GB2559899A

GB2559899A - Air-conditioning device

Info

Publication number: GB2559899A
Application number: GB1805551.7A
Authority: GB
Inventors: Iwasaki Kazuhisa
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2015-12-01
Filing date: 2015-12-01
Publication date: 2018-08-22
Anticipated expiration: 2035-12-01
Also published as: JP6545281B2; GB201805551D0; GB2559899B; WO2017094117A1; JPWO2017094117A1

Abstract

An air-conditioning device comprising a control device, the control device being equipped with: a volume calculation unit which calculates the piping volume of the overall piping through which a refrigerant flows while outdoor units and indoor units are in heating operation; a frequency table in which discharge pressure, the differential pressure between the discharge pressure and suction pressure, and the piping volume have been associated with the resonance frequency of the overall piping through which the refrigerant flows; a frequency estimation unit which estimates the resonance frequency with reference to the frequency table on the basis of the piping volume calculated by the volume calculation unit, the discharge pressure, and the differential pressure between the discharge pressure and the suction pressure; and a condition setting unit which sets the range of the operational frequency of a compressor so as to restrain the operational frequency of the compressor from becoming the resonance frequency estimated by the frequency estimation unit.

Description

(54) Title of the Invention: Air-conditioning device Abstract Title: Air-conditioning device (57) An air-conditioning device comprising a control device, the control device being equipped with: a volume calculation unit which calculates the piping volume of the overall piping through which a refrigerant flows while outdoor units and indoor units are in heating operation; a frequency table in which discharge pressure, the differential pressure between the discharge pressure and suction pressure, and the piping volume have been associated with the resonance frequency of the overall piping through which the refrigerant flows; a frequency estimation unit which estimates the resonance frequency with reference to the frequency table on the basis of the piping volume calculated by the volume calculation unit, the discharge pressure, and the differential pressure between the discharge pressure and the suction pressure; and a condition setting unit which sets the range of the operational frequency of a compressor so as to restrain the operational frequency of the compressor from becoming the resonance frequency estimated by the frequency estimation unit.

Compressor

41a Piping diameter acquisition unit 41b Circulation rate calculation unit 41c Volume estimation unit

Frequency estimation unit

Condition setting unit

Operation control unit

61a Discharge pressure sensor 62a Suction pressure sensor 71 Indoor gas temperature sensor AA Frequency table BB Operational condition CC Piping diameter table

FIG.

2/7

FIG. 2

CIRCULATION AMOUNT [CALCULATION UNIT

61a

S

DISCHARGE

PRESSURE

SENSOR

INDOOR GAS TEMPERATURE SENSOR

VOLUME

ESTIMATION

UNIT

- -_r

41b

VL

FREQUENCY

ESTIMATION

UNIT f_v (condition ™M SETTING

UNIT

A

FIG. 3

HIGH-PRESSURE PRESSURE	PRESSURE DIFFERENCE ((HIGH-PRESSURE PRESSURE)(LOW-PRESSURE PRESSURE))	RESONANCE FREQUENCY fminv [Hz]
a <VL	Of SVL^£	β >VL
LESS THAN	10 KOR LESS	A1	A2	A3
30 kg/cm²	10-15K	BI	B2	B3
	15-20K	C1	C2	C3
	20 KOR MORE	D1	02	03
30 kg/cm²	10 KOR LESS	E1	E2	E3
OR MORE	10-15K	F1	F2	F3
	15-20K	G1	G2	G3
	20 KOR MORE	H1	H2	H3

3/7

FIG. 4

START

~)

STl

ACQUIRE PIPE DIAMETER OF GAS PIPE 2a

ST3

CALCULATE PIPE VOLUME VL

ST4

ESTIMATE RESONANCE FREQUENCY fv

STS (LOWER-LIMIT OPERATING FREQUENCY fmin)?(RESONANCE FREQUENCY fv)?

YES

JR

YES, n-fv+Af ·Μ<·

OPERATION STATES OF OUTDOOR\Mnl UNIT 10 AND INDOOR UNITS 30 ^{x !}

ARE CHANGED?

4/7

FIG. 5 ί

5/7

FIG. 6

START HEATING OPERATION

ΞΞΞΞξΑ...........................ST3

CALCULATE PIPE VOLUME VL

ESTIMATE RESONANCE FREQUENCY fv

ST15a

ST 15b

NO

Γ / (LOWER-LIMIT OPERATING \ FREQUENCY fmina) < (.(RESONANCE FREQUENCY fv)?/ (LOWER-LIMIT OPERATING FREQUENCY fminb) <

.(RESONANCE FREQUENCY fv)?.

YES, _L^ES ST16a fmina=fv+Af

-...............................

V ST7

OPERATION STATES OF \ OUTDOOR UNITS 110AAND 110B OR INDOOR UNITS 30 .

. ARE CHANGED? / ^YES

ST16b fminb-fv+Af _,r n

NO

6/7

FIG. 7

210Α-»

200 /

205b

204a .2

oo

Ο

DESCRIPTION

Title of Invention

AIR-CONDITIONING APPARATUS

Technical Field [0001]

The present invention relates to an air-conditioning apparatus, with which pressure pulsation caused by driving a compressor is suppressed.

Background Ar [0002]

An air-conditioning apparatus includes a refrigerant circuit, in which an outdoor unit including a compressor, and an indoor unit are connected to each other through a refrigerant pipe, to perform a cooling operation, a heating operation, or another operation by driving the compressor. When the compressor is driven, pressure pulsation at a frequency corresponding to an operating frequency occurs. Here, the pipe of the air-conditioning apparatus through which refrigerant flows has a particular resonance frequency depending on a pressure state of the refrigerant, and a length or a volume of the pipe through which the refrigerant flows into the indoor unit, for example. Then, during the heating operation in which high-pressure gas refrigerant flows from the outdoor unit to the indoor unit, when a particular operating frequency of the compressor matches a resonance frequency unique to a pipe path, the gas refrigerant flowing through the pipe may pulsate to vibrate the pipe.

[0003]

As an apparatus in which the pressure pulsation is reduced, there has been proposed a method in which a muffler is installed on a discharge side of the compressor, or an air-conditioning apparatus in which a pressure pulsation reducing device is mounted (see Patent Literature 1, for example). In Patent Literature 1, there is disclosed a passage device, in which a plurality of small holes are formed in an inner pipe, through which the refrigerant flows, to spout a jet, and in which the refrigerant is spouted from the inner pipe to the outer periphery through the small holes to reduce pressure pulsation.

