U.S. patent application number 11/723970 was filed with the patent office on 2007-10-04 for waste heat collecting system having expansion device.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Hironori Asa, Atsushi Inaba, Hiroshi Kishita, Hiroshi Ogawa, Yasuhiro Takeuchi, Keiichi Uno, Kazuhide Utida.
Application Number | 20070227472 11/723970 |
Document ID | / |
Family ID | 38536963 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070227472 |
Kind Code |
A1 |
Takeuchi; Yasuhiro ; et
al. |
October 4, 2007 |
Waste heat collecting system having expansion device
Abstract
An object of the invention is to provide a waste heat collecting
system having an expansion device, in which an over expansion of
refrigerant is prevented so that a loss to be caused by the over
expansion is eliminated. A volume ratio of expansion for the
expansion device is selected at a value, at which proper expansion
of the refrigerant is achieved when the pressure difference between
the high pressure and the low pressure is minimum.
Inventors: |
Takeuchi; Yasuhiro;
(Kariya-city, JP) ; Utida; Kazuhide;
(Hamamatsu-city, JP) ; Uno; Keiichi; (Kariya-city,
JP) ; Inaba; Atsushi; (Kariya-city, JP) ;
Ogawa; Hiroshi; (Nagoya-city, JP) ; Asa;
Hironori; (Okazaki-city, JP) ; Kishita; Hiroshi;
(Anjo-city, JP) |
Correspondence
Address: |
POSZ LAW GROUP, PLC
12040 SOUTH LAKES DRIVE
SUITE 101
RESTON
VA
20191
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
448-8661
NIPPON SOKEN, INC.
Nishio-city
JP
445-0012
|
Family ID: |
38536963 |
Appl. No.: |
11/723970 |
Filed: |
March 22, 2007 |
Current U.S.
Class: |
123/41.19 ;
123/41.55 |
Current CPC
Class: |
F02G 5/00 20130101; F02G
2260/00 20130101; F01P 2060/14 20130101; Y02T 10/12 20130101; F01P
9/06 20130101; Y02T 10/166 20130101; F01P 3/20 20130101 |
Class at
Publication: |
123/041.19 ;
123/041.55 |
International
Class: |
F01P 3/22 20060101
F01P003/22; F01P 11/00 20060101 F01P011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2006 |
JP |
2006-81426 |
May 19, 2006 |
JP |
2006-140295 |
Claims
1. A waste heat collecting apparatus for a vehicle comprising: an
engine cooling circuit, through which engine cooling water is
circulated; and Rankine cycle having an expansion device, a
condensing device, a refrigerant pump, and a heating device, which
are connected in a closed circuit so that refrigerant is circulated
in the closed circuit by the operation of the refrigerant pump,
wherein the heating device is disposed in the engine cooling
circuit for heating the refrigerant of the Rankine cycle with the
heat of the engine cooling water, so that the refrigerant is
converted to high pressure and high temperature refrigerant, the
heating device is connected to an inlet side of the expansion
device for supplying the high pressure refrigerant to the expansion
device, the condensing device is connected to an outlet side of the
expansion device for cooling down and condensing the refrigerant
from the expansion device through heat exchange with the ambient
air, so that the pressure of the refrigerant at the outlet side of
the expansion device depends on a condensing capacity of the
condensing device, the expansion device is of a fixed displacement
type fluid machine, and an output shaft of the expansion device is
driven to rotate by expansion of the refrigerant in a working
chamber thereof, the expansion of the refrigerant is performed by a
pressure difference of the refrigerant between the high pressure at
the inlet side and low pressure at the outlet side of the expansion
device, and a volume ratio of expansion for the expansion device is
selected at a value, at which proper expansion of the refrigerant
is achieved when the pressure difference between the high pressure
and the low pressure is minimum.
2. A waste heat collecting apparatus according to claim 1, further
comprising: a refrigerating cycle having a compressor device
operatively connected to and driven by an engine, a condenser, and
an evaporator, wherein the condensing device of the Rankine cycle
is commonly used as the condenser for the refrigerating device.
3. A waste heat collecting apparatus according to claim 2, wherein
the volume ratio of expansion for the expansion device is selected
at a value between 1.5 and 2.5.
4. A waste heat collecting apparatus for a vehicle comprising:
Rankine cycle having an expansion device; a condensing device; a
refrigerant pump; and a heating device, wherein the expansion
device, the condensing device, the refrigerant pump, and the
heating device are connected in a closed circuit so that
refrigerant is circulated in the closed circuit by the operation of
the refrigerant pump, the expansion device generating a rotational
driving force by expansion of the refrigerant; an electric power
generator operatively connected to the expansion device for
generating the electric power when it is driven to rotate by the
rotational driving force of the expansion device; a pressure
detecting device for detecting a pressure difference of the
refrigerant between a pressure at a high pressure side of the
expansion device and a pressure at a low pressure side of the
expansion device; and a pressure increasing means for increasing
the pressure difference when the pressure difference detected by
the pressure detecting device is lower than a predetermined
pressure difference, so that the pressure difference becomes closer
to the predetermined pressure difference.
5. A rotational force generating apparatus comprising: a high
pressure generating device for generating a high pressure of
working fluid; a low pressure generating device for generating a
low pressure of the working fluid; an expansion device having a
fixed displacement and rotating an output shaft by a pressure
difference of the working fluid between the high pressure generated
by the high pressure generating device and the low pressure
generated by the low pressure generating device, wherein a volume
ratio of expansion for the expansion device is selected at a value,
at which proper expansion of the working fluid is achieved when the
pressure difference between the high pressure and the low pressure
is minimum.
6. A rotational force generating apparatus according to claim 5,
wherein the high pressure generating device comprises a heating
device for heating the working fluid with heat generated from a
vehicle.
7. A rotational force generating apparatus according to claim 6,
wherein the high pressure generating device comprises a heating
device for heating the working fluid with heat of engine cooling
water.
8. A rotational force generating apparatus according to claim 5,
wherein the low pressure generating device comprises a condensing
device for cooling down the working fluid by the ambient air, so as
to decrease the pressure of the working fluid, and the volume ratio
of expansion for the expansion device is selected at a value, at
which the proper expansion of the working fluid is achieved during
the summer season, during which the pressure generated at the low
pressure generating device becomes higher than the pressures in
other seasons.
9. A rotational force generating apparatus according to claim 5,
wherein the low pressure generating device comprises a condensing
device, which is commonly used for Rankine cycle and a
refrigerating cycle, and the volume ratio of expansion for the
expansion device is selected at a value between 1.5 and 2.5.
10. A rotational force generating apparatus according to claim 5,
wherein a motor generator is driven by the output shaft to generate
the electric power.
11. A control system for an expansion device comprising: an
expansion device for generating a rotational driving force by
expansion of high pressure and high temperature working fluid; an
electric power generator driven by the rotational driving force of
the expansion device; a pressure detecting device for detecting a
pressure difference of the working fluid between a pressure at a
high pressure side of the expansion device and a pressure at a low
pressure side of the expansion device; and a pressure increasing
means for increasing the pressure difference when the pressure
difference detected by the pressure detecting device is lower than
a predetermined pressure difference, so that the pressure
difference becomes closer to the predetermined pressure
difference.
12. A control system for an expansion device according to claim 11,
wherein the expansion device is of a scroll type device which
comprises: a movable scroll to be rotated by the expansion of the
working fluid, with respect to a fixed scroll, with an orbital
motion; and a crank device provided to the movable scroll for
generating the rotational driving force in accordance with the
orbital motion of the movable scroll, and the fixed scroll and the
movable scroll are pushed to each other, as a function of the crank
device, during the expansion of the working fluid.
13. A control system for an expansion device according to claim 11,
wherein the pressure detecting device comprises: a pressure sensor
for detecting a high pressure side pressure and a pressure sensor
for detecting a low pressure side pressure of the expansion device;
and a controller for calculating a difference between the high
pressure side pressure and the low pressure side pressure as the
pressure difference.
14. A control system for an expansion device according to claim 11,
wherein the pressure increasing means comprises: the electric power
generator; and a device for decreasing a number of rotational speed
of the electric power generator.
15. A control system for an expansion device according to claim 14,
wherein the device for decreasing the number of rotational speed of
the electric power generator is an inverter for controlling the
rotational speed of the electric power generator.
16. A control system for an expansion device according to claim 14,
wherein the device for decreasing the number of rotational speed of
the electric power generator comprises a magnetic flux density
increasing means for increasing the magnetic flux density by
increasing excitation of a coil for a rotor of the electric power
generator.
17. A control system for an expansion device according to claim 11,
wherein the expansion device is used for Rankine cycle, and the
pressure increasing means comprises: a condensing device provided
on a low pressure side of the Rankine cycle; and a device for
increasing condensing capacity at the condensing device.
18. A control system for an expansion device according to claim 17,
wherein the device for increasing condensing capacity at the
condensing device comprises a blower device for blowing air to the
condensing device, wherein the blower device increases the amount
of the air to the condensing device.
