Vehicle air conditioner using a hybrid compressor

BACKGROUND OF THE INVENTION

This application claims priority to prior applications JP 2002-014032, JP 2002-015391, and JP 2002-015393, the disclosures of which are incorporated herein by reference.

This invention relates to an air conditioner for a vehicle and particular to an air conditioner comprising a hybrid compressor which is adapted to obtain drive force from a prime mover, i.e., an engine mounted on the vehicle and from an electric motor different from the prime mover.

There is known an air conditioner mounted on a vehicle, i.e., an automobile. Such an automobile air conditioner includes a refrigerating or refrigerant cycle. The refrigerating cycle comprises a compressor connected as one of components thereof. The compressor may be of a type driven by an automobile engine or a type driven by a special electric motor mounted on an automobile.

Japanese Unexamined Utility Model Publication No. H6-87678 (JP 6-87678 U) discloses an automotive air conditioner using a compressor which can be driven by one of an automobile engine and an electric motor, i.e., a hybrid compressor. In the automotive air conditioner, the compressor is driven by the automobile engine when the automobile engine is operated. When the automobile engine is stopped, the compressor is driven by the electric motor.

However, in case where the compressor is driven by the automobile engine, a driving speed of the compressor depends upon the rotation speed of the engine. If an air-conditioning load is great, an air-conditioning ability may sometimes be insufficient. On the other hand, if the compressor is driven by the electric motor, the rotation speed of the compressor is restricted if the capacity of an electric power source of the automobile is insufficient. In this case also, if the air-conditioning load is great, the air-conditioning ability may sometimes be insufficient. The above-mentioned disadvantages result from the fact that the compressor is driven only by a selected one of the automobile engine and the electric motor.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an air conditioner for a vehicle, using a hybrid compressor and capable of achieving an excellent air-conditioning ability.

It is another object of the present invention to provide an air conditioner of the type described, which is improved in performance by appropriately controlling operation of a hybrid compressor.

It is still another object of the present invention to provide an air conditioner of the type described, which allows reduction in power consumption of a hybrid compressor during high-speed rotation of a prime mover as well as decrease in torque shock known in the art.

It is yet another object of the present invention to provide an air conditioner of the type described, which is capable of minimizing variation in air-conditioning ability even if the rotation speed of a prime mover for driving a hybrid compressor is varied.

It is a further object of the present invention to provide an air conditioner of the type described, in which an electric motor for driving a hybrid compressor can be optimally controlled even if an electric power is restricted.

It is a still further object of the present invention to provide an air conditioner of the type described, which is capable of minimizing variation in air-conditioning ability when a hybrid compressor is driven simultaneously by both of a prime mover and an electric motor.

Other objects of the present invention will be clear as the description proceeds.

According to an aspect of the present invention, there is provided an air conditioner for a vehicle, comprising a hybrid compressor which includes a first compression mechanism driven by a first drive source, a second compression mechanism driven by a second drive source, and a single discharge port connected to the first and the second compression mechanisms, a refrigerating cycle connected to the hybrid compressor, and a controller connected to the hybrid compressor for controlling an operation of the hybrid compressor in accordance with a control mode, the controller includes an operation mode setting portion for setting a first operation mode in which the first compression mechanism alone is driven, a second operation mode in which the second compression mechanism alone is driven, a third operation mode in which the first and the second compression mechanisms are simultaneously driven, and a fourth operation mode in which the first and the second compression mechanisms are simultaneously stopped, and a mode selecting portion connected to the operation mode setting portion for selecting, as the control mode, one of the first, the second, the third, and the fourth operation modes.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1

is a system diagram of an air conditioner according to a first embodiment of the present invention;

FIG. 2

is a block diagram of a controller in the air conditioner illustrated in

FIG. 1

;

FIG. 3

is a system diagram of an air conditioner according to a second embodiment of the present invention;

FIG. 4

is a block diagram of a controller in the air conditioner illustrated in

FIG. 3

;

FIG. 5

is a system diagram of an air conditioner according to a third embodiment of the present invention;

FIG. 6

is a block diagram of a controller in the air conditioner illustrated in

FIG. 5

;

FIG. 7

is a block diagram of another controller which can be used in the air conditioner illustrated in

FIG. 5

;

FIG. 8

is a system diagram of an air conditioner according to a fourth embodiment of the present invention;

FIG. 9

is a block diagram of a controller in the air conditioner illustrated in

FIG. 8

;

FIG. 10

is a system diagram of an air conditioner according to a fifth embodiment of the present invention;

FIG. 11

is a view showing the relationship between an automobile speed and a heat load upon a refrigerating cycle, illustrating an example of a compressor drive source switching condition;

FIGS. 12A and 12B

are views showing the relationship between an automobile speed and an outside air temperature, illustrating an example of the compressor drive source switching condition in presence and in absence of solar irradiation, respectively;

FIG. 13

is a system diagram of an air conditioner according to a sixth embodiment of the present invention;

FIG. 14

is a block diagram of a controller in the air conditioner illustrated in

FIG. 13

;

