JP2017002912A - Electric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric actuator of which light weight and compact in size are attained through a thin wall thickness at a housing and reliability in operation is improved by avoiding striking against a screw shaft.SOLUTION: In an electric actuator, a bag hole 12 storing a screw shaft 10 is formed at a housing, a cylindrical sleeve 17 is fitted into the bag hole under its whirl stopped state, an inner periphery of the sleeve 17 is formed with an axially extending concave groove 17a, an end part of the screw shaft 10 is provided with an engaging pin 15 buried therein and engaged with the concave groove 17a, and the screw shaft 10 is supported against the housing immovably and axial movable manner. There are provided a plurality of helical step-like steps 31, 32, 33 in such a direction as one in which a groove width is increased in a stepwise manner from one end surface of the concave groove 17a of the sleeve 17 in parallel with the concave groove 17a, so that when a reverse input from an output side is loaded, the screw shaft 10 is rotated and the engaging pin 15 is engaged with the step 31 to cause its rotation to be prevented and locked.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an electric actuator provided with a ball screw mechanism used in a drive unit of a general industrial electric motor or automobile, and more specifically, a rotation input from an electric motor is transmitted to a ball screw in an automobile transmission or a parking brake. The present invention relates to an electric actuator that converts a linear motion of a drive shaft through a mechanism.

  In electric actuators used in various drive units, a gear mechanism such as a trapezoidal screw or a rack and pinion is generally used as a mechanism for converting the rotational motion of the electric motor into a linear motion in the axial direction. 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.

  As a conventional electric actuator, for example, an electric motor supported by a housing can freely rotate a ball screw shaft constituting a ball screw, and an output member coupled to a nut by rotating the ball screw shaft. Displaceable in the axial direction. Since the ball screw mechanism has very low friction and high efficiency, the ball screw mechanism is also highly efficient against reverse input from the output side. Therefore, the reverse input is transmitted to the input side. That is, since the ball screw shaft is easily rotated by the thrust load acting on the output member side, it is necessary to hold the position of the output member when the electric motor is stopped.

  In addition, in the above-described electric actuator, an electric actuator is known that prevents the ball screw shaft from colliding with the inner wall of the housing by an inertia force by being pushed by a load when control becomes impossible due to a system error or the like. As shown in FIG. 7, the electric actuator 51 is used as an electric parking brake driving device, and includes a cylindrical motor housing 51a and a housing body 51b. An electric motor 52 is provided in the motor housing 51a. The electric motor 52 includes a rotating shaft 52a that functions as a rotation driving unit, a stator 52b, and a rotor 52c. The rotating shaft 52a is rotatably supported by the motor housing 51a via a bearing 53.

  The rotary shaft 52a is hollow and is configured such that one axial end (the right end in the figure) has a large diameter, and the outer peripheral surface thereof is supported by the inner peripheral surface of the motor housing 51a by a bearing 54. ing. The rotating shaft 52a has a plurality of claw portions 52d protruding in the axial direction from the axial end surface on the large diameter side.

  The housing main body 51b has a shape in which a large diameter cylindrical portion and a small diameter cylindrical portion are connected in the axial direction, and the outer ring 55 cannot be rotated on the inner peripheral surface of the large diameter cylindrical portion by press fitting or the like. It is attached. On the radially inner side of the outer ring 55, a roller 56 that is a locking member and a key 57 are disposed between the claw portions 52d. A flange 55a is formed at one axial end (right side in the drawing) of the outer ring 55 so as to protrude radially inward. The roller 56 is prevented from moving in the axial direction by the flange 55a.

  A rotary driven portion 59 is rotatably supported on the inner peripheral surface of the housing main body 51b via a bearing 58, and the rollers 56 are arranged so that the outer peripheral surface of the rotary driven portion 59 can roll. A nut 60 is attached to the inner peripheral surface of the rotation driven portion 59 so as not to rotate relative to the rotation driven portion 59 by a set screw or the like.

  A screw shaft 61 is provided so as to penetrate the nut 60. The screw shaft 61 is arranged so that one end portion (left end portion in the figure) is inserted inside the rotation shaft 52a. Further, on the outer peripheral surface of the screw shaft 61, a screw groove (not shown) is formed at a location facing the nut 60 in the radial direction. A screw groove (not shown) is formed on the inner peripheral surface of the nut 60 so as to correspond to the screw groove of the screw shaft 61. A large number of balls are movably arranged in a spiral space defined by the respective thread grooves.

  A cylindrical moving case 62 is disposed at the other end (right end in the figure) of the screw shaft 61, and via a key 62a disposed in a key groove formed at the end of the moving case 62, The screw shaft 61 is non-rotatably attached to the moving case 62.

  One end of a wire (not shown) is connected to the axial end surface (right end surface in the figure) of the moving case 62, and the moving case 62 is connected to a parking brake device as a driven member via this wire. When the wire moves to the left side, the parking brake device is operated to apply a braking force to a wheel (not shown), and when the wire moves to the right side, the parking brake device is released from braking.

