JP2020058215A - Electric actuator - Google Patents

Abstract

To provide an electric actuator that does not require control for matching phases between a transmitting mechanism side that transmits driving force from a motor to a ball screw and a braking mechanism side that stops driving the ball screw due to a reverse input.SOLUTION: An electric actuator includes: a cylindrical surface 41 that integrally rotates concentrically with a drive gear 33; an engagement surface 47; a cam surface 42 of a stationary portion 46 that is stationary; a holder 44 that holds a roller 43 between the cylindrical surface 41 and the cam surface 42; armature 48 whose rotation is stopped by the holder 44; and an electromagnetic clutch 50. The armature 48 always faces the engagement surface 47, and the electromagnetic clutch 50 switches between a connection state of the armature 48 and the engagement surface 47 and a release state of releasing it. In the connection state, the holder 44 rotates by torque from the drive gear side 33 and the roller 43 can engage with the cylindrical surface 41 and the cam surface 42, but in the release state, the phase of the holder 44 is maintained by a neutral spring 45, and the roller 43 is prevented from engaging with the cylindrical surface 41 and the like.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric actuator.

  2. Description of the Related Art In recent years, the electrification of vehicles has been advanced, and for example, a system for operating an automatic transmission, a brake, a steering, and the like of an automobile by the power of an electric motor is mounted. As an actuator used for such a purpose, an electric linear actuator that converts a rotational motion of a motor into a linear motion by a ball screw is known. An operation target to be moved in a linear direction is connected to the ball screw.

  The ball screw has excellent driving force transmission efficiency to the operation target, but when an external force is input from the operation target side to the ball screw (reverse input), the ball screw shaft is pushed back or pulled out in the axial direction. Is concerned. In order to solve this concern, conventionally, a braking mechanism for suppressing driving of the ball screw due to reverse input has been employed.

  The braking mechanism disclosed in Patent Literature 1 employs a drive gear having a plurality of engagement holes formed in a circumferential direction in a transmission mechanism that transmits rotational motion from a motor to a ball screw, and has a shaft with respect to the drive gear. A lock member is provided on the housing, the lock member being capable of moving in and out of the engagement hole and being disengageable from the engagement hole, and a sliding screw for converting the rotational motion of the lock motor into the forward and backward movement of the lock member, and moving the lock member forward. And the reverse input torque is received by the braking mechanism on the housing side.

JP 2017-184484 A

  However, in the braking mechanism of Patent Literature 1, when the drive gear is stopped at an arbitrary position, the position of the engagement hole may be shifted from the lock member depending on the stop position of the drive gear. In that case, there is a possibility that the lock member cannot be inserted into the engagement hole and cannot be locked. In order to suppress this, it is necessary to control the phase adjustment between the engagement hole on the transmission mechanism side and the lock member on the braking mechanism side by rotating the drive gear with a motor.

  Accordingly, the problem to be solved by the present invention is that there is no need to perform phase adjustment between the transmission mechanism that transmits the driving force from the motor to the ball screw and the braking mechanism that suppresses driving of the ball screw due to reverse input. It is to realize a simple electric actuator.

  In order to achieve the above object, a first means according to the present invention includes a motor, a ball screw for converting a rotational motion from the motor into a linear motion in an axial direction, and a driving force from the motor to the ball screw. An electric actuator comprising: a transmission mechanism that transmits a signal; a braking mechanism that suppresses driving of the ball screw; and a housing that supports the motor, the transmission mechanism, and the braking mechanism. A cylindrical surface that rotates concentrically with the drive gear to which it belongs, a cam surface formed on a fixed portion that is stationary with respect to the housing, an engaging element disposed between the cylindrical surface and the cam surface, It is possible to switch between a connected state in which the armature can be engaged with the cylindrical surface and the cam surface and a released state in which the engagement with the cylindrical surface and the cam surface can be released by controlling the energization of the electromagnet. An electromagnetic clutch kicked, is obtained by employing the structure having.

  According to the first means, when the electromagnetic clutch of the braking mechanism is in the connected state, the engaging element is engaged with the cylindrical surface that rotates concentrically with the drive gear and the cam surface of the fixed portion that is stationary with respect to the housing. Since the drive gear is in a possible state, when the drive gear is rotated, the rotational torque of the drive gear is received by the cam surface on the housing side via the engagement element, whereby the rotation of the drive gear is stopped. On the other hand, when the electromagnetic clutch is in a released state, the engagement element can release the engagement between the cylindrical surface on the drive gear side and the cam surface on the housing side, so that ball screw driving by motor driving is possible. Here, since the connection state and the release state can be switched by the energization control of the electromagnet, that is, by energizing the electromagnet or cutting off the energization, the phase between the transmission mechanism side and the braking mechanism side is changed. No control for matching is required.

  In the first means, the electromagnetic clutch may include a retainer that holds the engagement element, a neutral spring that is elastically deformed by a relative rotation of the retainer with respect to the cam surface, and a position that is different from the cylindrical surface. An engagement surface that rotates concentrically with the drive gear, and an armature that is always opposed to the engagement surface in a state of being prevented from rotating with respect to the retainer; A relative rotation of a retainer is provided so as to be movable between an engagement position for engaging the cylindrical surface and the cam surface and a neutral position for releasing the engagement, and the electromagnetic clutch is provided with It is good to be provided so that switching by the energization control can be performed between the connection state in which the armature is pressed against the engagement surface and the release state in which the pressing of the armature is released.With this configuration, when the electromagnetic clutch of the braking mechanism is in a connected state in which the armature is pressed against the engagement surface on the drive gear side, when the drive gear is rotated, the drive gear, the cylindrical surface, the retainer, and the armature are integrally formed. The engaging member is moved to the engaging position by the rotation of the retainer, and the rotational torque of the drive gear is received on the cam surface on the housing side via the engaging member, thereby stopping the rotation of the drive gear. Can be Here, since the armature, which has been prevented from rotating by the retainer, and the engagement surface always face each other, when switching to the connected state by controlling the energization of the electromagnet, there is no need to perform control for phase adjustment between the transmission mechanism side and the braking mechanism side. is there. On the other hand, when the electromagnetic clutch is in the released state in which the armature is not pressed against the engagement surface, the retainer is held at the neutral position by the neutral spring, and the engagement element does not engage with the cylindrical surface on the drive gear side and the cam surface on the housing side. Since it is at the neutral position, ball screw drive by motor drive is possible.

  More specifically, the electromagnetic clutch has a separation spring that presses the armature against the engagement surface when the motor is not driven, and the electromagnet separates the armature from the engagement surface when the motor is driven. It may be provided so as to be magnetically attracted to an inclined position. By doing so, the non-excited type electromagnetic clutch is provided, and when the motor is not driven, the armature and the engagement surface are maintained in a connected state by the spring force of the separation spring even when the energization of the electromagnet is cut off. While the power can be saved, the electromagnet is energized when the motor is driven, and the armature is kept in a released state away from the engagement surface by magnetic attraction, so that friction loss can be reduced.

  Further, the drive gear is formed of an external gear having a hollow shaft portion, the cylindrical surface of the braking mechanism is formed inside the hollow shaft portion, and the engagement surface is formed in an axial direction of the drive gear. One end side is formed in an annular shape, a rolling bearing is provided between the hollow shaft portion and the fixed portion, and the armature is fitted to the fixed portion so as to be movable in the axial direction. The electromagnet may be fixed to the housing such that the electromagnet faces the armature in the axial direction. With this configuration, while the drive gear and the cylindrical surface of the braking mechanism are formed of a single member, the concentricity of the drive gear, the fixed portion, and the armature can be favorably maintained by the rolling bearing.

  In the first means, the housing may have a snap-fit portion for fixing the electromagnet. With this configuration, the electromagnet can be easily fixed to the housing.

