JP2020048390A - Electric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric actuator which is lightweight and compact and has excellent operation stability. An electric motor having a bottomed tubular casing 11, a stator 15 fixed to the casing 11, and a rotor 16 arranged on the inner circumference of the stator 15 via a radial gap and holding a rotor magnet 16b. In the electric actuator 9 provided with the rolling bearing 20 mounted on the motor rotating shaft 14 constituting the rotor 16 and capable of supporting the radial load and the axial load, the axial central portion of the stator 15 (stator core 15a) is provided. P1 is arranged at a position offset to the opening side of the casing 11 from the axial central portion P2 of the rotor magnet 16b, and the rolling bearing 20 is arranged only on the opening side of the casing 11 with respect to the rotor magnet 16b. [Selection diagram] Fig. 1

Description

  The present invention relates to an electric actuator.

  Patent Literature 1 discloses an electric oil pump device mounted on a vehicle such as an automobile. This electric oil pump device has a configuration in which a pump unit and an electric motor (electric actuator) that drives the pump unit are combined. For the electric motor, a so-called radial gap type motor having a stator fixed to the inner peripheral surface of a bottomed cylindrical casing and a rotor arranged on the inner periphery of the stator via a radial gap is adopted. Have been. The rotor includes a rotor core holding a magnet on the outer periphery, and a rotating shaft having the rotor core mounted on the outer periphery.

  In the above-described electric oil pump device, an inner rotor, which is a component of the pump unit, is mounted on a rotating shaft of the electric motor. That is, the rotating shaft of the electric motor also functions as the rotating shaft of the pump unit. In this case, when the electric oil pump device (electric motor) is driven, an axial load is input to the rotating shaft from the pump unit side. If the rotating shaft moves in the axial direction in response to such an axial load being input to the rotating shaft, the operation accuracy of the electric motor and, consequently, the electric oil pump device becomes unstable. It is essential to take measures to regulate In Patent Literature 1, a rolling bearing capable of supporting both a radial load and an axial load is used as a bearing for supporting a rotating shaft. The rolling bearing is provided at two locations separated axially (on both sides in the axial direction of a rotor magnet). ), The axial movement of the rotating shaft is regulated.

  Further, the above-described electric oil pump device includes a circuit board that controls driving of the electric motor. The circuit board is disposed on the opposite side of the pump unit in the axial direction with respect to the stator (between the stator and the bottom of the casing). The circuit pattern on the circuit board includes terminals as conductive parts extending from the stator. And a terminal extending from the power supply is electrically connected.

JP 2017-204954 A

  As described above, the electric actuator of Patent Document 1 has a structure in which motor driving electric components such as a circuit board and terminals, a first rolling bearing, a rotor core (stator core), a second rolling bearing, and the like are arranged in the axial direction. Have. In this case, since it is necessary to use a large casing capable of accommodating the above-mentioned various components, it is unavoidable to increase the size and weight of the electric actuator in the axial direction. Therefore, there is room for improvement in the electric actuator of Patent Document 1.

  In view of the above circumstances, the present invention has a light weight, a compact, and a simple configuration, but can effectively restrict the axial movement of the motor rotating shaft when the electric motor is driven, thereby improving operation stability. An object is to provide an excellent electric actuator.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, among the rolling bearings for supporting the motor rotary shaft, which are often provided at two locations separated in the axial direction in a paired manner. The idea of omitting one of them and compensating for the reduced load capacity of the axial load by omitting one of the rolling bearings with an essential component of the electric motor has led to the invention of the present invention. .

  That is, the present invention conceived to achieve the above object has a bottomed cylindrical casing in which one end in the axial direction is open and the other end in the axial direction is closed, and is fixed to the casing. An electric motor having a rotor that holds a magnet and is disposed on an inner periphery of the stator through a radial gap and a rotor that holds a magnet, and is mounted on a motor rotating shaft that constitutes the rotor, and has a radial load and an axial direction. A rolling bearing capable of supporting a load, and an electric actuator in which another member that rotates integrally with the motor rotation shaft is mounted at one end of the motor rotation shaft, wherein the axial center portion of the stator is larger than the axial center portion of the magnet. The rolling bearing is disposed at a position offset to one side in the axial direction, and the rolling bearing is disposed only on one side in the axial direction relative to the magnet.