  Here, the moving case 62 has a linear groove extending in the axial direction formed on the inner peripheral surface, and a pin 62b is provided so as to engage with the linear groove. The case 62 is attached so as to be movable in the axial direction with respect to the housing main body 51b. That is, the moving case 62 is configured to be movable in the axial direction, although it cannot be rotated relative to the housing body 51b.

  The wire attached to the moving case 62 is always urged to the right side in the drawing by a spring or the like (not shown). That is, in a state where the parking brake device is operated, the moving case 62 and the screw shaft 61 are always pulled to the right in the axial direction.

  As shown in FIGS. 8A and 9A to 9C, a key groove 59b and three cam grooves 59c are formed at equal intervals on the outer peripheral surface of the rotationally driven 59. The cam surface 59a has a slope inclined to one side so as to move away from the axial center in a clockwise direction (approaching the inner peripheral surface of the outer ring 55). As shown in FIGS. 9A to 9C, the cam surface 59 a includes an inclined portion 59 d that can roll without causing the roller 56 to bite between the outer ring 55 and the rotation driven portion 59, and the roller 56. It has an inclined portion 59e that bites into both. In a state where the roller 56 is bitten between the outer ring 55 and the rotation driven portion 59, the distance between the key 57 and the claw portions 52d on both sides thereof is a, and the roller 56 is connected to the outer ring 55 and the rotation driven portion 59. When the distance between the left nail part 52d in FIG. 8A and b between the right nail part 52d in FIG. 8A is c and the distance between the right nail part 52d in FIG. It has become.

  As shown in FIGS. 7 and 8B, a roller clutch 63 having a function as a one-way clutch is attached to the inner peripheral surface of the housing main body 51b. A sleeve 64 formed in an annular shape is fitted to the outer peripheral surface of the rotationally driven portion 59 with a slight gap. The sleeve 64 is rotatably supported on the inner peripheral surface of the housing main body 51b via the roller clutch 63. The sleeve 64 is hardened by, for example, bearing steel, and the outer diameter surface thereof is a rolling surface of the roller clutch 63, and one of the axial side surfaces thereof is a sliding surface with the friction material. .

  As shown in FIG. 7, when the sleeve 64 rotates counterclockwise in the drawing, the roller clutch 63 enters a locked state because the roller as the rolling element bites. A friction material (friction means) 65 a is arranged on the outer peripheral surface of the rotationally driven portion 59 so as to be adjacent to the sleeve 64 in the axial direction, and the friction material 65 a is configured to rotate integrally with the rotationally driven portion 59. . Further, a screw 66 is provided on the outer peripheral surface of the rotationally driven portion 59. The screw 66 presses the axial end portion of the sleeve 64 via the friction material 65b, and abuts the sleeve 64 and the friction material 65a. I am letting. The screw 66 is a screw in a direction not loosened by frictional force when the rotary driven portion 59 is rotated in the biting direction of the roller clutch 63, and in this case, is a left screw.

  The roller clutch 63 is configured such that when the rotationally driven portion 59 rotates in the direction of arrow A in FIG. 9A, the sleeve 64 and the rotationally driven portion 59 rotate relative to each other. On the other hand, when rotating in the direction opposite to the arrow A direction, the unlocked state is established, and the sleeve 64 and the rotary driven portion 59 are allowed to rotate integrally.

  When the electric parking brake driving device is operated, electric power is supplied to the electric motor 52, and the rotation shaft 52a (see FIG. 8) rotates relative to the rotation driven portion 59. At this time, as shown in FIG. 9C, the claw portion 52d rotates in the direction of the arrow C, and the end of the claw portion 52d presses the key 57, so that the rotary shaft 52a (see FIG. 7) and the rotation driven The part 59 rotates integrally. At this time, since the rotationally driven portion 59 rotates in the C direction, the roller 56 is brought to the inclined portion 59d by itself so that it does not bite between the outer ring 55 and the rotationally driven portion 59. Then, as shown in FIG. 7, when the nut 60 rotates with the rotation of the rotary driven portion 59, the screw shaft 61 moves to the axial electric motor 52 side (left side in the figure). At this time, the moving case 62 supported by the screw shaft 61 also moves in the axial direction, transmits power to the parking brake device, which is a driven member, via the wire, and applies braking force to a wheel (not shown).

  The ball screw mechanism 67 is configured such that the screw shaft 61 moves to the left in the figure by rotating the rotary shaft 52a and the rotary driven portion 59 in the direction of arrow C in FIG. 9C. At this time, the state as shown in FIG. 7 is obtained, and the parking brake device, which is the driven member, is activated. Further, the ball screw mechanism is configured such that the screw shaft 61 moves to the right side of the figure by rotating the rotary shaft 52a and the rotary driven portion 59 in the direction opposite to the direction of arrow C in FIG. . At this time, the parking brake device as the driven member is in a released state.

