JP2007187067A - Water supply device for automatically adjusting pump stop rotating speed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water supply device using a pump rotating speed for stop determination while improving the reliability of stop determination by eliminating the need for adjusting a stop rotating speed after site installation and after a certain period. <P>SOLUTION: A too small water amount searching function is provided for intentionally making the rotating speed of the pump higher/lower independently of pressure control to determine a degree of using the amount of water with a pressure fluctuation during the operation. A system adjusts the stop rotating speed with the too small water amount searching function. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for operation control in a water supply apparatus that performs pressure control by changing a pump rotation speed.

  In the water supply apparatus, there is a method of performing pressure control (constant pressure control) by changing the pump rotation speed using an inverter or the like. In this case, a general method for determining whether to stop the pump when the amount of water is low is to stop the pump by detecting an insufficient amount of water using a mechanical contact such as a flow switch. However, with mechanical contacts, there are cases where the pump does not stop even though the amount of water is too small due to foreign matter mixing or deterioration between the contacts, and the water temperature overheats causing an accident.

  Therefore, a method is adopted in which stop determination is made based on pump rotation speed instead of using a flow switch. When performing constant pressure control, the pump rotation speed decreases as the water volume decreases. Therefore, when the rotation speed is lower than a certain rotation speed, it is determined that the water volume is too low and the pump is stopped.

For example, Patent Document 1 discloses a water supply device that can detect a closing operation state of zero water amount and enter a small water amount stop operation without using an expensive flow switch. Patent Document 2 discloses a water supply system that stops a small amount of water only by determining a pump operation frequency and a pipe pressure. Patent Document 3 discloses an automatic water supply method in which once the start pressure and stop pressure of the pump are set, the supply water pressure can be automatically adjusted even if the supply pressure drops below the stop pressure due to pump wear or the like. Reference 4 discloses an automatic water supply device that once sets the starting pressure of the pump, automatically adjusts the differential pressure between the stopping pressure and the starting pressure even if the stopping pressure changes due to pump wear or the like. Yes.
JP 2002-130141 A Japanese Patent Laid-Open No. 8-159078 Japanese Patent Laid-Open No. 10-9145 Japanese Patent Laid-Open No. 10-318181

  However, with the above method for determining stoppage based on the pump rotation speed, the pump rotation speed at which stop determination is made depends on the pump installation status (conditions on the pump suction side, etc.). In addition, since the pump rotational speed varies depending on the deterioration of the pump over time, it is necessary to readjust after a certain period of time, and adjustment takes time. Also, if an adjustment error occurs, an overheating accident will occur.

  An object of the present invention is to improve the reliability of stop determination by making it unnecessary to adjust the stop rotation speed performed after on-site installation and after a certain period in a water supply apparatus that performs stop determination at the pump rotation speed. is there.

  In order to achieve the above object, in the present invention, a pump, a pressure sensor for detecting the pressure on the discharge side of the pump, and a control for performing pressure control by inputting a signal of the pressure sensor and changing a pump rotation speed In the water supply apparatus comprising a panel, the control panel includes a pressure setter for inputting a target pressure value used for the pressure control, a pressure calculator for calculating a pressure from the input value of the pressure sensor, and the target pressure value A rotation speed converter that changes the pump rotation speed so that the pump rotation speed is compared, and an operation controller that compares the pump rotation speed and the stop rotation speed to determine whether the pump is stopped. And an automatic tuning function for automatically adjusting the stop rotational speed.

  By using the present invention, reliability is improved because a mechanical contact such as a flow switch is not used for stop determination, and trouble such as adjustment of stop determination rotation speed is omitted, adjustment errors, forgetting periodic adjustment, etc. Can prevent human error.

Embodiments of the present invention will be described below with reference to the drawings.
In the embodiment of the present invention, an inverter is used to change the rotational speed of the pump. A signal from a pressure sensor installed on the pump discharge side is input to the microcomputer used in the inverter, and the discharge pressure and rotation speed of the pump are controlled by the microcomputer. The auto-tuning algorithm is programmed and installed in the microcomputer. Further, a memory element for holding the adjusted stop rotation speed is used, and the microcomputer writes the adjustment value to the storage element when the stop rotation speed is updated so that the adjustment value can be held even when the power is shut off. . Embodiments of the present invention will be described below with reference to FIGS.

