JPH01301113A - Signal processing circuit for magneto-resistance element - Google Patents

Abstract

PURPOSE:To reduce the current consumption by setting a value of resistance larger than a magnetic resistance element connected to an end of the magneto- resistance element within a range wherein the sensitivity of the magneto- resistance element is allowed. CONSTITUTION:Values of resistances 14 and 14' larger than elements 6a and 6a' connected to ends of elements 6a and 6a' of the magneto-resistance elements 5 having the two magneto-resistance elements 6a and 6a' formed at the positions where the resistances vary in opposite-phase relation are set within the range wherein the sensitivity of the element 5 is allowed. Consequently, the current consumption of the magnetic encoder signal processing circuit 8' of the element 5 can be adjusted. Consequently, the current consumption is suppressed to a sufficiently small value.

Description

[Detailed Description of the Invention] [Industrial Application Field of the Invention] The present invention provides a magnetic resistance device useful for use in a magnetic encoder that uses a mover having multi-pole magnetic encoder magnetic poles and a magnetic resistance element. This field relates to a signal processing circuit for a magnetoresistive element, and is particularly useful for a magnetic encoder that has a fast response speed, can be backed up by a battery, and can determine an absolute value, and is useful for rotary type or linear type magnetic encoders. It is applicable to both.

[Prior Art] When performing positioning in various automatic devices, a means is required to measure the rotation angle and movement amount of a motor, etc., and to convert these into electrical signals. For this purpose, a device called an encoder is often used.

For example, regarding rotary encoders, there are two types: an incremental type that measures the number of pulses generated with one revolution, and an absolute type that reads a code recorded on the rotor. There are two types of detection methods: optical and magnetic. Recently, incremental magnetic encoders, which are inexpensive and have excellent reliability, have come into widespread use.

Figure 5 shows a conventional general rotary magnetic encoder 1.
This is an explanatory diagram of a magnetic encoder magnetic pole 2 in which the outer periphery is magnetized with 2 N poles and 2 S poles alternately and at fine pitches.
A magnetoresistive (effect) element (referred to as an MR sensor) 5 is disposed to face a magnet rotor 3 with a radial gap 4 in between. The magnet rotor 3 may be an integral type made of magnets, or may be formed by applying a magnetic layer to the outer periphery of a suitable rotor drum.

The N pole 2N and S pole 2S of the magnetic encoder magnetic pole 2 are each magnetized to have a width of λ (equal to the width expressed by 2π in electrical angle).

In addition, the magnetoresistive element 5 is a wire formed of a ferromagnetic thin film that constitutes the magnetoresistive element, in order to first explain the principle of the magnetic encoder 1, assuming that a ferromagnetic magnetoresistive effect element is used, for example. The magnetoresistive element (magnetoresistive body) 6 will be explained using FIG. 6.

This magnetoresistive element 6 is formed by forming a Ni-Co metal thin film (ferromagnetic metal thin film) on a glass substrate or the like by means such as vacuum deposition or etching to a thickness of approximately several thousand squares. 5 can be formed.

As shown in FIG. 6, if the magnetoresistive element 6 is arranged so that the direction of the current I flowing through it and the magnetic flux 7 are perpendicular, the magnetic flux 7 will flow from the north pole 2N to the south pole 2S. .

As shown in FIG. 7, this magnetoresistive element 6 causes a decrease in resistance value due to the lateral magnetic flux 7x within the magnetic flux 7. In addition, 7Y is 1M! Indicates the magnetic flux in the direction.

The rate of change in resistance of the magnetoresistive element 6 at this time is several percent, and when the width of one magnetic pole of the magnetic encoder magnetic pole 2 is λ, the change rate of the resistance of the magnetoresistive element 6 at the positions λ/4 and 3λ/4 is If the resistance value is R9 and the resistance change value is Δr, then magnetic ff1 (2N or 2S) and magnetoresistive element 6
The phase θ (−magnetic pole width 2N, 28 are respectively 2π in electrical angle)
The resistance value R<θ) at the phase θ is as follows.

