JPH04295550A - Refrigerating cycle apparatus - Google Patents

Abstract

PURPOSE:To provide a refrigerating cycle apparatus capable of escaping from a liquid back state quickly, thereby the life of a compressor can be extended. CONSTITUTION:A refrigerating cycle apparatus consists of a refrigerating cycle which is composed of a compressor 1, a condenser 3, an electronic expansion valve 4 and an evaporator 5, a detector that detects the superheat degree SH of refrigerant in the evaporator 5, a controller which controls the valve lift of the electronic expansion valve 4 so that refrigerant superheat degree is kept at a constant value of 5 degrees, for example, and a temperature detector which detects the refrigerant delivery temperature Td of the compressor 1. When the detected superheat degree SH is zero or lower, that means liquid back state, the valve lift of the expansion valve 4 is corrected corresponding to the detected refrigerant delivery temperature Td.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a refrigeration cycle device equipped with an electronic expansion valve.

0002

[Prior Art] A refrigeration cycle used in an air conditioner, etc. is equipped with an electronic expansion valve, and the opening degree of the electronic expansion valve is controlled so that the degree of superheating of the refrigerant in the evaporator remains at a constant value, thereby stabilizing the operation. There is something to aim for. An example is shown in FIG.

1 is a variable capacity compressor. This compressor 1
An outdoor heat exchanger 3 is connected to the discharge port of the unit via a four-way valve 2,
An indoor heat exchanger 5 is connected to the outdoor heat exchanger 3 via an electronic expansion valve (pulse motor valve; PMV) 4. The indoor heat exchanger 5 is connected to the suction port of the compressor 1 via the four-way valve 2. In other words, during cooling operation, the refrigerant flows in the direction of the solid arrow shown in the figure to form a cooling cycle.
The outdoor heat exchanger 3 is used as a condenser, and the indoor heat exchanger 5 is used as an evaporator.

During heating operation, the four-way valve 2 is switched to flow the refrigerant in the direction of the dashed arrow in the figure to form a heating cycle, with the indoor heat exchanger 5 serving as a condenser and the outdoor heat exchanger 3 serving as an evaporator. make it work

Furthermore, one end of the capillary tube 6 is connected to the connecting pipe between the outdoor heat exchanger 3 and the electronic expansion valve 4, and one end of the capillary tube 7 is connected to the connecting pipe between the electronic expansion valve 4 and the indoor heat exchanger 5. , those capillary tubes 6,7
Both ends are connected to the suction port of the compressor 1 via a bypass 8.

[0006] In the suction side piping of the compressor 1,
A temperature sensor 11 is located upstream of the connection part of the bypass 8.
is installed. Furthermore, the temperature sensor 1 is connected to the bypass 8.
2 is installed. Explain the action.

During cooling or heating operation, the operating frequency, or capacity, of the compressor 1 is controlled according to the air conditioning load. At the same time, the temperature of the refrigerant sucked into the compressor 1 is detected by a temperature sensor 11, and the saturated refrigerant temperature is detected by a temperature sensor 12. Then, the difference between the temperature T1 detected by the temperature sensor 11 and the temperature T2 detected by the temperature sensor 12 is detected as the refrigerant superheat degree (superheat) SH of the evaporator, and the refrigerant superheat degree SH is set to a predetermined constant value. The opening degree of the electronic expansion valve 4 is controlled so that

[0008]

By the way, in the above-mentioned refrigeration cycle, during so-called liquid back when liquid refrigerant is sucked into the compressor 1, the degree of superheat of the refrigerant becomes 0 degrees.

In this case, whether the liquid back amount is large or small, the opening degree correction amount of the electronic expansion valve 4 is kept constant, making it difficult to properly adjust the refrigerant flow rate. For this reason, it becomes difficult to escape from the liquid back state, resulting in problems such as an adverse effect on the life of the compressor 1.

Furthermore, when the capacity of the compressor decreases, the temperature of the case of the compressor decreases, resulting in a situation where the refrigerant dissolves into the lubricating oil in the compressor and the lubricating oil is diluted. If this happens, there is a risk of compressor failure. The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a refrigeration cycle device according to claim 1, which can quickly escape from the liquid back-up state, thereby making it possible to extend the life of the compressor. . A refrigeration cycle device according to a second aspect of the present invention aims to avoid a situation in which lubricating oil is diluted and thereby prevent a failure of a compressor.