  Thus, after the electric motor 52 is stationary in a state where the parking brake device is in operation, the moving case 62 and the screw shaft 61 are axially moved in the axial direction of FIG. An external load is applied to the right. This external load is converted into a force for rotating the driven part 59 in the direction of arrow B in FIG. Further, the rotationally driven portion 59 rotates in the direction of arrow B, and the roller 56 relatively moves to the inclined portion 59e and is caught between the outer ring 55 and the rotationally driven portion 59, so that the rotationally driven portion 59 rotates. Is blocked. This state is referred to as a position holding mechanism lock.

  When releasing the parking brake device as the driven member, when electric power is supplied to the electric motor 52 and the rotating shaft 52a rotates, the claw portion 52d moves in the direction of arrow A as shown in FIG. When one of the claw portions 52d presses the key 57, the rotation driven portion 59 is rotated in the arrow A direction. Then, since the roller 56 is pressed from the end surface of the claw portion 52d, the roller 56 moves to the inclined portion 59d and rotates integrally with the rotating shaft 52a and the rotationally driven portion 59 without biting.

  Here, suppose that the position holding mechanism is unlocked without applying a braking force to the rotationally driven portion 59. When the claw portion 52d is rotated in the direction of the arrow A along with the rotation of the rotation shaft 52a, the claw portion 52d pushes the roller 56 to the inclined portion 59d, and the other claw portion 52d presses the key 57, whereby the rotation shaft 52a and the rotation driven part 59 begin to rotate. However, immediately after that, when the rotationally driven portion 59 starts to rotate at a rotational acceleration larger than the rotational shaft 52a due to the force from the external load, the roller 56 once pushed to the claw portion 52d relatively moves to the inclined portion 59e. Will be. Then, the roller 56 may bite between the outer ring 55 and the rotation driven part 59 again. That is, this becomes a cause of shakiness of the position holding mechanism.

  Therefore, as shown in FIG. 9 (a), when releasing the parking brake device which is a driven member, there is a mechanism for applying a braking force to the rotation of the rotationally driven portion 59 due to the external load. Yes. As shown in FIGS. 7 and 8B, the roller clutch 63 provided in the housing main body 51b has a sleeve when the rotationally driven portion 59 is about to rotate in the direction of arrow A in FIG. 64 is locked so as not to rotate integrally with the rotary driven portion 59. At this time, the sleeve 64 is substantially fixed to the housing body 51b. On the other hand, the friction material 65 a is provided so as to come into contact with the sleeve 64, and rotates integrally with the rotation driven portion 59. Then, a frictional force is generated between the sleeve 64 and the friction material 65a, and the rotational acceleration in the direction of arrow A in FIG.

  Thereby, when releasing the operation of the parking brake device, the rotational acceleration of the rotationally driven portion 59 that receives an external load can be made smaller than the rotational acceleration of the rotational drive portion (rotating shaft 52a). For this reason, it is possible to prevent rattling from occurring in the position holding mechanism when releasing the operation of the parking brake device (see, for example, Patent Document 1).

Japanese Patent No. 4214371

  In such a conventional electric actuator 51, since the release and lock of the roller clutch 63 are repeated, abnormal noise and vibration are generated each time. In addition, such a clutch mechanism not only increases the number of parts but also makes assembly complicated, which has been an impediment to light weight, compactness, and cost reduction.

  The present invention has been made in view of such problems of the prior art. Even when a system error occurs and control becomes impossible, the present invention focuses on a safety mechanism in which the screw shaft does not collide with the housing. An object of the present invention is to provide an electric actuator that is lighter and more compact and that is improved in reliability by avoiding a collision of a screw shaft.

  In order to achieve such an object, the invention according to claim 1 of the present invention includes a housing, an electric motor attached to the housing, and a rotational force of the electric motor transmitted via a motor shaft, A ball screw mechanism that converts the rotational motion of the electric motor into a linear motion in the axial direction of the drive shaft. The ball screw mechanism is rotatable via a support bearing mounted on the housing and cannot move in the axial direction. And a nut having a spiral thread groove formed on the inner periphery thereof, and a nut inserted into the nut via a number of balls, integrated with the drive shaft, and on the outer periphery thereof. And a screw hole in which the screw shaft is accommodated in the housing, and a cylindrical sleeve is prevented from rotating in the bag hole. Mated with A concave groove extending in the axial direction is formed on the inner periphery of the sleeve, and a locking pin is implanted at an end of the screw shaft to be engaged with the concave groove. In the electric actuator supported so as to be non-rotatable and movable in the axial direction, a step portion that can hold the locking pin in the axial direction is formed in the groove of the sleeve.