FIG. 15

is a control characteristic chart showing an example of the relationship between an engine rotation speed and a motor target rotation speed in the controller illustrated in

FIG. 14

;

FIG. 16

is a characteristic chart showing an example of control in the controller illustrated in

FIG. 14

, in which the rotation speed and input electric power of an electric motor are controlled during electric power restriction;

FIG. 17

is a control characteristic chart showing an example in case where the electric motor is controllably turned on and off; and

FIG. 18

is a sectional view of a hybrid compressor which can be used in the air conditioner illustrated in each of

FIGS. 1

,

3

,

5

,

8

,

10

, and

13

.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although description will be made as regards an air conditioner which is mounted on an automobile and therefore may be called hereinunder an automobile air conditioner, the present invention is broadly applicable to various air conditioners for a vehicle without being limited only to the automobile air conditioner.

Referring to

FIG. 1

, description will be made about an air conditioner according to a first embodiment of the present invention.

To a refrigerating cycle

1

, a hybrid compressor

4

is connected as one of components thereof. The hybrid compressor

4

comprises a first compression mechanism driven by an automobile prime mover alone and a second compression mechanism driven by an electric motor alone and integrally coupled to the first compression mechanism. The automobile prime mover, i.e., an engine

2

generates drive force which can be transmitted through a belt and an electromagnetic clutch

3

to the first compression mechanism of the hybrid compressor

4

. The electric motor

5

generates drive force which can be transmitted directly to the second compression mechanism of the hybrid compressor

4

. A specific example of the hybrid compressor

4

will later be described in detail.

In the refrigerating cycle

1

, a high-temperature high-pressure refrigerant compressed by the hybrid compressor

4

is supplied to a condenser

6

as an external heat exchanger and cooled by heat exchange with outside air to be condensed and put into a liquid phase. The refrigerant is separated by a liquid receiver

7

into a gaseous-phase refrigerant and a liquid-phase refrigerant. The liquid-phase refrigerant is reduced in pressure by an expansion valve

8

into a low-pressure liquid-phase refrigerant. The low-pressure refrigerant flows into an evaporator

9

as an internal heat exchanger and is subjected to heat exchange with air blown by a fan or a blower

12

to be evaporated into a gaseous-phase refrigerant. The gaseous-phase refrigerant is sucked again into the hybrid compressor

4

to be compressed.

An air duct

13

for passage of air for room air-conditioning is provided with the blower

12

, the evaporator

9

, an air-mix damper

10

, and a heater core

11

. After passing through the evaporator

9

, the air passes through the heater core

11

at a ratio determined by an aperture of the air-mix damper

10

to be heated. On a downstream end of the air duct

13

, discharge ports

41

,

42

, and

43

such as DEF, VENT, and FOOT are formed. By dampers (not shown) corresponding to the respective discharge ports, a predetermined one or ones of the discharge ports are selected to deliver conditioned air into a room.

The automotive air conditioner illustrated in

FIG. 1

has an evaporator outlet air temperature sensor

14

for detecting an evaporator outlet air temperature Toff, i.e., an air temperature after the air passes through the evaporator

9

. The evaporator outlet air temperature sensor

14

produces a signal representative of the evaporator outlet air temperature Toff thus detected and supplies the signal to an air-conditioning controller

15

. Furthermore, the air-conditioning controller

15

is supplied with a signal group

16

representative of an outside air temperature Tout, a room air temperature Tr, a switching damper position INT of an inside/outside air switching damper

19

, an engine rotation speed Ne, a blower voltage BLV, and an evaporator inlet air temperature Teva. As output signals, an electric motor rotation speed control signal

17

and a clutch control signal

18

are produced.

When the second compression mechanism of the hybrid compressor

4

is driven by the electric motor

5

, the clutch

3

is turned off by the clutch control signal

18

. Then, the electric motor rotation speed control signal

17

as a duty signal is supplied to the electric motor

5

to control the rotation speed of the electric motor

5

. On the other hand, in case where the first compression mechanism of the compressor

4

is driven by the engine

2

, output of the electric motor rotation speed control signal

17

is stopped and the clutch

3

is turned on.

In case where the hybrid compressor

4

is driven simultaneously by the engine

2

and the electric motor

5

, the clutch

3

is turned on by the clutch control signal

18

and the electric motor rotation speed control signal

17

as a duty signal is supplied to the electric motor

5

to control the rotation speed of the electric motor

5

.

The air temperature after the air passes through the evaporator

9

is controlled by controlling the motor rotation speed and by controlling one/off of the clutch when the compressor is driven by the electric motor

5

and when the compressor is driven by the engine

2

, respectively.

Referring to

FIG. 2

in addition, an operation of the air-conditioning controller

15

will be described.

With reference to the evaporator outlet air temperature Toff, the outside air temperature Tout, the room air temperature Tr, the switching damper position INT of the inside/outside air switching damper

19

, the engine rotation speed Ne, the blower voltage BLV, and the evaporator inlet air temperature Teva, the air-conditioning controller

15

estimates and calculates power consumption or refrigerating ability LB which is given by:

LB=f(INT, Tout, Ne, Tr, BLV, Teva, Toff).

