JPH07318367A - Magnetic-flux response type magnetic scale device - Google Patents

Abstract

PURPOSE:To obtain a magnetic-flux response type magnetic scale device suitable for an IC pattern by setting a current flowing through the exciting coils of magnetic-flux response type magnetic heads at the constant current, and reducing the dissipation power. CONSTITUTION:Capacitors C1 and C2, switching means Q1-Q3 and a charging and discharging control means 21 are used, and the charging and discharging time of an exciting current I2 flowing through exciting coils 2B and 3B of magnetic-flux response type magnetic heads 2 and 3 is controlled. The constant exciting current I2 is supplied into the exciting coils 2B and 3B at the low dissipation power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic scale device using a magnetic flux response type magnetic head, and more particularly, to a magnetic flux response type magnetic head which is designed to make an exciting current supplied to an exciting coil of the magnetic flux response type magnetic head constant. Regarding improvement of a scale device.

[0002]

2. Description of the Related Art Conventionally, as a magnetic head of a magnetic scale device for detecting a relative displacement amount between two relatively moving objects, a magnetic flux response type magnetic head (magnetic modulation type magnetic head) is known. Is.

FIG. 7 shows the principle structure of such a magnetic response type magnetic scale device. In FIG. 7, reference numeral 1 denotes a magnetic scale in which a rectangular wave signal or a sine wave signal having a constant wavelength λ (for example, 200 μm) is recorded on a rod-shaped or band-shaped magnetic medium, and is attached to, for example, a moving table on which a workpiece of a machine tool is clamped. ing.

2 and 3 are attached to the fixed part of the machine tool so that they are in contact with the magnetic scale 1 on the moving table (n ± 1).
/ 4) First and second magnetic flux response type magnetic heads (hereinafter referred to as magnetic heads) arranged at intervals of λ (n is a positive number including 0), in order to increase the output. A multi-gap head is used.

These magnetic heads 2 and 3 are saturable cores 2.
It is composed of exciting coils 2B and 3B wound around A and 3A and output coils 2C and 3C.

[0006] 5 m times the angular frequency omega ₀ of the carrier signal: an oscillator for oscillating (m positive integer), the signal of omega _0/2 of the angular frequency downconverting unit 6 an output signal from the oscillator 5 Is supplied to the exciting coil 2B of the first magnetic head 2 and the phase is shifted by π / 4 through the phase shifter 7
To the exciting coil 3B of the magnetic head 3.

From the output coils 2C and 3C of the first and second magnetic heads 2 and 3, the first and second magnetic heads 2 are connected.
A modulation signal of each excitation signal according to the relative change amount x of 3 and 3 is obtained.

The modulation signals e ₁ = E ₁ obtained from the output coils 2C and 3C of the first and second magnetic heads 2 and 3, respectively.
sin 2πx / λ cos ω ₀ t and e ₂ = E ₁ co
s2πx / λ sin ω ₀ t (where E ₁ is a constant) is added by an adder 8 and a band pass filter (hereinafter referred to as “passband filter” that passes only the second harmonic wave (generally even harmonic wave) is allowed) BPF) to have a phase amount corresponding to the relative change amount x at the output terminal T ₁ and an angular frequency ω ₀ which is twice the angular frequency of the exciting current e =
It is calculated as e ₁ + e ₂ = E ₁ sin (ω ₀ t + 2πx / λ).

In this way, the amount of change x can be obtained by measuring the amount of phase modulation (0 to 2π) of the phase modulated signal e. Such a scale device is, for example, Japanese Patent Publication No.
It is publicly known as described in Japanese Patent Publication No. 8-36903.

First and second magnetic heads 2 as described above
The modulation signals e obtained by the output coils 2C and 3C are maintained with the excitation currents flowing through the excitation coils 2B and 3B of 3 and 3 being constant.
_In order to keep ₁ and e ₂ constant, the first and second magnetic heads 2 and 3 are excited at the input terminals T ₃ and T ₄ of the exciting coils 2B and 3B through a transformer 12 as shown in FIG. 6A. Supplying current.

