JPS63150623A - Phase adjusting circuit for magnetic head device - Google Patents

Abstract

PURPOSE:To accurately obtain 90 deg. as the phase difference between a sum and a difference signal found from the outputs of two magnetic heads which are almost electrically 90 deg. out of phase with a magnetic scale by varying the phase difference relatively by adjusting exciting currents to the magnetic heads. CONSTITUTION:The two magnetic heads 2 and 3 are arranged at a nearly 90 deg. angle to the magnetic scale 1. The outputs e1 and e2 of the magnetic heads 2 and 3 are added 17 and subtracted 19 to obtain signals eA and eB. The oscillation frequency of a reference signal oscillator 4, on the other hand, is divided 5 to 1/2n and the low-frequency component is extracted by an LPF 6 and amplified 7 and passed through variable shunting circuits 21 and 22 to adjust the exciting currents to exciting coils 2A and 3A, thereby setting the phase difference between the composite output signals eA and eB accurately to 90 deg.. Consequently, the accurate phase difference of 90 deg. is easily obtained. This is suitable to a phase detection type magnetic scale.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase IM adjustment circuit for a magnetic head device suitable for use in a phase detection type magnetic scale device.

[Summary of the invention]

The present invention relates to a phase adjustment circuit for a magnetic head device suitable for use in a phase detection type magnetic scale device, and the present invention relates to a phase adjustment circuit for a magnetic head device suitable for use in a phase detection type magnetic scale device. a combining means for additively and subtractively combining head output signals to generate a new two-channel combined output signal; and an excitation current to be supplied to each excitation winding of the two-channel magnetic herad. By adjusting the level of this excitation current, the phase difference of the two-channel combined output signal obtained at the output side of the combining means can be adjusted to exactly 9.
By setting the magnetic head to 0°, even when the two-channel magnetic heads are not arranged with an exact 90° phase difference with respect to the magnetic scale, the 2-channel magnetic head can be set with an accurate 90° electrical phase difference. The output signal of the channel can be obtained, and it can be used in a phase detection type magnetic scale device to read the magnetic scale with high precision and accuracy.

[Conventional technology]

Conventionally, as a position reading device for automatic processing equipment, in a magnetic scale device based on a magnetic grid-based side scale, a phase detection type magnetism is used, in which the magnetic grid formed on the magnetic scale is read by a phase detection circuit. Scale devices and the like are known.

In this phase detection type magnetic scale device, a read output signal is generally obtained by a signal processing circuit as shown in FIG. That is, in FIG. 6, the magnetic scale (1
1, by magnetically recording a sine wave etc., the characteristic wavelength λ
(for example, λ-200717m) is formed. In order to read the magnetic grating of this magnetic scale (1) as a scale scale, a pair of magnetic flux responsive heads +2
1, +3) are disposed opposite each other to the magnetic scale (1) with an interval of (m + -)λ (where m is an integer), that is, with an electrical phase difference of 90°. Usually, this magnetic flux responsive head +21, (31) has a multi-gap structure having a plurality of gaps formed corresponding to the characteristic wavelength λ of this magnetic grating, thereby increasing wavelength selectivity and improving reproduction characteristics. It is planned.

These magnetic flux-responsive heads (2) and +31 are supplied with an excitation signal having a frequency of □・r to each excitation coil (2A) and (3A), and respond to the magnetic flux generated by the magnetic scale (11). Detection coil (2B), -(
3B) outputs a signal with a frequency of fO. here,
Since the heads (2) and (31) are arranged with an interval of (m + -)λ, the magnetic flux h1. In response to ht, an output signal ehx + eht of λ...(3)...(4) is output.

Here, H, Et, and Ell in each equation are constants determined by the magnetic field strength of the magnetic scale (1), circuit constants, and the like. Note that the reference signal with a frequency of n-f, ) (where n is a positive integer) output from the reference signal oscillator (4) is passed through the first frequency down-down circuit (5), and the signal is passed through the low-pass filter. (6) and an excitation amplifier (7), this excitation signal is supplied to the excitation coils (2^) and (3A) of each head (21, +31).

