JPS595895A - Control device for pump - Google Patents

Abstract

PURPOSE:To control a hydraulic pressure stably in a wide flow amount range by a method wherein a reducing valve is provided in a delivery pipeline at the upstream side of a pressure switch while a small pipe, bypassing the reducing valve, is provided. CONSTITUTION:The pressure in the delivery pipe 5 is reduced to and kept in the constant pressure Pr by the reducing valve 11 within the wide range of the flow amount F3-F4, discharged from a valve 6. When the valve 6 is closed, the reducing valve 11 is closed, the pressures in the delivery pipe 5 and an expansion tank 8 are increased by a pressure difference between the pressures in the delivery pipe 13 and the delivery pipe 5 through a pressure transmitting pipe 12. When the pressure arrives at the upper limit value Ph of the pressure switch 7, the pump is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pump control device, and particularly to a pump control device suitable for stably controlling the pressure of fluid supplied by a pump.

Conventionally, as a device for controlling the pressure of fluid discharged from a pump and supplying fluid at a predetermined pressure to a demand location, etc.
The configuration shown in the figure is known.

As shown in FIG. 1, the suction port of the pump 1 is connected via a suction pipe 2 to a container 3 in which a fluid such as water is stored.
The discharge port is connected to JV! , a stop valve 4, a discharge pipe 5, and a valve 6. Further, the discharge pipe 5 is provided with a pressure switch 7 and an expansion tank 8. This pressure switch 7 operates within a pressure range set according to the desired fluid supply pressure.
When the pressure reaches the lower limit value or less, an on signal is output, and when the pressure reaches the upper limit value or more, an off signal is output. This signal is input to the motor control circuit 9, so that the electric motor 10 that drives the pump 1 is started or stopped.

The pre-ad expansion tank 8 prevents water hammer, etc., alleviates sudden pressure fluctuations in the pipe, and compensates for pressure drop in the discharge pipe 5 due to fluid leakage, etc. This prevents the vehicle from being started or stopped due to

The operation of the conventional example constructed as described above will be explained with reference to the discharge pressure P-flow cap F characteristic curve of the pump shown in FIG.

When the valve 6 is opened and the fluid flow rate becomes sufficiently larger than pl, and the pressure in the discharge pipe 5 becomes less than the lower limit value PL of the pressure switch 7, the pump 1o is operated, and the pump 1 starts to flow with the curve
Fluid is discharged at a pressure and flow rate along. When the valve 6 is closed in this state, the pressure inside the discharge pipe 5 is increased along the above curve (3), and when this pressure reaches the upper limit value PH of the pressure switch 7, the pressure switch 7 turns off the pressure. A signal is output and the motor 10 is stopped, thereby stopping the pump 1. Even when the pump 1 is stopped, the fluid pressure in the discharge pipe 5 is maintained at a substantially constant value by the pressure-accumulating fluid in the expansion tank 8.

Next, when the valve 6 is opened again, the fluid stored in the expansion tank 8 is sent out via the valve 6, so the pressure in the discharge pipe 5 is gradually reduced until the pressure reaches the lower limit PL. When this occurs, the electric motor 10 is operated again, and as described above, the fluid discharged by the pump 1 is maintained at least below the upper limit value. Further, if the flow rate is within the range of 11'1-F2, the pressure is maintained within the range of PL to PH.

However, when used in a region where the flow rate is below PL, the fluid pressure quickly reaches the upper limit PH, the pump 1 is stopped, and fluid is supplied from the expansion tank 8. If the capacity of the expansion tank 8 is small, the fluid pressure will immediately drop below the lower limit value PL, and the pump 1 will be operated again. However, since the flow rate used is small, the fluid pressure quickly reaches the upper limit value PH, and the pump 1 is immediately stopped.

In other words, in the conventional example described above, when the amount of fluid used at the demand location is small, the electric motor 1o and the pump 1 are repeatedly operated @
The system was frequently operated and stopped, which caused the following drawbacks and problems.

(1) The fluid supply pressure changes drastically between the upper limit value PH and the lower limit value PL of the pressure range set by the pressure switch 7 in a short period of time. As a result, for example, if we consider the case where it is applied as a general hot water supply system of NOYAWARE, the pressure balance between the hot water side and the cold water side of the mixer faucet will change, and the hot water temperature will change drastically. There it was again.
(2) The pressure switch 7 operates more frequently, shortening the life of its contacts, and (3) the fi motor 10 starts more frequently, causing the winding temperature to rise abnormally due to the starting current, causing the electric motor to This has the drawback of damaging the product and shortening its lifespan.

Conventionally, solutions to (2) and (3) above include increasing the capacity of the expansion tank 8, delaying the restart time of the motor using a delay relay, etc., and extending the stop period by several minutes, and increasing the capacity of the expansion tank 8. It has been proposed to make the set pressure range of the pump variable and adjust the set value according to conditions such as the installation location of the pump 1, but either method can slightly reduce the frequency of operation and stoppage. It was only a minor problem, and not a fundamental solution.

An object of the present invention is to provide a pump control device that can suppress frequent fluctuations in pressure over a wide flow rate range including low flow areas, and can reduce the frequency of starting and stopping the electric motor that drives the pump. It's about doing.

The present invention provides a pressure reducing valve in a discharge pipe on the upstream side of a pressure switch, sets a set pressure of the pressure reducing valve to a constant value within a set pressure range of the pressure switch, and provides a pressure reducing valve composed of a thin tube that bypasses the pressure reducing valve. By providing a transmission pipe, the fluid pressure can be stably controlled over a wide flow range of 1k.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 3 shows a system configuration diagram of an embodiment of the present invention. Components having the same functions and configurations as those of the conventional example shown in FIG.

