JP3311255B2 - Encoder signal transmission circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission circuit for an encoder, which transmits an encoder signal for detecting rotation of a motor to a receiving side located at a position distant from the motor to obtain information on the rotation of the motor.

[0002]

For example, an MR type encoder generates a sine wave signal synchronized with the rotation of the motor by a sensor such as a magnetoresistive element provided inside the motor, and transmits the generated sine wave signal. The signal is transmitted to the control circuit on the receiving side via the line. The control circuit on the receiving side performs signal processing such as shaping the sine wave signal transmitted as the encoder signal into a rectangular wave and then multiplying the signal to obtain detailed information on the rotation angle of the motor. Such an encoder is particularly suitable for detecting the rotation angle of a motor that rotates at high speed because the transmitted encoder signal is a sine wave and does not include harmonic components.

[0003] However, if the length of the transmission line is long to some extent, external noise is likely to be applied to the transmission line. Further, when the rotational speed of the motor is extremely high, the frequency band of the switching noise generated when the motor is controlled by PWM becomes high. Noise cannot be removed by a noise removal filter or the like provided on the receiving side. In such a state, the error component in the encoder signal increases and S / S
There is a problem that the N ratio deteriorates, and in some cases, the encoder may be in an erroneous detection state.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an encoder signal transmission capable of effectively eliminating the influence of noise applied to an encoder signal transmitted by a transmission line. It is to provide a circuit.

[0005]

To achieve the above object, an encoder signal transmission circuit according to claim 1 transmits an encoder signal generated by detecting rotation of a motor from a transmission side to a reception side. In an encoder that obtains information about the rotation of the motor on the receiving side based on an encoder signal, an anti-phase signal generating unit that generates an anti-phase signal of the encoder signal on the transmitting side, and arranged in a state close to each other, A pair of transmission lines for transmitting a positive-phase signal and a negative-phase signal of an encoder signal from the transmitting side to the receiving side, and a differential signal output for taking a difference between the positive-phase signal and the negative-phase signal on the receiving side and outputting the difference; Means.

[0006] According to this configuration, the negative-phase signal of the encoder signal generated on the transmitting side and the positive-phase signal of the encoder signal are transmitted to the receiving side by a pair of transmission lines arranged close to each other. Transmitted at the same time. On the receiving side, a difference between the positive-phase signal and the negative-phase signal is obtained by the differential signal output means, and detailed information on the rotation of the motor can be obtained based on the differential signal. Therefore, even when noise is superimposed on the positive-phase signal and the negative-phase signal transmitted by the pair of transmission lines, the noise component superimposed on each phase signal is canceled by calculating the difference between the two signals on the receiving side. As a result, a decrease in the S / N ratio can be reliably prevented.

In this case, the negative-phase signal generating means generates a negative-phase signal for each of the A-phase signal and the B-phase signal of the encoder signal, and outputs the A-phase signal and the B-phase signal. The positive-phase signal and the negative-phase signal for each of the phase signals may be transmitted by a pair of transmission lines, respectively. With such a configuration, even in the case of transmitting an encoder signal capable of detecting the rotation direction, The same operation and effect as those of the first aspect can be obtained.

Preferably, the pair of transmission lines are formed as a twisted pair, so that a normal phase signal and a negative phase signal transmitted by the pair of transmission lines are provided. When the noise is applied to the signal, the applied state of the noise to both signals is surely the same, so that the noise component can be more reliably removed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. In FIG. 1 showing the electrical configuration, a rotation detecting gear made of a magnetic material that rotates with its rotation is provided on a rotating shaft of a motor 1 composed of, for example, a switched reluctance motor, which is not specifically shown. And the magnetoresistive elements 2a and 2b
A change in magnetic resistance caused by the rotation of the gear is detected, and a sinusoidal A-phase signal and a B-phase signal whose phases are shifted from each other by 90 degrees are output.

The inverting amplifier 3a outputs a small-amplitude detection signal output from the magnetoresistive element 2a (for example, about P-P 0.3 V).
(For example, about P-P6V), and this is supplied as a positive-phase signal of an encoder signal (A-phase signal) to a signal line 4a as a transmission line and an inverting amplifier (a negative-phase signal generating means) 5a. I have.

The inverting amplifier 5a includes an inverting amplifier 3a.
Is further inverted (amplification ratio 1), and this is used as a transmission line signal line 6a as a reverse phase signal of the encoder signal.
To give to. The magnetoresistive element 2a and the inverting amplifiers 3a and 5a are provided on the transmission side, which is the main body of the motor 1.

