Power controllable type air conditioner

Abstract: In an air conditioner in which plural outdoor units are connected to plural indoor units, at least one outdoor unit is provided with a compressor having a power control mechanism for inhibiting a part of a compression work, and the power of the compressor is made variable by controlling the power control mechanism. The outdoor unit is provided with two heat exchangers which are designed in a substantially U-shaped form, and disposed in a main body of the outdoor unit so that the opening sides thereof are confronted to each other, and the refrigerating elements which constitutes a refrigerant circuit and contains at least the compressor, an accumulator, etc. are disposed in a space which is surrounded by the two heat exchangers.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner in which the power (capacity) of a compressor is controllable (variable) in accordance with an air conditioning load. 2. Description of the Related Art There is generally known an air conditioner (separation type air conditioner)in which plural indoor units are linked to plural outdoor units, and a compressor, a condenser, an expansion device and an evaporator are successively linked to one another to construct a refrigerant circuit. In this type air conditioner, the power (capacity) of the compressor as described above is controlled to be varied in accordance with an air conditioning load. In order to vary the power of the compressor, there has been hitherto proposed an inverter type compressor which controls its power by varying the frequency of power to be supplied to the compressor. Such an inventer type compressor is disclosed e.g. in US-A-4 878 357. However, when an inverter compressor is used in the air conditioner as described above, the price of the air conditioner rises up unavoidably. In addition, the frequency components may have various adverse effects on peripheral electrical elements such as a microcomputer, etc. which are disposed around the inverter compressor. For example, the peripheral electrical elements suffer noises or a condenser (electrical part) is broken down. On the other hand, there may be considered another type air conditioner which does not use any inverter compressor, and uses a rated compressor (a compressor whose power is invariable) and a refrigerant return mechanism for returning a part of refrigerant discharged from the rated compressor to a suck-in side of the compressor (for example, an accumulator) to perform multistage control operation with the rated compressor. However, this type air conditioner has such a disadvantage that the control operation cannot be smoothly performed, resulting in occurrence of hunting and limitation of the control range to an extremely narrow range. The occurrence of the hunting intensifies the fluctuation of a room temperature, so that a comfortable air conditioning atmosphere is unachievable. Such a phenomenon becomes a critical problem particularly to a so-called large-capacity type air conditioner having plural outdoor units. Further, when increase in power (horsepower) which is demanded in design (hereinafter referred to as "demand horsepower on design") is needed in the air conditioner as described above, it has been a general way to increase the number of outdoor units and link these plural outdoor units to one another to fabricate a so-called multi-type air conditioner. EP-A-0 204 521 discloses an air conditioner with multiple outdoor units connected to multiple indoor units wherein at least one outdoor unit comprises a compressor having a power control mechanism for inhibiting a part of a compression work. Each outdoor unit has its own closed-loop refrigeration cycle and heats or cools water which is supplied to a distribution network for heating or cooling a building by means of water-to-air heat exchangers. When the demand horsepower on design is increased to fabricate an air conditioner having a high efficiency, in some cases it is better to increase the horsepower of an outdoor unit itself rather than to increase the number of outdoor units. However, there has not been hitherto proposed any outdoor unit which is usable in a separation type air conditioner having a large horsepower. If the outdoor unit is designed to have a large capacity, the number of compressors must be increased, and the capacity of a heat exchanger, an accumulator, etc. must be also increased. However, there has not been hitherto proposed any technical idea for efficiently accommodating various elements (such as a compressor, a heat exchanger, an accumulator, etc.) constituting the refrigerant circuit into the main body of an outdoor unit, and effectively performing maintenance of these accommodated elements. