JP6736352B2 - Electric actuator - Google Patents

Description

The present invention relates to an electric actuator.

In recent years, in automobiles, electrification is progressing in order to save labor and reduce fuel consumption. For example, a system for operating an automatic transmission, a brake, a steering wheel, etc. by the power of an electric motor (motor) has been developed and put on the market. It has been thrown in. As an electric actuator used in such a system, a motion conversion mechanism that converts the rotational motion of the motor into a linear motion and outputs the linear motion, through a screw shaft arranged coaxially with the rotation center of the motor and a plurality of balls. There is one that employs a ball screw device including a nut member that is rotatably fitted to the outer periphery of a screw shaft (for example, Patent Document 1). In this case, when the nut member rotates around the axis of the screw shaft in response to the rotational movement of the motor, the screw shaft that constitutes the output member of the electric actuator linearly moves in the axial direction and operates the operation target in the axial direction.

JP, 2005-330942, A

By the way, in the electric actuator, the origin position of the output member is usually set in order to accurately manage and control the axial displacement of the screw shaft (output member). In an electric actuator that employs a casing having a tubular shape with a bottom as in Patent Document 1, the position at which the output member and the bottom of the casing contact in the axial direction can be set as the origin of the output member. .. That is, when a bottomed tubular casing is used, the bottom of the casing can be utilized as an origin positioning unit for determining the origin position of the output member.

However, it has been found that when the bottom part of the housing is used as the origin positioning part of the output member, a serious defect that the output member becomes inoperable may occur. The details will be described with reference to FIGS. 13 and 14A and 14B.

FIG. 13 is a partially enlarged cross-sectional view showing a main part of the electric actuator extracted. This electric actuator is arranged coaxially with the rotation center of a motor (not shown), and has a hollow screw shaft 101 provided with a spiral groove 101a on the outer peripheral surface, and is arranged on the outer periphery of the screw shaft 101 and on the inner peripheral surface. A ball screw device 104 including a nut member 102 provided with a spiral groove 102a and a plurality of balls 103 rotatably interposed between the spiral grooves 101a and 102a constitutes a motion conversion mechanism, and The output member 100 is composed of the screw shaft 101 and an inner member 105 that is fixed to the inner periphery of the screw shaft 101 and that has an operation portion that can operate the operation target in the axial direction. The ball screw device 104 and a motor (not shown) are provided with an opening 111 at one end in the axial direction (right side in the drawing) and a disk-shaped bottom 112 at the other end in the axial direction (left side in the drawing). It is housed in a bottomed cylindrical casing 110 provided.

When the output member 100 of this electric actuator has no bending, that is, when the axis of the output member 100 and the rotation center X of the motor match, as shown in FIG. Ob is located on a straight line Y connecting a contact point 101b between the spiral groove 101a of the screw shaft 101 and the ball 103 and a contact point 102b between the spiral groove 102a of the nut member 102 and the ball 103. In this case, when the nut member 102 rotates in response to the output of the motor, the ball 103 rolls smoothly in the direction indicated by the white arrow in FIG. The output member 100 smoothly moves linearly in the axial direction.

On the other hand, the output member 100 overruns when the output member 100 returns to the original position due to some trouble in the electric system of the electric actuator, and the output member 100 and the bottom portion 112 of the housing 110 strongly hit each other. In this case, the output member 100 is bent such that its axis X′ is displaced from the rotation center X of the motor [see FIGS. 13 and 14(b)]. In this case, the ball 103 also contacts the spiral groove 101a of the screw shaft 101 at contact points 101c other than the predetermined contact point 101b, so that the contact state between the screw shaft 101 and the nut member 102 and the ball 103 is three-point contact. (The center Ob of the ball 103 is displaced with respect to the straight line Y connecting the contact points 101b and 102b), and the ball 103 falls into a so-called locked state in which it cannot roll. Therefore, the rotational movement of the motor cannot be transmitted to the screw shaft 101, and the output member 100 becomes inoperable.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric actuator in which a ball screw device is adopted as a motion conversion mechanism, in which the output member operates in accordance with the return of the output member to the origin. To provide an electric actuator that is capable of easily setting the origin of an output member while effectively reducing the possibility of causing a serious defect that would be impossible, and thus has excellent output member operating accuracy and high reliability. It is in.

The present invention, which was devised to solve the above-mentioned problems, includes a motor unit that is driven by being supplied with electric power, a motion conversion mechanism unit that converts the rotational motion of the motor unit into a linear motion and outputs the linear motion, a motor unit, and A bottomed tubular housing that houses a motion conversion mechanism portion, has an opening at one end in the axial direction, and has a bottom portion at the end on the other axial direction, wherein the motion conversion mechanism portion is a motor. A screw shaft arranged coaxially with the rotation center of the rotor of the motor section, and a nut member that is rotatably fitted to the outer periphery of the screw shaft via a plurality of balls and is provided so as to transmit torque with the rotor of the motor section. In the electric actuator in which the output member including the screw shaft advances in one axial direction or retracts in the other axial direction according to the rotation direction of the nut member, the opening end surface of the housing and the output member facing the opening end surface An annular origin positioning member that determines the origin position of the output member by engaging both of them in the axial direction is provided between the end surface on the other side in the axial direction, and the origin positioning member provides an elastic restoring force in the axial direction. It is characterized by having. The "output member" in the present invention is an output member of the electric actuator.

If the origin positioning member as described above is provided, the origin position of the output member can be easily and accurately set without utilizing the bottom of the housing. In addition, since the origin positioning member has an elastic restoring force in the axial direction (elastic restoring force against the compressive load in the axial direction), a large impact load in the axial direction acts on the output member as the origin returns to the output member. Even in such a case, the output member can be pushed back to one side in the axial direction (the direction away from the bottom of the housing), that is, the impact load can be attenuated/relaxed. Therefore, it is possible to effectively reduce the possibility that the balls forming the ball screw device fall into a locked state in which the balls cannot roll.

