U.S. patent application number 10/791228 was filed with the patent office on 2004-09-23 for control device for hybrid compressor.
Invention is credited to Iguchi, Masao, Iwasa, Jiro, Kawaguchi, Masahiro, Odachi, Yasuharu, Yamanouchi, Akihito.
Application Number | 20040184926 10/791228 |
Document ID | / |
Family ID | 32984552 |
Filed Date | 2004-09-23 |
United States Patent
Application |
20040184926 |
Kind Code |
A1 |
Iwasa, Jiro ; et
al. |
September 23, 2004 |
Control device for hybrid compressor
Abstract
A control device for a hybrid compressor includes a motor driver
for driving an electric motor, a clutch controller for driving an
electromagnetic clutch and an engine drive timing controller. Power
is transmitted from an engine to the compressor when the
electromagnetic clutch is connected. The clutch controller sets a
connecting force of the electromagnetic clutch to transmit a second
starting torque of the compressor. The engine drive timing
controller is electrically connected to the motor driver and the
clutch controller. The engine drive timing controller commands the
motor driver to activate the electric motor to discharge liquid
refrigerant from the compression chambers to a predetermined level
so that the compressor reduces its starting torque to the second
starting torque before commanding the clutch controller to connect
the electromagnetic clutch to transmit the power from the engine to
the compressor.
Inventors: |
Iwasa, Jiro; (Kariya-shi,
JP) ; Kawaguchi, Masahiro; (Kariya-shi, JP) ;
Odachi, Yasuharu; (Kariya-shi, JP) ; Iguchi,
Masao; (Kariya-shi, JP) ; Yamanouchi, Akihito;
(Kariya-shi, JP) |
Correspondence
Address: |
KNOBLE YOSHIDA & DUNLEAVY, LLC
Eight Penn Center
Suite 1350
1628 John F. Kennedy Blvd.
Philadelphia
PA
19103
US
|
Family ID: |
32984552 |
Appl. No.: |
10/791228 |
Filed: |
March 2, 2004 |
Current U.S.
Class: |
417/223 ;
417/374 |
Current CPC
Class: |
F04C 2270/03 20130101;
F04C 2240/45 20130101; F04C 18/0215 20130101; F04C 28/06 20130101;
F04C 2270/07 20130101; F04B 35/002 20130101; F04B 49/06 20130101;
F04C 29/0085 20130101; F04C 23/008 20130101; F04C 29/005
20130101 |
Class at
Publication: |
417/223 ;
417/374 |
International
Class: |
F04B 049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2003 |
JP |
2003-067082 |
Claims
What is claimed is:
1. A control device for a hybrid compressor having compression
chambers to compress refrigerant gas, a certain amount of liquid
refrigerant in the compression chambers causing a maximum starting
torque of the compressor, the compressor being selectively driven
by a vehicle engine through an electromagnetic clutch and by a
compressor electric motor, comprising: a motor driver for driving
the electric motor; a clutch controller for driving the
electromagnetic clutch, power being transmitted from the engine to
the compressor when the electromagnetic clutch is connected, the
clutch controller setting a connecting force of the electromagnetic
clutch to transmit a second starting torque of the compressor; and
an engine drive timing controller electrically connected to the
motor driver and the clutch controller, the engine drive timing
controller commanding the motor driver to activate the electric
motor to discharge the liquid refrigerant from the compression
chambers to a predetermined level so that the compressor reduces
its starting torque to the second starting torque before commanding
the clutch controller to connect the electromagnetic clutch to
transmit the power from the engine to the compressor.
2. The control device according to claim 1, wherein the connecting
force of the electromagnetic clutch enables the transmission of
slightly above a stationary torque required for driving the
compressor at a stationary operation state.
3. The control device according to claim 1, wherein the engine
drive timing controller measures a predetermined amount of time
from the onset of the driving of the compressor by the electric
motor to commanding the clutch controller to connect the
electromagnetic clutch.
