WO2017145827A1

WO2017145827A1 - Electrically driven actuator

Info

Publication number: WO2017145827A1
Application number: PCT/JP2017/005023
Authority: WO
Inventors: 卓志松任; 池田　良則; 悠紀内藤
Original assignee: Ntn株式会社
Priority date: 2016-02-24
Filing date: 2017-02-10
Publication date: 2017-08-31
Also published as: JP2017150557A; JP6651381B2

Abstract

An electrically driven actuator (1) comprising a motor (A), a motion conversion mechanism (B), and an operating section (C), the motion conversion mechanism (B) having a ball screw shaft (33) and a ball screw nut (32) which is rotatably fitted on the outer periphery of the ball screw shaft (33), the ball screw shaft (33) and the operating section (C) moving forward to one axial side or backward to the other axial side according to the rotational direction of the ball screw nut (32), wherein an actuator head (39) serving as the operating section (C) is mounted in a removable manner to the end of the ball screw shaft (33), which is located on the one axial side thereof.

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, there is one that employs a ball screw mechanism (ball screw device) as a motion conversion mechanism that converts a rotational motion of a motor into a linear motion and outputs the motion (for example, Patent Document 1, Patent Document 1). 2). In this case, the ball screw shaft constituting the ball screw device constitutes the output member of the electric actuator.

JP-A-2005-330942 JP 2014-18007 A

By the way, in an electric actuator adopting a ball screw device as a motion conversion mechanism, depending on the use of the electric actuator, the shape of the operation target, etc., one end of the ball screw shaft in the axial direction (in the forward direction of the ball screw shaft). An operation unit for operating the operation target is provided at the end). In this regard, Patent Document 1 employs a configuration in which an operation unit is integrally provided on a ball screw shaft, and Patent Document 2 discloses that a ball screw shaft formed in a hollow shape is connected to a pulling rod having an operation unit in an axial direction. The pull rod is attached to the outer periphery of the base end so that it can be engaged on both sides.

However, in view of the recent situation where expansion of devices equipped with electric actuators is being studied, there is room for improvement in the configurations of

Patent Documents

1 and 2 when considering the reduction in cost and series of electric actuators by sharing parts. There is. That is, in any configuration of

Patent Documents

1 and 2, the output member including the operation unit and the ball screw shaft needs to be a dedicated part corresponding to the application, the shape of the operation target, and the like.

In view of the above circumstances, an object of the present invention is to realize a highly versatile electric actuator that can be applied to various devices, thereby contributing to cost reduction and series production of the electric actuator.

The present invention, which was created to solve the above problems, includes a motor unit that receives power to drive, a motion conversion mechanism unit that converts the rotational motion of the motor unit into a linear motion, and outputs the linear motion, and a motion conversion mechanism. And a ball screw nut in which the motion converting mechanism is rotatably fitted to the outer periphery of the ball screw shaft via a plurality of balls. In the electric actuator in which the ball screw shaft and the operation part move forward in one axial direction or move backward in the other axial direction according to the rotation direction of the ball screw nut, the operation part is arranged in the axial direction of the ball screw shaft. It is provided so that it can be attached or detached with respect to the edge part of one side.

According to such a configuration, for example, even when the electric actuator is deployed in various devices, the operation unit may be replaced, and the ball screw device including the ball screw shaft and, in some cases, components other than the operation unit are shared. Can be As a result, it is possible to realize a highly versatile electric actuator that can be applied to various devices with minimal changes, and can contribute to cost reduction and series production of the electric actuator.

In addition, if the operation unit can be attached to and detached from the end of one side of the ball screw shaft in the axial direction, it can be disassembled even if it is an electric actuator assembled with a motor unit, a motion conversion mechanism unit, etc. The actuator head can be easily replaced without any change. Therefore, there is an advantage that the maintainability can be improved.

The above-described present invention can be preferably applied to an electric actuator in which the ball screw shaft is arranged coaxially with the rotation center of the motor unit.

The motion conversion mechanism can be provided with a speed reducer that decelerates the rotation of the motor and transmits it to the ball screw nut. In this case, since a small motor can be employed, it is possible to realize an electric actuator that is lightweight and compact and has excellent mountability to the equipment used. 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 electric actuator having the above configuration can further include a hollow rotary shaft that supports the rotor core of the motor unit, and a rolling bearing that rotatably supports the hollow rotary shaft. Further, it is possible to adopt a configuration in which a torque is transmitted to the hollow rotating shaft and arranged on the inner periphery of the hollow rotating shaft, and the inner surface of the rolling bearing is provided on the hollow rotating shaft. By adopting such a configuration, a hollow rotary shaft that is compact in the axial direction can be used, so that the electric actuator can be made compact in the axial direction.

