WO2017203944A1

WO2017203944A1 - Electric actuator

Info

Publication number: WO2017203944A1
Application number: PCT/JP2017/017157
Authority: WO
Inventors: 卓志松任; 池田　良則; 悠紀内藤
Original assignee: Ntn株式会社
Priority date: 2016-05-23
Filing date: 2017-05-01
Publication date: 2017-11-30
Also published as: JP2017210976A; JP6736352B2

Abstract

Provided is an electric actuator (1) which is equipped with a motor (A), a motion conversion mechanism (B), and a bottomed cylindrical housing (2) housing those, wherein the motion conversion mechanism (B) has a screw shaft (33) and a nut member (32) that is rotatably fitted to the periphery of the screw shaft (33) via balls (34), an output member (3) including the screw shaft (33) moves linearly in an axial direction in association with the rotation of the nut member (32), an annular origin positioning member (90) for determining an origin position of the output member (3) is provided between an opening end face (20a1) of the housing (2) and an end face of the output member (3) opposite thereto through engagement of those in an axial direction, and the origin positioning member (90) provides an elastic restoring force in the axial direction.

Description

Electric actuator

The present invention relates to an electric actuator.

In recent years, in automobiles, electrification has progressed to save labor and reduce fuel consumption. For example, a system for operating an automatic transmission, a brake, a steering, and the like with the power of an electric motor (motor) has been developed and put on the market. It has been thrown. 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 it, via 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 motion of the motor, the screw shaft constituting the output member of the electric actuator linearly moves in the axial direction and operates the operation target in the axial direction.

JP-A-2005-330942

Incidentally, in the electric actuator, the origin position of the output member is usually set in order to accurately manage and control the axial displacement amount of the screw shaft (output member). As in Patent Document 1, in an electric actuator employing a casing having a bottomed cylindrical shape as a whole, the position where the output member and the bottom of the casing abut in the axial direction can be set as the origin of the output member. . That is, when a bottomed cylindrical casing is used, the bottom of the casing can be used 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 casing is used as the origin positioning part of the output member, there is a possibility of a serious defect that the output member becomes inoperable. Details thereof will be described with reference to FIGS. 13, 14A and 14B.

FIG. 13 is a partial enlarged cross-sectional view showing a main part of a conventional electric actuator. This electric actuator is arranged coaxially with the rotation center of a motor (not shown), 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 interposed between the

spiral grooves

101a and 102a in a rollable manner constitutes a motion conversion mechanism. The output member 100 is constituted by a screw shaft 101 and an inner member 105 which is fixed to the inner periphery of the screw shaft 101 and has an operation portion capable of operating an 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 figure) and a disk-shaped bottom 112 at the other end in the axial direction (left side in the figure). It is accommodated in a provided bottomed cylindrical casing 110.

When the output member 100 of the electric actuator is not bent, that is, when the axis of the output member 100 and the rotation center X of the motor coincide with each other, as shown in FIG. The contact point 101b between the spiral groove 101a of the screw shaft 101 and the ball 103 and the contact point 102b between the spiral groove 102a of the nut member 102 and the ball 103 are positioned on a straight line Y. In this case, when the nut member 102 rotates in response to the output of the motor, the ball 103 smoothly rolls in the direction indicated by the white arrow in FIG. 14A to transmit torque, so that the output member 100 including the screw shaft 101 is transmitted. Smoothly moves linearly in the axial direction.

On the other hand, for example, when some trouble occurs in the electric system of the electric actuator, the output member 100 overruns with the return of the origin of the output member 100, and the output member 100 and the bottom portion 112 of the housing 110 strongly collide with 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 14B). In this case, since the ball 103 is in contact with the spiral groove 101a of the screw shaft 101 even at a contact point 101c other than the predetermined contact point 101b, the contact state between the screw shaft 101 and the nut member 102 and the ball 103 is a 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, and the output member is operated as the output member returns to the origin. To provide an electric actuator that can easily set the origin of an output member while effectively reducing the possibility of occurrence of a serious defect that makes it impossible, and has excellent output member operation accuracy and high reliability. It is in.