19. A control system for an expansion device according to claim 11,
wherein the expansion device is used for Rankine cycle, and the
pressure increasing means comprises: a liquid pump for pressurizing
the working fluid in the low pressure side of the Rankine side and
for supplying the pressurized working pressure to the high pressure
side of the Rankine side; and a device for increasing a rotational
speed of the liquid pump.
20. A control system for an expansion device according to claim 19,
wherein the device for increasing the rotational speed of the
liquid pump comprises an inverter for controlling a rotational
speed of an electric motor for driving the liquid pump.
21. A control system for an expansion device according to claim 20,
wherein the device for increasing the rotational speed of the
liquid pump comprises a means for decreasing magnetic flux density
of the electric motor for driving the liquid pump by decreasing the
excitation for the electric motor.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based on Japanese Patent Application
Nos. 2006-81426 filed on Mar. 23, 2006 and 2006-140295 filed on May
19, 2006, disclosures of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a waste heat collecting
system having an expansion device, which is driven to rotate by
expansion of high-pressure and high-temperature refrigerant to
generate rotational driving force.
BACKGROUND OF THE INVENTION
[0003] According to a conventional technology, in which a
rotational force is obtained by use of waste heat generated in a
vehicle, refrigerant is heated by a heating device by use of heat
generated in the vehicle to produce high pressure refrigerant. The
high pressure refrigerant is supplied to a high pressure chamber of
an expansion device, so that an output shaft is rotated by pressure
difference between the high pressure chamber and a low pressure
chamber of the expansion device. An output (work volume) of the
expansion device is decided by "torque generated at the output
shaft X a number of rotation".
[0004] The expansion device gives a larger amount of the work
volume, as the pressure difference between the high pressure in the
high pressure chamber and the low pressure in the low pressure
chamber becomes larger. Therefore, the refrigerant discharged from
the low pressure chamber is cooled down by a condensing device.
[0005] Rankine cycle is known in the art as an apparatus for
generating the rotational force by use of the pressure difference
of the refrigerant, wherein the refrigerant is circulated in a
circuit having a refrigerant pump, a heating device, an expansion
device, and a condensing device.
[0006] When the Rankine cycle is mounted in the vehicle, the
pressure difference between the high pressure side and the low
pressure side varies depending on a change of the ambient
temperature due to a change of seasons, even after warm-up of an
engine is finished.
[0007] For example, the temperature of the engine cooling water is
maintained at a value between 80.degree. C. and 100.degree. C., so
that the pressure at the high pressure side is stably controlled at
a constant value, in such a system in which the refrigerant is
heated in a heating device by the engine cooling water (hot water)
and the refrigerant is cooled down in a condensing device by the
ambient air. On the other hand, the temperature of the ambient air
varies in a range of 0.degree. C. and 35.degree. C. depending on
the change of seasons. Therefore, the condensing capacity for the
refrigerant varies so that the pressure at the low pressure side
largely varies.
[0008] When a volume ratio of expansion for the expansion device is
considered, an expansion efficiency becomes maximum when a proper
expansion is obtained without causing any over expansion or any
insufficient expansion of the refrigerant. The proper expansion of
the refrigerant is realized at a pressure condition meeting a
designed pressure ratio, in case of the expansion device of a fixed
capacity type.
[0009] The volume ratio of expansion for the expansion device
should be considered in view of the influences to be caused
throughout the year. The volume ratio of expansion, at which a
waste heat collecting efficiency becomes maximum, is selected in
view of the change of the ambient temperature, because the pressure
at the high pressure side is controlled at a constant value by the
engine cooling water which is controlled at almost a constant
temperature. Namely, such a volume ratio of expansion, at which the
proper expansion is achieved at an average temperature throughout
the year, is generally selected.
[0010] In the case that the volume ratio of expansion is selected
in the above manner, the insufficient expansion may occur when the
actual temperature is lower than the ambient temperature for the
proper expansion, whereas the over expansion may occur when the
actual temperature is higher than the ambient temperature for the
proper expansion.
[0011] When the over expansion takes place, a loss is generated by
such over expansion. As a result, the output of the expansion
device is decreased and the necessary amount of the work volume may
not be obtained, when the actual temperature is higher than the
ambient temperature for the proper expansion.
[0012] For example, in a system or an apparatus, in which a motor
generator is driven by the expansion device, a necessary amount of
electric power may not be generated due to the loss caused by the
over expansion, when the ambient temperature is high, for example,
during the summer season.
[0013] It is, therefore, necessary to improve to decrease the loss
caused by the over expansion.
[0014] It is proposed in the art, for example, as disclosed in
Japanese Patent Publication No. H10-266980, that a bypass passage
is provided for communicating a working chamber (an expansion
chamber) with a low pressure side, wherein the working chamber is
even in a process of expansion (namely, the expansion process is
not yet finished). A valve device is further provided to open the
bypass passage, when the pressure in the working chamber reaches a
predetermined pressure (a pressure at which the over expansion may
occur). As a result, the over expansion is prevented.
[0015] According to the above prior art, however, the expansion
device becomes more complicated in structure, because the bypass
passage and the valve device are provided in the expansion device.
And the cost of the expansion device is also increased. In
addition, a failure probability will be increased, in case that an
additional device (the valve device) is provided.
[0016] Another conventional expansion device is known in the art,
for example, as disclosed in Japanese Patent Publication No.
H10-266980. According to such conventional expansion device, it is
a scroll-type device such that an expansion chamber is formed
between a fixed scroll and a movable scroll. In the expansion
device, a control passage is provided for communicating the
expansion chamber with a discharge space formed on a discharging
side of the working fluid. A valve device is provided in the
control passage for opening and closing the control passage in
accordance with a pressure difference between the expansion chamber
and the discharge space. In case that the pressure difference
between the high pressure side and the low pressure side of the
expansion device becomes lower than a predetermined value, the
expansion chamber is expanded to such a volume, to which the
working fluid can be expanded under such pressure difference. Then,
when the pressure in the expansion chamber becomes lower than the
pressure in the discharge space, the valve device is operated to
open the control passage. As a result, the pressures in the
expansion chamber and the discharge space are equalized to stop the
further expansion of the working fluid. Accordingly, an operation
of the over-expansion is prevented to achieve an efficient
operation.
SUMMARY OF THE INVENTION
[0017] The present invention is made in view of the above problems.
An object of the present invention is, therefore, to provide a
waste heat collecting system having an expansion device, which is
driven by the expansion of the refrigerant to generate the
rotational driving force, wherein a loss to be caused by the over
expansion of the refrigerant is suppressed without increasing a
complicated structure of the expansion device and a cost
increase.
[0018] Another object of the present invention is to provide a
waste heat collecting system having an expansion device, in which
the over expansion of the refrigerant is prevented to obtain a
stable operation for the expansion.
[0019] According to a feature of the present invention, a waste
heat collecting apparatus for a vehicle has: an engine cooling
circuit, through which engine cooling water is circulated; and
Rankine cycle having an expansion device, a condensing device, a
refrigerant pump, and a heating device, which are connected in a
closed circuit so that refrigerant is circulated in the closed
circuit by the operation of the refrigerant pump.
[0020] The heating device is disposed in the engine cooling circuit
for heating the refrigerant of the Rankine cycle with the heat of
the engine cooling water, so that the refrigerant is converted to
high pressure and high temperature refrigerant. The heating device
is connected to an inlet side of the expansion device for supplying
the high pressure refrigerant to the expansion device.
[0021] The condensing device is connected to an outlet side of the
expansion device for cooling down and condensing the refrigerant
from the expansion device through heat exchange with the ambient
air, so that the pressure of the refrigerant at the outlet side of
the expansion device depends on a condensing capacity of the
condensing device.
[0022] The expansion device is of a fixed displacement type fluid
machine, and an output shaft of the expansion device is driven to
rotate by expansion of the refrigerant in a working chamber
thereof, the expansion of the refrigerant is performed by a
pressure difference of the refrigerant between the high pressure at
the inlet side and low pressure at the outlet side of the expansion
device.
[0023] A volume ratio of expansion for the expansion device is
selected at a value, at which proper expansion of the refrigerant
is achieved when the pressure difference between the high pressure
and the low pressure is minimum.
[0024] According to another feature of the present invention, a
waste heat collecting apparatus for a vehicle has Rankine cycle,
which comprises: an expansion device; a condensing device; a
refrigerant pump; and a heating device, wherein the expansion
device, the condensing device, the refrigerant pump, and the
heating device are connected in a closed circuit so that
refrigerant is circulated in the closed circuit by the operation of
the refrigerant pump, the expansion device generating a rotational
driving force by expansion of the refrigerant.
[0025] The waste heat collecting apparatus further comprises: an
electric power generator operatively connected to the expansion
device for generating the electric power when it is driven to
rotate by the rotational driving force of the expansion device; a
pressure detecting device for detecting a pressure difference of
the refrigerant between a pressure at a high pressure side of the
expansion device and a pressure at a low pressure side of the
expansion device; and a pressure increasing means for increasing
the pressure difference when the pressure difference detected by
the pressure detecting device is lower than a predetermined
pressure difference, so that the pressure difference becomes closer
to the predetermined pressure difference.
