US20010018831A1 - Air conditioning system with compressor protection - Google Patents
Air conditioning system with compressor protection Download PDFInfo
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- US20010018831A1 US20010018831A1 US09/795,542 US79554201A US2001018831A1 US 20010018831 A1 US20010018831 A1 US 20010018831A1 US 79554201 A US79554201 A US 79554201A US 2001018831 A1 US2001018831 A1 US 2001018831A1
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- compressor
- protective
- protective value
- pressure side
- refrigerant
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60H—ARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES
- B60H1/00—Heating, cooling or ventilating [HVAC] devices
- B60H1/32—Cooling devices
- B60H1/3204—Cooling devices using compression
- B60H1/3225—Cooling devices using compression characterised by safety arrangements, e.g. compressor anti-seizure means or by signalling devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
- F25B49/022—Compressor control arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2500/00—Problems to be solved
- F25B2500/07—Exceeding a certain pressure value in a refrigeration component or cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/02—Compressor control
- F25B2600/021—Inverters therefor
Abstract
Description
- This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-60459 filed on Mar. 6, 2000.
- 1. Field of the Invention
- The present invention relates to an air conditioning system that carries out a protective control operation of a compressor when a high pressure in a refrigerant cycle of the air conditioning system becomes abnormally high, to prevent a failure of the compressor.
- 2. Description of Related Art
- In a known type of refrigerant cycle system having an accumulator, if a compressor is operated while a high pressure in the refrigerant cycle system is abnormally high, the compressor will fail. To prevent the failure of the compressor, a first protective value is set near an upper tolerable pressure limit of the compressor. When the high pressure of the refrigerant cycle system exceeds the first protective value, the compressor is forcefully turned off.
- Furthermore, a second protective value that is lower than the first protective value is set to prevent the high pressure from reaching the first protective pressure. When the high pressure exceeds the second protective value, a current rotational speed (capacity) of the compressor is maintained or reduced. Specifically, the second protective value is split into a low-pressure side second protective value and a high-pressure side second protective value. When the high pressure in the refrigerant cycle system exceeds the low-pressure side second protective value, the current compressor rotational speed is maintained. When the high pressure exceeds the high-pressure side second protective value, the compressor rotational speed is reduced. However, in the refrigerant cycle system, each one of the protective values is always the same regardless of operation time of the compressor. This causes the following problem at startup of the compressor.
- That is, at the startup of the compressor, the compressor rotational speed increases very rapidly from zero to a target rotational speed, and thereby the high pressure in the refrigerant cycle system also increases very rapidly.
- Also, at the startup of the compressor, gaseous refrigerant remained in a condenser near an outlet of the condenser is discharged from the outlet of the condenser without completely dissipating its heat. Thus, a gas to liquid ratio of refrigerant at the outlet of the condenser increases. In the refrigerant cycle system having the accumulator, a gas-liquid separator (receiver) that separates refrigerant into gas refrigerant and liquid refrigerant is not arranged between the condenser and a decompressor. As a result, refrigerant discharged from the outlet of the condenser is not separated into the gas refrigerant and the liquid refrigerant before entering into the decompressor. Thus, when the gas to liquid ratio of refrigerant is increased at the outlet of the condenser, a throttle degree of the decompressor increases, and thereby a high-pressure side refrigerant pressure of the refrigerant cycle system rapidly increases.
- As a result, as shown in FIG. 10, the high pressure exceeds the second protective values (HPV2, LPV2) at the startup of the compressor. In FIG. 10, PV1 indicates the first protective value, HPV2 indicates the high-pressure side second protective value, and LPV2 indicates the low-pressure side second protective value.
- When the high pressure exceeds the second protective values, the current compressor rotational speed is maintained or reduced. However, due to the rapid increase of the high pressure, the high pressure may also exceed the first protective value (PV1), causing forceful shutdown of the compressor. If this happens, the compressor needs to be restarted, and the restart of the compressor disadvantageously requires a certain amount of time.