The signal lines 4a and 6a are stranded together such that the two form a so-called twisted pair, and extend to a receiving side located slightly away from the transmitting side. The signal line 4a is connected to an inverting input terminal of a differential amplifier (differential signal generating means) 7a provided on the receiving side, and the signal line 6a is connected to the differential amplifier 7a.
a is connected to the non-inverting input terminal.

The output signal of the differential amplifier 7a is supplied to the signal line 4a
, 6a, subtracts the positive-phase signal from the negative-phase signal of the encoder signal, takes the difference, and outputs the difference to the comparator 8a. The comparator 8a shapes the waveform of the difference signal from the differential amplifier 7a to a rectangular wave by comparing the difference signal with the ground level, and outputs the rectangular wave to the control device 9.

Although only the signal transmission system for the A-phase signal output from the magnetoresistive element 2a has been described above, the signal transmission system for the B-phase signal output from the magnetoresistive element 2b has the same configuration. In FIG. 1,
The suffix a attached to the same reference numeral is changed to the suffix b. Although not specifically shown, an origin signal of the motor 1, which is also detected using a magnetoresistive element, is transmitted from the transmission side to the reception side. The above constitutes the encoder signal transmission circuit.

The control device 9 includes comparators 8a and 8b
By performing a predetermined process after multiplying the given rectangular wave A-phase signal and B-phase signal by an appropriate magnification (for example, 8 times), detailed rotational position information of the motor 1 can be obtained. I have. The control device 9 drives the motor 1 by switching the timing of energizing the windings of the motor 1 based on the rotational position information. Further, the control device 9 recognizes the rotation direction of the motor 1 by referring to the input timing of the rising edge of the A-phase signal and the B-phase signal.

Next, the operation of this embodiment will be described with reference to FIG. FIG. 2 is a diagram showing signal waveforms at respective parts (a) to (e) of the encoder signal transmission circuit shown in FIG. Note that only the A-phase signal will be described below. The inverting amplifier 3a outputs a positive-phase signal (see FIG. 2B) obtained by inverting and amplifying the A-phase signal (see FIG. 2A) from the magnetoresistive element 2a. The inverted signal is generated again by the inverting amplifier 5a (see FIG. 2).
(C)). These positive-phase and negative-phase signals are transmitted through the signal line 4a.
2 (a) and 6 (a), respectively.
As shown in FIG. 2C, it is assumed that impulsive noise is applied to the positive-phase and negative-phase signals.

These positive-phase and negative-phase signals are transmitted to the receiving side, and as described above, a differential signal obtained by subtracting the positive-phase signal from the negative-phase signal in the differential amplifier 7a is output to the comparator 8a. At this time, the noise applied to the signal lines 4a and 6a is canceled by subtracting the positive-phase signal from the negative-phase signal, and the waveform of the differential signal is a waveform in which the amplitude of the waveform of the negative-phase signal is doubled. (See FIG. 2D).

The difference signal is shaped into a rectangular wave (see FIG. 2 (e)) by the comparator 8a and supplied to the control device 9. The operation is exactly the same for the B-phase signal. Thus, the control device 9 performs signal processing such as multiplication as described above, and also refers to the origin signal to the motor 1.
When the detailed rotational position information is obtained, the motor 1 is driven by switching the timing of energizing the windings of the motor 1 based on the rotational position information.

The origin signal of the encoder is output once each time the motor 1 makes one rotation, and the pulse width of the signal is wider than the A-phase and B-phase signals. Even if the signal is applied, it can be removed by a filter provided on the receiving side, and it is not necessary to adopt the above-described transmission method as in the case of the A-phase and B-phase signals. The signal is transmitted to the receiving side, the waveform is shaped on the receiving side, and the resultant is given to the control device 9.

As described above, according to this embodiment, the A-phase signal and the B-phase signal of the encoder output by detecting the rotation of the motor 1 by the magnetoresistive elements 2a and 2b are inverted and amplified to the positive-phase signal. And outputs these positive-phase signals as negative-phase signals via the inverting amplifiers 5a and 5b.
The signals are transmitted from the transmitting side to the receiving side via the transmission lines a, 6a and 4b, 6b, and the differential signals of the positive-phase signal with respect to the negative-phase signal are obtained by the differential amplifiers 7a and 7b on the receiving side.

Therefore, the signal lines 4a, 6a and 4b, 6b
, The noise component can be removed on the receiving side, so that the reduction of the S / N ratio can be reliably prevented. It is possible to prevent erroneous operation in drive control of the motor 1 without erroneous acquisition.

Further, according to the present embodiment, since the signal lines 4a and 6a, 4b and 6b are respectively formed as twisted pairs, the state in which noise is applied to the positive phase signal and the negative phase signal is the same for both signals. In addition, since the noise component can be reliably removed, the malfunction can be more reliably prevented.

