EP1655553B1

EP1655553B1 - Air conditioner

Info

Publication number: EP1655553B1
Application number: EP05102202.8A
Authority: EP
Inventors: Woo Hyun Kim; Gyoo Ha Jung; Moon Soo Park
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2004-10-18
Filing date: 2005-03-18
Publication date: 2020-06-17
Anticipated expiration: 2025-03-18
Also published as: CN1763451A; EP1655553A2; CN100501257C; KR20060034109A; EP1655553A3

Description

According to the invention there is a method for controlling an air conditioner comprising operating a compressor to compress a refrigerant, supplying the compressed refrigerant, condensed by an outdoor heat exchanger, to indoor units through an outdoor expansion valve, and controlling an opening degree of the outdoor expansion valve according to opening degrees of indoor expansion valves of the indoor units when performing a cooling operation, and mean super heating temperatures of the indoor units, to control the quantity of the refrigerant supplied to the indoor units.
The opening degree of the outdoor expansion valve is gradually increased when the opening degrees of the indoor expansion valves of the indoor units exceed a first predetermined opening degree and the super heating temperatures of the indoor units exceed a predetermined super heating temperature, to increase the quantity of the refrigerant supplied to the indoor units, and the opening degree of the outdoor expansion valve is gradually decreased when the opening degrees of the indoor expansion valves of the indoor units during cooling operation are not more than a second predetermined opening degree and the super heating temperatures of the indoor units are not more than the predetermined super heating temperature, to decrease the quantity of the refrigerant supplied to the indoor units.
The first predetermined opening degree is higher than the second predetermined opening degree.
The predetermined super heating temperature is a super heating temperature for allowing the indoor units to have the optimum cooling efficiency.
According to a preferred embodiment an opening degree of the outdoor expansion valve is increased or decreased by a predetermined value at an interval of a predetermined time.
According to another embodiment of the invention there is an air conditioner comprising a compressor for compressing a refrigerant, an outdoor heat exchanger for condensing the compressed refrigerant, an outdoor expansion valve for supplying the condensed refrigerant to indoor units, and a control unit for controlling an opening degree of the outdoor expansion valve, according to opening degrees of indoor expansion valves of the indoor units and mean super heating temperatures of the indoor units when the indoor units perform a cooling operation, to control the quantity of the refrigerant supplied to the indoor units.
Generally, a multi-system air conditioner for simultaneously performing cooling and heating operations is configured such that a plurality of indoor air conditioning units are connected in parallel to at least one outdoor unit. The outdoor unit and the plurality of indoor units are electrically connected by communication lines and power lines, and include a plurality of refrigerant pipes and valves for controlling the flow and quantity of a refrigerant.
In a case when an insufficient quantity of refrigerant is supplied to the indoor heat exchanger (evaporator), the indoor heat exchanger (evaporator) cannot be filled with refrigerant in a saturated state and so a rear portion of the indoor heat exchanger (evaporator) is filled with the superheated refrigerant. This portion of the indoor heat exchanger, which is filled with the superheated refrigerant, cannot function as an evaporator, thereby decreasing the cooling capacity of the air conditioner.
Further, in the case where the practical super heating temperature is higher than the designed value, for example, the designed value is 5°C, and the practical super heating temperature is 10°C since the volume of the gaseous refrigerant is heavier than that of the gaseous refrigerant when the practical super heating temperature is 5°C, the quantity of the refrigerant circulated by the compressor is relatively decreased, thereby further deteriorating cooling capacity of the air conditioner. Moreover, since the compressor is operated at a higher temperature, the efficiency of a compressor motor is decreased.
JP H09 210491A discloses a method of controlling the cooling temperature of an air conditioned space wherein the valve travel of a utilization side expansion valve is controlled in reference to a value travel determined by each of first and second value travel determination devices when a super-cooling degree is in a range of predetermined threshold value.
The present invention seeks to provide a system which overcomes or substantially alleviates the problems discussed above.
According to the invention there is provided a method for controlling an air conditioner according to claim 1 and an air conditioner according to claim 5.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic view illustrating a refrigerant cycle of an air conditioner in accordance with an embodiment of the present invention;
Figure 2 is a block diagram of a system for controlling the air conditioner shown in Figure 1; and
Figures 3A and 3B are flow charts illustrating a method for controlling the air conditioner in accordance with an embodiment of the present invention.