- Furthermore, when the high pressure exceeds the low-pressure side second protective value (LPV2) and then the high-pressure side second protective value (LPV2), the compressor rotational speed is forcefully reduced. In this way, the high pressure decreases below the high-pressure side second protective value (HPV2). At this time point, the current compressor rotational speed is maintained to keep the high pressure between the high-pressure side second protective value (HPV2) and the low-pressure side second protective value (LPV2). However, the compressor rotational speed decreases at a maximum rate. Thus, the high pressure may continue to decrease and thereby may become lower than the low-pressure side second protective value (LPV2). In such a case, since the current operating condition of the air conditioning system has not been changed and thereby still causes the high pressure to increase. Thus, the high pressure may increase once again, and start performance of the compressor is deteriorated.
- The present invention addresses the above-described problems. Thus, it is an objective of the present invention to provide an air conditioning system having a refrigerant cycle system, which improves starting performance of a compressor while protecting the compressor.
- To achieve the objective of the present invention, an air conditioning system has a compressor protective control unit having first and second protective values. The first protective value is set for preventing a failure of a compressor. The second protective value is lower than the first protective value in order to prevent a high pressure in a refrigerant cycle system from reaching the first protective value. The compressor protective control unit maintains or reduces a capacity of the compressor when the high pressure in the refrigerant cycle system exceeds the second protective value. The compressor protective control unit turns off the compressor when the high pressure exceeds the first protective value. The compressor protective control unit sets the second protective value such that the second protective value used before an elapse of a predetermined time period from startup of the compressor is lower than the second protective value used after the elapse of the predetermined time period. Accordingly, the air conditioning system improves start performance of the compressor, while protecting the compressor.
- Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of a preferred embodiment when taken together with the accompanying drawings, in which:
- FIG. 1 is a schematic diagram of an air conditioning system of an electric vehicle according to a preferred embodiment of the present invention;
- FIG. 2 is a block diagram showing a control unit of the air conditioning system according to the embodiment;
- FIG. 3 is a flow diagram showing a control operation carried out by a microcomputer of the air conditioning system;
- FIG. 4 is a graph for setting an operation mode among a cooling mode, a blowing mode and a heating mode according to the first embodiment;
- FIG. 5A is a view showing a membership function used during the cooling mode, and
- FIG. 5B is a view showing an another membership function used during the cooling mode;
- FIG. 6 is a view showing a fuzzy rule used during the cooling mode;
- FIG. 7A is a view showing a membership function used during the heating mode, and
- FIG. 7B is a view showing an another membership function used during the heating mode;
- FIG. 8 is a view showing a fuzzy rule used during the heating mode;
- FIG. 9 is a flow diagram showing a protective control operation of a compressor according to the embodiment; and
- FIG. 10 is a graph showing characteristics of a high pressure, a target rotational speed and a rotational speed of a compressor at a start operation.
