JPS6239563Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Field of the Invention> This invention relates to a high frequency oscillation type proximity switch.

<Prior art and its problems> In general, high frequency oscillation type proximity switches
As shown in the figure, a parallel connection body of a coil 31 and a capacitor 32, an IC chip 33 that cooperates with this to configure an oscillation circuit, a current amplification circuit section 34, a surge absorption circuit section 35, and a constant voltage circuit section 36 The impedance of the coil 31 changes as the metallic object to be detected 38 approaches the coil 31, and the control circuit section 37 processes this impedance change as a signal. and outputs it to the outside. In addition, the above IC
The chip 33 includes, in addition to an oscillation circuit, a detection circuit, a trigger circuit, a waveform shaping circuit, and the like. Further, in FIG. 8, numeral 39 is a light emitting diode that indicates the operation of the proximity switch, and numeral 40 is a terminal connected to a power source and an output relay.

By the way, the structure of the conventional proximity switch is
As shown in the figure, a coil 31 forming part of the oscillation circuit is wound around a ferrite core 41, a capacitor 32 forming part of the oscillation circuit, a control circuit section 37, a light emitting diode 39, etc. are set. It is mounted on a wiring board 42, and the coil 31 and capacitor 32 are connected in parallel with a lead wire 43. Then, the ferrite core 41 is fitted into the cap 44, the wiring board 42 is fitted into the tube 45, and resin molded. The entire structure is inserted into a tube body 46. Note that the tube body 46 is formed with a threaded portion 47 for attaching a mounting fitting (not shown) and a through hole 48 for visually observing the light emitting diode 39 from the outside.

However, in the above conventional configuration, the coil 3
The lead wire 43 that connects the ferrite core 41 and the capacitor 32 is thin, with a diameter of about 100 μm, and when you pick up a device with which the ferrite core 41 and the wiring board 42 are connected, the ferrite core 41 may touch other parts, etc. If it gets caught, the lead wire 43 may break. Furthermore, before the sensor is assembled, the ferrite core 41 and the wiring board 42 are located with the tube 45 in between, so the lead wire 43 needs to be made long, which causes noise and prevents the proximity switch from being connected. may adversely affect the operating characteristics of
Due to the addition of stray capacitance between the lead wires 43, the oscillation constant differs for each product, causing variations in operating characteristics. Furthermore, a ferrite core 41 and a wiring board 4
2 are suspended in the air by a flexible lead wire 43, which has the disadvantage that it is difficult to attach the tube to the tube body 46.

Furthermore, a sensor is conventionally known in which a capacitor, such as a cylindrical paper capacitor, is set on the outer periphery of a coil concentrically with the coil (Japanese Patent Publication No. 51-9910).

Generally, when this type of sensor is assembled as a proximity switch, the magnetic flux emitted from the coil in the axial direction interlinks with a metallic object to be detected that approaches from the outside, creating an eddy current on this object. generate,
The structure is such that a loss corresponding to this eddy current is generated in the coil to lower the Q of the oscillation coil, and the amount of positive feedback necessary for oscillation is reduced, thereby stopping oscillation.

However, as mentioned above, if the capacitor is set concentrically with the coil, the magnetic flux that returns from one end of the coil in the axial direction to the other end through the outer circumference will cause the capacitor to pass through the capacitor at the outer circumference of the coil. An eddy current is constantly generated on the electrode of the capacitor, which is similar to the eddy current generated on a metallic object to be detected approaching from the outside, by interlinking with the constituent electrodes, and corresponds to this eddy current. There is a drawback that loss is caused by the electrodes and the Q of the oscillation coil is reduced, resulting in a reduction in detection sensitivity of the object to be detected.

