JPH0478217A - Output signal waveform shaping device for magneto-electric conversion element - Google Patents

Abstract

PURPOSE:To waveform-shape the output signal of a magneto-electron element by setting an upper limit value and a lower limit value in response to fluctuation of the output signal level of the magneto--electron element, and taking a median of the upper limit value and the lower limit value as a threshold level. CONSTITUTION:When the output signal of a magneto-resistance element MR element 1 rises and reaches a reference voltage Vref being a mean value between a upper limit value Vp and a lower limit value Vb, the level of output signal S of a waveform shaping device 3 goes from a low L to a high level H. Then the count of an upper limit counter 11 is decremented and the upper limit value Vp is decreased by a voltage (v) equivalent to one count. Succeedingly the output signal of the element 1 is decreased up to the voltage Vref, the level of the output signal of the waveform shaping device 3 is inverted to an L level. As a result, the count of a lower limit counter 12 is decremented by a signal inverted by an inverter 17 and lower limit value Vb is increased by the voltage (v). As a result, the upper limit value Vp and the lower limit value Vb change in following to the output signal of the element 1 and a waveform of the output signal of the element 1 is surely converted into a rectangular wave.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an output signal waveform shaping device for a magnetoelectric transducer, and in particular to a magnetoelectric transducer used to detect the amount of rotation of a rotating body or the amount of displacement of a moving body. The present invention relates to an output signal waveform shaping device.

(Prior Art) Magnetoelectric conversion elements such as magnetoresistive elements (MR elements) and Hall elements are used to detect the amount of rotation of a shaft and the amount of displacement of a moving body.

For example, a plurality of magnets with alternately reversed polarities are provided on the shaft or the object to be detected such as a moving object, and the MR element is arranged to face the magnets. In such a configuration, when the object to be detected is displaced with respect to the MR element, the plurality of magnetic poles sequentially approach the MR element and move away from it again, and the resistance value of the MR element changes It changes depending on the relative position with each magnet provided on the body. Therefore, M.R.
By applying a voltage to the element and extracting changes in the current flowing through the MR element, it is possible to detect the amount of displacement of the object to be detected based on the changes in the current.

FIG. 4 shows an example of a circuit and a signal waveform for detecting the amount of displacement of the object to be detected.

In the same figure (a), from the MR element 1, the MR element 1
A sinusoidal signal is output in accordance with a change in the relative position between the magnet and the magnet provided on the detected object. The output signal of the MR element 1 is amplified by an amplifier 2. The amplified signal is input to the waveform shaper 3, where it is compared with a reference voltage vref, and the comparison result is output as a rectangular wave. The output rectangular wave corresponds to the sinusoidal signal. FIG. 4(b) shows the input signal to the waveform shaper 3, that is, the amplified signal, and the rectangular wave signal output from the waveform shaper 3.

By measuring in advance the amount of displacement of the object to be detected corresponding to one cycle of the rectangular wave signal, the number of cycles (number of pulses) of the rectangular wave can be counted by a counting means (not shown) to calculate the amount of displacement of the object to be detected. Can be detected.

By the way, as shown by the dotted line in FIG. 4(b), the output of the MR element 1 deviates due to aging.

If this deviation is large, the output range of the MR element 1 deviates from the reference voltage vref, and as a result, the reference voltage Vref
waveform shaping based on .

To solve this problem, there is a device in which the midpoint potential of the sinusoidal waveform is set as the reference voltage Vrer to prevent the output of the MR element from deviating from the reference voltage vrer. An example of the circuit of this device is shown in FIG.

In the figure, the output of the MR element 1 is amplified by an amplifier 2 and input to a waveform shaper 3. On the other hand, waveform shaper 3
The voltage of the capacitor 4 is input as the reference voltage Vr8r. The potential of the capacitor 4 is held at the average value of the output of the MR element 1, that is, the midpoint potential.

(Problem to be solved by the invention) The above conventional device has the following problems.

That is, in this device, immediately after the power is turned on or when the output level of the MR element fluctuates, it takes time for the potential of the capacitor 4 to stabilize to the midpoint potential of the MR element 1. Therefore, when measuring minute displacements, the potential of the capacitor 4 is M
Since the midpoint potential of R element 1 is not reached, desired waveform shaping cannot be performed.

Similarly, when the movement of the object to be detected is not continuous but intermittent movement, for example, when detecting the amount of rotation of a car steering wheel that repeatedly rotates and stops irregularly, While the object to be detected (steering) is stopped, the output of MR element 1 does not change, so the potential of capacitor 4 becomes equal to the output of MR element 1. However, since the potential of capacitor 4 decreases due to discharge, Poor tracking ability when the body starts moving again.

The capacitance of the capacitor 4 may be increased in order to maintain the reference voltage Vref at the midpoint potential even when the object to be detected is stopped, and to obtain a stable reference voltage Vref even when starting up. However, if this is done, there is a problem that the follow-up performance after the power is turned on becomes worse.

