JPH068735B2 - Magnetic head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic head for a magnetic scale, and in particular to a 90 ° phase difference which is always accurately 90 ° depending on a relative displacement with respect to a magnetic scale on which a magnetic grating is recorded at a constant wavelength. The present invention relates to an improvement of a magnetic head configured so as to extract a two-channel sinusoidal signal having a magnetic field.

[Summary of the Invention] The present invention has two multi-gap heads, and each head generates two-phase signals having different phases according to the relative displacement with respect to the magnetic scale. It is a magnetic head which is always electrically or magnetically added or subtracted to generate sinusoidal electric signals having 90 ° different phases.

[Prior Art] In order to perform precise and highly accurate position reading from a magnetic scale on which a magnetic grating is recorded at a relatively coarse wavelength (generally 0.2 mm), a 2-channel multi-gap head is used. Correct for recording wavelength λ It was necessary to arrange so as to maintain the relationship (where n is an integer), and to take out two channels of electrical signals having an electrically accurate phase difference of 90 °.

However, due to variations in the thickness of the magnetic core material constituting the multi-gap head or restrictions on the method of assembling the magnetic core material, a magnetic head having a 90 ° phase difference between the electric signals of the two channels is realized. It was difficult.

Therefore, in order to solve these problems, for example, Japanese Patent Publication Sho 5
As disclosed in JP-A-5-38601, a method of interposing a spacer between the multi-gap heads so that the phase difference between the electric signals of the two channels falls within a certain variation range with respect to 90 °, or Japanese Patent Publication No. No. 25817, there is proposed a method of electrically correcting the deviation of the phase difference from the ideal value of 90 °.

[Problems to be Solved by the Invention] According to the former method described above, it takes a lot of time and effort to adjust the phase difference using the spacer, which is efficient and increases the number of parts. , Costly.

Further, in the latter method, an extra circuit for the correction is required, resulting in a high cost, and in the process of finely dividing the scale wavelength and performing an interpolation process to precisely read the scale signal, the two channels The signal phase difference is about 9
If it is not held at 0 °, an error will be mixed in even after it is electrically corrected. Therefore, it is possible to realize a magnetic head capable of outputting 2-channel electric signals having a phase difference of 90 ° as accurately as possible. It is a prerequisite.

Therefore, an object of the present invention is to provide a magnetic head for a magnetic scale, which constantly generates a two-channel sinusoidal electric signal having a phase difference of 90 ° and which enables highly accurate reading of a scale signal without phase adjustment. To provide.

[Means for Solving the Problems] In order to achieve the above object, the magnetic head of the present invention has at least two multi heads arranged so as to generate two-phase signals having different phases according to the relative displacement with respect to the magnetic scale. A gap head is provided, each head is provided with at least two sets of output signal generating means, and the two-phase signals are magnetically or electrically added or subtracted between the multi-gap heads to provide new two-channel signals. The output signal generating means is constituted so that the output signal generating means always generates electric signals having a phase difference of 90 °.

[Operation] The phase difference between the signals of the two channels output from the magnetic head of the present invention is always maintained at 90 °. Therefore, it is possible to avoid mixing of errors in the process of the interpolation processing. Further, the tolerance of the variation in the thickness of the magnetic core material constituting the magnetic head of the present invention is increased, the material unit price can be reduced, and the adjustment process for phase adjustment is not necessary. To be done.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the embodiments shown in the drawings.
FIG. 1 shows the basic configuration of an embodiment of a magnetic head according to the present invention.

In the figure, A ₁ and A ₂ are unit heads constituting the first multi-gap head A, B ₁ and B ₂ are unit heads constituting the second multi-gap head B, and MS is a magnetic scale. Coil LA ₁ and the coil LB ₁ of B ₁ unit heads A ₁ is connected to each output of the adder,
Coil LB ₂ of the coil LA ₂ and B ₂ of unit heads A ₂ are connected to each output of the subtraction. The output voltages of the unit heads A ₁ and A ₂ and B ₁ and B ₂ are e _A1 , e _A2 and e
_Assuming that e _B1 and e _B2 , the unit heads are arranged close to each other so as to generate the same phase and the same output voltage, the output voltage of each unit head can be expressed as follows.

e _A1 = e _A2 = e _A (1) e _B1 = e _B2 = e _B (2) | e _A | = | e _B (3) Here, the first and the first with respect to the recording wavelength λ of the magnetic scale MS. The distance between the two multi-gap heads A and B is nλ +
The output voltage generated in each unit head can be expressed as follows, where d is the relative position and x is the relative position.

That is, the first and second multi-gap heads A and B
The output voltages of are two-phase signals having the same amplitude and different phases by α.