The present invention, which has been devised to solve the above problems, includes a motor unit that is driven by receiving power supply, a motion conversion mechanism unit that converts the rotational motion of the motor unit into a linear motion, and outputs the motor unit, And a bottomed cylindrical housing having an opening at one end in the axial direction and a bottom at the other end in the axial direction. A screw shaft that is arranged coaxially with the rotation center of the rotor of the part, 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 be able to transmit torque. In the electric actuator in which the output member including the screw shaft moves forward in one axial direction or moves backward 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 same Between the end face on the other side in the axial direction Origin positioning annular member which determines the position of the origin of the output member is provided by engagement with both the axial direction, the raw point positioning member and having an elastic restoring force in the axial direction. The “output member” in the present invention is an output member of an electric actuator.

If the origin positioning member as described above is provided, the origin position of the output member can be set easily and accurately without using 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), if the axial dimension of the origin positioning member is appropriately set, the origin return of the output member is performed. As a result, even if the output member and the bottom of the housing are strongly abutted against each other, the origin positioning member is sandwiched between the opening end surface of the housing and the end surface on the other side in the axial direction of the output member facing this. The elastic restoring force in the axial direction is generated by crushing. Accordingly, it is possible to effectively reduce the possibility that the output member and the bottom portion of the housing will abut against each other, and in turn, the possibility that the ball constituting the ball screw device will fall into a locked state where it cannot roll.

In a 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 is opposed to the end surface of the output member via an axial gap. This is advantageous in reducing the possibility that the ball screw device falls into the locked state as the output member returns to the origin.

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, so that an increase in cost due to the provision of the origin positioning member is suppressed. This is advantageous.

The rotor of the motor unit may have a hollow rotating shaft that is rotatably supported by rolling bearings that are arranged at two locations that are spaced apart in the axial direction, with a nut member arranged on the inner periphery. The hollow rotary shaft may be provided with an inner raceway surface of one of the two rolling bearings. In this way, the hollow rotating shaft and thus the housing can be made compact in the axial direction. Thereby, it is possible to realize an electric actuator that is compact in the axial direction and excellent in mountability to a device used.

When the inner raceway surface is provided on the hollow rotary shaft, the electric actuator can be made more compact in the axial direction by arranging the inner raceway surface inside the axial width of the nut member.

The motion conversion mechanism may have a speed reducer that decelerates the rotation of the rotor and transmits it to the nut member. In this way, since a small motor can be employed, the electric actuator can be reduced in weight and size. A planetary gear speed reducer can be adopted as the speed reducer. If it is a planetary gear reducer, the reduction ratio can be easily adjusted by changing the gear specifications or changing the number of installation stages of the planetary gear, and even if the planetary 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 consequently the electric actuator.

The housing 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 cylindrical portion sandwiched from both sides in the axial direction by the structural members of the housing. The cylindrical portion can be provided with a radial through hole that allows the inside and outside of the housing to communicate with each other. The “electrical component” here is a concept including, for example, a power supply circuit for supplying driving power to the motor unit, a rotation angle detection sensor for use in rotation control of the motor unit, and the like.

According to the above configuration, it is possible to drive the motor unit only by assembling the casing by connecting the members constituting the casing in the axial direction. In particular, if a through-hole in the radial direction that connects the inside and outside of the housing is provided in the cylindrical portion of the terminal portion, the electrical wiring connected to the electrical component is connected to the outside in the radial direction of the housing through the through-hole. It can be pulled out. In this case, since the wiring work of the electric wiring can be completed in the state of the terminal unit alone, it is not necessary to carry out the complicated wiring work of the electric actuator at the assembly stage. Therefore, the assembling property and productivity of the electric actuator can be improved and the cost can be reduced.

At least a part of the stator of the motor part may be fitted into the cylindrical part of the terminal part. In this way, since the stator of the motor unit can be assembled to the inner periphery of the casing at the same time as the casing is assembled, the assembly of the electric actuator can be further enhanced.

As described above, according to the present invention, in the electric actuator in which the ball screw device is adopted as the motion conversion mechanism, there is an effect that a possibility that the output member becomes inoperable with the return of the origin of the output member may occur. Thus, it is possible to easily set the origin of the output member while reducing it. Thereby, the electric actuator which is excellent in the operation accuracy of the output member and rich in reliability can be provided.

