JP4821303B2 - Brushless motor and electric power steering apparatus using the same - Google Patents

Description

  The present invention relates to a cylindrical stator around which a coil is wound, a rotor having a magnetic pole and an output facing the stator, an angle detector for detecting a rotation angle of the rotor, the stator and the angle detector The present invention relates to a brushless motor having a frame in which the rotor is mounted and a bearing device that rotatably supports the rotor with respect to the frame, and an electric power steering apparatus using the brushless motor.

  In a motor used as a drive source for generating a steering assist force of an electric power steering device, it is high in order to obtain a suitable steering feeling while assisting the steering with many times the force according to the driver's steering. Controllability is required. The motor is required to be small and light in terms of reducing the weight of the vehicle body and ensuring safety during a collision. For this reason, in recent years, a brushless motor that is excellent in controllability and easily reduced in size and weight has been suitably used in place of the brushed DC motor.

Brushless motors for electric power steering systems have been thoroughly designed optimally because of their high required functions. Also in the rotor, a permanent magnet having the highest surface magnetic flux density in order to reduce the size, weight and inertia while ensuring the amount of magnetic flux required to obtain the torque required for a motor for an electric power steering device. Is used.
On the other hand, for the stator, a slot combination with a high winding coefficient and capable of concentrated winding is selected to reduce the size and weight and reduce copper loss, and the optimum design of the ratio of iron and copper machines by magnetic field analysis And magnetic path design optimization and high-density winding using split cores and flat wires.

The brushless motor for an electric power steering apparatus with such an optimal design has a motor constant (generated torque per unit copper loss, Nm / √W) that has almost reached the upper limit. The constants tend to be substantially the same.
On the other hand, not only the motor coil but also the parts that constitute the motor have a limit of the operating temperature, and if the temperature is exceeded due to copper loss, the motor will burn out.

Therefore, when trying to generate a larger torque while maintaining the physique of the motor, or to reduce the size and weight while maintaining the generated torque, heat transfer from the motor coil to the device to which the motor is mounted There is also a need for a means to increase acceptable copper loss by increasing heat transfer to the atmosphere environment.
Further, in the electric power steering apparatus, it is essential to reliably prevent the frame and the stator from idling in order to prevent self-steering, which is a failure that should not occur. Therefore, although the frame and the stator are generally widely used, in combination with a fitting method such as press-fitting, shrink-fitting, adhesion, etc., which may idle when loosened or peeled off, It is desirable to provide a mechanical detent.

For this reason, conventionally, it has a cylindrical housing in which the gear of the reduction gear is fitted, and a frame fitted on the opposite side of the gear of the housing, and a stator is fixed to the frame, The rotor is pivotally supported so that the resolver rotor is fixed to the rotor at a position facing the frame, the resolver stator facing the resolver rotor is attached to the housing, and the sensor connector opening attached to the resolver There is known a rotating electrical machine in which the motor is arranged toward the outside of the motor (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2005-117736 (first page, FIGS. 1 to 3)

  However, in the conventional example described in Patent Document 1, the heat generated by the motor coil wound around the stator is transferred to the housing of the speed reducer having a much larger heat capacity and surface area than the motor body. Even if an attempt is made to increase the allowable copper loss, it is difficult to reduce the distance between the stator and the reducer housing because the frame is attached to the reducer housing via the housing. Since there is a joint between the housings, it is difficult to reduce the thermal resistance at this joint, and it is difficult to diffuse the heat generated in the motor coil by heat transfer. There is. In addition, since the frame is formed from a thin steel plate, the cross-sectional area and the material are limited, so there is an unsolved problem that it is difficult to reduce the thermal resistance or use a material with high thermal conductivity. is there. Furthermore, in such a frame, there is an unsolved problem that it is difficult to perform a process for increasing the surface area of the frame, such as providing fins to promote conduction to the atmosphere environment, convection, and heat transfer by radiation. .

Furthermore, in the above frame, when a mechanical detent is to be provided between the frame and the stator, it is difficult in processing to provide the concave portion so as to be pushed out from the inner diameter side of the frame. On the other hand, when trying to provide a recess in the shape of a dent from the outside of the frame, there is also an unresolved problem that it is difficult to maintain the accuracy of the stator fixing part because post-cutting is impossible because a protrusion is formed on the inner diameter. is there.
Accordingly, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and provides a brushless motor that is small and lightweight, yet inexpensive and highly reliable, and electric power using this brushless motor. The object is to provide a steering device.

To achieve the above object, a brushless motor according to a first aspect of the present invention detects a cylindrical stator around which a coil is wound, a rotor having a magnetic pole and an output shaft facing the stator, and a rotation angle of the rotor. A brushless motor having an angle detector, a frame that houses the stator and the angle detector, and a bearing device that rotatably supports the rotor with respect to the frame. The flange portion fixed to the frame is integrally formed at the end portion, and is composed of a frame half that houses the stator and a frame half that houses the angle detector, and the flange portion of the frame half that houses the stator A stator yoke abutting portion that abuts the yoke of the stator on the inner side of the small diameter portion on the inner surface of the side end portion, and a stay that abuts the tip of the stator Forming a distal abutment portion, and wherein said that contacting the one end face of the stator to both the stator yoke abutting portion and the stator tip abutment portion.

According to a second aspect of the present invention, the brushless motor according to the first aspect of the present invention is characterized in that the frame half that houses the stator is formed of a material having a high thermal conductivity.
Furthermore, the brushless motor according to claim 3 is the invention according to claim 2, wherein the frame half that houses the stator is formed of any one of aluminum, aluminum alloy, magnesium, and magnesium alloy. It is said.

