JP2000173425A - Proximity switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of any detection error, eliminate any failure caused by a crack, and endure a long time usage, by providing a plurality of ventilation holes that axially penetrating through an annular clearance in a pot core. SOLUTION: A plurality of ventilation holes 36 are provided in a pot core 31, these ventilation holes 36 are provided through a clearance 34 in the pot core 31, are penetrated axially through it and are formed. In assembling this switch, when a detection coil is adequately shaken up to drive air out of the coil wound clearance 34 through the ventilation holes 36, the driven air is released to the atmosphere through inside of a head cap. Thus, even when the pot core 31 is formed in a pot shape, air close to the clearance 34 where the coil is arranged can be perfectly removed. Therefore, swelling or shrinking action following variation of ambient temperature caused by the air accumulating near the coil is eliminated, the detection coil is prevented from causing malfunction, and therefore, quality of products can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proximity switch for detecting an approaching detection object by a detection coil, and more particularly to a structure of the proximity switch.

[0002]

2. Description of the Related Art This type of proximity switch utilizes a non-contact type feature of a sensor to generate dust, temperature and humidity as in an automatic assembly factory or a waste disposal facility which has conventionally introduced a conveyor system. It is used in manufacturing sites that change greatly. Therefore, the detection coil and the electronic circuit for processing the detection signal, which constitute the sensor unit and are installed at the site, are sealed with a filling resin inside the head cap so as to withstand the above-mentioned environmental change. It has a dust-proof and moisture-proof structure.

FIG. 6 is a sectional view of a conventionally known proximity switch of this type, showing a typical configuration example. FIG.
, 1 is a proximity switch, 2 is a head cap, 3
Is a detection coil, 4 is a holder, 5 is a printed board, and 6 is a filler. 31 is a pot core and 32 is a coil.
A plan view of the pot core 31 is shown in FIG. Reference numeral 33 denotes a through hole through which the terminal of the coil passes, and reference numeral 34 denotes an annular gap in which the coil 32 is disposed. The detection coil 3, the holder 4, and the printed circuit board 5 are sealed inside the head cap 2 with a filler 6. Reference numeral 7 denotes a cable connected to the printed circuit board 5, reference numeral 8 denotes a back cover, and reference numerals 81 and 82 denote air vent holes and injection holes provided in the back cover 8.

When assembling the conventional proximity switch 1 as described above, a cable 7 is connected to the detection coil 3 and the punt board 5 which are connected via a holder 4 in advance. Then, the back cover 8 into which the cable 7 is inserted is separated,
The detection coil 3 and the printed board 5 are inserted into the head cap 2 that has been set up. Next, a liquid filler 6 is injected into the head cap 2 until the printed circuit board 5 is submerged, and then the back cover 8 is pushed down along the cable 7 to be closed.
Next, the air in the head cap 2 is removed from the air vent holes 81.
The filling material 6 is injected from the injection hole 82 while extracting the filler.
Thereafter, the injected filler is hardened, and the proximity switch 1 as shown in FIG. 6 is assembled.

[0005]

In such a conventional proximity switch 1, it is difficult to completely fill the filler 6 with air easily remaining inside the head cap 2. In particular, the pot core 31 is formed in a literal pot shape, and the cavity 34 is sealed toward the closed detection surface of the head cap 2. Therefore, the air in the gap portion 34 in which the coil 32 is arranged cannot be completely removed, and the air tends to remain and accumulate. Coil 32
When space is created around the air, the air expands and contracts due to changes in the ambient temperature. As a result, the detection coil 3 malfunctions, causing a detection error. In some cases, there is a problem that a gap near the detection coil 3 is enlarged and a part of the detection surface is cracked due to the above-described expansion / contraction action to cause a failure.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has a simple structure to effectively promote air bleeding in the vicinity of a detection coil sealed in the back of a head cap. It is an object of the present invention to realize a proximity switch that does not generate a detection error, has no failure due to a crack, and can be used for a long time.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a detection coil having a coil disposed in a cavity of a pot core is connected to a printed circuit board, and is filled with a filler so as to face a detection surface in the head cap. In a proximity switch that is fitted with a back cover on the lead-out side and leads out the cable connected to the printed circuit board from the back cover and closed, a plurality of ventilation holes penetrating in the axial direction are provided in the annular gap of the pot core A proximity switch. Further, in the above means 1, a proximity switch in which a lead wire of a detection coil is inserted into an air hole is provided. Further, in the above-mentioned means 1 or 2, a proximity switch is formed in which a ventilation hole is provided with an inclined surface to form a countersink.

