JPH03112352A - Brushless motor - Google Patents

Abstract

PURPOSE:To increase magnetic flux density of a position detecting magnet without reducing productivity by forming the magnet in a ring state, so magnetizing it as to become magnetically anisotropic, and caulking to fix it to a metal disc fixed to a rotor shaft. CONSTITUTION:A position detecting magnet 25 is formed of a plastic magnet material in which magnetic powder is, for example, mixed with nylon resin, in a ring state through molding. A magnetizing coil is buried at a position for forming the cavity 25a of the mold and a position for forming an outer periphery, and so magnetized simultaneously upon molding as to become magnetically anisotropic. This magnet 25 has an inner diameter slightly smaller than the outer diameter of a rotor shaft 2, and is caulked to be fixed to a metal disc 26 fixed to the shaft 2. The disc 26 is fixed to the shaft 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brushless electric motor having a position detection magnet separate from the permanent magnet of the rotor.

[Conventional technology]

This type of brushless electric motor generally has the structure shown in FIG. That is, the rotor 1 has a magnetic sleeve 3 fixed to the rotor shaft 2, and permanent magnets 4 having different poles arranged alternately in the circumferential direction on the outer periphery of the magnetic sleeve 3, and separate from the permanent magnets 4. A position detection magnet 5 made of ferrite or the like is fixed to the rotor shaft 2 at a distance from the permanent magnet 4.

The stator 6 surrounds the outer circumference of the permanent magnet 4 in a cylindrical shape, and has a plurality of magnetic pole pieces 7 protruding toward the outer circumferential surface of the permanent magnet 4.
A coil 9 is wound around the magnetic pole piece 7 via an insulating member 8. This stator 6 is fixed to the inner circumferential surface of a bottomed cylindrical housing 10 by press fitting, adhesive, or the like.

A bearing 11 is mounted at the center of the bottom of the housing 10, and a bearing stand 12 is mounted to the opening of the bearing 11 so as to close the opening. The bearing stand 12 is interposed between the permanent magnet 4 and the position detection magnet 5, and has a bearing 13 mounted in the center and an insertion hole 1 for the lead wire of the coil 9 near the periphery.
2a, and a peripheral wall 12b having a larger diameter is protruded from the surface on the side of the position detection magnet 5. The above rotor shaft 2 is
It is rotatably supported by both bearings 11 and 13.

The detection unit housing 14 has a bottomed cylindrical shape smaller than the housing 10, and is attached to the peripheral wall 12b of the bearing stand 12 by fitting its opening edge into the peripheral wall 12b. Therefore, the position detection magnet 5 is housed within the detection unit housing 14.

At the bottom of the detection unit housing 14, there is a fixing part 14 for mounting and fixing a wiring board 15 made of a printed wiring board, which will be described later.
A is provided protrudingly.

A plurality of (-3 for boat fishing) magnetic sensing elements (for example, Hall elements) 16 are provided on the wiring board 15 so as to face the outer peripheral surface of the position detection magnet 5 at predetermined intervals in the circumferential direction. . The reason why the magnetically sensitive element 16 is made to face the outer peripheral surface of the position detection magnet 5 is because the rotor 1 has a smaller radial play than a thrust play.

The magnetically sensitive element 16 outputs a detection signal (a voltage proportional to the amount of magnetic flux from the position detection magnet) when facing, for example, the N pole of the position detection magnet 5, and the detection signal is sent to the wiring board 15. The signal is inputted to a drive circuit (not shown) via a connected signal line 18. The drive circuit that receives this detection signal controls the energization of the coil 9 to rotate the motor.

The position detection magnet 5 in this device is fixed to the rotor shaft 2 by press-fitting or adhesive, but there is a risk of cracking in the former case and detachment in the latter case, so the finished dimensions are adjusted to high precision. must be maintained at
This requires severe press-fitting or bonding processing conditions, which poses a problem in terms of productivity.

Therefore, an improved position detection magnet shown in FIG. 6 has been proposed. This device is substantially different from the prior art example only in the position detection magnet, so the other members are given the same reference numerals as in the general example and the description thereof will be omitted.

This position detection magnet 5 is formed by simultaneous molding of a plastic magnet material together with a metal bushing 5a consisting of a small diameter part and a large diameter part formed by forging or cutting, and is attached to the rotor shaft 2. Press-fitted. Therefore, the risk of cracking or coming off as in the general example described above is reduced, and productivity is improved.

[Problem to be solved by the invention]

However, in the above-mentioned conventional brushless motor, since the position detection magnet 5 is formed by simultaneous molding with the bush 5a, the magnetizing coil cannot be located inside the magnet 5 ( For example, it cannot be embedded in a mold), so magnetization can only be applied to magnetic isotropy. From this, this magnet 5 has a limit in increasing the magnetic flux density,
Because the magnetic flux density cannot be increased, the magnetic sensing element 16
There was a risk that the detection accuracy would be reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a brushless motor in which the magnetic flux density of a position detection magnet can be increased without reducing productivity.

[Means to solve the problem]

In order to solve this problem, the brushless electric motor of the present invention includes a rotor, a stator, and a rotor in which a position detection magnet separate from the permanent magnet is fixed to the rotor shaft with a space between the permanent magnet and the permanent magnet. A brushless motor includes a housing to which a magnet is fixed, a bearing stand attached to an opening of the housing, and a plurality of magnetically sensitive elements arranged to face the outer peripheral surface of a position detection magnet. The detection magnet is formed into a ring shape from a plastic magnet material, magnetized to have magnetic anisotropy, and fixed by caulking to a metal disk fixed to the rotor shaft.

