U.S. patent application number 12/917127 was filed with the patent office on 2011-02-24 for waste heat utilization device for internal combustion engine.
This patent application is currently assigned to Sanden Corporation. Invention is credited to Yasuaki KANOU, Junichiro KASUYA.
Application Number | 20110041505 12/917127 |
Document ID | / |
Family ID | 41254850 |
Filed Date | 2011-02-24 |
United States Patent
Application |
20110041505 |
Kind Code |
A1 |
KASUYA; Junichiro ; et
al. |
February 24, 2011 |
Waste Heat Utilization Device for Internal Combustion Engine
Abstract
A waste heat utilization device (2) for an internal combustion
engine (6) includes a heat medium circuit (8) through which a heat
medium applied with waste heat from at least one of the engine and
a heat source of the engine is circulated as the engine is
operated, and a Rankine cycle circuit (4) through which a working
fluid is circulated. The Rankine cycle circuit includes a heating
unit (10, 12) for heating the working fluid by causing heat to
transfer to the working fluid from at least one of the heat medium
and the heat source, an expander (14) for expanding the working
fluid introduced therein from the heating unit to produce driving
force, and a condenser (16) for condensing the working fluid
introduced therein from the expander. The working fluid is
delivered from the condenser to the heating unit. The flow rate of
at least one of the heat medium and the heat source that transfer
heat to the working fluid in the heating unit is controlled in
accordance with an operating condition of the engine.
Inventors: |
KASUYA; Junichiro;
(Isesaki-shi, JP) ; KANOU; Yasuaki; (Maebashi-shi,
JP) |
Correspondence
Address: |
COHEN, PONTANI, LIEBERMAN & PAVANE LLP
551 FIFTH AVENUE, SUITE 1210
NEW YORK
NY
10176
US
|
Assignee: |
Sanden Corporation
Isesaki-shi
JP
|
Family ID: |
41254850 |
Appl. No.: |
12/917127 |
Filed: |
November 1, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2008/058384 |
May 1, 2008 |
|
|
|
12917127 |
|
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Current U.S.
Class: |
60/660 ;
60/670 |
Current CPC
Class: |
F02G 5/02 20130101; F01K
23/065 20130101; F02G 2260/00 20130101; Y02T 10/16 20130101; F01N
5/02 20130101; Y02T 10/166 20130101; F02G 5/04 20130101; Y02T 10/12
20130101 |
Class at
Publication: |
60/660 ;
60/670 |
International
Class: |
F01K 13/02 20060101
F01K013/02; F01K 23/06 20060101 F01K023/06 |
Claims
1. A waste heat utilization device for an internal combustion
engine, comprising: a heat medium circuit through which a heat
medium applied with waste heat from at least one of the engine and
a heat source of the engine is circulated as the engine is
operated; and a Rankine cycle circuit through which a working fluid
is circulated, the Rankine cycle circuit including a heating unit
for heating the working fluid by causing heat to transfer to the
working fluid from at least one of the heat medium and the heat
source, an expander for expanding the working fluid introduced
therein from the heating unit to produce driving force, and a
condenser for condensing the working fluid introduced therein from
the expander, the working fluid being delivered from the condenser
to the heating unit, wherein a flow rate of at least one of the
heat medium and the heat source that transfer heat to the working
fluid in the heating unit is restricted in accordance with an
operating condition of the engine.
2. The waste heat utilization device according to claim 1, wherein:
the heat medium is cooling water for cooling the engine, the heat
medium circuit is a cooling water circuit which includes a radiator
for cooling the cooling water and in which the cooling water is
circulated successively through the engine, the heating unit and
the radiator at a flow rate corresponding to the operating
condition of the engine, and the cooling water circuit further
includes a bypass passage bypassing the heating unit, and flow rate
proportioning control means for controlling distribution of the
cooling water to the bypass passage and the heating unit, to
restrict an amount of the cooling water flowing into the heating
unit while maintaining circulation of the cooling water through the
cooling water circuit.
3. The waste heat utilization device according to claim 2, wherein
the flow rate proportioning control means includes a differential
pressure sensor for detecting a differential pressure across the
heating unit, and a manipulating unit which is driven so as to
restrict the flow rate of the cooling water flowing into the
heating unit in accordance with the differential pressure detected
by the differential pressure sensor.
4. The waste heat utilization device according to claim 3, wherein:
the heating unit includes an evaporator connected in series with
the radiator as viewed in a flowing direction of the cooling water,
for heating the working fluid by causing heat to transfer to the
working fluid from the cooling water introduced therein via the
engine, and the flow rate proportioning control means further
includes a cooling water temperature sensor for detecting
temperature of the cooling water circulated through the cooling
water circuit, and drives the manipulating unit so as to cause the
cooling water delivered from the engine to flow only into the
bypass passage when the temperature of the cooling water detected
by the cooling water temperature sensor is lower than or equal to a
preset temperature.
5. The waste heat utilization device according to claim 4, wherein:
the heat source is an exhaust gas discharged from the engine
through an exhaust pipe, the heating unit includes an exhaust gas
heat exchanger arranged in the exhaust pipe, and the Rankine cycle
circuit further includes a working fluid pump which is driven to
circulate the working fluid.
6. The waste heat utilization device according to claim 5, wherein
the flow rate proportioning control means further includes a
cooling water temperature sensor for detecting temperature of the
cooling water circulated through the cooling water circuit, and
wherein, when the temperature of the cooling water detected by the
cooling water temperature sensor is lower than or equal to a preset
temperature, the flow rate proportioning control means stops
operation of the working fluid pump and drives the manipulating
unit so as to cause the cooling water delivered from the engine to
flow into the exhaust gas heat exchanger.
7. The waste heat utilization device according to claim 5, wherein
the flow rate proportioning control means further includes a second
bypass passage bypassing only the evaporator, and a second
manipulating unit arranged in the second bypass passage to restrict
the flow rate of the cooling water flowing into the evaporator in
accordance with the temperature of the cooling water detected by
the cooling water temperature sensor, and wherein, when the
temperature of the cooling water detected by the cooling water
temperature sensor is lower than or equal to the preset
temperature, the flow rate proportioning control means drives the
first-mentioned manipulating unit and the second manipulating unit
such that the cooling water delivered from the engine is introduced
only into the exhaust gas heat exchanger.
8. The waste heat utilization device according to claim 3, wherein
the manipulating unit is a linear three-way valve whose operating
position is continuously variable in accordance with the
differential pressure detected by the differential pressure
sensor.
9. The waste heat utilization device according to claim 3, wherein
the manipulating unit is a linear pump which is driven in a
continuously variable manner in accordance with the differential
pressure detected by the differential pressure sensor.
10. The waste heat utilization device according to claim 1,
wherein: the heat medium is cooling water for cooling the engine,
the heat source is an exhaust gas discharged from the engine
through an exhaust pipe, the heating unit includes an exhaust gas
heat exchanger arranged in the exhaust pipe for heating, by the
exhaust gas, the cooling water delivered from the engine, and an
evaporator for heating the working fluid by causing heat to
transfer to the working fluid from the cooling water delivered from
the exhaust gas heat exchanger, the heat medium circuit is a
cooling water circuit in which the cooling water is circulated
successively through the engine, the exhaust gas heat exchanger and
the evaporator at a flow rate corresponding to the operating
condition of the engine, and the cooling water circuit includes
heat absorption control means for restricting an amount of heat
absorption that the cooling water absorbs from the exhaust gas in
the exhaust gas heat exchanger, in accordance with the operating
condition of the engine.
11. The waste heat utilization device according to claim 10,
wherein: the heat absorption control means includes a sensing unit
for detecting the operating condition of the engine, and a
manipulating unit for restricting the amount of heat absorption in
accordance with a detection signal from the sensing unit, the
Rankine cycle circuit further includes a working fluid pump which
is driven to circulate the working fluid, and when the operating
condition of the engine detected by the sensing unit indicates that
the engine needs to be warmed up, the heat absorption control means
stops operation of the working fluid pump and also drives the
manipulating unit so as to increase the amount of heat
absorption.
12. The waste heat utilization device according to claim 11,
wherein: the cooling water circuit further includes an evaporator
bypass passage bypassing the evaporator, and a thermostat arranged
at a meeting point where the evaporator bypass passage joins a
downstream side of the evaporator and causing the cooling water to
pass through the evaporator when temperature of the cooling water
at the meeting point is higher than or equal to a preset
temperature, the sensing unit is a cooling water temperature sensor
for detecting temperature of the cooling water circulated through
the cooling water circuit, and when the temperature of the cooling
water detected by the cooling water temperature sensor is higher
than a second preset temperature which is higher than or equal to
the preset temperature, the heat absorption control means drives
the manipulating unit so as to decrease the amount of heat
absorption.
