JP2000258111A - Contact detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a contact detector to be used in various environments and to constitute a fail-safe safety system in a simple structure. SOLUTION: A contact detector 1 uses a flexible strain sensor 11 as a transducer. The sensor 11 is connected to a detecting member 16 which is displaced when a man or object comes into contact with the member 16 through a slider 15. When the member 16 is displaced, the electric resistance value of the sensor 11 varies and the strain of the sensor 11 in the direction of elongation can be detected. Prescribed tension is applied to the sensor 11 in a non-displaced state and the strain of the sensor 11 is detected from the variation of the electric resistance value from this state. Since the tension is preapplied to the sensor 11 in the above-mentioned way, the failure or abnormality of the sensor itself resulting from disconnection, coming off, etc., can be detected from the output signal of the sensor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact detecting device for detecting contact of a person or an object (hereinafter, simply referred to as "person"), and more particularly, to a space where a person and a machine work together. The present invention relates to a contact detection device used for the purpose of protecting human safety in a work space.

[0002]

2. Description of the Related Art In a work space, an accident may occur due to contact between a person and a machine. To prevent this,
Control is performed to monitor the entry of a person into the working area of the machine movable part (hereinafter referred to as “danger area”; the area other than the danger area is referred to as “safe area”), and to stop the operation of the machine when the entry is detected. is necessary.

[0003] Therefore, a work space is divided into a safety area and a danger area, and a device for detecting the presence of a person or the like (hereinafter referred to as "person detection") is installed at the boundary between these areas. Conventionally, such a device has used a contact detection device configured with a tread pressure sensor or a rope sensor as a transducer.

[0004]

However, in a contact detecting device using a tread pressure sensor or a rope sensor as a transducer, since these sensors have a contact contact structure,
There was a problem in terms of durability. Further, when a disconnection failure of a lead wire or the like or a contact failure due to oxidation / deterioration of a contact occurs, there is a risk that a detection signal is not output even if a human entry signal is input to the sensor.

That is, these contact detection devices do not guarantee the normality of detecting and notifying a failure or abnormality of the sensor itself, and do not have a so-called “fail-safe structure”. .

[0006] On the other hand, there has been proposed a method of ensuring safety by making the contact of the sensor a non-contact structure and combining sensors of a plurality of different types.
In this method, there is a problem that the entire system becomes complicated and too large.

[0007] In addition, there is a configuration using an optical sensor, but there is a restriction in mounting such as a short detectable distance, so that it may not be used depending on the environment. In view of such circumstances, an object of the present invention is to provide a contact detection device that can be used in various environments and that can constitute a fail-safe safety device with a simple structure.

[0008]

A contact detecting device according to the present invention comprises a detecting element (transducer) for generating an electric signal corresponding to a displacement of a sensing portion and a detecting member which is displaced by contact of a person or the like. The detection element generates a predetermined output signal in a state where the detection member is not displaced, and is configured to be connected, and the detection circuit indicates normal or abnormal based on the output signal from the detection element. Generate a detection signal.

The detection circuit receives an output signal from the detection element, and sets the output signal to be greater than or equal to a first threshold value set to be smaller than the predetermined output signal and to be larger than the predetermined output signal. When the value is within a predetermined range equal to or less than the second threshold value, a detection signal indicating normality is generated (claim 2).

Specifically, it is preferable to use a flexible strain sensor as the detection element. The flexible strain sensor is configured by covering a conductor extending in the longitudinal direction with a resin material having electrical insulation and elasticity, and generates an electrical signal according to the amount of strain in the extension direction.

The conductor is formed by dispersing a conductive filler (carbon, silver, copper, nickel, etc.) in a thermoplastic resin, an elastomer, a thermosetting resin, or the like. Various solvents and additives are added according to the required characteristics.

