JP2009171679A - Method of manufacturing segment magnets and method of manufacturing electric power steering devices - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a segment magnet that reduces cogging torque of a motor, and to prvide a method of manufacturing an electric power steering device that improves steering feeling. <P>SOLUTION: In the method of manufacturing segment magnets 52, magnetic powder is molded into a prism 50 having a rectangular sectional shape and is sintered; the sintered prism 50 is longitudinally cut into three or more magnetic plates 51 in the direction X of the long sides of the rectangle as its sectional shape; and magnetic flux is applied to these magnetic plates 51 in the direction of plate thickness to magnetize them. Thus multiple segment magnets 52 that can be used for the rotor 22 of a motor 20 are manufactured. In the process of molding the magnetic powder into the prism 50, pressure is applied to the prism 50 in the direction Z of its long axis and at the same time magnetic flux is applied to the prism 50 in the direction X of the long sides of the rectagule as its sectional shape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a plurality of segment magnets that can be attached to a rotor of a motor, and a method for manufacturing an electric power steering apparatus using a motor having these segment magnets as a drive source.

Conventionally, as a manufacturing method of this kind of segment magnet, there is known a manufacturing method in which a magnetic plate having the same shape as a segment magnet is formed from a magnetic powder, then sintered and further magnetized to complete a segment magnet. (For example, refer to Patent Document 1). As another conventional segment magnet manufacturing method, the prism 1 shown in FIG. 11 is formed from magnetic powder and then sintered, and the prism 1 is divided into a plurality of magnetic plates 2. A method is known in which one segment in the thickness direction is processed into a curved shape and then magnetized to complete the segment magnet 3. Further, in this manufacturing method, in order to easily magnetize the segment magnet, a magnetic flux is applied to the prism 1 at the time of molding together with pressure so as to be oriented (magnetic orientation). The orientation direction is shown as an arrow in FIG.
JP 2003-230239 A (paragraph [0005], FIG. 5 (b))

  By the way, in the conventional manufacturing method described above, in the step of forming the prism 1, the magnetic flux is applied to the long side direction H1 of the rectangle which is the cross-sectional shape of the prism 1, while the pressure is applied to the short side H2. . For this reason, the outer surface orthogonal to the pressurizing direction (short side direction H2) of the prism 1 receives the frictional force from the inner surface of the molding die, and the orientation direction of the portion closer to the outer surface of the prism 1 (FIG. 11 (the direction of the arrow 11) may be inclined with respect to the magnetic flux application direction (long side direction H1). And since the sintered prismatic body 1 was divided | segmented into the some magnetic body plate 2 by the magnetic flux provision direction (long side direction H1), one pair located in the both ends of the magnetic flux provision direction among the prismatic bodies 1 The segment magnets 3A, 3A formed by magnetizing the magnetic plates 2A, 2A are magnetized so as to generate a magnetic flux in a direction inclined with respect to the width direction, and the other magnetic plates 2B, 2B,. The segment magnets 3B, 3B,... That are magnetized are magnetized so as to generate a magnetic flux in a direction orthogonal to the width direction. Therefore, when a motor (not shown) is manufactured with segment magnets 3A, 3B,... Manufactured by a conventional manufacturing method, between a plurality of segment magnets 3A, 3B attached to one rotor, The electrical angle at which the magnetic attraction force is greatest differs from the stator teeth (not shown), and the cogging torque is large. Further, in an electric power steering apparatus (not shown) using the motor as a drive source, there has been a problem that steering feeling is deteriorated.

  The present invention has been made in view of the above circumstances, and provides a method of manufacturing a segment magnet capable of reducing the cogging torque of a motor and a method of manufacturing an electric power steering device capable of improving steering feeling. aimed to.

  The method of manufacturing the segment magnet (52) according to the invention of claim 1 made to achieve the above object is to form a magnetic powder into a rectangular column (50) having a rectangular cross section by a molding die (60). The sintered prisms (50) are vertically divided into three or more magnetic plates (51) in the long side direction (X) of the rectangular shape which is the cross-sectional shape, and the magnetic materials are further divided. In a method for producing a plurality of segment magnets (52) usable for a rotor (22) of a motor (20) by applying a magnetic flux in the thickness direction of the plate (51) and magnetizing the magnetic powder, In the forming step of forming (50), pressure is applied to the long axis direction (Z) of the prismatic body (50), and magnetic flux is applied to the long side direction (X) of the rectangle which is the cross-sectional shape of the prismatic body (50). It has a feature in the place of giving.

