JPH029692B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fluid flow rate detection device that outputs a signal proportional to a fluid flow rate and generates an on/off signal by comparing the signal with a set flow rate.

Configuration of conventional example and its problems As shown in FIG. 1, this type of conventional flow rate detection device has a blade wheel 2 that rotates in response to a fluid flow in a flow path 1, and a magnet 3 attached to the blade wheel 2. A magnetic detection element 4 detects the movement of the magnet 3 from outside the flow path 1, the obtained frequency signal is converted into a DC voltage signal by an F/V conversion circuit 5, and the signal is converted to a DC voltage signal by a voltage comparator 6. It was configured to obtain an output signal by comparing it with a set voltage. In this configuration, the F/V converter has an input frequency pulse integration circuit and a low-pass filter circuit, and is proportional to the input frequency, and requires a time constant several times the input pulse period or more to obtain a stable DC output voltage. It is. Therefore, when comparing the set flow rate with a low flow rate, there is a problem that the response speed is slow because the frequency of the input pulse is low.

When the on/off output of this flow rate detection device is used, for example, as a gas supply control signal for a gas water heater, problems such as increased after-boiling and slow start-up occur due to the delayed response.

Purpose of the invention The present invention solves such conventional problems,
It obtains a signal proportional to the flow rate and also obtains an on/off signal to detect the magnitude of the flow rate compared to the set flow rate without any time delay.The purpose is to improve responsiveness especially at low flow rate settings.

Structure of the Invention In order to achieve this object, the present invention includes a detection section that is provided in a fluid passage and generates a pulse signal with a frequency proportional to the flow rate of the fluid, and a detection section that is activated by the output signal of the detection section for a set time. a timer circuit that outputs a signal that turns on and can be retriggered; the output signal of the timer circuit is connected to a data input terminal; the output signal of the detection unit is connected to the trigger input terminal; and the output signal of the detection section is synchronized with the signal of the trigger input terminal. a data storage circuit that stores and holds the signal of the data input terminal and outputs it to its output terminal; and an AND circuit that calculates a logical product of the output of the data storage circuit and the output of the timer circuit; The output signal is used as a control output signal to an external device.

With this configuration, the flow rate is generated from the flow rate off state, a pulse is output from the detection unit, and the timer and data storage circuit are both off, and when the first signal pulse is input from the detection unit, the timer is activated and turned on. Therefore, the data storage circuit stores the signal immediately before the timer turns on and remains off. After that, when a second signal pulse is input at a shorter period than the timer setting time, the timer output remains on, so the data storage circuit stores it and turns on. At this point, both inputs of the AND circuit are turned on, and the output terminal is turned on, detecting that the flow is flowing. Furthermore, when the second signal pulse is input after the timer setting time has elapsed, the timer output is already off, and the data storage circuit remains off, just like when the first pulse was input, and the AND circuit The output continues to be off.

On the other hand, if the flow rate pulse period becomes longer than the timer setting time or the flow rate pulse stops while flow rate detection is on, the timer output will turn off at the timer setting time from the previous pulse input, and the data will be The output of the memory circuit remains on, but since one input signal of the AND circuit is turned off, its output signal is turned off, and the flow rate detection output is turned off at this point. The data storage circuit remains on after that, but when a subsequent signal pulse is input, it remembers that the timer output is off and is reset, returning to its original state.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 2 and 3. Note that parts in the figure that are the same as those in FIG. 1 are given the same numbers.

In FIG. 2, a detection unit 1 provided in a flow path 1
0 is configured such that a magnetic detection element 4 detects the movement of a magnet 3 fixed to a blade wheel 2 that rotates in response to a flow of fluid, and outputs a pulse signal with a frequency proportional to the flow rate. This signal is used for flow rate display, control, etc. as a signal proportional to the flow rate.The output signal of the detection unit 10 is shaped into a positive polarity constant pulse width signal by the waveform shaping circuit 11.
3 and the trigger input terminal 15 of the data storage circuit 14. The output terminal 16 of the timer circuit 12 is connected to the data input terminal 17 of the data storage circuit 14.
It is connected to one input terminal of the AND circuit 18.
The other input terminal of the AND circuit 18 is connected to the output terminal 19 of the data storage circuit 14, and an output signal is obtained at the output terminal 20 of the AND circuit 18. The timer circuit 12 has a set time adjustment VR 21 and a capacitor 22, which constitute a set time adjustment means.
It is triggered by the falling edge of the pulse at the input terminal 13 and turns on the output terminal 16 for a set time. If the next pulse is input within the set time, it will be re-triggered,
The output terminal is kept on again for the set time. The data storage circuit 14 stores the signal at the data input terminal 17 in synchronization with the rise of the pulse at the trigger input terminal, and holds it at the output terminal 19. Here, for ease of explanation, the waveform shaping circuit 11 is
data storage circuit 14 at the rising edge of the output signal of
, and the timer circuit 12 is started at the falling edge after a slight delay. Even if you configure it to connect and start at the same time,
The input signal 17 of the data input circuit 14 is the output signal 16 of the timer circuit 12, and the state of the output signal 16 is turned on as a result of activation by the input pulse, and the data 17 stored in the data storage circuit 14 is as follows. This is a signal before the output 16 of the timer circuit 12 changes due to the input pulse, and its context remains unchanged, and the waveform shaping circuit 11 is not essential in the configuration of the present invention.