In the state where the output member is located at the origin, it is preferable that the inner end surface of the bottom portion of the housing faces the end surface of the output member with an axial gap. This is advantageous in reducing the possibility that the ball screw device will fall into the locked state as the output member returns to the original position.

If the origin positioning member is made of an elastic material such as a rubber material, a resin material, or a thermoplastic elastomer, the origin positioning member having a predetermined shape can be easily manufactured. Therefore, the cost increase due to the provision of the origin positioning member is suppressed. It will be advantageous to do.

The rotor of the motor part may be one having a hollow rotary shaft rotatably supported by rolling bearings arranged at two positions axially separated from each other by disposing a nut member on the inner periphery. The hollow rotary shaft may be provided with the inner raceway surface of one of the two rolling bearings. With this configuration, the hollow rotary shaft, and eventually the housing, can be made compact in the axial direction. As a result, it is possible to realize an electric actuator that is compact in the axial direction and has excellent mountability on the device used.

When the hollow rotary shaft is provided with the inner raceway surface described above, if the inner raceway surface is arranged inside the axial width of the nut member, the electric actuator can be made more compact in the axial direction.

The motion conversion mechanism unit may include a speed reducer that decelerates the rotation of the rotor and transmits the decelerated rotation to the nut member. With this configuration, since a small motor can be adopted, the electric actuator can be reduced in weight and size. A planetary gear reducer can be used as the reducer. With a planetary gear reducer, for example, the reduction ratio can be easily adjusted by changing the gear specifications or changing the number of planet gears installed, and even if the planet gears are installed in multiple stages. There is an advantage that it is possible to avoid an increase in the size of the speed reducer and eventually the electric actuator.

The casing can be composed of a plurality of members coupled in the axial direction. In this case, the terminal portion holding the electrical component is provided with a tubular portion sandwiched from both sides in the axial direction by the constituent members of the casing. The cylindrical portion may be provided with a radial through hole that communicates the inside and outside of the housing. It should be noted that the “electrical component” here is a concept including, for example, a power supply circuit for supplying drive power to the motor unit, a rotation angle detection sensor used for rotation control of the motor unit, and the like.

According to the above configuration, the members that form the housing can be coupled in the axial direction and the motor can be driven only by assembling the housing. In particular, if a radial through hole that connects the inside and outside of the housing is provided in the tubular portion of the terminal portion, the electrical wiring connected to the electrical component can be connected to the outside of the housing in the radial direction through the through hole. Can be withdrawn. In this case, since the work of arranging the electric wiring can be completed in the state of the terminal unit alone, it is not necessary to carry out the tedious work of arranging the electric wiring in the assembly stage of the electric actuator. Therefore, it is possible to improve the assemblability and productivity of the electric actuator and reduce the cost thereof.

At least a part of the stator of the motor section may be fitted to the tubular section of the terminal section. With this configuration, since the stator of the motor unit can be assembled to the inner circumference of the casing at the same time as assembling the casing, it is possible to further enhance the assembling property of the electric actuator.

As described above, according to the present invention, in the electric actuator in which the ball screw device is adopted for the motion conversion mechanism, it is possible to cause a serious defect such that the output member becomes inoperable as the output member returns to the origin. It is possible to easily set the origin of the output member while reducing the number of points. As a result, it is possible to provide an electric actuator having excellent output member operation accuracy and high reliability.

It is a longitudinal section of an electric actuator in one embodiment of the present invention. It is the EE sectional view taken on the line of FIG. FIG. 3 is a vertical cross-sectional view in which a rotor of a motor and a motion conversion mechanism section are taken out and enlarged. It is the FF sectional view taken on the line of FIG. It is a longitudinal cross-sectional view showing a state in which a ring gear is incorporated in the casing. FIG. 3 is a vertical cross-sectional view in which a motor stator and a terminal portion are taken out and enlarged. FIG. 2 is a sectional view taken along the line GG of FIG. 1. It is the HH sectional view taken on the line of FIG. FIG. 2 is a left side view of the electric actuator shown in FIG. 1. FIG. 10 is a sectional view taken along the line I-I of FIG. 9. It is a schematic block diagram which shows the control system of the electric actuator of FIG. It is a block diagram which shows the control system of the electric actuator which concerns on other embodiment. It is a figure for demonstrating the problem which may occur in the conventional electric actuator, and is a partial expanded sectional view of the conventional electric actuator. FIG. 14 is an enlarged view of the Z portion of FIG. 13, where (a) is a state diagram when the output member of the actuator including the screw shaft is not bent, and (b) is a diagram where the output member is bent. FIG.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, "one side in the axial direction" and "the other side in the axial direction" are the right side and the left side of the paper in FIGS.

FIG. 1 shows a vertical sectional view of an electric actuator according to an embodiment of the present invention, FIG. 2 shows a sectional view taken along the line EE of FIG. 1, and FIG. 3 shows a rotor of a motor unit and motion conversion. The mechanical part is taken out and the longitudinal cross-sectional view which was expanded is shown. 1 and 2 show a state in which the output member 3 of the electric actuator is located at the origin. As will be described later in detail, “the state of being located at the origin” means that the ends 90a, 90b of the annular origin positioning member 90 on the one side and the other side in the axial direction face the head of the actuator head 39 facing each other in the axial direction. This is a state in which the end surface of the portion 39a and the opening end surface 20a1 of the casing 20 are in axial engagement with each other.

As shown in FIGS. 1 and 2, the electric actuator 1 includes a motor unit A that is driven by being supplied with electric power, and a motion conversion mechanism unit B that converts the rotational motion of the motor unit A into a linear motion and outputs the linear motion. An operation unit C for operating an operation target (not shown) and a terminal unit D are provided and housed/held in the housing 2.