Furthermore, a brushless motor according to a fourth aspect of the present invention is characterized in that, in any one of the first to third aspects of the invention, the frame half that houses the stator is integrally formed by casting.
Still further, a brushless motor according to a fifth aspect of the present invention is the invention according to any one of the first to fourth aspects, wherein a coil end portion projecting from both end faces of the stator and a frame half that houses the stator are provided. It is characterized in that a heat transfer material formed of a material having a higher thermal conductivity than air is inserted into at least one of the gaps between the small diameter portion .

A brushless motor according to a sixth aspect of the present invention is the brushless motor according to any one of the first to fifth aspects, wherein the output shaft is disposed on the flange portion side of the frame , and the output shaft is disposed in the frame . The preload-side bearing device, the magnetic pole of the rotor, the fixed-side bearing device, and the angle detector are arranged in that order.
Further, the brushless motor according to claim 7, in any one invention of claims 1 to 6, a fin-like ribs are formed a large number on the outer periphery of the frame halves to accommodate a pre-Symbol angles detector It is characterized by that.

Furthermore, the brushless motor according to an eighth aspect is characterized in that, in the invention according to the seventh aspect, the rib is formed integrally with a half frame that houses the angle detector .
Still further, according to a ninth aspect of the present invention, in the brushless motor according to any one of the first to eighth aspects, the frame half body that houses the stator has one or more recesses formed on the mating surface of the stator. The stator is characterized in that a convex portion engaging with the concave portion is formed on a fitting surface with the frame half body .

According to a tenth aspect of the present invention, the brushless motor according to the ninth aspect is characterized in that the recess is integrally formed with a half frame that houses the stator .
Furthermore, the brushless motor according to an eleventh aspect is characterized in that, in the invention according to the ninth aspect, the concave portion is constituted by a groove extending in the axial direction.
Furthermore, the brushless motor according to a twelfth aspect is characterized in that, in the invention according to the eleventh aspect, the length of the recess is selected to be not less than the axial length of the stator.

Still further, a brushless motor according to a thirteenth aspect is the invention according to any one of the ninth to twelfth aspects, wherein the convex portions of the stator are arranged at the same number as the number of slots and at equal intervals. It is a feature.
A brushless motor according to a fourteenth aspect of the present invention is the brushless motor according to any one of the first to thirteenth aspects, wherein the stator includes a stator yoke that extends in a circumferential direction that fits into a frame half that houses the stator, and A plurality of split cores extending inward from a circumferential central portion of the stator yoke and having a magnetic leg portion around which the motor coil is wound and having a T-shaped cross section perpendicular to the axial direction, The two ends in the circumferential direction are connected to the circumferential ends of the stator yokes of the adjacent split cores, and are formed in an annular shape.

Furthermore, the brushless motor according to claim 15 is the brushless motor according to claim 14, wherein the split core is a half part constituting a convex part that engages with the concave part at each circumferential end of the outer peripheral surface of the stator yoke. Is characterized by protruding.
Still further, the brushless motor according to claim 16 is characterized in that, in the invention according to claim 15, each split core is connected in an annular shape by welding halves of adjacent split cores. Yes.
An electric power steering apparatus according to a seventeenth aspect is characterized in that the brushless motor according to any one of the first to sixteenth aspects is applied as a motor that generates a steering assist force transmitted to a steering mechanism.

According to the first aspect of the present invention, the flange portion that is fixed to the attached portion is integrally formed with the frame half body that accommodates the stator , and inside the small diameter portion on the inner surface of the flange portion side end portion of the frame half body. A stator yoke abutting portion that abuts the yoke of the stator and a stator front end abutting portion that abuts the front end of the stator are formed, and one of the stators is formed on both the stator yoke abutting portion and the stator front end abutting portion. Since the end faces are in contact, there is no joint between the parts from the frame to the flange, and the stator can be brought close to, for example, a reducer as a mounted part. It is possible to reduce the thermal resistance of the motor, increase the heat transfer from the motor coil wound around the stator to the mounted part, and increase the allowable copper loss Can, it is possible to provide a small, lightweight brushless motor.

According to the second aspect of the present invention, since the frame half that houses the stator is formed of a material having high thermal conductivity, the thermal resistance from the stator around which the motor coil is wound to the mounted portion is reduced. Since the heat transfer from the motor coil to the mounted portion to which the brushless motor is mounted can be increased and the allowable copper loss can be increased, a small and lightweight brushless motor can be provided. .

Further, according to the invention of claim 3, since the frame half that houses the stator is formed of any one of aluminum, aluminum alloy, magnesium, and magnesium alloy having higher thermal conductivity than iron, the motor Since the thermal resistance between the stator on which the coil is wound and the mounted portion can be made smaller than the conventional example, the heat transfer from the motor coil to the mounted portion can be increased, and the allowable copper loss can be increased. A small, lightweight brushless motor can be provided.

Furthermore, according to the fourth aspect of the invention, the frame half that houses the stator is integrally formed by casting, so that the frame and the flange portion can be easily and integrally formed with high accuracy.
Still further, according to the invention of claim 5, at least one of the gaps existing between the coil end portions projecting from both end faces of the stator and the small-diameter portion of the frame half housing the stator is more than air. Since a heat transfer material formed of a material having high thermal conductivity is inserted, heat transfer from the coil end portion to the frame increases, and allowable copper loss can be increased, so that a small and light brushless motor can be provided. .