As the resin material, the following polymer substances are preferable. 1. Natural rubber, silicone rubber, urethane rubber, chloroprene rubber, acrylic rubber, butadiene rubber or phosphazene rubber 2. Rubber-like elastic body containing the above polymer compound (acrylonitrile butadiene copolymer, ethylene acrylate copolymer, styrene butadiene copolymer, ethylene butadiene copolymer) 3. Other elastomers (such as ethylene propylene copolymer (terpolymer), ethylene vinyl acetate copolymer, etc.) exhibiting sufficient elasticity and durability within the operating temperature range. According to the characteristics required and the use environment, an optimum material can be selected and formed into an arbitrary shape.

When the flexible strain sensor is connected to the detecting member, a predetermined tension is applied to the flexible strain sensor in a state where the detecting member is not displaced, and the flexible strain sensor is extended so as to be expanded by the displacement of the detecting member. I do.

A signal output from the flexible strain sensor (hereinafter referred to as "sensor output signal") is transmitted to a detection circuit. The detection circuit receives the sensor output signal and performs a level test using two preset threshold values. The first threshold value is set for a distortion amount smaller than the distortion amount at a predetermined tension. On the other hand, the second threshold value is set for a strain amount larger than the strain amount at a predetermined tension.

Here, the first threshold value is set to a value capable of identifying that the flexible strain sensor is in an abnormal state by coming off or loosening. It is preferable to set a value that can be regarded as contact.

According to this setting, the detection circuit is configured to determine whether the amount of strain in the extension direction of the flexible strain sensor is equal to or more than the amount of distortion corresponding to the first threshold value and equal to or less than the amount of distortion corresponding to the second threshold value. When it is within the range, that is, when the flexible strain sensor is functioning normally and a person or the like is not in contact with the detection member, a detection signal indicating normality is generated.

On the other hand, when the flexible strain sensor (including the detecting member) is in an abnormal state such as a mounting failure, the amount of distortion is smaller than the amount of distortion corresponding to the first threshold value.
Further, when a person or the like comes into contact with the detection member, the amount of distortion becomes the second.
Since the amount of distortion is larger than the amount of distortion corresponding to the threshold value, a detection signal indicating an abnormality is generated.

Further, even when a partial or complete disconnection occurs in the flexible strain sensor due to deterioration, the electric resistance value increases in the infinity direction and the sensor output signal becomes extremely large. And a detection signal indicating an abnormality is generated.

In order to more sensitively detect contact of a person or the like, the shape of the flexible strain sensor is optimized. Therefore, the conductor and the resin material are formed in a film shape. Further, the resin material is formed such that the width of both ends in the longitudinal direction is larger than the width of the middle part. Both ends are gripping portions for fixing the flexible strain sensor (claim 4).

It is preferable that the intermediate portion and both ends are connected smoothly. Using the contact detection device according to the present invention, when configuring a safety device for the purpose of safety protection in the work space, the detection member, a linear member such as a rope or a wire that separates the safety area and the danger area (Claim 5).

The detection circuit performs a level test based on an output signal from the detection element, and detects a contact of a detection member with a person. The detection signal is input to an AND circuit, and a control signal that is a logical product of the detection signal and a machine operation command is generated.

[0022]

According to the contact detecting device of the present invention, a predetermined output signal is output from the detecting element in a state where the detecting member is not displaced. It is output as an electrical signal. Therefore, it is possible to guarantee the normality of detecting and reporting a failure or abnormality of the sensor itself.

According to the second aspect of the present invention, by providing the first and second threshold values, while monitoring the contact of a person or the like based on the second threshold value, based on the first threshold value, It is possible to easily detect an abnormal state such as a defective mounting.

For this reason, the present contact detecting device can constitute a fail-safe safety device with a simple structure, and is more reliable than a device using a mechanical switch (a rope sensor or the like).

