WO2018088143A1

WO2018088143A1 - Electrically driven actuator

Info

Publication number: WO2018088143A1
Application number: PCT/JP2017/037564
Authority: WO
Inventors: 卓志松任; 公人牛田; 川合　正浩; 加藤　晃央
Original assignee: Ntn株式会社
Priority date: 2016-11-10
Filing date: 2017-10-17
Publication date: 2018-05-17
Also published as: JP2018078742A

Abstract

Provided is an electrically driven actuator 1 comprising an electric motor section A, a motion conversion mechanism section B, and a housing 8 in which the electric motor section A and the motion conversion mechanism section B are accommodated, the motion conversion mechanism section B having a threaded shaft 93 and a nut 92 which is fitted on the outer periphery of the threaded shaft 93 and which is rotatably supported relative to the housing 8 through a rolling bearing 9, the threaded shaft 93 moving axially forward and backward as the nut 92 rotates, wherein a third housing-forming member 83 of a plurality of housing-forming members which form the housing 8 is formed from an iron-based metallic material and has a load-receiving surface 83a which is in axial contact with the rolling bearing 9 to receive a thrust load acting on the rolling bearing 9.

Description

Electric actuator

The present invention relates to an electric actuator.

In recent years, automobiles have been electrified in order 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 (electric motor) has been developed. Has been put on.

As an electric actuator used in the above-mentioned system, there is one in which a screw mechanism (ball screw mechanism) is adopted as a motion conversion mechanism that converts a rotary motion of an electric motor into a linear motion and outputs it (for example, Patent Document 1). . In this case, when the nut of the screw mechanism is rotated about the axis of the screw shaft in response to the rotation of the motor, the output member (final output member) of the actuator including the screw shaft linearly moves in the axial direction.

In the electric actuator of Patent Document 1, a nut is provided integrally with the rotor of the electric motor, and the nut (rotor) is rotatably supported with respect to the casing of the electric actuator via a rolling bearing. .

JP 2014-18007 A

By the way, for example, when the final output member collides with an obstacle, a reverse input load is applied to the final output member. In the electric actuator of Patent Document 1, the above-mentioned reverse input load is a motor made of an aluminum alloy that constitutes a housing (via a screw shaft, a ball, a nut, a rolling bearing, and a retaining ring that positions the rolling bearing in the axial direction. (In particular, paragraph 0057 of Patent Document 1). In short, in the electric actuator of Patent Document 1, the thrust load acting on the rolling bearing as the reverse input load is applied is substantially received by the retaining ring.

However, when an excessive reverse input load is applied to the output member, the thrust load acting on the rolling bearing naturally increases, and the retaining ring may be deformed or broken. When the retaining ring is deformed or broken, the positional accuracy in the axial direction of the rolling bearing is distorted, and the rotational accuracy of the nut and the operating accuracy of the screw shaft (including the final output member) are reduced.

In view of the above circumstances, an object of the present invention is to provide a highly reliable electric actuator that can stably maintain the operation accuracy of a screw shaft.

In order to solve the above-mentioned problems, the present invention includes an electric motor unit, a motion conversion mechanism unit that converts the rotational motion of the electric motor unit into a linear motion, and a plurality of casing constituent members coupled in the axial direction. And a housing housing the electric motor unit and the motion conversion mechanism unit, and the motion conversion mechanism unit is fitted on the outer periphery of the screw shaft and the screw shaft arranged coaxially with the rotation center of the rotor of the electric motor unit. A plurality of casing constituent members in an electric actuator having a nut rotatably supported with respect to the casing via a rolling bearing, wherein the screw shaft moves forward and backward in the axial direction as the nut rotates Of these, at least one is formed of an iron-based metal material, and this iron-based metal casing component member has a load receiving surface that receives a thrust load acting on the rolling bearing by contacting the rolling bearing in the axial direction. Special to have To. The “casing component” here is a member that constitutes the casing by being coupled with another casing component.

According to the above configuration, the thrust load acting on the rolling bearing can be received by the casing constituent member made of ferrous metal. Iron-based metal casing components have high strength and rigidity, so even if an excessive thrust load is input to the load receiving surface via a rolling bearing, it can deform or break itself. Sex is reduced as much as possible. Moreover, since the iron-based metal casing constituent member is at least one member constituting the casing, the thrust load input to the load receiving surface can be dispersed throughout the casing. Therefore, even when a large thrust load is applied to the rolling bearing, it is difficult for the rolling bearing to have a misalignment in the axial position accuracy, and the rotation accuracy of the nut and, consequently, the operating accuracy of the screw shaft (including the actuator output member). Can be stably maintained.