13. The waste heat utilization device according to claim 11,
wherein: the sensing unit is an exhaust gas temperature sensor for
detecting temperature of the exhaust gas, and when the temperature
of the exhaust gas detected by the exhaust gas temperature sensor
is higher than a third preset temperature, the heat absorption
control means drives the manipulating unit so as to decrease the
amount of heat absorption.
14. The waste heat utilization device according to claim 11,
wherein: the cooling water circuit further includes an exhaust gas
heat exchanger bypass passage bypassing the exhaust gas heat
exchanger, and the manipulating unit is a linear three-way valve
which is driven in a continuously variable manner in accordance
with a signal from the sensing unit, the three-way valve
controlling distribution of the cooling water introduced therein
via the engine to the exhaust gas heat exchanger bypass passage and
the exhaust gas heat exchanger, to restrict an amount of the
cooling water flowing into the exhaust gas heat exchanger.
15. The waste heat utilization device according to claim 11,
wherein the manipulating unit is a linear damper which is driven in
a continuously variable manner in accordance with a signal from the
sensing unit, the damper controlling distribution of the exhaust
gas to an exchanger-side passage in the exhaust pipe in which the
exhaust gas heat exchanger is located and an exchanger-bypassing
passage in the exhaust pipe which bypasses the exhaust gas heat
exchanger, to restrict an amount of the exhaust gas from which heat
is transferred to the cooling water in the exhaust gas heat
exchanger.
Description
RELATED APPLICATIONS
[0001] This application is a Continuation Application of
International Application No. PCT/JP2008/058384 filed on 1 May
2008.
TECHNICAL FIELD
[0002] The present invention relates to waste heat utilization
devices for internal combustion engines, and more particularly, to
a waste heat utilization device suited for use with an internal
combustion engine mounted on a motor vehicle.
BACKGROUND ART
[0003] For such waste heat utilization devices for internal
combustion engines, techniques have been known in which, in an
internal combustion engine of a motor vehicle, for example, a
Rankine cycle circuit is constituted by using component parts of a
refrigeration cycle to recover waste heat of the engine as kinetic
energy so that the recovered kinetic energy may be used to assist
the shaft output of the engine.
[0004] Specifically, a cooling water circuit has been known wherein
a radiator is inserted in the cooling water circuit of an engine
and is connected in series with an evaporator of the refrigeration
circuit to efficiently cool the cooling water (cf. Patent Document
1: Japanese Patent No. 2540738).
[0005] Also, a Rankine cycle circuit has been known in which the
cooling water circuit is provided with an exhaust gas heat
exchanger for additionally heating, by the heat of the exhaust gas,
the cooling water that has been used to cool the engine, and the
cooling water thus heated by the exhaust gas heat exchanger is
delivered to the evaporator to efficiently recover the waste heat
of the engine (cf. Patent Document 2: Japanese Laid-open Patent
Publication No. 57-99222).
[0006] In the cooling water circuit disclosed in Patent Document 1,
however, if a large amount of cooling water is circulated through
the cooling water circuit, the resistance of the evaporator to the
flow of the cooling water can increase to an extent such that the
circulation of the cooling water through the cooling water circuit
is hindered, posing a problem that the cooling performance of the
radiator lowers.
[0007] In the Rankine cycle circuit disclosed in Patent Document 2,
on the other hand, since the cooling water is additionally heated
by the exhaust gas, the heat capacity of the evaporator has to be
increased in order to sufficiently absorb heat from the cooling
water, that is, to cool the cooling water to a cooling water
temperature low enough to satisfactorily cool the engine body,
giving rise to a problem that the size of the evaporator and of a
condenser inevitably increases. As a consequence, the waste heat
utilization device increases in size.
SUMMARY OF THE INVENTION
[0008] One object of the invention is to provide a waste heat
utilization device for an internal combustion engine which device
is reduced in size and weight and yet permits both of a cooling
water circuit of the engine and a Rankine cycle circuit to function
properly.
[0009] To achieve the object, one aspect of the present invention
provides a waste heat utilization device for an internal combustion
engine, comprising: a heat medium circuit through which a heat
medium applied with waste heat from at least one of the engine and
a heat source of the engine is circulated as the engine is
operated; and a Rankine cycle circuit through which a working fluid
is circulated, the Rankine cycle circuit including a heating unit
for heating the working fluid by causing heat to transfer to the
working fluid from at least one of the heat medium and the heat
source, an expander for expanding the working fluid introduced
therein from the heating unit to produce driving force, and a
condenser for condensing the working fluid introduced therein from
the expander, the working fluid being delivered from the condenser
to the heating unit, wherein a flow rate of at least one of the
heat medium and the heat source that transfer heat to the working
fluid in the heating unit is restricted in accordance with an
operating condition of the engine.
[0010] In the waste heat utilization device, when the flow rate of
the heat medium circulated through the heat medium circuit
increases due to increase in the output of the engine and
consequent increase of the waste heat, the flow rate of the heat
medium that transfers heat to the working fluid in the heating unit
is restricted. It is therefore possible to prevent the circulation
of the heat medium from being hindered by the resistance of the
heating unit to the flow of the heat medium.
[0011] Also, by restricting the flow rate of at least one of the
heat medium and the heat source that transfer heat to the working
fluid in the heating unit, it is possible to restrict the amount of
heat that the working fluid absorbs when the engine is operating
with a maximum output. Accordingly, the heat capacity of the
heating unit and of the condenser in the Rankine cycle circuit can
be reduced. It is therefore possible to reduce the size and weight
of the waste heat utilization device while at the same time
ensuring proper functioning of both the heat medium circuit of the
engine and the Rankine cycle circuit.
[0012] In the waste heat utilization device according to a
preferred embodiment, the heat medium is cooling water for cooling
the engine, and the heat medium circuit is a cooling water circuit
which includes a radiator for cooling the cooling water and in
which the cooling water is circulated successively through the
engine, the heating unit and the radiator at a flow rate
corresponding to the operating condition of the engine. In this
case, the cooling water circuit further includes a bypass passage
bypassing the heating unit, and flow rate proportioning control
means for controlling distribution of the cooling water to the
bypass passage and the heating unit, to restrict an amount of the
cooling water flowing into the heating unit while maintaining
circulation of the cooling water through the cooling water
circuit.
[0013] With this configuration, when the flow rate of the cooling
water circulated through the cooling water circuit increases, the
increased amount of cooling water can be made to flow to the bypass
passage, and not the heating unit, thereby preventing the
circulation of cooling water from being hindered by the flow
resistance of the heating unit.
[0014] In the waste heat utilization device according to a
preferred embodiment, the flow rate proportioning control means
includes a differential pressure sensor for detecting a
differential pressure across the heating unit, and a manipulating
unit which is driven so as to restrict the flow rate of the cooling
water flowing into the heating unit in accordance with the
differential pressure detected by the differential pressure
sensor.
[0015] With this configuration, the resistance of the heating unit
to the flow of the cooling water can be directly monitored in terms
of the differential pressure. Accordingly, the control
responsiveness of the flow rate proportioning control means
improves, making it possible to cause both of the cooling water
circuit and the Rankine cycle circuit to function properly and
reliably.
[0016] In the waste heat utilization device according to a
preferred embodiment, the heating unit includes an evaporator
connected in series with the radiator as viewed in a flowing
direction of the cooling water, for heating the working fluid by
causing heat to transfer to the working fluid from the cooling
water introduced therein via the engine. In this case, the flow
rate proportioning control means further includes a cooling water
temperature sensor for detecting temperature of the cooling water
circulated through the cooling water circuit, and drives the
manipulating unit so as to cause the cooling water delivered from
the engine to flow only into the bypass passage when the
temperature of the cooling water detected by the cooling water
temperature sensor is lower than or equal to a preset
temperature.
[0017] With this configuration, the cooling water can be prevented
from being excessively cooled due to excessive use of heat by the
Rankine cycle circuit. Especially at the start of the engine, the
function of the Rankine cycle circuit is stopped. Accordingly, the
engine can be quickly warmed up without being excessively cooled by
the cooling water, thus preventing deterioration in the fuel
efficiency of the engine and enabling both the cooling water
circuit and the Rankine cycle circuit to always function
properly.
