JP2542360B2 - Liquid flow rate detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for detecting a liquid flow rate in a gas instantaneous water heater or the like using a microcomputer.

(Prior Art) Conventionally, as a device for detecting a flow rate of a liquid flowing in a flow channel, that is, a supply amount of a fluid to a fluid device, a flow rate sensor provided in the middle of the flow channel as shown in the detection principle in FIG. It is known to convert the detection pulse from the above into a voltage and take in the voltage as flow rate data to calculate the flow rate.

However, the above-mentioned device has a problem in accuracy of water amount data due to fluctuations in power supply voltage and variations in circuit components,
In addition, it has a large number of parts and a high failure rate, and also has a drawback that it is necessary to lengthen the sampling time until the voltage becomes stable.

Therefore, in order to eliminate such a defect, the period of the detection pulse from the flow rate sensor is detected by counting a predetermined reference pulse, and the count value is processed by a microcomputer to prevent the fluctuation of the power supply voltage. It may be possible to calculate the flow rate without being affected.

(Problems to be Solved by the Invention) The width of this reference pulse is preferably small in order to improve the resolution of the flow rate data.

However, if, for example, an 8-bit microcomputer is used and the number of reference pulses generated in a certain detection pulse cycle is 411, the upper limit of the count value that can be accommodated in one byte of the 8-bit microcomputer is 256. It is not possible to handle values that exceed the limit, and the overflow exceeds the memory capacity of the microcomputer, and the actual number of reference pulses generated is 411.
155, which is the difference between the upper limit value 256 and the upper limit value 256, becomes a count value and is taken in as calculation data. The flow rate calculation unit multiplies the calculation data 155 by the reference pulse period, and the multiplication result gives the actual flow rate. The problem is that different flow rates are calculated.

The present invention has been made in view of such problems, and when detecting a flow rate using a microcomputer, an accurate flow rate can always be calculated even if the count value exceeds a predetermined upper limit value and overflows. The purpose is to do so.

(Means for Solving Problems) Means taken by the present invention for solving the above problems are
It consists of a flow rate detector that generates a detection pulse according to the flow rate, and a flow rate calculator that calculates the flow rate based on the flow rate data in the period from the input of this detection pulse to the input of the next detection pulse. The calculation unit, a free-running counter that counts the period using a reference pulse of a predetermined cycle, a storage unit that stores the count value, and whether the overflow has occurred based on an overflow signal generated by the free-running counter. Judgment means for making judgment and detecting the number of overflow occurrences, and when it is judged that there is overflow,
A value obtained by dividing the stored count value by a predetermined value N (N is a natural number exceeding the number of overflow occurrences), and a value obtained by dividing a value obtained by multiplying the upper limit value of the free running counter by the number of overflows by the predetermined value N; And a calculation means for calculating a flow rate based on the calculation data, the period of the reference pulse, and the predetermined value N. That is.

(Operation) By the above technical means, the reference value of a predetermined cycle is counted by the free running counter during the period from the input of the detection pulse generated according to the flow rate until the input of the next detection pulse Although the flow rate is calculated using the data of, the count value (stored value) by the free running counter when the determination means determines that there is an overflow as a result of the number of generated reference pulses exceeding the upper limit of the memory capacity of the microcomputer. Is a predetermined value N
(N is a natural number exceeding the number of overflows) and a value obtained by dividing the value obtained by multiplying the upper limit value by the number of overflows by the same predetermined value N are added so as to be within the range of the upper limit value. The calculated value is not taken in as the operation data, and the count value resulting from the overflow is not taken in as the operation data. Then, the calculating means calculates the flow rate based on the predetermined value N in addition to the calculated data and the cycle of the reference pulse.

(Effect) Since the present invention has the above configuration, it has the following advantages.

When calculating the flow rate using an 8-bit microcomputer with a limited storage capacity, a reference pulse during the period from the input of the detection pulse generated according to the flow rate to the input of the next detection pulse. Even if the number of occurrences of exceeds the predetermined upper limit of storage capacity and the free running counter overflows,
It is possible to always calculate an accurate flow rate without taking in incorrect calculation data.

(Example) Hereinafter, the details of the present invention will be described based on the case where the method of the present invention is used to detect the amount of water in a gas instantaneous hot water supply device.

The flow rate detecting unit is composed of a flow rate sensor (1), and the flow rate sensor (1) has a main body (3) having a passage (2) through which water passes as shown in FIG. An impeller (4) provided and rotationally driven by water flowing and passing through the passage (2), a magnetic rotor (6) provided at the tip of a rotating shaft (5) of the impeller (4), and a magnetic rotor ( The water supply pipe of the water heater body (8) as shown in FIG. 6, comprising a Hall element (7) for generating a detection pulse at a cycle proportional to the flow passing through the passage (2) by the magnetic field generated in the range of 6). The controller (10) provided in the middle of the road (9) and arranged in the water heater body (8) is contacted.

