JP2020141435A - Electric actuator - Google Patents

Abstract

To provide an electric actuator capable of appropriately regulating the back-and-forth movement of a screw shaft in the stopped state of an electric motor.SOLUTION: The electric actuator is provided with an electromagnetic brake 70 comprising: a brake rotor 71 provided so as to be integrally rotatable with an output shaft 10a of en electric motor 10; an armature 72 mutually moved between two positions, specifically a first position where the armature abuts against the brake rotor 71 in an axial direction and a second position where an axial gap Ga is formed between the armature and the brake rotor 71; a brake plate 73 unrotatably holding the brake motor 71 cooperatively with the armature 72 set at the first position; and a stator 74 generating a magnetic attraction force Ma for setting the armature 72 at the second position when the electric motor 10 is energized. The stator 74 includes a cylindrical part 74c storing the brake rotor 71 or the like in an inner periphery.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electric actuator.

In recent years, in vehicles such as automobiles, electrification has progressed in order to save labor and reduce fuel consumption. For example, a system has been developed in which an automatic transmission, a brake, a steering wheel, and the like are operated by the power of an electric motor. It has been put on the market. As an actuator used for such an application, for example, Patent Document 1 below discloses an actuator that employs a screw mechanism as a motion conversion mechanism that converts the rotary motion of an electric motor into a linear motion and outputs it. The screw shaft constituting this screw mechanism constitutes the output shaft (final output shaft) of the electric actuator, and operates the operation target by moving forward and backward in the axial direction.

The screw shaft can be moved forward and backward with high accuracy and smoothly. Therefore, the electric actuator having the screw shaft as the final output shaft has an advantage that the operation target can be operated with high accuracy, but for example, an external force is input to the operation target (screw shaft) when the electric motor is stopped. In that case, if no measures are taken, there is a possibility that the operation target may be erroneously operated. Therefore, the electric actuator of Patent Document 1 is provided with a lock mechanism portion capable of restricting the advance / retreat movement of the screw shaft while the electric motor is stopped.

The above-mentioned lock mechanism unit mainly receives a small electric motor (locking motor) provided separately from the electric motor for driving the screw shaft (driving motor) and the output of the locking motor in the axial direction. It is equipped with a movable lock member. On the power transmission path between the drive motor and the screw mechanism, a gear mechanism portion for transmitting the rotational movement of the drive motor to the nut of the screw mechanism is provided, and the lock member is a gear mechanism portion. It can be inserted and removed from the hole provided in the drive gear. The lock mechanism unit having the above configuration operates as follows, for example. First, when power is supplied to the drive motor, power is also supplied to the lock motor, and the lock member is held in a state of being separated from the hole of the drive gear. In this case, the drive gear is rotatable, and the rotational movement of the drive motor is transmitted to the nut via the gear mechanism, so that the electric actuator is in an unlocked state in which the screw shaft is allowed to move forward and backward. .. On the other hand, when the power supply to the drive motor is interrupted, the power supply to the lock motor is also interrupted. Along with this, when the lock member is inserted into the hole of the drive gear, the drive gear and the lock member are engaged in the rotation direction of the drive gear. As a result, the drive gear becomes non-rotatable, so that the electric actuator is in a locked state in which the forward / backward movement of the screw shaft is restricted.

To summarize the above, in the electric actuator of Patent Document 1, when the drive motor is driven, the lock motor is also driven to shift from the locked state to the unlocked state, and when the drive motor is stopped, the lock is released. It is configured to transition from state to locked state.

Japanese Unexamined Patent Publication No. 2017-184484

The lock mechanism portion cannot be put into a locked state that regulates the advance / retreat movement of the screw shaft unless the lock member is inserted into the hole provided in the drive gear. Therefore, for example, when the arrangement position of the hole portion and the arrangement position of the lock member are deviated in the rotation direction of the drive gear when an external force is applied to the operation target (on the extension line of the movement direction of the lock member). If there is no hole), there is a problem that the lock mechanism does not work effectively and the forward / backward movement of the screw shaft cannot be immediately regulated. In order to avoid such a problem, complicated control is required, which leads to an increase in the cost of the actuator.

