JPH0792063B2 - A pump automatic control system that controls the rotational speed of the pump by changing the storage target value. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention changes the control target value of the storage amount of liquid or the like in a tank mechanically or with time depending on the discharge amount from the tank. The present invention relates to a pump automatic control system that controls the rotation speed of a pump by changing the storage target value that automatically controls the rotation speed of the pump that transfers the liquid or the like so that the storage amount in the tank follows the control target value. .

(Prior Art) A pump is used for sending water for the purpose of being used for cooling, sprinkling, cleaning, or changing the storage place of other liquids.

Generally, the control system is configured so that the liquid always flows out at an appropriate pressure when the valve is opened at the place where the liquid is used.

A buffer tank may be provided when the operation of the pump cannot follow fluctuations in the usage amount and when it is desired to avoid operation of the pump at a minimum flow rate.

Tanks used for such purposes include open type tanks and pressure tanks. In order to know whether the amount of liquid stored in the tank is appropriate, the open type tank has a liquid level gauge Pressure gauges are often used in tanks.

Examples of conventional pump control systems include on / off control and rotation speed control systems.

FIG. 10 is a block diagram showing an example of a conventional pump rotation speed control system.

As shown in the figure, the pump 4 sucks the liquid through the pipe 6 from the lower tank 5 in which the liquid such as water to be pumped is contained, and the upper tank 9 through the pipe 7.
Supply to.

The driving force of the pump 4 is supplied to the pump 4 by the rotation of the motor 3 by the electric power supplied from the inverter 2 which receives the AC power source 1 as an input and restores the AC of another frequency to transmit the rotational force of the motor 3.

However, the output of the inverter 2 is the automatic controller 12
The flow rate of the liquid supplied to the tank 9 by the pump 4 is controlled by the automatic controller 12.

The automatic controller 12 compares the detection output of the liquid level sensor 11 that detects the amount of liquid stored in the tank 9 with the target value of the liquid level set by the liquid level setting means 13 and uses the pump 4 for the tank. If the amount of liquid outflowing from the tank 9 is larger than the amount of liquid replenished to the tank 9, the value detected by the liquid level sensor 11 becomes lower than the target value.
To increase the electric power supplied to the motor 3 by the inverter 2.

On the contrary, if the amount of liquid replenished by the pump 4 is larger than the amount of liquid flowing out from the tank 9, the value detected by the liquid level sensor 11 gradually rises and becomes higher than the target value.
A control signal is sent to the inverter 2 to reduce the electric power supplied to the motor 3 by the inverter 2.

When the flow rate flowing out from the pump 4 is extremely small or zero, the pump is in a state close to idling while the pump is filled with the liquid, and the liquid temperature in the pump is increased by stirring the liquid. It is expected that such a temperature increase may impair the life of the pump 4 itself and its peripheral devices and that the temperature may be altered depending on the liquid and may not be suitable for the purpose of use.

Conventionally, in order to avoid such a temperature rise, a configuration is used in which the flow rate detector 8 is used to forcibly stop the pump when the flow rate is below a certain amount.

When the flow rate detector 8 provided in the middle of the pipe 7 that delivers the liquid from the pump 4 detects that the flow rate is below a certain value and is extremely small, the information from the liquid level setting means 13 and the liquid level sensor 11 indicates that Even when it is determined that the pump 4 is still in the range where it continues to operate, the automatic controller 12 sends a control signal to the inverter 2 to stop the electric power sent to the motor 3 and stop the pump 4.

(Problems to be Solved by the Invention) As described above, when the flow rate of the liquid to be supplied to the tank by the pump is extremely small, the liquid in the pump is agitated by the rotation of the pump, and the temperature of the pump and the liquid in the pump are The flow rate detector 8 was required in order to prevent the rise of the flow rate.

An object of the present invention is to provide an automatic pump control system that can solve the above-mentioned problems without using a flow rate detector.