The housing 2 is composed of a plurality of members that are coaxially arranged and are coupled in the axial direction, and has a bottomed tubular shape as a whole. The casing 2 of the present embodiment includes a tubular casing 20 having both axial ends open, a cover 29 as a bottom that closes the end opening on the other axial side of the casing 20, and the casing 20 and the cover 29. It is arranged between the terminals and is composed of a combined body with the terminal body 50 that constitutes the terminal portion D. The cover 29 and the terminal body 50 are attached and fixed to the casing 20 with the assembling bolts 61 shown in FIGS.

The motor portion A is provided with a stator 23 fitted and fixed to the inner peripheral surfaces of the casing 20 and (the tubular portion 50A of) the terminal body 50, and a rotor 24 arranged to face the inner periphery of the stator 23 via a radial gap. And a radial gap type motor (specifically, a three-phase brushless motor having U-phase, V-phase, and W-phase) 25. The stator 23 includes an insulating bobbin 23b mounted on the stator core 23a and a coil 23c wound around the bobbin 23b. The rotor 24 includes a rotor core 24a, a permanent magnet 24b as a rotor magnet attached to the outer periphery of the rotor core 24a, and a rotor inner 26 as a hollow rotating shaft formed in a hollow shape and having the rotor core 24a attached to the outer periphery.

As shown in FIG. 3, the rotor core 24 a is fitted to the outer peripheral surface 26 b of the rotor inner 26 after the side plate 65 is set on the shoulder portion 26 a on one axial side of the rotor inner 26. The permanent magnet 24b (see FIG. 2) is fitted to the outer circumference of the rotor core 24a, and then is attached to the outer side of the rotor inner side of the rotor core 24a on the axially outer side of the rotor core 24a. It is positioned and fixed by a circlip 66 attached to the outside in the axial direction.

As shown in FIGS. 1 to 3, an inner raceway surface 27 a of a rolling bearing 27 is formed on the outer periphery of one end in the axial direction of the rotor inner 26, and an outer ring 27 b of the rolling bearing 27 is fixed to an inner circumferential surface of the casing 20. The bearing holder 28 is mounted on the inner peripheral surface thereof. Further, the rolling bearing 30 is mounted between the inner peripheral surface of the end portion of the rotor inner 26 on the other axial side and the outer peripheral surface of the cylindrical portion 29 a of the cover 29. With such a configuration, the rotor inner 26 is rotatably supported by the housing 2 via the rolling bearings 27 and 30.

As shown in FIGS. 1 to 3, the motion conversion mechanism unit B of the present embodiment includes a ball screw device 31 and a planetary gear speed reducer 10 as a speed reducer. It is arranged adjacent to one side in the axial direction.

The ball screw device 31 is rotatably fitted to a screw shaft 33 disposed coaxially with the rotation center of the rotor 24 and the outer circumference of the screw shaft 33 via a plurality of balls 34, and is capable of transmitting torque to the rotor inner 26. A nut member 32 arranged on the inner periphery of 26 and a top 35 as a circulation member are provided. A plurality of balls 34 are loaded between the spiral groove 32a formed on the inner peripheral surface of the nut member 32 and the spiral groove 33a formed on the outer peripheral surface of the screw shaft 33, and the top 35 is incorporated. .. As a result, when the screw shaft 33 linearly moves in the axial direction as the nut member 32 rotates, the balls 34 circulate between the spiral grooves 32a and 33a. The screw shaft 33 constitutes the output member 3 of the electric actuator 1 together with the inner member 36, the actuator head 39 as the operation portion C, and the like.

The screw shaft 33 is formed in a hollow shape having an axially extending hole portion (in the present embodiment, a through hole opened on both end surfaces in the axial direction) 33b, and the inner member 36 is accommodated in the hole portion 33b. There is. The inner member 36 is made of a resin material such as PPS, and has a circular solid portion 36a provided at one end in the axial direction and a flange portion 36b provided at the other end in the axial direction. It integrally has a tubular portion 36c that connects both portions 36a and 36b.

The inner member 36 accommodated in the hole portion 33b of the screw shaft 33 is fixedly connected to the screw shaft 33 by fitting a pin 37 so as to penetrate the circular solid portion 36a and the screw shaft 33 in the radial direction. It Both ends of the pin 37 project radially outward from the outer peripheral surface of the screw shaft 33, and a guide collar 38 is rotatably fitted on the projecting portion. The guide collar 38 is formed of, for example, a resin material such as PPS, and is fitted into an axial guide groove 20b (see also FIG. 5) provided on the inner circumference of the small-diameter cylindrical portion 20a of the casing 20. With such a configuration, when the nut member 32 rotates around the axis of the screw shaft 33 as the rotor 24 rotates, the screw shaft 33 (including the output member 3) linearly moves in the axial direction while being prevented from rotating. .. Whether the screw shaft 33 moves linearly (forward) from the other side in the axial direction toward the one side in the axial direction or linearly moves (retracts) from the one side in the axial direction toward the other side in the axial direction is basically determined. Specifically, it is determined according to the rotation direction of the nut member 32, but in the present embodiment, the screw shaft 33 can be moved backward by the spring force of the compression coil spring 48 (details will be described later).

As shown in FIGS. 1 and 2, an actuator head 39 as an operating portion C is detachably attached to an end portion of the screw shaft 33 on one axial side. Therefore, the output member 3 of the electric actuator 1 is composed of a combination of the screw shaft 33, the inner member 36, the pin 37, the guide collar 38, and the actuator head 39. The actuator head 39 of the present embodiment is a so-called push type that axially pressurizes the operation target as the screw shaft 33 linearly moves (forwards) in the one axial direction, and has a convex curved end surface. The head 39a, a base 39b fixed to the screw shaft 33, and a stepped cylindrical intermediate portion 39c provided between the head 39a and the base 39b are integrally provided.