  In FIG. 1, the block diagram of the water supply apparatus of Example 1 of this invention is shown. 1 is a commercial power supply. Reference numerals 2 and 3 denote inverters with a built-in pump control function. The pumps 6 and 8 are driven, and the pump speed can be freely changed by changing the frequency. The water supply device is normally composed of two pumps as a backup when one unit fails, and the water sent from the pumps 6 and 8 is supplied through the junction pipe 10 via the check valves 7 and 9. A pressure tank 11 is attached to the merging pipe 10 in order to suppress pressure pulsation absorption and pressure drop at the start of the pump. Moreover, in order to detect a pressure, the pressure sensor 12 is attached and the pressure signal is transmitted to each inverter by the cable 4. Reference numeral 5 is a wiring for sending the state of the inverter to the other side, and the state of the other side is monitored by the wiring 5 to perform an operation backup of the own pump and automatic backup at the time of failure.

  FIG. 2 shows a configuration diagram of the inverter. The inverter is equipped with an operator 13 for displaying an output frequency, a current value, and the like and setting a target pressure and the like. The operator 13 is operated by an MCU (microcomputer unit) 15, and when the setting value is changed by the operator 13, the MCU 15 stores and saves the setting value in the EEPROM 14 which is a storage element. In addition, when there is a value to be stored, the value can be stored in the EEPROM 14. The MCU 15 inputs the pressure signal of the pressure sensor to the equipped A / D converter, calculates the pressure value, and controls the rotation speed of the pump so that the pressure value becomes constant at the target pressure, Controls the operation of its own pump while monitoring the status of the counterpart inverter. At the same time, the inverter status is output to the counterpart inverter. The power section of the inverter rectifies the AC waveform from the commercial power supply by the converter section 16 and absorbs ripples by the capacitor 17 to generate a direct current, and then the MCU 15 turns on / off the switching element (transistor) 18. By this, an arbitrary frequency can be generated and the rotational speed of the pump can be changed.

  The operation is stopped when the amount of water used decreases, but the rotational speed of the pump is used to determine the stop of the excessive water amount. In addition, there is a method using a water meter or a flow switch, but the water meter is expensive and the flow switch is a mechanical contact point, so there is a high possibility of failure. FIG. 3 shows changes in pump characteristics (relationship between water volume and discharge pressure) depending on the pump rotation speed. The specification point in the figure is the customer's required specification (water quantity Qmax, pressure Haim), and the pump rotational speed Nmax that satisfies the specification point is determined from the specification point. This Haim is set as a target pressure, and the pump rotation speed is changed according to the amount of water so that the discharge pressure becomes Haim. As shown in the figure, the pump characteristic curve tends to decrease uniformly as Nmax changes from N1 to N1. The operating point in this case is the intersection of the characteristic curve and Haim in the figure because the discharge pressure constant control of the target pressure Hai is performed. Therefore, as the amount of water decreases from Qmax to Q1 and Q2, the pump rotation speed decreases. Using this characteristic, when the pump rotation speed falls to Ns, it is determined that the amount of water is too small Qs and the pump is stopped.

  Thus, when the pump rotation speed is used for the determination of the stop of the excessive water amount, it is necessary to determine and set the stop rotation speed Ns. However, since the pump characteristic curve varies depending on the pump installation situation (suction lift) at the site, Ns must be determined locally, and after a certain period of time, readjustment should be made in consideration of pump aging. It will be very time-consuming to do. In addition, if Ns is wrongly determined, there is a risk that the pump will not stop in spite of the insufficient amount of water and the water will overheat causing an overheating accident.

  In order to solve the above problem, the auto-tuning function of the stop rotational speed is programmed and installed in the MCU. The flowchart is shown in FIG. A feature is to use a search operation with a low water amount. The excessive water amount search operation is a method of estimating the amount of water used by intentionally increasing or decreasing the pump rotation speed regardless of the constant discharge pressure control and observing the pressure drop at that time. Specifically, once the pump rotation speed is increased to slightly increase the discharge pressure, then the discharge pressure is decreased to the rotation speed before the increase, and if the pressure drop is within the specified value within a certain time (several seconds), it is too low. This is a method of judging the amount of water and stopping the pump. Since the degree of pressure drop and the degree of water use are correlated, it is considered effective to determine the amount of water under this method.

