JPH0392715A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To perform high-speed comparing operation without the effect of external noises by detecting the alternating magnetic field of a magnetic recording medium which is rotated or moved together with an object to be measured, performing complete differential amplification of the detected signals whose phases are inverted,and comparing the magnitudes of the signals. CONSTITUTION:A sensor unit 2 is composed of magnetoresistance elements MR1 and MR2. Alternate magnetic poles are magnetized at a constant period. The alternate magnetic field of a magnetic recording medium which is rotated with the rotation of an object to be measured is detected. The detected signals whose phases are inverted an which are outputted from the sensor unit 2 undergo complete differential amplification in an initial differential amplifier circuit 3 and a next-stage differential amplifier circuit 4. As a result, the output signals from which noises in the same phase are removed are inputted into an operation amplifier 5. In the operation amplifier 5, comparing operation is performed in push-pull method. Thus, the high speed comparing operation can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in "Industry"] This invention relates to a magnetic encoder used for detecting angles and positions in industrial Roposo 1, etc.

"Prior Art" Conventionally, various magnetic encoders have been put into practical use that detect the rotation angle of an object to be measured using a magnetoresistive element. This type of magnetic encoder is pre-magnetized by a magnetic recording medium that rotates with the object to be measured. ``f magnetic pattern is detected by a magnetoresistive element, and the rotation angle is thereby obtained.For example, in an incremental type magnetic encoder, a magnetic recording medium has an alternating magnetic pole or a pin magnetized with a constant rotation +111. , I signal track, and an origin signal track whose origin position is magnetized are provided, and the A phase (approximate sine e.) signal and B phase (approximate cosine e. wave) signal and Z phase (
The origin index) is obtained, and based on this, the rotation angle and rotation direction are determined.

Next, an example of a double magnetic enocoater is shown in FIG. The magnetic encoder shown in this figure consists of a magnetic drum 1) having a rotational shear/yaf 1 and an M
It consists of an R (magnetoresistive effect fR) sensor 10 and a detection circuit l1. The M R sensor 10 is disposed facing the outer circumferential surface of the magnetic drum D with a predetermined cap spaced therebetween, and detects the strength of the magnetic field of the B, C, and C signals magnetized on the magnetic recording medium M at a predetermined period. 3 and outputs a level signal corresponding to the detected level. FIG. 8 shows the configuration of this MR sensor 10. MRI in this figure
~MR4 is an element that produces a magnetic resistance effect whose specific resistance value changes depending on the strength of the magnetic field when placed in a magnetic field.
411 is a magnetic wiping resistance element. this,
J: The magnetoresistive elements MR1 to MR4 are connected to form a Blinozi circuit, respectively. That is, the positive power supply FIE − is connected to the connection point of the magnetoresistive elements MRl and MR3.
4-V cc is supplied, while magnetoresistive element MR2
, MR/l are grounded. Then, the connection point of the magnetic wiping resistance element MRIM R 2 and the connection point of the magnetic resistance element MRIM R 2
3, the detection signal is taken out from the connection point of M R /I.

The detection circuit l1 generates an angle pulse signal Po from the output signal of the MR sensor 10 and outputs it. Figure 9 shows the detection circuit 1.
1 shows the electrical configuration of No. 1. In this figure, Rl and R2 are resistors for obtaining a high-ass electric current FA (10 V cc/2). lla is a dynamic amplifying section, which is composed of an operational amplifier PI, input resistors R3, R, i4, and a feedback resistor R6. This differential amplification hj section 11a differentially amplifies the detection signal of MR sensor +IO and outputs it.
7, R8, and a feedback resistor 1<9, which amplifies the output of the differential amplifier 1g and shifts the output. ll
c is a humpator, which compares the magnitude of the base pi pressure V ref and the output Vout of the amplification section 1lb. RIO, Rl
l is a resistor for obtaining the reference voltage Vrer, Rl2. R
l3 is the input resistance of the converter 11c, R l. 4 is a pull knob resistor, and R15 is a feedback resistor for hysteresis. VR is a variable resistor that sets the 1HFEVrer, and changes the duty ratio of the 41 waveform outputted to the output terminal 'I'1.

In such a configuration, the signal detected by the MR sensor 10 that receives the alternating magnetic field created by the rotation of the magnetic drum D is amplified by the differential amplification section 1la and the amplification section 1lb, as shown in FIG. 10(A). Approximate sine wave signal V011 is repeated. Then, this approximate 11 trisine wave signal Vout is )N'fJi
m fl\' re! and: 1 ;-' Pareto,
As a result, the rectangular-wave angular pulse signal Po shown in the figure (opening) is output to the output b::a'I'1. Also,
When an origin signal track whose origin position is magnetized is provided on the magnetic drum D and a Z-phase (origin intenox) signal is detected from the track, the signal waveform shown in FIG. When the voltage Vrar] is applied to the input voltage Vrar, the origin index pulse signal shown in (2) of the same figure is obtained.

