JPH04331488A - Encoder for ac synchronous motor and starting method for ac synchronous motor by use of said encoder - Google Patents

Abstract

PURPOSE:To provide a miniature encoder having reduced number of output wires with low cost and to facilitate the wiring work when an AC synchronous motor is started through the encoder. CONSTITUTION:A conventional encoder outputs two phase signals A and B, an original point signal Z, and pole position signals (U, V, W), i.e., total six types of signals. In the invention, a ZP signal where the pole position signal is superposed on the original point signal is generated in addition to the two phase signals A and B thus outputting total three types of signals. Consequently, the number of wires is decreased and a downsized encoder can be fabricated with low cost while furthermore wiring work to a controller can be facilitated when an AC synchronous motor is started.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder that is attached to a synchronous AC motor whose rotor is made of a permanent magnet, and a method for starting a synchronous AC motor using the encoder.

0002

2. Description of the Related Art FIG. 4 is a waveform diagram for explaining output signals of a general encoder. A and B in the same figure are two-phase signals,
Z is the origin signal (also called Z phase signal) indicating the origin, U, V
, W indicate three-phase magnetic pole position signals, respectively. Note that the A and B phase signals have a phase difference of 90 degrees from each other, for example,
It is assumed that the motor outputs 1000 pulses per revolution. Further, one origin signal is output per rotation of the motor. In other words, synchronous type A in which the rotor is made of a permanent magnet.
To control the C motor, it is necessary to detect the magnetic pole position, and for this reason conventionally two-phase signals A, B, origin signal Z,
Furthermore, when driving with a three-phase power supply, the three-phase magnetic pole position signal U
, V, and W are generally used. As a result, magnetic pole sensors and amplifier circuits for generating magnetic pole position signals are required for the number of signals, which not only increases the number of circuit components, but also increases the size of the encoder. If it is installed and controlled, the number of wires between the controller and the controller increases, causing problems in cost and reliability.

Furthermore, when starting a three-phase synchronous AC motor, for example, the drive current flowing through the three-phase stator coils is switched in a certain order (switching pattern) using a switching circuit, etc., to generate a rotating magnetic field, which causes the rotor to move. I'm trying to start the rotation. At this time, the rotor may rotate in the opposite direction to its original direction depending on the stop position of the rotor at the start of startup, so it is necessary to detect the rotor position and select a certain switching pattern corresponding to that position. (Regarding this point, if necessary, for example,
(See Publication No. 237490). For this reason, either a special magnetic sensor is installed to detect the position of the rotor, or
Otherwise, I use an encoder like the one above.

0004

[Problems to be Solved by the Invention] As described above, using an encoder having output characteristics as shown in FIG. 4 not only increases the number of circuit components but also increases the size of the encoder. When controlling the controller by attaching it to the controller, the number of wires between the controllers increases, causing problems in cost and reliability. Therefore, an object of the present invention is to provide a compact and inexpensive encoder that generates fewer signals, and to reduce wiring work when starting a synchronous AC motor using such an encoder.

[0005]

[Means for Solving the Problems] In order to solve such problems, the first invention provides an encoder that is used by being attached to a synchronous AC motor whose rotor is made of a permanent magnet, and which receives not only a two-phase signal but also a two-phase signal. It is characterized by generating a signal in which a magnetic pole position signal is superimposed on an origin signal. Further, in the second invention, an encoder that generates a signal obtained by superimposing a magnetic pole position signal on an origin signal in addition to the two-phase signal is attached to the synchronous AC motor whose rotor is made of a permanent magnet, and the synchronous AC motor When starting the motor, the stop position of the motor is detected based on the magnetic pole position signal from the encoder, a predetermined one is selected from a plurality of preset energization switching patterns, and the selected energization switching pattern is activated. The rotor is characterized in that the stator coils are sequentially energized to generate a rotating magnetic field, thereby rotationally driving the rotor.