According to a third aspect of the present invention, there is provided a flexible strain sensor comprising:
Unlike the conventional conductive rubber (gel), since the conductive filler is not directly kneaded into the resin material, it has sufficient elasticity (elongation of 1200 to 1500%). Also, if the types and shapes of the conductor and the resin material are appropriately selected according to the purpose of use, the characteristics of the sensor (characteristics relating to physical properties, characteristics against the environment, etc.) can be set optimally.

For this reason, the contact detecting device according to the third aspect of the present invention can be used in a wide variety of applications from a case where a slight displacement of several centimeters is required to a case where a large displacement of several tens cm or more is required. It can be applied to various environments. The structure is simple and there are few restrictions on installation.

According to the fourth aspect of the invention, the flexible strain sensor can be easily fixed by forming the grip portion. Also, since the strain energy is concentrated in the center,
Deformation of the grip portion can be prevented, and the grip portion can be securely fixed.

If the width of the central portion is made narrower to form a flexible strain sensor, the sensitivity of the sensor (the amount of strain with respect to an applied external force) becomes more sensitive. Therefore, the detection member is displaced even by a slight contact of a person or the like, and a detection signal indicating an abnormality can be generated.

According to the fifth aspect of the invention, a fail-safe safety device having a simple structure can be constituted by the present contact detection device. In addition, it can cope with various environments and the characteristics of the flexible strain sensor can be set arbitrarily, so that the range of use is wide.

[0030]

FIG. 1 shows an example of a safety device using a contact detection device 1 according to an embodiment of the present invention. 2 shows a work space in which a worker 2 and a machine (belt conveyor) 3 work together.

The structure of the contact detection device 1 will be described with reference to FIGS. FIG. 2 is a cross-sectional view of the contact detection device 1 according to the present embodiment. FIG. 3 is a plan view showing the flexible strain sensor 11 used in the contact detection device 1.

In the contact detecting device 1 according to the present embodiment, the flexible strain sensor 11 is used as a detecting element (transducer). The structure of the flexible strain sensor 11 will be described with reference to FIG.

The flexible strain sensor 11 is composed of a conductor 31 (portion shown by oblique lines), a resin material 32 and a lead wire 33. Since the electrical resistance value of the conductor 31 changes due to the strain in the extension direction of the flexible strain sensor 11, an electrical signal corresponding to the strain amount can be output through the lead wire 33.

The conductor 31 is formed in the shape of a thin film and extends in the longitudinal direction. The electric resistance between both ends e1 and e2 increases in proportion to the displacement (strain) of 0 to 30%. (At this time, the electric resistance value changes 2-3 times.)

The resin material 32 is made of silicon rubber having both electrical insulation and sufficient elasticity, and covers the thin-film conductor 31 so as to sandwich it. Resin 32
At both ends in the longitudinal direction, grip portions h1 and h2 formed with a width larger than the middle portion m are provided. There is a smooth connection between the middle part m and each of the gripping parts h1 and h2 (at least the x part shown in the figure needs to be connected smoothly, and the y part need not be).

The conductor 31 has a width smaller than the minimum width of the resin material 32 (the width at the middle part m in the figure) and uniform in the longitudinal direction. The lead wires 33 are electrically connected to both ends e1 and e2 of the conductor 31, and are exposed to the outside from both ends of the resin material 32. A terminal (not shown) is attached to the exposed portion, and a terminal portion is configured by the lead wire 33 and the terminal.

Referring to FIG. One of the grips h1 and h2 of the flexible strain sensor 11 is on a gripper 13 formed integrally with the base 12 of the contact detection device 1, and has a fixture 14a.
Is fixed so as to be tightened from above. Further, the other gripping part is a slider 15 that meshes with the base 12 so as to be movable in the extending direction of the flexible strain sensor 11.
Are similarly fixed by the fixture 14b.

One end of a detection member 16 (rope or wire) that is displaced by contact of a person or the like is connected to the slider 15. The detection member 16 is stretched so as to separate the danger area and the safety area in the work space.

