JPS63131892A - Pumping device - Google Patents

Abstract

PURPOSE:To dissolve the troubles due to steam by reducing the number of revolutions of a motor through taking a point, at which the temperature in the water passage for a pump reaches approximately 80 deg.C, as the boundary. CONSTITUTION:Between a heat exchanger 6 and the water suction opening 7 of a pump 3 are provided a boiler 8 together with a temperature sensor 9. The temperature sensor 9 detects the water temperature at about 65-80 deg.C, and then, with a control circuit 10 is combined such an element that reduces the number of revolutions of a motor 1 according to the signals from the sensor 9. Thereby, if the number of revolutions is reduced when the temperature rises, the negative pressure generated at the water suction opening 7 becomes small, and accordingly, the quantity of the generated steam is reduced so that the troubles due to steam can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a pump device configured to prevent abnormal operation from occurring due to changes in water temperature.

``Prior Art'' When a pump device pumps water, when the water temperature rises to the temperature at which steam is generated, the negative pressure on the water suction side disappears due to the pressure of the steam, making it difficult to absorb water.

For this reason, the pump device is generally configured so that the negative pressure on the water suction side is not utilized when operating the pump device when the water temperature is high.

However, when high-temperature water is circulated by a pump device, such as hot water circulation in a boiler, if there is resistance in the circulation path, negative pressure is generated on the water suction side of the pump device.

When such negative pressure is generated, this negative pressure disappears due to the generation of steam, and the suction force of the pump device ceases to act.

As a result, hot water circulation by the pump device may stop, or
Additionally, operational efficiency may deteriorate.

In particular, there is a natural change in the boiling point due to changes in water pressure, and on the water suction side, the pressure becomes extremely low due to the negative pressure of the pump device, so steam is generated at a lower temperature than under high pressure. .

If such steam generation occurs around the impeller of the pump device, the impeller will stop pumping.

Therefore, the condition will be the same as dry running, which will damage seals such as mechanical seals and cause water leakage.

In addition to such failures, the pump action becomes unstable when steam is generated, which may cause the amount of circulating water to change, the air in the water to be separated and stagnate and blow out, and to generate noise in the circulation path. This resulted in problems such as

[-Problems to be solved by the invention] The present invention was made in view of these circumstances,
The object of the present invention is to obtain a pump device that eliminates various problems caused by the generation of steam.

"Means for Solving the Problem" The present invention has an electric motor configured to be variable speed, a pump connected to the electric motor, a temperature sensor provided in the water passage of the pump, and a signal from the temperature sensor 9' as described above. The problem is solved by connecting the electric motor to a control circuit that changes speed, and reducing the rotational speed of the electric motor when the temperature of the water passage reaches about 80°C.

"Function" When the water temperature rises to about 80 degrees Celsius, where steam is generated, the temperature sensor generates a signal and transmits the signal to the control circuit, and the control circuit that receives this signal reduces the rotation speed of the motor. As a result, the pump action decreases due to the decrease in the rotational speed of the electric motor.

When the pumping action decreases, the negative pressure on the water suction side inevitably decreases, resulting in less steam generation and fewer obstacles to steam generation.

Although the amount of water decreases due to such a decrease in pumping action, stable operation can be achieved compared to various problems caused by steam generation.

When steam is generated under low pressure, by setting the temperature at about 80 DEG C. as a boundary, it is possible to accommodate a wide variety of water flow resistances in piping, boilers, and the like.

"Embodiment" The present invention will be explained based on an embodiment shown in the drawings. FIG. 1 shows an application example of a pump device according to an embodiment of the present invention, and FIG. The figure shows an example of characteristics for controlling the rotation speed.

In FIG. 1, the pump device includes a pump 3 equipped with an impeller 2 connected to an electric motor 1 capable of variable speed, and a heat exchanger 6 connected to a discharge port 4 of the pump 3 via a pipe 5. It is provided.

And between the heat exchanger 6 and the water suction lower of the pump 3,
A boiler 8 is provided, and the hot water is configured to circulate in the direction of the arrow shown on the piping 5.

