JPH0225092Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] This invention relates to refrigerators applied to refrigerator cases, vending machines, etc., and particularly relates to refrigerators that control the rotation speed of a compressor incorporated in the refrigerator. This invention relates to a rotation speed control device.

[Technical background of the invention and its problems] Generally, this type of refrigerator is used as a freezer case or a vending machine, and is designed to cool or freeze food stored inside. A refrigerator has a compressor, a condenser, a pressure reduction mechanism, and an evaporator connected in sequence to form a closed refrigeration cycle, and the refrigeration capacity is adjusted by controlling the rotational speed of the compressor.

A conventional refrigerator is configured as shown in Figure 1.
The compressor 1 and the condenser cooling fan motor 2 are connected to a commercial power source 4 via an electromagnetic switch 3, and when the electromagnetic switch 3 closes, the compressor 1 and the fan motor 2 are energized and driven. It's becoming like that. Specifically, when the pressure switch 5 is turned ON, the electromagnetic switch 3 is energized and closed, and the compressor 1 is turned on.
and the fan motor 2 is activated.

However, when the commercial power source 4 is directly input to the compressor 1 of the refrigerator via the electromagnetic switch 3, the compressor 1 is activated as shown by the broken line C in FIG. 4 by energizing the compressor 1. The motor rotation speed increases rapidly. Therefore, when the compressor 1 is started with the refrigerant trapped (mixed) inside the compressor 1, the internal pressure of the compressor 1 decreases rapidly, and when the liquid refrigerant evaporates, an oil forming phenomenon occurs. When the oil forming phenomenon occurs, the oil level of the lubricating oil rises, and problems such as valve damage due to liquid compression are likely to occur.

By the way, instead of directly inputting the commercial power source 4 to the compressor 1, in order to control the motor rotation speed of the compressor 1, a frequency signal is connected between the electromagnetic switch 3 and the compressor 1 as shown in FIG. Control circuit (inverter) 6
There is one in which the motor rotation speed of the compressor 1 is controlled.

In this case, the evaporator temperature from the evaporator air temperature sensor 7 and the preset temperature set from the evaporator air setting thermometer 8 are converted into signals and input to the frequency control circuit 6 . The frequency control circuit 6 senses the evaporator temperature, controls the frequency based on the difference from the set temperature, and uses a general control method to adjust and control the motor rotation speed of the compressor 1.

However, the adjustment control of the motor rotation speed of the compressor 3 by this control method is performed by sensing the evaporator temperature, regardless of the internal temperature of the compressor 1, so as shown by the dashed line B in FIG. , and the motor rotation speed increases rapidly. Therefore, as in the case shown in FIG. 1, an oil forming phenomenon occurs when the compressor is started, and problems such as valve damage due to liquid compression are likely to occur. In addition, in order to solve the above problem, for example, as shown in Japanese Utility Model Publication No. 52-7845, the temperature of the oil stored at the bottom of the compressor is detected,
A device is being considered that allows the compressor to rotate at a low speed when the oil temperature is low. However, like this,
When controlling the rotation speed of the compressor at startup by detecting only the compressor case temperature, the temperature of the oil stored in the compressor changes depending on the outside air temperature in the stopped state before starting operation, so the compression It was difficult to accurately detect whether liquid refrigerant was trapped inside the aircraft. In addition, as shown in Utility Model Application Publication No. 56-123979, it has been considered to rotate the compressor at a small capacity for a certain period of time when starting up the compressor, but this also applies when there is no liquid refrigerant in the compressor. Due to the small capacity rotation at startup, there was a drawback that the start-up immediately after restart during controlled operation was delayed, making it impossible to obtain a sufficient predetermined refrigerating capacity.

[Purpose of invention]

This invention takes the above points into consideration, effectively and reliably prevents liquid compression due to oil forming when starting the compressor, effectively prevents valve damage and breakage,
It is an object of the present invention to provide a rotation speed control device for a refrigerator that can smoothly and efficiently start up a compressor.

[Summary of the invention] In order to achieve the above-mentioned object, the revolution speed control device for a refrigerator according to this invention adjusts and controls the motor revolution speed of a compressor for refrigerant compression using a frequency control circuit. A first temperature sensor that detects temperature and a second temperature sensor that detects ambient temperature of the refrigerator are connected to the frequency control circuit, and the frequency control circuit controls the temperature of the compressor according to the difference in temperature detected by both temperature sensors. The motor rotation speed is controlled at startup.

