direction, and is inserted into the nut via a large number of balls so as not to rotate. A ball screw mechanism having a screw shaft supported so as to be movable in the axial direction, and converting the rotational motion of the electric motor into axial motion;
A speed reducer disposed between the nut of the ball screw mechanism and the motor shaft;
In the electric linear actuator in which the output shaft is connected coaxially with the screw shaft, and the linear clutch is disposed in the vicinity of the connecting portion of the output shaft,
The first gear is disposed between a first gear that constitutes the speed reducer and is formed on a flange provided on an outer periphery of the nut, and a second gear that is fixed to the motor shaft. An intermediate gear having a third gear meshing with the second gear and a fourth gear meshing with the second gear is fixed to the housing via two bearings, and one of the bearings is fixed to the housing An electric linear actuator, wherein the electric linear actuator is disposed in a separate bearing case.   The bearing case has a cylindrical shape whose one end is closed by a wall surface, a hole is formed in a substantially central portion of the wall surface, and the hole is press-fitted into a convex portion provided in the housing. The electric linear actuator according to claim 1, wherein the case is fixed to the housing.   3. The electric linear actuator according to claim 1, wherein a counterbore portion provided in a cylindrical shape is provided at an end portion of the intermediate gear, and one of the bearings is accommodated in the counterbore portion.   One of the bearings which fixes the said nut is stored in the circular hole provided in the said housing, This bearing is arrange | positioned in the back | inner side rather than the wall surface of the said bearing case. The electric linear actuator described.

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