  The method of manufacturing the segment magnet (52) according to the invention of claim 2 is to form a magnetic powder into a prismatic body (50) having a rectangular cross section with a molding die (60), and then sinter the sintered powder. The prismatic body (50) is vertically divided into three or more magnetic plates (51) in the long side direction (X) of the rectangle which is the cross-sectional shape, and further in the thickness direction of the magnetic plates (51). In a method for producing a plurality of segment magnets (52) usable for the rotor (22) of the motor (20) by applying a magnetic flux and magnetizing the magnetic powder into a prismatic body (50). It is characterized in that both magnetic flux and pressure are applied in the long side direction (X) of the rectangle which is the cross-sectional shape of the prismatic body (50).

  According to a third aspect of the present invention, there is provided a method of manufacturing the electric power steering apparatus (10), wherein the motor (20) including the segment magnet (52) manufactured by the method of manufacturing the segment magnet (52) according to the first or second aspect is electrically driven. It is characterized in that it is assembled as a drive source for the power steering device (10).

  In addition, in the manufacturing method of the segment magnet (52) of Claim 1 or 2, before the magnetization process which magnetizes a magnetic body plate (51), one side of a plate | board thickness direction is taken out of a magnetic body plate (51). Are processed into a curved surface (51W) that is curved in the width direction, and on the outer surface of the rotor (22) having a polygonal cross section, a flat surface on the opposite side of the curved surface (51W) of the magnetic plate (51) ( 51S) may be fixed, and a magnetic flux may be applied to the magnetic plate (51) fixed to the rotor (22) in the magnetizing step.

[Invention of Claim 1]
In the method of manufacturing a segment magnet according to the first aspect of the present invention, in the magnetic powder forming step, pressure is applied in the major axis direction of the prismatic body and magnetic flux is applied in the long side direction of the rectangle which is the cross-sectional shape of the prismatic body. Since the outer surface of the prismatic body receives frictional force from the inner surface of the molding die and the orientation direction of the portion near the outer surface has an inclination angle with respect to the magnetic flux application direction, the inclination angle is Although it may appear as an inclination angle with respect to the longitudinal direction of the magnetic material plate divided from the prism, it does not appear as an inclination angle with respect to the width direction. Therefore, regardless of whether or not the plurality of magnetic plates vertically divided from the prismatic body are magnetic plates located at both ends in the magnetic flux application direction, the segment magnet formed by magnetizing these magnetic plates is The magnet is magnetized so as to generate a magnetic flux in a direction orthogonal to the width direction. Therefore, in a rotor in which a plurality of segment magnets manufactured by the manufacturing method of the present invention are assembled, the electrical angle at which the magnetic attraction force is the greatest with respect to the teeth of the stator is the same between the segment magnets. Thus, the cogging torque can be suppressed.

[Invention of claim 2]
In the segment magnet manufacturing method according to the invention of claim 2, in the step of forming the prismatic body, both the magnetic flux and the pressure are applied in the long side direction of the rectangular shape having a cross-sectional shape. However, even if the frictional force is received from the inner surface of the molding die, the orientation direction of the portion near the outer surface is not inclined with respect to the magnetic flux application direction. Accordingly, regardless of whether or not the plurality of magnetic plates divided vertically from the prismatic body are magnetic plates positioned at both ends in the magnetic flux application direction, the segment magnet is formed by magnetizing the magnetic plates. Is magnetized so as to generate a magnetic flux in a direction orthogonal to the width direction. Therefore, in a rotor in which a plurality of segment magnets manufactured by the manufacturing method of the present invention are assembled, the electrical angle at which the magnetic attraction force is the greatest with respect to the teeth of the stator is the same between the segment magnets. Thus, the cogging torque can be suppressed.

[Invention of claim 3]
According to the method of manufacturing the electric power steering apparatus according to the invention of claim 3, the steering feeling of the electric power steering apparatus can be improved.

[First Embodiment]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a molding die 60 used in the segment magnet manufacturing method of the present embodiment. The molding die 60 includes a base die 61 and a movable die 62, and a prismatic molding chamber 63 is formed in the base die 61. The molding chamber 63 has an upper surface opening 63A that is open on the surface of the base mold 61 facing the movable mold 62, and the prismatic pressing protrusions 64 provided on the movable mold 62 extend from the upper surface opening 63A. The magnetic powder in the molding chamber 63 is molded into the prism body 50 by being inserted into the molding chamber 63. Here, in this embodiment, the direction from the upper surface opening 63 </ b> A to the back side in the molding chamber 63 is the major axis direction Z of the prismatic body 50.