[0008] After a small amount of filler is put into the head cap that has been leaned over, the detection coil to which the cable is connected and the printed circuit board are inserted. At this time, if necessary, the detection coil is slightly vibrated so that the air in the cavity of the pot core is sunk into the injected filler while being expelled from the vent hole. Subsequently, a second filler is additionally injected until the printed board is filled. Next, the back cover is put on the head cap, and the remaining filler is injected from the injection hole of the back cover. The injection of the filler is stopped before the filler is injected from the injection hole and overflows from the air vent hole. After that, the filler hardens,
Assembly of the proximity switch is completed.

[0009]

FIG. 1 is a sectional view showing the structure of a first embodiment of the present invention, and FIG.
1 is a plan view of a pot core as a main part in FIG. 1, and portions common to those in the conventional apparatus in FIGS. 1 and 2, reference numeral 1 denotes a proximity switch, and reference numeral 2 denotes a head cap of the proximity switch 1. 20 is a detection surface of the head cap 2, and 21 is a male screw provided on the outer periphery. The head cap 2 is integrally formed of a synthetic resin into a thin cylindrical cap shape, and the detection surface 20 is closed.

Reference numeral 3 denotes a detection coil. 31 is a pot core in the detection coil 3, and 32 is a coil. Also, 3
3 is a through hole through which the terminal of the coil 32 passes, and 34 is a coil 32
Are arranged, and 35 is a terminal. In the first embodiment of the present invention, a plurality of ventilation holes 3
6 are provided. As shown, the plurality of ventilation holes 36 are provided in the voids 34 of the pot core 31 and are formed so as to penetrate in the axial direction.

The pot core 31 is made of ferrite having a high magnetic permeability, and has a substantially E-shaped cross section. A coil 32 is arranged in an annular void portion 34 of the pot core 31 molded substantially in an E shape, and is wound around a central column portion. In the pot core 31, the terminal 35 of the coil 32 wound around the cylindrical portion is pulled out to the rear side from the through hole 33 with the pot-shaped opening facing the inner surface of the detection surface 20. 4 is a holder for connection, 5 is a printed circuit board, and 6 is a filler.

An oscillating circuit for oscillating the detection coil 3 and an output circuit for processing and outputting a detection signal of a detection object are mounted on the printed circuit board 5, and are connected to the detection coil 3 via a holder 4. An insulating material such as a synthetic resin which keeps a substantially solid state at normal temperature and is transformed into a liquid state by heating is used as the filler 6. The mutually connected detection coil 3 and printed circuit board 5 are hermetically sealed inside the head cap 2 by such a filler 6. 7
Denotes an input / output cable connected to the printed circuit board 5;
Reference numerals 1 and 72 denote core wires, and reference numeral 8 denotes a hollow back cover made of a rubber material from which the cable 7 is led out. Reference numerals 81 and 82 denote an air vent hole and an injection hole provided in the back cover 8, and reference numeral 83 shown by a dotted line denotes a circumferentially long retaining groove.