An iron-based metal casing constituent member can be a cast iron product or a forged product. In this way, this housing component can be mass-produced with low cost and high accuracy.

Of the plurality of casing constituent members, the remaining casing constituent members excluding the ferrous metal casing constituent members are preferably formed of an aluminum alloy having a low specific gravity and high thermal conductivity among metals. . Thereby, weight reduction of a housing | casing (electric actuator) and improvement of cooling efficiency can be aimed at.

The electric actuator having the above configuration is further provided with a speed reducer that decelerates the rotation of the rotor of the electric motor unit and transmits it to the nut for the purpose of reducing the size of the electric motor unit and, consequently, the weight and size of the electric actuator. Can do. In particular, the traction drive type planetary speed reducer has the feature of low backlash and low noise among various speed reducers, which is advantageous in realizing a quiet and excellent electric actuator. However, in a traction drive type planetary speed reducer, torque must be properly transmitted between components unless appropriate traction (radial preload) is applied to the inside (contact portion between the relatively rotating members). I can't. The traction can be applied, for example, by compressing an annular traction applying member in the axial direction to reduce the inner diameter dimension, but in this case, the axial compression allowance of the traction applying member is accurately maintained. Need to manage.

Therefore, in the present invention, the traction imparting member compressed in the axial direction (elastically compressed) is brought into contact with the iron-based metal casing constituent member in the axial direction. Since this casing member is formed of an iron-based metal material, it has high rigidity and a small amount of deformation due to temperature change. Accordingly, it is possible to stably maintain the axial compression allowance of the traction applying member, and thus the diameter reduction deformation amount, and it is possible to apply predetermined traction to the inside of the reduction gear.

In the above configuration, the nut can be arranged at a position shifted outward in the axial direction of the electric motor unit. In this case, compared with the case where the electric motor unit and the nut are overlapped in the radial direction (for example, Patent Document 1), the electric motor unit can be reduced in the radial direction, so that an electric actuator that is compact in the radial direction is realized. can do.

The electric motor unit is arranged on the inner diameter side of the rotor, and is a torque limiter arranged between the motor unit output shaft that outputs the rotation of the rotor, and the inner peripheral surface of the rotor and the outer peripheral surface of the motor unit output shaft facing each other. And can have. If it does in this way, overload to the component of an electric actuator can be prevented, and damage etc. of a component can be prevented. Thereby, the situation where the electric actuator becomes inoperable can be prevented as much as possible, and the reliability of the electric actuator can be further improved.

As described above, according to the present invention, it is possible to provide an electric actuator which is excellent in the operation accuracy of the screw shaft (including the output member of the actuator) and has high reliability.

FIG. 7 is a longitudinal sectional view of the electric actuator according to the embodiment of the present invention, and is a sectional view taken along the line HH in FIGS. 3 and 6. It is a longitudinal cross-sectional view of the electric actuator which concerns on one Embodiment of this invention, and is II sectional view taken on the line of FIG. It is a left view of FIG. FIG. 2 is a cross-sectional view taken along line EE in FIG. 1. FIG. 5 is a cross-sectional view taken along line FF in FIG. 1. FIG. 3 is a cross-sectional view taken along line GG in FIG. 2. FIG. 3 is a partially enlarged view of FIG. 2. FIG. 3 is a partially enlarged view of the vicinity of an outer diameter end portion of the speed reducer in a state before assembly of the electric actuator shown in FIGS. 1 and 2. It is a perspective view of the electric actuator shown in FIG. It is a perspective view of the electric actuator shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the terms “one side in the axial direction” and “the other side in the axial direction” are used to indicate the directionality in the axial direction. They are the opening side of the body 8 and the left side of the sheet (the closing side of the housing 8).

1 and 2 are longitudinal sectional views of an electric actuator according to an embodiment of the present invention. More specifically, FIG. 1 is a sectional view taken along line HH in FIGS. 2 is a cross-sectional view taken along the line II of FIG. 1 and 2 show a state where an output member of the electric actuator 1 (here, a screw shaft 93 of a ball screw 91 described later) is located at the origin.