(Means for Solving the Problems) In order to achieve the above object, a pump automatic control system for controlling a rotation speed of a pump by changing a storage target value according to the present invention is a tank for storing a fluid transferred by a pump. In a pump automatic control system that sets a target value of a numerical value related to the storage amount of the tank, and controls the rotation speed of the pump so that the detected value of the numerical value related to the storage amount of the tank approaches the target value, at least raises the target value. When the detected value does not exceed the target value by repeatedly changing with a waveform including a slope, the rotation speed of the pump is controlled so that the detected value approaches the target value, and the detected value exceeds the target value. When it exceeds, the rotation of the pump is stopped.

The numerical value regarding the storage amount may be a numerical value indicating the position of the liquid level in the tank.

Further, the numerical value regarding the storage amount may be a numerical value representing the pressure of the fluid stored in the tank.

The target value waveform may be a continuous repeating waveform of a triangular wave or a sawtooth wave.

Further, the waveform of the target value is a continuous waveform in which a single triangular wave or a single sawtooth wave, or a waveform in which a part of a single triangular wave is cut out, and a portion which does not change at a constant value are alternately repeated. You can also

(Example) The present invention will be described in more detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an automatic pump control system for controlling the rotational speed of a pump by changing a storage target value according to the present invention.

In this embodiment, the tank is of an open type, and the numerical value detected by the liquid level sensor 11 such as an ultrasonic sensor indicates the amount of liquid stored in the tank.

As shown in the figure, the pump 4 pipes the liquid from the lower tank 5 containing the liquid to be pumped by the pump 4.
The pipe 7 is sucked up through the pipe 7, and a flow rate detector such as a flow rate sensor or a flow switch as in the related art is not provided in the middle of the pipe 7.

As is conventional, the motor 3 is rotated by the electric power supplied from the inverter 2 that receives the AC power supply 1 and converts the AC frequency, and the rotational force of the motor 3 is transmitted to the pump 4.

The detection output given to the automatic controller 12 that controls the output of the inverter 2 for driving and controlling the pump 4 is only the output of the liquid level sensor 11.

It is the liquid level setting means 13 that gives the control target to the automatic control controller 12, and the liquid level setting means 13 controls the operation of the pump 4 in the program given to the computer incorporated in the automatic control controller 12, This is to write data for setting a target value for changing the liquid level in the tank 9 with time. Then, the change amount of the set liquid level necessary for this data is input from the set liquid level change amount setting device 14 configured by the data key, and the change speed of the set liquid level is set by the other data key. It is input from the liquid level change speed setting device 15.

Next, based on the data input from the set liquid level change amount setter 14 and the set liquid level change speed setter 15, the automatic controller 12 controls the pump 4 to control the change in the position of the liquid level. An example of the curve set as the value is shown in FIG.

Setting the target value H ₀ of the present invention is not constant as shown in FIG. 2, the change between the upper limit target value H _P and the lower limit target value H _B which is determined by the setting liquid level variation setter 14 There is.

The change is a combination of changes such as an ascending slope, a descending slope, a flat straight line, an ascending jump, a descending jump, and the like, and at least the waveform that always includes the ascending slope is repeated.

80% of the positions of the depth of the tank 9 in the example of FIG. 2 as the upper limit target value H _P of the liquid level WL, so that the change amount of the set target value H ₀ is 30%, setting solutions shown in Figure 1 since is set in terms variation setter 14 lower target value HB is 70% of the positions of the upper limit target value H _P.

The falling straight line (falling slope) of the set target value H ₀ is the time t
_It continues for a time td from ₂₀ to a time t ₂₁ , its rising straight line (a rising slope) continues for a time tu from a time t ₂₁ to a time t ₂₂ , and thereafter, the descending and ascending are repeated alternately. .

Such times td and tu are set to several minutes, for example, and are set by the set liquid level change speed setting device 15 in FIG.

In the liquid level setting means 13 of FIG. 1, all the liquid level change amount and the liquid level change speed of the target value are incorporated into the program from the beginning, and the set liquid level change amount setter 14 and the set liquid level change speed setting are set. It does not matter if the target value is set without an external setting device such as the device 15.