[0018] In the waste heat utilization device according to a
preferred embodiment, the heat source is an exhaust gas discharged
from the engine through an exhaust pipe, the heating unit includes
an exhaust gas heat exchanger arranged in the exhaust pipe, and the
Rankine cycle circuit further includes a working fluid pump which
is driven to circulate the working fluid.
[0019] The flow rate proportioning control means further includes a
cooling water temperature sensor for detecting temperature of the
cooling water circulated through the cooling water circuit, and
when the temperature of the cooling water detected by the cooling
water temperature sensor is lower than or equal to a preset
temperature, the flow rate proportioning control means stops
operation of the working fluid pump and drives the manipulating
unit so as to cause the cooling water delivered from the engine to
flow into the exhaust gas heat exchanger.
[0020] With the above configuration, at the start of the engine,
the function of the Rankine cycle circuit is stopped so that heat
may not be absorbed from the cooling water in the evaporator, and
since all of the cooling water circuited through the cooling water
circuit can be heated by the exhaust gas heat exchanger, the engine
can be warmed up more quickly.
[0021] In the waste heat utilization device according to a
preferred embodiment, the flow rate proportioning control means
further includes a second bypass passage bypassing only the
evaporator, and a second manipulating unit arranged in the second
bypass passage to restrict the flow rate of the cooling water
flowing into the evaporator in accordance with the temperature of
the cooling water detected by the cooling water temperature sensor.
When the temperature of the cooling water detected by the cooling
water temperature sensor is lower than or equal to the preset
temperature, the flow rate proportioning control means drives the
first-mentioned manipulating unit and the second manipulating unit
such that the cooling water delivered from the engine is introduced
only into the exhaust gas heat exchanger.
[0022] With this configuration, it is possible to stop the
absorption of heat from the cooling water in the evaporator at the
start of the engine, without the need to stop the Rankine cycle
circuit, and also all of the cooling water circulated through the
cooling water circuit can be heated. Further, since the evaporator
is bypassed, pressure loss in the cooling water circuit
attributable to the evaporator does not occur, facilitating the
circulation of the cooling water and making it possible to warm up
the engine even more quickly.
[0023] In the waste heat utilization device according to a
preferred embodiment, the manipulating unit is a linear three-way
valve whose operating position is continuously variable in
accordance with the differential pressure detected by the
differential pressure sensor. Alternatively, the manipulating unit
may be a linear pump which is driven in a continuously variable
manner in accordance with the differential pressure detected by the
differential pressure sensor.
[0024] With this configuration, the flow rate of the cooling water
flowing into the heating unit can be finely controlled in
accordance with the differential pressure detected by the
differential pressure sensor over the entire variation range of the
total flow rate of the cooling water. Accordingly, the accuracy of
flow rate proportioning control for the cooling water distributed
to the heating unit and the bypass passage improves, enabling the
cooling water circuit and the Rankine cycle circuit to function
even more properly.
[0025] In the waste heat utilization device according to a
preferred embodiment, the heat medium is cooling water for cooling
the engine, and the heat source is an exhaust gas discharged from
the engine through an exhaust pipe. In this case, the heating unit
includes an exhaust gas heat exchanger arranged in the exhaust pipe
for heating, by the exhaust gas, the cooling water delivered from
the engine, and an evaporator for heating the working fluid by
causing heat to transfer to the working fluid from the cooling
water delivered from the exhaust gas heat exchanger. Also, the heat
medium circuit is a cooling water circuit in which the cooling
water is circulated successively through the engine, the exhaust
gas heat exchanger and the evaporator at a flow rate corresponding
to the operating condition of the engine. Further, the cooling
water circuit includes heat absorption control means for
restricting an amount of heat absorption that the cooling water
absorbs from the exhaust gas in the exhaust gas heat exchanger, in
accordance with the operating condition of the engine.
[0026] With the above configuration, when the engine is operating
with a maximum output and thus the need to cool the engine is
highest, the cooling water can be made not to absorb heat from the
heat source, making it possible to reduce the heat capacity of the
evaporator and of the condenser in the Rankine cycle circuit. The
Rankine cycle circuit including the evaporator and the condenser,
and thus the waste heat utilization device can be reduced in size
and weight while ensuring proper functioning of the cooling water
circuit and the Rankine cycle circuit.
[0027] In the waste heat utilization device according to a
preferred embodiment, the heat absorption control means includes a
sensing unit for detecting the operating condition of the engine,
and a manipulating unit for restricting the amount of heat
absorption in accordance with a detection signal from the sensing
unit. In this case, the Rankine cycle circuit further includes a
working fluid pump which is driven to circulate the working fluid,
and when the operating condition of the engine detected by the
sensing unit indicates that the engine needs to be warmed up, the
heat absorption control means stops operation of the working fluid
pump and also drives the manipulating unit so as to increase the
amount of heat absorption.
[0028] With this configuration, the function of the Rankine cycle
circuit is stopped at the start of the engine, to stop absorption
of heat from the cooling water in the evaporator, whereby the
engine can be warmed up quickly.
[0029] In the waste heat utilization device according to a
preferred embodiment, the cooling water circuit further includes an
evaporator bypass passage bypassing the evaporator, and a
thermostat arranged at a meeting point where the evaporator bypass
passage joins a downstream side of the evaporator and causing the
cooling water to pass through the evaporator when temperature of
the cooling water at the meeting point is higher than or equal to a
preset temperature. In this case, the sensing unit is a cooling
water temperature sensor for detecting temperature of the cooling
water circulated through the cooling water circuit, and when the
temperature of the cooling water detected by the cooling water
temperature sensor is higher than a second preset temperature which
is higher than or equal to the preset temperature, the heat
absorption control means drives the manipulating unit so as to
decrease the amount of heat absorption.
[0030] With this configuration, when the amount of heat absorption
from the cooling water needs to be decreased, the control by the
heat absorption control means is executed preferentially over the
control by the thermostatic selector valve in order to avoid
interference, whereby the heat absorption control means can be made
to function with higher reliability.
[0031] In the waste heat utilization device according to a
preferred embodiment, the sensing unit is an exhaust gas
temperature sensor for detecting temperature of the exhaust gas,
and when the temperature of the exhaust gas detected by the exhaust
gas temperature sensor is higher than a third preset temperature,
the heat absorption control means drives the manipulating unit so
as to decrease the amount of heat absorption.
[0032] With this configuration, the responsiveness of the heat
absorption control can be greatly improved, compared with the case
where the manipulating unit is driven in accordance with the
detected cooling water temperature.
[0033] In the waste heat utilization device according to a
preferred embodiment, the cooling water circuit further includes an
exhaust gas heat exchanger bypass passage bypassing the exhaust gas
heat exchanger. In this case, the manipulating unit is a linear
three-way valve which is driven in a continuously variable manner
in accordance with a signal from the sensing unit, and the
three-way valve controls distribution of the cooling water
introduced therein via the engine to the exhaust gas heat exchanger
bypass passage and the exhaust gas heat exchanger, to restrict an
amount of the cooling water flowing into the exhaust gas heat
exchanger.
[0034] With this configuration, when the flow rate of the cooling
water circulated through the cooling water circuit increases, the
increased amount of cooling water can be made to flow into the
exhaust gas heat exchanger bypass passage, and not the exhaust gas
heat exchanger, while properly controlling the amount of heat
absorption by the cooling water so as to match the heat capacity of
the Rankine cycle circuit, whereby the circulation of the cooling
water can be prevented from being hindered by the resistance of the
exhaust gas heat exchanger to the flow of the cooling water. It is
therefore possible to maintain the engine cooling performance while
executing the heat absorption control by the heat absorption
control means.
[0035] In the waste heat utilization device according to a
preferred embodiment, the manipulating unit is a linear damper
which is driven in a continuously variable manner in accordance
with a signal from the sensing unit, and the damper controls
distribution of the exhaust gas to an exchanger-side passage in the
exhaust pipe in which the exhaust gas heat exchanger is located and
an exchanger-bypassing passage in the exhaust pipe which bypasses
the exhaust gas heat exchanger, to restrict an amount of the
exhaust gas from which heat is transferred to the cooling water in
the exhaust gas heat exchanger.
