JPS62160817A - Proximity switch device - Google Patents

Abstract

PURPOSE:To improve the detection speed by measuring the state of proximity at the frequency sweep period of an oscillation circuit so as to limit a switch response time thereby suppressing the variance in a detection response time. CONSTITUTION:An oscillation circuit 12 supplies an oscillation signal whose amplitude is constant and whose frequency is changed while using a sweep period through the sweeping in response to a start signal, an end signal generated at a prescribed period from a synchronizing signal generating circuit 11 to a BPF 13 using a coil L for proximity body detection as a component. The AC component whose peak value is changed in response to the approach of the proximity object and passing through the BPF 13 is detected by a detection circuit 14 and a voltage in response to the peak value is stored in a capacitor of the circuit 14. The object is detected at each sweep period in response to the approaching distance by the sequential decrease in the peak hold value, the decrease is always detected within the period at the response of the switch, the variance in the detection response time is suppressed and the detection speed is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a proximity switch device for detecting the approach of a nearby object.

[Prior art and its problems]

As shown in FIG. 5, a conventional proximity switch device includes an oscillation circuit 1 equipped with a resonant circuit consisting of a detection coil L and a capacitor C for sensing the approach of a nearby object, and this oscillation circuit 1.
The detection circuit 2 detects the presence or absence or magnitude of the oscillation width and generates an on/off output. When the nearby object is far from the detection coil L, the Q value of the detection coil is high and the oscillation width becomes large, but when the nearby object approaches, the Q value decreases and the high frequency of the detection coil L increases. Since the loss increases, the oscillation width decreases or stops. The detection circuit 2 outputs a signal according to the state of its oscillation width, and detects the presence or absence of the approach of a nearby object.

However, when the detection circuit 2 detects the oscillation width, the energy in the resonant circuit continues to increase and decrease from the time the detection coil LOQ value changes until the oscillation width ends. It takes. In particular, there has been a problem that the time from the oscillation stop state to the start of oscillation is long, resulting in variations in the detection response time of the proximity switch device.

[Summary of the invention]

The present invention has been made in view of the above circumstances, and the synchronous signal generation circuit starts sweeping with a start signal generated at a predetermined period, ends the sweep with an end signal, and the oscillation frequency changes during the sweep. An oscillation circuit is provided that sends out an oscillation signal with a constant oscillation width as the oscillation width changes, and a detection coil that is connected to this oscillation circuit and serves as a detection end for a nearby object is used as a component of a bandpass filter. The alternating current component passing through is detected by a detection circuit, the magnitude of the passing component is detected, and this detection operation is reset with an end signal, and the output circuit detects the passing component. is configured such that the magnitude determination result is sent to the outside in synchronization with the end signal, and each time the excavation frequency of the excavation circuit is swept, the magnitude of the output of the bandpass filter is determined, and the magnitude of the output of the bandpass filter is determined. The purpose of this invention is to determine the presence or absence of a nearby object, output the result from an output circuit, and keep the detection response time of the nearby object within a certain fixed time.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block connection diagram of the proximity switch device of the present invention, in which 11 is a synchronizing signal generation circuit, 12 is a frequency sweep oscillation circuit, 13 is a bandpass filter consisting of a detection coil L and a capacitor C, and 14 is a detection circuit. , 15 are output circuits, and each of these circuits has a concrete configuration shown in FIG. 2, and operates as described below. In Figure 2,
The synchronizing signal generating circuit 11 includes a charging/discharging circuit consisting of a series circuit of a resistor R2 and a capacitor C2, and an analog switch S for resetting the charging voltage v2 of the capacitor C2.
2, and a comparator U2 which inputs the charging voltage v2 of the capacitor C2 to its non-inverting input terminal and inputs the set reference voltage V1 to its inverting input terminal. Here, for later explanation, the output voltage of the comparator U2 will be expressed as 11.

The frequency sweep oscillation circuit 12 includes a charging/discharging circuit consisting of a resistor R1 and a capacitor CI connected in series, an analog switch SL for resetting the charging voltage v5 of the capacitor C1, and a non-inverting input terminal for inputting the charging voltage V3 of the capacitor C1. In addition, a comparator Ul and a comparator U1 input the charging voltage v2 of the capacitor C2 to the inverting input terminal.
It is composed of a JK flip-flop circuit FFI which uses the output voltage v5 as a clock pulse.

The bandpass filter 13 is composed of a detection coil L, a capacitor C5 connected in parallel with the detection coil L, and a resistor R5 connected in series with this parallel circuit, and receives the output v6 of the JK flip-flop circuit FFI. Ru.

The peak hold circuit 14 is composed of a comparator U5 and a diode DI, and an analog switch S5 that resets the charging voltage of the capacitor C11. The output circuit 15 also includes a comparator U1 that compares the charging voltage of the capacitor C11 with a predetermined set reference voltage V7.
1 and a D-type flip-flop circuit FF2, which inputs the output of the comparator U11 to the terminal.

