GB2522703A

GB2522703A - System and method for liquid cooling of an engine of a vehicle

Info

Publication number: GB2522703A
Application number: GB1401863.4A
Authority: GB
Inventors: Jane Summerfield; William Hutchins
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2014-02-04
Filing date: 2014-02-04
Publication date: 2015-08-05
Anticipated expiration: 2034-02-04
Also published as: GB2522703B; GB201401863D0

Abstract

The internal combustion engine cooling system has a radiator 12, primary pump 18, thermostatic valve 19, secondary pump 33 and an auxiliary device 31 such as a transmission system or an electric motor/generator. The radiator has an inlet to receive hot coolant and an outlet fluidly connected sequentially in series with the auxiliary device and secondary pump by an auxiliary conduit 32. The radiator also has a further port fluidly connected to the valve by a multi-directional conduit 17a. The auxiliary conduit intersects the multi-directional conduit at a junction such that the radiator outlet is also fluidly communicated with the valve, the valve being downstream of the auxiliary device and secondary pump. The valve controls a proportion of coolant flowing through the radiator. When coolant in an engine 11 is cold, such as during engine start, the valve prevents coolant from the radiator outlet and further port passing through. Coolant from the outlet thus passes through the auxiliary device to the further port and back to the outlet. Once the engine has warmed-up the valve permits coolant from the radiator outlet and further port to pass. This reverses the direction of coolant flowing in the multi-directional conduit.

Description

System and Method for Liquid Cooling of an Engine of a Vehicle

TECHNICAL FIELD

S This invention relates to liquid cooling of an engine of a vehicle, in particular an internal combustion engine. The invention has application to hybrid vehicles, in which the contribution of the internal combustion engine may be reduced in certain conditions of operation in favour of another energy source, such as an electric battery.

BACKGROUND TO THE INVENTION

Internal combustion engines require to be maintained at a stable operating temperature, and for this purpose liquid cooling is very common. The engine has a coolant jacket, and liquid coolant is circulated through the jacket to a liquid/air heat exchanger by means of coolant pump. The liquid coolant is typically water having certain additives to for example reduce the freezing point thereof and to inhibit corrosion. The heat exchanger is typically a finned radiator having an inlet tank to receive high temperature coolant from the coolant jacket, and an outlet tank from which lower temperature coolant is returned to the coolant jacket; between the inlet and outlet tanks are provided a plurality of finned tubes, typically vertically disposed.

The coolant circuit usually includes a thermostat to substantially prevent circulation of coolant through the radiator after a cold engine start. This arrangement allows the engine to reach operating temperature more quickly, at which point the thermostat opens to permit coolant flow through the radiator.

This kind of engine cooling system is very well known, and need not be described in further detail.

Hybrid vehicles typically comprise a liquid cooled internal combustion engine and an alternative means of providing motive power, typically a traction battery and electric motor. In one mode such vehicles may run solely on battery power, for example in city driving. In some circumstances the power supply and/or traction motor may require cooling.

All motor vehicles typically require a multi-speed transmission to give an acceptable compromise of acceleration, high cruising speed, low noise and low fuel consumption. In some circumstances the transmission may require cooling if under a high duty, for example whilst towing a trailer or whilst operating off-highway in a low S speed ratio.

The additional cooling requirement may be provided by a separate cooling circuit, but is typically integrated into the cooling circuit of the vehicle engine, for example by passing engine coolant directly to the device which requires cooling, or by passing engine coolant through a heat exchanger associated directly with the device which requires cooling.

It will be understood however that if the internal combustion engine is switched off, or if the thermostat prevents coolant flow through the radiator, cooled liquid from the engine cooling circuit is not available to cool another device.

Thus, for example, a hybrid vehicle adapted for off-highway use may run in electric mode off-highway at low speed in a high ratio. In such circumstances both the electric traction motor and the transmission (in particular the clutch pack) may require to be cooled, but because the internal combustion engine is not running, engine coolant does not circulate, and accordingly cooling of the motor and transmission must be provided in a different manner.

It would be desirable to utilize the engine coolant circuit to provide for cooling of auxiliary devices in circumstances where engine cooling is not required, such as where the thermostat prevents substantial flow of coolant through the usual radiator, or where the internal combustion engine is not running.

SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided a cooling system of a liquid cooled internal combustion engine, said system including a coolant circuit having an air liquid heat exchanger, a primary coolant pump, and a thermostatically controlled valve for determining the proportion of liquid coolant flowing through said heat exchanger, said heat exchanger having an inlet for hot coolant, a primary outlet for relatively cool coolant and wherein said valve is in the outlet path from said primary outlet, said heat exchanger further comprising a secondary outlet spaced from said primary outlet, an auxiliary device downstream of said secondary outlet and upstream of said valve, and a secondary coolant pump downstream of said secondary outlet and upstream of said valve, said secondary pump being operable to direct coolant from said secondary outlet to said primary outlet whilst said valve S substantially prevents coolant flow from the engine through said heat exchanger.

In an embodiment of the invention the thermostatically controlled valve substantially obstructs normal coolant flow from the primary outlet of the heat exchanger whilst allowing coolant flow to bypass the heat exchanger via a bypass conduit. By virtue of obstructing normal outlet flow, coolant flow to the inlet of the heat exchanger is also obstructed.

