JPH062121Y2 - Infrared detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an infrared detector for detecting incident infrared rays, which is provided with a chopper mechanism for periodically interrupting incident infrared rays with respect to a pyroelectric infrared element. .

(B) Prior art The applicant has already been aiming to reduce the size of the infrared detector.
An infrared detector shown in FIGS. 4 to 6 is being developed.

This infrared detector 10 is a core 1 in which a coil 11 is wound.
2. A rotor 14 formed of a permanent magnet is interposed in a magnetic circuit formed by the stators 13 and 13 connected to both ends of the core 12, and the rotor 14 is fixed by a fixed base 15 and a bearing member 16 to a shaft. The vane plate 17 is fixed to the rotor 14 while being supported, and the coil 11 is connected to an oscillation circuit (not shown) so that the vane plate 17 swings.
Pyroelectric infrared device 18 mounted on the fixed base 15 by swinging 7
The chopper mechanism 19 is configured to periodically interrupt the incidence of infrared rays on the.

As described above, the chopper mechanism 1 is moved by swinging the blade plate 17.
9, the infrared detector 10 can be downsized, but since the blade 17 is mechanically oscillated,
Since there is a risk of malfunction due to deterioration of the bearing portion due to long-term use or excessive impact from the outside, in order to obtain a more accurate detection signal as a detector, it is necessary to determine whether the blade plate 17 is operating normally. That is, the chopper mechanism 1
It is preferable to check whether 9 is operating normally and output an NG signal when it malfunctions.

(C) Problems to be Solved by the Invention However, the above-mentioned chopper mechanism 19, that is, the blade plate 1
For example, if the photoelectric sensor is used to detect the blade plate 17 in order to check the swing of the infrared ray detector 7, the configuration of the infrared detector 10 becomes large because the photoelectric sensor is incorporated, and the original purpose of downsizing is impaired. It causes a problem that

Therefore, an object of the present invention is to provide an infrared detector capable of checking the operation of the chopper mechanism without impairing the purpose of downsizing.

(D) Means for Solving the Problems This invention includes a pyroelectric infrared element, a chopper mechanism for connecting and disconnecting infrared rays incident on the pyroelectric infrared element, and an oscillation circuit for driving the chopper mechanism. An infrared detector, which compares an oscillation output cycle of the oscillation circuit with an output cycle of the pyroelectric infrared element and detects an abnormal operation of the chopper mechanism from a deviation of a predetermined amount of the cycle. Is an infrared detector provided with.

(E) Action The infrared detector of the present invention compares the output cycle of the oscillation circuit that drives the chopper mechanism with the output cycle of the pyroelectric infrared element in which infrared rays are interrupted by the chopper mechanism, by comparing means.
If there is no deviation of a predetermined amount in that cycle, it is determined to be normal operation,
If there is a deviation, it is determined as abnormal operation.

(F) Effects of the invention According to the above results, according to the invention, the operation of the chopper mechanism can be checked without directly detecting the chopper mechanism with the detector such as the photoelectric sensor, and the miniaturization of the infrared detector can be maintained. In this state, a detection signal with higher reliability can be obtained.

(G) Embodiment of the Invention One embodiment of the invention will be described in detail below with reference to the drawings.

FIG. 2 shows the infrared detector 1 shown in FIGS. 4 to 6 described above.
The chopper drive circuit which drives the coil 11 of the chopper mechanism 19 of 0 shows the intermediate point of resistance R1 and R2 connected in series, and the transistor Tr1, Tr2 connected in series.
By connecting both ends of the coil 11 to an intermediate point between and, and switching the transistors Tr1 and Tr2 alternately by the output of the oscillation circuit 20, the direction of the current flowing through the coil 11 is switched alternately to change the direction of the magnetic force. By alternately switching, the blade plate 17 shown in FIGS. 4 to 6 is swung.

FIG. 3 shows the relationship between the output of the oscillation circuit 20 described above, the open / closed state of the blade 17 of the chopper mechanism 19 that is opened / closed by the output, and the output of the pyroelectric infrared element 18 described above. Is normally operating by driving the oscillation circuit 20, the cycle of the oscillation output of the oscillation circuit and the output cycle of the pyroelectric infrared element 18 are synchronized,
However, if the chopper mechanism 19 does not operate normally,
Pyroelectric infrared device 1 synchronized with the driving of the chopper mechanism 19
The output cycle of No. 8 naturally deviates from the oscillation output cycle of the oscillation circuit 20.

Therefore, in order to check whether the chopper mechanism 19 is operating normally, the cycle of the oscillation output of the oscillation circuit 20 is compared with the output cycle of the pyroelectric infrared element 18, and the respective cycles are synchronized. It may be determined whether or not there is.

FIG. 1 shows the above-mentioned determination circuit, and the oscillation output of the oscillation circuit 20 is input to the chopper drive circuit 21 described in FIG. 2, and the circuit 21 drives the chopper mechanism 19 at the oscillation cycle of the oscillation circuit 20. To do.

The output signal of the pyroelectric infrared element 18 is converted into a rectangular wave by the comparator 22 and input to the comparator 23.

The oscillating output of the oscillating circuit 20 described above is input to the comparator 23, and the oscillating output is compared with the output of the pyroelectric infrared element 18 to determine the difference between the cycles of the two.

If the comparator 23 judges the deviation of the cycle of a predetermined amount or more, it outputs the judgment signal to the NG signal generating circuit 24 and outputs the NG signal, that is, a signal indicating that the chopper mechanism 19 is not operating normally. Is output.

Therefore, the abnormal operation of the chopper mechanism 19 can be detected by the output of this NG signal.

In the configuration of the present invention, the comparison means corresponds to the comparator 23 of the above-mentioned embodiment, but the present invention is not limited to the configuration of the embodiment.

[Brief description of drawings]

 FIG. 1 shows an embodiment of the present invention, FIG. 1 is a circuit diagram for determining an output cycle, FIG. 2 is a chopper drive circuit diagram, FIG. 3 is a waveform diagram of each element, and FIG. Fig. 5 is a front view thereof, and Fig. 6 is a side view thereof. 10 ... Infrared detector 18 ... Pyroelectric infrared element 19 ... Chopper mechanism 20 ... Oscillation circuit 23 ... Comparator

Claims (1)

[Scope of utility model registration request] 1. An infrared detector comprising a pyroelectric infrared device, a chopper mechanism for connecting and disconnecting infrared rays incident on the pyroelectric infrared device, and an oscillating circuit for driving the chopper mechanism. Infrared detection, characterized in that a comparison means is provided for comparing the cycle of the oscillating output with the cycle of the output of the pyroelectric infrared element and detecting an abnormal operation of the chopper mechanism from the deviation of a predetermined amount of the cycle. vessel.