Citation List

Patent Literature [0004]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2008-196848

Summary of Invention

Technical Problem [0005]

However, when a mechanism configured to reduce the pressure pulsation is arranged in a normal refrigerant circuit as in Patent Literature 1, or when a muffler is mounted, a space is required to be provided in a housing of the outdoor unit, and a large cost is required. Further, a pressure loss of fluid at a time when the refrigerant passes through the hole portion is large, and may lead to a reduction in performance. In order to suppress the pressure pulsation, it can also be considered to increase a pipe length such that an operating range of a com pressor frequency does not match a unique resonance frequency of a pipe system.

[0006]

Moreover, in order that the operating frequency of the compressor does not match the resonance frequency of the pipe system, it can be considered to increase a lower limit operating frequency of the compressor. However, the resonance frequency is different depending on a pipe volume, for example, and hence it is required to individually perform settings for each of air-conditioning apparatus that are different in diameter and length of pipes on the site, for example. Therefore, it is difficult to set an operating frequency that does not cause the vibration due to the pressure pulsation for any air-conditioning apparatus.

[0007]

The present invention has been made to solve the above-mentioned problems, and therefore has an object to provide an air-conditioning apparatus, which is capable of suppressing vibration due to pressure pulsation depending on an installation state of the air-conditioning apparatus without a large cost.

Solution to Problem [0008]

According to one embodiment of the present invention, there is provided an airconditioning apparatus, in which an outdoor unit including a compressor, and an indoor unit are connected to each other through a gas pipe and a liquid pipe, the airconditioning apparatus including: a discharge pressure sensor, which is configured to sense a discharge pressure of refrigerant discharged from the compressor; a suction pressure sensor, which is configured to sense a suction pressure of the refrigerant on a suction side of the compressor; and a controller, which is configured to set a range of an operating frequency of the compressor based on the discharge pressure sensed by the discharge pressure sensor, and the suction pressure sensed by the suction pressure sensor, the controller including: a volume calculation unit, which is configured to calculate, when the outdoor unit and the indoor unit are in a heating operation, a pipe volume of an entire pipe through which the refrigerant flows; a frequency table, in which the discharge pressure, a pressure difference between the discharge pressure and the suction pressure, the pipe volume, and a resonance frequency of the entire pipe through which the refrigerant flows are associated with one another; a frequency estimation unit, which is configured to estimate, based on the pipe volume calculated by the volume calculation unit, the discharge pressure, and the pressure difference between the discharge pressure and the suction pressure, the resonance frequency by referring to the frequency table; and a condition setting unit, which is configured to set the range of the operating frequency of the compressor so as to restrain the operating frequency of the compressor from matching the resonance frequency estimated by the frequency estimation unit.

Advantageous Effects of Invention [0009]

According to the air-conditioning apparatus of the embodiment of the present invention, the resonance frequency is estimated based on the pipe volume of the entire pipe through which the refrigerant flows, and the operating frequency of the compressor is set so that the compressor does not perform operation at the estimated resonance frequency, with the result that generation of noise due to the pressure pulsation can be suppressed depending on the installation state of the airconditioning apparatus without separately installing a muffler configured to cancel the resonance frequency.

Brief Description of Drawings [0010] [Fig. 1] Fig. 1 is a refrigerant circuit diagram for illustrating an example of an air-conditioning apparatus according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a functional block diagram for illustrating an example of a controller of Fig. 1.

[Fig. 3] Fig. 3 is a schematic diagram for illustrating an example of a frequency table in the controller of Fig. 2.

[Fig. 4] Fig. 4 is a flow chart for illustrating an operation example of the controller of Fig. 2.

[Fig. 5] Fig. 5 is a refrigerant circuit diagram for illustrating an example of an air-conditioning apparatus according to Embodiment 2 of the present invention.

[Fig. 6] Fig. 6 is a flow chart of an operation example of a controller of Fig. 5.

[Fig. 7] Fig. 7 is a refrigerant circuit diagram for illustrating an example of an air-conditioning apparatus according to Embodiment 3 of the present invention.

[Fig. 8] Fig. 8 is a flow chart for illustrating an operation example of a controller of Fig. 7.

Description of Embodiments [0011]

Embodiment 1

Fig. 1 is a refrigerant circuit diagram for illustrating an example of an airconditioning apparatus 1 according to Embodiment 1 of the present invention, and the air-conditioning apparatus 1 is described with reference to Fig. 1. The airconditioning apparatus 1 is configured to perform a cooling operation or a heating operation using a refrigeration cycle (heat pump cycle) through which refrigerant is circulated. In the air-conditioning apparatus 1 of Fig. 1, one outdoor unit 10 and two indoor units 30 are connected to each other through a gas pipe 2a and a liquid pipe 2b to form a refrigerant circuit. In the air-conditioning apparatus 1 of Fig. 1, there is illustrated a case in which the two indoor units 30 are connected to the outdoor unit 10, but any configuration may be adopted as long as one or more indoor units 30 are connected to the outdoor unit 10.

[0012]

The outdoor unit 10 includes a compressor 11, a flow switching device 14, and an outdoor heat exchanger 15, and the compressor 11, the flow switching device 14, and the outdoor heat exchanger 15 are connected in series through refrigerant pipes. The compressor 11 is configured to compress sucked refrigerant into a hightemperature and high-pressure state. The compressor 11 has an operating frequency thereof and hence a capacity thereof controlled by power supply frequency conversion by an inverter circuit, for example.

[0013]

The flow switching device 14 is formed of a four-way valve, for example, and is configured to switch a flow of the refrigerant between the cooling operation and the heating operation. The outdoor heat exchanger 15 is formed of a fin-and-tube heat exchanger, for example, and is configured to exchange heat between the refrigerant and air. The outdoor heat exchanger 15 serves as a condenser or a radiator configured to condense the refrigerant discharged from the compressor 11 during the cooling operation, and as an evaporator configured to evaporate the refrigerant that has flowed thereinto from the indoor units 30 during the heating operation.

Moreover, the outdoor unit 10 may include an outdoor fan configured to send air to the outdoor heat exchanger 15.

