JPH0456224B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of the Invention The present invention relates to a capacity control device for a refrigerator in which a compressor is driven by a prime mover such as a variable speed electric motor or an engine.

(b) Prior art Conventional capacity control devices generally control the rotation speed of a variable speed prime mover primarily based on refrigeration loads such as indoor temperature, outside air temperature, condensation temperature, and evaporation temperature. None of them took operational efficiency into consideration.

(c) Problems with the conventional technology For this reason, for example, when the cooling load is reduced during cooling operation, the rotation speed of the variable speed prime mover decreases and the rotation speed of the compressor also decreases, switching to operation commensurate with the light load. However, the load on the variable speed prime mover became too light, resulting in low efficiency, and it was forced to operate in an extremely unstable and highly vibrating state.

(d) Purpose of the Invention The present invention provides a refrigerator that controls the rotation speed of a compressor according to the refrigeration load and constantly applies a constant load to a variable speed prime mover to operate the prime mover in a stable and highly efficient manner. The present invention provides a capacity control device.

(E) Summary of the Invention The present invention provides a compressor, a condenser, an evaporator, a variable speed prime mover for driving the compressor, and a compressor provided between the output shaft of the variable speed prime mover and the input shaft of the compressor. In a capacity control device for a refrigerator equipped with a transmission,
A first detector that detects the condensation temperature of the condenser, a second detector that detects the evaporation temperature of the evaporator, and a third detector that detects the temperature difference between the temperature in the room cooled by the evaporator and the set temperature. A performance line of the refrigerator showing the relationship between the rotation speed of the compressor and the temperature difference using the condensing temperature as a parameter, and a performance line of the refrigerator showing the relationship between the rotation speed of the compressor and the power using the condensing temperature as a parameter. Memorizes the power line and the load performance line of the variable speed prime mover that shows the relationship between the rotation speed and power of the variable speed prime mover, and sets the compressor rotation speed from the evaporation temperature, condensation temperature, the temperature difference, and the chiller capacity line. At the same time, the rotation speed of the variable speed prime mover is set based on the required power of the refrigerator and the load performance line of the variable speed prime mover, and a signal is output to the variable speed prime mover so that the rotation speed of the compressor becomes the set value. By configuring a chiller capacity control device with a controller that outputs a signal to the transmission, the compressor can be driven at the optimal rotation speed according to the chilling load, and the variable speed prime mover can be operated even when the chilling load changes. The rotation speed of the engine is controlled to ensure highly efficient operation under constant load.

(F) Embodiment of the Invention Fig. 1 is a control circuit diagram showing an embodiment of the invention, in which 1 is a refrigerator consisting of a compressor 2, a condenser 3, a pressure reducing element 4, and an evaporator 5, and 6 is a variable speed refrigerator. A transmission is provided between the output shaft 7a of the prime mover 7 and the input shaft 2a of the compressor 2, 8 is a first detector that detects the condensation temperature (CT) of the condenser 3, and 9 is the evaporation temperature of the evaporator 5. A second detector 10 detects the temperature (ET); a third detector 10 detects the temperature difference (ΔT) between the indoor temperature and the cooling set temperature in the indoor space 11 cooled by the evaporator 5; The optimum rotation speed of the compressor 2 is set according to the refrigeration load from the first to third detectors 8, 9, and 10, and the rotation speed of the variable speed prime mover 7 is set in the rotation speed range for high efficiency operation by the transmission 6. It is a controller to

Fig. 2 is a characteristic diagram illustrating the operating performance curve of the variable speed prime mover 7. It has the performance to operate efficiently in the range from 100% output during full load operation to, for example, 85% output, and the above-mentioned High efficiency operation refers to operation within this range.

Next, the control operation of the present invention will be explained based on the performance characteristic diagram of the compressor 2 and variable speed prime mover 7 shown in FIG. In addition, Figure 3 shows the evaporation temperature (ET) as an example.
This figure shows the case where the temperature is 7.2℃, and the difference between the compressor rotation speed and the cooling temperature (△
Capacity line of the refrigerator 1 showing the relationship between T), C is the power line required by the refrigerator 1 showing the relationship between the rotation speed and power of the compressor 2 with the condensing temperature as a parameter, and C is the variable speed prime mover 7 is the full load (100%) performance line, and D is the 85% load performance line of variable speed prime mover 7. The performance characteristics corresponding to FIG. 3 when the evaporation temperature (ET) is different are also stored in the controller 12 in advance.

