WO2019059298A1

WO2019059298A1 - Electric actuator

Info

Publication number: WO2019059298A1
Application number: PCT/JP2018/034872
Authority: WO
Inventors: 慎太朗石川; 阿部　克史; 雄太中辻
Original assignee: Ntn株式会社
Priority date: 2017-09-22
Filing date: 2018-09-20
Publication date: 2019-03-28
Also published as: JP2019056459A

Abstract

An electric actuator 1 is provided with: an electric motor unit 4; a stationary member 6; a speed reducer 5 which transmits the rotation of the electric motor unit; an input rotating body 2 into which a driving force is input from outside; and an output rotating body 3 which is coupled to the speed reducer 5 and is capable of rotating relative to the input rotating body 2. The speed reducer 5 is provided with an internal gear 16 which performs an eccentric rotating motion relative to a center O of the output rotating body 3, and a support member 15 which is driven in rotation by the electric motor unit 4 and supports the internal gear 16. The support member 15 is supported by a pair of rolling bearings 17, 18, and a preload is applied to the pair of rolling bearings 17, 18.

Description

Electric actuator

The present invention relates to an electric actuator.

As an electric actuator capable of changing the rotational phase difference between the input side to which the driving force is input from the outside and the output side to which the input driving force is output, for example, an intake valve and an exhaust valve of an automobile engine It is known to be used in a variable valve timing device that changes the open / close timing of one or both of the valves.

Generally, this type of electric actuator includes an electric motor unit and a reduction gear that obtains driving force from the electric motor unit and decelerates and transmits rotational power (see Patent Document 1). When the reduction gear is not driven by the electric motor unit, when the member on the input side (for example, the sprocket) and the member on the output side (for example, the camshaft) rotate synchronously, and the reduction gear is driven by the electric motor unit The rotational phase difference of the member on the output side with respect to the member on the input side is changed by the reduction gear, whereby the opening / closing timing of the valve is adjusted.

JP 2014-152766 A

In the above-described electric actuator, since the eccentric rotating body which performs eccentric rotational movement is disposed in the reduction gear, a unbalanced load acts on various places inside the reduction gear due to the rotational movement of the eccentric rotation body. If the supporting rigidity for each component of the reduction gear is insufficient, this offset load causes each component to run out, resulting in increased friction, biting, malfunction such as vibration or noise, etc. It became clear that there was a fear.

Therefore, an object of the present invention is to increase the support rigidity of the components of the reduction gear in an electric actuator provided with a reduction gear having an eccentric rotation body.

As technical means for achieving the above-mentioned object, the present invention relates to an electric motor portion, a stationary member, a reduction gear transmitting rotation of the electric motor portion, and an input rotating body to which a driving force is inputted from the outside And an output rotary body coupled to the reduction gear and capable of relative rotation with respect to the input rotary body, wherein the reduction gear performs eccentric rotational movement with respect to the center of the output rotary body An eccentric rotating body, and a supporting member rotationally driven by the electric motor portion to support the eccentric rotating body are supported, the supporting member is supported by a pair of rolling bearings, and a preload is applied to each of the pair of rolling bearings It is characterized by As the reduction gear here, for example, a mechanism that changes the rotational phase difference of the output rotary body with respect to the input rotary body can be used by rotation of the support member.

As described above, by supporting the support member for supporting the eccentric rotary body by the pair of rolling bearings and applying a preload to each of the pair of rolling bearings, the support rigidity with respect to the support member is enhanced. Thus, the posture of the eccentric rotary body supported by the support member can be stabilized, and the swinging of the components of the reduction gear can be prevented. Therefore, it is possible to prevent an increase in friction due to the swinging, and occurrence of biting, vibration, noise and the like.

Each of the pair of rolling bearings has a first raceway surface and a second raceway surface. By providing each first raceway surface of the rolling bearing on the support member, it is possible to omit one bearing ring in each rolling bearing, so that the electric actuator can be made compact.

Further, by providing the second raceway surface of one of the rolling bearings of the pair of rolling bearings on the stationary member and providing the second raceway surface of the other rolling bearing on the input rotating body, the other race ring in each rolling bearing As a result, the motorized actuator can be made more compact.

The use of angular contact ball bearings as the pair of rolling bearings facilitates application of preload to the rolling bearings. It is preferable to use a nut as a preload applying member for applying a preload to the pair of rolling bearings. By adjusting the amount of tightening of the nut, it is possible to adjust the amount of preload, thus facilitating preload control.

By making the size of the rolling elements PCD of the pair of rolling bearings different from each other, the bearing span between the rolling bearings is expanded, so that the support rigidity to the support member can be further enhanced.

A support member and an eccentric rotating body are disposed on an inner diameter side of a motor core including a stator and a rotor of the electric motor unit. In addition, an input rotating body is disposed on the inner diameter side of the electric motor portion, with the output shaft rotating integrally with the output rotating body, and on the outer diameter side of the output shaft coaxially with the output shaft and permitting relative rotation with respect to the output shaft Place. With this configuration, the electric actuator can be made compact.