[0036] With this configuration, the amount of heat absorption by
the cooling water can be more accurately and quickly controlled so
as to match the heat capacity of the Rankine cycle circuit, so that
the accuracy and responsiveness of the heat absorption control
means can be significantly improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a schematic diagram illustrating a waste heat
utilization device for an internal combustion engine according to a
first embodiment of the present invention;
[0038] FIG. 2 is a flowchart illustrating a temperature-based valve
opening control routine executed by an ECU appearing in FIG. 1;
[0039] FIG. 3 is a flowchart illustrating a differential
pressure-based valve opening control routine executed by the ECU in
FIG. 1;
[0040] FIG. 4 is a schematic diagram illustrating a waste heat
utilization device for an internal combustion engine according to a
second embodiment of the present invention;
[0041] FIG. 5 is a schematic diagram illustrating a waste heat
utilization device for an internal combustion engine according to a
third embodiment of the present invention;
[0042] FIG. 6 is a schematic diagram illustrating a waste heat
utilization device for an internal combustion engine according to a
fourth embodiment of the present invention;
[0043] FIG. 7 is a flowchart illustrating a temperature-based valve
opening control routine executed by an ECU appearing in FIG. 6;
[0044] FIG. 8 is a flowchart illustrating a differential
pressure-based valve opening control routine executed by the ECU in
FIG. 6;
[0045] FIG. 9 is a schematic diagram illustrating a waste heat
utilization device for an internal combustion engine according to a
fifth embodiment of the present invention;
[0046] FIG. 10 is a schematic diagram illustrating a waste heat
utilization device for an internal combustion engine according to a
sixth embodiment of the present invention;
[0047] FIG. 11 is a flowchart illustrating a temperature-based
valve opening control routine executed by an ECU appearing in FIG.
10;
[0048] FIG. 12 is a schematic diagram illustrating a waste heat
utilization device for an internal combustion engine according to a
seventh embodiment of the present invention;
[0049] FIG. 13 is a flowchart illustrating an engine warm-up
control routine executed by an ECU appearing in FIG. 12;
[0050] FIG. 14 is a flowchart illustrating a heat absorption
control routine executed by the ECU in FIG. 12;
[0051] FIG. 15 is a schematic diagram illustrating a waste heat
utilization device for an internal combustion engine according to
an eighth embodiment of the present invention;
[0052] FIG. 16 is a flowchart illustrating an engine warm-up
control routine executed by an ECU appearing in FIG. 15; and
[0053] FIG. 17 is a flowchart illustrating a heat absorption
control routine executed by the ECU in FIG. 15.
DETAILED DESCRIPTION OF THE DRAWINGS
[0054] Referring to the accompanying drawings, a first embodiment
of the present invention will be described first.
[0055] FIG. 1 schematically illustrates the configuration of a
waste heat utilization device 2 for an internal combustion engine
according to the first embodiment. The waste heat utilization
device 2 comprises a Rankine cycle circuit 4 through which a
refrigerant as a working fluid is circulated, and a cooling water
circuit (heat medium circuit) 8 through which is circulated cooling
water (heat medium) for cooling an engine (internal combustion
engine) 6 of a motor vehicle, for example.
[0056] The Rankine cycle circuit 4 is a closed circuit which
includes an evaporator (heating unit) 10, an exhaust gas heat
exchanger (heating unit) 12, an expander 14, a condenser 16, a
receiver 18 and a refrigerant pump (working fluid pump) 20
successively inserted in a circulation path for the refrigerant in
the mentioned order as viewed in the flowing direction of the
refrigerant.
[0057] The evaporator 10, which is a heat exchanger, heats the
refrigerant by allowing heat to transfer from the cooling water
circulated through the cooling water circuit 8 to the refrigerant
circulated through the Rankine cycle circuit 4.
[0058] The exhaust gas heat exchanger 12 is arranged in an exhaust
pipe 22 into which an exhaust gas (heat source) is discharged from
the engine 6, to additionally heat, by the exhaust gas flowing
through the exhaust pipe 22, the refrigerant that has been heated
by the cooling water in the evaporator 10.
[0059] The expander 14 is a fluid machine for producing a rotative
driving force by expanding the refrigerant which has been heated by
the evaporator 10 and the exhaust gas heat exchanger 12 into a
superheated vapor state. Also, the expander 14 is connected with an
electric generator 24, which converts the rotative driving force
produced by the expander 14 to electric power so that the electric
power may be used by devices external to the waste heat utilization
device 2.
[0060] The condenser 16 is a heat exchanger for transferring heat
from the refrigerant discharged from the expander 14 to outside air
to condense the refrigerant into a liquid phase. The receiver 18
separates the refrigerant condensed by the condenser 16 into two,
gas and liquid phases and delivers only the separated liquid-phase
refrigerant to the pump 20. The pump 20 feeds the liquid-phase
refrigerant under pressure to the evaporator 10.
[0061] On the other hand, the cooling water circuit 8 includes a
radiator 26, a thermostat 28 and a water pump 30 which are inserted
in a cooling water circulation path extending from the engine 6, in
the mentioned order as viewed in the flowing direction of the
cooling water.
[0062] The radiator 26 is connected in series with the evaporator
10 and transfers heat from the cooling water discharged from the
evaporator 10 to the outside air to further cool the cooling
water.
[0063] The thermostat 28 is a mechanical selector valve capable of
allowing the cooling water to pass either through the radiator 26
or a bypass passage 32 bypassing the radiator 26, depending on the
temperature of the cooling water. The bypass passage 32 branches
off from a passage 8a of the circulation path connecting between
the evaporator 10 and the radiator 26, bypasses the radiator 26 and
is connected to one inlet port of the thermostat 28. Thus, the
thermostat 28 controls the flow rate of the cooling water passed
through the radiator 26 in accordance with the cooling water
temperature, to keep the temperature of the body of the engine 6
nearly constant, thereby preventing overheating of the engine
6.
[0064] The pump 30 is mounted to the engine 6 and operates in
accordance with the rotating speed of the engine 6 so that the
cooling water may be appropriately circulated through the cooling
water circuit 8.
[0065] In this embodiment, a linear three-way valve (manipulating
unit; three-way valve) 34 is inserted in the circulation path
between the engine 6 and the evaporator 10. The three-way valve 34
is an electric motor-operated valve having a driving section
applied with an input signal, and a single valve element driven in
a continuously variable manner in proportion to the input signal to
distribute the cooling water introduced into one inlet port to two
output ports. The three-way valve is capable of finely adjusting
the flow rates of the cooling water distributed to the respective
outlet ports.
[0066] Specifically, the inlet port of the three-way valve 34 is
connected with a passage 8b of the cooling water circuit 8
extending from the engine 6. One of the outlet ports is connected
to a bypass passage 36 bypassing the evaporator 10 and
communicating with the downstream side of the evaporator 10, and
the other outlet port is connected to a passage 8c extending to the
evaporator 10.
[0067] Also, the three-way valve 34 has such a structure as not to
constitute a large pressure loss element within the whole cooling
water circuit 8. The cooling water introduced from the passage 8b
is distributed to the bypass passage 36 and the passage 8c by the
three-way valve 34.
[0068] Part of the bypass passage 36 is shared by the bypass
passage 32 bypassing the radiator 26. A cooling water pressure in
this shared passage 8d and that in the passage 8c are introduced
and input to a differential pressure sensor 38, which detects a
differential pressure .DELTA.P across the evaporator 10.
[0069] The engine 6 is mounted with various other sensors including
a temperature sensor 40 attached to the bypass passage 32 to detect
the cooling water temperature T, an engine temperature sensor 42
for directly detecting the temperature Te of the body of the engine
6, and a rotating speed sensor 44 for detecting the rotating speed
of the engine 6.
[0070] The sensors 38, 40, 42 and 44 serving as sensing units and
the three-way valve 34 serving as a manipulating unit are
electrically connected to an electronic control unit (ECU) 46 for
performing overall control of the vehicle including the waste heat
utilization device 2. Based on detection signals input from the
differential pressure sensor 38 and the temperature sensor 40, the
ECU 46 outputs a signal to the three-way valve 34 to control the
openings of the outlet ports to desired openings.
[0071] Specifically, in accordance with the differential pressure
.DELTA.P across the evaporator 10, detected by the differential
pressure sensor 38, differential pressure-based valve opening
control for driving the three-way valve 34 is executed as a sub
control routine. This sub control routine is executed under the
control of temperature-based valve opening control as a main
control routine whereby the initiation and termination of the
differential pressure-based valve opening control are controlled in
accordance with the cooling water temperature T detected by the
temperature sensor 40. The main and sub control routines are
executed by the ECU 46 (flow rate proportioning control means).
[0072] Referring now to the flowchart of FIG. 2, the
temperature-based valve opening control will be explained.
[0073] Upon start of the temperature-based valve opening control,
the control routine proceeds to S1 ("S" represents "Step", and this
applies to the following description as well).