Therefore, a main object of the present invention is to appropriately regulate the forward / backward movement of the screw shaft when an external force is applied to the screw shaft while the drive motor is stopped, without requiring complicated control. It is an object of the present invention to provide a low-cost electric actuator.

The present invention, which was devised to achieve the above object, includes a drive unit having an electric motor and a motion conversion mechanism unit that converts the rotational motion of the drive unit into a linear motion, and the motion conversion mechanism unit is the drive unit. In an electric actuator having a nut that rotates in response to the rotational movement of the motor and a screw shaft that moves forward and backward in the axial direction as the nut rotates, a brake provided in the drive unit so as to be integrally rotatable with the output shaft of the electric motor. An armature that moves between two positions, a first position that abuts the rotor and the brake rotor in the axial direction, and a second position that forms an axial gap between the rotor and the brake rotor, and an armature located in the first position An electromagnetic brake is provided with a brake plate that non-rotatably holds the brake rotor in cooperation with the motor and a stator that generates a magnetic attraction force to position the armature in the second position when the electric motor is energized. The stator is provided with a tubular portion that houses a brake rotor, an armature, and a brake plate on the inner circumference.

According to the above configuration, when the energization of the electric motor is stopped, the armature is positioned in the first position without the magnetic attraction force acting on the armature, so that the brake rotor cannot rotate between the armature and the brake plate. Since it is sandwiched between the armatures, the rotation of the motor output shaft that rotates integrally with the brake rotor is restricted. As a result, the rotation of the nut that rotates in response to the rotational movement of the motor output shaft and the advance / retreat movement of the screw shaft are regulated in a locked state. On the other hand, when the electric motor is energized, the armature moves to the second position (moves from the first position to the second position), an axial gap is formed between the armature and the brake rotor, and the brake rotor cannot rotate. Since the pinching force to be pinched is released, the rotation of the motor output shaft is allowed. As a result, the lock is released so that the nut can rotate and the screw shaft can move forward and backward. In short, in the electric actuator according to the present invention, the brake rotor that rotates integrally with the motor output shaft is switched between a non-rotatable state and a non-pinched state as the armature moves between two positions. The locked state and unlocked state can be switched. Therefore, the forward / backward movement of the screw shaft in the stopped state of the electric motor can be appropriately regulated without requiring complicated control.

Further, since the stator constituting the electromagnetic brake is provided with a tubular portion in which the brake rotor, the armature and the brake plate are housed in the inner circumference, the stator can be utilized as one component of the casing of the electric actuator. In this case, since it is not necessary to separately provide the electric actuator with a dedicated component for accommodating the electromagnetic brake, it is possible to contribute to cost reduction of the electric actuator.

If the drive unit is further provided with a planetary gear reducer that reduces the rotation of the electric motor and outputs the speed, the electric motor can be miniaturized, which is advantageous in reducing the weight and compactness of the electric actuator. At this time, the sun gear of the planetary gear reducer may be provided integrally with the brake rotor, or the ring gear of the planetary gear reducer may be provided integrally with the stator.

The present invention is preferably applied to, for example, an electric actuator of a type in which the output shaft and the screw shaft of an electric motor are arranged in parallel and the rotational motion of the drive unit is transmitted to the motion conversion mechanism unit via the gear mechanism unit. Can be done.

From the above, according to the present invention, it is possible to appropriately regulate the screw shaft from moving forward and backward in the axial direction when the drive unit (electric motor) is stopped without requiring complicated control. The actuator can be provided at low cost.

It is a schematic vertical sectional view of the electric actuator which concerns on one Embodiment of this invention. FIG. 1 is a cross-sectional view taken along the line AA of FIG. (A) is a partially enlarged view of the electric actuator when the electric motor is driven, and (b) is a partially enlarged view of the electric actuator when the electric motor is stopped. It is a partially enlarged view of the electric actuator which concerns on 2nd Embodiment of this invention. It is a partially enlarged view of the electric actuator which concerns on 3rd Embodiment of this invention. It is a partially enlarged view of the electric actuator which concerns on 4th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The "one side in the axial direction" used in the following description is the left side of the paper surface in FIG. 1, and the "other side in the axial direction" is the right side of the paper surface in FIG.