The electric actuator described above can be applied to a continuously variable valve timing device that changes the opening / closing timing of the valve by changing the rotational phase difference of the camshaft with respect to the sprocket. In this case, the input rotary body can be provided with a sprocket, and the output shaft can be used as a camshaft.

According to the present invention, in the electric actuator provided with the reduction gear having the eccentric rotation body, it is possible to increase the support rigidity for the components of the reduction gear. Therefore, the operation of the electric actuator can be stabilized.

It is a longitudinal cross-sectional view of the electrically-driven actuator which concerns on one Embodiment of this invention. It is an exploded perspective view of an electric actuator concerning this embodiment. FIG. 2 is a cross-sectional view taken along line AA in FIG. FIG. 2 is a cross-sectional view taken along line B-B in FIG. It is a graph which shows the relationship between a motor rotational speed, a sprocket (input rotary body) rotational speed, and an output rotational phase angle difference. It is a longitudinal cross-sectional view of the electrically-driven actuator as a comparative example. It is a longitudinal cross-sectional view of the electrically-driven actuator which concerns on other embodiment of this invention. FIG. 8 is a cross-sectional view taken along the line CC in FIG. 7; FIG. 8 is a cross-sectional view taken along line DD in FIG. 7;

Hereinafter, the present invention will be described based on the attached drawings. In each drawing for explaining the present invention, components such as members or components having the same function or shape are denoted by the same reference numerals as long as discrimination is possible, and then the explanation thereof will be described. I omit it.

FIG. 1 is a longitudinal sectional view of an electric actuator according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of the electric actuator according to the present embodiment.

As shown in FIGS. 1 and 2, the electric actuator 1 according to the present embodiment includes an input rotary body 2, an output rotary body 3, an electric motor unit 4, a reduction gear 5, and a casing 6 for housing these. The main component is

The input rotating body 2 is a member that is rotationally driven by a driving force from an external driving source (not shown). The output rotary body 3 is a member for outputting the driving force input to the input rotary body 2 to the outside, and a shaft 7 as an output shaft is disposed on the inner periphery thereof. The input rotary body 2 is disposed on one side in the axial direction of the electric actuator 1 and on the outer diameter side of the shaft 7 with a gap from the outer peripheral surface of the shaft 7. The output rotary body 3 is disposed on the other side of the electric actuator 1 in the axial direction. The output rotating body 3 is coupled to the shaft 7 so as to be capable of transmitting torque, and in the present embodiment, the output rotating body 3 and the shaft 7 are connected to be capable of transmitting torque via the serrations 8. From this configuration, the output rotating body 3 is disposed coaxially with the input rotating body 2 and is relatively rotatable with respect to the input rotating body 2 (the rotation axes of the input rotating body 2 and the output rotating body 3 Indicated).

The input rotary body 2 is formed in a cylindrical shape that opens at both end portions in the axial direction, and a large diameter large diameter portion 2b having a small diameter portion 2a and an outer diameter dimension larger than the outer diameter dimension of the small diameter portion 2a. And an intermediate diameter portion 2c located between the small diameter portion 2a and the large diameter portion 2b and having an outer diameter size larger than the outer diameter size of the small diameter portion 2a and smaller than the outer diameter size of the large diameter portion 2b Prepare.

The slide bearing 9 is disposed on the inner periphery of the small diameter portion 2a, and the rolling bearing 10 is disposed on the inner periphery of the large diameter portion 2b. When the shaft 7 is inserted into the inner periphery of the input rotor 2 and connected to the output rotor 3, a slide bearing disposed between the inner peripheral surface of the input rotor 2 and the outer peripheral surface of the shaft 7 The shaft 7 is rotatably supported relative to the inner peripheral surface of the input rotary body 2 by 9 and the rolling bearing 10. Thereby, relative rotation between input rotary body 2 and output rotary body 3 and shaft 7 is allowed, and radial runout of shaft 7 is reduced to reduce power transmission efficiency associated with radial runout of shaft 7 Can be controlled. When the slide bearing 9 is an oil-impregnated bearing and the rolling bearing 10 is a deep groove ball bearing, the reduction in power transmission efficiency can be more effectively suppressed.

As shown in FIG. 2, the casing 6 is divided into a bottomed cylindrical casing main body 6a and a lid 6b for the convenience of assembly. The casing body 6a and the lid 6b are integrated using fastening means such as bolts. The lid 6 b has a tubular shape for drawing out to the outside a feed line for supplying power to the electric motor unit 4 and a signal line connected to a rotation number detection sensor (not shown) for detecting the rotation number of the electric motor unit 4. The projections 6c and 6d are provided. As shown in FIG. 1, a deep groove ball bearing 22 as a bearing is disposed between the cover 6 b of the casing 6 and the output rotary body 3, and the output rotary body 3 is opposed to the casing 6 by the bearing 22. Is rotatably supported.

