ITTO990898A1 - MULTIPLE AIR CONDITIONER HAVING A PLURALITY OF BY-PASS LINES AND METHOD TO CONTROL THE QUANTITY OF BYPASSED REFRIGERANT. - Google Patents

Description

DESCRIPTION

de! patent for Industrial Invention -

Background of the invention

1. Field of the invention

The present invention relates to a multi-type air conditioner having a compressor and a plurality of internal heat exchangers connected to the compressor and, more particularly, to a multi-type air conditioner having a plurality of by-pass lines and a method of controlling a bypassed amount of refrigerant to be supplied to a plurality of internal heat exchangers without an inverter-type compressor, selectively opening / closing the plurality of by-pass lines based on an average temperature of the internal heat exchangers in function.

2. Description of the prior art

Generally, an air conditioner serves to cool / heat the air in a room by exchanging heat between the room air and a heat exchanger medium (hereafter referred to as refrigerant) which undergoes a phase change as it circulates in a closed path.

Recently, a multi-type air conditioner has been employed having a compressor to which a plurality of heat exchangers are connected, to cool / heat a plurality of rooms more efficiently with a relatively low cost.

This multi-type air conditioner is briefly described with reference to Fig. 1.

As shown in Fig. 1, the multi-type air conditioner comprises a compressor 1, an external heat exchanger 2, and three internal heat exchangers 3a, 3b and 3c. A discharge opening of the external heat exchanger 2 is connected to the inlets of the respective internal heat exchangers 3a, 3b and 3c through a refrigerant pipe 8b having three branches. Furthermore, secondary solenoid valves 4a, 4b and 4c and secondary capillary tubes 5a, 5b and 5c are connected in series to the inlet side of the respective internal heat exchangers 3a, 3b and 3c, to control the flow rate of the refrigerant to be supplied to the respective internal heat exchangers 3a, 3b and 3c and, respectively, to depressurize the refrigerant. A primary solenoid valve 6 and primary capillary tubes 7 are connected in parallel to the discharge opening of the external heat exchanger 2. In addition, a by-pass line 10 connects the end of the external heat exchanger 2 with the inlet of compressor 1, to bypass compressor 1 a certain amount of the refrigerant that passes through the external heat exchanger 2. The by-pass line 10 comprises a by-pass pipe 11, a by-pass valve 12 to open / close the by-pass tube 11 and a capillary tube 13 to expand the bypassed refrigerant.

The refrigerant is compressed at high temperature and high pressure in the compressor 1, condensed in the external heat exchanger 2, distributed in the three internal heat exchangers 3a, 3b and 3c, subjected to heat exchange in the respective internal heat exchangers 3a, 3b and 3c with the ambient air of the respective positions, and gathered to flow back into compressor 1.

In such a multi-type air conditioner, the compressor 1 has a capacity corresponding to the three internal heat exchangers 3a, 3b and 3c. Consequently, when the internal heat exchangers 3a, 3b and 3c are partially operated, the refrigerant is supplied in excess to the operating internal heat exchanger. In particular when one of the internal heat exchangers 3a, 3b and 3c is operated alone, the refrigerant overload causes the internal heat exchanger to freeze in operation, and the liquid refrigerant is fed to compressor 1, leading to a decrease reliability of compressor 1.

To overcome the above problems, the multi-type air conditioner has a function of controlling the opening / closing of respective valves 4a, 4b, 4c, 6 and 12 based on the number of indoor heat exchangers in operation. The open / close states of valves 4a, 4b, 4c, 6 and 12 are varied according to the number of heat exchangers in operation, as shown in Table 1 below.