4. The control device according to claim 1, wherein the engine
drive timing controller commands the motor driver to stop the
electric motor before commanding the clutch controller to connect
the electromagnetic clutch.
5. The control device according to claim 4, wherein the
electromagnetic clutch is connected when the compressor is in a
stop state.
6. The control device according to claim 1, further comprising a
judgment means electrically connected to the engine drive timing
controller for judging whether or not the liquid refrigerant exists
in the compression chambers, the engine drive timing controller
commanding the motor driver to activate the electric motor to
discharge the liquid refrigerant from the compression chambers when
the judgment means judges that at least a predetermined amount of
the liquid refrigerant exists in the compression chambers, the
engine drive timing controller commanding the clutch controller to
connect the electromagnetic clutch to transmit the power from the
engine to the compressor after discharging the liquid
refrigerant.
7. The control device according to claim 1, wherein the
electromagnetic clutch further comprising a first rotor and a
second rotor that constitute a connecting portion of the
electromagnetic clutch, the first rotor being connected to the
engine and rotated in accordance with the rotation of the engine,
the second rotor being connected to the compressor and rotated in
accordance with the rotation of the compressor, the engine drive
timing controller commanding the motor driver to drive the electric
motor in such a manner that a rotational speed of the first rotor
is substantially the same as that of the second rotor before
commanding the clutch controller to connect the electromagnetic
clutch.
8. The control device according to claim 7, wherein the engine
drive timing controller commands the motor driver to stop the
electric motor after commanding the clutch controller to connect
the electromagnetic clutch.
9. A control device for a hybrid compressor having compression
chambers to compress refrigerant gas, a certain amount of liquid
refrigerant in the compression chambers causing a maximum starting
torque of the compressor, comprising: a first drive source for
providing first power to the compressor; an electromagnetic clutch
for transmitting the first power from the first drive source to the
compressor; a second drive source for providing second power to the
compression unit; a second drive source driver for driving the
second drive source; a clutch controller for driving the
electromagnetic clutch, the first power being transmitted from the
first drive source to the compressor when the electromagnetic
clutch is connected, the clutch controller setting a connecting
force of the electromagnetic clutch to transmit a second starting
torque of the compressor; and a drive timing controller
electrically connected to the second drive source driver and the
clutch controller, the drive timing controller commanding the
second drive source driver to activate the second drive source to
discharge liquid refrigerant from the compression chambers of the
compressor to a predetermined level so that the compressor reduces
its starting torque the second starting torque before commanding
the clutch controller to connect the electromagnetic clutch to
transmit the first power.
10. The control device according to claim 9, wherein the first
drive source is an engine for driving a vehicle.
11. The control device according to claim 9, wherein the second
drive source is an electric motor.
12. The control device according to claim 9, wherein the connecting
force of the electromagnetic clutch enables the transmission of
slightly above a stationary torque required for driving the
compressor at a stationary operation state.
13. The control device according to claim 9, wherein the drive
timing controller measures a predetermined amount of time from the
onset of the driving of the compressor by the second drive source
to commanding the clutch controller to connect the electromagnetic
clutch.
14. The control device according to claim 9, wherein the drive
timing controller commands the motor driver to stop the second
drive source before commanding the clutch controller to connect the
electromagnetic clutch.
15. The control device according to claim 14, wherein the
electromagnetic clutch is connected when the compressor is in a
stop state.
16. The control device according to claim 9, further comprising a
judgment means electrically connected to the drive timing
controller for judging whether or not the liquid refrigerant exists
in the compression chambers, the drive timing controller commanding
the motor driver to activate the second drive source to discharge
the liquid refrigerant from the compression chambers when the
judgment means judges that at least a predetermined amount of the
liquid refrigerant exists in the compression chambers, the drive
timing controller commanding the clutch controller to connect the
electromagnetic clutch to transmit the first power after
discharging the liquid refrigerant.