  According to the above configuration, first, the axial center portion of the stator is arranged at a position offset to one side in the axial direction from the axial center portion of the magnet (rotor magnet). , A magnetic force that constantly urges this to one side in the axial direction acts. This prevents the motor rotation shaft from moving in the axial direction even when an axial load (particularly, a load urging the motor rotation shaft to the other axial side) acts on the motor rotation shaft when the electric motor is driven. be able to. In addition, the rolling bearing that is mounted on the motor rotating shaft and can support the radial load and the axial load is arranged on one side in the axial direction than the magnet, so that the magnetic force acts on the motor rotating shaft by the magnetic force. can do.

  On the other hand, the rolling bearing is arranged only on one side in the axial direction of the magnet. In short, the arrangement of the rolling bearing on the other side in the axial direction with respect to the magnet is omitted. For this reason, the axial dimension of the rotary shaft or the casing on which the rolling bearing is mounted can be reduced as compared with a conventional (Patent Document 1) electric actuator in which rolling bearings are arranged on both axial sides of the magnet. As a result, the weight reduction and simplification due to the elimination of the rolling bearing, and the reduction in weight and size due to the shortening of the rotating shaft and the casing that can be executed with the elimination of the rolling bearing are realized. Can be.

  A cylindrical portion projecting to one side in the axial direction may be provided at the bottom of the casing, and the other end of the motor rotation shaft may be fitted to the inner periphery of the cylindrical portion. With this configuration, the motor rotating shaft can be supported in the radial direction even at a position separated from the rolling bearing in the axial direction, which is advantageous in preventing whirling of the motor rotating shaft.

  The motor rotating shaft may be provided with a stepped surface facing the end surface on one side in the axial direction of the cylindrical portion via an axial gap. With this configuration, even when an axial load that urges the motor rotating shaft toward the other side in the axial direction acts on the motor rotating shaft, the motor rotating shaft and the bottom of the casing are less likely to abut in the axial direction. This is advantageous in preventing the shaft and / or the bottom of the casing from being deformed.

  An annular member may be interposed in the axial gap. This is advantageous in restricting the movement of the motor rotation shaft to the other side in the axial direction, so that the operation stability of the electric actuator is improved. At this time, if an annular member made of an elastic material is used, the annular member functions as a damper, which is more advantageous in preventing the motor rotation shaft and / or the bottom of the casing from being deformed.

  The configuration of the present invention in which the axial central portion of the stator is arranged at a position offset to one side in the axial direction from the axial central portion of the magnet (rotor magnet) uses a stator and a magnet whose axial dimensions are different from each other. It can also be adopted in cases.

  As another member attached to one end of the motor rotation shaft, for example, a pump rotor can be mentioned. That is, the electric actuator according to the present invention can be preferably used as an actuator for driving an electric pump.

  From the above, according to the present invention, the movement stability in the axial direction of the motor rotating shaft at the time of driving the electric motor can be effectively controlled while having a lightweight, compact, and simple configuration. It is possible to provide an electric actuator excellent in the above.

1 is a schematic longitudinal sectional view of an electric oil pump device including an electric actuator according to one embodiment of the present invention. FIG. 7 is a diagram illustrating a relationship between an offset amount between a stator and a magnet and an urging force generated by disposing the stator and the magnet at offset positions. It is a longitudinal section of the electric actuator concerning other embodiments of the present invention. (A) Drawing and (b) are figures showing typically an important section of an electric actuator concerning other embodiments of the present invention.

