JPS6184519A - Position signal detecting device - Google Patents

Abstract

PURPOSE:To output a position signal of high precision without any adjustment by connecting a low-pass filter to the output of an MR sensor and obtaining a position detection signal from a difference between output waveforms of the DC output voltage of the filter and the MR sensor. CONSTITUTION:A DC voltage is impressed to the DC voltage impression terminal 33 of the MR sensor to which a couple of magneto-resistance effect elements 34 and 35 are connected in series. The magneto-resistance effect elements 34 and 35 are arrayed at pitch a half as large as the pitch of teeth and grooves of a stator, and when the resistance of one is large, that of the other is small. Therefore, the voltage waveform 43 at an output terminal 36 contains a DC component 144. The low-pass filter 37 is connected to an output terminal 36. A differential amplifier 39 amplifies the difference between the output waveform 43 of the MR sensor and the DC component 44 and outputs the output waveform of a since wave containing no DC component. A comparator circuit 40 obtains a position signal 19 from the waveform and a 0-cross point.

Description

TECHNICAL FIELD The present invention relates to a position signal detection device for detecting the position of a movable element that moves relative to a stator, and in particular to a position signal detection device for detecting the position of a moving element that moves relative to a stator. The present invention relates to a circuit that generates and outputs a position detection signal from a sine wave signal output from a magnetoresistive element in accordance with the displacement of a moving element.

Prior Art Conventionally, the position signal detection device of this company, as shown in Fig. 4, has a bridge circuit (IIIR sensor) composed of magnetoresistive elements 1 to 4 attached to a moving element, and a The structure is such that a DC voltage is applied, the bridge output is converted to a position signal 19 by a differential amplifier 7, 1tI@I, . The MR sensor is excited by a permanent magnet, and when positioned on teeth or grooves formed on a stator, the magnetic flux density passing through each of the magnetoresistive elements 1 to 4 changes, so that the magnetoresistive element l The voltage waveform ■2 output from the connection point 5 between and 2 and 6i! The magnetoresistive elements 1 to 4 are arranged at positions such that the phase difference between the voltage waveforms 13 outputted from the connection point 6 between the magnetoresistive elements 3 and 4 is 180°.

Therefore, when the mover moves on the stator, the output voltage waveform 12 at the connection point 5 is as shown in FIG.

The waveform is a DC component determined by the ratio of the resistance values of the magnetoresistive elements 1 and 2 when there is no magnetic flux, and an AC component corresponding to the displacement of the mover is superimposed, and the output waveform 13 at the connection point 6 is the output voltage waveform described above. The waveform has an opposite phase to that of 12. Since the difference between the two waveforms is amplified by the differential amplifier 7, the intersection points 14 to 17 of the two waveforms become position detection timings.

6(A) shows the output signal 8 of the differential amplifier 7, and FIG. 6(B) shows the position signal 19 output from the comparator circuit 9.
shows.

The above shows the output voltage waveforms 12 and 13 from the I'lR sensor.
If the 1σ current components of the output voltage waveforms 12 and 13 are equal, but if the initial resistance values of the magnetoresistive elements 1 to 4 when not energized are not equal, as shown in FIG. Because of the difference, the intersection point 2 of output voltage waveforms 12 and 13
4 is off. Then, the output 8 of the differential amplifier 7 becomes as shown in FIG. 8(A).

The O intersection will contain an error of 26 in the detection position.

Therefore, the position signal 19 output from the comparator circuit 9 is as shown in FIG.
Standing points cause position detection errors.

That is, the conventional position signal detection device has a drawback in that the first position detection accuracy is low.

In order to improve the position detection accuracy, it is necessary to correct the difference in the DC component at the connection point 5.6 of the MR sensor. 9th
The figure shows a correction circuit that corrects the DC component of the R sensor output. That is, the signals input from connection points 5 and 6 have their DC components removed separately by differential amplifiers 23 and 30, respectively, and The output waveforms of amplifiers 29 and 30 are combined and output. The variable resistor 2 is a resistor for adjusting the comparison voltage of the differential amplifiers 29 and 30. This circuit consists of an MR sensor and two differential amplifiers.
9 and 30 are combined into one set, and the weight is 2g!
It is difficult to adjust, and the ∆ reliability also decreases.

Release 1! II. OBJECT It is an object of the present invention to solve the above-mentioned conventional drawbacks and to provide a position signal detection device capable of outputting a highly accurate position detection signal with no rA adjustment.