[0074] In S1, it is determined whether or not the cooling water
temperature T detected by the temperature sensor 40 indicates a
value lower than or equal to a preset temperature T.sub.L. If the
result of the decision is affirmative (Yes), that is, if it is
judged that the cooling water temperature T is lower than or equal
to the preset temperature T.sub.L, the control routine proceeds to
S2. On the other hand, if the result of the decision is negative
(No), that is, if it is judged that the cooling water temperature T
is higher than the preset temperature T.sub.L, the control routine
proceeds to S3.
[0075] In S2, the differential pressure-based valve opening control
is terminated if it is under execution, and then the control
routine proceeds to S4.
[0076] In S4, the three-way valve 34 is forcibly driven so that the
bypass passage 36 may be fully open while the passage 8c totally
closed, whereupon the control routine returns.
[0077] In S3, on the other hand, the differential pressure-based
valve opening control is executed, whereupon the control routine
returns.
[0078] Referring now to the flowchart of FIG. 3, the differential
pressure-based valve opening control executed in S3 will be
described.
[0079] Upon start of the differential pressure-based valve opening
control, the control routine first proceeds to S11.
[0080] In S11, it is determined whether or not the differential
pressure .DELTA.P detected by the differential pressure sensor 38
indicates a value lower than or equal to a preset differential
pressure .DELTA.P.sub.H. If the result of the decision is
affirmative (Yes), that is, if it is judged that the differential
pressure .DELTA.P is lower than or equal to the preset differential
pressure .DELTA.P.sub.H, the control routine proceeds to S12. On
the other hand, if the result of the decision is negative (No),
that is, if it is judged that the differential pressure .DELTA.P is
higher than the preset differential pressure .DELTA.P.sub.H, the
control routine proceeds to S13.
[0081] In S12, the three-way valve 34 is driven so as to increase
the flow rate of the cooling water distributed to the passage 8c
and decrease the flow rate of the cooling water distributed to the
bypass passage 36, whereupon the control routine returns.
[0082] On the other hand, in S13, the three-way valve 34 is driven
so as to increase the flow rate of the bypass passage 36 and
decrease the flow rate of the passage 8c, whereupon the control
routine returns.
[0083] According to this embodiment, the differential
pressure-based valve opening control is executed in the
aforementioned manner, whereby the flow rate Fe of the cooling
water distributed to the evaporator can be restricted to a fixed
rate or below even in cases where the total flow rate Ft of cooling
water fluctuates due to change in the operating condition of the
engine 6. It is therefore possible to prevent the circulation of
the cooling water through the cooling water circuit 8 from being
hindered by the resistance of the evaporator 10 to the flow of the
cooling water, so that the cooling performance of the radiator 26
can be maintained.
[0084] By monitoring the differential pressure .DELTA.P across the
evaporator 10, moreover, it is possible to directly detect a
substantially large differential pressure .DELTA.P caused, for
example, by the deposition of scale inside the evaporator 10. The
cooling water circuit 8 and the Rankine cycle circuit 4 can
therefore be made to function properly and reliably.
[0085] Also, since the three-way valve 34 is used as a manipulating
unit, the cooling water distribution can be continuously controlled
over the entire fluctuation range of the total flow rate Ft of the
cooling water.
[0086] Accordingly, the accuracy of the differential pressure-based
valve opening control improves, with the result that the cooling
water circuit 8 and the Rankine cycle circuit 4 can be made to
function more properly.
[0087] Further, by executing the temperature-based valve opening
control, it is possible to control the cooling water distribution
such that, when the cooling water temperature T is low, the total
flow rate of cooling water is equal to the bypass passage-side flow
rate, namely, Ft=Fb, or in other words, the evaporator-side flow
rate is equal to zero, namely, Fe=0. The cooling water can
therefore be prevented from being excessively cooled due to
excessive use of heat by the Rankine cycle circuit 4, so that fuel
can be satisfactorily atomized in the engine 6, making to possible
to improve the output and fuel efficiency of the engine 6.
[0088] In particular, the function of the Rankine cycle circuit 4
can be stopped at the start of the engine 6 during which the
cooling water temperature T is low. Thus, the engine 6 is prevented
from being excessively cooled by the cooling water and can be
quickly warmed up, making it possible to minimize deterioration in
the fuel efficiency at the start of the engine 6. Accordingly, both
of the cooling water circuit 8 and the Rankine cycle circuit 4 can
be made to properly function in accordance with the operating
condition of the engine 6 only at suitable times in appropriate
environments.
[0089] A second embodiment will be now described.
[0090] As shown in FIG. 4, a waste heat utilization device 48
according to the second embodiment uses a linear electric
motor-driven pump (manipulating unit; pump) 50 as the manipulating
unit, instead of the three-way valve 34, and a check valve 52 is
inserted in the bypass passage 36. In the other respects, the
configuration of the second embodiment is substantially identical
with that of the first embodiment.
[0091] The linear electric motor-driven pump 50 is arranged in the
passage 8c and is driven such that a rotating speed thereof is
continuously variable in proportion to the differential pressure
.DELTA.P detected by the differential pressure sensor 38. Namely,
in the second embodiment, when the differential pressure .DELTA.P
detected by the differential pressure sensor 38 is judged to be
lower than or equal to the preset differential pressure value
.DELTA.P.sub.H, the rotating speed of the pump 50 is increased, as
distinct from the differential pressure-based valve opening control
of the first embodiment. On the other hand, when the differential
pressure .DELTA.P is judged to be higher than the preset
differential pressure value .DELTA.P.sub.H, the rotating speed of
the pump 50 is decreased. That is to say, differential
pressure-based rotating speed control is executed.
[0092] Like the first embodiment, the differential pressure-based
rotating speed control is terminated when the cooling water
temperature T detected by the temperature sensor 40 is judged to be
lower than or equal to the preset temperature T.sub.L, and is
executed when the cooling water temperature T is judged to be
higher than the preset temperature T.sub.L. Thus, the differential
pressure-based rotating speed control is executed under the control
of temperature-based rotating speed control (flow rate
proportioning control means).
[0093] In this manner, also in the second embodiment, the cooling
water can be prevented from being excessively cooled due to
excessive use of heat by the Rankine cycle circuit 4, as in the
first embodiment, whereby both of the cooling water circuit 8 and
the Rankine cycle circuit 4 can be made to function properly and
reliably.
[0094] Especially in the second embodiment, the pump 50 is used as
the manipulating unit, and accordingly, a large amount of cooling
water can be introduced into the evaporator 10 by making use of the
driving pressure of the pump 50. Also, since the check valve 52 is
arranged in the bypass passage 36, the backflow of the cooling
water from the bypass passage 36 can be appropriately prevented. It
is therefore possible to improve the responsiveness and efficiency
of the Rankine cycle circuit 4, and as a consequence, the cooling
water circuit 8 and the Rankine cycle circuit 4 can be made to
function even more properly.
[0095] A third embodiment will be now described.
[0096] As shown in FIG. 5, a waste heat utilization device 54
according to the third embodiment uses a flow sensor 56 as the
sensing unit, instead of the differential pressure sensor 38 of the
first embodiment. In the other respects, the configuration of the
third embodiment is substantially identical with that of the first
embodiment.
[0097] The flow sensor 56 is arranged in the passage 8c, and the
three-way valve 34 is driven such that an opening thereof is
proportional to the flow rate F of cooling water detected by the
flow sensor 56. Specifically, in the third embodiment, when the
cooling water flow rate F detected by the flow sensor 56 is judged
to be lower than or equal to a preset flow rate F.sub.H, the
three-way valve 34 is driven so as to increase the flow rate of the
passage 8c and decrease the flow rate of the bypass passage 36, as
distinct from the differential pressure-based valve opening control
of the first embodiment and the differential pressure-based
rotating speed control of the second embodiment. On the other hand,
when the flow rate F is judged to be higher than the preset flow
rate F.sub.H, the three-way valve 34 is driven so as to increase
the flow rate of the bypass passage 36 and decrease the flow rate
of the passage 8c. That is to say, flow rate-based valve opening
control is executed.
[0098] Also, like the first and second embodiments, the flow
rate-based valve opening control is executed and terminated in
accordance with the relationship between the cooling water
temperature T detected by the temperature sensor 40 and the preset
temperature T.sub.L. Thus, the flow rate-based valve opening
control is executed under the control of the temperature-based
valve opening control (flow rate proportioning control means).
[0099] In this manner, also in the third embodiment, the cooling
water can be prevented from being excessively cooled due to
excessive use of heat by the Rankine cycle circuit 4, as in the
first and second embodiments, whereby both of the cooling water
circuit 8 and the Rankine cycle circuit 4 can be made to function
properly and reliably.