  Thus, the housing, the electric motor attached to the housing, and the rotational force of the electric motor are transmitted via the motor shaft, and the rotational motion of the electric motor is converted into a linear motion in the axial direction of the drive shaft. A ball screw mechanism, and the ball screw mechanism is rotatably supported via a support bearing mounted on the housing and is not axially movable, and a nut having a helical thread groove formed on the inner periphery thereof; The screw shaft is inserted into the nut through a large number of balls, is integrated with the drive shaft in a coaxial manner, and includes a screw shaft having a spiral screw groove corresponding to the screw groove of the nut formed on the outer periphery. A bag hole for receiving the screw shaft is formed in the housing, and a cylindrical sleeve is fitted to the bag hole in a state of being prevented from rotating, and a concave groove extending in the axial direction is formed on the inner periphery of the sleeve. Of screw shaft In the electric actuator in which the locking pin is implanted in the part and engaged with the groove so that the screw shaft cannot be rotated with respect to the housing and can be moved in the axial direction, the locking pin is inserted into the groove of the sleeve. Since a step that can be held in the axial direction is formed, when a reverse input from the output side is applied, the screw shaft is rotated by this reverse input, and the locking pin moves from the groove to engage the step. Even if it is stopped and its rotation is blocked and locked, and it becomes uncontrollable due to a system error, it can prevent the screw shaft from colliding with the housing, and the thinner housing makes it lighter It is possible to provide an electric actuator that can be made compact and can improve the reliability by avoiding the collision of the screw shaft.

  Preferably, as in the invention described in claim 2, if a plurality of step portions of the sleeve are formed in a spiral step shape with respect to the axis of the screw shaft, the sleeve is held at an appropriate position of the screw shaft. Even if the reverse input is constantly loaded, the screw shaft can be held at a predetermined position, so that the degree of design freedom is increased and the application range of the electric actuator is expanded.

  According to a third aspect of the present invention, a flat surface is formed on the outer periphery of the sleeve, and a flat surface is formed in the bag hole of the housing corresponding to the flat surface. If the sleeve is fitted in the bag hole in the matched state, the sleeve can be prevented from rotating with respect to the housing.

  According to a fourth aspect of the present invention, the locking pins are fixed at opposing positions in the circumferential direction of the screw shaft, accommodate these locking pins, and face the inner periphery of the sleeve. If the concave groove is formed, the phase alignment of the screw shaft with respect to the sleeve is simplified, and the number of assembling operations can be reduced.

  Further, as in the invention described in claim 5, if the sleeve is made of sintered metal formed by MIM, even if it has a high workability and a complicated shape, it can be easily and accurately obtained. Can be formed into shapes and dimensions.

  An electric actuator according to the present invention transmits a rotational force of a housing, an electric motor attached to the housing, and the electric motor via a motor shaft, and the rotational motion of the electric motor in the axial direction of the drive shaft. A ball screw mechanism for converting into linear motion, and this ball screw mechanism is supported by a support bearing mounted on the housing so as to be rotatable and non-movable in the axial direction, and has a spiral thread groove on the inner periphery. And a nut that is inserted into the nut through a large number of balls, is coaxially integrated with the drive shaft, and a helical thread groove corresponding to the thread groove of the nut is formed on the outer periphery. The housing is formed with a bag hole that accommodates the screw shaft, and a cylindrical sleeve is fitted in the bag hole while being prevented from rotating. A concave groove extending in the axial direction is formed on the inner periphery, a locking pin is implanted at an end of the screw shaft and engaged with the concave groove, and the screw shaft cannot rotate with respect to the housing, and In the electric actuator supported so as to be movable in the axial direction, a step portion that can hold the locking pin in the axial direction is formed in the concave groove of the sleeve, so when a reverse input from the output side is loaded, When the screw shaft rotates due to reverse input, the locking pin moves from the concave groove and is locked to the stepped portion, and the rotation is blocked by the sleeve, resulting in a locked state, resulting in a system error resulting in loss of control. However, it is possible to prevent the screw shaft from colliding with the housing, and to reduce the weight and size of the housing by reducing the thickness of the housing, and to provide an electric actuator that improves the reliability by avoiding the collision of the screw shaft. It is possible.

It is a longitudinal section showing one embodiment of an electric actuator concerning the present invention. It is a longitudinal cross-sectional view which shows the ball screw mechanism of FIG. It is a principal part enlarged view which shows the intermediate | middle gear part of FIG. It is a principal part enlarged view which shows the sleeve of FIG. (A) is explanatory drawing which shows the time of locking of the ball screw mechanism of FIG. 1, (b) is explanatory drawing which shows the time of unlocking of (a). It is a perspective view which shows the sleeve and screw shaft of FIG. It is a longitudinal cross-sectional view which shows the electric parking brake drive device to which the conventional electric actuator is applied. (A) is the cross-sectional view along the VIIIa-VIIIa line of the electric parking brake drive device of FIG. 7, (b) is the cross-sectional view along the VIIIb-VIIIb line same as the above. (A)-(c) is a principal part expanded sectional view which shows operation | movement of the electric parking brake drive device of FIG.