Referring to the drawings, there is shown in Figure 1 the air conditioner comprising an outdoor unit 120, first to fourth indoor units 140a,140b,140c and 140d and a mode change unit (MCU) 160.
The outdoor unit 120 includes a four-way valve 124 for determining the direction of the flow of a refrigerant discharged from a compressor 122. That is, the four-way valve 124 changes the direction of the channel of the refrigerant in a main cooling mode such that the refrigerant in a high-temperature and high-pressure state discharged from the compressor 122 flows to a main cooling electric valve 186a and an outdoor heat exchanger 126, and changes the direction of the channel of the refrigerant in a main heating mode such that the refrigerant is supplied to the first to fourth indoor units 140a,140b,140c and 140d through a backflow prevention valve 188 and the MCU 160. The outdoor heat exchanger 126 exchanges heat between the refrigerant and outdoor air, flowing into the outdoor unit 120 through an outdoor fan 102. The outdoor unit 120 further includes an outdoor electric expansion valve 128 for expanding the refrigerant, a liquid receiver 130 for separating refrigerant in a liquid state from refrigerant in a gaseous state, and an accumulator 132. The flow of the refrigerant between the first to fourth indoor units 140a,140b,140c and 140d and the outdoor unit 120 is achieved by a high-pressure gas pipe 134 and a low-pressure gas pipe 136.
Hereinafter, the states of the refrigerant in the pipes and the positions of the valves of the outdoor unit 120 will be described. The low-pressure gas pipe 136 is connected to an inlet side of the compressor 122 via the accumulator 132, and a high-pressure liquid pipe 138 is connected to the outdoor electric expansion valve 128 via the liquid receiver 130. A bypass valve 182a and a backflow prevention valve 182b, connected in parallel to the outdoor electric expansion valve 128, are opened in a cooling mode, and a part of the refrigerant in the liquid state discharged from the outdoor heat exchanger 126 passes through the bypass valve 182a and the backflow prevention valve 182b and bypasses the outdoor electric expansion valve 128. On the other hand, the bypass valve 182a and the backflow prevention valve 182b are closed in a heating mode, and the refrigerant passes through the outdoor electric expansion valve 128, thereby being expanded.
A high-pressure branch pipe 184, branched from the high-pressure gas pipe 134, is connected between the four-way valve 124 and an inlet of the outdoor heat exchanger 126. The main cooling electric valve 186a serving as a switch valve and the backflow prevention valve 182b for preventing the backflow of the refrigerant are installed in the high-pressure branch pipe 184. The backflow prevention valve 188 for preventing the backflow of the refrigerant is installed between the four-way valve 124 and the high-pressure liquid pipe 138.
The first to fourth indoor units 140a,140b,140c and 140d are connected in parallel to the outdoor unit 120, and respectively include first to fourth indoor heat exchangers 142a,142b,142c and 142d, first to fourth indoor electric expansion valves 144a,144b,144c and 144d and first to fourth pairs of temperature sensors 174a-174a', 174b-174b', 174c-174c' and 174d-174d' serve to detect a difference of temperatures between inlets and outlets of the first to fourth indoor heat exchangers 142a,142b,142c and 142d thereby checking super heating temperatures of the first to fourth indoor heat exchangers 142a,142b,142c and 142.
The MCU 160 determines cooling and heating operations of the first to fourth indoor units 140a,140b,140c and 140d. First to fourth heating electric valves 162a,162b,162c and 162d are respectively installed in first to fourth high-pressure gas branch pipes 166a,166b,166c and 166d branched from the high-pressure gas pipe 134 in the MCU 160. Further, first to fourth cooling electric valves 164a,164b,164c and 164d are respectively installed in first to fourth low-pressure gas branch pipes 168a,168b,168c and 168d branched from the low-pressure gas pipe 136. The first heating electric valve 162a and the first cooling electric valve 164a are connected to a first refrigerant pipe 170a connected to the first indoor heat exchanger 142a, and the second to fourth heating electric valves 162b,162c and 162d are sequentially connected to second to fourth refrigerant pipes 170b, 170c and 170d.