As shown in FIGS. 1 and 2, the electric actuator 1 includes an electric motor unit A that generates a rotational driving force, a motion conversion mechanism unit B that converts the rotational motion of the electric motor unit A into a linear motion, and outputs the linear motion. And a housing 8 accommodating these.

The casing 8 of the present embodiment has four casing constituent members (first casing constituent member 81 to fourth casing constituent member 84) arranged in a row from the other side in the axial direction toward one side in the axial direction. ) And has a bottomed cylindrical shape as a whole. The first casing constituent member 81 is formed in a bottomed cylindrical shape, and the second to fourth casing constituent members 82 to 84 are formed in a cylindrical shape having both ends opened. As shown in FIGS. 9 and 10, the first to fourth housing constituting members 81 to 84 are coupled and integrated using a bolt member 85. The fourth casing component member 84 integrally has a flange portion 84a provided with a bolt insertion hole 84b. When the electric actuator 1 is fixed to a device not shown, the bolt insertion hole 84b is inserted. A bolt member (not shown) is fastened to the device used.

Of the first to fourth casing constituent members 81 to 84, the third casing constituent member 83 is formed of a ferrous metal material, and the remaining casing constituent members, that is, the first casing constituent member 81, The second casing constituent member 82 and the fourth casing constituent member 84 are formed of an aluminum alloy having a small specific gravity and a high thermal conductivity. This is because the electric actuator 1 is preferably made lighter and more compact in order to improve the mountability of the electric actuator 1 on the equipment used, and the internal temperature of the housing 8 can be increased as the electric motor unit A is driven. It is for suppressing it. Therefore, as described above, if most of the housing 8 is made of an aluminum alloy, the cooling efficiency can be increased while reducing the weight of the housing 8 (the electric actuator 1).

From the viewpoint of reducing the manufacturing cost, it is preferable that the third casing constituent member 83 made of iron-based metal is a cast iron product or a forged product, and the first casing constituent member 81 and the second casing. Both the constituent member 82 and the fourth casing constituent member 84 are preferably aluminum die cast products.

As shown in FIGS. 1 and 3, the first casing component member 81 is provided with a terminal portion D having a connector 101, and the connector 101 protrudes outward in the axial direction of the first casing component member 81. . In the connector 101, terminals for power supply and signal lines are provided, the terminals for power supply are electrically connected to the stator coil 51c, and the terminals for signal lines are connected to a sensor (not shown) (for example, It is electrically connected to a rotation angle detection sensor of the electric motor.

The electric motor part A includes an electric motor 29, a motor part output shaft 6, and a torque limiter 7. The electric motor 29 includes a stator 51 fixed to the casing 8 (first and second casing constituent members 81 and 82), and a rotor 52 disposed to face the stator 51 via a radial gap. It is a radial gap type.

As shown in FIGS. 1, 2 and 5, the stator 51 includes a stator core 51a made of a plurality of electromagnetic steel plates laminated in the axial direction, a bobbin 51b made of an insulating material mounted on the stator core 51a, and a bobbin 51b wound around the bobbin 51b. And a rotated stator coil 51c.

The rotor 52 includes an annular rotor core 52a, a plurality of magnets 52b attached to the rotor core 52a, and a cylindrical (hollow) rotor inner 52c fixed to the inner periphery of the rotor core 51a. The rotor core 52a is formed of a plurality of electromagnetic steel plates laminated in the axial direction. The rotor inner 52c is formed to be longer in the axial direction than the rotor core 52a, and end portions on one side and the other side of the rotor inner 52c protrude outward in the axial direction of the rotor core 52a. The rotor inner 52c is rotatably supported with respect to the housing 8 by

bearings

53 and 54 fixed to the outer peripheral surfaces of the end portions on one side and the other side in the axial direction. As the

bearings

53 and 54, a rolling bearing capable of supporting both a radial load and an axial load, for example, a deep groove ball bearing is used.

As shown in FIG. 1 and FIG. 2, the motor part output shaft 6 is formed in a cylindrical shape with both ends in the axial direction being opened, whereby the electric motor part A (the electric motor 29) is formed as a hollow motor. It has the structure of. The motor unit output shaft 6 is fitted to the inner periphery of the rotor inner 52c with a gap fit, and is rotatable relative to the rotor inner 52c.

