JPH029693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fluid flow rate measuring device that continuously detects the flow rate of a fluid. It can be used as a measuring device.

Configuration of conventional example and its problems Conventionally, this type of flow measuring device detects the rotation of a rotor placed in a fluid flow path and determines the flow rate value from the frequency. In order to do this, means are taken to determine the flow rate value from the period of the detection signal.

Figure 1 is a configuration diagram of a conventional flow rate measuring device;
The figure is an operation flowchart of a conventional flow rate measuring device, and FIG. 3 is a timing chart illustrating the operation of the conventional flow rate measuring device.

In FIG. 1, a flow rate detection unit 1 includes a rotor blade 2 placed in a fluid flow path, a magnet piece 3 rotated at the tip of the rotor blade 2, and a magnet piece 3 provided outside the fluid flow path facing the magnet piece 3. and a magnetic sensor 4. The flow rate signal from the flow rate detection section 1 is connected to a pulse input port 7 of a one-chip microcomputer 6 via a waveform shaping circuit 5. One-chip microcomputer 6
To do this, the microprocessor 8, the clock generation circuit 9, and the reference frequency from the clock generation circuit 9 are counted, and the microprocessor 8 reads out the counted value.
It includes a counter 10 which can be reset, a memory 11 and an output interface 12 which provides signals to external equipment.

The operation will be explained with reference to FIGS. 2 and 3. The counter 10 and memory 11 are initialized at 13, the pulse input port 7 is read at 14, and the pulse input port 7 is read at 15.
If the pulse input from the flow rate detection section 1 is not checked at step 16, the flow returns to step 16 and the pulse input is received. During this time, the counter 10 continues counting the clocks. When a pulse input is detected, the count value of the counter 7 is read in step 17 and saved in the memory 11. At step 18, the counter 10 is reset and restarted in preparation for the next cycle measurement. At step 19, a reciprocal calculation is performed from the saved count value, that is, the period, to obtain the flow rate value. 20
After performing the necessary output processing at step 16, the process returns to step 16 to continue measurement. Figure 3a shows the fluid flow rate, b shows the flow rate pulse signal, and c shows the changes over time in the measured flow rate signal. At time t ₁ , the flow rate changes from Q ₀
When the flow rate decreases to Q ₁ , the frequency of the flow rate pulse signal decreases, and the next pulse is input only after the period τ ₁ has elapsed. At this point, the microprocessor 8 can know that the flow rate has decreased, and the frequency of the flow rate pulse signal decreases from the period τ ₁ . It is possible to determine the flow rate _Q1 and transmit changes in the flow rate signal to external equipment. When the flow rate increases to Q ₂ at time t ₂ , the flow rate Q ₂ ′ obtained after time τ ₂ is smaller than Q _{2 because the flow rate change occurs in the middle of the pulse input, and it takes even more time to obtain the accurate flow rate Q 2 .} τ ₃ (τ ₃ is the flow rate
_Q2 ) In other words, a detection delay longer than the period of the flow rate pulse signal always occurs. This means that the detection speed of the flow rate change when changing from a large flow rate to a small flow rate is particularly slow. Since the hot water continues to burn at the previously required combustion rate for a while, the temperature of the hot water rises, which is dangerous. Although the detection speed can be increased by increasing the rotational speed of the rotor blade 2 relative to the flow rate, there is a limit due to mechanical constraints such as mechanical inertia and shaft wear. It had the following problems.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
In particular, the purpose is to increase the detection speed for changes in flow rate from large flow rates to small flow rates.