In this configuration, the analog switch S2 is closed when the output VlI of the comparator U2 is at a high level "H", and the analog switch Sl is closed when the output VlI of the comparator U2 is high level "H".
is closed at a high level "H", and the analog switch S5 is closed when the output VI1 of the comparator U2 is at a high level "H".
'', the output vII of the humparator U2 is configured to be input to the clock terminal of the D-type flip-flop circuit FF2.

Next, the operation of the embodiment of the present invention configured as described above will be explained in detail using the time charts of FIGS. 3 and 4.

First, when power is supplied to the synchronizing signal generating circuit 11 and the oscillating circuit 20, the photoelectric voltage 1n2 of the capacitor C2 increases in proportion to time as shown in FIG.

When this charging voltage v2 reaches the set reference voltage v1, the output V+1 of the comparator U2 becomes H". This closes the analog switch S2 and discharges the capacitor C2. This discharge causes the output vl
l becomes a low level "L".

That is, the output v11 becomes a one-shot pulse with a predetermined period. This becomes a synchronization signal, and the charging voltage v2 has a sawtooth lightning voltage waveform.

On the other hand, the capacitor C1 is also charged, and when this charging voltage v5 reaches the voltage v2 as shown in FIG.
The output v5 of the comparator U1 becomes ``H''. As a result, the analog switch S1 closes, the capacitor CI is discharged, and the output v5 returns to the low level ``L'' ◇In other words, the output V5 becomes a one-shot pulse. When the output v5 returns to "L", the analog switch Sl opens (so the capacitor CI starts charging again.Then, as shown in Figure 3, the interval between the one-shot pulses of the output v5 widens. To go.

Next, when the one-shot pulse is input to the clock terminal of the JK flip-flop FFI, its output Vo
Y-flip. Therefore, the oscillation frequency is swept over time like the output v6 in FIG. 3.

On the other hand, for each one-shot pulse of the output V4, the oscillation frequency f changes as shown in FIG. 4. Here,
fl is the resonance frequency of the bandpass filter 13. This band-pass filter 13 receives an alternating current that has the same oscillation amplitude and whose oscillation frequency decreases over time. Here, the AC component passing through the bandpass filter 13 is f
It is maximum at l. As shown in FIG. 4, the magnitude of this passing component is large when the nearby object is not approaching, and becomes small when the nearby object is approaching.

Next, the peak hold circuit 14 applies the maximum passing voltage (at fl>) to the capacitor C11 during the frequency sweep.
The capacitor C11 is charged by 1ft, and the charge in the capacitor C11 is reset by closing the analog switch S5 by the pulse of the output v11, and the capacitor C11 is charged while the maximum value for each frequency sweep is updated. Then, the comparator UII compares the charging voltage of the capacitor CI+ with v7, and when there is no neighbor, K is
The output of comparator U4 becomes "H". The D-type flip-flop FF2 outputs a one-shot pulse of the output v11 to the Q terminal, which is the voltage input to the D terminal.

Therefore, when there is no nearby body, the output of the comparator U11 is "H", and 'H' is outputted to the Q terminal.

Regarding the detection circuit 14, in addition to the peak hold method, there is also a method of extracting the amplitude change of the signal after passing through the band pass filter 13 using AM detection, comparing it with a reference voltage using a comparator, and calculating d. Can be adopted.

[Effects of the present invention]

As explained above, according to the present invention, since the approach of a nearby object is configured to be measured using the frequency sweep period of the oscillation circuit, the switch response time is always within this period, and the detection response time is In addition to suppressing variations in the detection speed and increasing the detection speed, it is also possible to extract an amplitude signal according to the distance to the nearby object, making it possible to use it as a distance meter.

[Brief explanation of drawings]

FIG. 1 is a block connection diagram of the proximity switch device of the present invention,
2 is a detailed circuit diagram, FIGS. 3 and 4 are time charts of signals of various parts of the circuit shown in FIG. 2, and FIG. 5 is a block connection diagram of a conventional proximity switch device. 11... Synchronization signal generation circuit, 12... Frequency sweep oscillation circuit, 13... Band pass filter, 14...
・Detection circuit, 15...output circuit. Patent applicant: Yamatake Honeywell Co., Ltd. (2 others) Figure 4: 111111111

Claims (1)

[Claims] A synchronization signal generation circuit, the synchronization signal generation circuit starts the sweep with a start signal generated at a predetermined period, and ends the sweep with an end signal, and the oscillation frequency changes during the sweep and the oscillation width remains constant. An oscillation circuit that sends out an oscillation signal, a bandpass filter that is connected to this oscillation circuit and has a detection coil that serves as a detection end for nearby objects, and an alternating current that is connected to this bandpass filter and passes through this bandpass filter. Detects the component and detects the magnitude of the passed component, and also connects to a detection circuit that is reset by the above-mentioned termination signal and which is connected to this detection circuit and determines the magnitude of the passed component detected by this detection circuit. A proximity switch device consisting of an output circuit that sends out the size determination result to the outside in synchronization with the end signal.