FIG. 1 is a schematic vertical sectional view of an electric actuator 1 according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA of FIG. The electric actuator 1 includes a drive unit 2 that generates a rotational drive force, a motion conversion mechanism unit 3 that converts the rotational drive force (rotational motion) output from the drive unit 2 into a linear motion, and a drive unit 2. The gear mechanism unit 4 that transmits the rotational motion to the motion conversion mechanism unit 3, the support unit 5 that supports the motion conversion mechanism unit 3, and the operation unit 6 that outputs (transmits) the linear motion of the motion conversion mechanism unit 3 to the operation target. And. The drive unit 2 includes a motor unit 8, a speed reduction mechanism unit 9, and a lock mechanism unit 7.

The motor unit 8 mainly includes an electric motor 10 and a motor case 11 accommodating the electric motor 10. The motor case 11 includes a case main body 12 and a sealing member 13 that seals an end opening on one side of the case main body 12 in the axial direction. The motor terminals (not shown) of the electric motor 10 are connected to a power power source via conductive members and power lines (not shown). As the electric motor 10, a DC motor with a brush or a brushless motor capable of detecting and controlling the amount of rotation of the output shaft 10a is used.

The speed reduction mechanism unit 9 includes a speed reducer that decelerates and outputs the rotation of the electric motor 10 and a speed reducer case 16 that houses the speed reducer. The speed reducer case 16 is separably connected to a stator 74 (details will be described later) of an electromagnetic brake 70 arranged adjacent to one side in the axial direction thereof.

The speed reducer is composed of a planetary gear speed reducer 15. That is, the speed reducer includes a sun gear 17 provided so as to be rotatable integrally with the output shaft 10a of the electric motor 10, a ring gear 18 provided on the radial outer side of the sun gear 17 (here, the inner circumference of the speed reducer case 16). A plurality of (for example, three) planetary gears 19 arranged between the sun gear 17 and the ring gear 18 and meshing with the sun gear 17 and the ring gear 18, and a planetary gear holder 20 and a planetary gear carrier 21 that rotatably hold the planetary gear 19. To be equipped. The planetary gear carrier 21 integrally has an annular portion 21a connected to the planetary gear 19 and a cylindrical portion 21b extending axially from the inner diameter end of the annular portion 21a to the other side in the axial direction, and causes the planetary gear 19 to revolve. Take out and output. The cylindrical portion 21b of the planetary gear carrier 21 is rotatably connected to the rolling bearing 45 (inner ring) and the gear boss 44, which will be described later.

The speed reducer 15 having the above configuration decelerates the rotational movement of the output shaft 10a of the electric motor 10 and then transmits the speed to the gear mechanism unit 4 and further to the motion conversion mechanism unit 3. As a result, the rotational torque of the gear mechanism portion 4 can be increased, so that a small electric motor 10 can be adopted.

The motion conversion mechanism unit 3 is composed of a ball screw 30. The ball screw 30 includes a screw shaft 31 arranged in parallel with the output shaft 10a of the electric motor 10, a nut 32 rotatably fitted to the outer periphery of the screw shaft 31 via a large number of balls 33, and a circulation member. It is equipped with a screw 34. A large number of balls 33 are loaded between the spiral groove 31a formed on the outer peripheral surface of the screw shaft 31 and the spiral groove 32a formed on the inner peripheral surface of the nut 32, and the frame 34 is incorporated. With such a configuration, when the screw shaft 31 moves back and forth in the axial direction as the nut 32 rotates, the ball 33 circulates between the spiral grooves 31a and 32a.

The screw shaft 31 constitutes an output member of the electric actuator 1, and an operation unit 6 for operating an operation target (not shown) is provided at one end on one side in the axial direction thereof. In the illustrated example, the operation unit 6 is composed of a radial through hole into which a connecting member for connecting the operation target and the screw shaft 31 is inserted.