17. The control device according to claim 9, wherein the
electromagnetic clutch further comprising a first rotor and a
second rotor that constitute a connecting portion of the
electromagnetic clutch, the first rotor being connected to the
first drive source and rotated in accordance with the rotation of
the first drive source, the second rotor being connected to the
compressor and rotated in accordance with the rotation of the
compressor, the drive timing controller commanding the second drive
source driver to drive the second drive source in such a manner
that a rotational speed of the first rotor is substantially the
same as that of the second rotor before commanding the clutch
controller to connect the electromagnetic clutch.
18. The control device according to claim 17, wherein the drive
timing controller commands the motor driver to stop the second
drive source after commanding the clutch controller to connect the
electromagnetic clutch.
19. A method for controlling a hybrid compressor in an
air-conditioner system from a stop state, the compressor having
compression chambers for compressing refrigerant gas, a certain
amount of liquid refrigerant in the compression chambers causing a
maximum starting torque of the compressor, the compressor being
selectively driven by a vehicle engine through an electromagnetic
clutch and by a compressor electric motor, the method comprising
the steps of: setting a first value of electric current applied to
the electromagnetic clutch to be smaller than a second value of the
electric current that generates a connecting force of the
electromagnetic clutch for transmitting the maximum starting torque
of the compressor, the first value enabling the power transmission
from the engine to the compressor at a second starting torque with
the liquid refrigerant at a predetermined level in the compression
chambers; driving the compressor only by the electric motor from
the stop state for a predetermined amount of time; discharging the
liquid refrigerant to the predetermined level from the compression
chambers; applying the first value of the electric current to the
electromagnetic clutch; and transmitting power from the engine to
the compressor through the electromagnetic clutch.
20. The method according to claim 19, further comprising the steps
of: measuring a predetermined amount of time since the onset of the
driving of the compressor only by the electric motor; stopping the
electric motor when the predetermined amount of time has elapsed;
and connecting the electromagnetic clutch after the stop of the
electric motor.
21. The method according to claim 19, further comprising the step
of maintaining the first value during a stationary state of the
compressor.
22. The method according to claim 19, further comprising the step
of starting the engine before driving the compressor by the
electric motor.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a hybrid compressor in use
for an air-conditioner system in an idle stop vehicle or a hybrid
vehicle and more particularly relates to a control device for the
hybrid compressor that compresses refrigerant gas by power from an
electric motor even when an engine is stopped.
[0002] Japanese Unexamined Utility Model Publication No. 6-87678
generally discloses a hybrid compressor. A compression unit in the
hybrid compressor is selectively driven either by a vehicle engine
or an electric motor. Power is transmitted between the engine and
the compression unit through an electromagnetic clutch. When
air-conditioning is unnecessary or when the compression unit is
driven by the electric motor, the electromagnetic clutch is in a
blocking state or de-energized so that the engine power is not
transmitted to the compression unit.
[0003] Meanwhile, due to static friction of sliding portions and
compressed liquid refrigerant that has been accumulated in
compression chambers of the compression unit, a starting torque of
the hybrid compressor is larger than a stationary torque that is
required for driving the hybrid compressor at a stationary
operation state. To transmit a torque corresponding to the starting
torque of the hybrid compressor, an electromagnetic clutch exerts a
connecting force or a combining power that is large enough to
maintain the contact between the power source and the hybrid
compressor. That is, a value of electric current is applied to the
electromagnetic clutch to generate the above-described connecting
force. The constant electric current value for the starting torque
is applied to electromagnetic clutch in prior art. However, when
the compressor is driven at the stationary operation state by the
engine, the torque of the compressor is reduced, and the necessary
connecting force is also reduced. Thus, while the compressor is
driven at the stationary operation state by the engine, the
electromagnetic clutch consumes unnecessary electric power.
SUMMARY OF THE INVENTION
[0004] The present invention provides a control device that reduces
a starting torque of a hybrid compressor upon an engine drive.