The operation of the pump 4 is controlled with respect to the target value set in this way. The control is performed by the liquid level sensor 11 shown in FIG.
The liquid level WL detected by is always the set target value H ₀
The automatic control controller 12 sends an appropriate control signal to the inverter 2 while comparing the liquid level sensor output with the set target value H ₀ to drive the pump 4 via the motor 3.

However, the pump 4 is operated so that the liquid level WL of the tank 9 approaches the set target value H ₀ when the position of the liquid level WL is equal to or lower than the set target value H ₀ .

When the set target value H ₀ is lower than the liquid level WL, the pump 4 is decelerated indefinitely and stopped.

This can prevent the liquid temperature from rising abnormally.

The reason will be described below.

As described above, the pump and the temperature of the liquid in the pump are likely to rise when the flow rate of the liquid to be replenished to the tank by the pump is extremely small, and the position of the liquid level WL is the set target value H _0.
This is the case when it is lower and still very close.

When the set target value H ₀ is lower than the position of the liquid level WL, the pump always stops. Therefore, only the case where the set target value H ₀ is higher than the position of the liquid level WL will be described below.

Since the position of the liquid level WL usually does not rise except to let the liquid flow in by a pump, during the slope where the waveform of the set target value H ₀ rises, at least the flow rate according to the slope is flowed and the pump Also, an abnormal increase in the liquid temperature in the pump is unlikely to occur.

Moreover, the condition that does not cause this abnormal rise at all is that the waveform portion has a slight inclination that is not more than an abnormal rise in the liquid temperature when there is no change in the liquid level WL, so the selection range is extremely high. wide. While the waveform of the set target value H ₀ is falling, the pump flows into the tank according to the difference between the set target value H ₀ and the position of the liquid level WL. It is rare that the slope of the decrease in WL and the slope of the set target value H ₀ are parallel, and the difference between them is very small and is accompanied by an increase in the temperature of the pump and the liquid in the pump. At least, the probability of occurrence is much smaller than that in the case where a slight amount of liquid continues to flow from the tank when the set target value is kept constant. Moreover, the set target value H ₀
Since the waveform of shifts to the next rising slope, it can be controlled within a range where the influence on the rise in liquid temperature is extremely small.

Furthermore, if the pattern of the liquid level lowering situation due to the outflow of liquid from the tank can be predicted to some extent, such a condition can be easily avoided by setting the descending slope of the waveform so as to deviate from that tendency. it can.

Hereinafter, the relationship between the pump flow rate and the liquid temperature in the pump will be described for each situation that flows out from the outlet 10 of the tank 9.

FIG. 3 shows a case where the amount of outflow from the tank 9 is relatively large. FIG. 3 (a) shows the tank liquid level, FIG. 3 (b) shows the pump flow rate, and FIG. 3 (c) shows the change in pump liquid temperature. Is shown. Of the curves in the figure, the solid line is the set target value H ₀ , and the dotted line is the liquid level.
The change in the height of WL is shown. (The same applies to FIG. 4 and thereafter.) In this case, in order to compensate for the liquid flowing out from the tank 9,
There are many pump flow rates, and the set target value is
Times at which H ₀ rises with time t ₃₁ to t ₃₂ and t _{33 to} t ₃₄
For example, the pump flow rate is lower during the time t ₃₂ to t ₃₃ and t _{34 to} t ₃₅ when the set target value H ₀ falls with time than during Therefore, there is almost no rise in the pump liquid temperature as shown in FIG.

The height of the liquid level WL follows the set target value H ₀ of FIG. 10A and almost matches the set target value.

FIG. 4 shows a case where the amount of outflow from the tank 9 is medium and is almost equal to the amount of decrease of the set target value H ₀ , and a little more than that, and FIG. 4 (a) shows the tank liquid level, (B) shows the pump flow rate, and (c) shows the change in the pump liquid temperature.