FIG. 3 shows a second embodiment of the present invention having the same operation and effect as the first embodiment. Only parts different from the first embodiment will be described. In the second embodiment, the non-inverting amplifier 10a and the inverting amplifier 11 serving as a negative-phase signal generating means
a. In this case, the amplification factors of both are set to be the same.

The output terminal of the non-inverting amplifier 10a is connected to the non-inverting input terminal of the differential amplifier 7a via the signal line 4a, and the output terminal of the inverting amplifier 11a is connected to the signal line 6a.
Is connected to the inverting input terminal of the differential amplifier 7a. The B-phase signal output from the magnetoresistive element 2b has the same configuration as described above, and the other configuration is the same as that of the first embodiment. According to the second embodiment configured as described above, the output signal of the non-inverting amplifier 10a becomes a positive-phase signal of the A-phase signal, and the output signal of the inverting amplifier 11a becomes a negative-phase signal.

The present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications or extensions are possible. It is applied to an encoder that outputs an A-phase signal and a B-phase signal, but does not detect the rotation direction and outputs 1
You may apply to the encoder which outputs only one signal. The signal lines 4a and 6a, 4b and 6b do not necessarily have to be configured as a twisted pair, but may be arranged close to each other. The present invention may be applied to a relative encoder that does not output an origin signal. The portion of the control device 9 that controls the driving of the motor 1 may be configured as a separate control device. The encoder is not limited to the one using the magnetoresistive element, but may be an optical encoder.

[0026]

Since the present invention is as described above,
The following effects are obtained. According to the encoder signal transmission circuit of the first aspect, the opposite-phase signal of the encoder signal generated on the transmission side is transmitted simultaneously with the positive-phase signal of the encoder signal by a pair of transmission lines arranged in a state close to each other. The signal is transmitted to the receiving side, and a difference between the positive-phase signal and the negative-phase signal is obtained by the differential signal output means on the receiving side, and detailed information on the rotation of the motor is obtained based on the differential signal. Even if noise is applied to the positive-phase signal and the negative-phase signal transmitted by the above, the noise component can be removed by taking the difference between the two signals on the receiving side, and the reduction of the S / N ratio can be ensured. It is possible to prevent the erroneous detection of the encoder.

According to the encoder signal transmission circuit of the present invention, since the positive-phase signal and the negative-phase signal for each of the A-phase signal and the B-phase signal are transmitted by a pair of transmission lines, the rotation direction is also detected. The same operation and effect as those of the first aspect can be obtained also in the case of transmitting a possible encoder signal.

According to the encoder signal transmission circuit of the third aspect, since the pair of transmission lines is formed as a twisted pair, when noise is applied to the positive-phase signal and the negative-phase signal transmitted by the pair of transmission lines. In addition, since the applied state of the noise to both signals surely becomes the same, the noise component can be more reliably removed.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing signal waveforms of various parts when noise is applied to a signal line;

FIG. 3 is an electrical configuration diagram of main parts showing a second embodiment of the present invention.

[Explanation of symbols]

1 is a motor, 4a, 6a and 4b, 6b are signal lines (transmission lines), 5a and 5b are inverting amplifiers (reverse-phase signal generating means), 7a and 7b are differential amplifiers (differential signal generating means), and 11a is 3 shows an inverting amplifier (a negative-phase signal generating means).

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01D 5/00-5/62 G08C 25/00 G01B ⁷ /00-7/34 G01B 11/00-11 / 30

Claims (3)

(57) [Claims] An encoder that transmits an encoder signal generated by detecting rotation of a motor from a transmission side to a reception side and obtains information on rotation of the motor at the reception side based on the encoder signal. A negative-phase signal generating means for generating a negative-phase signal of the encoder signal on the side; and a pair of negative-phase signal generating means for transmitting the positive-phase signal and the negative-phase signal of the encoder signal from the transmission side to the reception side, which are arranged close to each other. An encoder signal transmission circuit, comprising: a transmission line according to (1), and a difference signal output unit that calculates and outputs a difference between the positive-phase signal and the negative-phase signal on a receiving side. 2. The anti-phase signal generating means generates an anti-phase signal for each of the A-phase signal and the B-phase signal of the encoder signal, and outputs a non-phase signal and an anti-phase signal for each of the A-phase signal and the B-phase signal. 2. The encoder signal transmission circuit according to claim 1, wherein the phase signals are transmitted by a pair of transmission lines, respectively. 3. The transmission line according to claim 1, wherein the pair of transmission lines are configured as a twisted pair.
An encoder signal transmission circuit as described in the above.