Hybrid compressor system

BACKGROUND OF THE INVENTION

The present invention relates to a hybrid compressor system including a hybrid compressor, a drive source of which is switched between an electric motor and an engine for driving a vehicle, for compressing refrigerant.

A hybrid compressor in an air conditioning system for a vehicle is disclosed in Japanese Unexamined Patent Publication No. 2002-67673. An electromagnetic clutch is arranged on a power transmission path between the engine and the hybrid compressor. When a drive source of the hybrid compressor is switched from an electric motor to an engine, the electromagnetic clutch is switched on or connected after a rotational speed of the electric motor becomes equal to a rotational speed of the engine.

Therefore, even when the drive source is switched, the hybrid compressor continuously compresses refrigerant. Namely, air conditioning is continuously conducted by the air conditioning system. Therefore, comfortable cooling feeling can be offered. Furthermore, since the drive source is smoothly switched, unpleasant shock caused by a rotational speed differential between the hybrid compressor and the engine upon switching on the electromagnetic clutch can be avoided.

However, a complicated control, in which the electric clutch is switched on after the rotational speed of the electric motor becomes equal to the rotational speed of the engine, is required. Therefore, a computing load on a control device increases.

SUMMARY OF THE INVENTION

The present invention provides a hybrid compressor system that smoothly switches a drive source of a hybrid compressor from an electric motor to an engine without a break of air conditioning and a complicated control.

In accordance with a preferred embodiment of the present invention, a hybrid compressor system has a hybrid compressor for compressing refrigerant, a first drive source, and a second drive source. The first drive source is operatively connected to the compressor through a first power transmission path. The second drive source is operatively connected to the compressor through a second power transmission path. The compressor is selectively driven by one of the first drive source and the second drive source. The hybrid compressor system also includes a first one-way clutch, a driver for driving the second drive source, a sensor for detecting a rotational state of the first drive source and a controller. The first one-way clutch is arranged on the first power transmission path between the compressor and the first drive source for permitting power transmission from the first drive source to the compressor. The controller is electrically connected to the driver and the sensor. When a drive source of the compressor is switched from the second drive source to the first drive source, the controller orders the driver to stop the second drive source after the rotation of the first drive source is detected.

The present invention also provides a method for switching a drive source of a hybrid compressor from a stopped state of an engine for running a vehicle to a normal running state. The compressor is operatively connected to the engine through a power transmission path and selectively driven by one of the engine and an electric motor. A starter motor is operatively connected to the engine. A preferred method includes the steps of providing a one-way clutch on the power transmission path between the compressor and the engine, driving the compressor by the electric motor during an idle stop of the vehicle, detecting a rotational speed of the engine, driving the electric motor such that the electric motor drives the hybrid compressor at a second predetermined speed when the rotational speed of the engine is detected, and stopping the electric motor when the detected rotational speed of the engine exceeds a predetermined value. The predetermined value ranges between a third predetermined rotational speed of the engine that corresponds to a first predetermined rotational speed of the compressor and a fourth rotational speed of the engine that corresponds to the second predetermined rotational speed of the compressor. The compressor is driven at the first predetermined rotational speed when power is transmitted from the starter motor to the compressor through the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. Aspect of the invention may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1

is a longitudinal cross-sectional view of a compressor;

FIG. 2

is a flow chart Illustrating control for switching a drive source of the compressor from an electric motor unit to an engine;

FIG.

3

(

a

) Is a timing graph illustrating the drive source of the compressor; and

FIG.

3

(

b

) is a timing graph illustrating rotational speeds of the engine and the electric motor unit regarding the control In FIG.

2

.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment according to the present invention will be described now. As shown in

FIG. 1

, a hybrid compressor C, which constitutes a refrigerating cycle in an air conditioning system for a vehicle, has a housing

11

for compressing refrigerant. A piston type variable displacement compression unit

12

is accommodated in the housing

11

. The compression unit

12

includes a rotary shaft

13

, a swash plate

14

, a pair of shoes

15

and a piston

16

. The swash plate

14

is rotated by the rotation of the rotary shaft

13

. The rotational movement of the swash plate

14

is converted into the reciprocating movement of the piston

16

, thereby compressing a refrigerant gas.