An object of the present invention is to solve the problems of the prior art described above, and to reliably detect the movement of a detected object that repeatedly rotates and stops, and even when the output of the MR element fluctuates due to aging, etc. Another object of the present invention is to provide an output signal waveform shaping device for a magnetoelectric conversion element that can convert the output of the MR element into a rectangular wave.

(Means and Effects for Solving the Problems) In order to solve the above-mentioned problems and achieve the objects, the present invention provides means for holding an upper limit value and a lower limit value of an output signal of a magnetoelectric transducer, and waveform shaping means for converting the output signal of the magnetoelectric transducer into a rectangular wave using a value obtained based on the average value of the value and the lower limit value as a threshold; means for increasing the lower limit value by a predetermined amount while increasing the lower limit value by a predetermined amount; The present invention is characterized in that it includes means for decreasing the lower limit value by a predetermined amount when the level becomes equal to or lower than the lower limit value.

In the present invention having the above characteristics, an upper limit value and a lower limit value can be set according to fluctuations in the output signal level of the magnetoelectric transducer, and the output signal of the magnetoelectric transducer is set using the median value of the upper limit value and the lower limit value as a threshold value. can be waveform shaped.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and the same reference numerals as in FIG. 4 indicate the same or equivalent parts.

In the figure, a plurality of magnetic poles 5 provided on an object to be detected (not shown) are arranged facing the MR element 1. The M
A power supply voltage is applied to both ends of the R element 1, and when the magnetic pole 5 is displaced, the magnetic field applied to the MR element 1 changes in accordance with the displacement, and a voltage signal corresponding to the amount of change is output from the MR element 1. Output. The voltage signal output from the MR element 1 is supplied to the plus input terminal of the upper limit comparator 6, the minus input terminal of the lower limit comparator 7, and the plus input terminal of the waveform shaper 3.

Upper limit value setting counter (hereinafter referred to as upper limit counter) 1
1, a count value that is scheduled to represent the expected upper limit value of the output voltage of the MR element 1 is set in the preset unit 1 when the power is turned on.
It is preset from 5.

When a signal is supplied to the up terminal U of the upper limit counter 11, the preset count value is incremented, and when a signal is supplied to the down terminal U, the preset count value is decremented. The count value of the upper limit counter 11 is converted into an analog value by the D/A converter 8, and the upper limit value is converted to an analog value by the average value circuit 1.
0 and the negative input terminal of the upper limit comparator 6.

The output signal of the upper limit comparator 6 is supplied to the up terminal U of the upper limit counter 11 via an AND gate 13. Therefore, when the output voltage of the MR element 1 reaches the upper limit value, a signal for incrementing the count value in response to the clock signal is supplied to the up terminal U of the upper limit counter 11.

The output signal of the waveform shaper 3 is supplied to the down terminal of the upper limit counter 11.

On the other hand, a count value representative of the expected lower limit value of the output voltage of the MR element 1 is preset into the lower limit value setting counter (hereinafter referred to as lower limit counter) 12 from the preset unit 16 when the power is turned on. Similarly to the upper limit counter 11, the count value of the lower limit counter 12 also changes according to the input signal.

The count value of the lower limit counter 12 is converted into an analog value by the D/A converter 9, and is supplied to the average value circuit 10 and the positive input terminal of the lower limit comparator 7 as the lower limit value.

The output signal of the lower limit comparator 7 is supplied to the down terminal of the lower limit counter 12 via an AND gate 14. Therefore, when the output voltage of the MR element 1 drops to the lower limit value, a signal for decrementing the count value is supplied to the down terminal of the lower limit counter 12 in response to the clock signal.

The output signal of the waveform shaper 3 is inverted by an inverter 17 and supplied to the up terminal U of the lower limit counter 12 .

The average value circuit 10 outputs the average value of the input upper limit value and lower limit value. The average value is supplied to the waveform shaper 3 as a reference voltage Vref'.

Next, MR element 1 based on the circuit configured as described above.
The midpoint potential correction operation will be explained.

FIG. 2 is a timing chart for explaining the operation of this embodiment. In the figure, the output signal waveform of the MR element 1 is shown in a simplified manner for ease of explanation.

In the figure, the output signal of the MR element 1 rises and the reference voltage Vre, which is the average value of the upper limit value Vp and the lower limit value vb, increases.
When reaching f, the level of the output signal S of the waveform shaper 3 changes from low "L2" to high "H#". When the output level of the waveform shaper 3 becomes "H#", the count value of the upper limit counter 11 is decremented, and the voltage V corresponding to one count value is
The upper limit value Vp decreases by this amount.

When the output voltage of the MR element 1 further increases and reaches the upper limit value Vp, the output signal of the upper limit comparator 6 becomes "H". As a result, the AND gate 13 opens, the output signal of the AND gate 13 becomes "H" in response to the tarlock signal, and the count value of the upper limit counter 11 is incremented.

That is, the upper limit value Vp is increased.