It can be expressed as R(θ)=R−Δr−cosθ (1).

The lateral magnetic flux 7X is related to two phases θ and the distance between the magnetoresistive element 6 and the magnetic encoder pole 2, and the magnetoresistive element 6 also takes a resistance value R corresponding thereto.

In the case of the magnetoresistive element 5, unlike a magnetic sensor such as a Hall element, there is no lateral magnetic flux at the center of the magnetic field (the magnetic field state at the middle of the north pole 2N and the south pole 2S). Similar to the magnetic field, it has the characteristic that the output signal does not change.

The magnetoresistive element 5 having the single magnetoresistive element 6 described above obtains 2A-phase and B-phase magnetic echoder signals. Therefore, as shown in FIG. 8, four magnetoresistive elements 6a are used.

6b, 6a', and 6b' are formed sequentially shifted by λ/4 to obtain A-phase and B-phase magnetic encoder signals.

This magnetoresistive element 5 includes two magnetoresistive elements 6a and 6a' to obtain an A-phase magnetic encoder signal.
Magnetoresistive elements 6b and 6b' are formed to obtain a B-phase magnetic encoder signal.

When the width of one magnetic pole (N pole 2N or S pole 28) of the magnetic encoder magnetic pole 2 is λ (2π in electrical angle), the magnetoresistive elements 6a and 6a' have opposite phases to each other.
They are formed with a width offset of /2.

Similarly, what are the magnetoresistive elements 6b and 6b'?

They are formed to be shifted by a width of λ/2 so that they have opposite phases to each other.

Also, magnetoresistive elements 6a and 6b, and 6a' and 6
b' are formed to be shifted from each other by a width of λ/4.

Therefore, the magnetoresistive elements 5 are sequentially shifted by λ/4 pitch,
Magnetoresistive elements 6a, 6b.

6a' and 6b'' are formed.

Conventionally, as a circuit for processing the magnetic encoder signal from the magnetoresistive element 5 formed in this manner, the method shown in FIG. was.

The magnetic encoder signal processing circuit 8 of the magnetoresistive element 5 shown in FIG. 9 includes resistors 9-1.・ ・.

9-4 configures a bridge to convert resistance changes into voltage changes, and comparators 10-1 and 10-2 convert two signals with different 90' phases as shown in FIG. 10 (a>, (b)). It is possible to obtain rectangular wave encoder signals 1.1-1.11-2.

By counting the rectangular wave encoder signals 11-1, 11-2 using a counter, the rotation angle of the magnetic encoder can be measured.

The magnetic encoder signal processing circuit 8 of the magnetoresistive element 5 shown in FIG. It is used as a signal output, and is useful as it is often used in conventional magnetic encoders.

However, according to such conventional methods, the resistance values of the magnetoresistive elements 6a and 6a' and 6b and 6b' are determined by their shapes. 20.2
1 is inevitably determined, so the current consumption cannot be reduced. In other words, the current consumption cannot be controlled because it depends on the resistance values of the magnetoresistive elements 6a, 6a', 6b, and 6b'. It had the drawback of not being able to do so.

For this reason, when an incremental magnetic encoder is formed into a magnetic encoder whose absolute value is known (referred to as an electronic absolute encoder)7, especially in the case of a magnetic encoder with battery backup, the current consumption is reduced. But for something like this.

Magnetic encoder signal processing circuit 8 for conventional magnetoresistive element 5
A device that cannot control the current consumption and consumes a large amount of current, such as the above, is unsuitable.

[Problem to be solved by the invention] In the case of an incremental magnetic encoder that is formed into a magnetic encoder whose absolute value is known (referred to as an electronic absolute encoder), especially in the case of a magnetic encoder with battery backup, it is difficult to reduce the current consumption. An object of the present invention is to obtain a magnetic encoder signal processing circuit for a magnetoresistive element configured to control and reduce current consumption.