A power transmission mechanism Pr is arranged at one end of the housing

11

outside the housing

11

, such that the axis of the power transmission mechanism PT corresponds to the axis of the rotary shaft

13

, for transmitting power to the rotary shaft

13

. The power transmission mechanism PT includes a pulley

17

and an electric motor unit

38

as an electric motor or a second drive source.

The pulley

17

is rotatably supported by the housing

11

. The pulley

17

transmits power from an engine E (internal combustion engine) as a first drive source for driving a vehicle to the rotary shaft

13

. A starter motor S is operatively coupled to the engine E for starting up the engine E. During a starting period of the engine E by the starter motor S, or during a time when the starter motor S starts the engine E, power is transmitted from the starter motor S to the pulley

17

via the engine E. In the present specification, a rotational state of the engine E includes not only a independent rotation of the engine E but also a dependent rotation of the engine E when driven by the starter motor S.

The electric motor unit

38

is utilized to drive the rotary shaft

13

when the engine E is in a stopped state. The air conditioning system includes the electric motor unit

38

. Therefore, air conditioning is capable of being continuously conducted even when the engine E is in the stopped state. The air conditioning system in the present preferred embodiment is suitable for an idle stop vehicle and a hybrid vehicle.

Next, an exemplary power transmission mechanism PT will be described. The rotary shaft

13

of the compression unit

12

is rotatably supported by the housing

11

and protrudes thorough the front wall of the housing

11

to the outside of the housing

11

. A boss

35

protrudes from the front wall of the housing

11

. The boss

35

receives the rotary shaft

13

through a bearing.

The pulley

17

includes a first pulley member

18

and a second pulley member

19

. The first and second pulley members

18

and

19

are arranged in the identical axis. A belt

20

engages with the outer periphery of the first pulley member

18

from the engine E. A bearing

25

is interposed between the first pulley member

18

and the boss

35

of the housing

11

. The first pulley member

18

is rotatably supported by the boss

35

of the housing

11

through the bearing

25

.

A hub

30

is fixed to the front end of the rotary shaft

13

. A first one-way clutch

31

is interposed between the hub

30

and the second pulley member

19

. Namely, the first one-way clutch

31

is arranged on a first power transmission path between the rotary shaft

13

and the engine E. The second pulley member

19

is supported by the hub

30

through the first one-way clutch

31

. The first pulley member

18

is connected to the second pulley member

19

through a power-transmitting pin

28

and a rubber damper

29

. The power-transmitting pin

28

functions as a breaking type torque limiter. The rubber damper

29

helps to compensate the variation in the transmitted torque between both the pulley members

18

and

19

.

The first one-way clutch

31

includes a roller type clutch mechanism

31

a

and a bearing

31

b

. With respect to a predetermined rotational direction, the clutch mechanism

31

a

permits power transmission from the second pulley member

19

to the hub

30

, and blocks power transmission from the hub

30

to the second pulley member

19

. When the electric motor unit

38

is in a stopped state and the first pulley member

18

is rotated by the drive of the engine E in the predetermined rotational direction, the second pulley member

19

is rotated through the power-transmitting pin

28

and the rubber damper

29

in the predetermined rotational direction. As a result, the rotational power of the second pulley member

19

is transmitted to the rotary shaft

13

through the first one-way clutch

31

and the hub

30

.

On the other hand, when the engine E is in the stopped state and the rotary shaft

13

is rotated by the electric motor unit

38

in the predetermined rotational direction, the rotational power of the rotary shaft

13

is transmitted to the first one-way clutch

31

through the hub

30

. However, since the clutch mechanism

31

a

of the first one-way clutch

31

blocks the power transmission from the hub

30

to the second pulley member

19

, the power of the electric motor unit

38

is not transmitted to the engine E. Namely, the power of the electric motor unit

38

is utilized only for driving the compression unit

12

through the rotary shaft

13

.