The electric actuator 1 is provided with a bottomed tubular shaft case 35 having a tubular portion 35a and a bottom portion 35b, and a part of the screw shaft 31 is housed in the shaft case 35. The shaft case 35 of the present embodiment is integrally provided with a flange portion 35c extending radially outward from one end of the tubular portion 35a in the axial direction, and the flange portion 35c is a bearing constituting the support portion 5. It is separably connected to the case 51.

The electric actuator 1 is provided with a position detecting device for detecting the axial position (advancing / retreating movement amount) of the screw shaft 31. This position detection device includes, for example, a magnetic sensor (not shown) as a stroke sensor attached to the motor case 11 and a permanent magnet 37 as a sensor target attached to the screw shaft 31. The permanent magnet 37 is attached to the screw shaft 31 via the holding member 38. In this case, when the screw shaft 31 moves forward and backward, the magnetic sensor detects a change in the magnetic field (for example, the direction and strength of the magnetic flux density) of the permanent magnet 37 that moves accordingly, so that the screw shaft 31 moves forward and backward. The amount is detected.

At the end of the screw shaft 31 on the other side in the axial direction, a rotation regulating portion 60 for restricting the rotation of the screw shaft 31 around its axis is provided. As shown in FIG. 2, the rotation restricting portion 60 is inserted (press-fitted) into the radial through hole 31b provided in the screw shaft 31, and both ends of the support pin 61 projecting to the outside of the screw shaft 31. A guide roller 62 that is fitted onto the protruding portion of the support pin 61 and rotatably supported by the support pin 61, and a guide roller 62 that is provided on the inner peripheral surface of the tubular portion 35a of the shaft case 35 and extends in the axial direction. It is provided with a pair of guide grooves 35d that are rotatably fitted.

As described above, the electric actuator 1 of the present embodiment is provided with a position detecting device for detecting the axial position of the screw shaft 31, and the screw shaft 31 is a guide roller 62 attached to the screw shaft 31. Can move forward and backward by rolling along the guide groove 35d provided in the shaft case 35, so that the forward and backward limits of the screw shaft 31 can be controlled. Therefore, the screw shaft 31 basically does not move forward or backward beyond a predetermined stop position. However, when the screw shaft 31 malfunctions due to a failure of the position detection device and retracts beyond a predetermined stop position (moves to the other side in the axial direction), the other end of the screw shaft 31 becomes the bottom portion 35b of the shaft case 35. There is a risk that the shaft case 35 will be deformed or damaged due to collision with the shaft case 35.

Therefore, in the present embodiment, a cushioning member 63 made of an elastic material such as rubber, resin, or a thermoplastic elastomer is provided between the screw shaft 31 and the bottom portion 35b of the shaft case 35. As a result, even if the screw shaft 31 collides with the bottom portion 35b of the shaft case 35, the impact load is relaxed by the cushioning member 63, so that the possibility that the shaft case 35 is damaged can be reduced.

The cushioning member 63 of the present embodiment has a columnar insertion portion 64 inserted into a recess 31d opened in an end surface 31c on the other side in the axial direction of the screw shaft 31, and a screw shaft 31 and a bottom portion 35b of the shaft case 35. It is composed of a flange-shaped cushioning portion 65 interposed between them. A through hole 66 in the radial direction is provided in the insertion portion 64 of the cushioning member 63, and the cushioning member 63 is attached and fixed to the screw shaft 31 by inserting the support pin 61 into the through hole 66. In short, the support pin 61 not only functions as a support shaft for the guide roller 62, but also functions as a mounting member for the cushioning member 63. With such a configuration, an assembly including a screw shaft 31, a support pin 61, a guide roller 62, a cushioning member 63, and the like can be easily assembled.