As shown in FIG. 1, the electric motor unit 4 is a radial gap type motor having a stator 11 fixed to a casing main body 6 a and a rotor 12 disposed to face the inner side in the radial direction of the stator 11 with a gap. It is. The stator 11 is composed of a stator core 11a made of a plurality of electromagnetic steel plates stacked in the axial direction, a bobbin 11b made of an insulating material mounted on the stator core 11a, and a stator coil 11c wound around the bobbin 11b. The rotor 12 is configured of an annular rotor core (rotor inner) 12 a and a plurality of magnets 12 b attached to the rotor core 12 a.

The reduction gear 5 has a first external tooth portion 13 formed of a plurality of curved teeth (projections) provided on the outer peripheral surface of the input rotary body 2 and a plurality of curved shapes provided on the outer peripheral surface of the output rotary body 3. A so-called second external tooth portion 14 composed of the following teeth (protrusion), a cylindrical support member 15 that rotates integrally with the rotor 12, and an annular internal gear 16 disposed on the inner periphery of the support member 15. It is a cycloid reducer.

The support member 15 integrally includes a small diameter cylindrical portion 15a fixed to the inner periphery of the rotor core 12a, and a large diameter cylindrical portion 15b which is larger in diameter than the small diameter cylindrical portion 15a and protrudes axially from the rotor core 12a. In the central region in the axial direction of the inner peripheral surface of the support member 15, a cylindrical surface-shaped eccentric inner peripheral surface 15a1 eccentric to the respective rotational axes O of the input rotating body 2 and the output rotating body 3 is formed. Of the inner peripheral surface of the support member 15, the region other than the eccentric inner peripheral surface 15 a 1 is formed coaxially with the rotation axis O of the input rotating body 2 and the output rotating body 3. Further, the outer peripheral surface of the support member 15 is a cylindrical surface formed coaxially with the rotation axis O of the input rotating body 2 and the output rotating body 3. Accordingly, the support member 15 has a thick portion and a thin portion when viewed in a radial cross section passing through the eccentric inner circumferential surface 15a1 (see FIGS. 3 and 4).

The support member 15 is supported by a pair of rolling

bearings

17 and 18 arranged to sandwich the internal gear 16 from both sides in the axial direction. Specifically, one rolling bearing 17 is disposed between the inner periphery of the support member 15 (in the present embodiment, the large diameter cylindrical portion 15b) and the outer periphery of the casing 6, and the rolling bearing 17 makes the support member 15 a casing. 6 is rotatably supported. Further, the other rolling bearing 18 is disposed between the inner periphery of the support member 15 (in the present embodiment, the small diameter cylindrical portion 15a) and the outer periphery of the input rotating body 2 (in the present embodiment, the intermediate diameter portion 2c) The support member 15 is rotatably supported by the input rotary body 2 by the rolling bearing 18.

The internal gear 16 has a first internal gear 19 and a second internal gear 20 on its inner periphery. The first internal tooth portion 19 and the second internal tooth portion 20 are each formed of a plurality of curved (trocolloid-based curved) teeth (protrusions) provided on the inner peripheral surface of the internal gear 16. The first internal teeth 19 are provided on the input rotary body 2 side in the axial direction, and the second internal teeth 20 are provided on the output rotary body 3 side in the axial direction. In addition, the first internal tooth portion 19 radially faces the first external tooth portion 13 provided on the input rotary body 2, and the second internal tooth portion 20 is provided on the second outer side provided on the output rotary body 3. It faces the tooth portion 14 in the radial direction. The number of teeth of the first internal teeth 19 is larger than the number of teeth of the first external teeth 13, and the number of teeth of the second internal teeth 20 is larger than the number of teeth of the second external teeth 14. Further, the numbers of teeth of the first external teeth 13 and the second external teeth 14 are different, and the numbers of teeth of the first internal teeth 19 and the second internal teeth 20 are also different. In this embodiment, the number of teeth of the first internal tooth portion 19 is set to 24 and the number of teeth of the first external tooth portion 13 is increased by one, and the number of teeth of the second internal tooth portion 20 is set to 20. The number of teeth is one greater than the number of teeth (19) of the second outer teeth portion 14.

The internal gear 16 is rotatably supported on the support member 15 by a needle roller bearing 21 as a bearing member disposed between the outer peripheral surface thereof and the eccentric inner peripheral surface 15a1 of the support member 15. There is. Further, the internal gear 16 is disposed on the inner periphery of the small diameter cylindrical portion 15 a of the support member 15 via the needle roller bearing 21 so that the rotation shaft O of the input rotating body 2 and the output rotating body 3 is It is arranged eccentrically.

FIG. 3 is a cross-sectional view (a cross-sectional view taken along line AA in FIG. 1) cut at a point where the first internal teeth 19 and the first external teeth 13 face each other, and FIG. 20 is a cross-sectional view (a cross-sectional view taken along the line BB in FIG. 1) cut at a location where the second external gear portion 20 and the second external gear portion 14 face each other.