  In the case where an electromagnetic clutch having the above-mentioned engaging element, an armature, or the like is employed, the fixing portion includes a shaft extending concentrically with the drive gear, and includes a member connected to the housing, and the armature includes the shaft. And the electromagnet may be fixed to the shaft. This makes it possible to assemble the electromagnetic clutch on the fixed portion, thereby improving the assemblability. In addition, since the electromagnet and the armature are arranged on the same shaft, the distance between the electromagnet and the armature can be improved. The air gap can be easily managed, and the suction force of the electromagnetic clutch can be stabilized.

  Here, the fixing portion may be formed of a non-magnetic material. By doing so, it is possible to suppress magnetic flux leakage from the electromagnet to the fixed portion.

  In the case where an electromagnetic clutch having the above-mentioned engaging element, an armature, or the like is employed, the fixing portion includes a shaft extending concentrically with the drive gear, and includes a member connected to the housing, and the armature includes the shaft. A cylindrical non-magnetic member fitted to the shaft is fixed to the shaft, and the electromagnet is fixed to the outer periphery of the non-magnetic member. You may do so. This makes it possible to assemble the electromagnetic clutch on the fixed portion, thereby improving the assemblability. In addition, since the electromagnet and the armature are arranged on the same shaft, the distance between the electromagnet and the armature can be improved. The air gap can be easily managed, and the suction force of the electromagnetic clutch can be stabilized. Further, since a non-magnetic material is interposed between the electromagnet and the shaft of the fixed portion, it is possible to suppress magnetic flux leakage from the electromagnet to the fixed portion.

  It is preferable that at least one of the engaging surface and the pressed surface of the armature that are in contact with each other in the connected state is formed of a non-magnetic material. With this configuration, when the armature is attracted by the electromagnet, it is possible to suppress magnetic flux leakage from the armature to the engagement surface on the drive gear side.

  In order to achieve the above object, a second means according to the present invention comprises a motor, a ball screw for converting a rotational motion from the motor into a linear motion in an axial direction, and a driving force from the motor to the ball screw. An electric actuator comprising: a transmission mechanism that transmits a signal; a braking mechanism that suppresses driving of the ball screw; and a housing that supports the motor, the transmission mechanism, and the braking mechanism. An engaging member disposed so as to be axially movable with respect to the rotating shaft or the drive shaft in a state where the rotating shaft or the drive shaft of the motor belongs to be integrally concentrically rotatable; and A braking member that is stationary with respect to the housing in an opposed state, a connected state in which the engaging member is pressed against the braking member, and a released state in which the pressing of the engaging member is released is performed. An electromagnetic clutch provided to be switchable by energization control of the stone, is obtained by employing the structure having.

  According to the second means, when the electromagnetic clutch of the braking mechanism is in a connected state in which the engaging member on the transmission mechanism side is pressed against the braking member on the housing side, when the reverse input is transmitted from the ball screw to the transmission mechanism, the transmission is performed. The engaging member attempts to rotate integrally with the rotating shaft belonging to the mechanism or the drive shaft of the motor, and the rotating torque is transmitted from the engaging member to the braking member on the housing side, and the frictional force between the braking member and the engaging member causes rotation. The rotation of the shaft or drive shaft is braked. Here, since the engagement member and the braking member which is always axially opposed to the engagement member can be switched to the connected state by controlling the energization of the electromagnet, the phase between the transmission mechanism side and the braking mechanism side during the switching can be changed. No control for matching is required. On the other hand, when the electromagnetic clutch is in the released state in which the engaging member is not pressed against the braking member, the rotating shaft is not braked, so that the ball screw can be driven by the motor.

  In the second means, the electromagnetic clutch includes an armature that always faces the engaging member at a position opposite to the braking member with respect to the engaging member in the axial direction, and the armature is used when the motor is not driven. A separation spring that presses the engaging member against the braking member via an armature, and an elastic member that pushes the engaging member to a position away from the braking member when the motor is driven, has the electromagnet, The armature may be magnetically attracted to a position apart from the engagement member when the motor is driven. In this way, the non-excited electromagnetic clutch is provided, and when the motor is not driven, the engagement member and the braking member are indirectly maintained in a connected state by the spring force of the separation spring even when the energization of the electromagnet is interrupted. While the power can be saved, when the motor is driven, the electromagnet is energized, the armature is separated from the engaging member by magnetic attraction, and the engaging member is separated from the braking member by the spring force of the elastic member. The frictional loss can be reduced.

  In the second means, the housing may have a snap-fit portion for fixing the electromagnet. With this configuration, the electromagnet can be easily fixed to the housing.

  In the second means, for example, the rotation shaft is formed of a boss of a drive gear belonging to the transmission mechanism, and the engagement member is attached to the rotation shaft in a state in which the engagement member can rotate concentrically with the rotation shaft. It is fitted so as to be movable in the axial direction.

  In the second means, the transmission mechanism has a speed reducer that reduces the rotation input from the drive shaft of the motor and outputs the reduced rotation to the ball screw side, and the engagement member includes a drive shaft and the drive shaft. The drive shaft may be fitted so as to be movable in the axial direction so as to be integrally concentrically rotatable. In this way, when the motor is driven, the ball screw can be driven by increasing the torque with the speed reducer, but the rotation of the drive shaft of the motor is prevented because the speed reducer functions as a speed increase device against reverse input. Therefore, it is possible to reduce the holding torque necessary for the electromagnetic clutch, and to reduce the size and power consumption of the electromagnetic clutch.

  In the second means, for example, the braking member and the engaging member are connected by a frictional force acting between the friction surfaces.

  In the second means, it is preferable that the braking member and the engaging member are connected to each other by engagement of the face spline portions. With this configuration, a large holding torque can be obtained as compared with the case of the frictional force, and the size and power consumption of the electromagnet can be reduced.

  As described above, the present invention employs the above-described first or second means to transmit a driving force from a motor to a ball screw, and a braking mechanism that suppresses driving of the ball screw due to reverse input. It is possible to eliminate the need for control for performing phase matching with the above.

Sectional view showing an electric actuator according to a first embodiment of the present invention. Sectional drawing which shows the cutting surface of the II-II line of FIG. Enlarged view of the vicinity of the electromagnetic clutch in FIG. Exploded perspective view of the braking mechanism according to the first embodiment Enlarged view around the roller in FIG. Sectional view of the vicinity of an electromagnetic clutch of an electric actuator according to a second embodiment of the present invention. Sectional view near the electromagnet of the electric actuator according to the third embodiment of the present invention Sectional view near the armature of an electric actuator according to a fourth embodiment of the present invention Sectional view near the armature of an electric actuator according to a fifth embodiment of the present invention Sectional drawing which shows the principal part of the electric actuator which concerns on 6th Embodiment of this invention. FIG. 10 is a partially enlarged cross-sectional view showing a released state of the electromagnetic clutch of FIG. 10. Sectional view showing a main part of an electric actuator according to a seventh embodiment of the present invention. FIG. 10 is a perspective view showing a modified example of the braking member and the engaging member according to FIGS.

  As an example of the present invention, an electric actuator according to a first embodiment will be described with reference to FIGS. This electric actuator corresponds to the above-described first means.

  As shown in FIG. 1, the electric actuator includes a motor 10, a ball screw 20 that converts a rotary motion from the motor 10 into a linear motion, and a transmission mechanism (31 to 31) that transmits a driving force from the motor 10 to the ball screw 20. 34), a braking mechanism (41-52) for suppressing driving of the ball screw 20, and a housing 60 for supporting the motor 10, the transmission mechanism, and the braking mechanism.

  The motor 10 has a drive shaft 11 that outputs rotation. The drive shaft 11 includes a rotation shaft of a rotor that rotates inside the motor 10. The motor 10 is a DC motor that can be driven by a DC power supply. The housing 60 has a motor case 61 that houses the motor 10.