A sealed space

27

is defined in the first and second pulley members

18

and

19

. A second one-way clutch

44

is arranged on the rotary shaft

13

. The electric motor unit

38

includes a rotor

45

and a stator

49

. The rotor

45

is mounted on the rotary shaft

13

through the second one-way clutch

44

in the sealed space

27

. Namely, the second one-way clutch

44

is arranged on a second power transmission path between the rotary shaft

13

and the electric motor unit

38

. The rotor

45

includes an iron core

45

a

and a coil

45

b

formed around the iron core

45

a

. The stator

49

is made of a magnet and is arranged around the outer periphery of the rotor

45

in the sealed space

27

. Therefore, when electric power is supplied to the coil

45

b

from an external device, the rotor

45

is rotated.

The second one-way clutch

44

includes a clutch mechanism

44

a

and a bearing

44

b

similarly to the first one-way clutch

31

. With respect to the predetermined rotational direction, the clutch mechanism

44

a

permits power transmission from the rotor

45

to the rotary shaft

13

, and blocks power transmission from the rotary shaft

13

to the rotor

45

.

Therefore, when the electric motor unit

38

is started, in a state when the engine E is in the stopped state, the rotational power of the rotor

45

is transmitted to the rotary shaft

13

through the second one-way clutch

44

. On the other hand, when the electric motor unit

38

is in the stopped state and the rotary shaft

13

is rotated by the drive of the engine E, the rotational power of the rotary shaft

13

is not transmitted to the rotor

45

. Therefore, a load on the engine E to drive the rotor

45

is reduced.

Next, an exemplary control device that constitutes a preferred hybrid compressor system with the compressor C will be described. As shown in

FIG. 1

, the control device for the compressor C includes an air conditioner ECU (Electric Control Unit)

51

that is similar to a computer, or a controller, an information detector

52

for communicating various information to the air conditioner ECU

51

and a driver

53

for driving the electric motor unit

38

. The air conditioner ECU

51

is electrically connected to the information detector

52

and the driver

53

. The information detector

52

includes various switches and various sensors (not shown) for detecting air conditioning information, such as an air conditioning switch and a temperature sensor. The information detector

52

also includes a rotational speed sensor

52

a

for detecting a rotational speed Ne of the engine E, or for detecting a rotational state of the engine E.

The air conditioner ECU

51

controls the switch of a drive source (electric motor unit

38

/engine E) of the compressor C based on the air conditioning information and the rotational speed Ne of the engine E from the information detector

52

. Namely, for example, when the vehicle is in an idle stop state (the engine E is in the stopped state), the air conditioner ECU

51

orders the driver

53

to start the electric motor unit

38

based on air conditioning (cooling) request, and the drive source of the compressor C is switched from the engine E to the electric motor unit

38

. When the vehicle is in a normal running state (the engine E runs), the air conditioner ECU

51

orders the driver

53

to stop the electric motor

53

, and the drive source of the compressor C is switched from the electric motor unit

38

to the engine E. The compression unit

12

of the compressor C is a variable displacement type. When the engine E runs and air conditioning is unnecessary, the air conditioner ECU

51

changes the displacement of the compressor C to the minimum.

When the air conditioner ECU

51

switches the drive source of the compressor C from the electric motor unit

38

to the engine E, the air conditioner ECU

51

performs a preferred sequence control according to a pre-memorized program as shown in FIG.

2

through FIG.

3

(

b

).

When the electric motor unit

38

is in the stopped state, the rotational speed of the compressor C (the rotary shaft

13

) is determined based on a pulley ratio between the power transmission mechanism PT and the engine E and the information about the rotational speed Ne of the engine E from the rotational speed sensor

52

a

. The pulley ratio between the power transmission mechanism PT and the engine E is not one to one. For illustration purposes, however, the pulley ratio between the power transmission mechanism PT and the engine E is assumed as one to one in the present preferred embodiment.

