JP2000324882A - Encoder for detecting magnetic pole of pm motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a signal transmission method, to enable detection with a small-scale circuit, and to enable omission of wiring by outputting a duty factor representing a magnetic pole position as a pulse signal continuously, and detecting the magnetic pole position. SOLUTION: Four signals of phase A/phase B/phase Z/RT are outputted from a position detector, and an RT signal is a pulse signal which represents position (mechanical angle) information by a duty factor. Namely, a mechanical angle is represented by a duty factor of on-duration/ off-duration, and the period of repetition represents one rotation of the mechanical angle, and the position of a magnetic pole is detected by on-time/off-time. A controller receives this signal, computes on-time/off-time, and confirms a present magnetic pole position. After controlling power on the controller side is supplied, identification of the initial value of the magnetic pole is performed, and operation is made possible, and zero degree of the mechanical angle is detected by an input of phase Z. Detection of the pole position becomes feasible by counting pulses of phases A and B, after inputting the phase Z.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an encoder for detecting a magnetic pole of a PM motor.

[0002]

2. Description of the Related Art As shown in FIG.
When performing variable speed of the motor 2, it is necessary to detect and control the position of the magnetic pole, and for that purpose, an encoder (also referred to as a position detector) 3 for detecting the magnetic pole position is required. As shown in FIG. 8, there are many balanced-type outputs having high noise immunity, and two twisted-pair wires are used for the original signal. Therefore, when transmitting three signals, six signal lines are required. In a conventional PM motor magnetic pole detection encoder, the method of detecting the magnetic pole position is as follows.
One.

[Method 1] In this method, as shown in FIG. 9, an A / B / Z phase and a U / V / W
This is a method of detecting a magnetic pole position using a phase. Therefore, in order to detect the position of the magnetic pole, three 180 ° ON / OFF signals (U / V / W) are used (120 ° phase difference) to detect the current magnetic pole position. According to the instantaneous signal of the U / V / W phase, the mode is divided into six modes as shown in FIG.
An accuracy of 60/6 = 60 degrees is obtained, and position detection is performed. This signal matches the electrical angle, and if the number of poles of the motor is different, the relationship between the mechanical angle and the electrical angle changes. For example, in the case of two poles: one mechanical angle = one electrical angle, and in the case of eight poles: one mechanical angle = four electrical angles.

[Method 2] As shown in FIG. 10, this method is a method of continuously transmitting position data detected internally using serial transmission. In this method, high resolution can be realized by reducing the number of wirings and increasing the transmission data length per transmission as shown in FIG. The transmission section is configured to use a dedicated IC so as not to burden the control device.

[Method 3] As shown in FIG. 11, this method is a method of outputting a C phase which also serves as a U / V / W phase signal to a Z phase. Compared to Method 1, this method does not have a dedicated signal line, and can incorporate U / V / W signal states into the Z-phase signal, thereby achieving line saving. Therefore, as shown in FIG. 5, the A / B phase signal for discriminating the normal rotation / reversal is a signal having a phase difference of 90 degrees, and four modes are established according to the logic relationship of the A / B phase. . A signal to be output is determined for each mode, and the state of the Z / U / V / W phase is output.

[0006]

[Method 1] In this method, the A / B / Z phase and the U / V
/ W phase is used to detect the magnetic pole position.
Although it can be detected with an accuracy of 0 degrees, it must be selected for each number of poles of the motor, and it has disadvantages such as an increase in the number of encoders and a large number of wires (requiring 12 wires excluding the power supply wire). .

[Method 2] In this method, since the angle data is transferred by serial transmission, in other words, the mechanical angle of the motor is transferred by serial data.
Can be realized by one type irrespective of the number of poles of the motor (calculation for each number of poles on the receiving side), and line saving can be achieved. However, configuring the transmission unit with a dedicated IC or the like has a disadvantage in that the price of the components constituting the serial transmission unit increases, resulting in an increase in the overall price.

[Method 3] In this method, since the signals of the U / V / W phases are also used as the Z phase and output, the line saving can be realized compared to the method 1. However, similarly to the method 1, there is a disadvantage that it is necessary to select for each number of poles of the motor, or the magnetic pole position cannot be detected unless the motor starts rotating. A / B
If all phase combinations are not performed once, the Z phase /
The state of the U / V / W phase is not known, and rotation for one cycle of the A phase is required.

