JP2007259561A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor that makes it possible to meet demand for size reduction and reduce a number of parts, by devising the disposition of a rotor and a rotation detecting means. <P>SOLUTION: The motor 1 includes: the cylindrical rotor 4 rotatably supported in a housing 2 and the rotation detecting means 9 for detecting the rotational position of the rotor 4, disposed inside the rotor 4. The rotation detecting means 9 includes: a core 9a part of which is fixed on the housing 2 and which has an extended portion extended inward of the rotor 4 and a coil 9c provided on the extended portion; and an annular magnetic material 9d that is fixed on the inner surface of the rotor 4 and an uneven surface 9e formed by providing its portion opposed to the core 9a with recesses and projections arranged in the circumferential direction. Thus, the magnetic material 9d fixed on the inner surface of the rotor 4 is taken as an object of detection for detecting the rotational position of the rotor 4. Therefore, it is possible to reduce the size of and the number of parts of the motor 1 and simplify its structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor that is miniaturized by devising the arrangement of a rotor and rotation detection means.

  The electric power steering device drives a steering assist motor in accordance with the rotation operation of the steering wheel, assists the steering by adding the rotational force of the motor to the steering mechanism, and depends on the mounting position of the motor. Type, rack assist type, etc. In the column assist type, a motor is attached to the outside of the column housing that supports the steering shaft, and there is a demand for miniaturization of the motor as much as possible in order to secure sufficient space for the driver's feet in the passenger compartment. is there. In addition, the rack assist type has a motor mounted on a rack housing in the engine room, and is arranged in a limited space in the engine room. Similarly, there is a demand for miniaturizing the motor as much as possible. There is.

  Brushless motors are widely used as steering assist motors. In a brushless motor, rotation detection means for detecting the rotation position of the rotor is necessary for drive control of the motor, and this rotation detection means is generally disposed on one side of the rotor. It became longer in the axial direction and required a large arrangement space. Thus, in order to reduce the size of the motor, proposals have been made in which the arrangement of the rotor and the rotation detecting means is devised (see, for example, Patent Document 1).

In Patent Document 1, a resolver is mainly used as rotation detection means. The resolver detects the rotational position using the fact that the inductance of the stator winding changes according to the rotation angle when the magnetic rotor and the stator with the winding rotate on the same axis. It has a known configuration. In Patent Document 1, a rotor core is attached to the outer periphery of a rotating body fixed to a rotating shaft of a motor, and the stator core is fixed to the inner periphery of a fixed cylinder fixed to the motor housing and surrounding the outer side of the rotating body. Mounting and arranging these rotating bodies and fixed cylinders so as to overlap the inside or outside of the rotor constitutes a resolver, thereby reducing the space required for the resolver on one side of the rotor and reducing the size of the motor. Has achieved.
Japanese Utility Model Publication No. 5-23775

  However, in this configuration, the resolver configured separately from the rotor is merely arranged so as to overlap in the radial direction of the rotor, and the rotor core and the stator core, and the rotating body for attaching them. And a fixed cylinder are required, and there are problems that the number of parts is large and the configuration is complicated.

  Patent Document 1 also describes a configuration using other rotation detection means such as an optical sensor and a magnetic sensor. Also in these, a rotating body that rotates integrally with the rotor is provided on the rotating shaft of the motor, and the detection target provided on the rotating body is detected by each detecting means, and the number of parts is the same as in the resolver. There are many problems that the configuration is complicated.

  The present invention has been made in view of such circumstances, and the arrangement of the rotor and the rotation detection means is devised, and the rotor also serves as a rotating body of the rotation detection means, so that the number of parts can be met while meeting the demand for downsizing. An object of the present invention is to provide a motor capable of reducing the above and simplifying the configuration.

  According to a first aspect of the present invention, there is provided a motor comprising: a cylindrical rotor rotatably supported by a housing; and a rotation detection unit that is disposed inside the rotor and detects a rotation position of the rotor. The detection means includes a core part of which is fixed to the housing and extends to the inside of the rotor, a coil provided on the extension part, a core that is fixed to the inner surface of the rotor, and the core And an annular magnetic body having a concavo-convex surface formed by arranging concavo-convex in the circumferential direction on the opposite portion.

