JPH0342390Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a fail-safe receiving circuit suitable for a photoelectric obstacle detection device applied to, for example, a safety device.

<Prior Art> For example, an obstacle detection device using a spatial propagation medium such as light is used to remotely detect the presence or absence of an obstacle at a railroad crossing or the like. In this obstacle detection device, a transmitting section and a receiving section are arranged around a detection area, and a spatial propagation signal such as light emitted from the transmitting section crosses the detection area and reaches the receiving section. Do it like this. If some obstacle enters the detection area, the obstacle blocks the propagation path of the spatially propagated signal and prevents it from reaching the receiving section. Therefore, by continuing to send a spatially propagated signal from the transmitting section and monitoring the reception output of the receiving section, it becomes possible to remotely detect obstacles at, for example, a railroad crossing. Furthermore, by feeding the output of the receiver to a drive device such as a relay, it becomes possible to take safety measures, such as stopping the train if there is an obstacle such as a car at a railroad crossing. .

<Problems to be Solved by the Invention> However, in order to use the above-described obstacle detection device at railroad crossings, for example, the following problems must be overcome.

In other words, obstacle detection devices used in places where a high degree of safety is required, such as at railroad crossings, have extremely high reliability of operation, but furthermore, even if a failure occurs, A so-called fail-safe function must be provided to ensure that the consequences of a failure are always guided in a safe direction.

Conventionally, there has been a demand for devices of this type, especially for the receiving circuit on the receiving section side, to have reliable fail-safe properties.

SUMMARY OF THE INVENTION In view of the conventional situation, it is an object of the present invention to provide a receiving circuit that has a reliable fail-safe function and thereby enables an obstacle detection device with extremely high reliability.

<Means for Solving the Problems> As a means for solving the above-mentioned problems, the present invention provides a sensor that receives an intermittently transmitted pulse-like spatial propagation signal, and an amplifier that amplifies the output of this sensor. an integrating circuit that time-integrates the output of this amplifier circuit, and a Schmitt circuit that generates a detection output when the output of this integrating circuit exceeds a predetermined level, and the integrating circuit is charged and discharged by a four-terminal capacitor. The capacitor is configured with a circuit to provide a predetermined charging/discharging time constant, and a diode is inserted in series in the forward direction in the charging path of the capacitor.

<Function> With the above means, first, by selecting the time constant during charging of the integrating circuit, high frequency noise can be removed, and by selecting the time constant during discharging, the above-mentioned The reduced pulse width of the detected signal can be extended to a predetermined width by noise filtering, thereby ensuring sufficient detection output energy to operate a drive device such as a relay when the signal is detected. I try to do that.

Further, for example, if the diode is disconnected or short-circuited, in either case, the detection output will be in a safe direction, that is, in this case, the detection output will be zero or small, and will become an output corresponding to the obstacle detection state.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described based on the drawings. In the figures, the same reference numerals indicate the same or corresponding parts.

FIG. 1 shows the configuration of an obstacle detection device to which a receiving circuit according to the present invention is applied.

The obstacle detection device shown in the figure is of a photoelectric type and uses light as a space propagation signal medium. It consists of this obstacle detection device, a transmitting section 1, and a receiving section 2.

The transmitter 1 includes a pulse signal generator 11, a drive circuit 12, and a light projector 13, and transmits an output Vx that generates optical pulses of a predetermined width at regular intervals toward the receiver 2. The transmitter 1 and the receiver 2 are
They are arranged so as to face each other, sandwiching a detection area into which an obstacle 4 may enter.

The main part of the receiving section 2 is constituted by a receiving circuit according to the present invention.

This receiving section 2 includes a sensor section 21 that senses pulsed optical signals that are intermittently transmitted from the transmitting section 1.
an amplifying circuit 22 using, for example, an operational amplifier, which amplifies the output of this sensor section 21; and an integrating circuit 23 which integrates the output Vp of this amplifying circuit 22 over time.
a receiving circuit comprising a Schmitt circuit 24 that performs level verification of the output Vi of the integrating circuit 23;
A smoothing circuit 25 is provided for averaging the level of the detection output Vs of the Schmitt circuit 24 over time. The output Vo of this smoothing circuit 25 drives a drive device 3 such as a relay. Note that Vcc indicates the power supply for operation.

