JP2549898Y2 - Two-wire sensor switch - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-wire sensor switch which is connected in series to a load and controls the switching of the load.

[0002]

2. Description of the Related Art As an example of this type of sensor switch, there is, for example, a two-wire photoelectric switch in which light is to be measured. For example, as shown in FIG. 4, a sensor main body 1 having an output transistor built therein is connected in series with a power supply 2 and a load 3, and light from a light emitting element of the light projector 4 is projected toward a light receiving element of the sensor main body 1. Is set to be

In this configuration, the detected object passes through the optical axis between the projector 4 and the sensor body 1 so as to block the optical axis, and the passage is detected. There are two types, a normal open mode in which the transistor is turned on and a normally closed mode in which the output transistor is turned off at the time of detection.

For example, in a normally open mode sensor switch, when light from the light projector 4 is incident on the sensor body 1, the output transistor of the sensor body 1 is off. However, when the light is blocked by a detection object (not shown) and the amount of light incident on the sensor main body 1 decreases, the output transistor turns on when the measured signal level of the amount of incident light falls below a predetermined operation level, and the load is reduced. 3 is energized.

In this type of photoelectric switch, an operation indicator is generally provided to display whether or not the sensor body has detected an object to be detected. As a configuration for this purpose, for example, as shown in FIG.
A series circuit of an operation indicator lamp 5 and a switching element 6 is provided in parallel with a, and the switching element 6 is turned on by a signal from a detection circuit 1b when an object to be detected is detected. Has become.

In this type of two-wire sensor switch, not only the operation state is displayed, but also, for example, whether or not the amount of light incident on the light receiving element at the time of incident light is appropriately secured. It is desirable to be able to confirm at. This makes it easy to determine whether the light intensity from the light projector 4 is sufficient, whether the optical axis is properly set, or whether the amount of incident light is excessively reduced due to contamination of the lens. Because it is possible, it is convenient for setting and maintenance of the sensor.

For this purpose, a configuration in which a stability indicator lamp 7 is provided as shown in FIG. 5 is conventionally provided. In general, the stability indicator 7 is connected in parallel with the output transistor 1a together with the switching element 8. With this configuration, when the amount of incident light on the light receiving element of the sensor body exceeds the stable range level and is a sufficient value, the switching element 8 is turned on by a signal from the detection circuit 1b, and the stability indicator 7 is turned on.

[0008]

By the way, in the two-wire sensor switch, the sensor body 1 is used in series with the load 3, so that its output characteristics are required to be as close as possible to the mechanical contacts. Specifically, it is desired that the leakage current IOFF when the output is off is as small as possible and the residual voltage VON when the output is on is as low as possible.

However, in the above-described conventional configuration, there is no problem in the normally open mode, but in the normally closed mode, the leakage current IOFF when the output is turned off.
Becomes large and this becomes a problem.

That is, in the normally closed mode, the operation indicator 5 and the stability indicator 7 are turned on when the output transistor 1a is off. For this reason, each lighting current ILED of the indicators 5 and 7 must be viewed as a leakage current IOFF. In addition, since a small operating current IOP always flows into the detection circuit 1b, the leakage current IOFF when the output is turned off eventually becomes two operating lights IOP of the detection circuit.
7 and a lighting current of 2.ILED (IOFF =
IOP + 2 · ILED), which cannot be ignored. For this reason, it may not be used especially for a load such as a sequencer that is considered to be in the ON state even with a small current.

In order to avoid this, for example, Japanese Patent Application Laid-Open
It is also conceivable to use the technique disclosed in Japanese Patent No. 84534. In this case, as shown in FIG. 6, an operation indicator lamp 9 and a limiting resistor 9a are provided in a power supply path to the detection circuit 1b, and a bypass transistor 10 is connected in parallel with these. When the operation indicator lamp 9 is to be turned on, the operation current flowing into the detection circuit 1b is turned off by turning off the bypass transistor 10, and the operation indicator lamp 9 is turned on.
Is turned on.

However, in the above configuration, although there is no problem in the normally closed mode, there is a problem that the residual voltage VON when the output is turned on becomes large in the normally open mode.

That is, in the normally open mode, the operation indicator 9 is turned on when the output is turned on. When the operation indicator light 9 is turned on, it is connected in series with the detection circuit 1b, so that the shared voltage VL is added to the operation voltage VOP of the detection circuit 1b. That is, in this case, the residual voltage VON between both terminals of the output transistor 1a depends on the operating voltage VOP of the detection circuit 1b, the operation indicator lamp 9, and the limiting resistor 9a.
(VON = VOP + VL), which results in a relatively large value. In the above configuration, if not only the operation indicator lamp 9 but also the stable state indicator lamp is turned on, the shared voltage will be further increased, and the residual voltage VON when the output is turned on is further increased. Will be expensive.