- An air conditioning system of an electric vehicle according to a preferred embodiment of the present invention will be described with reference to FIGS.1-9. First, constructions of an interior
air conditioning unit 1 placed in an interior of a passenger compartment and arefrigerant cycle system 9 will be described with reference to FIG. 1. - As shown in FIG. 1, the interior
air conditioning unit 1 includes an air conditioning case 2. The air conditioning case 2 defines an air passage that leads conditioned air into the interior of the passenger compartment. At upstream of the air conditioning case 2, an insideair suction port 3, an outside air suction port 4 and an inside/outsideair switching door 5 are arranged. The insideair suction port 3 is provided for sucking inside air from the passenger compartment. The outside air suction port 4 is provided for sucking outside air outside the passenger compartment. The inside/outsideair switching door 5 is disposed for selectively opening and closing the insideair suction port 3 and the outside air suction port 4. The inside/outsideair switching door 5 is driven by a servo motor 6 (see FIG. 2). - A
fan 7 for generating an air flow in the air passage is disposed downstream of the inside/outsideair switching door 5. Thefan 7 is driven by ablower motor 8. Aninterior evaporator 10 constituting a part of therefrigerant cycle system 9 is disposed downstream of thefan 7. Theinterior evaporator 10 is used for cooling air by a heat absorbing reaction of refrigerant flowing through theinterior evaporator 10 during a cooling mode which will be described in detail below. - An
interior condenser 11 constituting a part of therefrigerant cycle system 9 is located downstream of theinterior evaporator 10. Theinterior condenser 11 is used for heating air by heat radiating reaction of refrigerant flowing through theinterior condenser 11 during a heating mode which will be described in detail below. - An
air mixing door 12 is located adjacent to theinterior condenser 11. Theair mixing door 12 adjusts the amount of air passing through theinterior condenser 11 and the amount of air bypassing theinterior condenser 11. Theair mixing door 12 is driven by a servo motor 13 (see FIG. 2). - At a downstream side of the air conditioning case2, a face air outlet, a foot air outlet and a defroster air outlet are provided. The face air outlet is provided for blowing conditioned air toward the upper half body of a passenger in the passenger compartment. The foot air outlet is provided for blowing conditioned air toward the feet of the passenger in the passenger compartment. The defroster air outlet is provided for blowing conditioned air toward an inner surface of a windshield. An air outlet mode switching member is provided for opening and closing the face air outlet, the foot air outlet and the defroster air outlet.
- The
refrigerant cycle system 9 is a heat pump type refrigerant cycle system that cools and heats the passenger compartment by use of theinterior evaporator 10 and theinterior condenser 11, respectively. Besides theevaporator 10 and thecondenser 11, therefrigerant cycle system 9 further includes acompressor 14, anexterior heat exchanger 15, aheating capillary tube 16, a coolingcapillary tube 17, anaccumulator 18 and solenoid valves 19-21, all of which are fluidly connected by arefrigerant pipe 22. -
Exterior fans 23 for blowing air toward theexterior heat exchanger 15 are arranged adjacent to theexterior heat exchanger 15. Theexterior fans 23 are driven by an exterior fan motor 24 (FIG. 2). - The
compressor 14 sucks, compresses and then discharges refrigerant when it is driven by an electric motor 25 (FIG. 2). Theelectric motor 25 and thecompressor 14 are integrally arranged within a sealed case. A rotational speed of theelectric motor 25 is controlled by an inverter 26 (FIG. 2) to be linearly changed. Energization of theinverter 26 is controlled by a control device 27 (FIG. 2). - The
exterior heat exchanger 15 acts as an evaporator during a heating mode and acts as a condenser during a cooling mode. - The
heating capillary tube 16 acts as decompressing means during the heating mode. The coolingcapillary tube 17 acts as decompressing means during the cooling mode. Eachcapillary tube heating capillary tube 16 or the coolingcapillary tube 17. - The
accumulator 18 is arranged in therefrigerant cycle system 9 between thecompressor 14 and theinterior evaporator 10 or theexterior heat exchanger 15. Theaccumulator 18 is a gas-liquid separator for separating refrigerant from theinterior evaporator 10 or theexterior heat exchanger 15 into gas refrigerant and liquid refrigerant. Because of theaccumulator 18, thecompressor 14 can always suck the gaseous refrigerant. - Energization of each one of the solenoid valves19-21 is controlled by the control device 27 (FIG. 2).