[0014]

An oil separator 12 and a check valve 13 are connected between the compressor 11 and the flow switching device 14. The oil separator 12 is provided on a discharge side of the compressor 11 to separate refrigerating machine oil from refrigerant gas, which is discharged from the compressor 11 and in which the refrigerating machine oil is mixed. The oil separator 12 is connected to the flow switching device 14 and an accumulator 20 such that the refrigerant that has turned into a gas state flows to the flow switching device 14 side, and the refrigerating machine oil passes through an oil return bypass 24 to flow to a suction side of the compressor 11.

[0015]

On the oil return bypass 24, an oil return bypass capillary 24a and an oil return bypass solenoid valve 24b are provided. The oil return bypass capillary 24a is configured to adjust a flow rate of the refrigerating machine oil flowing through the oil return bypass 24. The oil return bypass solenoid valve 24b is connected in parallel to the oil return bypass capillary 24a to adjust the flow rate of the refrigerating machine oil flowing through the oil return bypass 24 by opening and closing control. [0016]

The check valve 13 is provided in a refrigerant pipe between the oil separator 12 and the flow switching device 14, and is configured to prevent back flow of the refrigerant to the discharge side of the compressor 11 when the compressor 11 is stopped. In Fig. 1, there is illustrated the case in which the oil separator 12 and the check valve 13 are provided. However, any one of the oil separator 12 and the check valve 13 may be provided, or the compressor 11 and the flow switching device 14 may be directly connected to each other.

[0017]

Further, the air-conditioning apparatus 1 includes a sub-outdoor heat exchanger 16 connected between the check valve 13 and the flow switching device

14. The sub-outdoor heat exchanger 16 is formed of a fin-and-tube heat exchanger, for example, and is configured to exchange heat between the refrigerant that has flowed thereinto via the flow switching device 14 and the air as with the outdoor heat exchanger 15. Between the sub-outdoor heat exchanger 16 and the compressor 11, a sub-flow switching device 22a formed of a four-way valve or a three-way valve, for example, is provided. Moreover, an on-off valve 22b is provided on the outdoor heat exchanger 15 side, and a volume of the refrigerant flowing through the outdoor heat exchanger 15 and the sub-outdoor heat exchanger 16 during operation can be controlled with the sub-flow switching device 22a and the on-off valve 22b.

[0018]

Then, when the sub-flow switching device 22a connects the discharge side of the compressor 11 to the sub-outdoor heat exchanger 16 during the cooling operation, the refrigerant that has been discharged from the compressor 11 flows into the sub-outdoor heat exchanger 16. When the sub-flow switching device 22a connects the sub-outdoor heat exchanger 16 to the accumulator 20 during the heating operation, the refrigerant that has flowed out of the sub-outdoor heat exchanger 16 is returned to the accumulator 20.

[0019]

The air-conditioning apparatus 1 also includes an intermediate heat exchanger 17 and a flow control valve 18, which are provided between the outdoor heat exchanger 15 and the indoor units 30. The intermediate heat exchanger 17 is configured to exchange heat between the refrigerant flowing through a liquid pipe 10x and the refrigerant flowing through a bypass pipe 19. The bypass pipe 19 branches off from the liquid pipe 10x between the intermediate heat exchanger 17 and the flow control valve 18 to allow the refrigerant to flow into the intermediate heat exchanger

17. In the bypass pipe 19, there is provided a bypass flow control valve 19a configured to adjust a flow rate of the refrigerant flowing through the bypass pipe 19. The bypass flow control valve 19a is formed of a valve having an opening degree that is variably controllable, for example, an electronic expansion valve, and serves as a pressure reducing valve or an expansion valve. The flow control valve 18 is provided on a downstream side of a branch point of the bypass pipe 19, is formed of a valve having an opening degree that is variably controllable, for example, an electronic expansion valve, and serves as a pressure reducing valve or an expansion valve.

[0020]

Further, on the suction side of the compressor 11, there is provided the accumulator 20 configured to accumulate excess refrigerant circulating through the refrigerant circuit. Moreover, between the outdoor unit 10 and the indoor units 30, there are provided on-off valves 3a and 3b, which are configured to be opened or closed by a controller 40 or manually, and are installed to adjust a variation in pressure in the refrigeration cycle.

[0021]

The two indoor units 30 are connected in parallel to the outdoor unit 10 via the gas pipe 2a and the liquid pipe 2b, and each include an indoor heat exchanger 31 and an expansion valve 32 connected in series to the indoor heat exchanger 31. A case in which the two indoor units 30 have the same components is exemplified.

The indoor heat exchanger 31 is formed of a fin-and-tube heat exchanger, for example, and is configured to exchange heat between the refrigerant and the air.

The indoor heat exchanger 31 serves as an evaporator during the cooling operation, and as a condenser (or radiator) during the heating operation. The expansion valve 32 serves as a pressure reducing valve or an expansion valve, and is configured to reduce a pressure of and expand the refrigerant. It is preferred to form the expansion valve 32 of a valve having an opening degree that is variably controllable, for example, an electronic expansion valve.

[0022]

Next, the flow of the refrigerant during the heating operation of the airconditioning apparatus 1 is described with reference to Fig. 1. During the heating operation, a refrigerant passage in the flow switching device 14 is switched such that the outdoor heat exchanger 15 serves as the evaporator and the indoor heat exchanger 31 serves as the condenser. First, the refrigerant discharged from the compressor 11 passes through the oil separator 12, the check valve 13, and the flow switching device 14 to flow into the indoor units 30 through the gas pipe 2a. Thereafter, the refrigerant transfers heat to indoor air in the indoor heat exchanger 31 to heat the indoor air. The refrigerant that has flowed out of the indoor heat exchanger 31 flows into the outdoor unit 10 via the expansion valve 32 and the liquid pipe 2b, and passes through the intermediate heat exchanger 17 to flow into the outdoor heat exchanger 15. After the refrigerant exchanges heat with outdoor air in the outdoor heat exchanger 15, the refrigerant is accumulated as low-temperature and low-pressure refrigerant in the accumulator 20.