Herein, the air-conditioning controller

15

serves as a power estimating portion or an ability estimating portion.

With reference to the power consumption or the refrigerating ability LB, the air-conditioning controller

15

serves as a compressor drive control portion and controls driving of the hybrid compressor

4

in accordance with a control mode which will presently be described.

In the air-conditioning controller

15

, selection is made of a first operation mode in which the first compression mechanism alone is driven, a second operation mode in which the second compression mechanism alone is driven, and a third operation mode in which the first and the second compression mechanisms are simultaneously driven, and a fourth operation mode in which the first and the second compression mechanisms are simultaneously stopped. In this case, the air-conditioning controller

15

serves as an operation mode setting portion.

Furthermore, the air-conditioning controller

15

selects, as the control mode, one of the first, the second, the third, and the fourth operation modes with reference to the power consumption or the refrigerating ability LB. In this case, the air-conditioning controller

15

serves as a mode selecting portion.

Referring to

FIG. 3

, description will be made of an automotive air conditioner according to a second embodiment of the present invention. Similar parts are designated by like reference numerals and description thereof will be omitted. In this automotive air conditioner also, the air-conditioning controller

15

selects, as the control mode, one of the first, the second, the third, and the fourth operation modes.

In the automotive air conditioner illustrated in

FIG. 3

, the signal representative of the air temperature detected by the evaporator outlet air temperature sensor

14

is supplied to the air-conditioning controller

15

. Furthermore, the air-conditioning controller

15

is supplied with the signal group

16

representative of a condenser inlet air temperature Tcon, a condenser inlet air speed Vcon, the evaporator inlet air temperature Teva, an evaporator inlet air humidity Heva, an evaporator inlet air speed Veva, and the like. The electric motor rotation speed control signal

17

and the clutch control signal

18

are supplied from the air-conditioning controller

15

to the hybrid compressor

4

.

Referring to

FIG. 4

in addition, an operation of the air-conditioning controller

15

will be described.

With reference to the signal group

16

representative of the condenser inlet air temperature Tcon, the condenser inlet air speed Vcon, the evaporator inlet air temperature Teva, the evaporator inlet air humidity Heva, the evaporator inlet air speed Veva, and the like, the air-conditioning controller

15

estimates and calculates a heat load in an automobile, i.e., an air-conditioning load LA given by:

LA=f(Tcon, Vcon, Teva, Heva, Veva).

Herein, the air-conditioning controller

15

serves as a heat load estimating portion.

With reference to the relationship between the air-conditioning load LA and a predetermined value d, the air-conditioning controller

15

serves as a compressor drive control portion and controls driving of the hybrid compressor

4

in accordance with the control mode to select simultaneous operation of the first and the second compression mechanisms or operation of the first or the second compression mechanism. Specifically, if LA≧d, the simultaneous operation is selected. On the other hand, if LA<d, the operation of the first or the second compression mechanism is selected. Thus, when the load is great, the simultaneous operation is selected so as to avoid insufficiency in air-conditioning ability. When the load is small, the operation of the first or the second compression mechanism is selected so as to produce desired air-conditioning ability with small power consumption without affecting other apparatuses and other operating conditions.

Referring to

FIG. 5

, description will be made of an automotive air conditioner according to a third embodiment of the present invention. Similar parts are designated by like reference numerals and description thereof will be omitted. In this automotive air conditioner also, the air-conditioning controller

15

selects, as the control mode, one of the first, the second, the third, and the fourth operation modes.

In the automotive air conditioner illustrated in

FIG. 5

, the signal representative of the evaporator outlet air temperature Toff detected by the evaporator outlet air temperature sensor

14

is supplied to the air-conditioning controller

15

. Furthermore, the air-conditioning controller

15

is supplied with the signal group

16

representative of the outside air temperature Tout, solar irradiation Rsun, the room air temperature Tr, an automobile speed SP, a refrigerant pressure Pd in a high pressure part, and the like. The electric motor rotation speed control signal

17

and the clutch control signal

18

are supplied from the air-conditioning controller

15

to the hybrid compressor

4

.

Referring to

FIG. 6

in addition, an operation of the air-conditioning controller

15

will be described.

With reference to the signals representative of, for example, the outside air temperature Tout, the automobile speed SP, and the solar irradiation Rsun, the air-conditioning controller

15

estimates and calculates the air-conditioning load LA given by:

LA=f(Tout, SP, Rsun).

Herein, the air-conditioning controller

15

serves as a heat load estimating portion.

With reference to the relationship between the air-conditioning load LA and the predetermined value d, the air-conditioning controller

15

serves as a compressor drive control portion and controls driving of the hybrid compressor

4

in accordance with the control mode to select simultaneous operation of the first and the second compression mechanisms or operation of the first or the second compression mechanism. Specifically, if LA≧d, the simultaneous operation is selected. On the other hand, if LA<d, the operation of the first or the second compression mechanism is selected. Thus, when the load is great, the simultaneous operation is selected so as to avoid insufficiency in air-conditioning ability. When the load is small, the operation of the first or the second compression mechanism is selected so as to produce desired air-conditioning ability with small power consumption without affecting other apparatuses or other operating conditions.