[Example of idea]

Hereinafter, preferred embodiments of this invention will be described with reference to the accompanying drawings.

In this invention, the refrigerator is used in equipment that refrigerates or freezes food storage, such as a freezer case or a food vending machine, and a compressor 10, a condenser, a pressure reduction mechanism, and an evaporator are connected in sequence to create a closed refrigerator. A cycle is constructed. The refrigerator is operated by a 50Hz or 60Hz commercial power source 11, as shown in FIG.

The commercial power source 11 is electrically connected to a condenser cooling fan fan motor 13 etc. via an electromagnetic switch 12, and by closing this electromagnetic switch 12,
Each fan motor 13 is energized. The electromagnetic switch 12 is excited and opened/closed by operating a pressure switch 14.

On the other hand, the electromagnetic switch 12 is electrically connected to the compressor 10 via a frequency control circuit (inverter) 16. The frequency control circuit 16 adjusts and controls the motor rotation speed of the compressor 10. This frequency control circuit 16 receives the evaporator temperature from the evaporator air temperature sensor 17 and the evaporator air setting thermometer 1.
The set temperature from 8 is converted into a signal and input, while detected temperature signals are input from a compressor case temperature sensor 20 and a refrigerator ambient temperature sensor 21 attached to the compressor case 10a. this house,
The refrigerator ambient temperature sensor 21 is installed at a location that is not affected by the heat dissipation and heat absorption effects of the condenser and evaporator.

The frequency control circuit 16 also includes a compressor case temperature sensor 20 and a refrigerator ambient temperature sensor 21.
The compressor 10 has a comparison calculation circuit that compares and calculates input temperature signals from the compressor 10 based on the temperature difference signal.
Adjusts and controls the motor rotation speed at startup. Furthermore, a timer circuit (not shown) is provided in the frequency control circuit 16, and when controlling the motor rotation speed of the compressor 10 based on the temperature difference signal,
By the timer operation of the timer circuit, the engine is operated at low rotation speed for a certain period of time (area a) as shown by the solid line A in Figure 4.
Thereafter, the motor rotation speed is increased to the normal speed as shown in region b.

Next, the effects of this invention will be explained.
When the pressure switch 14 is turned on, the electromagnetic switch 12 is energized and closed, the refrigerator is energized, and the refrigerator starts operating.

First, at the time of start of operation when the ambient temperature of the refrigerator is low, such as in winter, the compressor, condenser, etc. are also in a low temperature state equivalent to the ambient temperature of the refrigerator, and liquid refrigerant gradually builds up inside the compressor due to the long period of stoppage. is in a sleepy state. When the temperature difference between the compressor case temperature and the refrigerator ambient temperature is low, such as at the time of starting operation, the compressor 10 is controlled by the frequency control circuit such that the motor rotation speed is increased as shown by the solid line A in FIG. 16. With this adjustment control, the motor of the compressor 10 is operated at low speed for a predetermined period of time, during which time the refrigerant trapped in the compressor is smoothly gasified, and oil forming phenomenon is prevented. After a certain period of time, the frequency control circuit 16
A timer circuit built into the compressor allows the compressor motor rotation speed to increase to normal rotation.

When the motor rotation speed of the compressor 10 reaches normal rotation, the operation of the refrigerator is adjusted and controlled in that rotation range by signals from the evaporator internal temperature sensor 17 and its air setting thermometer 18, and the inside of the refrigerator is controlled. It is gradually cooled down and reaches a predetermined temperature. After the temperature inside the refrigerator reaches a predetermined temperature, the compressor 10 is turned on and off to enter a controlled operation in order to maintain the temperature inside the refrigerator at a predetermined temperature. When restarting the compressor 10 during controlled operation of the compressor 10, even when the ambient temperature of the refrigerator is low, the compressor has a heat capacity, so the temperature does not drop, and the temperature of the compressor remains low compared to the ambient temperature of the refrigerator. The case temperature is sufficiently high, and the refrigerant in the compressor 10 is gasified and separated from the lubricating oil, so that so-called refrigerant stagnation does not occur.