An example of the procedure for assembling the proximity switch 1 according to the first embodiment of the present invention will be described below. First, the detection coil 3 and the printed circuit board 5 are connected by the holder 4, and the terminal 35 of the coil 32 is connected to the through-hole 33.
And soldered to the printed circuit board 5.
The cable 7 is inserted into the hollow portion of the back cover 8, and the two stripped core wires 71 and 72 are connected to the printed circuit board 5.
The back cover 8 fitted on the cable 7 is slid and slightly separated from the printed circuit board 5 as in the above-described conventional case.

Here, the head cap 2 is placed upright, and the liquid filler 6 is poured from above about 程度 of the depth. The detection coil 3 and the printed circuit board 5 connected to the cable 7 are inserted and immersed in the head cap 2 into which the filler 6 has flowed. At this time, it is preferable that the detection coil 3 is appropriately shaken so that the gap 3 around which the coil 32 is wound is formed.
The air in 4 is expelled from vent hole 36. The expelled air passes through the inside of the head cap 2 and is released to the atmosphere. The pot core 31 submerged in the liquid filler 6 forms the detection surface 2
When it reaches 0, the insertion of the detection coil 3 is stopped.
Subsequently, the filler 6 is additionally injected until the printed board 5 is filled.

After the filler 6 has been added, the back cover 8 that has been separated is pushed down while following the cable 7, and the tip is fitted to the head cap 2 to close the opening. Then
While bleeding the internal air from the air vent hole 81 of the back cover 8,
The filler 6 is injected under pressure from the injection hole 82. Immediately before the liquid level of the filler 6 injected into the injection hole 82 is about to overflow from the air vent hole 81, the injection of the filler 6 is stopped. As a result, the tip of the cable 7 connected to the detection coil 3 and the printed circuit board 5 is buried in the head cap 2 without any gap. Thereafter, the injected filler 6 is solidified, and the proximity switch 1 as shown is completed. Since the filler 6 filling the circumferentially long slot 83 is solidified integrally, the back cover 8 is prevented from rotating and coming off.

Second Embodiment FIG. 3 is a plan view of a pot core 31 according to a second embodiment.
In the second embodiment, the left and right through-holes 3 of the first embodiment are used.
3 is omitted. Further, the hollow portion of the shaft center around which the coil 32 is wound is filled, and the sectional shape in the axial direction is molded into a complete E-shape. Since there is no concave portion on the axis, stagnation of bubbles near the pot core 31 can be eliminated.
Further, the number of air holes 36 formed in the annular gap portion 34 is also increased, and the diameter is made large. It is more desirable to form a countersink by adding an inclined surface to the entrance of each of the ventilation holes 36. Further, one of the ventilation holes 36 is selected, and is also used as a drawing hole through which the terminal 35 of the coil 32 is inserted.

Here, the operation of the application example of the proximity switch 1 having the above-described configuration will be described by exemplifying a case where the operation is applied to a transport control device as shown in FIG. As shown in FIG. 5, the proximity switch 1 uses nuts 22 and 22 that are screwed into male threads 21 provided on the outer periphery of the head cap 2 to detect a detection surface on a transport path V of a belt conveyor system in a bottling factory. 20 are installed facing each other from above. On the other hand, optical sensors L, L for detecting bins B1, B2,... That are sequentially conveyed are also installed in the lateral direction upstream of the conveying path V provided with the branch path v. By the oscillation circuit mounted on the printed circuit board 5, the exciting current flows into the detection coil 3 while the detection coil 3 is in the ON state, and the magnetic field of the magnetic flux φ is formed.

After the contents are poured into the bins B1, B2,..., The metal lids Ca are successively covered, and the bins B1, B2,. When the transported bins B1, B2,... Reach a predetermined position, first, the optical sensors L, L
Are sequentially detected. At the same time, when the bins B1, B2,... Approach the operating distance of the proximity switch 1, the metal cover Ca of the magnetic material enters into the magnetic field of the magnetic flux φ, and an eddy current e is generated therein. For this reason, the oscillating circuit is affected by the eddy current loss generated in the metal cover Ca, and an output signal is output from the cable 7 to the control device Co by utilizing the effect.