Referring to

FIG. 7

in addition to

FIG. 5

, description will be made of another example of the air-conditioning controller

15

. This air-conditioning controller

15

also selects, as the control mode, one of the first, the second, the third, and the fourth operation modes.

In this example, with reference to the signal representative of the high-pressure-part refrigerant pressure Pd, the air-conditioning load LA in the automobile is estimated and calculated by:

LA=f(Pd).

Herein, the air-conditioning controller

15

serves as a heat load estimating portion.

With reference to the relationship between the air-conditioning load LA and the predetermined value d, the air-conditioning controller

15

serves as a compressor drive control portion and controls driving of the hybrid compressor

4

in accordance with the control mode to select simultaneous operation of the first and the second compression mechanisms or operation of the first or the second compression mechanism. Specifically, if LA≧d, the simultaneous operation is selected. On the other hand, if LA<d, the operation of the first or the second compression mechanism is selected. Thus, when the load is great, the simultaneous operation is selected so as to avoid insufficiency in air-conditioning ability. When the load is small, the operation of the first or the second compression mechanism is selected so as to produce a desired air-conditioning ability with small power consumption without affecting other apparatuses or other operating conditions.

Referring to

FIG. 8

, description will be made of an automotive air conditioner according to a fourth embodiment of the present invention. Similar parts are designated by like reference numerals and description thereof will be omitted. In this automotive air conditioner also, the air-conditioning controller

15

selects, as a control mode, one of the first, the second, the third, and the fourth operation modes.

In the automotive air conditioner illustrated in

FIG. 8

, the signal representative of the air temperature detected by the evaporator outlet air temperature sensor

14

is supplied to the air-conditioning controller

15

. Furthermore, the air-conditioning controller

15

is supplied with the signal group

16

representative of the outside air temperature Tout, the room air temperature Tr, the inside/outside air switching damper position INT, the automobile speed SP, the blower voltage BLV, and the evaporator inlet air humidity Heva, and the like. The electric motor rotation speed control signal

17

and the clutch control signal

18

are supplied from the air-conditioning controller

15

to the hybrid compressor

4

.

Referring to

FIG. 9

in addition, an operation of the air-conditioning controller

15

will be described.

With reference to the signal group

16

representative of the inside/outside air switching damper position INT, the outside air temperature Tout, the automobile speed SP, the room air temperature Tr, the blower voltage BLV, the evaporator inlet air humidity Heva, and the like, the air-conditioning controller

15

estimates and calculates the air-conditioning load LA in the automobile by:

 LA=f(INT, Tout, SP, Tr, BLV, Heva).

Herein, the air-conditioning controller

15

serves as a heat load estimating portion.

With reference to the relationship between the air-conditioning load LA and the predetermined value d, the air-conditioning controller

15

serves as a compressor drive control portion and controls driving of the hybrid compressor

4

in accordance with the control mode to select simultaneous operation of the first and the second compression mechanisms or operation of the first or the second compression mechanism. Specifically, if LA≧d, the simultaneous operation is selected. On the other hand, if LA<d, the operation of the first or the second compression mechanism is selected. Thus, when the load is great, the simultaneous operation is selected so as to avoid insufficiency in air-conditioning ability. When the load is small, the operation of the first or the second compression mechanism is selected so as to produce desired air-conditioning ability with small power consumption without affecting other apparatuses or other operating conditions.

With each of the above-mentioned automotive air conditioners in

FIGS. 1

,

3

,

5

, and

8

, the drive systems of the hybrid compressor is appropriately switched so that sufficiently large air-conditioning ability can be exhibited in dependence upon the situations, thereby avoiding insufficiency in air-conditioning ability. Furthermore, in dependence upon various other conditions related to the heat load of the automobile, the operation of one of the prime mover and the electric motor and the simultaneous operation by both of these drive sources can be optimally switched. As a consequence, it is possible to achieve optimal control of air-conditioning under any situation. As a result, it is possible to realize both of comfortable air-conditioning and power saving.

Referring to

FIG. 10

, description will be made of an automotive air conditioner according to a fifth embodiment of the present invention. Similar parts are designated by like reference numerals and description thereof will be omitted. In this automotive air conditioner also, the air-conditioning controller

15

selects, as the control mode, one of the first, the second, the third, and the fourth operation modes.

In the automotive air conditioner illustrated in

FIG. 10

, the signal representative of the evaporator outlet air temperature Toff detected by the evaporator outlet air temperature sensor

14

is supplied to the air-conditioner controller

15

for controlling air-conditioning. Furthermore, the air-conditioning controller

15

is supplied with the signal group

16

including the outside air temperature Tout, the room air temperature Tr, the solar irradiation Rsun, a heater hot water temperature Tw, a residual charge Bt of a battery as electric power supply means (which is detected by electric power source detecting means), the engine rotation speed Ne, the automobile speed SP, and an accelerator aperture ACC. As output signals, the electric motor rotation speed control signal

17

and the clutch control signal

18

are produced.