When the inner raceway surface is provided on the hollow rotary shaft, the inner raceway surface can be disposed inside the axial width of the ball screw nut. Thereby, the electric actuator can be made more compact in the axial direction.

The electric actuator having the above-described configuration includes a plurality of members coupled in the axial direction, and includes a housing that houses the motor unit and the motion conversion mechanism unit, and a terminal unit that holds a power feeding circuit for supplying power to the motor unit. Further, it can be provided. In this case, the terminal portion can be held from both sides in the axial direction by the constituent members of the casing. Thereby, the assembly property of the electric actuator can be improved.

The terminal portion may have an opening for pulling out a lead wire connected to the power feeding circuit to the outer diameter side of the casing on the outer peripheral portion thereof. In this way, for example, it is possible to easily realize an electric actuator in which a plurality of electric actuators each having a ball screw shaft are connected in series and each ball screw shaft can be individually linearly moved. Such an electric actuator can be mounted on a device that has two or more operation targets, for example, a DCT (Dual Clutch Transmission), which is a type of automatic transmission, and the entire device including the electric actuator is light and compact. Can contribute.

As described above, according to the present invention, it is possible to provide an electric actuator that can be applied to various devices and has high versatility. Thereby, it can contribute to the cost reduction and series production | generation of an electric actuator.

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 perspective view of the operation part which concerns on other embodiment. It is a schematic perspective view of the operation part which concerns on other embodiment. It is a schematic perspective view of the operation part which concerns on other embodiment. 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.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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 of FIG. 1, and FIG. 3 is a motor rotor and motion conversion mechanism. The longitudinal cross-sectional view which took out and expanded the part is shown. 1 and 2 show a state where the output member of the electric actuator (the ball screw shaft of the ball screw device constituting the electric actuator) is located at the origin. In the present embodiment, the “state located at the origin” refers to the end face of the ball screw shaft 33 (the spring mounting collar 36 connected to the ball screw shaft 33) by the spring force (elastic restoring force) of a compression coil spring 48 as an urging member described later. Is in a state where it is in mechanical contact with the end face of the cover 29 facing this. 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. The casing 2 of the present embodiment has an end on one side in the axial direction (the right side in FIG. 1 and FIG. 2), and the other side in the axial direction (the left side in FIG. 1 and FIG. 2). ) Of the cylindrical casing 20 having an open end, a cover 29 that closes the end opening on the other axial side of the casing 20, and a terminal that is disposed between the casing 20 and the cover 29 and constitutes the terminal portion D It consists of a combination with the main body 50. 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 radial gap type motor (in detail, a U-phase, a stator having a stator 23 fixed to the casing 20 and a rotor 24 disposed to face the inner periphery of the stator 23 via a radial gap. 3 phase brushless motor having a V phase and a W phase) 25. 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 attached to the outer periphery of the rotor core 24a, and a rotor inner 26 formed as a hollow shaft and supporting the rotor core 24a (mounted on the outer periphery) as a hollow rotary shaft.

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 on the outer periphery of the rotor core 24a, the side plate 65 attached to the outer side of the other end of the rotor core 24a in the axial direction on the rotor inner 26, and the axially outer side thereof. It is positioned and fixed by a circlip 66 attached to.

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 B of the present embodiment includes a ball screw device 31 and a planetary gear speed reducer 10 as a speed reducer.

The ball screw device 31 is arranged coaxially with the rotor 24 (rotor inner 26), and is rotatable on the outer periphery of the ball screw shaft 33 via a ball screw shaft 33 constituting an output member of the electric actuator 1 and a plurality of balls 34. A fitted ball screw nut 32 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 ball screw nut 32 and the spiral groove 33a formed on the outer peripheral surface of the ball screw shaft 33, and the top 35 is assembled. ing. With such a configuration, when the ball screw shaft 33 moves back and forth in the axial direction (linear motion), the ball 34 circulates between the

spiral grooves

32a and 33a.

The ball 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 spring mounting collar 36 is accommodated in the hole portion 33b. ing. The spring mounting collar 36 is made of, for example, a resin material such as PPS, and has a circular solid portion 36a provided at one end in the axial direction and a flange-shaped spring receiver provided at the other end in the axial direction. The part 36b and the cylinder part 36c which connects both

parts

36a and 36b are integrally provided.