  As shown in FIG. 2, the shape of the cross section orthogonal to the long-axis direction Z in the molding chamber 63 is a rectangle. Further, the base mold 61 is provided with an electromagnetic coil 65, and a magnetic flux directed in the long side direction X of a rectangle that is a cross-sectional shape of the molding chamber 63 can be applied to the magnetic powder in the molding chamber 63. Specifically, the opposing walls 63X and 63X of the base mold 61 that face each other in the long side direction X of the cross-sectional shape of the molding chamber 63 are made of a magnetic material, and the opposing walls 63Y that face each other in the short side direction Y. 63Y and the bottom wall 63S of the molding chamber 63 (see FIG. 1) and the pressing protrusion 64 (see FIG. 1) of the movable mold 62 are made of a non-magnetic material. The opposing walls 63X, 63X of the magnetic material are connected to each other outside the opposing wall 63Y of the non-magnetic material, thereby forming a C-shaped magnetic path 61J. The electromagnetic coil 65 is wound around a part of the magnetic path 61J.

  Hereinafter, a method for manufacturing the segment magnet 52 shown in FIG. 6 using the molding die 60 will be described. First, as a molding process, a predetermined amount of magnetic powder is stored in the molding chamber 63 of the base mold 61 shown in FIG. 1, and the pressing protrusion 64 of the movable mold 62 is pushed into the molding chamber 63 by a hydraulic press (not shown). At the same time, a direct current is applied to the electromagnetic coil 65. Then, the magnetic powder in the molding chamber 63 is molded into a prismatic body 50 having a rectangular cross section. At this time, the prismatic body 50 is shaped by receiving pressure directed in the long axis direction Z (see FIG. 3), and is oriented in the long side direction X (see FIG. 3) of the rectangle which is the cross-sectional shape of the prismatic body 50. Orientation (magnetic orientation) is performed by receiving magnetic flux.

  Next, a sintering process is performed in which the prismatic body 50 taken out from the molding die 60 is sintered in a heating furnace (not shown). Then, as shown in FIG. 4, the prismatic body 50 (see FIG. 3) taken out from the sintering furnace is divided into three or more (for example, five) magnetic plates 51 in the magnetic flux application direction. I do. In this processing step, one surface in the thickness direction of the magnetic plate 51 is processed into a curved surface 51W curved in the width direction.

  In the case of distinguishing the sintered magnetic body located at both ends in the magnetic flux application direction of the prismatic body 50 of the sintered magnetic body 51 from the sintered magnetic body located at the intermediate portion, it was located at both ends. The reference numeral “51A” is attached to the sintered magnetic body, the reference numeral “51B” is attached to the sintered magnetic body located in the middle portion, and the reference numeral “51” is attached when they are not distinguished.

  Next, an assembling step for fixing the magnetic material plate 51 to the outer surface of the rotor 22 shown in FIG. 5 is performed. Here, the rotor 22 has a structure in which the outer peripheral surface of the cylindrical body is planarized into a polygonal shape. In addition, the opposite side of the magnetic plate 51 to the curved surface 51W is a flat surface 51S, and an adhesive is applied to the flat surface 51S. Then, the rotor 22 is attached to the outside of the jig shaft 31 shown in FIG. 5, the rotational position of the rotor 22 is controlled by the servo motor 32, and the magnetic plate 51 is gripped by the hand 35 of a robot (not shown). Then, the flat surface 51S of the magnetic plate 51 is sequentially bonded and fixed to each flat surface of the rotor 22.

  Next, a magnetization process is performed. In this magnetizing step, an electromagnetic coil 69 is disposed oppositely to the magnetic plate 51 fixed to the rotor 22 as shown in FIG. As a result, the magnetic plate 51 is magnetized so that the N pole and the S pole are polarized in the orientation direction (magnetic orientation direction) of the magnetic plate 51, and the magnetic plate 51 becomes the segment magnet 52. Further, the direction of the magnetic flux is made different between the adjacent electromagnetic coils 69 and 69. Thereby, between the segment magnets 52 and 52 adjacent to each other on the outer surface of the rotor 22, the N pole and the S pole are magnetized so as to be opposite to each other.