  An aluminum alloy housing, an electric motor attached to the housing, a reduction mechanism that transmits the rotational force of the electric motor via a motor shaft, and the rotational movement of the electric motor is driven via the reduction mechanism A ball screw mechanism for converting the shaft into a linear motion in the axial direction, and this ball screw mechanism is supported by a support bearing mounted on the housing so as to be rotatable and non-movable in the axial direction. A nut formed with a helical thread groove, and a helical screw that is inserted into the nut through a large number of balls, is coaxially integrated with the drive shaft, and corresponds to the thread groove of the nut on the outer periphery A groove hole is formed in the housing, and a bag hole for accommodating the screw shaft is formed in the housing, and a cylindrical sleeve is fitted to the bag hole in a non-rotating state, A groove extending in the axial direction is formed on the inner periphery of the sleeve of the sleeve, and a locking pin is implanted at the end of the screw shaft and engaged with the groove, so that the screw shaft cannot rotate with respect to the housing. Further, in the electric actuator supported so as to be movable in the axial direction, the axis of the screw shaft extends in a direction in which the groove width gradually increases in parallel with the groove from one end surface of the groove of the sleeve. On the other hand, a plurality of spiral stepped steps are formed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a longitudinal sectional view showing an embodiment of an electric actuator according to the present invention, FIG. 2 is a longitudinal sectional view showing a ball screw mechanism of FIG. 1, and FIG. 3 is a main part showing an intermediate gear portion of FIG. 4 is an enlarged view of the main part showing the sleeve of FIG. 1, FIG. 5 (a) is an explanatory view showing the ball screw mechanism of FIG. 1 locked, and FIG. 4 (b) is the unlocking of FIG. FIG. 6 is a perspective view showing the sleeve and the screw shaft of FIG.

  As shown in FIG. 1, the electric actuator 1 includes a cylindrical housing 2, an electric motor M attached to the housing 2, and an intermediate gear meshing with an input gear 3 attached to a motor shaft 3a of the electric motor. A speed reduction mechanism 6 comprising a gear 4 and an output gear 5 meshing with the intermediate gear 4, and a ball screw mechanism for converting the rotational motion of the electric motor M into the linear motion in the axial direction of the drive shaft 7 via the speed reduction mechanism 6. 8 and.

  The housing 2 is made of an aluminum alloy such as A6063TE or ADC12, and includes a first housing 2a and a second housing 2b abutted on the end face thereof, and is fixed integrally by a fixing bolt (not shown). . An electric motor M is attached to the first housing 2a, and a through hole 11 and a bag hole 12 for accommodating the screw shaft 10 are formed in the first housing 2a and the second housing 2b. .

  The motor shaft 3a of the electric motor M is rotatably supported by a rolling bearing 13 composed of a deep groove ball bearing mounted on the second housing 2b. Yes. The output gear 5 that meshes with the intermediate gear 4 that is a spur gear is integrally fixed to a nut 18 that constitutes a ball screw mechanism 8 that will be described later via a key 14.

  The drive shaft 7 is formed integrally with a screw shaft 10 constituting the ball screw mechanism 8, and a locking pin 15 is implanted at one end portion (right end portion in the figure) of the drive shaft 7. A cylindrical sleeve 17 described later is fitted into the bag hole 12 of the second housing 2b. Then, a locking pin 15 of the screw shaft 10 is engaged with a concave groove 17a formed in the inner periphery of the sleeve 17 so as to extend in the axial direction, and the screw shaft 10 is supported to be non-rotatable and movable in the axial direction. Has been.

  As shown in an enlarged view in FIG. 2, the ball screw mechanism 8 includes a screw shaft 10 and a nut 18 that is externally inserted to the screw shaft 10 via a ball 19. The screw shaft 10 has a spiral thread groove 10a formed on the outer periphery. On the other hand, the nut 18 is extrapolated to the screw shaft 10, and a helical screw groove 18 a corresponding to the screw groove 10 a of the screw shaft 10 is formed on the inner periphery, and a large number of screws 18 a and 18 a are formed between these nuts 18. A ball 19 is accommodated so as to roll freely. The nut 18 is supported by the first and second housings 2a and 2b via the two support bearings 20 and 20 so as to be rotatable and non-movable in the axial direction. Reference numeral 21 denotes a piece member that constitutes a circulation member by connecting the thread grooves 18a of the nut 18, and the piece member 21 allows an infinite circulation of a large number of balls 19.

  The cross-sectional shape of each of the thread grooves 10a and 18a may be a circular arc shape or a gothic arc shape, but here, a gothic arc shape that allows a large contact angle with the ball 19 and a small axial clearance can be set. Is formed. Thereby, the rigidity with respect to an axial load becomes high and generation | occurrence | production of a vibration can be suppressed.