Each head (21, (31) detection coil (2B),
The output signals 8 @ and e2 outputted from (3B) are sent to the summing amplifier (
11). Note that one output signal e2 is supplied to the summing amplifier (11) with the carrier wave phase advanced by 90° by the phase shifter (10). Therefore, the summing amplifier (11) outputs an output signal ep of p. The output signal ep shown in equation (5) is a phase modulated signal whose amplitude Ep is constant and whose phase varies as a function of the position X on the magnetic scale 11). Note that the preamplifiers (81, (91) equalize the signal levels of the respective output signals e' 1 +132 and supply them to the summing amplifier (11).

Note that in each of the above equations, only the necessary signal components are described to simplify the explanation, but in reality, the excitation signal component of the magnetic head and its harmonic components, as well as the twice the carrier frequency Contains signal components and their harmonic components. Therefore, in order to extract only the signal components necessary for phase modulation No. 13 as shown in equation (5),
The output signal ep from this summing amplifier (11) is applied to a band-pass filter (12) whose center frequency is the carrier frequency 10.
) is output via. The output from this band pass filter (12) is supplied to an amplitude limiting circuit (14) via a buffer amplifier (13), and after being amplitude limited by this amplitude limiting circuit (14), the output is passed through a waveform shaping circuit. (15
) is converted into a square wave signal es.

This rectangular wave signal es is subjected to interpolation processing of, for example, □ by the interpolation processing circuit (16) (16), thereby performing measurement with a resolution of □. In this interpolation process, a reference signal with a frequency of n.0 from the reference signal oscillator (4) is used as an interpolation clock.

[Problem that the invention seeks to solve]

In order to read the magnetic scale (1) with high density and high precision in such a phase detection type magnetic scale device, 2.
It is necessary that the output signals of the two magnetic flux responsive heads (2+ +3) have a correct relationship of □ with respect to the recording wavelength λ of the magnetic scale (1), that is, an electrical phase difference of 90". be.

However, it is a magnetic flux responsive head! 2) Due to variations in the parts that make up +31 or management constraints during the manufacturing process, we have realized a magnetic head device in which the electrical phase difference of the output signals of the magnetic flux response type heads (2) and +3) is set to the correct 60°. It was extremely difficult to do so.

Generally, the recording wavelength λ of the magnetic scale (1) is often 200 μm, and to explain this case as an example, this magnetic flux responsive head (21 (31 magnetic cores) is used).

Approximately 50IIIL material is used for the spacers, etc., but considering that there is a thickness deviation of about 10% and variations in the adhesive between laminated layers, this phase difference is ±30° with respect to the ideal value of 90°. In order to keep the phase difference within an allowable range for a magnetic head device, for example, 90° ± 15°, the phase difference between the magnetic flux response type heads (2) and (3) has a different thickness. It was a hassle to make adjustments by selecting and combining adjustment spacers. Even if a magnetic head device within this tolerance is used in history, the deviation from this ideal value of 90' is ±15°.
This has the disadvantage of having to be adjusted using electrical means such as a variable phase shifter.

To this point, the present invention can achieve these two-channel outputs (
The purpose of this is to make it possible to set the phase difference of No. 3 to the ideal value of 90°.

[Means for solving problems]

As shown in FIG. 1, the phase adjustment circuit of the magnetic head device of the present invention comprises a two-channel magnetic head (
The output signals el and el of 2) and (3) are combined additively and subtractively to create a new 2-channel combined output signal e^
and a synthesis means (17) for generating eB (18)
(19) and a current adjustment device that can relatively vary the level of the excitation current supplied to the excitation windings (2A) and (3^) of the two-channel magnetic heads (2) and (3). means (7), (21), and (22), and by adjusting the level of this excitation current, this combining means (1)
7) The phase difference between the two-channel composite output signals e^ and eB obtained on the output side of (18) and (19) is made to be exactly 90°.