As shown in FIG. 1, the gear mechanism unit 4 accommodates a drive gear 41 that is rotationally driven by receiving the output of the drive unit 2, a driven gear 42 that meshes with the drive gear 41, and a drive gear 41 and a driven gear 42. The gear case 43, the gear boss 44 arranged on the inner circumference of the drive gear 41, and a pair of rolling bearings (for example, deep groove ball bearings) 45, 46 that rotatably support the gear boss 44 with respect to the casing of the electric actuator 1. Be prepared. The driven gear 42 has a cylindrical nut mounting portion 42a into which the outer peripheral surface of the nut 32 is press-fitted. The gear boss 44 is arranged coaxially with the output shaft 10a of the electric motor 10, and the inner peripheral surface of the cylindrical portion 21a of the planetary gear carrier 21 and the inner peripheral surface of the drive gear 41 are press-fitted onto the outer peripheral surface thereof. ..

With the above configuration, when the output shaft 10a of the electric motor 10 rotates and the rotational driving force is transmitted to the gear boss 44 via the speed reducer 15, the gear boss 44 and the drive gear 41 rotate integrally and the drive gear 41 The driven gear 42 that meshes with the driven gear 42, and the nut 32 of the ball screw 30 fixed to the driven gear 42 rotate integrally. As a result, the screw shaft 31 of the ball screw 30 moves back and forth in the axial direction according to the rotation direction of the nut 32, and the operation target connected to the operation portion 6 of the screw shaft 31 is operated.

In the present embodiment, the driven gear 42 has a larger diameter and a larger number of teeth than the drive gear 41. Therefore, the rotational motion input to the gear mechanism portion 4 is transmitted to the nut 32 after being decelerated and the torque is increased. As a result, the electric motor 10 can be further miniaturized.

The gear case 43 has a cylindrical portion 43a that accommodates a part of the screw shaft 31. A tubular boot 47 is attached between the cylindrical portion 43a and the screw shaft 31. The boot 47 is made of an elastic material such as resin, rubber, or a thermoplastic elastomer, and integrally has a small-diameter tubular portion 47a and a large-diameter tubular portion 47b, and a bellows portion 47c connecting both tubular portions 47a and 47b. The small diameter tubular portion 47a is tightened and fixed to the screw shaft 31 by the boot band 48A, and the large diameter tubular portion 47b is tightened and fixed to the cylindrical portion 43a of the gear case 43 by the boot band 48B. With such a configuration, foreign matter is prevented from entering the gear case 43. A boot cover 49 for protecting the boot 47 is arranged on the outer periphery of the boot 47. The boot cover 49 of the present embodiment is provided integrally with the case body 12 constituting the motor case 11.

The support portion 5 includes a support bearing 50 that rotatably supports the nut 32 of the ball screw 30, and a bearing case 51 that houses the support bearing 50. The bearing case 51 is separably connected to the gear case 43 arranged adjacent to one side in the axial direction.

The support bearing 50 is a rolling bearing (ball bearing) including an outer ring 50a and an inner ring 50b, a ball 50c rotatably arranged between them, and a cage (not shown) holding the ball 50c. Double row angular contact ball bearings capable of supporting radial and bidirectional axial loads are used. Between the bearing case 51 and the support bearing 50, a flanged cylindrical sleeve 52 having a flange portion inward in the radial direction is arranged, and the outer ring 50a of the support bearing 50 is the collar portion of the sleeve 52. And the retaining ring 53 mounted on the inner peripheral surface of the sleeve 52 are sandwiched between the sleeve 52 and the retaining ring 53, so that the positioning is performed in the axial direction. On the other hand, the inner ring 50b of the support bearing 50 is positioned in the axial direction by being sandwiched between the driven gear 42 and the stop ring 54 mounted on the outer peripheral surface of the nut 32.

Hereinafter, the lock mechanism portion 7 used in the electric actuator 1 of the present embodiment will be described in detail. The lock mechanism unit 7 has a function of switching between an unlocked state that allows the advancing / retreating movement of the screw shaft 31 and a locked state that restricts the advancing / retreating movement of the screw shaft 31.

As shown in FIG. 1, the lock mechanism portion 7 is composed of an electromagnetic brake 70 arranged between the electric motor 10 and the planetary gear reducer 15. As shown in FIGS. 3A and 3B, the electromagnetic brake 7 mainly includes a brake rotor 71, an armature 72 arranged on one side in the axial direction of the brake rotor 71, and an annular portion of the brake rotor 71 (the annular portion). A brake plate 73 arranged on the other side in the axial direction of 71b), a stator 74, and a pressing spring 75 are provided.