This means that even if a capacitor other than a cylindrical paper capacitor is set around the outer circumference of the coil,
The capacitor electrodes have similar disadvantages insofar as they are placed in the magnetic path of the magnetic flux radiated by the coil. Furthermore, if a capacitor such as a cylindrical paper capacitor is set around the outer circumference of the coil as in the past, the outer diameter of this sensor becomes large, and if this type of sensor is assembled as a proximity switch, the entire switch becomes large. It has the disadvantage of

<Purpose of the invention> This invention was made to improve the above-mentioned drawbacks; it is small and compact, easy to assemble, there is no risk of disconnection during assembly, and the Q of the coil is not connected to the electrode of the capacitor. Therefore, it is an object of the present invention to provide a proximity switch which minimizes stray capacitance generated between a coil and a capacitor, and which has a constant oscillation constant and little variation in operating characteristics.

<Configuration and effects of the invention> The proximity switch according to this invention includes a coil wound around a ferrite core, a capacitor connected in parallel to this coil, and a control circuit that outputs a signal in response to changes in the impedance of the coil. ,
A first wiring board attached to the back surface of the ferrite core, a plurality of lead terminals fixed to the first wiring board, and a plurality of lead terminals printed on the first wiring board and individually attached to the lead terminals. A printed pattern and a second layer on which the capacitor circuit is formed.
a wiring board, and a tubular body for housing each of the components, the capacitor is mounted on the printed pattern, and the lead terminal is electrically fixed directly to the second wiring board. There is.

In the above configuration, by winding the coil in the annular recess formed on the surface of the ferrite core,
The magnetic flux radiated from the axis of the coil passes through the ferrite core at the outer periphery of the coil, circulates within the ferrite core, and does not pass through the electrodes of the capacitor attached to the back of the ferrite core. There is no risk that the magnetic flux will interlink with the electrodes of the capacitor and generate eddy currents on the electrodes of the capacitor, and therefore the Q of the oscillation coil can be maintained high.

In addition, by wrapping a coil around the surface of the ferrite core and attaching a capacitor to the back of the ferrite core, the outer diameter of this sensor does not become larger than the ferrite core, and this type of sensor can be assembled as a proximity switch. In this case, the entire switch becomes smaller.

Further, the capacitor is attached to the printed pattern of a first wiring board attached to the back surface of the ferrite core, and a control circuit is formed on the plurality of lead terminals fixed to the first wiring board. Since they are electrically fixed directly to the second wiring board, even if you pick them up, they are interconnected as a single unit, so the ferrite core will not be drawn to other parts. There is no risk of the wire getting caught and breaking, and it is easy to attach the wire to the pipe body.

Furthermore, since the ferrite core and the first and second wiring boards are connected by short lead terminals, it is possible to eliminate the cause of noise generation and improve the yield of operating characteristics of the proximity switch.

In this way, according to this invention, it is small and compact, easy to assemble, there is no risk of disconnection during assembly, and the Q of the coil is not reduced by the electrodes of the capacitor. Therefore, it is possible to minimize the stray capacitance generated between the coil and the capacitor, and provide a proximity switch with a constant oscillation constant and little variation in operating characteristics.

<Description of Embodiment> An embodiment of this invention will be described below with reference to the drawings.

In FIG. 1, numeral 1 is a ferrite core 1, and a coil 3 constituting a part of an oscillation circuit is wound around an annular recess formed on the front surface of the ferrite core 1.
A capacitor 5 is attached to the. Further, the coil 3 and the capacitor 5 are connected in parallel through a lead wire 6 inserted into the ferrite core 1. 7,7
is a pair of lead terminals 7, 7, and the parallel connection of the coil 3 and capacitor 5 is controlled by the lead terminals 7, 7, as shown in FIG. It is electrically connected to section 8.

Note that in FIGS. 1 and 2, the same parts as in the conventional configuration are given the same numbers as in FIG. 9, and detailed explanation thereof will be omitted. In addition, in FIG. 2, 9 is a synthetic resin for molding the control circuit section 8, 10 is a cable connected to an external output relay or power source, 1
1 is the rubber packing for the shield.