The air-conditioning controller

15

also serves as selecting means for selecting a compressor drive source. In case where the hybrid compressor

4

is driven by the electric motor

5

, the air-conditioning controller

15

is responsive to the clutch control signal

18

and turns off the clutch

3

. Then, the air-conditioning controller

15

supplies the electric motor

5

with the electric motor rotation speed control signal

17

as a duty signal to control the rotation speed of the electric motor

5

. On the other hand, in case where the compressor

4

is driven by the engine

2

, the air-conditioning controller

15

stops output of the electric motor rotation speed control signal

17

and turns on the clutch

3

. Thus, the evaporator outlet air temperature Toff is controlled by controlling the rotation sped of the electric motor

5

and by controlling on/off of the clutch or the displacement of the compressor when the compressor is driven by the electric motor

5

and when the compressor is driven by the engine

2

, respectively.

Hereinafter, various embodiments of control will be described.

<Switching Condition upon High-speed Running>

In case where the compressor is driven by the engine, the rotation speed of the compressor is increased following an increase in rotation speed of the engine when the automobile is running at a high speed (for example, 80 km/h to 120 km/h). In a fixed displacement compressor in which the evaporator outlet air temperature Toff is controlled by controlling on/off of the clutch

3

, an on/off cycle of the clutch is shortened following an increase in the driving speed of the compressor so that stop and restart of the compressor are frequently repeated. At the restart of the compressor, torque shock may be caused when the clutch is turned on and additional power will be consumed in order to re-establish a difference in pressure between a discharge side and a suction side. Therefore, while the automobile is running at a high speed so that the on/off cycle of the clutch is shortened, the compressor is driven by the electric motor. In this event, on/off control of the clutch is not carried out. It is therefore possible to prevent occurrence of the torque shock and increase in compressor power consumption as mentioned above.

Not only when the automobile is running at a high speed but also when the heat load upon the refrigerating cycle is low, for example, when the outside air temperature is low, on/off control of the compressor clutch is frequent. Therefore, also in the situation where a refrigerating cycle heat load is low, it is preferable to select the electric motor as the compressor drive source. It is noted here that the refrigerating cycle heat load is a value correlated with the compressor power and estimated by the outside air temperature, the room air temperature, the blower air delivery, the inside/outside air switching mode, the evaporator outlet air temperature Toff, the solar irradiation, and so on.

For example, control may be carried out as illustrated in FIG.

11

. Specifically, as the refrigerating cycle heat load is increased, a switching point of switching from the engine into the electric motor is set at a higher automobile speed. It is assumed that the automobile speeds at the switching points under the refrigerating cycle heat loads q

1

and q

2

are represented by s

1

and s

2

, respectively. Then, if q

1

>q

2

, the relationship s

1

≧s

2

holds true. Thus, when the refrigerating cycle heat load is reduced and when the automobile speed (or the engine rotation speed) is increased, the compressor is driven by the electric motor.

It is preferable that, by detecting the three factors including the outside air temperature Tout (during introduction of the outside air) or the room air temperature Tr (during circulation of the inside air), the evaporator inlet air temperature Teva, and the blower voltage BLV, the refrigerating cycle heat load Q is estimated by:

(during introduction of outside air)

Q = f(Tout, Teva, BLV)

(during circulation of inside air)

Q = f(Tr, Teva, BLV)

Alternatively, the refrigerating cycle heat load may be estimated by the outside air temperature and the solar irradiation. In this case, as illustrated in

FIGS. 12A and 12B

, the switching point is changed in dependence upon presence/absence of solar irradiation to determine the compressor drive source. Since the refrigerating cycle heat load during introduction of the outside air is different from that during circulation of the inside air, the switching point may be changed in dependence upon the introduction or the circulation mode. Herein, let the automobile speeds of the switching points at particular outside air temperatures t

1

and t

2

be represented by s

1

and s

2

, respectively. Then, if t

1

>t

2

, the relationship s

1

≧s

2

holds true. Thus, when the outside air temperature is lowered and when the automobile speed is increased, the compressor is driven by the electric motor.

<Compressor drive source Switching Control When Automobile is Stopped>

It is assumed that the automobile is in an idling state and that the engine is automatically stopped by an idling stop mechanism, for example, in a hybrid automobile. In this event, the drive force of the engine is not available. In view of the above, it is preferable that to detect the engine rotation speed and, if the engine rotation speed is not higher than a predetermined value (for example, not higher than 1000 rpm), to drive the compressor by the electric motor.

<Requirements for Electric Motor Drive>

Basically, the compressor drive source is determined by the above-mentioned switching conditions. It is noted here that, in order to use the electric motor as the compressor drive source, the under-mentioned conditions must be met.

<Switching Condition by Refrigerating Cycle Heat Load>

In summer, the room air temperature at the start of the air conditioner is often kept at a high temperature of 60-70° C. After the air conditioner is started, a seat, a dashboard, and other parts hold heat. Therefore, if the ability of the compressor is insufficient, the room air temperature may quickly be elevated by after heat of the seat and the like.