[0005] In accordance with the present invention, a control device
is used for a hybrid compressor that has compression chambers to
compress refrigerant gas. A certain amount of liquid refrigerant in
the compression chambers causes a maximum starting torque of the
compressor. The compressor is selectively driven by a vehicle
engine through an electromagnetic clutch and by a compressor
electric motor. The control device includes a motor driver for
driving the electric motor, a clutch controller for driving the
electromagnetic clutch and an engine drive timing controller. Power
is transmitted from the engine to the compressor when the
electromagnetic clutch is connected. The clutch controller sets a
connecting force of the electromagnetic clutch to transmit a second
starting torque of the compressor. The engine drive timing
controller is electrically connected to the motor driver and the
clutch controller. The engine drive timing controller commands the
motor driver to activate the electric motor to discharge the liquid
refrigerant from the compression chambers to a predetermined level
so that the compressor reduces its starting torque to the second
starting torque before commanding the clutch controller to connect
the electromagnetic clutch to transmit the power from the engine to
the compressor.
[0006] The present invention also provides a method for controlling
a hybrid compressor in an air-conditioner system from a stop state.
A certain amount of liquid refrigerant in the compression chambers
causes a maximum starting torque of the compressor. The compressor
is selectively driven by a vehicle engine through an
electromagnetic clutch and by a compressor electric motor. The
method includes the step of setting a first value of electric
current applied to the electromagnetic clutch to be smaller than a
second value of the electric current that generates a connecting
force of the electromagnetic clutch for transmitting a maximum
starting torque of the compressor. The first value enables the
power transmission from the engine to the compressor at a second
starting torque with the liquid refrigerant at a predetermined
level in the compression chambers. The method also includes the
steps of driving the compressor only by the electric motor from the
stop state for a predetermined amount of time, discharging the
liquid refrigerant to a predetermined level from the compression
chambers, applying the first value of the electric current to the
electromagnetic clutch and transmitting power from the engine to
the compressor through the electromagnetic clutch.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The features of the present invention that are believed to
be novel are set forth with particularity in the appended claims.
The invention together with objects and advantages thereof, may
best be understood by reference to the following description of the
presently preferred embodiments together with the accompanying
drawings in which:
[0008] FIG. 1 is a longitudinal cross-sectional view of the
compressor according to a preferred embodiment;
[0009] FIG. 2 is a graph showing compressor torque and the contrast
between the preferred embodiment and a prior art device in electric
current applied to the electromagnetic clutch;
[0010] FIG. 3 is a flow chart illustrating steps involved in a
preferred process of controlling the drive source for the
compressor according to the present invention; and
[0011] FIG. 4 is a longitudinal cross-sectional view of the
compressor according to a first alternative embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] A preferred embodiment according to the present invention
will now be described. First, a hybrid compressor will be
schematically described. As shown in FIG. 1, a hybrid compressor C
constitutes a part of a refrigerating cycle of a vehicle
air-conditioner system for compressing refrigerant gas and includes
a housing 11. The housing 11 accommodates an electric motor 12 and
a scroll type compression unit 13. An engine E for driving a
vehicle is operatively connected to the compression unit 13.
[0013] The compressor C includes the electric motor 12. The
compressor C is selectively driven by the electric motor 12 and the
engine E. When the engine E is not rotating in a stop state, the
compression unit 13 is driven by the electric motor 12. Thereby,
the compression unit 13 compresses the refrigerant gas even when
the engine E is in the stop state. The air-conditioner system in
the present preferred embodiment is suitable for an idle stop
vehicle or a hybrid vehicle.
[0014] Next, the compressor C will be described in detail. A rotary
shaft 14 is rotatably accommodated in the housing 11. The electric
motor 12 includes a rotor 15 and a stator 16. The rotor 15 is
rotatably fixed to the rotary shaft 14. The stator 16 is fixedly
arranged on the inner circumferential surface of the housing 11 so
as to surround the rotor 15. The electric motor 12 rotates the
rotor 15 and the rotary shaft 14 when electric power is supplied to
the stator 16.