  The nut 18 is made of case-hardened steel such as SCM415 or SCM420, and its surface is subjected to hardening treatment in a range of 55 to 62 HRC by vacuum carburizing and quenching. Thereby, the buffing etc. for the scale removal after the heat treatment can be omitted, and the cost can be reduced. On the other hand, the screw shaft 10 is formed in a columnar shape from medium carbon steel such as S55C or case-hardened steel such as SCM415 and SCM420, and the screw groove 10a is formed by rolling rather than machining such as turning. And the hardening process is given to the range of 55-62HRC on the surface by induction hardening or carburizing hardening. Thereby, mass productivity improves and cost reduction can be achieved.

  The output gear 5 constituting the speed reduction mechanism 6 is integrally fixed to the outer peripheral surface 18b of the nut 18, and two support bearings 20 and 20 are press-fitted on both sides of the output gear 5 via a predetermined shimiro. . Thereby, even if a thrust load is applied from the drive shaft 7, it is possible to prevent the axial displacement between the support bearings 20 and 20 and the output gear 5. Further, the two support bearings 20 and 20 are constituted by sealed deep groove ball bearings having shield plates 20a and 20a attached to both ends, and leakage of the lubricating grease enclosed in the bearings to the outside and from the outside This prevents wear powder from entering the bearing.

  Further, in the present embodiment, the support bearing 20 that rotatably supports the nut 18 is composed of deep groove ball bearings having the same specifications, and thus is loaded from the drive shaft 7 through the thrust load and the output gear 5 described above. Both radial loads can be applied, and confirmation work for preventing misassembly during assembly can be simplified, and assembling workability can be improved. Here, the deep groove ball bearings having the same specifications refer to bearings having the same inner diameter, outer diameter, width dimension, rolling element size, number, bearing internal clearance, and the like.

  Further, here, one (left side in the figure) of the pair of support bearings 20 and 20 is attached to the first housing 2a via a washer 27 made of a ring-shaped elastic member. This washer 27 is formed by press working from an austenitic stainless steel plate (JIS standard SUS304 type or the like) having high strength and wear resistance, or a rust-proof cold rolled steel plate (JIS standard SPCC type or the like). It consists of a wave washer. The inner diameter D is formed larger than the inner ring outer diameter d of the support bearing 20. As a result, the axial backlash of the pair of support bearings 20 and 20 can be eliminated, smooth rotation performance can be obtained, and the inner ring that the washer 27 abuts only on the outer ring of the support bearing 20 and becomes a rotating ring. Therefore, even if a reverse thrust load is generated and the nut 18 is pressed against the first housing 2a, the inner ring of the support bearing 20 is prevented from coming into contact with the first housing 2a to increase the frictional force. , It can be prevented from being locked.

  As shown in FIG. 3, the intermediate gear 4 constituting the speed reduction mechanism 6 is rotatably supported on a gear shaft 22 implanted in the first and second housings 2 a and 2 b via a rolling bearing 23. . Of the end portions of the gear shaft 22, for example, when press-fitting the end portion on the first housing 2a side, the end portion on the second housing 2b side is set to be a clearance fit, thereby making misalignment (assembly error). Allowing smooth rotation performance can be ensured. In the present embodiment, the rolling bearing 23 includes an outer ring 24 made of a steel plate press-fitted into the inner diameter 4 a of the intermediate gear 4, and a plurality of needle rollers 26 accommodated in the outer ring 24 via a cage 25 so as to be freely rollable. And so-called shell-type needle roller bearings. Thereby, availability is high and cost reduction can be achieved.

  Moreover, ring-shaped washers 28 and 28 are mounted on both sides of the intermediate gear 4 to prevent the intermediate gear 4 from directly contacting the first and second housings 2a and 2b. Here, the width of the tooth portion 4b of the intermediate gear 4 is formed smaller than the tooth width. As a result, the contact area with the washer 28 can be reduced, and the frictional resistance during rotation can be suppressed and smooth rotation performance can be obtained. Here, the washer 28 is a flat washer formed by pressing from an austenitic stainless steel plate having high strength and high wear resistance, or a cold-rolled steel plate treated with rust prevention. In addition to this, for example, it is formed of a thermoplastic synthetic resin such as PA (polyamide) 66 filled with a predetermined amount of a fibrous reinforcing material such as brass, sintered metal, or GF (glass fiber). May be.

  Furthermore, the width of the rolling bearing 23 is set smaller than the tooth width of the intermediate gear 4. Thereby, wear and deformation of the bearing side surface due to friction can be prevented, and smooth rotation performance can be obtained.

  As shown in FIG. 4, the sleeve 17 that supports the screw shaft 10 so as not to rotate and to be movable in the axial direction is fitted in the bag hole 12 of the second housing 2 b. Specifically, flat surfaces 17b and 17b are formed at opposite phases on the outer periphery of the sleeve 17, and at the opposite phases of the bag holes 12 of the second housing 2b corresponding to these flat surfaces 17b and 17b. Also, flat surfaces 12a and 12a are formed. An annular groove 29 is formed at the opening end of the bag hole 12 of the second housing 2b, and a retaining ring 30 is attached to the annular groove 29 so that the flat surfaces 17b and 12a are aligned with each other, and the sleeve 17 Is fitted toward the bottom 12b, and is positioned and fixed in the axial direction in a state in which the sleeve 17 is prevented from rotating with respect to the second housing 2b.