- The
control device 27 of the vehicle air conditioning system according to the present embodiment will be described with reference to FIG. 2. - The
control device 27 includes a known microcomputer, an A/D converter circuit, a timer and the like. The microcomputer includes a CPU, a ROM, a RAM and the like. - The
control device 27 is activated when a key switch (not shown) is turned on and power from a battery (not shown) is supplied to thecontrol device 27. The key switch is turned on or off when the vehicle passenger turns a key cylinder (not shown) with a key in a corresponding direction. - With reference to FIG. 2, an inside
air temperature sensor 28 measures an inside air temperature of the passenger compartment. An outsideair temperature sensor 29 measures an outside air temperature of the passenger compartment. Asolar radiation sensor 30 measures the amount of solar radiation reaching the interior of the passenger compartment. An exteriorrefrigerant sensor 31 measures a temperature of refrigerant at an outlet of theexterior heat exchanger 15. Apost-evaporator sensor 32 measures a temperature (hereinafter called “post-evaporator temperature”) of air right after passing through theinterior evaporator 10. Apressure sensor 33 measures a pressure (hereinafter called “high pressure) of refrigerant at the high pressure side of therefrigerant cycle system 9. Signals outputted from these sensors 28-33 are fed to input terminals of thecontrol device 27. Furthermore, signals outputted from an air conditioning setting member (such as a temperature setting unit) provided on acontrol panel 34 are also fed to the input terminals of thecontrol device 27. - The signals outputted from the sensors28-33 and the signals outputted from the
control panel 34 are converted from analog to digital by the A/D converter circuit before entering the microcomputer. - Control signals are outputted from output terminals of the
control device 27 to theblower motor 8, theservo motors exterior fan motor 24 and theinverter 26. - A control process that is carried out by the microcomputer when the key switch is turned on will be discussed with reference to a flow diagram shown in FIG. 3.
- When a control routine shown in FIG. 3 starts, an initialization is performed at
step 100. Then, atstep 110, the signals from the sensors 28-33 and the signals from thecontrol panel 34 are read. Next, atstep 120, a target air temperature TAO that is a target temperature of air blown into the passenger compartment from the air conditioning system is computed according to the following equation (1) stored in the ROM: - TAO(° C.)=Kset×Tset−Kr×Tr−Kam×Tam−Ks×Ts+C (1)
- where:
- Tset is a set air temperature of the passenger compartment set by the vehicle passenger through the temperature setting unit provided on the
control panel 34; - Tr is the inside air temperature measured by the inside
air temperature sensor 28; - Tam is the outside air temperature measured by the outside
air temperature sensor 29; - Ts is the amount of solar radiation measured by the
solar radiation sensor 30; - Kset, Kr, Kam and Ks are gains; and
- C is a constant.
- Then, at
step 130, an air suction mode is selected between the inside air mode and the outside air mode based on the target air temperature TAO using a control characteristic (not shown). Then, control moves to step 140 where a blower voltage applied to theblower motor 8 is controlled based on the TAO using a control characteristic (not shown). - At
step 150, an operation mode is selected among the cooling mode, the blowing mode and the heating mode based on a difference between the TAO and a sucked air temperature Tin, as shown in FIG. 4. The sucked air temperature Tin is the inside air temperature Tr (Tin=Tr) during the inside air mode, and is the outside air temperature Tam (Tin=Tam) during the outside air mode. - During the cooling mode, the
exterior fans 23 are operated. Furthermore, in therefrigerant cycle system 9, thesolenoid valve 19 is opened, and thesolenoid valves refrigerant cycle system 9 is circulated through thecompressor 14, theinterior condenser 11, theexterior heat exchanger 15, the coolingcapillary tube 17, theinterior evaporator 10, theaccumulator 18 and thecompressor 14 in this order. In addition, in the interiorair conditioning unit 1, theair mixing door 12 is positioned to completely close off an inlet opening of theinterior condenser 11 so that all air bypasses theinterior condenser 11. - During the blowing mode, both the
compressor 14 and theexterior fans 23 are turned off. - During the heating mode, the
exterior fans 23 are operated. Furthermore, in therefrigerant cycle system 9, thesolenoid valves solenoid valve 20 is opened. In this way, refrigerant in therefrigerant cycle system 9 is circulated through thecompressor 14, theinterior condenser 11, theheating capillary tube 16, theexterior heat exchanger 15, theaccumulator 18 and thecompressor 14 in this order. In addition, in the interiorair conditioning unit 1, theair mixing door 12 is positioned to fully open the inlet opening of theinterior condenser 11 so that all air passes through theinterior condenser 11. - At the following
step 160, the rotational speed (i.e., rotation number) of thecompressor 14 is controlled as follows for each of the cooling mode and the heating mode. During the blowing mode, the control operation ofstep 160 is not performed. - (Cooling Mode)
- First, a deviation En between the target air temperature TAO and the post-evaporator temperature TE measured by the
post-evaporator temperature sensor 32, is computed according to the following equation (2). - E n =TAO−TE (2)
- Then, a change rate Edot of the deviation En is computed according to the following equation (3).