According to the invention of claim 6, the output shaft is disposed on the flange portion side of the frame , and the preload-side bearing device, the rotor magnetic pole, and the fixed-side bearing device are arranged in the frame with respect to the output shaft. And since the angle detectors are arranged in that order, the distance between the stator around which the motor coil is wound and the mounted portion can be shortened, so that the thermal resistance can be made smaller than the conventional example, Since heat transfer from the motor coil to the mounting portion increases and allowable copper loss can be increased, a small and lightweight brushless motor can be provided. Furthermore, even if the frame and rotor are displaced in the axial direction when the motor temperature changes due to the difference in coefficient of linear expansion between the frame material and the rotor material, the angle detector is arranged near the fixed bearing device. An axial displacement between the rotating portion and the fixed portion is unlikely to occur, and a reduction in accuracy and malfunction due to an axial displacement of the angle detector can be suppressed, and a highly reliable brushless motor can be provided.

Furthermore, according to the invention according to claim 7, since the ribs of the fin shape is formed a large number on the outer periphery of the frame halves to accommodate the angles detectors, electric to ambient environment, convection, heat transfer by radiation Therefore, the angle detector is less susceptible to the heat generated by the copper loss of the motor coil, and it is possible to suppress drift and deterioration of accuracy due to the temperature rise of the angle detector. A highly brushless motor can be provided. And since the copper loss which a motor coil can accept | permit can be enlarged, a small and lightweight brushless motor can be provided. Furthermore, even if the frame thickness of this portion is reduced for weight reduction, the rigidity of the frame can be maintained by the fin-like ribs, so that a small and lightweight brushless motor can be provided.

Furthermore, according to the invention according to claim 8, since the rib is integrally formed with the half frame that accommodates the angle detector , the fin-like rib can be easily provided, and it is inexpensive but reliable. A brushless motor that is high, small, and lightweight can be provided.
Still further, according to the invention according to claim 9, wherein the frame halves for accommodating the stator is formed at one position or more recesses on the mating surface of the stator, the stator is the fitting surface between the frame halves Since the convex portion that engages with the concave portion is formed, the concave portion and the convex portion function as a mechanical detent between the frame and the stator, reliably preventing idling of the stator and highly reliable brushless. A motor can be provided.

Further, the invention according to claim 10, since it is integrally molded into the frame with a recess for accommodating the stator, it is possible to easily form a mechanical detent between the frame and the stator, An inexpensive and highly reliable brushless motor can be provided.
Further, according to the invention of claim 11, since the concave portion of the frame half body is constituted by the groove extending in the axial direction, the stator can be easily fitted to the frame, while being inexpensive. A highly reliable brushless motor can be provided.

Furthermore, according to the invention according to claim 12, recess, since its length is selected in axial length than the length of the stator, fitting the stator of the same shape in the axial direction Therefore, it is possible to fit a stator in which electromagnetic steel plates punched in the same shape are stacked, and it is possible to provide a brushless motor that is inexpensive but highly reliable.
Furthermore, according to the invention of claim 13, since the number of convex portions of the stator is the same as the number of slots and arranged at equal intervals, a uniform magnetic path can be formed, cogging torque and A high-performance brushless motor with small torque ripple can be provided.

According to the fourteenth aspect of the present invention, the stator is inward from a circumferential base extending in the circumferential direction that fits into a frame half that houses the stator, and from a circumferential central portion of the circumferential base. A plurality of split cores having a T-shaped cross section perpendicular to the axial direction and a yoke around which a motor coil is wound, and a stator having a split core adjacent to both ends in the circumferential direction of the stator yoke Since it is formed in an annular shape connected to the circumferential end of the yoke, it is possible to configure the stator by connecting the stator yoke of each divided core after winding the motor coil around the divided core. Can be formed.

  According to the fifteenth aspect of the present invention, since the split core is formed so that the half portions constituting the convex portions respectively engaging with the concave portions protrude from the circumferential end of the outer peripheral surface of the stator yoke. The area of the joint part between the cores can be widened only by a half portion, whereby the stator rigidity is increased, and a high-performance brushless motor with low noise and vibration can be provided.

Furthermore, according to the invention of claim 16, since each split core is connected in an annular shape by welding the halves of adjacent split cores, magnetic flux generated in the motor coil of the split core Makes it possible to provide a high-performance brushless motor that can hardly pass through the welded portion, can suppress an increase in iron loss while increasing the rigidity of the stator, has low noise and vibration, and has low iron loss.
Still further, according to the invention according to claim 17, since the brushless motor according to any one of claims 1 to 16 is applied as the motor that generates the steering assist force transmitted to the steering mechanism, it is small and lightweight. An electric power steering device that is inexpensive and highly reliable can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram showing an embodiment in which the present invention is applied to an electric power steering apparatus. In the figure, reference numeral 1 denotes an electric power steering apparatus. The electric power steering apparatus 1 is a driver. Is provided with a steering mechanism 2 for steering.
The steering mechanism 2 includes a steering shaft 4 having an input shaft 4a and an output shaft 4b through which a steering force applied from a driver is transmitted to the steering wheel 3, and the steering shaft 4 is one end of the input shaft 4a. Is connected to the steering wheel 3, and the other end is connected to one end of the output shaft 4b via a steering torque sensor 5 as steering torque detecting means.

  The steering force transmitted to the output shaft 4 b is transmitted to the lower shaft 7 via the universal joint 6 and further transmitted to the pinion shaft 9 via the universal joint 8. The steering force transmitted to the pinion shaft 9 is transmitted to the tie rod 11 via the steering gear 10 to steer a steered wheel (not shown). Here, the steering gear 10 is configured in a rack and pinion type having a pinion 10a connected to the pinion shaft 9 and a rack 10b meshing with the pinion 10a, and the rotational motion transmitted to the pinion 10a is linearly moved by the rack 10b. It has been converted to movement.