As described above, in the conventional two-wire sensor switch, when the operation indicator and the stable status indicator are provided, the leakage current increases in the normally closed mode, and the residual voltage increases in the normally open mode. The problem arose.

The present invention has been made in view of the above circumstances, and accordingly, an object of the present invention is to maintain a high level of output characteristics such as leakage current and residual voltage while enabling operation indicator lamps and the like to be turned on. The present invention is to provide a two-wire sensor switch capable of performing the following.

[0016]

A two-wire sensor switch according to the present invention includes a detection circuit for comparing a measured signal level of an object to be measured with a predetermined operation level, and a comparison result of the detection circuit and an operation mode setting. The output switching circuit connected in series to the power supply and the load is opened and closed according to one of the normal close mode and the normally open mode set by the means, and is normally closed in the case of the normally closed mode. The output switching circuit is opened when an object to be detected is detected, and in the normally open mode, the normally open output switching circuit is closed when an object to be detected is detected. In the one that turns on the indicator light in the state where the detected object is detected,
A first switching element connected in series with the indicator light and connected in series with the output switching circuit so as to be in parallel with the output switching circuit; Is connected to a common connection point between the third switching element and the indicator light and the first switching element interposed in series on the line on the detection circuit side to form a series circuit with the indicator light, and the series circuit is the third circuit. A switching element group consisting of a second switching element connected in parallel to the switching element of the above is provided, and the first switching element is closed and the indicator light is connected to the output switching circuit. A parallel connection state in which power is supplied to the detection circuit via the third switching element while being in parallel and the third switching element is closed; The switching element is opened and the second switching element is closed, and the indicator light is connected in series with the power supply path to the detection circuit in series connection. The first switching element is opened and the third switching element is closed. A control circuit that can be switched between an off state and an on state when the output lamp is turned on while the output switching circuit is on. It is characterized in that when the indicator lamp is turned on in the state described above, the indicator lamp is connected in series, and when the indicator lamp is turned off, the indicator lamp is turned off.

[0017]

The operation will be described with reference to FIG. 1 which illustrates the configuration of the present invention. The output switching circuit 11 is connected in series to a load 12 and a power supply 13 as shown in the figure. The detection circuit 14 compares a measurement signal level of an object to be measured such as light, a sound wave, a magnetic field, and the like with a predetermined operation level, and outputs a switching operation signal Ss depending on which of a normally open mode and a normally closed mode. . That is, for example, in the normally open mode, the output switching circuit 11 is always open, and when an object to be detected is detected due to the fluctuation of the measurement signal level, the output switching circuit 1
The switching operation signal Ss is output so as to close the output switching circuit 1. In the normally closed mode, on the contrary, the output switching circuit 11 is always closed. The switching operation signal Ss is output so that the switching circuit 11 is opened. Also, the first switching element 1
7, a second switching element 16 and a third switching element 15 constitute a switching element group, which is controlled by the control circuit 19 to open and close as follows.

That is, in the normally closed mode,
The output switching circuit 11 is normally closed and the indicator light 1
The indicator lamp 18 is turned on when the output switching circuit 11 is opened by detecting the object to be detected and turning off the object 8. When the indicator lamp 18 is turned on, both the first and third switching elements 17 and 15 are open and the second switching element 16 is closed (in a series connection state).
4 is turned on by the operating current flowing through the power supply path to the power supply circuit 4, and no extra lighting current flows, so that the leakage current when the output switching circuit 11 is off is small.
When the indicator lamp 18 is turned off, the first switching element 17 is opened and the third switching element 15 is closed (off state).
A current flows through the power supply path to the detection circuit 14 via the interface, and there is no problem in supplying the operation current.

On the other hand, in the normally open mode, the output switching circuit 11 is always open and the
Is turned off, and the indicator lamp 18 is turned on when the object to be detected is detected and the output switching circuit 11 is closed. Indicator 1
8 is turned on, the second switching element 16 is turned on.
Is opened and the first and third switching elements 17 and 15 are closed (parallel connection state), so that the indicator lamp 18 is in parallel with the output switching circuit 11 and is interposed in series in the power supply path to the detection circuit 14. The detection circuit 14
Therefore, the residual voltage VON when the output is turned on can be kept low, without the shared voltage of the indicator lamp 18 being added to the operating voltage. When the indicator lamp 18 is turned off, the first switching element 17 is opened and the third switching element 15 is closed (off state), so that the power supply path to the detection circuit 14 via the third switching element 15 is provided. Current flows through the circuit, and there is no problem in supplying the operating current.