[0006]

[Function] By using three types of output signals from the encoder: a two-phase signal and a signal obtained by superimposing a magnetic pole position signal on an origin signal, the encoder can be made smaller and lower in cost.
In addition, wiring work when starting a synchronous AC motor using such an encoder is reduced and reliability is improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a waveform diagram for explaining an output signal of an encoder according to the present invention, and FIG. 2 is a partially enlarged view thereof. As is clear from these figures, in addition to the two-phase signals A and B, there are a total of three types of signals, for example, a signal ZP in which a magnetic pole position signal P synchronized with the B signal is superimposed on an origin signal Z synchronized with the A signal. The feature is that it outputs a signal of . For this purpose, for example, in the case of an optical type, a disk having three types of concentric slits is placed between the light emitting element and the light receiving element, and the two-phase signals A and B are obtained using the same concentric slits as in the conventional method. On the other hand, in order to make the ZP signal as shown in FIG. 1, we took measures such as forming a narrow slit corresponding to the Z signal and a relatively wide slit corresponding to the P signal. to remove it. In addition, in the case of the magnetic type, a magnetic material is used instead of the slit, so by considering the size of this magnetic material and its placement position, it is possible to extract the ZP signal as a single signal in the same way. Become.

FIG. 3 is a schematic diagram showing an embodiment in which a synchronous AC motor is started using the encoder as described above. In the figure, 1 is a servo motor drive unit, 2 is a synchronous AC motor (also simply referred to as a motor), 3 is the encoder explained in FIG. 1 or 2, 4A to 4C are amplifiers, and 5A
, 5B is a synchronization detection circuit, and 6 is a switching pattern discrimination circuit. The A signal and B signal outputted from the encoder 3 are respectively given to the servo motor drive unit 1 via amplifiers 4A and 4B, and the ZP signal is given to synchronous detection circuits 5A and 5B via an amplifier 4C, respectively, for synchronization. The detection circuit 5A extracts the Z signal by performing synchronous detection with the A signal, and the synchronous detection circuit 5B extracts the P signal by performing synchronous detection with the B signal. This P signal is given to the switching pattern discrimination circuit 6, which selects the energization switching pattern according to the magnetic pole position of the rotor, thereby making it possible to start the synchronous AC motor smoothly without reversing the rotation. At this time, it goes without saying that the number of wires between the servo motor drive unit 1 and the encoder 2 is smaller than in the past, and as a result, the wiring work is also significantly reduced.

[0009]

According to the present invention, since the number of output signals of the encoder is reduced, the encoder can be made smaller and cheaper. Further, when such an encoder is used to start a synchronous AC motor, there are advantages such as the number of wires connected to the controller is reduced, wiring work is significantly reduced, and reliability is improved.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram for explaining an output signal of an encoder according to the present invention.

FIG. 2 is a partially enlarged view of FIG. 1;

FIG. 3 is a schematic diagram showing an embodiment in which a synchronous AC motor is started using an encoder such as that shown in FIG. 1 or 2;

FIG. 4 is a waveform diagram for explaining output signals of a general encoder.

[Explanation of symbols]

1 Servo motor drive section 2 Synchronous AC motor 3 Encoder 6 Switching pattern discrimination circuit 4A amplifier 4B Amplifier 4C amplifier 5A synchronous detection circuit 5B Synchronization detection circuit

Claims (2)

[Claims] [Claim 1] A synchronous AC whose rotor is made of a permanent magnet.
An encoder used by being attached to a motor, comprising: 2
An encoder for a synchronous AC motor, characterized in that it generates a signal in which a magnetic pole position signal is superimposed on an origin signal in addition to a phase signal. [Claim 2] A synchronous AC whose rotor is made of a permanent magnet.
An encoder is attached to the motor that generates a signal in which a magnetic pole position signal is superimposed on the origin signal in addition to the two-phase signal, and when starting the synchronous AC motor, the motor is stopped based on the magnetic pole position signal from the encoder. The position is detected, a predetermined one is selected from among a plurality of preset energization switching patterns, and the stator coils are sequentially energized in the selected energization switching pattern to generate a rotating magnetic field, and the rotor A method for starting a synchronous AC motor, characterized in that it rotates.