[0100] Especially in the third embodiment, the flow sensor 56 is
used as the sensing unit. Thus, the evaporator-side flow rate Fe
can be kept constant with higher accuracy, and since the
controllability of the cooling water circuit 8 and of the Rankine
cycle circuit 4 improves, the circuits 4 and 8 can be made to
function optimally.
[0101] A fourth embodiment will be now described.
[0102] As shown in FIG. 6, in a waste heat utilization device 58 of
the fourth embodiment, the exhaust gas heat exchanger 12, which is
provided in the Rankine cycle circuit 4 in the first embodiment, is
incorporated into the cooling water circuit 8. Thus, the cooling
water heated by the engine 6 is further heated by the exhaust gas
heat exchanger 12.
[0103] Also, the three-way valve 34 is connected such that in
accordance with a differential pressure .DELTA.P which is the
pressure difference across a heating unit 37 constituted by the
evaporator 10 and the exhaust gas heat exchanger 12 and which is
detected by the differential pressure sensor 38, the cooling water
is caused to bypass the heating unit 37.
[0104] Further, the temperature sensor 40 is arranged in that
passage 8e in the circulation path of the cooling water circuit 8
which extends from the thermostat 28 to the engine 6, and the
exhaust gas heat exchanger 12 is connected with one outlet port of
the three-way valve 34 through a passage 8f constituting the
circulation path of the cooling water circuit 8. In the other
respects, the configuration of the fourth embodiment is
substantially identical with that of the first embodiment.
[0105] In this embodiment, temperature-based valve opening control
is executed as shown in the flowchart of FIG. 7. Specifically, when
differential pressure-based valve opening control is terminated in
S2, the control routine proceeds to S5. In S5, the pump 20 is
stopped, and then in S6, the three-way valve 34 is driven so that
the passage 8f may be fully open. In the other respects, the
temperature-based valve opening control of this embodiment is
identical with that of the first embodiment.
[0106] The differential pressure-based valve opening control of
this embodiment is executed as shown in the flowchart of FIG. 8. If
it is judged in S11 that the differential pressure .DELTA.P is
lower than or equal to the preset differential pressure
.DELTA.P.sub.H, the control routine proceeds to S14 in which the
three-way valve 34 is driven so as to increase the flow rate of the
passage 8f. In S13, on the other hand, the flow rate of the bypass
passage 36 bypassing the heating unit 37 is increased. In the other
respects, the differential pressure-based valve opening control is
executed in the same manner as in the first embodiment (flow rate
proportioning control means).
[0107] Thus, also in the fourth embodiment, it is possible to
prevent the circulation of the cooling water through the cooling
water circuit 8 from being hindered by the resistance of the
heating unit 37 to the flow of the cooling water, as in the
foregoing embodiments, whereby the cooling performance of the
radiator 26 can be maintained.
[0108] Especially, in the temperature-based valve opening control
executed in the fourth embodiment, when the cooling water
temperature T is lower than or equal to the preset temperature
T.sub.L, the differential pressure-based valve opening control is
terminated and then the operation of the pump 20 of the Rankine
cycle circuit 4 is stopped. At the start of the engine 6,
therefore, the function of the Rankine cycle circuit 4 is stopped
without fail so that heat may not be absorbed from the cooling
water, and at the same time the cooling water is introduced at the
maximum flow rate F.sub.t into the exhaust gas heat exchanger 12 so
that the cooling water may be heated. Since the engine 6 can be
warmed up more quickly as a result, the fuel efficiency can be
further improved at the start of the engine 6, and also both of the
cooling water circuit 8 and the Rankine cycle circuit 4 can be made
to function properly.
[0109] A fifth embodiment will be now described.
[0110] As shown in FIG. 9, a waste heat utilization device 60
according to the fifth embodiment uses the linear pump
(manipulating unit; pump) 50 as the manipulating unit, instead of
the three-way valve 34, and executes the temperature-based rotating
speed control as well as the differential pressure-based rotating
speed control, as in the second embodiment. Also, the check valve
52 is arranged in the bypass passage 36. In the other respects, the
configuration of this embodiment is substantially identical with
that of the fourth embodiment.
[0111] Also in the waste heat utilization device 60 of the fifth
embodiment, the cooling performance of the radiator 26 can be
maintained irrespective of change in the operating condition of the
engine 6, like the fourth embodiment, whereby the engine 6 can be
quickly warmed up, making it possible to cause both of the cooling
water circuit 8 and the Rankine cycle circuit 4 to function
properly.
[0112] Especially in the fifth embodiment, since the pump 50 is
used as the manipulating unit as in the second embodiment, a large
amount of cooling water can be introduced to the heating unit 37 by
utilizing the driving pressure of the pump 50. Also, the check
valve 52 inserted in the bypass passage 36 serves to satisfactorily
prevent the backflow of the cooling water from the bypass passage
36. Accordingly, the engine 6 can be warmed up even more quickly,
so that the cooling water circuit 8 and the Rankine cycle circuit 4
can be made to function more properly.
[0113] A sixth embodiment will be now described.
[0114] As shown in FIG. 10, a waste heat utilization device 62
according to the sixth embodiment uses the three-way valve 34 as
the manipulating unit, like the fourth embodiment. The sixth
embodiment differs from the fourth embodiment in that it
additionally uses solenoid valves (second manipulating unit) 64 and
66 as a manipulating unit and additionally has a bypass passage
(second bypass passage) 68 bypassing the evaporator 10 only.
[0115] Each of the solenoid valves 64 and 66 is a two-way solenoid
valve with one inlet port and one outlet port and has a driving
section electrically connected to the ECU 46. In accordance with an
on-off contact signal input to the driving section, each solenoid
valve drives its valve element to selectively permit or block the
inflow of the cooling water.
[0116] The solenoid valve 64 is inserted in the bypass passage 68.
The bypass passage 68 branches off from a passage 8g of the cooling
water circuit 8 extending from the exhaust gas heat exchanger 12 to
the evaporator 10, and therefore, the cooling water can be made to
flow into the bypass passage 36 while bypassing only the evaporator
10. On the other hand, the solenoid valve 66 is inserted in the
shared passage 8d of the bypass passages 32 and 36.
[0117] Also, in the sixth embodiment, temperature-based valve
opening control and differential pressure-based valve opening
control similar to those of the fourth embodiment are executed, but
in the sixth embodiment, the solenoid valves 64 and 66 are also
driven in addition to the three-way valve 34.
[0118] Referring now to the flowchart of FIG. 11, there is
illustrated the temperature-based valve opening control executed in
this embodiment. As illustrated, when the differential
pressure-based valve opening control is terminated in S2, the
control routine proceeds to S7, in which the solenoid valve 64 is
opened while the solenoid valve 66 is closed. Then, in S6, the
three-way valve 34 is driven such that the passage 8f is fully
opened.
[0119] On the other hand, when the differential pressure-based
valve opening control is executed in S3, the control routine
proceeds to S8, wherein the solenoid valves 64 and 66 are both
closed (flow rate proportioning control means).
[0120] Thus, also in the sixth embodiment, the cooling performance
of the radiator 26 can be maintained irrespective of change in the
operating condition of the engine 6, and also the engine 6 can be
quickly warmed up, like the fourth and fifth embodiments.
Accordingly, both of the cooling water circuit 8 and the Rankine
cycle circuit 4 can be made to function properly and reliably.
[0121] Especially, in the sixth embodiment, the solenoid valves 64
and 66 are opened and closed, respectively, when the engine 6 is
warmed up. Accordingly, the cooling water passed through the
exhaust gas heat exchanger 12 can be introduced into the bypass
passage 68 bypassing the evaporator 10. Thus, it is possible to
prevent the evaporator 10 from absorbing heat from the cooling
water, without the need to stop the pump 20, that is, without the
need to stop the function of the Rankine cycle circuit 4.
[0122] Also, since the cooling water is not passed through the
evaporator 10 during the warm-up of the engine 6, the number of
pressure loss elements that induce pressure loss within the whole
cooling water circuit 8 can be reduced. Accordingly, circulation of
the cooling water through the cooling water circuit 8 is further
facilitated during the warm-up of the engine 6, and since the
engine 6 can be warmed up even more quickly, the cooling water
circuit 8 and the Rankine cycle circuit 4 can be made to function
more properly.
[0123] A seventh embodiment will be now described.