[0020]

As described above, according to the two-wire sensor switch of the present invention, the output characteristics such as the leakage current and the residual voltage can be maintained at a high level while the indicator lamp can be turned on. It has an excellent effect that it can be done.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. In this embodiment, the present invention is applied to, for example, a reflection type photoelectric switch. As is well known, a light emitting element and a light receiving element are provided in a sensor main body, and the light emitting element and the light receiving element are arranged so as to face a passage area of the object to be detected. The object is detected by the light from the light projecting element being reflected by the object and entering the light receiving element.

FIG. 2 shows the electrical configuration of the light receiving side of the sensor body 20. The power supply is connected between the collector and emitter (output terminals A and B) of the output transistor 21 corresponding to the built-in output switching circuit. 40 and the load 50 are connected in series.

The detection circuit 22 is provided with a light receiving element. The light receiving signal is amplified by a light receiving amplifier, and the output transistor 21 performs a switching operation based on a comparison between the level of the amplified measurement signal and a predetermined operation level. Signal Ss
Is output.

The sensor body 20 includes the detection circuit 22
Is provided with a mode changeover switch 23 corresponding to an operation mode setting means for giving a signal to the normal close mode and the normal open mode.

If the mode changeover switch 23 is set to the normally closed mode, the switching operation signal Ss from the detection circuit 22 is at a high level when no object is detected (when the amount of light incident on the light receiving element is small). , The output transistor 21 is in an ON state. And
When an object to be detected is detected (when the amount of light incident on the light receiving element increases), the switching operation signal Ss from the detection circuit 22 goes low and the output transistor 21
Is turned off.

If the mode changeover switch 23 is set to the normally open mode, the switching operation signal S from the detection circuit 22 is output when no object is detected.
s is at a low level, and the output transistor 21 is off. Then, when an object to be detected is detected, the switching operation signal Ss from the detection circuit 22 goes high and the output transistor 21 is turned on.

The diode indicated by reference numeral 24 is an operation indicator light, and is a red light emitting diode.
The diode indicated by reference numeral 25 is a stable indicator light corresponding to the indicator light of the present invention, and is a green light emitting diode. Among them, the operation indicator light 24 is connected in parallel with the output terminals A and B in series with the operation display transistor 26, and the stability indicator light 25 is the first transistor 27 corresponding to the first switching element of the present invention. And also connected in parallel between the output terminals A and B.

Here, the common connection point between the cathode of the stability indicator light 25 and the collector of the first transistor 27 is connected to the second transistor 2 corresponding to a second switching element.
8 is connected to the positive power supply terminal V + of the detection circuit 22. Further, a third transistor 29 corresponding to a third switching element is connected to a series circuit of the stability indicator 25 and the second transistor 28 so as to be bypassed. The terminal Vo is connected to the output terminal B. Thereby, the detection circuit 22
Has a form in which the respective lines of the power supply path are connected in parallel with the output transistor 21.

The above-described first to third transistors 2
Reference numerals 7 to 29 denote a parallel connection state in which the stability indicator 25 is connected in parallel to the output transistor 21 and a series connection state which is interposed in the power supply path to the detection circuit 22 in series, as will be apparent from the operation description to be described later. A switching element group for switching to a connection state is formed, and is turned on and off by a control circuit 30 together with the operation display transistor 26. Also,
Particularly, in the present embodiment, the second and third transistors 28,
Reference numeral 29 functions not only as a switching element for switching the current path of the stability indicator 25, but also as a regulator transistor. That is, when the transistors 28 and 29 are turned on, the base current is analog-controlled by the control circuit 30 to supply a constant operating voltage VOP to the power supply terminal V + of the detection circuit 22.

Next, the operation of the present embodiment will be described.
In the photoelectric switch of the present embodiment, a normal open mode and a normally closed mode can be selected by switching the mode changeover switch 23. Therefore, the description will be made separately for each mode.

(1) When Normally Closed Mode is Set When Not Detected When no object is detected, the operation display transistor 26 and the third transistor 29 are turned on, and the first and second transistors are turned on. Transistors 27 and 28 are off. Therefore, the operation indicator light 24 is turned on and the stability indicator light 25 is turned off, and the detection circuit 22
Power is supplied through the transistor 29 of FIG. At this time, the switching operation signal Ss from the detection circuit 22 is at the high level, and the output transistor 21 is in the ON state, so that the load 50 is energized.