The spring mounting collar 36 housed in the hole 33b of the ball screw shaft 33 is connected to the ball screw shaft 33 by fitting a pin 37 so as to penetrate the circular solid portion 36a and the ball screw shaft 33 in the radial direction. Fixed. Both end portions of the pin 37 protrude radially outward from the outer peripheral surface of the ball 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 a guide groove 20b (see also FIG. 5) extending in the axial direction provided on the inner periphery of the small diameter cylindrical portion 20a of the casing 20. With such a configuration, when the ball screw nut 32 rotates around the axis of the ball screw shaft 33 as the motor 25 rotates, the ball screw shaft 33 linearly moves in the axial direction while being prevented from rotating. Whether the ball screw shaft 33 linearly moves (forwards) in one axial direction or linearly moves (retreats) in the other axial direction basically depends on the rotational direction of the ball screw nut 32. In this embodiment, the ball screw shaft 33 can be moved backward by the spring force of the compression coil spring 48 as an urging member (details will be described later).

As shown in FIGS. 1 and 2, an actuator head 39 as an operation portion C is detachably attached to an end portion on one axial side of the ball screw shaft 33. The actuator head 39 of this embodiment has a base portion 39a that is press-fitted and fixed in the hole portion 33b of the ball screw shaft 33, and a head portion 39b that is directly or indirectly engaged with an operation target (not shown) in the axial direction. Then, as the ball screw shaft 33 linearly moves (advances) in one axial direction, the tip surface of the head 39b presses the operation target in the axial direction.

In this embodiment, the actuator head 39 is press-fitted and fixed to the ball screw shaft 33. However, as long as the actuator head 39 can be attached to and detached from the ball screw shaft 33, other fixing methods may be employed. . For example, a method of fitting screw grooves provided on the inner periphery of the ball screw shaft 33 and the outer periphery of the base portion 39a of the actuator head 39, a fixing method using an easily removable fastener such as a bolt or a pin, and the like are adopted. Can do. The same applies to an actuator head 39 (see FIG. 11) according to another embodiment to be described later.

As shown in FIGS. 1 to 4, the planetary gear speed reducer 10 includes a ring gear 40 fixed to the casing 20, a sun gear 41 press-fitted and fixed to the inner peripheral surface of the step portion of the rotor inner 26, and a ring gear 40 and a sun gear 41. And a plurality of (four in this embodiment) planetary gears 42 meshed with both

gears

40, 41, and a planetary gear carrier 43 and a planetary gear holder 44 holding the planetary gears 42 rotatably.

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.

The planetary gear carrier 43 is rotatable relative to the rotor inner 26 and, as shown in FIGS. 1 to 3, is a cylinder disposed between the inner peripheral surface of the rotor inner 26 and the outer peripheral surface 32b of the ball screw nut 32. It has the part 43a integrally. The outer peripheral surface of the cylindrical portion 43 a faces the inner peripheral surface of the rotor inner 26 (and the inner peripheral surface of the sun gear 41) via a radial gap, and the inner peripheral surface of the cylindrical portion 43 a is press-fitted into the outer peripheral surface 32 b of the ball screw nut 32. It is mated. By the planetary gear speed reducer 10 having the above configuration, the rotation of the rotor inner 26 of the motor 25 is decelerated and transmitted to the ball screw nut 32. Thereby, since rotational torque can be increased, the small motor 25 can be employ | adopted and the electric actuator 1 can be reduced in weight and compact as a whole.

As shown in FIGS. 1 to 3, a thrust washer 45 is disposed between the end face on one axial side of the ball screw nut 32 and the casing 20, and is attached to the outer periphery of the tip of the cylindrical portion 29 a of the cover 29. A needle roller bearing 47 as a thrust bearing is disposed between the thrust receiving ring 46 and the end face on the other axial side of the ball screw nut 32. Due to the presence of such a needle roller bearing 47, a thrust load when the ball screw shaft 33 linearly moves (advances) in one axial direction is smoothly supported.

As shown in FIGS. 1 and 2, a compression coil spring 48 as an urging member is disposed between the inner peripheral surface 29 b of the cylindrical portion 29 a of the cover 29 and the outer peripheral surface of the ball screw shaft 33. . One end and the other end in the axial direction of the compression coil spring 48 are in contact with the needle roller bearing 47 and the spring receiving portion 36b of the spring mounting collar 36, respectively. The ball screw shaft 33 connected to the spring mounting collar 36 is always urged toward the origin by the spring force of the compression coil spring 48 thus provided. In this way, for example, when the driving power is not properly supplied to the motor unit A (motor 25), the ball screw shaft 33 is automatically returned to the origin, and the operation of the operation target (not shown) is adversely affected. The possibility of exerting can be reduced as much as possible.