- E dot =E n −E n-1 (3)
- In this embodiment, En is renewed every four seconds, so that En-1 is a previous value obtained four seconds before En.
- Then, a change rate Δf of the compressor rotational speed which increases or decreases relative to the previous rotational speed fn-1 of the
compressor 14 measured four seconds before, is computed. The change rate Δf of the compressor rotational speed is computed through a fuzzy logic based on membership functions shown in FIGS. 5A and 5B and also based on rule values shown in FIG. 6 using the above computed En and Edot. The membership functions and the rule table are stored in the ROM. Specifically, based on CF1 obtained from FIG. 5A and CF2 obtained from FIG. 5B, a goodness of fit CF is computed according to the following equation (4). - CF=CF1×CF2 (4)
- Then, based on the computed goodness of fit CF and a rule value obtained from FIG. 6, the change rate Δf of the compressor rotational speed is computed according to the following equation (5).
- Δf=Σ(CF×rule value)/ΣCF (rpm/4 sec) (5)
- A next compressor rotational speed fn is computed according to the following equation (6).
- f n =f n-1 +Δf (rpm/4 sec) (6)
- Then, the energization of the
inverter 26 is controlled in such a way that an actual compressor rotational speed becomes the computed next compressor rotational speed fn. - (Heating Mode)
- During the heating mode, a target pressure (hereinafter called “target high pressure”) SPO of refrigerant in the high pressure side of the
refrigerant cycle system 9 is determined based on the target air temperature TAO. Then, a deviation En between the target high pressure SPO and the high pressure SP measured by thepressure sensor 33 is computed according to the following equation (7). - E n =SPO−SP (7)
- Then, a rate of change Δf of the compressor rotational speed, which increases or decreases relative to the previous compressor rotational speed fn-1 measured four seconds before, is computed. The change rate Δf of the compressor rotational speed is computed through a fuzzy logic based on membership functions shown in FIGS. 7A and 7B and also based on a rule table shown in FIG. 8 using the above computed En and Edot. The membership functions and the rule table are stored in the ROM. Specifically, based on CF1 obtained from FIG. 7A and CF2 obtained from FIG. 7B, a goodness of fit CF is computed according to the above equation (4). Then, based on the computed goodness of fit CF and a rule value obtained from the rule table shown in FIG. 8, the change rate Δf of the compressor rotational speed is computed according to the above equation (5).
- Thereafter, a next compressor rotational speed fn is computed according to the above equation (6). Then, the energization of the
inverter 26 is controlled in such a way that an actual compressor rotational speed becomes the computed next compressor rotational speed fn. - In the above-described control operation of the compressor rotational speed, when the high pressure SP becomes abnormally high, a torque applied on an output shaft (not shown) of the
electric motor 25 becomes high, thereby causing overheating and braking of a winding (not shown) of theelectric motor 25. In the present embodiment, a control operation (hereinafter called “a protective control operation of thecompressor 14”) for preventing an occurrence of such an incidence is carried out. - The protective control operation of the
compressor 14 is a main feature of the present embodiment and thereby is described in detail with reference to FIG. 9. Similar to the routine shown in FIG. 3, a routine shown in FIG. 9 starts when the key switch is turned on. - When the routine shown in FIG. 9 starts, control routine moves to step200 where it is determined whether the current operation mode is the cooling mode. When the operation mode is the cooling mode, control routine moves to step 210. When the operation mode is not the cooling mode, control routine moves to step 220.