Figure 1 illustrates a refrigerant cycle of an air conditioner in a main net cooling mode. In the main cooling mode, the sum total of cooling capacities required by the whole indoor units is larger than the sum total of heating capacities required by the whole indoor units. In the main cooling mode, a large portion of the refrigerant discharged from the compressor 122 is condensed by the outdoor heat exchanger 126 and supplied to the MCU 160, and the remainder of the refrigerant is directly supplied to the MCU 160 through the high-pressure gas pipe 134. In Figure 1, the section expressed by a thick solid line is a high-pressure section of the refrigerant and the section expressed by a dotted line is a low-pressure section of the refrigerant.
Since the first and second cooling electric valves 164a and 164b in the MCU 160 are opened, the first and second indoor units 140a and 140b perform cooling operations. Since the third heating electric valve 162c and the third cooling electric valve 164c are closed, the third indoor unit 140c does not perform any operation. Further, since the fourth heating electric valve 162d is opened, the fourth indoor unit 140d performs a heating operation.
As shown in Figure 2, the outdoor unit 120 of the air conditioner further comprises an outdoor unit microcomputer 202 for controlling the component of the outdoor unit 120. The first to fourth indoor units 140a,140b,140c and 140d respectively further comprises first to fourth indoor unit microcomputers 206a,206b,206c and 206d for controlling the components of the first to fourth indoor units 140a,140b,140c and 140d. The MCU 160 further comprises an MCU microcomputer 204 for controlling the first to fourth cooling electric valves 164a,164b,164c and 164d, and the first to fourth heating electric valves 162a,162b,162c and 162d.
Figures 3A and 3B are flow charts illustrating a method for controlling the air conditioner in accordance with an embodiment of the present invention. As shown in Figures 3A and 3B, the whole system of the air conditioner is initialised (302), and the sum total of cooling capacities required by the first to fourth indoor units 140a,140b,140c and 140d is compared to the sum total of heating capacities required by the first to fourth indoor units 140a,140b,140c and 140d (304). When the sum total of heating capacities required by the first to fourth indoor units 140a,140b,140c and 140d is higher than the sum total of cooling capacities required by the first to fourth indoor units 140a,140b,140c and 140d, the air conditioner is operated in a net heating mode (306). On the other hand, when the sum total of cooling capacities required by the first to fourth indoor units 140a,140b,140c and 140d is higher than the sum total of heating capacities required by the first to fourth indoor units 140a,140b,140c and 140d, the air conditioner is operated in a net cooling mode (308).
In the main cooling mode, the opening degree of the outdoor electric expansion valve 128 is controlled according to a rate of heating operation (310). In this mode, the refrigerant for cooling flows to the first and second indoor units 140a and 140b, which are required to perform cooling operations via the outdoor heat exchanger (i.e. condenser) 126 and the outdoor electric expansion valve 128, and a refrigerant for heating flows to the fourth indoor unit 140d, which is required to perform a heating operation, via the main cooling electric valve 186a and the high-pressure gas pipe 134. With reference to Figure 1, since two indoor units, i.e. the first and second indoor units 140a and 140b, are required to perform cooling operations, and one indoor unit, i.e. the fourth indoor unit 140d, is required to perform a heating operation, the degree of opening of the outdoor electric expansion valve 128 is increased so that a larger quantity of the refrigerant is supplied to the first and second indoor units 140a and 140b. The relation between the rate of heating operation and the degree of opening of the outdoor electric expansion valve 128 is stated by a lookup table. The outdoor unit microcomputer 202 controls the degree of opening of the outdoor electric expansion valve 128 based on the lookup table figures. One example of the lookup table will be described, as follows. Here, the lower the rate of heating operation is, the higher the degree of opening of the outdoor electric expansion valve 128.

