JPH06106018B2 - Rotational position detector for transistor motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational position detection device for a transistor motor, and more particularly to a transistor motor for driving a rotating drum such as a video tape recorder, which detects the rotational position of a head provided on the rotating drum. Rotation position detection device.

In a conventional rotary drum for driving a rotary head in, for example, a rotary two-head type video tape recorder, a direct drive type transistor motor is generally used for driving the rotary drum. Then, in order to detect the positions of the two rotary heads, a head position sensor (hereinafter, such a sensor is referred to as a head phase sensor) is individually provided, and the output of this sensor is used for phase control of the rotary drum or 2 It is used to switch the playback output signals from the two rotary heads.

When the head phase sensor is used for switching the output signal of the head, as shown in FIG. 1, two small magnets 44 and 45 are provided in the rotating part (rotor) at symmetrical positions with respect to the rotating shaft, and the stationary part is used. A magnetic head or coil 46 for detecting the magnetic flux of these magnets is usually attached to the (stator) to form a set of phase sensors. However, in such a detection device, a magnet having a magnetomotive force needs to be provided in the rotating portion, and the stationary portion needs detection means such as a magnetic head or a coil.
In terms of space, the space for the phase sensor is relatively large when viewed from the entire rotary drum, and there are many problems such as the need for gap adjustment.

Therefore, a main object of the present invention is to provide a rotational position detecting device for a transistor motor suitable for reduction in size and weight.

According to the present invention, in a rotational position detecting device for a transistor motor, the transistor motor is of an axial gap type and includes a rotor and a stator, the rotor having a rotor plate rotating about the rotation shaft, and the rotation shaft mounted on the rotor plate. It includes a plurality of field magnets which are arranged so as to surround and are provided so that the polarities are alternately inverted. The stator includes a stator plate and a plurality of armature coils arranged on the stator plate so as to surround the rotating shaft, and generate a rotating magnetic field by switching the current flowing through itself. The rotor rotates due to electromagnetic coupling between the field magnets and the armature coils. The rotational position detection device is provided on the rotor plate in the vicinity of a predetermined field magnet of the plurality of field magnets, and does not contribute to electromagnetic coupling among magnetic fluxes generated from the predetermined field magnet. A leakage flux reducing member that reduces the leakage flux, a magnetic sensitive element that is placed at a predetermined position on the stator plate and that detects the amount of leakage flux that does not contribute to electromagnetic coupling from a plurality of field magnets, and a rotor plate. The relative position of the rotor with respect to the stator is detected by detecting the decrease in the amount of leakage magnetic flux due to the fact that the upper leakage magnetic flux reducing member has passed over the magnetic sensitive element on the stator as a change in the output signal of the magnetic sensitive element. And a position determining means for determining.

In the transistor motor rotational position detecting device according to the present invention, only the leakage magnetic flux generated from the predetermined field magnet among the plurality of field magnets on the rotor plate is reduced by the leakage flux reducing member. Therefore, among the leakage fluxes emitted from the plurality of field magnets, the leakage flux amount is reduced only for a predetermined field magnet, so that the leakage flux caused by passing over the magnetic sensing element on the stator is reduced. Can be detected as a change in the output signal of the magnetically sensitive element. Therefore, the position detecting means can determine the relative influence of the rotor on the stator in response to the change in the output signal from the magnetically sensitive element. As described above, since it is not necessary to attach a dedicated magnet for detecting the rotational position to the rotor, it is possible to obtain a rotational position detecting device suitable for reduction in size and weight.

The above and other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings.