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a large-capacity type air conditioner in which plural outdoor units are linked to plural indoor units and which can control (vary) the power thereof with no inverter compressor. In order to achieve the above object, according to the present invention, an air conditioner is provided with the features of claim 1. In the air conditioner according to the present invention, the outdoor unit is further provided with a refrigerant return mechanism for returning a part of refrigerant discharged from the compressor to the suck-in side of the compressor, the power being variable by controlling the power control mechanism and the refrigerant return mechanism. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a refrigerant circuit diagram showing an embodiment of an air conditioner according to the present invention; Fig. 2 is a cross-sectional view showing a power control (save) mechanism when a piston is shifted to the top dead center; Fig. 3 is a cross-sectional view showing a power control (save) mechanism when a piston is shifted to the bottom dead center; Fig. 4 is a table showing a stepwise control of compression power of 15kW (20ps); and Fig. 5 is a table showing a stepwise control of compression power of 12kW (16ps). DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Preferred embodiments according to the present invention will be described hereunder with reference to the accompanying drawings. Fig. 1 shows an outdoor unit used in an air conditioner according to the present invention. In Fig. 1, reference numeral 1 represents an outdoor unit of 15kW (20 horsepower [ps]) (hereinafter referred to as "master unit"), and reference numeral 3 represents an outdoor unit of 7kW (10[ps]) (hereinafter referred to as "sub unit"). These master and sub units 1 and 3 are linked to each other through refrigerant pipes 50. First, the "master unit" 1 will be described. The master unit 1 has three compressors, that is, a rated compressor (scroll compressor) 15 of 7kW (10ps), a rated compressor (rotary compressor) 17 of 4kW (5ps), and a compressor 19 having a maximum power of 4kW (5ps) and also having a power control mechanism for controlling the output power of the compressor 19 to inhibit a part of a compression work of the compressor 19 (hereinafter referred to as "P/C compressor"). The "P/C compressor" 19 will be described hereunder. The P/C compressor 19 has a control port 19a in its cylinders (as described later) in which refrigerant is compressed. When a high-pressure valve 19b is opened to apply high pressure to the control port 19a (a low-pressure valve 19c is closed), an internal power control mechanism (as described later) works to operate the P/C compressor 19 at a full power mode of 4kW (5ps). On the other hand, when the low-pressure valve 19c is opened to apply low pressure to the control port 19a (the high-pressure valve 19b is closed), the internal power control mechanism works to operate the P/C compressor at a half power mode of 2kW (2.5ps). The details of the power control mechanism will be described with reference to Figs. 2 and 3. Figs. 2 and 3 are diagrams showing the detailed construction of a power save mechanism which is an embodiment of the power control mechanism. As shown in Figs. 2 and 3, the power save mechanism has a rotational compression element in a hermetic chamber 118 of the compressor 19. The rotational compression element is provided with an intermediate partition plate 127, and a pair of cylinders 121 and 122 which are disposed at both sides of the intermediate partition plate 127. In the rotational compressor element thus constructed, first holes 123 and 124 are formed in the inner side walls of the cylinders 121 and 122 respectively, second holes 125 and 126 are formed in the cylinders 121 and 122 respectively so as to intercommunicate with the first holes 123 and 124 respectively, and a third hole 128 is formed in the intermediate partition plate 127 so as to intercommunicate with the second holes 125 and 126. Further, pistons 129 and 130 are provided in the second holes 125 and 126 of the cylinders 121 and 122 respectively, and a coil spring (a leaf spring or