U.S. patent application number 11/290760 was filed with the patent office on 2006-07-27 for engine cooling system.
Invention is credited to Ian Pegg, Mitchell Piddock, Les Routledge.
Application Number | 20060162676 11/290760 |
Document ID | / |
Family ID | 34044069 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060162676 |
Kind Code |
A1 |
Pegg; Ian ; et al. |
July 27, 2006 |
Engine cooling system
Abstract
A cooling system for an internal combustion engine is disclosed
in which the supply of coolant to a cylinder block 6 is controlled
independently of the coolant supply to a cylinder head 10 so that
the temperatures of the cylinder block 6 and the cylinder head 10
can be optimised to produce improved performance and economy.
Inventors: |
Pegg; Ian; (Chelmsford,
GB) ; Routledge; Les; (Hockley, GB) ; Piddock;
Mitchell; (Brentwood, GB) |
Correspondence
Address: |
FORD GLOBAL TECHNOLOGIES, LLC.
FAIRLANE PLAZA SOUTH, SUITE 800
330 TOWN CENTER DRIVE
DEARBORN
MI
48126
US
|
Family ID: |
34044069 |
Appl. No.: |
11/290760 |
Filed: |
March 16, 2006 |
Current U.S.
Class: |
123/41.1 |
Current CPC
Class: |
F01P 2023/08 20130101;
F01P 7/165 20130101; F01P 2003/021 20130101; F01P 7/167 20130101;
F01P 11/029 20130101; F01P 2007/146 20130101; F01P 2025/32
20130101; F01P 7/164 20130101; F01P 2025/33 20130101; F01P 2025/31
20130101; F01P 2003/024 20130101; F01P 2007/143 20130101; F01P
2003/027 20130101 |
Class at
Publication: |
123/041.1 |
International
Class: |
F01P 7/16 20060101
F01P007/16 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 4, 2004 |
GB |
0426647.4 |
Claims
1. A cooling system for an internal combustion engine comprising a
cooling circuit including passages formed in a cylinder head of the
engine and in a cylinder block of the engine and at least one
conduit connecting the passages in the cylinder head and cylinder
block to an inlet to a pump used to circulate the coolant through
the cooling circuit wherein the pump is a variable flow rate pump
controlled by an electronic control unit, the coolant passages in
the cylinder block are connected by a first coolant supply conduit
to an outlet from the pump, the coolant passages in the cylinder
head are connected by a second coolant supply conduit to an outlet
from the pump, the flow through at least one of the first and
second coolant supply passages is controlled by an electronically
controlled flow control valve operably connected to an electronic
controller used to control the opening and closing of the
electronically controlled flow control valve and the flow through
the other of the first and second coolant supply passages has a
predetermined flow restriction to prevent unlimited flow
therethrough.
2. A cooling system as claimed in 1 wherein the predetermined flow
restriction is formed by one of an orifice and the use of a coolant
supply passage having a relatively small cross-sectional flow area
representing a restriction to flow for at least a portion of the
length of the other coolant supply passage.
3. A cooling system as claimed in claim 1 or in claim 2 wherein the
electronic control unit is formed as part of the electronic
controller used to control opening and closing of the first
electronically controlled flow control valve.
4. A cooling system as claimed in any of claims 1 to 3 wherein the
cooling system further comprises at least one temperature sensor
operably connected to the electronic controller to sense the
temperature of a part of the cylinder head and to supply a signal
indicative of the sensed temperature to the electronic controller,
at least one temperature sensor operably connected to the
electronic controller to sense the temperature of a part of the
cylinder block and to supply a signal indicative of the sensed
temperature to the electronic controller, the electronic controller
is operable, at least during normal engine running, to control the
opening and closing of the electronically controlled flow control
valve based upon at least one of the signals received from the
cylinder head and cylinder block temperature sensors and the
electronic control unit is operable, at least during normal engine
running, to control the flow rate from the variable flow rate pump
based upon at least one of the signals received from the cylinder
head and cylinder block temperature sensors.
5. A cooling system as claimed in claim 4 wherein, during normal
engine running, the flow from the variable flow rate pump is
controlled to provide the minimum required flow based upon at least
one of the signals received from the cylinder head and cylinder
block temperature sensors.
6. A cooling system as claimed in claim 4 or in claim 5 wherein the
cooling system further comprises at least one coolant temperature
sensor operably connected to the electronic controller for sensing
the temperature of the coolant exiting the cylinder head and the
electronic controller is operable to control the opening and
closing of the electronically controlled flow control valve based
upon the signals received from at least one of the cylinder head
and cylinder block temperature sensors and from the coolant
temperature sensor.
7. A cooling system as claimed in claim 4 in claim 5 wherein the
cooling system further comprises at least one coolant temperature
sensor operably connected to the electronic controller for sensing
the temperature of the coolant exiting at least one of the cylinder
block and the cylinder head and the electronic control unit is
operable to control the flow from the variable flow rate pump based
upon the signals received from at least one of the cylinder head
and cylinder block temperature sensors and from the coolant
temperature sensor.