It is sufficient to always perform the underwater amount search operation at a time interval that does not cause overheating. However, during this underwater amount search operation, pressure fluctuation occurs, and therefore it cannot be performed frequently. Therefore, the stop rotational speed is adjusted using the excessive water amount search operation.
At the start of initial operation after installation (step 4000), the stop rotational speed is not determined (step 4010). In this case, the time is measured (step 4030), and after a certain period of time T (set to a time that does not cause overheating) has elapsed (step 4050), an excessive water amount search operation is always performed (step 4060), and the result at this time is used. Set the stop rotation speed for the time being. If it is determined that the amount of water is too small (step 4070), [pump rotation speed + α] in which the water amount search operation is performed is set as the stop rotation speed (step 4080). The pump rotation speed -α] is set to the stop rotation speed (step 4090). This α is a tolerance and is a value determined by the maximum rotation speed of the pump to be used. Note that the stop rotational speed set at this time is stored in the EEPROM so as to be stored even when the commercial power supply is shut off (step 4100). The next opportunity to perform the search operation for the insufficient water amount is to measure the time when the pump rotation speed is equal to or lower than the stop rotation speed (step 4020), and the measurement time is elapsed for the time T (step 4040). Do not search for too little water at higher speeds. By using this method, the underwater amount search operation is frequently performed until it stops for the first time. However, since the stop rotational speed is determined thereafter, the underwater amount search operation is performed only at the time of the underwater amount.

  Moreover, the problem that the stop rotational speed changes due to deterioration of the pump over time is solved as follows. The program constantly monitors the pump speed so that the minimum pump speed is memorized. If the pump deteriorates over time, the characteristics of the pump will deteriorate, so operation at the minimum rotational speed cannot be performed. Therefore, if a time during which the pump rotational speed does not reach the minimum rotational speed has elapsed for a certain time Tr (for example, 24 hours), a program is constructed that considers that there is a possibility of deterioration over time and increases the stop rotational speed by + α.

After the pump is stopped and the stop rotational speed is determined, it may be stopped without searching for an insufficient amount of water below the stop rotational speed, but updating of the stop rotational speed and calculation of the stop rotational speed during aged deterioration are possible. Considering that the margin α has a tolerance α, it is more certain that the underwater search operation is performed. (Even if it is updated by mistake, it will be corrected again by the low water volume search operation)
These functions can be realized by using an EEPROM for storing set values and measurement time and an MCU in which the above program is mounted.

It is a block diagram of the water supply apparatus of Example 1 of this invention. It is a block diagram of an inverter required in order to implement this invention. FIG. 6 is a graph showing changes in pump characteristics when the pump rotation speed is increased or decreased. It is an algorithm of the auto-tuning function of the stop rotational speed in the present invention.

Explanation of symbols

1 Commercial power supply to drive the inverter 2 Inverter (Built-in pump control function)
3 Inverter (Built-in pump control function)
4 Pressure signal transmission cable 5 Inverter operation state transmission cable 6 Pump 7 Check valve to prevent backflow of water 8 Pump 9 Check valve to prevent backflow of water 10 Junction pipe 11 Pressure tank 12 Pressure sensor 13 Inverter state To monitor and set target pressure, etc. 14 Memory element (EEPROM) for saving setting and measurement time
15 Microcomputer 16 Converter section 17 Capacitor 18 Inverter section

Claims (4)

A pump,
A pressure sensor for detecting the pressure on the discharge side of the pump;
In a water supply apparatus including a control panel that inputs a signal of the pressure sensor and performs pressure control by changing a pump rotation speed,
The control panel includes a pressure setter for inputting a target pressure value used for the pressure control, a pressure calculator for calculating a pressure from the input value of the pressure sensor, and the pump rotation speed so as to be the target pressure value. A rotation speed converter that changes the pressure, and an operation controller that compares the pump rotation speed and the stop rotation speed to determine pump stop,
A water supply apparatus comprising an auto-tuning function for automatically adjusting the stop rotation speed in accordance with the installation state of the pump. In the water supply apparatus of Claim 1,
The auto-tuning function is provided with a function of automatically adjusting the stop rotation speed in accordance with deterioration of the pump over time. In the water supply apparatus of Claim 1 or Claim 2,
The control panel has a function of searching for a small amount of water to estimate pump use stoppage by estimating the degree of use of the amount of water by intentionally raising and lowering the rotation speed of the pump regardless of the target pressure at certain time intervals,
The water supply device characterized in that the auto tuning function adjusts the stop rotation speed based on the pump rotation speed at which the underwater amount search function is performed and the determination of the pump stop. In the water supply apparatus of Claim 2,
The auto tuning function has a function of storing the minimum value of the pump rotation speed when the pressure control is performed,
A water supply apparatus having a function of measuring a time when the pump rotation speed does not become a minimum value and determining that the pump rotation speed is continued for a certain period of time, and re-adjusting the stop rotation speed.

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