JPH0517646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a magnetic proximity switch that detects the approach of an external permanent magnet.

[Background technology] A reed switch enclosed in a glass tube is used as a magnetic proximity switch to detect the approach of a permanent magnet, but in addition to problems such as vibration during use, destruction due to impact, malfunction, and changes in characteristics. There were various problems such as chattering during contact, contact welding, and states king.

For this reason, some proposals have been made to use a Hall element in the detection part, but the sensitivity of the Hall elements currently in circulation is such that stable operation cannot be achieved unless a magnetic flux density of several hundred Gauss is applied. However, this requires a large permanent magnet, which is the object to be detected, and its use as a magnetic proximity switch is limited.

[Purpose of the invention]

The present invention focuses on the above-mentioned conventional circumstances, and provides a compact magnetic proximity switch that can achieve high sensitivity and arbitrary directivity with a long detection distance even if the permanent magnet of the detected object is not large. There is something to do.

[Disclosure of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 8.
This will be explained with reference to the figures.

The bottom surface of a switch case 1 formed into a box shape by plastic molding of synthetic resin serves as a detecting section 2 of a magnetic proximity switch. Further, the switch case 1 is provided with a mounting hole 1a and a positioning projection 1b. This switch case houses a Hall IC ₃ , and the magnetic sensing part 4 of the Hall IC ₃ is brought into contact with the inner bottom surface 5 of the switch case 1 as close as possible. The magnetically sensitive portion 4 is usually small, about several minutes to several tenths of one square millimeter. The Hall IC ₃ has a Hall element A, a stabilizing circuit B, an amplifying circuit D, and a switching transistor Q formed on the same chip.

The yoke 6 may be made of any magnetic material, such as a soft magnetic material or a ferromagnetic material such as iron, permalloy, or nickel.
A folded projecting portion is formed as a magnetic flux collecting portion 7 in the middle portion, and open ends 8 are formed at both ends of the yoke 6. In addition to being folded back, the magnetic collecting part 7 may also be formed by cutting and bending or welding a separate member, which are included in the present invention.

Then, the magnetic collecting part 7 is brought into contact with the rear surface of the Hall IC ₃ which is closest behind the magnetic sensing part 4, and the open ends 8 are connected to the Hall IC 3.
It is open on the side of IC ₃ . Note that the yoke 6 can have any shape selected to obtain various characteristics of directivity and detection distance as shown in FIGS. 8a to 8d, and will be described in detail later. In addition to the Hall element, a magnetic transducer such as a magnetoresistive transducer is used as the magnetically sensitive element 3.

Since the magnetic collecting part 7 is in contact with the rear surface of the magnetic sensing part 4 in this way, the magnetic flux F of the permanent magnet M of the detected object arriving from the direction of the detecting part 2 of the switch case 1 is guided to the open ends 8, 8. The magnetic flux passes through the deflection yoke 6 and is focused on the magnetic flux collecting section 7, and the magnetic flux density of the magnetic flux collecting section 7 becomes high density, so that even a small permanent magnet M can be detected from a long distance.

Next, the operation will be explained with reference to FIGS. 4 to 7.

Fix the switch case 1 to the machine body, etc., and set the shortest distance y to the permanent magnet M attached to the detected object, and set the position of the shortest vertical distance y to 0 (zero). Let x′ be moved.

Its operation is firstly shown in Fig. 6, where the permanent magnet M
When is in the position shown in the figure, most of the magnetic flux F passes through only one arm of the yoke 6, and very little magnetic flux _F1 passes through the magnetically sensitive part 4 of the Hall IC ₃ . does not operate yet, and the switching transistor Q of the Hall IC ₃ is in an off state.

Then, when the permanent magnet M moves to the left and comes to the position shown in _FIG . Q is turned on, and the load L is driven by the power supplies Vc.c., G connected to the terminals t ₁ , t ₂ , t ₃ .

When the permanent magnet M moves further to the left than in FIG. 7, the magnetic flux decreases and the Hall element A turns off further away than when it was turned on. This is illustrated in the fifth
In the figure, line S ₁ is the on curve of the present invention, S ₂ is the off curve,
S ₃ and S ₄ are on/off curves of a conventional example in which a Hall IC is used alone.

