JPS6126461A - Rotating speed detector of motor - Google Patents

Abstract

PURPOSE:To accurately detect the rotating speed of a motor with a simple and inexpensive constitution by folding and disposing a conductor of rectangular shape for generating a speed detection signal so as to superpose the rise and the fall of the rectangular shape. CONSTITUTION:A conductor for generating a speed detection signal is circulated at the conductor 11-1 of front side from a terminal T1 to an intermediate terminal CT clockwise, connected with the conductor 11-2 of back side at the terminal CT, and circulated from the terminal CT to a terminal T2 counterclockwise. The conductors 11-1 and 11-2 are folded in a zigzag shape, and reversed at the rises and falls of front and back sides. Further, the sum of the areas of a range crossing the leakage magnetic flux from a drive coil becomes substantially the same at the conductors 11-1 and 11-2 of front and back sides.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a rotational speed detection device for a motor, and particularly to a rotational speed detection device suitable for a motor in which the rotor is an annular magnet and the stator is a drive coil. .

[Background of the invention]

Conventionally, the rotor is an annular magnet and the stator is a drive coil.
Devices that perform detection by magnetic means are used. In the magnetic detection means, a conductor for speed detection is arranged opposite to a rotor consisting of an annular magnet magnetized with multiple poles in the circumferential direction so that the magnetic flux that moves as the rotor rotates crosses it. There is a method of detecting the rotational speed based on the signal period induced between both ends of this conductor.

In the above method, noise proportional to the switching frequency of the drive coil current is superimposed on the speed detection conductor due to the leakage magnetic flux caused by the drive coil current for applying rotational force to the rotor, so the S/N ratio of the speed detection device is decreases, and the rotational speed detection accuracy decreases.

FIG. 2 is a sectional view of a motor to which the above-mentioned rotational speed detection device is added.

In Figure 2, 1 is the base, 2 and 3 are the bearings, and 4
is the rotating shaft, 5 is the magnet holder, and 6 is the annular shape for the main magnetic pole.
Magnet, 7 is an annular magnet dedicated to rotation speed detection, 8
is the core, and 9 is the drive coil.

10 is a substrate.

The rotating shaft 4 is supported by the base 1 through bearings 2 and 3, and is fixed to a magnet holder 5.

As shown in FIG. 2, the magnet holder 5 is attached with an annular magnet 6 for a main magnetic pole and an annular magnet 7 dedicated to rotational speed detection, which are arranged concentrically around the rotating shaft 4. A core 8 and a coil 9, which are integrally attached to the base 1, are arranged concentrically facing the annular magnet 6. Further, the annular magnet 7 is magnetized so that a predetermined number of magnetic poles are lined up along the circumferential direction. A substrate 10 is attached to the core 8 facing the annular magnet 7. As shown in FIG. 3, a series of speed detection signal generating conductors 11 are printed and wired on this base Fi 10. As shown in FIG. The conductor 11 is connected to the annular magnet 7
An annular magnet 7 that faces the magnetic pole array for speed detection and extends in the radial direction at multiple locations, that is, rotates.
It has a zigzag structure so that the magnetic flux generated from the detection magnetic pole array interlinks with and crosses a part of the conductor 11. Furthermore, the N
A relative positional relationship is defined between the positions of the poles and S poles and the positions of the radially extending portions of the conductor 11. for example,
When one of the radially extending portions of the conductor 11 faces the north pole of the magnet 7, the positions on both sides thereof face the south poles on both sides of the north pole of the magnet 7. Make it.

In such a configuration, when the magnet 7 attached to the magnet holder 5 rotates, the magnetic flux generated from each magnetic pole array crosses the conductor 11 while interlinking with the conductor 11, so that a voltage is generated at both ends of the conductor 11. Since the frequency of this voltage is proportional to the change in magnetic flux that crosses the conductor 11 within a unit time, that is, the rotation speed of the magnet 7,
The rotational speed of the motor is detected from that frequency. but,
Since the magnetic flux generated from the drive coil 9 that provides rotational force also crosses the conductor 11, the voltage from the drive coil 9, which is a noise component, is superimposed on both ends of the conductor 11.

FIGS. 4(a) and 4(b) are simplified diagrams for explaining the influence of leakage magnetic flux from the drive coil 9 on the conductor 11 in FIG. 3. Note that a zigzag portion of the conductor 11 for obtaining signal components is partially omitted. Also, (a
) and (b) are different in the shape of the conductor 11.

In FIGS. 4(a) and 4(b), the leakage magnetic flux from the drive coil 9 passing through area A is φa, and similarly,
If the B region is φb and the c region is φC, Fig. 4(a)
In this case, all of φa, φb, and φC interlink with the conductor 11, so the noise voltage c induced across the conductor 11
A becomes .

On the other hand, in the case of FIG. 4(b), φa and φb are the same as above, but φC does not interlink with the conductor 11, so the conductor 11
The noise voltage BB induced across both ends of is as follows.

