JPH0819238A - Position detector for motor - Google Patents

Abstract

PURPOSE:To obtain a position detector for a motor whose PG output is not influenced by the flux of a driving magnetized part and which facilitates the improvement of an S/N ratio by a method wherein the pitches of a PG magnetized part and a PG pattern are specified to be constant in relation to the driving magnetized part. CONSTITUTION:An annular driving magnet 2 which rotates with a rotary unit 1 is magnetized so as to have N-poles and S-poles alternately in its circumferential direction to provide a driving magnetized part 2a. A PG magnetized part 4 is formed in a part of the end surface of the driving magnet 2. A PG pattern is provided so as to face the PG magnetized part 4. If the pitch between a pair of the N-pole and the S-pole of the driving magnetized part 2a is defined as one pitch, the PG magnetized part 4 is magnetized so as to have a half pitch and, further, have a pitch agree with the pitch of the PG pattern. The PG magnetized part 4 may be composed of a pair of N-pole and S-pole only and the boundary between the N-pole and the S-pole may be made to agree with the boundary between the N-pole and the S-pole of the driving magnetized part 2a and the polarity of the PG magnetized part 4 may be opposite to the polarity of the driving magnetized part 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for a rotating body in a motor, and more particularly to a position detecting device capable of eliminating noise due to a drive magnetizing section.

[0002]

2. Description of the Related Art For example, a video tape recorder (VTR)
In the case of a cylinder motor or the like, it is necessary to constantly detect the reference position during one rotation, and therefore a rotational position detection device is incorporated. FIG. 7 shows an example of such a VTR cylinder motor. In FIG. 7, a stator core 35 is fixed on a substrate 37 via a core holder 38. The stator core 35 has a plurality of salient poles radially, and a drive coil 36 is wound around each salient pole. The stator core 35,
The drive coil 36, the substrate 37, etc. constitute a stator. Although not shown in detail, the fixed cylinder 32 is fixed substantially integrally with the stator core 35.

A cup-shaped rotor case 21 is arranged so as to cover the stator core 35 from above. The rotor case 21 is rotatably supported by an appropriate bearing mechanism. An annular drive magnet 22 is fixed to the inner surface of the peripheral wall of the rotor case 21, and the inner peripheral surface of the drive magnet 22 faces the outer peripheral surface of the stator core 35 and the tip surfaces of the salient poles with a proper gap. There is. Rotor case 2
A rotary cylinder (not shown) is fixedly attached substantially to the unit 1,
There is an appropriate gap between the lower peripheral edge of the rotary cylinder and the upper peripheral edge of the fixed cylinder 32, and the magnetic head mounted on the lower peripheral edge of the lower surface of the rotary cylinder rotates within the gap. An annular magnet 23 is fixed to the lower end surface of the drive magnet 22 via a shield ring 24. The magnet 23 is provided with a position detecting magnetized portion (hereinafter referred to as “PG magnetized portion”) that constitutes a part of the position signal generator (hereinafter referred to as “PG”).
A flexible circuit board 39 is fixed on the board 37, and a position detection pattern (hereinafter referred to as “PG pattern”) 26 is formed on a surface of the flexible circuit board facing the magnet 23.

In FIG. 8A showing the relationship between the PG magnetized portion 28 formed on the magnet 23 and the PG pattern 26, the PG magnetized portion 28 is arranged with four magnetic poles at a predetermined magnetizing pitch. . On the other hand, the PG pattern 26 has four PG power generation line elements arranged at the same pitch as the pitch of the PG magnetized portions 28.

The magnetic pole of the drive magnet 22 is detected by a hall element or the like, and the energization of each drive coil 36 is switched according to the detection signal, so that the rotor case 21, the rotary cylinder, etc. substantially integrated with the drive magnet 22 rotate. Driven. As the magnet 23 rotates together with the drive magnet 22 and the magnetic flux of the PG magnetized portion 28 crosses the PG pattern 26, the PG pattern 26 outputs a PG signal as is well known. This PG signal serves as a reference signal for one rotation.