8. A cooling system as claimed in any of claims 1 to 7 wherein the
electronically controlled flow control valve controls the flow of
coolant through the first coolant supply conduit to the cylinder
block, at least one cylinder head temperature sensor is operably
connected to the electronic controller to sense the temperature of
a part of the cylinder head and to supply a signal indicative of
the sensed temperature to the electronic controller and the
temperature of the cylinder head is controlled by the electronic
control unit, at least during normal engine running, by varying the
flow from the variable flow rate pump to maintain the temperature
as sensed by the or each cylinder head sensor within a
predetermined desired range based upon the sensed temperature of
the cylinder head and at least one cylinder block temperature
sensor is operably connected to the electronic controller to sense
the temperature of a part of the cylinder block and to supply a
signal indicative of the sensed temperature to the electronic
controller and the temperature of the cylinder block is controlled,
at least during normal engine running, by the electronic controller
opening and closing the electronically controlled flow control
valve to maintain the temperature of the cylinder block within a
predetermined desired temperature range based upon the sensed
temperature of the cylinder block.
9. A cooling system as claimed in any of claims 1 to 7 wherein the
electronically controlled flow control valve controls the flow of
coolant through the second coolant supply conduit to the cylinder
head, at least one cylinder head temperature sensor is operably
connected to the electronic controller to sense the temperature of
a part of the cylinder head and to supply a signal indicative of
the sensed temperature to the electronic controller and the
temperature of the cylinder head is controlled, at least during
normal engine running, by the electronic controller opening and
closing the electronically controlled flow control valve to
maintain the temperature of the cylinder head within a
predetermined desired temperature range based upon the sensed
temperature of the cylinder head and at least one cylinder block
temperature sensor is operably connected to the electronic
controller to sense the temperature of a part of the cylinder block
and to supply a signal indicative of the sensed temperature to the
electronic controller and the temperature of the cylinder block is
controlled by the electronic control unit, at least during normal
engine running, by varying the flow from the variable flow rate
pump to maintain the temperature as sensed by the or each cylinder
block sensor within a predetermined desired range based upon the
sensed temperature of the cylinder block.
10. A method for cooling an internal combustion engine having a
cylinder head, a cylinder block, a first coolant supply conduit to
supply coolant from a an electronically controlled variable flow
rate pump to passages formed in the cylinder block, a second
coolant supply conduit for independently supplying coolant from the
pump to passages formed in the cylinder head, an electronically
controlled flow control valve to control the flow of coolant though
one of the first and second coolant supply conduits, a
predetermined flow restriction to prevent unlimited flow through
the other of the first and second coolant supply conduits wherein
the method comprises opening and closing the or each electronically
controlled flow control valve and changing the flow rate from the
variable flow rate pump to maintain, at least during normal engine
running, the temperature of the cylinder block within a desired
temperature range and the temperature of the cylinder head within a
desired temperature range.
11. A method as claimed in claim 10 wherein at least one
temperature sensor is provided to sense the temperature of a part
of the cylinder head and at least one temperature sensor is
provided to sense the temperature of a part of the cylinder block
and the method further comprises opening an closing the or each
electronically controlled flow control valve and varying the flow
rate from the pump based upon the signals received from cylinder
head and cylinder block temperature sensors.
12. A cooling system substantially as described herein with
reference to the accompanying drawing.
13. A method for cooling an internal combustion engine
substantially as described herein with reference to the
accompanying drawing.
Description
[0001] This invention relates to internal combustion engines and in
particular to a cooling system for an internal combustion
engine.
[0002] It is well known to provide an internal combustion engine
with a cooling system in which coolant is circulated through a
cylinder block and cylinder head of the engine and through a
radiator before being returned to the engine by a pump.
[0003] Such a cooling system provides adequate cooling for the
engine but cannot accommodate different cooling requirements during
different operating conditions nor provide optimised cooling for
the cylinder head and the cylinder block.
[0004] For example, internal combustion engine emissions of CO and
HC are relatively high after a cold start particularly in the case
of high speed direct injection diesel engines for passenger cars
and light duty trucks. The problem is compounded by any catalyst
fitted to the engine being below its light-off temperature and so
unable to actively reduce emissions. In addition, engine fuel
economy is worse when the engine is cold due to lower thermal
efficiency, poor combustion and higher friction.
[0005] A second problem is that NOx emissions need to be reduced
from I.C. engines which can be achieved via lower engine metal
temperatures but this has the disadvantage with a conventional
cooling system of lower general metal temperatures which will tend
to increase friction.
[0006] With a conventional cooling system it is difficult to cool
sufficiently the cylinder head valve bridges without over cooling
other parts of the engine and power ratings of an engine are often
restricted due to excessive temperatures in the valve bridge
region. Therefore effective cooling of this region would allow
higher thermal loadings without the need to increase the coolant
bulk flow rate and therefore increased thermal inertia and slower
warm-up rates which would result in increased CO & HC emissions
and reduced fuel economy during warm-up.
[0007] For a high speed direct injection (HSDI) diesel engine a
lower cylinder head temperature would give lower NOx and a hotter
cylinder bore will produce lower friction leading to lower fuel
consumption. Hotter cylinder heads however give lower CO,
especially during warm-up.
[0008] The inventors have realised that what is required is a
cooling system that will allow the cylinder head flame face to
warm-up quicker especially under light load running from a cold
start, whilst being able to cool the cylinder head or at least
portions of it such that it runs colder after the exhaust system
temperature has risen. This would then allow a better CO to NOx
trade-off.
