JP2008295140A - Motor for electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely ensure fixing strength under efficient work without damaging a magnet and without increasing the number of part items when mounting a magnet cover. <P>SOLUTION: Eight folding pieces 40 are respectively uniformly formed on the peripheral edge of each through-hole 38 provided on the bottom face of a magnet cover 36. When the magnet cover is mounted to a rotor core 32 and a magnet 34, the eight folding pieces are made to face thinned parts 42, formed on the end face of the rotor core 32, so as to be fitted and integrated with the thinned parts 42 by folding work of the folding pieces 40. By this, it does not require fitting when mounting. Consequently, it facilitates mounting work. It is also possible to reduce another component (material) such as an adhesive. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor for an electric power steering apparatus in which a stator and a rotor are opposed to each other at a predetermined interval, and the rotor is rotated using a change in magnetic force, and more particularly to a brushless motor for an electric power steering apparatus. is there.

    Conventionally, an electric power steering unit has been applied as an assist in operating a steering in a vehicle.

  A motor (hereinafter referred to as an “EPS motor”) that is a drive source of the electric power steering unit is a rotor configured by surrounding a rotor core and a magnet in layers on the outer periphery of a rotating shaft (shaft), like a general motor. And a stator part provided on the inner peripheral side of the motor case and provided at a predetermined interval so as to face the rotor part from the peripheral surface. As the drive classification, those belonging to “brushless motor” are frequently used.

  Here, the rotor portion is covered with a pair of cup-shaped magnet covers so that the end surfaces of the respective rotor cores contact the bottom surface in the axial direction of the shaft. The pair of magnet covers cover the magnet that directly faces the stator portion.

  The magnet cover is made of a non-magnetic material that has a role of preventing the scattering of the magnet and does not affect the magnetic circuit, and is generally made of a thin metal.

Here, the magnet cover is fixed by a so-called press-fitting method, which is tightly accommodated with respect to the outermost periphery of the magnet (see Patent Document 1), the inner peripheral surface of the magnet cover, the end surface of the rotor core, and the outer periphery of the magnet. The adhesive was injected (applied) between and fixed (see Patent Document 2).
Japanese Patent Laid-Open No. 3-89821 Japanese Patent Laid-Open No. 5-20979

  However, of the above-described conventional magnet cover fixing structure, in the press-fitting method as in Patent Document 1, the press-fitting load management for realizing both the securing of the fixing strength and the load that does not damage the magnet is complicated. The complexity has led to a decrease in assembly work efficiency and an increase in cost.

  In addition, in the fixing structure using an adhesive, the work process for injecting or applying the adhesive is increased, and the solidification management of the adhesive is troublesome, the work efficiency is lowered, and the number of parts by adding the adhesive is reduced. Increase and cost increase.

  In consideration of the above facts, the present invention is a motor capable of reliably securing the fixing strength under efficient work without damaging the magnet and increasing the number of parts when attaching the magnet cover. Is the purpose.

  In order to achieve the above object, the present invention provides a motor for an electric power steering apparatus in which a stator and a rotor are opposed to each other at a predetermined interval and the rotor is rotated by using a change in magnetic force. A shaft for outputting rotational force to the outside, a rotor core attached to the outer periphery of the shaft and fixed to rotate together with the shaft, a magnet attached to the outer periphery of the rotor core, and the rotor core and the magnet A cup-shaped magnet cover attached so as to cover the outer periphery of the magnet from the end face side, an end face of the rotor core, and an opposing surface of the magnet cover are provided with uneven portions, respectively, at least in the shaft rotation direction and the magnet cover attachment direction. A fitting hand that fits the concave and convex portions to each other so as to prevent movement. It is characterized by having, when.

  In the above invention, the fitting means includes a recessed portion provided in the rotor core, and a bent piece that is formed on the magnet cover and is bent after being assembled at the predetermined position to crimp the recessed portion. It is characterized by.

  Further, in the above invention, the fitting means is applied to the magnet cover before or after the concave portion provided in the rotor core and the magnet cover are assembled to the predetermined position, and the concave portion. And a convex portion fitted to the head.

  Furthermore, in the above invention, the fitting means includes a circular recessed portion provided in the rotor core and a circular hole formed in the magnet cover and coaxial with the recessed portion in the assembled state at the predetermined position. It is comprised by the compression deformation part which crimps the said recessed part by compressively deforming a peripheral part.

  As described above, according to the present invention, when the magnet cover is attached, the fixing strength can be ensured surely under an efficient work without damaging the magnet and without increasing the number of parts. The effect that a motor for a power steering apparatus can be provided is achieved.

  FIG. 1 shows an electric power steering motor (EPS motor) 10 according to the present embodiment.

  As for the EPS motor 10, the main components are accommodated in the cylindrical case 12, and the internal space is almost sealed.

  A shaft 14 protrudes from the end surface (FIG. 1) of the case 12.