  The ball screw 20 is interposed between a ball screw shaft 21 having a spiral groove on the outer periphery, a ball screw nut 22 having a spiral groove on the inner periphery, and a spiral groove of the ball screw shaft 21 and a spiral groove of the ball screw nut 22. And a large number of balls 23 that can be circulated between the spiral grooves.

  The rotation of the ball screw shaft 21 is restricted by the engagement of the housing 60 with a rotation restricting portion provided at the rear end (the right end in FIG. 1). The ball screw nut 22 receives a driving force from the motor 10 and rotates in the forward or reverse direction. When the ball screw nut 22 rotates, the ball screw shaft 21 advances and retreats in the axial direction while the ball 23 circulates.

  Here, the axial direction is a direction along the axis of relative rotation between the ball screw nut 22 and the ball screw shaft 21. Hereinafter, the circumferential direction around the axial center line is referred to as “circumferential direction”, and the direction perpendicular to the axial direction is referred to as “radial direction”.

  The drive shaft 11 of the motor 10 is oriented in the axial direction, and is arranged in parallel with the ball screw shaft 21. FIG. 1 shows a state where the ball screw shaft 21 is arranged at an initial position where it is most retracted. Rotational motion from the motor 10 is converted into an axial linear motion of a ball screw shaft 21 parallel to the drive shaft 11 in the ball screw 20. The forward end (the left end in FIG. 1) of the ball screw shaft 21 in the forward direction functions as an actuator head for operating the operation target.

  As shown in FIGS. 1 and 2, the transmission mechanism includes a pinion gear 31, a speed reducer 32, a drive gear 33, and a driven gear 34 in order from the motor 10 to the ball screw 20.

  The pinion gear 31 is attached to the drive shaft 11 of the motor 10.

  The reduction gear 32 is a gear transmission that reduces the rotation input from the drive shaft 11 and outputs the rotation to the ball screw 20 side. The speed reducer 32 is configured as a planetary gear speed reducer, and as shown in FIGS. 1 and 3, a pinion gear 31 that rotates as a sun gear, and a planet carrier that outputs a rotation that is reduced in comparison to the rotation of the pinion gear 31. Axis 32a. The housing 60 has a speed reducer case 62 also serving as an internal gear of the speed reducer 32. The reduction gear case 62 and the motor case 61 are fastened in the axial direction by a screw member (not shown).

  The drive gear 33 outputs the driving force transmitted from the motor 10 to the ball screw 20 as shown in FIGS. The drive gear 33 is composed of an external gear having an external tooth part 33a and a hollow shaft part 33b integrally.

  The external gear portion 33 a of the drive gear 33 meshes with the driven gear 34. The driven gear 34 is fixed to the outer periphery of the ball screw nut 22.

  As shown in FIG. 3, the hollow shaft portion 33b of the drive gear 33 has a stepped hole shape and extends to both axial sides with respect to the external tooth portion 33a. The small-diameter hole portion of the hollow shaft portion 33b is integrally and rotatably connected to the planet carrier shaft 32a.

  As shown in FIGS. 1 and 3, the housing 60 has bearing cases 63 and 64 divided into two parts in the axial direction. The bearing cases 63 and 64 accommodate the drive gear 33, the driven gear 34, most of the ball screw shaft 21, and the ball screw nut 22. These bearing cases 63 and 64 are fastened in the axial direction by screw members (not shown). The bearing case 63 and the speed reducer case 62 are fastened in the axial direction by a screw member (not shown).

  As shown in FIG. 3, a rolling bearing 71 is provided between the outer periphery of the planet carrier shaft 32a and the inner periphery of the bearing case 63. A rolling bearing 72 is provided between the outer periphery of the large-diameter hole side of the hollow shaft portion 33 b and the inner periphery of the bearing case 64. The planet carrier shaft 32a and the drive gear 33 are supported by the housing 60 via rolling bearings 71 and 72.

  As shown in FIG. 1, a rolling bearing 73 is provided between the ball screw nut 22 and the bearing case 64. The ball screw 20 is supported by the housing 60 via a rolling bearing 73.

  A shaft cover 65 is attached to the bearing case 64. The shaft cover 65 is a mating portion that accommodates the rear end side of the ball screw shaft 21 and prevents the ball screw shaft 21 from rotating with respect to the housing 60. The bearing case 64 and the shaft cover 65 are fastened in the axial direction by a screw member (not shown).

  An axially expandable and contractable boot 66 is mounted between the bearing case 63 and the front end side of the ball screw shaft 21. The boot 66 is for watertightly sealing between the housing 60 and the ball screw shaft 21. The joints between the covers (61, 62, 63, 64) of the housing 60 are properly sealed watertight with a spigot structure, an O-ring or the like.

  As shown in FIGS. 2 and 3, the above-described braking mechanism has a cylindrical surface 41 that rotates concentrically with the drive gear 33 and gradually narrows from the center in the circumferential direction toward both ends in the circumferential direction. A cam surface 42 forming a wedge space, a roller 43 disposed between the cylindrical surface 41 and the cam surface 42, a retainer 44 holding the roller 43, and a relative rotation of the retainer 44 with respect to the cam surface 42 And a neutral spring 45 that is elastically deformed.

  The cylindrical surface 41 is formed inside the large-diameter hole portion of the hollow shaft portion 33b of the drive gear 33. The cylindrical surface 41 is continuous over the entire circumference in the circumferential direction.

  The cam surface 42 is formed on a fixed portion 46 that is stationary with respect to the housing 60. The radial distance between the cam surface 42 and the cylindrical surface 41 is determined from the position of the roller 43 in FIGS. 2 and 3 which is located at the center in the circumferential direction of the cam surface 42 on both sides in the circumferential direction (counterclockwise and counterclockwise in FIG. 2). ) Gradually getting smaller. Although the example in which the cam surface 42 is configured by a single plane is shown, the cam surface may be configured by a plurality of surfaces, or may be configured by a single curved surface.

  The fixing portion 46 is formed of a cam ring member formed separately from the housing 60, as shown in FIGS. A key groove 46 a is formed on the inner periphery of the fixing portion 46. The bearing case 64 has a support shaft portion 64a extending in the axial direction. The support shaft portion 64a is located at a position facing the drive shaft 11 of the motor 10 in the axial direction. The fixing portion 46 is fixed to the support shaft portion 64a by a key (not shown) driven into the key groove 46a. The support shaft portion 64a supports the fixed portion 46, the drive gear 33, and the drive shaft 11 of the motor 10 on the same axis. The means for fixing the fixing portion 46 and the support shaft portion 64a is not particularly limited, and examples thereof include serration fitting and screw fastening. Further, the fixing portion 46 may be formed integrally with the housing 60 as a part of the bearing case 64.

  The outer periphery of the fixed portion 46 has a shape protruding in the radial direction at an intermediate position in the axial direction, and a plurality of cam surfaces 42 are formed in the protruding portion at intervals in the circumferential direction. That is, a plurality of wedge spaces are formed, and the roller 43 is arranged in each wedge space. Outer diameters of both ends of the outer periphery of the fixed portion 46 located on both sides in the axial direction with respect to the cam surface 42 are smaller than the cam surface 42. A rolling bearing 74 is provided between the end of the fixed portion 46 on the motor 10 side and the inner periphery of the hollow shaft portion 33b of the drive gear 33. The rolling bearing 74 is for rotatably supporting the drive gear 33 with respect to the fixed portion 46.

