JPS6059964A - Brushless dc motor - Google Patents

Abstract

PURPOSE:To reduce the size of a motor by providing a frequency generator FG magnet multipolarly magnetized in the end direction at a rotor yoke, and oppositely arranging the magnet and an FG pattern through an axial air gap at a stator side. CONSTITUTION:An FG magnet 9 is provided at the rotor side of a motor and, an FG pattern 10 is provided through an axial air gap 12 at the stator side of the motor. the magnet 9 is multipolarly magnetized in the end direction. The pattern 10 is composed at the conductor connection 10a at the same pole pitch P as the magnet 9, a voltage is induced by the relative rotation to the magnet 9 at every conductor, a frequency output voltage V proportional to the rotating speed applied in phase is produced from the output terminal of the pattern 10, and the output voltage is fed back as a speed signal to control the speed of a DC motor. Thus, the thickness of the axial air gap can be shortenend, thereby reducing the size of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless DC motor, and particularly to a brushless DC motor, in which the return magnetic circuit of a frequency generator disposed in the motor also serves as a stator.

A frequency generator is installed in the motor for brushless DC speed control.The voltage generated by this generator is taken out as a speed signal and this signal is fed back and given to the DC motor speed control. However, the construction space of the frequency generator has an adverse effect on the miniaturization of this DC motor. In other words, in the past, as the return magnetic circuit of a frequency generator, a separate component was installed in the DC motor, which was completely heat-generating than the motor's stator. This made the entire device thicker, which made it difficult to downsize the motor. It's hindering.

Taking these points into consideration, the present invention has a configuration in which the return magnetic circuit, which is one of the components of the frequency generator, is not provided in particular and is used as the stator of the motor, thereby reducing the size and manufacturing of the device. This results in lower costs.

That is, the present invention applies a current to the stator windings through semiconductors such as transistors and thyristors, and sequentially switches the magnetic polarity while controlling the timing, thereby creating a magnetic field with a radial gap interposed between the stator and rotor magnets. In a brushless DC motor that generates a desired torque, a frequency generator magnet is provided on the rotor yoke and magnetized with multiple poles in the direction of the end surface, and a frequency generator magnet is provided on the stator side facing the magnet with an axial gap interposed therebetween. 4.
! be a sign.

The present invention will be described with reference to the embodiments shown in the figures. FIG. 1 is a side sectional view, FIG. 1 is an oblique view showing the end face of the frequency generator (hereinafter abbreviated as FG) magnet 9, and FIG. 3 is an oblique view of the FG pattern io.

In the figure, / is the motor rotor (yoke), C is the rotor magnet, 3 is the motor stator coil, and Da is the stator (yoke).
, is the housing, 6 is the rotor shaft of the motor, ri is the bearing, g is the shield plate, 9 is the FG magnet on the rotor side, IO is the FG pattern on the stator side, / is the rotor and stator in the motor The gap /λ in the radial direction between them is the gap in the coaxial direction, that is, the gap between the FG magnet 9 and the FG pattern IO. In particular, Fig. 2 visually shows that the annular F'G magnet 9 is magnetized with multiple poles in the end face direction, and Fig. 3 shows that the annular FG pattern IO is an FG magnet? The printed wiring 10a is shown in a methodical manner with a pitch P8 of a width t, which is the same as the magnetization pitch of the magnetic poles QNSNS....

The present invention has a structure in which a frequency generator is disposed in a brushless DC tanabata, and the timing of the energizing current to be applied to the wound coil J of the stator L is determined by a semiconductor such as a transistor or a thyristor. By sequentially switching the magnetic polarity N5NS..., magnetic torque is generated through the radial gap // between the stator and rotor magnets of the DC motor, and the rotation of the motor rotor shaft 6 is Furthermore, in the present invention, the yG magnet pattern is provided on the rotor side of the motor, and the FG pattern IO is provided on the tanabata stator side with an axial gap of /2 interposed between them.
As shown in the figure, the FG magnet t is multi-pole magnetized in the direction of the end surface, and the N pole of the FG magnet t - the air gap saw F0 pattern/θ - the stator (circumferential direction) - the white plate of the air gap saw FG magnet t - the rotor (Yoke) l (circumferential direction) - A magnetic circuit of a frequency generator passing through the N pole of the FG magnet 9 is created.

Furthermore, as mentioned above, the conductor connection 10a of the ya pattern 10 is constructed with the same pole pitch p as that of the F'G-q magneto, and a voltage is generated in each conductor by relative rotation with the PG magnet. A frequency output voltage V proportional to the rotational speed is taken out from the output terminal of the FG/<turn io, and this output voltage is fed back as a speed signal to control the speed of the brushless DC motor.

As described above, the present invention does not have a return magnetic circuit part unlike the conventional one, so it is possible to shorten the thickness of the gap in the axial direction of the device, reduce dust in the motor, and use such parts. The brushless motor according to the present invention is mainly used as a spindle motor for floppy disks and a motor for VTRs.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of an apparatus according to an embodiment of the present invention, and FIG.
Magnetic visualization slope of G magnet 9 FIG. 3 is a slope view of the FG pattern. In the figure, / is the rotor (yoke), C is the rotor magnet, 3 is the stator winding, Da is the stator (yoke), Y is the housing, and 6
9 is the rotor shaft, 9 is the frequency generator pattern, 10 is the pattern for the frequency generator, // is the Tanabata gap, and lλ is the frequency generator gap.

Claims (1)

[Claims] l The magnetic polarity is sequentially switched while timing the current flowing through the stator windings through semiconductors such as F transistors and thyristors [a radial gap is interposed between the stator and rotor magnets] A frequency generator magnet, which is installed in the rotor yoke and magnetized with multiple poles in the direction of the end face, and which is opposed to the magnet through an axial gap, is installed in the rotor yoke in a brushless DC top-to-column system that generates magnetic torque. A brushless DC motor characterized by comprising a frequency generator pattern provided on the stator side. 2. The brushless DC motor according to claim 1, wherein the conductive wire of the frequency generator pattern has the same polar pitch as the frequency generator magnet.