JPS5846813B2 - Proximity switch sensing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sensing unit in a high frequency overcurrent horizontal type proximity switch.

Conventionally, the critical point adjustment of high frequency overcurrent horizontal type proximity switch is
This is generally done by changing the threshold value of an analog comparator.

However, although the threshold value of an analog comparator is stabilized by a reference voltage source, the input signal undergoes temperature drift in a high frequency circuit, resulting in a critical point fluctuation.

In addition, the critical point of a proximity switch is usually expressed in terms of the distance between the sensing part and the detected object.
It is difficult to directly set this critical distance using the voltage value that is the threshold value of the comparator, and the adjustment of this critical distance is similar to the actual alignment, after setting the object to be detected at the required critical distance. is determined by adjusting the threshold to the point at which the output signal of is inverted, so that this adjustment is very inconvenient if there is a considerable distance between the sensitive part and the electronic circuit device containing the comparator.

The present invention eliminates the above-mentioned drawbacks, eliminates temperature trifle in the high-frequency circuit, and provides a sensing section device that allows the critical distance to be determined in units of distance at the sensing section. Embodiments will be described in detail below based on drawings showing embodiments.

FIG. 1 is a block diagram of a high-frequency overcurrent horizontal proximity switch using a sensing section according to the present invention, and the electrical operation will be explained first.

Reference numeral 1 designates a first sensing coil that is sensitive to a metal object 2 to be detected, which is spaced close to and spaced from the end face of the coil; This is the same second sensing coil.

The first and second sensing coils 1 and 3 are made with the same wire diameter, number of turns, bobbin diameter, bobbin material, winding shape, etc. in order to have almost the same electrical and temperature sensitivity characteristics. The rain sensing coil is wound around the rain sensing coil and is placed close to the rain sensing coil so that the temperature of the rain sensing coil is always the same.

Capacitors 4 and 5 are connected in parallel to the rain sensing coils 1 and 3, respectively, to form resonant circuits 6 and 7, and the resonant circuits 6 and 7 are connected through resistors 8 and 9 of the same value in series, respectively. , are connected to the high frequency generation circuit 10.

Note that one ends of the resonant circuits 6 and 7 are commonly grounded.

Each impedance of both resonant circuits 6, 7 is measured by their high frequency terminal voltages e1, e2, and each terminal voltage e1.
e2 is a high frequency amplifier circuit 11, 12, a rectifier circuit 13.
14 to each DC voltage E1. E2, and its DC voltage E1. E2 is differentiated by a differential amplifier 15, and the output voltage E3 of the differential amplifier 15 is determined by a zero cross comparator 16 as to whether the voltage E3 is positive or negative.

Therefore, when the impedances of both the resonant circuits 6 and 7 are equal, the output voltage E3 of the differential amplifier 15 is zero, and this zero output corresponds to the threshold of the zero-cross comparator.

When the impedances of both resonance circuits 6 and 7 are different, a positive or negative polarity voltage is output to the output E3 of the differential amplifier 15, and the zero cross comparator 16 is turned ON or 0FF (1 or 0) depending on the polarity. Outputs a binary signal of 0).

A metal body 17 is opposed to the second sensing coil 3 and is movable back and forth within the magnetic field of the sensing coil. The distance d between the coil end face and the metal body 17 is
1 is adjustable.

As mentioned above, the first and second rain sensing coils 1 and 3 have almost the same electrical and temperature sensitivity characteristics, so when the same type of metal is located at the same distance from the end face of each coil, Both resonant circuits 6, 7, each including a sensing coil 1.3, exhibit equal impedance, and the output of the differential amplifier 15 becomes zero.

Therefore, when the distance d2 between the coil end face of the first sensing coil 1 and the metal body 2 to be detected is equal to the distance d1 between the coil end face of the second sensing coil 3 and the metal body 17, the differential amplifier 1
The output of 5 becomes zero.