At this time, the output signal corresponding to the occurrence of the eddy current loss of the proximity switch 1 detects that the head of the bins B1, B2,. Further, when the bin B3 whose head is not covered with the metal cover Ca approaches the proximity switch 1, no eddy current loss occurs. That is, the presence or absence of the metal cover Ca of the bins B1, B2,... Is detected based on the output signal of the proximity switch 1. Then, the control device Co
Is the transport path V based on the output signal from the proximity switch 1.
A control signal is sent to a busher P provided downstream of the bin B, and the bin B3 is pushed out to the branch path v. In this way,
The presence or absence of the metal cover Ca of the bins B1, B2, B3,.

In the above description, the case where the present invention is applied to an oscillation type proximity switch is shown. However, the present invention can be applied to a capacitance type proximity switch, a magnetic type proximity switch, and the like. Further, the case where all the head caps are made of resin has been described, but the present invention can also be applied to a head cap having a cylindrical portion made of metal.

[0021]

According to the present invention, a detection coil in which a coil is arranged in a gap portion of a pot core is connected to a printed circuit board, sealed with a filler so as to face a detection surface in a head cap, and a back side is provided on a lead-out side of the head cap. In a proximity switch in which a lid is fitted and a cable connected to a printed circuit board is led out from a back lid and closed, a proximity switch provided with a plurality of ventilation holes penetrating in an axial direction in an annular gap portion of a pot core is provided. Configured. Further, in the above means 1, a proximity switch in which the terminal of the detection coil is inserted into the ventilation hole is configured. Furthermore, in the above-mentioned means 1 or 2, a proximity switch in which a ventilation hole is provided with an inclined surface and formed in a countersink shape is formed. As a result,
According to the present invention, even when the pot core is formed in a pot shape, air near the gap where the coil is arranged can be completely extracted. Therefore, there is no expansion / contraction effect due to a change in the ambient temperature due to the air accumulated near the coil as in the related art, and the detection coil does not malfunction. In addition, the quality of the product can be improved without inconvenience such that the gap near the detection coil is enlarged and a part of the detection surface is cracked to cause a failure.

Therefore, according to the present invention, with a simple configuration, air bleeding near the detection coil sealed in the back portion of the head cap is effectively promoted, and no detection error occurs, and a failure due to a crack or the like is caused. A proximity switch that can withstand long-term use can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a first embodiment of the present invention.

FIG. 2 is a plan view of the pot core according to the first embodiment.

FIG. 3 is a plan view of a pot core according to a second embodiment.

FIG. 4 is a configuration explanatory diagram of an application example of the embodiment of the present invention.

FIG. 5 is a sectional view showing the operation of the proximity switch.

FIG. 6 is a cross-sectional view illustrating a configuration of a conventional proximity switch.

FIG. 7 is a plan view of a pot core of a conventional proximity switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Proximity switch 2 Head cap 3 Detecting coil 4 Holder 5 Printed circuit board 6 Filler 7 Cable 8 Back cover 20 Detecting surface 21 Male screw 31 Pot core 32 Coil 33 Through hole 34 Void 35 Terminal 36 Vent hole 81 Air vent hole 82 Injection hole 83 slot

Claims (3)

[Claims] 1. A detection coil having a coil disposed in a gap portion of a pot core is connected to a printed circuit board, sealed with a filler so as to face a detection surface in a head cap, and a back cover is fitted to a lead-out side of the head cap. In a proximity switch, a cable connected to the printed circuit board is drawn out from the back cover and closed, and a plurality of ventilation holes penetrating in an axial direction are provided in an annular gap portion of the pot core. And proximity switch. 2. The proximity switch according to claim 1, wherein a lead wire of a detection coil is inserted into the ventilation hole. 3. The proximity switch according to claim 1, wherein the ventilation hole is formed in a countersink shape by providing an inclined surface.