3 to 7 show the process of attaching a capacitor chip 14 as a capacitor 5 to the ferrite core 1. As shown in FIG.

First, as shown in FIG. 3, a counter electrode is formed on the first wiring board 12 using a printed pattern 13 of copper foil or the like. Then, as shown in FIG. 4, the capacitor chip 14 is set by brazing across the opposing electrodes. Next, as shown in FIGS. 5 and 6, the first wiring board 12 on which the capacitor chip 14 is set is fixed with resin to the back surface of the ferrite core 1, that is, the opposite surface to which the coil 3 is attached. At this time, as shown in FIG. 6, the lead wire 6 connecting the coil 3 and the capacitor chip 14 is inserted into the groove 15 formed in the ferrite core 1, and one end of the lead wire 6 is brazed together with the lead terminals 7, 7. do. Note that the lead wire 6 may be used as the lead wire 6 at the lead-out end at the start and end ends of the coil 3. Furthermore, the seventh
As shown in the figure, the ferrite core 1 is fitted into the cap 16, and the first wiring board 12, capacitor chip 14, etc. are molded with synthetic resin 17.

In the above configuration, by winding the coil 3 in the annular recess formed on the surface of the ferrite core 1, the magnetic flux radiated from the axis of the coil 3 passes through the ferrite core 1 at the outer circumference of the coil 3. Therefore, since the magnetic flux circulates within the ferrite core 1 and does not pass through the electrodes of the capacitor chip 14 mounted on the back surface of the ferrite core 1, the magnetic flux interlinks with the electrodes of the capacitor chip 14 and There is no risk of generating eddy currents on the electrodes, and therefore the Q of the oscillation coil 3 can be maintained high.

Furthermore, by winding the coil 3 on the surface of the ferrite core 1 and mounting the capacitor chip 14 on the back surface of the ferrite core 1, the outer diameter of this sensor does not become larger than the ferrite core 1, and this kind of When the sensor is assembled as a proximity switch, the entire switch becomes smaller.

Further, the capacitor chip 14 is connected to a first wiring board 1 mounted on the back surface of the ferrite core 1.
The plurality of lead terminals 7, 7 fixed to the first wiring board 12 are directly electrically connected to the second wiring board 42 on which the control circuit part 8 is formed. Because they are stuck to each other, even when you pick them up, they are interconnected as a single unit, so the ferrite core 1 may catch on other parts and break. There is no fear and the installation work to the pipe body is easy.

Furthermore, since the ferrite core 1 and the first and second wiring boards 12 and 42 are connected by short lead terminals 7 and 7, the cause of noise generation is eliminated and the yield of operating characteristics of the proximity switch is improved. can be improved.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view of a proximity switch according to an embodiment of the invention, Fig. 2 is an assembled sectional view of the same, Figs. 3 to 7 are explanatory views showing the process of attaching a capacitor chip to a ferrite core, FIG. 8 is a block diagram of a proximity switch, and FIG. 9 is an exploded perspective view of a conventional proximity switch. 1... Ferrite core, 3... Coil, 5...
Capacitor, 7... Lead terminal, 8... Control circuit section, 12... First wiring board, 13... Print pattern, 14... Capacitor chip, 42... Second
wiring board, 46... tube body.

Claims (1)

[Scope of utility model registration request] A proximity switch that includes a coil wound around a ferrite core, a capacitor connected in parallel to this coil, and a control circuit section that outputs a signal in response to a change in the impedance of the coil, which is attached to the back surface of the ferrite core. a first wiring board; a plurality of lead terminals fixed to the first wiring board; a printed pattern printed on the first wiring board and individually wired to the lead terminals; It is equipped with a second wiring board on which a circuit section is formed and a pipe body that houses each of the above components, and the capacitor is mounted on the printed pattern and the lead terminal is directly connected to the second wiring board. Proximity switch characterized by being firmly fixed.