Structure of the Invention In order to achieve the above object, the present invention includes a flow rate detection section that is placed in a fluid flow path and generates a flow rate pulse signal with a frequency proportional to the flow rate, and a reference frequency that is higher in frequency than the flow rate pulse signal and has a constant frequency. a clock generating section that generates a reference frequency; a counter section that counts a reference frequency; a counter control means that resets and starts the counter each time the flow rate pulse signal is input; and a counter section that counts the reference frequency; a flow rate calculation means for calculating the flow rate by calculating the reciprocal of the flow rate pulse signal period; a period storage means for storing and updating the period of the flow rate pulse signal determined each time the flow rate pulse signal is input; and a time elapse detection means that compares the counting progress with the cycle data of the cycle storage means and detects the elapse of time for every integer multiple of the previously determined cycle, and the next flow rate pulse is input from the time of input of the flow rate pulse signal. Flow rate that obtains a flow rate signal that is 1/N of the previously determined flow rate outputted from the flow rate calculation means by a multiple N of the previous determined cycle of the elapsed time at each time interval of the previously determined cycle of the period storage means until the time is determined. When the flow rate changes from a large flow rate to a small flow rate, the flow rate is calculated at a time point corresponding to an integral multiple of the period during the high flow rate before the next flow rate pulse signal is input. It is possible to detect a decrease in

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 4, 5, and 6. Note that the same parts as in the conventional example are given the same numbers.

In FIG. 4, the flow rate detection section 1 consists of a rotary blade 2, a magnet piece 3, and a magnetic sensor 4. The flow rate signal from the magnetic sensor 4 is connected to a pulse input port 7 of a one-chip microcomputer 6 via a waveform shaping circuit. The one-chip microcomputer includes a microprocessor 8, a clock generation circuit 9, and a counter 10 that counts the reference frequency of the clock generation circuit 9 and whose counted value can be read and reset by the microprocessor 8 via the counter control section 20.
, a determined cycle storage section 21 that stores the determined cycle of the flow rate pulse signal, and a cycle comparison loop counter 2
2 and an output interface 12.
The flow rate calculation means is obtained by calculating the stored cycle data with the microprocessor 8, and the time elapse detection means is obtained by using the microprocessor 8 to read the data during counting from the counter 10 and compare it with the data in the cycle storage section 21. can get.

In FIG. 5, at 23, the value of the counter is initialized to φ and the value of the period comparison loop counter 22 is initialized to N=2. At 24, the pulse input port 7 is read, and at 25, the presence or absence of pulse input is determined. If there is no flow rate pulse input yet, the process branches to 26, reads the data during counting from the counter 10, and uses the values of the determined cycle storage section 21 and the cycle comparison loop counter 22 to determine at 27 whether N times the previous cycle has passed. . If the time has not passed, return to 28. If the flow rate has elapsed, the flow rate is determined at step 28 using the determined period τ ₀ and the loop counter value N, and the output interface 1
A flow rate signal is output to the outside via step 2. If the characteristic of the frequency of the flow rate detector 1 with respect to the flow rate Q is =1/K・Q...Equation (1), then the measured flow rate obtained by correcting the flow rate is
Q' (where K is a proportionality constant) Q'=K・=K/τ ₀ ×N...Let's find it using equation (2). At this point, the true flow rate Q is
It should be smaller than Q′. When the previously determined flow rate is Q ₀ , equation (2) can be expressed as Q'=Q ₀ /N...Equation (3).

Then, at 29, the value of the periodic loop counter 22 is set to 1.
Increase and return to 28. When an input pulse is detected at 25, the data of the counter 10 is saved to the determined period storage section 21 at 30. At this point, the deterministic period is updated to the new value τ ₁ . At step 31, the counter 10 is reset and restarted for the next cycle measurement. 32, the true flow rate is calculated from the determined period τ ₁ as Q ₁ =K/τ ₁
Find it in step 33 and update the output. At 34, the value of the period comparison loop counter 22 is set to N=2 again at 28
Return to and repeat the operation.

FIG. 6 is a timing chart for explaining the operation, and symbols a, b, and c in the figure show changes over time in the fluid flow rate, flow rate pulse signal, and detected flow rate signal, respectively.
In Figure 6, at time t ₁ the flow rate changes from Q ₀ to
When it decreases to Q _{1 , a measured value of Q 0 / 2 is} obtained by the operation shown in _FIG . 3 measurements are obtained. The flow rate pulse signal is input at time t ₂ and the true flow rate value is determined by the period τ ₀ measured by the counter 10.
Q ₁ is obtained. Characteristic 35 indicated by a broken line in FIG. 6c is a flow rate signal obtained only by conventional periodic measurement. In this way, a change in flow rate can be detected without waiting for the next flow rate pulse signal when the flow rate decreases. Also, wait for N times the confirmation period to pass.
Since the flow rate data of Q ₀ /N is obtained, the measured data will not overshoot or undershoot with respect to the true flow rate.