FIG. 2 is an illustrative view for explaining a relationship among a field magnet, an armature coil, and a magnetically sensitive element included in the transistor motor according to the embodiment of the present invention. In the figure, the transistor motor includes a disc 1 as a rotor and a permanent magnet 2 provided on the disc 1 and uniformly magnetized with 8 poles, and further as an output level changing means which is a feature of this embodiment. The protruding portion 3 is provided so as to protrude inward from the outer peripheral portion of the disc 1. That is, the magnetic resistance between the disc 1 and the permanent magnet 2 becomes small in the portion where the protrusion 3 is provided, and most of the magnetic flux emitted from the outer peripheral portion of the permanent magnet 2 passes through the protrusion 3 and circles. Reach plate 1. Therefore, the amount of leakage magnetic flux in the vicinity where the protrusion 3 is provided is smaller than that in the portion where the protrusion 3 is not provided. The disc 1 is integrally fixed to the rotary shaft by another metal fitting (not shown). The disc 1 is made of, for example, a soft magnetic material, is provided in close contact with one surface of the permanent magnet 2, and has a magnetic path for short-circuiting the magnetic flux of the magnet 2.

FIG. 2 (b) shows the stator plate 4, which is provided with six fan-shaped coils 5 made by winding a thin wire a large number of times and arranged in concentric circles at a pitch of 60 °. There is.
Further, on the stator plate 4, Hall elements 6 and 7 as a rotational position detecting sensor of the rotor are arranged 180 ° with respect to the rotation axis.
° Placed symmetrically. When the transistor motor is assembled as shown in FIG. 2C, these Hall elements 6 and 7 are arranged so as to face the rotation locus drawn by the protrusion 3 due to the rotation of the disc 1.

For example, as shown in FIG. 2C, when the protrusion 3 of the disk 1 faces the Hall element 6, the detected amount of magnetic flux of the Hall element 6 is the Hall element in which the protrusion 3 does not face. 7
Is less than the detected amount of magnetic flux. When the disc 1 rotates and the protrusion 3 is located on the Hall element 7, the amount of magnetic flux detected by the Hall element 7 is smaller than the amount of magnetic flux detected by the Hall element 6. Furthermore, when the protrusion 3 does not face either of the Hall elements 6 and 7,
The amounts of magnetic flux detected in the Hall elements 6 and 7 are almost equal.

FIG. 3 is a waveform diagram for explaining the operation of the transistor motor shown in FIG. 2 and the operation of the signal generating circuit shown in FIG. 4 described later.

3 (a) and 3 (b) respectively show the Hall element 6
And 7 are output signals. As shown in the figure, the output signals of the Hall elements 6 and 7 are both sinusoidal signals whose output signal level decreases when they face the protrusion 3. FIG. 3 (c) shows a signal obtained by subtracting the signal of FIG. 3 (b) from the signal of FIG. 3 (a). As shown,
In the signal shown in FIG. 3, when the projection 3 passes over the Hall element 6, the pulse is in the negative direction, and when the projection 3 passes over the Hall element 7, the pulse is in the positive direction.

However, if the permanent magnet 2 has uneven magnetization,
Even if the signal of FIG. 3 (b) is subtracted from the signal of FIG. 3 (a), the sine wave component (steady change component) of FIGS. 3 (a) and 3 (b) is not completely canceled out. Not necessarily the third
The waveform as shown in FIG. 7C cannot be obtained. For example, as shown in FIG. 3 (d), the signal has a noise component mixed therein. Therefore, if only the pulse component generated by the protrusion 3 is extracted by the level discrimination from the signal waveform shown in FIG. 3 (d), as shown in FIG. 3 (e), the desired rotational position of the rotor is represented. The signal is obtained.

FIG. 4 is a specific electric circuit diagram of a signal generating circuit included in an embodiment of the present invention. In the configuration, the output signal α of the Hall element 6 and the output signal β of the Hall element 7 are given to the differential amplifier 100. The differential amplifier 100 is for subtracting the output signal β from the output signal α, and as is well known, the voltage dividing resistors 8 and 12 for dividing the power source + V, the input resistors 9 and 10, the grounding resistor 11, And an operational amplifier 13. The output of the differential amplifier 100 is supplied to the-side level discriminator 200 and the + side level discriminator 300.