The output voltage E3 becomes a critical point that inverts the zero-cross comparator 16, so that the critical distance of the metal body 2 to be detected is equal to the distance d1 between the coil end face of the second sensing coil 3 and the metal body 17, To adjust the critical distance of the metal body 2 to be detected, the distance d1 between the coil end face of the second sensing coil 3 and the metal body 17 is adjusted to a length equal to the critical distance using the critical distance adjustment device 18, in units of length. , and can be adjusted as the actual length.

Further, each of the resonant circuits 6°7 including the sensing coils 1 and 3 is connected to the metal bodies 2 and 17 at a distance d1. Even if the sensitivity is non-linear with respect to the displacement d2, since the equilibrium point of both resonance circuits 6 and 7 is taken as the critical point, no problem occurs in setting the critical distance.

2 to 4 show respective embodiments of the sensing section device according to the present invention constructed based on the above operating principle, and will be described in detail below with reference to the drawings.

FIG. 2 shows a first embodiment, in which a first sensing coil 20 is wound around an annular groove 23 carved near an end surface 22 of a bobbin 21 made of an insulating material, and a second sensing coil 24 teeth,
The bobbin 25 is wound around an annular groove 27 carved near the end face 26 of the bobbin 25.

The bobbin 21 and the bobbin 25 are arranged coaxially with the coil 20 and the coil 24 facing oppositely outward, and a magnetic shielding material 28 is inserted between the bobbins to form an inner cavity 30 of a tubular case 29 which also serves as a magnetic shield. It is fixedly inserted into the

The bobbin end face 22 on the first sensing coil 20 side and the end face 31 of the case 29 on the coil side are aligned on the same plane, and the bobbin end face 28 on the second sensing coil 24 side is the other end face of the case 29. 32, the end face 32
A side case end 33 protrudes from the bobbin end face 26.

This case end 33 is provided with a critical distance adjustment device 34, which adjusts the outer end lumen 3 of the case end 33.
A threaded rod 36 is screwed into the nut 35 that is fitted into the screw rod 36, and a metal plate 38 is fixed to the inner tip 37 of the threaded rod 36, and the other end of the screw rod 36 is a rotating knob 39.

The critical distance adjustment device 34 is a device for adjusting the distance d1 between the coil end surface 39 of the second sensing coil 24 on the metal plate 38 side and the surface 40 of the metal plate 330 facing the coil end surface 39.

The outer coil end surface 41 of the first sensing coil 20 faces the metal object 42 to be detected, and the distance d2 therebetween is equal to the distance d1 between the coil end surface 39 of the second sensing coil 24 and the surface 40 of the metal plate 38. , the critical distance of the metal object 42 to be detected is reached.

Note that the distance d3 between the coil end surface 39 of the second sensing coil 24 and the bobbin end surface 26 is made equal to the distance d4 between the coil end surface 41 of the first sensing coil 20 and the bobbin end surface 22, or the distance d3 is slightly increased. By making it small, a critical distance can be set until the detected metal body 41 comes into contact with the opposing bobbin end face 22.

A male screw 43 is provided with a required length on the outside of the case 29.
This male screw 43 is connected to an appropriate fixing member 44) 45,
46 is used for fixing.

FIG. 3 shows a second embodiment. In the figure, the same members and parts as in FIG. 2 are denoted by the same reference numerals, and their explanations are omitted, and the same applies to the case of FIG. 4.

The first and second rain sensing coils 20 and 24 are provided at both ends of a common bobbin 21a, and both coils 20 and 24 are provided at both ends of a common bobbin 21a.
, 24, the bobbin end faces 22, 26 and the coil end face 41.
Distance from 39 d3. d4 are precisely and equally provided, and electrically, both bobbin end faces 22, 26 are connected to the metal body 4 to be detected.
2 and the metal plate 38 are in contact with each other, the resonant circuits 6 and 7
The terminal voltages el and e2 are made equal.

At the case end 33 on the second sensing coil 24 side, a critical distance adjustment device 34 consisting of a micrometer 47 is provided.

The movable shaft 48 of the micrometer 47 is aligned with the axis of the bobbin 21a and is provided so as to be movable toward the second sensing coil 24.
will be permanently installed.