[0009] In addition the inventors have realised that if the cylinder
bore temperature could be separately controlled then an optimum
friction to wear ratio could be achieved. That is to say, if the
local oil film temperature that the piston rings and skirt see can
be managed better without a major impact on the emissions the
friction could be reduced without compromising wear or emissions
and so the fuel economy could be influenced largely independently
from the emissions. For example, if the oil film temperature could
be maintained during normal engine running in the range of approx.
110 to 130.degree. C., this will give low friction and keep the oil
in good condition for a long period of time.
[0010] It is known from GB-A-2,377,253 to provide a cooling system
for an engine in which the flow of coolant through the engine can
be controlled by the use of an electronically controlled flow
control valve independently of the flow being produced by the
system pump. Although this system is able to provide improved
performance with respect to a conventional cooling system no
provision is made for independently cooling the cylinder head and
the cylinder block and so the flow of coolant to the engine always
has to be a compromise and, particularly at high engine loads and
speeds, the cylinder block may be overcooled in order to prevent
critical areas in the cylinder head becoming too hot.
[0011] It is further known from EP-A-0894953 to provide a cooling
system in which separate flow paths are provide to the cylinder
head and cylinder block of an engine. However, this system has the
disadvantages that the pump is positioned downstream from the
cylinder head and the cylinder block and so is likely to suffer
from cavitation in use and the two flow paths are not totally
independent because the flow to the cylinder block is diverted from
the flow from the cylinder head. With such an arrangement it would
not be possible to control the temperature of the cylinder block
independently from the temperature of the cylinder head because the
two flow paths are interlinked and so the flow through the two flow
paths would need to be a compromise to account for the often
different requirements of the cylinder head and cylinder block.
[0012] It is an object of the invention to provide an improved
cooling system for an internal combustion engine.
[0013] According to a first aspect of the invention there is
provided a cooling system for an internal combustion engine
comprising a cooling circuit including passages formed in a
cylinder head of the engine and in a cylinder block of the engine
and at least one conduit connecting the passages in the cylinder
head and cylinder block to an inlet to a pump used to circulate the
coolant through the cooling circuit wherein the pump is a variable
flow rate pump controlled by an electronic control unit, the
coolant passages in the cylinder block are connected by a first
coolant supply conduit to an outlet from the pump, the coolant
passages in the cylinder head are connected by a second coolant
supply conduit to an outlet from the pump, the flow through at
least one of the first and second coolant supply passages is
controlled by an electronically controlled flow control valve
operably connected to an electronic controller used to control the
opening and closing of the electronically controlled flow control
valve and the flow through the other of the first and second
coolant supply passages has a predetermined flow restriction to
prevent unlimited flow therethrough.
[0014] The predetermined flow restriction may be formed by one of
an orifice and the use of a coolant supply passage having a
relatively small cross-sectional flow area representing a
restriction to flow for at least a portion of the length of the
other coolant supply passage.
[0015] Preferably, the electronic control unit may be formed as
part of the electronic controller used to control opening and
closing of the first electronically controlled flow control
valve.
[0016] The cooling system may further comprise at least one
temperature sensor operably connected to the electronic controller
to sense the temperature of a part of the cylinder head and to
supply a signal indicative of the sensed temperature to the
electronic controller, at least one temperature sensor operably
connected to the electronic controller to sense the temperature of
a part of the cylinder block and to supply a signal indicative of
the sensed temperature to the electronic controller, the electronic
controller is operable, at least during normal engine running, to
control the opening and closing of the electronically controlled
flow control valve based upon at least one of the signals received
from the cylinder head and cylinder block temperature sensors and
the electronic control unit is operable, at least during normal
engine running, to control the flow rate from the variable flow
rate pump based upon at least one of the signals received from the
cylinder head and cylinder block temperature sensors.
[0017] During normal engine running the flow from the variable flow
rate pump may be controlled to provide the minimum required flow
based upon at least one of the signals received from the cylinder
head and cylinder block temperature sensors.
[0018] The cooling system may further comprise at least one coolant
temperature sensor operably connected to the electronic controller
for sensing the temperature of the coolant exiting the cylinder
head and the electronic controller is operable to control the
opening and closing of the electronically controlled flow control
valve based upon the signals received from at least one of the
cylinder head and cylinder block temperature sensors and from the
coolant temperature sensor.
[0019] The cooling system may further comprise at least one coolant
temperature sensor operably connected to the electronic controller
for sensing the temperature of the coolant exiting at least one of
the cylinder block and the cylinder head and the electronic control
unit is operable to control the flow from the variable flow rate
pump based upon the signals received from at least one of the
cylinder head and cylinder block temperature sensors and from the
coolant temperature sensor.
[0020] The electronically controlled flow control valve may control
the flow of coolant through the first coolant supply conduit to the
cylinder block, at least one cylinder head temperature sensor may
be operably connected to the electronic controller to sense the
temperature of a part of the cylinder head and to supply a signal
indicative of the sensed temperature to the electronic controller
and the temperature of the cylinder head may be controlled by the
electronic control unit, at least during normal engine running, by
varying the flow from the variable flow rate pump to maintain the
temperature as sensed by the or each cylinder head sensor within a
predetermined desired range based upon the sensed temperature of
the cylinder head and at least one cylinder block temperature
sensor may be operably connected to the electronic controller to
sense the temperature of a part of the cylinder block and to supply
a signal indicative of the sensed temperature to the electronic
controller and the temperature of the cylinder block may be
controlled, at least during normal engine running, by the
electronic controller opening and closing the electronically
controlled flow control valve to maintain the temperature of the
cylinder block within a predetermined desired temperature range
based upon the sensed temperature of the cylinder block.