As a result, eB' in equation (2) becomes smaller than eA in equation (1), so by changing the shape of the conductor 11, the noise component is reduced, but the detection accuracy of the rotational speed is improved. This is an amount of noise that cannot be ignored.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotation speed detection device that can improve the conventional problems and detect the rotation speed of a motor with high precision using a simple and inexpensive method.

[Summary of the invention]

In order to achieve the above object, the motor rotation speed detection device of the present invention is configured to detect the rotation speed of a motor having a main pole annular magnet on the rotor and a motor drive coil on the status. In a detection device using a conductor, the conductor is provided with a first conductor having a rectangular wave shape and circulating to the right, and a second conductor having a similar rectangular wave shape to the first conductor and circulating to the left, The above two conductors are arranged so that the rising edge (or falling edge) and falling edge (or rising edge) of the rectangular shape overlap each other, and are connected in a folded manner.
It is characterized by being interlinked with magnetic flux.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic structural diagram of a speed detection signal generating conductor showing an embodiment of the present invention.

In FIG. 1, after the conductor 11-1 on the front side indicated by a solid line makes one circuit clockwise from the terminal T1 to the intermediate terminal CT,
At the intermediate terminal CT, the conductor 11-2 on the back side indicated by the dotted line
The structure is such that the circuit from the intermediate terminal C'T to the terminal T2 goes around once in the counterclockwise direction, which is the opposite of the above.

Further, as shown in FIG. 1, the conductors 11-1 and 11-2 are formed in a zigzag shape so that the rise (or fall) of the front and back surfaces are in opposite directions.

Furthermore, as shown in FIGS. 4(a) and 4(b), the sum of areas of the A region, B region, and C region interlinked with the leakage magnetic flux (φa, φb, φC) from the drive coil 9 is Conductor 11-
1 and the conductor 11-2 on the back side are made to be almost the same. With this structure, the voltage e (H induced at both ends of the conductor 11 due to the linkage with the leakage magnetic fluxes φa, φb, and φC, which are noise components) is ec=−((φa+φb + φC) t − (φδ+φb+φc))=O...(3), that is, the voltage generated on the front side conductor 11-1 and the back side conductor 11
Since the voltages generated at -2 have the same magnitude and opposite polarity, the noise voltage ec becomes zero. Thereby, a highly accurate rotation speed can be obtained from the output signal of the terminals T l + T 2 .

On the other hand, the voltage induced by the magnetic flux generated from the detection magnetic pole array of the annular magnet 7, which is a signal component, flows through the zigzag shape of the front conductor 11-1 and the back conductor 11-2 (
For example, if the front side is a mountain, the back side is a valley).Since they are arranged 180 degrees apart, they are added together, and the size is twice as large as when the conductor 11 is only on one side. This causes the terminal Ti.

The circuit for obtaining the rotational speed from the output signal of T2 can be simple.

Next, the above-mentioned speed detection signal generating conductor 11-1.

The board on which 11-2 is mounted will be described.

In the above-mentioned FIG. 2, the substrate 1o is mounted opposite the annular magnet 7 dedicated to rotational speed detection.
In FIG. 1, since it is possible to reduce noise and produce a large output, it is possible to detect the speed by attaching a board to the end of the base 1 so as to face the annular magnet 6 for the main pole. In that case, the annular magnet 7 is naturally unnecessary.

Further, the conductors 11-1 and 11-2 may be placed on both sides of the substrate, but there is also a method in which two substrates having conductors on only one side are placed one on top of the other.

Furthermore, the substrate may be in the form of a film sheet.

〔Effect of the invention〕

As explained above, according to the present invention, since the rectangular conductor for generating the speed detection signal is arranged in a folded manner so that the rising and falling edges of the rectangle overlap each other, the conductor is not affected by leakage magnetic flux. Highly accurate motor rotational speed can be obtained from a large detection signal without any interference.

[Brief explanation of drawings]

Fig. 1 is a schematic structural diagram of a speed detection signal generating conductor showing an embodiment of the present invention, Fig. 2 is a sectional view of a motor equipped with a rotational speed detection device, and Fig. 3 is a conventional speed detection signal generating conductor. FIGS. 4(a) and 4(b), which are schematic diagrams of the structure of the conductor, are diagrams for explaining the influence of leakage magnetic flux on the conductor. 1: Base, 2, 3: Bearing, 4: Rotating shaft, 5: Magnet holder, 6: Annular magnet for main pole, 7:
Annular magnet exclusively for rotational speed detection, 8: Core, 9: Drive coil, 1o: Substrate, 11° Fig. 1 Fig. 2 Fig. 3 Fig. Tl 'l'n

Claims (1)

[Claims] In order to detect the rotational speed of a motor that is equipped with a main pole annular magnet on the rotor and a motor drive coil on the status, a detection device using a conductor that interlinks with the magnetic flux has a rectangular waveform on the right side of the conductor. The first one being orbited
, and a second conductor having a rectangular wave shape similar to that of the first conductor and circulating to the left, and connecting the two conductors with rectangular rising (or falling) and falling (or falling) (or rising) A rotational speed detection device for a motor, characterized in that the device is arranged so as to overlap each other, connected in a folded manner, and interlinked with magnetic flux.