A steering assist mechanism 12 that transmits a steering assist force to the output shaft 4b is connected to the output shaft 4b of the steering shaft 4. The steering assist mechanism 12 includes a reduction gear 13 connected to the output shaft 4 b and a brushless motor 14 that generates a steering assist force connected to the reduction gear 13.
The brushless motor 14 receives the steering torque applied to the steering wheel 3 detected by the steering torque sensor 5 and transmitted to the input shaft 4a, and the vehicle speed output from the vehicle speed sensor 15 that detects the vehicle speed. Drive control is performed by the control device 16 to which the detection value is inputted.

  The control device 16 calculates a steering assist command value by referring to a control map storing a relationship between the steering torque and the steering assist command value using the vehicle speed detection value as a parameter, and calculates the calculated steering assist command value and the brushless motor. The motor current command value is calculated by performing feedback control based on the motor current flowing through the motor, and the calculated motor current command value is supplied to the motor drive circuit 17 configured by an inverter circuit. A three-phase motor drive current is formed based on a current command value and an angle detection signal from a resolver that detects a rotor rotation angle of the brushless motor 14 described later, and the three-phase motor drive current is supplied to the brushless motor 14. The brushless motor 14 generates a steering assist force corresponding to the steering assist command value.

  As shown in FIGS. 2 to 4, the brushless motor 14 has a frame 23 that houses a stator 21 and a resolver 22 as a rotation angle detector that detects a rotor rotation angle. It is divided into two parts, a cylindrical frame half 23A for housing and a frame half 23B for housing the resolver 22, both of which are screwed at the joint surface.

  The frame half body 23A is integrally formed with a flange portion 24 attached to the reduction gear 13 as the attached portion at the end of the outer peripheral surface opposite to the frame half body 23B, and on the frame half body 23B side. A projecting portion 25 having an internal thread formed on the outer peripheral surface and a projecting plate portion 26 forming a cable lead-out port are integrally molded, and the stator 21 extending in the axial direction from the end surface on the frame half body 23B side is fitted to the inner peripheral surface. The diameter part 27 and the small diameter part 29 which accommodates the preload bearing apparatus 28 in the tip are formed. The preload bearing device 28 includes, for example, a deep groove ball bearing 28a and a preload spring 28b that presses an outer ring of the deep groove ball bearing 28a toward the frame half body 23B in the axial direction. Further, the inner peripheral surface of the large-diameter portion 27 of the frame half body 23A has the same number of slots as the brushless motor extending from the end surface on the frame half body 23B side in the axial direction with a length substantially equal to the axial length of the stator 21. Concave portions 30 having a circular arc cross section are formed at equal intervals.

Here, the frame half body 23A is formed by casting one of aluminum, aluminum alloy, magnesium, and magnesium alloy having higher thermal conductivity than the steel plate constituting the conventional frame by casting with a die casting machine, and the projecting portion 25. The protruding plate part 26, the large diameter part 27, the small diameter part 29, and the concave part 30 are integrally formed.
Further, as is particularly apparent in FIGS. 3 and 6, the frame half body 23 </ b> B is formed with a large-diameter portion 31 that accommodates the resolver 22 on the inner peripheral surface opposite to the frame half-body 23 </ b> A. A small-diameter portion 33 that is coupled to 31 and fits with a fixed bearing device 32 constituted by, for example, a deep groove ball bearing is formed, and a fin-like rib that protrudes in a radial direction at a position facing the resolver 22 in the outer peripheral portion A number 34 is integrally molded at a predetermined interval in the circumferential direction, and a cable outlet 35 is integrally molded at a position facing the protruding plate portion 26 of the frame half 23A in the outer peripheral portion.

Here, similarly to the frame half 23A of the frame half 23B, any one of aluminum, aluminum alloy, magnesium and magnesium alloy is cast by a die casting machine, and the large diameter portion 31, the small diameter portion 33, the rib 34 and the cable lead-out The mouth 35 is integrally molded.
As described above, both the frame halves 23A and 23B are manufactured by casting, but a portion requiring high accuracy such as an inlay portion is appropriately cut.
The stator 21 is fitted in the large diameter portion 27 of the frame half body 23A. As clearly shown in FIGS. 5 and 6, the stator 21 has a configuration in which T-shaped split cores 41 in which 12 electromagnetic steel plates are laminated are connected in an annular shape.

  As shown in FIG. 5, each of the divided cores 41 has a cross section perpendicular to the axial direction, and a stator yoke 42 whose outer peripheral surface is arcuate and extends in the circumferential direction, and a circle on the inner peripheral surface of the stator yoke 42. A magnetic leg portion 43 extending inward toward the central axis is formed at the center portion in the circumferential direction, and is formed of a T-shaped iron core. A hat portion 43 a is formed at the tip of the magnetic leg portion 43. A motor coil 44 is wound around the magnetic leg 43 by concentrated winding. The hat portion 43 a has a shape in which a slight slot opening width is formed in a state where 12 T-shaped split cores 41 are combined into an annular shape, and the slot opening width is a magnet wire used for the motor coil 44. Is set below the diameter. The surface of the stator yoke 42 fitted to the frame half 23A has substantially the same curvature as that of the frame, but since the portion of the magnetic leg 43 that is directly behind the neck is flattened, the surface of the stator yoke 42 goes to the frame half 23A. It becomes the shape which carries out line contact at two points at the time of fitting.