As described above, since the internal gear 16 is disposed eccentrically with respect to the rotation axis O of the input rotary body 2 and the output rotary body 3, as shown in FIG. 3, the central axis P1 of the first internal gear 19 is Also, the distance E is decentered in the radial direction with respect to the rotation axis O of the first external gear portion 13. Thereby, the first internal tooth portion 19 and the first external tooth portion 13 are engaged with each other in a part in the circumferential direction (right side in FIG. 3) and are engaged with each other, and a point on the opposite side in the radial direction They are not in engagement with each other apart from each other (on the left side of FIG. 3). Further, as shown in FIG. 4, the central axis P2 of the second internal gear 20 is also eccentric by a distance E in the radial direction with respect to the rotation axis O of the second external gear 14. As a result, the second internal tooth portion 20 and the second external tooth portion 14 engage with each other in a part in the circumferential direction (left side in FIG. 4) in close proximity to each other, and a point on the opposite side in the radial direction They are separated from each other and do not engage with each other (right side in FIG. 4). In FIGS. 3 and 4, since the directions of arrows are different from each other, the eccentric directions of the first internal gear 19 and the second internal gear 20 are shown in opposite directions in the respective drawings. However, the first internal teeth 19 and the second internal teeth 20 are eccentric by the same distance in the same direction.

Subsequently, the operation of the electric actuator according to the present embodiment will be described with reference to FIGS. 1 to 4.

In the state where the electric motor unit 4 is not energized and the driving force is not supplied from the electric motor unit 4 to the reduction gear 5, when the input rotating body 2 is rotationally driven by the external driving force, the rotation of the input rotating body 2 is an internal gear. By being transmitted to the output rotary body 3 via 16, the output rotary body 3 rotates in synchronization with the input rotary body 2. That is, the teeth (the first external teeth 13 and the first internal teeth 19, the second external teeth 14 and the teeth provided with the input rotor 2 and the internal gear 16, the internal gear 16 and the output rotor 3) Since the second internal teeth 20) circumferentially engage with each other in a partial region in the circumferential direction, when the input rotary body 2 rotates, the input rotary body is maintained while maintaining the engagement relationship thereof 2 and the internal gear 16 and the output rotating body 3 rotate synchronously. That is, the input rotary body 2 and the output rotary body 3 rotate at the same rotational phase (rotational phase difference is zero).

On the other hand, when the electric motor unit 4 is energized and the driving force is supplied from the electric motor unit 4 to the reduction gear 5, the rotor 12 and further the support member 15 coupled to the rotor core 12 b of the rotor 12 It rotates integrally about the rotation axis O. The internal gear 16 performs eccentric rotational movement with respect to the input rotating body 2 and the output rotating body 3 under the pressing force of the rotation of the support member 15 having the thin portion and the thick portion. That is, while the internal gear 16 revolves around the rotation axis O of the input rotary body 2 and the output rotary body 3, the internal gear 16 rotates on center axes P1 and P2 of the first internal gear 19 and the second internal gear 20. Do. Each time the support member 15 makes one rotation (revolution), the internal gear 16 is rotationally driven by the engagement portions of the first internal teeth 19 and the first external teeth 13 being shifted in the circumferential direction by one tooth. The input rotary body 2 is decelerated and rotated (rotation).

Further, due to the eccentric rotational movement of the internal gear 16, in the relationship between the internal gear 16 and the output rotary body 3, the second internal gear 20 and the second external gear 20 each time the support member 15 makes one revolution (revolution). The engagement position with 14 is shifted in the circumferential direction by one tooth. Thus, the output rotating body 3 is rotated relative to the internal gear 16. As described above, the rotational torque from the electric motor unit 4 is transmitted to the internal gear 16 while being decelerated, and thus the torque from the electric motor unit 4 is superimposed on the torque from the input rotary body 2. It is possible to change the rotational phase difference of the output rotary body 3 with respect to 2 in the forward and reverse directions (differential).

Here, assuming that the reduction ratio of the reduction gear 5 is i, the motor rotational speed is n _m , and the rotational speed of the sprocket (input rotating body 2) is n _S , the output rotational phase angle difference is (n _m −n _S ) / i (See FIG. 5).

Further, assuming that the number of teeth of the first internal gear 19 is z1 and the number of teeth of the second internal gear 20 is z2, the reduction gear ratio by the reduction gear according to the present embodiment can be obtained by the following equation 1.

Reduction ratio = z1 × z2 / | z1-z2 | .. Formula 1

For example, when the number of teeth (z1) of the first internal teeth 19 is 24, and the number of teeth (z2) of the second internal teeth 20 is 20, the reduction ratio is 120 from the above equation (1). As described above, in the reduction gear 5 according to the present embodiment, it is possible to obtain high torque by a large reduction ratio.