[0021] Alternatively, the electronically controlled flow control
valve may control the flow of coolant through the second coolant
supply conduit to the cylinder head, at least one cylinder head
temperature sensor may be operably connected to the electronic
controller to sense the temperature of a part of the cylinder head
and to supply a signal indicative of the sensed temperature to the
electronic controller and the temperature of the cylinder head may
be controlled, at least during normal engine running, by the
electronic controller opening and closing the electronically
controlled flow control valve to maintain the temperature of the
cylinder head within a predetermined desired temperature range
based upon the sensed temperature of the cylinder head and at least
one cylinder block temperature sensor is operably connected to the
electronic controller to sense the temperature of a part of the
cylinder block and to supply a signal indicative of the sensed
temperature to the electronic controller and the temperature of the
cylinder block is controlled by the electronic control unit, at
least during normal engine running, by varying the flow from the
variable flow rate pump to maintain the temperature as sensed by
the or each cylinder block sensor within a predetermined desired
range based upon the sensed temperature of the cylinder block.
[0022] Preferably, the temperature of the coolant exiting the
cylinder head may be sensed.
[0023] When the temperature of the coolant exiting the cylinder
head is above a predetermined maximum thermostat operating
temperature the flow from the pump is increased from the normal low
flow rate in order to reduce the coolant temperature.
[0024] Advantageously, the passages formed in the cylinder head and
the passages formed in the cylinder block may be connected in
parallel by separate conduits to a return circuit used to return
coolant to the inlet to the pump so as to provide totally
independent control of the temperature of the cylinder head and the
cylinder block.
[0025] Alternatively, the passages formed in the cylinder head and
the passages formed in the cylinder block are connected by a common
conduit to a return circuit used to return coolant to the inlet to
the pump such that the coolant from the cylinder block passes
through at least one of the passages in the cylinder head to the
common conduit.
[0026] A radiator may be connected in the return circuit between
the cooling passages in the cylinder block and the cylinder head
and the inlet to the pump.
[0027] A vehicle compartment heater may be connected in the return
circuit between the cooling passages in the cylinder block and the
cylinder head and the inlet to the pump.
[0028] A degas reservoir may be connected in the return circuit
between the cooling passages in the cylinder block and the cylinder
head and the inlet to the pump.
[0029] The radiator, compartment heater and degas reservoir may be
connected in parallel between two common points of the return
circuit.
[0030] A valve controlled bypass circuit may be connected in
parallel to the radiator to allow coolant to bypass the radiator
when the temperature of the coolant is below a predetermined
minimum temperature.
[0031] The first coolant supply passage may provide at least a
general coolant flow through the cylinder block.
[0032] The first coolant supply passage may provide a directed
coolant flow to the cylinder block to cool specific regions of the
cylinder block.
[0033] The second coolant supply passage may provide at least a
general coolant flow through the cylinder head.
[0034] The second coolant supply passage may provide a directed
coolant flow to the cylinder head to cool specific regions of the
cylinder head.
[0035] The coolant from the cylinder block may be used to provide a
general coolant flow to the cylinder head and the flow through the
second coolant supply passage may be used to provide a directed
coolant flow to the cylinder head to cool specific regions of the
cylinder head.
[0036] According to a second aspect of the invention there is
provided a method for cooling an internal combustion engine having
a cylinder head, a cylinder block, a first coolant supply conduit
to supply coolant from a an electronically controlled variable flow
rate pump to passages formed in the cylinder block, a second
coolant supply conduit for independently supplying coolant from the
pump to passages formed in the cylinder head, an electronically
controlled flow control valve to control the flow of coolant though
one of the first and second coolant supply conduits, a
predetermined flow restriction to prevent unlimited flow through
the other of the first and second coolant supply conduits wherein
the method comprises opening and closing the or each electronically
controlled flow control valve and changing the flow rate from the
variable flow rate pump to maintain, at least during normal engine
running, the temperature of the cylinder block within a desired
temperature range and the temperature of the cylinder head within a
desired temperature range.
[0037] At least one temperature sensor may be provided to sense the
temperature of a part of the cylinder head and at least one
temperature sensor may be provided to sense the temperature of a
part of the cylinder block and the method may further comprises
opening an closing the or each electronically controlled flow
control valve and varying the flow rate from the pump based upon
the signals received from cylinder head and cylinder block
temperature sensors.
[0038] Preferably, the temperature of the coolant exiting the
cylinder head may be sensed and the method may further comprises
opening an closing the or each electronically controlled flow
control valve and varying the flow rate from the pump based upon
the signals received from cylinder head and cylinder block
temperature sensors and from the coolant sensor.
[0039] The invention will now be described by way of example with
reference to the accompanying drawing of which:--
[0040] FIG. 1 is a schematic diagram of a cooling system for an
internal combustion engine according to a first embodiment of the
invention;
[0041] FIG. 2 is a schematic diagram of a cooling system for an
internal combustion engine according to a second embodiment of the
invention;
[0042] FIG. 3 is a schematic diagram of a cooling system for an
internal combustion engine according to a third embodiment of the
invention; and
[0043] FIG. 4 is a schematic diagram of electronically controlled
flow control valve for use in controlling the flow of coolant to a
cylinder block or cylinder head of the internal combustion
engine.