[0006]

The power generation signal waveforms by the four PG power generation line elements of the motor position detection device described above are shown in FIGS. 8 (B) (C) (D) (E), respectively. Since the magnetic pole pitch of the PG magnetized portion 28 matches the pitch of each power generating line element, each power generating line element outputs a wave-shaped signal at a cycle corresponding to these pitches. As shown in FIG. 8E, the PG output obtained by synthesizing the power generation signals of these power generating line elements has a negative signal with a large peak in the center, plus signals with large peaks on both sides thereof, and further on both sides thereof. It consists of a negative signal and a plus signal with small peaks on both sides. P
The G signal is obtained by waveform-shaping the first plus signal having a large peak, and the plus signals having a small peak on both sides become noise with respect to the PG signal. In the above-mentioned conventional example, when the peak value of the first plus signal of the large peak is S, the peak value of the plus signal of the small peaks on both sides is about S / 3, and the noise component for the PG signal is large. The signal-to-noise ratio (S / N) of the signal had deteriorated.

Further, in the conventional motor position detecting device,
Since there was no relationship between the pitch of the PG pattern and the pitch of the drive magnetization, each power generation line element of the PG pattern was affected by the magnetism of the drive magnetization, and the power generation output of each power generation line element was synthesized. Since the output contains a noise component larger than the above noise component, the signal-to-noise ratio (S / N) of the PG signal is further deteriorated.

The present invention has been made in order to solve the problems of the prior art as described above, and makes the pitch of the PG magnetized portion and the pitch of the PG pattern constant in relation to the drive magnetized portion. An object of the present invention is to provide a motor position detection device capable of improving the signal-to-noise ratio of PG output by defining.

[0009]

In order to achieve the above object, the present invention is a drive in which an N-pole and an S-pole are alternately magnetized in a circumferential direction on an annular drive magnet that rotates integrally with a rotating body. In a position detecting device for a motor, which comprises a magnetizing portion, a PG magnetizing portion formed on a part of an end surface of the drive magnet, and a PG pattern arranged at a position facing the PG magnetizing portion, When the pair of N poles and S poles of the magnetic portion was one pitch, the PG magnetized portion was magnetized at 1/2 pitch and matched with the pitch of the PG pattern. The PG magnetizing section has only a pair of N and S poles, and the boundary between the N and S poles is made to coincide with the boundary between the N and S poles of the driving and magnetizing section. The polarity of the magnetized portion may be opposite. You may form only a pair of PG magnetization on the end surface of a drive magnet.

[0010]

When the magnetic fluxes of the drive magnetized portion and the PG magnetized portion cross the PG pattern, each power generation line element of the PG pattern generates a signal corresponding to the magnetic flux of the drive magnetized portion and the PG magnetized portion. The signals generated in the respective power generation line elements of the PG pattern are combined, and the signal that rises first among the combined signals is used as the position signal. When the pair of N pole and S pole of the drive magnetizing unit is set to one pitch. , The PG magnetized portion is magnetized at a 1/2 pitch and coincides with the pitch of the PG pattern.
A signal corresponding to the drive magnetized portion is canceled from the position signal obtained by synthesizing the power generation signals of the power generating line elements of the G pattern, and a position signal that is not affected by the drive magnetized portion can be obtained.
The first rising signal of this position signal rises largely and becomes a signal with a good signal-to-noise ratio. In addition, the PG magnetized portion has only a pair of N and S poles, and its boundary is made to coincide with the boundary between the N and S poles of the drive magnetized portion, and the polarities of the PG magnetized portion and the drive magnetized portion are set. Even when is set to the opposite pole, the initial rising signal is large and a position signal having a good signal-to-noise ratio can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a motor position detecting device according to the present invention will be described below with reference to the drawings. First,
An overall configuration of a motor having a position detection device according to the present invention will be schematically described. In FIG. 2, the stator core 15 is fixed on the substrate 17 via the core holder 18. The stator core 15 has a plurality of salient poles radially,
A drive coil 16 is wound around each salient pole. A stator is composed of the stator core 15, the drive coil 16, the substrate 17, and the like. Core holder 1 (not shown)
A shaft is rotatably supported on the inner peripheral side of 8 via an appropriate bearing, and a cup-shaped rotor case 1 is fixed to the shaft. The rotor case 1 covers the stator core 15 from above. A ring-shaped drive magnet 2 is fixed to the inner surface of the peripheral wall of the rotor case 1, and the inner peripheral surface of the drive magnet 2 faces the outer peripheral surface of the stator core 15 and the tip surfaces of the salient poles with a proper gap. There is. Drive magnet 2
A PG magnetized portion 4 is formed on the lower end surface of the. The PG magnetized portion 4 may be directly formed on the drive magnet 2, or the separately formed PG magnetized portion 4 may be fixed to the drive magnet 2. A flexible circuit board 19 is provided on the board 17.
Is fixed, and the PG magnetized portion 4 of the flexible circuit board 19 is fixed.
A PG pattern is formed on the surface opposite to.