[0023]

Here, the outdoor unit 10 includes the controller 40 configured to control driving of components, such as the compressor 11 and the flow switching device 14. The indoor units 30 each have mounted therein a controller 50 configured to control driving of actuators (for example, expansion valve 32 and indoor fan, which is not shown) mounted in the indoor unit 30. In Fig. 1, a state in which the controller 50 is mounted in each of the two indoor units 30 is illustrated as an example, but one controller may control both of the two indoor units 30. Moreover, when the controllers 50 are mounted in both of the indoor units 30, the controllers 50 are configured to be able to communicate via wire or wirelessly to/from each other. Further, the controllers 50 mounted in the indoor units 30 are configured to be able to communicate via wire or wirelessly to/from the controller 40 mounted in the outdoor unit 10. Each of the controller 40 and the controllers 50 is formed of a microcomputer capable of controlling the actuators, for example.

[0024]

Specifically, the outdoor unit 10 includes a discharge pressure sensor 61a, a discharge temperature sensor 61b, a suction pressure sensor 62a, a suction temperature sensor 62b, a refrigerant temperature sensor 63, an intermediate temperature sensor 65, an outside air temperature sensor 64, a subcooling temperature sensor 66, and a return temperature sensor 67. The discharge pressure sensor 61a is provided between the oil separator 12 and the flow switching device 14, and is configured to sense a pressure (high pressure) of the refrigerant discharged from the compressor 11. The discharge temperature sensor 61 b is provided between the compressor 11 and the oil separator 12, and is configured to sense a temperature of the refrigerant discharged from the compressor 11. The suction pressure sensor 62a is provided on an upstream side of the accumulator 20, and is configured to sense a pressure (low pressure) of the refrigerant to be sucked into the compressor 11. The suction temperature sensor 62b is provided between the accumulator 20 and the compressor 11, and is configured to sense a temperature of the refrigerant to be sucked into the compressor 11.

[0025]

The outside air temperature sensor 64 is configured to sense a temperature around the outdoor unit 10. The refrigerant temperature sensor 63 is provided between the outdoor heat exchanger 15 and the intermediate heat exchanger 17, and is configured to sense a temperature of the refrigerant passing a point between the outdoor heat exchanger 15 and the intermediate heat exchanger 17. The intermediate temperature sensor 65 is provided between the branch point of the bypass pipe 19 and the flow control valve 18, and is configured to sense an intermediate temperature of the refrigerant passing through the liquid pipe 10x. The subcooling temperature sensor 66 is provided to the bypass pipe 19, and is configured to sense a temperature of the refrigerant that has passed through the intermediate heat exchanger 17. The return temperature sensor 67 is provided between the flow switching device 14 and the accumulator 20, and is configured to sense a return temperature of the refrigerant returning to the accumulator 20.

[0026]

Meanwhile, each of the indoor units 30 includes an indoor gas pipe temperature sensor 71 and an indoor liquid temperature sensor 72. The indoor gas pipe temperature sensor 71 is provided to the gas pipe 2a connected to the indoor heat exchanger 31, and is configured to sense a gas pipe temperature of the refrigerant on a gas side of the indoor heat exchanger 31. The indoor liquid temperature sensor 72 is provided to the liquid pipe 2b connected to the indoor heat exchanger 31, and is configured to sense a temperature of the refrigerant on a liquid side of the indoor heat exchanger 31.

[0027]

Then, pressure information sensed by each pressure sensor, and temperature information sensed by each temperature sensor are transmitted as signals to the controller 40 and the controllers 50. The controller 40 and the controllers 50 control the actuators based on the signals transmitted from each pressure sensor and each temperature sensor.

[0028]

Here, when the above-mentioned heating operation is performed, noise caused by pressure pulsation may be generated. In other words, the pressure pulsation occurs when the refrigerant gas is discharged from the compressor 11, and the pressure pulsation vibrates the pipes of the air-conditioning apparatus 1 to generate vibration sound. In particular, when the pressure pulsation matches a resonance frequency determined depending on a pipe volume (pipe length) of the airconditioning apparatus 1, the pipes of the entire air-conditioning apparatus 1 may vibrate abnormally. To address this problem, the controller 40 has a function of setting an operating range of the operating frequency of the compressor 11 so as to prevent the pipes of the air-conditioning apparatus 1 from vibrating abnormally.

[0029]

Fig. 2 is a functional block diagram for illustrating an example of the controller in Fig. 1, and the controller 40 is described with reference to Fig. 1 and Fig. 2. The controller 40 of Fig. 2 includes a volume calculation unit 41, a frequency estimation unit 42, a condition setting unit 43, an operation control unit 44, and a data storage unit 45.

[0030]

The volume calculation unit 41 is configured to calculate, when the outdoor unit 10 and the indoor units 30 are in operation, a pipe volume VL of the entire pipe through which the refrigerant flows. In this case, the pipe volume VL of the entire pipe is a total of pipe volumes inside the outdoor unit 10 and the indoor units 30, and pipe volumes of the gas pipe 2a and the liquid pipe 2b. The pipe volumes (pipe lengths) inside the outdoor unit 10 and the indoor units 30 are known at the time of manufacture, and are stored in the data storage unit 45 in advance. Meanwhile, the pipe volumes of the gas pipe 2a and the liquid pipe 2b are different depending on lengths of pipes on the site of an installation location. Therefore, the volume calculation unit 41 calculates the pipe volume VL considering the gas pipe 2a and the liquid pipe 2b, which have different pipe volumes depending on the installation location and other factors. The volume calculation unit 41 calculates a volume VL of the entire pipe through which the refrigerant flows using an operating frequency f of the compressor 11, a discharge pressure, a pressure difference between the discharge pressure and a suction pressure, and a pipe diameter of the gas pipe 2a. Specifically, the volume calculation unit 41 includes a pipe diameter acquisition unit 41a, a circulation amount calculation unit 41b, and a volume estimation unit 41c. [0031]

The pipe diameter acquisition unit 41a is configured to acquire the pipe diameter of the gas pipe 2a connected to the outdoor unit 10 and each of the indoor units 30. In this case, the data storage unit 45 has stored therein table information in which capacities (horsepowers) of the outdoor unit 10 and the indoor units 30 are associated with the pipe diameter, for example, and the pipe diameter acquisition unit 41a refers to the table information stored in the data storage unit 45 to acquire the pipe diameter of the gas pipe 2a. The case in which the pipe diameter acquisition unit 41a acquires the pipe length from the data storage unit 45 is exemplified, but the pipe diameter acquisition unit 41a may acquire a pipe diameter input by an operator using a keyboard and other input devices, for example.