[0011]

[Means for Solving the Problems] A refrigeration cycle device according to claim 1 includes a refrigeration cycle in which a compressor, a condenser, an electronic expansion valve, and an evaporator are connected in sequence, and means for detecting the degree of superheating of a refrigerant in the evaporator. a means for controlling the opening degree of the electronic expansion valve so that the refrigerant superheat degree is a constant value; a means for detecting the temperature of the refrigerant discharged from the compressor; and means for correcting the opening degree of the electronic expansion valve according to the detected temperature.

[0012] The refrigeration cycle device according to claim 2 comprises a compressor;
A refrigeration cycle in which a condenser, an electronic expansion valve, and an evaporator are sequentially connected, a means for detecting the degree of superheating of a refrigerant in the evaporator, and an opening degree of the electronic expansion valve is controlled so that the degree of superheating of the refrigerant is kept at a constant value. a means for detecting the temperature of the compressor; a means for detecting the temperature of the condenser; a means for determining the difference between the two detected temperatures; A second control means for controlling the opening degree of the electronic expansion valve and a first control means for controlling the degree of opening of the electronic expansion valve and the first control means for controlling the degree of opening of the electronic expansion valve until a certain period of time has elapsed from the start of operation, and after the elapse of the certain period of time, controlling the first control means according to the temperature difference. means for selectively controlling the control means or controlling the second control means; and means for selecting whether to continue or cancel the control of the second control means once it is executed, depending on the degree of superheating of the refrigerant. .

[0013]

In the refrigeration cycle device according to the first aspect of the present invention, the opening degree of the electronic expansion valve is controlled so that the degree of superheating of the refrigerant in the evaporator becomes a constant value. However, when the degree of superheat of the refrigerant becomes zero or less,
The opening degree of the electronic expansion valve is corrected according to the temperature of the refrigerant discharged from the compressor.

[0014] The refrigeration cycle device according to the second aspect includes a first control means for controlling the opening degree of the electronic expansion valve so that the degree of superheating of the refrigerant in the evaporator becomes a constant value, and There is a second control means that controls the opening degree of the electronic expansion valve so that the difference becomes a constant value, and the control of the first control means is executed until a certain period of time has elapsed from the start of operation. However, after a certain period of time has elapsed, the control of the first control means or the control of the second control means is selectively executed depending on the temperature difference. Once the control of the second control means is executed, its continuation or cancellation is selected depending on the degree of superheating of the refrigerant.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In the drawings, the same parts as those in FIG. 9 are designated by the same reference numerals, and detailed explanation thereof will be omitted. Figure 1
As shown in the figure, a temperature sensor 10 is installed on the discharge side piping of the compressor 1.
Attach.

[0016] Furthermore, a control section 20 is provided, and the control section 20
A four-way valve 2, an electronic expansion valve 4, an operating device 21, an indoor temperature sensor 22, an inverter circuit 23, and a temperature sensor 10,
Connect 11 and 12.

The inverter circuit 23 rectifies the voltage of a commercial AC power supply (not shown), converts it into AC of a predetermined frequency (and voltage) by switching in accordance with a command from the control section 20, and outputs the same. The output of this inverter circuit 23 is supplied to the compressor 1 as driving power. The control unit 20 performs overall control of the refrigeration cycle, and is composed of a microcomputer and its peripheral circuits. The control unit 20 has the following functional means in addition to normal operating functions. (1) Degree of superheating of refrigerant in the evaporator (difference between temperature T1 detected by temperature sensor 11 and temperature T2 detected by temperature sensor 12) SH
means to detect. (2) The detected degree of refrigerant superheating SH is a constant value, for example 5 de
Means for controlling the opening degree of the electronic expansion valve 4 so that g.

(3) Means for correcting the opening degree of the electronic expansion valve 4 in accordance with the discharge refrigerant temperature Td of the compressor 1 detected by the temperature sensor 10 when the detected refrigerant superheat degree SH is zero or less. Next, the operation will be explained with reference to FIGS. 2 to 6. First, cooling operation will be explained. The cooling operation mode and desired indoor temperature are set using the operating device 21, and the operation is started. Then, the control unit 20 drives the inverter circuit 23 and starts the compressor 1.

In this case, the refrigerant discharged from the compressor 1 flows in the direction of the solid arrow shown in the figure to form a cooling cycle.
The outdoor heat exchanger 3 works as a condenser, and the indoor heat exchanger 5 works as an evaporator. This cools the room.

During this heating operation, the control section 20 controls the operation device 2.
The difference between the indoor temperature set in step 1 and the temperature detected by the indoor temperature sensor 22 is determined as the air conditioning load, and the output frequency of the inverter circuit 23 is controlled according to the determined air conditioning load. That is,
When the temperature difference is large, the output frequency of the inverter circuit 23 is increased, and as the temperature difference becomes smaller, the output frequency is lowered.