1 is a longitudinal sectional view of an electric actuator according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line EE in FIG. 1. It is the longitudinal cross-sectional view which took out the rotor and motion conversion mechanism part of the motor, and was expanded. FIG. 5 is a cross-sectional view taken along line FF in FIG. 1. It is a longitudinal cross-sectional view which shows the state which integrated the ring gear in the casing. It is the longitudinal cross-sectional view which took out the stator and terminal part of the motor, and was expanded. FIG. 2 is a cross-sectional view taken along line GG in FIG. 1. FIG. 2 is a cross-sectional view taken along line HH in FIG. 1. It is a left view of the electric actuator shown in FIG. FIG. 10 is a cross-sectional view taken along the line II in 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 conceptual diagram for demonstrating the problem which may occur with the conventional electric actuator. It is the Z section enlarged view of Drawing 13, and is a figure showing the state where there is no bending in the output member of the actuator containing a screw axis. It is a Z section enlarged view of Drawing 13, and is a figure showing the state where bending has arisen in the output member of an actuator.

Hereinafter, embodiments of the present invention will be described 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 in FIG.

FIG. 1 is a longitudinal sectional view of an electric actuator according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line EE in FIG. 1, and FIG. The longitudinal cross-sectional view which took out and expanded the mechanism part is shown. 1 and 2 show a state where the output member 3 of the electric actuator is located at the origin. As will be described in detail later, “the state of being located at the origin” means that the head 90 of the actuator head 39 in which the

end portions

90a, 90b on one side and the other side of the annular origin positioning member 90 face each other in the axial direction. This is a state in which the end face of the portion 39a and the opening end face 20a1 of the casing 20 are in a position to be engaged in the axial direction.

As shown in FIGS. 1 and 2, the electric actuator 1 includes a motor unit A that is driven by the supply of 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, which are accommodated and held in the housing 2.

The housing 2 is composed of a plurality of members coupled in the axial direction in a coaxial arrangement, and has a bottomed cylindrical shape as a whole. The casing 2 of this embodiment includes a cylindrical casing 20 having both ends opened in the axial direction, a cover 29 serving as a bottom portion that closes the end opening on the other axial side of the casing 20, and the casing 20 and the cover 29. It consists of the coupling | bonding body with the terminal main body 50 which is arrange | positioned between and comprises the terminal part D. FIG. The cover 29 and the terminal main body 50 are fixedly attached to the casing 20 by assembly bolts 61 shown in FIGS.

The motor part A includes a stator 23 fitted and fixed to the inner peripheral surface of the casing 20 and the terminal main body 50 (the cylindrical part 50A thereof), and a rotor 24 disposed opposite to the inner periphery of the stator 23 via a radial gap. And a radial gap type motor 25 (specifically, a three-phase brushless motor having a U phase, a V phase, and a W phase). The stator 23 includes an insulating bobbin 23b attached to 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 that is formed in a hollow shape and has 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 setting the side plate 65 on the shoulder portion 26 a on one axial side of the rotor inner 26. After the permanent magnet 24b (see FIG. 2) is fitted to the outer periphery of the rotor core 24a, the side plate 65 attached to the axially outer side of the other end of the rotor core 24a in the axial direction of the rotor inner 26, and its 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 the rolling bearing 27 is formed on the outer periphery of one end of the rotor inner 26 in the axial direction, and the outer ring 27 b of the rolling bearing 27 is fixed to the inner peripheral surface of the casing 20. The bearing holder 28 is attached to the inner peripheral surface. Further, a rolling bearing 30 is mounted between the inner peripheral surface of the other end in the axial direction of the rotor inner 26 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 with respect to 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. Adjacent to one side in the axial direction.

The ball screw device 31 is rotatably fitted to the outer periphery of the screw shaft 33 via a plurality of balls 34 and a screw shaft 33 arranged coaxially with the rotation center of the rotor 24, so that torque can be transmitted to the rotor inner 26. The nut member 32 arrange | positioned at the inner periphery of 26 and the 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. . Thereby, when the screw shaft 33 linearly moves in the axial direction as the nut member 32 rotates, the ball 34 circulates 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 and the actuator head 39 as the operation portion C.

The screw shaft 33 is formed in a hollow shape having a hole portion 33b extending in the axial direction (in this embodiment, through holes opened on both end surfaces in the axial direction) 33b, and the inner member 36 is accommodated in the hole portion 33b. Yes. The inner member 36 is made of, for example, a resin material such as PPS, and has a circular solid portion 36a provided at an end portion on one side in the axial direction, a flange portion 36b provided at an end portion on the other side in the axial direction, It has integrally the cylinder part 36c which connects both

parts

36a and 36b.