As described above, it is necessary for the constant exciting current to flow through the first and second magnetic heads 2 and 3 when the saturable cores 2A and 3A of the first and second magnetic heads 2 and 3 are shown in FIG. 6B. This is because it has such a saturation characteristic 10. That is, FIG. 6B
The horizontal axis represents the exciting current I ₂ supplied to the exciting coils 2B and 3B from the oscillator 5 via the transformer 12, and the vertical axis represents the peak voltage value E ₂ p output to the secondary coil 12b side of the transformer 12. -P is shown.

Namely, the exciting current I ₂ saturated is sufficiently large to saturable core 2A and 3A, and until the voltage value E ₂ p-p becomes stable region 11, it is necessary to flow the exciting current I ₂ Occurs.

Now, as shown in FIG. 6A, the primary of the transformer 12 is
Connect oscillator 5 and variable resistor VR to side coil 12a
The primary current I₁Flow to the secondary coil 12b
Exciting current I₂To flow the primary coil and
The voltage across the secondary coil is E₁And E₂And each
The number of turns of the coil is n₁And n₂Then E₁n₁= E
₂n₂So that the number of turns of the coil of the transformer 12 becomes the first
And the second magnetic heads 2 and 3 should be selected.
It

In addition to the inconvenience of selecting the transformer 12 having a different winding ratio for each magnetic head, the resistance value Rr of the internal resistance of the inductance L ₀ of the first and second exciting coils 2B and 3B varies. Therefore, the number of coil windings n
_{Even if 1} and n ₂ are determined, as shown in FIG.
There is a trouble that the exciting current I ₂ flowing through the exciting coils 2B and 3B cannot be made constant unless the primary current I ₁ is finely adjusted by the variable resistor VR connected to the primary side. In particular, the magnetic scale 1 and the first and second magnetic heads 2 and 3
In this case, the variable resistor VR of the detection circuit system arranged at the separated position must be adjusted every time the magnetic scale 1 changes, so that the exciting current is made constant. However, the detection circuit system has to correspond to the magnetic head on a one-to-one basis, it is difficult to obtain a stable output, and it is difficult to form an IC.

Further, the operational amplifier 13 is used to flow a constant exciting current I ₂ through the input terminals T ₃ and T ₄ of the exciting coils 2B and 3B of the first and second magnetic heads 2 and 3, respectively. Is also known and is shown in FIG. 6C.

In FIG. 6C, the carrier signal current (excitation signal) from the oscillator 5 is applied to the resistor R at the inverting input terminal of the operational amplifier 13.
Supplied through ₄ . The non-inverting input terminal of the operational amplifier 13 is grounded, and the capacitor C ₃ and the feedback resistor R ₅ connected in parallel are connected between the inverting input terminal and the output terminal of the operational amplifier 13. The capacitor C ₃ is a high frequency cutting capacitor, and includes the first and second magnetic heads 2 and 3.
The exciting current I ₂ supplied to the terminals via terminals T ₃ and T ₄ is supplied as the output current of the operational amplifier 13. The peak value I ₂ p-p of the exciting current I ₂ supplied to the exciting coils 2B and 3B of the first and second magnetic heads 2 and 3 is fed back to the inverting input terminal of the operational amplifier 13 via the control circuit 14. To be done.

The control circuit 14 is composed of resistors R ₆ and R ₀ connected in series, and the exciting coil 2B of the first and second magnetic heads 2 and 3 is located at the connection midpoint of these resistors R ₆ and R _0.
And the peak exciting current I ₂ p−p flowing in 3B is fed back to the inverting input terminal of the operational amplifier 13.

[0018]

Using the operational amplifier 13 shown in FIG. 6C, the exciting current I ₂ p-p of the inverted peak flowing in the resistor R ₀ of the control circuit 14 is controlled to be constant. Then, if the dropped voltage is fed back by the resistor R ₀ , the differential operation of the operational amplifier 13 causes the first and second magnetic heads 2 to operate.
It is possible to keep the exciting current I ₂ flowing through the exciting coils 2B and 3B of Nos. 3 and 3 constant. In this case, the resistance value Rr of the internal resistance of the exciting coils 2B and 3B of the first and second magnetic heads 2 and 3 and the resistance value of the resistor R ₀ of the control circuit 14 are both 5.
The voltage drop is small at about Ω, and for example, the exciting current I ₂ = 12
Although the power can be reduced to 0 mA, the operational amplifier 13
Also, since the exciting current is passed, the power consumption increases, that is, the driving voltage of the operational amplifier 13 is as large as ± 5V = 10V,
Even when the exciting current I ₂ = 120 mAp-p, the power consumption of this portion was as large as 1/2 × 10 V × 120 mA, and it was difficult to form an IC due to heat generation. Also, IC
There is a problem that external components such as a power transistor are required to realize the above.