[0021] When the output frequency of the inverter circuit 23 increases, the capacity of the compressor 1 increases, and the cooling capacity increases. When the output frequency of the inverter circuit 23 becomes lower, the capacity of the compressor 1 decreases, and the cooling capacity decreases. In this way, the indoor temperature converges toward the set indoor temperature. next,
The heating operation will be explained. The heating operation mode and desired indoor temperature are set using the operation unit 23, and the operation is started. Then, the control unit 20 drives the inverter circuit 23 to start the compressor 1, and also switches the four-way valve 2.

In this case, the refrigerant discharged from the compressor 1 flows in the direction of the dashed arrow in the figure to form a heating cycle.
The indoor heat exchanger 7 works as a condenser, and the outdoor heat exchanger 5 works as an evaporator. This heats the room.

During this heating operation, the control unit 20 calculates the difference between the set indoor temperature and the temperature detected by the indoor temperature sensor 22,
The output frequency of the inverter circuit 23 is controlled according to the calculated temperature difference. That is, control is performed to increase the output frequency of the inverter circuit 23 when the temperature difference is large, and to lower the output frequency as the temperature difference becomes smaller.

As the output frequency of the inverter circuit 23 increases, the capacity of the compressor 1 increases, and the heating capacity increases. When the output frequency of the inverter circuit 23 becomes lower, the capacity of the compressor 1 decreases, and the heating capacity decreases. In this way, the indoor temperature converges toward the set indoor temperature.

During this cooling or heating operation, a part of the refrigerant passes through the capillary tubes 6 and 7 and enters the bypass pipe 8, and the refrigerant that has entered the bypass pipe 8 is guided to the suction port of the compressor 1. At this time, the temperature of the refrigerant that has entered the bypass pipe 8 (saturated refrigerant temperature) is detected by the temperature sensor 12. Furthermore, when the refrigerant that has passed through the four-way valve 2 is sucked into the compressor 1, the temperature of the refrigerant is detected by the temperature sensor 11. Here, the control unit 20 executes the control shown in FIG. 2.

A predetermined control interval (for example, 1 minute)
The detected temperatures T1 and T2 of the temperature sensors 11 and 12 are respectively
The difference between both detected temperatures (=T1 - T2) is determined. This temperature difference corresponds to the refrigerant superheat degree SH.

In order to keep the refrigerant superheat degree SH within a constant value SHo, for example 5 degrees, a correction amount (drive pulse number) ΔPLS for the current opening degree of the electronic expansion valve 4 is determined by PI control.

In this PI control, the difference ΔSH1 (=SHn - SHn-1) between the current degree of refrigerant superheating SHn and the previous degree of refrigerant superheating SHn-1 is calculated, and the difference ΔSH1 and the diagram stored in the internal memory are calculated. The value of P is selected from the P value selection conditions of 3.

At the same time, the difference ΔSH2 (=SHn - SHo) between the current refrigerant superheat degree SHn and the constant value SHo is calculated, and the difference ΔSH2 and the difference ΔSH2 are stored in the internal memory.
The value of I is selected from the I value selection conditions. Also, the detected temperature Td of the temperature sensor 10 is taken in, and the detected temperature Td
Find the amount of change ΔTd. In other words, ΔTd=Tdn −
Tdn-1.

If the detected refrigerant superheat degree SH is greater than zero, the correction amount ΔPLS obtained by PI control is determined as the actual correction amount ΔPLS', and the opening degree of the electronic expansion valve 4 is corrected by the correction amount ΔPLS'. do.

When the detected refrigerant superheat degree SH is zero or less, that is, when a liquid back phenomenon to the compressor 1 is occurring, the above-determined ΔTd and the coefficient selection conditions shown in FIG. 5 stored in the internal memory are used. Select the value of coefficient K from . Then, by integrating the coefficient K to the correction amount ΔPLS obtained by PI control, the actual correction amount ΔPLS' (=K・ΔPLS
), and the opening degree of the electronic expansion valve 4 is corrected by the correction amount ΔPLS'.

[0032] In this way, when liquid back occurs,
By adding correction based on the discharge refrigerant temperature Td of the compressor 1 to the opening degree control of the electronic expansion valve 4 based on the refrigerant superheat degree SH, it becomes possible to adjust the refrigerant flow rate in consideration of the liquid back amount. Therefore, the exit from the liquid back-up state becomes faster, and as shown in FIG. can reduce the negative effects of A second embodiment of the invention is shown in FIG.