As shown in an enlarged view in FIG. 7, an annular recess 521 having an inner diameter dimension larger than that of the other part is formed on the inner peripheral surface of the rotor inner 52 c, and the annular recess 521 is formed, for example, of the rotor inner 52 c as shown in FIG. 1. It is formed at the end on the other side in the axial direction. An annular space is formed between the inner peripheral surface of the annular recess 521 of the rotor inner 52c facing each other and the outer peripheral surface of the motor unit output shaft 6, and the torque limiter 7 is disposed in this annular space.

The torque limiter 7 transmits the rotational power output from the electric motor 29 to the motor unit output shaft 6. On the other hand, when an overload is applied, the torque limiter 7 cuts off the torque transmission, and the rotor 52 (rotor inner 52 c) of the electric motor 29 and the motor. The relative rotation of the part output shaft 6 is allowed. As long as it has such a function, the torque limiter 7 having an arbitrary configuration can be adopted. However, in the present embodiment, a multi-plate clutch which is a kind of a friction clutch is used as the torque limiter 7.

The configuration of the torque limiter 7 will be described with reference to FIGS. The multi-plate clutch as the torque limiter 7 includes a pair of

first friction plates

71 and 71 that are spaced apart in the axial direction and a second friction plate 72 that is disposed between the pair of

first friction plates

71 and 71. And an elastic member 73 such as a wave spring in which the first friction plate 71 and the second friction plate 72 are brought into pressure contact with each other, and a pressing plate 74. The pressing plate 74 is positioned in the axial direction by a retaining ring 75 fitted in an annular groove on the inner peripheral surface of the rotor inner 52 c, and applies a predetermined pressing force (axial load) to the elastic member 73.

A female serration 522 extending in the axial direction is formed on the inner peripheral surface of the annular recess 521 provided in the rotor inner 52c, and the first friction plate 71 and the pressing plate 74 are fitted to the female serration 522. A male serration 6a extending in the axial direction is formed on the outer peripheral surface of the motor unit output shaft 6, and a second friction plate 72 is fitted to the male serration 6a. A frictional force is generated between the first friction plate 71 and the second friction plate 72 by the biasing force of the elastic member 73.

When the torque acting between the electric motor 29 and the motor unit output shaft 6 is less than the friction force acting between the

friction plates

71 and 72, the

friction plates

71 and 72 rotate together. Rotational power is transmitted to the motor unit output shaft 6 via both

friction plates

71 and 72. Thereby, the speed reducer 20 (details will be described later) connected to the motor unit output shaft 6 and the motion conversion mechanism B connected to the output side of the speed reducer 20 are driven. On the other hand, when the torque acting between the electric motor 29 and the motor unit output shaft 6 exceeds the friction force acting between the

friction plates

71 and 72, one friction plate slides with respect to the other friction plate. Torque transmission between the motor 29 and the motor unit output shaft 6 is interrupted. Thereby, relative rotation of the motor part output shaft 6 and the rotor inner 52c is permitted.

As shown in FIGS. 1 and 2, the motion conversion mechanism B has a screw shaft 93 that is formed with a spiral groove on the outer peripheral surface and is coaxial with the rotation center of the rotor 52 of the electric motor 29, and an inner peripheral surface. And a plurality of balls 94 disposed between the screw shaft 93 and the spiral groove of the nut 92, and the screw shaft 93 and the nut 92. It consists of a ball screw 91 provided with a top (not shown) as a circulating member disposed therebetween. An actuator head 100 as an operation unit C that operates an operation target (not shown) is provided at the end of one side in the axial direction of the screw shaft 93. The actuator head 100 is integrally provided at the end. Accordingly, the screw shaft 93 constitutes an output member of the electric actuator 1. The operation unit C (actuator head 100) can be provided separately from the screw shaft 93, and the one corresponding to the application is selected and used.

The nut 92 is connected to the output member (motor unit output shaft 6) of the electric motor unit A and is driven to rotate. Although details will be described later, in the present embodiment, since the rotational motion of the electric motor portion A is transmitted to the nut 92 via the speed reducer 20, the carrier 24 constituting the output member of the speed reducer 20 is provided on the nut 92. It is fixed by appropriate means such as press fitting.

The nut 92 is disposed at a position shifted to one side in the axial direction from the electric motor part A, and does not overlap with the rotor inner 52c of the electric motor part A and the motor part output shaft 6 in the radial direction. In this case, since the inner diameter dimension D1 of the rotor inner 52c and the inner diameter dimension D2 of the motor unit output shaft 6 can be made smaller than the outer diameter dimension D3 of the nut 92, a small electric motor 29 having a small radial dimension is used. be able to. Thereby, the electric motor part A and by extension the electric actuator 1 can be made compact in the radial direction.