In this case, while the set target value H ₀ of FIG. 11A is increasing at times t _{41 to} t ₄₃ and t _{44 to} t ₄₆ , the pump flow rate is large as shown in FIG. At the times t _{43 to} t ₄₄ and t _{46 to} t _{47 when the} set target value H ₀ is descending, it is necessary to replenish the liquid amount of the slight difference between the tank outflow amount and the change of the set target value. Time t ₄₃ to t ₄₄ and t ₄₆
At ~ t _47, etc., the rotational energy of the pump is used to calculate
The pump fluid temperature is raised as shown in the figure, but it is cooled during the rising time of the set target value H ₀ that immediately follows, and at times t _{41 to} t ₄₂ , t ₄₄
Ambient temperature T, the liquid temperature of the pump is relatively quickly as ~t ₄₅
It decreases to H ₀ and keeps a constant value TH ₀ until the next rise.

Therefore, the peak value of the pump liquid temperature is only TH _P as shown in the figure, and this value is much lower than the maximum limit THL at which the rise of the pump liquid temperature is allowed. There is no worry of adverse effects.

For example, in a water supply water supply pump, under the same conditions as in the case of FIG. 4, the degree to which the water temperature rises is 1 to 2 ° C. on average.
Can be designed within.

Fig. 5 shows that the amount of outflow from the tank is medium and the set target value
The case where the amount of decrease of H ₀ is slightly smaller is shown. FIG. 7A shows the tank liquid level height, and FIG.

In this case, time t _{53 to} t ₅₄ , t _{56 to} t ₅₇ when the set target value H ₀ is falling and initial time t _{51 to} t ₅₂ , when the set target value H ₀ is rising in FIG. Set target value H ₀ such as t _{54 to} t ₅₅
When the position of the liquid level WL indicated by a thicker dotted line is higher than that, it is not necessary to replenish the tank 9 with liquid, and the operation of the pump 4 is stopped. Therefore, the pump 4 is operating only at a part of the set target value H ₀ at times t _{52 to} t ₅₃ , t _{55 to} t ₅₆ , but its flow rate is the amount of liquid flowing out from the tank 9. As a result, there is a flow rate that is much larger than the flow rate that accompanies the rise in the liquid temperature, because the set target value H ₀ is increased by the amount of the liquid required to follow the rising slope.

Of course, the liquid temperature does not rise during the period in which the pump 4 is stopped, so in the case of FIG. 5, the liquid temperature does not rise and is constant.

Note the much the case of FIG. 5 and in the outflow from Similarly tank 9, when slightly less than the amount of downward movement of the set target value H _0, as shown in FIG. 6, descends set target value H ₀ After reaching the lower limit target value HB, the liquid level WL position indicated by the thick dotted line does not rise immediately until it reaches the lower limit target value HB, for example, the set target value at times t _{63 to} t _{64 in} FIG. H ₀ is set to a constant value equal to the lower limit target value HB, and the set target value H ₀ is increased from the time t _{64 in} FIG. 6 when the set target value H ₀ and the position of the liquid level WL coincide. , If the set target value H ₀ is set in a waveform in which a triangular waveform and a constant value equal to the lower limit target value HB are alternately repeated, the operation stop time of the pump 4 becomes long, and the operation start and stop within the same time The number of repetitions is also reduced, which can be useful for energy saving and extending the life of the pump 4 and related equipment. It

The setting target value H ₀ of such an intermittent triangular wave is written in advance in the detection information of the liquid level sensor 11 of this embodiment, the data of the liquid level setting means 13, and the computer incorporated in the automatic control controller 12. The stored program can be set over time while the computer itself determines.

FIG. 7 shows a case where the amount of liquid used is extremely small, or even when the amount of liquid used is zero, the amount of liquid flowing out from the tank 9 is extremely small due to liquid leakage in the piping system. The height of the liquid level in the tank, the figure (b) shows the change of the pump flow rate.