  The roller 43 has a cylindrical surface that can contact the cylindrical surface 41 and the cam surface 42. As shown in FIG. 5, the roller 43 is engaged with the cylindrical surface 41 and the cam surface 42 by the relative rotation of the retainer 44 with respect to the fixing portion 46 (refer to the position of the roller 43 drawn by a dashed line in FIG. 5). ) And a neutral position for releasing the engagement (see the position of the roller 43 drawn by a solid line in the figure). The roller 43 is engaged with the cylindrical surface 41 and the cam surface 42 when the retainer 44 is relatively rotated with respect to the fixed portion 46, and transmits the rotational torque to the cam surface 42.

  As shown in FIGS. 3 and 4, the retainer 44 is formed of an engaging member that retains each roller 43 with a cage-shaped pocket 44d. The overall shape of the retainer 44 is formed by, for example, press working, and a material thereof is, for example, a steel plate.

  The retainer 44 has an inward flange 44a located on the rolling bearing 74 side. The retainer 44 is rotatably fitted on the outer periphery of the fixed portion 46 on the inner periphery of the flange 44a. The flange 44a is located between the end surface of the inner race of the rolling bearing 74 and the end surface of the fixing portion 46 that faces the axial direction, and the axial movement of the retainer 44 is restricted by these end surfaces. .

  The neutral spring 45 elastically holds the retainer 44 so that the roller 43 is at the neutral position. The neutral spring 45 is formed of a metal spring having a pair of engaging pieces 45a formed on both ends of a C-shaped ring portion so as to face outward. The ring portion of the neutral spring 45 is fitted in a concave portion 46b formed in the fixed portion 46. The concave portion 46b has a constant depth in the axial direction on the end face of the fixing portion 46. The pair of engagement pieces 45a are inserted into cutouts 44b formed in the retainer 44 from cutouts formed in the outer wall of the recess 46b. The pair of engagement pieces 45a press the notch portion of the concave portion 46b and the notch portion 44b of the retainer 44 in opposite directions in the circumferential direction. Due to the pressing, the retainer 44 is held at a phase at which the roller 43 is in the neutral position.

  The above-described braking mechanism includes an engagement surface 47 that concentrically rotates with the drive gear 33 at a position different from the cylindrical surface 41, and an armature 48 that always faces the engagement surface 47 while being prevented from rotating with respect to the retainer 44. And an electromagnetic clutch 50 for transmitting and interrupting torque between the armature 48 and the engagement surface 47.

  The engagement surface 47 is located on one end side (the right side in FIGS. 3 and 4) of the drive gear 33 in the axial direction, and is formed in a continuous annular shape in the circumferential direction.

  The armature 48 is formed of an annular member which is fitted to the fixing portion 46 so as to be movable in the axial direction. The armature 48 is slidably fitted to one end of the outer periphery of the fixed portion 46 on the inner diameter surface.

  The armature 48 has an engagement hole 48a at a portion different from the side surface portion that faces the engagement surface 47 in the axial direction all around the circumferential direction. The retainer 44 has an engagement protrusion 44c inserted into the engagement hole 48a. The armature 48 is prevented from rotating with respect to the retainer 44 by the circumferential engagement between the engagement protrusions 44c and the engagement holes 48a. The engagement hole 48a and the engagement protrusion 44c may be provided at one or a plurality of locations.

  The electromagnetic clutch 50 has a separation spring 51 that presses the armature 48 against the engagement surface 47 when the motor 10 is not driven, and an electromagnet 52 that faces the armature 48 in the axial direction on the same side as the separation spring 51 with respect to the armature 48. .

  The electromagnet 52 includes a field core and an electromagnetic coil supported by the field core. The electromagnet 52 is fixed to the bearing case 64 so as to face the armature 48 in the axial direction.

  The electromagnet 52 is fitted on the support shaft 64a on the inner periphery of the field core. The electromagnet 52 has an axial projection formed on the end surface of the field core, and is prevented from rotating with respect to the bearing case 64 by fitting the projection with a hole formed in the bearing case 64. ing.

  The bearing case 64 has a snap-fit portion 64b for fixing the electromagnet 52. The electromagnet 52 has a peripheral groove 52a formed on the outer periphery of the field core. The snap-fit portion 64b has a cylindrical shape fitted to the outer periphery of the field core of the electromagnet 52, and is engaged with the peripheral groove portion 52a by a claw formed on the inner peripheral side of the cylinder. In this engagement state, the snap-fit portion 64b restricts the axial movement of the electromagnet 52 toward the armature 48 with respect to the bearing case 64 so that the snap-fit portion 64b can prevent the electromagnet 52 from rotating and maintain the engagement with the support shaft portion 64a. . Thereby, the electromagnet 52 is fixed to the bearing case 64.

  The separation spring 51 is interposed between the field core of the electromagnet 52 and the armature 48. The separation spring 51 is supported in the radial direction by a circumferential groove 48 b formed on the inner diameter side of the armature 48. The separation spring 51 presses the circumferential groove portion 48b in the axial direction at a plurality of positions even in the circumferential direction. Although the wave washer is illustrated as the separation spring 51, a coil spring may be employed.

  When the controller (not shown) cuts off the power supply to the electromagnet 52, the armature 48 is pressed against the engagement surface 47 by the separation spring 51. Therefore, the electromagnetic clutch 50 is brought into a connection state in which the armature 48 is pressed against the engagement surface 47 by the separation spring 51. On the other hand, when the controller energizes the electromagnet 52, the electromagnet 52 magnetically attracts the armature 48, whereby the armature 48 is moved to a position away from the engagement surface 47 against the separation spring 51. For this reason, the electromagnetic clutch 50 is in a released state in which the pressing of the armature 48 against the engagement surface 47 is released. As described above, the electromagnetic clutch 50 is provided so as to be switchable between the connected state and the released state by controlling the energization of the electromagnet 52. In the released state, the separation spring 51 is accommodated in the circumferential groove 48b, and the armature 48 is magnetically attracted to the electromagnet 52. The amount by which the armature 48 separates from the retainer 44 in the axial direction is limited by the separation spring 51 or the electromagnet 52. In any case, the armature 48 is connected to the neutral spring 45 from the concave portion 46b of the fixing portion 46. Is restricted to a position where escape of the vehicle can be suppressed.

  The operation of the electric actuator shown in FIG. 1 will be described. This electric actuator also energizes the electromagnet 52 of the electromagnetic clutch 50 when energizing the motor 10 to drive the motor 10, and shuts off the energization of the electromagnet 52 when the energization of the motor 10 is stopped to stop driving the motor 10. The power supply is also cut off.

  1 and 3 in which the energization of the motor 10 and the electromagnet 52 is cut off, the armature 48 is pressed against the engagement surface 47 by the spring force of the separation spring 51, and the engagement surface 47 Is connected to the drive gear 33 by a frictional force acting between the armature 48 and the armature 48. Further, the retainer 44 is held in a phase for keeping the roller 43 at the neutral position with respect to the cam surface 42 by the spring force of the neutral spring 45.

  At this time, when the ball screw nut 22 is rotated by a reverse input in the axial direction given to the ball screw shaft 21 from the outside, the driven gear 34 is rotated integrally with the ball screw nut 22. The drive gear 33 meshing with the driven gear 34 is also rotated, and the armature 48 connected to the engagement surface 47 on the drive gear 33 is also rotated. Rotated. For this reason, the neutral spring 45 is elastically deformed so that the distance between the pair of engagement pieces 45a becomes narrower, and the roller 43 held in the pocket 44d of the holder 44 is moved by the pocket 44d. By being pushed in the rotation direction, it is moved to the engagement position (see FIGS. 2 and 5), and is brought into a state of engaging with the cylindrical surface 41 on the drive gear 33 side and the cam surface 42 of the fixed portion 46. In this engaged state, the rotational torque of the drive gear 33 is received by the cam surface 42 of the fixed portion 46 via the roller 43, and the rotation of the drive gear 33 is forcibly stopped. Therefore, the rotation of the driven gear 34 is also stopped, and the rotation of the ball screw nut 22 due to the reverse input is stopped.