  Further, a front bracket 16 having a substantially L-shaped cross section is provided on the left end side of the case 12 in FIG. 1. In this embodiment, the front bracket 16 is provided with a disk-shaped motor flange. Part 18 is attached. The motor flange portion 18 has a role of connecting and fixing to a transmission mechanism portion (gear box unit) (not shown) provided for electric power steering, for example.

  The shaft 14 is supported by bearings 20 (only the left end portion is shown in FIG. 1) provided at the left and right end portions of the case 12 in FIG. 1, and is fitted to the rotor portion 22 inside the case 12.

  Further, a stator portion 24 is attached to the inner peripheral surface of the case 12 and faces the outer peripheral surface of the rotor portion 22. A stator coil 24 </ b> A is wound around the stator portion 24.

  By causing a change in the magnetic field between the stator portion 24 and the rotor portion 22, both of them rotate relative to each other (substantially, the rotor portion 22 rotates), and this rotational driving force is transmitted via the shaft 14. It can output to the outside (for example, the above-mentioned gearbox).

  Further, a resin mold body 26 is detachably disposed at the other inner end of the case 12 (the right end in FIG. 1). A rotation sensor (for example, a hall element) (not shown) for detecting the rotation angle of the rotor portion 22 is attached to the resin mold body 26, and a substrate 28 on which electrical components for controlling the drive of the rotor portion 22 are mounted. It is installed. Electrical connection to the outside (electric power for energizing the stator coil 24A, etc.) is made through the connection terminals 30 provided on the substrate 28.

  As shown in FIGS. 2 and 3, the rotor portion 22 includes a cylindrical rotor core 32 fitted to the outer periphery of the shaft 14 and a magnet 34 attached to the outer periphery of the rotor core 32. The rotor core 32 and the magnet 34 are covered with a magnet cover 36 at the end surfaces and the peripheral surface. The main purpose of the magnet cover 36 is to prevent the magnet 34 from scattering.

  The magnet cover 36 is composed of a pair and each has a cup shape (see FIG. 2B).

  On the bottom surface of the cup-shaped magnet cover 36, a through hole 38 through which the shaft 14 passes is provided at the center thereof. The magnet cover 36 is mounted so that the through-holes 38 are passed from both ends of the shaft 14 so that the opening surfaces thereof face each other, and the bottom surface is in contact with the end surfaces of the rotor core 32 and the magnet 34.

  Here, the inner diameter of the through hole 38 is larger than the outer diameter of the shaft 14 (about twice in the present embodiment), and the bent piece 40 divided into eight equal parts on the peripheral surface of the through hole 38. Is formed. The bent piece 40 can be bent approximately 90 ° inside the magnet cover 36, but is in a so-called flat state with the bottom surface until it is attached to the end surface of the rotor core 32.

  On the other hand, a so-called meat stealing portion 42 is provided on the end surface of the rotor core 32 at a position facing the bent piece 40 when the magnet cover 36 is attached. That is, the meat stealing portion 42 is a space that is continuous in the axial direction in consideration of die cutting of the rotor core 32 and is discontinuous in the circumferential direction.

  Therefore, in the present embodiment, eight meat stealing portions 42 are formed in the circumferential direction corresponding to the number (eight) of the bent pieces 40. The meat stealing portion 42 is formed in a range where magnetic saturation is not caused.

  When the magnet cover 36 is attached, the bottom surface of the magnet cover 36 comes into close contact with the end surfaces of the rotor core 32 and the magnet 34. At this time, when the bent piece 40 is bent approximately 90 ° toward the rotor core 32, the bent piece 40 is The meat stealing portion 42 is entered and crimped.

  By this caulking, the magnet cover 36 can become a part of the rotor portion 22 that rotates integrally with the rotor core 32.

  The operation of the present embodiment (the procedure for assembling the rotor portion 22) will be described below.

  When the rotor portion 22 is configured on the shaft 14 of the EPS motor 10, first, the cylindrical rotor core 32 is fitted to the outer periphery of the shaft 14.

  The rotor core 32 is provided with a circular hole with a predetermined dimensional tolerance that is fitted to the outer diameter of the shaft 14 in advance in the shaft core. Further, the meat stealing portion 42 is formed so as to penetrate both end faces of the rotor core 32. The reason for penetrating the both end faces is for die cutting, and in practice (to achieve the present invention), grooves of a predetermined depth may be formed on both end faces. In other words, it suffices if there is a recessed portion that can be fitted to the bent piece 40 described later.

  Next, the magnet 34 is attached to the outer periphery of the rotor core 32. The magnet 34 receives the magnetic force from the stator portion 24 and rotates the rotor core 32.

Here, a magnet cover 36 is attached to the magnet 34 to prevent scattering when the magnet 34 is missing.

  The magnet cover 36 has a cup shape, and is attached so that the opening surfaces of the shaft 14 are opposed to each other through the through holes 38 so that the bottom surfaces thereof are in contact with the end surfaces of the rotor core 32 and the magnet 34.