Note that the MR sensor 10 may be configured by a Brisso circuit in which the magnetoresistive elements M R 3 and MR 4 are replaced with fixed gripping resistors R a and R h, respectively, as shown in FIG. As shown in the figure, the magnetoresistive elements MRI and MR2 may be connected in series, and the detection signal may be obtained from their connection point.

"Problems to be Solved by the Invention" By the way, the above-described magnetic encoder has the following problems. That is, (1.) The differential amplifier section 11a does not become a complete differential amplifier circuit because a bias voltage is applied to the positive phase input fi:ta of the operational amplifier OP1, and therefore the influence of unbalanced noise is reduced. easy to receive.

(2) The MR sensor 10 is connected to the magnetic element MRI~MR/
When drawing with four elements of I, the sensor 10 becomes larger and the cost increases by 1.

(3) As shown in Figures 11 and 12, M Rsen →
When No-10 is composed of two magnetic components, MRI and MR2, there is no noise, so
Unbalanced noise appears in the detection signal.

(4) Since the MR sensor 10 is driven by a constant voltage, the temperature coefficient of its detection signal is poor and the temperature drift is large.

(5) I can't get enough of the converter IIC's 7 Izma/n, Offse, ]/Marshin.

(6) Since the comparator 11C cannot sufficiently take the potential gradient at the time of hysteresis/invalid +-, the amount of positive feedback is increased, so that hysteresis/input <, high rate operation is performed. It's difficult.

This invention was made in view of the circumstances mentioned above.
A small and inexpensive 2-element MR sensor can be used to reduce the influence of external noise, temperature 1i, drift 1 or 7, and high speed rotation 11! The object of the present invention is to provide a magnetic encoder that can easily detect angles even when the angle is small.

"Means for Solving the Problem" The first invention provides first and second detection signals that are output from a sensor unit and whose phases are inverted to each other and are input to the first input terminals of first and second differential amplification means, respectively. and each second human power Djf1 of the first and second differential amplifying means is supplied! is connected across through a resistor, and the first and second detection signals are differentially amplified and outputted from the output terminals of the first and second differential amplification means. It is characterized by comprising a width circuit and a comparison circuit that compares the magnitude of the differential output signal of the fully differential amplifier circuit.

Further, in a second invention, the sensor section includes a first circuit in which a first resistor is connected in series to a first magnetoresistive element, and a second resistor is connected in series to a second magnetoresistive element. When a positive electric current Fi [pressure is applied to one end of each of the first and second circuits, the other end is grounded, and the other end of the first magnetic resistor 8 is grounded. From the connection point of the magnetoresistive element and the first magneto-resistance element and the connection point of the second magneto-resistance element and the second magneto-resistance element, respectively,
and extracting a second detection signal.

"Operation" According to the first invention, the in-phase noise of the detected signal 5) outputted from the senosa section and whose phase has been inverted by Lt is canceled by the complete 2C: dynamic amplification circuit. And the ax motion output signal is
Comparisons are made using the 7-pull method for comparison.

Further, according to the second invention, the first and second magnetic resistance elements are driven at a substantially constant current by resistors connected in series with each other. This reduces the temperature trifle 1 of the detection signal output from the sensor section.

Embodiment 1 Hereinafter, a practical example of the investigation of IIr<L lever will be explained with reference to the drawings. Fig. 1 is a circuit diagram showing the electrical structure of a magnetic encoder 1 according to a practical example of the present invention. This magnetic encoder 1 detects the magnetization pattern of pitch signal tracks magnetized at a constant wavelength on the magnetic drum D shown in FIG. In Fig. 1, 2 is a sensor unit, and 1G is also formed by magnetoresistive elements MRI and MR2.These magnetoresistive elements MRI and MR2
are arranged at positions facing the magnetic recording medium and from which detection signals whose phases are inverted with respect to each other are obtained. In such a sensor unit 2, the positive power supply voltage +Vcc is supplied to the terminal T1, and the terminals T2, 'F. The resistors R, , R, are connected in series to each of the resistors R, , R, and the other ends of the resistors R, , R are connected to ground, forming a single-wire resistor BR. For these grip resistors R,,R, metal film resistors whose temperature coefficient is 1/10 or less compared to the magnetoresistive elements MRI and MR2 are used, and the resistance value is as follows. It is used that is approximately 1 to 10 times larger than 2. This results in
The magnetoresistive elements MRI and MR2 are driven with a substantially constant current. dl. d2 is the bridge circuit B mentioned above.
This is the signal output terminal of R.