Next, the specific structures of the drive magnet 2 and the PG magnetizing portion will be described. In FIG. 1, a ring-shaped drive magnet 2 is fixed to the inner surface of the peripheral wall of the rotor case 1. The drive magnet 2 is formed with a drive magnetized portion 2a in which a plurality of magnetic poles are arranged at equal intervals in the circumferential direction and their polarities are alternately inverted. The drive magnetized portion 2a is magnetized in the radial direction. A position detecting magnetized portion (PG magnetized portion) 4 is also formed on the axial end surface of the drive magnet 2. As shown in FIG. 4 (A), when the pair of north and south poles of the drive magnetized portion 2a has a pitch of 1, the PG magnetized portion 4 is 1/2
It is magnetized at the pitch. The PG magnetizing unit 4 is composed of four magnetic poles in which N poles and S poles are alternately arranged.
The four magnetic poles of the PG magnetized portion 4 are arranged corresponding to the two adjacent magnetic poles. The magnetizing direction of the PG magnetizing portion 4 is the central axis direction orthogonal to the magnetizing direction of the drive magnetizing portion 2a.

In FIG. 4A, reference numeral 6 is a position detection pattern (PG) formed on the flexible circuit board 19.
Pattern). The PG pattern 6 has four power generating line elements. The respective power generating line elements are arranged radially with respect to the rotation center of the motor, and the inner ends and the outer ends of the adjacent power generating line elements are alternately connected in series by a conductive wire, and a PG signal is output from both ends thereof. The arrangement pitch of each power generation line element is the same as the arrangement pitch of the PG magnetized portions 4 and is 1/2 of the pitch of the drive magnetized portions 2a.

The PG signal output operation of the above-described embodiment will be described. Energize the drive coil 16 shown in FIG.
The drive coil 16 corresponding to the rotational position of the drive magnet 2
Drive magnet 2 by switching the power supply to
Then, the drive magnet 2 is biased by the magnetic force generated between the salient pole of the stator core 15 and the rotor including the drive magnet 2, the rotor case 1, the FG magnet 3, the PG magnet 4 and the like rotates. When the rotor rotates, the magnetic fluxes of the drive magnetizing unit 2a and the PG magnetizing unit 4 cross each power generating line element of the PG pattern 6, and each power generating line element generates a signal corresponding to each magnetic flux. The signals corresponding to the drive magnetizing unit 2a generated by the element are canceled each other, and the PG signal is not influenced by the drive magnetizing unit 2a. The reason is shown in FIG.

FIG. 3A shows a case where the boundary between the magnetic poles of the drive magnetized portion 2a passes through the position of the power generating line element, and power is generated by the power generating line element, but these power generation signals are in opposite directions. Cancel each other out. FIG. 3B shows the drive magnet 2
3A shows a case in which the magnetic pole boundary of the drive magnetized portion 2a passes through the position of the power generating line element, with a slight advance from the position of FIG.
At this time, the signals generated by the power generating line elements are in opposite directions and cancel each other out. 3 (C) (D) (E) (F) show the power generation signal of each power generation line element on the time axis.
The output of the PG pattern 6 is a combination of these power generation signals. These power generation signals cancel each other out, and the signal generated by the drive magnetizing unit 2a is not output from the PG pattern 6.

On the other hand, when the magnetic flux of the PG magnetizing section 4 crosses each power generation line element of the PG pattern 6, a PG signal is output from the PG pattern 6. This PG signal output operation is shown in FIG. As shown in FIG. 4A, since the magnetic pole pitch of the PG magnetized portion 4 and the pitch of each power generation line element of the PG pattern 6 match, the magnetic flux of the PG magnetized portion 4 crosses each power generation line element. As a result, each power generation line element outputs a wavy signal at a cycle corresponding to the pitch of each power generation line element, as shown in FIGS. 4 (B), (C), (D), and (E). The power generation signal waveforms of the power generation line elements are 360 ° out of phase with each other and the rising and falling edges are synchronized, and the output of the PG pattern 6 formed by combining these power generation signals is shown in FIG. As shown, it is composed of a central large peak negative signal, a large peak positive signal on both sides thereof, a negative signal on both sides thereof, and a small peak positive signal on both sides thereof.

