JPS6331469Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a proximity switch that detects the presence or absence of a stationary or moving metal object in a non-contact manner, especially when the detection position is moved, such as when detecting the ignition timing of an internal combustion engine. It concerns the required proximity switch.

Conventionally, there has been a device of this type as shown in FIG. In this figure, 1 is a core, 2 is a coil wound around this core 1, 2a and 2b are lead wires of the coil 2, and 3 is a capacitor connected in parallel with the coil 2 and forming a resonant circuit.
4 is an oscillation circuit that provides oscillation energy to the resonant circuit; 5 is a detection circuit that detects the oscillation state of the oscillation circuit 4; 6 is an output circuit that amplifies the output signal of the detection circuit 5; 7 is the core 1 and coil 2
8 is a circuit section in which the capacitor 3, oscillation circuit, detection circuit 5 and output circuit 6 are housed; 8a and 8b are respectively for supplying power to the circuit section 8 and transmitting output signals to the outside. A lead wire 9 for taking out is a metal object to be detected.

Next, the operation will be explained. If the metal body 9 is not present or is sufficiently far away from the detection unit 7, the resonant circuit composed of the coil 2 and the capacitor 3 is in an oscillating state by receiving oscillation energy from the oscillation circuit 4, and the coil 2 An alternating current flows due to oscillation, and an alternating magnetic field is generated from the core 1.
Furthermore, the oscillation state of the oscillation circuit 4 is simultaneously detected by the detection circuit 5.
The output signal corresponding to the oscillation state is amplified by the output circuit 6 and output to the outside via the lead wire 8b.

When the metal body 9 is sufficiently close to the detection part 7,
A part of the alternating magnetic flux generated from the core 1 will pass through the metal body 9, and if the metal body 9 is non-magnetic, there will be a joule loss due to eddy current generated in the metal body 9, and if the metal body 9 In the case of a magnetic material, losses such as hysteresis loss occur in the metal body 9 in addition to this. Here, since the oscillation energy imparted from the oscillation circuit 4 to the resonant circuit is finite, the oscillation voltage decreases in accordance with the amount of loss, this decrease is detected by the detection circuit 5, and is transmitted via the output circuit 6. It is output to the lead wire 8b.

Here, the change in the loss with respect to the position x of the metal body 9 is shown by a curve ₁₀ in _{FIG .}
If you want to set the detection area between points A _2a , use the curve 10 above.
In this case, it is necessary to move the core 1 and coil 2 shown in FIG. 1, so it is necessary to move the detection unit 7. If the section 7 and the circuit section 8 are separate bodies, the lead wires 2a and 2b will be bent, and the detection section 7 and the circuit section 8 will be bent.
If they are integrated, the lead wires 8a and 8b
When the lead wires 2a and 2b are subjected to a bending action, the stray capacitance between the lines changes, and the oscillation frequency changes, resulting in a decrease in detection accuracy, and when the lead wires 2a and 2b are subjected to a bending action. 2b or the lead wires 8a and 8b are subjected to bending action, in order to prevent wire breakage due to the bending action, the length must be increased to prevent stress concentration on each lead wire, and the device is large. There were drawbacks such as the shape and ease of assembly.

This idea was made in order to eliminate the above-mentioned drawbacks of the conventional ones.The core is provided with a gap that constitutes an air magnetic path, and the core is provided with a gap that forms an air magnetic path, and the rotation axis is in the same direction as the winding axis of the coil. It is an object of the present invention to provide a proximity switch which does not require bending of the lead wire by holding it so as to be rotatable and moving the detection section only by moving the core. This idea will be explained below with reference to the drawings.

FIG. 3 shows an embodiment of the detection section used in this invention. In Fig. 3, 1 is a core having a gap 1a provided to form an air magnetic path, and is rotatable around the same rotation axis as the winding axis of the coil 2 wound around the core 1. It is maintained like this.

An embodiment of the proximity switch of this invention using the detection section shown in FIG. 3 is shown in FIGS. 4 to 7. In these figures, 12 is a bobbin for winding the coil 2 and holding the core 1, which includes an upper bobbin 12a, a lower bobbin 12b, an upper winding core 12c,
Lower winding core 12d, joint portion 12e, hinge portion 12f
It becomes more.