Note that FIG. 2 is a circuit diagram showing another example of the above-mentioned Brifuji circuit BR, and parts corresponding to those in FIG. 1 are denoted by the same symbols.
73 is attached.

3 is the t sword stage differential 1119 differential b'+l1il path,
A complete differential input/output type amplification circuit ll+3 is replaced by I'f7j+ by the performance C. Zunawa I'), Kono Mai ii + 1] Sochu rlt
'A:'J3-1, 3-2 positive phase inputs: 1 and 1 are the detection signals of sensor unit and 2, respectively, or human power input R
,, I'2. is supplied via a feedback resistor R7, and each negative phase input terminal is connected via a resistor R7, and a feedback resistor R7.
．． , R o to each output terminal. And each output resistance: 1 to each output resistance R,. ,R. ．． A differentially amplified signal is output via the . 4 is a next-stage differential amplifier 1 circuit. This second-stage differential booster circuit 4 is a completely differential output type one-width circuit similar to the first-stage differential booster circuit 3, and the operational amplifier circuits 4 to l,/ I-2
Each positive-phase input terminal of ?is an operational amplification? ．． ”6 3-l,
3-2 output signal or resistor R, , R, 3
On the other hand, each inverse input terminal is connected to each other via a resistor R14, and feedback resistors R,5,R
．． ．． It is connected to each output terminal of C through. VR has a variable resistance and has an operational amplifier 4. -1.4 Adjust the offset l and bias of the signal supplied to the positive phase input terminal of -2.

Reference numeral 5 denotes an operational amplifier configured to perform a humperate operation. When the output signal of the operational amplifier PH4-2 is supplied via the input resistor R16, the positive phase input terminal of the operational amplifier 5 is connected to the output terminal via the feedback resistor Rll1. The phase input terminal is supplied with the output signal of the operational amplifier 4-1 via the input resistor Rl7.The output terminal is supplied with the output signal of the operational amplifier 4-1 via the input resistor Rl7.
It is pulled up to cc.

In such a configuration, when a positive power supply voltage +Vcc is supplied to the magnetic enhancer 1, the sensor unit 2 detects an alternating magnetic field generated by the rotation of the detection target, and outputs signals dl and d2 with a phase inversion. Provides an approximate sinusoidal signal. These approximate sine wave signals are completely differentially amplified in the first-stage differential width amplifier circuit 3 and the second-stage differential amplifier circuit 4, and as a result, approximate sine wave signals with common-mode noise canceled are output. . Here, the first stage differential amplifier circuit 3
The output signal of
After the imbalance due to variations in the resistance values of RI and MR2 and variations in the resistance value of the resistor RR is corrected by Nl'+, it is manually inputted to the next-stage differential amplifier circuit 4. The output signal from the next-stage differential amplifier circuit 4 is then manually input to the operational amplifier circuit 5.

FIG. 3 is a diagram showing the operation of the operational amplifier 5, showing the signal waveform input to the iE phase input terminal and the negative phase input terminal of the operational amplifier 5, and the humperate output waveform supplied to the output terminal Tout. are shown in comparison. In this figure, (a) is a waveform diagram showing the signal input to the positive phase input terminal and negative phase input terminal of the operational amplifier 5 after adjustment of the offset sensor 1, and (r+) is the waveform diagram shown in (a) of the figure. Compatible combo 1
- It is a waveform diagram showing the output. (c) is ofse・,1・
It is a waveform diagram showing the signals input to the positive 411 input terminal and the negative phase input 6'a of the operational amplifier 5 when not in tune, and (2) is a waveform diagram showing the signals input to the positive phase input terminal 6'a of the operational amplifier 5, and (2) is a waveform diagram showing the signals inputted to the positive phase input terminal 6'a of the operational amplifier 5. - It is a waveform diagram showing the output.

In this way, in calculation increase gain 5, since the converting operation is performed by the Pson Yuble method, it is possible to obtain a large electric current {j′I{tri degree) at the time of converting, and as a result, a high-speed pumping operation with less jitter and hysteresis is possible. It becomes possible.

Next, FIG. 4 is a diagram showing the operation of the operational amplifier 5 when the second embodiment is applied to detecting a Z-phase (origin index) signal. In this figure, (a) is a waveform diagram showing the signals manually input to the positive-phase input terminal and the negative-phase input terminal of the operational amplifier 5, and (b) is a waveform diagram showing the humperate output corresponding to (a) in the figure. It is a diagram. This comparison 1・
The output is an index pulse that represents the origin position where only one magnetic pole is magnetized on the magnetic drum D. When generating this index pulse, an off-set bias is actively added to the Z-phase signals whose phases are reversed to each other. It looks like this.