  Here, in the present embodiment, as described above, in the step of forming the prismatic body 50, pressure is applied to the long axis direction Z (see FIG. 3) of the prismatic body 50, and a rectangular shape that is a cross-sectional shape of the prismatic body 50 is formed. Since the magnetic flux is applied in the long side direction X (see FIG. 3), the outer surface of the prismatic body 50 receives frictional force from the inner surface of the molding die 60, and the orientation direction of the portion closer to the outer surface is the magnetic flux applying direction. Even if it has an inclination angle α (see FIG. 3) with respect to (long-side direction X), the inclination angle α is relative to the longitudinal direction of the magnetic plate 51 divided from the prism body 50 (the axial direction of the rotor 22). Although it may appear as an inclination angle, it does not appear as an inclination angle with respect to the width direction (see FIG. 4). Therefore, regardless of whether the plurality of magnetic plates 51 divided vertically from the prism body 50 are the magnetic plates 51A positioned at both ends in the magnetic flux application direction or the other magnetic plates 51B. The segment magnet 52 formed by magnetizing the body plate 51 is magnetized so as to generate a magnetic flux in a direction orthogonal to the width direction. Thereby, in the rotor 22 (FIG. 8) in which the plurality of segment magnets 52 manufactured by the manufacturing method of the present embodiment is assembled, the teeth 21 </ b> T of the stator 21, which will be described later, between the plurality of segment magnets 52, 52. In contrast, the electric angle at which the magnetic attraction force is maximized is the same, and the cogging torque can be suppressed.

  The above is description of the manufacturing method of the segment magnet 52 of this embodiment. Next, a method for manufacturing the electric power steering apparatus 10 (see FIG. 7) using the motor 20 having the segment magnets 52 as a drive source will be described. As shown in FIG. 7, the electric power steering apparatus 10 includes a linear motion shaft 12 accommodated in a shaft case 11 so as to be linearly movable. A stator 21 is fitted in an intermediate portion in the longitudinal direction of the shaft case 11. As shown in FIG. 8, the stator 21 has a structure in which a plurality of teeth 21 </ b> T are projected from the inner surface of a cylindrical body that is press-fitted and fixed to the inner surface of the shaft case 11. A coil 21C is wound around each tooth 21T. Further, as shown in FIG. 7, a rotor 22 is loosely fitted in a cylindrical space between the stator 21 and the linear motion shaft 12, and both end portions are rotatably supported by the shaft case 11. Then, the motor 20 is constituted by the stator 21 and the rotor 22, and the segment magnet 52 of the rotor 22 and the teeth 21T of the stator 21 are opposed to each other in the radial direction of the stator 21, as shown in FIG.

  As shown in FIG. 7, a ball screw 24 is formed in an intermediate portion in the axial direction of the linear motion shaft 12, and a ball nut 23 screwed into the ball screw 24 is fitted and fixed inside the rotor 22. Further, a rack 30 is formed at a position near one end of the linear motion shaft 12, and a handle 28 is connected to a pinion 34 meshing with the rack 30 via a steering shaft 29. In the electric power steering apparatus 10, both ends of the linear motion shaft 12 are connected to a pair of steered wheels 13 and 13 of a vehicle (not shown), while the shaft case 11 is fixed to a vehicle body (not shown). And assembled into the vehicle. The linear motion shaft 12 is linearly moved by the steering torque when the handle 28 is steered, and the motor 20 is driven in accordance with the steering torque. The rotation output of the motor 20 is converted into an axial force of the linear motion shaft 12 by a ball screw mechanism 25 including a ball screw 24 and a ball screw 24, and steering of the handle 28 is assisted.

  Here, since the electric power steering device 10 of the present embodiment uses the motor 20 having the segment magnet 52 manufactured by the above-described manufacturing method as a drive source, the steering feeling can be improved as compared with the related art.

[Second Embodiment]
9 and 10 show a molding die 70 used in the segment magnet manufacturing method of the present embodiment. A molding chamber 73 formed in the base mold 71 of the molding mold 70 has a shape corresponding to the prismatic body 50 (see FIG. 3) described in the first embodiment, and goes from the upper surface opening 73A to the back side. The direction corresponds to the long side direction X (see FIG. 3) in the cross-sectional shape of the prismatic body 50. Further, the bottom wall 73S of the molding chamber 73 and the pressing protrusion 74 in the movable mold 72 are made of a magnetic material, and the side wall portion 73Z surrounding the molding chamber 73 is made of a non-magnetic material. As shown in FIG. 10, a sliding communication is provided that includes a standing communication wall 78 that is bent upward outside the side wall portion 73 </ b> Z and extends upward, and is slidably joined to the standing communication wall 78. A wall 79 projects from the pressing protrusion 74. Thereby, the annular magnetic path 71J partially including the magnetic powder in the molding chamber 73 is configured, and the electromagnetic coil 75 is wound in the middle of the annular magnetic path 71J.