The present invention provides a magnetic flux response type magnetic scale device which solves the above problems, and its object is to supply a constant exciting current with low power consumption regardless of the internal impedance of the magnetic head. It is intended to obtain a magnetic flux response type magnetic scale device suitable for use as an IC.

[0020]

Means for Solving the Problems The magnetic flux response type magnet of the present invention
The scale device has a magnetic flux
Exciting current I supplied to the response type magnetic heads 2 and 3₂One
In a magnetic flux response type magnetic scale device adapted to be standardized
And exciting current I₂A first control having a frequency corresponding to
Signal φ₁First and third switching hands controlled by
Dan Q₁And Q₃And the exciting current I₂Has a frequency corresponding to
Second control signal φ₂Second switchon controlled by
Means Q₂And the first and second switching means Q₁Over
And Q₂Between the first voltage source and the reference voltage position.
Densa C₁And the third switching means Q₃And magnetic flux response
A second coil connected in series with the answer type magnetic heads 2 and 3.
Indexer C₂And the first and second capacitors C₁And C
₂Charging and discharging time control means 21 for controlling the charging and discharging time of
Equipped with the first control signal φ₁And the first capacitor C ₁To
The second capacitor C that is charged₂Discharge the above
The second capacitor C is controlled by the charge / discharge time control means.₂Discharge of
First capacitor C based on current₁Control the charging time of
To stop charging, and the second control signal φ₂And the first conde
Sensor C₁To discharge the electric charge of the second capacitor C₂To
Exciting current I of the magnetic flux response type magnetic heads 2 and 3 when charged
₂It is designed to keep constant.

[0021]

In the magnetic flux response type magnetic scale device of the present invention, the exciting current I ₂ supplied to the exciting coils 2B and 3B of the magnetic heads 2 and 3 is charged / discharged by the capacitors C ₁ and C ₂ and the switching means Q _{1 to} Q _3. Is used to make it constant, reduce power consumption, and be suitable for an IC.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic flux response type magnetic scale device of the present invention will be described below with reference to FIGS. Figure 1 is a block diagram showing an embodiment of a magnetic flux response type magnetic scale device of the present invention, in FIG. 1, the angular frequency of the square wave or sine wave, etc. from the oscillator 5 to the input terminal T ₂ ω _0/2 An excitation signal is supplied as a carrier signal of the.

This excitation signal is supplied to the fourth switching means (for example, the source or drain of MOSFET) Q ₄ via the inverting circuit 16, the non-inverting circuit 17 and the resistor R ₁ . The fourth gate of the switching means Q ₄ are supplied control signals from the even discharge time control means 21 will be described later, controls the "on", "off" of the fourth switching means Q ₄ is performed.

The first to third switching means Q ₁ , Q ₂ , Q ₃ are connected in series with the fourth switching means Q _4, and the third switching means Q ₃ constitutes a resistor R constituting a voltage detecting means. Grounded through ₂ .

A first capacitor C ₁ is connected between the series connection point of the first and second switching means Q ₁ and Q ₂ and the ground. Although the ground potential is shown in the figure, the ground potential may be a reference voltage value having a predetermined voltage value.
The output terminal of the _second switching means Q ₂ is connected in series with the input terminal of the third switching means Q ₃ and
And the first input terminal T ₃ of the second magnetic heads 2 and 3. The first and second magnetic heads 2 and 3 are connected between the first input terminal T ₃ and the second input terminal T _4, and the first and second magnetic heads 2 and 3 are connected between the second input terminal T ₄ and the ground or the reference voltage value. Two capacitors C ₂ are connected.