bellows may be used insofar as these members are formed of elastic member) 132 is bridged over both the pistons 129 and 130. The rotational compression element is further provided with fourth holes 133 and 134 which intercommunicate with the second holes 125 and 126 of the cylinders 121 and 122 respectively through recess portions 131 which are formed in the cylinders 121 and 122, and the intercommunication between each of the fourth holes 133 and 134 and the low-pressure side or high-pressure side is selectively allowed by the switching operation of the switching valve 19b, 19c. According to the control of the power save mechanism 113 thus constructed, the pressure at the low-pressure side is applied as back pressure to the second holes 125 and 126 through the passage 135, the fourth holes 133 and 134 and the recess portion 131 to move the pistons 129 and 130 to the top dead center. Accordingly, as shown in Fig. 2, the first holes 123 and 124 are opened, so that the gas (refrigerant) being compressed in one cylinder 121 flows through the first hole 123, the second hole 125, the third hole 128, the second hole 126 and the first hole 124 into the other cylinder 122 under suck-in operation to thereby inhibit about a half of compression work from being performed in the compressor 19 On the other hand, in normal operation, the pressure at a high-pressure side is applied as back pressure to the second holes 125 and 126 through the passage 135, the fourth holes 135 and 134 and the recess portion 131 to move the pistons 129 and 130 to the bottom dead center, and the first holes 123 and 124 are closed, whereby the gas (refrigerant) flow between the cylinders 121 and 122 is inhibited. According to the power save mechanism 113 as described above, about 50% output power can be saved (i.e., about a half of the compression work of the compressor 19 is inhibited). Accordingly, 2kW (2.5ps) output power can be saved for the compressor of 4kW (5 ps). The ON/OFF operation of the power save mechanism 113 is performed by opening/closing the valves 19b and 19c in response to an instruction from a controller (not shown). Returning to Fig. 1, the master unit 1 is further provided with an accumulator 23, an oil separator 25, a four-way change-over valve 27, two heat exchangers 29 and 31, expansion devices 30 and 32, a receiver tank 33, etc. as well as the three compressors 15, 17 and 19. Reference numeral 34 represents an oil line, and it is connected to a balance pipe 36. The refrigerant which is passed through the oil separator 25 is normally directed to the four-way change-over valve 27. In order to further and more finely control the power of the compressor, an external save valve 26 serving as a refrigerant return mechanism is provided. In this embodiment, the external save valve 26 is disposed between the oil separator 25 and the accumulator 23 as shown in Fig. 1. When the refrigerant return mechanism is opened, a part of the compressed refrigerant (which corresponds to 0.7kW (1ps), for example) is returned to the accumulator 23 (the suck-in side of the compressor) while bypassing the four-way change-over valve 27. Next, the sub unit 3 will be described. The sub unit 3 has an accumulator 52, a rated compressor 53, a four-way change-over valve 54, a heat exchanger 55, an expansion valve 56, a receiver tank 57, etc. as shown in Fig. 1. The rated compressor 53 has a power of 7kW (10ps). The master unit 1 and the sub unit 3 are connected to the indoor units 51 through the refrigerant pipes 50. Each of the indoor units 51 mainly contains an expansion device 58 such as an electrical control valve or the like, and a heat exchanger 59 therein. According to this embodiment, the total horsepower of the three compressors 15, 17 and 19 of the master unit 1 is equal to 15kW (20ps) (= 7kW + 4kW + 4kW (10ps + 5ps + 5ps)), and thus the total capacity of the two heat exchangers 29 and 31 is equal to 15kW (20ps (7.4kW + 7.4kW (10ps + 10ps)). The air taken from the air suck-in ports 35 is heat-exchanged in the heat exchangers 29 and 31, and then discharged through a discharge fan 37 provided on the ceiling face. As shown in Fig. 1, a service panel 39 and a pipe connection portion 41 are provided at the center of the front face of the main body 10 of the master unit 1. The pipe connection portion 41 comprises various service valves for the gas pipe and the liquid pipe, etc. In the pipe connection portion 41, a service valve (narrow pipe) 41a of the