As the actuator head 39, a so-called push-pull type in which an operation target can be operated on both sides in the axial direction can be adopted. The type and shape of the actuator head 39 to be used is determined in consideration of the device (shape or operation mode of the operation target) on which the electric actuator 1 is mounted.

An annular origin positioning member 90 is provided between the head portion 39a of the actuator head 39 and the housing 2 (casing 20) to determine the origin position of the output member 3. In the present embodiment, the origin positioning member 90 is engaged with the end surface of the output member 3 (the end surface on the other axial side of the head portion 39b of the actuator head 39) that faces the end portion 90a on one axial side in the axial direction. In this state, the actuator head 39 is fixed to the outer peripheral surface of the intermediate portion 39c. As shown in FIG. 1 and FIG. 2, the origin position of the output member 3 is such that the end portion 90a on one axial side of the origin positioning member 90 is axially aligned with the end surface on the other axial side of the head portion 39b of the actuator head 39. While being engaged, the end portion 90b of the origin positioning member 90 on the other side in the axial direction is set to a position that engages with the opening end surface 20a1 of the casing 20 in the axial direction.

As shown in FIGS. 1 and 2, when the output member 3 is located at the origin, the inner end surface of the bottom portion (cover 29) of the housing 2 is the end surface on the other axial side of the flange portion 36b of the inner member 36. And an axial gap 4 therebetween.

The origin positioning member 90 has an elastic restoring force against a compressive load in the axial direction. The origin positioning member 90 having the above configuration is made of an elastic material, here a rubber material. The origin positioning member 90 may be formed of an elastic material other than a rubber material, for example, a resin material or a thermoplastic elastomer.

As shown in FIGS. 1 to 4, the planetary gear speed reducer 10 is arranged between the ring gear 40 fixed to the casing 20, the sun gear 41 fixed to the rotor inner 26, and the ring gear 40 and the sun gear 41. The planetary gear carrier 43 includes a plurality of (four in the present embodiment) planetary gears 42 that mesh with 40 and 41, a planetary gear carrier 43 that holds the planetary gear 42 rotatably, and a planetary gear holder 44. The orbital motion of the planetary gear 42 is taken out and output.

The sun gear 41 is press-fitted into the stepped inner peripheral surface 26c of the rotor inner 26. By doing so, the connection workability at the time of assembly is good. Even if such a coupling structure is adopted, it is sufficient that the sun gear 41 can rotate integrally with the rotor inner 26 before deceleration, so that the torque transmission performance required between the two can be sufficiently secured. Further, since the rotor inner 26 and the sun gear 41 are connected at a position directly below the rolling bearing 27 that supports the rotor inner 26, the rotation accuracy of the sun gear 41 is also good.

As shown in FIG. 4, notches 40a that project outward in the radial direction are provided on the outer circumference of the ring gear 40 at a plurality of locations (four locations in the illustrated example) that are spaced apart in the circumferential direction, and each notch 40a is an inner circumference of the casing 20. It is fitted into axial grooves 20e (see also FIG. 5) provided at a plurality of locations (four locations in the illustrated example) spaced apart in the circumferential direction of the surface 20c. As a result, the ring gear 40 is prevented from rotating with respect to the casing 20.

As shown in FIGS. 1 to 3, the planetary gear carrier 43 has a cylindrical portion 43 a interposed between the inner peripheral surface of the rotor inner 26 and the outer peripheral surface 32 b of the nut member 32. The planetary gear carrier 43 is rotatable relative to the rotor inner 26, and is connected to the nut member 32 so that torque can be transmitted. In the present embodiment, the outer peripheral surface of the cylindrical portion 43a faces the inner peripheral surface 26d of the rotor inner 26 (and the inner peripheral surface of the sun gear 41) via a radial gap, and the inner peripheral surface 43b of the cylindrical portion 43a is in contact with the nut member 32. Is press-fitted and fixed to the outer peripheral surface 32b. If such a connecting structure is adopted, not only the connecting workability at the time of assembly is good, but also stable torque transmission is possible even for high torque after deceleration.

The rotation of the rotor 24 of the motor 25 is decelerated and transmitted to the nut member 32 by the planetary gear reducer 10 having the above configuration. As a result, since the rotational torque can be increased, the small motor 25 can be adopted.

As shown in FIGS. 1 to 3, a thrust washer 45 is disposed between the end surface of the nut member 32 on one axial side and the casing 20, and the thrust washer is attached to the outer periphery of the tip portion of the cylindrical portion 29 a of the cover 29. A needle roller bearing 47 as a thrust bearing is arranged between the receiving ring 46 and the end surface of the nut member 32 on the other axial side.

As shown in FIGS. 1 and 2, the motion conversion mechanism portion B is disposed on the radially outer side of the screw shaft 33 (between the inner peripheral surface 29b of the cylindrical portion 29a of the cover 29 and the outer peripheral surface of the screw shaft 33). The compressed coil spring 48 is provided. The ends on one side and the other side in the axial direction of the compression coil spring 48 are in contact with the flange portions 36b of the inner member 36 connected to the needle roller bearing 47 and the screw shaft 33, respectively.

The output member 3 including the screw shaft 33 is constantly urged toward the other side (origin side) in the axial direction by the spring force of the compression coil spring 48 provided in the above mode. By doing so, for example, when the drive power is not appropriately supplied to the motor 25, the output member 3 is automatically returned to the home position, which may adversely affect the operation of the operation target (not shown). Can be reduced. Further, if the compression coil spring 48 is provided in the above-described mode, it is possible to apply axial pressure to the nut member 32. As a result, the response delay due to the operating clearance provided between the nut member 32 and the screw shaft 33 can be eliminated, and the operability of the screw shaft 33, and by extension, the output member 3, can be improved.