As shown in

FIG. 2

, when the vehicle is in the idle stop state (the engine E is in the stopped state) and the compressor C is driven by the electric motor unit

38

, in a step S

101

, the air conditioner ECU

51

monitors whether the starter motor S is started based on the information about the rotational speed Ne of the engine E from the rotational speed sensor

52

a

. Namely, the air conditioner ECU

51

monitors whether the engine E is changed from the stopped state to a rotational state (a dependent rotational state), more specifically, whether the rotational speed Ne of the engine E exceeds zero. If the judgment is NO in the step S

101

, or if the rotational speed No is zero, it is continuously monitored whether the starter motor S is started.

If the judgment is YES in the step S

101

, it is judged that the engine E is changed from the stopped state to the rotational state. The air conditioner ECU

51

orders the driver

53

to drive the electric motor unit

38

at a rotational speed Nm of a predetermined value &ggr; in a step S

102

. When the electric motor unit

38

runs at the predetermined value &ggr; of the rotational speed Nm, the electric motor unit

38

drives the compressor C at a second predetermined rotational speed of the compressor C that corresponds to a fourth rotational speed of the engine E. As shown in FIG.

3

(

b

), the predetermined value &ggr; corresponding to the fourth predetermined rotational speed of the engine E is higher than a predetermined value &agr; of the rotational speed Ne of the engine E, or a third predetermined rotational speed of the engine E. The third predetermined rotational speed of the engine E corresponds to a first predetermined rotational speed of the compressor C. The predetermined value &agr; is determined by the rotational speed of the starter motor S, that is, the predetermined value &agr; corresponds to a theoretical rotational speed of the compressor C (the rotary shaft

13

) when the compressor C is hypothetically driven by the starter motor S through the engine E. The theoretical rotational speed of the compressor C means a rotational speed of the compressor C when the power is hypothetically transmitted from the engine E that is driven by the starter motor S to the compressor C in a state that the electric motor unit

38

is in the stopped state. Namely, if the power is transmitted from the starter motor S to the compressor C through the engine E when the engine E is driven by the starter motor S, the compressor C is driven by the starter motor S at the theoretical rotational speed.

In FIG.

3

(

b

), it is shown that the rotational speed Nm of the electric motor unit

38

is at the predetermined value &ggr; even before the starter motor S starts for easy understanding. However, the rotational speed Nm of the electric motor unit

38

practically varies in accordance with a cooling load.

In a state when both the electric motor unit

38

and the engine E are in a rotational state, the first one-way clutch

31

alternates the two drive sources in such a manner that the first one-way clutch

31

permits power transmission from one drive source driving the compressor C at a higher speed than the other. Namely, when the electric motor unit

38

is capable of rotating the rotary shaft

13

faster than the engine E, the electric motor

38

rotates the rotary shaft

13

. When the engine E is capable of rotating the rotary shaft

13

faster than the electric motor unit

38

, the first one-way clutch

31

transmits the power from the engine E to the rotary shaft

13

, and the engine E rotates the rotary shaft

13

. Therefore, as mentioned above, when the electric motor unit

38

is driven at the rotational speed Nm of the predetermined value &ggr; during the starting period of the engine E, the electric motor unit

38

drives the compressor C. Therefore, a load for driving the compressor C, during the starting period of the engine E, is applied to the electric motor unit

38

, not to the starter motor S.

In a step S

103

, it is judged whether the rotational speed Ne of the engine E exceeds a predetermined value &bgr;, or a predetermined value. As shown in FIG.

3

(

b

), the predetermined value &bgr; is lower than the predetermined value &ggr; corresponding to the fourth predetermined rotational speed of the engine E and is higher than the predetermined value &agr; of the rotational speed Ne of the engine E when driven by the starter motor S. When the rotational speed Ne of the engine E exceeds the predetermined value &bgr;, the engine E has successfully started up. If the judgment is NO in the step S

103

, the process switches to the step S

102

, and the rotational speed Nm of the electric motor unit

38

is kept at the predetermined value &ggr;. Then, it is continuously monitored whether the engine E starts up in the step S

103

.