As shown in FIG. 3, the difference between this embodiment and the conventional example shown in FIG. The valve 11 is bypassed and a pressure transmission pipe 11 made of a thin tube is provided. The pressure reducing valve 11 has a wide flow rate range (F3~F
In 4), the pressure of the inflowing fluid is reduced to a constant value PR and the fluid is allowed to flow out. The pressure transmission pipe 12 is a thin tube that increases the secondary pressure of the pressure reducing valve 11 to the primary pressure (pump discharge pressure) when the flow rate decreases and the pressure reducing valve 11 is closed.

The operation of the embodiment configured as described above will be explained with reference to the delivery fluid pressure Kerr flow rate characteristic curve (2) of the pressure reducing valve 11 shown in No. 4Z. In addition, what is shown by the broken line I in the figure shows the discharge pressure-flow rate characteristic curve l of the pump, similar to that shown in FIG.

As shown in the figure, the upper limit PH of the pressure switch 7 in this embodiment is 0.9 Ky/era, the upper limit PL is 0.6 to 9/i, and the secondary pressure PR of the pressure reducing valve 11 is 0.7K? / ca, and the set flow rate of the pressure transmission pipe 12 is such that the reduced pressure of the pressure reducing valve 11 is 0.5 K9
It is set to be 60t/, H when /cj.

Because of this setting, when the pump 1 is driven with the valve 6 closed, the discharge pipe 5 and the discharge pipe 1
Immediately after the fluid pressure in pump 1 reaches the upper limit PH,
is stopped and held at 0.9 F=q/crA.

At this time) the pressure inside the expansion tank 8 is also 0.9Kg/ad
It has become. Next, when the valve 6 is opened, the fluid in the expansion tank 8 is sent out through the discharge pipe 5, and the pressure in the discharge u5 is reduced to the lower limit value pL (0, 6y, y/F
). Pressure switch 7 is activated from 2' to drive pump 1, and fluid is discharged from discharge pipes 13 and 5.
It is sent out from valve 6 through. At this time, the pressure in the discharge pipe 13 is the discharge pressure of the pump 1, and the pressure in the discharge v5 is equal to the flow rate discharged from the valve 6 from F3 to F4 (60 to
Within a wide range of 670 t/H), the pressure of PR (0.7 Kg/ttl) is kept constant and reduced by the pressure reducing valve 11. Further, when the valve 6 is closed, the pressure reducing valve 11 is closed, and the pressure difference between the pressure inside the discharge pipe 13 and the pressure inside the discharge pipe 5 causes the pressure to flow between the discharge pipe 5 and the expansion tank 8 through the pressure transmission pipe 12.
The pressure inside is gradually increased, and the pressure inside is turned on by pressure switch 7.
When the upper limit of PH (o-9"9/ttl) is reached, pump 1 is stopped.

As mentioned above, in the conventional type, the flow rate is less than or equal to the flow rate J"l (510 z/H in the illustrated example) corresponding to the upper limit value PH (the normal practical flow rate range is 200 to s o o t).
/H. ), the motor 10 stops operating, that is, the pump 1 starts and stops frequently, and the fluid delivery pressure fluctuates drastically. However, according to this embodiment, the pressure reducing valve reduces the flow rate to Fs. (60 t/H in the illustrated example) or less, the constant pressure PR (0,7
Kg/J), and the flow rate corresponding to the upper limit PH of the pressure switch is approximately 20 L/H, so the wide flow rate range shown by (8) in the figure (approximately 20 t in the illustrated example) It is possible to send fluid at a stable pressure from /H to about 950 t/I ( ).Incidentally, the conventional stability control node was in a narrow range as shown by ) in the figure.

In addition, according to this embodiment, if the flow rate is about 2 ot/H or more, the pressure switch is operated frequently, so the frequency of running and stopping the electric motor is significantly reduced, and the pressure switch has a long lifespan. In addition to being able to extend
Damage to the electric motor can be prevented and its life can be extended.

In addition, the set flow rate of the pressure transmission pipe in the above example was set to 6°t/H.
However, the set flow rate is not limited to this, and the set flow rate can be arbitrarily set depending on the pipe size.

For example, by adjusting the pipe size and reducing the set flow rate, it is possible to widen the flow rate range in which phase-stable operation can be achieved.

As explained above, according to the present invention, it is possible to not only suppress drastic fluctuations in pressure but also to control the pressure to a constant value over a wide flow rate range including a low flow rate region. Furthermore, since the frequency of stopping the electric motor that drives the pump and the +tms degree of the pressure switch can be reduced, damage to the viewing rock is prevented and the life of the electric motor and pressure switch is significantly extended.

[Brief explanation of the drawing]

Fig. 1 is a system configuration diagram of a conventional example, Fig. 2 is a diagram showing a pump discharge pressure-flow rate characteristic curve for purposes of explanation, Fig. 3 is a system configuration diagram of an embodiment of the present invention, and Fig. 4 is a diagram showing a pump discharge pressure-flow rate characteristic curve. It is a figure which shows the delivery fluid pressure Kerr flow rate characteristic curve of the illustrated example. 11...Pressure reducing valve, 12...Pressure transmission pipe. Figure 1 Wave body flow rate F → Figure 3 Figure 4 Fluid flow 1 (++)

Claims (1)

[Claims] (1) A device installed in a discharge pipe of a pump driven by an electric motor to detect the discharge pressure of the pump, and when the detected pressure reaches a lower limit value or less of a set pressure range, drives the electric motor to reach the upper limit value. In a pump control device comprising a pressure switch that outputs a signal to stop the electric motor when the electric motor A pump control device characterized in that it is configured by providing a conduction pipe.