In this case, the pump 4 is operating at time t _72-
such as t _73, t ₇₅ ~t _76, and increases the set target value H _0, because it is very short time just before reaching the upper limit target value H _P, although no increase liquid temperature, for a short time In addition, since the pump 4 starts and stops the operation, it may adversely affect the pump and other devices.

Therefore, in this case, if the waveform of the set target value H ₀ is set to repeat the intermittent triangular wave as shown in FIG. 8, the pump stop time can be made longer as at times t _{82 to} t _{83 in} the figure. At the same time, since the time from the start of pump operation to the stop becomes longer as shown at times t _{83 to} t _{84 in} the figure, there is no fear of adverse effects on the pump and other devices.

Further, as shown in FIGS. 5 and 6, when the outflow amount from the tank is almost equal to the decreasing change of the set target value H ₀ , and when the tank outflow amount is accompanied by a slight change, the pump is started. The frequency of stoppages may increase.

In order to avoid this, as shown in FIG.
Position of the WL is, after the time t ₉₁ which exceeds the set target value H _0, when meeting the set target value H ₀ again while the set target value H ₀ is lowered (time t _92), the set target The value H ₀ is lowered stepwise to the lower limit target value HB of the liquid level, and then the set target value is raised at a predetermined slope from the time when the set target value H ₀ and the position WL of the liquid level match for the first time (time t ₉₃ ). As described above, a program written in advance in a computer incorporated in the automatic control controller 12 can cause the computer to change the set target value over time while making a judgment.

The various cases of the flow rate of the liquid flowing out of the tank 9 have been described above with reference to FIGS. 3 to 9.

In this way, the set target value H ₀ is not a constant value as in the past,
It is repeatedly changed, and the set target value H ₀ is compared with the position of the liquid level WL in the tank, and the pump 4 is operated only when the position of the liquid level WL is lower than or equal to the set target value H _0. As long as the pump 4 is controlled so that the position of WL approaches the set target value H _0, and the pump 4 is stopped during other time zones, as described above, the flow rate flowing out from the pump 4 is small. Therefore, the chances of raising the temperature of the liquid in the pump are reduced.

Even if the liquid temperature is raised as shown in Fig. 4,
The amount is small, and the liquid temperature in the pump can be made to have a sufficient margin with respect to the permissible limit of the liquid temperature increase by appropriately setting the repetition period of the triangular wave.

In the above description, when the portion of the triangular wave having the set target value H ₀ is changed to the sawtooth wave, the sawtooth wave including the descending slope (the rising slope is not included is not included in the present invention. However, the effect is small, and the same effect as described above can be obtained only in the case of a sawtooth wave including a rising slope.
In this case, when the set target value H ₀ decreases stepwise from the rising portion to the lower limit target value HB, the pump always stops, so in the case of a sawtooth wave, compared to a triangular wave, the pump operation stops, Opportunity to start driving increases.

In the above explanation, all are open tanks, and the numerical value related to the storage amount is the output of the liquid level sensor.However, a pressure tank is used, and the output of the pressure sensor attached to this tank is used as the numerical value related to the storage amount. Gives the same effect.

In this case, compared to the pressure tank and the pressure switch system, in the pressure switch system, the intermittent operation of the pump is performed even when the flow rate into and out of the tank is large, but in the system of the present invention, the flow rate above a certain level. If there is, it is also excellent in that the operation is always continued.

Others that work in the same way as the pressure tank, for example, instead of the tank, the measured value corresponding to the numerical value related to the storage amount of the tank is obtained from the pressure at a certain place provided in the middle of the transfer pipe that is sent from the pump 4 to the fluid use place. The information can be obtained and given to the automatic control controller.

The setting target value can be set in an analog manner by using hardware such as a triangular wave oscillation circuit and controlled in an analog manner.

(Effects of the Invention) As described above, according to the present invention, the target value of the numerical value regarding the storage amount of the tank is periodically changed, and the pump is operated only when the position of the liquid level of the tank is lower than or equal to the target value. Control so that the pump and the liquid inside the pump will not rise abnormally, and the rising slope that will not cause an abnormal rise in the temperature of the pump and the liquid inside the pump is included in the waveform of repeated changes in the target value. Without using a flow rate detector such as a switch, it is possible to reliably prevent an abnormal rise in the temperature of the pump and the liquid inside the pump with a simple configuration that requires only one type of numerical value detector for the storage amount of the tank.

