JPH0442629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a frequency generator using a magnetoresistive element for detecting the movement of a moving body.

BACKGROUND TECHNOLOGY AND PROBLEMS Conventionally, frequency generators 1 to 7 have been used as frequency generators that use magnetoresistive elements (hereinafter referred to as MR elements) to detect the rotation speed, rotation direction, rotation position, etc. of a rotating body. The one shown in the figure is known.

The one shown in Fig. 1 has four MR elements A ₁ , B ₁ ,
A ₂ and B ₂ are used and connected as shown in the figure to provide power supply terminals 1 and 2 and midpoint terminals A ₀ and B ₀ .
As the MR elements A ₁ to _{B 2} , a ferromagnetic material such as nickel cobalt whose electrical resistance changes depending on the direction of the magnetic field is used. This ferromagnetic material is formed as a thin film on a substrate in a predetermined shape, and each ferromagnetic material is connected by a thin film conductor. The substrate on which the elements A ₁ to B ₂ are formed is placed close to the magnetic signal 3 magnetically recorded on the rotating body as shown. in this case,
Each element A ₁ to B ₂ is arranged at an interval of 1/8λ with respect to the wavelength λ of the magnetic signal 3. In addition, magnetic signal 3
shall generate a magnetic field of sufficient strength to saturate magnetize the elements A ₁ to _{B 2} .

FIG. 2 shows an equivalent circuit when the elements A ₁ to B ₂ are used as a frequency generator.

External resistors R ₁ and R ₂ are connected to the elements A ₁ to B ₂ , and the entire structure is a bridge. Above resistance
The midpoint potential of the C ₀ point determined by R ₁ and R ₂ and the potential of the B ₀ point are compared by the differential amplifier 4, and the above
The potential at point _C0 and the potential at point _A0 are compared by differential amplifier 5. Also, power supply voltage V ₁ is applied to terminal 1,
Terminal 2 is held at reference potential _E1 .

In the configurations shown in FIGS. 1 and 2, when the rotating body rotates in the direction of the arrow a, the direction of the magnetic field for each of the elements A ₁ to B ₂ changes. As a result, the output voltage OUT ₁ shown in FIG. 3 is obtained from the differential amplifier 4,
An output voltage OUT ₂ delayed by π/2 from the above OUT ₁ is obtained from the differential amplifier 5. These output voltages
OUT ₁ and OUT ₂ have frequencies that correspond to the rotational speed of the rotating body. When the rotating body rotates in the direction of arrow b, the phase relationship of OUT ₁ and OUT ₂ is reversed,
OUT ₁ will lag behind OUT ₂ by π/2. Therefore, by detecting the phase relationship between OUT ₁ and OUT ₂ , it is possible to know the rotational direction, rotational position, etc. of the rotating body.

The frequency generator shown in FIGS. 1 and 2 is
A drift occurs due to the temperature difference between the external resistors R ₁ and R ₂ and the elements A ₁ to B ₂ , which has the drawback of causing an error in detecting the stop position especially when the rotating body is stopped.

The ones shown in FIGS. 4 and 5 use eight MR elements A ₁ to A ₄ , B ₁ to B ₄ and alternately
Two sets of bridge circuits are constructed by arranging the bridge circuits with a distance of 1,000 mm and connecting them with conductors. And Motoko
Terminals 1 and 2 of the bridge circuit consisting of A ₁ to _{A 4}
By applying the voltages V ₁ and E ₁ to the differential amplifier 4 and the voltages at the midpoints A ₀₁ and A ₀₂ to the differential amplifier 4, the output voltage OUT ₁ shown in FIG. 3 is obtained. In addition, voltages V 2 and ₇ are applied to terminals 6 and 7 of the bridge circuit composed of elements B ₁ to B ₄
By adding E ₂ and applying the voltage at the midpoints B ₀₁ and B ₀₂ to the differential amplifier 5, the output voltage shown in Fig. 3 is obtained.
Get OUT ₂ .

The frequency generator shown in Figs. 4 and 5 is 8
Since the elements A ₁ to A ₄ and B ₁ to _{B 4} are formed on the same substrate, there is no temperature difference between the elements and therefore temperature drift is eliminated, but there is a drawback that the number of elements increases.

6 and 7, four MR elements A ₁ , A ₂ , B ₁ , B ₂ are connected in parallel to provide terminal 1, and external resistors R ₃ , R ₄ , R ₅ are connected in parallel. , _R6 are connected to provide terminal 2. In this case, the number of elements can be reduced, but since external resistors R ₄ to _{R 6} are used, there is a drawback that temperature characteristics deteriorate.

OBJECTS OF THE INVENTION The present invention provides a frequency generator that eliminates the above-mentioned drawbacks.