[Means for Solving the Problems of the Invention] The present invention has been made to achieve the above-mentioned problems.
One ends of the two magnetoresistive elements of a magnetoresistive element having two magnetoresistive elements formed at positions where resistance changes in opposite phases to each other are commonly connected and connected to one power source. The other ends of the two magnetoresistive elements are each connected to the other power supply side via a resistor having a higher resistance value than the magnetoresistive element. The above problem is solved by providing a potential difference measurement signal processing circuit that measures the potential difference at the connection point between the magnetoresistive element and the resistor.

[Function] Connected to the other ends of the two magnetoresistive elements 6a and 6a', respectively, of the magnetoresistive element 5, which has two magnetoresistive elements 6a and 6a' formed at positions where the resistance changes in opposite phases to each other. Magnetoresistive elements 6a and 6a'
By setting the resistance value of the resistor 14, 14' which has a higher resistance value within the range allowed by the sensitivity of the magnetoresistive element 5, the magnetic encoder signal processing circuit 8 of the magnetoresistive element 5
As a result, the current consumption can be kept to a sufficiently small value.

[Embodiments of the Invention] The present invention is also applicable to linear magnetic encoders, but since the explanation will be redundant, in the embodiments shown below, a rotary magnetic encoder will be explained.

FIG. 1 shows an embodiment of a magnetic encoder signal processing circuit 8' for a magnetoresistive element according to the present invention. In particular, only the A-phase magnetic encoder signal processing circuit is shown, but the B-phase magnetic encoder signal processing circuit 8' is shown in FIG. The signal processing circuit can also be constructed in a similar manner, so a description thereof will be omitted.

In order to obtain a magnetic encoder signal for phase A, two magnetoresistive elements 6a of magnetoresistive element 5 are formed with a λ/2 pitch phase shift so that their resistances change to opposite q-phases.
, 6a' are at one end of each other.

They are commonly connected and connected to the positive power source side of the power source battery 12. The negative power supply side of the power supply battery 12 is connected to the ground 13. Magnetoresistive element 6a.

The other end of 6a' is a magnetoresistive element 1-6a, respectively.
It is connected to the ground 13 side via a resistor 14°14' having a higher resistance value than 6a'.

a connection point 18 between the magnetoresistive element 6a and the resistor 14;
Connection point 1 between magnetoresistive element 6a' and resistor 14'
In order to detect the potential difference with 9, the above connection point 18.19
is input to the comparator 17 in the potential difference detection signal processing circuit 1?816 of the magnetic encoder signal processing circuit 8', and λ/
The magnetic encoder signal 11-1 shown in FIG. 1A is obtained in which the output signal changes at an interval of 2 degrees. By 6b and 6b'.

Similarly, the first output signal changes at intervals of λ/2 degrees.
When the magnetic encoder signal 11-2 shown in Figure 0 (b) is obtained, the magnetic encoder signals 11-1 and 11-2 are mutually λ/4.
Since the phases are shifted by degrees, two rectangular magnetic encoder signals 11-1 and 11-2 having different phases by λ/4 degrees can be obtained from the output terminal of the potential difference detection signal processing circuit 16.

This square wave magnetic encoder signal tti.

By adding 11-2 to a double rotation direction discrimination circuit (not shown), a clockwise rotation pulse and a counterclockwise rotation pulse are obtained, and this up signal or down signal is generated.

By adding it to the up/down counter, you can obtain the current rotation angle.