  The motor according to the second invention is characterized in that the uneven surface in the first invention is a corrugated surface.

  According to the first invention, an annular magnetic body having a concavo-convex surface is fixed to the inner surface of the rotor, and the inductance of the coil provided in the core extending inside the rotor changes according to the position facing the concavo-convex surface. Since the rotational position of the rotor is detected using the magnetic material fixed to the rotor as the detection target, the motor can be reduced in size while reducing the number of parts and simplifying the structure. Can be

  According to the second invention, since the uneven surface is a corrugated surface, the rotation detecting means obtains an output that gradually changes according to the rotation of the rotor as an output value, and accurately detects the rotational position of the rotor. Can do.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a longitudinal sectional view schematically showing a configuration of a motor according to Embodiment 1 of the present invention, and FIG. 2 is a magnetic body used in rotation detection means provided in the motor of Embodiment 1. FIG. As shown in FIG. 1, the motor 1 includes a stator 3 that is fitted and fixed to an inner peripheral surface of a cylindrical housing 2, and a rotor 4 that is rotatably supported inside the housing 2.

  On the inner circumference of the stator 3, a plurality of cores are equally arranged in the circumferential direction so as to face each other, and a coil is provided in each core, and a magnetic pole is formed by flowing current through the coils.

  The rotor 4 includes a disc portion 4a that is press-fitted and fixed to the rotary shaft 5, and a cylindrical portion 4b that is coaxially connected to the outer peripheral edge of the disc portion 4a. A plurality of permanent magnets 6, 6... Are fixedly arranged on the outer surface of the cylindrical portion 4 b of the rotor 4 so that the polarities are alternately arranged in the circumferential direction. The housing 2 has end walls on both sides in the axial length direction, each of the end walls is provided with an opening, and the bearings 7 and 8 are respectively fitted in the openings of the end walls. . As shown in the figure, the bearings 7 and 8 support the rotating shaft 5 at positions on both sides of the rotor 4, and the rotor 4 is aligned with both ends of the stator 3 in the axial direction, and has a slight air gap in the radial direction. They are opposed to each other.

  In the motor 1 configured as described above, currents are passed through two opposing coils of the stator 3 to form magnetic poles, respectively, and these two magnetic poles generate a field as a set, and currents that flow through these sets of coils. Are rotated in one direction, and the permanent magnets 6, 6... Receive a rotational force from the rotating field, and the rotor 4 rotates.

  The motor 1 according to the present invention operating in this way detects the rotational position of the rotor 4 in order to switch the current flowing through the coils of the stator 3 in a timely manner in accordance with the positions of the permanent magnets 6, 6. A rotation detecting means 9 is provided. The rotation detection means 9 includes a core 9a and a magnetic body 9d.

  The core 9a includes a cylindrical portion and a plurality of projecting portions 9b that project from the one end surface of the cylindrical portion so as to be evenly spaced in the circumferential direction. Coils 9c are provided on the protruding portions 9b of the core 9a. Such a core 9a is inserted into the rotor 4 on the protruding portion 9b side, and is positioned so that the end surfaces of the protruding portions 9b face the inner surface of the rotor 4 with an appropriate distance from each other. It is being fixed to the inner surface of the housing 2 at the other end surface of a part.

  The magnetic body 9d is an annular member having substantially the same diameter as the core 9a. As shown in FIG. 2, an uneven surface 9e formed by arranging unevenness in the circumferential direction is formed on one end surface. The contour shape of the concavo-convex surface 9e is a waveform, and the plurality of concave portions and convex portions are formed so as to have the same shape. Such a magnetic body 9d is positioned so that the convex portion of the uneven surface 9e faces the protruding portion 9b of the core 9a with a slight air gap therebetween, and the disc portion of the rotor 4 on the other side plane. It is fixed to the inner surface of 4a.

  In the rotation detection means 9 configured as described above, when the rotor 4 rotates, the magnetic body 9d also rotates with this rotation. Since the magnetic body 9d has an uneven surface 9e having a wavy contour shape, the distance between the magnetic body 9d and the projecting portion 9b changes periodically and periodically according to the rotation of the rotor 4. In this state, when an electric current is passed through the coil 9c of the projecting portion 9b, the output voltage of the coil 9c periodically changes gradually according to the change in the distance between the magnetic body 9d and the projecting portion 9b as described above. It will be. The obtained output voltage is a two-phase AC voltage that is 90 degrees out of phase, as in a known resolver, and the rotational position of the rotor 4 can be obtained from this output voltage.