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

  FIG. 1 shows a schematic longitudinal sectional view of an electric oil pump device 1 used for supplying hydraulic oil to a transmission of an automobile, for example. An electric oil pump device 1 shown in FIG. 1 includes a driving unit 2 corresponding to an electric actuator 9 according to an embodiment of the present invention, and a pump unit that sucks and discharges hydraulic oil as the driving unit 2 is driven. 3 is provided. The casing of the electric oil pump device 1 has a bottomed cylindrical motor casing 11 in which one end in the axial direction (left side in the drawing) is open and the other end in the axial direction (right side in the drawing) is closed. And a pump plate 7 fixed to one end of the motor casing 11. For example, a trochoid pump or a vane pump can be adopted as the pump unit 3, and in the illustrated example, a trochoid pump is adopted. Hereinafter, the drive unit 2 (the electric actuator 9) will be described in detail.

  The electric actuator 9 functioning as the drive unit 2 of the electric oil pump device 1 includes a bottomed cylindrical motor casing (casing) 11, an electric motor 10 housed on the inner periphery of the casing 11, and a rolling bearing 20. .

  The casing 11 includes a cylindrical body 12 having both ends opened in the axial direction, and a cover 13 for closing the other end of the cylindrical body 12. The cylindrical body 12 has a stator fixing portion 12a in which the stator 15 of the electric motor 10 is fixed on the inner peripheral surface, a bearing fixing portion 12b in which the outer ring 22 of the rolling bearing 20 is fixed on the inner peripheral surface, and the pump cover 7 is fixed. And the integrated pump cover fixing portion 12c.

  The cover 13 integrally includes a bottom portion 13a, an outer cylindrical portion 13b extending to one side in the axial direction from an outer diameter end of the bottom portion 13a, and an inner cylindrical portion 13c extending to one side in the axial direction from near the center of the bottom portion 13. Have.

  The electric motor 10 is a radial gap type motor (for example, a U-phase, a V-phase, and a W-phase) including a stator 15 fixed to the casing 11 and a rotor 16 opposed to the stator 15 via a radial gap. Three-phase brushless motor).

  The stator 15 includes a cylindrical stator core 15a formed by laminating a plurality of electromagnetic steel plates in the axial direction, a bobbin 15b made of an insulating material mounted on the stator core 15a, and a coil (stator) wound around the bobbin 15b. Coil 15c). An electric component (driving electric component) for driving the electric motor 10 is arranged between the stator 15 and the bottom 13b of the cover 13. FIG. 1 shows a bus bar 18 having a terminal electrically connected to the coil 15c as the above-mentioned driving electric component. The bus bar 18 constitutes a power supply circuit for supplying drive power to the electric motor 10, and is electrically connected to a power supply via a lead wire (not shown).

  The rotor 16 has a cylindrical rotor core 16a formed by laminating a plurality of electromagnetic steel plates in the axial direction, a plurality of magnets (rotor magnets) 16b attached to the rotor core 16a, and the rotor core 16a mounted on the outer peripheral surface. And a motor rotation shaft 14. The rotor magnet 16b of the present embodiment has the same axial dimension as the stator core 15a. Although illustration is omitted, the rotor 16 has a structure in which a portion (magnet attachment portion) corresponding to a rotor core is integrally provided on the motor rotation shaft 14 and the rotor magnet 16b is directly attached to the magnet attachment portion. May be.

  The motor rotation shaft 14 is provided with a small-diameter portion 14a having one end protruding outside the casing 11, a large-diameter portion 14b having an outer peripheral surface to which the rotor core 16a is fixed, and between the small-diameter portion 14a and the large-diameter portion 14b. A projection 14c protruding radially and a cylindrical portion 14d provided at the other end are integrally provided. The inner rotor 4 of the pump rotor 6 composed of the inner rotor 4 and the outer rotor 5 is fixed to the outer peripheral surface on one end side of the small diameter portion 14a. The holding member 30 holding the magnet 31 is fitted and fixed to the concave portion 14e defined on the inner periphery of the cylindrical portion 14d. The magnet 31 constitutes a rotation detecting device for detecting the amount of rotation of the motor rotation shaft 14, and a magnetic sensor (for example, a hall sensor) (not shown) faces the magnet 31 on the bottom 13 b of the cover 13. Be placed.

