JPS601416Y2 - Rotation speed detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational speed detection device for a motor rotor.

FIG. 1 shows a partial configuration diagram of an embodiment of a conventional device for detecting the rotational speed of a rotor of a motor.

As shown in FIG. 1A, field magnetic poles 1a that generate a radial magnetic field for driving a motor are arranged in a rotor 1 at a constant pitch so that different polarities alternate in the circumferential direction of the rotor. There is.

Further, speed detection magnetic poles 1b are provided on the end face of the rotor 1 at a pitch smaller than that of the magnetic poles 1a.

Furthermore, for example, if the magnetic poles 1b are arranged as shown in Figure 1, a single strip of conductor 2 bent in a wavy manner at the same pitch as the magnetic poles 1b is printed from a printed circuit board as shown in Figure 1. A speed detecting magnetic field change detecting means is disposed facing the magnetic pole 1b.

When the rotor 1 rotates, the interaction between the magnetic poles 1b and the conductor 2 generates a voltage in the conductor 2 with a frequency proportional to the rotation speed of the rotor.

For example, a frequency-voltage converter (not shown) is connected to both ends of the conductor 2 to detect the rotation speed.

However, in order to obtain an accurate rotational speed signal in a device with such a configuration, there are restrictions on the concentricity or gap between the rotor and the magnetic field change detection means, and therefore a high degree of dimensional accuracy is required in the structure. Further, there is a drawback that the disturbance magnetic field adversely affects the detection signal of the magnetic field detection means.

Furthermore, when the magnetic flux on the back side of the magnetic pole is guided to the back side using a magnetic material as described in Japanese Utility Model Application Publication No. 48-4000 (2000), the height is limited due to the magnetic material, making it thinner. This has the disadvantage that it becomes a hindrance to the process of development, and the structure becomes complicated.

An object of the present invention is to provide a rotational speed detection device that eliminates the above-mentioned drawbacks by using magnetic poles for driving a motor for speed detection.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a sectional view of the main parts of a motor having a rotational speed detection device according to the present invention.

In the figure, reference numeral 4 denotes a base, and a rotary shaft 5 is rotatably provided at the center of the base, and an annular field rotor 6 is supported on this rotary shaft 5 via a support member 7.

Inside the rotor 6 are magnetic poles 9 around which an armature winding 8 is wound.
is fixed.

Magnetic poles 6a for driving a motor are arranged on the rotor 6 as shown in FIG. 3A, for example, and magnetic members serving as magnetic poles 10 for speed detection are magnetically coupled to the magnetic poles 6a, respectively.

In addition, the inside of the speed detection magnetic poles 10 is bent in a wave shape at the same pitch as the arrangement pitch of the speed detection magnetic poles 10, as shown in the opening of FIG. A single conductor 11 printed and wired on the peripheral wall surface.
A disc-shaped magnetic field change detection means 12 having a shape is fixed.

In this configuration, when the rotor 6 rotates, a voltage having a frequency proportional to the rotational speed of the rotor 6 is generated across the conductor 11 due to the interaction between the speed detection magnetic pole 10 and the conductor 11.

For example, a frequency-voltage converter (not shown) is connected to both ends of the conductor 11 to detect the rotational speed.

FIG. 4A is a partial configuration diagram of another embodiment according to the present invention, and the opening is a developed view of the rotor 6 and the speed detection magnetic pole 10. The number of poles is doubled.

The magnetic member constituting the speed detection magnetic pole 10 has two pole pieces 10a and 10b and is arranged on the motor drive magnetic pole 6a, and each pole piece is arranged alternately in the circumferential direction of the rotor 6. They are arranged at a constant pitch so that different polarities are lined up.

Further, the conductor 11 of the magnetic field change detection means 12 is printed and wired to be bent in a wave shape at the same pitch as the arrangement pitch of the pole pieces, as described above.

In this embodiment, the number of poles of the speed detection magnetic poles 10 is twice the number of poles of the motor drive magnetic poles 6a, but the number is not limited to double, but can be increased by an integral number.

According to this configuration, a high detection frequency can be selected even if the number of motor drive magnetic poles 6a is small.

In addition, some motors have the field rotor 6 magnetized in a sine or skew manner in order to smooth the rotation, and the rotor with such a configuration has a magnetized magnetic pole border. It was considered inappropriate to use it for speed detection because it was not clear.

However, as mentioned above, even in such a rotor, by providing magnetic poles for speed detection, it becomes possible to clearly define the boundary between the magnetic poles, so that accurate speed detection can be performed while rotating smoothly. In addition, by increasing the number of magnetic poles, high frequencies can be detected.

As explained above, the rotational speed detection device according to the present invention is
A magnetic member having a plurality of pole pieces at the tip shown in Fig. 4A is used to create a magnetic flux for speed detection, and the polarity of the pole pieces is alternately different by using the polarity of adjacent magnetic poles. As a result, the structure becomes simpler and thinner than when using the front and back polarities of one magnetic pole.

[Brief explanation of the drawing]

Fig. 1 is a partial configuration diagram of a conventional rotational speed detection device, Fig. 2 is a sectional view of the main part of a motor having a rotational speed detection device according to the present invention, and Fig. 3 is an illustration of a rotational speed detection device according to the present invention. FIG. 4 is a partial configuration diagram of another embodiment of the rotational speed detection device according to the present invention. Explanation of the symbols of the main parts, 4...Base, 5...
... Rotating shaft, 6 ... Field rotor, 1
0... Magnetic pole for speed detection, 8... Armature winding, 11... Conductor, 12... Magnetic field change detection means.

Claims (1)

[Scope of utility model registration request] A rotation speed detection device for an electric motor having a rotor in which magnetic poles that generate a radial magnetic field are arranged at a constant pitch so that magnetic poles of different magnetic properties are arranged alternately in the circumferential direction. a magnetic member having a plurality of pole pieces at the tip of the other end; and a magnetic field change detection means for detecting a change in the magnetic field formed by the pole pieces,
A rotational speed detection device characterized in that the pole pieces are arranged at a constant pitch so as to have alternately different polarities in the circumferential direction.