Rate of Heating Operation 0∼10% 11∼20% 21∼30% 31∼40% 41∼50% 51∼60%

Opening Degree of Outdoor Electric Expansion Valve 100% 50% 30% 20% 15% 12.5%
As long as the degree of opening of the outdoor electric expansion valve 128 is controlled according to the rate of heating operation requirements in the main net cooling mode (310), the opening degrees of the first and second indoor electric expansion valves 144a and 144b and mean super heating temperatures of the first and second indoor units 140a and 140b, which perform cooling operation can be detected (312). When the degree of opening of the first and second indoor electric expansion valves 144a and 144b exceed 85% and the mean super heating temperatures of the first and second indoor units 140a and 140b, which perform cooling operations, exceed a target super heating temperature (for example, a super heating temperature representing the optimum cooling efficiency), the outdoor electric expansion valve 128 is opened by 1% per predetermined time (for example, 20 seconds) (314). Each of the mean super heating temperatures is an average of the temperature difference between the inlet and the outlet of the corresponding indoor unit, which are periodically detected. In a case when the opening degrees of the first and second indoor electric expansion valves 144a and 144b are comparatively high and the mean super heating temperatures of the first and second indoor units 140a and 140b exceed the target super heating temperature, the refrigerant passing through the first and second indoor heat exchangers 142a and 142b is excessively rapidly vaporized, thereby causing difficulties in achieving a sufficient cooling operation and in supplying a sufficient quantity of the refrigerant to the first and second indoor units 140a and 140b. Accordingly, in this case, the opening degree of the outdoor electric expansion valve 128 is gradually increased so that a larger quantity of the condensed refrigerant is supplied to the first and second indoor units 140a and 140b. In the opposite case, the air conditioner is continuously operated in the main cooling mode under the condition that the degree of opening of the outdoor electric expansion valve 128 is controlled according to the current rate of heating operation (316).
During the main cooling mode (316), the degree of opening of the first and second indoor electric expansion valves 144a and 144b and the mean super heating temperatures of the first and second indoor units 140a and 140b, which perform cooling operations, are detected (324). When the degree of opening of the first and second indoor electric expansion valves 144a and 144b are 100%, i.e. the first and second indoor electric expansion valve 128 is opened by 1% per predetermined time (for example, 20 seconds) (326). Since the quantity of the refrigerant supplied to the first and second indoor units 140a and 140b is sufficient under the condition that the first and second indoor electric valves 144a and 144b are completely opened, the degree of opening of the outdoor electric expansion valve 128 is gradually increased so that the quantity of the refrigerant supplied to the first and second indoor units 140a and 140b is increased. In the opposite case, the air conditioner is continuously operated in the main cooling mode under the condition that the degree of opening of the outdoor electric expansion valve 128 is controlled according to the current rate of heating operation (328).
As apparent from the above description, the present invention provides an air conditioner and a method for controlling the same, in which the quantity of a refrigerant supplied to indoor heat exchangers (evaporators) is controlled according to opening degrees of indoor electric expansion valves and super heating temperatures of the indoor heat exchangers (evaporators), thereby increasing cooling efficiency of the air conditioner.
Although an embodiment of the invention has been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles of the invention, the scope of which is defined in the claims and the foregoing description should be regarded as a description of a preferred embodiment only.

Claims

A method for controlling an air conditioner operable in a main heating mode (306) and a main cooling mode (308), the method comprising:
operating a compressor (122) to compress a refrigerant,

supplying the compressed refrigerant, condensed by an outdoor heat exchanger (126), to indoor units (140a, 140b, 140c, 140d) through an outdoor expansion valve (128), and

when in the main cooling mode (308), controlling an opening degree of the outdoor expansion valve (128) according to:
a rate of heating operation (310),

opening degrees of indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units when performing a cooling operation, and

mean super heating temperatures of the indoor units (140a, 140b, 140c, 140d),

to control the quantity of the refrigerant supplied to the indoor units (140a, 140b, 140c, 140d),