2 In the present invention, unlike the conventional case, the magnetic resistance element 6
Instead of using the midpoint potential between a and 6a' and 6b and 6b' as the output voltage for the magnetic encoder, the connection point 18 between the magnetoresistive element 6a and the resistor 14, and the connection point 18 between the magnetoresistive element 6a and the resistor 14, The signal processing circuit 16 obtains a magnetic encoder signal for the A phase (the same applies for the B phase) by using the connection point 19 of the magnetoresistive elements 6b and 6b'. Because there are
Since the resistors 14 and 14° can be selected with appropriate resistance values, by selecting the resistors 14 and 14' with an appropriate resistance value higher than the magnetoresistive elements 6a and 6a' (resistance By obtaining an appropriate resistance value higher than the magnetoresistive elements 6a and 6a' for the magnetoresistive elements 15 and 15', the value of the current flowing to the magnetoresistive element 5 can be adjusted, and therefore the magnetoresistive element 5 can be used. It can be expected that the current flowing through the magnetic encoder will be reduced.

This prevents the power supply battery from being significantly consumed, thereby further improving the lifespan and performance of the magnetic encoder using battery backup.

Further, as shown in FIG. 2, magnetoresistive elements 6a, 6
A resistor 14.14 having a higher resistance value than the magnetoresistive elements 6a and 6a' is connected to the connection point 18.19 on the other end of a'.
' through the earth 13 side, and the resistor 14.14'
The magnetoresistive elements 6a, 6a' are connected in parallel to each other.
A semiconductor switch 22,22' having an electrical contact is connected to the connection point 18,19 and the ground side 13, respectively.

When active, the semiconductor switches 22 and 22' forming electrical switching circuits are connected to #, resistor 15, and 15 degrees, respectively, and ground 13.
When inactive, one end of each resistor 15.15° is disconnected from the ground 13 side. When this semiconductor switch 22.22° is inactive, the resistance 14.14'
The resistor 14 and 14' having a higher resistance value than the magnetoresistive elements 6a and 6a' are selected.

By using the above-mentioned resistors 14 and 14°, it is possible to control the consumption of the power supply current during battery backup, so it is possible to expect the effect of reducing the consumption of the power supply battery 12.

Now magnetoresistive elements 6a, 6a', resistance 14.1
The resistance values of 4' and 15.15' are R1 and R, respectively.
1', R2, R2°, R,, R,', the resistance 14.14' is at least twice the resistance value R,, R,' of the magnetoresistive elements 6a, 6a', and more preferably 10 times. By doing so, the current consumption of the power supply battery 12 can be significantly reduced.

Needless to say, the resistance value must be determined within a range allowed by the sensitivity of the magnetoresistive element 5, and within a range where disturbing electrical noise will not be a problem.

To explain this with reference to FIG. 3, when the magnetoresistive element 6a is Rs, the magnetoresistive element R5
When the sensitivity is maximum, it is unnecessary to make the resistance values of the resistor R1 and the magnetoresistive element RS equal, since there is less noise during battery backup and responsiveness is not required than during battery backup.

Therefore, by setting the resistance value of the resistor R1 to be higher than that of the magnetoresistive element R9, the power consumption can be reduced.

Here, a resistor R2 and a semiconductor switch 2 are connected in parallel with the resistor R1.
2 and turn on the semiconductor switch 22 during backup.
If the resistor R2 is turned off, it is possible to use a resistor R2 having a very small resistance value.

Therefore, the magnetoresistive elements Rs and R2.

R,”==R2 is sufficient.

As a result, R+>2R2, which is preferable.

The current consumption of the power supply battery 12 can be significantly reduced by selecting the resistor R1 such that R1>5R2, and more preferably, R1 is 10-R1-100/R1>2R2. It is clear that it can be done.

In addition, if you do this, during battery backup,
Generally, an actuator such as a motor that is mechanically coupled to the magnetic encoder is at rest, so it can be expected that the current consumption of the power source battery can be reduced to the extent allowed by the aforementioned sensitivity.