As shown in FIGS. 1 and 4, a rotation prevention mechanism for the screw shaft 93 is provided on the inner periphery of the hollow motor portion output shaft 6. That is, the anti-rotation mechanism for the screw shaft 93 is provided in the axial range of the electric motor portion A. As a result, the electric actuator 1 can be made more compact in the axial direction than in the case where the rotation prevention mechanism for the screw shaft 93 is provided on the outer side in the axial direction of the electric motor portion A (for example, Patent Document 1).

The anti-rotation mechanism of the present embodiment is fixed to a first casing constituent member 81 constituting the casing 8 and has a cylindrical guide member 95 disposed on the inner diameter side of the motor unit output shaft 6 and a screw shaft 93. A pin 96 having a radially outer end projecting radially outward of the screw shaft 93, and a guide collar 97 rotatably fitted to the projecting portion of the pin 96. Formed in collaboration. The guide member 95 has a cylindrical portion 95 a disposed between the inner peripheral surface of the motor unit output shaft 6 and the outer peripheral surface of the screw shaft 93. A guide groove 95b extending in the axial direction is formed on the inner diameter surface of the cylindrical portion 95a, and a guide collar 97 is fitted into the guide groove 95b. With the above configuration, the screw shaft 93 can smoothly advance and retreat (linear motion) in the axial direction in a state in which the screw shaft 93 is prevented from rotating with respect to the housing 8.

As shown in FIGS. 1 and 2, the nut 92 is rotatably supported with respect to the housing 8 by a rolling bearing 9 having an inner ring fixed to the outer peripheral surface thereof. As the rolling bearing 9, a double row deep groove ball bearing that can support both a radial load and an axial load, in particular, a high load supporting ability is used. Further, if a double row deep groove ball bearing is used as the rolling bearing 9, the nut 92 can have a double-sided structure, so that the nut 92 is inclined with respect to the axial direction, and the rotational accuracy of the nut 92 is reduced. There is also an advantage that it can be prevented.

The outer ring of the rolling bearing 9 has an axial end surface on one side and the other end thereof on the shoulder surface 84c of the fourth casing component member 84 and an end surface 83a on the axial direction one side of the third casing component member 83, respectively. It is in contact. That is, the rolling bearing 9 is positioned in the axial direction by holding the outer ring between the third housing constituent member 83 and the fourth housing constituent member 84 from both axial sides. In this case, the rolling bearing 9 can be positioned and fixed as the casing 8 is assembled (the first to fourth casing constituent members 81 to 84 are combined and integrated using the bolt member 85). Assemblability is good. The inner ring of the rolling bearing 9 is sandwiched between a flange portion provided on the outer periphery of one end of the nut 92 in the axial direction and the carrier 24 of the speed reducer 20.

As shown in FIGS. 1 and 2, the electric actuator 1 according to the present embodiment transmits torque between the motor unit output shaft 6 of the electric motor unit A and the nut 92 constituting the motion conversion mechanism unit B (ball screw 91). It has the reduction gear 20 arrange | positioned on the path | route. In this case, since the high torque torque reduced by the speed reducer 20 is transmitted to the nut 92, the electric motor 29 can be reduced in size, and the electric actuator 1 can be reduced in weight and size through this. it can.

As shown in FIG. 6, the speed reducer 20 of the present embodiment is a traction drive type planetary speed reducer, and is arranged on the radially outer side of the sun roller 21, the plurality of planetary rollers 23, the carrier 24, and the planetary roller 23. And an annular traction applying member 22. In the present embodiment, the end of one side in the axial direction of the motor unit output shaft 6 is used as the sun roller 21, and the outer ring of the rolling bearing (for example, deep groove ball bearing) 25 is used as the planetary roller 23. The inner ring of each rolling bearing 25 is press-fitted and fixed to the hollow shaft 26.

FIG. 8 schematically shows an enlarged view of the vicinity of the outer diameter end portion of the speed reducer 20 in a state before the electric actuator 1 (housing 8) is assembled. As shown in FIG. 8, the traction imparting member 22 integrally includes a main body portion 22a having a U-shaped cross section and flange portions 22b provided on both axial sides of the main body portion 22a. In a state before the casing 8 is assembled (before the second casing constituent member 82 and the third casing constituent member 83 are combined and integrated), as shown by a solid line in FIG. A flange portion 22b on one axial side of the traction imparting member 22 arranged on the inner periphery of the body constituting member 82 protrudes from the end surface on the one axial side of the second casing constituting member 82 by a dimension t.