  As described above, in the motor 1 shown in FIG. 1, the rotation detecting means 9 is fixed to the inner surface of the housing 2 and the core 9a provided with the coil 9c, and the disk portion 4a of the rotor 4 so as to face the core 9a. Since the rotor 4 also serves as the rotating body of the rotation detecting means 9, the number of parts can be reduced and the structure can be simplified. Further, it is not necessary to secure a space for arranging the rotation detecting means 9 on one side of the rotor 4, and the motor 1 can be reduced in size.

  The motor 1 configured as described above is used, for example, as a steering assist motor of an electric power steering apparatus. FIG. 3 is a schematic diagram showing an example of an electric power steering apparatus including the motor 1 according to the present invention.

  The electric power steering apparatus includes a rack shaft 20 that is supported so as to be movable in the axial direction in a rack housing 21 that extends in the left-right direction of a vehicle body (not shown), and a pinion housing 31 that crosses the rack housing 21 in the middle. And a known rack and pinion type steering mechanism including a pinion shaft 30 rotatably supported therein. Both ends of the rack shaft 20 projecting outward from both sides of the rack housing 21 are connected to the left and right front wheels 23, 23 via separate tie rods 22, 22, and pinions projecting outward from one side of the pinion housing 31. The upper end of the shaft 30 is connected to the steering wheel 41 via the steering shaft 40. A pinion (not shown) is formed at the lower portion of the pinion shaft 30 extending into the pinion housing 31. The pinion is formed on the outer surface of the rack shaft 20 at an appropriate length at the intersection with the rack housing 21. Meshed with the rack teeth.

  With the above configuration, when the steering wheel 41 is rotated for steering, this rotation is transmitted to the pinion shaft 30 via the steering shaft 40, and the rotation of the pinion shaft 30 is caused in the axial direction of the rack shaft 20. As a result of this movement, the left and right front wheels 23, 23 are pushed and pulled through the respective tie rods 22, 22 to steer.

  In the middle of the column housing 42 that supports the steering shaft 40, a torque sensor 50 that detects a steering torque applied to the steering shaft 40 by a rotation operation of the steering wheel 41 is provided, and the present invention is located below the torque sensor 50. The motor 1 which concerns on is attached.

  The motor 1 is attached to the outside of the column housing 42 with its axis substantially orthogonal, and for example, a worm fixed to an output end extending inside the column housing 42 is attached to a worm wheel that is externally fixed to the steering shaft 40. The transmission is configured so that the rotation of the motor 1 is decelerated by the worm and the worm wheel and transmitted to the steering shaft 40. According to this configuration, the rotation of the motor 1 is transmitted to the steering shaft 40 at a reduced speed, and a rotational force is applied to the pinion shaft 30 connected to the lower end of the steering shaft 40. The steering performed as described above is assisted.

  The motor 1 is driven in accordance with a control command given from the assist control unit 60 via a motor drive circuit (not shown). The detected value of the steering torque by the torque sensor 50 is given to the assist control unit 60. The assist control unit 60 issues a control command to the motor 1 based on this, and performs an assist control operation for increasing / decreasing the driving current of the motor 1. Do. Further, the motor 1 for steering assistance is provided with a motor current sensor 11, and the detected value of the drive current of the motor 1 by the motor current sensor 11 is given to the assist control unit 60, and the motor current value and the drive current value are And a feedback control is performed to correct the drive current supplied to the steering assist motor 1 based on the deviation.

  The motor 1 according to the present invention used in the electric power steering apparatus configured as described above is shortened in length in the axial direction. Therefore, in the column assist type electric power steering apparatus in which the motor 1 is attached to the outside of the column housing 42 as shown in the figure and is configured to transmit to the steering shaft 40, the protrusion length of the motor 1 to the outside of the column housing 42 is shown. Therefore, the driver's foot space in the passenger compartment can be sufficiently secured.