Here, the integration circuit 23 is constituted by a charging/discharging circuit using a four-terminal capacitor C1.
A diode D1 is inserted in series in the forward direction in the charging path of the capacitor C1. In this case, the time constant during charging is determined by the resistor Rp inserted in series with the diode D1, and the time constant during discharging is determined by the input resistance Ri (represented by the broken line in the figure) of the Schmitt circuit 24. Therefore, they are set individually.

Note that the resistor R1 is a leakage resistor, and has a relationship of R1>Ri with respect to the input resistor Ri of the Schmitt circuit 24.

The Schmitt circuit 24 is used as a level discrimination circuit, and its output is activated and assumes a high level only when its input level exceeds a predetermined threshold value Vth. This Schmitt circuit 24 consists of transistors Q1, Q2 and a resistor R.
2, R3, R4, R5, R6, etc. The detection output Vs of this Schmitt circuit 24 is
The signal is sent to the smoothing circuit 25 via the coupling capacitor C3.

The smoothing circuit 25 converts the detection output Vs of the Schmitt circuit 24 into direct current using diodes D2 and D3, and then smoothes it using a capacitor C2. As a result, a direct current output Vo corresponding to the active state duration of the detection output Vs of the Schmitt circuit 24 is obtained. This DC output Vo drives a drive device 3 such as a relay. The capacitor C2 used here is also of the four-terminal type described above.

FIG. 2 shows an example of operating waveforms in each part of the apparatus shown in FIG. 1 in a time-corresponding manner.

In FIGS. 1 and 2, if there is no obstacle 4 between the transmitter 1 and the receiver 2,
Manual force to generate a light pulse of a predetermined time width from the transmitter 1
Every time Vx is transmitted, the sensor section 21 receives it, and the amplification circuit 22 outputs its amplified output Vp. When the output Vp of the amplifier circuit 22 rises, the level of the output Vi of the integrating circuit 23 gradually increases at a constant rate over time. Thereafter, when the output Vp of the amplifier circuit 22 rises, the output Vi of the integrating circuit 23 gradually decreases at a constant rate.

Here, the output Vi level of the integrator circuit 2 is determined by the Schmitt circuit 24 after a certain delay time τ ₀ has passed since the output Vp of the amplifier circuit 22 has risen.
exceeds the input threshold Vth. At this point, the output Vs of the Schmitt circuit 24 becomes active and rises to a high level. At this time, the rise delay time τ ₀ depends on the charging constant set by the resistor Rp. Therefore, by appropriately selecting the value of the resistor Rp, it is possible to selectively remove the noise Vn having a pulse width less than a predetermined time width, that is, τ ₀ .

The output Vi level of the integrating circuit 23 is the above threshold
When Vth is exceeded, the output Vp of the amplifier circuit 22 falls from a high level to a low level after some remaining time τ ₁ has passed. At this time, the output Vi level of the integrating circuit 23 gradually decreases at a constant rate. The active state, that is, the high level state of the detection output Vp of the Schmitt circuit 24 is maintained until the output level Vi becomes lower than a predetermined threshold value Vth. At this time, the fall delay time τ _Z from when the output Vp of the amplifier circuit 22 falls until the detection output Vs of the Schmitt circuit 24 falls is
depends on the discharge time constant determined by the input resistance Ri. Therefore, by appropriately designing the input resistance Ri, the output of the Schmitt circuit 24 can be
It becomes possible to extend the pulse width of Vi over a certain period of time, that is, the fall delay time τ ₂ or more. This allows the pulse width w to be reduced to τ ₁ for filtering against high frequency noise.
It can be extended to (τ ₁ +τ ₂ ).

As a result, the output Vo of the smoothing circuit 25 is almost at zero level when the output Vx from the transmitter 1 is not detected (there is an obstacle), while it is at the above-mentioned level when it is detected (no obstacle). By extending the pulse width by the fall delay time τ ₂ , a high level close to the saturation level can always be obtained reliably. In this case, if there is no obstacle 4 between the transmitting section 1 and the receiving section 2, the output of the Schmitt circuit 24
Vs has a pulse width greater than a predetermined value, and the smoothing circuit 25
The output Vo takes a high level state, and takes a low level state when there is an obstacle 4.

As described above, by selecting the time constant during charging of the integrating circuit 23, it is possible to remove pulse noise Vn that is less than a predetermined width, and
By selecting the time constant during discharge, the pulse width of the detected signal can be extended beyond a predetermined length. Thereby, sufficient output energy to operate the relay etc. can be secured.