The control unit (10) is composed of an 8-bit microcomputer, and the flow rate calculation unit (11) calculates the actual flow rate based on the detection pulse generated by the flow rate sensor (1).

The procedure of the flow rate calculation by the flow rate calculation unit (11) will be described below based on the flowchart shown in FIG.

The flow rate calculation unit (11) receives the detection pulse from the water amount sensor (1) at the interrupt detection unit (12), and determines the length of the pulse cycle by a free running counter (13) as a predetermined reference pulse. To count. This reference pulse is set to 1 ms, and this reference pulse is counted by the free running counter (13) during the period from the input of the detection pulse from the water amount sensor (1) to the input of the next detection pulse.

At this time, when a new detection pulse is accepted by the interrupt detection unit (12), the current count value of the free running counter (13) is stored and the count value is reset and restarted.

Then, the actual flow rate is calculated by the calculating means (14) based on the data of the count value (stored value) of the reference pulse counted in the period until a new detection pulse is accepted by the interrupt detection section (12). However, prior to this, whether the number of reference pulses actually generated during the above period exceeds 256, which is the count value (upper limit of the memory capacity of the microcomputer) that can be stored in a predetermined 1 byte. , That is, whether or not the free running counter (13) has overflowed.

Whether or not this overflow has occurred is detected by an overflow occurrence flag that is usually built in the microcomputer, and a determination is made based on the detection result.

Therefore, if it is determined that there is no overflow,
The count value (memorized value) of the free-running counter (13) is used as it is as data, so that it is taken into the calculation means (14) as flow rate data with the reference pulse number of 1 ms. On the other hand, when it is judged that there is an overflow, , The count value (memorized value) of the free running counter (13) at the interval (m
The reference pulse of (s) is treated as a counted pulse, and is taken into the calculating means (14) as flow rate data.

That is, for example, when the flow rate is 10 / min as shown in FIG. 3, the number of reference pulses generated during the period from the input of the detection pulse from the water amount sensor (1) to the input of the next detection pulse is It is 41, and the count value of the free running counter (13) that counts this pulse number is also 41. Therefore, in this case, the count value that fits in one byte is 25.
Since the occurrence of overflow is not detected because it is a value within 6, it is determined that there is no overflow, and the count value (memorized value) 41 of this free running counter (13) is as it is as the data obtained by counting the reference pulse of 1 ms. 14).

However, as shown in FIG. 4, when the flow rate is 1 / min,
Although the reference pulse number actually generated during the period from the input of the detection pulse from the water amount sensor (1) to the input of the next detection pulse is 411, the count value 256 that fits in one byte is 256. In order to exceed, the count value of the free running counter (13) overflows once
It becomes 155. At this time, since the occurrence of overflow is detected once and it is determined that there is overflow, the count value (stored value) 155 of the free running counter (13) is divided by a natural number larger than the number of overflows, for example, 2, that is, 1 / Double the value, and add the value 256 corresponding to overflow to 1/2, which is also the value 1/2, so that the value falls within the range of the count value 256 that fits in 1 byte (155/2 + 128 = 205). , The reference pulse of 2 ms is treated as counted, and the data is taken in by the calculating means (14).

In this way, when the count value of the reference pulse by the free running counter (13) overflows once without exceeding the upper limit value 256 of 1 byte, it is divided by a natural number larger than the overflow count 1, for example, 2, By multiplying by 1/2 and treating it as counted by the reference pulse of 2ms, the data that cannot be stored in 1 byte with the reference pulse of 1ms can be stored in the range of 1 byte and 1 byte can be used effectively. can do.

In the above embodiment, the case where the overflow occurred once while the reference pulse was counted by the free running counter (13) was explained. However, when the overflow occurred several times, the free running counter (1
By treating the count value of 3) as a reference pulse of Nms (N is a natural number exceeding the number of overflows) so that it falls within the range of 1 byte, the same effect as above can be obtained. That is, in this case, the count value (memorized value) by the free running counter (13)
Is multiplied by 1 / N and the value obtained by multiplying the number of overflows by 256, which is the upper limit value that fits in 1 byte, is also multiplied by 1 / N, and the value of the actually generated reference pulse number of 1 ms is the upper limit. The value treated as counted by Nms pulse so that it falls within the range of value 256 is taken in as calculation data,
The calculated data, the cycle of the reference pulse, and the predetermined value N
The flow rate is calculated based on and.

The number of overflow occurrences during counting of the reference pulse by the free running counter (13) at this time can be detected by counting the number of overflow occurrence detections by the overflow occurrence flag.

Thus, the flow rate calculation section (11) calculates the actual flow rate by the calculation means (14) based on the above data.