FIG. 4 shows a specific circuit example of the potential difference measuring circuit 16 of the signal processing circuit 8' of the magnetic encoder of the magnetoresistive element shown in FIG. 23 and 24 to the input terminal of an amplifier 25 in the potential difference measuring circuit 16, and the amplifier 25 is connected to the positive input of the comparator 17. Amplifier 2
Negative feedback is provided between the negative input terminal and the output terminal of 5 through a resistor 26 to determine the gain. A connection point 27 between the resistor 24 and the positive input terminal of the amplifier 25 is connected via a resistor 28 to a connection point 30 of a resistor 31.29. resistance 3
One end of the power supply battery 12 is connected to the positive terminal side of the power supply battery 12 . One end of the resistor 29 is connected to the positive input terminal of the comparator 17 connected to the negative terminal side of the power supply battery 12.
A feedback resistor 32 is connected between the output terminals of the comparator 17, and a feedback resistor 32 is connected to the negative input terminal of the comparator 17 between a resistor 35 connected to the positive side of the power supply battery 12 and a resistor 36 connected to the ground 13 side. A variable tap 34 of a variable resistor 33 is connected.

[Effects of the Invention] According to the magnetic encoder signal processing circuit for a magnetoresistive element of the present invention, even if the resistance value of the magnetoresistive element is determined, a resistor with a higher resistance value than the magnetoresistive element connected thereto. 1.It has the effect of reducing current consumption without increasing the number of components, and especially when used in magnetic encoders with battery backup, it can extend the life of the product's battery. This makes it possible to further improve the reliability of the magnetic encoder.

[Brief explanation of the drawing]

1 and 2 are magnetic encoder signal processing circuits of the magnetoresistive element of the present invention, FIG. 3 is a partial explanatory diagram of the same, FIG. 4 is a concrete magnetic encoder signal processing circuit of the same, and FIG. 5 is a magnetic encoder signal processing circuit of the present invention. A schematic explanatory diagram of a conventionally known incremental type rotary magnetic encoder, FIGS.
The figure is an explanatory diagram of a magnetic encoder processing circuit of a conventional magnetoresistive element, and Figures 10 (a> and (b) are encoder signal waveform diagrams obtained from the same magnetic encoder. [Explanation of symbols... Rotary magnetic encoder 2... Magnetic encoder magnetic pole. 3... Magnet rotor, 4... Air gap. 5... Magnetoresistive element. 6.6a, 6a', 6b, 6b' --- Magnetoresistive element, 7. ...Magnetic flux. 8.8°, 8'''...Magnetic encoder signal processing circuit, 9-1...., 9-4...Resistor. 10-1.10-2...Comparator. 11-1.11-2... Magnetic encoder signal. 12... Power supply battery, 13... Earth. 14.14", 15.15'... Resistance. 16... Potential difference of magnetoresistive element Measurement processing circuit. 17... Comparator. 18.19... Connection point. 20.21... Current (current flowing through the magnetoresistive element). 22.22'... Semiconductor switch. 23.24... - Resistor, 25... Amplifier. 26... Resistor, 27... Connection point. 28. 29... Resistor, 30... Connection point. 31... Resistor. 32... Feedback resistor. 33...Variable resistance, 34...Variable tap. 35.36...Resistance.

Claims (2)

[Claims] (1) One ends of the two magnetoresistive elements of a magnetoresistive element having two magnetoresistive elements formed at positions where resistance changes in opposite phases to each other are commonly connected and connected to one power source, and the two magnetoresistive elements are connected to one power source. The other end of each magnetoresistive element is connected to the other power supply side via a resistor having a higher resistance value than the magnetoresistive element, and a potential difference measurement signal processing circuit is provided to measure the potential difference at the connection point between the magnetoresistive element and the resistor. A signal processing circuit using a magnetoresistive element featuring Naruko. (2) In claim (1), the other end of the magnetoresistive element with respect to the power supply connection side is connected to a resistor having at least two or more different resistance values by electrical switching, and the magnetoresistive element and 1. A signal processing circuit for a magnetoresistive element, comprising a potential difference measurement signal processing circuit that measures a potential difference at a connection point with a resistor.