The brake rotor 71 has a hub portion 71a rotatably provided with the output shaft 10a of the electric motor 10 and an annular portion 71b interposed between the armature 72 and the brake plate 73. The annular portion 71b of the present embodiment is a separate member from the hub portion 71a and is fixed to the hub portion 71a by an appropriate means, but it can also be provided integrally with the hub portion 71a. One end surface of the annular portion 71b is located slightly on one side in the axial direction with respect to one end surface of the hub portion 71a.

The stator 74 extends axially from the coil portion 74a, the core portion 74b holding the coil portion 74a, and the outer peripheral portion of the end portion on the other side in the axial direction of the core portion 74b, and extends the brake rotor 71, the armature 72, and the brake plate 73. It has a tubular portion 74c housed in the inner circumference. In the stator 74, one end of the core portion 74b in the axial direction is separably connected to the case body 12 of the motor case 11, and the other end of the tubular portion 74c in the axial direction is a speed reducer. It is fixedly held by being separably connected to the case 16. Therefore, the core portion 74b and the tubular portion 74c have a function as a casing of the electric actuator 1. The coil constituting the coil portion 74a is connected to a power power source (for example, a power power source to which the electric motor 10 is connected) via a conductive member or a power line (not shown).

The brake plate 73 is fixedly arranged at a predetermined position in the axial direction, and the armature 72 is arranged between the brake rotor 71 and the stator 74 in a state where the armature 72 can be moved in the axial direction. More specifically, the armature 72 is in axial contact with the brake rotor 71 (in cooperation with the brake plate 73 to hold the brake rotor 71 non-rotatably) in the first position [see FIG. 3 (b)]. An axial gap Ga is formed between the brake rotor 71 and the brake rotor 71 so that the brake rotor 71 can move between the two positions of the second position [see FIG. 3A] that allows the rotation of the brake rotor 71. In FIG. 3A, the gap width of the axial gap Ga is exaggerated for ease of understanding, but the actual gap width is about 0.5 mm.

The pressing spring 75 is composed of a compression coil spring arranged in a compressed state between an annular protrusion provided on the inner diameter portion of the stator 74 (core portion 74b) and the armature 72, and the armature 72 is attached to the other side in the axial direction. It is gaining momentum.

The electromagnetic brake 70 as the lock mechanism unit 7 has the above configuration, and switches between the unlocked state and the locked state by operating as follows.

First, as shown in FIG. 3A, when the electric motor 10 is energized and the output shaft 10a of the electric motor 10 is rotationally driven, the coil portion 74a of the stator 74 is energized. .. When the coil portion 74a is energized, the coil portion 74a generates a magnetic circuit M, and the armature 72 resists the urging force of the pressing spring 75 in the axial direction due to the magnetic attraction force Ma generated by the generation of the magnetic circuit M. It is sucked to one side (sucked by the stator 74). As a result, the armature 72 is located at the second position, and an axial gap Ga is formed between the armature 72 and the brake rotor 71. Therefore, no braking force (friction force) acts on the brake rotor 71, and the output shaft 10a of the electric motor 10 provided with the brake rotor 71 integrally rotatable is also allowed to rotate. If the rotation of the output shaft 10a is allowed, the rotation of the nut 32 of the ball screw 30 that rotates in response to the rotational movement of the output shaft 10a, and the advance / retreat movement of the screw shaft 31 are also allowed. In short, the electromagnetic brake 70 holds the electric actuator 1 in the unlocked state when the electric motor 10 is energized.

