JPH0741075Y2 - Detection switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a detection switch used for detecting the piston position of a fluid pressure cylinder.

[Conventional technology]

Conventionally, a fluid pressure cylinder such as a hydraulic cylinder or a pneumatic cylinder is provided with a detection switch for detecting the stroke position of the piston.

A conventional detection switch is composed of a reed switch operated by a magnetic field of a permanent magnet attached to a piston, and a light emitting diode for on-operation display connected in series to the reed switch, and when the reed switch is turned on, A current flows through the light emitting diode through the power supply and the load connected in series to the detection switch, and it is displayed that the detection switch is in the ON state.

[Problems to be solved by the device]

However, since the light emitting diode provided in the conventional detection switch is turned on or off depending on the operating state of the detection switch, when the light emitting diode is turned on, it is connected to the detection switch together with its operating state. It can be assumed that various environmental conditions related to the operation of the detection switch are normal, such as that the power supply is normal and the lead wire of the detection switch is not broken, but when the light emitting diode is off. It is impossible to determine whether the light has been turned off due to the normal operation of the detection switch or has been turned off due to some abnormality such as power failure or disconnection.

In particular, the detection switch used to detect the stroke position of a fluid pressure cylinder is susceptible to vibration due to the operation of the fluid pressure cylinder, bending of the lead wire, pulling, etc. It took a lot of time and effort to discover.

In view of the above problems, the present invention provides a detection switch that can display a state other than the normal detection operation state of the detection switch, such as a disconnection of a lead wire or a power failure, so that a failure can be easily detected. It is an object.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, a detection switch according to the present invention includes a detection sensor that performs an on / off operation when an object is approached, an on-display light emitting diode that indicates that the detection sensor is turned on, and the detection sensor. And an off display light emitting diode for displaying that it has been turned off,
The ON display light emitting diode is connected in series with the detection sensor to form a first series body, and the OFF display light emitting diode is a voltage for decreasing the voltage applied to the OFF display light emitting diode. The first series body and the second series body are connected to each other in series to form a second series body.
A series body is connected in parallel.

[Action]

When the detection sensor is turned on, a current flows through the on-display light emitting diode connected in series with the detection sensor to perform light emission display.

At this time, the voltage is also applied to the second series body, but the voltage applied to the off-display light emitting diode is reduced by the voltage drop element, so that the current flowing through the off-display light emitting diode becomes almost zero and the off-display light emitting diode is turned off. No light emitting display is performed by the light emitting diode.

When the detection sensor is turned off, a current flows through the off display light emitting diode connected in parallel with the detection sensor to perform light emission display.

When the state of the power supply or the lead wire is abnormal or malfunctions, neither the ON display light emitting diode nor the OFF display light emitting diode emits light.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a detection switch 1 according to the present invention.

The detection switch 1 includes a reed switch 11 which is turned on by a magnetic field having a certain strength or more, a red light emitting on-display light emitting diode 12 which indicates that the reed switch 11 is turned on,
It has a green light-emitting off-display light emitting diode 13 for indicating that the reed switch 11 is off.

The on-display light-emitting diode 12 is connected in series with the reed switch 11 to form the first series body 3, and the off-display light-emitting diode 13 includes the diode 14 and the constant current diode 15.
Is connected in series to form a second series body 4,
The series body 3 and the second series body 4 are connected in parallel, and both ends thereof are terminals 5 and 6.

The diode 14 operates as a voltage drop element for dropping the voltage applied to the on-display light emitting diode 12. That is, the diode 14 utilizes these forward voltage drops together with the off-display light emitting diode 13, and acts so as to allow an extremely small current to flow through the second series body 4 unless a voltage higher than a certain level is applied.

The constant current diode 15 is also generally called “CRD”,
This is for limiting the current flowing in the off display light emitting diode 13. The constant current diode 15 also functions as a voltage drop element for dropping the voltage applied to the on-display light emitting diode 12, like the diode 14 described above.

Next, the operation of the detection switch 1 configured as described above will be described.

Various appropriate loads and power supplies such as a relay, a logic gate element, an input interface circuit of a computer, and an input circuit of a sequencer are connected between the terminals 5 and 6.