The inner member 36 accommodated in the hole 33b of the screw shaft 33 is connected and fixed 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. The Both end portions of the pin 37 protrude radially outward from the outer peripheral surface of the screw shaft 33, and a guide collar 38 is rotatably fitted on the protruding portion. The guide collar 38 is formed of a resin material such as PPS, for example, and is fitted into an axial guide groove 20b (see also FIG. 5) provided on the inner periphery of the small diameter cylindrical portion 20a of the casing 20. With this 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 linearly moves (forwards) from the other side in the axial direction toward one side in the axial direction or linearly moves (retreats) from one side in the axial direction toward the other side in the axial direction is basically determined. Specifically, although it is determined according to the rotation direction of the nut member 32, in this 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 FIG. 1 and FIG. 2, an actuator head 39 as an operation portion C is detachably attached to one end of the screw shaft 33 in the axial direction. Therefore, the output member 3 of the electric actuator 1 is composed of a combined body such as 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 pressurizes an operation target in the axial direction as the screw shaft 33 linearly moves (advances) in one axial direction, and has a convex curved tip surface. The head portion 39a, a base portion 39b fixed to the screw shaft 33, and a stepped cylindrical intermediate portion 39c provided between the head portion 39a and the base portion 39b are integrally provided.

As the actuator head 39, a so-called push-pull type that can operate the operation target 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 equipment used (the shape and operation mode of the operation target) on which the electric actuator 1 is mounted.

An annular origin positioning member 90 is disposed between the head 39a of the actuator head 39 and the housing 2 (casing 20) in order 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 side in the axial direction of the head 39b of the actuator head 39) facing the end portion 90a on the one axial direction 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 FIGS. 1 and 2, the origin position of the output member 3 is such that the end portion 90a on the one side in the axial direction of the origin positioning member 90 is in the axial direction with the end face on the other side in the axial direction of the head 39b of the actuator head 39. While being engaged, the end portion 90b on the other side in the axial direction of the origin positioning member 90 is set to a position where it is engaged 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 36 b of the inner member 36. And an axial gap 4.

The origin positioning member 90 has an elastic restoring force against an axial compressive load. The origin positioning member 90 having the above configuration is formed 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 reducer 10 is disposed 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. 40 (41 in this embodiment), a planetary gear carrier 43 and a planetary gear holder 44 that rotatably hold the planetary gear 42, and the planetary gear carrier 43 includes: The revolution movement of the planetary gear 42 is taken out and output.

The sun gear 41 is press-fitted into the inner circumferential surface 26c of the step portion of the rotor inner 26. If it does in this way, the connection workability at the time of an assembly will be favorable. Even if such a connection structure is adopted, the sun gear 41 only needs to be able to rotate integrally with the rotor inner 26 before being decelerated, so that the torque transmission performance required between them 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 rotational accuracy of the sun gear 41 is also good.

As shown in FIG. 4, the outer periphery of the ring gear 40 is provided with notches 40 a projecting radially outward at a plurality of locations (four locations in the illustrated example) spaced apart in the circumferential direction. The grooves are fitted in axial grooves 20e (see also FIG. 5) provided at a plurality of locations (four locations in the illustrated example) separated in the circumferential direction of the surface 20c. Thereby, 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 43a interposed between the inner peripheral surface of the rotor inner 26 and the outer peripheral surface 32b 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 as to transmit torque. In the present embodiment, the outer peripheral surface of the cylindrical portion 43 a faces the inner peripheral surface 26 d of the rotor inner 26 (and the inner peripheral surface of the sun gear 41) via a radial gap, and the inner peripheral surface 43 b of the cylindrical portion 43 a is the nut member 32. The outer peripheral surface 32b is press-fitted and fixed. If such a connection structure is adopted, in addition to good connection workability at the time of assembly, stable torque transmission is possible even for high torque after deceleration.

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

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

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

The output member 3 including the screw shaft 33 is always urged toward the other side in the axial direction (origin side) by the spring force of the compression coil spring 48 provided in the above-described manner. In this way, for example, when the driving power is not properly supplied to the motor 25, the output member 3 is automatically returned to the origin, and the possibility of adversely affecting the operation of the operation target (not shown) is possible. Can be reduced. Further, if the compression coil spring 48 is provided in the above-described manner, an axial pressure can be applied to the nut member 32. Thereby, the response delay resulting from the operation gap provided between the nut member 32 and the screw shaft 33 can be eliminated, and the operability of the screw shaft 33 and thus the output member 3 can be improved.