[Effect]

Two-channel magnetic heads (2) and (3) according to the present invention
) was read on the magnetic scale (1) (No. 8 01 and el are 2π el−Et sin −x −−−(6)λ 2π ez=E2sin−(x+d)−・(7)λ. However, d = (m + −) λ+ΔZ.

Δ2 is a deviation from the ideal value (m + −) λ.

This formula (7) is 2π θ7 = E2sin (□λ+φ) λ 2π It can be rewritten as Here φ=-d.

Output signals e1 and e of these magnetic heads (2) and (3)
The addition signal e^ of 2 is e^ =e I +e2, and this subtraction No. 18 e8 is eB=81 132. In the present invention, the current 1IliI adjustment means (7)
Since the level of the excitation current can be varied by (21) and (22), the output voltage level of the magnetic head (2) +31 can be varied by changing the level of the excitation current as shown in FIG. and E2 can be made equal, and when the constants E1 and E2 are made equal and set to "1", for example, . . . (9) is obtained. Equations (8) and (9) can be expressed in hectors as shown in FIG. 2, and the phase difference 0 between e^ and θB is always 90° regardless of the value of the angle φ.

〔Example〕

Hereinafter, one embodiment of the phase adjustment circuit of the magnetic head device of the present invention will be described with reference to FIGS. 1, 2, and 3. In FIG. 1, parts corresponding to those in FIG. 6 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In this example, the magnetic scale + 1) of the magnetic scale (1) on which a magnetic grating with a characteristic wavelength λ (for example, λ = 200 μm) is formed by magnetically recording a sine wave or the like as shown in Fig. 6 is used. In order to read the grating as a scale graduation, a pair of magnetic flux-responsive heads (2) and (3) move each other (
The magnetic scale (11) is disposed so as to be movable relative to the magnetic scale (11) with an interval of λ, that is, with an electrical phase difference of 90°.

In this example, the excitation current obtained at the output side of the excitation amplifier (7) is supplied to the excitation coil (2^) of the magnetic flux responsive head (2) via the variable shunt circuit (21), and this excitation increase @5 (The excitation current of the output of 71 is connected to the variable shunt circuit (22
) to the excitation coil (3A) of the magnetic flux responsive head (3).
). In this case, the relationship between the excitation current and the output voltage of the magnetic flux responsive head is generally as shown in Figure 3. When the electromagnetic current reaches a predetermined value of 1 eP, the output voltage increases, and this I
E, more like this? When the fl magnetic current is increased, this output voltage exhibits a characteristic of gradually decreasing, and in this example, this predetermined value I E
This magnetic flux responsive head uses the excitation current IEO as the center current, which increases from the point 7 and obtains an output voltage of 0.7■ρ, which is 0.7 times the maximum output voltage Vp. 21 (31 excitation coil (2^) (3A) is supplied.

In this example, the output signal obtained from the detection coil (2B) of the magnetic flux responsive head (2) is eh12π eb+ = E 1 sin -x - cos2πro
tλ :Qt cos2πft) t...13
) are supplied to one input terminal of the adder circuit (17) and (one), respectively. Here, 01 indicates that this head (2)
Signal E i that read the scale of π Cale (1)! lin
x ), λ Also, the output signal obtained from the detection coil (3B) of the magnetic flux responsive head (3) eh2 2π ehz −Et sin −(x +d) −cos
2yr r ,) tλ 䋋e2cos2πrot ... (4a) is supplied to the other input terminal of the adder circuit (17) (here, 02 is jTE at which this head (3) has read the 2π scale of the magnetic scale (1) No. E 2 sin −(x +
d) Invert this output signal ehz together with λ to an inverter circuit (
18) to the other input terminal of the adder circuit (19). Here, d = (m + -) λ + ΔZ, and this ΔZ indicates a mechanical deviation from the ideal value <m + -) λ between the magnetic flux responsive heads (2) and (3). Addition number 1-1 obtained on the output side of this addition circuit (17) eA ・ cos2 π r Ot =
(ex +62) ・cos2 π r
ot to the summing amplifier (1) via the level adjustment circuit (20).
1) and obtained at the output side of this adder circuit (19).
et)・cos2πrot and the phase of the carrier signal is 90
'It is supplied to the summing amplifier (11) via a 90° phase shifter (10) and a level adjustment circuit (20). In this case, in the level adjustment circuit (20), the addition signal eA
And decrease! The maximum levels of the signals eB are made equal.