In this case, the third transistor 29 shares the residual voltage VON between the output terminals A and B in this embodiment with the constant operating voltage VOP supplied to the detection circuit 22. (VON = VOP + Vreg)
It is relatively low because it corresponds to 3).

At the time of detection (turn-off of the operation indicator lamp 24) When the detected object enters the detection area, light reflected by the detected object enters the light receiving element.
When the measurement signal level of the light receiving signal rises and exceeds a predetermined operation level, the switching operation signal Ss from the detection circuit 22 goes low. As a result,
The output transistor 21 is turned off, and the load 50 is turned off. At the same time, the operation display transistor 26 is also turned off by a signal given from the detection circuit 22 to the control circuit 30, so that the operation indicator lamp 24 is turned off, indicating that the output is turned off.

At this time, the leakage current IOFF flowing between the output terminals A and B is equal to the operating current IOP of the detection circuit 22 (IOFF = I0) because both the indicators 24 and 25 are turned off.
P), extremely small.

At the time of detection (lighting of the stability indicator lamp 25) If the amount of light emitted from the light emitting element is sufficient and the optical axis is appropriately set, the amount of reflected light entering the light receiving element from the object to be detected is also reduced. It rises sufficiently, and the measured signal level of the received light signal becomes sufficiently high to enter a stable region. Then, the detection circuit 2
2 supplies a stable display signal Sst to the control circuit 30. The first and third transistors 2 and 3
7, 29 are turned off and the second transistor 28 is turned on. As a result, the stability indicator light 25 is connected in series with the power supply path to the detection circuit 22 in series, so that the stability indicator light 25 is turned on by the operating current IOP flowing into the detection circuit 22.

Accordingly, the leakage current IOFF flowing between the output terminals A and B at this time becomes equal to the operating current IOP of the detection circuit 22 while the stability indicator 25 is lit (IOF).
F = IOP), very small.

(2) When Normal Open Mode is Set Non-Detection When no object is detected, the operation display transistor 26 and the first and second transistors 2
7, 28 are off, and the third transistor 29 is on. Therefore, power is supplied to the detection circuit 22 through the third transistor 29, and the operation indicator 24
The stability indicator 25 is off. At this time, since the switching operation signal Ss from the detection circuit 22 is at a low level and the output transistor 21 is off, the load 50 is disconnected.

At the time of detection (lighting of the operation indicator lamp 24) When the detected object enters the detection area, the measured signal level of the received light signal rises, and when this exceeds a predetermined operation level, the detection circuit 22 Becomes high level, the output transistor 21
Is turned on, and the load 50 is energized. At the same time, the first transistor 26 is turned on by a signal supplied from the detection circuit 22 to the control circuit 30.
The operation indicator lamp 24 is turned on to indicate that the output has been turned on.

When the output is turned on, there has conventionally been a problem that the residual voltage VON between the output terminals A and B becomes high. However, in this embodiment, since the indicator lamp is not in a state in which the indicator lamp is interposed in series in the power supply path to the detection circuit 22, the residual voltage VON is equal to the constant voltage operating voltage VOP supplied to the detection circuit 22. And Vreg3 shared by the third transistor 29 (VON = VOP + Vreg3), which is relatively low.

At the time of detection (lighting of the stability indicator 25) If the light emitting amount from the light emitting element is sufficient and the optical axis is set appropriately, the reflected light amount incident on the light receiving element from the object to be detected is also reduced. It becomes sufficient, and the measurement signal level of the received light amount becomes sufficiently high to enter a stable region. Then, the stable display signal Sst is given from the detection circuit 22 to the control circuit 30. This time, the operation display transistor 26 is turned off,
The first transistor 27 turns on.

As a result, the operation indicator 24 is turned off and the stability indicator 25 is turned on. If the operation indicator 24 is turned off when the stability indicator 25 is turned on, the advantage that the minimum load current can be reduced can be obtained.

As described above, according to the present embodiment, in the case of the normally closed mode, the stability indicator 25 is turned on by the operating current flowing into the detection circuit 22, so that the leakage current IOFF, which tends to be a problem in this mode, is extremely small. Can be suppressed. Further, in the case of the normally open mode, the operation indicator lamp 24 and the stability indicator lamp 25 are connected in parallel with the output transistor 21, so that the residual voltage VON when the output is turned on, which tends to be a problem in this mode, can be extremely reduced. it can.