[0044] With particular reference to FIG. 1 there is shown an
internal combustion engine having a cylinder block 6 and a cylinder
head 10 and a cooling system therefor.
[0045] The cooling system comprises of a pump 1 to circulate
coolant from a pump outlet through a cooling circuit including
respective passages (not shown) formed in the cylinder head 10 and
in the cylinder block 6 through a return circuit 50 back to an
inlet of the pump 1.
[0046] The coolant is delivered to the cylinder block 6 through a
first coolant supply conduit 5. The flow through the first coolant
supply conduit 5 is controlled by an electronically controlled flow
control valve 2. The electronically controlled flow control valve 2
is controlled by an electronic controller (not shown) and is shown
in greater detail in FIG. 4 from which it can be seen that the
electronically controlled flow control valve 2 comprises of an
electronically controlled vacuum actuator 31 connected by means of
a linkage 33 to a shaft 34 upon which is mounted a flap valve 30. A
rotary potentiometer 32 is attached to one end of the shaft 34 to
provide a feedback from the electronically controlled flow control
valve 2 to the electronic controller of the position of the flap
valve 30.
[0047] The flap valve 30 is biased by a spring (not shown) into a
fully open position so that in the event of an electrical or
electronic failure the cylinder block 6 is not starved of
coolant.
[0048] A micro-switch (not shown) is used to provide a signal
indicative of the fully closed position which can be used to
periodically update the calibration of the feedback from the
potentiometer 32 and determine the fully closed position. However,
it will be appreciated that calibration could be achieved in other
ways such as by using a positive end stop.
[0049] In the fully closed position a small calibrated flow of
coolant can still pass by the flap valve 2.
[0050] It will be appreciated that other types of valve could be
used and that the invention is not limited to the use of a flap
valve.
[0051] The coolant is supplied to the cylinder head 10 through a
second coolant supply conduit 4 which includes a predetermined flow
restriction to prevent unlimited flow through the second coolant
supply passage 4. In this case the predetermined flow restriction
is in the form of an orifice 3 but alternatively, at least a
portion of the second coolant supply passage 4 could have a
relatively small cross-sectional flow area so as to provide the
predetermined flow restriction. It will be appreciated that if the
internal diameter of any conduit, tube or pipe used to form the
second coolant supply conduit 4 is relatively small it will provide
an increased resistance to flow and so will act in a similar manner
to an orifice. As yet another alternative the restriction to flow
of the passages in the cylinder head could be used to prevent
unlimited flow.
[0052] The coolant supplied to the cylinder block 6 from the first
coolant supply conduit 5 passes through the internal passages
formed in the cylinder block 6 and is transferred to the cylinder
head 10 by a first return conduit 11 where it flows through the
passages in the cylinder head 10 before flowing to a common inlet
point `PI` of the return circuit 50 through a common return conduit
12.
[0053] The temperature of the coolant exiting the cylinder head 10
is sensed by a coolant sensor 28 which sends a signal to the
electronic controller indicative of the temperature of the coolant
exiting the cylinder head 10.
[0054] A cylinder block sensor 26 is located on the cylinder block
6 at a position where it can provide an accurate indication of the
temperature of the temperature of the wall of one of the cylinders
of the engine. It will be appreciated that in practice there may be
a cylinder block temperature sensor associated with each of the
cylinders of the engine but for the purposes of this description
only one temperature sensor 26 is shown and described.
[0055] A cylinder head temperature sensor 27 is located on the
cylinder head 10 at a position where it can accurately sense the
temperature of the cylinder head in a critical region such as for
example in the region of a cylinder head valve bridge. The cylinder
head sensor 27 provides a signal indicative of the sensed
temperature to the electronic controller. It will be appreciated
that in practice there may be a cylinder head temperature sensor
associated with each of the cylinders of the engine but for the
purposes of this description only one temperature sensor 27 is
shown and described.
[0056] The pump 1 is driven by a belt from the engine but is a
variable flow rate pump 1 that is to say it is a variable
displacement pump and the flow rate from the pump 1 can be
controlled independently of the rotational speed of the engine. It
will be appreciated that the pump could alternatively be driven
independently of the engine by an electric or hydraulic motor and
in this case either a fixed displacement pump or a variable
displacement pump could be used because the speed of the pump could
be controlled independently of engine speed. The term `variable
flow rate pump` is used in this document to refer to any such
pump.
[0057] The flow from the variable flow rate pump 1 is controlled by
an electronic control unit (not shown) which in this case is formed
as part of the electronic controller used to control the
electronically controlled flow control valve 2 but could be a
separate electronic control unit.
[0058] The return circuit 50 has a common outlet point `PO`
connected to the inlet to the variable flow rate pump 1 by a supply
conduit 18.
[0059] The return circuit 50 comprises of a degas supply conduit 13
connected from the common inlet point `PI` to a degas reservoir 14
which is connected by a degas return conduit 9 to the common outlet
point `PO`, a cabin heater supply conduit 7 connected between the
common inlet point `PI` and a cabin heater 15 which is connected to
the common outlet point `PO` by a cabin heater return conduit 11, a
radiator supply conduit 8 which is connected to the common inlet
point `PI` by a bypass conduit 20 and supplies coolant to a
radiator 16 which is connected to a bypass thermostat 17 by a
radiator return conduit 22 and a bypass thermostat return conduit
21 connecting the bypass thermostat 17 to the common outlet point
`PO`.