In this embodiment, a temperature sensor 13 is attached to the bottom of the case of the compressor 1, a temperature sensor 14 is attached to the outdoor heat exchanger 3, and a temperature sensor 15 is attached to the indoor heat exchanger 5.
are installed respectively. The temperature sensor 10 in the case of the first embodiment is excluded. The control unit 20 includes the following functional means in addition to normal operation functions. (1) Degree of superheating of refrigerant in the evaporator (difference between temperature T1 detected by temperature sensor 11 and temperature T2 detected by temperature sensor 12) SH
means to detect. (2) The detected degree of refrigerant superheating SH is a constant value, for example 5 de
A first control means for controlling the opening degree of the electronic expansion valve 4 so that the opening degree is within the range of g.

(3) Difference ΔT(
= T3 - T4 ). (4) The detected temperature difference ΔT is a constant value, for example 15 degrees
A second control means for controlling the opening degree of the electronic expansion valve 4 so that the following is achieved.

(5) The control of the first control means is executed from the start of operation until a fixed time, for example, 5 minutes, has elapsed based on the count of the internal timer, and after the elapse of the fixed time, the control of the first control means is executed according to the temperature difference ΔT. means for selectively executing the control or the control of the second control means; (6) Means for selecting whether to continue or cancel the control of the second control means once executed, depending on the refrigerant superheat degree SH. The other configurations are the same as in the first embodiment. Explain the action.

During cooling or heating operation, a part of the refrigerant passes through the capillary tubes 6 and 7 and enters the bypass pipe 8.
The refrigerant that has entered the bypass pipe 8 is guided to the suction port of the compressor 1. At this time, the temperature of the refrigerant entering the bypass pipe 8 (
saturated refrigerant temperature) is detected by the temperature sensor 12. Furthermore, when the refrigerant that has passed through the four-way valve 2 is sucked into the compressor 1, the temperature of the refrigerant is detected by the temperature sensor 11. Here, the control unit 20 executes the control shown in FIG. 8.

A predetermined control interval (for example, 1 minute)
The detected temperatures T1 and T2 of the temperature sensors 11 and 12 are respectively
The difference between both detected temperatures (=T1 - T2) is determined. This temperature difference corresponds to the refrigerant superheat degree SH.

In order to keep the refrigerant superheat degree SH within a constant value SHo, for example 5 degrees, a correction amount (drive pulse number) ΔPLS for the current opening degree of the electronic expansion valve 4 is determined by PI control.

In this PI control, the difference ΔSH1 (=SHn - SHn-1) between the current degree of refrigerant superheating SHn and the previous degree of refrigerant superheating SHn-1 is calculated, and the difference ΔSH1 and the diagram stored in the internal memory are calculated. The value of P is selected from the P value selection conditions of 3.

At the same time, the difference ΔSH2 (=SHn - SHo) between the current refrigerant superheat degree SHn and the constant value SHo is calculated, and the difference ΔSH2 and the difference ΔSH2 are stored in the internal memory.
The value of I is selected from the I value selection conditions. Then, the opening degree of the electronic expansion valve 4 is corrected by the obtained correction amount ΔPLS. Up to this point, the control is executed by the first control means, and this is performed unconditionally for 5 minutes from the start of operation based on the count of the internal timer.

After 5 minutes have elapsed since the start of operation, the temperature at the bottom of the case of the compressor 1 (temperature T detected by the temperature sensor 13)
3) and the temperature of the condenser (temperature T4 detected by temperature sensor 14 or 15), the difference ΔT (=T3 - T4) is determined.

Detected temperature difference ΔT and set value 10deg
If the temperature difference ΔT is larger than the set value 10 degrees, the control of the first control means is continued. This is based on the determination that the compressor 1 is operating at a high operating frequency and the refrigerant does not dissolve into the lubricating oil in the compressor 1, that is, there is no fear of dilution of the lubricating oil.

[0043] However, if the temperature difference ΔT is the set value 10deg
It may be smaller than. This often occurs when the compressor 1 is operating at a low operating frequency,
There is a risk that the refrigerant will dissolve into the lubricating oil in the compressor 1, that is, the lubricating oil will be diluted. In this case, the opening degree of the electronic expansion valve 4 is controlled so that the temperature difference ΔT is a constant value, for example, 15 degrees. In other words, this is execution of control by the second control means.