Details of the cover 29 will be described with reference to FIG. 9 and FIG. 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 (mass productivity) 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 cross-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, FIG. 7 is a cross-sectional view taken along the line GG in FIG. 1, and FIG. It is a HH arrow directional cross-sectional view. As shown in FIG. 6, the terminal portion D has a short cylindrical portion constituting a part of the housing 2 and a disk-shaped portion extending radially inward from the other axial end of the short cylindrical portion. And a bus bar 51 and a printed circuit board 52 screwed to the terminal main body 50 (the disk-shaped portion thereof). As shown in FIGS. 7 and 8, the terminal main body 50 (the short cylindrical portion thereof) is provided for attaching the through-hole 50A through which the assembly bolt 61 shown in FIGS. And a through hole 50B through 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 body 50 is formed of a resin material such as PPS, for example.

The terminal part D (terminal body 50) holds a power feeding circuit for supplying driving power to the motor 25. 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, and the lead wire is an opening 50c (see FIG. 1) provided in the outer peripheral portion (short cylindrical portion) of the terminal body 50. Is pulled out to the outer diameter side of the housing 2 and connected to a controller 81 (see FIG. 12 or FIG. 13) of the control device 80.

The electric actuator 1 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 stroke control (amount of displacement in the axial direction) of the ball screw shaft 33. This is a stroke detection sensor 55 used for detection. 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 having a disk shape, and a pulsar ring 54 attached to the end portion on the other side in the axial direction of the rotor inner 26 and the shaft Oppositely arranged via a directional gap. 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 ball screw shaft 33, more specifically, on the inner periphery of the cylindrical portion 36c of the spring mounting collar 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 spring mounting collar 36 so as to face the stroke detection sensor 55 via a radial clearance. Permanent magnets 57 are attached to two locations separated from each other. The stroke detection sensor 55 comprising a Hall sensor detects the axial and radial magnetic fields formed around the permanent magnet 57, and calculates the axial displacement of the ball screw shaft 33 based on the detected magnetic field. To do.

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 connected to the housing through the opening 50c (see FIG. 1) of the terminal body 50. 2 is pulled out to the outer diameter side and connected to the control device 80 (see FIG. 12 or 13).

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 among the sub-assemblies of the stator 23 and the terminal body 50 of the motor 25 shown in FIG. 6, the cover 29 and the terminal body 50 are assembled to the casing 20. Fastened with bolts 61 (see FIGS. 9 and 10). Thereby, the electric actuator 1 is completed.

As described above, in the electric actuator 1 according to the present invention, the actuator head 39 as the operation portion C is provided so as to be attachable to and detachable from the end portion on one side in the axial direction of the ball screw shaft 33. In this way, for example, even when the electric actuator 1 is deployed in various devices, the actuator head 39 may be replaced, and the ball screw device 31 and, in some cases, components other than the actuator head 39 may be shared. it can. As a result, a highly versatile electric actuator that can be applied to various devices with minimal changes can be realized, and the electric actuator 1 can be reduced in cost and series. Further, if the actuator head 39 can be attached to and detached from the end on one side in the axial direction of the ball screw shaft 33, the electric actuator 1 in which the motor part A, the motion conversion mechanism part B, etc. are assembled, Since the actuator head 39 can be easily replaced without disassembling this, there is also an advantage that the maintainability can be improved.

As other usable actuator heads 39, those exemplified in FIGS. 11A to 11C can be cited. The actuator head 39 shown in FIG. 11A is a so-called push type similar to the actuator head 39 shown in FIGS. 1 and 2, and the head 39 b has two places where the pressing surfaces capable of pressing the operation target in the axial direction are separated from each other. 1 is different from the actuator head 39 shown in FIGS. Further, the actuator head 39 shown in FIGS. 11B and 11C is a so-called push-pull type that can operate the operation target on both sides in the axial direction. The actuator head 39 of FIG. 11B is a type in which the head 39b is connected to the operation target by a pin, and the actuator head 39 shown in FIG. 11C is provided with a thread groove formed on the outer periphery of the head 39b. It is a type that is connected to an operation object by screwing into a thread groove.