Details of the cover 29 that functions as the bottom of the housing 2 will be described with reference to FIGS. 9 and 10. 9 is a left side view of FIG. 1, and FIG. 10 is a sectional view taken along the line I-I shown in FIG. 9. The cover 29 is formed of a metal material excellent in workability and thermal conductivity, for example, an aluminum alloy, a zinc alloy or a magnesium alloy. Although illustration is omitted, a cooling fin for increasing the cooling efficiency of the electric actuator 1 may be provided on the outer surface of the cover 29. As shown in FIG. 10, the outer peripheral surface of the cylindrical portion 29a of the cover 29 is provided with a bearing mounting surface 63 on which the rolling bearing 30 is mounted and a fitting surface 64 on which the thrust receiving ring 46 is fitted. There is. Further, as shown in FIG. 9, a through hole (not shown) in which the assembly bolt 61 of the electric actuator 1 is inserted and a mounting bolt for mounting the electric actuator 1 in a device to be used are inserted in the cover 29. A through hole 62 is provided.

Next, the terminal portion D will be described with reference to FIGS. 1 and 6 to 8. 6 is a longitudinal sectional view in which the stator 23 and the terminal portion D of the motor 25 shown in FIG. 1 are taken out and enlarged (vertical sectional view of a subassembly in which the stator 23 and the terminal portion D are assembled), and FIG. 1 is a sectional view taken along the line GG of FIG. 1, and FIG. 8 is a sectional view taken along the line HH of FIG. As shown in FIGS. 1 and 6, the terminal portion D includes a tubular portion 50A that forms a part of the housing 2, and a disk-shaped portion that extends radially inward from an end portion of the tubular portion 50A on the other axial side. It is provided with a resin-made terminal main body 50 integrally having a portion 50B, a bus bar 51 screwed to (the disc-shaped portion 50B of) the terminal main body 50, and a perforated disc-shaped printed board 52. As shown in FIGS. 7 and 8, the terminal body 50 (the cylindrical portion 50A thereof) has a through hole 50C into which the assembly bolt 61 shown in FIGS. And a through hole 50D into which the bolt is inserted, and is sandwiched between the casing 20 and the cover 29 by the assembly bolt 61 (see FIGS. 1 and 2).

The terminal portion D (terminal body 50) collectively holds electric components such as a power supply circuit for supplying drive power to the motor 25 and various sensors described later. As shown in FIGS. 7 and 8, the power supply circuit connects the coils 23c of the stator 23 to the terminals 51a of the bus bar 51 for each of the U phase, V phase, and W phase, and further, as shown in FIG. The terminal 51 b of 51 and the terminal block 50 a of the terminal body 50 are fastened with screws 70. The terminal block 50a has a terminal 50b to which a lead wire (not shown) is connected. The lead wire has a radial through hole 50c (see FIG. 1) provided in the tubular portion 50A of the terminal body 50. It is pulled out to the outside of the housing 2 in the radial direction via the controller 2 and is connected to the controller 81 (see FIG. 11 or 12) of the control device 80.

The electric actuator 1 of this embodiment is equipped with two types of sensors, and these two types of sensors are held in the terminal portion D. As shown in FIG. 1 and the like, one of the two types of sensors is a rotation angle detection sensor 53 used for rotation control of the motor 25, and the other is a displacement of the screw shaft 33 (output member 3) in the axial direction. It is a stroke detection sensor 55 used for detecting the amount. As the rotation angle detecting sensor 53 and the stroke detecting sensor 55, Hall sensors, which are a kind of magnetic sensor, are used.

As shown in FIGS. 1 and 8, the rotation angle detecting sensor 53 is attached to the printed circuit board 52, and an axial gap is provided between the rotation angle detecting sensor 53 and the pulsar ring 54 attached to the other end of the rotor inner 26 in the axial direction. It is arranged opposite. The rotation angle detecting sensor 53 determines the timings at which electric currents flow in the U phase, V phase, and W phase of the motor 25, respectively.

As shown in FIGS. 2, 7, and 8, the stroke detection sensor 55 extends in the axial direction and is attached to a strip-shaped printed circuit board 56 whose other end in the axial direction is connected to the printed circuit board 52. .. The printed circuit board 56 and the stroke detection sensor 55 are arranged on the inner circumference of the hole 33b of the screw shaft 33, more specifically, on the inner circumference of the cylindrical portion 36c of the inner member 36 housed in the hole 33b. A permanent magnet 57 as a target is attached to the inner periphery of the cylindrical portion 36c of the inner member 36 so as to face the stroke detection sensor 55 with a radial gap. Then, the stroke detecting sensor 55 detects the axial and radial magnetic fields formed around the permanent magnet 57, respectively, and calculates the axial displacement of the screw shaft 33 based on the detected magnetic fields.

Although not shown in detail, the signal line of the rotation angle detecting sensor 53 and the signal line of the stroke detecting sensor 55 are both radial through holes 50c provided in the tubular portion 50A of the terminal body 50. It is pulled out to the outer diameter side of the housing 2 via (see FIG. 1) and is connected to the control device 80 (see FIG. 11 or 12).

The procedure for assembling the electric actuator 1 having the above configuration will be briefly described. First, as shown in FIG. 5, the ring gear 40 is incorporated into the casing 20. Next, the rotor 24 of the motor 25 and the subassembly of the motion converting mechanism B shown in FIG. 3 are inserted into the casing 20. At this time, the planetary gear 42 and the ring gear 40 are engaged with each other, the guide collar 38 is fitted in the guide groove 20b of the casing 20, and the bearing holder 28 is fitted in the inner peripheral surface 20c of the casing 20. Then, of the stator 23 of the motor 25 and the subassembly of the terminal portion D (terminal body 50) shown in FIG. 6, the stator 23 is fitted to the inner circumference of the casing 20, and then the cover 29 and the terminal body 50 are attached to the casing 20. Are fastened with the assembly bolts 61 (see FIGS. 9 and 10). As a result, the electric actuator 1 is completed.