Therefore, the number of parts constituting the pump system is small, the cost can be reduced, and the reliability of the system can be improved.

Further, since the storage amount can be controlled finely and accurately, it is easy to downsize the tank.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a system according to the present invention. FIG. 2 is a graph showing an example of set target values for the tank liquid surface position for controlling the pump in the embodiment of FIG. FIG. 3 is a graph showing an example of changes in the tank liquid level, the pump flow rate, and the pump liquid temperature when the outflow amount of the tank is relatively large. FIG. 4 is a graph showing an example of changes in the tank liquid level, the pump flow rate, and the pump liquid temperature when the tank outflow amount is medium and slightly larger than the set target liquid level lowering amount. FIG. 5 is a graph showing an example of changes in the tank liquid level and the pump flow rate when the tank outflow amount is medium and is slightly smaller than the set target value liquid level descent amount. FIG. 6 is a graph showing an example of changes in tank liquid level and pump flow rate when the set target value is an intermittent repetitive waveform of a triangular wave with the outflow amount under the same conditions as in FIG. . FIG. 7 is a graph showing an example of changes in tank liquid level and pump flow rate when the tank outflow amount is extremely small. FIG. 8 is a graph showing an example of changes in the tank liquid level and the pump flow rate when the set target value is the intermittent repetitive waveform of a triangular wave with the tank outflow amount under the same conditions as in FIG. 7. . FIG. 9 is a graph showing an example of changes in the tank liquid level and the pump flow rate when the tank outflow amount is almost equal to the set target value liquid level lowering amount and is accompanied by a short period of minute fluctuations. FIG. 10 is an explanatory diagram showing an example of the configuration of a conventional pump automatic control system. 1 …… AC power supply 2 …… Inverter 3 …… Motor 4 …… Pump 5 …… Lower tank 6,7 …… Pipe 8 …… Flow rate detector 9 …… Upper tank 10 …… Upper tank outlet 11 …… Liquid level sensor 12 …… Automatic controller 13 …… Liquid level setting means 14 …… Set liquid level change amount setter 15 …… Set liquid level change speed setter HB …… Liquid level lower limit target value H ₀ …… Liquid upper limit target value WL ...... liquid surface of the set target value H _P ...... liquid surface of the surface

Claims (5)

[Claims] 1. A target value of a storage amount of a tank for storing a fluid transferred by a pump is set, and a rotational speed of the pump is set so that a detected value of the storage amount of the tank approaches the target value. In the pump automatic control system for controlling, the target value is repeatedly changed with a waveform including a slope that increases at least, and when the detected value does not exceed the target value, the detected value of the pump approaches the target value. While controlling the rotation speed, when the detected value exceeds the target value,
As a result, the rotation of the pump is stopped, and a pump automatic control system for controlling the rotation speed of the pump by changing the storage target value. 2. The automatic pump for controlling the rotation speed of the pump by changing the storage target value according to claim 1, wherein the numerical value relating to the storage amount is a numerical value representing the position of the liquid level in the tank. Control system. 3. A pump for controlling the rotational speed of a pump by changing the storage target value according to claim 1, wherein the numerical value relating to the stored amount is a numerical value representing the pressure of the fluid stored in the tank. Automatic control system. 4. The waveform of the target value is a continuous repeating waveform of a triangular wave or a sawtooth wave.
An automatic pump control system for controlling the rotational speed of a pump by changing the storage target value described in the item. 5. The target value waveform alternates between a single triangular wave, a single sawtooth wave, or a waveform obtained by cutting a part of a single triangular wave, and a portion that does not change at a constant value. An automatic pump control system for controlling the rotational speed of a pump by changing the storage target value according to claim 1 which is a continuous waveform repeated in the above.