Structure of the Invention The position signal detection device of the present invention includes a movable element which is held at a constant interval from a stator and which moves in the longitudinal direction with respect to a stator in which teeth and grooves are alternately formed at a constant pitch in the longitudinal direction. Mounted fa′! A resistance effect element and a permanent magnet table for exciting the magnetoresistive element are mounted, and when a direct current voltage is applied to the magnetoresistive element and the movable element is moved, from the magnetoresistive element A position signal detection device that outputs a position signal according to an output signal waveform, a low-pass filter connected to the output of the magnetoresistive element, an output voltage of the low-pass filter, and an output waveform of the magnetoresistive element. and a comparator circuit for comparing.

Embodiments of the Invention Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the unreleased 1g+.

That is, a DC voltage is applied to the DC voltage application terminal 33 of the MR sensor in which a pair of magnetoresistive elements 34 and 35 are connected in series. The magnetoresistive elements 34 and 35 are arranged, for example, at 1/2 pitch to one pitch of teeth and grooves of the stator, and when the resistance of one is large, the resistance of the other is small. Therefore, the voltage waveform 43 of the output terminal 3B is
As shown in the figure, it includes a DC component 44. &
Either one of the resistance effect elements 34 or 35 may be omitted and replaced with a simple fixed resistor, or a constant '+ti' may be input to the DC voltage application terminal 33.

A low-pass filter 37 is connected to the output terminal 3B, and the output of the low-pass filter 37 and the output terminal 38 of the MR sensor are input to the differential amplifier 33. The DC component 44 of the MR sensor output waveform 43 is outputted from the low-pass filter 37 (see FIG. 2). At the detection position 45, the output waveform 43 has a voltage equal to the DC component 44. Therefore, the differential amplifier 33 amplifies the difference between the MR sensor output waveform 43 and its DC component 44, and outputs a sinusoidal output waveform 46 containing no DC component as shown in FIG. 3(A). . The 0 intersection 47 of the output waveform 4B is taken as the 1-position detection timing, and the position signal 13 output from the comparator circuit 40 has a pulse waveform that is inverted at every position detection timing 47, as shown in FIG.

This embodiment has the advantage that it is possible to remove the direct current component of the output of the MR sensor without using two differential amplifiers and to output an accurate position signal without adjustment. In addition, in order to obtain a position signal, the conventional position signal detection device
Although a bridge circuit consisting of four MR elements is required, this embodiment has the advantage that one or two IR elements are sufficient.

Effects of the Invention As described above, in the present invention, a low-pass filter is connected to the output of the MR sensor, and a position detection signal is obtained by the difference between the direct voltage output from the low-pass filter and the output waveform of the MR sensor. This configuration has the effect of outputting highly accurate position signals without any adjustment. Furthermore, there is an advantage that the number of MRJI's can be reduced compared to the conventional method.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a diagram showing the R sensor output waveform and its DC component in the above embodiment, and Figs. 3 (A) and (B) are diagrams showing the above embodiment. Fig. 4 is a circuit diagram showing an example of a conventional position signal detection device, and Fig. 5 is a diagram showing the output waveform of the differential amplifier and the position signal of the above-mentioned conventional position signal detection device. FIG. 6 is a waveform diagram showing the differential amplifier output and position signal in the conventional example, and FIG. 7 is a waveform diagram showing the differential amplifier output and position signal in the conventional example.
A waveform diagram showing the MR sensor output when there is a difference in the DC component of the sensor output, Figure 058 is a diagram showing the differential amplifier output and position signal of the above conventional example, and Figure 9 is a circuit for correcting the DC component of the NR processor. FIG. 2 is a circuit diagram showing a conventional example including. In the figure, 1 to 4: magnetoresistive element, 5° 6: connection point, 7: differential amplifier, 8: output signal of differential amplifier, 9:
Comparator circuit, 10: Position signal output terminal, 11: Direct i'it pressure application terminal, 12.13: MR sensor output voltage waveform, +4, 17, 24: Position detection timing,
13: Position signal, 26: Position detection error, 28: Variable resistor, 2!3, 30: Differential amplifier, 33: DC voltage application terminal, 34, 35: Magnetoresistive element, 38: MR
Sensor output terminal, 37 two low-pass filters, 33: differential amplifier, 40: comparator circuit, 41: position signal output terminal, 43: MR sensor output waveform, 44: DC component of MR sensor output, 45: detection position, 4B: Differential amplifier output waveform, 47: Position detection timing.

Claims (1)

[Claims] A magnetoresistive element attached to a mover that is held at a constant interval and moves in the length direction with respect to a stator in which teeth and grooves are alternately formed at a constant pitch in the length direction, and the magnetoresistive element. A permanent magnet for exciting the effect element is mounted, and when the movable element is moved by applying a DC voltage to the magnetoresistive element, the position is determined according to the signal waveform output from the magnetoresistive element. A position signal detection device that outputs a signal, comprising: a low-pass filter connected to the output of the magnetoresistive element; and a comparator circuit that compares the output voltage of the low-pass filter with the output waveform of the magnetoresistive element. A position signal detection device characterized by: