JPH0727432A - Controlling method for air conditioning refrigerator - Google Patents

Abstract

PURPOSE:To normally operate a refrigerator without stopping even when the refrigerator is started in the case where a cooler is set to a low load state. CONSTITUTION:Chilled water temperature to be fed from an evaporator 1 is measured by a temperature measuring unit 11, and a pressure of the evaporator 1 is measured by a pressure measuring unit 21. Circulating refrigerant amount is normally controlled based on the measured value of the unit 11. However, if a pressure of the evaporator 1 is lower than a set lower limit pressure value, control based on the measured chilled water temperature is preferentially operated to forcibly maintain or regulate openings of a suction vane 8 and a bypass valve 9 by pressure switches 14, 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an air conditioning refrigerator, and more particularly, to a normal air conditioning refrigerator even when the refrigerator is started under a low load condition. The present invention relates to a control method for operating a vehicle.

[0002]

2. Description of the Related Art A refrigerating machine for supplying cold water to a cooler of an air conditioning machine in an air conditioning facility equipped with the air conditioner and the refrigerating machine and a conventional control device therefor include, for example, one shown in FIG. This refrigerator R has an evaporator 1, a centrifugal compressor 2, a condenser 3, and a float valve 4, in which a refrigerant made of, for example, a CFC-based substance circulates to cool the air-conditioning cold water to a predetermined temperature. It is a device that cools down to and supplies it to the cooler 5. That is, when the liquid refrigerant is evaporated in the evaporator 1, the heat of vaporization is absorbed and the cold water in the cold water pipe 6 arranged in the evaporator 1 is cooled. The evaporated refrigerant is absorbed by the centrifugal compressor 2, is pressurized in the centrifugal compressor 2, and is then sent to the condenser 3 as a high-pressure and high-temperature gas. In the condenser 3, the refrigerant deprived of heat by the cooling water passing through the cooling water pipe 7 arranged in the condenser 3 liquefies, and then passes through the orifice by the float valve 4. It is sent to the evaporator 1 in a state where the pressure is drastically reduced. Cold water is cooled in this refrigeration cycle, and the cold water is supplied to the cooler 5.

A basic refrigeration cycle at this time is shown in FIG.
Describing with reference to the Mollier diagram shown in FIG. 3, point A is a state in which the refrigerant exits the evaporator 1 and enters the centrifugal compressor 2, and is on the saturated vapor line. If this refrigerant gas is compressed by adiabatic compression, it changes from A to B. When the compressed refrigerant is cooled in the condenser 3, the pressure remains unchanged and only the enthalpy decreases, and when all the refrigerant becomes liquid, it reaches the point C on the saturated liquid line. Further, when this liquid refrigerant is adiabatically expanded through the gap (orifice) of the float valve 4, the state of the refrigerant shifts from C to D. afterwards,
Entering the evaporator 1, heat is taken from the surroundings and enthalpy increases,
When it completely evaporates, the point A is reached. The amount of heat used for freezing in this cycle is the difference in enthalpy between points A and D,
The refrigeration capacity is represented by the product of this enthalpy difference and the refrigerant circulation amount.

In actual operation, the refrigerating capacity of the refrigerator R is controlled according to the heat load of the cooler 5 in order to bring the cold water to the set temperature. The heat load changes depending on the weather and the condition of equipment usage. Therefore, even when the cold water is supplied to the cooler 5 at a constant temperature, the temperature when returning to the refrigerator R is not always constant.

Specifically, in the rated operation state,
The cold water (for example, 7 ° C.) exiting the refrigerator R rises in temperature (for example, 5 ° C.) due to the heat load of the cooler 5 and has a high temperature (12
C) and returns to the refrigerator R, and in the refrigerator R, the refrigerant circulates in an amount commensurate with cooling the cold water to cool the cold water (-
The operation is performed in a cycle in which the temperature is kept at 5 ° C.) and a constant cold water temperature (7 ° C.) is supplied to the cooler 5.

However, when the heat load of the cooler 5 is reduced and the temperature rise of the cold water is reduced (for example, 3 ° C.), the cold water returns to the refrigerator R at a temperature (10 ° C.) lower than the normal temperature. At this time, if the refrigerant circulation amount in the refrigerator R is the same as that at the time of rating,
The cold water outlet temperature has a lower value (5 ° C.) than the temperature when supplied to the cooler 5.

Therefore, in order to keep the temperature of the cold water supplied from the refrigerator R to the cooler 5 at a constant value, the temperature measuring device 11
At, the temperature of the cold water supplied from the refrigerator R is measured, and this temperature is transmitted from the temperature measuring device 11 to the capacity controller 12,
The capacity controller 12 calculates the refrigerant circulation amount based on the measured temperature, and operates the opening degree of the suction vane 8 and the bypass valve 9 based on the calculated refrigerant circulation amount to reduce the refrigerant circulation amount and to perform refrigeration. The capacity is controlled.