[0032]

The circulation amount calculation unit 41b is configured to calculate, based on the discharge pressure sensed by the discharge pressure sensor 61a, the suction pressure sensed by the suction pressure sensor 62a, and a saturated gas pressure corresponding to the return temperature sensed by the return temperature sensor 67, a circulation amount of the refrigerant flowing through the refrigerant circuit during operation. As a method of calculating the circulation amount of the refrigerant, various known methods can be used.

[0033]

The volume estimation unit 41c is configured to calculate, based on the pipe diameter of the gas pipe 2a acquired by the pipe diameter acquisition unit 41a, and the circulation amount of the refrigerant calculated by the circulation amount calculation unit 41 b, the pipe volume VL of the refrigerant circuit through which the refrigerant flows during operation. At this time, the volume estimation unit 41 c calculates a pressure loss in the gas pipe 2a based on the discharge pressure sensed by the discharge pressure sensor 61a, and a saturated gas pressure corresponding to the gas pipe temperature sensed by the indoor gas pipe temperature sensor 71. Thereafter, the volume estimation unit 41 c computes the pipe length of the gas pipe 2a based on the circulation amount of the refrigerant, the pressure loss, and the pipe diameter. Then, the volume estimation unit 41c determines the pipe volumes of the gas pipe 2a and the liquid pipe 2b assuming that the gas pipe 2a and the liquid pipe 2b have substantially the same pipe length, and adds, to the determined pipe volumes, the pipe volumes of the outdoor unit 10 and the indoor units 30, to thereby calculate the pipe volume VL of the entire pipe.

[0034]

The frequency estimation unit 42 is configured to estimate, based on the pipe volume VL calculated by the volume calculation unit 41, the discharge pressure, and the pressure difference between the discharge pressure and the suction pressure, a resonance frequency fv by referring to a frequency table. Here, the data storage unit 45 has stored therein the frequency table used in estimating the resonance frequency fv, and the frequency estimation unit 42 estimates, based on the discharge pressure, the pressure difference, and the pipe volume VL, the resonance frequency fv by referring to the frequency table.

[0035]

Fig. 3 is a schematic diagram for illustrating an example of the frequency table. The frequency table stores the discharge pressure, the pressure difference between the discharge pressure and the suction pressure, the pipe volume, and the resonance frequency fv of the entire pipe through which the refrigerant flows in a state of being associated with one another. Specifically, the discharge pressure is classified into a case of less than 30 kg/cm² and a case of 30 kg/cm² or more, for example, and a pressure difference ΔΡ is classified into four ranges (10 K or less, 10 K to 15 K, 15 K to 20 K, and 20 K or more) for each range of the discharge pressure. Further, for each of the four ranges of the pressure difference ΔΡ, the pipe volume VL is classified into three ranges ((lower limit threshold a)<VL, (lower limit threshold a)<VL<(upper limit threshold β), VL>(upper limit threshold β)), and the resonance frequency fv=A1 to H3 is stored for each range. For example, when the high-pressure pressure is 30 kg/cm² or more, the pressure difference is in the range of from 10 K to 15 K, and (lower limit threshold a)<(pipe volume VL)<(upper limit threshold β), the frequency estimation unit 42 estimates that the resonance frequency fv=F2.

[0036]

The condition setting unit 43 of Fig. 2 is configured to set operation conditions of the compressor 11 so as to restrain the operating frequency f of the compressor 11 from matching the resonance frequency fv estimated by the frequency estimation unit 42. Here, in the data storage unit 45, a lower limit operating frequency fmin and an upper limit frequency fmax of the operating frequency f of the compressor 11 are set. Then, the operation control unit 44 controls the operating frequency f within a range between the lower limit operating frequency fmin and the upper limit frequency fmax. The condition setting unit 43 sets the operation conditions so as to prevent the resonance frequency fv from being contained in the range between the lower limit operating frequency fmin and the upper limit frequency fmax.

[0037]

In particular, the resonance frequency fv is empirically generated in a low frequency range of from about 10 Hz to about 25 Hz in many cases. Therefore, when the resonance frequency fv is more than the lower limit operating frequency fmin, the compressor 11 may be operated with the operating frequency f being the resonance frequency fv to generate abnormal vibration. To address this problem, when the resonance frequency fv is more than the lower limit operating frequency fmin (fv>fmin), the condition setting unit 43 sets the lower limit operating frequency fmin to fmin=fv+Af, which is larger than the resonance frequency fv by a correction value Af, and stores the set lower limit operating frequency fmin in the data storage unit 45. The correction value Af is set in advance considering a variation among the pipes on the site (variation in sensing accuracy), but may be changed suitably. In this manner, the resonance frequency fv may be excluded from the operating range of the compressor 11 to correct the abnormal vibration of the pipes in the airconditioning apparatus 1, and hence suppress the generation of noise. The condition setting unit 43 may set the lower limit operating frequency fmin to the resonance frequency fv (fmin=fv).

[0038]

Meanwhile, when the resonance frequency fv is the lower limit operating frequency fmin or lower (fv<fmin), the condition setting unit 43 does not change the operation conditions, and the lower limit operating frequency fmin is stored in the data storage unit 45 without being changed. Then, the operation control unit 44 controls the compressor 11 based on the operation conditions stored in the data storage unit 45.

[0039]

Moreover, when the outdoor unit 10 and the indoor units 30 that are in operation are changed, the pipe volume through which the refrigerant flows may be changed to change the resonance frequency fv. Therefore, when operation states are changed, the calculation of and the determination as to the resonance frequency fv are performed again.

[0040]

Fig. 4 is a flow chart for illustrating a flow of control processing in Embodiment 1, and an operation example of the controller is described with reference to Fig. 1 to Fig. 4. First, when the air-conditioning apparatus 1 is powered on, the pipe diameter acquisition unit 41a acquires, based on the capacities (horsepowers) of the outdoor unit 10 and the indoor units 30, pipe diameters of the gas pipe 2a and the liquid pipe

2b by referring to the data storage unit 45 (Step ST1). Thereafter, an instruction to start operation is issued to the indoor units 30 through operation of a switch on a remote controller by a user.