As described above, as the PG signal,
The first plus signal with the large peak is obtained by waveform shaping, and the plus signals with the small peaks on both sides become noise with respect to the PG signal.
In the above embodiment, when the peak value of the first plus signal of the large peak is S, the peak value of the plus signals of the small peaks on both sides is about 0.2 to 0.3S. However, when the pair of N pole and S pole of the drive magnetized portion 2a is set to one pitch, the PG magnetized portion 4 is magnetized at ½ pitch and coincides with the pitch of the PG pattern 6.
Since the relationship between the drive magnetizing unit 2a, the PG magnetizing unit 4, and the PG pattern is set to a constant relationship, the peak value of the plus signal of the small peaks on both sides becomes large due to the influence of the drive magnetizing unit 2a. Rather, a PG output having a better signal-to-noise ratio can be obtained as compared with the conventional motor position detecting device, and the position signal obtained by shaping the waveform of the PG output is highly accurate.

Next, another embodiment of the device of the present invention will be described. In the example shown in FIG. 5, the PG magnetizing unit 60 is provided with a pair of N
In this example, only the pole and the S pole are used. Also in this example, when the pair of N poles and S poles of the drive magnetizing unit are set to one pitch, the PG magnetizing unit 6
0 is magnetized at a 1/2 pitch and coincides with the pitch of each power generating line element of the PG pattern 6. And PG
Non-magnetized portions 61, 61 are provided on both sides of the magnetized portion 60.

FIGS. 5B, 5C, 5D and 5E show the output of each power generating line element of the PG pattern 6 when the drive magnet 2 constituting the rotor of the motor rotates. Since the PG magnetizing unit 60 includes only a pair of N and S poles, each power generation line element generates a wave-shaped signal for one cycle. Since the phases of these signal waveforms are shifted by 360 ° and the rising and falling are synchronized, the output of the PG pattern 6 formed by combining these power generation signals is as shown in FIG.
As shown in (2), it consists of a minus signal with a small peak at both ends, two plus signals with a large peak following it, and one minus signal with a large peak in the center. Therefore, according to this embodiment, the signals on both sides of the first plus signal do not become noise signals and become noise components, and the position signal with a better signal-to-noise ratio and high accuracy is obtained. Can be obtained. In the case of this embodiment as well, the drive magnetizing unit 2 appearing in each power generation line element of the PG pattern 6 is formed.
The signals corresponding to a are canceled by each other, and the PG output is not affected by the drive magnetizing unit 2a.

In the embodiment shown in FIG. 5, the PG magnetizing portion is formed by a pair of Ns.
Although the example has only the pole and the S pole, and there is no magnetized portion on both sides thereof, even if there is a magnetized portion on both sides of the PG magnetized portion consisting of a pair of N pole and S pole only. If the magnetized portion is weak, a PG signal having a good signal-to-noise ratio can be obtained. An example thereof is shown in FIG. In FIG. 6 (A), on both sides of the PG magnetized portion 62 consisting of only a pair of N and S poles, weak magnetized portions 63, 6 under the influence of drive magnetization, for example.
There are three. Also in this example, the pair of N poles and S of the drive magnetizing unit 2a
When the poles are set to 1 pitch, the PG magnetized portions 62 are magnetized at 1/2 pitch and match the pitch of each power generation line element of the PG pattern 6. The boundary between the pair of N and S poles of the PG magnetized portion 62 coincides with the boundary between the N and S poles of the drive magnetized portion 2a, and further, the polarity of the PG magnetized portion 62 and the drive magnetized portion 2a. The polarity is opposite to that of.