As shown in FIG. 1, the support member 15 of the reduction gear 5, which is a member to which the driving force is input from the electric motor unit 4, is disposed on the outer diameter side, and the output rotating body 3 is disposed on the inner diameter side. However, it is also possible to reverse these positional relationships between the outer diameter side and the inner diameter side. However, when the driving force from the electric motor unit is input on the inner diameter side of the reduction gear and output on the outer diameter side, a motor output shaft is provided on the inner diameter side of the electric motor unit. On the other hand, since members serving as the input shaft of the reduction gear must be connected, the reduction gear is disposed in series in the axial direction of the electric motor portion, and the axial dimension of the entire electric actuator is increased.

In the electric actuator according to the present embodiment, as shown in FIG. 1, the support member 15 of the reduction gear 5 to which the driving force is input from the electric motor unit 4 is disposed on the outer diameter side, and on the inner diameter side of the support member 15. By arranging a part or all of the output rotating body 3, the driving force from the electric motor unit 4 is input on the outer diameter side of the reduction gear 5 and output on the inner diameter side. As a result, each component of the decelerator 5 such as the support member 15 and the output rotating body 3 can be disposed on the inner diameter side of the motor core including the stator 11 and the rotor 12. As a result, since the reduction gear 5 does not have to be arranged in series in the axial direction with respect to the electric motor unit 4, the axial size of the electric actuator can be reduced. As shown in FIG. 1, on the inner diameter side of the motor core (the stator 11 and the rotor 12), the support member 15, the first external gear 13, the second external gear 14, and the internal gear 16 are components of the reduction gear 5. And by arranging the needle roller bearing 21, the axial miniaturization of the electric actuator is realized. In addition, the part of the reduction gear arrange | positioned at the internal-diameter side of a motor core may not be the case where it is all the reduction gears, but may be the one part.

By the way, in the electric actuator according to the present embodiment, since the internal gear 16 is an eccentric rotating body that performs the above-described eccentric rotational movement, the weight balance of the rotating internal gear 16 becomes uneven. Further, the meshing positions of the

internal teeth

19 and 20 and the

external teeth

13 and 14 change in the circumferential direction every moment. From the above factors, the internal gear 16 which is an eccentric rotating body, and further, the needle roller bearing 21 receives a biased load and tries to swing. It becomes clear that this swinging becomes particularly remarkable when only one axial side of the support member 15 is supported by the bearing 17 as in the electric actuator 1 ′ shown as a comparative example in FIG. The The reasons are described below.

In the electric actuator 1 of the present embodiment, it is difficult in space to directly support the internal gear 16 performing eccentric rotational movement by bearings, so the internal gear 16 is indirectly connected by the support member 15 via the needle roller bearing 21. Are supported. However, as in the case of the electric actuator 1 'of the comparative example, when only one axial side of the support member 15 is supported by the bearing 17, the support member 15 is in a cantilevered state, so that the unbalanced load from the internal gear 16 is supported. It can not be stably supported by the member 15. Therefore, a whirling of the internal gear 16 is generated, which propagates to peripheral members of the internal gear 16 (the support member 15, the output rotary body 3, etc.), causing an increase in friction, biting, or generation of vibration or noise. There is a fear. In addition, there is a possibility that the shaft 7 may be misaligned.

In the comparative example of FIG. 6, it is also conceivable to support the other axial side (right side in FIG. 6) of the support member 15 with the advantageous slide bearing in the space surface. Therefore, relative relative movement between the support member 15 and the input rotary body 2 is permitted. Therefore, the effect of restricting the swinging of the internal gear 16, the support member 1, the output rotary body 3 and the like becomes insufficient.

In view of the above problems, in the present embodiment, as shown in FIG. 1, the support member 14 is supported by a pair of rolling

bearings

17 and 18 disposed on both sides in the axial direction sandwiching the internal gear 16 and the rolling

bearing

17 , 18 are preloaded. From such a configuration, since the support rigidity against the unbalanced load is increased, the swinging of the support member 15 itself is suppressed. Further, since the postures of the internal gear 16 as the eccentric rotating body and the needle roller bearing 21 are restrained by the support member 15, it is possible to prevent their swinging, and also the swinging of the output rotating body 3. It can be prevented. Thus, since the support rigidity for each component of the reduction gear 5 is improved, problems such as increase in friction, biting, vibration / noise, misalignment of the shaft 7 and the like can be avoided. It can be stabilized.

As a preload applying member for applying a preload to the rolling

bearings

17 and 18, it is preferable to use a nut 25 as shown in FIG. 1 in consideration of the ease of control of the preload amount. Specifically, a male screw 7a is provided at the axial end of the shaft 7, and a nut 25 is screwed into the male screw 7a. The bearing surface of the nut 25 is brought into contact with the end face of the output rotary body 3. By tightening the nut 25, the tightening force from the shoulder 7 b of the shaft 7 is the deep groove ball bearing 10 on the input rotary body 2 side, the input rotary body 2, the rolling bearing 18 on the input rotary body 2 side, the support member 15, It propagates to the rolling bearing 17 on the side of the output rotary body 3 and the casing 6 which is a stationary member, and a preload is applied to each of the rolling

bearings

17 and 18. When applying a preload, it is preferable to elastically deform the rolling elements (balls) of the rolling

bearings

17 and 18 so as to make both the axial bearing gap and the radial axial gap negative. In the case where accurate preload amount management is not so important, etc., a snap ring is mounted on the outer peripheral surface of the shaft 7 and this snap ring is brought into contact with the end face of the output rotary body 3 to preload the rolling

bearings

17 and 18. May be given.