The voltage at the connection point between the _third switching means Q ₃ and the resistor R ₂ is the peak hold circuit 18, the integrating circuit 19 and the comparator 2 which constitute the charge / discharge time control means 21.
0 to control the fourth switching means Q ₄ "on" and "off".

The first control signal φ ₁ for "on" and "off" shown in the waveform diagram of FIG.
And the third switching means Q ₁ and Q ₃ are supplied to the gates to “on” the first and third switching means.
The second control signal φ ₂ for “on” and “off” which is “off” controlled and inverted by the inversion circuit 16 shown in FIG. 2B is supplied to the second switching means Q ₂ and the peak hold circuit 18. 2 switching means Q ₂ "ON""OFF"
The peak hold circuit 18 is reset while being controlled. In FIG. 1, V _REF is a reference voltage source for the comparator 20.

Peaks constituting the charge / discharge time control means 21
The principle structure of the hold circuit 18 is shown in FIG. V in FIG.
_inIs a resistor R which constitutes the voltage detecting means shown in FIG.₂
It is the voltage drop signal across and is supplied with the waveform of Figure 2F.
It Such a voltage drop signal V_inThrough the diode D
Holding capacitor C_HIs charged to
Unless the reset switch sw is turned on,
There is no voltage drop signal V _inHold. Voltage drop after charging
Down signal V_inIs a holding capacitor C_HLower than the charging voltage of
If the voltage remains, diode D is connected in the reverse direction
Therefore, neither discharge nor charge is performed, and the holding capacitor C is used._HIs
It is designed to hold the peak value. Peak hole in Figure 1
The error due to the forward voltage drop of the diode D
In order to eliminate it, use two operational amplifiers and a diode.
Reset switch made to be an ideal diode
sw is the second control shown in FIG. 2B obtained from the inverting circuit 16.
Signal φ₂Made to be reset when is turned on
Has been.

The output waveform 18D of the peak hold circuit 18 shown in FIG. 2G is supplied to the integration circuit 19 shown in FIG. 1 as V _in , and the integrated waveform 19E shown in FIG. 2H is output to V _out . An example of such an integrating circuit 19 is shown in FIG. That is, the capacitor C ₃ is connected between the output terminal of the operational amplifier OP ₁ and the inverting input terminal, the resistor R ₈ is connected between the inverting input terminal and the ground, and the output 18D of the peak hold circuit 18 is connected to the non-inverting input terminal. If the resistor R ₂ shown in FIG. 4 is connected between the input terminals supplied as V _in and the capacitor C ₄ is connected between the connection point of the non-inverting input terminal and the resistor R ₂ and the ground, the output of the integrating circuit 19 V _out is the resistance value of the resistor R ₈ is R ₀₈ , and the capacitance value of the capacitor C ₃ is C
_{If it is 03,} it will be expressed by Equation 1. The integrated output is obtained.

[0030]

[Equation 1]

The operation of the magnetic flux response type magnetic scale device for supplying the constant exciting current I ₂ to the first and second magnetic heads 2 and 3 as described above will be described below.

At the input terminal T ₂ of FIG. 1, a forward rotation circuit 17 and an inverting circuit 16 are driven by a carrier signal (for example, a clock signal of 25 kHz) having a frequency corresponding to the excitation signal, as shown in FIGS. 2A and 2B. Third switching means Q ₁
˜Q ₃ and the reset switch sw (see FIG. 3) of the peak hold circuit 18 form the first and second control signals φ ₁ and φ ₂ for “on” and “off” control, and the first control signal φ ₁ Thus, when the first switching means Q ₁ and the third switching means Q ₃ are turned “on” (high level), the second control signal φ ₂ turns the _second switching means Q ₂ “off” (low level). At the same time, the reset switch sw of the peak hold circuit 18 is in the “off” state,
The peak hold circuit 18 is reset when the second control signal φ ₂ is “on” (high level).

Therefore, the reset switch sw of the peak hold circuit 18 is turned on, the charge stored in the holding capacitor C _H is discharged, and the potential at the voltage detection point R ₂ C in FIG. 2F becomes zero level. The output waveform 18D of the peak hold circuit 18 also becomes zero level as shown in FIG. 2G.