[0015] An electromagnetic clutch 17 is arranged on a power
transmission path between the compressor C and the engine E. The
electromagnetic clutch 17 is rotatably supported at the outside of
the housing 11 and includes a rotor 19, a hub 20, an armature 22
and a magnetic coil 23. The rotor 19 is coupled to a belt 18 that
transmits power from the engine E. The hub 20 is fixed to the
rotary shaft 14. The armature 22 is supported by the hub 20 through
an elastic member 21. The magnetic coil 23 is supported by the
housing 11. The elastic member 21 exerts elastic force to separate
the armature 22 from the rotor 19.
[0016] When an electric current is applied to the electromagnetic
clutch 17 to energize the magnetic coil 23, a suction force based
on an electromagnetic force is applied to the armature 22.
Accordingly, the armature 22 moves against the elastic force of the
elastic member 21 to press-contact the end surface of the rotor 19.
The rotor 19 is electrically connected to or temporarily combined
with the armature 22 by a press-contacting force corresponding to a
value of the electric current that is applied to the magnetic coil
23. When the electromagnetic clutch 17 is in a connecting state,
the electromagnetic clutch 17 transmits power from the engine E to
the rotary shaft 14.
[0017] Then, when the magnetic coil 23 is de-energized, the
electromagnetic suction force that has been applied to the armature
22 dissipates. Accordingly, the armature 22 moves due to the
elastic force of the elastic member 21 to separate from the end
surface of the rotor 19 in a blocking state. That is, the
connection between the rotor 19 and the armature 22 is released.
When the electromagnetic clutch 17 is in the blocking state, the
electromagnetic clutch 17 does not transmits the power form the
engine E to the rotary shaft 14 and also does not transmit
unnecessary power from the electric motor 12 to the engine E.
[0018] The compression unit 13 includes a fixed scroll member 25
having a fixed spiral wall 25a and a fixed base plate 25b as well
as a movable scroll member 26 having a movable spiral wall 26a and
a movable base plate 26b. The fixed scroll member 25 is fixedly
arranged in the housing 11. A crankshaft 14a is secured to the end
surface of the rotary shaft 14. The movable scroll member 26 is
supported by the crankshaft 14a so as to rotate relative to the
fixed scroll member 25. The fixed spiral wall 25a of the fixed
scroll member 25 engages with the movable spiral wall 26a of the
movable scroll member 26. The distal end surfaces of the fixed
spiral wall 25a and the movable spiral wall 26a respectively
contact the movable base plate 26a and the fixed base plate 25a.
Accordingly, compression chambers 27 are defined by the fixed
spiral wall 25a and the fixed base plate 25b of the fixed scroll
member 25 as well as the movable spiral wall 26a and the movable
base plate 26b of the movable scroll member 26.
[0019] The refrigerant gas is introduced into the compression
chambers 27 from a suction chamber 28 that is defined in the
housing 11. As the compression chambers 27 are moved inwardly by
the orbital movement of the movable scroll member 26 relative to
the fixed scroll member 25 based on the rotation of the rotary
shaft 14, the compression chambers 27 reduce their volume. Thereby,
the refrigerant gas is compressed to a predetermined pressure value
in the compression chambers 27. When the compression chambers 27
have approached the center of the fixed scroll member 25, the
compressed refrigerant gas is discharged from the compression
chambers 27 into a discharge chamber 29 that is defined in the
housing 11.
[0020] Next, a control device for controlling the compressor C will
be described in detail. Still referring to FIG. 1, the control
device for the compressor C includes an air-conditioner ECU 51, an
information detector 52 that provides information to the
air-conditioner ECU 51, a motor driver 53 for driving the electric
motor 12 and a clutch controller 54 for driving the electromagnetic
clutch 17. The air-conditioner ECU 51 is electrically connected to
the motor driver 53 and the clutch controller 54. The
air-conditioner ECU 51 functions as an electronic control unit that
is similar to a computer. The air conditioner ECU 51 communicates
with an engine ECU 61 which functions as an electronic control unit
similar to a computer. The information detector 52 includes
switches and sensors, which are not shown, such as an
air-conditioner switch, a temperature sensor and a
temperature-setting device for detecting all kinds of information
for the air-conditioning.