[Table 1]

As shown in Table 1, when one of the internal heat exchangers (e.g. heat exchanger 3a) is operated alone, the primary solenoid valve 6, the bypass valve 12 and the corresponding secondary solenoid valve 4a are open. , while the other valves are closed. Consequently, while the refrigerant is supplied to the internal heat exchanger 3a in operation by the external heat exchanger 2, part of the refrigerant is bypassed, through the by-pass line 10, to the compressor 1. As described, since part of the refrigerant is bypassed while the refrigerant passes through the external heat exchanger 2, the amount of refrigerant to be supplied to the internal heat exchanger 3a is decreased, so as to prevent the internal heat exchanger 3a from freezing due to refrigerant overload to the heat exchanger internal 3a. In such a situation, the refrigerant is supplied to the internal heat exchanger 3a passing through the primary solenoid valve 6, not the primary capillary tube 7. As a result, over-expansion of the refrigerant is prevented.

When more than two internal heat exchangers are operated simultaneously, the secondary solenoid valve of the internal heat exchanger which is not in operation, the primary solenoid valve 6 and the by-pass valve 12 are closed. In particular, when the two internal heat exchangers (for example the internal heat exchangers 3a and 3b) are operated simultaneously, the refrigerant passes through the external heat exchanger 2 and then distributed to the two internal heat exchangers 3a and 3b in function. In this case, although the quantity of refrigerant to be supplied to the two internal heat exchangers 3a and 3b exceeds the capacities of the internal heat exchangers 3a and 3b, the quantity is not so high that the internal heat exchangers 3a and 3b are frozen. Consequently, when the two internal heat exchangers 3a and 3b are in operation, the by-pass valve 12 is closed.

The conventional multi-type air conditioner, however, has the drawback that since the amount of refrigerant to be bypassed through the by-pass line is constant, the capacity of the internal heat exchangers of the same model cannot be varied. Consequently, such conventional multi-type air conditioner may not satisfy the user's need when the user wishes to use the respective internal heat exchangers in different sized rooms.

Also, during low temperature operation, and particularly when the two internal heat exchangers <'> are operated simultaneously, freezing of the internal heat exchangers often occurs. When an indoor heat exchanger is operated alone in overload operation, since the amount of bypassed refrigerant is constant, the amount of refrigerant to be supplied to the running indoor heat exchanger may be insufficient. This requires a procedure to control the amount of refrigerant to be supplied to the indoor heat exchanger according to the operating conditions such as low temperature operation, overload operation, etc., but the conventional multi-type air conditioner may not satisfy this. requirement.

To overcome the previous problems, a multi-type air conditioner that employs an inverter has been suggested. In this type of multi-type air conditioner, the amount of refrigerant is controlled by controlling the rotation frequency of the compressor by means of a converter and an inverter.

Consequently, the amount of refrigerant to be supplied to the internal heat exchanger is easily controlled based on the capacity and load of the internal heat exchanger without the by-pass line. Such a multi-type air conditioner that employs the inverter, however, has the drawback of being less competitively priced due to its expensive inverter.

Summary of the invention

The present invention was developed to overcome the aforementioned problems of the prior art and, consequently, an object of the present invention is to provide a multi-type air conditioner capable of supplying an appropriate amount of refrigerant to internal heat exchangers based on the capacity and load of internal heat exchangers, without using an expensive inverter.

Another object of the present invention is to provide a method for controlling the amount of refrigerant that is bypassed from an external heat exchanger to a compressor so as to supply an appropriate amount of refrigerant to the internal heat exchangers in the multi-type air conditioner.

The above object is achieved by means of a multi-type air conditioner according to the present invention, comprising: a compressor not of the inverter type; an external heat exchanger; a first connecting pipe for supplying refrigerant from the non-inverter type compressor to the external heat exchanger; a second connecting tube, one end of which is branched into a plurality of lines for discharging the refrigerant from the external heat exchanger; a plurality of internal heat exchangers connected to the plurality of lines of the second connecting pipe; a third connecting pipe for collecting the refrigerant from the plurality of internal heat exchangers and for feeding the collected refrigerant to the compressor; a plurality of electronic expansion valves respectively connected to the plurality of lines of the second connecting tube; a plurality of by-pass lines, each having a by-pass pipe connecting the external heat exchanger with the third connecting pipe, a capillary pipe connected to the by-pass pipe and a bypass valve, to bypass part of the refrigerant from the heat exchanger external to the compressor, the by-pass valve and the capillary tube being connected in series along the by-pass tube; and means for controlling the amount of refrigerant bypassed by the heat exchanger external to the compressor, controlling the by-pass valve of each by-pass line based on the average temperature of the internal heat exchangers which are in operation.

