KR20220070948A - Super slim type proximity sensor detecting ferrous metal or nonferrous metal combined electrostatic capacity type and inductor type - Google Patents

Abstract

Disclosed is a proximity sensor for detecting a ferrous or nonferrous metallic object, which is a super-slim proximity sensor capable of overcoming the thickness limitation of a sensor. The present invention provides a super-slim proximity sensor comprising: a sensor housing; an oscillation part mounted on a printed circuit board inside the sensor housing to provide voltage; an inductor having voltage, which is generated from the oscillation part, applied thereto to form a magnetic field and outputting the increase and decrease of magnetic force lines caused by approaching ferrous metal or nonferrous metal; a detection part for outputting a potential difference between the voltage generated by the oscillation part and the voltage outputted through the inductor, as a signal waveform; a comparison part for reading the signal waveform outputted from the detection part and comparing the same with the signal waveform of the voltage generated by the oscillation part; and a control part for receiving the signal waveform compared and outputted from the comparison part and determining whether to generate a signal from an output part. The inductor is formed in the shape of a pattern wound spirally on top of the printed circuit board and grounding condensers are connected to both contact points of the inductor and the oscillation part, respectively.

Description

Super slim type proximity sensor detecting ferrous metal or nonferrous metal combined electrostatic capacity type and inductor type}

The present invention relates to a proximity sensor, and more particularly, to an ultra-slim proximity sensor for detecting ferrous or non-ferrous metal.

A proximity sensor, a sensor that operates a switch when an object is adjacent, operates a switch by judging whether an object is adjacent by using the principle of a capacitive method or an inductor method (high frequency oscillation type).

In the case of the capacitive method, the sensor detects an object by using the capacitance between the object and the sensor is inversely proportional to the distance between the two. When a ferrous or non-ferrous metal object approaches a magnetic field, an eddy current is generated inside the conductor by electromagnetic induction, and the eddy current generates a magnetic field that opposes the field generated by the sensing coil. At this time, in the sensing coil, as the loss resistance (R) and the inductance (L) change, a change in frequency occurs, and an output is generated by sensing the change in frequency. That is, the inductor method can detect only ferrous or non-ferrous metal objects, unlike the capacitive method.

On the other hand, a proximity sensor for detecting a ferrous or non-ferrous metal object is used in various industrial sites, and in this case, it is often required to install the proximity sensor even in a very narrow space. However, in the case of an inductor-type proximity sensor, there is a limit to reducing the thickness of the proximity sensor due to the characteristics of the inductor element, and the current limit is 7 to 8 mm in thickness including the sensor housing.

[Prior Patent Literature]

- Korean Patent Registration No. 10-1998362 (Registered on July 3, 2019)

- Korean Patent No. 10-1421110 (Registered on July 14, 2014)

An object of the present invention is to provide an ultra-slim proximity sensor capable of overcoming the limit of sensor thickness in a proximity sensor for detecting ferrous or non-ferrous metal objects.

The present invention in order to solve the above problems, the sensor housing; an oscillator mounted on a printed circuit board inside the sensor housing to provide a voltage; an inductor receiving the voltage generated from the oscillation unit to form a magnetic field and outputting an increase or decrease of a magnetic force line by an approaching ferrous or non-ferrous metal; a detector for outputting a potential difference between the voltage generated by the oscillator and the voltage output through the inductor as a signal waveform; a comparator for reading a signal waveform output from the detection unit and comparing it with a signal waveform of the voltage generated by the oscillator; and a control unit that receives the signal waveform compared and output by the comparator and determines whether or not a signal is generated through the output unit, wherein the inductor is formed in a spirally wound pattern on the printed circuit board, and the inductor And it provides an ultra-slim proximity sensor, characterized in that each ground capacitor is connected to both contacts of the oscillation unit.

In addition, the outer diameter of the pattern is 11 to 13 mm, the pattern interval is 0.08 to 0.12 mm, the pattern thickness is 0.08 to 0.12 mm, the pattern rotation is 23 to 25 turns, and the thickness of the proximity sensor is based on the housing thickness Provides an ultra-slim proximity sensor, characterized in that less than 5 mm.

According to the present invention, in the proximity sensor for detecting ferrous or non-ferrous metal, a capacitive method and an inductor method are mixed, an inductor formed in a spirally wound pattern on a printed circuit board is applied, and both contacts of the oscillation unit are applied. By connecting each grounding capacitor, it is possible to provide an ultra-slim proximity sensor that can detect ferrous or non-ferrous metals while increasing the sensing distance.