wherein the opening degree of the outdoor expansion valve (128) is gradually increased (314) when the opening degrees of the indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units (140a, 140b, 140c, 140d) when performing a cooling operation exceed 85% and the mean super heating temperatures of the indoor units (140a, 140b, 140c, 140d) exceed a predetermined super heating temperature (312), to increase the quantity of the refrigerant supplied to the indoor units when the opening degrees of the indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units (140a, 140b, 140c, 140d) when performing a cooling operation do not exceed 85% and the mean super heating temperatures of the indoor units (140a, 140b, 140c, 140d) do not exceed a predetermined super heating temperature, controlling the opening degree of the outdoor expansion valve (128) according to the rate of heating operation (316), and

wherein the opening degree of the outdoor expansion valve (128) is gradually decreased when the opening degrees of the indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units (140a, 140b, 140c, 140d) during cooling operation are not more than 25% and the mean super heating temperatures of the indoor units (140a, 140b, 140c, 140d) are not more than the predetermined super heating temperature, to decrease the quantity of the refrigerant supplied to the indoor units (140a, 140b, 140c, 140d) when the opening degrees of the indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units (140a, 140b, 140c, 140d) during cooling operation are more than 25% and the mean super heating temperatures of the indoor units (140a, 140b, 140c, 140d) are more than the predetermined super heating temperature (318), controlling the opening degree of the outdoor expansion valve (128) according to the rate of heating operation (322).
The method as claimed in claim 1 wherein the predetermined super heating temperature is a super heating temperature for allowing the indoor units (140a, 140b, 140c, 140d) to have the optimum cooling efficiency.
The method as claimed in claim 1 wherein the opening degree of the outdoor expansion valve (128) is increased or decreased by a predetermined value at an interval of a predetermined time.
The method as claimed in claim 3 wherein the predetermined value is 1% and the predetermined time is 20 seconds.
An air conditioner operable in a main heating mode (306) and a main cooling mode (308), the air conditioner comprising:
a compressor (122) for compressing a refrigerant,

an outdoor heat exchanger (126) for condensing the compressed refrigerant,

an outdoor expansion valve (128) for supplying the condensed refrigerant to indoor units (140a, 140b, 140c, 140d), and

a control unit (202) configured to control, when in the main cooling mode (308), an opening degree of the outdoor expansion valve (128), according to:
a rate of heating operation (310),

opening degrees of indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units (140a, 140b, 140c, 140d), and

mean super heating temperatures of the indoor units when the indoor units (140a, 140b, 140c, 140d) perform a cooling operation,

to control the quantity of the refrigerant supplied to the indoor units,

wherein the opening degree of the outdoor expansion valve (128) is gradually increased when the opening degrees of the indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units (140a, 140b, 140c, 140d) when performing a cooling operation exceed 85% and the mean super heating temperatures of the indoor units (140a, 140b, 140c, 140d) exceed a predetermined super heating temperature, to increase the quantity of the refrigerant supplied to the indoor units when the opening degrees of the indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units (140a, 140b, 140c, 140d) when performing a cooling operation do not exceed 85% and mean super heating temperatures of the indoor units (140a, 140b, 140c, 140d) do not exceed a predetermined super heating temperature (312), the opening degree of the outdoor expansion valve (128) is controlled according to the rate of heating operation (316), and

wherein the opening degree of the outdoor expansion valve (128) is gradually decreased when the opening degrees of the indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units (140a, 140b, 140c, 140d) during cooling operation are not more than 25% and the mean super heating temperatures of the indoor units (140a, 140b, 140c, 140d) are not more than the predetermined super heating temperature, to decrease the quantity of the refrigerant supplied to the indoor units (140a, 140b, 140c, 140d) when the opening degrees of the indoor expansion valves (144a, 144b, 144c, 144d) of the indoor units (140a, 140b, 140c, 140d) during cooling operation are more than 25% and the mean super heating temperatures of the indoor units (140a, 140b, 140c, 140d) are more than the predetermined super heating temperature (318), the opening degree of the outdoor expansion valve (128) is controlled according to the rate of heating operation (322).