On the other hand, the refrigerating machine R is provided with various kinds of safety equipment in order to avoid mechanical damage to the refrigerating machine R when an abnormal state deviates from a normal operating state. The pressure detector 21 is one of them. For example, when the pressure of the evaporator 1 is abnormally lowered, the temperature of the refrigerant in a saturated state is reduced accordingly, the temperature of the surrounding cold water is also lowered, and finally the cold water is frozen and the pipe 6 is damaged. In some cases. Therefore, when the pressure of the evaporator 1 is constantly detected by the pressure detector 21 and the pressure of the evaporator 1 falls below a limit value (for example, -48 cmHg) or less, the safety device 22 which receives the pressure measurement signal supplies power. The power of the device 23 is cut off to stop the operation of the refrigerator R.

[0009]

However, in the case of the above control method, the temperature of the cold water is measured by the temperature measuring device 11, and the suction vane 8,
Since the bypass valve 9 is operated, there are the following problems.

Since the temperature measuring device 11 has a heat capacity, it takes time to balance the temperature of the actual cold water. Therefore, the temperature measurement by the temperature measuring device 11 is
When the temperature of cold water is changing, there is always a delay in following the temperature change.

While the refrigerator is stopped, the cold water in the cold water pipe is in a stagnant state, so its temperature rises to near room temperature, which is lower than the cold water temperature during operation (for example, 7 ° C.). And the temperature is high. When the refrigerator is started from this state, the chilled water temperature stabilizes until the actual chilled water temperature and the chilled water temperature measured by the temperature measuring device 11 are balanced.
Since the cold water temperature is higher than the set temperature, the capacity controller 12 operates the suction vane 8 and the bypass valve 9 so as to quickly approach the set temperature and operate at 100% of the refrigerating capacity. Further, as described above, since the temperature measurement is delayed, the cold water temperature measured by the temperature measuring device 11 is
Since the temperature is input to the capacity controller 12 at a temperature higher than the actual cold water temperature, the refrigerator R is operated at a higher capacity than actually required, and is operated excessively by the time delay. Become.

Even in such an operating state, the cooler 5
If the heat load of No. 2 is within the designed range, even if it is operated at 100% of the refrigeration function power, the refrigeration cycle is in the designed state, so no particular problem occurs. If it is decreasing (low load state), the refrigerating capacity becomes too large compared to the capacity to be actually cooled, the evaporation pressure in the evaporator falls below the designed state, and the safety device operates. Sometimes the refrigerator stopped.

Therefore, a main object of the present invention is to control a refrigerator without cooling the chilled water with a refrigeration capacity larger than necessary even when the refrigerator is started when the cooler is in a low load state. . Even in such a case, the refrigerator is controlled so that the refrigerator can be normally operated without stopping the refrigerator due to the operation of the safety device.

[0014]

In order to solve the above problems, the present invention comprises an evaporator, a condenser and a compressor,
By circulating the refrigerant through the compressor between the evaporator and the condenser, the cold water in the pipe arranged in the evaporator is cooled and the circulation amount of the refrigerant is adjusted. In an air-conditioning refrigerator equipped with a capacity controller, while measuring the pressure of the evaporator and the outlet temperature of cold water, a control index value is set to the evaporator pressure, and the measured value of the evaporator pressure is the control value. When the condition is equal to or more than the index value for use, the refrigerant circulation amount of the refrigerator is controlled by operating the capacity controller based on the measured value of the cold water outlet temperature, and the measured value of the evaporator pressure is for the control. When it is below the index value, prioritizing the refrigerant circulation amount control based on the measured value of the cold water outlet temperature, the point of forcibly operating the capacity adjuster to maintain or reduce the refrigerant circulation amount, That is the configuration

[0015]

According to the control method of the present invention, when the pressure in the evaporator is equal to or higher than the set index value for control, the control based on the chilled water outlet temperature is performed as in the conventional case. When the value is below the control index value, the control based on the cold water outlet temperature is prioritized and the operation of not increasing or decreasing the refrigerant circulation amount is forcibly performed.

More specifically, for example, the control index value is set to -40 cmHg which is 1 cmHg smaller than -39 cmHg during normal operation, and the evaporator internal pressure is -40.
When it is cmHg or more, the refrigerant circulation amount is controlled based on the cold water outlet temperature, and when the evaporator internal pressure is lower than -40 cmHg, preferably the refrigerant based on the cold water outlet temperature is preferably firstly stepwise. Priority is given to the control of the circulation amount, and the opening amounts of the suction vane and the bypass valve, which are capacity regulators, are kept constant, and the refrigerant circulation amount is kept constant. Next, if this control also causes the evaporator internal pressure to drop,
The opening degree of the suction vane and the bypass valve is adjusted to forcibly reduce the refrigerant circulation amount.

As described above, according to the present invention, when the evaporator internal pressure becomes lower than the predetermined value, the control for maintaining or reducing the refrigerant circulation amount is preferentially performed regardless of the chilled water outlet temperature. Freezing of cold water due to decrease in evaporator pressure,
There will be no damage to the pipes and power interruption due to abnormal drop in evaporator pressure.