In this example, the other configuration is the same as that shown in FIG. 6.

Since this example is configured as described above, the output signals eh1 and eh2 are sent to the detection coils (2B) and (3B) of the two-channel magnetic flux responsive heads (2) and (3), respectively.
as el++ = e, cos2rt (o tel+2=
e 2 cos2πr Ot is iit. Therefore, as the output signal eACO32πrot of the adder circuit (17), e A CO32πft) t = (es +e,
) -cos'1rtrot is obtained, and a signal of -e2cos2πrot is obtained at the output of the inverter circuit (18), so the output signal e B of the addition H circuit (19)
es cos2n f o t as cos2πfot
= (et-et) -cos2πrot is obtained. Here, to simplify the explanation, carrier wave signal cos2πr
I will explain by deleting ot. That is, the addition signal e^ is e A xel +e2, and the subtraction signal eB is eB"el et 2π. Here, φ=-d.

λ In this example, variable shunt circuits 1M ('21) and (22
) to make these constants E1 and E2 equal.

When the constants E1 and E2 are made equal, for example, "1", the following equations are obtained: (8) (9). When these equations (8) and (9) are expressed as vectors, they become as shown in Figure 2π2, and in this case, et=sin x
Since the maximum amplitude value of λ 2π and the maximum λ maximum amplitude value of e2=sin(X+φ) are equal, they have the same radius, and this added signal e
The phase difference θ between ^ and the subtraction signal eB is always 90° regardless of the value of the angle φ=2π □d. In other words, even if the mechanical installation of the magnetic flux responsive heads (2) and (3) with respect to the magnetic λ scale (1) does not electrically create a 90° phase difference, the phase difference between the addition signal eA and the subtraction signal eB θ is exactly 90'.

This subtracted signal e B cos2πrot is passed through a 90° phase shifter (lO) to eB (2rc f□ t +
90)=eBsin2πfot is obtained, which is supplied to the summing amplifier 'aI (11) via the level adjustment circuit (20), and this sum signal 6ACO52πfot is supplied to the summing amplifier (11) via the level adjustment circuit (20). supplied to In this case, the level adjustment circuit (2o) makes the levels of the signals e and eII+ the same, and the phase difference between the signals e^ and eB is exactly 90'' as described above.
Therefore, as the output signal op of this summing amplifier (11), a phase modulation signal of 2π = Ep sin (2πf,)t+x)λ as shown in equation (5) is obtained, and the other conditions are the same as in Fig. 6. Operates with high precision and precision magnetic scale (11 readings).

As mentioned above, in this example, two-channel magnetic flux responsive heads (2) and (3) are used for the magnetic scale +11.
Even when the magnetic scale cannot be mechanically installed in the correct -λ relationship due to variations in parts or management constraints due to overproduction, there is an advantage in being able to read the magnetic scale (11) with high precision and precision.

Further, FIG. 4 shows another embodiment of the present invention, and in this FIG. 4, an adjustment circuit (
23) and an excitation amplifier (7a) to the excitation coil (2A) of the magnetic flux responsive head (2).

In this case, the excitation level adjustment circuit (23) is constructed so that the excitation current supplied to the excitation coil (2A) can be varied around the current IEO as shown in FIG. Further, the excitation signal obtained at the output side of the low-pass filter (6) is supplied to the excitation coil (3A) of the magnetic flux responsive head (3) via the 45° phase shifter (24) and the excitation amplifier (7b). . In this case, excitation coil (3A)
The excitation current supplied to is approximately 1 t as shown in FIG.
Make it so that it becomes o. Further, the 45° phase shifter (24) shifts the phase of the carrier wave signal CO3πfat, and the first
This function is equivalent to the 90° phase shifter (10) shown in the figure.