An operation mode of the electric actuator 1 having the above configuration will be briefly described with reference to FIGS. 1 and 11. For example, when an operation amount is input to a vehicle upper ECU (not shown), the ECU calculates a required position command value based on the operation amount. As shown in FIG. 11, the position command value is sent to the controller 81 of the control device 80, and the controller 81 calculates the control signal of the motor rotation angle required for the position command value and sends this control signal to the motor 25.

When the rotor 24 rotates based on the control signal sent from the controller 81, this rotational motion is transmitted to the motion conversion mechanism section B. Specifically, when the rotor 24 rotates, the sun gear 41 of the planetary gear reducer 10 connected to the rotor inner 26 rotates, and along with this, the planet gear 42 revolves and the planet gear carrier 43 rotates. As a result, the rotational movement of the rotor 24 is transmitted to the nut member 32 connected to the planetary gear carrier 43. At this time, the revolution speed of the planetary gear 42 reduces the rotational speed of the rotor 24, so that the rotational torque transmitted to the nut member 32 increases.

When the nut member 32 rotates in response to the rotational movement of the rotor 24, the output member 3 including the screw shaft 33 advances in the rotation-stopped state. At this time, the screw shaft 33 moves forward to a position based on the control signal of the controller 81, and the actuator head 39 mounted on the end of the screw shaft 33 on one axial side operates (pressurizes) an operation target (not shown).

As shown in FIG. 11, the axial position (axial displacement) of the screw shaft 33 is detected by the stroke detection sensor 55, and the detection signal is sent to the comparison unit 82 of the control device 80. Then, the comparison unit 82 calculates the difference between the detection value detected by the stroke detection sensor 55 and the position command value, and the controller 81 based on this calculated value and the signal sent from the rotation angle detection sensor 53. A control signal is sent to the motor 25. In this way, the position of the screw shaft 33 (output member 3) is feedback-controlled. Therefore, when the electric actuator 1 of this embodiment is applied to, for example, shift-by-wire, the shift position can be reliably controlled. The electric power for driving the motor 25, the sensors 53, 55, etc. is supplied from an external power source (not shown) such as a battery provided on the vehicle side to a power supply circuit held in the control device 80 and the terminal section D. It is supplied to the motor 25 or the like via the motor.

In the electric actuator 1 described above, between the opening end surface 20a1 of the housing 2 (casing 20) and the end surface on the other axial side of the output member 3 (head portion 39a of the actuator head 39) facing this, An annular origin positioning member 90 that determines the origin position of the output member 3 by axially engaging both end faces is provided. If such an origin positioning member 90 is provided, the origin position of the output member 3 can be easily and accurately set without utilizing the bottom portion (cover 29) of the housing 2. In addition, since the origin positioning member 90 has an elastic restoring force in the axial direction, even if a large impact load in the axial direction acts on the output member 3 as the output member 3 returns to the origin, the origin member 3 will not move. It can be pushed back to one side in the axial direction (the direction away from the cover 29), that is, the impact load can be attenuated/relaxed. Therefore, it is possible to effectively reduce the possibility that the balls 34 constituting the ball screw device 31 fall into a locked state in which they cannot roll (see FIG. 14B).

In particular, in the present embodiment, as shown in FIGS. 1 and 2, an annular protrusion having a substantially triangular cross-section that protrudes to the other side in the axial direction is provided integrally with the origin positioning member 90, so that The other side can be compressed preferentially over the one side in the axial direction. This allows the origin positioning of the output member 3 during normal operation to be easily performed by preferentially compressing the other side of the origin positioning member 90 in the axial direction, and at the same time, the impact load in the axial direction and the like are large. This is because when the compressive load acts on the output member 3, the above impact load is efficiently alleviated on one axial side of the origin positioning member 90.

Further, in the present embodiment, when the output member 3 is located at the origin, the inner end surface of the cover 29 is separated from the end surface of the output member 3 (the other axial direction of the flange portion 36b of the inner member 36) through the axial gap 4. Since the output member 3 is returned to the origin, it is possible to effectively reduce the possibility that the output member 3 and the cover 29 collide with each other in the axial direction. Therefore, the possibility that the ball screw device 31 will fall into a locked state can be reduced more effectively. Therefore, according to the present invention, the origin of the output member 3 can be easily determined while effectively reducing the possibility of causing a serious defect such that the output member 3 becomes inoperable as the output member 3 returns to the origin. Since it is possible to set the electric actuator 1, it is possible to realize a highly reliable electric actuator 1 which is excellent in the operation accuracy of the output member 3.

Further, the rotor inner 26 as a hollow rotating shaft has one end in the axial direction rotatably supported by a rolling bearing 27 arranged in proximity to one end in the axial direction of the rotor core 24a, and the other end in the axial direction of the rotor core 24a. The end portion on the other side in the axial direction is rotatably supported by the rolling bearing 30 which is arranged in the vicinity of the end portion on the other side. With such a structure, the rotor inner 26 can be made compact in the axial direction. In addition to this, the structure in which the rolling bearing 27 is arranged inside the axial width of the nut member 32 is combined, so that the electric actuator 1 can be made more compact in the axial direction.

Further, as long as the rotor 24 is rotationally balanced, the rolling bearings 27 and 30 supporting the rotor inner 26 only have to support a radial load of about the weight of the rotor 24. In this case, the rotor inner 26 integrally including the inner raceway surface 27a of the rolling bearing 27 does not need to be formed of a high-strength material, and may be formed of an inexpensive mild steel material in which heat treatment such as quenching and tempering is omitted. The required strength can be secured. Particularly, in the electric actuator 1 of the present embodiment, since the rotational movement of the motor 25 is transmitted to the nut member 32 via the planetary gear reducer 10, no radial load is generated, and the linear movement of the screw shaft 33 does not occur. The reaction force (thrust load) generated therewith is directly supported by the needle roller bearing 47. Therefore, the rolling bearing 27 only needs to have a radial positioning function, and thus the rotor inner 26 integrally including the inner raceway surface 27a of the rolling bearing 27 is sufficient in the above material specifications. Thereby, the cost of the electric actuator 1 can be reduced.