Between the flange portion 22b on the other side in the axial direction of the traction imparting member 22 and the housing 8 (second housing constituent member 82), an iron-based metal adjusting member 28 having an annular shape is disposed. The adjustment member 28 adjusts the protruding amount of the flange portion 22b on the one axial side of the traction imparting member 22 before the housing 8 is assembled.

Then, when the casing 8 is assembled (the first to fourth casing constituent members 81 to 84 are coupled and integrated using the bolt member 85), the traction imparting member 22 is connected to the third casing constituent member 83. The pressure surface 83b is pressurized on the other side in the axial direction and is compressed and deformed in the axial direction. Thus, when the traction imparting member 22 is compressed and deformed in the axial direction, the main body portion 22 is reduced in diameter so that the main body portion 22 of the traction imparting member 22 bulges inward in the radial direction (two-dot chain line in FIG. 8). (However, the degree of deformation is exaggerated in FIG. 8). Accordingly, traction (radial preload) is applied to the inside of the speed reducer 20, more specifically, to the contact portion between the traction applying member 22 and the planetary roller 23, and further to the contact portion between the planetary roller 23 and the sun roller 21. Is done.

The electric actuator 1 of the present embodiment having the above configuration operates in the following manner because the torque limiter 7 is disposed between the rotor 52 of the electric motor 29 and the motor unit output shaft 6. First, during normal times, the rotational power of the electric motor 29 is transmitted to the nut 92 of the ball screw 91 via the torque limiter 7, the motor unit output shaft 6, and the speed reducer 20, so that the nut 92 is the axis of the screw shaft 93. Rotate around. Then, depending on the rotation direction of the nut 92 (the rotation direction of the rotor 52 of the electric motor 29), the screw shaft 93 having the actuator head 100 moves forward in one axial direction or retreats in the other axial direction. Manipulate the target.

For example, when an axial impact load is applied to the electric actuator 1 while the screw shaft 93 (actuator head 100) is operating the operation target, a reverse input load is applied to the screw shaft 93. Since this reverse input load is transmitted to the nut 92 through the screw shaft 93 and the ball 94, the rolling bearing 9 that rotatably supports the nut 92 with respect to the housing 8 is provided on the other side in the axial direction. A thrust load to be pressurized is applied. This thrust load is received by the third casing constituent member 83 in which the end surface 83a on one side in the axial direction is in contact with the end surface on the other side in the axial direction of the rolling bearing 9 (outer ring). That is, in the present embodiment, the end surface 83a on the one axial side of the third housing component 83 constitutes the “load receiving surface” in the present invention.

Thus, in the electric actuator 1 of the present embodiment, the third casing component member 83 can receive the thrust load acting on the rolling bearing 9. Since the third casing constituent member 83 is formed of an iron-based metal material and has high strength and rigidity, when a large thrust load is input to the end surface 83a as a load receiving surface via the rolling bearing 9 However, the possibility that the third casing constituting member 83 itself is deformed or damaged is reduced as much as possible. In addition, since the third casing component member 83 is one member that configures the casing 8, the thrust load input to the end surface 83 a can be dispersed throughout the casing 8. Therefore, even when a large thrust load is applied to the rolling bearing 9, the positional accuracy of the rolling bearing 9 in the axial direction or the like is not likely to be distorted. Therefore, the rotational accuracy of the nut 92, and thus the screw shaft 93 (including the electric actuator 1). The operation accuracy of the output member is stably maintained.

Further, the third casing constituent member 83 is in contact with the traction applying member 22 in the axial direction in the axial direction. The traction imparting member 22 imparts traction to the inside of the speed reducer 20 composed of a traction drive type planetary speed reducer by being compressed in the axial direction and deformed in a reduced diameter. Since the third casing component member 83 is formed of an iron-based metal material, the third casing component member 83 is highly rigid and has a small amount of deformation accompanying a temperature change. For this reason, if the traction imparting member 22 in the axially compressed state is in contact with the third casing component member 83 in the axial direction, the axial compression allowance required for the traction imparting member 22, and thus The amount of reduced diameter deformation can be stably maintained. Therefore, predetermined traction can be stably given to the inside of the speed reducer 20, and the operation accuracy of the speed reducer 20 can be stably maintained.