 The actual flow rate is calculated by the following arithmetic expression.

If there is no overflow If there is an overflow Thus, the flow rate detecting device of the present invention is implemented, and in the case of the gas instantaneous hot water supply device, the detected flow rate is used as the data of the amount of water supplied to the heat exchanger (15), and the necessary heat load calculating section of the control section (10). Incorporated in (16).

On the other hand, the water heater main body (8) is provided with the water temperature sensor (17) together with the flow sensor (1) in the water supply conduit (9) communicating with the inlet of the heat exchanger (15), and at the outlet of the heat exchanger (15). The hot water supply temperature sensor (18) is provided in the hot water supply pipe (16) to be connected, and the gas pipe (20) for supplying gas to the burner (19) has a solenoid valve (21), a governor (22), and a proportional valve (23). Is equipped with.

In addition, a fan (24) for supplying air required for combustion is installed in the water heater body (8).

Further, a controller (25) is provided separately from the water heater main body (8), and the controller (25) is provided with a power switch (26) and a temperature setting unit (27).

The motors of the incoming water temperature sensor (17), the hot water temperature sensor (18), the solenoid valve (21), the proportional valve (23), the power switch (26), the temperature setting section (27) and the fan (24) are respectively The control unit (10) is electrically connected to the control unit (10) like the flow sensor (1).

The incoming water temperature sensor (17) and the outgoing hot water temperature sensor (18) detect the incoming water temperature to the heat exchanger (15) and the outgoing hot water temperature from the heat exchanger (15), respectively, and generate a voltage signal according to the temperature. ,
The temperature setting section (27) generates a voltage signal according to the set temperature.

These voltage signals are converted into incoming water temperature data, outgoing hot water temperature data, and set temperature data by the A / D conversion unit (25) of the control unit (10) and are taken into the required heat load calculation unit (16).

The required heat load calculation unit (16) is the flow rate calculation unit (11) described above.
The required heat load is calculated on the basis of the flow rate data calculated by the above and each of the above data, and a signal corresponding to the calculated value is generated to generate a proportional valve drive circuit (28) and a fan motor drive circuit (2
9) is operated to open the proportional valve (23) and fan (2
Control the number of rotations of the motor of 4 ').

A block diagram of this water heater is shown in FIG. 7, and a flow chart is shown in FIG.

The electromagnetic valve (21) opens a water faucet (not shown) at the end of the hot water supply pipe (16) to cause water flow in the water supply pipe (9), which the flow sensor (1) detects. Then, when the signal reaches the control unit, a valve opening signal is generated from the control unit (10) to open the valve.

Although not shown in the drawing, an igniter that generates an ignition in synchronization with the opening of the solenoid valve (21) is provided near the burner (19). Ignite the injected gas.

Needless to say, the liquid flow rate detection device of the present invention is not limited to the detection of the amount of water in the gas instantaneous water heater as described above, but can be applied to the detection of the liquid flow rate in any fluid equipment.

[Brief description of drawings]

FIG. 1 is a flow chart of a liquid flow rate detecting method showing an embodiment of the present invention, showing an example when an overflow occurs once. FIG. 2 is a waveform diagram for explaining the detection principle. FIG. 4 is an explanatory view showing the generation state of the reference pulse when the flow rate is 1 / min, FIG. 5 is a sectional view of the flow rate sensor, and FIG.
The figure is a schematic view of a gas instantaneous hot water heater using the device of the present invention,
FIG. 7 is the same block diagram, FIG. 8 is a flowchart, and FIG.
The figure is a waveform diagram for explaining the conventional principle of water flow detection. (1): Flow rate sensor (flow rate detection part) (11): Flow rate calculation part (12): Interrupt detection part (storage means) (13): Free running counter (14): Calculation means

Continuation of front page (56) Reference JP-A-55-85219 (JP, A) JP-A-55-42008 (JP, A)

Claims (1)

(57) [Claims] 1. A flow rate detecting section for generating a detection pulse according to a flow rate, and a flow rate calculating section for calculating a flow rate based on flow rate data in a period from the input of this detection pulse to the input of the next detection pulse. The flow rate calculation unit comprises a free running counter that counts the period using a reference pulse of a predetermined cycle, a storage unit that stores the count value, and an overflow based on an overflow signal generated by the free running counter. When it is determined that there is an overflow, the stored count value is divided by a predetermined value N (N is a natural number exceeding the number of overflows). Multiply the value and the upper limit of the free running counter by the number of overflow occurrences. A value obtained by adding the value obtained by dividing the value by the same predetermined value N so as to be within the range of the upper limit value is taken in as operation data, and the operation data, the cycle of the reference pulse, and the predetermined value N are set. A liquid flow rate detection device comprising: a calculation unit that calculates a flow rate based on the calculation unit.