The means for controlling the amount of bypassed refrigerant comprise a plurality of temperature sensors for detecting the temperatures of the respective internal heat exchangers and for generating temperature signals; and a microcomputer for receiving temperature signals and for applying control signals to the plurality of by-pass valves.

Another foregoing object is achieved by a method of controlling the amount of refrigerant bypassed for a multi-type air conditioner having a non-inverter-type compressor, and first and second by-pass lines for bypassing different amounts of refrigerant from the heat exchanger external to the compressor, where the control method comprises the steps of: (1) obtaining the average temperature of the internal heat exchangers in operation; (2) closing the first and second by-pass lines if the average temperature obtained from step (1) exceeds a first predetermined temperature range; (3) open the first by-pass line and close the second. by-pass line if the average temperature has been maintained within the first predetermined temperature range for a predetermined period of time; (4) closing the first by-pass line and opening the second by-pass line if the average temperature has been maintained within a second predetermined temperature range for a predetermined period of time; and (5) opening the first and second bypass lines if the average temperature has been maintained within a third predetermined temperature range for a predetermined period of time.

If the average temperature is within a first predetermined temperature range after the execution of step (5), a compressor stop step (6) is performed. If the compressor is stopped in step (2), a compressor run step (7) is performed.

Preferably, the first, second and third predetermined temperature ranges are respectively equal to 5 ± 0.5 ° C, 3 ± 0.5 ° C and 0 ± 0.5 ° C. It is also preferable that the predetermined time period is 5 minutes ± 30 seconds.

According to the previous multi-type air conditioner and the method for controlling the amount of bypassed refrigerant, the opening / closing of the first and second by-pass lines is systematically controlled by comparing the average temperature of the internal heat exchangers in operation with the first, second and third predetermined degrees. Accordingly, the appropriate amount of refrigerant is supplied to the respective internal heat exchangers, regardless of the number and capacity, or operating conditions such as overload operation, low temperature operation or the like, of the internal heat exchangers that are in operation.

Brief description of the drawings

The foregoing object and other advantages of the present invention will become more evident by describing in detail its preferred embodiments with reference to the accompanying drawings, in which:

Fig. 1 is a diagram of the refrigerant cycle of a conventional multi-type air conditioner;

Fig. 2 is a diagram of the refrigerant cycle of a multi-type air conditioner according to a preferred embodiment of the present invention; Figs. 3A and 3B are respectively viewed to show the by-pass part of the refrigerant cycle of a multi-type air conditioner according to another preferred embodiment of the present invention;

Fig. 4 is a flow chart for illustrating a method of controlling the amount of refrigerant bypassed in the multi-type air conditioner according to the present invention; And

Fig. 5 is a graph to show the operations of the first and second by-pass valves and of the compressor with respect to the average temperature of the internal heat exchanger according to the method of Fig. 4.

Detailed description of the preferred embodiment As shown in Fig. 2, a multi-type air conditioner according to an embodiment of the present invention comprises a compressor 21 of the non-inverter type, an external heat exchanger 22, three internal heat exchangers 23a, 23b and 23c, three electronic expansion valves 24a, 24b and 24c, three connecting tubes 25a, 25b and 25c to connect the previous elements 21, 22, 23a, 23b, 23c, 24a, 24b, 24c, 25a, 25b and 25c in one closed path, a pair of by-pass lines 30a and 30b and a control part.