It is preferable to use an angular ball bearing having a contact angle (indicated by an alternate long and short dash line in FIG. 1) as the rolling

bearings

17 and 18 for supporting the support member 15 so that the preload can be reliably applied. At this time, the

angular ball bearings

17 and 18 are arranged in a back face arrangement in which the back faces of the outer rings are opposed to each other. In addition, between the input rotary body 2 and the slide bearing 9, between the output rotary body 3 and the slide bearing 9, between the output rotary body 2 and the support member 15, and between the support member 15 and the casing 6 so that preload can be applied. Etc., respectively, provide an axial gap. Further, axial gaps are provided on both axial sides of the internal gear 16 so that axial movement thereof is permitted.

In order to make the electric actuator 1 compact, it is necessary to make the input rotary body 2 and the support member 15 face in the axial direction and in the radial direction, and to make them as close as possible to each other in both directions. A similar relationship is also sought between the support member 15 and the casing 6. In order to respond to such a demand, in the present embodiment, as shown in FIG. 1, the races normally used for rolling bearings are omitted, and the outer raceway surfaces of the rolling

bearings

17 and 18 supporting the support member 15 (first The raceway surfaces 17a and 18a are formed directly on the inner peripheral surface of the support member 15, and the inner raceway surfaces 17b and 18b (second raceway surface) are formed on the outer peripheral surface of the casing 6 and the input rotary body 2 (middle diameter portion 2c). It is directly formed on the outer peripheral surface. From this configuration, the electric actuator 1 can be miniaturized.

When the casing 6 is a resin molded product, at least the inner raceway surface 17b of the rolling bearing 17 on the output rotating body 3 side is formed of a metal material such as steel, and the rolling fatigue life and the like at the inner raceway surface 17b is secured. It is preferable to do. In this case, the metal material portion including the inner raceway surface 17b is fixed to the resin casing 6 by means such as insert molding. Of course, the entire casing 6 may be formed of a metal material.

As shown in FIG. 1, it is preferable that the balls PCD (D1, D2: rolling elements PCD) of the rolling

bearings

17, 18 supporting the support member 15 have different sizes. As a result, the bearing span between the rolling

bearings

17 and 18 supporting the support member 15 is substantially expanded, so that the support rigidity to the support member 15 can be enhanced. In particular, by making the ball PCD (D2) of the rolling bearing 17 on the output rotating body 3 side larger than the ball PCD (D1) of the rolling bearing on the input rotating body 2 side, the inner diameter side of the rolling bearing 17 on the output rotating body 3 side Can be used as a housing space for the support member 15 and the bearing 22. Therefore, the size of the electric actuator 1 can be further reduced.

Next, the operation when the electric actuator according to the present invention is applied to a variable valve timing device will be described.

When used as a variable valve timing device, in the electric actuator 1, as shown by a two-dot chain line in FIG. 1, a sprocket 23 to which the driving force is transmitted from the engine is integrally provided to the input rotating body 2 (see FIG. 2) . Further, the shaft 7 is used as a camshaft for driving at least one of an intake valve and an exhaust valve of the engine. Other than that, the configuration is substantially the same as that of the electric actuator according to the above embodiment.

In the electric actuator 1, when the engine is started and the driving force is transmitted from the crankshaft to the sprocket 23 through the timing chain, the camshaft 7 rotates in synchronization with the sprocket 23. That is, in this case, the reduction gear 5 is not driven by the electric motor unit 4, and the input rotating body 2 and the internal gear 16, and the internal gear 16 and the output rotating body 3 rotate while maintaining mutual engagement. The camshaft 7 rotates in synchronization with the sprocket 23.

Thereafter, when the engine shifts to a low rotation range such as idle operation and the camshaft 7 drives the intake valve of the engine, the rotor 12 of the electric motor unit 4 is sprocket 22 by known means, for example, electronic control. Relatively slower or faster than the rotation speed of.

As a result of this relative rotation, the output rotor 3 is decelerated and rotated with respect to the input rotor 2 by the operation of the above-described reduction gear 5, and the rotational phase difference of the camshaft 7 with respect to the sprocket 22 is changed. As a result, the rotation of the engine during idle operation can be stabilized and fuel consumption can be improved. Further, when the operation of the engine shifts from the idle state to the normal operation, for example, at the time of high rotation, the speed difference of the relative rotation of the electric motor portion 4 with respect to the sprocket 23 is increased. The rotational phase difference can be changed to a rotational phase difference suitable for high rotation, and it is possible to achieve high output of the engine.