Details of the cover 29 functioning 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 cross-sectional view taken along the line II in FIG. 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 not shown, 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, 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 are provided on the outer peripheral surface of the cylindrical portion 29 a of the cover 29. Yes. Further, as shown in FIG. 9, a through hole (not shown) through which the assembly bolt 61 of the electric actuator 1 is inserted and a mounting bolt for attaching the electric actuator 1 to a device to be used are inserted into the cover 29. A through hole 62 is provided.

Next, the terminal part D will be described with reference to FIG. 1 and FIGS. 6 is a longitudinal sectional view (a longitudinal sectional view of a subassembly in which the stator 23 and the terminal portion D are assembled) taken out from the stator 23 and the terminal portion D of the motor 25 shown in FIG. 1, and FIG. 1 is a cross-sectional view taken along line GG in FIG. 1, and FIG. 8 is a cross-sectional view taken along line HH in FIG. As shown in FIGS. 1 and 6, the terminal portion D has a cylindrical portion 50 </ b> A that constitutes a part of the housing 2, and a disk shape that extends radially inward from the other axial end of the cylindrical portion 50 </ b> A. A resin-made terminal main body 50 integrally having a portion 50B, a bus bar 51 screwed to the terminal main body 50 (the disk-shaped portion 50B thereof), and a perforated disk-shaped printed circuit board 52 are provided. As shown in FIGS. 7 and 8, the terminal main body 50 (the cylindrical portion 50A) is provided for attaching the through-hole 50C through which the assembly bolt 61 shown in FIGS. Through holes 50D through which the bolts are inserted, and are sandwiched between the casing 20 and the cover 29 by the assembly bolts 61 (see FIGS. 1 and 2).

The terminal part D (terminal body 50) collectively holds electrical components such as a power supply circuit for supplying driving power to the motor 25 and various sensors described later. As shown in FIGS. 7 and 8, the power feeding circuit connects the coils 23c of the stator 23 to the terminals 51a of the bus bar 51 for each of the U phase, the V phase, and the W phase. 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 cylindrical portion 50A of the terminal body 50. Through the casing 2 and is connected to a 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 an axial displacement of the screw shaft 33 (output member 3). This is a stroke detection sensor 55 used for detecting the amount. As the rotation angle detection sensor 53 and the stroke detection sensor 55, a Hall sensor which is a kind of magnetic sensor is used.

As shown in FIGS. 1 and 8, the rotation angle detection sensor 53 is attached to a printed circuit board 52, and via a pulsar ring 54 attached to an end on the other axial side of the rotor inner 26 and an axial clearance. Opposed. The rotation angle detection sensor 53 determines the timing for supplying current to each of the U phase, V phase, and W phase of the motor 25.

As shown in FIGS. 2, 7, and 8, the stroke detection sensor 55 is attached to a belt-like printed board 56 that extends in the axial direction and has an end on the other side in the axial direction connected to the printed board 52. . The printed circuit board 56 and the stroke detection sensor 55 are disposed on the inner periphery of the hole 33b of the screw shaft 33, more specifically, on the inner periphery of the cylindrical portion 36c of the inner member 36 accommodated 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 via a radial gap. The stroke detection sensor 55 detects the axial and radial magnetic fields formed around the permanent magnet 57, and calculates the axial displacement amount of the screw shaft 33 based on this.

Although detailed illustration is omitted, the signal line of the rotation angle detection sensor 53 and the signal line of the stroke detection sensor 55 are both through holes 50c in the radial direction provided in the cylindrical 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 connected to the control device 80 (see FIG. 11 or FIG. 12).

The assembly procedure of the electric actuator 1 having the above configuration will be briefly described. First, as shown in FIG. 5, the ring gear 40 is assembled in the casing 20. Next, the rotor 24 of the motor 25 and the subassembly of the motion conversion 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 into the guide groove 20 b of the casing 20, and the bearing holder 28 is fitted into the inner peripheral surface 20 c of the casing 20. Then, after the stator 23 is fitted to the inner periphery of the casing 20 in the subassembly of the stator 23 and the terminal portion D (terminal body 50) of the motor 25 shown in FIG. Are fastened by an assembly bolt 61 (see FIGS. 9 and 10). Thereby, the electric actuator 1 is completed.