The first connecting pipe 25a connects one end of the non-inverter type compressor 21 with one end of the external heat exchanger 22, while the other end of the external heat exchanger 22 is connected to one end of the second connecting pipe 25b . The other end of the second connecting tube 25b is branched into three lines which are respectively connected to the internal heat exchangers 23a, 23b and 23c. Furthermore, the respective internal heat exchangers 23a, 23b and 23c are connected with the electronic expansion valves 24a, 24b and 24c through the three branches of the second connecting tube 25b. It is preferable that the electronic expansion valves 24a, 24b and 24c are connected to each side of the inlets of the respective internal heat exchangers 23a, 23b and 23c, while load sensors 27a, 27b and 27c of the internal heat exchanger are connected with each side of the outputs of the respective internal heat exchangers 23a, 23b and 23c. The load sensors 27a, 27b and 27c of the internal heat exchanger detect the temperatures of the refrigerant leaving the respective internal heat exchangers 23a, 23b and 23c.

The third connecting pipe 25c connects the other ends of the respective internal heat exchangers 23a, 23b and 23c with the other end of the compressor 21. The third connecting pipe 25c is branched into three lines which are connected to the other ends of the respective exchangers of internal heat 23a, 23b and 23c.

Furthermore, the pair of by-pass lines 30a and 30b are connected in parallel between the external heat exchanger 22 and the compressor 21. The by-pass lines 30a and 30b bypass part of the refrigerant from the external heat exchanger 22 to the compressor 21. The by-pass lines 30a and 30b respectively comprise a pair of by-pass pipes 31a and 31b, a pair of by-pass valves 32a and 32b for opening / closing the by-pass pipes 31a and 31b, and a pair of capillary tubes 33a and 33b. It is preferable that the by-pass lines 30a and 30b respectively bypass different quantities of refrigerant, so that the first by-pass line 30a bypasses a greater quantity of refrigerant than that of the second by-pass line 30b.

Furthermore, the construction of the by-pass lines -30a and 30b is not limited to what is shown in Fig. 2, but may present variations such as those shown in Fig. 3A and 3B. More specifically, in the first variation shown in Fig.3A, the refrigerant coming from the compressor 21 passes to the external heat exchanger 22, to the capillary tubes 33a and 33b and then to the by-pass valves 32a and 32b, while in the second variation shown in the Fig. 3B, the refrigerant coming from the compressor 21 passes respectively to the external heat exchanger 22, to the by-pass lines 30a and 30b and then to a common capillary tube 33.

The control part controls the by-pass valves 32a and 32b of the by-pass lines 30a and 30b, and includes three temperature sensors 28a, 28b and 28c to detect the temperatures of the respective internal heat exchangers 23a, 23b and 23c , and a microcomputer 29 to insert signals based on the temperatures detected by the temperature sensors 28a, 28b and 28c of the respective internal heat exchangers 23a, 23b and 23c, and to apply control signals to the corresponding by-pass valves 32a and 32b.

The operation of the multi-type air conditioner according to a preferred embodiment of the present invention is as follows.

First, the refrigerant discharged from the compressor 21 passes through the external heat exchanger 22 where the heat exchange with the ambient air is carried out by the refrigerant. The refrigerant, which has carried out the heat exchange with the ambient air, passes through the three branches of the second connecting pipe 25b to be depressurized by means of the electronic expansion valves 24a, 24b and 24c. In this case, the electronic expansion valves 24a, 24b and 24c are opened / closed by means of the control signals applied by the respective indoor units in which the respective indoor heat exchangers 23a, 23b and 23c are used. The degrees of opening of the electronic expansion valves 24a, 24b'and 24c are controlled based on the temperatures detected by the load sensors 27a, 27b and 27c of the internal heat exchanger connected to each side of the outputs of the respective internal heat exchangers 23a , 23b and 23c. In other words, the degrees of opening of the electronic expansion valves 24a, 24b and 24c are detected to be controlled based on the loads of the respective internal heat exchangers 23a, 23b and 23c. In this case, since the electronic expansion valves 24a, 24b and 24c are connected adjacent to the respective internal heat exchangers 23a, 23b and 23c, the feedback control is performed precisely according to the loads of the respective internal heat exchangers 23a, 23b and 23c.

