JPH02197245A - Brushless motor - Google Patents

Abstract

PURPOSE:To suppress the temperature rise and lowering of sensitivity of a magnetic induction element by forming a position-sensing magnet from plastic magnet materials. CONSTITUTION:A rotor shaft 2 is rotatably retained by a housing 9 and the bearing 11 of a bearing stand 10. A sensing magnet(MG) 22 is fixed at the rotor shaft 2 protruding through said bearing stand 10 by a press fit or adhesion, etc., via bush 23. A magnetic induction element 13 is arranged to face the outer periphery of said MG 22 to enable the polarity checking thereof. Said MG 22 is formed into a disc of ferrite or rare earth plastic magnet materials. The MG 22 is small in thermal conductivity to suppress a temperature rise by the heat entering via the rotating shaft 2. Thus, it is possible to suppress the temperature rise of said magnetic induction element 13 arranged in close vicinity to the sensing magnet.

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.

[Prior Art] This type of brushless electric motor is generally shown in FIG. That is, the rotor 1 includes a rotor shaft 2, a yoke 3 fixed to the outer periphery of the rotor shaft 2, and a permanent magnet 4 fixed to the outer periphery of the rotor shaft 2. The stator 5 surrounds the outer periphery of the rotor 1 in a cylindrical shape, and includes a plurality of magnetic pole pieces 6 that protrude toward the outer periphery of the rotor 1.
6. A coil 8 is wound around the insulating member 7 through the insulating member 7.

The stator 5 is fixedly held on the inner peripheral wall of a bottomed cylindrical housing 9 made of a non-magnetic metal material.

A bearing pedestal 10 made of a non-magnetic metal material is attached and fixed to the opening of the housing 9 so as to close the opening.
A rotor shaft 2 is rotatably held.

The space S formed by the housing 9 and the bearing pedestal 10 houses four permanent magnets of the rotor 1, but the rotor shaft 2 protrudes through the bearing pedestal 10, and its rotation Child shaft 2. A position detection magnet 12 is provided. In this case, the rotor shaft 2 also passes through the position detection magnet 12. A magnetically sensitive element 13 is disposed facing the position 12 of the borax stone 12. 14 is a detection part cover made of a non-magnetic metal material.

[Problems to be Solved by the Invention] In recent years, there has been a demand for brushless electric motors I31'c*, R'72, and higher output, and therefore the @motor m1 body tends to become hot. By the way, the detection sensitivity of a magnetically sensitive element such as a Hall element decreases as the temperature increases. For example, in the case of a Hall element, the operating temperature range is -55°C to 125'°C, and when this range is exceeded, the detection sensitivity of the magnetically sensitive element decreases, making it difficult to control the current flow to the coil properly, and therefore the electric motor normal rotation cannot be expected.

In the conventional example described above, the effect of thermally shielding the coil 8 and the magnetically sensitive element 13, which are heat generating sources, by interposing the bearing stand IO therebetween is expected.

However, in the conventional example, even if the bearing pedestal is made of synthetic resin, the rotor shaft 2 passes through the bearing pedestal 10 and enters the detection part cover 14. 12 also becomes hot, and as it rotates, heat is dissipated. Therefore, the magnetically sensitive element 13
Suppression of temperature rise is still not sufficient.

The present invention has been made in view of the above-mentioned reasons, and an object of the present invention is to provide a brushless electronic device that can suppress the decrease in sensitivity of the magnetically sensitive element by suppressing the temperature rise of the magnetically sensitive element! It is provided by I machine.

[Means for Solving the Problem] In order to solve the problem, the brushless electric motor according to claim (1) includes a position detection magnet made of a plastic magnet material.

Further, in the brushless electric motor according to claim (2), the tip of the rotor shaft is further prevented from penetrating the position detection magnet and is not exposed on the outside of the position detection magnet.

[Function] In the brushless electric motor according to claim (1), since the detection magnet has a lower thermal conductivity than the conventional sintered grinding stone, the temperature rise of the detection magnet is suppressed, and therefore the detection magnet It is possible to suppress the temperature rise of the magnetically sensitive element disposed in close proximity to the magnetically sensitive element.

Since the brushless electric motor according to claim (2) has a smaller exposed area of the rotor shaft, it is possible to further suppress the temperature rise of the magnetic sensing element than the brushless motor according to claim (1).

[Example] Hereinafter, an example of the invention described in claim (1) will be described based on FIG. 1. Note that the same reference numerals are given to the members that are actually the same as those of the prior art shown in FIG. 3.

The rotor 1 includes a rotor shaft 2, a yoke 3 fixed to the outer periphery of the rotor shaft 2, and a permanent magnet 4 fixed to the outer periphery of the rotor shaft 2. The yoke 3 is formed of a magnetic material into a cylindrical shape having a shorter axial length than the rotor shaft 2, and is press-fitted or bonded onto the rotor shaft 2. The permanent magnet 4 is segmented into a cylindrical shape or into a plurality of arc shapes and is adhered to the outer peripheral surface of the sleeve 3 with an adhesive or the like. This permanent magnet 4 is magnetized with different poles in the radial direction, and is arranged so that the different poles (4 poles in this embodiment) are present alternately and at equal intervals on the entire outer circumference. .

The stator 5 is made by punching and laminating magnetic materials such as silicon steel plates, and basically surrounds the outer periphery of the rotor 1 in a cylindrical shape and has a plurality of (mains) protruding toward the outer circumferential surface of the rotor 1. In the embodiment, there are six magnetic pole pieces 66, -. Further, a coil 8 is wound around the magnetic pole piece 6 with an insulating member 7 interposed therebetween.