[0021] A starting torque of the compressor C is defined as a torque
required from a stop state for initially rotating the compression
unit 13 and other associated sliding portions that constitute the
compressor C. The maximum value of the starting torque is
determined based on the structure of the vehicle air-conditioner
system, the structure of a vehicle that utilizes the vehicle
air-conditioner system and the use environment. The starting torque
of the compressor C is substantially at the maximum when a
relatively large amount of liquid refrigerant has been accumulated
in the compression chambers 27 of the compression unit 13.
[0022] As shown in FIG. 2, assuming a large amount of accumulated
liquid refrigerant in the compression chambers 27, a value of the
electric current 11 applied to the electromagnetic clutch 17 is
conventionally determined in such a manner that a connecting force
of the electromagnetic clutch 17 is large enough to transmit a
maximum starting torque A of the compressor C as indicated by a
dotted line. In the present preferred embodiment, before the engine
E drives the compression unit 13, the electric motor 12 drives the
compression unit 13 from a stop state to discharge the accumulated
liquid refrigerant from the compression chambers 27 during an EM
drive period. One definition of the duration of the EM drive period
or a predetermined amount of time Tm is an amount of time for the
electric motor activation that is necessary to minimize the
remaining amount of the liquid refrigerant in the compression
chambers 27 after which the remaining amount remains constant.
After the liquid refrigerant discharge is substantially completed,
the compressor C halts its rotation. After a predetermined amount
of time, the electric motor 12 is stopped, and the engine E now
drives the compressor C during an engine drive period. Thus, the
subsequent starting torque of the compressor C is reduced from the
maximum starting torque A to a predetermined minimal torque which
is defined as a second starting torque B. Due to the predetermined
minimal second torque B of the compressor C, the necessary
connecting force of the electromagnetic clutch 17 is
correspondingly relatively small as indicated by a reduced amount
of current 12. Therefore, the clutch controller 54 sets the value
of the electric current 12 applied to the magnetic coil 23 in such
a manner that the connecting force of the electromagnetic clutch 17
is smaller than a maximum starting connecting force required for
transmitting the maximum starting torque A of the compressor C.
Namely, the value of the electric current 12 applied to the
magnetic coil 23 is smaller than the above conventional value 11,
but the connecting force of the electromagnetic clutch 17 is large
enough to transmit the second starting torque B that is slightly
larger than a stationary torque C required for driving the
compressor C at a stationary operation state. Meanwhile, when the
stating torque of the compressor C is the maximum starting torque A
due to the accumulated liquid refrigerant in the compression
chambers 27 of the compression unit 13, it is difficult to steadily
start the compressor C by the engine E due to sliding of connecting
portions in the electromagnetic clutch 17.
[0023] The air-conditioner ECU 51 gives commands to the motor
driver 53 and the clutch diver 54 according to the operational
requirements of the compressor C based on the air-conditioning
information from the information detector 52 and according to
operational information on the engine E offered from the engine ECU
61. When the vehicle is in an idle stop state or when the engine E
is in a stop state, the air-conditioner ECU 51 commands the clutch
controller 54 to block the electromagnetic clutch 17 or to
de-energize the magnetic coil 23 according to the operational
requirements of the compressor C based on the air-conditioning
information from the information detector 52. In addition, the
air-conditioner ECU 51 commands the motor driver 53 to drive the
electric motor 12 based on the same information. Therefore, the
compression unit 13 is driven by the electric motor 12.