The embodiment described above has the advantage that it can be driven with a single power supply and does not require a reference voltage for a comparator or a bias M # (+V cc/2) as a virtual ground potential. Further, offset 1 and bias adjustment can be performed using only the variable resistor VR.

Next, a modification of the magnetic encoder 1 will be explained. FIG. 5 shows a circuit 1χ1 for showing a variation 1 [two examples of the next stage circuit A high voltage IIE is applied to each positive phase input terminal of the operational amplifier 4-14-2 via resistors R53 to R56, and an input voltage R is applied to each negative phase input terminal.
5 1. It is said that R 5 2 was added (in 14 years). The operation thereof is the same as the embodiment described above.

Figure 6 shows the bias. l. '． FIG. 1 is a diagram showing an example of an IF circuit, and FIG.
It is a circuit diagram with R removed and five circuit diagrams.
Signal output terminal a in the various bias adjustment circuits shown in 2)
, a' are connected. In this figure, (opening) and (c) are both circuits that obtain a high-ass voltage (-; ■cc/2) using resistance scales 61 to R64 and a variable resistor VR. , is a circuit for obtaining a bias l6 pressure by providing a differential amplification circuit in the fil shown in FIG.

In addition, -1, magnetic low resistance in the above-mentioned case
l. MR2 is driven with a constant current by the gripping resistors R, , R2 connected in series, or this is as follows.
By adding a constant current element or a constant current circuit, it is possible to completely drive at constant current and further increase the temperature coefficient.

Furthermore, in the second embodiment, the magnetoresistive element MR]
．． The two elements of MR2 constitute the sensor unit 1 and 2, or the sensor unit 1 and 2 are composed of four elements of magnetic low resistance elements.
It is also possible to use the sensor unit of the type that constitutes the 7 circuits (see FIG. 8) as is.

In addition, in the double cusp example, r1t? Ii source is used or it is also possible to use equilibrium 71 b+'-.

"Effects of the Invention" As explained above, according to the first invention, the fully differential amplifier circuit cancels out the common mode noise, roughly compares the differential output signal using the push-pull method, and eliminates external noise. This has the effect of being less susceptible to the effects of turbulence and facilitating high-speed comparator operation.

Also, according to the second invention, is it a magnetic low resistance element? Since the sensor is driven in eight currents, the temperature coefficient of the detection signal becomes smaller, which has the effect of reducing the temperature drift of the detection signal output from the sensor section.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the electrical configuration of a magnetic encoder 1 according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing another example of the Brinnon circuit BR in the embodiment, and FIGS. 4
The figure is a waveform diagram showing the operation in the same embodiment, and FIGS. 5 and 6 do not show modified examples of the same embodiment.
1 is a diagram for explaining a conventional example. 2 ・Sensor unit, 3... first stage differential amplifier circuit, 4
...Next-stage differential amplifier circuit, v R ・Variable resistor, 5
・ Operational amplifier manufacturer Yamaha Co., Ltd.

Claims (2)

[Claims] (1) A magnetic recording medium whose alternating magnetic poles are magnetized at a constant cycle and rotates or moves with the rotation or movement of an object to be measured, a sensor section that detects the alternating magnetic field of the magnetic recording medium, and an output of the sensor section. In a magnetic encoder configured with a detection circuit that generates and outputs an angle signal or a position signal from a signal, first and second detection signals output from the sensor section and whose phases are inverted with respect to each other are first and second detection signals, respectively. is supplied to the first input terminal of the differential amplifying means of the first
and second input terminals of the second differential amplification means are connected to each other via a resistor, and the first and second detection signals are differentially amplified, respectively, and the first and second differential amplification means A magnetic encoder comprising: a fully differential amplifier circuit that outputs from an output terminal of the fully differential amplifier circuit; and a comparison circuit that compares the magnitude of a differential output signal of the fully differential amplifier circuit. (2) The sensor section includes a first circuit in which a first resistor is connected in series to a first magnetoresistive element, and a second circuit in which a second resistor is connected in series to a second magnetoresistive element. A positive power supply voltage is applied to one end of each of the first and second circuits, each other end is grounded, and a connection point between the first magnetoresistive element and the first resistor. The magnetic encoder according to claim 1, wherein the first and second detection signals are respectively taken out from a connection point between the second magnetoresistive element and the second resistor.