[0060] It will be appreciated that the invention is not limited to
a return circuit configured as shown or to the use of a radiator,
cabin heater, bypass thermostat or degas reservoir.
[0061] Operation of the return circuit 50 is in most respects
conventional in that when the temperature of the coolant is low the
bypass thermostat is operational to allow coolant to flow between
the common inlet point `PI` and the common outlet point `PO`
through the bypass conduit 20 and the bypass return conduit 21
without passing through the radiator 16 to speed up engine warm up
and to improve cold start cabin heater performance. During this
period any flow through the degas reservoir 14 will be detrimental
to engine warm up as it will cause cold fluid stored in the degas
reservoir 14 to be displaced via the degas return conduit 9 to
merge with the coolant flowing through the bypass return conduit 21
thereby lowering the temperature of the coolant supplied to the
variable flow rate pump 1 through the supply conduit 18. After the
engine has warmed up sufficiently, the bypass thermostat 17 will
open and coolant will begin to flow through the radiator 16.
[0062] During `normal engine running` the electronic controller is
operable to monitor the outputs from the cylinder block temperature
sensor 26 and from the cylinder head temperature sensor 27 and
control the cooling system accordingly. The term `normal engine
running` as meant herein means when the engine is operating
normally with the temperature of the coolant being at a normal
(hot) temperature so that the thermostat 17 is within its normal
operating range which in this case is 85 to 105.degree. C. and
excludes any period of running when the thermostat is closed or the
temperature of the coolant exceeds the maximum temperature of the
thermostat 17.
[0063] Therefore during normal engine running the variable flow
rate pump 1 is operated at the minimum possible flow rate to reduce
the power requirements for the variable flow rate pump 1 and the
signal from the cylinder block temperature sensor 26 is used by the
electronic controller to open and close the electronically
controlled flow control valve 2 so as to maintain the temperature
of the cylinder block 6 or to be more precise the part of the
cylinder block 6 being monitored within a predetermined temperature
range such as for example between 110 and 130.degree. C. Therefore
if the temperature of the sensed part rises above the upper
temperature limit of the predetermined temperature range then the
electronically controlled flow control valve 2 will be opened
slightly so as to reduce the temperature by allowing more coolant
to flow through the passages in the cylinder block 6. Conversely,
if the temperature of the sensed part falls below the lower
temperature limit of the predetermined temperature range then the
electronically controlled flow control valve 2 will be closed
slightly so as to increase the temperature by allowing less coolant
to flow through the passages in the cylinder block 6. In practice
the electronically controlled flow control valve 2 may be arranged
to continuously adjust its position to try and maintain the
temperature at a specific temperature such as for example
120.degree. C. with a small plus and minus range such as plus or
minus 1.degree. C., this small plus or minus range is also a
predetermined desired temperature range as meant herein. It will be
understood that the movement of the valve can be controlled in many
ways and the invention is not limited to the specific control
technique employed.
[0064] During normal engine running the signal from the cylinder
head sensor 27 is used by the electronic controller to maintain the
temperature of the cylinder head 10 or to be more precise the
temperature of the part of the cylinder head 10 which is being
sensed within a predetermined range of temperatures. If the
temperature exceeds the upper limit for this range then the
electronic controller will increase the flow rate from the variable
flow rate pump 1 and if the temperature falls below the minimum
temperature then the flow rate from the variable flow rate pump 1
will be reduced. At all times the flow from the variable flow rate
pump 1 will be maintained at the lowest level possible. In this way
the temperature of the cylinder head 10 is controlled independently
from the temperature of the cylinder block 6 while minimising the
power requirements of the variable flow rate pump 1.
[0065] It will be appreciated that in practice the control of the
variable flow rate pump 1 may be more complex than that described
to prevent sudden changes in temperature. For example the desired
temperature range may include a mid-point or set point and the flow
from the pump 1 may be increased or decreased proportionally based
upon the difference in measured temperature from the set-point.
[0066] The cooling system is arranged to function differently when
the engine is operating with a coolant temperature greater than the
upper temperature limit at which the thermostat 17 can operate.
Under these conditions it is desirable to maintain control over the
coolant temperature and reduce it to a temperature within the
normal temperature range of the thermostat 17. Therefore, when the
signal from the coolant sensor 28 indicates that the temperature of
the coolant exiting the cylinder head 10 is above a predetermined
maximum temperature, the electronic controller is operable to
increase the flow rate through at least one of the cylinder head 10
and the cylinder block 6 by either temporarily increasing the flow
rate from the pump 1 to a higher flow rate or opening further the
electronically controlled flow control valve 2 or doing both of
these actions. This will help to reduce the temperature of the
coolant and, during this period, primary control is based upon the
signal received from the coolant sensor 28. This period of control
will be maintained until the temperature of the coolant has dropped
to a lower level well within the normal operating range of the
thermostat 17. When this lower temperature is reached control will
revert back to that based primarily on the measured cylinder block
6 and cylinder head 10 temperatures.