That is, since the magnetic flux density penetrating the magnetic sensing part 4 is increased by the magnetic collecting part 7, it is clear that the vertical distance y to be detected also becomes longer, and since the leakage magnetic flux in the directivity is reduced, the fifth As shown in the figure, the slope is steeper than before, and there is no malfunction due to noise caused by external magnets, and the influence of the material of the machine body to which it is attached is reduced, regardless of whether it is magnetic or non-magnetic. The perpendicular distance y of detection increases and the usable range expands, and if the detection distance remains the same, a smaller or less expensive permanent magnet M can be used.

Next, if the shape of the yoke 6 is as shown in FIG. 8b other than that shown in FIG. If the leakage is ignored, the magnetic flux density can be made high in proportion to the area ratio, but the directivity will be a little wider than that shown in Figure a.

Next, in FIG. 3c, the open ends 8, 8 are narrowed, so the directivity is further narrowed. In Figure d, the open ends 8, 8 are brought close to the magnetic sensing part 4 by bending them, so the directivity is even narrower. Since it passes directly through the ends 8, 8, it is slightly shorter, but the directivity is much narrower and sharper than the conventional one using only the Hall element 3.

〔Effect of the invention〕

As explained above, according to the magnetic proximity switch of the present invention, the magnetic sensing element 3 such as a Hall element is housed in the switch case 1, the magnetic sensing part 4 of the magnetic sensing element 3 is opposed to the outer wall of the switch case 1, and the magnetic sensing element 3 such as a Hall element is housed in the switch case 1. The open end 8 of the yoke 6, which is open at one end, corresponds to the magnetic sensing part 4 of the magnetic sensing element 3 in the switch case, and the open end 8 is arranged on the side of the magnetic sensing part, and only the magnetic collecting part 7 in the middle of the yoke The structure is characterized in that a yoke 6 is disposed close to the rear of the magnetically sensitive element, and other than the magnetically collecting part 7 is spaced apart from the magnetically sensitive part 4. Compared to using a magnetically sensitive element alone, Since the magnetic flux density of the magnetic sensing part 4, which has an extremely small area, is made high by the magnetic collecting part 7 of the yoke 6, the detection distance is increased, malfunctions due to external magnetic field noise are reduced, and the permanent magnet M of the detected object is increased. Since it can also be made smaller, the installation space can be expanded, and inexpensive permanent magnets can be used. A device in which the Hall element is directly mounted as a chip on the substrate and the yoke is disposed on the rear surface of the chip can be made even smaller and more sensitive.

[Brief explanation of the drawing]

1 to 8 a to 8 d show embodiments of the present invention; FIG. 1 is a perspective view, FIG. 2 is a circuit diagram, FIG. 3 is a perspective view of the yoke, and FIG. 4 is an installation and operating state. 5 is an operating characteristic diagram, FIG. 6 is a front view of the main parts in the OFF state, FIG. 7 is a front view of the main parts in the ON state, and FIGS. 8 a to d are each of the yoke 6. FIG. 6 is an operational characteristic diagram corresponding to different embodiments. FIG. 8e is an operating characteristic diagram of a conventional example. 1... Switch case, 2... Detection section, 3...
Magnetically sensitive element, 4... Magnetically sensitive part, 6... Yoke, 7...
Magnetic collecting part, 8...open end.

Claims (1)

[Scope of Claims] 1. A magnetically sensitive element such as a Hall element is housed in a switch case, and the magnetically sensitive part of the magnetically sensitive element is opposed to the outer wall of the switch case, and the magnetically sensitive part of the magnetically sensitive element in the switch case is , the open end of the yoke, which is open at one end, is arranged to the side of the magnetically sensitive part, and only the magnetically collecting part in the middle of the yoke is brought close to the rear of the magnetically sensitive part, and the rest of the magnetically collecting part is located outside the magnetically sensitive part. A magnetic proximity switch characterized by having yokes arranged further apart. 2. The magnetic proximity switch according to claim 1, wherein the magnetic sensing element is a chip-shaped Hall element directly attached to the substrate, and the magnetic collecting part of the yoke is arranged directly on the rear surface of the chip. 3. The magnetic proximity switch according to claim 1 or 2, wherein the magnetically sensitive element is a Hall IC in which a Hall element, a regulator circuit, a shot trigger circuit, and an amplifier circuit are formed on the same chip. 4. A magnetic proximity switch according to any one of claims 1 to 3, wherein at least a magnetic sensing element and a yoke are housed in a switch case and sealed by resin filling.