  Here, the sleeve 17 has a plurality of spiral stepped step portions 31, 32, and 33 formed in the inner periphery from one end face of the concave groove 17 a to the axial center of the screw shaft 10. Yes. Specifically, step portions 31, 32, 33 are formed in a direction in which the groove width increases stepwise in parallel with the concave groove 17 a, and these step portion wall surfaces 31 a, 32 a, 33 a are connected to the screw shaft 10. It is formed along the lead angle of the screw groove 10a, and the step width surfaces 31b, 32b, 33b of the step portions 31, 32, 33 are set wider than the pitch of the screw groove 10a (see FIG. 6). . Here, the “lead” is a length that moves in the axial direction when the screw shaft 10 makes one rotation, and the “lead angle” means a thread winding coil and one point above it. An angle formed by a plane perpendicular to the passing screw axis 10 and “pitch” refer to a distance between two corresponding points of adjacent threads. For example, in a single-threaded screw with a screw thread along a single helical winding at a distance of one point on the screw in the axial direction, pitch = lead, and two helical windings on one cylinder. In a double thread wound at equal intervals, the lead = 2 × pitch.

Next, the operation of the safety mechanism according to the present invention will be described with reference to FIG.
As shown in FIG. 5 (a), when the screw shaft 10 is a right-hand screw and receives a load in the right direction in the drawing, and the shaft is operated in the left direction in the drawing against the load, the nut 18 is usually rotated. Accordingly, the locking pin 15 of the screw shaft 10 slides along the stepped wall surface 31b (stepped portion side). The screw shaft 10 is supported to the sleeve 17 so as not to rotate and to be movable in the axial direction, but a reverse input from the output side (right direction in the figure) is loaded and the torque of the electric motor is OFF. At this time, by this reverse input, the screw shaft 10 rotates clockwise (clockwise direction) as indicated by an arrow in the figure, and the locking pin 15 is locked to the step portion 31. Specifically, it moves along the stepped wall surface 31b of the stepped portion 31 and abuts on the stepped portion width surface 31a, and the locking pin 15 is fixed in the axial direction. As a result, the screw shaft 10 is prevented from rotating by the sleeve 17 and is locked, and even when a system error occurs and control becomes impossible, the screw shaft 10 is prevented from colliding with the second housing 2b. In addition, it is possible to provide an electric actuator that can be reduced in weight and size by reducing the thickness of the housing and can improve the reliability by avoiding the collision of the screw shaft 10.

  On the other hand, when the screw shaft 10 is unlocked, as shown in FIG. 5B, the screw shaft 10 is moved to the left by applying a load greater than the reverse input by operating the shaft in the right direction in the figure from the input side. It rotates (counterclockwise direction), and the locking pin 15 moves upward from the step portion 31. That is, the locking pin 15 of the screw shaft 10 is disengaged from the stepped portion 31 to be unlocked, and the screw shaft 10 is supported so as to be non-rotatable and axially movable with respect to the sleeve 17. To return to the normal state.

  In the present embodiment, as shown in FIG. 6, a plurality of spiral stepped steps 31, 32, 33 are formed on the inner periphery of the sleeve 17, so that the screw shaft 10 can be held at an appropriate position. it can. Thereby, even if the reverse input is constantly loaded, the screw shaft 10 can be held at a predetermined position, and the degree of freedom in design is increased and the application range of the electric actuator is expanded.

  Locking pins 15, 15 are fixed at opposing positions in the circumferential direction of the screw shaft 10, and the grooves 17 a, 17 a that house the locking pins 15, 15 and prevent the screw shaft 10 from rotating are sleeves 17. Therefore, the phase alignment of the screw shaft 10 with respect to the sleeve 17 is simplified, and the number of assembling operations can be reduced.

  The sleeve 17 may be formed from medium carbon steel such as S55C or case-hardened steel such as SCM415 or SCM420 by forging or cold forging. In the present embodiment, the sleeve 17 is made of a metal powder in a plastic form. It consists of a sintered alloy that is adjusted and molded by an injection molding machine. In this injection molding, first, metal powder and a binder made of plastic and wax are kneaded by a kneader, and the kneaded product is granulated into pellets. The granulated pellets are molded by so-called MIM (Metal Injection Molding), which is supplied to a hopper of an injection molding machine and pushed into a mold in a heated and melted state. A sintered alloy formed by such an MIM can be easily and accurately formed into a desired shape / dimension even if it has a high workability and a complicated shape.