In this 4th I21, the respective output signals e A cos2πrot and eBSin2πrot of the addition directions 11!3 (17) and (19) are adjusted by a level adjustment circuit (20).
is supplied to the summing amplifier (11) via the summing amplifier (11). The rest of FIG. 4 is constructed similarly to FIG. 1.

In the fA4 diagram, by adjusting the excitation level adjustment circuit (23), the magnetic flux response type heads (2) and (3) can be adjusted.
) reading signals 01 and e2 of the magnetic scale (L) obtained at the detection coils (2B) and (3B), that is, 2π 81 = Ez sin x λ 2π e 2 = E 2 sin (-x+φ) can be made equal to the addition circuit (1
The phase difference between 8A and eB of the output signals of 7) and (19) can be electrically accurately set to 90°. Therefore, it goes without saying that in this example, the same effects as shown in FIG. 1 can be obtained.

In addition, in Figures 1 and 4, magnetic flux response type heads (2
) and (3) are added to the adder circuits (17) and (1).
9) and the inverter circuit (18) to generate the addition signal e^
``'e1+e2 and subtraction signal eB -el -82 are obtained, but instead of this, this addition circuit (17) (19
) and the fifth without using the inverter circuit (18).
It may be configured as shown in the figure. In other words, in Fig. 5, magnetic flux response type herads (2) and (3) with multi-gap structure are shown.
two detection coils (2B□) (2B2 ) and <
3Bt ) (3B2 ) is provided, and this detection coil (
Output terminal (17a) (1
7b), an addition signal e A cos2tcr □ t is obtained, and a subtraction signal e B cos2π is sent to the output terminals (19a) and (19b) from the detection coils (2B2) and (3B2).
Of course, it is also possible to obtain rOt.

It should be noted that the present invention is not limited to the above-described embodiments; it goes without saying that various other configurations may be adopted without departing from the gist of the present invention.

(Effects of the Invention) According to the present invention, a two-channel magnetic head (21 (31
Even when ■ is not arranged with an accurate mechanical □λ, that is, an electrical phase difference of 90°, with respect to the magnetic scale (1),
It is possible to obtain two-channel output signals with an accurate electrical phase difference of 90°, and the advantage is that it can be used in a phase detection type magnetic scale device to perform high-precision and high-precision magnetic scale reading. be.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of a phase adjustment circuit of a magnetic head device of the present invention, FIGS. 2 and 3 are diagrams for explaining the present invention, and FIG. 4 is a diagram showing another embodiment of the present invention. FIG. 5 is a block diagram showing an example of a magnetic head device used in the present invention, and FIG. 6 is a block diagram showing an example of a conventional phase detection type magnetic scale device. (11 is a magnetic scale, (2) and (3) are each a magnetic flux responsive head, (2A) and (3^) are each an excitation coil,
(2B) and (3B) are respectively detection coils, (4) is a reference signal oscillator, (7) is an excitation amplifier, (10) is a 90° phase shifter, (11) is a summing amplifier, (17) and (1) ) are adder circuits, (18) are inverter circuits, (20
2) and (21) and (22) are variable shunt circuits, respectively.

Claims (1)

[Claims] Generates a new two-channel composite output signal by additively and subtractively combining the output signals of two channels of magnetic heads arranged so as to electrically have a phase difference of approximately 90 degrees with respect to the magnetic scale. and current adjusting means capable of relatively varying the level of the excitation current supplied to each excitation winding of the two-channel magnetic head, and adjusting the level of the excitation current. A phase adjustment circuit for a magnetic head device, characterized in that the phase difference between the two channels of combined output signals obtained on the output side of the combining means is precisely 90°.