JPH01412A - movement detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a movement detection device using an MR element (magnetoresistive effect element), and particularly to a movement detection device that can simultaneously determine movement speed and movement direction. Regarding.

"Prior Art" In rotation detection, when detecting the rotation speed and rotation direction at the same time, two signals with different phases are generally used. For example, in a magnetic rotary encoder, two sets of MR elements are arranged with a phase difference of π/2,
The direction of rotation is detected from the phase difference between these output signals, and the number of rotations is detected from the frequency (for example, Japanese Patent Laid-Open No. 104262/1982).

However, the conventional rotation detection device has the drawback that it requires a large number of detection elements because it requires two signals, and also has the disadvantage that it requires a large number of detection elements because it requires two signals. The drawback was that the processing circuit required for detection was complicated. Moreover, such problems are not limited to rotation detection, but also occur in other movement detection.

This invention was made in view of the above-mentioned circumstances.
It is an object of the present invention to provide a movement detection device that can detect both the movement direction and movement speed using phase signals, thereby reducing the number of detection elements and simplifying the processing circuit.

"Means for solving the problem" In order to solve the above problem, in the first invention,
A comparator having a dead zone at a predetermined level, a series-connected pair of magnetoresistive elements to which a predetermined voltage is applied, and a magnet attached to a moving body and configured to pass near the pair of magnetoresistive elements. , the voltage obtained at the connection point of each of the magnetoresistive elements and the reference voltage are applied to one and the other input terminals of the comparator, respectively; It is set so that the difference between the voltage and the reference voltage falls within the dead zone.

Further, in the second invention, instead of the reference voltage applied to the comparator, a voltage obtained at the connection point of the second pair of magnetoresistive elements connected in series to which the predetermined voltage is applied in the opposite direction is used. There is.

"Operation" Each time the magnet passes near a pair of magnetoresistive elements, a pulse is output from the comparator, and the duty ratio of the output pulse from the comparator is reversed depending on the moving direction of the magnet.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the first invention, in which reference numerals 1 and 2 represent MR elements connected in series between a power supply Vc and a ground point. 3 is a comparator,
The non-inverting input terminal is the MR element l.

The inverting input terminal is connected to the reference power source 4. This comparator 3 performs a comparison operation when the difference between the two input terminal potentials exceeds a predetermined dead zone, and maintains the previous state without performing the comparison operation while the input terminal potential difference is within the dead zone. Further, the voltage value Vs of the reference power supply 4 is M
R element! , 2 are set to be equal to the potential Va at the midpoint a when no external magnetic field is applied.

Next, the operation of this embodiment with the above configuration will be explained.

First, the basic operation of the MR element will be explained with reference to FIGS. 2 and 3.

Now, as shown in FIG. 2, when the magnet 7, which is generating a magnetic field perpendicular to the longitudinal direction of the MR element 8, passes near the MR element 8 from the left to the right in the drawing (in the direction of the arrow), The resistance of the MR element 8 changes as shown in FIG. That is, when the MR element 8 is near the magnet 7, its resistance value decreases, and at its lowest value, it decreases to about 3% of the resistance value when not receiving an external magnetic field.

Therefore, the series-connected MR elements 1. shown in FIG.
When the magnet 7 passes near 2 in the direction, the voltage V
a increases by 3% from the initial value as shown by the solid line in Figure 4.
When it increases, it starts to decrease, and then when it decreases by 3% from the initial value, it increases again and returns to the initial value. Then, as the voltage Va changes, the comparator 3 performs the following operation. First, at time 1+ when the voltage Va rises and the difference from the voltage Vs exceeds the dead zone E of the comparator 3 to the positive side,
The output signal So of the comparator 3 becomes “H” level (
(see Figure 4 (b)), the voltage Va decreases and the voltage V
At time t, when the difference with s exceeds the dead zone E of the comparator 3 on the negative side, the signal SO becomes a "yes" level. Then, after time t, the difference between the voltage Va and the voltage Vs does not exceed the dead zone E to the positive side, so the signal SO
maintains the "L" level. Note that the initial value of the signal SO may be "H" level depending on the operating state of Moe (
After time t (see - dotted chain line in FIG. 4(b)), it is always at the "L" level. Therefore, when the magnet 7 passes continuously in six directions, the signal So is at the "H" level only during the period corresponding to times t1 to t2.