  In the present embodiment, the magnetic powder is accommodated in the molding chamber 73 of the molding die 70 and the pressing protrusion 74 is pushed into the molding chamber 73, and a DC current is applied to the electromagnetic coil 75 to cause the prismatic body 50 (FIG. 3). Thereby, the prismatic body 50 is shaped by receiving both magnetic flux and pressure in the long side direction X (see FIG. 3) of the rectangle which is the cross-sectional shape. Therefore, even if the outer surface of the prismatic body 50 receives a frictional force from the inner surface of the molding die 70, the orientation direction of the portion near the outer surface is not inclined with respect to the magnetic flux application direction. Therefore, all the segment magnets 52 formed by magnetizing the plurality of magnetic plates 51 divided vertically from the prismatic body 50 are magnetized so as to generate a magnetic flux in a direction orthogonal to the width direction. Therefore, even if the several segment magnet 52 manufactured with the manufacturing method of this embodiment is used, the cogging torque of a motor can be suppressed similarly to 1st Embodiment.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.
(1) Although the segment magnet 52 is fixed to the outer surface of the rotor 22 in the embodiment, the segment magnet may be embedded in the rotor.

  (2) In the first embodiment, the magnetic material plate 51 is magnetized after being assembled to the rotor 22 to be magnetized into the segment magnet 52. However, the magnetic material plate 51 is magnetized before being assembled to the rotor 22, and the segment magnet is magnetized. It may be 52.

  (3) In the first embodiment, the example in which the present invention is applied to a rack electric power steering apparatus in which a motor is connected to the linear motion shaft 12 by a so-called ball screw mechanism is shown. However, the motor is linearly moved by a rack and pinion mechanism. The present invention may be applied to a pinion electric power steering device connected to the shaft 12, or may be applied to a column electric power steering device in which a motor is gear-connected to the middle of the steering shaft.

Side sectional view of a molding die used in the method for manufacturing a segment magnet according to the first embodiment of the present invention. Plan sectional view of the mold Perspective view of prismatic body Perspective view of magnetic plate Perspective view of device for assembling magnetic plate to rotor Front view of the rotor viewed from the axial direction Side sectional view of electric power steering device Cross section of motor Front sectional view of a molding die used in the method for manufacturing a segment magnet according to the second embodiment Side sectional view of the mold Perspective view of a prismatic body used in a conventional method of manufacturing a segment magnet

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 20 Motor 22 Rotor 50 Square column body 51 Magnetic body plate 51S Flat surface 51W Curved surface 52 Segment magnet X Long side direction Z Long axis direction

Claims (3)

The magnetic powder is molded into a rectangular column having a rectangular cross section by a molding die and then sintered, and the sintered rectangular column is formed into three or more magnetic plates in the direction of the long side of the rectangle which is the cross sectional shape. In the method of manufacturing a plurality of segment magnets that can be used for a rotor of a motor by vertically dividing and further magnetizing by applying a magnetic flux in the thickness direction of the magnetic plates,
In the forming step of forming the magnetic powder into the prismatic body, pressure is applied in the major axis direction of the prismatic body, and magnetic flux is applied in the long side direction of the rectangle that is the cross-sectional shape of the prismatic body. A method for manufacturing a segment magnet. The magnetic powder is molded into a rectangular column having a rectangular cross section by a molding die and then sintered, and the sintered rectangular column is formed into three or more magnetic plates in the direction of the long side of the rectangle which is the cross sectional shape. In the method of manufacturing a plurality of segment magnets that can be used for a rotor of a motor by vertically dividing and further magnetizing by applying a magnetic flux in the thickness direction of the magnetic plates,
A method of manufacturing a segment magnet, wherein in the forming step of forming the magnetic powder into the prismatic body, both magnetic flux and pressure are applied in a long side direction of a rectangle which is a cross-sectional shape of the prismatic body.   A method for manufacturing an electric power steering apparatus, comprising assembling a motor including the segment magnet manufactured by the method for manufacturing a segment magnet according to claim 1 or 2 as a drive source of the electric power steering apparatus.

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