- At
step 210, it is determined whether a predetermined time period (2 minutes, for example) has elapsed from time of switching on of the key switch, i.e., from time of startup of thecompressor 14. In this embodiment, the predetermined time period is the time period required for refrigerant at the outlet of theexterior heat exchanger 15 to be completely turned into liquid refrigerant from the time of startup of thecompressor 14 during the cooling mode. - If the determination at
step 210 is “YES”, control routine proceeds to step 220. If the determination atstep 210 is “NO”, control routine proceeds to step 230. - Protective values for limiting the high pressure SP during a normal operating period are set at
step 220. That is, a first protective value SPa is set to 27.5 kg/cm2G. A high-pressure side second protective value SPb is set to 24 kg/cm2G. A low-pressure side second protective value SPc is set to 22 kg/cm2G. - The first protective value SPa is set around an upper tolerable pressure limit of the
compressor 14 to prevent a failure of the compressor 14 (electric motor 25), that may be caused when thecompressor 14 is operated while the high pressure of therefrigerant cycle system 9 is abnormally high. - The second protective values SPb and SPc are set below the first protective value SPa in order to prevent the high pressure SP from reaching the first protective value SPa. The low-pressure side second protective value SPc is lower than the high-pressure side second protective value SPb.
- At
step 230, protective values for limiting the high pressure SP during the startup period of thecompressor 14 are set. That is, a first protective value SPa is set to 27.5 kg/cm2G. The high-pressure side second protective value SPb is set to 23 kg/cm2G. The low-pressure side second protective value SPc is set to 19 kg/cm2G. - In other words, the second protective values SPb and SPc before elapse of the predetermined time period are set lower than the second protective values SPb and SPc after the elapse of the predetermined time period, respectively. Furthermore, a difference between the high-pressure side second protective value SPb and the low-pressure side second protective value SPc before the elapse of the predetermined time period is set greater than a difference between the high-pressure side second protective value SPb and the low-pressure side second protective value SPc after the elapse of the predetermined time period.
- At the
next step 240, it is determined whether the high pressure SP is higher than the first protective value SPa. If the determination atstep 240 is “YES”, control routine moves to step 250 where thecompressor 14 is forcefully turned off. If the determination atstep 240 is “NO”, control routine moves to step 260. - At
step 260, it is determined whether the high pressure SP is higher than the high-pressure side second protective value SPb. If the determination atstep 260 is “YES”, control routine moves to step 270. Atstep 270, the change rate Δf of the compressor rotational speed is set to −600 rpm/4 sec to forcefully reduce the compressor rotational speed fn. If the determination atstep 260 is “NO”, control moves to step 280. In this embodiment, as is obvious from the rule table shown in FIG. 6, −600 rpm/4 sec is the change rate Δf of the compressor rotational speed required for achieving a maximum degree of reduction in the compressor rotational speed fn. - At
step 280, it is determined whether the high pressure SP is higher than the low-pressure side second protective value SPc. If the determination atstep 280 is “YES”, control routine moves to step 290 where the change rate Δf of the compressor rotational speed is set to zero, thereby forcefully maintaining the current compressor rotational speed fn. - According to the above-described embodiment, the second protective values SPb and SPc before the elapse of the predetermined time period are lower than the second protective values SPb and SPc after the elapse of the predetermined time period, respectively.
- In this way, even if the high pressure SP rises quickly at the startup of the
compressor 14, the compressor rotational speed fn is forcefully reduced and maintained at the early stage, so that the high pressure SP is effectively prevented from exceeding the first protective value SPa, thereby preventing the forceful stop of thecompressor 14. - The difference between the high-pressure side second protective value SPb and the low-pressure side second protective value SPc before the elapse of the predetermined time period is increased in comparison to the difference between the high-pressure side second protective value SPb and the low-pressure side second protective value SPc after the elapse of the predetermined time period. Thus, the time period provided for maintaining the rotational speed fn is lengthened, allowing prevention of problematic hunting of the high pressure SP at the startup of the
compressor 14. - Although the present invention has been fully described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.