[0041]

When the heating operation is instructed by the user (Step ST2), the controller 40 collects information sensed by the sensors installed in the outdoor unit 10 and the indoor units 30, and the operating frequency f of the compressor 11. Thereafter, the pipe diameter acquisition unit 41 a acquires the pipe diameters of the gas pipe 2a and the liquid pipe 2b. Moreover, the circulation amount calculation unit 41b calculates, based on the discharge pressure, the suction pressure (return temperature), and the operating frequency of the compressor 11, the circulation amount of the refrigerant flowing through the entire air-conditioning apparatus 1. Then, the volume estimation unit 41c computes the pressure loss of the gas pipe 2a based on the discharge pressure and the saturated gas pressure corresponding to the indoor gas pipe temperature, and calculates, based on the pipe diameters, the circulation amount of the refrigerant, and the pressure loss, the pipe volume VL of the entire pipe through which the refrigerant flows (Step ST3).

[0042]

Next, based on the pipe volume, the high-pressure pressure sensed by the discharge pressure sensor 61a, the low-pressure pressure sensed by the suction pressure sensor 62a, and the pressure difference between the high-pressure pressure and the low-pressure pressure, the resonance frequency fv at the pipe volume is estimated based on the resonance frequency table (Step ST4, see Fig. 7). Thereafter, the condition setting unit 43 determines whether the resonance frequency fv is contained in the operating range of the compressor 11 (Step ST5). When the lower limit operating frequency fmin is the resonance frequency fv or less (YES in Step ST5), it means that the resonance frequency fv is present within the range of the operating frequency of the compressor 11. In this case, it is determined that the pipes of the air-conditioning apparatus 1 may vibrate abnormally, and the range of the operating frequency of the compressor 11 is changed (Step ST6). Specifically, the lower limit operating frequency fmin is set to the value obtained by adding the correction value Af to the resonance frequency fv (fmin=fv+Af), and the value is stored in the data storage unit 45.

[0043]

In contrast, when the lower limit operating frequency fmin is more than the resonance frequency fv (NO in Step ST5), it is determined that the entire pipe through which the refrigerant flows during operation does not resonate in the operating range of the compressor 11. As a timing to change the lower limit operating frequency fmin, when the outdoor unit 10 and the indoor units 30 that are in operation are changed, the pipe volume through which the refrigerant flows is changed. The resonance frequency fv may change with this change, and hence at the timing when the operation states are changed again (YES in Step ST7), the calculation of and the determination as to the resonance frequency fv are performed again (Step ST3 to Step ST6).

[0044]

According to Embodiment 1 described above, the resonance frequency fv is estimated based on the pipe volume VL of the entire pipe through which the refrigerant flows, and the operating frequency of the compressor 11 is set so as not to perform operation at the estimated resonance frequency fv, with the result that the generation of noise caused by the pressure pulsation can be suppressed depending on the installation state of the air-conditioning apparatus 1 without separately installing a muffler configured to cancel the resonance frequency fv.

[0045]

In other words, when the muffler or another device is mounted as in the related art, a space is required to be provided in a housing of the outdoor unit 10, and a large cost is required. Further, a pressure loss of fluid at a time when the refrigerant passes through a hole portion is large, and may lead to a reduction in performance.

In order to suppress the pressure pulsation, it can also be considered to increase the pipe length such that the range of the operating frequency of the compressor 11 does not match the unique resonance frequency of the pipe system. Alternatively, in order to prevent the operating frequency f of the compressor 11 from matching the resonance frequency of the pipe system, it can be considered to uniformly increase the lower limit operating frequency fmin of the compressor 11, for example.

However, the resonance frequency fv is different depending on the pipes on the site and other factors, and hence the lower limit operating frequency is required to be set individually for each air-conditioning apparatus 1. Therefore, in order to set an operating frequency that encompasses all air-conditioning apparatus 1, lower limit operating frequencies of all the air-conditioning apparatus may be increased. Then, in an operation under a state of a low load, for example, in an operation in which only an indoor unit having a small capacity is operated, an increased frequency of starting and stopping and other problems remain.

[0046]

In contrast, in order to take into consideration the installation state of the airconditioning apparatus 1, for example, the pipes on the site, the controller 40 of Fig. 3 estimates the resonance frequency fv based on the pipe volume VL of the entire pipe through which the refrigerant flows. Then, the operating frequency of the compressor 11 is set so as not to perform operation at the estimated resonance frequency fv. Then, the generation of noise caused by the pressure pulsation can be suppressed depending on the installation state of the air-conditioning apparatus 1 without using the muffler or another device.

[0047]

Further, with the condition setting unit 43 comparing the resonance frequency fv with the lower limit operating frequency fmin in the range of the operating frequency f, and setting, when the resonance frequency fv is more than the lower limit operating frequency fmin, the resonance frequency fv as the lower limit operating frequency fmin, the occurrence of the pressure pulsation during operation at a low operating frequency can be prevented reliably based on an empirical rule that the resonance frequency fv tends to exist in a low frequency range.

[0048]

Moreover, when the volume calculation unit 41 includes the pipe diameter acquisition unit 41 a configured to acquire the pipe diameter of the gas pipe 2a, the circulation amount calculation unit 41b configured to calculate the circulation amount of the refrigerant flowing through the outdoor unit 10 and the indoor units 30 that are in operation, and the volume estimation unit 41c configured to estimate the pipe volume of the gas pipe 2a, and calculate the pipe volume VL of the entire pipe through which the refrigerant flows based on the pipe diameter and the circulation amount of the refrigerant, the pipe volume of the gas pipe 2a can be estimated accurately, and the resonance frequency fv can be derived accurately considering the fact that the gas pipe 2a has a different pipe length depending on the installation location and other factors.

[0049]

Embodiment 2

Fig. 5 is a refrigerant circuit diagram for illustrating an example of an airconditioning apparatus according to Embodiment 2 ofthe present invention, and an air-conditioning apparatus 100 is described with reference to Fig. 5. In the airconditioning apparatus 100 of Fig. 5, parts having the same configurations as those of the air-conditioning apparatus 1 of Fig. 1 are denoted by the same reference symbols, and a description thereof is omitted. The air-conditioning apparatus 100 of Fig. 5 is different from the air-conditioning apparatus of Fig. 1 in that two outdoor units 110A and 110B are connected in parallel to the indoor units 30.