On the other hand, when the magnet 7 passes near the MR element 1.2 in the direction B, the voltage Va is ? As shown by the knee-dot chain line, this is an inverted waveform for six directions. therefore,
The waveform of the output signal SO of the comparator 3 also becomes an inverted waveform of the waveform shown in FIG. 4(b). Even in this case, the initial value of the signal So may be at the "L" level depending on the previous operating state (see the dashed line in FIG. 4(C)), but at the time t
From 2 onwards, the level is always "H". Therefore, when the magnet 7 passes continuously in the B direction,
The signal SO is in the period corresponding to time t1 to t2.
“It becomes a level.

When detecting rotation, for example, as shown in FIG. 5, the magnet 7 is attached to the rotating body 10, and the MR element 1.
2 is provided on the board 1! is placed near the rotating body IO.

Now, assuming that the rotating body 10 rotates clockwise CW, the magnet 7 is the substrate 1! always cross from the same direction. If these directions are the six directions shown in Fig. 1, the output signal So of the comparator 3 will be as shown in Fig. 6 (a).
Board I! “H” only at the timing when magnet 7 passes nearby
It becomes a pulse signal that reaches the level. On the other hand, when the rotating body 10 rotates counterclockwise CCW, the signal SO is as shown in FIG.
As shown in FIG. 3, the pulse signal becomes "L" level only at the timing when the magnet 7 passes near the substrate II.

Therefore, the rotation speed can be detected from the number of pulses of the signal So, and the rotation direction can be detected from the duty ratio of the signal So.

Next, FIG. 7 is a diagram showing the configuration of an embodiment of the second invention, and in the figure,! -, 2'' are MR elements connected in series, and are arranged parallel to the MR element 1.2.The characteristics of the MR elements 1', 2'' are as follows:
It is similar to the MR element 1°2 shown in the figure. however,
MR element 1-.

2' and MR element 1.2 have opposite directions of applied voltage Vc. In this embodiment, the voltage Vs
Instead, the voltage vb obtained at the connection point between the MR elements 1'' and 2' is applied to the inverting input terminal of the comparator 3 (as shown in the diagram).

Now, the magnet 7 moves in six directions from the left side of the drawing, and the MR element 1
．． 2 and I-, 2-, the voltages Va and Vb change symmetrically in opposite directions, resulting in waveforms shown by solid lines and broken lines in FIG. 8(A), respectively. As a result, the signal So is from time t3 to time t when Va>Vb.
4, the signal becomes "H" level, and at time t4
Thereafter, the signal becomes "L" level.

On the other hand, the magnet 7 moves from the right side of the drawing to the left side and the MR element 1
．． 2 and 1-12'', the voltage V
Since the relationship between a and vb is reversed, the waveform of each voltage becomes a waveform obtained by interchanging the solid line and the broken line shown in FIG. 8(a). Therefore, the output signal SO of the comparator 3 is at the "L" level only in the period from time t3 to t4, and is at the "H" level after time t4, as shown in FIG. In this modification, rotation detection can be performed by adopting the configuration shown in FIG. 5, similar to the embodiment shown in FIG. That is, when the rotating body IO rotates clockwise CW and counterclockwise CCW, the voltages Va and Vb are respectively 9th
As shown in Figures (A) and (C), as a result, the signal S
o are as shown in (b) and (d) of the same figure, respectively. Therefore, the signal S.

The rotation speed can be detected from the number of pulses, and the rotation direction can be detected from the duty ratio.