  On the other hand, in the ON state in which the motor 10 and the electromagnet 52 are energized, the retainer 44 is held in a phase that maintains the roller 43 at the neutral position with respect to the cam surface 42 by the spring force of the neutral spring 45. , The armature 48 is moved in the axial direction against the separation spring 51 by the magnetic attraction of the electromagnet 52, moves away from the engagement surface 47 on the drive gear 33 side, and is held in a state of being magnetically attracted to the electromagnet 52. . For this reason, the rotation torque of the drive gear 33 given from the motor 10 is not transmitted to the cam surface 42 of the fixed portion 46, and the drive gear 33 is free to rotate either clockwise or clockwise in FIG. (Free rotation). In this state, the rotation between the armature 48 and the retainer 44 is maintained by the engagement hole 48a and the engagement protrusion 44c.

  When the state is switched to the OFF state after the ON state, the separation spring 51 compressed in the axial direction by the armature 48 in the ON state rebounds, and the spring force causes the armature 48 to engage with the drive gear 33 side. It is pressed against the mating surface 47.

  When the drive gear 33 is turned on after the rotation of the drive gear 33 due to the reverse input is stopped in the above-mentioned OFF state, the neutral spring 45 elastically deformed by the relative rotation of the retainer 44 due to the reverse input repels. Then, the retainer 44 is rotated back by the spring force, and the roller 43 held in the pocket 44d is returned to the neutral position.

  Here, since the armature 48 stopped by the retainer 44 and the engagement surface 47 always face each other, when the connection state is switched by the energization control of the electromagnet 52, the engagement surface 47 on the transmission mechanism side and the engagement surface 47 on the brake mechanism side are used. It is not necessary to control the drive of the motor 10 for performing phase adjustment with the armature 48. Therefore, this electric actuator eliminates the need for control for performing phase adjustment between the transmission mechanism that transmits the driving force from the motor 10 to the ball screw 20 and the braking mechanism that suppresses driving of the ball screw 20 due to reverse input. be able to.

  As described above, the electric actuator includes a cylindrical surface 41 that rotates concentrically with the drive gear 33 belonging to the transmission mechanism, a cam surface 42 formed on the fixed portion 46 that is stationary with respect to the housing 60, and a cylindrical surface 41. Roller 43 disposed between the cylindrical surface 41 and the cam surface 42, and a connected state in which the roller 43 can be engaged with the cylindrical surface 41 and the cam surface 42, and a release capable of releasing the engagement with the cylindrical surface 41 and the cam surface 42. A transmission mechanism for transmitting the driving force from the motor 10 to the ball screw 20 by employing a braking mechanism having an electromagnetic clutch 50 provided so as to be able to switch between a state and an energization control (ON / OFF control) of the electromagnet 52. Thus, it is possible to realize an electric actuator that does not require control for performing phase matching with the braking mechanism that suppresses driving of the ball screw 20 due to reverse input.

  The electric actuator has a separation spring 51 that presses the armature 48 against the engagement surface 47 when the electromagnetic clutch 50 is not driven by the motor 10, and the electromagnet 52 separates the armature 48 from the engagement surface 47 when the motor 10 is driven. Is provided so as to magnetically attract the magnetic force to the position, so that the electromagnetic clutch 50 becomes a non-excitation type. When the motor 10 is not driven, even if the energization of the electromagnet 52 is interrupted, the armature 48 And the engagement surface 47 are maintained in a connected state, so that power can be saved. On the other hand, when the motor 10 is driven, the electromagnet 52 is energized, and the armature 48 is separated from the engagement surface 47 by magnetic attraction. , The friction loss of the driving force of the motor 10 can be reduced.

  Also, in this electric actuator, the drive gear 33 is formed of an external gear having a hollow shaft portion 33b, the cylindrical surface 41 of the braking mechanism is formed inside the hollow shaft portion 33b, and the engagement surface 47 is formed on the drive gear 33. One end in the axial direction is formed in an annular shape, and a rolling bearing 74 is provided between the hollow shaft portion 33b and the fixed portion 46, and the armature 48 is fitted to the fixed portion 46 so as to be movable in the axial direction. Since the electromagnet 52 is fixed to the housing 60 so as to face the armature 48 in the axial direction, the drive gear 33 and the cylindrical surface 41 of the braking mechanism are constituted by a single member. In addition, the concentricity of the drive gear 33, the fixed portion 46, and the armature 48 can be favorably maintained by the rolling bearing 74.

  Further, in this electric actuator, since the housing 60 has the snap-fit portion 64b for fixing the electromagnet 52, the electromagnet 52 can be easily fixed to the housing 60.

  The electromagnetic clutch 50 is exemplified by an electromagnetic disk clutch type in which a disk-shaped armature 48 always faces the engaging surface 47 in the entire circumferential direction, but the shapes of the armature and the engaging surface are relative to each other in the circumferential direction. Any relationship may be used as long as the relationship is possible regardless of the relationship. For example, one may have an annular surface shape, and the other may have an arcuate surface shape that is axially opposed to one.

  In the first embodiment, the electromagnet 52 is fixed to the bearing case 64 of the housing 60, but the electromagnet 52 may be fixed to the fixing portion 46 side. FIG. 6 shows a second embodiment as an example. In the description of the example of FIG. 6, only the differences from the first embodiment will be described.

  6 includes a cam ring member including a shaft 46c having a smaller diameter than the cam surface 42. The shaft 46c extends concentrically with the drive gear 33 from the recess 46b. The shaft 46c forms an end on the bearing case 64 side (opposite the motor side) of both ends of the fixed portion 46.

  The fixing part 46 is formed of a non-magnetic material. Here, the non-magnetic material is a concept including a paramagnetic material and a diamagnetic material. For example, nonmagnetic steel, aluminum and the like can be mentioned as paramagnetic substances, and copper, zinc and the like can be mentioned as diamagnetic substances. Examples of the nonmagnetic steel include an austenitic stainless steel having a magnetic permeability of 1.02 or less and a high manganese steel.

  The neutral spring 45 is fitted into the concave portion 46b from the end of the shaft 46c. The inner circumference of the armature 48 is fitted to the outer circumference of the shaft 46c from the end of the shaft 46c. The separation spring 51 is fitted in a circumferential groove formed in a field core of the electromagnet 52. The inner periphery of the electromagnet 52 is press-fitted from the end of the shaft 46 to the outer periphery of the shaft 46c. By this press fit, the electromagnet 52 is fixed to the shaft 46c. In order to determine the fitting position, a shoulder 46d is formed on the shaft 46c to receive the end face of the field core of the electromagnet 52 in the axial direction. The armature 48 is disposed closer to the cam surface 42 and the engagement surface 47 than the shoulder 46d.

  The inner peripheral end of the shaft 46c is fitted to the support shaft 64a of the bearing case 64. It should be noted that the rotation of the shaft 46c with respect to the support shaft portion 64a may be replaced with a D-cut, a two-plane width, a spline fit, or the like instead of the key.

  A female screw 46e is formed on the remaining portion of the inner periphery of the shaft 46c. The female screw 46e passes inside the cam surface 42. The inner peripheral end of the shaft 46c is fitted to the support shaft portion 64a, and the male screw member 67 is screwed into the female screw 46e from the outside of the bearing case 64, whereby the fixing portion 46 is connected to the bearing case 64 of the housing 60. ing.

  According to the second embodiment, the neutral spring 45 is fitted in the concave portion 46b of the fixing portion 46, the armature 48 is fitted on the shaft 46c, and the electromagnet 52 holding the separation spring 51 is fitted and fixed on the shaft 46c. These can be assembled. Furthermore, when the rolling bearing 74, the engaging element 43, and the retainer 44 are arranged in a state where the rolling bearing 74, the engaging element 43, and the retainer 44 are arranged between the inside of the drive gear 33 and the fixed portion 46, the drive gear 33, the fixed portion 46, and the electromagnetic clutch can be assembled concentrically. Can be.