Next, the operation will be explained. In Figure 3,
As in the conventional example, an alternating current flows through the coil 2 due to the oscillation energy given from the oscillation circuit 4.
An alternating magnetic flux due to this alternating current is generated as a magnetic path through the core 1 and the gap 1a forming an air magnetic path. Since the metal body 9 is arranged so that it can pass through the gap 1a, the loss experienced by the coil 2 with respect to the movement x of the metal body 9 changes as shown by the curve 10 shown in FIG. 2, as in the conventional example. Here, if it is necessary to move the detection section from A ₁ to _{A 2} to A _1a to _{A 2a} as in the conventional example, it is only necessary to rotate the core 1 by Δx shown in FIG. There is no need to move it at all.

I will explain in more detail. Coil 2 is fixed, and core 1 is rotated around the same rotation axis as the winding axis of coil 2, so core 1 and coil 2 will move relative to each other. The magnetomotive force is transmitted to the core 1 without being affected by this relative movement, the electromagnetic coupling state between the coil 2 and the core 1 remains unchanged, and the position of the gap 1a forming the air magnetic path is changed. Since the core 1 shown in FIG. 3 can be moved from the curve 10 to the curve 11 shown in FIG. 2, it is only necessary to rotate the core 1 shown in FIG. 3 by Δx.

In addition, as shown in FIGS. 4 to 7, the bobbin 12
is divided into an upper bobbin 12a and a lower bobbin 12b, and is hinged at a hinge part 12f,
The upper bobbin 12a can be opened as shown in FIG. 8 or closed as shown in FIGS. 4 and 7. A part of the core 1 is sandwiched between the upper winding core 12c and the lower winding core 12d, and the upper bobbin 1 is
The rotation can be easily maintained by simply joining the coil 2a and the lower bobbin 12b, and by winding the coil 2 around the core portion obtained by the upper winding core 12c and the lower winding core 12d, no special Winding is possible without using special equipment or methods.

Furthermore, as shown in FIG. 8, if the bobbin 12 is made of a resin molded product having a hinge portion 12f, handling and assembly will be further facilitated.
For example, after inserting the core 1 between the upper winding core 12c and the lower winding core 12d, the joint part 12e
The assemblability is further improved by heat-sealing the lower bobbin 12b to the lower bobbin 12b.

In addition, in the above embodiment, the central axis of rotation of the core 1 is the same as the winding axis of the coil 2, but
This central axis only needs to be within the winding plane of the coil 2.

As explained in detail above, this invention has a gap in the core and is configured to be held rotatable around a rotation axis that is in the same direction as the coil winding axis and within the winding plane. As a result, the detection section can be moved with high precision, and the device can be made smaller.
Furthermore, by making the bobbin around which the coil is wound separable, and by providing a hinge portion on the bobbin, assembly becomes easy and an inexpensive product can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional proximity switch, Fig. 2 is an operation curve diagram showing the operation of the proximity switch, Fig. 3 is a perspective view showing an embodiment of the detection section of this invention, and Fig. 4 is a diagram showing the operation of the proximity switch. One embodiment of the invention is shown, and FIG. 3 is a front view of a proximity switch using the detection section, FIG. 5 is a side view, and FIG.
A sectional view taken along the - line in the figure, Fig. 7 is also the 5th section.
8 is a sectional view taken along the - line in the figure, and FIG. 8 is a perspective view of the upper bobbin of the embodiment shown in FIGS. 3 to 7 with the upper bobbin opened. In the figure, 1 is the core, 1a is the gap, 2 is the coil, 2a and 2b are the lead wires, 3 is the capacitor, and 4
is an oscillation circuit, 5 is a detection circuit, 6 is an output circuit, 7 is a detection section, 8 is a circuit section, 8a and 8b are lead wires, 9
is a metal body, 10 and 11 are curved lines, 12 is a bobbin, 1
2a is the upper bobbin, 12b is the lower bobbin, 12c
12d is an upper winding core, 12d is a lower winding core, 12e is a joint portion, and 12f is a hinge portion. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims for Utility Model Registration] (1) A core around which a coil is wound, a capacitor that forms a resonant circuit together with the coil, an oscillation circuit that provides oscillation energy to the resonant circuit, and a device that detects the oscillation state of this oscillation circuit. A proximity switch comprising a detection circuit and an output circuit for amplifying the output signal of the detection circuit, wherein the core is provided with a gap forming an air magnetic path for detecting a stationary or moving metal object, and the core is further provided with a gap that forms an air magnetic path for detecting a stationary or moving metal object. A proximity switch characterized in that it is held rotatably about a rotation axis that is in the same direction as the winding axis of the coil and within the winding plane. (2) The proximity switch according to claim 1, wherein the coil is wound around the core via a bobbin, and the bobbin is separable. (3) The divided bobbins are joined at the hinge,
The proximity switch according to claim 2, which is characterized in that it can be opened and closed by the hinge portion.