As described above, by applying the electric actuator according to the present invention to the variable valve timing device, it is possible to change the opening / closing timing of the valve by changing the rotational phase difference of the camshaft with respect to the sprocket according to the operating condition of the engine. It is. Moreover, by adopting the electric actuator according to the present invention, it is possible to provide a variable valve timing device which is compact and excellent in mountability. The electric actuator according to the present invention is not limited to the variable valve timing device, and is required to switch between the synchronous rotation on the input side and the output side and the rotation having a rotational phase difference on the input side and the output side. The present invention is also applicable to other devices (for example, a power steering system).

The configuration of the present invention described above can be widely applied to an electric actuator including an eccentric rotating body that performs eccentric rotational movement with respect to the center O of the output rotating body 3 as the reduction gear 5. Based on FIGS. 7 to 9, an electric actuator provided with another speed reducer 5 having such an eccentric rotating body will be described. 7 is a longitudinal sectional view of the electric actuator, FIG. 8 is a sectional view taken along the line CC in FIG. 7, and FIG. 9 is a sectional view taken along the line DD in FIG. In FIG. 7, the electric motor unit 4 disposed on the outer diameter side of the support member 15 is not shown.

The electric actuator according to the present embodiment differs from the electric actuator according to the above embodiment in the configuration of the reduction gear. The other configuration is basically the same.

As shown in FIGS. 8 and 9, the reduction gear 5 has a plurality of first outer teeth 31 provided with a plurality of teeth (projections) on the outer peripheral surface of the input rotating body 2 and a plurality of outer peripheral surfaces of the output rotating body 3. Second external teeth 32 provided with the teeth (protrusions), a cylindrical support member 15 that rotates integrally with the rotor 12, and a needle roller bearing 21 as a bearing member on the inner periphery of the support member 15 And the plurality of first rollers 34 disposed between the inner peripheral surface of the cylindrical member 33 and the first external teeth 31, the inner peripheral surface of the cylindrical member 33 and the second external teeth A plurality of second rollers 35 disposed between the portion 32 and a holder 36 rotatably holding the first roller 34 and the second roller 35.

The first external teeth 31 and the second external teeth 32 have a plurality of teeth arranged at equal intervals in the circumferential direction, and curved tooth gaps are formed between the teeth. The number of teeth of the first external teeth 31 and the number of teeth of the second external teeth 32 are set to different numbers.

The cage 36 is rotatably disposed between the cylindrical member 33 and the first external gear 31 and between the cylindrical member 33 and the second external gear 32, and formed in two rows in the axial direction. The first roller 34 is accommodated in one of them, and the second roller 35 is accommodated one by one in the other. Also, each

roller

34, 35 is held movably in the radial direction in the pocket.

The

rollers

34 and 35 are disposed rollably on the smooth inner surface of the cylindrical member 33. Here, the cylindrical member 33 is disposed via the needle roller bearing 21 on the inner peripheral surface of the support member 15 (small diameter cylindrical portion 15a) which is eccentric with respect to the central axes of the input rotating body 2 and the output rotating body 3 Because of this, the inner circumferential surface of the cylindrical member 33 is also disposed eccentrically with respect to the central axes of the input rotating body 2 and the output rotating body 3. Therefore, as shown in FIGS. 8 and 9, the centers Q1 and Q2 of the circles passing through the central axes of the

rollers

34 and 35 aligned on the inner peripheral surface of the cylindrical member 33 are also each of the input rotating body 2 and the output rotating body 3 A distance F is offset in the radial direction with respect to the central axis O. For this reason, the first roller 34 and the second roller 35 have external teeth (the first external teeth 31 or the second external teeth 31 or 32) facing each other at a part (upper side in FIGS. 8 and 9) in the circumferential direction of each track. It is disposed at a position (into the tooth groove) in close engagement with the tooth groove of the external tooth portion 32), and is opposed at the opposite point (the lower side of FIGS. 8 and 9) It is arrange | positioned in the position which is separated and engaged with the tooth space of the external tooth part which does

In the state where the electric motor unit 4 is not energized and the driving force is not supplied from the electric motor unit 4 to the reduction gear 5, when the input rotating body 2 is rotationally driven by the external driving force, the rotation of the input rotating body 2 is first By being transmitted to the output rotary body 3 via the roller 34, the holder 36, and the second roller 35, the output rotary body 3 rotates in synchronization with the input rotary body 2. That is, the first external teeth 31 and the first roller 34 provided on the input rotary body 2 and the second external teeth 32 and the second roller 35 provided on the output rotary body 3 are parts of the circumferential direction. Since the first roller 34 and the second roller 35 are held by the retainer 36, they are engaged with each other at the point, so that when the input rotary body 2 rotates, the input rotary body 2 is maintained while maintaining the engagement relationship. The first roller 34, the second roller 35, the holder 36, and the output rotor 3 rotate in synchronization.