The − side level discriminator 200 discriminates the level of the output of the differential amplifier 100 by a constant negative reference voltage −VS (see FIG. 3 (d)). This − side level discriminator 200 is connected to resistors 14, 15 and 16 for generating a reference voltage −VS from a power source −V, an operational amplifier 19, and a differential amplifier 100 connected to the − side input terminal of the operational amplifier 19. Input resistance 17 that receives the output of
A grounding resistor 20 connected to the + side input terminal of the operational amplifier 19,
Backflow prevention diodes 18 and 21 connected in parallel with the operational amplifier 19, and a resistor 2 inserted between the power sources + V and -V for adjusting the peak value of the output pulse of the operational amplifier 19.
2,23,24 and 25 are included.

On the other hand, the + side level discriminator 300 is for level discriminating the output of the differential amplifier 100 with a positive constant reference voltage + VS (see FIG. 3 (d)). This + level discriminator 300
Has the same configuration as the-side level discriminator 200 described above except that the + reference voltage + VS is obtained from the power source + V by the resistors 26, 27 and 28.

Output of − side level discriminator 200 and + side level discriminator 300
The output of each is given to the addition circuit 400. The adder circuit 400 is for adding the input inputs. This adding circuit 400 includes an operational amplifier 41, a resistor 38 interposed between the − side input terminal of the operational amplifier 41 and the − side level discriminator 200, a − side input terminal of the operational amplifier 41, and a + side input terminal.
A resistor 39 interposed between the side level discriminator 300, a grounding resistor 42 interposed between the + side input terminal of the operational amplifier 41 and the ground, and a resistor 40 connected in parallel with the operational amplifier 41. including. The output of the adder circuit 400 is a capacitor 4 for removing the DC component.
Given to 3.

Next, the specific operation of the signal generating circuit will be described with reference to FIGS. The differential amplifier 100 subtracts the output signal B of the hall element 7 from the output signal α of the hall element 6. Therefore, a signal as shown in FIG. 3 (d) is obtained from the differential amplifier 100. This differential amplifier 10
The output of 0 is given to the − side level discriminator 200, and the reference voltage −
Level discrimination by VS. Therefore, the-side level discriminator
From 200, a negative pulse indicating that the protrusion 3 and the Hall element 6 face each other is output. On the other hand, the output of the differential amplifier 100 is given to the + side level discriminator 300 and level discriminated by the reference voltage + VS. Therefore, the positive-side level discriminator 300 outputs a positive pulse indicating that the protrusion 3 and the Hall element 7 face each other. The negative pulse from the − side level discriminator 200 and the positive pulse from the + side level discriminator 300 are given to the addition circuit 400 and added. The output of the adder circuit 400 is given to the capacitor 43, and its DC component is removed. Therefore, from the capacitor 43, a signal as shown in FIG. 3 (e), that is, the facing of the protrusion 3 and the Hall element 6 is represented by a negative pulse, and the facing of the protrusion 3 and the Hall element 7 is positive. A signal representing the pulse is output.

When the above-mentioned rotational position detecting device is used as a video head position detecting device for a video tape recorder, for example, the rotational position of the protrusion 3 shown in FIG. 2 and one rotational position of a plurality of video heads should be matched. You can leave it.

In the above embodiment, the three-phase eight-pole transistor motor has been described, but the present invention is also applicable to a transistor motor having an arbitrary total number or an arbitrary number of poles such as two-phase or four-phase or six-pole or ten-pole. .

Further, a plurality of magnetic responsive elements for coil switching position detection are arranged in the stator of an ordinary transistor motor, and one or two of these magnetic responsive elements are Hall elements for detecting the rotor rotational position. It is also possible to combine the two.

In addition, in the above-described embodiment, an example in which the Hall elements 6 and 7 are symmetrically arranged by 180 ° with respect to the rotation axis for use in the rotary 2 head type video tape recorder is shown. It is not limited to such a thing. That is, the Hall elements may be arranged at positions such that their output levels change to the same phase or opposite phase. When the mutual output levels change in phase, subtracting the other output from the one output eliminates the steady change component, and a signal indicating the facing of the protrusion can be obtained. On the other hand, when the output levels of the two change in opposite phases, by adding the outputs of the other, the steady change component can be erased and a signal indicating the facing of the protrusion can be obtained.