In FIG. 3, a is the output signal waveform of the waveform shaping circuit, b is the signal waveform of the output terminal 16 of the timer circuit, c is the signal waveform of the output terminal 19 of the data storage circuit, and d is the signal waveform of the output terminal 20 of the AND circuit. It is. When the detection unit 10 detects the flow and the first input pulse is generated at t1, the data of b is held in c at the rising edge of the first input pulse, and c continues to be off. At the falling edge t2 of the input pulse, the timer is activated and b turns on, but at this time c is off, so the output d of the AND circuit remains off. After that, when the second input pulse occurs at t2, the timer set time T
Since this time has not been reached, the "on" signal of the timer is stored in c. At this point, both b and c are turned on, so the output signal d of the AND circuit is also turned on. At the falling edge t2' of the second input pulse, the timer is re-triggered and from this point on it remains on again for the set time. When the next input pulse enters at t3, the output b of the timer has not reached the set time T, so the output of b is stored in the data storage circuit again, c continues to be on, and the output d of the AND circuit is turned on. Continue.

Next, the flow rate flowing through the flow path decreases, the period of the input pulse becomes longer, and when the timer set time T elapses before the next input pulse enters at t4, the output b of the timer turns off at this point, and one side of the AND circuit Since the input of is turned off, its output d is turned off, detecting that the flow rate of flow path 1 has become below the set value, and transmitting it to the external device. Even when the next input pulse comes in at t5, the output b of the timer is already off, so the data storage circuit stores OFF and the output d is also turned off, returning to the same state as the initial t1. Furthermore, t3
After that, if the flow rate stops and there are no further input pulses, the state shown at t4 in the same figure will continue, and the output c of the data storage circuit will continue to be on, but at the time of t4. The output b of the timer turns off at , and since there is no input pulse to start the timer, the output b continues to be off. Therefore, the output d of the AND circuit turns off at time t4 and will not turn on thereafter unless an input pulse occurs.

Here, the set time T of the timer circuit 12 corresponds to the input pulse period corresponding to the set flow rate.

As a result of the above operation, the determination of whether the flow rate is large or small relative to the set flow rate is performed using one period of the input pulse when determining the flow rate to be on, and within the period of the timer that corresponds to the pulse period of the set flow rate when determining the flow rate to be off. The detection is performed quickly in a minimum amount of time, and even when the flow rate is stopped, the detection output can be reliably turned off within the timer setting. Also, by changing the setting time T with the setting time adjustment VR21,
You can change the flow rate setting for detection.

Effects of the Invention As described above, the flow rate detection device of the present invention provides the following effects.

(1) A timer circuit that outputs a signal that is activated by the pulse signal of the detector and remains on for a set time and can be retriggered, and a data storage that stores and retains the output signal of the timer circuit in synchronization with the pulse signal of the detector. Since it is configured with a circuit, the magnitude of the flow rate can be determined within the timer setting time corresponding to the detection setting flow rate, and the flow rate can be detected with little time delay.

Furthermore, in the case of a rapid increase in flow rate, the output signal of the data storage circuit is determined within one period of the detection pulse, so that the more rapid the change, the shorter the time required to detect the change.

(2) By installing an AND circuit that obtains the logical product of the output signal of the timer circuit and the output signal of the data storage circuit, when the flow rate changes from large to small, the timer can be activated without waiting for the next pulse detection. Since the output signal turns off at the set time, the response time at the time of off detection does not become longer than the pulse period corresponding to the set flow rate. Even when the flow rate suddenly stops and the detection pulse disappears, or when the pulse output disappears due to an abnormality in the detection part, OFF detection can be performed in a short time, and safety is high.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional flow rate detection device;
The figure is a configuration diagram of one embodiment of the present invention, and FIG. 3 is a signal waveform diagram illustrating its operation. 10...detection section, 12...timer circuit, 14
...Data storage circuit, 18...AND circuit.

Claims (1)

[Claims] 1. A detection section provided in a fluid passage and generating a pulse signal with a frequency proportional to the flow rate of the fluid, and a detection section that outputs a signal activated by the output signal of the detection section and turned on for a set time. , a retriggerable timer circuit, an output signal of the timer circuit is connected to a data input terminal, an output signal of the detection section is connected to the trigger input terminal, and a signal of the data input terminal is synchronized with the signal of the trigger input terminal. It has a data storage circuit that stores and outputs the data to its output terminal, and an AND circuit that calculates the logical product of the output of the data storage circuit and the output of the timer circuit, and outputs the output signal of the AND circuit to an external device. A fluid flow rate detection device configured to output a control output signal. 2. The fluid flow rate detecting device according to claim 1, wherein the timer circuit has a set time adjusting means, and the set time can be changed by an electric signal.