liquid pipe and a service valve (thick pipe) 41b of the gas pipe are vertically arranged on a line so that the service valve 41a is located at a higher position than the service valve 41b. As compared with the case where the service valves 41a and 41b are laterally arranged (prior art), the vertical arrangement of the service valves 41a and 41b can reduce the lateral dimension of the master unit 1 to a smaller size. The service valve (thick pipe) 41b of the gas pipe is located at a lower position than the service valve (narrow pipe) 41a of the liquid pipe because a connection work of the gas pipe which is led from the four-way change-over valve is facilitated. The link portion of the four-way change-over valve 27 to the gas pipe faces downwardly, so that it is difficult to lead upwardly the gas pipe which is led from the link portion of the four-way change-over valve 27 of the master unit 1. Accordingly, it is rather easier to lead the gas pipe downwardly. When the service panel 39 is opened (detached), the compressors 15, 17 and 19 are exposed to the outside as shown in Fig. 1. In the air conditioner as described above, the P/C compressor 19 is most preferentially driven for a longer time as compared with the other compressors 15 and 17. Accordingly, in general, maintenance is more frequently performed on the P/C compressor 19 than the other compressors 15 and 17. Therefore, in consideration of facility of maintenance, the P/C compressor 19, the compressor 17 and the compressor 15 are disposed in this order from the front side of the front face of the main body 10 so that the P/C compressor 19 is located and exposed at the forefront of the front face of the main body 10 of the master unit 1. Further, flow dividers 45 which are connected to the heat exchangers 29 and 31 are disposed at the back face side of the main body in the master unit 1 as shown in 5. When the flow dividers 45 are disposed at the back face side of the main body, the opening space S at the front face side of the main body can be kept broader as compared with the case where the flow dividers 45 are arranged at the front face side of the main body. As described above, according to this embodiment, when the service panel 39 is opened (detached), the compressors, etc. are frequently exposed to the outside, so that the facility of the maintenance is enhanced. Next, the power control operation of the compressor will be described in detail. According to this embodiment, the compression power is controlled at 17 stages (levels) in the horsepower range from 0kW (0ps) to 15kW (20ps) as shown in Fig. 6. For example, when a demand horsepower is equal to 1.1kW (1.5ps), the P/C compressor 19 is operated and all the other compressors 15 and 17 are stopped. Further, the low-pressure valve 19c is opened and the high-pressure valve 19b is closed. In addition, the external save valve 26 is opened. Through this operation, the power control mechanism is operated to drive the P/C compressor 19 at 1.8kW (2.5ps) (half power). At the same time, the refrigerant return mechanism is operated to return the refrigerant corresponding to 0.7kW (1ps) to the accumulator, so that totally power of 1.1kW (1.5ps) (= 3.7kW/2 - 0.7kW (6ps/2 - 1ps)) is obtained. When the demand horsepower is equal to 1.8kW (2.5ps), the P/C compressor 19 is operated at a half power, and all the other compressors are stopped. Further, only the low-pressure valve 19c is opened. When the demand horsepower is equal to 3kW (4ps), the P/C compressor 19 is operated, and all the other compressors 15 and 17 are stopped. Further, the high-pressure valve 19b is opened and the low-pressure valve 19c is closed. In addition, the external save valve 26 is opened. Through this operation, the P/C compressor 19 is driven at 3.7kW (5ps) (full power). At the same time, the refrigerant return mechanism is operated to return the refrigerant corresponding to 0.7kW (1ps), so that totally 3kW (4ps) power is obtained. As described above, the P/C compressor 19 and the 3.7kW (5ps) rated compressor (A/C compressor) 17 are alternately driven until the demand horsepower reaches 7.4kW (10ps) as shown in Fig. 4, and if occasion demands, the power is stepwise controlled by opening/closing the external save valve 26. When the demand horsepower is equal to 8.5kW (11.5ps), the 7.4kW (10ps) rated compressor (scroll) 15 is driven, and the P/C compressor 19 is driven. Further, the low-pressure valve 19c is opened and the high-pressure valve 