  The motor rotating shaft 14 has a rolling bearing 20 mounted on the outer peripheral surface on the other end side of the small diameter portion 14a, and a cylindrical portion 14d provided on the other end fitted to the inner circumference of the inner cylindrical portion 13c of the cover 13. , And rotatably supported by the casing 11. At this time, the other end surface (step surface) 14f of the large diameter portion 14b faces the one end surface 13c1 of the inner cylindrical portion 13c via the axial gap 19.

When the above-described support structure is employed, when the motor rotation shaft 14 rotates, the cylindrical portion 14 d of the motor rotation shaft 14 needs to slide smoothly with respect to the inner cylindrical portion 13 c of the cover 13. For this reason, the fit between the outer peripheral surface of the cylindrical portion 14d and the inner peripheral surface of the inner cylindrical portion 13c is "clear fit" or "intermediate fit" defined in JIS B 0401-1: 1998. Although not shown, in order to prevent the cover 13 from being worn due to the rotation of the motor rotation shaft 14 as much as possible,
-The inner peripheral surface of the inner cylindrical portion 13c is formed of a resin having excellent slidability.
A plain bearing having excellent slidability such as a sintered oil-impregnated bearing or a resin bearing is fitted to the inner periphery of the inner cylindrical portion 13c or the outer periphery of the cylindrical portion 14d.
-The inner cylindrical portion 13c itself is constituted by the above-described slide bearing.
You may take measures such as.

  The rolling bearing 20 is a deep groove ball bearing capable of supporting a radial load and an axial load, and includes an inner ring 21 fixed to an outer peripheral surface of a small diameter portion 14 a of a motor rotating shaft 14, and a cylindrical body 12 forming a casing 11. An outer ring 22 fixed to the inner peripheral surface of the bearing fixing portion 12b, a plurality of balls 23 disposed between the inner ring 21 and the outer ring 22, and a retainer (not shown) that holds the balls 23 are provided. The rolling bearing 20 is arranged on one side in the axial direction of the rotor magnet 16b held on the motor rotating shaft 14, and is arranged adjacent to one side in the axial direction of the projection 14c provided on the rotating shaft 14 here.

  The electric actuator 9 is configured such that the axial center P2 of the rotor magnet 16b held on the motor rotating shaft 14 and the axial center P1 of the stator 15 (stator core 15a) are displaced in the axial direction, more specifically. Is characterized in that the axial central portion P1 of the stator core 15a is arranged at a position (dimension x) offset to one axial side from the axial central portion P2 of the rotor magnet 16b.

  In the present embodiment, a protrusion 14c is provided on the motor rotation shaft 14 such that one end is located on the same plane as one end of the stator core 15a, and the protrusion 14c and the outer circumferential surface of the large diameter portion 14b of the motor rotation shaft 14 are provided. By sandwiching the rotor magnet 16b (the rotor magnet 16b having the same axial dimension as the axial dimension of the stator core 15a) with the fitted retaining ring 17, the axial central portion P1 is larger than the axial central portion P2. It is arranged at a position offset by x to one side in the axial direction. Therefore, the axial dimension of the protrusion 14c is the same as the offset amount x described above.

  As described above, the electric motor 10 is driven by arranging the central portion P1 in the axial direction of the stator 15 (stator core 15a) at a position offset to one side in the axial direction from the central portion P2 in the axial direction of the rotor magnet 16b. Then, a magnetic force F is applied to the motor rotating shaft 14 to constantly urge the motor rotating shaft 14 to one side in the axial direction. When the electric motor 10 is driven, the inner rotor 4 or the like as another member fixed to the motor rotation shaft 14 rotates and hydraulic oil is pumped from the pump unit 3. (Hereinafter, referred to as “reverse input load F ′”). Even when such a reverse input load F 'acts, the magnetic force F can prevent the motor rotation shaft 14 from moving in the axial direction (the other side in the axial direction). Further, since the rolling bearing 20 mounted on the motor rotating shaft 14 and capable of supporting the radial load and the axial load is disposed on one axial side of the rotor magnet 16b, the magnetic force F acts on the motor rotating shaft 14. Can be supported.

