JPH0575664U - Rotation detection sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a rotation detection sensor in which the detection voltage of a detected object by a Hall element is increased and a gap between the detected object and the Hall element can be increased. [Structure] Two Hall elements 1 facing the detected part 11
2 is arranged, and the permanent magnet 13 is arranged so as to face the detected portion with the Hall element 12 interposed therebetween. A ferromagnetic member 14 extends from the permanent magnet between the two Hall elements. The electromotive force difference generated in the Hall element is amplified by the differential amplifier circuit.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a rotation detecting sensor using a hall element.

[0002]

[Prior Art]

 4 and 5 are sectional views showing a conventional rotation detecting sensor of this type. In FIG. 4, reference numeral 1 denotes a gear-shaped product made of a magnetic material as a detected part whose rotation is to be detected, 2 denotes a two-element type Hall element as a magnetic detection element arranged facing the gear-shaped product 1, 3 Is a permanent magnet which is adjacent to the two-element type Hall element 2 and is opposed to the gear-shaped product 1 and which gives a uniform magnetic field to the two-element type Hall element 2. 1 is a backup yoke arranged to face 1 to make the magnetic flux of the permanent magnet 3 uniform, 5 is a housing for accommodating these members, and 6 is a printed wiring board for taking out signals from the two-element type hall element 2. .. Further, in FIG. 5, 7 and 8 are Hall elements embedded in the two-element type Hall element of FIG.

In the conventional rotation detecting sensor configured as described above, as shown in FIG. 4, the gear-shaped product 1 as the detected portion is the middle of the hall elements 7 and 8 of the two-element type hall element 2. When they are located at, the electromotive forces generated in both Hall elements 7 and 8 become substantially equal, and the signal of the output stage (not shown) becomes L level or H level.

On the other hand, as shown in FIG. 5, when the gear position of the gear-shaped product 1 deviates from the center of the Hall elements 7 and 8, the magnetic flux from the permanent magnet 3 is as shown by the arrow in the figure. Focus on hall elements 8. As a result, a difference occurs in the Hall electromotive forces of the Hall elements 7 and 8, and the above output stage signal is inverted.

By repeating the above operation, a signal pulse proportional to the number of teeth of the gear-shaped product 1 is obtained.

Further, FIG. 6 is a sectional view showing an essential part of a similar conventional rotation detecting sensor disclosed in Japanese Utility Model Laid-Open No. 3-48715. In this conventional example, a yoke 9 having a thin tip is interposed between the two-element type Hall element 2 and the permanent magnet 3 in FIG. 4 to concentrate the magnetic flux from the permanent magnet 3 on the two-element type Hall element 2. We are trying to improve

[0007]

[Problems to be solved by the device]

 However, in the conventional rotation detection sensor described above, the rotation of the detected portion is detected based on the difference between the starting forces of the two Hall elements, but the detection sensitivity is low, so the gap between the detected portion and the Hall element is reduced. There was a problem that it could not be expanded.

Therefore, in view of the above-mentioned conventional problems, the present invention increases the detection voltage of the detected portion by the hall element by interposing a strong magnetic material between the two hall elements, and detects the detected portion. It is an object of the present invention to provide a rotation detection sensor that allows a large air gap between the Hall element and the Hall element.

[0009]

[Means for Solving the Problems]

 In order to achieve the above object, the rotation detecting sensor according to the present invention includes two Hall elements arranged to face the detected portion and the hall element sandwiching the Hall element to face the detected portion. It is characterized by comprising a permanent magnet, a ferromagnetic member extending from the permanent magnet between two Hall elements, and a differential amplifier circuit for amplifying an electromotive force difference generated in the Hall element. ..

[0010]

[Action]

 With the above configuration, the ferromagnetic member interposed between the Hall elements further acts to further enhance the magnetic flux from the permanent magnet applied to the Hall element when one of the detected portion and the hall element approaches.

[0011]

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a rotation detection sensor according to the present invention, and FIG. 2 is a circuit diagram showing the configuration of a circuit portion of this embodiment.

In FIG. 1, 11 is a rotation detection target such as a gear, 12 is a 2-element type or 1-element type Hall element arranged facing the detection target, 13 is a permanent magnet, and 14 is a permanent magnet. It is a strong magnetic member extending from 13 between the two Hall elements 12 and acting to concentrate the magnetic flux from the permanent magnet 13 on one Hall element 12 during operation.

In FIG. 2, 12 is the Hall element shown in FIG. 1, 15 is an amplifier for amplifying the electromotive force from these Hall elements 12, and 16 is the difference between the outputs from these amplifiers 15. It is a differential amplifier section.

The present embodiment configured as described above operates as follows. When the convex portion of the detected portion 11 is located in the middle of the Hall element 12, the electromotive forces generated in these Hall elements 12 are almost equal, and the output from the differential amplifier 16 in FIG. 2 is L or H. Maintained in one of the levels.

When the convex portion of the detected portion 11 is displaced from the middle of the Hall element 12, the magnetic flux from the permanent magnet 13 is concentrated on the Hall element 12 shown by A in FIG. The magnetic flux density in the permanent magnet 13 → the Hall element 12 of A, the ferromagnetic member 14 → the air gap → the magnetic path of the detected portion 11 is increased.

Therefore, the Hall electromotive force difference from the circuit section in FIG. 2 is greatly enhanced as compared with the case where the ferromagnetic member 14 is not provided, and is output from the differential amplification section 16 of the circuit section. As described above, according to the present embodiment, the detection efficiency is significantly improved.

The size and height of the ferromagnetic member 14 are determined according to the shape of the Hall element.

[0018]

[Effect of the device]

 As described above, according to the present invention, by extending the ferromagnetic member from the permanent magnet between the two Hall elements that are arranged to face the detected part, the magnetic flux passing through one of the Hall elements during operation. There is an effect that the density can be greatly increased, therefore the rotation detection efficiency can be greatly improved and the gap between the detected portion and the Hall element can be enlarged.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a rotation detecting sensor according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a circuit section of the embodiment shown in FIG.

FIG. 3 is a sectional view showing a state of magnetic flux during operation of the embodiment of FIG.

FIG. 4 is a cross-sectional view showing a configuration of a conventional rotation detection sensor.

5 is a cross-sectional view showing a state of magnetic flux in the conventional example of FIG.

FIG. 6 is a cross-sectional view showing the configuration of another conventional example.

[Explanation of symbols]

 11 Detected Section 12 Hall Element 13 Permanent Magnet 16 Differential Amplifier Section

Claims (1)

[Scope of utility model registration request] 1. A hall element disposed opposite to a detected portion, a permanent magnet disposed opposite to the detected portion with the hall element interposed therebetween, and two hall elements formed from the permanent magnets. A rotation detecting sensor comprising: a ferromagnetic member extending between the two and a differential amplifier circuit for amplifying an electromotive force difference generated in the Hall element.