On the other hand, the slot side of the stator yoke 42 has a linear shape orthogonal to the neck centerline of the magnetic leg portion 43. The portion where the adjacent split core 41 abuts is a linear shape of ± 15 ° intersecting at the center of rotation with respect to the center line of the magnetic leg portion 43 to which the motor coil 44 is applied, and is in a shape in surface contact with each other. .
Further, convex half portions 45 each having a quarter of a cross section engaging with the concave portion 30 of the frame half body 23A are formed over the entire axial direction at both ends in the circumferential direction on the outer peripheral surface of the outer peripheral side base portion 42. Yes. Therefore, when the split cores 41 are connected to each other, as shown in an enlarged view in FIG. 5, the concave portions 30 that are engaged with the concave portions 30 formed in the frame half body 23A having a semicircular cross section at both the convex half portions 45 are the same. A convex portion 46 having a shape in which the central point is slightly shifted to the stator central axis side with respect to the central point of the concave portion 30 of the frame half body 23A is formed. Then, with the divided cores 41 connected in an annular shape, the convex portion 46 is welded by laser welding or the like, whereby the annular stator 21 is configured, and the stator 21 has a large diameter of the frame half body 23A. The convex portion 46 is engaged with the concave portion 30 and is fitted to the portion 27. At this time, the stator yoke butting portion 47 that abuts the yoke 43 of the stator 21 formed on the frame half body 23A and the stator tip butting portion 48 that abuts the tip of the stator 21 are in contact with the end face of the stator 21 at both portions. Further, a gap between the coil end at that portion is filled with a heat transfer body 49 made of an epoxy resin.

The end of each phase of the motor coil 44 is connected to a four-layered annular bus bar 50 that is insulated for each of the Y connection midpoint, U phase, V phase, and W phase, and this bus bar 50 is connected to the frame half body 23A. Shrink fit.
Thus, by using the split core system for the stator 21, a space for passing a winding nozzle necessary for winding in the integral core system, and a space for guiding the winding when dropping into the slot. For example, a useless slot space that is generated only for the winding configuration is not required, so that high-density winding is possible.

  In the split core 41, the slot opening width formed by the hat portion 43a is set to be equal to or smaller than the diameter of the magnet wire used for the motor coil 44, so that even if the motor coil 44 is loosened or disconnected, it becomes an air gap. Since it is not bitten, the steering wheel lock due to the motor lock, which is a failure that should not occur in the electric power steering apparatus, can be prevented.

Further, the divided core 41, the surface to be fitted to the frame halves 23A of the stator yoke 42, by which is shaped to line contact at two points during the frame fitting, the reaction force magnetic leg portion 56 at the time of torque generation Even if it is applied, the T-shaped split core 41 is unlikely to fall down, so noise and vibration can be reduced.
Further, in the T-shaped split core 41, the slot side of the stator yoke 42 is formed in a linear shape orthogonal to the center line of the neck of the magnetic leg portion 56, so that the stator yoke 42 does not interfere during winding, so that high-density winding is possible. A line is possible.

  Furthermore, in the T-shaped split core 41, a semi-cracked convex half 45 is provided on the outer peripheral side of the portion where the stator yoke 42 of the adjacent split core 41 abuts. The abutting area is larger than that of the divided core method, and the T-shaped split core 41 is not easily tilted even if a reaction force is applied to the magnetic leg portion 56 when torque is generated. Furthermore, since the convex half portion 45 protruding to the outer peripheral side is welded, the magnetic flux passing through the welded portion is small and the hysteresis loss can be reduced. These effects can reduce noise, vibration, and iron loss.

Further, since the convex portion 46 protrudes to the outer peripheral side, it is possible to prevent magnetic path narrowing due to the fact that the slot side of the stator yoke 42 has a linear shape orthogonal to the neck centerline of the magnetic leg portion 56. it can.
Moreover, since the convex part 46 has a large gap in the radial direction but almost no gap in the rotational direction with respect to the concave part 30 provided in the frame half 23A, when the divided cores 41 are welded to each other, The frame half body 23A can be shrink-fitted without removing beads and bulges generated in the above. Further, only the ambient temperature of the brushless motor 14 rapidly increases and only the frame half body 23A becomes high temperature, or the frame half body 23A is cracked due to an unexpected external force, etc. Since the stator 21 does not idle even when the tightening allowance is lost, it is possible to reliably cause a phenomenon such as torque reduction, torque ripple, torque difference due to the rotation direction, and self-steer that is a failure that should not occur in the electric power steering apparatus. Can be prevented.

Further, as described above, the concave portion 30 of the frame half body 23A extends in the same shape from the side where the frame half body 23B is attached to the stator fitting portion to a position slightly deeper than the stator yoke butting portion. There is no need to change the shape of the electromagnetic steel sheet depending on the direction of the accumulated pressure, and the stator 21 can be composed of a T-shaped electromagnetic steel sheet having the same shape.
These features are obtained by connecting the same number of T-shaped split cores 41 as the number of slots, and the same effect can be obtained even when applied to a developed core type stator that becomes an annular stator 21 by bending the connecting portion. It is done.
In addition, a resolver stator 21 s constituting the resolver 22 is fitted in the large diameter portion 31 of the frame half body 23B.

  On the other hand, on the frame halves 23A and 23B, a rotor 51 is rotatably supported by a preload bearing device 28 and a fixed bearing device 32 held by them. The rotor 51 is formed between the output shaft 52 protruding from the frame half body 23A, the small diameter portions 53 and 54 fitted into the inner rings of the preload bearing device 28 and the fixed bearing device 32, and the small diameter portions 53 and 54. A shaft 56 having a large-diameter portion 55, a magnetic pole portion 57 fixed at a position facing the stator 21 of the shaft 56, and a small-diameter portion 54 are disposed outside, and the resolver 22 is opposed to the resolver stator 21s. It is comprised with the resolver rotor 22r to comprise. Thus, the rotor 51 is assembled in the order of the preload bearing device 28, the magnetic pole portion 57, the fixed bearing device 32, the resolver rotor 22r, and the lock nut 75 when viewed from the flange portion 24 side of the frame half body 23A.