As a result, the operation indicator 24 and the stability indicator 2
5, the leakage current IOFF is small and the residual voltage V
Excellent output characteristics with low ON can be obtained. Of course, since the operation indicator 24 is provided, the output state can be easily checked, and since the stability indicator 25 is provided, the measurement signal level can be easily checked, and the adjustment work at the time of installation and maintenance is extremely easy. Needless to say,

FIG. 3 shows a second embodiment of the present invention. The difference from the first embodiment is that a regulator transistor 31 for making the operating voltage VOP supplied to the detection circuit 22 constant is provided exclusively. The other points are the same as in the first embodiment, and the same portions are denoted by the same reference numerals and description thereof will be omitted.

In addition, the present invention is not limited to the above-described embodiments, and can be variously modified and implemented without departing from the gist, for example, as described below.

(A) In each of the above embodiments, the mode changeover switch 23 is provided as the mode setting means. However, if the normal close mode and the normal open mode are set at the time of factory shipment, for example, the switch 23 is used.
Can also be omitted. In this case, a jumper wire or a predetermined pattern of the printed circuit board is used as the mode setting means, and the mode is set to one of the modes depending on whether the jumper wire is connected or the pattern on the printed circuit board is cut. And the control circuit controls the switching element group according to the set mode.

Even with such a configuration, it is needless to say that the indicator lamp can be turned on without deteriorating the output characteristics.
There is also an advantage that the sensor switch of the two modes can be manufactured by using common parts, thereby enabling cost reduction.

(B) In each of the above embodiments, a two-wire sensor switch connected to a DC power supply has been exemplified. However, the present invention is not limited to this.
It may be configured to connect to an AC power supply via a rectifier circuit.

(C) In each embodiment, the case has been described in which the two indicator lamps, the operation indicator lamp 24 and the stability indicator lamp 25, are turned on. However, the present invention is not limited to this, and only one of the indicator lamps is turned on. It may be a configuration to make it.

In addition, the present invention is not limited to the photoelectric switch, but a proximity switch for detecting the approach of a metal object using electromagnetic action, an ultrasonic sensor for measuring an ultrasonic wave, and a pressure measurement. It can be widely applied to target pressure sensor switches and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a circuit diagram showing a first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a block diagram showing a connection state of a transmission type photoelectric switch.

FIG. 5 is a circuit diagram showing a conventional example provided with an indicator light.

FIG. 6 is a circuit diagram showing another conventional example provided with an indicator light.

[Explanation of symbols]

 Reference Signs List 21 output transistor (output switching circuit) 22 detection circuit 24 operation indicator 25 stability indicator 27 first transistor 28 second transistor 29 third transistor 30 control circuit 40 power supply 50 load

Claims (1)

(57) [Scope of request for utility model registration] A detection circuit for comparing a measurement signal level to be measured with a predetermined operation level; and a comparison result of the detection circuit and one of a normally closed mode and a normally open mode set by an operation mode setting means. Opening and closing an output switching circuit connected in series to a power supply and a load according to the operation mode, and opening the output switching circuit that is normally closed in the case of the normally closed mode when the object to be detected is detected. In the case of the normally open mode, the output switching circuit that is normally open is closed when the object is detected, and the object is detected in any of the modes. In a state where the indicator light is turned on in the state, the indicator light is connected in series with A first switching element connected so that a path is parallel to the output switching circuit, a line on the detection circuit side of a connection point to which the indicator light is connected in a power supply path to the detection circuit; Connected in series with the third switching element and a common connection point between the indicator light and the first switching element to form a series circuit with the indicator light, and the series circuit is connected to the third switching element. A switching element group comprising a second switching element connected so as to be in parallel with the element; and providing the switching element group with the first switching element closed so that the indicator lights the output switching circuit. Parallel connection for supplying power to the detection circuit via the third switching element and closing the third switching element. The first and third switching elements are opened and the second switching element is closed and the second switching element is closed, and the indicator lamp is connected in series to a power supply path to the detection circuit, and the first switching element And a control circuit capable of switching between an open state and a closed state in which the third switching element is closed. The control circuit displays the display when the output lamp is turned on while the output switching circuit is on. When the lamp is in the parallel connection state, the indicator lamp is in the series connection state when the indicator lamp is turned on in the state where the output switching circuit is off, and when the indicator lamp is turned off, the extinguishing state is used. A two-wire sensor switch.