This coil 8 is connected to a drive circuit (not shown) by a lead wire.

The housing 9 is formed of a non-magnetic material into a cylindrical shape with a bottom, and the stator 5 is fixedly held on the inner circumferential wall of the housing 9 by press-fitting or the like. Further, a ζ bearing 11 is mounted at the center of the bottom of the housing 9.

The bearing stand 10 is made of a non-magnetic metal material and is fixedly attached to the opening of the housing 9 so as to close the opening.

Further, a bearing 11 is mounted in the center of the bearing pedestal 10, so that the rotor shaft 2 is rotatably held by the housing 9 and the bearings 11, 11 of the bearing pedestal 10.

The position detection magnet 22 is formed into a disk shape from a ferrite-based or rare earth-based plastic magnet material, and is magnetized in the same manner as the permanent magnet 4 of the rotor 1. The detection magnet 22 is fixed to the rotor shaft 2 protruding through the bearing stand 10 via a bushing 23 by press-fitting, adhesion, or the like. In addition, if the detection magnet 22 and the bushing 23 are molded at the same time and the bushing 23 is fixed to the rotor shaft 2, production will be easier than the method in which the sintered magnet is directly fixed to the rotor shaft. Become.

The detection part cover 4 is made of a non-magnetic metal material and is formed into a bottomed cylindrical shape having an inner diameter smaller than the inner diameter of the housing 9 but sufficiently larger than the outer diameter of the detection magnet 12, so as to cover the detection magnet 22. It is attached to the bearing stand 10 in a manner similar to that shown in FIG. 14
A is an N through hole provided at the center of the bottom, into which the tip of the rotor shaft 2 is inserted to about half the thickness.

The magnetically sensitive element 3 such as a Hall element is connected to the detection magnet 2
It is arranged so as to face the outer periphery of the detection magnet 22 so that the polarity of the detection magnet 22 can be detected. Specifically, the gap between the magnetic sensing element 13 and the detection magnet 22 is 0.5 mm to 1
．． Set it to about 0mm. This magnetically sensitive element 13 and the detection magnet 22 constitute a detection section R. Further, the detection signal of the magnetically sensitive element 13 is inputted to a drive circuit (not shown) through a signal line 13a.

The magnetically sensitive element 13 detects the position of the rotor 1 by detecting the polarity of the detection magnet 22, and a drive circuit (not shown) activated by the detection signal controls energization of the coil 8.

It should be noted that the magnetic sensing element 13 is connected to the detection magnet 2 in the axial direction.
There is no problem even if it is of a type that faces the end face of No. 2.

Next, an embodiment of the invention as claimed in claim (2) will be described based on FIG. This embodiment differs substantially from the previous embodiment only in the rotor shaft, sensing magnets, and bushings.

Therefore, the same reference numerals as in the previous embodiment are given to the members other than these, and detailed explanation will be omitted.

The rotor shaft 32 of this embodiment has a slightly shorter length than that of the previous embodiment. On the other hand, the center hole 42a of the detection magnet 42
does not penetrate through the hole, but is drilled only up to about half the thickness from the bearing stand 10 side. Therefore, the bushing 43 is located in the center hole 4.
．． The length in the axial direction corresponds to the depth of 2 a, and the rotor shaft 3
The tip of No. 2 fits within this center hole 42a. In other words, the tip of the rotor shaft 32 does not pass through the position detection magnet 42 and is not exposed on the outside of the position detection magnet 42.

[Effects of the Invention] Since the brushless electric motor of the present invention is configured as described above, it has the following effects.

In the brushless motor according to claim 11, since the detection magnet has a lower thermal conductivity than a conventional sintered magnet, the temperature rise of the detection magnet is suppressed, and therefore the magnetic Temperature rise of the sensing element can be suppressed.

Since the brushless electric motor according to claim (2) has a smaller exposed area of the rotor shaft, it is possible to further suppress the temperature rise of the magnetic sensing element than the brushless motor according to claim (1).

Therefore, in both cases, by suppressing the temperature rise of the magnetically sensitive element, a decrease in the sensitivity of the magnetically sensitive element can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the invention as claimed in claim (1), FIG. 2 is a longitudinal sectional view showing an embodiment of the invention as claimed in claim (2), and FIG. , is a vertical cross-sectional view of a conventional example. ■-rotor, 2.32-trochanter shaft, 3-sleeve, 4-permanent magnet, stator, 6-ground pole, 8-coil, 1-housing, bearing stand, magnetic sensing element, detection cover, 42-position Detection magnet, detection part (12+13). insulation members,

Claims (2)

[Claims] (1) A rotor with permanent magnets arranged on its outer periphery, a plurality of magnetic pole pieces that surround the outer periphery of the rotor in a cylindrical shape, protrude toward the outer circumferential surface of the rotor, and surround the magnetic pole pieces with an insulating member interposed therebetween. a stator having a coil wound thereon, a housing having a bottomed cylindrical shape and holding one of the rotors and the stator, and a bearing stand holding the other rotor by closing an opening of the housing; A position detection magnet provided on the rotor shaft that protrudes through the bearing base from the space formed by the housing and the bearing base, a magnetically sensitive element facing the position detection magnet, and a position detection magnet and magnetic a sensing element cover that covers the sensing element;
In a brushless motor in which the position of the rotor is detected by a magnetic sensing element, and a drive circuit activated by the position detection signal controls energization of the coil, the position detection magnet is formed of a plastic magnet material. Brush electric motor. (2) The brushless electric motor according to claim 1, wherein the tip of the rotor shaft does not pass through the position detection magnet and is not exposed on the outside of the position detection magnet.