Further, since the control method is switched on the basis of the pressure in the evaporator, even when the refrigerator is started,
A large follow-up delay unlike the case of using the cold water outlet temperature as a reference is not seen, and excessive circulation of the refrigerant is eliminated, so that the cold water can be cooled efficiently and appropriately.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing a control circuit for controlling the air conditioning refrigerator R and the refrigerator R according to the present invention. Although the basic structure of the refrigerator R is the same as the conventional one, the description thereof will be omitted. However, the control circuit according to the present invention is additionally provided with pressure switches 14 and 15 to detect the pressure in the evaporator. In response to a signal from the pressure measuring device 21, the opening degrees of the suction vane 8 and the bypass valve 9 are forcibly operated under the pressure condition described later.

During operation of the air conditioner, the refrigerator R supplies cold water to the cooler 5 as shown in the above-mentioned prior art.
At this time, the chilled water from the refrigerator R is cooled at the set temperature by the cooling 5
In order to supply the cooling water to the fuel cell, the temperature of the supplied cold water is measured by the temperature measuring device 11, and feedback control is performed to operate the suction vane 8 and the bypass valve 9 based on the measured temperature.

In the present invention, the pressure in the evaporator 1 measured by the pressure measuring device 21 is, for example, -4.
A lower limit value (control index value) of 0 cmHg is provided. Then, when the pressure inside the evaporator 1 falls below this lower limit value, the pressure switch 1 that receives a signal from the pressure measuring device 21
4 is a suction vane 8 and a bypass valve 9 by a capacity controller 12.
The operation of is stopped to prevent the refrigerant circulation amount of the refrigerator R from further increasing.

Even if this operation is performed, the pressure measuring device 21 is still
When the pressure in the evaporator 1 measured by means of a decrease, for example, the measured pressure value becomes -41 cmHg, a command from the pressure switch 15 gives priority to the control by the capacity controller 12, and the refrigeration The openings of the suction vane 8 and the bypass valve 9 are adjusted so as to reduce the refrigerant circulation amount of the machine R, and the refrigerant circulation amount of the refrigerator R is forcibly reduced.

It should be noted that the pressure signal measured by the pressure measuring device 21 is directly transmitted to the capacity adjusting device 12 without using the pressure switches 14 and 15 and compared with the lower pressure limit value set in the capacity adjusting device 12. If the measured pressure falls below the lower limit pressure value, the opening of the suction vane 8 and the bypass valve 9 may be forcibly adjusted prior to the control based on the signal from the temperature measurement value 11. .

[Embodiment] First, in the case of the conventional refrigerator shown in FIG. 3, the refrigerator R is stopped for a while, and the cold water temperature measured by the temperature measuring device 11 is about 20 ° C. near room temperature.
Restart from the temperature of ℃. At this time, the set temperature of the chilled water to be fed is about 7 ° C., and the heat load on the cooler 5 is made as small as possible. If the refrigerator R is started from this state, the refrigerating capacity of the refrigerator R against the load of the cooler 5 becomes too large, the pressure in the evaporator 1 falls below -48 cmHg, and the safety device 22 operates to shut off the power. Then, the refrigerator R has stopped.

On the other hand, as shown in FIG. 1, pressure switches 14 and 15 are added to the control circuit, the lower limit value at which the pressure switch 14 works is -40 cmHg, and the lower limit value at which the pressure switch 15 works is -41 cmHg. As a result, when the operation was started under the control according to the present invention, the safety device 22 did not work at the time of starting the refrigerator R, and it was possible to continue and operate normally.

[0026]

As is apparent from the above description, according to the present invention, even when the refrigerator is started when the cooler is in a low load state, the safety device operates because the refrigerant is not circulated more than necessary. There is no longer any need to stop the refrigerator, and normal operation can be continued.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit of an air conditioner refrigerator and a control device according to the present invention.

FIG. 2 is a Mollier diagram showing a basic refrigeration cycle.

FIG. 3 is a diagram showing a circuit of an air conditioning refrigerator and a conventional control device.

[Explanation of symbols]

R ... Refrigerator, 1 ... Evaporator, 2 ... Centrifugal compressor, 3 ... Condenser, 4 ... Float valve, 5 ... Cooler, 8 ... Suction vane, 9
… Bypass valve, 11… Temperature measuring instrument, 12… Volume controller,
21 ... Pressure measuring device, 14/15 ... Pressure switch

Claims (1)

[Claims] 1. A pipe comprising an evaporator, a condenser and a compressor, and a pipe disposed in the evaporator by circulating a refrigerant between the evaporator and the condenser with the compressor interposed therebetween. While cooling the cold water inside, in an air-conditioning refrigerator equipped with a capacity controller for adjusting the circulation amount of the refrigerant, while measuring the pressure of the evaporator and the outlet temperature of the cold water, for controlling the evaporator pressure When the index value is set and the measured value of the evaporator pressure is under the condition of the control index value or more, the refrigerant circulation of the refrigerator by the operation of the capacity controller based on the measured value of the chilled water outlet temperature. Control the amount, when the measured value of the evaporator pressure is below the control index value, prior to the refrigerant circulation amount control based on the measured value of the chilled water outlet temperature, maintain the refrigerant circulation amount or Force to reduce The method of the air conditioning refrigeration, which comprises operating amount control.