JPS5814010A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To make it possible to perform highly accurate detection, by providing a gear comprising a magnetic material on a rotary shaft of a rotary body, detecting the change in magnetic flux due to the rotation of the gear by a magnetic sensor comprising ferromagnetic resistor elements, and measuring the number of rotation. CONSTITUTION:On a substrate 5, a plurality of magnetic resistor elements 6 are arranged in the direction at a right angle with the magnetic flux directed from a permanent magnet 4a toward the gear 3 comprising a magnetic material, and a conductor 7 is connected. The elements 6 are divided into two groups R1 and R2. The end of the group R1 is connected to a bonding pad part 8, and the end of the group R2 is connected to a bonding pad part 9. The connecting part of both groups is connected to a bonding pad part 10 of a center tap. A power source E is connected between the bonding pad parts 8 and 9. The change in resistance value due to the change in the magnetic flux caused by the rotation of gear 3 is taken out of the bonding pad part 10. The number of rotation of the gear 3 is measured. Since the magnetic resistance elements 6 are used, the temperature characteristics and accuracy are excellent, and the highly accurate detection is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic sensor used to measure the rotation speed of a rotating body such as a motor.

FIG. 1 is a configuration diagram showing a state in which the rotational speed of a motor is measured with a magnetic sensor, in which (a) is a side view and (a) is a front view.

Moreover, FIG. 2 is an explanatory diagram of a conventional magnetic sensor. 1st
In the figure, 1 is a motor, 2 is a rotating shaft of the motor 1, 3 is a gear made of a magnetic material fixed to the rotating shaft 2, and 4 is a gear 3.
This is a magnetic sensor installed near the teeth of the tooth. When the rotating shaft 2 of the motor 1 rotates, the gear 3 also rotates, and the magnetic sensor 4 detects changes in magnetic flux caused by the passage of the teeth of the gear 3, and an output signal corresponding to the rotation speed of the motor 1 can be obtained.

In FIG. 2, 41 is a permanent magnet that supplies magnetic flux toward the center of the gear 3, and 4b is a detection element made of a semiconductor magnetoresistive element fixed to the surface of the permanent magnet 4a facing the gear 3. A magnetic flux passing through the gear 3 is generated by the permanent magnet 4a as shown by the arrow, and a magnetic bias is applied. When the gear 3 rotates in this state, the amount of magnetic flux passing through the detection element 4a changes depending on the presence or absence of teeth, and the resistance value changes in accordance with this change. When this change is extracted as an electrical signal, the rotation speed of the motor can be determined. However, in conventional magnetic sensors, the temperature coefficient of resistance is 3% IC because a solid gold semiconductor magnetoresistive element is used.
It is difficult to compensate for this temperature to a large extent. Maku,
Since the mean free path of carriers in the device is long, the shape effect of the device is large, and there is a limit to how small the device can be made. Furthermore, since the photo roughy method cannot be used completely, there is a limit to the processing accuracy.

The present invention has been made in order to eliminate these conventional drawbacks, and it is an object of the present invention to provide a magnetic sensor with better temperature characteristics and accuracy than the conventional ones.

FIG. 3 is an explanatory diagram of one embodiment of the magnetic sensor of the present invention, and FIG.
The figure is a partially enlarged view, and FIG. 5 is a circuit diagram. 5 is a substrate, 6 is a plurality of ferromagnetic magnetoresistive elements arranged in a direction perpendicular to the magnetic flux flowing from the permanent magnet 4a toward the gear 3, and TFi is a conductor that connects all of the elements 6. Element 6Vi, two groups R
1tR, the end of one group R1 is a bonding pad section 8, and the end of the other group R is a bonding pad section 9.
The connection parts of both groups are pulled out and connected to the center tap's pounding pad part 10. As shown in FIG.
is connected, and a signal is taken out from the bonding pad section 10.

In this embodiment, the directions of the current flowing through the element 6 and the magnetic flux are perpendicular to each other, and the magnetic flux is also perpendicular to the film thickness direction of the element 6, so that sensitivity is improved.

Such a ferromagnetic magnetoresistive element has a resistance temperature coefficient of 0.
Temperature compensation is easy because the temperature is about 1°C for 3 cm, which is one order of magnitude smaller than that of an equal body. Furthermore, since the mean free path of the carrier is as small as about 50X, the film thickness can be reduced to about t-1OO1 and the film width is about t2 μm, so it is possible to manufacture a compact and highly accurate device. In addition, since the device can be manufactured using photolithography, it is possible to manufacture it with high precision, eliminating the need for offset voltage adjustment by inserting an external resistor, and related to this, temperature compensation. A highly superior ferromagnetic magnetoresistive element can be obtained.

FIGS. 6 and 7 are explanatory diagrams of other embodiments.

In the embodiment shown in Fig. 6, the magnetic flux direction is perpendicular to the current direction of all elements and parallel to the film thickness direction, and in the embodiment shown in Fig. 7, the magnetic flux direction is set parallel to the current direction of the elements. As described above, according to the present invention, since a ferromagnetic magnetoresistive element is used, it is easy to guarantee the temperature of the element.
It can operate at temperatures as high as 0.degree. C., and can be made into a fine shape, making it possible to perform highly accurate detection. Furthermore, since the element can be processed with high precision, offset adjustment of the element is not necessary.

[Brief explanation of drawings]

Figure 1lc1 is a configuration diagram of the state in which the rotation speed of the motor is measured with a magnetic sensor, Figure 82 is an explanatory diagram of a conventional magnetic sensor, #I
Fig. 3 is an explanatory diagram of an example of the magnetic sensor of the present invention, Fig. 4 is a partially enlarged view, Fig. 5 is a circuit diagram, and Figs. 6 and 7 are explanatory diagrams of other embodiments. be. 3...Gear 1.4@Fist@...Permanent magnet, 6...Φ
Ferromagnetic magnetoresistive resistor, T...φ conductor, 8.8.10
...Ponding pad part.

Claims (1)

[Claims] In a magnetic sensor in which a gear made of a magnetic material is provided on the rotating shaft of a rotating body, changes in magnetic flux due to the rotation of this gear are detected by a detection element, and output as an electrical output to measure the rotational speed of the rotating body. , A magnetic sensor characterized in that a ferromagnetic magnetoresistive element is used as the detection element.