If the reverse input load F 'is larger than the magnetic force F acting on the motor rotation shaft 14, it is not possible to effectively prevent the motor rotation shaft 14 from moving to the other axial side. Therefore, it is necessary to set the offset amount x so that a magnetic force F larger than the reverse input load F 'can be obtained. Therefore, when it is assumed that the offset amount necessary to cancel the reverse input load F 'is x', the offset amount x is set to be larger than x '. Further, the present inventors have verified that the axial magnetic force (biasing force) F acting on the motor rotating shaft 14 by displacing P1 and P2 in the axial direction is equal to the offset amount x of P1 and P2. Until the offset amount reaches a predetermined value, the value increases substantially in proportion to the value of the offset amount x, but gradually decreases when the offset amount x exceeds the predetermined value. Therefore, the offset amount x is the maximum force (urging force) exerting the F ₁ is set to be equal to or less than the offset amount x _1, which may (or, see Figure 2).

  Further, the rolling bearing 20 is disposed only on one axial side of the rotor magnet 16b. In short, the arrangement of the rolling bearing on the other axial side with respect to the rotor magnet 16b is omitted. For this reason, the axial dimension of the motor rotating shaft 14 and the casing 11 (the cylindrical body 12) to which the rolling bearings are mounted is reduced as compared with the conventional (Patent Document 1) electric actuator in which rolling bearings are arranged on both axial sides of the rotor magnet. can do. Thereby, weight reduction and simplification due to the elimination of the rolling bearing, and reduction in weight and size by shortening the size of the motor rotating shaft 14 and the casing 11 that can be executed with the elimination of the rolling bearing are achieved. Can be realized. In addition, even if the arrangement of the rolling bearing on the other side in the axial direction with respect to the rotor magnet 16b is omitted, the arrangement space for the electric components for driving the electric motor 10 to be secured between the bottom portion 13a of the casing 11 and the stator 15 is required. No effect.

  Therefore, the electric actuator 9 according to the present invention has a lightweight, compact and simple configuration, but can effectively restrict the axial movement of the motor rotation shaft 14 when the electric motor 10 is driven, and operate. It has the feature of being excellent in stability.

  In particular, in the present embodiment, the other end of the motor rotation shaft 14 is fitted to the inner periphery of the inner cylindrical portion 13c provided on the bottom portion (the cover 13) of the casing 11, and at a position axially separated from the rolling bearing 20. The motor shaft 14 is supported in the radial direction. Thereby, whirling of the motor rotation shaft 14 can be effectively prevented. Further, since the other end of the motor rotation shaft 14 is supported by (the cover 13 of) the casing 11 which is an essential component of the electric actuator 9, it is possible to avoid an increase in the size and weight of the electric actuator 9.

  Further, the motor rotating shaft 14 is provided with a stepped surface 14 f which faces the one end surface 13 c 1 of the inner cylindrical portion 13 c of the cover 13 via the axial gap 19. In this way, for example, even when a reverse input load F ′ that exceeds the magnetic force F acts on the motor rotating shaft 14, the motor rotating shaft 14 and the casing 11 hardly end up in the axial direction. This is advantageous in preventing the motor rotation shaft 14 and / or the casing 11 from being deformed.

  As described above, the electric actuator 1 according to the embodiment of the present invention has been described. However, the electric actuator 1 can be appropriately changed without departing from the gist of the present invention.

  For example, as shown in FIG. 3, an annular member 24 may be interposed in an axial gap 19 formed between the motor rotation shaft 14 and the cover 13. With this configuration, even when the reverse input load F ′ acts on the motor rotating shaft 14, the movement of the motor rotating shaft 14 to the other side in the axial direction can be effectively restricted. 9 has improved operational stability. At this time, if the annular member 24 is formed of an elastic material, the annular member 24 functions as a damper, which is more advantageous in preventing the motor rotation shaft 24 and / or the cover 13 from being deformed.