  Here, as clearly shown in FIG. 6 in particular, the magnetic pole portion 57 includes a cylindrical rotor yoke 58 through which the shaft 56 is inserted, and eight permanent magnets bonded to the outer peripheral surface of the rotor yoke 58 at equal intervals in the circumferential direction. The magnet 59 includes a cap 60 made of austenitic nonmagnetic stainless steel that covers the outer peripheral surfaces of the permanent magnets 59. And the permanent magnet 59 used as a magnetic pole is a segment magnet divided | segmented for every pole, The shape is formed in the saddle shape which shifted the circular arc center of the outer peripheral side intentionally from the rotation center.

  The outer peripheral part of the permanent magnet 59 constituting the magnetic pole part 57 is covered with a cap 60, and the cap 60 is a clearance fit, but is fixed to the permanent magnet 58 by using an adhesive together. It is fixed more firmly by caulking the end face of the steel plate with rivets. Further, the preload bearing device 28 prevents the excessive preload due to the displacement between the shaft 56 and the inner ring by fitting the retaining ring 61 after the inner ring is press-fitted into the shaft 56. Further, the fixed bearing device 32 prevents the shaft 56 and the inner ring from being displaced due to the axial load applied to the shaft 56 by press-fitting the inner ring into the shaft 56 and then tightening the inner ring with the lock nut 75 via the resolver rotor 22r.

The resolver rotor 22r has a small diameter of a resolver shaft 73 that is externally fitted to a shaft 56 having a large diameter portion 71 that abuts the inner ring of the fixed bearing device 32 in the axial direction and a small diameter portion 72 that is connected to the large diameter portion 71. It is fitted on the portion 72 and its axial position is fixed by a lock nut 75.
And the brushless motor 14 which has the said structure is attached to the reduction gear 13 as a to-be-attached part as shown in FIG. Here, as shown in FIG. 7, the reduction gear 13 is rotatably supported by the housing 81 and the worm gear 84 that is rotatably supported by the housing 81 by a pair of bearing devices 82 and 83 and meshes with the worm gear 84. The worm wheel 85 is supported.
A motor mounting portion 86 is formed on an end surface orthogonal to the central axis of the worm gear 84 of the housing 81, and the mounting end of the frame half body 23 </ b> A of the brushless motor 14 is in-line coupled to the motor mounting portion 86, and the flange portion 24. Is screwed.

Next, the operation of the first embodiment will be described.
Assuming that the vehicle is now stopped, in this state, when the steering wheel 3 is turned to the right (or left), the steering torque applied to the steering wheel 3 is the steering torque. The detected steering torque detected by the sensor 5 is input to the control device 16, and the zero vehicle speed detection value detected by the vehicle speed sensor 15 is input to the control device 16.

  For this reason, the control device 16 refers to the control map based on the steering torque and the detected vehicle speed value, calculates a relatively large steering assist command value, and feeds back the deviation between the steering assist command value and the detected motor current value. A motor current command value is calculated by performing control, and this motor current command value is output to the motor drive circuit 17, so that the motor drive circuit 17 performs three-phase based on the rotor rotation angle detected by the resolver 22. A motor current is output to the brushless motor 14.

Accordingly, the brushless motor 14 is rotationally driven to generate a relatively large steering assist force, which is transmitted to the worm gear 84 of the reduction gear 13 through the output shaft 52 and meshed with the worm gear 84. A large steering assist torque can be applied to the output shaft 4b of the steering shaft 4 in the same direction as the rotation direction of the steering wheel 3 by rotating the shaft 85, and the steering wheel 3 can be lightly steered.
When the vehicle is driven from this state, the calculated steering assist command value becomes a small value even if the steering torque is the same as the vehicle speed detection value increases, and the brushless motor 14 is driven to rotate accordingly. The steering assist force generated by the brushless motor 14 is smaller than that at the time of stationary, and the optimum steering assist force corresponding to the vehicle speed can be generated.

  At this time, a relatively large motor current is supplied to the motor coil 44 of the stator 21 in the brushless motor 14 to generate a rotating magnetic field to rotationally drive the rotor 51. However, the motor driving current is large. Due to the current, the motor coil 44 generates heat. This heat generation is conducted to the frame half body 23a through the split core 41 of the stator 21, and the frame half body 23a is any one of aluminum, aluminum alloy, magnesium and magnesium alloy having a higher thermal conductivity than a normal steel frame. In addition, since the flange portion 24 attached to the motor attachment portion 86 in the housing 81 of the reduction gear 13 as the attachment portion is integrally formed by casting, the frame half body 23A and the flange portion 24 are Since there is no joint between them and the thermal resistance between the stator and the housing 81 of the reduction gear 13 is reduced, the heat generated in the motor coil 44 is effectively transferred to the housing 81 of the reduction gear 13 and the motor coil. The copper loss which 44 can accept | permit can be made larger than a prior art example. In addition, since the stator 21 is disposed on the flange portion 24 side, the distance between the stator 21 and the housing 81 of the reduction gear 13 can be minimized so that the thermal resistance can be reduced, and a greater heat transfer effect can be achieved. can do.