Further, in the above-described embodiment, the example in which the protrusion 3 is provided on the disk 1 is shown as an example of the output level changing means, but the field magnet 2 itself may be provided with the protrusion, or the field magnet 2 may be provided. The depression may be formed in a part of the rotation circumference of the.
Further, a magnetic piece may be bonded between the disc 1 and the permanent magnet 2.

As described above, according to the present invention, the leakage flux reducing member that reduces the leakage flux for a predetermined field magnet among the plurality of field magnets provided on the rotor plate is provided,
It is necessary to attach a magnet for detecting the rotational position to the rotor by detecting the decrease in the amount of magnetic flux leaked by the magnetic flux reducing member passing over the magnetic sensitive element on the stator as a change in the output signal of the magnetic sensitive element. Therefore, a rotational position detection device for a transistor motor that is suitable for size and weight reduction can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a transistor motor provided with a conventional rotational position detecting device. FIG. 2 is a diagram showing a configuration of a transistor motor provided with a rotational position detecting device according to an embodiment of the present invention. FIG. 3 is a waveform diagram for explaining the operation of the transistor motor shown in FIG.
FIG. 4 is a specific electric circuit diagram of a signal generating circuit included in an embodiment of the present invention. In the figure, 1 is a disk for holding a magnet, 2 is a permanent magnet, 3
Is a protrusion, 4 is a stator, 5 is an armature coil, 6 and 7 are Hall elements, 100 is a differential amplifier, 200 is a-side level discriminator, 300 is a + side level discriminator, and 400 is an adding circuit.

Claims (3)

[Claims] 1. A rotational position detecting device for an axial gap type transistor motor including a rotor and a stator, wherein the rotor is a rotor plate rotating about a rotating shaft, and the rotating shaft is provided on the rotor plate. It is arranged to surround
And a plurality of field magnets provided so that the polarities thereof are alternately inverted, the stator is disposed on the stator plate and the stator plate so as to surround the rotary shaft, and a current flowing through the stator plate. And a plurality of armature coils that generate a rotating magnetic field by switching the, the rotor is rotated by electromagnetic coupling between the plurality of field magnets and the plurality of armature coils, the rotational position detection device is A leakage magnetic flux, which is provided on the rotor plate in the vicinity of a predetermined field magnet of the plurality of field magnets and which does not contribute to the electromagnetic coupling, among magnetic fluxes emitted from the predetermined field magnet. A magnetic flux sensitive member that is placed at a predetermined position on the stator plate and that detects the amount of magnetic flux that does not contribute to the electromagnetic coupling from the plurality of field magnets, The rotor for the stator is detected by detecting a decrease in the amount of leakage magnetic flux due to the leakage flux reducing member on the rotor plate passing over the magnetic sensitive element on the stator as a change in the output signal of the magnetic sensitive element. And a position determining means for determining the relative position of the transistor motor. 2. The leakage flux reducing member is placed on the rotor near the predetermined field magnet to reduce a magnetic resistance between the rotor plate and the predetermined field magnet. The rotational position detecting device for a transistor motor according to claim 1, further comprising a magnetic resistance reducing member for controlling the rotational position. 3. The magnetically sensitive element is placed on the stator plate at a position facing each other with the rotary shaft interposed therebetween, and detects the amount of leakage magnetic flux from the plurality of field magnets that does not contribute to the electromagnetic coupling. A difference detecting unit including first and second Hall elements, wherein the position determining unit detects a difference between output signals from the first and second Hall elements and outputs a difference detection signal; Level comparison means for comparing the level of the signal with first and second predetermined threshold levels, and the relative position of the rotor with respect to the stator based on the output signal from the level comparison means. The rotational position detecting device for a transistor motor according to claim 1, wherein the rotation position detecting device is determined.