The operation mode of the electric actuator 1 having the above configuration will be briefly described with reference to FIGS. For example, when an operation amount is input to an 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 a motor rotation angle control signal necessary 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 B. Specifically, when the rotor 24 rotates, the sun gear 41 of the planetary gear speed reducer 10 connected to the rotor inner 26 rotates, and accordingly, the planetary gear 42 revolves and the planetary gear carrier 43 rotates. Thereby, the rotational motion 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 moves forward while being prevented from rotating. 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 one end of the screw shaft 33 in the axial direction operates (pressurizes) an operation target (not shown).

The axial position of the screw shaft 33 (the amount of displacement in the axial direction) is detected by the stroke detection sensor 55 as shown in FIG. 11, 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 is based on the 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. For this reason, 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 portion D. Via the motor 25 and the like.

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 side in the axial direction of the output member 3 (head 39a of the actuator head 39) opposed thereto, An annular origin positioning member 90 that determines the origin position of the output member 3 by engaging the both end surfaces in the axial direction is provided. If such an origin positioning member 90 is provided, the origin position of the output member 3 can be set easily and accurately without using 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, if the axial dimension of the origin positioning member 90 is set appropriately, the output member 3 and the housing are brought together with the return of the origin of the output member 3. Even if the bottom portion of the body 2 is strongly abutted against, the origin positioning member 90 is in front of the opening end surface 20a1 of the housing 2 and the end surface on the other side in the axial direction of the output member 3 facing this (the head of the actuator head 39). The elastic restoring force in the axial direction is generated by being sandwiched between the portion 39b and the other end surface of the portion 39b in the axial direction. As a result, the possibility that the output member 3 and the cover 29 abut against each other strongly, and the possibility that the ball 34 constituting the ball screw device 31 becomes in a locked state [see FIG. Can be reduced.

In particular, in the present embodiment, as shown in FIGS. 1 and 2, an annular protrusion having a substantially triangular cross-section projecting to the other side in the axial direction is provided integrally with the origin positioning member 90, thereby The other side can be preferentially compressed over one side in the axial direction. This is because it is possible to easily position the origin of the output member 3 during normal operation by preferentially compressing the other side in the axial direction of the origin positioning member 90, and a large impact load such as an axial load. This is because when the compressive load acts on the output member 3, the impact load is efficiently reduced on one side in the axial direction of the origin positioning member 90.

In the present embodiment, in the state where the output member 3 is located at the origin, the inner end surface of the cover 29 is connected to the end surface of the output member 3 via the axial gap 4 (the other axial direction of the flange portion 36b of the inner member 36). Therefore, the possibility that the output member 3 and the cover 29 abut against each other in the axial direction can be further effectively reduced as the output member 3 returns to the origin. Therefore, the possibility that the ball screw device 31 falls into the locked state can be further effectively reduced. Therefore, according to the present invention, the origin of the output member 3 can be easily reduced while effectively reducing the possibility of occurrence of a serious defect such that the output member 3 becomes inoperable when the output member 3 returns to the origin. Since it becomes possible to set, the electric actuator 1 which is excellent in the operation accuracy of the output member 3 and has high reliability can be realized.

Further, the rotor inner 26 as a hollow rotating shaft is rotatably supported at one end in the axial direction by a rolling bearing 27 disposed in the vicinity of one end in the axial direction of the rotor core 24a, and the other in the axial direction of the rotor core 24a. The other end portion in the axial direction is rotatably supported by a rolling bearing 30 disposed close to the end portion on the 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 disposed on the inner side of the axial width of the nut member 32 can be combined to make the electric actuator 1 more compact in the axial direction.

In addition, if the rotation balance of the rotor 24 is taken, the rolling

bearings

27 and 30 that support the rotor inner 26 may support a radial load 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. For example, the rotor inner 26 may be formed of an inexpensive mild steel material in which heat treatment such as quenching and tempering is omitted. Necessary strength can be ensured. In particular, in the electric actuator 1 of the present embodiment, since the rotational motion of the motor 25 is transmitted to the nut member 32 via the planetary gear speed reducer 10, no radial load is generated, and the linear motion of the screw shaft 33 is not caused. The accompanying reaction force (thrust load) is directly supported by the needle roller bearing 47. Accordingly, since the rolling bearing 27 only needs to have a radial positioning function, the rotor inner 26 integrally including the inner raceway surface 27a of the rolling bearing 27 is sufficient for the material specifications as described above. 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 mounted even when the nut member 32 is loaded with the thrust load. Since it is possible to rotate with low torque, it is possible to promote downsizing of the motor 25.

