JPH0221728B2 - - 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 rotary 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 facing outside the fluid flow path. 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 process returns to step 16 and waits for the pulse input. 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. From flow rate Q ₀ at time t ₁
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 number τ ₁ has elapsed, and only at this point can the microprocessor 8 know that the flow rate has decreased, and the frequency of the flow rate pulse signal decreases. ₁ , the flow rate _Q1 can be determined and the change in the flow rate signal can be transmitted to an external device. 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 cycle for the flow rate Q ₂ ), that is, a detection delay longer than the cycle 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 fuel continues to burn at the previously required combustion rate for a while, the hot water temperature rises, which is dangerous. The detection speed can be increased by increasing the rotational speed of the rotary blade 2 relative to the flow rate, but 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 counter unit that counts a reference frequency; a counter control unit that resets and starts the counter unit each time the flow rate pulse signal is input; and a counter control unit that resets and starts the counter unit each time the flow rate pulse signal is input. a flow rate calculation means for calculating the flow rate by calculating the reciprocal of the cycle of the flow rate pulse signal, which is a count value; a cycle storage means for storing and updating the determined cycle each time the flow rate pulse signal is input; and a count of the counter. and a time elapse detection means that compares the elapsed time with the previous cycle data of the cycle storage means and detects the elapse of time for every integer multiple of the previous determined cycle. Until it is input, at each time interval of the previous confirmed cycle in the cycle storage means, the time elapsed is calculated by the multiple N of the previous confirmed cycle to 1/(N+1) of the previously confirmed flow rate calculated from the previous confirmed cycle. It consists of a flow rate correction calculation means for obtaining a flow rate signal, and when the flow rate changes from a large flow rate to a small flow rate, it takes a time equivalent to an integral multiple of the cycle at the time of high flow rate before the next flow rate pulse signal is input. It is possible to detect a decrease in flow rate at a certain point in time.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below as shown in FIGS. 4, 5, and 6.
This will be explained in detail using figures. 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 the pulse input port 7 of the 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=1. 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 detection unit 1 with respect to the flow rate Q is =1/K・Q...Equation 1, the measured flow rate Q' obtained by correcting the flow rate is (K is a proportionality constant) Q'=K・=K /τ ₀ ×(N+1) ... will be calculated using equation (2).

When the previously determined flow rate is Q ₀ , equation (2) can be expressed as Q'=Q ₀ /(N+1)...Equation (3).

When reading 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
, and update the output in step 33. At step 34, the value of the period comparison loop counter 22 is set to N=1 again and the value is set to 2.
Return to step 8 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 Q ₀ decreases to ₁ , _{a measured value of Q 0 / 2 is} obtained by the operation shown in _FIG . A measurement value of Q ₀ /4 is obtained at 3·τ ₀ . A flow rate pulse signal is input at time _t2 , and the true flow rate value _Q1 is obtained from the cycle _τ1 measured by the counter 10. 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 after the flow rate decreases. Also, at the time when N times the fixed period has elapsed,
Since the flow rate data of Q ₀ /N+1 is obtained, the flow rate can be determined in advance and the response time can be shortened. Therefore, during the period τx in FIG. 6, a value smaller than the true flow rate value _Q1 is detected, but it is corrected to the true value at time _t2 . The overshoot Qx becomes large when the period τx is short, and becomes a small value when the period τx is long, so it is not a big problem in practice.

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.

Effects of the Invention As described above, according to the present invention, (1) The period storage means for storing the determined period, and the progress of counting of the counter and the data of the period storage means are compared, and the time elapses at every integer multiple of the determined period. The output flow rate signal is predicted and corrected by the flow rate correction calculating means every time an integer multiple of the previous fixed cycle has elapsed since the input of the flow rate pulse signal. A decrease in the flow rate can be predicted and detected without waiting for the input of the flow rate pulse signal. Furthermore, the larger the previous flow rate, the shorter the period of this correction, so it 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 an instantaneous water heater, when the water flow suddenly changes from a large flow to a small flow, the over input of the combustion amount can be minimized and the risk of abnormal rise in water temperature or boiling occurs. This can be effectively prevented.

(2) Since the configuration is configured to obtain a flow rate signal of 1/(N+1) of the previously determined flow rate every time N times the determined cycle, the flow rate is predicted and determined in advance, and the response time is extremely shortened. Can be shortened. It has many 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 section each time the flow rate pulse signal is input; and a counter control means that resets and starts the counter section each time the flow rate pulse signal is inputted; a flow rate calculation means for calculating the flow rate; a period storage means for storing and updating a determined period each time the flow rate pulse signal is input; , a time elapse detection means for detecting the elapse of time for every integer multiple of the previous determined cycle, and from the input of the flow rate pulse signal until the input of the next flow pulse, the previous cycle storage means For each time interval of the confirmed cycle, 1/(N+1) of the previously confirmed flow rate calculated from the previous confirmed cycle by the multiple N of the previous confirmed cycle of time elapsed.
A fluid flow rate measurement device comprising a flow rate correction calculation means for obtaining a flow rate signal.