Therefore, when the surface 46 of the metal plate 380 comes into contact with the bobbin end face 26, the scale of the micrometer 47 is set to O, and the reading value of the micrometer 47 is determined as the distance d1− between the bobbin end face 26 and the metal plate 38. When d3 is determined, a highly accurate critical distance corresponding to the distance d1-d3 can be set between the metal object 42 to be detected and the opposing bobbin end surface 22.

Further, when the distance d2-d4 between the metal object 42 to be detected and the opposing bobbin end face 22 is an unknown distance, when the metal plate 38 is moved with the micrometer 47 and the output of the zero cross comparator 16 is reversed. By reading the value on the micrometer 47, you can find out the unknown distance.

FIG. 4 shows a third embodiment, in which a bobbin 21 has first and second sensing coils 20 and 24 wound around each end.
In a, except for the bobbin end surface 22 on the first sensing coil 20 side, the rest of the periphery is molded with an insulating material 49, and a male screw ring 50 is formed around the outer periphery of the end of the insulating material 49 on the second sensing coil side.
is insert molded.

A metal nut with a lid 51 is screwed into the male screw ring 50,
The lid 52 of the nut with lid 51 acts on the second sensing coil 24 in the same way as the metal plate 38, and the latch 53 cooperates with the male screw ring 50 to control the coil of the second sensing coil 24. The distance d1 between the end surface 39 and the inner surface of the lid 52 is adjusted, and serves as a critical distance adjustment 34.

As described above, the present invention can mechanically determine the critical distance of a high-frequency overcurrent horizontal proximity switch by setting the same distance as the required critical distance in another part, and Since a distance adjustment device is provided in the sensing part, it is easy to set the critical distance, and
Excluding electrical critical distance variation factors such as temperature drift,
Provides a stable proximity switch with a set critical distance.

[Brief explanation of the drawing]

The figures show embodiments of the present invention; FIG. 1 is an electrical block diagram of a proximity switch to which a sensing device according to the present invention is applied, and FIG. 2 is an electrical block diagram of a proximity switch to which a sensing device according to the present invention is applied. Similarly, FIG. 3 is a longitudinal sectional view of the main part of the second embodiment, and FIG. 4 is a longitudinal sectional view of the third embodiment. 1...First sensing coil, 2...Metal object to be detected by bending, 3...Second sensing coil, 4, 5...
... Capacitor, 6.7 ... Resonance circuit, 8,9
...Resistor, 10...High frequency generation circuit,
11, 12...High frequency amplifier circuit, 13.14.
... Rectifier circuit, 15 ... Differential amplifier, 1
6...Zero cross comparator, 17...
...Metal body, 18...Critical distance adjustment device, 20
......First sensing coil, 21...Bobbin, 22...End face, 23...Annular groove,
24...Second sensing coil, 25...
Bobbin, 26... End face, 27... Annular groove, 28... Shield material, 29... Case, 30... Inner cavity, 31, 32...
End face, 33...Case end, 34...
Critical distance adjustment device, 35... Nando, 36...
...Threaded rod, 37...Tip, 38...
...Metal plate, 39...Coil end face, 40...
...Surface, 41...Coil end face, 42...
...Metal object to be detected, 43...Male screw, 44.
...Fixing member, 45, 46...Nut,
47...Micrometer, 48...Movable shaft, 49...Insulating material, 50...Male nut) R, 51--Nut with lid .

Claims (1)

[Claims] 1. A first sensing coil whose impedance is sensitive to the metal object to be detected, which is spaced close to and separated from the end face of the coil, and the first sensing coil has an equal impedance and is not electromagnetically coupled to the first sensing coil. A critical distance is set between the coil end face of the first sensing coil and the metal object to be detected, and a second sensing coil that is provided as shown in FIG. an adjusting means comprising a metal body facing the end face of the coil in the magnetic field of the second sensing coil, and capable of freely setting the distance between the metal body and the end face of the second sensing coil. 1. A sensing device for a proximity switch, comprising: a critical distance adjusting device.