1 is a perspective view showing the appearance of an ultra-slim proximity sensor according to an embodiment of the present invention;
2 is a block diagram illustrating the structure of an ultra-slim proximity sensor according to an embodiment of the present invention;
3 is a view showing the physical structure of the inductor formed in a pattern in the present invention by way of example.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, similar reference numerals are given to similar parts throughout the specification, and the detailed configuration direction of the present invention will be described with reference to the drawings. Also, throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

1 is a perspective view showing an appearance of an ultra-slim proximity sensor according to an embodiment of the present invention, and FIG. 2 is a block diagram illustrating the structure of an ultra-slim proximity sensor according to an embodiment of the present invention.

1 and 2, the ultra-slim proximity sensor 100 according to the present invention includes a sensor housing 110, an oscillation unit 120, an inductor 130, a detection unit 140, a comparison unit 150, a control unit ( 160 ) and an output unit 170 . At this time, the oscillation unit 120 , the inductor 130 , the detection unit 140 , the comparison unit 150 , the control unit 160 , and the output unit 170 are printed circuit boards (PCB) inside the sensor housing 110 . is mounted on

The oscillation unit 120 is not particularly limited as long as it is configured to provide a voltage and achieve continuous oscillation. For example, the device used in the oscillation unit 120 is an active device transistor, and such a transistor depends on the device characteristics. Accordingly, a field effect transistor (FET) or a bipolar transistor (BJT) can be appropriately selected, and a negative resistance condition is generated on the input side, and impedance matching is performed on the output side so that the output frequency signal is well output. Here, the transistor satisfies the configuration as an oscillator even if any of the three terminals is grounded, but it is preferable to have a structure in which the source is grounded in the case of an FET, and the emitter is grounded in the case of a BJT, like a general amplifier. .

In addition, the oscillator 120 may be configured to include a capacitor in the oscillator 120 to receive a portion of the output voltage insufficient to achieve continuous oscillation. In addition to having the field effect transistor (FET) or bipolar transistor (BJT) to convert the voltage output from the capacitor into an input, the sine wave oscillated by the FET or BJT may vary according to temperature change. Therefore, it can be configured by further providing an FET or BJT in order to prevent it from being changed by a temperature change.

The inductor 130 is an element that receives the voltage generated by the oscillation unit 120 and forms a magnetic field and outputs an increase or decrease of a magnetic force line by an approaching ferrous or non-ferrous metal. The inductor 130 is the voltage of the oscillation unit 120 . A magnetic field is formed by the , and the magnetic field changes according to the distance between the adjacent ferrous or non-ferrous metal object. The detection using the inductor 130 is to interfere with or increase the magnetic flux of the inductor 130 by an eddy current caused by electromagnetic induction when a ferrous or non-ferrous metal object approaches the inductor 130 in which a magnetic field is formed. Inductor 130 The voltage output through the oscillator 120 has a potential difference from the input voltage provided by the oscillator 120 .

3 is a view exemplarily showing the physical structure of the inductor 130 formed in a pattern in the present invention.

Referring to FIG. 3 , in the present invention, the inductor 130 is formed in a spirally wound pattern 131 on the printed circuit board, unlike a conventional inductor formed in a coil shape. Therefore, in the case of an inductor-type proximity sensor using a conventional coil, there was a limitation in reducing the thickness of the proximity sensor due to the characteristics of the inductor element. can be dramatically slimmed down. In FIG. 3 , the pattern 131a indicated in red indicates that it is formed on the upper surface of the printed circuit board, and the pattern indicated in blue 131b indicates that it is formed on the lower surface of the printed circuit board.

Specifically, the pattern image 131 may be in the form of a square or rectangular shape with rounded corners as a whole, the outer diameter (D) is 11 to 12 mm, the pattern interval is 0.08 to 0.12 mm, and the pattern thickness is 0.08 to 0.12 mm, and the number of pattern rotations may be 23 to 25 turns, and accordingly, the thickness of the proximity sensor 100 is 5 mm or less based on the sensor housing 110 thickness (T), preferably 4.25 mm or less, more Preferably, it is possible to super slim down to a level of 3.5 mm or less.

