JPH0435861B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a proximity switch sensor used in a high frequency oscillation type proximity switch in which a sensor having a detection coil and a detection circuit section are separated.

Background of the Invention In high frequency oscillation type proximity switches, in order to detect metal objects in narrow areas, a separate structure is adopted in which the sensor and detection circuit are separated and connected using a connecting cable such as a coaxial cable. There are many. In recent years, as the range of use of proximity switches has expanded, there has also been a demand for smaller sensors. By the way, the smaller the sensor is, the thinner the lead wire of the detection coil is used. Therefore, the detection coil and the coaxial cable cannot be directly connected, and it is necessary to use some kind of terminal inside the sensor to connect the coaxial cable and the detection coil. In order to make the sensor smaller, it is desirable to make these terminals as small as possible. In addition, the capacitors that make up the sensor's detection coil and resonant circuit are often installed in the detection circuit to keep the sensor small, but in order to avoid the effects of the direct current resistance of the coaxial cable and temperature changes, as well as a decrease in the Q of the resonant circuit. It is preferable to provide a capacitor on the sensor side.

Purpose of the Invention The present invention has been made in view of the characteristics of the proximity switch sensor, and it contributes to miniaturization of the sensor and can omit terminal parts for connecting the end of the coil and the coaxial cable. The purpose of the present invention is to provide a proximity switch sensor.

Structure and Effects of the Invention The present invention is a proximity switch sensor that includes a detection coil embedded in a core and is separated from a detection circuit section via a connecting cable. A chip capacitor, one end of which is connected to a metal film provided on the back side, one end of a detection coil wrapped around and fixed to the other end, and one end of a connection cable connected to this end, and the metal film on the back side of the core and the cable. A connection line connected via a connection line at an end of the apparatus.

According to the present invention having such characteristics, since the sensor is provided with a capacitor, it is possible to reduce the effects of direct current resistance and temperature changes of the coaxial cable connecting the sensor and the detection circuit section. In addition, a chip capacitor is used as the capacitor, and since the chip capacitor is connected to the metal film provided on the back of the core, there is no need to provide any other connection terminals, and the sensor itself can be made smaller. . Furthermore, since it does not have a connecting terminal, assembly time can be reduced and work efficiency can be improved.

DESCRIPTION OF EMBODIMENTS FIG. 1 is a block diagram showing a general sensor-separated type proximity switch. In this figure, sensor 1
and the detection circuit section 2 are connected by a coaxial cable 3. A detection coil 4 is provided in front of the sensor 1, and a capacitor 5 connected in parallel with the detection coil 4 may be provided on the sensor 1 side as shown in the figure, or may be provided on the detection circuit section 2 side. However, in either case, a resonant circuit is formed together with the detection coil 4. On the detection circuit section 2 side, an oscillator 6 whose oscillation frequency is set to the resonance frequency of this resonance circuit is connected to the end of the coaxial cable 3. The oscillator 6 is constantly oscillating while the proximity switch is in operation, and the oscillation level decreases as the object 7 approaches. The output of the oscillator 6 is given to a detection/level discriminator 8, and this level change is read to obtain an object detection signal. This signal is outputted to the outside via the output section 9. The power supply circuit 10 supplies power to each part.

FIG. 2 is a diagram showing the structure of the proximity switch sensor 1 according to the present invention. In this figure, the detection coil 4
is the core 12 provided at the tip of the coil case 11
It will be buried in an annular groove. Metal vapor deposition is performed on the back surface of the core 12, and the inside of the sensor 1 is connected to the detection coil 4.
electrostatically shielded from Now, in the present invention, a chip capacitor 5 is added to this metal vapor deposited film 13.
One end 50a of the lead frame 14 is connected to the lead frame 14. Chip capacitor 50 is a hybrid IC
This is a capacitor that is used as an internal circuit component for devices such as other devices, and is not molded as an individual component.
The hot end side of one end of the detection coil 4 is wound and fixed around the other end 50b of this chip capacitor 50, and the end 50b of the chip capacitor 50 is fixed.
The core wire 3a of the coaxial cable 3 is connected to the core wire 3a by soldering. Further, the cold end side of the detection coil 4 is wound around and fixed to one end of a lead frame 14, and the other end of the lead frame 14 is connected to the mesh wire portion 3b of the coaxial cable 3. Note that the cold end side of the detection coil 4 may be connected to the metal vapor deposited film 13 on the back surface of the core 12, or may be connected by being wound around the end portion 50a of the chip capacitor 50. In this way, the chip capacitor 5
0 is used as a terminal block for the detection coil 4 to configure a parallel resonance circuit and connect it to a coaxial cable. After that, the coil case 11 is embedded in the case 15 of the sensor 1 and fixed. Note that the gaps in the sensor 1 are filled with epoxy resin or the like to fix each part.

If the terminal of the detection coil is directly wound around one end of the chip type capacitor and used as a connection terminal in this way, there is no need to provide another connection terminal, and the sensor itself can be miniaturized.

In this embodiment, a metal vapor deposited film is connected to the back surface of the core 12 for shielding, but a printed circuit board with copper foil may be attached to the front surface, or another metal plate may be attached to the front surface. Good too. Furthermore, the cold end side of the detection coil 4 may be connected to this metal film without being connected to the lead frame.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the structure of a general sensor-separated type proximity switch, and FIG. 2 is a sectional view showing the structure of the sensor portion of the proximity switch according to the present invention. DESCRIPTION OF SYMBOLS 1... Sensor, 2... Detection circuit section, 3... Coaxial cable, 4... Detection coil, 5... Capacitor, 50... Chip capacitor, 6... Oscillator, 12... Core, 13
...Metal deposition film, 14...Lead frame, 15...Case.

Claims (1)

[Scope of Claims] 1. A proximity switch sensor including a detection coil embedded in a core and separated from a detection circuit section via a connecting cable, comprising: a capacitor forming a resonant circuit with the coil; a chip capacitor, one end of which is connected to a metal film provided on the back surface of the core, one end of the detection coil wrapped around and fixed to the other end, and one end of the connection cable connected to the other end; A proximity switch sensor comprising: a metal film and a connection line connecting the other end of the connection cable.