- For example, in the above embodiment, the high-pressure side second protective value SPb and the low-pressure side second protective value SPc are provided as the second protective value. Furthermore, both the high-pressure side second protective value SPb and the low-pressure side second protective value SPc before the elapse of the predetermined time period are set below the high-pressure side second protective value SPb and the low-pressure side second protective value SPc after the elapse of the predetermined time period, respectively. Alternatively, only one of the high-pressure side second protective value SPb and the low-pressure side second protective value SPc before the elapse of the predetermined time period can be set below the corresponding one of the high-pressure side second protective value SPb and the low-pressure side second protective value SPc after the elapse of the predetermined time period.
- Furthermore, instead of providing both the high-pressure side second protective value SPb and the low-pressure side second protective value SPc as the second protective value, it is possible to use only one of the high-pressure side second protective value SPb and the low-pressure side second protective value SPc.
- In the above-described embodiment, the difference between the high-pressure side second protective value SPb and the low-pressure side second protective value SPc before the elapse of the predetermined time period is made greater than the difference between the high-pressure side second protective value SPb and the low-pressure side second protective value SPc after the elapse of the predetermined time period. This can be accomplished without lowering the low-pressure side second protective value SPc by setting the high-pressure side second protective value SPb before the elapse of the predetermined time period to be higher than the high-pressure side second protective value SPb after the elapse of the predetermined time period.
- In the above-described embodiment, whether the high pressure SP exceeds each one of the protective values SPa, SPb and SPc is determined by measuring the high pressure SP with the
pressure sensor 33 and comparing the measured high pressure SP with each one of the protective values SPa, SPb and SPc. However, the high pressure SP can be estimated based on, for example, an output electric current of theinverter 26. - In the above-described embodiment, “the predetermined time period” is the time period required for refrigerant discharged from the outlet of the
exterior heat exchanger 15 to be completely turned into liquid refrigerant after the startup of thecompressor 14 during the cooling mode. However, “the predetermined time period” can be made longer than this time period. - In the above-described embodiment, the
capillary tubes - In the above-described embodiment, the target rotational speed fn of the
compressor 14 is automatically determined based on a thermal load of the vehicle interior atstep 160. Alternatively, the target rotational speed fn can be determined based on the set air temperature of the passenger compartment, that is set through the temperature setting unit. - Furthermore, in the above-described embodiment, when the high pressure SP exceeds each one of the protective values SPa, SPb and SPc, the protective control operation is carried out by changing the rotational speed of the
compressor 14. Instead of changing the rotational speed of thecompressor 14, a displacement of the compressor can be changed. - In the above-described embodiment, during the predetermined time period after the startup of the
compressor 14, the second protective values SPb and SPc are set to be lowered, and the difference between the high-pressure side second protective value SPb and the low-pressure side second protective value SPc is made larger. Although this operation is only conducted during the cooling mode in the above-described embodiment, this operation can be also conducted during the heating mode. - In the above-described embodiment, the temperature of air blown out from the air conditioning system is controlled through the fuzzy logic. This temperature can be controlled through any other means.
- In the above-described embodiment, the present invention is typically applied to the air conditioning system of the electric vehicle. The present invention is not limited to this and can be applied to an air conditioning system of an engine vehicle or a hybrid vehicle or an air conditioning system of a home or a building.
- Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.
Claims (12)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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JP2000-060459 | 2000-03-06 | ||
JP2000-60459 | 2000-03-06 | ||
JP2000060459A JP4273613B2 (en) | 2000-03-06 | 2000-03-06 | Air conditioner |
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US20010018831A1 true US20010018831A1 (en) | 2001-09-06 |
US6381971B2 US6381971B2 (en) | 2002-05-07 |
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US09/795,542 Expired - Lifetime US6381971B2 (en) | 2000-03-06 | 2001-02-28 | Air conditioning system with compressor protection |
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Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
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US20040206102A1 (en) * | 2003-04-16 | 2004-10-21 | Toshinobu Homan | Air conditioner with control of compressor |
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Publication number | Publication date |
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JP4273613B2 (en) | 2009-06-03 |
JP2001248881A (en) | 2001-09-14 |
US6381971B2 (en) | 2002-05-07 |
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