JPS6316594B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to means for improving the self-priming performance of a pump device using a variable speed rotary positive displacement pump.
This is particularly effective when the working fluid has low viscosity.

Configuration of conventional examples and their problems Displacement pumps are self-priming due to their operating principle, but rotary displacement pumps in particular have sufficient self-priming for low viscosity fluids such as water. However, I could not say that.

Figures 1 to 2 for conventional pump devices of this type
This will be explained using figures.

A vane pump 2 is installed above a water storage tank 1, and a pump suction port 3 and the water storage tank 1 communicate with each other through a suction channel 4. A nozzle 7 is installed from the pump discharge port 5 through a discharge flow path 6.

The pump 2 is driven by a motor 8, and the rotation speed of the motor 8 can be changed by a variable speed circuit 9. Therefore, the pump 2 can be set to a desired rotational speed within a predetermined rotational speed range.

In the pump device configured in this way, when drawing up water from the water storage tank 1 by self-priming, the self-priming ability of the pump is insufficient, and it takes a very long time for the pump 2 to self-prime, or it may continue to self-prime forever. I had a problem with not doing it.

Technical Problem of the Invention In order to solve the problems caused by the lack of self-priming performance as shown in the above-mentioned conventional example, a basic technical problem is to improve the self-priming performance of the pump itself.

In a rotary positive displacement pump, the factors that determine the level of self-priming are considered to be mainly the pump internal clearance, the viscosity of the working fluid, and the pump rotation speed. Among these, the internal clearance of the pump has a limit in terms of processing accuracy and processing cost, and it cannot be expected to exceed a certain level. The viscosity of the working fluid cannot be selected from the pump side.

Therefore, the present inventors investigated the relationship between pump rotation speed and self-priming pressure.

Conventionally, as shown in FIG. 2, it was thought that as the rotation speed increases, the self-suction pressure increases between the pump rotation speed N and the self-suction pressure -Ps. Such a relationship was established in general vacuum pumps and the like.

However, when we investigated the case of a rotary displacement pump that uses a low-viscosity fluid as the working fluid, we found that the self-priming pressure reaches its maximum value at a certain rotation speed, and at lower or higher rotation speeds, as shown in Figure 3. The results showed that the self-priming pressure decreased significantly.

This result can be understood to be because the low viscosity fluid remaining in the seal portion inside the pump is removed due to centrifugal force as the pump rotation speed increases.
Furthermore, when the pump rotational speed is low, the displacement volume of the pump is small, so it is thought that self-priming is basically difficult to achieve.

Therefore, since self-priming depends on the pump rotation speed, self-priming can be easily achieved by automatically detecting the optimum rotation speed of the pump and controlling the pump rotation speed to this rotation speed. It was necessary to ensure sufficient self-priming ability.

In the present invention, as a means to automatically control the pump rotation speed during self-priming, a sensor and a calculation device that detect the integral of the pump suction side pressure by the pump rotation speed and calculate the value that maximizes the self-priming pressure are provided. The pump is provided with an optimum self-priming rotation speed selection means consisting of a circuit, and a pump variable speed circuit for adjusting the pump rotation speed to this rotation speed.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

A vane pump 2 is installed above the water storage tank 1, and the pump suction port 3 and the water storage tank 1 are communicated through a suction passage 4. A nozzle 7 is installed at the pump discharge port 5 via a discharge flow path 6.

The pump 2 is driven by a motor 8, and the rotation speed of the motor 8 can be changed by a variable speed circuit 9.

Furthermore, in this embodiment, a pressure sensor 10 for detecting self-suction pressure is installed in the suction passage 4, a rotation speed sensor 11 for detecting the motor rotation speed is installed in the motor 8,
Further, these sensors are connected to an arithmetic circuit 12 that calculates the pump rotation speed at which the self-priming pressure is maximized. The output of this arithmetic circuit 12 is also coupled to a variable speed circuit 9 to maintain the pump rotational speed during self-priming.

In addition, a pressure switch 13 is provided in the discharge passage 6, and when the pump self-priming continuous rotation ends, the pump 2 starts discharging, and the pressure in the discharge passage 6 rises, the pressure switch 13 is turned ON. A signal is input to the arithmetic circuit 12, and the pump rotation speed at the time of pump self-priming is shifted to the normal pump rotation speed.

Note that the same members as in FIG. 1 are given the same reference numerals.

In the above configuration, since the pump rotation speed during self-priming is set so that the self-priming force is maximized, a pump device with excellent self-priming performance can be obtained. Furthermore, this embodiment has a feature that it is very easy to use because the operations from setting the pump rotation speed during self-priming to transition to normal operation are performed automatically.

Effects of the Invention As described above, the pump device according to the present invention provides the following effects.

Since the pump rotation speed is controlled to the optimum speed when the pump self-primes, the self-priming performance of the rotary positive displacement pump can be dramatically improved, and the usability of the pump can be greatly improved.

[Brief explanation of the drawing]

Figure 1 is a system configuration diagram showing a conventional pump device, Figure 2 is a characteristic diagram showing the general relationship between pump self-priming pressure and rotation speed, and Figure 3 is a pump self-priming seen in a rotary displacement pump. A characteristic diagram showing the relationship between pressure and rotation speed, and FIG. 4 is a system configuration diagram showing an embodiment of the pump device of the present invention. 2... Pump, 4... Pump suction path, 9... Rotation speed variable circuit, 10... Pressure sensor, 11... Rotation speed sensor, 12... Arithmetic circuit.

Claims (1)

[Claims] 1 A rotary positive displacement pump, a pressure sensor provided in the pump suction passage, a rotation speed sensor that detects the pump rotation speed, and the pressure sensor and the rotation speed sensor are used to increase the pump self-priming pressure due to an increase in the pump rotation speed. an arithmetic circuit that detects the increment and calculates the gradient of the pump self-priming pressure with respect to the pump rotational speed, and calculates the pump rotational speed at which the pump self-priming pressure is maximum; and a calculation circuit that calculates the pump rotational speed based on the output from the arithmetic circuit. A pump device comprising: the variable speed circuit for controlling speed.