[0067] One of the benefits of this cooling system is that because
the variable flow rate pump 1 is always operated at the lowest
possible flow rate then a low flow rate of coolant is returning to
the return circuit 50 from the engine. The volume of coolant
passing through the degas reservoir 14 is therefore reduced thereby
reducing the volume of cold coolant flowing from the degas
reservoir 14 back to the variable flow rate pump 1. This alleviates
the need to have a separate control valve preventing the flow of
coolant to the degas reservoir during cold start-up conditions and
hence reduces the cost and complexity of the cooling system.
[0068] With particular reference to FIG. 2 there is shown an
internal combustion engine having a cylinder block 6 and a cylinder
head 10 and a cooling system which in many respects is the same as
that previously described with reference to FIG. 1 and so will not
be described further in great detail.
[0069] The primary difference between the system shown in FIG. 1
and that shown in FIG. 2 is that an orifice 102 or other flow
restriction is used to control the flow of coolant to the cylinder
block 6 and an electronically controlled flow control valve 103 is
used to control the flow of coolant to the cylinder head 10.
[0070] The return circuit 50 is as previously described and
operates as described above.
[0071] As before, the temperature of the coolant exiting the
cylinder head 10 is sensed by a coolant sensor 28 which sends a
signal to the electronic controller indicative of the temperature
of the coolant exiting the cylinder head 10, a cylinder block
sensor 26 is located on the cylinder block 6 at a position where it
can provide an accurate indication of the temperature of the
temperature of the wall of one of the cylinders of the engine and a
cylinder head temperature sensor 27 is located on the cylinder head
10 at a position where it can accurately sense the temperature of
the cylinder head in a critical region such as for example in the
region of a cylinder head valve bridge.
[0072] The pump 1 is driven by a belt from the engine and is a
variable flow rate pump 1.
[0073] An electronic controller (not shown) is used to control the
electronically controlled flow control valve 103.
[0074] During `normal engine running` the electronic controller is
operable to monitor the outputs from the cylinder block temperature
sensor 26 and from the cylinder head temperature sensor 27 and
control the cooling system accordingly. As before normal engine
running means when the engine is operating normally with the
temperature of the coolant being at a normal (hot) temperature so
that the thermostat 17 is within its normal operating range which
in this case is 85 to 105.degree. C. and excludes any period of
running when the thermostat is closed or the temperature of the
coolant exceeds the maximum temperature of the thermostat 17.
[0075] Therefore during normal engine running the signal from the
cylinder block temperature sensor 26 is used by the electronic
controller to control the flow from the pump 1 so as to maintain
the temperature of the cylinder block 6 or to be more precise the
part of the cylinder block 6 being monitored within a predetermined
temperature range and the signal from the cylinder head sensor 27
is used by the electronic controller to maintain the temperature of
the cylinder head 10 or to be more precise the temperature of the
part of the cylinder head 10 which is being sensed within a
predetermined range of temperatures by opening and closing the
electronically controlled flow control valve 103.
[0076] The temperature range in each case could be significant such
as a difference of several tens of degrees centigrade or could be
very small such as plus or minus 0.5.degree. C. so that in practice
the temperature is maintained at a constant predetermined
temperature. The term opening and closing of a valve does not mean
that a valve is moved from a fully open position to a fully closed
position or vice-versa but means that, if more cooling is required,
the valve is opened gradually until the required level of cooling
is obtained and vice versa. This type of control reduces the risk
of thermal stresses being set-up due to rapid changes in coolant
temperature.
[0077] It will be appreciated that when the engine is started from
cold it is desirable to warm up the engine as quickly as possible.
However, because the temperatures of the cylinder block 6 and the
cylinder head 10 will be much lower than those desired for
efficient operation, the electronic controller will automatically
fully close the electronically controlled flow control valve 103
and the pump 1 will be operated at its minimum flow rate. This will
help with engine warm up and in particular will allow the cylinder
head 10 to warm up quickly to reduce emissions. However, if more
coolant flow is required for any reason such as to improve the
output from the cabin heater or to help to reduce the temperature
differential between various parts of the engine then the
electronic controller is arranged to open the valve 103 and
increase the flow of coolant from the pump 1 in order to meet these
requirements.
[0078] A secondary benefit is that because a lower flow rate of
coolant is returning to the return circuit 50 from the engine the
volume of coolant passing through the degas reservoir 14 is reduced
thereby reducing the volume of cold coolant flowing from the degas
reservoir 14 back to the variable flow rate pump 1. As before, this
alleviates the need to have a separate control valve preventing the
flow of coolant to the degas reservoir during cold start-up
conditions and hence reduces the cost and complexity of the cooling
system.
[0079] If the sensed temperature of the coolant exiting the
cylinder exceeds the upper limit at which the thermostat 17 can
operate that is to say the thermostat is already fully open then
the electronic controller continues to monitor the signals from the
cylinder block and head temperature sensors 26 and 27 but these are
not used to control the electronically controlled flow control
valve 103. Instead, the electronic controller opens the
electronically controlled flow control valve 103 to reduce the
coolant temperature to a more acceptable lower level. As soon as
the temperature of the coolant exiting the cylinder head 10 is
sensed by the coolant sensor 28 to have fallen below a lower limit
then control will revert to that in which the signals from the
cylinder block and cylinder head temperature sensors 26 and 27 are
used by the electronic controller to control the electronically
controlled flow control valve 103.