First, for example, for 10 minutes after the start of operation, the compressor 2 is driven by the shaft power from the variable speed prime mover 7 with the signal command from the controller 12 masked and the gear ratio of the transmission 6 set to 1:1. Perform refrigeration operation. Through this operation, the condensation temperature (CT) and evaporation temperature (ET) are detected by the first and second detectors 8 and 9, and the temperature difference (△T) between the indoor temperature and the cooling set temperature is also detected by the third detector. Detected at 10. As a result of these detections, for example, the evaporation temperature (ET) is 7.2
℃, when the condensing temperature (CT) is 45℃ and the cooling temperature difference (△T) is 3.5℃, the condensing temperature CT in the capacity line (A) of refrigerator 1 is drawn from the point shown in Figure 3.
When the point of intersection with the =45°C line is found, the required cooling capacity is found to be 3300 kal/h, and the optimal rotation speed of 2300 rpm corresponding to the refrigeration load of the compressor 2 is set. In addition, the power required by refrigerator 1 at the intersection with the condensing temperature CT = 45℃ line in power line B is
1.78 PS is obtained, and the intersection point with the 85% load performance line N of the variable speed prime mover 7 indicates that in order to operate the variable speed prime mover 7 with high efficiency, it is sufficient to set this rotation speed to 1980 rpm, which is calculated by the controller 12. The set rotation speed command is given to the variable speed prime mover 7, and the prime mover 7
A command is issued from the controller 12 to the transmission 6 to increase the speed of the transmission 6 by switching the rotation speed of the compressor 2 to 1980 rpm and maintaining the rotation speed of the compressor 2 at the above-mentioned 2300 rpm.

By the above control operation, the compressor 2 is operated at a rotation speed of 2300 rpm to exhibit the necessary cooling capacity of 3300 kcal/h, and at the same time, the variable speed prime mover 7 is operated with high efficiency at a rotation speed of 1980 rpm.

In this way, optimal operation corresponding to the refrigeration load is performed, and even when the refrigeration load fluctuates, the load is detected based on the evaporation temperature, condensation temperature, and cooling temperature difference (△T), and the operation is adjusted to match the refrigeration load. The compressor 2 and the variable speed prime mover 7 are operated at the optimum rotational speed.
In this case, depending on the refrigeration load, the transmission 6 may be decelerated or may not be increased or decelerated.

(G) Effects of the Invention With the device of the present invention, the compressor is operated at the optimum rotation speed commensurate with the refrigeration load, and the variable speed prime mover is operated in a high efficiency rotation speed range. It can perform reliably under stable operation, and even when the refrigeration load changes, it can detect the refrigeration load based on the evaporation temperature, condensation temperature, and the temperature difference between the room temperature and the set temperature. It is possible to reliably control the rotational speed of the variable speed prime mover to a highly efficient rotational speed range according to the refrigeration load, and to exhibit optimal refrigeration capacity.

[Brief explanation of the drawing]

Figure 1 is a control circuit diagram showing an embodiment of the device of the present invention, Figure 2 is a characteristic diagram illustrating the operating performance curve of a variable speed prime mover, and Figure 3 is a performance characteristic diagram illustrating an example of a compressor and variable speed prime mover. It is. 1... Refrigerator, 2... Compressor, 6... Transmission,
7...Variable speed prime mover, 12...Controller.

Claims (1)

[Claims] 1. A refrigeration system equipped with a compressor, a condenser, an evaporator, a variable speed prime mover that drives the compressor, and a transmission provided between the output shaft of the variable speed prime mover and the input shaft of the compressor. In the machine capacity control device, a first detector detects the condensing temperature of the condenser, a second detector detects the evaporation temperature of the evaporator, and the temperature between the temperature of the room cooled by the evaporator and the set temperature. A third detector that detects the difference, a performance line of the refrigerator that shows the relationship between the temperature difference and the rotation speed of the compressor with the condensing temperature as a parameter, and the rotation speed and power of the compressor with the condensing temperature as a parameter. The power line of the refrigerator, which shows the relationship between The rotation speed of the variable speed prime mover is set from the required power of the refrigerator and the load performance line of the variable speed prime mover, and a signal is output to the variable speed prime mover. 1. A capacity control device for a refrigerator, comprising: a controller that outputs a signal so that the number reaches a set value.