Note that the noise Vn to be removed includes not only noise contained in the received signal but also noise caused by abnormal oscillation of the amplifier circuit 22 and the like.

Furthermore, in the circuit described above, if the integrating circuit 2
If a short circuit occurs in the diode D1 inserted on the charging side of the capacitor C1, in addition to the input resistance Ri of the Schmitt circuit 24, the charging side resistance Rp will also be connected to the capacitor C1.
, and the discharge time constant decreases significantly. As a result, the fall delay time τ ₂ is short-circuited, the output pulse width of the Schmitt circuit 24 is reduced, and the level of the output Vo of the smoothing circuit 25 is significantly reduced. In other words, a failsafe is performed such that the output Vo is in the same state as when the obstacle 4 is detected.

On the other hand, if a disconnection failure occurs in the diode D1, the capacitor C1 will not be charged, so the output Vi level of the integrating circuit 23 will not be able to exceed the input threshold Vth of the Schmitt circuit 24. Therefore, in this case as well, a failsafe is performed in which the output Vo goes into the obstacle detection state.

Furthermore, by using four-terminal type capacitor C1 of the integrating circuit 23 and capacitor C2 of the smoothing circuit 25, the capacitor C1,
Even when a disconnection failure occurs in C2 as well as a short-circuit failure, fail-safe operation is performed such that the output Vo becomes an obstacle detection state.

FIG. 3 shows the main parts of another embodiment of the present invention.

In the embodiment described above, the output Vp of the amplifier circuit 22
is given directly to the integrating circuit 23, but it may also be given via a waveform shaping circuit 26, as partially shown in FIG. The waveform shaping circuit 26 can be easily constructed using a transistor Q3, a resistor R7, and a capacitor C4. FIG. 4 shows an example of the operation of the waveform shaping circuit 26. In the same figure, Vp
indicates the output of the amplifier circuit 22, and Vp' indicates the output obtained by waveform shaping the output Vp. By performing waveform shaping in this manner, level fluctuations in the output Vp of the amplifier circuit 22, etc. can be suppressed, thereby making the above-described detection operation more reliable.

Although some embodiments of the present invention have been shown above, the present invention is not limited to the above embodiments, and may be configured to use, for example, a sound wave or the like as a spatially propagated signal.

<Effects of the invention> As described above, the receiving circuit according to the invention includes a sensor section that senses a spatially propagated signal, an amplifier circuit that amplifies the output of this sensor section, and an integration circuit that integrates the output of this amplifier circuit over time. and a Schmitt circuit that detects the level of the output of this integrating circuit.The integrating circuit is configured with a charging/discharging circuit using a 4-terminal capacitor to perform high frequency noise filtering and pulse width amplification. By inserting a diode in series in the forward direction in the charging path, there is less risk of malfunction, and a fail-safe function is provided to ensure safe operation in the event of a failure. The effect is that it is possible to construct an obstacle detection device etc. equipped with the following.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of the configuration of an obstacle detection device using one embodiment of the receiving circuit according to the present invention, and FIG.
The figure is a waveform chart showing an example of the operation of the circuit shown in Fig. 1, Fig. 3 is a circuit diagram partially showing another embodiment of the receiving circuit according to the present invention, and Fig. 4 is the part shown in Fig. 3. This is a waveform chart showing an example of the operation. DESCRIPTION OF SYMBOLS 1... Transmission part, 2... Receiving part, 3... Drive device, 21... Sensor part, 22... Amplification circuit, 23
...Integrator circuit, 24...Schmitt circuit, Rp...
...Resistor that determines the charging time constant, Ri...Resistor that determines the discharge time constant, D1...Diode.

Claims (1)

[Scope of utility model registration request] A receiving circuit that senses a pulse-like spatial propagation signal that is intermittently transmitted and emits a detection output of a certain level or higher, comprising: a sensor section that senses the spatial propagation signal; and an amplifier circuit that amplifies the output of the sensor section. , comprising an integrating circuit that time-integrates the output of the amplifier circuit, and a Schmitt circuit that generates a detection output when the output level of the integrating circuit is equal to or higher than a predetermined value, and the integrating circuit is connected to a discharge circuit using a four-terminal capacitor. 1. A receiving circuit characterized in that a diode is inserted in series in a forward direction in a charging path of a four-terminal capacitor of said integrating circuit.