On the other hand, when the electric motor (not shown) disposed on the outer diameter side of the support member 15 is energized, the support member 15 rotates integrally with the roller of the electric motor by the driving force of the electric motor. . Along with this, the first roller 34 and the second roller 35 reciprocate in the radial direction with respect to the input rotating body 2 and the output rotating body 3. At this time, the first roller 34 rotates along the tooth groove of the first external gear 31 of the input rotary body 2 and moves to the next tooth groove while moving the support member 15 every rotation. 36 move in the circumferential direction by one tooth of the first external gear 31. As a result, the holder 36 is decelerated and rotated with respect to the input rotary body 2 that is rotationally driven.

In addition, when the holder 36 rotates, the second roller 35 held by the holder 36 also rotates. At the same time, since the second roller 35 reciprocates in the radial direction along with the rotation of the support member 15, the second roller 35 rotates along the tooth groove of the second external gear portion 32 while the next tooth groove is rotated. Move to At this time, when the second roller 35 pushes the wall of the tooth groove, the output rotary body 3 having the second external teeth 32 receives a circumferential force and rotates. Thereby, the output rotary body 3 rotates one tooth of the second external gear 32 with respect to the holder 36 each time the support member 15 makes one rotation.

In the reduction gear 5 having such a configuration, the first roller 34 and the second roller 35 function as an eccentric rotating body that performs eccentric rotational movement with respect to the rotation axis O of the input rotating body 2 and the output rotating body 3. Also in the reduction gear 5, the same effects as described above can be obtained by applying the configurations described in the embodiment shown in FIGS. For example, as shown in FIG. 7, by supporting the support member 15 with a pair of rolling

bearings

17 and 18 and applying a preload to each of the rolling

bearings

17 and 18, the support rigidity for the support member 15 is increased, The operation of the electric actuator can be stabilized.

As mentioned above, although the embodiment of the electric actuator concerning the present invention was described, the present invention is not limited at all to the above-mentioned embodiment, and within the range which does not deviate from the gist of the present invention, it can carry out with various forms. Of course it is.

Reference Signs List 1 electric actuator 2 input rotary body 3 output rotary body 4 electric motor unit 5 reduction gear 6 casing (stationary member)
7 shaft (output shaft)
DESCRIPTION OF SYMBOLS 11 Stator 12 Rotor 13 1st external gear part 14 2nd external gear part 15 Support member 16 Internal gear (eccentric rotary body)
17 rolling bearing 17a first raceway surface 17b second raceway surface 18 rolling bearing 18a first raceway surface 18b second raceway surface 19 first internal gear 20 second internal gear 21 needle roller bearing (bearing)
23 Sprocket 31 first external gear 25 nut (preload member)
32 second external gear 33 cylindrical member 34 first roller (eccentric rotating body)
35 Second roller (eccentric rotating body)
36 Retainer

Claims

An electric motor unit, a stationary member, a reduction gear for transmitting the rotation of the electric motor unit, an input rotating body to which a driving force is input from the outside, and the reduction gear connected to the input rotating body In an electric actuator provided with a rotatable output rotating body,
The reduction gear comprises: an eccentric rotating body performing eccentric rotational movement with respect to a center of the output rotating body; and a support member which is rotationally driven by the electric motor unit and supports the eccentric rotating body.
An electric actuator characterized in that the support member is supported by a pair of rolling bearings, and a preload is applied to each of the pair of rolling bearings.
The electric actuator according to claim 1, wherein the rolling bearing has a first raceway surface and a second raceway surface, and the first raceway surfaces of the pair of rolling bearings are provided on the support member.
The electric actuator according to claim 2, wherein a second raceway surface of one of the pair of rolling bearings is provided on the stationary member, and a second raceway surface of the other rolling bearing is provided on the input rotary body.
The electric actuator according to any one of claims 1 to 3, wherein angular ball bearings are used as the pair of rolling bearings.
The electric actuator according to any one of claims 1 to 4, wherein a nut is used as a preload applying member for applying a preload to the pair of rolling bearings.
The electric actuator according to any one of claims 1 to 5, wherein rolling elements PCD of the pair of rolling bearings have different sizes.
The electric actuator according to any one of claims 1 to 6, wherein the support member and the eccentric rotary body are disposed on an inner diameter side of a motor core including a stator and a rotor of the electric motor unit.
An output shaft that rotates integrally with the output rotor is disposed on the inner diameter side of the electric motor unit, and an input that allows relative rotation with respect to the output shaft coaxially with the output shaft on the outer diameter side of the output shaft The electric actuator according to any one of claims 1 to 7, wherein a rotating body is disposed.
The electric actuator according to any one of claims 1 to 6, wherein the reduction gear changes a rotational phase difference of the output rotary body with respect to the input rotary body by rotation of a support member.
The electric actuator according to any one of claims 1 to 7, applied to a variable valve timing device which changes the opening / closing timing of the valve by changing the rotational phase difference of the camshaft with respect to the sprocket.