The integrating circuit 19 is discharged with a time constant of R ₀₈ · C ₀₃ , and gradually reaches the zero level as shown by the integrated output waveform 19E in FIG. 2H. When the integrated output waveform 19E gradually decreases and reaches the zero level and is lower than the reference voltage value V _R of the reference voltage source V _REF of the comparator 20, the output waveform 20F of the comparator 20 shows the reference voltage source V _REF as shown in FIG. 2I. By making the reference voltage value V _R high, the fourth switching means Q ₄ is turned “on”.

As described above, when the fourth control means Q ₄ is "on" and the first control signal φ ₁ shown in FIG. 2A is turned "on" and goes to a high level, the first and third switching means Q ₄ are turned on. ₁ and Q ₃ are “turned on”, the first capacitor C ₁ is a carrier signal of a frequency corresponding to the excitation signal supplied to the input terminal T ₂ , and the resistor R ₁ → the fourth switching means Q ₄ → the first The switching means Q ₁ → is charged through the path of the first capacitor C ₁ , and the waveform at the point Q ₁ A is gradually charged to the “OFF” position of the fourth switching means Q ₄ as shown in FIG. 2C.

[0036] The third switching means Q ₃ also charge charged in the second capacitor C ₂ to be "on" and the second capacitor C ₂ → terminal T ₄ → the magnetic head 2
And 3 → terminal T ₃ → third switching means Q ₃ → resistor R ₂ → discharging in the path of the reference voltage position. As a result, the second
Capacitor C ₂ of the discharge current flows into the resistor R _2, the voltage (R ₂ C between the resistors R ₂ corresponding to the inflow current of
2F rises to a predetermined peak value P and attenuates as shown in FIG. 2F.

The peak hold circuit 18 holds this peak value P to generate the peak hold waveform 18D shown in FIG. 2G.
Is supplied to the integrating circuit 19.

V _in (18 _{in the} integrating circuit 19 shown in FIG.
In D), if the current flowing when the second capacitor C ₂ is discharged is I _f , then V _in ≈I _f · R _2. Therefore, if I _f is small if the resistance R ₂ is constant, V _in becomes small. , V _in
= V _out becomes longer. If I _f is large, V _in
= V _out becomes shorter. Accordingly, the time for charging the first capacitor C ₁ is controlled. Therefore, the exciting current I ₂ supplied to the magnetic heads 2 and 3 is given by Equation 1 and is given by Equation _{2 when} the resistance value of the resistor R ₂ is R ₀₂ .

[Equation 2] And, it will work so that it becomes a constant value.

When the voltage value of the integrated waveform 19E of FIG. 2H, which has been time-integrated by the integrating circuit 19, exceeds the reference value V _R of the reference voltage source V _REF of the comparator 20, the output 20F of the comparator 20 is as shown in FIG. 2I. When turned off, the fourth switching means Q ₄ is turned off and charging of the first capacitor C ₁ is stopped. Since the reference value V _R of the reference voltage source V _REF has variations in the impedances of the magnetic heads 2 and 3, it is set to the best voltage, which will be described later, and the time constant of the integrating circuit 19 is proportional to 1 / Z as described above. Magnetic head 2
A constant exciting current can be obtained regardless of the impedances of 3 and 3.

Next, when the first control signal φ ₁ goes low and the second control signal φ ₂ goes high, the first and third switching means Q ₁ and Q ₃ are turned off, Since the second switching means Q ₂ is in the “on” state, the electric charge stored in the first capacitor C ₁ is stored in the capacitor C ₁ → second switching means Q ₂ → terminal T ₃
→ magnetic heads 2 and 3 → terminal T ₄ → second capacitor C
It is charged second to the capacitor C ₂ in ₂ system path. This charging current is applied to the exciting coils 2B and 3B of the magnetic heads 2 and 3.
The exciting current I ₂ flows into the.

By repeating the above operation, the exciting current I ₂ flowing through the magnetic heads 2 and 3 is changed to the first capacitor C ₁
The charging / discharging time control means 21 controls the time depending on the charging time.