Moreover, since the electric actuator 1 of this embodiment has the torque limiter 7 in the electric motor part A, the forward movement of the screw shaft 93 (actuator head 100) is restricted by colliding with an obstacle. Even in such a situation, the torque transmission path can be blocked by causing slippage between the rotor inner 52c and the motor unit output shaft 6. For this reason, it is possible to prevent an excessive load from acting on the speed reducer 20 and the ball screw 91 (motion conversion mechanism B), and to prevent them from being damaged.

As described above, the electric actuator 1 of the present embodiment is excellent in the operation accuracy of the screw shaft 93 and the speed reducer 20, and damage to the speed reducer 20 and the motion conversion mechanism B (ball screw 91) is as much as possible. It is highly reliable that can be prevented. Furthermore, the electric actuator 1 according to the present embodiment is light and compact, has excellent mountability with respect to the equipment used, has good assemblability, and can be manufactured at low cost.

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 electric actuator 1 described above, a traction drive type planetary speed reducer is adopted as the speed reducer 20, but the configuration of the speed reducer 20 is arbitrary, and other speed reducers (for example, planetary gear speed reducers) are used. It can also be adopted. Further, the reduction gear 20 is not an essential configuration, and the present invention can also be applied to the electric actuator 1 in which the reduction gear 20 is omitted.

Further, in the electric actuator 1 described above, only the third casing constituent member 83 among the first to fourth casing constituent members 81 to 84 configuring the casing 8 is formed of an iron-based metal material. However, if the weight of the housing 8 and the decrease in cooling efficiency are not a problem, the other housing components may be formed of an iron-based metal material.

Further, as the electric motor 29 of the electric motor portion A, an axial gap type may be adopted instead of the radial gap type as described above. Moreover, in the electric actuator 1 demonstrated above, although the motion conversion mechanism part B was comprised with the ball screw 91, this invention uses the slide screw from which the ball | bowl 94 and the circulation member were abbreviate | omitted for the motion conversion mechanism part B. It can be preferably applied to cases.

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 6 Motor part output shaft 7 Torque limiter 8 Case 9 Rolling bearing 20 Reduction gear 22 Traction provision member 29 Electric motor 52 Rotor 83 3rd housing | casing structural member (casing structural member made from a ferrous metal)
83a End surface (load receiving surface)
91 Ball screw 92 Nut 93 Screw shaft 100 Actuator head A Electric motor part B Motion conversion mechanism part C Operation part D Terminal part

Claims

An electric motor unit, a motion conversion mechanism unit that converts the rotational motion of the electric motor unit into a linear motion, and a plurality of casing constituent members coupled in the axial direction, and the electric motor unit and the motion conversion mechanism unit A housing that accommodates the motion conversion mechanism, the screw shaft disposed coaxially with the rotation center of the rotor of the electric motor unit, and the outer periphery of the screw shaft, and through the rolling bearing An electric actuator having a nut rotatably supported with respect to the housing, wherein the screw shaft moves forward and backward in the axial direction as the nut rotates,
At least one of the plurality of casing constituent members is formed of an iron-based metal material, and the casing constituent member made of iron-based metal abuts on the rolling bearing in the axial direction and acts on the rolling bearing. An electric actuator having a load receiving surface for receiving a thrust load.
The electric actuator according to claim 1, wherein the iron-based metal casing constituent member is a cast iron product or a forged product.
3. The electric actuator according to claim 1 or 2, wherein, among the plurality of casing constituent members, the remaining casing constituent members excluding the ferrous metal casing constituent members are formed of an aluminum alloy.
A traction drive planetary speed reducer that decelerates the rotation of the rotor and transmits it to the nut;
An annular traction imparting member that imparts traction to the inside of the planetary reducer by being compressed in the axial direction and contracting in diameter is compressed with the iron-based metal casing constituent member and the shaft in a compressed state in the axial direction. The electric actuator according to any one of claims 1 to 3, wherein the electric actuator is in contact in a direction.
The electric actuator according to any one of claims 1 to 4, wherein the nut is disposed at a position shifted outward in the axial direction of the electric motor unit.
The electric motor unit is disposed on the inner diameter side of the rotor, and outputs between a motor unit output shaft that outputs rotation of the rotor, and an inner peripheral surface of the rotor and an outer peripheral surface of the motor unit output shaft facing each other. The electric actuator according to any one of claims 1 to 5, further comprising a torque limiter disposed.