Further, if the needle roller bearing 47 is disposed within the axial range between the rolling

bearings

27 and 30, the screw shaft 33 is moved along with the linear movement of the screw shaft 33 (output member 3). Accordingly, the operation accuracy and durability of the output member 3 can be improved, and a needle roller bearing 47 that is compact in the axial direction can be employed. In the present embodiment, the needle roller bearing 47 is disposed near the center in the axial direction between the rolling

bearings

27 and 30. In this case, it is more advantageous for the moment load. As a result, extremely small ones can be employed as the needle roller bearing 47, the thrust receiving ring 46, and the like. Therefore, the axial dimension L (see FIG. 1) of the electric actuator 1 (housing 2) by providing the needle roller bearing 47 and the thrust receiving ring 46 can be prevented as much as possible.

Further, downsizing of the motor part A (motor 25) realized by providing the planetary gear speed reducer 10 and the needle roller bearing 47 in the motion conversion mechanism part B, and the cylindrical part 43a of the rotor inner 26 and the planetary gear carrier 43 are realized. Combined with the overlapping structure in the radial direction of the nut member 32, the radial dimension M (see FIG. 1) of the housing 2 can be made as small as possible. Thereby, the electric actuator 1 can be made more compact, and the mountability with respect to the equipment used is improved.

Further, since the rotor 24 (rotor inner 26) and the nut member 32 of the motor part A are separated from each other, for example, even when the ball screw device 31 having different specifications is adopted, the motor part A and the motion conversion mechanism part B A part (the 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 with a wide variety of deployments in which parts are shared.

The power supply circuit for supplying drive power to the motor 25, the 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 the sandwich structure in which the casing 20 and the cover 29 are sandwiched in the axial direction is employed, the assemblability is good. In particular, in this embodiment, as shown in FIGS. 1 and 6, a part of the stator 23 of the motor 25 (the outer periphery of the other end in the axial direction) is fitted to the inner periphery of the cylindrical portion 50 </ b> A of the terminal body 50. Match. In this case, since the stator 23 can be assembled to the inner periphery of the housing 2 at the same time as the housing 2 is assembled, the assemblability can also be improved from this point.

The cylindrical portion 50A of the terminal body 50 has a through hole 50c that allows the inside and outside of the housing 2 to communicate with each other. The lead wire connected to the power feeding circuit and the signal wire (electrical) connected to the

sensors

53 and 55 described above. Wiring) is pulled out radially outward of the housing 2 through the through hole 50c. In this case, it is necessary to complete the above-described electrical wiring operation with the terminal body 50 alone, that is, the electrical system necessary for operating the electric actuator 1 appropriately and accurately is the housing 2 (electric actuator 1). Can be held together by the terminal body 50 before assembly. As a result, it is not necessary to separately perform troublesome wiring work in the assembly stage of the electric actuator 1, so that the assemblability of the electric actuator 1 can be further improved.

In addition, if the wiring work of the electric wiring can be completed with the terminal body 50 alone, for example, even when the specification change occurs in the motor 25, the planetary gear reducer 10 or the like, the coupling partner member (here, In particular, the terminal body 50 can be shared as long as the shape of the coupled portion of the casing 20) is the same. As a result, it is possible to easily cope with the development of various types (series) of electric actuators 1 by sharing parts and members.

In addition, a sandwich structure in which the terminal body 50 is sandwiched between the casing 20 and the cover 29 in the axial direction is adopted, and lead wires of the power feeding circuit and signal lines of the sensor can be drawn to the outer diameter side of the housing 2. By adopting the hollow screw shaft 33, the two electric actuators 1 (units of the motor part A, the motion conversion mechanism part B and the terminal part D) are arranged continuously in the axial direction. An electric actuator capable of individually operating two operation objects can also be realized. Such an electric actuator can be preferably mounted on, for example, a DCT which is a kind of automatic transmission, and can contribute to the compactness of the entire DCT.

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

As mentioned above, although the electric actuator 1 which concerns on one Embodiment of this invention was demonstrated, embodiment of this invention is not restricted 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, since the origin positioning member 90 having a predetermined shape can be easily manufactured by using an elastic material, it is advantageous in suppressing an increase in cost due to the additional provision of the origin positioning member 90.

Further, as the thrust bearing disposed adjacent to the other axial side of the nut member 32, a rolling bearing other than the needle roller bearing 47, for example, a cylindrical roller bearing may be employed. However, the needle roller bearing 47 is preferable in consideration of the load supporting ability and the axial dimension of the bearing.