6B, 6C and 6D show the power generation waveforms of the power generation line elements of the PG pattern 6 when the drive magnet 2 constituting the rotor rotates in the above embodiment.
It shows in (E). Since there are weakly magnetized portions 63 and 63 having the same pitch on both sides of the PG magnetized 62, the power generation waveforms of the respective power generating line elements are positive and negative signals of small peaks before and after and positive and negative signals of large peaks between them. Further, the phase is shifted by 360 ° and the rising and falling are synchronized. The output signal of the PG pattern 6 formed by combining the power generation waveforms of the power generation line elements is shown in FIG.
As shown in, two positive signals with small peaks on both sides, two negative signals with intermediate peaks following, two positive signals with large peaks following, and one negative signal with large peaks following Consists of. The plus signals of the small peaks on both sides are the weak magnetized portions 63,
It is caused by the presence of 63. The PG signal is obtained by waveform-shaping the first plus signal having a large peak. Therefore, the plus signals with extremely small peaks on both sides become noise with respect to the PG signal.
However, assuming that the peak value of the first plus signal of the large peak is S, the peak value of the plus signal of the small peaks on both sides is about 0.03S, which is a negligible amount of a very small signal. A signal to noise ratio is obtained.

The present invention is not limited to VTR cylinder motors, but can be applied to any motor that requires a position detection signal, such as a disk drive motor.

[0023]

According to the invention described in claim 1, when the pair of the N pole and the S pole of the drive magnetizing portion is set to 1 pitch, the position detecting magnetizing portion is magnetized at 1/2 pitch and Since the pitch of the position detection pattern is matched, the signal generated by the drive magnetizing unit generated by the position detecting pattern is canceled so that the position detection output is not affected by the magnetic flux of the drive magnetizing unit and is used as the position signal. Since the first signal on the plus side of the position detection pattern output has a high peak, the signal-to-noise ratio is extremely good, and a highly accurate position signal can be obtained.

According to the second aspect of the present invention, the position detecting magnetized portion is composed of only a pair of N and S poles, and the boundary between the N and S poles is the N pole of the drive magnetized portion. Since the polarities of the position detecting magnetized portion and the drive magnetized portion are made opposite to each other while matching the boundary of the S pole, the output of the position detection pattern formed by combining the power generation signals of the respective power generating line elements is: The peak of the first signal on the plus side is high, the signal-to-noise ratio is very good,
A highly accurate position signal can be obtained. Further, the signals corresponding to the drive magnetized portions appearing in each of the power generation line elements of the position detection pattern are canceled out from each other, and the position signal that is not affected by the drive magnetized portion can be obtained.

According to the second and third aspects of the present invention, the position detecting magnetized portion only needs to form a pair of magnetic poles, and the structure of the position detecting magnetized portion can be simplified.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a drive magnetizing unit and a position detecting magnetizing unit applicable to the device of the present invention.

FIG. 2 is a front sectional view showing an embodiment of the device of the present invention having a drive magnetizing portion and a position detecting magnetizing portion.

FIG. 3 is a waveform diagram showing an operation of canceling the influence of the drive magnet due to the position detection pattern in the above embodiment.

FIG. 4 is a waveform diagram showing a position signal output operation based on the position detection pattern in the above embodiment.

FIG. 5 is a waveform diagram showing a modification of the device of the present invention and a position signal output operation thereof.

FIG. 6 is a waveform diagram showing still another modification of the device of the present invention and a position signal output operation thereof.

FIG. 7 is a front sectional view showing an example of a conventional motor with a position detection device.

FIG. 8 is a waveform diagram showing the position signal output operation of the above conventional example.

[Explanation of symbols]

 1 Rotor Case as Rotor 2 Drive Magnet 4 Position Detection Magnetization Part 6 Position Detection Pattern 2a Drive Magnetization Part

Claims (3)

[Claims] 1. A drive magnetizing portion formed by alternately magnetizing an N pole and an S pole in a circumferential direction on an annular drive magnet that rotates integrally with a rotating body, and formed on a part of an end surface of the drive magnet. A position detecting device for a motor, comprising: the position detecting magnetized part and a position detecting pattern arranged at a position facing the position detecting magnetizing part; and a pair of N poles of the drive magnetizing part. A position detecting device for a motor, wherein when the S pole is set to 1 pitch, the position detecting magnetized portion is magnetized at a 1/2 pitch and coincides with the pitch of the position detecting pattern. 2. The position detecting magnetized portion is composed only of a pair of N pole and S pole, and the boundary between the N pole and the S pole is N of the drive magnetized portion.
2. The motor position detection device according to claim 1, wherein the position detection magnetized portion has the same polarity as the boundary between the pole and the S pole, and the drive magnetized portion has opposite polarities. 3. A motor position detecting device according to claim 2, wherein only a pair of position detecting magnetized magnets are formed on the end face of the drive magnet.