Due to the above-mentioned problems of the prior art, the following functions are required. 1. It is realized by one type of position detector regardless of the number of motor poles. 2. Position detection is performed with the motor stopped. 3. Realize line saving. 4. Realize low cost. An object of the present invention is to provide a PM motor magnetic pole detection encoder that satisfies the above requirements.

[0010]

According to a first aspect of the present invention, there is provided a PM motor magnetic pole detection encoder which outputs a duty ratio representing a magnetic pole position as a pulse signal to detect a magnetic pole position. By doing so, the wiring can be omitted and the cost can be reduced. Claim 2 of the present invention to achieve the above object
The PM motor magnetic pole detection encoder according to claim 1 is characterized in that, by continuously outputting the pulse signal, reliability can be improved and a problem of synchronization with the control side can be solved.

[0011]

FIG. 1 shows the configuration of a position detector according to an embodiment of the present invention. As shown in FIG. 6, the signals output from the position detector are four signals of A phase / B phase / Z phase / RT, and the A phase / B phase / Z phase are the same as the conventional signals. The present invention is characterized in that an RT signal is output. The RT signal has a position (mechanical angle) as shown in FIG.
Is a pulse signal represented by a duty ratio.

That is, the mechanical angle is represented by a duty ratio of ON width / OFF width, and the magnetic pole position is detected based on ON time / OFF time. The repetition cycle indicates one rotation of the mechanical angle, and the magnetic pole position is detected based on the ON time / OFF time. The logic of ON / OFF may be reversed. When the magnetic pole position is close to 0 degrees, the width of OFF becomes shorter and the width of ON becomes longer. When the magnetic pole position is closer to 360 degrees, the width of OFF becomes longer and the width of ON becomes shorter. I do.

The control device receives this signal and turns it on.
Calculate the / OFF time and confirm the current magnetic pole position. After turning on the control power supply on the control device side, the initial value of the magnetic pole is identified, operation is enabled, and a mechanical angle of 0 degree is detected by inputting the Z phase.

After the Z-phase input, by counting the A / B-phase pulses, the magnetic pole position can be detected. Therefore, the accuracy of the initial magnetic pole position detection is not required to be high performance. Position detection is sufficient. Further, the control device does not require a dedicated IC, and can be directly measured by the CPU using an interrupt signal input of the CPU, or can be realized by a combination of inexpensive ICs. Further, by continuously outputting the RT signal, it is possible to improve reliability and to solve the problem of synchronization with the control side.

[0015]

As described above, according to the present invention, the following effects can be obtained as specifically described based on the embodiments. 1. A signal of the mechanical angle can be received, and the control side converts the value into an electrical angle value and uses it for control, so that it can be realized with one type of encoder regardless of the number of poles of the motor. 2. By making one signal to be added, line saving can be realized. 3. Since the signal transmission method is simple, detection can be performed with a small-scale (low-cost) circuit. 4. Even if the motor is not rotating, the position can be detected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a detector according to one embodiment of the present invention.

FIG. 2 is a time chart showing an RT signal output.

FIG. 3 is a time chart illustrating signal output of each phase of a position detection method (method 1) according to the related art.

FIG. 4 is a time chart showing signal output of each phase of a position detection method (method 2) according to the related art.

FIG. 5 is a time chart showing signal output of each phase of a position detection method (method 3) according to the related art.

FIG. 6 is a time chart showing signal output of each phase according to one embodiment of the present invention.

FIG. 7 is a configuration diagram of a variable speed PM motor.

FIG. 8 is an explanatory diagram showing a signal form of a variable speed PM motor.

FIG. 9 is a configuration diagram of a position detector according to the related art.

FIG. 10 is a configuration diagram of a position detector according to the related art.

FIG. 11 is a configuration diagram of a position detector according to the related art.

[Explanation of symbols]

 1 variable speed device 2 PM motor 3 position detector A, B, C, Z, U, V, W, RT signals

Claims (2)

[Claims] 1. A duty ratio representing a magnetic pole position is output as a pulse signal in order to detect a magnetic pole position.
A PM motor magnetic pole detection encoder characterized in that the wiring can be omitted and the cost can be reduced. 2. The method according to claim 1, wherein by continuously outputting the pulse signal, reliability can be improved and a problem of synchronization with a control side can be solved.
M motor magnetic pole detection encoder.