  On the other hand, in the rack assist type electric power steering apparatus in which the motor 1 is attached to the rack housing 21 and is configured to transmit power to the rack shaft 20, the motor 1 is downsized, which leads to securing the engine room space. For example, it becomes easy to secure a crushable zone for absorbing impact energy at the time of an automobile collision and to secure an installation space when the motor 1 is increased in output for a medium-sized vehicle.

  FIG. 4 is a longitudinal sectional view schematically showing the configuration of the motor according to the second embodiment of the present invention, and FIG. 5 is a magnetic body used in the rotation detecting means provided in the motor according to the second embodiment. FIG.

  In the second embodiment, the core 9a of the rotation detecting means 9 includes a cylindrical portion and a plurality of protruding portions 9b that protrude outward and are equally distributed in a direction orthogonal to one end surface of the cylindrical portion. It has. Coils 9c are provided on the protruding portions 9b of the core 9a. Such a core 9a is positioned so that the protruding portion 9b side is inserted inside the rotor 4 and the end surface of the protruding portion 9b is opposed to the inner peripheral surface of the rotor 4 with an appropriate distance therebetween. The other end surface of the cylindrical portion is fixed to the inner surface of the housing 2.

  The magnetic body 9d is an annular member having an outer diameter that is substantially the same as the inner diameter of the cylindrical portion 4b of the rotor 4, and as shown in FIG. 5, the inner circumferential surface is provided with unevenness in the circumferential direction. An uneven surface 9e is formed. The uneven surface 9e is a corrugated surface having a corrugated contour shape, and the shapes of the plurality of concave portions and convex portions are respectively the same. Such a magnetic body 9d is positioned so that the convex portion of the concave-convex surface 9e faces the protruding portion 9b of the core 9a with a slight air gap, and the inner surface of the cylindrical portion 4b of the rotor 4 is positioned on the outer peripheral surface. It is internally fitted and fixed to the peripheral surface.

  As described above, in the motor 1 shown in FIG. 4, the rotation detecting means 9 is fixed to the inner surface of the housing 2, and the core 9a provided with the coil 9c and the cylindrical portion 4b of the rotor 4 so as to face the core 9a. Since the magnetic body 9d fixed to the inner peripheral surface is provided, the diameter of the magnetic body 9d can be made larger than that in the first embodiment, and the rotational position of the rotor 4 can be detected with higher accuracy.

  Since other configurations are the same as those of the first embodiment shown in FIG. 1, the same reference numerals as those in FIG. 1 are attached to corresponding components, and detailed description of the configurations and operations is omitted.

  The motor 1 in the above-described embodiment is configured so that the core 9a of the rotation detecting means 9 and the magnetic body 9d face each other in either the axial length direction or the radial direction of the rotating shaft 5. Needless to say, both may be combined. The magnetic body 9d described above has the concavo-convex surface 9e having a corrugated contour shape. However, the contour shape of the concavo-convex surface 9e may be a shape other than a corrugated shape such as a rectangle or a sawtooth shape.

1 is a longitudinal sectional view schematically showing a configuration of a motor according to Embodiment 1 of the present invention. FIG. 3 is a perspective view of a magnetic body used in rotation detection means provided in the motor according to the first embodiment. It is a mimetic diagram showing an example of an electric power steering device provided with a motor concerning the present invention. It is a longitudinal cross-sectional view which shows schematically the structure of the motor which concerns on Embodiment 2 of this invention. It is a perspective view of the magnetic body used for the rotation detection means with which the motor of Embodiment 2 was equipped.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor, 2 Housing, 3 Stator, 4 Rotor, 5 Rotating shaft, 6 Permanent magnet, 7, 8 Bearing, 9 Rotation detection means, 9a Core, 9c Coil, 9d Magnetic body, 9e Uneven surface

Claims (2)

  A motor comprising: a cylindrical rotor rotatably supported by a housing; and a rotation detection means that is disposed inside the rotor and detects a rotation position of the rotor. The rotation detection means is connected to the housing. The core is fixed to the inner surface of the rotor and has an extending portion that extends to the inside of the rotor, and the inner surface of the rotor is fixed to the inner surface of the rotor. And a ring-shaped magnetic body having an uneven surface formed in parallel.   The motor according to claim 1, wherein the uneven surface is a corrugated surface.

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