Next, output voltages of new two channels connected additively or subtractively between the multi-gap heads A and B are e ₁ ,
If we say e ₂ , If the phase difference between the output voltages e ₁ and e ₂ is θ, As is clear from the above equation, the phase difference θ between the output voltages e ₁ and e ₂ is the phase difference α between the output voltages e _A and e _{B of} the first and second multi-gap heads A and B. Regardless of, always keep 90 °.

The operating principle of the present invention can be easily understood from the vector diagram shown in FIG.

Also, the distance between A ₁ and A ₂ of both multi-gap heads, B ₁
The output voltage of the same phase was obtained by setting the interval between B ₂ and B ₂ as an integral multiple of the recording wavelength λ of the magnetic scale.
It can also be configured as an integral multiple of λ. However, in this case, the phase of the output voltage between the unit heads differs by 180 °, so e ₁
In order to obtain the output voltage of the unit head B ₁ , the connecting direction of the coil of the unit head B ₁ is reversed, and in order to obtain the output voltage of e ₂ , the connecting direction of the coil of the unit head B ₂ is the forward direction (reverse to that of FIG. Direction).

In the above embodiment, the first and second multi-gap heads are
Although it has been described that the unit heads are used, the number of unit heads may be 2m.

FIG. 3 shows another embodiment of the present invention in which the magnetic yoke portion MA ₁ of the _first multi-gap head A and the magnetic yoke portion MB _{1 of} the second multi-gap head B are connected by a saturable core M _1. The magnetic fluxes flowing into the respective magnetic yoke parts are added by the saturable core M ₁ .

Similarly, the magnetic yoke portion M of the first multi-gap head A is
A ₂ and the magnetic yoke portion M of the second multi-gap head B
B ₂ and S ₂ are connected by a saturable core M ₂ , and the magnetic flux flowing into each magnetic yoke portion is subtracted by the saturable core M ₂ .

Therefore, by winding the signal windings L ₁ and L ₂ around the saturable cores M ₁ and M ₂ , a magnetic flux response type magnetic head that generates a two-channel output voltage corresponding to the added or subtracted magnetic flux is provided. can get.

The above description can be described as mathematical expressions as follows.

Now, assuming that the magnetic fluxes flowing in the magnetic yoke parts MA _{1 to} MB ₂ of each head are φ _A1 , φ _A2 , φ _B1 , and φ _B2, and the magnetic fluxes flowing into the saturable cores M ₁ and M ₂ are φ ₁ and φ _2. , Φ ₁ = φ _A1 + φ _B1 (8) φ ₂ = φ _A2 −φ _B2 (9) Here, if the magnetic yoke and the saturable core are set to φ _A1 = φ _A2 = φ _A (10) φ _B1 = φ _B2 = φ _B (11), φ ₁ = φ _A + φ _B (12) φ ₂ = Φ _A −φ _B The magnetic flux of (13) flows in.

And here, the magnetic fluxes φ _A and φ _B correspond to the scale signal,
Since the output voltage corresponds to the magnetic flux φ ₁ and φ ₂ , (12)
It is clear that the expressions (13) and (13) are completely equivalent to the above e ₁ and e ₂ .

[Effect of the Invention] As is apparent from the above description, according to the present invention, the output voltage of two channels of the magnetic head of the present invention is always 90.
Since the phase difference of .degree. Is held, it is possible to read the magnetic scale signal with high accuracy without inducing an error during the interpolation processing.

Further, since the tolerance of the variation in the thickness of the magnetic core material constituting the magnetic head of the present invention is increased, it is possible to reduce the cost by reducing the unit price of the material.

Further, an adjustment process for keeping the phase difference between the output voltages of the two channels within a certain allowable range and a spacer for the adjustment are not required, so that the cost can be reduced and the efficiency can be improved. become.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the principle configuration of an embodiment of the present invention,
FIG. 2 is a vector diagram for explaining the operation, and FIG. 3 is a schematic perspective view showing the main part of another embodiment of the present invention. A, B ... First and second multi-gap heads, A ₁ to
B ₂ ... Unit head.

Claims (2)

[Claims] 1. At least two multi-gap heads are provided so as to generate two-phase signals having different phases according to relative displacement with respect to a magnetic scale, and each head has at least two sets of output signal generating means. A new two-channel output signal generating means is provided by magnetically or electrically adding or subtracting the two-phase signals between the multi-gap heads, and the output signal generating means always provides a 90 ° phase. A magnetic head characterized in that the magnetic head is configured to generate different electric signals. 2. A saturable core portion provided commonly to each of the multi-gap heads, wherein the two-phase signals are magnetically added or subtracted. The magnetic head according to item 1.