In addition, in the flowchart of Figure 5, 23
The first time after initialization, there is no fixed cycle data, so the flow rate pulse input is waited, and the above operations become effective from the second time onwards. Furthermore, considering the case where the flow rate becomes zero from _Q0 to time t1 and the flow stops, it is sufficient to consider the case where the generation of flow rate pulses stops and there is no pulse at time t2 in FIG. 6. In this case Z ₀
The correction calculation is repeated every cycle, and the obtained flow rate signal thereafter approaches zero as time passes from Q ₀ /4...Q ₀ /5...Q ₀ /N. At this time, the flow rate signal obtained over time approaches zero as much as possible, but does not become zero. When this device is applied to an instantaneous water heater, the combustion amount is adjusted based on the obtained flow rate signal, and combustion is turned on/off by comparing the flow rate signal obtained by a flow rate determination device (not shown) with the set value. Since combustion is stopped before the detected flow rate signal becomes zero, there is no problem.

Effects of the Invention As described above, according to the present invention, (1) The period storage means for storing the determined period is compared with the counting progress of the counter and the data of the period storage means, and the time is calculated for each integer multiple of the determined period. A time elapse detection means for detecting the elapsed time is provided, and the flow rate is predicted and corrected by the flow rate correction calculation means every time an integral multiple of the previous determined period elapses from the input of the flow rate pulse signal, so that the next flow rate pulse signal Changes in flow rate can be detected without waiting for input.
Flow rate detection with little time delay is possible. This is particularly effective when there is a large flow rate change from a large flow rate to a small flow rate. When this is used to calculate the required amount of heat for instantaneous water heaters, it is possible to minimize the over input of the combustion amount when the flow rate suddenly changes from large to small, effectively reducing the risk of abnormal rises in water temperature and boiling. can be prevented.

(2) Since the configuration is configured to obtain a flow rate signal of 1/N of the previously determined flow rate every time N times the determined cycle, the measured data will not overshoot or undershoot the true flow rate value. Stable measurements can be made.

etc., it has great effects.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional flow rate measuring device;
The figure is a flowchart of a conventional flow rate measuring device, Figures 3a, b, and c are timing charts showing the operation of a conventional flow rate measuring device, and Figure 4 is a configuration of a flow rate measuring device according to an embodiment of the present invention. 5 is the same flowchart, and FIGS. 6a, b, and c are the same timing chart. 1 ...Flow rate detection section, 7...Pulse input port,
8... Microprocessor, 9... Clock generation circuit, 10... Counter, 20... Counter control section, 21... Determined cycle storage section, 22... Cycle comparison loop counter.

Claims (1)

[Claims] 1. A flow detection section that is placed in the fluid flow path and generates a flow rate pulse signal with a frequency proportional to the flow rate, a clock generation section that generates a constant reference frequency that is higher in frequency than the flow rate pulse signal, and a clock generation section that counts the reference frequency. a counter section; a counter control means for resetting and starting the counter each time the flow rate pulse signal is input; and a counter control means for calculating the reciprocal of the flow rate pulse signal period, which is a count value of the counter, each time the flow rate pulse signal is input. A flow rate calculation means for calculating the flow rate, a period storage means for storing and updating the period of the flow rate pulse signal determined each time the flow rate pulse signal is input, and a comparison between the count progress of the counter and the period data of the period storage means. and a time elapse detection means for detecting the elapse of time every integer multiple of the previous determined cycle, and the previously determined cycle of the cycle storage means is detected from the time of input of the flow rate pulse signal until the next flow rate pulse is inputted. A fluid flow rate measuring device comprising a flow rate correction calculation means for obtaining a flow rate signal equal to 1/N of the previously determined flow rate outputted from the flow rate calculation means by a multiple N of the previous determined period of time elapsed at each time interval of the cycle.