When correcting the variation in the impedance Z due to the winding error of the exciting coils 2B and 3B and the output coils 2C and 3C of the magnetic heads 2 and 3, for example, the variation in the impedance Z of each magnetic head is measured. Then, a normal distribution curve 22 is obtained as shown in FIG. 5, so that when the exciting current I ₂ is “on” (when the first capacitor C ₁ is charged) centered on the average impedance Z ₀ obtained in each measurement. By selecting the reference voltage V _R of the reference voltage source V _REF of the comparator 20 so that it becomes 1/2 of the time, it becomes possible to set the above-mentioned best voltage.

Since the present invention is constructed and operates as described above, the charging current to the _first capacitor C ₁ can be extremely small, and a large discharging current at the time of discharging, that is, the exciting current I
_{Since 2} is obtained, the exciting current I flowing through the magnetic heads 2 and 3
₂ is consumed only by the internal resistance Rr of the exciting coils of the first and second magnetic heads 2 and 3 and the resistance value R ₀₂ of the resistance R ₂ of the voltage detecting means connected in series with the third switching means Q _3. Since the internal resistance Rr and the resistance value R ₀₂ of the resistance R ₂ are both as small as about 5Ω, the large exciting current I ₂ for saturating the saturable cores 2A and 3A of the magnetic heads 2 and 3 is small. It can be covered by power consumption.

Further, by setting the reference voltage V _{R of the} comparator to the best voltage and making the time constant of the integrating circuit proportional to 1 / Z, a constant exciting current can be flowed regardless of variations in the impedance of the magnetic head, and IC It is possible to obtain a magnetic flux response type magnetic scale device suitable for high efficiency.

[0045]

According to the magnetic flux response type magnetic scale device of the present invention, a constant exciting current can flow regardless of the impedance variation of the magnetic head, and the exciting coil of the magnetic head can be formed by the charging / discharging circuit combining the switching means and the capacitor. Since an exciting current is supplied to the device, it is possible to obtain a device with low power consumption suitable for IC.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a magnetic flux response type magnetic scale device of the present invention.

FIG. 2 is a waveform explanatory view of a magnetic flux response type magnetic scale device of the present invention.

FIG. 3 is a principle diagram of a peak hold circuit used in the present invention.

FIG. 4 is a configuration diagram showing an embodiment of an integrating circuit used in the present invention.

FIG. 5 is an explanatory diagram of impedance of a magnetic head.

FIG. 6 is an explanatory diagram of an exciting current of a conventional magnetic flux response type magnetic head.

FIG. 7 is an explanatory diagram of a conventional magnetic flux response type magnetic scale device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic scale 2,3 Magnetic flux response type magnetic head 16 Inversion circuit 17 Forward rotation circuit 18 Peak hold circuit 19 Integration circuit 20 Comparator 21 Charge / discharge time control means

Claims (3)

[Claims] 1. A magnetic flux response type magnetic scale device adapted to make an exciting current supplied to a magnetic flux response type magnetic head constant, which is controlled by a first control signal having a frequency corresponding to the exciting current. First and third switching means, second switching means controlled by a second control signal having a frequency corresponding to the exciting current, between the first and second switching means, and a reference voltage position. A first capacitor connected between the first and second capacitors, a second capacitor connected in series with the third switching means and the magnetic flux response type magnetic head, and charging and discharging of the first and second capacitors. Charging / discharging time control means for controlling the time, charging the first capacitor with the first control signal and discharging the second capacitor to control the charging / discharging time. Means controls the charging time of the first capacitor based on the discharge current of the second capacitor to stop charging, and discharges the electric charge of the first capacitor by the second control signal, A magnetic flux response type magnetic scale device, characterized in that the excitation current of the magnetic flux response type magnetic head is kept constant by charging the second capacitor. 2. The charging / discharging time control means controls the charging time of the first capacitor based on a voltage detecting means for detecting a voltage corresponding to a discharging current of the second capacitor. The magnetic flux response type magnetic scale device according to claim 1. 3. The magnetic flux response type magnetic scale device according to claim 1, wherein the charge / discharge time control means comprises a maximum value hold circuit, an integrating circuit, a comparator and a fourth switching means. .