  Further, in the embodiment described above, a deep groove ball bearing is used as the rolling bearing 20. However, the rolling bearing 20 may include other rolling bearings that can support a radial load and an axial load, for example, an angular ball bearing, It may be replaced with a self-aligning ball bearing or a tapered roller bearing.

  In the embodiment described above, the axial dimension of the stator core 15a and the axial dimension of the rotor magnet 16b are the same. However, as schematically shown in FIGS. Even if the axial dimensions of the rotor core 16a are different from each other, the axial central portion P1 of the stator core 15a can be arranged at a position offset to one axial side from the axial central portion P2 of the rotor magnet 16b.

  FIG. 4A shows an example in which a stator core 15a having an axial dimension larger than the axial dimension of the rotor magnet 16b is used, and the other end of the stator core 15a and the rotor magnet 16b on the other axial side is used. P1 is located on one side in the axial direction rather than P2 by disposing the stator core 15a on one side in the axial direction and one end in the axial direction of the rotor magnet 16b on one side in the axial direction. It is located at a position offset from. FIG. 4B shows an example in which a rotor magnet 16b having an axial dimension larger than the axial dimension of the stator core 15a is used, and one end of the stator core 15a and the rotor magnet 16b on one axial side is used. By arranging them on the same plane and positioning the other axial end of the rotor magnet 16b on the other axial side than the axial other end of the stator core 15a, P1 is located on one axial side of P2. It is located at a position offset from.

  Further, in the embodiment described above, the electric actuator 9 according to the present invention is used for the driving unit 2 of the electric oil pump device 1, but the electric actuator 9 according to the present invention is used as a driving unit of the electric air pump device. It is also possible.

  The present invention is not limited to the above-described embodiment at all, and it is needless to say that the present invention can be carried out in various other forms without departing from the gist of the present invention. It is indicated by the appended claims, and includes equivalents described in the claims, and all modifications within the scope.

DESCRIPTION OF SYMBOLS 1 Electric oil pump apparatus 2 Drive part 3 Pump part 4 Inner rotor (other members)
Reference Signs List 9 electric actuator 10 electric motor 11 motor casing 13 cover 13b bottom 13c inner cylindrical part (cylindrical part)
14 Motor rotating shaft 14f Step surface 15 Stator 15a Stator core 15c Stator coil 16 Rotor 16a Rotor core 16b Magnet (rotor magnet)
18 Busbar (Electric parts for driving)
19 Axial gap 20 Rolling bearing 24 Annular member F Magnetic force (biasing force)
P1 Central part in the axial direction of the stator P2 Central part in the axial direction of the magnet x Offset

Claims (6)

A bottomed cylindrical casing in which one end in the axial direction is open and the other end in the axial direction is closed,
An electric motor having a stator fixed to the casing, and a rotor arranged on the inner periphery of the stator via a radial gap and holding a magnet;
A rolling bearing mounted on a motor rotating shaft that constitutes the rotor, and capable of supporting a radial load and an axial load,
An electric actuator in which another member that rotates integrally with the motor rotation shaft is attached to one end of the motor rotation shaft,
An axial center portion of the stator is arranged at a position offset to one axial side from an axial center portion of the magnet, and the rolling bearing is arranged only on one axial side of the magnet. Electric actuator.   The electric actuator according to claim 1, wherein a cylindrical portion protruding to one side in the axial direction and fitted with the other end of the motor rotation shaft is provided at a bottom of the casing.   The electric actuator according to claim 2, wherein the motor rotation shaft is provided with a step surface facing an end surface of the cylindrical portion on one side in the axial direction with an axial gap therebetween.   The electric actuator according to claim 3, wherein an annular member is interposed in the axial gap.   The electric actuator according to any one of claims 1 to 4, wherein an axial dimension of a stator core constituting the stator and an axial dimension of the magnet are different from each other.   The electric actuator according to claim 1, wherein the other member is a pump rotor.

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