  Furthermore, in the above embodiment, since any one of aluminum, aluminum alloy, magnesium and magnesium alloy is cast by a die-cast machine, the wall thickness is reduced as in the case of squeezing a thin steel plate as in the conventional example. Since there is no restriction and the specific gravity is about 1/3 that of the thin steel plate, the thickness can be about three times as large as the thickness of the cylindrical portion of the conventional thin steel plate frame. In addition, the aluminum alloy is a material having a thermal conductivity three times that of iron, and further provided with a stator tip abutting portion 48 and filled with a heat transfer body 49 between the coil ends, thereby causing a copper loss. The heat of the coil end can be transferred to the frame half body 23 </ b> A via the stator tip butting portion 48 and the heat transfer body 49. Because of these effects, the amount of heat more than 10 times can be transferred to the housing 81 of the reduction gear 13 while the frame has the same weight as the conventional example, so that the copper loss that the motor coil 44 can tolerate is significantly larger than the conventional example. can do.

  In addition, since the magnetic pole portion 57 of the rotor 51 and the stator 21 have a slot combination of 8 poles and 12 slots, the configuration is four times that of the most basic 2 pole 3 slot type. As described above, the configuration of the magnetic pole portion 57 and the stator 21 is 2n times as large as the basic configuration (n is an integer), so that there is an advantage that the rotor vibration during rotation can be reduced because the radial magnetic attractive force is canceled. Further, since the winding coefficient of this slot combination is “0.866” and concentrated winding, there is an advantage that a large torque can be obtained against copper loss.

  However, since the amount of change in interlinkage magnetic flux due to each magnetic pole appears directly as cogging torque and torque ripple, the cogging torque and torque ripple that give the driver unpleasant vibration and noise are reduced for application to the electric power steering system. There is a need to. In the present embodiment, the permanent magnet 59 serving as the magnetic pole is a segment magnet divided for each pole, and the shape thereof is formed in a saddle shape in which the arc center on the outer peripheral side is intentionally shifted from the rotation center. With such a magnetic pole, the amount of change in the interlinkage magnetic flux can be converted into a sine wave, and the cogging torque and the torque ripple when the sine wave is energized can be reduced.

  Further, in the frame half body 23B, the fin-like ribs 34 are provided at positions where the resolver 22 is included, so that heat transfer by conduction, convection, and radiation to the atmosphere environment of this part is increased as compared with the conventional example. In addition, the fixed side of the resolver 22 is not easily affected by the heat generated by the copper loss of the motor coil 44, and it is possible to prevent drift of the resolver signal, a decrease in accuracy, and malfunction.

  Further, since the resolver 22 is disposed at the nearest position of the fixed bearing device 32, the axial displacement between the resolver stator 21s and the resolver rotor 22r is prevented by the difference in linear expansion coefficient between the frame material and the shaft material when the motor temperature changes. be able to. In particular, in the case of a combination having a large difference in linear expansion coefficient between the shaft material and the frame material as in this embodiment, the effect is remarkable.

Further, by mechanically positioning the magnetic pole part 57 and the resolver rotor 22r, there is no torque drop or torque ripple that occurs when the phase of both of them deviates, a torque difference due to the rotation direction, or even an electric power steering device. It is possible to surely prevent a phenomenon such as self-steering.
Further, by covering the permanent magnet 59 constituting the magnetic pole portion 57 with the cap 60, even if the permanent magnet 59 is chipped or cracked, or the permanent magnet 59 is peeled off from the rotor yoke 58, the permanent magnet 59 is in the air. Since it does not bite into the gap, it is possible to reliably prevent the wheel steering lock due to the motor lock, which is a failure that should not occur in the electric power steering apparatus.

Next, a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment, the frame halves 23A and 23B divided into two in the first embodiment described above are integrally configured.
That is, in the second embodiment, as shown in FIG. 8, a flange portion 42 is integrally formed on the outer peripheral portion, and a large-diameter portion 91 that houses the stator 21, and a fixed bearing device that is connected to the large-diameter portion 91. A cylindrical frame 23 having a small-diameter portion 92 that fits 32 and a middle-diameter portion 93 that accommodates the resolver 22 connected to the small-diameter portion 92 is configured, and the end surface of the frame 23 on the flange portion 24 side A bearing holder 94 for housing the preload bearing device 28 is connected in-situ, and a bus bar 50 for connecting the terminal ends of the motor coils 44 of each phase and a cable outlet 35 of the motor cable are arranged on the flange portion 24 side. 4 has the same configuration as that of the above-described first embodiment except that it is the same as that of the first embodiment. Fine description thereof will be omitted this.

  According to the second embodiment, in addition to the structure of the frame 23 being integrated, the bus bar 50 that connects the terminal ends of the motor coils 44 of the respective phases is arranged on the flange portion 24 side, so that the fins are fixed to the stator 21. Since the contact portion between the portion where the rib 34 is provided is eliminated and the distance from the stator 21 to the portion where the fin-like rib 34 is provided is shortened, the copper loss that the motor coil 44 can tolerate is further increased. can do.

In addition, in the said 1st and 2nd embodiment, although the case where the stator 21 was made into the split core system was demonstrated, it is not limited to this, The expansion | deployment core system which forms the stator integrated with the laminated steel plate It may be.
In the first and second embodiments, the case where the resolver 22 is applied as a rotation angle detector that detects the rotor rotation angle has been described. However, the present invention is not limited to this. Arbitrary rotation angle detectors, such as a detection element and a rotary encoder, can be applied.