[0050]

In the air-conditioning apparatus 100 of Fig. 5, the outdoor units 110Aand 110B are connected in parallel to each other through gas branch pipes 102a and 102b and via a distributor 103a, and the distributor 103a is connected to the indoor units 30 through a gas pipe 102c. Moreover, the outdoor units 110Aand 110B are connected in parallel to each other through liquid branch pipes 102p and 102q and via a distributor 103p, and the distributor 103p is connected to the indoor units 30 through a liquid pipe 102r. In Fig. 1, the case where the distributor 103a and the distributor 103p are mounted in the air-conditioning apparatus 100 is exemplified, but the connection may be via a T tube, for example.

[0051]

Fig. 6 is a flow chart for illustrating an operation example of the air-conditioning apparatus of Fig. 5, and the operation example of the air-conditioning apparatus 100 is described with reference to Fig. 5 and Fig. 6. In the flow chart of Fig. 6, the same steps as those in the flow chart of Fig. 4 are denoted by the same reference symbols, and a description thereof is omitted. In Fig. 6, the condition setting unit 43 of Fig. 2 compares each of lower limit operating frequencies fmina and fminb of the outdoor units 110Aand 110B, respectively, with the resonance frequency fv (Steps ST15a and ST15b). When the lower limit operating frequency fmina is more than the resonance frequency fv (NO in Step ST15a), it is determined that there is no point at which the pipes of the system resonate in the operating range of the compressor 11 on the outdoor unit HOAside. Similarly, when the lower limit operating frequency fminb is more than the resonance frequency fv (NO in Step ST15b), it is determined that there is no point at which the pipes of the system resonate in the operating range of the compressor 11 on the outdoor unit 110B side.

[0052]

In contrast, when the lower limit operating frequency fmina is the resonance frequency fv or less (YES in Step ST15a), it means that the resonance frequency fv exists in the operating range of the compressor 11 on the outdoor unit 110A side. In this case, the lower limit operating frequency fmina is set to a value of the resonance frequency fv+Af (Step ST16a). Similarly, when the lower limit operating frequency fminb is the resonance frequency fv or less (YES in Step ST15b), it means that the resonance frequency fv exists in the operating range of the compressor 11 on the outdoor unit HOAside. In this case, the lower limit operating frequency fminb is set to a value of the resonance frequency fv+Af (Step ST16b).

[0053]

Even with the air-conditioning apparatus 100 including the two outdoor units 110Aand 110B as in Embodiment 2 described above, the resonance frequency fv is calculated considering pipe lengths of the gas branch pipes 102a and 102b and the liquid branch pipes 102p and 102q. Therefore, as in Embodiment 1, with the operating frequency of the compressor 11 being set so as not to perform operation at the estimated resonance frequency fv, the generation of noise caused by the pressure pulsation can be suppressed depending on an installation state of the airconditioning apparatus 100 without using the muffler or another device.

[0054]

Embodiment 3

Fig. 7 is a refrigerant circuit diagram for illustrating an example of an airconditioning apparatus according to Embodiment 3 of the present invention, and an air-conditioning apparatus 200 is described with reference to Fig. 7. In the airconditioning apparatus 100 of Fig. 7, parts having the same configurations as those of the air-conditioning apparatus 1 of Fig. 1 are denoted by the same reference symbols, and a description thereof is omitted. The air-conditioning apparatus 100 of Fig. 7 is different from the air-conditioning apparatus of Fig. 1 in that three outdoor units 210A, 210B, and 210C are connected in parallel to the indoor units 30.

[0055]

In the air-conditioning apparatus 200 of Fig. 7, the outdoor units 210Aand 210B are connected in parallel to each other through gas branch pipes 202a and 202b and via a distributor 205a, and the distributor 205a is connected in parallel to the outdoor unit 210C through gas branch pipes 203a and 203b and via the distributor 205a. The distributor 205b is connected to the indoor units 30 through a gas pipe 204a, and the outdoor units 210A, 210B, and 210C are in a state of being connected in parallel to one another. Moreover, the outdoor units 210B and 210C are connected in parallel to each other through liquid branch pipes 202p and 202q and via a distributor 205p, and the distributor 205p is connected to the outdoor unit 210A through liquid pipes 202r and 202s and via a distributor 205r. The distributor 205r is connected to the indoor units 30 through a liquid pipe 202t, and the outdoor units 210A, 210B, and 210C are in a state of being connected in parallel to one another. [0056]

Fig. 8 is a flow chart for illustrating an operation example of the controller of Fig. 7, and the operation example of the air-conditioning apparatus 100 is described with reference to Fig. 7 and Fig. 8. In the flow chart of Fig. 8, the same steps as those in the flow chart of Fig. 4 are denoted by the same reference symbols, and a description thereof is omitted. In Fig. 8, the condition setting unit 43 of Fig. 2 compares each of lower limit operating frequencies fmina, fminb, and fminc of the outdoor units 210A to 210C, respectively, with the resonance frequency fv (Steps ST25a to ST25c). When the lower limit operating frequency fmina is more than the resonance frequency fv (NO in Step ST25a), it is determined that there is no point at which the pipes of the system resonate in the operating range of the compressor 11 on the outdoor unit 210A side. Similarly, when the lower limit operating frequency fminb is more than the resonance frequency fv (NO in Step ST25b), it is determined that there is no point at which the pipes of the system resonate in the operating range of the compressor 11 on the outdoor unit 21 OB side. Similarly, when the lower limit operating frequency fminc is more than the resonance frequency fv (NO in Step ST25c), it is determined that there is no point at which the pipes of the system resonate in the operating range of the compressor 11 on the outdoor unit 210C side. [0057]

In contrast, when the lower limit operating frequency fmina is the resonance frequency fv or less (YES in Step ST25a), it means that the resonance frequency fv exists in the operating range of the compressor 11 on the outdoor unit 110A side. In this case, the lower limit operating frequency fmina is set to a value of the resonance frequency fv+Af (Step ST26a). Similarly, when the lower limit operating frequency fminb is the resonance frequency fv or less (YES in Step ST25b), it means that the resonance frequency fv exists in the operating range of the compressor 11 on the outdoor unit 210B side. In this case, the lower limit operating frequency fminb is set to a value of the resonance frequency fv+Af (Step ST26b). Similarly, when the lower limit operating frequency fminc is the resonance frequency fv or less (YES in Step ST25c), it means that the resonance frequency fv exists in the operating range of the compressor 11 on the outdoor unit 210C side. In this case, the lower limit operating frequency fminc is set to a value of the resonance frequency fv+Af (Step ST26c). [0058]

Even with the air-conditioning apparatus 100 including the three outdoor units 210A, 210B, and 21OC as in Embodiment 3 described above, the resonance frequency fv is calculated considering pipe lengths of the gas branch pipes and the liquid branch pipes. Therefore, as in Embodiment 1, with the operating frequency of the compressor 11 being set so as not to perform operation at the estimated resonance frequency fv, the generation of noise caused by the pressure pulsation can be suppressed depending on an installation state of the air-conditioning apparatus 200 without using the muffler or another device.