  In addition, since the air gap between the electromagnet 52 and the armature 48 is arranged on the same shaft 46c, the management of the air gap between the electromagnet 52 and the armature 48 is facilitated. The force (magnetic force by which the electromagnet 52 attracts the armature 48) can be stabilized. That is, in the first embodiment, since the electromagnet 52 is fixed to the bearing case 64 and the armature 48 is fitted to the end of the fixing portion 46, the dimensional error and the assembly error of the housing 60 are reduced in the arrangement of the electromagnet 52 with respect to the armature 48. In contrast to the structure having an adverse effect, in the second embodiment, the dimensional error and the assembly error of the housing 60 do not affect the arrangement of the electromagnet 52 with respect to the armature 48. Therefore, the electromagnet 52 can be appropriately arranged with respect to the armature 48 only by determining the fitting position of the electromagnet 52 by the shoulder 46d.

  Further, in the second embodiment, since the fixing portion 46 is formed of a non-magnetic material, it is possible to suppress magnetic flux leakage from the electromagnet 52 to the fixing portion 46 when the electromagnet 52 is energized. Therefore, even if the electromagnet 52 is fitted to the shaft 46c of the fixed portion 46, it is possible to suppress an adverse effect on the attraction force of the electromagnetic clutch.

  FIG. 7 shows a third embodiment as another example in which the electromagnet 52 is fixed to the fixing portion 46 side. In the description of the example of FIG. 7, only the differences from the second embodiment will be described.

  The outer diameter of the shaft 46c of the fixing portion 46 shown in FIG. 7 is smaller than that of the second embodiment. This is for disposing the cylindrical non-magnetic body 46f fitted to the shaft 46c. The non-magnetic body 46f is fixed to the shaft 46c by pressing the inner circumference of the cylindrical non-magnetic body 46f into the outer circumference of the shaft 46c.

  The material forming the fixed portion 46 is formed of a paramagnetic material or a soft magnetic material that is more easily magnetized than the nonmagnetic material 46f.

  The electromagnet 52 is fixed to the outer periphery of the non-magnetic member 46f by press fitting to the outer periphery of the non-magnetic member 46f fixed to the shaft 46c. The shoulder 46d of the shaft 46c regulates the fitting position of the non-magnetic body 46f and the electromagnet 52.

  According to the third embodiment, as in the second embodiment, it is possible to assemble the electromagnetic clutch on the fixed portion 46, so that the assemblability can be improved, and the electromagnetic clutch can be mounted on the same shaft 46c. Since the electromagnet 52 and the armature 48 are arranged at the same time, the management of the air gap between the electromagnet 52 and the armature 48 is facilitated, and the attraction force of the electromagnetic clutch can be stabilized. Further, since the non-magnetic material 46f is interposed between the electromagnet 52 and the shaft 46c of the fixed part 46, the leakage of the magnetic flux from the electromagnet 52 to the fixed part 46 can be suppressed. For this reason, even if the fixing portion 46 is not made of a non-magnetic material, it is possible to suppress an adverse effect on the attraction force of the electromagnetic clutch.

  The countermeasures against magnetic flux leakage outside the magnetic circuit between the electromagnet 52 and the armature 48 can be taken at a place other than between the electromagnet 52 and the fixed part 46. FIG. 8 shows a fourth embodiment as an example. In the description of the example in FIG. 8, only differences from the second embodiment will be described.

  The engagement surface 47 shown in FIG. 8 is formed of a non-magnetic material. The engagement surface 47 is made of a friction material fixed to the hollow shaft portion 33b.

  According to the fourth embodiment, when the electromagnet 52 attracts the armature 48, it is possible to suppress magnetic flux leakage from the armature 48 to the engagement surface 47 on the drive gear side. Therefore, even if the drive gear including the hollow shaft portion 33b is not made of a non-magnetic material, it is possible to suppress the adverse effect on the attraction force of the electromagnetic clutch.

  FIG. 9 shows a fifth embodiment as another example in which a countermeasure against magnetic flux leakage is performed at a portion other than between the electromagnet 52 and the fixed portion 46. In the description of the example in FIG. 9, only differences from the second embodiment will be described.

  The armature 48 shown in FIG. 9 has a pressed surface 48a formed of a non-magnetic material. The pressed surface 48a is located at a position facing the engagement surface 47 in the axial direction, and is a portion that comes into contact with the engagement surface 47 in the above-described connection state. The pressed surface 48a is made of a friction material fixed to the groove of the armature 48. The rest of the armature 48 other than the friction material is formed of a ferromagnetic material.

  According to the fifth embodiment, when the electromagnet 52 attracts the armature 48, it is possible to suppress magnetic flux leakage from the armature 48 to the engagement surface 47 on the drive gear side. For this reason, even if the drive gear including the engagement surface 47 and the hollow shaft portion 33b is not made of a non-magnetic material, it is possible to suppress the adverse effect on the attraction force of the electromagnetic clutch.

  Although illustration is omitted, the third to fifth embodiments may be combined as appropriate. For example, both the engaging surface and the pressed surface may be formed of a non-magnetic material, A non-magnetic material in the shape of a circle may be employed.

  As another example of the present invention, FIGS. 10 and 11 show a sixth embodiment corresponding to the above-described second means. In the following, only differences from the first embodiment will be described. The electric actuator according to the second embodiment is different in that another braking mechanism is employed instead of the braking mechanism of the first embodiment.

  The braking mechanism according to the sixth embodiment includes a rotating shaft 81 formed of a boss of a drive gear 80, and an engaging member 91 disposed on the rotating shaft 81.

  The rotating shaft 81 has a spline shaft portion 81a at a position different from a bearing fitting surface for the rolling bearing 100 interposed between the rotating shaft 81 and the bearing case 110. The spline shaft portion 81a is rotatably supported by the bearing case 110 via the rolling bearing 100. Although the hollow boss portion is illustrated as the rotating shaft 81, any rotating shaft capable of disposing the engaging member on the outer periphery may be used, and a solid shaft may be used.

  The engagement member 91 has a spline hole 91a corresponding to the spline shaft 81a. The engagement member 91 is arranged so as to be concentrically rotatable integrally with the rotation shaft 81 and axially movable with respect to the rotation shaft 81 by spline fitting between the spline hole portion 91a and the spline shaft portion 81a.

  The braking mechanism includes a braking member 92 that is stationary with respect to the bearing case 110 while always facing the engaging member 91 in the axial direction, and an electromagnetic clutch 120 that transmits and disconnects torque between the engaging member 91 and the braking member 92. And

  The braking member 92 is an annular plate that is axially opposed to the engaging member 91 in the entire circumferential direction. The braking member 92 is fixed to the bearing case 110. This fixing may be performed by appropriate means such as insert molding of the braking member 92 with external teeth and the bearing case 110, and screwing the braking member 92 to the bearing case 110.

  The engagement member 91 and the braking member 92 have friction surfaces 91b and 92a facing each other. The friction surfaces 91b and 92a are each formed in a flat annular shape along the radial direction.

  The electromagnetic clutch 120 includes an armature 121 that always faces the engaging member 91 in the axial direction at a position opposite to the braking member 92 with respect to the engaging member 91, and the engaging member 91 via the armature 121 when the motor is not driven. A spring 122 for pressing the armature 121 against the armature 121 on the opposite side of the armature 121 with respect to the armature 121 in the axial direction, and the engaging member 91 is separated from the brake member 92 when the motor is driven. And an elastic member 124 that pushes to an inclined position.