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, the structure in which the rolling bearing 27 is disposed inside the axial width of the ball screw nut 32 is combined to shorten the axial dimension L (see FIG. 1) of the housing 2 of the electric actuator 1. can do.

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 this embodiment, since the rotational motion of the motor 25 is transmitted to the ball screw nut 32 via the planetary gear speed reducer 10, no radial load is generated, and the straight line of the ball screw shaft 33 is not generated. The reaction force (thrust load) generated along with the movement is supported by a dedicated 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, since the needle roller bearing 47 is disposed within the axial range between the rolling

bearings

27 and 30 that support the rotor inner 26, it is advantageous against moment load, and a small-sized one can be used as the bearing. . In particular, as in the present embodiment, when the needle roller bearing 47 is disposed near the center in the axial direction between the rolling

bearings

27 and 30 that support the rotor inner 26, it is extremely advantageous with respect to the moment load, and the needle shape The size reduction of the roller bearing 47 can be further promoted. As a result, extremely small ones can be employed as the needle roller bearing 47 and the thrust receiving ring 46, and the electric actuator 1 can be made more compact through this.

The planetary gear carrier 43 and the ball screw nut 32 are formed by using the cylindrical portion 43a of the planetary gear carrier 43 as an output portion of the planetary gear speed reducer 10 and press fitting the cylindrical portion 43a to the outer peripheral surface 32b of the ball screw nut 32. Are connected so as to be able to transmit torque, so that the connection workability during assembly is good, and stable torque transmission is possible even for high torque after deceleration.

Further, the size reduction of the motor part A (motor 25) by providing the planetary gear speed reducer 10 in the motion conversion mechanism part B, and the radial direction of the rotor inner 26, the cylindrical part 43a of the planetary gear carrier 43 and the ball screw nut 32 are achieved. In combination with this superposition structure, the radial dimension M (see FIG. 1) of the housing 2 of the electric actuator 1 can also be reduced. Thereby, the electric actuator 1 can be made more compact, and the mountability with respect to the equipment used is further improved.

Further, the sun gear 41 of the planetary gear speed reducer 10 is press-fitted and fitted to the inner peripheral surface of the rotor inner 26, so that the rotor inner 26 and the sun gear 41 are connected so that torque can be transmitted. Good connection workability. 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 deceleration, and therefore the torque transmission performance required between the two can be sufficiently ensured. Furthermore, 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.

In addition, since the rotor inner 26 and the ball screw nut 32 have a separate structure, for example, even when the ball screw device 31 having different specifications is used, the rotor inner 26 (and thus the motor part A) can be shared. As a result, the versatility is further improved, and it becomes easier to realize a series of electric actuators 1 by developing a variety of products that share parts.

Further, a sandwich structure in which the power feeding circuit, the rotation angle detection sensor 53, the stroke detection sensor 55, and the like are held by the terminal body 50 and the terminal body 50 (terminal portion D) is sandwiched between the casing 20 and the cover 29 in the axial direction. As a result, it is easy to assemble. Furthermore, the lead wire of the power feeding circuit and the signal line of the sensor are drawn out to the outer diameter side of the housing 2 through the sandwich structure and the opening 50c provided in the outer peripheral portion (short cylindrical portion) of the terminal body 50. Depending on the possible structure, a plurality of electric actuators 1 (units of motor part A, motion conversion mechanism part B and terminal part D) are arranged in the axial direction, and a plurality of operation objects are individually operated. Possible electric actuators can also be realized.

The electric actuator 1 according to the present embodiment is characterized by the combination of the characteristic configurations described above, which is lightweight and compact, excellent in mountability to equipment used, low in cost, and easy to series. .

Finally, the operation mode of the electric actuator 1 of the present embodiment will be briefly described with reference to FIGS. 1 and 12. 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. 12, 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 (rotor inner 26) rotates based on the control signal sent from the controller 81, this rotational motion is transmitted to the motion converting mechanism B. Specifically, when the rotor inner 26 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 inner 26 is transmitted to the ball screw nut 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 inner 26, so that the rotational torque transmitted to the ball screw nut 32 increases.

When the ball screw nut 32 rotates in response to the rotational motion of the rotor inner 26, the ball screw shaft 33 moves linearly (advances) in one axial direction while being prevented from rotating. At this time, the ball screw shaft 33 moves forward to a position based on the control signal of the controller 81, and the actuator head 39 fixed to one end of the ball screw shaft 33 in the axial direction operates an operation target (not shown).