Further, as described above, if the thrust load acting on the nut member 32 is directly supported by the needle roller bearing 47, the nut member 32 can be supported even when the thrust load is applied to the nut member 32. Since the motor 25 can be rotated with a low torque, the motor 25 can be downsized.

Further, if the needle roller bearing 47 is arranged within the axial range between the rolling bearings 27 and 30, the screw shaft 33 (output member 3) moves linearly in the axial direction, and the screw shaft 33 moves. Since it is advantageous for the moment load acting on the output member 3 and the like, it is possible to improve the operation accuracy and the durable life of the output member 3 and to employ the needle roller bearing 47 that is compact in the axial direction. In the present embodiment, the needle roller bearing 47 is arranged near the center in the axial direction between the two rolling bearings 27, 30, which is more advantageous for the moment load. As a result, extremely small needle roller bearings 47, thrust receiving rings 46, etc. can be adopted. Therefore, it is possible to prevent the axial dimension L (see FIG. 1) of the electric actuator 1 (the housing 2) from being lengthened by providing the needle roller bearing 47 and the thrust receiving ring 46.

Further, downsizing of the motor unit A (motor 25) realized by providing the planetary gear reducer 10 and the needle roller bearing 47 in the motion converting mechanism unit B, and the rotor inner 26 and the cylindrical portion 43a of the planetary gear carrier 43 are realized. Also, in combination with the radial overlapping structure of the nut member 32, the radial dimension M (see FIG. 1) of the housing 2 can be made as small as possible. As a result, the electric actuator 1 can be made more compact, and the mountability of the device can be improved.

Further, since the rotor 24 (rotor inner 26) of the motor section A and the nut member 32 are formed as separate structures, for example, even when the ball screw device 31 having different specifications is adopted, the motor section A and the motion conversion mechanism section B are not provided. A part (planetary gear reducer 10) can be shared. As a result, the versatility is improved, and it becomes easy to realize a series of electric actuators 1 by developing a variety of products in which parts are shared.

Further, a power supply circuit for supplying drive power to the motor 25, electrical components such as the rotation angle detection sensor 53 and the stroke detection sensor 55 are collectively held by the terminal main body 50, and this terminal main body 50 (terminal portion D). Since a sandwich structure in which the casing 20 and the cover 29 are sandwiched in the axial direction is adopted, the assemblability is good. In particular, in the present embodiment, as shown in FIG. 1 and FIG. 6, a part of the stator 23 of the motor 25 (outer circumference of the other end in the axial direction) is fitted to the inner circumference of the tubular portion 50A of the terminal body 50. It fits. In this case, since the stator 23 can be assembled to the inner circumference of the housing 2 at the same time as the housing 2 is assembled, the assembling property can be improved also from this point.

Further, the tubular portion 50A of the terminal body 50 has a through hole 50c for communicating the inside and outside of the housing 2, and has a lead wire connected to a power supply circuit and a signal wire (electrical wire) connected to the sensors 53 and 55 described above. The wiring) is drawn out to the outside in the radial direction of the housing 2 through the through hole 50c. In this case, it is necessary to complete the above-mentioned work of arranging the electric wiring by the terminal body 50 alone, that is, the electric system required for operating the electric actuator 1 appropriately and accurately is the housing 2 (electric actuator 1). Can be collectively held by the terminal main body 50 before assembly. As a result, it is not necessary to separately perform a troublesome wiring work at the assembly stage of the electric actuator 1, so that the assemblability of the electric actuator 1 can be further improved.

Further, if the wiring work of the electric wiring can be completed by the terminal main body 50 alone, for example, even if the specifications of the motor 25, the planetary gear reducer 10 or the like are changed, the mating member of the terminal main body 50 (here, In particular, the terminal main body 50 can be shared as long as the shape of the joined portion of the casing 20) is the same. As a result, it is possible to easily deal with a wide variety of electric actuators 1 (serialization) by sharing parts and members.

Further, a sandwich structure in which the terminal main body 50 is sandwiched between the casing 20 and the cover 29 in the axial direction is adopted, and the lead wire of the power feeding circuit and the signal wire of the sensor can be drawn out to the outer diameter side of the housing 2. , And the hollow screw shaft 33, the two electric actuators 1 (the motor unit A, the motion conversion mechanism unit B and the terminal unit D are unitized) are arranged in series in the axial direction, It is also possible to realize an electric actuator that can individually operate two operation targets. It should be noted that such an electric actuator can be preferably mounted in, for example, a DCT, which is a type of automatic transmission, and can contribute to downsizing of the entire DCT.

Since the electric actuator 1 of the present embodiment has the characteristic configuration as described above, the output member 3 has excellent operation accuracy, is highly reliable, is lightweight and compact, and is excellent in mountability on a device used. It is easy to assemble and can be manufactured at low cost, and it is easy to develop multiple products (serialization) by sharing parts.

Although the electric actuator 1 according to the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this.

For example, in the embodiment described above, the origin positioning member 90 formed of an elastic material such as a rubber material is used. However, as the origin positioning member 90, an elastic body such as a compression coil spring, or the elastic body is used. You may comprise with the member provided. However, if the elastic material is used, the origin positioning member 90 having a predetermined shape can be easily manufactured, which is advantageous in suppressing an increase in cost due to the additional provision of the origin positioning member 90.

A rolling bearing other than the needle roller bearing 47, for example, a cylindrical roller bearing, may be used as the thrust bearing adjacent to the other side of the nut member 32 in the axial direction. However, the needle roller bearing 47 is preferable in consideration of the load bearing capacity and the axial dimension of the bearing.