  The bearing case 110 is further divided into a disk case portion 111 and a magnet case portion 112 in order to accommodate the engaging member 91, the armature 121, and the like having a larger diameter than the rolling bearing 100. The magnet case portion 112 has a snap-fit portion 112a for fixing the electromagnet 123. The armature 121 is fitted to a support shaft formed on the magnet case 112 so as to be movable in the axial direction. A separation spring 122 is interposed between the armature 121 and the field core of the electromagnet 112.

  The elastic member 124 is formed of an annular metal spring loosely fitted to the spline shaft portion 81a. Although the coil spring is illustrated as the elastic member 124, a wave washer may be employed. The rotating shaft 81 is provided with a shoulder 82 that receives the elastic member 124 in the axial direction. The elastic member 124 is interposed between the shoulder 82 and the engaging member 91.

  Further, a retaining ring 83 is attached to the rotating shaft 81 at a position on the armature 121 side with respect to the engaging member 91. The retaining ring 83 regulates the axial movement of the engaging member 91 pushed by the spring force of the elastic member 124. When the engaging member 91 and the braking member 92 come into contact with each other in the axial direction (see FIG. 10), a small gap is formed between the retaining ring 83 and the engaging member 91, and a large gap is formed as compared with this gap. Is generated between the armature 121 and the electromagnet 123. As shown in FIG. 11, when the axial movement of the engaging member 91 is restricted by the retaining ring 83, the gap between the friction surface 91b of the engagement member 91 and the friction surface 92a of the braking member 92 is set. This is for bringing the state into a non-contact state and making the state between the engaging member 91 and the facing surfaces 91c and 121a of the armature 121 in a non-contact state.

  When a controller (not shown) cuts off the power supply to the electromagnet 123, the armature 121 is moved toward the engagement member 91 by the separation spring 122. Since the separation spring 122 exerts a predominant spring force as compared with the elastic member 124, the engaging member 91 is pressed against the braking member 92 against the elastic member 124 by the armature 121 pressed by the separation spring 122. Therefore, the electromagnetic clutch 120 is brought into a connected state in which the friction surface 91b of the engagement member 91 is pressed against the friction surface 92a of the braking member 92 (see FIG. 10). At this time, the engaging member 91 and the braking member 92 are connected by a frictional force acting between the friction surface 91b and the friction surface 92a. On the other hand, when the controller energizes the electromagnet 123, the electromagnet 123 magnetically attracts the armature 121, so that the armature 121 is moved toward the electromagnet 123 against the separation spring 122, and the elastic member 124 The engaging member 91 is moved to a position away from the braking member 92 by the spring force of the repulsion. As a result, the electromagnetic clutch 120 enters a released state in which the pressing of the engaging member 91 against the braking member 92 is released. As described above, the electromagnetic clutch 120 is provided so as to be switchable between the connected state and the released state by controlling the energization of the electromagnet 123. In the released state, the armature 121 is magnetically attracted to the electromagnet 123 in a state where the separation spring 122 is compressed in the axial direction, and the engaging member 91 is held by the elastic member 124 in contact with the retaining ring 83. The three members 91, the braking member 92 and the armature 121 are kept in a non-contact state (see FIG. 11).

  The point that the energization control of the electromagnet 123 is synchronized with the motor is the same as in the first embodiment. In the OFF state in FIG. 10 in which the energization of the electromagnet 123 is interrupted, the engaging member 91 is pressed against the braking member 92 by the separation spring 122 of the electromagnetic clutch 120, and accordingly, the distance between the engaging member 91 and the braking member 92 is increased. Are connected by the frictional force acting on them. At this time, if the drive gear 80 is to be rotated by a reverse input, the rotation torque is transmitted from the engaging member 91 to the braking member 92 via the rotating shaft 81, so that the torque between the braking member 92 and the engaging member 91 is reduced. The frictional force acts as a braking force, so that the rotation of the rotating shaft 81 is braked and the rotation of the drive gear 80 is stopped.

  In the ON state of FIG. 11 in which the electromagnet 123 is energized, the armature 121 is moved in the axial direction against the separation spring 122 by the magnetic attraction of the electromagnet 123, moves away from the engaging member 91, and moves to the electromagnet 123. While being magnetically attracted, the engaging member 91 is held at a position separated from the braking member 92 by the elastic member 124. Therefore, the drive gear 80 rotates freely (free rotation).

  When the state is switched to the OFF state after the ON state, the separation spring 122 compressed in the axial direction by the armature 121 in the ON state is repelled, and the spring force causes the engaging member 91 to move through the armature 121. Is pressed against the braking member 92.

  Here, the engagement member 91 and the braking member 92 axially opposed to the engagement member 91 can be switched to the connected state by controlling the energization of the electromagnet 123. It is not necessary to control the motor for performing phase adjustment between the motor and the braking member 92 on the braking mechanism side. Therefore, this electric actuator can also eliminate the need for control for performing phase adjustment between the transmission mechanism that transmits the driving force from the motor to the ball screw and the braking mechanism that suppresses driving of the ball screw due to reverse input. .

  In addition, the electric actuator includes an armature 121 in which the electromagnetic clutch 120 always faces the engaging member 91 at a position opposite to the braking member 92 with respect to the engaging member 91 in the axial direction, and an armature 121 when the motor is not driven. A separation spring 122 that presses the engaging member 91 against the braking member 92 via the intervening member, and an elastic member 124 that presses the engaging member 91 to a position away from the braking member 92 when the motor is driven. Sometimes, the armature 121 is magnetically attracted to a position distant from the engaging member 91, so that the electromagnetic clutch 120 becomes a non-excitation type, and when the motor is not driven, even if the energization of the electromagnet 123 is cut off, Since the engagement member 91 and the braking member 92 are indirectly maintained in a connected state by the spring force of the separation spring 122, power can be saved. When the motor is driven, the electromagnet 123 is energized, and the armature 121 is separated from the engaging member 91 by magnetic attraction, and the engaging member 91 is separated from the braking member 92 by the spring force of the elastic member 124 to a released state. Therefore, friction loss can be reduced.

  As a further modification example from the sixth embodiment, an electric actuator according to a seventh embodiment is shown in FIG. In the following, only differences from the sixth embodiment will be described. The electric actuator according to the seventh embodiment is different from the electric actuator according to the sixth embodiment in that the mating partner of the engaging member is changed.

  In the seventh embodiment, a spline shaft portion is omitted from the rotation shaft 131 of the drive gear 130. A drive shaft 140 of the motor penetrates through the hollow planetary carrier shaft 32 a and the rotary shaft 131, which are output shafts of the speed reducer, and extends to a position closer to the electromagnet 123 than the braking member 92. The drive shaft 140 has a spline shaft 141. The spline shaft 141 projects from the rotation shaft 131. The engagement member 150 is spline-fitted to the spline shaft 141. The drive shaft 140 is provided with a shoulder 142 that receives the elastic member 151 in the axial direction. In addition, a retaining ring 143 is attached to the drive shaft 140 at a position on the armature 121 side with respect to the engaging member 150.

  In the seventh embodiment, when the transmission mechanism is operated by the reverse input, the reverse input torque reduced by the speed reducer is transmitted to the drive shaft 140 of the motor via the drive gear 130 and the planetary carrier shaft 32a. Since the engaging member 151 is fitted movably in the axial direction with respect to the drive shaft 140 in a state in which the engagement member 151 can be concentrically rotated integrally with the drive shaft 140 of the motor, the torque is increased by the speed reducer when the motor is driven. On the other hand, the reduction gear serves as a speed-up gear for reverse input, so that the holding torque required to prevent the rotation of the drive shaft 140 of the motor can be reduced. It is possible to reduce the size and power consumption of the electromagnet 123 and the separation spring 122 of the electromagnetic clutch.