6 [Function] According to the present invention, since the position detection magnet is magnetically anisotropic, it is possible to increase the magnetic flux density compared to a magnet that is magnetically isotropic.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 4. Note that the general example (Fig. 5) and the conventional example (Fig. 6) are substantially different only in the position detection magnet, so the members that are substantially the same as those explained in these examples include the same parts. The detailed explanation will be omitted by attaching the symbol .

The rotor 1 includes a rotor shaft 2, a magnetic sleeve 3, and a permanent magnet 4.
and a position detection magnet 25, which will be described in detail later.

The stator 6 has a plurality of magnetic pole pieces 7 protruding toward the outer circumferential surface of the permanent magnet 4, and a coil 9 is wound around the magnetic pole pieces 7 via an insulating member 8, and is press-fitted or glued into the housing 10. It is fixed by etc.

A bearing 11 is mounted on the housing 10, and a bearing stand 12 is attached to the opening thereof. In addition, this housing lO is
Although it is preferable to use an iron plate with a thickness of about 1.0 mm in terms of magnetic properties, a non-magnetic metal plate may also be used.

The bearing stand 12 is interposed between the permanent magnet 4 and the position detection magnet 5, and rotatably supports the rotor shaft 2 by its bearing 13 and the bearing 11 of the housing 10. Further, a peripheral wall 12b having a larger diameter than that of the position detecting magnet 5 is protruded from the surface of the position detecting magnet 5.

The detection unit housing 14 is fitted into and attached to the peripheral wall 12b of the bearing stand 12, and a wiring board 15 is placed and fixed on the fixed part 14a.

A plurality of (-3 for boat fishing) magnetic sensing elements (for example, Hall elements) 16 are spaced at predetermined intervals in the circumferential direction and are attached to the outer circumferential surface of the position detection magnet 5 by about 0.5 to 1°0 m+. They are provided on the wiring board 15 so as to face each other with a gap therebetween.

Next, the position detection magnet 25 will be explained in detail. Position detection magnet 2
5 is made of a plastic magnet material, for example, nylon resin mixed with magnetic powder, and is formed into a ring shape as shown in FIG. 2 using a molding die.

- Specifically, the outer diameter is about 20 mvA and the thickness is about 1.5 m.
m, and the inner hole 25a has a large diameter part of about 15 mm and a diameter of about 13 m.
It consists of a small diameter part of m. This small diameter portion has a thickness of approximately 0.5 mm, and a stepped portion 25b is formed perpendicular to the axis thereof. In addition, magnetizing coils (not shown) are embedded in the position where the inner hole 25a of the molding die is formed and the position where the outer periphery is formed, and magnetization is carried out to create magnetic anisotropy at the same time as molding. be done. In this case, the magnetization pattern of the north and south poles is the permanent magnet 4.
Do the same as the one above.

This position detection magnet 25 has an outer diameter of about 15 mm, a thickness of about 1 mm, and has an inner diameter slightly smaller than the outer diameter of the rotor shaft 2, and is attached to a metal disk 26 fixed to the rotor shaft 2. It is fixed by caulking. Specifically, as shown in FIG. 3, the metal disk 26 is inserted into the inner hole 25a of the position detection magnet 25, and in this state, the end surface on the large diameter side is punched using, for example, a heated punch. As shown in Figure 4, it is deformed under pressure. The metal disk 26 is then fixed to the rotor shaft 2 by press fitting or the like.

In this way, this brushless motor detects =9=8 every time the magnetically sensitive element 16 faces a predetermined polarity of the position detection magnet 25, and the drive circuit that receives the detection signal energizes the coil 9. It rotates under control.

〔Effect of the invention〕

Since the brushless electric motor of the present invention is configured as described above,
Since the position sensing magnet is magnetically anisotropic, it can have a higher magnetic flux density than a magnetically isotropic one. Moreover, after the position sensing magnet is formed by molding,
The magnetic flux density of the position detecting magnet can be increased without reducing productivity because it is fixed to a metal disc and the rotor shaft is securely fixed to the rotor shaft.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the position detection magnet, FIG. 3 is a longitudinal sectional view of the main part thereof, and FIG. FIG. 5 is a longitudinal sectional view showing a general example, and FIG. 6 is a longitudinal sectional view showing a conventional example. 10-1-rotor, 2-rotor shaft, 3-magnetic yoke, 4-permanent magnet, 5-position detection magnet, 6-stator, 7--magnetic pole piece, 8-insulating member, 9-coil , 10--housing, 11--bearing, 12-bearing stand,
12b - Peripheral wall, 13 - Bearing, 15 - Connection board, 16 - Magnetic sensing element, 25 - Position detection magnet, 25a - Inner hole, 25b - Step part, 26 - Metal disc.

Claims (1)

[Claims] (1) A magnetic sleeve is fixed to the rotor shaft, permanent magnets with different poles alternately located in the circumferential direction are arranged on the outer periphery of the magnetic sleeve, and a position detection magnet separate from the permanent magnet is permanently installed. A rotor is fixed to the rotor shaft with a space between the magnets, and a permanent magnet of the rotor is surrounded by a cylindrical outer circumference, and a plurality of magnetic pole pieces protrude toward the outer circumferential surface of the permanent magnet. A stator has a coil wound around it through an insulating member, a housing that is approximately cylindrical in shape with a bottom and has the stator fixed to its inner circumferential surface, and a permanent magnet and a position detection magnet. A brushless motor includes a bearing stand attached to an opening of a housing, and a plurality of magnetically sensitive elements arranged to face the outer peripheral surface of a position detection magnet, wherein the position detection magnet is a plastic magnet. It is formed into a ring shape using a material and is magnetized to have magnetic anisotropy.
A brushless electric motor is characterized by being caulked and fixed to a metal disk fixed to a rotor shaft.