[0080] It will be appreciated that with this embodiment and that
shown in FIG. 1 the coolant returning from the cylinder block 6 to
the return circuit can be used to provide a general cooling flow
through the passages formed in the cylinder head 10 and the flow
through the second coolant supply passages can be used to supply a
directed flow to the cylinder head 10 by using a number of jets or
nozzles aimed at specific parts of the cylinder head 10 such as the
valve bridges. Alternatively, the flow from the second supply
conduit can be used to provide a primary general flow through the
passages in the cylinder head 10 and the flow from the cylinder
block can be used to provide a supplementary general flow through
the passages in the cylinder head or may be directed through
different passages from the flow from the second coolant supply
conduit 4.
[0081] With particular reference to FIG. 3 there is shown a further
or third embodiment of the invention which in many respects is the
same to the second embodiment shown in FIG. 2 and for which only
significant differences will be described in detail.
[0082] The primary difference between this embodiment and the
embodiment shown in FIG. 2 is that instead of the return conduit
from the engine cylinder block 6 being connected to the cylinder
head 10, as it is in FIG. 2, the return conduit 19 is connected
directly to the return circuit 50 and in this case is connected to
the common input point `PI` so as to form parallel flow paths.
[0083] As with the previously described embodiment the electronic
controller is operable during normal engine running to vary the
flow from the pump 1 and open and close the electronically
controlled flow control valve 103 to control the temperature of the
cylinder block 6 and the cylinder head 10 to maintain them at a
predetermined temperature or within a predetermined range of
temperatures. As before the electronically controlled flow control
valve 103 is not moved in a step fashion from a fully closed
position to fully open position or vice-versa but is moved in a
controlled manner in the desired direction until the desired
temperature is attained.
[0084] As before, during start-up from cold the electronically
controlled flow control valve 103 is automatically maintained
closed and the pump 1 is operated with minimum flow to speed up
engine warm up. However, if more coolant flow is required for any
reason such as to improve the output from the cabin heater or to
help to reduce the temperature differential between various parts
of the engine then the electronic controller is arranged to open
the valve 103 and increase pump flow in order to meet these
requirements.
[0085] The arrangement shown in FIG. 3 has the advantage that the
cooling of the cylinder head 10 is totally independent from the
cooling of the cylinder block 6 but has the disadvantage that a
larger capacity pump is required to support the separate parallel
flow paths. That is to say with this arrangement the flow path from
the pump 1 through the second coolant supply conduit 4, the
cylinder head 10 and the return conduit 11 from the cylinder head
10 to the common input point `PI` of the return circuit 50 and the
flow path from the pump 1 through the first coolant supply conduit
5, the cylinder block 6 and the return conduit 19 to the common
input point `PI` of the return circuit are arranged in parallel.
With such an arrangement the flow from the cylinder block 6 cannot
be used to supplement the flow from the second coolant supply
conduit 4 and so in practice a larger pump is likely to be
required. For example, if for a particular point in time the
cylinder head requires a flow of 5 litres per second and the
cylinder block requires a flow rate of 4 litres per second the pump
will only need to supply 5 litres per second if the cooling system
is arranged as shown in FIG. 2 but will need to supply 9 litres per
second if the cooling system shown in FIG. 3 is used.
[0086] It will be appreciated that with this parallel flow
arrangement a coolant sensor could also be provided to monitor the
temperature of the coolant leaving the cylinder block or the
coolant sensor associated with the cylinder head coolant flow could
be replaced by such a sensor.
[0087] It will be appreciated that such a parallel flow arrangement
could also be applied to the situation shown in FIG. 1 in which the
flow to the cylinder head 10 is limited by an orifice 3 and the
flow to the block 6 is controlled by a valve 2.
[0088] Therefore in summary a number of different embodiments of
the invention have been disclosed all of which use separate coolant
supply passages to the cylinder block and the cylinder head and use
a valve to control the flow of coolant to one of the coolant supply
passages.
[0089] By using a cooling system according to the invention the
cylinder head can be allowed to warm up quickly after a cold start
and during normal engine running the cylinder block can be
maintained at a temperature to produce low friction and minimal oil
degradation while the cylinder head temperature is controlled to
allow lower cylinder head temperatures and hence reduced NOx
emissions while allowing the power rating for the components of the
cylinder head to be increased by providing the required cooling
thereto and in particular by providing focussed cooling of the
critical components.
[0090] It will be appreciated that one of the advantages of the
invention is that for all embodiments a single thermostat is used
to control the temperature of the coolant during normal engine
running. This minimises the cost of the system and prevents any
problems that can occur if multiple thermostats are used such as
thermostat fight.
[0091] A further advantage of a cooling system according to this
invention is that only one degas connection point is required, this
simplifies the system and produces a very cost efficient system as
no additional piping or control valves are required. As previously
mentioned because a cooling system according to the invention uses
a low flow of coolant during cold start-up conditions, no
additional valves are required to prevent cold coolant from being
purged from the degas reservoir during these conditions. Such a
cooling system is therefore less expensive to produce and will have
good warm up properties.
[0092] It will be appreciated by those skilled in the art that
although the invention has been described by way of example with
reference to a number of specific embodiments it is not limited to
these embodiments and that various alternative embodiments or
modifications to the disclosed embodiments could be made without
departing from the scope of the invention.
* * * * *