In view of the above, if the electric motor alone is selected as the compressor drive source and if the room air temperature is quickly elevated because of a large amount of after heat of the seat and the like, the engine must immediately be selected as the compressor drive source. Therefore, if the compressor drive source is switched from the engine into the electric motor alone and when the room air temperature after switching is elevated by a predetermined value Ty° C. (for example, 5° C.) or more with respect to the room air temperature at the time instant of switching, the engine should be selected as the compressor drive source at the time instant of temperature elevation by the predetermined value.

If the value of Ty is too small, idle stop will be canceled every time so that the engine will be operated when the automobile is stopped at a red light. Therefore, the value of Ty is preferably equal to about 5° C.

Consideration will be made about the case where the room air temperature is slowly elevated while the compressor is driven by the electric motor alone. In this case, if Ty is equal to 5° C., it takes a time before the room air temperature is elevated by 5° C. from a desired temperature. This may result in long-time continuation of an uncomfortable situation where the room air temperature is higher than the desired temperature. Taking the above into consideration, the value of Ty is reduced by a preselected value at the time instant when a predetermined time period (for example, one minute) has lapsed after the drive source is switched into the electric motor. For example, Ty may be changed from 5° C. to 3° C. In this event, if the room air temperature is elevated by 3° C. or more from the desired temperature, the drive source is switched from the electric motor into the engine. It is therefore possible to prevent long-time continuation of the uncomfortable situation where the room air temperature is elevated by 5° C. or more from the desired temperature.

Thus, with the automotive air conditioner illustrated in

FIG. 10

, it is possible to reduce power consumption of the compressor particularly when the automobile is running at a high speed and to prevent occurrence of large torque shock particularly when the compressor is rotated at a high speed.

Referring to

FIG. 13

, description will be made of an automotive air conditioner according to a sixth embodiment of the present invention. Similar parts are designated by like reference numerals and description thereof will be omitted. In this automotive air conditioner also, the air-conditioning controller

15

selects, as the control mode, one of the first, the second, the third, and the fourth operation modes.

In the automotive air conditioner illustrated in

FIG. 13

, the air duct

13

is provided with an outside air inlet port

22

and an inside air inlet port

23

formed on an inlet or upstream end thereof and switched by the switching damper

19

in order to select sucked air. Furthermore, by adjusting an aperture of the air-mix damper

10

using an air-mix damper actuator

21

, a mixing ratio of the air passing through the evaporator

9

alone and the air passing through the heater core

11

is adjusted. On a downstream end of the air duct

13

, the discharge ports

41

,

42

, and

43

such as DEF, VENT, and FOOT are formed. By dampers

24

,

25

, and

26

, a predetermined one or ones of the discharge ports are selected.

The air-conditioning controller

15

includes a main controller

31

and a clutch drive

32

for controllably driving the electromagnetic clutch

3

. The main controller

31

supplies the above-mentioned clutch control signal to the clutch drive

32

, a motor control signal to a motor drive of the electric motor

5

, and an air-mix damper aperture signal to the air-mix damper actuator

21

.

Referring to

FIG. 14

in addition, description will continue.

Various sensors for controlling air-conditioning include the evaporator outlet air temperature sensor

14

for detecting the evaporator outlet air temperature Toff, a room air temperature sensor

27

for detecting the room air temperature Tr, an outside air temperature sensor

28

for detecting the outside air temperature Tout, and a solar irradiation sensor

29

for detecting the solar irradiation Rsun.

The main controller

31

includes a switching time motor target rotation speed calculator

33

, a motor rotation speed feedback calculator

34

, a drive source switching controller

35

, a clutch drive controller

36

, a motor target rotation speed calculator

37

, and a motor drive controller

38

. The switching time motor target rotation speed calculator

33

is supplied with the engine rotation speed signal Ne and calculates a first motor target rotation speed Nmo

1

. The motor rotation speed feedback calculator

34

calculates a second motor target rotation speed Nmo

2

with reference to an evaporator temperature target value To and the evaporator outlet air temperature Toff. The drive source switching controller

35

produces a switching control signal with reference to the high-pressure-part refrigerant pressure Pd, the automobile speed SP, the solar irradiation Rsun, and the outside air temperature Tout. The clutch drive controller

36

produces the clutch signal with reference to the evaporator temperature target value To and the evaporator outlet air temperature Toff. The motor target rotation speed calculator

37

calculates the sum of the first and the second motor target rotation speeds Nmo

1

and Nmo

2

to produce a motor target rotation speed Nmo. By the use of the motor target rotation speed Nmo, a motor rotation speed Nm, motor electric power consumption W, and the switching control signal, the motor drive controller

38

calculates a motor drive control signal D given by:

D=f(Nmo,Nm).

If W>C, the motor drive control signal D is not increased. Herein, C represents a predetermined value of motor input electric power. The motor driver control signal D is supplied to a motor drive

39

. The clutch drive

32

controls the operation of the clutch

3

in response to the switching control signal and the clutch signal.