Subsequently, the output signal of the MR element 1 starts to fall, and at the point when it drops to the reference voltage Vref, the level of the output signal S of the waveform shaper 3 is inverted to "L#". The count value of the lower limit counter 12 is decremented by the signal, and the lower limit value vb is increased by the voltage V.

When the output voltage of the MR element 1 further decreases and reaches the lower limit value vb, the output signal of the lower limit comparator 7 becomes "H".As a result, the AND gate 14 opens, and the AND gate 14 opens in response to the clock signal. The output signal becomes "H", and the count value of the lower limit counter 120 is decremented. That is, the lower limit value vb is lowered.

In this way, the upper limit value Vp preset when the power is turned on
The upper limit value Vp and the lower limit value vb do not remain fixed, but in response to the output from the waveform shaper 3, the upper limit value Vp and the lower limit value vb
Updated to narrow the gap. Furthermore, if the output signal of the MR element 1 deviates from the range of the updated upper limit value Vp and lower limit value vb, the upper limit value Vp and the lower limit value vb are changed so that the range of the upper limit value Vp and lower limit value vb is expanded. The lower limit value vb was changed.

As a result, the upper limit value Vp and the lower limit value vb are MR element 1
The waveform of the output signal of the MR element is reliably converted into a rectangular wave according to the reference voltage Vref, which is the average value thereof.

Note that in order to absorb fluctuations in the output signal of the MR element 1 due to the influence of noise, a reference voltage with hysteresis may be set as a threshold, and waveform shaping may be performed based on this threshold. .

FIG. 3 shows a timing chart when waveform shaping is performed according to a reference voltage with hysteresis. As shown in the figure, when the output of MR element 1 increases, waveform shaping is performed using the upper threshold Thl, and when the output of MR element 1 decreases, waveform shaping is performed using the lower threshold Th2. be exposed. The upper threshold Thl and lower threshold Th2 can be set using a well-known circuit configuration by applying a Schmitt circuit.

In this embodiment, the upper limit value and the lower limit value are made to follow the output signal of the MR element 1 by a combination of a logic circuit and an analog circuit, and the waveform is shaped according to the midpoint potential of the output signal obtained based on the result. It was configured as follows. However, the present invention is not limited to the circuit configuration shown in the above embodiment, but may be configured by a microcomputer. That is, the output signal of the MR element 1 is converted into an A/D
The average value of the output signal may be detected by converting the signal, inputting the value into a microcomputer, and processing by software.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects can be obtained.

(1) Even if the output range of the magnetoelectric transducer changes due to aging or temperature changes, the reference voltage for waveform shaping can be made to follow the fluctuations in the output range, allowing accurate waveform shaping.

(2) Since the upper and lower limit values for generating the reference voltage for waveform shaping can be held as digital values, accurate waveform shaping can be performed even when the displacement of the object to be detected is not continuous or immediately after the power is turned on.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Figs. 2 and 3 are timing charts of waveform shaping, Fig. 4 is a circuit diagram of a conventional device and its output waveform diagram, and Fig. 5 is a diagram of other devices. FIG. 2 is a circuit diagram of a conventional device. 1... MR element, 3... Waveform shaper, 5... Magnetic pole, 6... Upper limit comparator, 7... Lower limit comparator, 10...
Average value circuit, 11... Upper limit counter, 12... Lower limit counter Agent Patent attorney Michito Hiraki and 1 other person ■ Figure 4 Figure 5 Procedure amendment (voluntary) February 1991 Mr. Commissioner of the Japan Patent Office 1゜Indication of the case Patent Application No. 188040/1999 2゜Name of the invention Output signal waveform shaping device of magnetoelectric transducer (532) Honda Motor Co., Ltd. Famille Nishi-Shinjuku No. 403 Drawing 6゜Contents of amendment The correction program for Figure 1 of the drawing is shown in the attached sheet.

Claims (3)

[Claims] (1) means for holding an upper limit value and a lower limit value of an output signal of the magnetoelectric transducer, and a means for rectangulating the output signal of the magnetoelectric transducer element using a value obtained based on the average value of the upper limit value and the lower limit value as a threshold value; waveform shaping means for converting into a wave; means for decreasing the upper limit value by a predetermined amount while increasing the lower limit value by a predetermined amount in response to the output of the waveform shaping means; and an output signal level of the magnetoelectric conversion element. means for increasing the upper limit value by a predetermined amount when the output signal level becomes equal to or higher than the upper limit value, and decreasing the lower limit value by a predetermined amount when the output signal level becomes equal to or less than the lower limit value. An output signal waveform shaping device for a magnetoelectric transducer, characterized by: (2) The output signal waveform shaping device for a magnetoelectric conversion element according to claim 1, wherein the means for holding the upper limit value and the lower limit value is a digital counter. (3) The digital counter is a digital counter in which numerical values that are scheduled to represent the expected upper and lower limit values of the output signal of the magnetoelectric transducer are preset when the power is turned on. Output signal waveform shaping device for magnetoelectric transducer.