[0026] According to a further feature of the present invention, a
rotational force generating apparatus has a high pressure
generating device for generating a high pressure of working fluid;
a low pressure generating device for generating a low pressure of
the working fluid; and an expansion device having a fixed
displacement and rotating an output shaft by a pressure difference
of the working fluid between the high pressure generated by the
high pressure generating device and the low pressure generated by
the low pressure generating device.
[0027] In the rotational force generating apparatus, a volume ratio
of expansion for the expansion device is selected at a value, at
which proper expansion of the working fluid is achieved when the
pressure difference between the high pressure and the low pressure
is minimum.
[0028] According to a still further feature of the present
invention, a control system for an expansion device has: an
expansion device for generating a rotational driving force by
expansion of high pressure and high temperature working fluid; an
electric power generator driven by the rotational driving force of
the expansion device; and a pressure detecting device for detecting
a pressure difference of the working fluid between a pressure at a
high pressure side of the expansion device and a pressure at a low
pressure side of the expansion device.
[0029] The control system for the expansion device has a pressure
increasing means for increasing the pressure difference when the
pressure difference detected by the pressure detecting device is
lower than a predetermined pressure difference, so that the
pressure difference becomes closer to the predetermined pressure
difference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description made with reference to the accompanying
drawings. In the drawings:
[0031] FIG. 1 is a schematic diagram showing a structure of an
engine cooling circuit, a refrigerating cycle, and Rankine cycle
according to a first embodiment of the present invention;
[0032] FIG. 2 is a cross sectional view schematically showing a
fluid machine;
[0033] FIG. 3 is an explanatory view showing a fixed scroll and a
movable scroll, which are engaged with each other;
[0034] FIGS. 4A to 4C are P-V diagrams respectively showing a
relation between a pressure applied to an expansion device and a
volume of a working chamber;
[0035] FIG. 5 is a graph showing a relation between a volume ratio
of expansion and a capacity ratio of the expansion with respect to
ambient temperature;
[0036] FIG. 6 is a schematic diagram showing a system structure of
a second embodiment of the present invention;
[0037] FIG. 7 is a flow chart showing a routine for carrying out an
increase of a pressure difference in the second embodiment;
[0038] FIG. 8 is a schematic diagram showing a system structure of
a third embodiment of the present invention;
[0039] FIG. 9 is a flow chart showing a routine for carrying out
the increase of the pressure difference in the third
embodiment;
[0040] FIG. 10 is a schematic diagram showing a system structure of
a fourth embodiment of the present invention; and
[0041] FIG. 11 is a flow chart showing a routine for carrying out
the increase of the pressure difference in the fourth
embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
First Embodiment
[0042] A system structure of a waste heat collecting apparatus will
be explained with reference to FIG. 1. The waste heat collecting
apparatus according to an embodiment of the present invention gets
a rotational energy, by use of Rankine cycle 110, out of heat in
engine cooling water (hot water) circulated in an engine cooling
circuit 1, to generate electric power. As shown in FIG. 1, a part
of the Rankine cycle 110 is commonly used in a refrigerating cycle
3 for an air conditioning apparatus mounted in an automotive
vehicle.
[0043] The engine cooling circuit 1 has a main circuit, in which
the engine cooling water is circulated from a radiator 4, a water
pump 5, an engine (a water jacket), a heating device 111, and back
to the radiator 4. The engine cooling circuit 1 has an air
conditioning hot water circuit, in which the engine cooling water
(hot water) is circulated from the engine (the water jacket), a
heater core 8, and back to the engine. The heating device 111 is a
component of the Rankine cycle 110, which will be below.
[0044] The radiator 4 cools down the engine cooling water through
heat exchange between the engine cooling water and the external
air, which is supplied to the radiator 4 by a vehicle travel and/or
a radiator fan. A radiator bypass passage 4a is provided to bypass
a heat exchanging portion of the radiator 4, and a thermostat 4b is
provided for controlling a flow ratio between a flow amount to the
heat exchanging portion and to the bypass passage 4a. The
thermostat 4b has a valve, which opens and closes a fluid passage
or changes an opening degree of the fluid passage in accordance
with temperature of the engine cooling water, to control the flow
amount of the engine cooling water flowing through the heat
exchanging portion of the radiator 4. As a result, the temperature
of the engine cooling water is stably controlled at a value between
80.degree. C. and 100.degree. C.
[0045] The water pump 5 is operated by the electric power from a
battery 11 mounted in the vehicle or driven by an output of the
engine 6, to circulate the engine cooling water in the engine
cooling circuit 1.
[0046] The engine 6 is an internal combustion engine for producing
a rotational force by combustion of fuel. The temperature of the
engine 6 is controlled by the engine cooling water flowing through
the water jacket formed in the engine 6, so that the temperature is
controlled at a value within a predetermined range.
[0047] The heater core 8 is a heat exchanger provided in a unit
casing 12 of the air conditioning apparatus for heating the air to
be blown into a passenger room by a blower device 13, through heat
exchange between the air and the engine cooling water.
[0048] The refrigerating cycle 3 has a closed circuit, through
which refrigerant is circulated from a compressor 14, a condensing
device 113, a receiver 16, a depressurizing device 17, an
evaporator 18, and back to the compressor 14. An operation of the
refrigerating cycle 3 is controlled by an electronic control unit
(ECU) 133.
[0049] The compressor 14 is operatively connected to the engine 6
via an electromagnetic valve 14b, a pulley 14a, and a driving belt
22, so that the rotational driving force of the engine 6 is
transmitted to the compressor 14. The compressor 14, accordingly,
draws the refrigerant, and compresses and pumps out the same.
[0050] The condensing device 113 is a heat exchanger for cooling
the high pressure and high temperature refrigerant from the
compressor 14 through heat exchange with external air supplied
thereto by the vehicle travel or by a condenser fan 142, so that
the refrigerant is condensed and liquefied. The condenser fan 142
may be commonly used as the radiator fan.
[0051] The receiver 16 separates the refrigerant, which is
condensed at the condensing device 113, into a liquid phase
refrigerant and a gas phase refrigerant, and supplies the
liquid-phase refrigerant to the depressurizing device 17.
[0052] The depressurizing device carries out an adiabatic expansion
of the liquid-phase refrigerant separated at the receiver 16.
[0053] The evaporator 18 is arranged in the unit casing 12 of the
air conditioning apparatus for cooling the air passing through the
evaporator by heat exchange between atomized refrigerant and the
air blown into the passenger room by the blower device 13. The
atomized refrigerant is vaporized in the evaporator 18 by absorbing
vaporization heat, so that the air passing through the evaporator
18 is cooled down.
[0054] The gas phase refrigerant vaporized in the evaporator 18 is
sucked again into the compressor 14, so that the above operation is
repeated so long as the compressor 14 is in operation.
[0055] The unit casing 12 has the blower device 13, which is
operated by the electric power from the battery 11, the evaporator
18 for cooling down the air blown into the passenger room by the
blower device 13, and the heater core 8 for heating the air.
[0056] A heater core bypass passage 23 is formed in the unit casing
12 and an air-mix door 24 is provided at an upstream side of the
heater core 8 for controlling a ratio of the air flow, namely a
ratio of the air flow between the air flowing through the heater
core 8 and the air flowing through the heater core bypass passage
23. The air-mix door 24 is controlled manually or by an actuator
controlled by the ECU 133. The temperature of the air blown into
the passenger room is controlled by changing the ratio of the air
flow by the air-mix door 24.
[0057] The Rankine cycle 110 is formed by a closed circuit, in
which the refrigerant is circulated from the condensing device 113,
the receiver 16, a refrigerant pump 114, the heating device 111, an
expansion device 112, and back to the condensing device 113. An
operation of the Rankine cycle 110 is controlled by the ECU
133.
[0058] The condensing device 113 and the receiver 16 are commonly
used in the Rankine cycle 110 and the refrigerating cycle 3. And
the refrigerant circulated in both cycles are the same to each
other.
[0059] The condensing device 113 is provided at the downstream side
of the expansion device 112 and cools down the refrigerant in the
Rankine cycle 110. Therefore, the condensing device 113 functions
as a low pressure generator for generating low pressure at an
outlet side of the expansion device 112 and also functions as a
heat exchanger for cooling down the refrigerant. The refrigerant at
the inlet side of the condensing device 113 is at high pressure and
high temperature when the refrigerating cycle 3 is in its
operation, whereas the pressure of the refrigerant at the inlet
side of the condensing device 113 is lower than that at the outlet
side of the heating device 111 when the Rankine cycle 110 is in its
operation.
[0060] The receiver 16 supplies the gas phase refrigerant to the
refrigerant pump 114 during the operation of the Rankine cycle
110.
[0061] The refrigerant pump 114 is driven to rotate by an electric
motor (a motor generator) 120 to pressurize and supply the
refrigerant from the receiver 16 to the heating device 111. The
motor generator 120 generates a rotational force to drive the
refrigerant pump 114, when electric power is supplied from the
battery 11 through an inverter 141. On the other hand, the motor
generator 120 generates electric power when it is driven to rotate
by the output of the expansion device 112.