The refrigerant passes through the electronic expansion valves 24a, 24b and 24c, and then performs the heat exchange with the ambient air at the respective internal heat exchangers 23a, 23b and 23c to cool the internal air of the respective rooms. Then, the refrigerant flows back to compressor 21.

In this situation, the control part detects the temperatures of the respective internal heat exchangers in operation, and applies opening / closing signals to the by-pass valves 32a and 32b of the by-pass lines 30a and 30b. Consequently, the amount of refrigerant to be bypassed is controlled through the by-pass lines 30a and 30b.

The foregoing will be described in more detail with reference to Figs. 4 and 5.

First of all, the average temperature (hereinafter referred to as 'Ta') of the internal heat exchangers in operation is obtained by means of the temperature detected by the corresponding temperature sensors 28a, 28b and 28c connected to the respective internal heat exchangers 23a, 23b and 23c (Phase SI). In this case, by detecting the control signals of the internal heat exchangers 23a, 23b and 23c, or by detecting the open or closed state of the electronic expansion valves 24a, 24b and 24c which are opened or closed by means of the control signals of the exchangers internal heat exchanger 23a, 23b and 23c, it is determined whether the internal heat exchanger is in operation. If it is determined that an indoor heat exchanger is in operation, the temperature of the indoor heat exchanger in operation is considered to be Ta.

Next, it is determined whether Ta exceeds the first predetermined field (hereafter referred to as 'Τι'). If Ta exceeds Ti, it is determined that the internal heat exchanger is in normal operation, so that the microcomputer 29 applies the CLOSE signal to the by-pass valves 32a and 32b (Step S3). Consequently, the by-pass lines 30a and 30b are closed, so that the refrigerant is not bypassed to the compressor 21 by the external heat exchanger 22. It is then determined whether the compressor 21 is in a STOP state (Phase S4) . If it is determined that the compressor 21 is not running, the control signals are applied to drive the compressor 21 (Step S5).

If Ta does not exceed Ti, it is determined whether Ta has been within Ti for a predetermined period of time (Step S6). If it is determined that Ta has been within Ti for the predetermined period of time (as shown in line Φ of Fig. 5), the microcomputer 29 applies the OPEN signal to the first by-pass valve 32a and the CLOSE signal to the second relief valve. by-pass 32b (Phase S7). Since the first by-pass line 30a is open while the second by-pass line 30b is closed, part of the refrigerant is bypassed through the first by-pass line 30a from the external heat exchanger 22.

It is then determined whether Ta has been maintained within a second predetermined range (hereinafter referred to as <Λ> Τ2 ') for a predetermined period of time (Step S8). If Ta tends to decrease and is maintained within T2 for the predetermined period of time as shown in line © in Fig. 5, the microcomputer 29 applies the CLOSE signal to the first by-pass valve 32a, while applying the OPEN signal to the second valve of by-pass 32a (Phase S9). Since the first by-pass line 30a is closed while the second by-pass line 30b is open, part of the refrigerant is bypassed from the external heat exchanger 22 to the compressor 21 through the second by-pass line 30b. In this case, the amount of bypassed refrigerant is greater than that of the bypassed refrigerant in the

Step S7.

Then, it is determined whether Ta has been held within a third predetermined range (hereafter referred to as 'T3') for a predetermined period of time.

(SIO phase). If it is determined that Ta has been maintained

within T3 for the predetermined time period shown in line ® in Fig. 5, the microcomputer

29 applies the OPEN signal to the bypass valves 32a and 32b (Phase SII). After receiving the opening signal, the by-pass valves 32a and 32b are open, so that the refrigerant is bypassed from the external heat exchanger 22 to the compressor 21 through the pair of by-pass lines 30a and 30b.

U.-ΐ. As a result, the amount of refrigerant bypassed

is maximized. In this case, it is preferable that

T3 equals zero degrees Celsius (0 ° C), which is the freezing temperature for the internal heat exchangers. For reference, Ti and T2 are equal to 5 ± 0.5 ° C and 3 ± 0.5 ° C respectively. It is also preferable that the predetermined time period

is approximately five (5) minutes (± 30 seconds).