19b is closed. In addition, the external save valve 26 is opened. With this operation, the rated compressor 15 is driven at 7.4kW (10ps), and the power control mechanism works to operate the P/C compressor 19 at 1.8kW (2.5ps) (half power). At the same time, the refrigerant return mechanism works to return the refrigerant corresponding to 0.7kW (1ps), so that totally 8.5kW (11.5ps) power is obtained. As described above, the rated compressor 15 is continued to be driven, and the P/C compressor 19 and the 3.7kW (5ps) rated compressor 17 are alternately driven. Further, the external save valve 26 is opened/closed case by case, whereby the stepwise power control can be performed. In short, according to this embodiment, by controlling the P/C compressor 19 and the external save valve 26, a demanded variable output power can be obtained by only the rated compressor in place of the inverter compressor. Accordingly, the adverse effects such as the noises, etc. by the inverter compressor can be prevented, and a low-price air conditioner can be provided. Fig. 5 is a table showing the control operation of another embodiment. According to this embodiment, the master unit 1 includes a 6kW (8ps) rated compressor (scroll) 15, a 3kW (4ps) rated compressor (rotary) 17, and a 3kW (4ps) P/C compressor 19. Overall, the master unit 1 has horsepower of 12kW (16ps). In this case, the stepwise power control can be performed every 0.7kW (1ps) from 0kW (0ps) to 12kW (16ps) as show in Fig. 5. For example, when the demand horsepower is equal to 3.7kW (5ps), the P/C compressor 19 and the 2.9kW (4ps) rated compressor 17 are driven, and the low-pressure valve 19c is opened while the high-pressure valve 19b is closed. Further, the external save valve 26 is opened. With this operation, the rated compressor 17 is driven at 2.9kW (4ps), and the P/C compressor 19 is driven at 1.5kW (2ps) (half power). At the same time, the refrigerant return mechanism is operated to return the refrigerant corresponding to 0.7kW (1ps), so that totally 3.7kW (5ps) power is obtained. When the demand horsepower is equal to 11kW (15ps), the 5.9kW (8ps) rated compressor 15 and the 2.9kW (4ps) rated compressor 17 are driven, and the P/C compressor 19 is driven. Further, the high-pressure valve 19b is opened and the low-pressure valve 19c is closed. Further, the external save valve 26 is opened. Through this operation, the rated compressor 15 is driven at 5.9kW (8ps), the rated compressor 17 is driven at 2.9kW (4ps), and the power control mechanism works to drive the P/C compressor 19 at 1.5kW (2ps) (half power). At the same time, the refrigerant return mechanism is operated to return the refrigerant corresponding to 0.7kW (1ps), so that totally 11kW (15ps) power is obtained. According to the present invention, in the relatively-large capacity of air conditioner in which plural outdoor units are connected to plural indoor unit, the compression work can be partially inhibited (i.e., the compression power is made controllable (variable) without inverter compressor. Therefore, the adverse effects such as noises, etc. due to the inverter compressor can be prevented, and the low-price air conditioner can be provided.

Claims: An air conditioner in which plural outdoor units (1, 3) are connected to plural indoor units characterised in that at least one outdoor unit (1) is provided with a compressor (19) having a power save mechanism (113) for inhibiting a part of a compression work, and the other outdoor units (3) are equipped with rated compressors, the respective outdoor units being connected to one another through refrigerant pipes (50) through which refrigerant compressed by the compressors flows, thereby forming a refrigeration cycle. An air conditioner according to claim 1, wherein the at least one outdoor unit which is provided with a compressor (19) having a power save mechanism (113) comprises at least one further compressor. An air conditioner according to claim 1 or 2 in which the at least one outdoor unit which is provided with a compressor having a power save mechanism further comprises a refrigerant return mechanism (26) for returning a part of refrigerant discharged from said compressor to a suck-in side of said compressor.

Inventors: SHIINA TAKAO, SHIMOTANI MAKOTO, SHIINA, TAKAO, SHIMOTANI, MAKOTO
Applicants: SANYO ELECTRIC CO, SANYO ELECTRIC CO., LTD.
Application year: 1997
Main classification: F24F1
IPC codes: F25D23, F25B49, F24F3, F25B1, F25B13, F24F1, F24F11