[0062] The liquid phase refrigerant pressurized by the refrigerant
pump 114 is heated at the heating device 111 by the heat exchange
with the engine cooling water circulating in the main circuit of
the engine cooling circuit. Therefore, the refrigerant is heated to
super heated steam of the refrigerant, to which expansion energy is
given. The heating device 111 works as a high pressure generating
device for generating high pressure energy at the inlet side of the
expansion device 112.
[0063] The expansion device 112 is a fixed capacitor type expansion
device, an output shaft of which is rotated by the pressure
difference between the high pressure and the low pressure. Namely,
the super heated steam of the refrigerant passing through the
heating device 111 is supplied to the inlet side of the expansion
device 112, and the outlet side of the expansion device 112 is
connected to the inlet side of the condensing device 113.
Accordingly, the output shaft of the expansion device 112 is
rotated by the pressure difference between the high pressure of the
super heated steam of the refrigerant at the inlet side of the
expansion device 112 and the low pressure generated at the
condensing device 113 at the outlet side of the expansion device
112.
[0064] The output shaft of the expansion device 112 drives an input
shaft of the motor generator 120. The output shaft of the expansion
device 112, the input shaft of the motor generator 120, and a
driving shaft of the refrigerant pump 114 are formed by a common
shaft 29. Accordingly, when the expansion device 112 generates the
rotational force, the motor generator 120 as well as the
refrigerant pump 114 is rotated by such rotational force. On the
other hand, when the rotational force is generated at the motor
generator 120, the expansion device 112 as well as the refrigerant
pump 114 is rotated by the rotational force.
[0065] The Rankine cycle 110 has a pressure equalization device 30,
which opens or closes a communication between the high pressure
side and the low pressure side of the expansion device 112. The
pressure equalization device 30 is provided in the inside of the
expansion device 112, as described below. It may be, however,
provided at an outside of the expansion device 112. The pressure
equalization device 30 makes the pressure difference smaller by
communicating the high pressure side and the low pressure side of
the expansion device 112 with each other, when the expansion device
112 is not operated or when the operation of the expansion device
112 is stopped.
[0066] The inverter 141 controls the operation of the motor
generator 120. Namely, the inverter 141 controls the power supply
from the battery 11 to the motor generator 120, when the motor
generator 120 is operated as the electric motor, whereas the
inverter controls the charging current from the motor generator 120
to the battery 11 depending on a charged condition thereof, when
the motor generator 120 is operated as the electric power generator
by the rotational force generated at the expansion device 112.
[0067] The ECU 133 controls, in addition to the above operation of
the inverter 141, the electrical components for the Rankine cycle
110 and the refrigerating cycle 3. A power switch (for example, an
ignition switch) 31 is provided to the ECU 133, to stop the
operation of the ECU 133, the Rankine cycle 110, and the
refrigerating cycle 3, by cutting off the power supply from the
battery 11, when the power switch 31 is turned off.
[0068] The refrigerant pump 114, the expansion device 112, and the
motor generator 120 are coaxially arranged and integrally formed as
a fluid machine of a pump-expansion-generator device, as shown in
FIG. 2.
[0069] The common shaft 29 is rotatably supported by first and
second bearings 32 and 33 in the fluid machine.
[0070] The fluid machine has first to fifth housing parts 34 to 38,
which are firmly connected with each other by, for example, bolts,
in an axial direction.
[0071] The first housing part 34 accommodates the pressure
equalization device 30, the second housing part 35 is used as a
fixed scroll 41 of the expansion device 112, the third housing part
36 accommodates a movable scroll 42 of the expansion device 112 and
the motor generator 120, the fourth housing part 37 accommodates
the refrigerant pump 114, and the fifth housing part 38 closes an
accommodating chamber for the refrigerant pump 114.
[0072] A part of the third housing part 36 is formed as a shaft
housing 39 for supporting the first bearing 32.
[0073] The expansion device 112 has a structure similar to a well
known scroll type compressor, in which inlet side and outlet side
are reversed.
[0074] The expansion device 112 has the fixed scroll 41 integrally
formed as the second housing part 35, the movable scroll 42 engaged
with the fixed scroll 41 and rotated with an orbital motion, an
auto-rotation preventing device 43 for preventing the auto-rotation
of the movable scroll 42, and an output portion 44 for generating
the rotational force from the orbital motion of the movable scroll
42.
[0075] The fixed scroll 41, which is integrally formed as the
second housing part 35, has a base plate 41a and a fixed scroll
wrap 41b.
[0076] A right-hand side of the base plate 41a (in FIG. 2) is
formed on a plane perpendicular to an axial direction, and a seal
member formed at a forward end of a movable scroll wrap 41b
(described below) slides on the base plate 41a.
[0077] The fixed scroll wrap 41b is a vortical wrap extending in
the axial direction from the base plate 41a.
[0078] A high pressure chamber 45 is formed between the first and
second housing parts 34 and 35. The high pressure chamber 45 is a
space for communicating an inlet port 46 formed at the base plate
41a with a high pressure port 47, through which the super heated
steam of the refrigerant is introduced from the heating device
111.
[0079] A low pressure chamber 48 is formed in the inside of the
third housing part 36. The low pressure chamber 48 is a space for
communicating a space (referred to as a discharge portion 49)
formed at an outer periphery of the fixed and movable scrolls 41
and 42 with a low pressure port 50, through which the refrigerant
flows back to the condensing device 113. The motor generator 120 is
accommodated in the above space.
[0080] The movable scroll 42 forms a pair with the fixed scroll 41
and rotates with respect to the fixed scroll 41 with the orbital
motion. The movable scroll 42 is pushed toward the fixed scroll by
the shaft housing 39, so that multiple working chambers (expansion
chambers) V are formed by spaces surrounded by the fixed scroll 41
and the movable scroll 42, as shown in FIG. 3. A sliding plate 52
is interposed between the movable scroll 42 and the shaft housing
39, to enable a smooth rotation of the movable scroll 42.
[0081] The movable scroll 42 has a base plate 42a and a movable
scroll wrap 42b.
[0082] A left-hand side of the base plate 42a (in FIG. 2) is formed
on a plane perpendicular to the axial direction, and a seal member
formed at a forward end of the fixed scroll wrap 41b slides on the
base plate 42a.
[0083] The movable scroll wrap 42b is a vortical wrap extending in
the axial direction from the base plate 42a. As shown in FIG. 3,
the movable scroll wrap 42b is engaged with the fixed scroll wrap
41b at such a position, in which the movable scroll 42 is displaced
by an angle of 180.degree. with respect to the fixed scroll 41.
[0084] When the movable scroll 42 rotates with the orbital motion,
the working chamber V surrounded by the fixed and movable scrolls
41 and 42 moves from a center portion to an outer periphery, and a
volume of the working chamber V is increased in accordance with the
above movement to the outer periphery. When the super heated steam
of the refrigerant is introduced from the inlet port 46 into the
working chamber V at the center portion, the expansion energy of
the super heated steam works to expand the volume of the working
chamber V. When the movable scroll 42 is rotated by the above
expanding energy in the working chamber V, the movable scroll 42 is
rotated by the orbital motion. When the working chamber V moves to
the outer periphery of the scrolls 41 and 42, and the working
chamber V is communicated with the discharge portion 49, the
refrigerant is discharged from the working chamber V to the low
pressure chamber 48.
[0085] The auto-rotation preventing device 43 (a crank device 43)
prevents the auto-rotation of the movable scroll 42, in order to
achieve the orbital motion. The auto-rotation preventing device 43
has a pin 51 fixed to the movable scroll 42 and extending in the
axial direction, and a groove 51a formed in the shaft housing 39
and extending in a radial direction, wherein the pin 51 is engaged
in the groove 51a in order to prevent the auto-rotation but to
allow the orbital motion of the movable scroll 42.
[0086] The output portion 44 generates the rotational force from
the orbital motion of the movable scroll 42, as already explained,
and has a cylindrical boss 53 and an eccentric shaft portion 54.
The cylindrical boss 53 is integrally formed with the movable
scroll 42, extending from the base plate 42a in the right-hand
direction. The eccentric shaft portion 54 is formed at a left-hand
end of the common shaft 29, wherein the shaft portion 54 is
eccentric to the rotating center of the common shaft 29. The
eccentric shaft portion 29 is inserted into an inside of the
cylindrical boss 53 and rotationally connected with the cylindrical
boss via a bearing 55.
[0087] According to the above structure, the cylindrical boss 53
rotates with the orbital motion together with the movable scroll
42, and the eccentric shaft portion 54 is rotated together with the
common shaft 29.
[0088] As above, the orbital motion of the movable scroll 42 caused
by the expanding energy of the refrigerant is converted into the
rotation of the common shaft 29 through the rotation of the
eccentric shaft portion 54.
[0089] The pressure equalization device 30 communicates or cuts off
the communication between the high pressure side and the low
pressure side of the expansion device 112. A major portion of the
pressure equalization device 30 is accommodated in the first
housing part 34.