  As the metal powder, a material that can be subsequently carburized and hardened, for example, C (carbon) is 0.13 wt%, Ni (nickel) is 0.21 wt%, Cr (chromium) is 1.1 wt%, Cu (copper) Exemplifies SCM415 which is 0.04 wt%, Mn (manganese) is 0.76 wt%, Mo (molybdenum) is 0.19 wt%, Si (silicon) is 0.20 wt%, and the rest is Fe (iron). Can do. The sleeve 17 is performed by adjusting the carburizing quenching and tempering temperatures.

  In addition to this, as the material of the sleeve 17, Ni is contained in an amount of 3.0 to 10.0 wt% and has excellent workability and corrosion resistance (FEN8 of Japanese Powder Metallurgy Industry Standard), or C is 0.07 wt%. %, Cr is 17 wt%, Ni is 4 wt%, Cu is 4 wt%, and the remainder is precipitation hardened stainless steel SUS630 made of Fe or the like. This SUS630 can appropriately increase the surface hardness in the range of 20 to 33 HRC by solution heat treatment, and can ensure toughness and high hardness.

  In the present embodiment, the embodiment in the case where there is a reduction gear has been described. However, the embodiment is not particularly limited to the case in which there is a reduction gear, and can be implemented even when there is no reduction gear.

  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.

  An electric actuator according to the present invention includes a ball screw mechanism that is used in a drive unit of a general industrial electric motor, an automobile, or the like, and that converts a rotational input from an electric motor into a linear motion of a drive shaft via the ball screw mechanism. Applicable to electric actuators.

DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Housing 2a 1st housing 2b 2nd housing 3 Input gear 3a Motor shaft 4 Intermediate gear 4a Inner gear 4b Inner diameter 4b Tooth part 5 Output gear 6 Reduction mechanism 7 Drive shaft 8 Ball screw mechanism 10 Screw shaft 10a, 18a Thread groove 11 Through-hole 12 Bag hole 12a, 17b Flat surface 12b Bottom surface of bag hole 13, 23 Rolling bearing 14 Key 15 Locking pin 16 Retaining ring 17 Sleeve 17a Groove 18 Nut 18b Nut outer surface 19 Ball 20 Support bearing 20a Shield plate 21 Piece member 22 Gear shaft 24 Outer ring 25 Cage 26 Needle rollers 27, 28 Washers 29 Annular groove 30 Retaining rings 31, 32, 33 Step portions 31a, 32a, 33a Step portion wall surfaces 31b, 32b, 33b Step portions Width surface 51 Electric actuator 51a Motor housing 51b Housing body 52 Electric Motor 52a Rotating shaft 52b Stator 52c Rotor 52d Claw 53, 54, 58 Bearing 55 Outer ring 55a Flange body 56 Roller 57, 62a Key 59 Rotated driven part 59a Cam surface 59b Key groove 59c Cam groove 59d, 59e Inclined part 60 Nut 61 Screw shaft 62 Moving case 62b Pin 63 Roller clutch 64 Sleeve 65a, 65b Friction material 66 Screw 67 Ball screw mechanism a, b, c Distance between key and claw part d Inner ring outer diameter D of support bearing Washer inner diameter M Electric motor

Claims (5)

A housing;
An electric motor attached to the housing;
A ball screw mechanism that transmits the rotational force of the electric motor via a motor shaft and converts the rotational motion of the electric motor into a linear motion in the axial direction of the drive shaft;
The ball screw mechanism is rotatably supported via a support bearing mounted on the housing and is not axially movable, and a nut having a helical thread groove formed on the inner periphery,
The nut is inserted through a large number of balls, is integrated with the drive shaft coaxially, and includes a screw shaft in which a spiral screw groove corresponding to the screw groove of the nut is formed on the outer periphery. With
A bag hole for accommodating the screw shaft is formed in the housing, and a cylindrical sleeve is fitted in the bag hole while being prevented from rotating,
A concave groove extending in the axial direction is formed on the inner periphery of the sleeve, and a locking pin is implanted at the end of the screw shaft and engaged with the concave groove, so that the screw shaft cannot rotate with respect to the housing. And an electric actuator supported so as to be axially movable,
An electric actuator characterized in that a step portion capable of holding the locking pin in the axial direction is formed in the concave groove of the sleeve.   The electric actuator according to claim 1, wherein a plurality of step portions of the sleeve are formed in a spiral step shape with respect to the axis of the screw shaft.   A flat surface is formed on the outer periphery of the sleeve, and a flat surface is formed in the bag hole of the housing corresponding to the flat surface, and the sleeve is fitted into the bag hole in a state where the flat surfaces are aligned with each other. The electric actuator according to claim 1 combined.   The said latching pin is fixed to the position where the circumferential direction of the said screw shaft opposes, These latching pins are accommodated, The said recessed groove is formed facing the inner periphery of the said sleeve. Electric actuator.   The electric actuator according to claim 1, wherein the sleeve is made of a sintered metal formed by MIM.

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