[0124] A waste heat utilization device 70 according to the seventh
embodiment is configured as illustrated in FIG. 12. Specifically,
compared with the cooling water circuit of the fourth embodiment,
the radiator 26 and the differential pressure sensor 38 are omitted
from the cooling water circuit 8, the bypass passage 36 is directly
connected to one inlet port of the thermostat 28, and the bypass
passage (exhaust gas heat exchanger bypass passage) 68 branches off
from the bypass passage (evaporator bypass passage) 36. Further, in
addition to the temperature sensors 42 and 44 mounted on the engine
6, an exhaust gas temperature sensor (sensing unit) 41 for
detecting the temperature Tg of the exhaust gas discharged from the
engine 6 is attached to the exhaust pipe 22.
[0125] Also, the condenser 16 is provided with an electric fan 17.
The fan 17 is configured to operate when a temperature difference
.DELTA.T between outside air temperature To detected by an outside
air temperature sensor, not shown, and the condensation temperature
Tc peculiar to the refrigerant becomes larger than or equal to a
preset temperature difference .DELTA.Ts.
[0126] In this embodiment, heat absorption control is executed, as
a sub control routine, to drive the three-way valve 34 in
accordance with the cooling water temperature T detected by the
temperature sensor 40. This sub control routine is executed under
the control of engine warm-up control as a main control routine,
which executes and terminates the heat absorption control in
accordance with the temperature Te of the body of the engine 6
detected by the temperature sensor 42. These control routines are
executed by the ECU 46 (heat absorption control means).
[0127] Referring now to the flowchart of FIG. 13, the engine
warm-up control will be explained.
[0128] Upon start of the engine warm-up control, the control
routine proceeds to S21.
[0129] In S21, it is determined whether or not the body temperature
Te of the engine 6 detected by the temperature sensor 42 indicates
a value lower than or equal to a preset temperature T.sub.L1. If
the result of the decision is affirmative (Yes), that is, if it is
judged that the engine body temperature Te is lower than or equal
to the preset temperature T.sub.L1, the control routine proceeds to
S22. On the other hand, if the result of the decision is negative
(No), that is, if it is judged that the engine body temperature Te
is higher than the preset temperature T.sub.L1, the control routine
proceeds to S23.
[0130] In S22, the heat absorption control is terminated if the
control is under execution, and then the control routine proceeds
to S24. If the heat absorption control is already terminated, the
control routine proceeds to S24 with the heat absorption control
kept terminated.
[0131] In S24, the pump 20 of the Rankine cycle circuit 4 is
stopped, whereupon the control routine proceeds to S25.
[0132] In S25, the three-way valve 34 is forcibly driven so as to
fully open the passage 8f and totally close the bypass passage
36.
[0133] In S23 which is executed following S21, the heat absorption
control is started if the control is not executed. If the heat
absorption control is already under execution, the control is
continuously executed.
[0134] Referring now to the flowchart of FIG. 14, the heat
absorption control executed in S23 will be explained.
[0135] Upon start of the heat absorption control, the pump 20 is
operated, whereupon the control routine proceeds to S31.
[0136] In S31, it is determined whether or not the cooling water
temperature T detected by the temperature sensor 40 indicates a
value lower than or equal to a preset temperature T.sub.L2. If the
result of the decision is affirmative (Yes), that is, if the
cooling water temperature T is judged to be lower than or equal to
the preset temperature T.sub.L2, the control routine proceeds to
S32. On the other hand, if the result of the decision is negative
(No), that is, if the cooling water temperature T is judged to be
higher than the preset temperature T.sub.L2, the control routine
proceeds to S33.
[0137] In S32, the three-way valve 34 is driven so as to increase
the flow rate of the passage 8f and decrease the flow rate of the
bypass passage 36.
[0138] In S33, on the other hand, the three-way valve 34 is driven
so as to increase the flow rate of the bypass passage 36 and
decrease the flow rate of the passage 8f.
[0139] In the above heat absorption control, the exhaust gas
temperature sensor 41 may be used as the sensing unit in place of
the temperature sensor 40, and a determination may be made in S31
as to whether or not the exhaust gas temperature Tg detected by the
exhaust gas temperature sensor 41 indicates a value lower than or
equal to a preset temperature (third preset temperature) T.sub.L3.
Preferably, the preset temperature (second preset temperature)
T.sub.L2, which is compared with the cooling water temperature T,
is set so as to be higher at least than the preset temperature
(preset temperature) Tt of the thermostat 28.
[0140] Thus, in the seventh embodiment, the heat absorption control
is performed on the cooling water circulated through the cooling
water circuit 8. Specifically, the operation of the three-way valve
34 is controlled to restrict the amount of heat that the cooling
water absorbs from the exhaust gas in the exhaust gas heat
exchanger 12, in accordance with the operating condition of the
engine 6 so that the temperature T of the cooling water flowing
into the engine 6 may become lower than or equal to the preset
temperature T.sub.L2.
[0141] In the Rankine cycle circuit 4, on the other hand, heat is
absorbed from both the body of the engine 6 and the exhaust gas
discharged from the engine 6 by means of the evaporator 10 through
the medium of the cooling water circulated through the cooling
water circuit 8, to recover waste heat from the engine 6. In this
case, by setting the amount of heat absorption from the exhaust gas
to a very small value by the aforementioned heat absorption
control, it is possible to cause the Rankine cycle circuit 4, that
is, the evaporator 10, to absorb heat substantially only from the
body of the engine 6, namely, from the high-temperature cooling
water returned directly from the engine 6 after cooling the engine
body.
[0142] Accordingly, the amount of heat that needs to be absorbed
from the high-temperature cooling water heated by the engine 6
which is operating with the maximum output can be regarded as a
maximum amount of heat absorption, and the heat capacity of the
evaporator 10 and of the condenser 16 may be set on the basis of
the maximum amount of heat absorption. Since the amount of heat
absorbed from the exhaust gas need not be taken into account, the
heat capacity of the evaporator 10 and of the condenser 16 can be
reduced. Consequently, it is possible to reduce the size and weight
of the Rankine cycle circuit 4 and thus of the waste heat
utilization device while ensuring proper functioning of the cooling
water circuit 8 and the Rankine cycle circuit 4.
[0143] Also, the heat absorption control is executed under the
control of the engine warm-up control. Thus, when the body
temperature Te of the engine 6 is lower than or equal to the preset
temperature T.sub.L1 and the engine 6 needs to be warmed up, the
heat absorption control is terminated, the pump 20 is stopped to
cause the Rankine cycle circuit 4 to cease functioning, and the
three-way valve 34 is driven so that the passage 8f may be fully
opened. Accordingly, during the warm-up of the engine 6, the
cooling water circulated through the cooling water circuit 8 can be
positively heated by the heat of the exhaust gas while at the same
time excessive absorption of heat by the Rankine cycle circuit 4 is
prevented, whereby the engine 6 can be quickly warmed up.
[0144] Further, since the preset cooling water temperature
T.sub.L2, which serves as the drive condition for driving the
three-way valve 34, is set so as to be higher than the preset
temperature Tt of the thermostat 28, interference between the heat
absorption control and the control by the thermostat 28 is avoided,
thereby permitting reliable functioning of the heat absorption
control and the engine warm-up control.
[0145] The use of the exhaust gas temperature sensor 41 as the
sensing unit, in place of the cooling water temperature sensor 40,
is preferred from the point of view of the heat absorption control
which is executed so that the maximum amount of heat to be absorbed
from the cooling water flowing into the evaporator 10 may not
exceed the heat capacity of the evaporator 10, because the
responsiveness of the heat absorption control can be improved,
compared with the case where the temperature sensor 40 is used as
the sensing unit.
[0146] When the engine 6 operates with the maximum output, the
total flow rate Ft of the cooling water increases, and as the total
flow rate Ft thus increases, the exhaust gas heat exchanger 12
comes to act as a pressure loss element within the cooling water
circuit 8. As a result, the resistance to the flow of the cooling
water increases, hindering the circulation of the cooling water
through the cooling water circuit 8 and lowering the engine cooling
performance.
[0147] According to this embodiment, the flow rate proportioning
control is executed in such a manner that when the engine 6 is
operating with the maximum output, the cooling water is circulated
so as to bypass the exhaust gas heat exchanger 12, whereby the flow
rate Fhe of the cooling water distributed to the exhaust gas heat
exchanger can be restricted to a certain low fixed rate or below.
It is therefore possible to prevent the circulation of the cooling
water through the cooling water circuit 8 from being hindered by
the resistance of the exhaust gas heat exchanger 12 to the flow of
the cooling water, thus providing the advantage that the engine
cooling performance can be maintained. If the cooling water remains
stagnant in the exhaust gas heat exchanger 12, however, the
stagnant cooling water is heated to a boiling point by the exhaust
gas, exerting an adverse influence on the whole cooling water
circuit 8. It is therefore preferable that the flow rate Fhe of the
cooling water distributed to the exhaust gas heat exchanger should
be reduced not to zero but to a certain appropriate rate.