If Ta does not increase beyond Ti while the by-pass lines 30a and 30b are open as a result of the execution of step 11 (Step S12), the microcomputer 29 applies a STOP signal to compressor 21 (Step S13). As a result, the compressor 21 is stopped, whereby liquid refrigerant is prevented from flowing into the compressor 21 by freezing the internal heat exchangers.

When the aforementioned phases are finished, the SI phase is restarted. When Ta increases beyond Ti as a result of performing steps S7, S9, SII or S13 (as shown in line ® in Fig. 5), the by-pass lines 30a and 30b are closed as a result of the determination in step S2. If compressor 21 is in a STOP state as a result of step S13, compressor 21 is again operated (Step S5).

As described above, according to the present invention, by comparing Ta of the internal heat exchangers in operation with Ti, T2 and T3, the opening / closing of the by-pass lines 30a and 30b is checked. Consequently, without the expensive inverter-type compressor, the appropriate amount of refrigerant is supplied to the respective internal heat exchangers, regardless of the number and capacity, or operating conditions such as overload operation, low temperature operation or the like of the exchangers. internal heat sink in operation. Furthermore, since the capacity of the indoor heat exchanger can be varied within a reasonable degree that does not exceed the total capacity of the compressor, the multi-type air conditioner according to the present invention can satisfy the various demands of a user.

While the present invention has been shown and described in particular with reference to a preferred embodiment thereof, those skilled in the art will understand that various changes in shape and details can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (5)

CLAIMS 1. Multi-type air conditioner comprising: a compressor not of the inverter type; an external heat exchanger; a first connecting pipe for supplying refrigerant from the non-inverter type compressor to the external heat exchanger; a second connecting tube, one end of which is branched into a plurality of lines, and for discharging the refrigerant from the external heat exchanger; a plurality of internal heat exchangers respectively connected to the plurality of lines of the second connecting pipe; a third connecting pipe for collecting refrigerant from the plurality of internal heat exchangers and for feeding the collected refrigerant to the compressor; a plurality of electronic expansion valves respectively connected to the plurality of lines of the second connecting tube; a plurality of by-pass lines, each having a by-pass tube connecting the external heat exchanger with the third connecting tube, a capillary tube connected to the by-pass tube and a by-pass valve for bypassing part of the refrigerant from the heat exchanger external to the compressor, the by-pass valve and the capillary tube being connected in series along the by-pass tube; and means for controlling the amount of refrigerant bypassed by the heat exchanger external to the compressor by controlling the by-pass valve of each of the by-pass lines based on the average temperature of the internal heat exchangers in operation. An air conditioner according to claim 1, wherein the means for controlling the amount of bypassed refrigerant comprises: a plurality of temperature sensors for detecting the temperatures of the respective internal heat exchangers and for generating temperature signals; And a microcomputer for receiving the temperature signals and for applying control signals to the plurality of by-pass valves. 3. Air conditioner according to claim 1, wherein the plurality of by-pass lines respectively have different capacities. 4. Method for controlling the amount of refrigerant bypassed for a multi-type air conditioner having a non-inverter-type compressor and first and second by-pass lines for bypassing different amounts of refrigerant from the external heat exchanger to the compressor, in which the control method includes the steps of: (1) obtain the average temperature of the internal heat exchangers in operation; (2) closing the first and second bypass lines if the average temperature obtained from step (1) exceeds a first predetermined temperature range; (3) opening the first by-pass line and closing the second by-pass line if the average temperature has been maintained within the first predetermined temperature range for a predetermined period of time; (4) closing the first by-pass line and opening the second by-pass line if the average temperature has been maintained within a second predetermined temperature range for a predetermined period of time; And (5) opening the first and second bypass lines if the average temperature has been maintained within a third predetermined temperature range for a predetermined period of time. 5. Method according to claim 4, further comprising the steps of: (6) stopping the compressor if the average temperature is within a first predetermined temperature range after performing step (5); And (7) start the compressor if in step (2) the compressor has been stopped,