That is, if the temperature difference ΔT is smaller than 15 degrees, the opening degree of the electronic expansion valve 4 is reduced by a predetermined value. If the temperature difference ΔT is greater than 15 degrees, the electronic expansion valve 4
Increase the opening degree by a predetermined value. If the temperature difference ΔT is equal to 15 degrees, the opening degree of the electronic expansion valve 4 is maintained as it is. In this way, by increasing the temperature difference ΔT to 15 degrees, it is possible to eliminate the fear that the refrigerant will dissolve into the lubricating oil in the compressor 1, that is, the lubricating oil will be diluted.

Once the control of the second control means is executed, the refrigerant superheat degree SH is compared with the set value 2deg, and if the refrigerant superheat degree SH is larger than the set value 2deg, the control of the second control means is continued. continue. However, when the refrigerant superheat degree SH falls below the set value 2deg, the control of the second control means is canceled and the original control of the first control means is restored.

As described above, by appropriately executing the second control means based on the temperature difference ΔT, it is possible to avoid a situation where the lubricating oil in the compressor 1 is diluted, and to prevent a failure of the compressor 1. It can be prevented. Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without changing the gist.

[0047]

[Effect of the invention] As described above, according to this invention,

[
The refrigeration cycle device of claim 1 controls the opening degree of the electronic expansion valve so that the degree of superheating of the refrigerant in the evaporator becomes a constant value, and also controls the degree of opening of the electronic expansion valve so that the degree of superheating of the refrigerant in the evaporator becomes zero or less. Since the opening degree of the electronic expansion valve is corrected according to the temperature of the discharged refrigerant, it is possible to quickly escape from the liquid back state, thereby extending the life of the compressor.

The refrigeration cycle device according to the second aspect of the present invention includes a first control means for controlling the opening degree of the electronic expansion valve so that the degree of superheating of the refrigerant in the evaporator becomes a constant value, and a first control means for controlling the opening degree of the electronic expansion valve so that the degree of superheating of the refrigerant in the evaporator becomes a constant value; It is equipped with a second control means for controlling the opening degree of the electronic expansion valve so that the difference is a constant value, and the first control means executes the control from the start of operation until a certain period of time has elapsed, and after the elapse of the certain period of time, the above control is performed. The control of the first control means or the control of the second control means is selectively executed according to the temperature difference, and once the control of the second control means is executed, the control is continued or canceled according to the degree of superheating of the refrigerant. Since this configuration is selected, it is possible to avoid a situation where the lubricating oil is diluted and prevent a failure of the compressor.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment.

FIG. 3 is a diagram showing a format of P value selection conditions in the same embodiment.

FIG. 4 is a diagram showing the format of I value selection conditions in the same embodiment.

FIG. 5 is a diagram showing a format of coefficient selection conditions in the same embodiment.

FIG. 6 is a diagram showing an example of a change in the refrigerant superheat degree SH in the same example.

FIG. 7 is a diagram showing the overall configuration of a second embodiment of the invention.

FIG. 8 is a flowchart for explaining the operation of the embodiment.

FIG. 9 is a diagram showing the configuration of a conventional refrigeration cycle device.

[Explanation of symbols]

1... Variable capacity compressor, 3... Outdoor heat exchanger, 4... Electronic expansion valve, 5... Indoor heat exchanger, 11, 12... Temperature sensor, 20
...control section.

Claims (2)

[Claims] 1. A refrigeration cycle in which a compressor, a condenser, an electronic expansion valve, and an evaporator are sequentially connected, a means for detecting a degree of superheat of a refrigerant in the evaporator, and a means for detecting a degree of superheat of a refrigerant in the evaporator, and a means for detecting a degree of superheat of a refrigerant in the evaporator, and a means for detecting a degree of superheat of a refrigerant in the evaporator. means for controlling the opening degree of the electronic expansion valve; means for detecting the temperature of the refrigerant discharged from the compressor; and means for controlling the opening degree of the electronic expansion valve according to the detected temperature when the degree of superheating of the refrigerant is zero or less. A refrigeration cycle device comprising: means for correcting. 2. A refrigeration cycle in which a compressor, a condenser, an electronic expansion valve, and an evaporator are sequentially connected; a first control means for controlling the opening degree of the electronic expansion valve; a means for detecting the temperature of the compressor; a means for detecting the temperature of the condenser; a means for determining the difference between the two detected temperatures; A second control means controls the opening degree of the electronic expansion valve so that the difference becomes a constant value, and a second control means controls the opening degree of the electronic expansion valve until a certain time elapses from the start of operation. means for selectively controlling the first control means or the second control means according to the temperature difference;
Once the control of the second control means is executed, its continuation;
A refrigeration cycle device comprising means for selecting release in accordance with the degree of superheating of the refrigerant.