[0090] The pressure equalization device 30 has a bypass passage 56,
a valve device 57, and an electromagnetic valve 58. The bypass
passage 56 is a communication passage formed in the second housing
part 35 for connecting the high pressure chamber 45 with the
discharge portion 49.
[0091] The valve device 57 has a piston 57a slidably inserted into
a cylinder formed in the first housing part 34 and extending in the
axial direction. The valve device 57 further has a valve body 57b
connected to the piston 57a to open and close the bypass passage
56. A compression coil spring 57d is inserted into a back pressure
chamber 57c formed by the cylinder for biasing the piston 57a in a
valve closing direction (in a direction to close the bypass passage
56). The bypass passage 56 is closed by the valve body 57b, when
the pressure in the back pressure chamber 57c is increased.
[0092] The electromagnetic valve 58 is operated by the ECU 133 to
control the pressure in the back pressure chamber 57c. When the
electric power is supplied to the electromagnetic valve 58, the
high pressure is supplied from the high pressure chamber 45 to the
back pressure chamber 57c, whereas the low pressure is supplied
from the low pressure chamber 48 to the back pressure chamber 57c
when the power supply to the electromagnetic valve 58 is cut
off.
[0093] Therefore, when the electric power is supplied to the
electromagnetic valve 58, the pressure in the back pressure chamber
57c is increased so that the valve body 57b is strongly pushed
together with the spring force of the spring 57d to the bypass
passage 56, to close the bypass passage 56. The communication
between the high pressure chamber 45 and the low pressure chamber
48 through the bypass passage 56 is cut off.
[0094] On the other hand, when the power supply to the
electromagnetic valve 58 is cut off, the pressure in the back
pressure chamber 57c is decreased so that the piston 57a compresses
the spring 57d by the pressure in the high pressure chamber 45. The
valve body 57b is moved in the leftward direction to open the
bypass passage 56. Accordingly, the high pressure chamber 45 and
the low pressure chamber 48 are communicated with each other
through the bypass passage 56, to equalize the pressure in the high
pressure side and low pressure side.
[0095] The motor generator 120 has a stator 61 and a rotor 62. The
stator 61 has a stator core 61a fixed to an inner peripheral
surface of a motor housing 36a formed by the third housing part 36,
and a stator coil 61b wound on the stator core 61a. The rotor 62
has permanent magnets firmly inserted and held in a rotor core
mounted to the common shaft 29.
[0096] When the electric power is supplied to the stator coil 61b
through the inverter 141, the rotor 62 and the common shaft 29 are
driven to rotate. On the other hand, when the common shaft 29 is
rotated, the electric power is generated at the stator coil 61b by
the rotation of the rotor 62.
[0097] More exactly, the electric power is supplied to the stator
coil 61b from the battery 11 through the inverter 141 at a start-up
operation of the Rankine cycle 110. The rotor 62 is thereby driven
to rotate, to operate the motor generator 120 as the electric motor
for driving the expansion device 112 and the refrigerant pump
114.
[0098] On the other hand, when the expansion device 112 is in its
operation, the refrigerant pump 114 and the rotor 62 are driven to
rotate by the rotational driving force generated at the expansion
device 112, so that the motor generator 120 is operated as the
electric power generator. The electric power generated at the motor
generator 120 is charged into the battery 11.
[0099] The refrigerant pump 114 is a rolling piston type pump
arranged in the fourth housing part 37, and has a pump housing 63,
an eccentric cam 64, a pump rotor 65, and a vane 66.
[0100] The pump housing has an cylindrical center housing 63a and
first and second side housings 63b and 63c, which are connected to
the fourth housing part 37 by a fixing means, such as bolts. The
first side housing 63b supports the second bearing 33.
[0101] The eccentric cam 64 is formed at a right hand end of the
common shaft 29. The eccentric cam 64 having a circular cross
section is eccentric to the rotating center of the common shaft 29,
and accommodated in the inside of the center housing 63a. The pump
rotor 65 is an annular member provided at an outer periphery of the
eccentric cam 64. An outer diameter of the pump rotor 65 is smaller
than an inner diameter of the center housing 63a. The pump rotor 65
rotates with an orbital motion within the space of the center
housing 63a, in accordance with the rotation of the eccentric cam
64.
[0102] A lubricating passage 29a is formed in the common shaft 29
for introducing the refrigerant (together with lubricating oil
contained in the refrigerant) from the low pressure chamber 48 to
the inside of the pump rotor 65. An orifice 29a is formed at an end
of the lubricating passage 29a, at a side to the pump rotor 65.
[0103] The vane 66 is slidably supported by the center housing 63a
in a radial direction and biased by a spring (not shown) inwardly
in the radial direction. The vane 66 defines a pump chamber P
between the pump rotor 65 and the center housing 63a.
[0104] A pump inlet port 67 and a pump outlet port (not shown) are
respectively formed at both sides of the pump rotor 65, adjacent to
the vane 66. A pump inlet pipe 68 connected to the pump inlet port
67 is provided at the fourth housing part 37, which accommodates
the refrigerant pump 114. The pump inlet pipe 68 is connected, at
the other end thereof, to an outlet port of the receiver 16 for the
liquid phase refrigerant.
[0105] The pump outlet port (not shown) is communicated with a pump
discharge chamber 69, which is formed in the fourth housing part 37
for accommodating the refrigerant pump 114. A pump outlet pipe 71
is provided in the fourth housing part 37 for communicating the
pump discharge chamber 69 with the inlet side of the heating device
111. A check valve 72 is provided at an opening portion of the pump
outlet port, which opens to the pump discharge chamber 69, so that
the refrigerant is allowed to flow only in a direction from the
pump outlet port to the pump discharge chamber 69.
[0106] In the refrigerant pump 114, the refrigerant is sucked into
the pump chamber P from the pump inlet pipe 68 through the pump
inlet port 67, in accordance with the rotation (the orbital motion)
of the pump rotor 65 driven by the common shaft 29. The refrigerant
is then pumped out from the pump chamber P to the pump outlet pipe
71 through the pump outlet port (not shown) and the pump discharge
chamber 69.
[0107] An operation of the Rankine cycle will be explained. The ECU
133 starts the operation of the Rankine cycle 110, when the ECU 133
determines that the charged amount of the electric power in the
battery is lower than a predetermined value and that it is in a
condition that the operation of the Rankine cycle is possible
(namely, when the temperature of the engine cooling water is higher
than a predetermined temperature). More specifically, the current
supply to the electromagnetic valve 58 is cut off during a period
shortly after the start-up of the Rankine cycle 110, so that the
bypass passage 56 is opened by the valve device 57. And the motor
generator 120 is operated as the electric motor to drive the
refrigerant pump 114 and the expansion device 112.
[0108] In this operation, the refrigerant pump 114 sucks the
refrigerant from the receiver 16 and pumps out the pressurized
refrigerant to the heating device 111. The refrigerant is heated at
the heating device 111 through the heat exchange with the engine
cooling water and supplied into the expansion device 112. The
refrigerant introduced into the expansion device 112 through the
high pressure port 47 directly flows from the high pressure chamber
45 to the low pressure chamber 48 through the bypass passage 56,
because the bypass passage 56 is opened by the high pressure
refrigerant introduced into the high pressure chamber 45. Then, the
refrigerant returns to the inlet side of the condensing device 113
through the low pressure port 50.
[0109] When a predetermined time (a time during which the
refrigerant is sufficiently heated at the heating device 111 to
super heated steam of the refrigerant) has passed by since the
motor generator 120 had been operated as the electric motor, the
ECU 133 turns on the electromagnetic valve 58 to close the bypass
passage 56 by the valve device 57. As a result, the super heated
steam of the refrigerant in the high pressure chamber 45 is
introduced into the working chamber V through the inlet port
46.
[0110] The super heated steam of the refrigerant introduced into
the working chamber V at the center portion increases the volume of
the working chamber V by its expanding energy, so that the movable
scroll 42 is rotated with the orbital motion. The working chamber V
moves from the center portion to the outer periphery, as the volume
of the working chamber V is increased. When the working chamber V
becomes in communication with the discharge portion 49, the
refrigerant flows from the working chamber V to the low pressure
chamber 48. The refrigerant returns to the inlet side of the
condensing device 113 through the low pressure port 50, so that the
refrigerant is circulated through the condensing device 113, the
receiver 16, the refrigerant pump 114, the heating device 111, and
the expansion device 112.
[0111] The orbital movement of the movable scroll 42 is converted
into the rotation at the output portion 44 to rotate the common
shaft 29. The refrigerant pump 114 and the motor generator 120 are
thereby driven to rotate.
[0112] When the rotational driving force of the expansion device
112 reaches such a value, at which the refrigerant pump 114 can be
rotated in a normal condition, the ECU 133 switches over the
operation of the motor generator 120 from the electric motor to the
power generator, so that the electric power generated at the motor
generator 120 is charged into the battery 11 through the inverter
141.