The other end of the detecting member 16 is fixed to a fixed wall 17. A predetermined tension T is applied to the flexible strain sensor 11 in a state where the detection member 16 is not displaced.
When a person or the like comes into contact with the detection member 16 and is displaced, a strain ε in the extension direction is generated in the flexible strain sensor 11, and the electrical resistance value r of the conductor 31 changes.

Referring to FIG. The sensor output signal (analog signal) is transmitted to the detection circuit 4. The detection circuit 4
It can include any known window comparator circuit, and determines whether the sensor output signal is within a predetermined range and generates a detection signal indicating normal or abnormal.

Referring to FIG. The window comparator circuit sets two level test values v1 and v2. v
According to 1 and v2, the sensor output signal e is
Values (P ⁰ , P ^1/2 , P ¹ ). The window is set at P1 ^{/ 2} . v1 corresponds to a strain amount ε1 smaller than the strain amount ε0 at the tension T, and v2 corresponds to a strain amount ε2 larger than the strain amount ε0 at the tension T.

That is, v1 = f (ε1), v2 = f (ε2) The detection circuit 4 generates a detection signal indicating normality in the input range of P ^1/2 and abnormal in the input ranges of P ⁰ and P ^1. Is generated.

That is, the strain amount ε of the flexible strain sensor 11 is
A detection signal indicating normality is generated when the value is within the range of the following equation (1), and a detection signal indicating abnormality is generated when the value is outside the range.

.Epsilon.1 .ltoreq..epsilon..ltoreq..epsilon.2 (1) Therefore, the detection signal indicating normality is that the detection member 16 is not in contact with a person or the like, the distortion amount .epsilon. Is small, and the tension is appropriately maintained. Since the signal is output when the machine is in operation, it can be used as a signal for permitting the operation of the machine.

On the other hand, a detection signal indicating an abnormality is generated when the flexible strain sensor 11 is loosened or detached (ε <ε1) on either the gripper 13 or the slider 15 or when a person or the like comes into contact with the detection member 16. Or when a partial or complete disconnection occurs due to the deterioration of the flexible strain sensor 11 (ε
2 <ε), it can be used as a signal to prohibit the operation of the machine.

The AND circuit 5 receives a detection signal indicating normality or abnormality and generates a control signal for operating or stopping the machine by a logical product of the detection command and the operation command. Thus, a failure or abnormality of the contact detection device 1 can be detected from any change in the sensor output signal in the rising direction or the falling direction.

Therefore, according to the present invention, a so-called fail-safe safety device that guarantees the normality of detecting and reporting a failure or abnormality of the sensor itself can be configured with a simple and inexpensive structure. .

The types and shapes of the conductor 31 and the resin material 32 are arbitrary, and various flexible strain sensors can be manufactured according to required characteristics and use environment. Characteristic examples are shown in FIGS. 3b and 3c.

In the flexible strain sensor 11 ', the amount of strain of the conductor 31 at the intermediate portion m is approximately three times as large as that of the flexible strain sensor 11 for the same displacement of the detection member 16. Therefore, the contact detection device using the flexible strain sensor 11 ′
Even a slight contact of a person or the like can be detected sensitively.

In the flexible strain sensor 11 ″, the both ends e 1 and e 2 of the conductor 31 are connected to the holding portions h 1 or h 1 of the resin material 32.
2). This allows
It is possible to cope with restrictions such as wiring.

In addition to changing the width and thickness, they can be arranged side by side, formed into a layered shape, a rod shape (linear shape), and formed into any desired shape. The same applies to the resin material.

Therefore, the contact detecting device according to the present invention is not limited to a belt conveyor, and is installed in any work space where a person may come into contact with a machine, such as an automatic door, an electric shutter or a movable roller. Can be used as

In the above-described contact detection device, since only one flexible strain sensor is used, it can detect only contact with a person or the like. By using two or more flexible strain sensors, it is possible to determine from which direction a person or the like comes into contact.