When the reed switch 11 is off, no current flows through the first series body 3 so that the on-display light emitting diode 12 does not emit light, and a current flows through the second series body 4 and the off display light emitting diode 13 emits light. To do.

As a result, it is displayed that the reed switch 11 is off.

The reed switch 11 is driven by a magnetic field such as a permanent magnet.
When is turned on, a current flows through the first series body 3, and the on-display light emitting diode 12 emits light. Along with this, the voltage across the first series body 3, that is, the voltage across the second series body 4 drops to about 1 volt, so that the current flowing through the second series body 4 becomes almost zero, and the current is off. The light emission of the display light emitting diode 13 stops.

As a result, it is displayed that the reed switch 11 is on.

Further, when the power supply is cut off, or when the lead wires connected to the terminals 5 and 6 are broken, for example, no current flows in the light emitting diode 12 for ON display and the light emitting diode 13 for OFF display. Does not emit light. Therefore, since neither the on-display light-emitting diode 12 nor the off-display light-emitting diode 13 emits light, it is displayed that some failure or abnormality such as power failure or disconnection has occurred.

Therefore, by accommodating the detection switch 1 in a small case, mounting it on the outer peripheral surface of the cylinder tube of the fluid pressure cylinder, and adjusting the magnetic field of the permanent magnet mounted on the piston to perform on / off operation,
It can be used to detect the stroke position of the piston.

In that case, when the lead wire connected to the detection switch 1 is broken due to vibration caused by the operation of the fluid pressure cylinder, neither the on-display light emitting diode 12 nor the off-display light emitting diode 13 is turned on. With this, it is possible to easily detect the disconnection.

FIG. 2 is a circuit diagram of a detection switch 1a according to another embodiment of the present invention.

In this detection switch 1a, two ON display light emitting diodes 12 are connected in parallel in opposite directions. Whereas the above detection switch 1 is for a DC power supply, this detection switch 1a is for an AC power supply.

In the above-described embodiment, since the current flowing through the second series body 4 when the reed switch 11 is turned off becomes a leakage current,
This is preferably as small as possible. From this point of view, it is better to use a high-luminance red light emitting diode as the off-display light-emitting diode 13 and a low-luminance green light-emitting diode as the on-display light-emitting diode 12. In addition, emission colors other than these may be used. It may have the same emission color. In that case, the ON state or the OFF state may be displayed by the position of emitting light, a symbol, a code, or the like. The on-display light emitting diode 12 and the off-display light emitting diode 13 may be enclosed in one element.

In the above-described embodiment, the reed switch 11 may be replaced with a magnetic sensor such as a magnetoresistive element or a Hall element, or another detection sensor. The diode 14 may be omitted depending on the voltage used and the rating of the parts used. A resistor may be used instead of or together with the diode 14 and the constant current diode 15. In the case of an AC power supply, it is possible to use a capacitor or a coil. Instead of the terminals 5 and 6, lead wires may be integrally connected.

In addition, the circuit, structure, type and number of parts used, etc. of the detection switches 1 and 1a can be variously changed other than those described above.

[Effect of device]

According to the present invention, it is possible to provide a detection switch that can display a state other than the normal detection operation state by the detection switch, such as a disconnection of a lead wire or a power failure, and can easily find a failure.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a detection switch according to the present invention, and FIG. 2 is a circuit diagram of a detection switch according to another embodiment of the present invention. 1, 1a ... Detection switch, 3 ... First series body, 4 ... Second series body, 11 ... Reed switch (detection sensor), 12 ... On display light emitting diode, 13 ... Off display light emitting diode,
14 ... Diode (voltage drop element), 15 ... Constant current diode (voltage drop element).

Claims (1)

[Scope of utility model registration request] 1. A detection sensor for performing an on / off operation when a detection object approaches, an on-display light emitting diode for indicating that the detection sensor is on, and an off-display light emitting diode for indicating that the detection sensor is off. And the on-display light-emitting diode is connected in series with the detection sensor to form a first series body, and the off-display light-emitting diode supplies a voltage applied to the off-display light-emitting diode. A detection switch comprising a second series body connected in series with a voltage lowering element for lowering the voltage, and the first series body and the second series body being connected in parallel.