JPS63137398A - Crime preventing magnetic sensor - 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] [Field of Industrial Application] The present invention is for detecting the opening and closing of shutters, etc. in a non-contact manner, and is used in a detector used for crime prevention or remote control signal output. .

[Conventional technology]

Conventionally, this type of detector has pasted a retroreflective sheet on the surface of a movable part such as a shutter, projected infrared light or other light toward the sheet, and detected the state by receiving the light reflected from the retroreflective sheet. A method using a so-called reflective photoelectric switch is often used.

Another method is to attach a magnetic material to the movable part and use the magnetic force of the magnetic material to directly open and close the reed switch.

[Problem that the invention seeks to solve]

Among the conventional methods, the method using light has the problem that the surface of the reflective sheet attached to the chassis surface etc. becomes dirty over a long period of time, resulting in a decrease in reflectance and a decrease in the amount of reflected light, resulting in malfunction. In addition, large insects may approach and block the light, or moisture in the air may adhere to the surface of the reflective sheet, lowering the reflectance, causing light attenuation.
There are many 4 movements.

On the other hand, in the case of a method in which a magnetic material and a reed switch are combined, the problem is that the distance over which the approach of the magnetic material and the R distance can be detected is short. Special Public Service 1986-1
9115, there is a method to lengthen the detection distance by placing a rotating permanent magnet between the magnetic response switch and the operating magnetic body, but this is still insufficient to detect the opening and closing of something like a shutter. It is. In addition, since this method has physical moving parts, there are problems with reliability and durability, and there is also the possibility of malfunction due to vibrations applied from the outside and internal dirt. Also, since a reed switch is used, the durability of the contacts is also outstanding.

[Means for solving problems]

In the present invention, a ferromagnetic magnetoresistive element is used to electrically amplify the output due to the approach and separation of the operating magnetic body, thereby extending the detectable distance. In addition, a bias permanent magnet is placed between two magnetic magnetoresistive elements,
Furthermore, the detection distance has been increased, and the problems of the conventional technology have been overcome.

〔Example〕

A detailed explanation will be given below based on specific examples.

Figure 1 shows the detection section used in the Fi1% security sensor of the present invention, and shows the positional relationship between the ferromagnetic magnetoresistive element and the permanent magnet for bias, and the positional relationship between the operating magnetic body and the detection section. ing.

A bias permanent magnet 2 is sandwiched between two ferromagnetic magnetoresistance elements l, and the lines of magnetic force emitted from the surface of the operating magnetic body (in this case, the sheet-shaped magneto-ft 3) located in the front (X direction) are configured to detect. Two ferromagnetic magnetoresistive elements having almost the same characteristics are used and are arranged back to back, with the bias permanent magnet 188 placed between them. The permanent magnet for bias has a long protruding shape in the detection direction
Place it on the side where the i1 resistance element is applied. The center of this magnetized surface is located in the X direction relative to the contact portion with the ferromagnetic magnetoresistive element. In other words, the length m of the bias permanent magnet is two or more times the length I of the ferromagnetic magnetoresistive element.

FIG. 2 is a block diagram showing the configuration of the security magnetic sensor of the present invention. A is a detection unit consisting of a ferromagnetic magnetoresistive element and a bias permanent magnet shown in FIG.
The two ferromagnetic magnetoresistive elements have a bridge configuration. In this detection section, a potential difference is generated between two ferromagnetic magnetoresistive elements in a bridge configuration by the approach of the sheet-shaped magnet 3, and this is amplified by the output of the next differential amplifier B. The output of this differential amplifier inverts the comparator C and operates the output circuit. Each of these blocks is supplied with tR from a power supply section (not shown).

With the above configuration, the detection section receives the lines of magnetic force coming from the sheet-shaped magnet attached to the closed shutter surface, and drives the relay of the output section. When the shutter is opened, the sheet-like magnet moves away from the crime prevention magnetic sensor, so its magnetic force decreases. The detection section detects this, and the state of the relay in the output section changes to emit a signal. By selecting the relay used in the output section, the contact capacity of the no-voltage contact output can be freely selected.
This is more advantageous than the conventional method using a reed switch, which generally has a small contact capacity.

A ferromagnetic magnetoresistive element utilizes the magnetoresistive effect of a ferromagnetic material, and is completely different in principle from a Hall element or a semiconductor magnetoresistive element.

Typically, this type of magnetoresistive element has a practical detection distance of 10+
Although it is common that the distance is less than 100 w, a detection distance of 100 or more was obtained with the configuration of the present invention. As the operating magnetic material, a 40 x 80 x 2 (m) magnetic sheet made of a composite material of ferrite powder and synthetic rubber was used. As a bias permanent magnet, deformation of the magnet sheet due to temperature change may cause the detection distance to vary depending on the method of processing the contact surface between the bias permanent magnet and the 0 ferromagnetic material fj1 resistive element, which is made by cutting the magnet sheet into pieces. Since it was found that this had an effect on the quality of the product, we adopted a fixing method using a spacer instead of using a single adhesive. When used by adhering, it is necessary to use a buffer to absorb the deformation of the bias permanent magnet.

[Effects of invention]

According to the present invention, the detection distance can be increased to 100 m or more using the magnetic field line detection method, thereby avoiding all the problems caused by light attenuation in conventional methods that use light, such as anti-qJ type photoelectric switches. In addition, problems such as the insufficient sensing distance, which was a problem with systems that use a reed switch and a magnetic sheet, and the durability and vibration resistance of systems that have a mechanical drive part, can be solved by using a ferromagnetic magnetoresistive element. The problem was solved at once by detecting the problem.

As described above, the present invention has a great effect on improving the installation stability and reliability of security magnetic sensors used in shutters, etc., and has a wide range of applications as a non-contact detector for moving objects other than shutters. Expansion is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the detection section of the present invention, and the second [
2I is a block diagram of the present invention.

Claims (1)

[Claims] Two ferromagnetic magneto-resistance elements, including a ferromagnetic magneto-resistance element that detects the approach and separation of the magnetic material for operation, a permanent magnet for bias, an amplifier, a comparator, an output circuit, and a power supply circuit. A bias permanent magnet is arranged between the bias permanent magnets, and the ferromagnetic magnetoresistance element is arranged so as to be closer to the N pole and the S pole at either end of the magnetized surface of the bias permanent magnet. A magnetic sensor for crime prevention.