If the judgment is YES in the step S

103

, the process proceeds to a step

8104

where the air conditioner ECU

51

orders the driver

53

to stop the electric motor unit

38

. Therefore, as shown in FIG.

3

(

b

), the relationship between the rotational speed Ne of the engine E and the rotational speed Nm of the electric motor unit

38

is inverted. As shown in FIG.

3

(

a

) and FIG.

3

(

b

), when the rotational speed Ne of the engine E becomes higher than the rotational speed Nm of the electric motor unit

38

, the drive source of the compressor C is automatically and immediately switched from the electric motor unit

38

to the engine E through the first one-way clutch

31

without an external control such as an electromagnetic clutch.

The following effects are obtained in the above-constructed present preferred embodiment.

(1) As mentioned above, the electric motor unit

38

is stopped after the engine E starts up. Therefore, due to the simple control, the drive source of the compressor C is smoothly switched from the electric motor unit

38

to the engine E without a break of air conditioning. The simplification of the control reduces a computing load on the air conditioner ECU

51

.

(2) When the drive source of the compressor C is switched from the electric motor unit

38

to the engine E, the electric motor unit

38

is stopped at a suitable time after the engine E starts up. This preferred operational sequence promotes startability of the engine E. It is assumed that the electric motor unit

38

is stopped before the engine E starts up, or during the starting period of the engine E. In this case, the drive source is switched from the electric motor unit

38

to the engine E during the starting period of the engine E. Therefore, startability of the engine E deteriorates. To avoid the problem, the electric motor unit

38

is stopped after the engine E starts up in the present preferred embodiment.

Particularly, in the present preferred embodiment, the driver

53

is ordered to drive the electric motor unit

38

at the rotational speed higher than the theoretical rotational speed of the compressor C, which determined by the rotational speed of the starter motor S, during the starting period of the engine E. Therefore, the compressor C is driven by the electric motor unit

38

during the starting period of the engine E. If the drive source of the compressor C is switched from the electric motor unit

38

to the engine E (strictly the starter motor

8

for starting the engine E) during the starting period of the engine E, a load on the starter motor S increases. However, the drive source is switched from the electric motor unit

38

to the engine E after the engine E starts up. Therefore, the load on the starter motor

5

does not increase. As a result, the startability of the engine E is satisfactory even by a small starter motor S.

The following alternative embodiments may be practiced according to the present invention.

When the drive source of the compressor C is switched from the electric motor unit

38

to the engine E, the electric motor unit

38

is stopped as soon as the rotational speed Ne of the engine E exceeds the predetermined value &bgr; in the present preferred embodiment. The electric motor unit

38

may be stopped at a predetermined period after the rotational speed No of the engine E exceeds the predetermined value &bgr; (for example with a timer), or the air conditioner ECU

51

may delays for a predetermined period to stop the electric motor E after the rotational speed Ne of the engine E exceeds the predetermined value &bgr;.

When the drive source of the compressor C is switched from the electric motor unit

38

to the engine E, the electric motor unit

38

may be stopped after the starter motor S starts up (the rotational speed Ne of the engine E becomes equal to the predetermined value &agr;). In this alternative embodiment, the drive source of the compressor C is not switched from the electric motor unit

38

to the engine E during an initial period when the rotational speed of the starter motor S is increased (when the rotational speed Ne is smaller than the predetermined value &agr;). Therefore, a load on the starter motor S can be reduced for starting the motor S, and the starter motor S can be miniaturized.

Although the roller type first one-way clutch

31

is used in the preferred embodiment, the one-way clutch

31

may be changed to other types of one-way clutches such as, for example, a sprag type. The first one-way clutch

31

may not include the bearing

31

b.

In the preferred embodiment, the electric motor unit

38

is installed in the power transmission mechanism PT. The electric motor unit

38

may be accommodated in the housing

11

with the compression unit

12

, or the electric motor unit

38

may be arranged separately from the compressor C.

The compression unit

12

is not limited to the piston type. The compression unit

12

may be a scroll type, a vane type and a helical type.

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.