Further, in the embodiment described above, the planetary gear reducer 10 is provided in the motion conversion mechanism section B, but a reducer other than the planetary gear reducer 10 may be adopted.

Further, the speed reducer including the planetary gear speed reducer 10 does not necessarily have to be provided, and may be omitted if not necessary. When the planetary gear reducer 10 is omitted, the rotor 24 (rotor inner 26) of the motor 25 and the nut member 32 of the ball screw device 31 may be directly connected so that torque can be transmitted. Then, it becomes necessary to adopt different shapes for at least one of the rotor inner 26 and the nut member 32. Therefore, when the planetary gear reducer 10 is omitted, for example, a cylindrical intermediate member is arranged between the inner peripheral surface 26d of the rotor inner 26 and the outer peripheral surface 32b of the nut member 32, and the outer peripheral surface of this intermediate member is arranged. It is preferable that each of the inner peripheral surface and the inner peripheral surface be coupled to the inner peripheral surface 26d of the rotor inner 26 and the outer peripheral surface 32b of the nut member 32 so that torque can be transmitted (not shown). As a result, even when the planetary gear reducer 10 is omitted, it is possible to share the motor unit A (motor 25) and the ball screw device 31, so that the cost increase can be suppressed.

Further, in the embodiment described above, the stroke detection sensor 55 is used. However, the stroke detection sensor 55 may be used as needed, and depending on the device used, the stroke detection sensor 55 may be used. May be omitted.

An example of the operation mode of the electric actuator 1 when the stroke detection sensor 55 is not used will be described with reference to FIG. FIG. 12 is an example of pressure control, and a pressure sensor 83 is provided for an operation target not shown. When an operation amount is input to an ECU (not shown), the ECU calculates a required pressure command value. When this pressure command value is sent to the controller 81 of the control device 80, the controller 81 calculates a control signal of the motor rotation angle required for the pressure command value, and sends this control signal to the motor 25. Then, similarly to the case described with reference to FIG. 11, the screw shaft 33 advances to the position based on the control signal of the controller 81, and the actuator head 39 attached to the axial one end of the screw shaft 33 is An operation target (not shown) is operated.

The operating pressure of the screw shaft 33 is detected by a pressure sensor 83 installed outside and feedback-controlled. Therefore, when the electric actuator 1 that does not use the stroke detection sensor 55 is applied to, for example, a brake-by-wire, it is possible to reliably control the hydraulic pressure of the brake.

As described above, when the stroke detecting sensor 55 is not used, the screw shaft 33 may be solid and the inner member 36 may be omitted. However, when the solid screw shaft 33 is used and the compression coil spring 48 is provided, as the screw shaft 33, one having a flange portion at the end portion on the other axial side thereof is adopted.

The present invention is not limited to the embodiments described above, and it goes without saying that the present invention can be implemented in various forms within the scope of the present invention, and the scope of the present invention is It is indicated by the scope of the claims and further includes equivalent meanings to the claims and all modifications within the scope.

DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Housing 3 Output member 4 Axial gap 10 Planetary gear reducer 20 Casing 24 Rotor 25 Motor 26 Rotor inner (hollow rotating shaft)
27 Rolling Bearing 27a Inner Raceway Surface 29 Cover (Bottom of Case)
30 Rolling Bearing 31 Ball Screw Device 32 Nut Member 33 Screw Shaft 34 Ball 47 Needle Roller Bearing (Thrust Bearing)
50 Terminal body 50A Cylindrical part 50c Through hole 90 Origin positioning member A Motor part B Motion conversion mechanism part C Operation part D Terminal part

Claims (8)

A motor unit that receives electric power and drives, a motion conversion mechanism unit that converts the rotational motion of the motor unit into a linear motion and outputs the linear motion, the motor unit and the motion conversion mechanism unit, and one side in the axial direction. A bottomed cylindrical casing having an opening at the end of the motor and a bottom at the end on the other side in the axial direction, and the motion converting mechanism is disposed coaxially with the rotation center of the rotor of the motor. And a nut member that is rotatably fitted to the outer periphery of the screw shaft via a plurality of balls and is provided so as to transmit torque with the rotor of the motor unit. In an electric actuator in which the output member including the screw shaft is advanced in one axial direction or retracted in the other axial direction according to the direction,
An annular origin positioning member that determines the origin position of the output member by axially engaging both of the opening end surface of the housing and the end surface of the output member facing the other end in the axial direction. is provided, the raw point positioning member has have a resilient restoring force to axial compressive loads,
An electric actuator , wherein an inner end surface of a bottom portion of the housing and an end surface of the output member face each other with an axial gap therebetween when the output member is located at the origin . The electric actuator according to claim 1 , wherein the origin positioning member is made of an elastic material. The rotor has a hollow rotary shaft that is rotatably supported with respect to the housing by rolling bearings that are arranged on the inner periphery of the nut member and that are arranged at two locations that are separated in the axial direction,
The electric actuator according to claim 1 or 2 , wherein the hollow rotary shaft has an inner raceway surface of one of the two rolling bearings. The electric actuator according to claim 3 , wherein the inner raceway surface is arranged inside an axial width of the nut member. The electric actuator according to claim 3 or 4 , wherein a thrust bearing is arranged adjacent to the other side of the nut member in the axial direction, and the thrust bearing is arranged within an axial range between the two rolling bearings. The motion converting mechanism portion, an electric actuator according to any one of claim 1 to 5, further comprising a reduction gear for transmitting the nut member by decelerating the rotation of the rotor. The housing is composed of a plurality of members that are coupled in the axial direction,
The terminal portion holding the electrical component has a tubular portion sandwiched by the constituent members of the housing from both sides in the axial direction, and the tubular portion has a radial through hole that communicates the inside and outside of the housing. electric actuator according to any one of claim 1 to 6 with. The electric actuator according to claim 7 , wherein at least a part of a stator of the motor section is fitted in the tubular section.

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