[0113] The ECU 133 cuts off the electric power supply to the
electromagnetic valve 58, when the charged amount in the battery 11
reaches a predetermined charge amount or when the ECU 133
determines any abnormal condition. Then, the bypass passage 56 is
opened to equalize the pressure at the inlet side and the outlet
side of the expansion device 112, because the super heated steam of
the refrigerant supplied to the high pressure chamber 45 flows to
the low pressure chamber 48 through the bypass passage 56. The
rotation of the expansion device 112 is stopped as a result of the
decrease of the pressure difference between the inlet and outlet
sides thereof, so that the operation of the Rankine cycle 110 is
stopped.
[0114] In the above Rankine cycle 110, the high pressure to be
applied to the expansion device 112 is obtained by the super heated
steam of the refrigerant, which is heated by the engine cooling
water. The temperature of the engine cooling water is maintained at
a temperature of 80.degree. C. to 100.degree. C., by the operation
of the thermostat 4b. Therefore, the high pressure applied to the
expansion device 112 is stable throughout one year.
[0115] On the other hand, the low pressure to be applied to the
expansion device 112 changes depending on the condensing capacity
of the condensing device 113. The condensing capacity of the
condensing device 113 changes in accordance with a change of
ambient temperature. Accordingly, the low pressure applied to the
expansion device 112 largely changes even during a normal constant
operation after a warming-up operation of the Rankine cycle
110.
[0116] A volume ratio of expansion for the expansion device 112
should be decided under the consideration of circumstances
throughout the year, in case of the fixed capacitor type expansion
device.
[0117] The volume ratio of the expansion is expressed by the
following formula: Volume ratio=Vout1/Vin1=Vout2/Vin2,
[0118] wherein "Vin1" or "Vin2" is a volume of the working chamber
V formed at the center portion (the high pressure side) shortly
after the inlet port 46 is closed, whereas "Vout1" or "Vout2" is
the volume of the working chamber V formed at the outer periphery
shortly before the working chamber V is communicated with the
discharge portion 49, as indicated in FIG. 3.
[0119] The volume ratio of the expansion is generally selected at
such a value, at which energy collecting efficiency is maximum.
When the high pressure to the expansion device 112 is constant due
to the constant temperature of the engine cooling water, the
variation of the ambient temperature should be taken into
consideration. Namely, the volume ratio of the expansion is
selected based on an average temperature throughout the year, at
such a value at which a proper expansion is realized.
[0120] In the case that the volume ratio for the proper expansion
is selected as above, an over expansion or an insufficient
expansion may not occur at a predetermined ambient temperature, at
which the proper expansion is realized, as shown in FIG. 4B.
[0121] However, the insufficient expansion occurs, as shown in FIG.
4C, when the ambient temperature is lower than the predetermined
ambient temperature for the proper expansion. And the over
expansion occurs, as shown in FIG. 4A, when the ambient temperature
is higher than the predetermined ambient temperature for the proper
expansion.
[0122] A hatched area A in each of FIGS. 4A to 4C shows an actual
expanding power (energy), which is obtained at the expansion device
112 by the flow-in, the expansion, and the flow-out of the super
heated steam of the refrigerant. An area surrounded by a dotted
line B in each of FIGS. 4A to 4C shows a theoretical expanding
power. A white area C shows a power lost. PH designates the
pressure at the high pressure side of the expansion device 112, and
PL designates the pressure at the low pressure side of the
expansion device 112.
[0123] As shown in FIG. 4A, there is a loss caused by the over
expansion, when the over expansion of the refrigerant takes place.
When the ambient temperature is very much high, for example, in the
summer season, a necessary amount of the electric power may not be
obtained at the motor generator 120 because of the loss caused by
the over expansion.
[0124] In the conventional system, a priority is given to get the
maximum work volume out of the heat of the engine cooling water.
However, it is more preferable to constantly generate the electric
power necessary for the vehicle than to increase the amount of the
generated electric power, in the case that the electric power is
generated.
[0125] In other words, it is more preferable to suppress the loss
and to get the necessary electric power in the circumstance of the
high ambient temperature, such as in the summer season, than to get
the maximum generated amount of the electric power throughout the
year.
[0126] According to the above embodiment, however, the volume ratio
of the expansion is decided as below. The pressure difference
between the high pressure side and the low pressure side of the
expansion device 112 varies in a certain range, even when the
Rankine cycle 110 is in the constant operation after the warming-up
operation for the engine 6 has been ended. The volume ratio of the
expansion for the expansion device 112 is selected at such a value,
at which the proper expansion is realized (in other words, the over
expansion or the insufficient expansion may not occur) even when
the pressure difference is at its minimum amount within the above
range.
[0127] More exactly, the pressure is almost constant at the high
pressure side of the expansion device 112 throughout the year, but
the pressure at the low pressure side varies depending on the
change of the ambient temperature, so that the pressure difference
between the high pressure side and the low pressure side becomes
smaller in the summer season. The volume ratio of the expansion for
the expansion device 112 is selected at such a value, at which the
proper expansion is realized (in other words, the over expansion or
the insufficient expansion may not occur) even at the highest
ambient temperature in the daytime of the summer season, for
example, at an estimated road temperature in, the daytime of the
summer season, at an estimated highest temperature in the daytime
of the summer season, or an average temperature of the highest
temperatures of the day for a period of one month in which the
average temperature is the highest among the months.
[0128] According to the above embodiment, the condensing device 113
is commonly used for the Rankine cycle 110 and the refrigerating
cycle 3, so that the condensing capacity for the refrigerant is
relatively large. The refrigerant for the Rankine cycle 110 is the
same to that for the refrigerating cycle 3, for example, HFC, HC or
the like.
[0129] In the above Rankine cycle 110, the pressure at the high
pressure side of the expansion device 112 is stably maintained at a
value between 2.0 MPa and 2.5 MPa, because the temperature of the
engine cooling water is stably maintained at the value between
80.degree. C. to 100.degree. C.
[0130] On the other hand, the ambient temperature, which affects
the condensing capacity of the condensing device 113, largely
varies throughout the year. The pressure at the low pressure side
(the outlet side) of the expansion device 112 is increased to 1.1
MPa, when the ambient temperature is 30.degree. C., whereas the
pressure at the low pressure side (the outlet side) of the
expansion device 112 is decreased to 0.5 MPa, when the ambient
temperature is 0.degree. C.
[0131] A relation between the volume ratio of the expansion and a
capacity ratio of the expansion, with respect to the ambient
temperature (5.degree. C. to 30.degree. C.), is shown in FIG.
5.
[0132] As shown in FIG. 5, the proper expansion can be achieved at
the volume ratio of the expansion which is around 2, when the
ambient temperature is high (at 30.degree. C.). The volume ratio of
the expansion, at which the proper expansion will be achieved, is
increased, as the ambient temperature is decreased.
[0133] According to the above embodiment, the volume ratio of the
expansion for the expansion device 112 is selected at the value, at
which the proper expansion (no over expansion, no insufficient
expansion) is achieved in the summer season. More exactly, the
pressure at the high pressure side is between 2.0 MPa to 2.5 MPa,
the pressure at the low pressure side is around 1.1 Mpa, and the
volume ratio of the expansion is about 2.0.
[0134] Namely, the volume ratio of the expansion for the expansion
device 112 is selected at the value, at which the proper expansion
is achieved at the high ambient temperature (for example, at the
temperature between 30.degree. C. and 35.degree. C.) in the summer
season. The volume ratio of the expansion is preferably selected at
a value between 1.8 and 2.2, and most preferably at the value of
2.0.
[0135] According to the waste heat collecting apparatus of the
above embodiment, the volume ratio of the expansion for the
expansion device 112 is selected at such a value, at which the
proper expansion is carried out at a side of the smaller pressure
difference, within a range of variation for the pressure
difference. Namely, the volume ratio of the expansion is selected
at the value in a range of 1.5 and 2.5, at which the proper
expansion is carried out in the summer season, in which the
pressure at the low pressure side becomes higher. The pressure at
the low pressure side varies depending on the change of the ambient
temperature.
[0136] According to the above structure, the over expansion in the
expansion device 112 can be prevented, even when the pressure at
the low pressure side is increased as a result of the increase of
the ambient temperature. As a result, a stable operation for the
electric power generation can be realized within a wide range of
the temperature, in which the vehicle is actually used.
[0137] Furthermore, as the volume ratio of the expansion is
selected at such value, at which the proper expansion is carried
out in the summer season, a stable amount of the electric power is
generated throughout the year. And the conventional bypass passage
and the valve device, which are required in the prior art, are no
longer necessary.
[0138] The generation of the loss caused by the over expansion can
be prevented, without causing the complicated structure and
increase of the cost for the expansion device 112. The necessary
amount of the electric power for the vehicle can be generated
throughout the year. A failure probability for the expansion device
112 is decreased as a result of the simple structure of the
expansion device 112, and thereby a reliability of the Rankine
cycle 110 can be increased.
[0139] The above explained embodiment may be modified in various
ways, as in the following manner.