[0059]

Embodiments of the present invention are not limited to Embodiments described above, and various modifications may be made thereto. For example, there has been exemplified the case in which the condition setting unit 43 of Fig. 2 compares the lower limit operating frequency fmin with the resonance frequency fv, and sets the operation conditions such that the lower limit operating frequency fmin is more than the resonance frequency fv. However, the present invention is not limited thereto unless the resonance frequency fv is contained in the range of the operating frequency. For example, the condition setting unit 43 may be configured to set, when the resonance frequency fv is contained between the lower limit operating frequency fmin and the upper limit frequency fmax, the operation conditions so as to exclude only the resonance frequency fv from the operating range.

[0060]

Moreover, in Embodiments 2 and 3 described above, there has been exemplified the case in which the range of the operating frequency f of each of the outdoor units 110A, 110B, and 210Ato 210C is compared with the resonance frequency fv. However, the smallest lower limit operating frequency fmin may be selected from among lower limit operating frequencies fmin during operation, and the selected lower limit operating frequency fmin may be compared with the resonance frequency fv.

Reference Signs List [0061]

1,100,200 air-conditioning apparatus 2a gas pipe 2b liquid pipe

3a on-off valve 3b on-off valve 10, 110A, 110B, 210A, 210B, 210C outdoor unit 10x liquid pipe 11 compressor 12 oil separator 13 check valve 14 flow switching device 15 outdoor heat exchanger 15a on-off valve 16 sub-outdoor heat exchanger 17 intermediate heat exchanger 18 flow control valve 19 bypass pipe 19a bypass flow control valve 20 accumulator 22a sub-flow switching device 22b oil return bypass solenoid valve 24 oil return bypass 24a oil return bypass capillary 24b oil return bypass solenoid valve 30 indoor unit 31 indoor heat exchanger 32 expansion valve 40 controller 41 volume calculation unit 41a pipe diameter acquisition unit

41b circulation amount calculation unit 41c volume estimation unit 42 frequency estimation unit 43 condition setting unit44 operation control unit 45 data storage unit 50 controller 61a discharge pressure sensor 61b discharge temperature sensor 62a suction pressure sensor 62b suction temperature sensor 63 refrigerant temperature sensor 64 outside air 65 intermediate temperature sensor 66 subcooling 67 return temperature sensor 71 indoor gas pipe 72 indoor liquid temperature sensor 102a, 102b, 202a,

202b, 203a, 203b gas branch pipe 102c, 204a gas pipe 102p, 102q, 202p,

202q, 202r, 202s liquid branch pipe 102r, 202t iquid pipe 103a, 103p, 205a,

205b, 205p, 205r distributor fmin, fmina, fminb, fminc lower limit operating frequency fv resonance frequency VL pipe volume f operating frequency fmax upper limit frequency fv resonance frequency ΔΡ pressure difference Af correction value a lower limit threshold β upper limit threshold temperature sensor temperature sensor temperature sensor

Claims

CLAIMS [Claim 1]

An air-conditioning apparatus, in which an outdoor unit and an indoor unit are connected to each other through a gas pipe and a liquid pipe, the outdoor unit including a compressor, the air-conditioning apparatus comprising:

a discharge pressure sensor configured to sense a discharge pressure of refrigerant discharged from the compressor;

a suction pressure sensor configured to sense a suction pressure of the refrigerant on a suction side of the compressor; and a controller configured to set a range of an operating frequency of the compressor based on the discharge pressure sensed by the discharge pressure sensor, and the suction pressure sensed by the suction pressure sensor, the controller including a volume calculation unit configured to calculate, when the outdoor unit and the indoor unit are in a heating operation, a pipe volume of an entire pipe through which the refrigerant flows, a frequency table, in which the discharge pressure, a pressure difference between the discharge pressure and the suction pressure, the pipe volume, and a resonance frequency of the entire pipe through which the refrigerant flows are associated with one another, a frequency estimation unit configured to estimate, based on the pipe volume calculated by the volume calculation unit, the discharge pressure, and the pressure difference between the discharge pressure and the suction pressure, the resonance frequency by referring to the frequency table, and a condition setting unit configured to set the range of the operating frequency of the compressor so as to restrain the operating frequency of the compressor from matching the resonance frequency estimated by the frequency estimation unit.
[Claim 2]

The air-conditioning apparatus of claim 1, wherein the condition setting unit is configured to compare the resonance frequency with a lower limit operating frequency in the range of the operating frequency, and set, when the resonance frequency is more than the lower limit operating frequency, the resonance frequency as the lower limit operating frequency.
[Claim 3]

The air-conditioning apparatus of claim 1 or 2, further comprising an indoor gas pipe temperature sensor configured to sense a gas pipe temperature of the refrigerant that flows from the gas pipe to the indoor unit, wherein the volume calculation unit includes:

a pipe diameter acquisition unit configured to acquire a pipe diameter of the gas pipe;

a circulation amount calculation unit configured to calculate, based on the discharge pressure, the suction pressure, the gas pipe temperature sensed by the indoor gas pipe temperature sensor, and the operating frequency of the compressor, a circulation amount of the refrigerant flowing through the outdoor unit and the indoor unit that are in operation; and a volume estimation unit configured to estimate a pipe volume of the gas pipe and calculate the pipe volume of the entire pipe through which the refrigerant flows based on the pipe diameter acquired by the pipe diameter acquisition unit, and the circulation amount of the refrigerant calculated by the circulation amount calculation unit.
[Claim 4]

The air-conditioning apparatus of any one of claims 1 to 3, wherein the outdoor unit includes a plurality of outdoor units, which are connected in parallel to the indoor unit, and wherein the condition setting unit is configured to set the range of the operating frequency of the compressor for each of the plurality of outdoor units.