Furthermore, although the case where the frame halves 23A and 23B are cast in the first embodiment and the frame 23 is cast using a die cast machine in the second embodiment is described, the present invention is not limited to this. In the case of sand mold, magnesium and magnesium alloy, other casting methods such as injection molding may be applied.
Furthermore, in the first and second embodiments described above, the case where the brushless motor 14 of the present invention is applied to an electric power steering apparatus has been described. The present invention can be applied as a rotational drive source for arbitrary devices such as in-vehicle devices.

It is a schematic block diagram which shows 1st Embodiment at the time of applying the brushless motor by this invention to an electric power steering apparatus. It is an external appearance perspective view of the flange part side of the brushless motor of this invention. It is an external appearance perspective view by the side of the frame half body 23B of the brushless motor by this invention. FIG. 3 is an enlarged vertical sectional view of the brushless motor of FIG. 2. It is sectional drawing on the AA line of FIG. It is a disassembled perspective view of the brushless motor of this invention. It is sectional drawing which shows the state which attached the brushless motor of this invention to the reduction gear. It is a longitudinal cross-sectional view which shows the 2nd Embodiment of this invention. It is a B arrow external view of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering mechanism, 3 ... Steering wheel, 4 ... Steering shaft, 4a ... Input shaft, 4b ... Output shaft, 10 ... Steering gear, 12 ... Steering assist mechanism, 13 ... Reduction gear, 14 ... Brushless motor, 16 ... control device, 17 ... motor drive circuit, 21 ... stator, 22 ... resolver, 23 ... frame, 23A, 23B ... half frame, 24 ... flange, 28 ... preload bearing device, 30 ... recess, 32 DESCRIPTION OF SYMBOLS ... Fixed bearing apparatus, 41 ... Split core, 42 ... Stator yoke, 43 ... Magnetic leg part, 44 ... Motor coil, 46 ... Convex part, 51 ... Rotor, 52 ... Output shaft, 57 ... Magnetic pole part, 58 ... Rotor yoke, 59 ... permanent magnet, 60 ... cap, 81 ... housing, 84 ... worm gear, 85 ... worm wheel, 86 ... motor mounting part, 9 ... large-diameter portion, 92 ... the small-diameter portion, 93 ... medium diameter

Claims (17)

A cylindrical stator around which a coil is wound, a rotor having a magnetic pole and an output shaft opposed to the stator, an angle detector for detecting the rotation angle of the rotor, and a frame that houses the stator and the angle detector And a brushless motor having a bearing device that rotatably supports the rotor with respect to the frame,
The frame includes a frame half in which a flange portion fixed to the attached portion is integrally formed at an end, and the stator is accommodated, and a frame half that accommodates the angle detector, and accommodates the stator. A stator yoke abutting portion for abutting the yoke of the stator on the inner side of the small-diameter portion on the inner surface of the flange portion side end portion of the frame half body, and a stator tip abutting portion for abutting the tip of the stator; A brushless motor , wherein one end face of the stator is brought into contact with both a yoke abutting portion and a stator tip abutting portion . The brushless motor according to claim 1, wherein the frame half that houses the stator is formed of a material having high thermal conductivity. The brushless motor according to claim 2, wherein the frame half that houses the stator is formed of any one of aluminum, an aluminum alloy, magnesium, and a magnesium alloy. The brushless motor according to any one of claims 1 to 3, wherein the frame half that houses the stator is integrally formed by casting. A transmission formed of a material having a thermal conductivity higher than that of air in at least one of the gaps existing between the coil end portions projecting on both end faces of the stator and the small-diameter portion of the frame half that houses the stator. The brushless motor according to any one of claims 1 to 4, wherein a heat material is interposed. The output shaft is disposed on the flange side of the frame , and a preload-side bearing device, a magnetic pole of the rotor, a fixed-side bearing device, and the angle detector are disposed in that order with respect to the output shaft. The brushless motor according to claim 1, wherein the brushless motor is provided. Brushless motor according to any one of claims 1 to 6, characterized in that the fin-like ribs are formed a large number on the outer periphery of the frame halves to accommodate a pre-Symbol angles detector. The brushless motor according to claim 7, wherein the rib is formed integrally with a half frame that houses the angle detector . Frame half which accommodates the stator, the formed one or more recesses in the mating surface of the stator, the stator protrusion for engaging in the recess in the fitting surface between the frame halves are formed The brushless motor according to claim 1, wherein the brushless motor is provided. The brushless motor according to claim 9, wherein the concave portion is integrally formed with a frame half that houses the stator .   The brushless motor according to claim 9, wherein the recess is configured by a groove extending in an axial direction.   The brushless motor according to claim 11, wherein a length of the concave portion is selected to be equal to or longer than an axial length of the stator.   The brushless motor according to any one of claims 9 to 12, wherein the convex portions of the stator are arranged in the same number as the number of slots and at equal intervals. The stator includes a stator yoke that extends in a circumferential direction that fits into a frame half that houses the stator, and a magnetic leg that extends inward from a circumferential central portion of the stator yoke and on which a motor coil is wound. A plurality of split cores having a T-shaped cross section perpendicular to the axial direction at the portion are connected to the circumferential ends of the stator yokes of the adjacent split cores at both ends in the circumferential direction of the stator yoke. The brushless motor according to any one of claims 1 to 13, wherein the brushless motor is formed in an annular shape.   15. The brushless motor according to claim 14, wherein the split core is formed with projecting half portions constituting projecting portions engaging with the recessed portions at both ends in the circumferential direction of the outer peripheral surface of the stator yoke. The brushless motor according to claim 15, wherein each divided core is connected in an annular shape by welding the halves of adjacent divided cores.   An electric power steering device, wherein the brushless motor according to any one of claims 1 to 16 is applied as a motor that generates a steering assist force transmitted to a steering mechanism.

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