In the above description, an example is shown in which a flexible strain sensor is used. However, in the present invention, another detecting element can be configured as a transducer. That is, a pressure sensor, a resistance wire strain gauge, or the like, and a detection member are connected via an elastic body (a coil spring, a plate spring, or the like) and a predetermined output signal is provided in a state where the detection member is not displaced by applying a load in advance. Can be obtained.

Further, if a fixed electrode and a movable electrode which are disposed to face each other are provided and the movable electrode is connected to a detecting member to constitute a contact detecting device, a contact of a person or the like can be prevented from a change in capacitance between the electrodes. Can be detected. In the state where the detection member is not displaced, since a predetermined charge is stored between the electrodes, it is possible to generate a detection signal in which this state is normal.

By providing a fixed core (iron core) and a movable core, which are similarly arranged, and forming a coil on one or both of them to constitute a contact detection device, the contact of a person or the like between the iron cores can be reduced. It can be detected from a change in the magnetic field. It goes without saying that fail-safe is also guaranteed in this case.

As described above, the contact detecting device according to the present invention can be used for all kinds of detecting elements provided that a predetermined displacement can be applied to the sensing portion of the detecting element in a state where the detecting member is not displaced. Can be configured using.

[Brief description of the drawings]

FIG. 1 is an example of a safety device configured using a contact detection device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the same contact detection device.

FIG. 3 is a flexible strain sensor constituting the contact detection device according to the first embodiment.

FIG. 4 is a diagram illustrating processing of a sensor output signal by a window comparator circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Contact detection apparatus 2 Worker 3 Machine (belt conveyor) 4 Detection circuit 5 AND circuit 11 Flexible strain sensor 16 Detection member

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Asahi Sugimoto 3-2-1 Koganei Kitamachi, Koganei-shi, Tokyo 18-21 Koganei Public Employee Housing 18-21 (72) Inventor Hiroyasu Ikeda 720-floor Kita-Akitsu, Torozawa-shi, Saitama A Tokorozawa 402 (72) Inventor Shujiro Doda 307-3 Nishikawara, Okayama City, Okayama Prefecture F-term (reference) 2F063 AA26 AA49 AA50 BA29 BD15 CA29 DA05 EC02 EC03 EC04

Claims (5)

[Claims] A detecting element for generating an electric signal corresponding to a displacement of a sensing portion, and a detecting member which is displaced by a contact of a person or an object, wherein the detecting element is provided in a state where the detecting member is not displaced. And a detection circuit for generating a detection signal indicating normality or abnormality based on an output signal from the detection element. 2. The detection circuit receives an output signal from the detection element, and the output signal is greater than or equal to a first threshold value set smaller than the predetermined output signal and larger than the predetermined output signal. 2. The contact detection device according to claim 1, wherein a detection signal indicating normality is generated when the detection value is within a predetermined range equal to or less than the set second threshold value. 3. The detecting element is formed by covering a conductor extending in a longitudinal direction with a resin material having electrical insulation and elasticity, and generates an electric signal according to an amount of strain in an extending direction. A flexible strain sensor, wherein the flexible strain sensor and the detection member are provided with a predetermined tension to the flexible strain sensor in a state where the detection member is not displaced, and the extension of the flexible strain sensor is caused by the displacement of the detection member. 3. The contact detection device according to claim 1, wherein the contact detection device is connected so as to cause the following. 4. The flexible strain sensor according to claim 1, wherein the conductor and the resin material are formed in a film shape, and the width of both ends in the longitudinal direction of the resin material is larger than the width of an intermediate portion. 4. The contact detecting device according to claim 3, wherein a grip portion is provided on the touch panel. 5. A contact detection device used for the purpose of safety protection in a space where a person and a machine work jointly, wherein said detection member is a linear member separating a safety region and a danger region, and said detection circuit is provided. The contact detection device according to any one of claims 1 to 4, wherein the device detects a human contact with the detection member based on a signal from the detection element.