Here, the inductance varies depending on the size (pattern area), the number of turns, etc. of the inductor 130 , which affects the sensing distance. As the size increases, the sensing distance also increases. Therefore, it is not easy to develop a small proximity sensor that can be used in a narrow space, and most of the small sensors have a very short sensing distance.

Accordingly, in the present invention, the inductor method is basically applied, but the coil-type inductor is excluded and the corresponding inductor is replaced with the PCB pattern 131, and by applying the capacitance-type measurement method to increase the sensing distance. We tried to increase the sensing distance by making the frequency change sensitive.

That is, as shown in FIG. 1 , by connecting ground capacitors C1 and C2 to both contacts of the inductor 130 and the oscillator 120 , respectively, the bandwidth changed when ferrous and non-ferrous metal objects approach is relatively reduced. It detects even from a long distance so that the switch can be operated. For example, the structure of the inductor 130 on the PCB pattern 131 as shown in FIG. 3 can be manufactured with an outer diameter (D) of 12 mm, a pattern spacing of 0.1 mm, a pattern thickness of 0.1 mm, and 24 turns to produce a capacity value of about 4.4 μH. Also, two 300 pF capacitors C1 and C2 are mounted to make a capacitance reference value, and when viewed from the inductor 130 , the series summed capacitor capacitance can be adjusted to about 150 pF. In this way, an oscillation frequency band of about 6.2 MHz is created, and when this frequency is approached by a ferrous or non-ferrous metal object, the changed bandwidth is sensed to operate the switch.

The detection unit 140 outputs a potential difference between the voltage generated by the oscillator 120 and the voltage output through the inductor 130 as a signal waveform.

The comparator 150 reads the signal waveform output from the detection unit 140 and compares it with the signal waveform of the voltage generated by the oscillator 120 , and the comparator 150 reads the signal waveform output from the inductor 130 . It may be composed of a double rectifying circuit to be rectified while minimizing voltage loss, and the voltage rectified by the double rectifying circuit is amplified to the input voltage provided by the oscillator 120 through an amplifier, and then the voltage difference between the input voltage and the output voltage. is provided to the control unit 160 .

The control unit 160 may receive the signal waveform compared and output by the comparator 150 , determine whether a signal is generated or not, and transmit, for example, a flickering signal of a square wave through the output unit 170 .

Meanwhile, the oscillation unit 120 , the detection unit 140 , the comparison unit 150 , and the control unit 160 may be mounted on a printed circuit board in an integrated form in the microprocessor chip 200 .

In the present invention, the sensor housing 110 is not particularly limited in its material or shape as long as it can be manufactured in a thin shape while protecting the printed circuit board, and may be applied as, for example, a plastic injection molding.

Preferred embodiments of the present invention described above are disclosed to solve the technical problem, and various modifications, changes, additions, etc. will be possible within the spirit and scope of the present invention by those of ordinary skill in the art to which the present invention pertains. , such modifications and changes should be regarded as belonging to the following claims.

100: proximity sensor 110: sensor housing
120: oscillator 130: inductor
131: on PCB pattern 140: detection unit
150: comparison unit 160: control unit
170: output unit 200: microprocessor chip
D : Outer diameter of pattern T : Thickness of sensor housing
C1, C2: capacitor

Claims (2)

sensor housing;
an oscillator mounted on a printed circuit board inside the sensor housing to provide a voltage;
an inductor receiving the voltage generated from the oscillation unit to form a magnetic field and outputting an increase or decrease of a magnetic force line by an approaching ferrous or non-ferrous metal;
a detector for outputting a potential difference between the voltage generated by the oscillator and the voltage output through the inductor as a signal waveform;
a comparator for reading a signal waveform output from the detection unit and comparing it with a signal waveform of the voltage generated by the oscillator; and
a control unit receiving the signal waveform compared and output by the comparator and determining whether a signal is generated through the output unit;
including,
The inductor is formed in a spirally wound pattern on the printed circuit board, and a ground capacitor is connected to both contacts of the inductor and the oscillator, respectively. The method of claim 1,
The outer diameter of the pattern is 11 to 13 mm, the pattern interval is 0.08 to 0.12 mm, the pattern thickness is 0.08 to 0.12 mm, the number of pattern rotations is 23 to 25 turns, and the thickness of the proximity sensor is 5 based on the thickness of the housing Ultra-slim proximity sensor, characterized in that less than mm.

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