When the compressor case temperature is high and the temperature difference between the compressor case temperature and the surrounding temperature of the refrigerator is above a certain level, the compressor 1
0 is controlled by the frequency control circuit 16 so that it immediately enters operation in range b after startup.

In this case, the timer circuit incorporated in the frequency control circuit 16 is not activated, and as in the case of the operation control of the refrigerator shown in FIG. Adjusted as shown in . Therefore, after the compressor 10 is restarted, a predetermined refrigerating capacity can be obtained in a short time. In this manner, the rise of the motor rotation speed is selected when the compressor is started, depending on the temperature difference detected by the compressor case temperature sensor 20 and the refrigerator ambient temperature sensor 21.

In other words, by detecting the temperature difference between the compressor case temperature and the refrigerator ambient temperature, when this temperature difference is low, it is determined that the compressor is in a starting state where liquid refrigerant is stagnant, and the temperature difference is detected. When the refrigerant is large, it is determined that it is time to restart during controlled operation when the liquid refrigerant is not stagnant in the compressor.
This controls the rotation speed when starting the compressor.

As a result, the motor rotation speed of the compressor 10 can be adjusted more accurately when restarting, compared to a system in which only the compressor case temperature is detected to control the rotation speed of the compressor at startup.

[Effects of the invention] As described above, the refrigerator rotation speed control device according to the invention includes a first temperature sensor that detects the case temperature of the compressor and a second temperature sensor that detects the ambient temperature of the refrigerator. is connected to a frequency control circuit, and this frequency control circuit controls the motor rotation speed when starting the compressor according to the temperature difference detected by both temperature sensors. In such cases, by rotating the compressor motor at low speed, oil forming phenomenon inside the compressor can be effectively prevented, preventing liquid compression operation due to oil forming, and preventing valve breakage. The compressor can be started smoothly without causing damage or damage.

Furthermore, during controlled operation of the refrigerator, the difference in temperature detected by both temperature sensors is large, and the compressor can be restarted in accordance with this large temperature difference. In this case, since the operation can be controlled to rapidly increase the motor rotation speed of the compressor, the predetermined refrigerating capacity can be obtained immediately after restarting the compressor, and the refrigerator can be operated with high efficiency. Even when the refrigerator is operated at high efficiency, there is no overload on the compressor due to liquid compression, etc., and compared to systems that only detect the compressor case temperature and control the compressor rotation speed at startup, This provides effects such as being able to accurately adjust the rotation speed of the compressor motor at the time of restart.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram showing conventional electrical wiring for driving a refrigerator, Figure 2 is a wiring diagram showing a rotation speed control device for a refrigerator having a frequency control circuit, and Figure 3 is a diagram of a refrigerator according to this invention. FIG. 4 is a wiring diagram showing an embodiment of the rotation speed control device of FIG. 10...Compressor, 10a...Compressor case, 1
1... Power source, 12... Electromagnetic switch, 13... Fan motor, 14... Pressure switch, 16... Frequency control circuit, 17... Evaporator internal air temperature sensor,
20... Compressor case temperature sensor (first temperature sensor), 21... Refrigerator ambient temperature sensor (second temperature sensor).

Claims (1)

[Claims for Utility Model Registration] 1. In a refrigerator rotation speed control device that adjusts and controls the motor rotation speed of a refrigerant compressor using a frequency control circuit, a first temperature sensor that detects the case temperature of the compressor and the refrigerator A second temperature sensor that detects the ambient temperature of the compressor is connected to the frequency control circuit, and the frequency control circuit controls the motor rotation speed at the time of starting the compressor in accordance with the temperature difference detected from both temperature sensors. A rotation speed control device for a refrigerator, characterized by the following. 2 The frequency control circuit has a comparison calculation circuit that compares and calculates the detection signals from the first and second temperature sensors, and when the temperature difference from both temperature sensors is less than a predetermined value, the frequency control circuit causes the compressor to rotate at a low speed for a certain period of time. A rotation speed control device for a refrigerator according to claim 1 of the utility model registration claim. 3. The rotational speed control device for a refrigerator according to claim 1, wherein the second temperature sensor is installed at a location that is not subjected to the heat radiation action or heat absorption action of the condenser and evaporator of the refrigerator.