[0148] The fan 17 associated with the condenser 16 is driven when
the condition is fulfilled that the temperature difference .DELTA.T
between the outside air temperature To and the condensation
temperature Tc peculiar to the working fluid is larger than or
equal to the preset temperature difference .DELTA.Ts. Accordingly,
if .DELTA.T becomes smaller than .DELTA.Ts due to increase in the
vehicle speed, the fan 17 is stopped. It is therefore possible to
reduce the electric power required to drive the fan 17, making the
waste heat utilization device 70 energy-saving.
[0149] An eighth embodiment will be now described.
[0150] A waste heat utilization device 72 according to the eighth
embodiment is configured as illustrated in FIG. 15. Specifically,
compared with the seventh embodiment, a linear damper (manipulating
unit) 74 is used as the manipulating unit, in place of the linear
three-way valve 34, and the bypass passage 36 is removed. In the
other respects, the configuration of the eighth embodiment is
identical with that of the seventh embodiment.
[0151] The damper 74 is arranged inside the exhaust pipe 22 and
connected through a driving section 74b to a partition wall 74a
which partitions the interior of the exhaust pipe 22 into a passage
(exchanger-side passage) 22a in which the exhaust gas heat
exchanger 12 is arranged and a bypass passage (exchanger-bypassing
passage) 22b which bypasses the exhaust gas heat exchanger 12.
[0152] The driving section 74b is electrically connected to the ECU
46 such that the damper 74 is driven in a continuously variable
manner in proportion to an input signal supplied to the driving
section 74b, so as to be able to finely adjust the amount of the
exhaust gas that contacts with a tube serving as the cooling water
path of the exhaust gas heat exchanger 12. Thus, the damper
functions as a manipulating unit for heat absorption control
(exhaust gas flow rate proportioning control).
[0153] Referring now to the flowcharts of FIGS. 16 and 17, there
are illustrated engine warm-up control and heat absorption control
executed in this embodiment. When the heat absorption control is
terminated in S22 of the engine warm-up control, the control
routine proceeds to S24 and then to S26. In S26, the driving
section 74b of the damper 74 is forcibly driven so as to maximize
the flow rate of the passage 22a, namely, fully open the passage
22a, and completely close the bypass passage 22b.
[0154] In the heat absorption control, on the other hand, when the
temperature T is judged to be lower than or equal to the preset
temperature T.sub.L2 in S31, the control routine proceeds to S34,
in which the damper 74 is driven so as to increase the opening area
of the passage 22a and decrease the opening area of the bypass
passage 22b.
[0155] If the result of the decision in S31 is negative (No), that
is, if the temperature T is judged to be higher than the preset
temperature T.sub.L2, the control routine proceeds to S35. In S35,
the damper 74 is driven so as to increase the opening area of the
bypass passage 22b and decrease the opening area of the passage
22a.
[0156] In this manner, according to the eighth embodiment, the heat
absorption control is executed by using the damper 74 as the
manipulating unit. Accordingly, like the seventh embodiment, the
amount of heat that needs to be absorbed from the cooling water
heated by the engine 6 which is operating with the maximum output
can be regarded as a maximum amount of heat absorption, and the
heat capacity of the evaporator 10 and of the condenser 16 may be
set on the basis of the maximum amount of heat absorption.
[0157] Also, the heat absorption control is executed under the
control of the engine warm-up control, as in the seventh
embodiment. Thus, the engine 6 can be quickly warmed up, and since
interference between the heat absorption control and the control
performed by the thermostat 28 is avoided, the heat absorption
control can be made to function more reliably.
[0158] Especially, in the eighth embodiment, the absorption of heat
from the exhaust gas can be directly controlled by executing the
exhaust gas flow rate proportioning control. Accordingly, compared
with the seventh embodiment in which the cooling water flow rate
proportioning control is executed, the amount of heat absorbed into
the cooling water can be accurately and promptly controlled so as
to match the heat capacity of the evaporator 10 in the Rankine
cycle circuit 4, making it possible to further improve the accuracy
and responsiveness of the heat absorption control. Consequently,
the Rankine cycle circuit 4 including the evaporator 10 and the
condenser 16, and therefore, the waste heat utilization device 72
can be further reduced in size and weight while at the same time
the cooling water circuit 8 and the Rankine cycle circuit 4 can be
made to function more properly.
[0159] While the embodiments of the present invention have been
described above, it is to be noted that the present invention is
not limited to the foregoing embodiments alone and may be modified
in various ways without departing from the scope of the
invention.
[0160] For example, in the first to third embodiments, the
temperature sensor 40 is used as a sensing unit. Some other sensor
may be used insofar as it is capable of measuring the temperature
of the cooling water circulated through the cooling water circuit
8, and the temperature sensor 42 attached to the engine 6 may be
used instead for the purpose.
[0161] Also, in the first to third embodiments, the differential
pressure sensor 38 and the flow sensor 56 are used as sensing
units. If the flow rate Fe of the cooling water distributed to the
evaporator 10 can be restricted to a certain fixed rate or below,
the sensors 38 and 56 may be omitted. Specifically, the total flow
rate Ft of cooling water may be calculated by the ECU 46 on the
basis of the signal from the rotating speed sensor 44 mounted on
the engine 6, and the three-way valve 34 may be controlled in
accordance with the calculation result.
[0162] Further, in the fourth to sixth embodiments, the operation
of the three-way valve 34 and the pump 50, which are manipulating
units, is controlled in accordance with the detection signals from
the differential pressure sensor 38 and the temperature sensor 40,
to control the flow rate of the cooling water distributed to the
heating unit 37. That is to say, the flow rate proportioning
control, which is executed to quickly complete the warm-up of the
engine 6 while maintaining the cooling performance of the radiator
26, can be regarded as controlling the amount of heat applied to
the cooling water circulated through the cooling water circuit 8.
Accordingly, the amount of heat transferred to the Rankine cycle
circuit 4 may be calculated in advance by the ECU 46 on the basis
of the cooling water temperature detected by the temperature sensor
40, and the operation of the above manipulating units may be
controlled so that the calculated amount of heat may remain almost
constant. Also in this case, it is possible to significantly
improve the functioning of the cooling water circuit 8 and the
Rankine cycle circuit 4. Alternatively, the flow rate of the
cooling water flowing into the evaporator 10 via the exhaust gas
heat exchanger 12 may be calculated by the ECU 46 on the basis of
the differential pressure across the heating unit 37, detected by
the differential pressure sensor 38, and the actual cooling water
temperature may be multiplied by the cooling water flow rate to
obtain the total amount of heat applied to the cooling water.
[0163] Furthermore, although in the sixth embodiment, the three-way
valve 34 is used as a manipulating unit, the pump 50, which is used
in the fifth embodiment as a manipulating unit, may be used
instead. Also in this case, it is possible to speed up the warm-up
of the engine 6 and also to cause the cooling water circuit 8 and
the Rankine cycle circuit 4 to function properly.
[0164] In the seventh and eighth embodiments, moreover, the
operation of the three-way valve 34 or the damper 74, which are
manipulating units, is controlled in accordance with the outputs
from sensing units including the cooling water temperature sensor
40 or the exhaust gas temperature sensor 41, and the engine
temperature sensor 42. Alternatively, the engine rotating speed
sensor 44 may be used in place of the temperature sensors 40, 41
and 42. Generally, the ECU 46 is input with the signal from the
rotating speed sensor 44. Thus, by using the input signal from the
rotating speed sensor, it is possible to execute the heat
absorption control by means of simplified configuration,
eliminating the need for the temperature sensors 40, 41 and 42 and
thereby reducing the cost of the waste heat utilization device
72.
[0165] The foregoing embodiments are explained with reference to
the case where the flow rate proportioning control or the heat
absorption control is executed for the waste heat utilization
device mounted on a motor vehicle. The present invention is,
however, equally applicable to various other types of internal
combustion engine than the engine 6 and can also be applied to
various heat medium circuits in which a heat medium applied with
waste heat from an internal combustion engine or from a heat source
of the engine is circulated as the engine is operated. Further,
where the flow rate of at least one of a heat medium and a heat
source that transfer heat to a refrigerant in a heating unit is
controlled in accordance with the operating condition of the
internal combustion engine, the flow rate proportioning control and
the heat absorption control may be executed in combination.
* * * * *