JPH0514829U - Magnetic detection device - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention relates to a magnetic detection device that outputs a change in magnetic flux density due to the rotation of a magnet as an electric signal, and is intended to improve the detection accuracy by concentrating the magnetic flux. is there. By mounting a comparator 9 composed of an iron-based metal lead (comb) on the back side of the Hall element 1 mounted on the printed circuit board 2 facing the rotating magnet 6 and directly behind the printed circuit board, This iron-based metal comb focuses the magnetic flux of the magnet 6 on the Hall element 1 to improve the detection accuracy of the magnetic detection device.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a magnetic detection device that detects a change in magnetic flux density due to movement of a magnet and outputs it as an electric signal.

[0002]

[Prior Art]

 A conventional technique will be described with reference to FIG. According to the figure, 1 is a hall element which is a magnetoelectric conversion element, 2 is a printed circuit board for double-sided mounting, and the Hall element 1 is mounted on the surface of the printed circuit board 2 by soldering. The printed circuit board 2 is mounted with other electronic circuit components constituting the magnetic detection device. Reference numeral 3 denotes a housing, which forms the shape of this magnetic detection device, in which all components including the printed circuit board 2 are housed and sealed with resin 5. Reference numeral 4 is a stopper plate made of a non-magnetic material, which is arranged on the front surface of the Hall element 1, and is fixed to the housing 3 by insert molding. Of the Hall element 1 is made as thin as possible, and the distance from the magnet 6 magnetized on the cylindrical circumferential surface is made as small as possible.

FIG. 4 is a circuit diagram of the magnetic detection device, in which 1 is a Hall element, 7 is a comparator, and 8 is a resistor, and the comparator 7 has a hysteresis width.

FIG. 5 shows how the magnetic flux emitted from the magnet 6 crosses the Hall element 1.

The operation of this conventional magnetic detection device will be described. When the magnet 6 rotates about a cylindrical axis, the leakage magnetic flux leaking from the surface of the magnet 6 becomes an alternating magnetic field penetrating the hall element 1 and is applied to the hall element 1. Therefore, the output of the comparator 7, that is, the rectangular wave signal corresponding to the rotation of the magnet 6 is detected at the SIG terminal in FIG. 4, and the rotation speed of the magnet 6 is measured by measuring the frequency of this rectangular wave signal. Is.

[0006]

[Problems to be solved by the device]

 However, in the above-described conventional magnetic detection device, the leakage magnetic flux leaking from the magnet 6 is severely attenuated as shown in FIG. 5, so that even if the distance (air gap) between the surface of the magnet 6 and the Hall element 1 is increased, the Hall element is slightly increased. The magnetic flux density penetrating 1 is remarkably reduced, the Hall element output that can invert the comparator cannot be obtained, and the required output signal cannot be obtained. In order to avoid this, it is necessary to use expensive magnet materials to increase the surface magnetic flux density of the magnet 1 and to strictly control the air gap. For this air gap control, strict machining accuracy is required for each part. Or a special adjustment inspection process was required.

Conventionally, in order to suppress such magnetic flux attenuation and concentrate the magnetic flux, a back yoke made of a soft iron material or a ferrite material is provided at a position on the surface of the printed circuit board 2 which is directly behind the Hall element 1 to disperse the magnetic flux. Although the suppression method is also used, since the surface mountable area of the printed circuit board 2 is occupied, the printed circuit board 2 becomes large by that amount, which hinders the miniaturization of the product shape.

The present invention solves such a conventional problem, and a special magnet for increasing the surface magnetic flux density by effectively concentrating the magnetic flux without using a back yoke material, It provides an excellent magnetic detection device that does not require strict air gap management.

[0009]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention mounts and arranges a comparator composed of a ferrous metal comb on almost the back side of a printed circuit board on which a magnetoelectric conversion element is mounted.

[0010]

[Action]

 By placing the comparator composed of the iron-based metal comb as described above on the almost back side of the printed circuit board on which the magnetoelectric conversion element is mounted, the comb of the comparator has the same magnetic flux focusing effect as the back yoke. In addition to preventing the divergence of magnetic flux, no new parts are added on the printed circuit board, so the product shape can be kept small.

[0011]

【Example】

 The magnetic detection device of the present invention will be described with reference to the embodiment of FIG. In the description, the same parts as those in the prior art are denoted by the same reference numerals, and the description will be omitted. FIG. 1 is a side cross-sectional view, and 9 is an integrated circuit using iron-based lead frames (combs) as terminals. This is a surface-mount type comparator made up of a circuit, and this terminal (which is generally called a comb, henceforth called the comb) is iron-based, and the iron-based metal has a magnetic flux focusing effect. Paying attention to this, the comparator 9 having the iron-based comb is mounted and arranged almost directly behind the hall element 1 via the printed board 2.

In the magnetic detection device configured as described above, the magnetic flux emitted from the magnet 6 tends to collect toward the iron-based comb of the comparator 9 as shown in FIG. Effectively crosses the Hall element 1, that is, the apparent sensitivity of the Hall element 1 is improved. Therefore, even if the air gap slightly fluctuates, the fluctuation of the magnetic flux density in the portion of the Hall element 1 is small and stable operation is possible. Moreover, since no new member is used to concentrate the magnetic flux, it is not necessary to increase the board area or add an additional part.

[0013]

[Effect of the device]

 As is apparent from the above embodiments, the present invention comprises a magnetoelectric conversion element, a double-sided mounting type printed circuit board on which the magnetoelectric conversion element is mounted, and an iron-based metal comb for comparing voltage signals obtained from the magnetoelectric conversion element. Since the comparator has a built-in comparator and is mounted on the back side of the printed circuit board of the magnetoelectric conversion element, the comb of the comparator can have a magnetic flux focusing effect similar to the back yoke. In addition, it is possible to keep the product shape small because no new parts are added on the printed circuit board.

[Brief description of drawings]

FIG. 1 is a side sectional view of an embodiment of a magnetic detection device of the present invention.

FIG. 2 is a sectional view of an essential part for explaining a state in which the magnetic flux of the magnet crosses a Hall element which is a magnetoelectric conversion element.

FIG. 3 is a side sectional view of a conventional magnetic detection device.

[Figure 4] Circuit diagram

FIG. 5 is a cross-sectional view of an essential part for explaining a state in which the magnetic flux of the magnet crosses a Hall element that is a magnetoelectric conversion element.

[Explanation of symbols]

 1 Hall element 2 Printed circuit board 6 Magnet 9 Comparator

Claims (1)

[Scope of utility model registration request] 1. A magnet, a magnetoelectric conversion element for detecting a magnetic flux of the magnet, a double-sided mounting type printed board on which the magnetoelectric conversion element is mounted, and an iron-based metal comb for comparing voltage signals obtained from the magnetoelectric conversion element. Composed by
A magnetic detection device comprising a comparator mounted and arranged substantially on the back side of the printed circuit board of the magnetoelectric conversion element.