JPS63160419A - Magnetic rotary encoder - Google Patents

Abstract

PURPOSE:To always obtain an encoder output having a prescribed duty cycle by setting a value to a sample/hold circuit when the encoder reaches the prescribed number of revolutions and subtracting the value from a detection signal so as to automate the zero adjustment of the detection signal. CONSTITUTION:A low pass filter 4 applies low frequency filtering to a detection signal S1 to output a signal S3, which is a center level of the detection signal S1. On the other hand, an F/V converter 5 applies F/V conversion to the detection signal S1 to detect the number of revolutions, and a comparator 7 compares an output S2 of the F/V converter 5 with a prescribed value to detect that the number of revolutions reaches a prescribed value. A sample/hold circuit 6 holds the output S3 of the low pass filter 4 by using the detection signal from the comparator 7 and the output S3 is subtracted from the detection signal S1 to adjust zero level automatically. Then the result is amplified by an operational amplifier 8 and its signal S4 is converted into a square wave by a comparator 3. Thus, the encoder output S5 whose duty cycle is 50% is always obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic rotary encoder.

[Conventional technology]

FIG. 3 is a circuit diagram of a conventional example of a magnetic rotary encoder.

An operational amplifier 2 changes the resistance change of a detection signal (sine wave) from the magnetic sensor 1 into a voltage, which is converted into a square wave by a comparator 3.

[Problem that the invention seeks to solve]

The conventional magnetic rotary encoder described above has the disadvantage that the zero output level of the magnetic sensor fluctuates due to fluctuations in temperature and clearance, and the duty cycle of the encoder output changes.

[F-stage to solve problems]

The magnetic rotary encoder of the present invention includes: a low-pass filter that low-pass filters the detection signal of the magnetic sensor; and an F/V converter i that converts the frequency/voltage of the detection signal of the magnetic sensor.

A comparator that outputs a detection signal when the output of the F/V converter is above a certain value, a sample-and-hold circuit that holds the output of the low-pass filter using the detection signal of the comparator, and a sample-and-hold circuit that uses the detection signal from the detection signal. and a subtraction circuit that subtracts the hold value.

[Effect]

Therefore, the detection signal of the magnetic sensor automatically goes to zero level. Ii, and an encoder output with a predetermined duty cycle is always obtained.

[Example j Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the magnetic rotary encoder of the present invention, and FIGS. 2(1) to 2(5) are waveform diagrams of signals S and -s5 at respective parts thereof.

The magnetic rotary encoder of this embodiment has an operational amplifier 2
A low-pass filter 4, an F/V converter 5, a sample/hold circuit 6, and a comparator 7 are provided between the comparator 3 and the comparator 3.

The low-pass filter 4 low-pass filters the detection signal S, and outputs a signal S3. This signal S3 becomes the center level of the detection signal SL. On the other hand, the F/V converter 5 converts the detection signal SL into
/V conversion to detect the rotation speed. The comparator 7 detects that the rotational speed has reached a constant value by comparing the output S2 of the F/V converter 5 with a constant ifi. The sample-and-hold circuit 6 receives the output S of the low-pass filter 4.
3 is held by the detection signal from the comparator 7 (indicating that the rotational speed has exceeded a certain level E). This output S3 is subtracted from the detection signal Sl, and the zero level is automatically adjusted. The signal S4 is then amplified by the operational amplifier 8.
is converted into a square wave by the comparator 3, and an encoder output S5 with a duty cycle of 50% is always obtained.

〔Effect of the invention〕

As explained hereafter, the present invention modulates the detection signal of the magnetic sensor in a low frequency range, sets a value in the sample/hold circuit when the encoder reaches a certain rotating tool 1-, and calculates this value from the detection signal. By reducing , the detection signal is automatically zero-adjusted, and the effect is that an encoder output with a predetermined duty cycle can always be obtained.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of an embodiment of the magnetic rotary encoder of the present invention, and Figures 2 (1) to (5) are signals 5t of each part.
- The waveform diagram of S5, and FIG. 3 is a circuit diagram of a conventional example. ! ... Magnetic sensor, 2,8... Operational amplifier. 3.7... Comparator, 4... Low pass filter, 5... F/V converter. 6... Sample/hold circuit.

Claims (1)

[Claims] In a magnetic rotary encoder, a low-pass filter that low-pass filters a detection signal of a magnetic sensor, an F/V converter that converts the detection signal of a magnetic sensor from frequency to voltage, and an output of the F/V converter. a comparator that outputs a detection signal when is above a certain value, a sample-and-hold circuit that holds the output of the low-pass filter using the detection signal of the comparator, and a subtractor that subtracts the hold value of the sample-and-hold circuit from the detection signal. A magnetic rotary encoder characterized by having a circuit.