[0140] The refrigerant pump 114, the expansion device 112, and the
motor generator 120 are integrally formed in the single fluid
machine. However, those components may be respectively formed as
independent fluid machines.
[0141] The refrigerant pump is driven by the expansion device 112.
However, the refrigerant pump 114 may be driven by an electric
motor exclusively provided for the refrigerant pump.
[0142] The motor generator 120 is driven to rotate by the expansion
device 112. However, any other components, such as a blower fan
device, a supercharger device, the compressor 14, and so on may be
driven by the expansion device 112.
[0143] Furthermore, the rotational force of the expansion device
112 may be charged or stored as a kinetic energy in a spring, a
flywheel, and the like.
[0144] Some of the components are commonly used for the Rankine
cycle 110 and the refrigerating cycle 3. The Rankine cycle 110 and
the refrigerating cycle 3 may be formed as the independent
cycles.
[0145] In the above embodiment, the waste heat from the engine (the
heat in the engine cooling water) is used to heat the refrigerant
to obtain the high pressure energy. The refrigerant maybe, however,
heated by the waste heat, such as the heat in exhaust gas of the
engine 6, the heat generated at the battery 11, the heat generated
at the inverter 141, the heat in compressed air by a supercharger,
and so on.
[0146] The refrigerant may be, furthermore, heated by combustion
energy by a burner, the solar heat, and so on.
[0147] In the above embodiment, the Rankine cycle 110 is used for
collecting the waste heat to convert the collected heat into the
rotational force. Any other device than the Rankine cycle 110 may
be used for operating the expansion device 112, which is driven by
the pressure difference.
[0148] In the above embodiment, the refrigerant is cooled down by
the external air, to generate the low pressure. The engine cooling
water may be used to cool down the refrigerant, when the heating
capacity for heating the refrigerant is large, for example in case
of heating the refrigerant by exhaust gas of the engine 6.
[0149] In such a case, the pressure at the low pressure side will
become stable, whereas the pressure at the high pressure side
varies. Therefore, the volume ratio for the expansion is selected
at the value, at which the proper expansion is achieved even when
the pressure at the high pressure side is decreased within a range
of variation for the pressure difference.
Second Embodiment
[0150] A second embodiment of the present invention will be
explained with reference to FIGS. 6 and 7. A structure will be
explained with reference to FIG. 6. The second embodiment shows a
control system for an expansion device, which is applied to an
expansion device 112 to be used in Rankine cycle 110 to be mounted
in an automotive vehicle.
[0151] The vehicle, to which the present invention is applied, is a
general passenger car, which is equipped with a water-cooled
internal combustion engine (not shown) as a driving source for a
vehicle travel. An alternator 150 is mounted in the vehicle, which
is driven by the engine to generate electric power. The electric
power generated by the alternator 150 is charged into a battery 11
through an inverter 141, and the electric power charged in the
battery 11 is supplied to vehicle electrical loads 160, such as
head lamps, a wiper motor, an audio equipment, and so on.
[0152] The Rankine cycle 110 collects waste heat (thermal energy of
engine cooling water) generated at the engine, to convert the waste
energy into electric energy and to use it. The Rankine cycle 110
has a liquid pump 114, a heating device 111, the expansion device
112, and a condensing device 113, wherein those components are
connected in a closed circuit.
[0153] The pump 114 is a fluid machine driven by an electric motor
(not shown) for circulating refrigerant (the working fluid) in the
Rankine cycle 110. An operation of the electric motor is controlled
by a pump inverter (not shown).
[0154] The heating device 111 is a heat exchanger having two fluid
passages formed in the inside thereof, wherein the refrigerant from
the pump 114 and high-temperature engine cooling water flows
through the respective fluid passages. The heating device 111 heats
the refrigerant through a heat-exchange between the refrigerant and
the engine cooling water, so that the refrigerant is heated to
high-pressure and high-temperature super heated steam of the
refrigerant.
[0155] The expansion device 112 is a fluid machine for producing a
rotational driving force by expansion of the super heated steam of
the refrigerant heated by the heating device 111. The expansion
device 112 is formed as the scroll type expansion device having a
fixed scroll and a movable scroll.
[0156] An expansion chamber is formed between the fixed scroll and
the movable scroll, wherein the movable scroll is rotated with
respect to the fixed scroll with an orbital motion when the super
heated steam of the refrigerant is expanded in the expansion
chamber. A crank device is provided at the movable scroll, so that
the rotational driving force can be taken out in accordance with
the orbital motion of the movable scroll.
[0157] The crank device has a driving pin, which is eccentric to a
shaft, and a cylindrical bushing having a hole eccentric to the
shaft. The crank device biases the movable scroll toward the fixed
scroll during the expansion of the refrigerant.
[0158] The condensing device 113 is a heat exchanger for condensing
and liquefying the refrigerant through the heat-exchange with
cooling air. A blower device 142 is provided to the condensing
device 113 for supplying the cooling air toward a heat-exchange
portion of the condensing device 113. An outlet side of the
condensing device 113 is connected to the liquid pump 114.
[0159] A pressure sensor 131 of a high pressure side is provided at
an inlet side of the expansion device 112, that is between the
heating device 111 and the expansion device 112, for detecting
refrigerant pressure of the high pressure side of the Rankine cycle
110 (hereinafter also referred to as a high pressure side pressure
P1). A pressure signal detected at the pressure sensor 131 is
outputted to a controller 133 (described below).
[0160] A pressure sensor 132 of a low pressure side is provided at
an outlet side of the expansion device 112, that is between the
expansion device 112 and the condensing device 113, for detecting
refrigerant pressure of the low pressure side of the Rankine cycle
110 (hereinafter also referred to as a low pressure side pressure
P2). A pressure signal detected at the pressure sensor 132 is
likewise outputted to the controller 133.
[0161] The controller 133 has a calculating portion for calculating
a pressure difference .DELTA.P at the expansion device 112, which
is a difference between the high pressure side pressure P1 and the
low pressure side pressure P2 respectively detected at the pressure
sensors 131 and 132. The calculated pressure difference .DELTA.P is
outputted to the inverter 141.
[0162] An electric power generator 120 (e.g. a synchronous
generator) is connected to the expansion device 112. The electric
power generator 120 is, for example, a three-phase alternating
current generator, which has a rotor 121 (for example, a rotor
having permanent magnets) connected to the crank device (the shaft)
of the expansion device 112, and a stator 122 having a three-phase
coil arranged at an outer periphery of the rotor 121. The electric
power generator 120 generates electric current at the stator 122 in
accordance with rotation of the rotor 121 driven by the rotational
driving force of the expansion device 112.
[0163] An operation of the above generator 120 is controlled by the
inverter 141 connected to the stator 122. Namely, the inverter 141
controls the electric current at the stator 122 to control the
rotational speed of the rotor 121 during an operation of the
electric power generation at the generator 120. Accordingly, the
amount of electric power generated is controlled. The electric
power generated is charged into the battery 11. The inverter 141
controls the rotational speed of the rotor 121 in accordance with
the pressure difference .DELTA.P supplied from the controller
133.
[0164] An operation of the control system for the expansion device
(the Rankine cycle 110) will be explained with reference to a flow
chart shown in FIG. 7.
[0165] The liquid pump 114 and the blower device 142 are activated
to start the operation of the Rankine cycle 110, when the
temperature of the engine cooling water becomes higher than a
predetermined temperature so that a sufficient amount of waste heat
can be obtained from the engine.
[0166] More in detail, the liquid phase refrigerant from the
condensing device 113 is pressurized by the liquid pump 114 and
supplied to the heating device 111. The liquid phase refrigerant is
heated at the heating device 111 to the super heated steam of the
refrigerant through the heat exchange with the high temperature
engine cooling water. The super heated steam of the refrigerant is
supplied to the expansion device 112. The super heated steam of the
refrigerant is expanded and depressurized in the expansion device
in an isentropic manner. As a result, the movable scroll is rotated
with the orbital motion to generate the rotational driving force
through the crank device connected to the movable scroll. The
electric power generator 120 is driven by the rotational driving
force, and the electric power generated at the generator 120 is
charged into the battery 11 through the inverter 141. The electric
power charged in the battery is used for the electrical loads 160
of the vehicle. As a result, a load to the alternator 150 is
decreased. The refrigerant depressurized in the expansion device
112 is condensed and liquefied in the condensing device 113, and
sucked into the liquid pump 114.
[0167] In the above operation of the Rankine cycle 110, a
pressurizing capacity of the liquid pump 114 is adjusted in
consideration of a heating capacity at the heating device 111 and a
condensing capacity at the condensing device 113. Further, the
pressurizing capacity of the liquid pump 114 is adjusted such that
the pressure difference .DELTA.P at the expansion device 112 is
controlled at a predetermined pressure difference .DELTA.Pth (also
referred to as a preset pressure difference), which is necessary
for the expansion device 112 and the electric power generator 120
to achieve a target rotational speed for the efficient operation
(power generation).