Generally speaking, the boiler 8 is equipped with a temperature sensor 9 and is configured to detect water temperature.

The temperature sensor 9 is an element whose resistance changes with changes in temperature, such as a thermistor, and a control circuit 10 that controls the rotation speed of the electric motor 1 based on a signal from the temperature sensor 9 is formed.

The control circuit 10 is configured to detect the rotation speed of the electric motor 1 using an encoder 11 provided in the electric motor 1 and maintain the rotation speed at a predetermined rotation speed.

The electric motor 1 can be easily and accurately controlled by using a type of electric motor that is easy to control, such as a transistor motor.

The thermistor 9 is combined with a control circuit 10 with an element that detects a water temperature of about 65 to 80°C and uses the signal to reduce the rotation speed of the electric motor 1. It is composed of

In Fig. 2, the operating characteristics of the water temperature and the pump are that when the water temperature is below 65°C, the motor 1 is operated at 5,000 revolutions/minute, and when the water temperature is 80°C, the motor 1 is operated at 3,000 revolutions/minute. The temperature is inversely proportional to the temperature change during that time.

In such a configuration, when the boiler 8 is operated and the water temperature rises, and the pump device is operated, the electric motor 1 is operated at 5,000 revolutions/minute if the water temperature is 65°C or less. The amount of water discharged is large and the pump performance is improved.

Then, when the water temperature rises and exceeds 65°C, the resistance change of the temperature sensor 9 acts as a signal to the control circuit 10 to reduce the rotation speed of the electric motor 1, and the rotation speed of the electric motor 11M1 changes as shown in FIG. It changes so that it can be changed.

When the temperature rises like this, when the rotation speed of the electric m'+ decreases, the negative pressure generated in the water suction lower becomes smaller, so less steam is generated, and impeller 2 avoids problems such as air generation. can.

Of course, when the water temperature approaches 100°C, it becomes difficult to reduce the amount of steam generated due to the decrease in the rotational speed of the electric motor 1, but it is possible to reduce the rotational speed of the electric motor 1 to about 60% at a boundary of about 80°C. By doing so, the pump device can be operated stably within a practical range without causing an extreme drop in water volume.

In other words, if the rotational speed of the electric motor 1 is lowered to a low rotational speed of 60% or less, the amount of water pumped becomes extremely small, which seems to cause problems in practicality.

Also, the boundary where the rotation speed is reduced to about 60% is set to 90%, for example.
If the temperature is set to a temperature as high as ℃, if the negative pressure of the water suction lower becomes large, practical operation will not be possible.

Under these circumstances, in order to construct a motor that can be used in a wide range of applications, it is preferable to reduce the rotational speed to about 60% with the limit at about so'c.

Of course, as long as the idea of the present invention is not departed from, the temperature is not limited to 80°C and the rotation speed is 60%, and the boundary temperature can be set in the range of 60 to 90°C depending on the negative pressure. Moreover, it is possible to reduce the rotation speed by about 50 to 80%.

In addition to controlling the rotation speed in inverse proportion to temperature changes, the same effect can be obtained by using a switch that operates at a boundary temperature to change the number of poles of the motor and lower the rotation speed.

"Effects of the Invention" According to the present invention, when the water temperature rises and steam is generated, the capacity of the pump is reduced to avoid troubles caused by the steam, and stable operation can be continued. When used in combination with a heat exchanger, etc., the effect of stable operation can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows an example of application of a pump device according to an embodiment of the present invention, and FIG. 2 shows an example of characteristics for controlling the number of revolutions. 1... Electric motor, 2... Impeller, 3... Pump, 4... Discharge port, 5... Piping, 6... Heat exchanger, 7... Water inlet, 8...・Boiler, 9...
-Temperature sensor, 10...control circuit.

Claims (1)

[Claims] The electric motor is configured to be variable speed, a pump is connected to the electric motor, a temperature sensor is provided in the passageway of the pump, and a signal from the temperature sensor is connected to a control circuit for changing the speed of the electric motor, so that the temperature of the passageway is approximately A pump device characterized in that the number of rotations of the electric motor is reduced at a point at which the temperature reaches 80° C.