JPS61201486A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To bypass a leakage magnetic field from a magnet for driving a motor to the magnetic shield side, and to reduce an effect on a magneto- sensitive section by forming a magnetic shield into a substrate to which the magneto-sensitive section is shaped. CONSTITUTION:A ferromagnetic alloy consisting of nickel and cobalt is deposited under a vacuum extending over the whole surface of the surface of a glass substrate 1, and shielding sections 11 and 12 continuing to terminal sections 4 and 6 are formed on both sides of magneto-sensitive sections 2 and 3 by using a photoengraving technique. Accordingly, since the shielding sections 11 and 12 are shaped, informations regarding revolution having high precision are acquired, and the shielding sections are formed at the same time as the terminal sections and the magneto-sensitive sections through the photoengraving technique,thus manufacturing a magnetic sensor through processes quite the same as conventional devices.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic sensor for detecting the rotational speed of a video capstan motor or the like.

(Prior Art) A conventional magnetic sensor belonging to this type will be explained with reference to FIGS. 3 and 4.

FIG. 3 is a plan view of a magnetic sensor disclosed in, for example, Japanese Unexamined Patent Publication No. 59-19810. In the figure, the magnetic sensor is constructed by depositing a ferromagnetic alloy of nickel and cobalt or nickel and iron over the entire surface of a glass substrate 1 by vacuum evaporation, and then forming two magnetically sensitive parts 2 and 3 by photolithography. and a terminal section 4 connected to these.・Form 5 and 6, and further apply bias magnetic field 7 to 4.
It is added in the 5° direction.

FIG. 4 is a schematic perspective view of the above-mentioned magnetic sensor attached to a brushless motor. By attaching the motor and connecting the terminals 4 and 6 on both sides to the battery 9, rotation information of the motor was obtained from the intermediate terminal 5.

(Problems to be Solved by the Invention) However, in the magnetic sensor having such a structure, the leakage magnetic field from the motor drive magnet 10 affects the magnetic sensing parts 2 and 3, and only inaccurate rotation information can be obtained. The problem was that it could not be done.

- (Means for solving the problem) In order to solve the above problem, in the present invention, a magnetic shield is provided in the substrate 1 on which the magnetically sensitive parts 2 and 3 are formed.

(Function) With the above structure, the motor drive magnet 10
The leakage magnetic field from the magnetic field is bypassed to the magnetic shield side to reduce the influence on the magnetically sensitive part.

(Example) Embodiments of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a plan view of a magnetic sensor according to the present invention, in which a ferromagnetic alloy made of nickel and cobalt is vacuum-deposited over the entire surface of a glass substrate 1, and terminals are provided on both sides of magnetically sensitive parts 2 and 3. Shield parts 11 and 12 connected to parts 4 and 6 are formed using photolithography. The terminal portion 5 is connected to the magnetic sensing portions 2 and 3 as in the conventional example.

Specifically, the thickness of the nickel-cobalt alloy film was 1000 mm, the distance between the magnetically sensitive parts 2 and 3 and the shield parts 11 and 12 on both sides was 0.2 mm, and the distance between the magnetically sensitive parts 2 and 3 was 0.2 mm. The length of the two is 2m, and the distance between them is 0.
22m+w and bias magnetic field 7 at 45°.
150 gauss in the direction of the magnetic sensor, and as in the conventional example shown in FIG. 4, the magnetic sensor is attached to the brushless motor near the outer circumferential surface of the rotation signal magnetized ring 8 provided on the outer circumference so as to be opposite to the outer circumferential surface. It was installed on.

In order to measure the accuracy of the magnetic sensor, the output from the central terminal section 5 of the magnetic sensor is connected to an amplifier 1 as shown in FIG.
3, the signal frequency was removed by a discriminator 14, and frequency analysis was performed by a frequency analyzer 15 to extract a waveform component caused by the motor drive magnet 10. In the example shown in FIG. 3, there are 8 N and S poles, so there are 47 components per rotation.

As a result of comparing the conventional example and the magnetic sensor of the present invention, it was found that the conventional example had -30 dB, but the above example had -38 dB.
dB, an improvement of 8 dB.

(Effects of the invention) - As mentioned in item 2, by providing the shield parts 11 and 12 according to the present invention, highly accurate rotation information can be obtained. Since they are formed at the same time, they can be manufactured using the same process as before.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a magnetic sensor according to the present invention, Fig. 2 is a block diagram of a circuit for measuring the accuracy of the magnetic sensor, Fig. 3 is a plan view of a conventional magnetic sensor, and Fig. 4 is a brushless magnetic sensor. It is a model perspective view attached to a motor. 1...Substrate, 2,3...Magnetic sensitive part, 4,5゜6
...Terminal section, 7.. Bias magnetic field, 8.. Magnetized ring, 9.. Battery, 10.. Motor driving magnet, 11.12.. Shield section, 13.. Amplifier ,
14... Discriminator, 15... Frequency analyzer. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] A magnetic sensor using a ferromagnetic thin film resistance element, characterized in that a shield part is formed around a magnetically sensitive part and made of the same material.