When the hybrid compressor

4

is driven substantially simultaneously by both of the engine

2

and the electric motor

3

, control is carried out in the following manner.

With reference to the engine rotation speed Ne of the automobile, the switching time motor target rotation speed calculator

33

calculates the first motor target rotation speed Nmo

1

as a feed-forward value, given by:

Nmo

1

=f(Ne).

Furthermore, with reference to the evaporator temperature target value To and the evaporator outlet air temperature Toff, the motor rotation speed feedback calculator

33

calculates the second motor target rotation speed Nmo

2

as a feedback value, given by:

Nmo

2

=f(To, Toff).

The motor target rotation speed calculator

37

calculates a sum of the first and the second motor target rotation speeds Nmo

1

and Nmo

2

to produce the motor target rotation speed Nmo as:

Nmo=Nmo

1

+Nmo

2

.

The motor target rotation speed Nmo is supplied to the motor drive controller

38

. With reference to the motor target rotation speed Nmo and the motor rotation speed Nm, the motor drive controller

38

produces the motor drive control signal D given by:

D=f(Nmo,Nm).

The motor drive control signal is delivered to the motor drive

39

to control the rotation speed of the motor.

For example, characteristics illustrated in

FIG. 15

are obtained by the above-mentioned control.

FIG. 15

shows the result of calculation of the motor target rotation speed Nmo with respect to the engine rotation speed Ne under a given condition.

Generally, it is required to drive the hybrid compressor simultaneously by both of the drive sources when the cooling ability of the cooler is insufficient by the use of only one of the drive sources. In this event, with respect to the evaporator temperature target value, the motor rotation speed is controlled in response to the variation in engine rotation speed and variation in evaporator outlet air temperature Toff. Basically, the above-mentioned control is carried out, for example, in the following manner.

When the engine rotation speed Ne is reduced, Nmo is increased and Nm is increased.

When the engine rotation speed Ne is increased, Nmo is decreased or maintained and Nm is decreased or maintained.

In the control described in conjunction with

FIG. 14

, the motor rotation speed is controlled in the following manner with reference to the electric power consumption W of the motor and with respect to the predetermined value C of the motor input electric power. A specific example of the control when the electric power is restricted is illustrated in FIG.

16

. Specifically, if the motor input electric power is higher than the predetermined value C, the motor drive control signal D is not increased. For example, the motor rotation speed is decreased. If the motor input electric power is lower than the predetermined value C, control is carried out in the manner similar to that mentioned above.

For example, if the motor can not be controlled (started) at the target rotation speed due to the restriction in electric power or restriction in rotation speed at which the electric motor can be started, the motor rotation speed may be controlled in the following manner. Specifically, the motor is started at a possible start-up rotation speed. At a predetermined time interval, start-up operation of the electric motor (at the rotation speed at which the motor can be started) and motor stop operation or low-speed rotation are repeatedly alternately carried out. An example of the control is illustrated in FIG.

17

. In the figure, the rotation at the rotation speed allowing the electric motor to start up and the stop of the electric motor are repeatedly alternately carried out at the predetermined time interval.

In the control described in conjunction with

FIG. 14

, when the drive source of the compressor is switched, i.e., from the motor drive to the engine drive or from the engine drive to the motor drive, switching control may be carried out, for example, by determining the necessity of switching with reference to the heat load (outside air temperature, solar irradiation, automobile speed, etc.) of the refrigerating cycle of the automobile.

By the above-mentioned control, when the compressor is driven simultaneously by both of the engine and the motor, it is possible to optimally control, particularly, the motor rotation speed in dependence upon the situation, thereby appropriately controlling the temperature of the cooler to suppress the variation in discharge temperature. For the insufficiency in refrigerating ability, appropriate control of the cooler temperature is possible. In case where the electric power is restricted, the rotation speed of the electric motor and consequently the electric power consumption of the electric motor can be appropriately controlled.

Therefore, in the automotive air conditioner illustrated in

FIG. 13

, it is possible to optimally control driving of the compressor when the hybrid compressor is driven simultaneously by both of the drive sources. Even under the situation in which the refrigerating ability of the refrigerating cycle is insufficient, appropriate control of the cooler temperature can be carried out. If the engine rotation speed is varied, appropriate control of the cooler temperature by the electric motor is carried out. It is therefore possible to make a passenger feel comfortable without variation in cooler temperature or discharge temperature. Since the appropriate control by the electric motor can be carried out even if the electric power is restricted, the electric power consumption of the electric motor can be reduced.

With reference to

FIG. 18

, description will be directed to the hybrid compressor

4

.

In

FIG. 18

, the hybrid compressor

4

has a first compression mechanism

51

and a second compression mechanism

52

. The hybrid compressor

4

is used, for example, in a refrigerant cycle of an air conditioning system mounted in a vehicle known in the art.