Summary of the Invention The present invention provides three pairs of MR elements, the first pair and the second pair are shifted by λ/4, and
The third pair is shifted by λ/8 from the first or second pair. Thereby, temperature characteristics can be improved while reducing the number of elements.

Embodiment FIGS. 8 to 11 show a first embodiment of the present invention, and the same parts as in FIGS. 1 to 7 are given the same reference numerals.

As shown in FIG. 8, this embodiment uses six MR elements A ₁ A ₂ , B ₁ B ₂ , C ₁ C ₂ , and these elements _{are arranged} on _a substrate _. Arranged in the order of ₁ C ₁ . In this case, the first pair of elements A ₁ and A ₂ are arranged at an interval of λ/4, and the second pair of elements B ₁ and B ₂ are arranged at an interval of λ/4.
are arranged at an interval of λ/4, and the first pair and the second pair are arranged with a shift of λ/4. In addition, a third pair of elements C ₁ and C ₂ are arranged at an interval of λ/4, and
This third pair is shifted by λ/8 from the second pair. Furthermore, as shown in the equivalent circuit of FIG. 9, terminals are provided at the midpoints A ₀ , B ₀ , and C ₀ of each pair, and terminal 1 is provided at one end of the elements A ₁ , B ₁ , and C ₁ . A terminal 2 is provided at one end of A ₂ , B ₂ , and C ₂ .

Figure 10 shows the circuit configuration when used as a frequency generator. The voltages at midpoints A ₀ and B ₀ are applied to the differential amplifier 4, and the voltages at midpoints B ₀ and C ₀ are applied to the rotation direction detection terminals. I try to take it out from 8 and 9.

If the rotating body rotates in the direction of arrow a in this state,
Output voltages A _{0 -OUT} , B ₀ -OUT, and C ₀ -OUT shown in FIG. 11 are obtained from each midpoint of A ₀ , B ₀ , and C ₀ . In this case, a 180° phase difference occurs between A ₀ −OUT and B ₀ −OUT, and a 90° phase difference occurs between C ₀ −OUT and A ₀ −OUT or B ₀ −OUT. arise. Therefore, the output voltage OUT ₀ shown by the dotted line in FIG. 11 is obtained from the differential amplifier 4, and the rotational direction and rotational position can be determined based on the voltages at the terminals 8 and 9.

Note that in this example, the third pair of elements C ₁ and C ₂ is shifted by λ/8 with respect to the second pair of elements B ₁ and B ₂ , but the third pair is shifted from the second pair of elements B 1 and B 2. ₁ and A ₂ may be arranged so as to be shifted by λ/8 with respect to the first pair. In addition, the rotation direction and rotation position are detected at C ₀ point.
Detection may be performed based on the voltage at point _A0 .

FIG. 12 shows a second embodiment, in which the elements
This is a case where the third pair of elements C ₁ and C ₂ is arranged outside the second pair of elements B ₁ and B ₂ with a shift of λ/8. still,
In the case of FIG. 8 according to the first embodiment described above, the third
The pair is placed inside the second pair and shifted by λ/8.

Effects of the Invention Since six MR elements are formed close to each other on the same substrate, their temperature characteristics are the same and no drift occurs. The number of MR elements used can be reduced from eight in the conventional case shown in FIGS. 4 and 5 to six. The rotational direction and rotational position can be detected by the midpoint output of the third pair and the midpoint output of the first or second pair.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing an example of a conventional frequency generator, Figure 2 is an equivalent circuit diagram, Figure 3 is an output waveform diagram,
Fig. 4 is a block diagram showing another conventional example, Fig. 5 is an equivalent circuit diagram, Fig. 6 is a block diagram showing still another conventional example, Fig. 7 is an equivalent circuit diagram, and Fig. 8 is the book. A configuration diagram showing the first embodiment of the invention, FIG. 9 is an equivalent circuit diagram,
Figure 10 is a circuit configuration diagram, Figure 11 is an output waveform diagram,
FIG. 12 is a configuration diagram showing a second embodiment of the present invention. Note that in the symbols used in the drawings, 3... is a magnetic signal, A ₁ A ₂ , B ₁ B ₂ , C ₁ C ₂ ... is a magnetoresistive element.

Claims (1)

[Claims] 1. A first pair in which a pair of magnetoresistive elements are arranged at an interval of λ/4 with respect to the wavelength λ of a magnetic signal recorded on a moving body; a second pair and a third pair having the same configuration, the first pair and the second pair are shifted by λ/4, and the third pair is arranged to be shifted from the first pair or the second pair. The third pair is arranged to be shifted by λ/8 with respect to the second pair, and a signal having a frequency corresponding to the moving speed of the moving object is extracted from the first and second pair, and the third
A frequency generator configured to extract a signal indicating a moving direction of the mobile body from the pair and the second pair or the third pair.