  Next, the bent piece 40 provided at the periphery of the through hole 38 on the bottom surface is bent inward by approximately 90 °. Since the meat stealing portion 42 faces the bending direction, the bent piece 40 is fitted to the meat stealing portion 42 and crimped. By this caulking, the magnet cover 36 is integrated with the rotor core 32 and the magnet 34.

  As described above, in the present embodiment, eight bent pieces 40 are uniformly formed on the periphery of the through hole 38 provided in the bottom surface of the magnet cover 36, and the rotor core 32 is attached to the rotor core 32 and the magnet 34. It is made to oppose the meat stealing part 42 formed on the end face, and is fitted and integrated with the meat stealing part 42 by the bending work of the folding piece 40. Thereby, it is possible to eliminate the need to manage the press-fit load for realizing both the securing of the fixed strength and the load that does not damage the magnet. Moreover, other components (materials), such as an adhesive agent, can be reduced.

  In addition, it is not essential that the bent pieces 40 are even in the circumferential direction, or eight pieces, and any shape may be used as long as the correspondence with the meat stealing portion 42 is taken.

  Hereinafter, modifications of the present embodiment will be shown.

(Modification 1)
In FIG. 4, the bottom surface of the magnet cover 36 is not processed except for the through-hole 38 that penetrates the shaft 14, the meat stealing portion 42 on the rotor core 32 side is circular, and the bottom surface of the magnet cover 36 is directed from the outside to the inside. By applying the punching process and the embossing process, the fitting of the processed part 43 to the meat stealing part 42 is realized. In this case, in order to simplify the punching or embossing (load reduction), the portion 43 fitted to the meat stealing portion 42 may be thinned in advance. The reason why the meat stealing portion 42 is circular is that the ease of stamping or embossing is taken into consideration, and the meat stealing portion 42 may not be circular.

(Modification 2)
FIG. 5 shows that eight small circular holes 44 are formed on the bottom surface of the magnet cover 36 at the periphery of the through-hole 38 that penetrates the shaft 14 evenly in the circumferential direction, and the meat stealing portion 42 on the rotor core 32 side is The fitting to the meat stealing portion 42 is realized by making the shape slightly larger than the small circular hole 44 and punching the bottom surface of the magnet cover 36 from the outside to the inside. In this case, the reason why the meat stealing portion 42 is circular is that a versatile punching machine can be used. If a dedicated punching machine is prepared, the circle is not essential.

It is the schematic of the EPS motor which concerns on this Embodiment. (A) is a front view (without a magnet cover) of the end face of the rotor portion, and (B) is a right side cross-sectional view of FIG. 2 (A) according to the present embodiment. 4A is a front view of the bottom (outside) of the magnet cover, and FIG. 3B is a right side cross-sectional view of FIG. 4A is a front view of an end face of a rotor portion (with a magnet cover), and FIG. 4B is a right side cross-sectional view of FIG. FIG. 5A is a front view of an end surface of a rotor portion (with a magnet cover), and FIG. 5B is a right side cross-sectional view of FIG.

Explanation of symbols

10 EPS motor (motor)
12 Case 14 Shaft 16 Front bracket 18 Motor flange portion 20 Bearing 22 Rotor portion (rotor)
24 Stator portion 24A Stator coil 26 Resin mold body 28 Substrate 30 Connection terminal 32 Rotor core 34 Magnet 36 Magnet cover 38 Through hole 40 Bending piece (fitting means)
42 Meat stealing part (fitting means, recessed part)

Claims (4)

A motor that rotates a rotor by using a change in magnetic force so that a stator and a rotor face each other at a predetermined interval,
The rotor is
A shaft for outputting rotational force to the outside;
A rotor core attached to the outer periphery of the shaft and fixed to rotate together with the shaft;
A magnet attached to the outer periphery of the rotor core, and a cup-shaped magnet cover attached to cover the outer periphery of the magnet from the rotor core and the end face side of the magnet;
Fitting means for fitting the concavo-convex portions to each other so as to prevent movement in at least the shaft rotation direction and the magnet cover attachment direction, respectively, by providing concavo-convex portions on the end surface of the rotor core and the facing surface of the magnet cover.
An electric power steering apparatus motor comprising: The fitting means is
A recessed portion provided in the rotor core;
A bent piece that is formed on the magnet cover and that is crimped after being assembled to the predetermined position, to bend the recessed portion;
The motor for an electric power steering apparatus according to claim 1, comprising: The fitting means is
A recessed portion provided in the rotor core;
Before the magnet cover is assembled to the predetermined position, or after the magnet cover is assembled, a convex portion that is applied to the magnet cover and fitted into the concave portion,
The motor for an electric power steering apparatus according to claim 1, comprising: The fitting means is
A circular concave portion provided in the rotor core and a concave portion formed by compressing and deforming a peripheral portion of a circular hole formed in the magnet cover and coaxial with the concave portion in the assembled state at the predetermined position. The motor for an electric power steering apparatus according to claim 1, further comprising: a compression deformation portion that caulks.

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