[0024] On the other hand, when the vehicle is in a traveling state
or when the engine E is in a running state, the air-conditioner ECU
51 commands the clutch controller 54 to connect the electromagnetic
clutch 17 or to energize the magnetic coil 23 according to the
operational requirements of the compressor C based on the
air-conditioning information from the information detector 52. In
addition, the air-conditioner ECU 51 commands the motor driver 53
to stop the electric motor 12 or to de-energize the stator 16 based
on the same information. Therefore, the compression unit 13 is
driven by the engine E.
[0025] In the process where the compression unit 13 is initially
driven by the electric motor 12 and then substantially driven by
the engine E, the air-conditioner ECU 51 functions as an engine
drive timing controller and performs unique control as shown in
flow chart in FIG. 3 according to a pre-stored program.
[0026] The air-conditioner ECU 51 judges whether or not the engine
E is in the running state or an ON state in step (hereinafter
referred to as S) 101. If the judgment is NO in the S101 because
the engine E is not in a running state, the process proceeds to
"return." If the judgment is YES in the S101 because the engine E
is in the running state, the process proceeds to S102. The
air-conditioner ECU 51 judges in the S102 whether or not the
operation of the compression unit 13 or the air-conditioner system
is required based on the air-conditioner information from the
information detector 52. If the judgment is NO in the S102 since
the operation of the compression unit 13 is not required, the
process proceeds to "return."
[0027] On the other hand, if the judgment is YES in the S102
because the operation of the compression unit 13 is required, the
process proceeds to S103. The air-conditioner ECU 51 commands the
motor driver 53 to activate the electric motor 12 in S103. Thereby,
the electric motor 12 is activated to drive the compression unit
13. When a relatively large amount of the liquid refrigerant is
accumulated in the compression chambers 27 after the vehicle has
stopped for a relatively long period of time, at least a part of
the liquid refrigerant is discharged to the outside due to the
action of the compression unit 13 or the orbital movement of the
movable scroll member 26 relative to the fixed scroll member 25. In
S104, the air-conditioner ECU 51 monitors whether or not the
predetermined amount of time Tm has elapsed since the activation of
the electric motor 12. The predetermined time Tm is a required
amount of time to discharge large amount of the liquid refrigerant
in the compression chambers 27 so as to reduce the starting torque
of the compressor C from the maximum starting torque A to the
second starting torque B that is steadily transmitted by the
electromagnetic clutch 17.
[0028] If the judgment is YES in the S104 because the electric
motor 12 and the compression unit 13 have operated for the
predetermined time Tm, the air-conditioner ECU 51 commands the
motor driver 53 to stop or turn off the electric motor 12 in S105.
After the electric motor 12 is stopped, the air-conditioner ECU 51
commands the clutch controller 54 to connect or turn on the
electromagnetic clutch 17 from the blocking state in S106. Thus,
the electromagnetic clutch 17 transmits the power from the engine E
to the compression unit 13, and the compression unit 13 is driven
by the engine E.
[0029] As described above, the clutch controller 54 sets the
connecting force of the electromagnetic clutch 17 to be smaller
than the maximum starting connecting force. However, since the
substantial amount of the liquid refrigerant is discharged from the
compressor C by the activation of the electric motor 12, the
starting torque of the compressor C is reduced without the initial
large amount of the liquid refrigerant in the compression chambers
27. Therefore, even though the connecting force of the
electromagnetic clutch 17 is relatively small due to the relatively
small value of the electric current, the electromagnetic clutch 17
transmits the sufficient power from the engine E to the rotary
shaft 14 to steadily drive the compressor C from the stop
state.
[0030] According to the present preferred embodiment, following
advantageous effects are obtained and described with respect to
FIGS. 1 through 3. (1) Before the compression unit 13 is driven by
the engine E, the air-conditioner ECU 51 commands the motor driver
53 to activate the electric motor 12 to drive the compression unit
13. A major portion of the existing liquid refrigerant is
discharged from the compression chambers 27 of the compression unit
13 due to the orbital movement of the movable scroll member 26
relative to the fixed scroll member 25. A substantial amount of the
liquid refrigerant no longer exists in the compression chambers 27
when the engine E starts to drive the compression unit 13.