The axial position (the amount of axial displacement) of the ball screw shaft 33 is detected by the stroke detection sensor 55 as shown in FIG. 12, 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 actuator head 39 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.

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 ball screw shaft 33 is formed in a hollow shape by providing holes 33b (through holes in the axial direction) that are opened on both end surfaces of the ball screw shaft 33 in the axial direction. The stroke detection sensor 55 is disposed on the inner periphery of the ball screw shaft 33. However, the ball screw shaft 33 is provided with an axially extending hole 33b that is opened only on the other end surface in the axial direction. It is also possible to form a hollow shape.

In the embodiment described above, the compression coil spring 48 is provided as a biasing member that constantly biases the ball screw shaft 33 toward the origin, but the compression coil spring 48 requires a function of biasing. It may be provided according to the intended use, and may be omitted if not required.

In the embodiment described above, the planetary gear speed reducer 10 is adopted as the speed reducer constituting the motion conversion mechanism B, but a speed reducer having another mechanism may be adopted. Further, the present invention can be applied not only to the electric actuator 1 provided with a reduction gear but also to the electric actuator 1 not provided with a reduction gear. Although illustration is omitted, when the reduction gear is omitted, the ball screw nut 32 and the rotor inner 26 may be connected so as to be able to transmit torque directly.

In the embodiment described above, the stroke detection sensor 55 is used. However, depending on the equipment used, the stroke detection sensor 55 may not be used.

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. 13 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 motor rotation angle control signal necessary for the pressure command value and sends this control signal to the motor 25. Then, similarly to the case described with reference to FIG. 12, the ball screw shaft 33 advances to a position based on the control signal of the controller 81, and is an actuator head fixed to one end of the ball screw shaft 33 in the axial direction. 39 operates an operation target not shown.

The operation pressure of the ball screw shaft 33 (actuator head 39) is detected by a pressure sensor 83 installed outside and is 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.

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.

DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Case 10 Planetary gear speed reducer (speed reducer)
20 Casing 23 Stator 24 Rotor 25 Motor 26 Rotor inner (hollow rotating shaft)
29 cover 31 ball screw device 32 ball screw nut 33 ball screw shaft 34 ball 39 actuator head 40 ring gear 41 sun gear 42 planetary gear 43 planetary gear carrier 47 needle roller bearing 48 compression coil spring (biasing member)
50 Terminal body 50c Opening 55 Stroke detection sensor 57 Permanent magnet A Motor part B Motion conversion mechanism part C Operation part D Terminal part L Axial dimension of the casing M Radial dimension of the casing

Claims

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 it, and an operation unit that operates an operation target by receiving the output of the motion conversion mechanism unit And the motion conversion mechanism section includes a ball screw shaft and a ball screw nut rotatably fitted to the outer periphery of the ball screw shaft via a plurality of balls, and the rotation of the ball screw nut. Depending on the direction, in the electric actuator in which the ball screw shaft and the operation part advance in the axial direction one side or retract in the axial direction other side,
The electric actuator is characterized in that the operation portion is detachably attached to an end portion on one axial side of the ball screw shaft.
The electric actuator according to claim 1, wherein the ball screw shaft is disposed coaxially with a rotation center of the motor unit.
The electric actuator according to claim 1 or 2, wherein the motion conversion mechanism section further includes a speed reducer that decelerates the rotation of the motor section and transmits it to the ball screw nut.
The electric actuator according to claim 3, wherein the speed reducer is a planetary gear speed reducer.
A hollow rotary shaft that supports the rotor core of the motor unit, and a rolling bearing that rotatably supports the hollow rotary shaft;
The ball screw nut is disposed on the inner periphery of the hollow rotary shaft so that torque can be transmitted to the hollow rotary shaft,
The electric actuator according to any one of claims 1 to 4, wherein an inner raceway surface of the rolling bearing is provided on the hollow rotary shaft.
The electric actuator according to claim 5, wherein an inner raceway surface of the rolling bearing is disposed inside an axial width of the ball screw nut.
It is composed of a plurality of members coupled in the axial direction, and further includes a housing that houses the motor unit and the motion conversion mechanism unit, and a terminal unit that holds a power feeding circuit for supplying the power to the motor unit,
The electric actuator according to any one of claims 1 to 6, wherein the terminal portion is clamped from both sides in the axial direction by the constituent members of the casing.
The electric actuator according to claim 7, wherein the terminal portion has an opening for pulling out a lead wire connected to the power feeding circuit to an outer diameter side of the casing on an outer peripheral portion thereof.