In the embodiment described above, the planetary gear speed reducer 10 is provided in the motion conversion mechanism B, but a speed reducer other than the planetary gear speed reducer 10 may be employed.

Further, it is not always necessary to provide a speed reducer such as the planetary gear speed reducer 10, and may be omitted if not necessary. When the planetary gear speed 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 connected so as to be able to transmit torque directly. Then, it is necessary to adopt a different shape for at least one of the rotor inner 26 and the nut member 32. Therefore, when the planetary gear speed reducer 10 is omitted, for example, a cylindrical intermediate member is disposed 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 Each of the inner peripheral surface is preferably coupled to the inner peripheral surface 26d of the rotor inner 26 and the outer peripheral surface 32b of the nut member 32 so as to be able to transmit torque (not shown). As a result, even when the planetary gear speed reducer 10 is omitted, the motor part A (motor 25) and the ball screw device 31 can be shared, so that an increase in cost can be suppressed.

In the embodiment described above, the stroke detection sensor 55 is used. However, the stroke detection sensor 55 may be used as necessary, 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 on 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 motor rotation angle control signal necessary for the pressure command value and sends this control signal to the motor 25. As in the case described with reference to FIG. 11, the screw shaft 33 moves forward to a position based on the control signal of the controller 81, and the actuator head 39 attached to one end of the screw shaft 33 in the axial direction 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. For this reason, when the electric actuator 1 that does not use the stroke detection sensor 55 is applied to, for example, brake-by-wire, the brake hydraulic pressure can be reliably controlled.

As described above, when the stroke detection sensor 55 is not used, the screw shaft 33 may be a solid one 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, a screw shaft 33 having a flange portion at the other end in the axial direction is employed.

The present invention is not limited to the above-described embodiments, and can of course be implemented in various forms without departing from the gist of the present invention. The equivalent meanings recited in the claims, and all modifications within the scope.

1 Electric Actuator 2 Housing 3 Output Member 4 Axial Clearance 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 housing)
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

A motor unit that is driven by the supply of electric power, a motion conversion mechanism unit that converts the rotational motion of the motor unit into a linear motion and outputs the motor unit, and the motor unit and the motion conversion mechanism unit are accommodated in one axial direction. A bottomed cylindrical casing having an opening at the other end and a bottom at the other end in the axial direction, and the motion conversion mechanism is arranged coaxially with the rotation center of the rotor of the motor A screw shaft, and a nut member rotatably fitted to the outer periphery of the screw shaft via a plurality of balls, and provided with a rotor and a torque member capable of transmitting torque. In the electric actuator in which the output member including the screw shaft moves forward in one axial direction or moves backward in the other axial direction depending on the direction,
An annular origin positioning member that determines the origin position of the output member by engaging with the opening end surface of the housing and the end surface on the other side in the axial direction of the output member facing the same in the axial direction. And the origin positioning member has an elastic restoring force in the axial direction.
2. The electric actuator according to claim 1, wherein an inner end surface of the bottom portion of the housing faces the end surface of the output member via an axial gap in a state where the output member is located at the origin.
The electric actuator according to claim 1 or 2, wherein the origin positioning member is made of an elastic material.
The rotor has a hollow rotating shaft that is rotatably supported with respect to the casing by rolling bearings that are arranged at two locations spaced apart in the axial direction, with the nut member disposed on the inner periphery,
The electric actuator according to any one of claims 1 to 3, wherein the hollow rotary shaft has an inner raceway surface of one of the two rolling bearings.
The electric actuator according to claim 4, wherein the inner raceway surface is disposed inside an axial width of the nut member.
6. The electric actuator according to claim 4, wherein a thrust bearing is adjacently disposed on the other axial side of the nut member, and the thrust bearing is disposed within an axial range between the two rolling bearings.
The electric actuator according to any one of claims 1 to 6, wherein the motion conversion mechanism further includes a speed reducer that decelerates the rotation of the rotor and transmits the reduced speed to the nut member.
The housing includes a plurality of members coupled in the axial direction,
The terminal part holding the electrical component has a cylindrical part that is sandwiched from both sides in the axial direction by the constituent members of the casing, and the cylindrical part has a radial through hole that communicates the inside and outside of the casing. The electric actuator according to any one of claims 1 to 7.
The electric actuator according to claim 8, wherein at least a part of the stator of the motor part is fitted into the cylindrical part.