  In the above-described sixth and seventh embodiments, as the electromagnetic clutch, the electromagnetic disk clutch type in which the disk-shaped braking member and the engaging member are connected by the frictional force between the friction surfaces of each other has been exemplified, but any engagement is possible. It may be changed to an electromagnetic clutch of the shape.

  Specifically, as shown in FIG. 13, the braking member 160 and the engaging member 170 are connected by meshing of the face spline portions 161 and 171 with each other. The face spline portion 161 of the braking member 160 is constituted by a large number of teeth 162 extending radially from the annular center of the braking member 160. The face spline portion 171 of the engaging member 170 is constituted by a number of radial teeth corresponding to the face spline portion 161. The opposing teeth of the face spline portions 161 and 171 can mesh at any rotational position of the engaging member 170.

  As described above, in the case of the connection state due to the engagement of the face spline portions 161 and 171, the holding torque can be made larger than the holding torque due to the frictional force between the flat friction surfaces as shown in FIGS. 10 and 12. Consequently, the size and power consumption of the electromagnet 123 and the like can be reduced.

  In each of the above-described embodiments, the roller is exemplified as the engaging element.However, the cam surface has a cylindrical shape, and the engaging element employs a sprag that can be tilted between the engaging position and the neutral position, The tilt position of the sprags may be controlled by the relative rotation of the cage with respect to the cam surface.

  The embodiments disclosed this time should be considered in all respects as illustrative and not restrictive. Therefore, the scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 10 Motor 11,140 Drive shaft 20 Ball screw 31 Pinion gear 32 Reduction gear 32a Planet carrier shaft 33,80,130 Drive gear 33a External tooth part 33b Hollow shaft part 34 Driven gear 41 Cylindrical surface 42 Cam surface 43 Engager (roller)
44 Cage 45 Neutral spring 46 Fixed part 46c Shaft 46f Non-magnetic material 47 Engagement surface 48, 121 Armature 48a Pressed surface 50, 120 Electromagnetic clutch 51, 122 Release spring 52, 123 Electromagnet 60 Housing 64b, 112a Snap fit part 81 , 131 rotating shafts 91, 150, 170 engaging members 92, 160 braking members 124, 151 elastic members 161, 171 face spline section

Claims (16)

A motor, a ball screw that converts a rotational motion from the motor into a linear motion in the axial direction, a transmission mechanism that transmits a driving force from the motor to the ball screw, and a braking mechanism that suppresses driving of the ball screw, An electric actuator comprising: a housing that supports the motor, the transmission mechanism, and the braking mechanism;
The braking mechanism has a cylindrical surface that rotates concentrically with a drive gear belonging to the transmission mechanism, a cam surface formed on a fixed portion that is stationary with respect to the housing, and a gap between the cylindrical surface and the cam surface. Switching between the arranged engaging element and a connected state in which the engaging element can be engaged with the cylindrical surface and the cam surface and a released state in which the engaging element can be disengaged from the cylindrical surface and the cam surface by controlling the energization of the electromagnet. And an electromagnetic clutch provided so as to be capable of being provided. The electromagnetic clutch is configured to retain the engagement element, a neutral spring that is elastically deformed by relative rotation of the retainer with respect to the cam surface, and coaxially rotate integrally with the drive gear at a position different from the cylindrical surface. An engagement surface, and an armature that always faces the engagement surface in a state where the armature is prevented from rotating with respect to the retainer,
The engagement element is provided so as to be movable between an engagement position for engaging the cylindrical surface and the cam surface by a relative rotation of the retainer with respect to the cam surface, and a neutral position for releasing the engagement. Yes,
2. The electromagnetic clutch according to claim 1, wherein the electromagnetic clutch is provided so as to be able to switch between the connected state in which the armature is pressed against the engagement surface and the released state in which the armature is released from being pressed by controlling the energization of the electromagnet. 3. Electric actuator.   The electromagnetic clutch has a separation spring that presses the armature against the engagement surface when the motor is not driven, and the electromagnet magnetically attracts the armature to a position away from the engagement surface when the motor is driven. The electric actuator according to claim 2, which is provided as follows.   The drive gear is formed of an external gear having a hollow shaft portion, the cylindrical surface of the braking mechanism is formed inside the hollow shaft portion, and the engagement surface is located at one end of the drive gear in the axial direction. A ring bearing is provided between the hollow shaft portion and the fixed portion, and the armature is fitted to the fixed portion so as to be movable in the axial direction. 4. The electric actuator according to claim 2, comprising a member, wherein the electromagnet is fixed to the housing so as to face the armature in the axial direction. 5.   The electric actuator according to claim 1, wherein the housing has a snap-fit portion for fixing the electromagnet. The fixing portion includes a shaft extending concentrically with the drive gear, and includes a member connected to the housing,
The electric actuator according to claim 2, wherein the armature is fitted to the shaft so as to be movable in an axial direction, and the electromagnet is fixed to the shaft.   The electric actuator according to claim 6, wherein the fixing portion is formed of a non-magnetic material. The fixing portion includes a shaft extending concentrically with the drive gear, and includes a member connected to the housing,
The armature is fitted movably in the axial direction with respect to the shaft,
A cylindrical non-magnetic body fitted to the shaft is fixed to the shaft,
The electric actuator according to claim 2, wherein the electromagnet is fixed to an outer periphery of the nonmagnetic body.   The electric actuator according to any one of claims 6 to 8, wherein at least one of the engagement surface and the pressed surface of the armature that are in contact with each other in the connected state is formed of a non-magnetic material. A motor, a ball screw that converts a rotational motion from the motor into a linear motion in the axial direction, a transmission mechanism that transmits a driving force from the motor to the ball screw, and a braking mechanism that suppresses driving of the ball screw, An electric actuator comprising: a housing that supports the motor, the transmission mechanism, and the braking mechanism;
An engagement member disposed so as to be axially movable with respect to the rotation shaft or the drive shaft in a state in which the braking mechanism is coaxially rotatable integrally with the rotation shaft or the drive shaft of the motor belonging to the transmission mechanism; A braking member that is stationary with respect to the housing in a state always facing the engaging member in the axial direction, a coupled state in which the engaging member is pressed against the braking member, and a released state in which the pressing of the engaging member is released. An electric actuator, comprising: an electromagnetic clutch provided to be switchable by energization control of an electromagnet.   An armature that always faces the engaging member in the axial direction at a position opposite to the braking member with respect to the engaging member; and the armature via the armature when the motor is not driven. A spring that presses the braking member against the braking member, and an elastic member that pushes the engaging member to a position away from the braking member when the motor is driven, and the electromagnet moves the armature when the motor is driven. The electric actuator according to claim 10, wherein the electric actuator is provided so as to be magnetically attracted to a position apart from the engagement member.   The electric actuator according to claim 10 or 11, wherein the housing has a snap-fit portion for fixing the electromagnet.   The rotation shaft is formed of a boss portion of a drive gear belonging to the transmission mechanism, and the engagement member is fitted to the rotation shaft so as to be axially movable in a state where the engagement member is rotatable integrally and concentrically with the rotation shaft. The electric actuator according to any one of claims 10 to 12, wherein the electric actuator is provided. The transmission mechanism has a speed reducer that reduces the rotation input from the drive shaft of the motor and outputs the reduced rotation to the ball screw side,
The electric actuator according to any one of claims 10 to 13, wherein the engagement member is fitted movably in the axial direction with respect to the drive shaft in a state where the engagement member is rotatable concentrically with the drive shaft. .   The electric actuator according to any one of claims 10 to 14, wherein the braking member and the engaging member are connected by a frictional force acting between friction surfaces of each other.   The electric actuator according to any one of claims 10 to 15, wherein the braking member and the engaging member are connected to each other by meshing face spline portions.

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