[0168] In the case that the respective capacities for the heating
device, the condensing device and so on become off-balanced due to
any reason during the operation of the Rankine cycle 110, the
actual pressure difference .DELTA.P may become lower than the
predetermined pressure difference .DELTA.Pth. If it happened, an
operation of an over-expansion would take place in the expansion
device 112. Accordingly, the rotational speed of the electric power
generator 120 is actively controlled in accordance with the
pressure difference .DELTA.P detected by a pressure detecting
device 130 (the pressure sensors 131 and 132).
[0169] As shown in FIG. 7, the controller 133 (the inverter 141)
starts the operation of the Rankine cycle 110 at a step S100. The
controller 133 determines at a step S110 whether the pressure
difference .DELTA.P is lower than the predetermined pressure
difference .DELTA.Pth. As already explained above, the pressure
difference .DELTA.P is calculated by the controller 133 based on
the high pressure side pressure P1 and the low pressure side
pressure P2 detected by the pressure sensors 131 and 132. The
controller 133 controls the inverter 141, at a step S120, such that
the rotational speed of the electric power generator 120 is
decreased by a predetermined amount, when the pressure difference
.DELTA.P is lower than the predetermined pressure difference
.DELTA.Pth.
[0170] In the case of NO at the step S110, namely when the pressure
difference .DELTA.P is higher than the predetermined pressure
difference .DELTA.Pth, the controller 133 controls the inverter
141, at a step S130, so that the rotational speed of the electric
power generator 120 is controlled at the target rotational speed.
The process goes back to the step S110 from the step S120 or S130,
to repeat the above operation.
[0171] As above, the rotational speed of the electric power
generator 120 is decreased at the step S120. The rotational speed
of the expansion device 112 is correspondingly decreased. Since the
expansion device 112 works as a fluid flow resistance to the
refrigerant, which is circulated in the Rankine cycle 110, the high
pressure side pressure P1 of the expansion device 112 can be
increased Accordingly, the pressure difference .DELTA.P is
increased toward the predetermined pressure difference .DELTA.Pth.
As above, since the actual pressure difference .DELTA.P is
controlled at the value higher than the predetermined pressure
difference .DELTA.Pth, the operation of the over-expansion at the
expansion device 112 can be prevented, and a stable expanding
operation can be realized.
[0172] The expansion device 112 is formed as the scroll type
expansion device having the crank device for preventing an
auto-rotation of a movable scroll. In the scroll type expansion
device 112 having the crank device, a magnitude relation between
the pressure in the working chamber (the expansion chamber) and the
pressure in a discharge space for the refrigerant is repeatedly
reversed by the operation of the crank device, when the over
expansion takes place. Then, the movable and fixed scrolls are
separated from or brought into contact with each other, to thereby
generate chattering noise. Furthermore, in the operation of the
over expansion of the scroll type expansion device 112, a force for
biasing the movable scroll toward a thrust plate of the fixed
scroll becomes smaller so that the movable scroll may be inclined
against the fixed scroll. As a result, a slanted wear may be
caused. As above, in the scroll type expansion device 112 having
the crank device, to suppress the over expansion is extremely
effective for preventing the generation of the chattering noise and
the slanted wear.
[0173] When the pressure difference .DELTA.P becomes lower than the
predetermined pressure difference .DELTA.Pth, exciting current of
the electric power generator 120 may be increased to increase
magnetic flux density, as the means for increasing the pressure
difference .DELTA.P, in place of the inverter 141 of the electric
power generator 120 (the means for decreasing the number of
rotation). Namely, the rotor 121 of the electric power generator
120 is formed by the electric coil, instead of the permanent
magnets, the magnetic flux density is increased by increasing the
exciting current to such electric coil. As a result, the necessary
torque for the electric power generator 120 is increased to thereby
decrease the number of rotation. Accordingly, the pressure
difference .DELTA.P can be increased.
Third Embodiment
[0174] A third embodiment of the present invention is shown in
FIGS. 8 and 9. In the third embodiment, the condensing device 113
and the blower device 142 are formed as the means 140A for
increasing the pressure difference .DELTA.P. The same reference
numerals are used in the third embodiment to designate the same or
similar components and parts in the third embodiment.
[0175] The blower device 142 of the third embodiment is formed as
an electrical blower device for blowing the cooling air to the
condensing device 113, as shown in FIG. 8. A rotational speed of
the electrical blower device 142 is controlled by the controller
133. An operation of the third embodiment will be controlled by a
flow chart shown in FIG. 9. In FIG. 9, the steps S120 and S130 of
FIG. 7 are replaced by steps of S120A and S130A.
[0176] When the controller 133 determines, at the step S110, that
the pressure difference .DELTA.P at the expansion device 112 is
lower than the predetermined pressure difference .DELTA.Pth, the
controller 133 controls to increase the rotational speed of the
blower device 142 by a predetermined rotational speed. Namely, the
amount of the cooling air to be supplied to the condensing device
113 is increased by a predetermined amount.
[0177] In the case of NO at the step S110, namely when the pressure
difference .DELTA.P is higher than the predetermined pressure
difference .DELTA.Pth, the controller 133 controls the blower
device 142, at a step S130A, so that the rotational speed of the
electric blower device 142 is controlled at the target rotational
speed. The process goes back to the step S110 from the step S120A
or S130A, to repeat the above operation.
[0178] As above, the operation for condensing the refrigerant is
facilitated in the condensing device 113, when the rotational speed
of the blower device 142 is increased at the step S120A, so that
the pressure P2 at the low pressure side is decreased. As a result,
the pressure difference .DELTA.P is increased to become close to
the predetermined pressure difference .DELTA.Pth. The over
expansion of the expansion device 112 is likewise prevented, as in
the same manner to the third embodiment. And the stable expansion
operation can be achieved based on the predetermined pressure
difference .DELTA.Pth.
Fourth Embodiment
[0179] A fourth embodiment of the present invention is shown in
FIGS. 10 and 11. In the fourth embodiment, the liquid pump 114, an
electric motor 143 for driving the liquid pump 114, and an inverter
144 for controlling the electric motor 143 are formed as the means
140B for increasing the pressure difference .DELTA.P. The inverter
144 reads the pressure difference .DELTA.P from the controller 133
to control the electric motor 143. The same reference numerals are
used in the fourth embodiment to designate the same or similar
components and parts in the second embodiment.
[0180] An operation of the fourth embodiment will be controlled by
a flow chart shown in FIG. 11. In FIG. 11, the steps S120 and S130
of FIG. 7 are replaced by steps of S120B and S130B.
[0181] When the controller 133 determines, at the step S110, that
the pressure difference .DELTA.P at the expansion device 112 is
lower than the predetermined pressure difference .DELTA.Pth, the
controller 133 controls to increase the rotational speed of the
electric motor 143 through the inverter 144 by a predetermined
rotational speed. Namely, a pressurizing capacity of the liquid
pump 114 is increased by a predetermined amount.
[0182] In the case of NO at the step S110, namely when the pressure
difference .DELTA.P is higher than the predetermined pressure
difference .DELTA.Pth, the controller 133 controls the electric
motor 143, at a step S130B, so that the rotational speed of the
liquid pump 114 is controlled at the target rotational speed. The
process goes back to the step S110 from the step S120B or S130B, to
repeat the above operation.
[0183] As above, the pressurizing capacity of the liquid pump 114
is increased at the step S120B, so that the pressure P1 at the high
pressure side is increased. As a result, the pressure difference
.DELTA.P is increased to become close to the predetermined pressure
difference .DELTA.Pth. The over expansion of the expansion device
112 is likewise prevented, as in the same manner to the second
embodiment. And the stable expansion operation can be achieved
based on the predetermined pressure difference .DELTA.Pth.
[0184] When the pressure difference .DELTA.P becomes lower than the
predetermined pressure difference .DELTA.Pth, exciting current of
the electric motor 143 may be decreased to decrease magnetic flux
density, as the means for increasing the pressure difference
.DELTA.P, in place of the inverter 144 (the means for increasing
the number of rotation) of the electric motor 143. Namely, the
rotor of the electric motor 143 is formed by an electric coil, the
magnetic flux density is decreased by decreasing the exciting
current to such electric coil. As a result, the necessary torque
for the electric motor 143 is decreased to thereby increase the
number of rotation. Accordingly, the pressurizing capacity of the
liquid pump 114 is increased so that the pressure difference
.DELTA.P can be increased.
(Other Modifications)
[0185] In the above embodiments, the pressure sensor 131 on the
high pressure side and the pressure sensor 132 on the low pressure
side are respectively arranged between the heating device 111 and
the expansion device 112 and between the expansion device 112 and
the condensing device 113. However, the pressure sensor 131 may be
arranged between the liquid pump 114 and the heating device 111,
where as the pressure sensor 132 may be arranged between the
condensing device 113 and the liquid pump 114.
[0186] The expansion device control system of the present invention
is applied to the control system for the expansion device 112 for
the Rankine cycle 110. However, the control system of the present
invention may be applied to a control system for an expansion
device for Brayton cycle (a turbine device).
[0187] The Rankine cycle 110 is applied to the vehicle, however, it
may be used for other industrial purposes.
* * * * *