In this example, the MR elements l, 2°1',
2- are set to have the same characteristics, the voltages Va and Vb
There is no need to particularly consider the setting values of , etc., and there is an advantage that manufacturing is easy.

Further, since the voltages Va and vb change in opposite directions, the difference between them is large (6%), and the comparison in the comparator 3 becomes clear.

Although each of the embodiments described above relates to rotation detection, the present invention is not limited to rotation detection, but can also detect the moving speed and direction of linear movement.

1. Effects of the Invention As described above, in the first invention, a comparator having a dead zone of a predetermined level, a pair of series-connected magnetoresistive elements to which a predetermined voltage is applied, and a magnetic A magnet configured to pass near the pair of resistive elements, and a voltage obtained at the connection point of each magnetoresistive element and a reference voltage are applied to one and the other input terminals of the comparator. , and since the difference between the voltage at the connection point and the reference voltage when the magnetoresistive element is not receiving a magnetic field is set to fall within the dead zone, the phase II signal (output signal of the comparator) Both the rotational direction and rotational speed can be detected, thereby reducing the number of detection elements and eliminating the need for phase determination, thereby simplifying the processing circuit. Furthermore, since the configuration is simplified, there are advantages in improving the yield and reducing the manufacturing cost in manufacturing.

Furthermore, in the second invention, instead of the reference voltage applied to the comparator, a voltage obtained at the connection point of the second pair of magnetoresistive elements connected in series to which the predetermined voltage is applied in the opposite direction is used. By using this method, in addition to the effect of the first invention, there is an advantage that setting of a reference voltage, etc. is not necessary.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the configuration of an embodiment of the first invention, Fig. 2 is a diagram for explaining the usage condition of the MR element for deafness, Fig. 3 is a characteristic diagram of the MR element, and Fig. 4 is A waveform diagram showing the waveforms of each part of the circuit in the same embodiment, FIG. 5 is a perspective view showing the configuration when rotation detection is performed in the same embodiment, and FIG. 6 is an output from the comparator 3 in the mode shown in FIG. A waveform diagram showing signals, FIG. 7 is a circuit diagram showing the configuration of the main part of an embodiment of the second invention, FIG. 8 is a waveform diagram showing waveforms of each part of the circuit in the same embodiment, and FIG. 9 is the same. FIG. 7 is a waveform diagram showing waveforms of various parts of the circuit when rotation detection is performed in the embodiment. 1.2...MR element (magnetoresistive element pair; first magnetoresistive element pair), I-, 2'...MR element (
2nd magnetoresistive element pair), 3... Comparator, 4... Reference power supply, 7... Magnet, Vs.
...Reference voltage.

Claims (2)

[Claims] (1) A comparator having a dead zone at a predetermined level and a pair of magnetoresistive elements connected in series to which a predetermined voltage is applied;
a magnet attached to a moving body and configured to pass near the pair of magnetoresistive elements, and a voltage and a reference obtained at the connection point of each of the magnetoresistive elements at one and the other input terminals of the comparator. voltages are applied to each, and
A movement detection device characterized in that the difference between the voltage at the connection point and the reference voltage when the magnetoresistive element is not receiving a magnetic field is set to fall within the dead zone. (2) a comparator having a dead zone at a predetermined level; a first pair of magnetoresistive elements connected in series to which a predetermined voltage is applied; and the first magnetoresistive element to which the predetermined voltage is applied in opposite directions; a second pair of magnetoresistive elements connected in series provided near the pair; and a magnet attached to a moving body and configured to pass near the first and second pair of magnetoresistive elements. , applying voltages obtained at the connection points of the first and second pairs of magnetoresistive elements to one and the other input terminals of the comparator, respectively;
A movement detection device characterized in that the difference in voltage obtained at each of the connection points when the magnetoresistive element is not receiving a magnetic field is set to fall within the dead zone.