On the other hand, when the energization of the electric motor 10 is stopped (interrupted), the energization of the coil portion 74a of the stator 74 is also stopped. As a result, the magnetic circuit M disappears, and the magnetic force Ma attracting the armature 72 no longer acts on the armature 72. Therefore, the armature 72 receives the urging force of the pressing spring 75 and is pressed to the other side in the axial direction to brake. It moves to the first position where it abuts in the axial direction with the rotor 71. When the armature 72 is positioned at the first position, the brake rotor 71 is non-rotatably sandwiched by the cooperation of the armature 72 and the brake plate 73, so that the rotation of the output shaft 10a of the electric motor 10 is restricted. If the rotation of the output shaft 10a is regulated, the rotation of the nut 32 that rotates in response to the rotational movement of the output shaft 10a, and the advance / retreat movement of the screw shaft 31 are also regulated. Therefore, even when an external force is input to the screw shaft 31 while the electric motor 10 is stopped, the screw shaft 31 and the operation target are held at predetermined positions.

As described above, in the electric actuator 1 according to the present invention, the brake rotor 71 is non-rotatably sandwiched as the armature 72 moves between two positions in conjunction with the drive or stop of the electric motor 10. The locked state that regulates the advancing / retreating movement of the screw shaft 31 and the unlocking state that allows the advancing / retreating movement of the screw shaft 31 are switched only by switching between the state of being held and the state of not being pinched. Therefore, the advancing / retreating movement of the screw shaft 31 in the stopped state of the electric motor 10 can be appropriately regulated without requiring complicated control.

Since the electromagnetic brake 70 used in the present invention is a so-called friction type non-excitation electromagnetic brake, the braking force thereof is a tooth type electromagnetic brake that generates a braking force by meshing tooth surfaces among the electromagnetic brakes. It is inevitably smaller than the brake. However, in the present invention, since the brake rotor 71 is provided so as to be integrally rotatable on the output shaft 10a of the electric motor 10, the rotational torque acting on the brake rotor 71 is relatively small, so that the friction type non-excited electromagnetic wave is provided. Sufficient braking force can be secured even with a brake.

Further, the stator 74 of the electromagnetic brake 70 is provided with a tubular portion 74c in which the brake rotor 71, the armature 72 and the brake plate 73 are housed in the inner circumference, and the stator 74 is utilized as a constituent member of the casing of the electric actuator 1. There is. By doing so, it is not necessary to separately provide the electric actuator 1 with a dedicated component for accommodating the electromagnetic brake 70, which can contribute to the cost reduction of the electric actuator 1.

Combined with the effects described above, according to the present invention, the screw shaft 31 is appropriately regulated to move forward and backward while the electric motor 10 is stopped, without requiring complicated control. It is possible to realize a highly reliable electric actuator 1 at low cost.

Although the electric actuator 1 according to the embodiment of the present invention has been described above, the electromagnetic brake 70 as the lock mechanism unit 7 may have a configuration as shown in FIGS. 4 to 6, for example.

In the second embodiment shown in FIG. 4, the brake rotor 71 is integrally provided with the sun gear 17 of the speed reducer 15. More specifically, the hub portion 71a constituting the brake rotor 71 is extended to the other side in the axial direction, the sun gear 17 of the planetary gear reducer 15 is provided in the extension portion 71c, and the extension portion 71c is output from the electric motor 10. It is fixed to the shaft 10a. According to such a configuration, the number of parts and the number of assembly steps are reduced as compared with the first embodiment shown in FIG. 1, in which the hub portion 71a and the sun gear 17 are individually provided and both are individually fixed to the output shaft 10a. Therefore, the cost of the electric actuator 1 can be reduced.

In the third embodiment shown in FIG. 5, the ring gear 18 of the planetary gear reducer 15 is integrally provided on the stator 74 (cylindrical portion 74c) of the electromagnetic brake 70, and the ring gear 18 is provided in the embodiment shown in FIGS. 1 and 4. The speed reducer case 16 provided is omitted. Along with this, the gear case 43 is connected to the tubular portion 74c of the stator 74. Further, the hub portion 71a of the brake disc 71 is integrally rotatably fixed to the outer diameter surface (small diameter outer diameter surface) of one end of the sun gear 17 of the planetary gear reducer 15, and the sun gear 17 and the brake disc 71 (hub portion 71a) are fixed. Are overlapped in the axial direction. In this way, in addition to being able to omit the seal ring (a member for ensuring the sealing property of the connecting portion and having an elliptical cross section shown in FIGS. 1 and 5) provided at the connecting portion between the cases. , The electric actuator 1 can be made compact in the axial direction.