The first compression mechanism

51

comprises a first fixed scroll

60

having a first fixed end plate

60

a

and a first fixed spiral element

60

b

, a first orbital scroll

61

having a first orbital end plate

61

a

, and a first orbital spiral element

61

b

. The first fixed scroll

60

and the first orbital scroll

61

engage to form a first plurality of pairs of fluid pockets

62

. The first compression mechanism

51

also comprises a first drive shaft

63

, which engages the first orbital scroll

61

and provides an orbital movement to the first orbital scroll

61

, and an electromagnetic clutch

64

corresponding to the above-mentioned clutch

3

. The electromagnetic clutch

64

comprises a clutch armature

64

a

fixed to the first drive shaft

63

, a pulley

64

b

connected to an engine or electric motor (not shown) of a vehicle via a belt (not shown), and an electromagnet

64

c

for connecting and disconnecting the clutch armature

64

a

and the pulley

64

b

. Further, the first compression mechanism

51

comprises a first rotation prevention device

65

for preventing the rotation of the first orbital scroll

61

, and a first inlet port

66

formed through a casing. A first discharge port

60

a

′ is formed through a first surface of the first end plate

60

a

of first fixed scroll

60

. The engine of a vehicle for use in driving first compression mechanism

51

may include either an internal combustion engine or an electric motor for driving a vehicle.

The second compression mechanism

52

comprises a second fixed scroll

70

having a second fixed end plate

70

a

and a second fixed spiral element

70

b

, a second orbital scroll

71

having a second orbital end plate

71

a

and a second orbital spiral element

71

b

. The second fixed scroll

70

and the second orbital scroll

71

engage to form a second plurality of pairs of fluid pockets

72

, the second compression mechanism

52

also comprises a second drive shaft

73

engaging, which engages the second orbital scroll

71

and provides an orbital movement to the second orbital scroll

71

, a second rotation prevention device

74

for preventing the rotation of the second orbital scroll

71

, and a second inlet port

75

formed through the casing. A second discharge port

70

a

′ is formed through a second surface of the second fixed end plate

70

a

of the second fixed scroll

70

. An electric motor

76

is provided for driving the second drive shaft

73

of the second compression mechanism

52

. The electric motor

76

has a rotor

76

a

which is fixed to the second drive shaft

73

and a stator

76

b.

The first fixed scroll

60

of the first compression mechanism

51

and the second fixed scroll

70

of the second compression mechanism

52

are disposed back-to-back, and the fixed scrolls are formed integrally. Thus, together, the end plates

60

a

and

70

a

form a shared end plate. A discharge path

80

is formed between the end plates

60

a

and

70

a

and within the shared end plate. An outlet port

81

is formed at a downstream end of the discharge path

80

. The first discharge port

60

a

′ formed through the first end plate

60

a

of the first compression mechanism

51

and the second discharge port

70

a

′ formed through the second end plate

70

a

of the second compression mechanism

52

are connected to an upstream end of the discharge path

80

via a check valve

82

. The first compression mechanism

51

and the second compression mechanism

52

, thus configured, are formed integrally in the hybrid compressor

4

.

When the hybrid compressor

4

is driven by an engine, the electromagnetic clutch

64

is activated, the rotational output of the engine is transmitted to the first drive shaft

63

of the first compression mechanism

51

via the clutch armature

64

a

, and the first orbital scroll

61

is driven in its orbital movement by the first drive shaft

63

. The refrigerant introduced from the first inlet port

66

flows into the fluid pockets

62

. The fluid pockets

62

move toward the center of the first fixed scroll

60

while being reduced in volume, whereby the refrigerant in the fluid pockets

62

is compressed. The compressed refrigerant is discharged to the discharge path

80

through the first discharge port

60

a

formed through the first end surface of the first end plate

60

a

of the fixed scroll

60

via the check valve

82

. The discharged then flows out to a high pressure side of an external refrigerant circuit through the outlet port

81

.

In this condition, electric power need not be, and generally is not, supplied to the electric motor

76

provided for driving the second drive shaft

73

of second compression mechanism

52

and, consequently, the electric motor

76

does not rotate. Therefore, the second compression mechanism

52

does not operate. Because the second discharge port

70

a

′ of the second compression mechanism

52

is closed by the check valve

82

, the refrigerant discharged from the first compression mechanism

51

does not flow backward into the second compression mechanism

52

.

When the hybrid compressor

4

is driven by the electric motor

76

, the electric motor

76

is activated, the rotational output of the electric motor

76

is transmitted to the second drive shaft

73

of the second compression mechanism

52

, and the second orbital scroll

71

is driven in its orbital movement by the second drive shaft

73

. The refrigerant introduced from the second inlet port

75

flows into the fluid pockets

72

. The fluid pockets

72

move toward the center of the second fixed scroll

70

while being reduced in volume, whereby the refrigerant in the fluid pockets

72

is compressed. The compressed refrigerant is discharged to the discharge path

80

through the second discharge port

70

a

′ formed through the second end surface of the second end plate

70

a

of the second fixed scroll

70

via the check valve

82

, and the discharged refrigerant then flows out to a high pressure side of an external refrigerant circuit through the outlet port

81

.