Therefore, as shown in FIG. 2, the starting torque of the
compressor C is smaller for the engine E than that before
discharging the liquid refrigerant.
[0031] (2) The clutch controller 54 sets the connecting force of
the electromagnetic clutch 17 to be smaller than for the maximum
starting torque A of the compressor C. That is, the value of the
electric current applied to the electromagnetic clutch 17 is
smaller than the conventional value as shown in FIG. 2. Thus,
electric power consumption of the electromagnetic clutch 17 is
substantially reduced. In the preferred embodiment, since the
starting torque of the compressor C is reduced for the engine E,
the electromagnetic clutch 17 provides the sufficient connecting
force with the reduced electric power consumption for transmitting
the torque that is smaller than the maximum starting torque A of
the compressor C.
[0032] (3) The air-conditioner ECU 51 commands the motor driver 53
to stop the electric motor 12 before commanding the clutch
controller 54 to connect the electromagnetic clutch 17. Thus, when
the electromagnetic clutch 17 is connected and the compression unit
13 is driven by the engine E, the compressor C is in the stop state
in which a relatively large amount of a torque is required for
starting the compressor C. However, in the present preferred
embodiment, the starting torque of the compressor C has been
substantially reduced from the maximum starting torque A by the
electric motor 12 before the electromagnetic clutch 17 is connected
for the engine E to drive the compression unit 13. Thus, even
though the electromagnetic clutch 17 provides the relatively small
connecting force, the compressor C is steadily driven at an initial
stage from the stop state before reaching the stationary state.
Therefore, it is especially effective to reduce the stating torque
of the compressor C before the engine E starts to drive the
compressor C from the stop state.
[0033] According to the present invention, the following
alternative preferred embodiment is practiced. In the
above-described preferred embodiment, before the compression unit
13 is driven by the engine E, the compression unit 13 is driven by
the electric motor 12. However, as shown in FIG. 4, a judgment
means is electrically connected to the air-conditioner ECU 51 for
judging whether or not the liquid refrigerant is accumulated in the
compression chambers 27 in a first alternative embodiment. Only
when the judgment means judges that the liquid refrigerant is equal
to or more than a predetermined amount in the compression chambers
27, the engine drive timing controller commands the motor driver 53
to activate the electric motor 12 to drive the compression unit 13
before the engine E drives the compression unit 13. If the vehicle
has been in the stop state at least for a predetermined period of
time since switching off a vehicle-start switch, the judgment means
judges that the predetermined amount of the liquid refrigerant
exists in the compression chambers 27.
[0034] With respect to FIG. 3, the S105 and the S106 in the
above-described preferred embodiment are changed in a second
alternative process. Namely, the electric motor 12 is stopped after
the electromagnetic clutch 17 is connected. The rotor 19 or a first
rotor is rotated in accordance with the rotation of the engine E,
and the hub 20 or a second rotor is rotated integrally with the
rotary shaft 14 in accordance with the rotation of the rotary shaft
14. The rotor 19 and the hub 20 constitute a connecting portion of
the electromagnetic clutch 17. The air-conditioner ECU 51 receives
information on a rotational speed of the engine E from the engine
ECU 61. In reference to the information on the rotational speed of
the engine E, the air-conditioner ECU 51 adjusts a rotational speed
of the electric motor 12 through the motor driver 53 to
substantially correspond to the rotational speed of the rotor 19.
In this way, the rotational speed of the rotor 19 is substantially
the same as that of the hub 20. In this state where a rotational
speed of the rotor 19 from the engine E is substantially the same
as that of the hub 20 from the compression unit 13 in the
connecting portion of the electromagnetic clutch 17, the
electromagnetic clutch 17 is connected. Thereby, shock upon the
connection is substantially prevented.
[0035] 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.
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