In the fourth embodiment shown in FIG. 6, the sun gear 17 of the speed reducer 15 is integrally provided on the hub portion 71a of the brake rotor 71, and the ring gear 18 of the speed reducer 15 is integrally provided on the tubular portion 74c of the stator 74. .. In short, the electric actuator 1 of this embodiment also has the characteristic configuration adopted in the embodiments shown in FIGS. 4 and 5. In this way, it is possible to simultaneously realize cost reduction by reducing the number of parts and assembly man-hours and compactness in the axial direction.

In the embodiment described above, the motion conversion mechanism unit 3 is composed of the ball screw 30, but the present invention can also be applied to the electric actuator 1 in which the motion conversion mechanism unit 3 is composed of the slip screw. The sliding screw is a screw mechanism in which a ball 33 and a frame 34 are omitted, and substantially consists of a screw shaft 31 and a nut 32 rotatably fitted around the screw shaft 31.

Further, in the embodiment described above, the speed reduction mechanism unit 9 is provided in the drive unit 2, but the speed reduction mechanism unit 9 may be omitted. Although not shown, when the reduction mechanism portion 9 is omitted, the output shaft 10a of the electric motor 10 and the gear boss 44 of the gear mechanism portion 4 may be integrally rotatably connected.

Further, in the embodiment described above, the reduction mechanism is formed in the gear mechanism portion 4 by increasing the number of teeth of the driven gear 42 as compared with the drive gear 41, but the reduction mechanism in the gear mechanism portion 4 is omitted. It doesn't matter. That is, the number of teeth of the drive gear 41 and the driven gear 42 can be the same.

The present invention is not limited to the above-described embodiments, and it is needless to say that the present invention can be carried out in various forms without departing from the gist of the present invention. Indicated by the scope of claims and further includes the equal meanings set forth in the claims, and all modifications within the scope.

1 Electric actuator 2 Drive part 3 Motion conversion mechanism part 10 Electric motor 10a Output shaft 15 Planetary gear reducer 17 Sun gear 18 Ring gear 30 Ball screw 31 Screw shaft 32 Nut 70 Electromagnetic brake 71 Brake rotor 71a Hub part 71b Ring part 72 Armature 73 Brake Plate 74 Stator 74a Coil part 74b Core part 74c Cylindrical part 75 Pressing spring M Magnetic circuit Ma Magnetic attractive force

Claims (4)

A drive unit having an electric motor and a motion conversion mechanism unit that converts the rotational motion into a linear motion are provided, and the motion conversion mechanism unit generates a nut that rotates in response to the rotational motion of the drive unit and the rotation of the nut. In an electric actuator having a screw shaft that moves forward and backward in the axial direction.
An axial gap is formed in the drive unit between a brake rotor provided so as to be rotatable integrally with the output shaft of the electric motor, a first position in which the brake rotor abuts in the axial direction, and the brake rotor. An armature that moves between two positions at the second position, a brake plate that cooperates with the armature at the first position to non-rotatably hold the brake rotor, and the electric motor when the electric motor is energized. An electromagnetic brake is provided with a stator that generates a magnetic attraction to position the armature in the second position.
An electric actuator characterized in that the stator is provided with a tubular portion that houses the brake rotor, the armature, and the brake plate on the inner circumference. The drive unit further includes a planetary gear reducer that reduces the rotation of the electric motor and outputs the speed.
The electric actuator according to claim 1, wherein the sun gear of the planetary gear reducer is integrally provided with the brake rotor. The drive unit further includes a planetary gear reducer that reduces the rotation of the electric motor and outputs the speed.
The electric actuator according to claim 1, wherein the ring gear of the planetary gear reducer is integrally provided with the stator. The electric motor according to any one of claims 1 to 3, wherein the output shaft of the electric motor and the screw shaft are arranged in parallel, and the rotational movement of the drive unit is transmitted to the nut via the gear mechanism unit. Actuator.

Images