In an embodiment of the invention the secondary coolant pump is downstream of the auxiliary device; several such auxiliary devices may be provided, in series or in parallel, and in one embodiment are upstream of the secondary coolant pump. Such auxiliary devices may be directly cooled or may be indirectly cooled by means of, for example, a subsidiary liquid coolant circuit; in this latter arrangement the auxiliary device may be a liquid/liquid heat exchange device.

Coolant flow through a plurality of auxiliary devices may be apportioned by suitable valves and/or flow restrictors; such valves and/or restrictors may be adjustable, and may be responsive to coolant temperature and/or to the temperature of the respective auxiliary device.

The heat exchanger is typically a multi-tube finned radiator having elongate inlet and outlet tanks generally orthogonal to the tube direction; the tube direction may be vertical or horizontal.

The outlet tank is typically of substantially constant cross-sectional area, and includes a baffle to prevent substantial flow between the primary and secondary outlets, in particular when said secondary pump is operating.

The primary pump is in one embodiment downstream of the thermostatically controlled valve and upstream of the internal combustion engine. The thermostatically controlled valve may be responsive to the temperature of coolant in the inlet path of the heat exchanger, and may allow flow proportion in the range 0-100%.

The invention also comprises a vehicle having a liquid cooled internal combustion engine and incorporating the aforesaid cooling system, in particular a hybrid vehicle having both an internal combustion engine and an electric motor for providing motion S thereof. The electric motor may be a traction motor of any suitable kind, and a traction battery may be provided for powering said motor.

According to an aspect of the vehicle there is provided a method of using the liquid coolant of an internal combustion engine to cool an auxiliary device when coolant flow through a heat exchanger of said circuit is substantially blocked by a thermostatically controlled valve in the outlet path from a primary outlet of said heat exchanger, the method comprising providing a secondary outlet of said heat exchanger; locating said auxiliary device downstream of said secondary outlet; providing a pump downstream of said secondary outlet and upstream of said valve; and activating said pump to provide a reverse flow coolant circuit from the secondary outlet to the primary outlet and via said heat exchanger to the secondary outlet.

Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination.

Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF DRAWINGS

Other features of the invention will be apparent from the following description of embodiments of the invention, described by way of example only with reference to the accompanying drawings in which:-Fig. 1 illustrates a conventional liquid cooling circuit of an internal combustion engine.

Fig. 2 illustrates an embodiment of the present invention.

Fig. 3 illustrates flow paths of Fig. 2 for an engine at normal operating temperature (thermostatic valve open).

Fig. 4 illustrates flow paths of Fig. 2 for a cold engine (thermostatic valve closed).

Fig. 5 is an enlarged portion of the flow circuit of Fig. 4 illustrating cooling of two auxiliary devices; and

S

Fig. 6 is a partial cross-section through a radiator lower tank illustrating a baffle thereof.

DESCRIPTION OF EMBODIMENTS

Fig. 1 illustrates a conventional liquid cooling circuit 10 of an internal combustion engine 11. A radiator 12 comprises an upper tank 13, a lower tank 14 and a plurality of vertical finned tubes 15 which connect the tanks 13, 14.

The cooling circuit comprises a forward conduit 16 for passage of hot coolant from the engine 11 to the upper tank 13, and a return conduit 1 7a, 1 Yb for the passage of relatively cool coolant to the engine. A pump 18, typically a mechanical engine driven pump, assists circulation, and in this embodiment is located in the return conduit.

Arrows indicate the flow of circulating fluid.

The return conduit 17a, 17b includes a thermostatically controlled valve 19 having a bypass conduit 20 from the forward conduit 16. The valve 19 is responsive to engine temperature, typically coolant temperature in the forward conduit, to open the bypass conduit 20 and substantially close the upstream portion 17a of the return conduit when the engine has not reached operating temperature. In this condition coolant does not flow through the radiator 12, and accordingly the warm-up time of the engine is reduced since coolant flows only in the circuit comprising the engine 11, forward conduit 16, bypass conduit 20 and return conduit 17b.

As the engine 11 approaches operating temperature, the valve 19 closes the bypass conduit 20 and connects the upstream portion 17a of the return conduit with the downstream portion 17b. Operation of the valve may be progressive. When the engine has reached normal operating temperature, the bypass conduit is substantially closed, and coolant flows through the radiator 12.

The circuit of Fig. 1 is conventional. It will be understood that the radiator 12 may have a horizontal flow direction, and that the pump 18 may be located in the forward

S

conduit upstream of the connection of the bypass conduit 20. The pump 18 may be electrically driven if desired, and may have a variable rate of flow.

Fig. 2 illustrates an embodiment of the invention, corresponding to the coolant circuit S of Fig. 1; common features are identified with the same reference numerals.

In Fig. 2, cooling of an auxiliary device 31 is required, and for this purpose an auxiliary coolant conduit 32 is provided from a second outlet of the lower tank 14 via an auxiliary pump 33 to the upstream portion 17a of the return conduit. A sensor, not shown (for example a thermostat), is provided to indicate when cooling is required for the auxiliary device 31. A baffle 34 is provided to substantially prevent flow between the outlets of the lower tank 14, for reasons which are described below. Operation of the coolant circuit of Fig. 2 is as follows.

When the auxiliary device 31 does not require cooling, the coolant circuit operates as described with reference to Fig. 1. Coolant may flow in the auxiliary conduit 32 if the pump 33 permits passage therethrough. If desired a valve (not shown) may be provided to obstruct such flow provided that adequate engine cooling can be provided by return flow through the return conduit 17a.

When the auxiliary device 31 requires to be cooled, two modes of operation are possible.

If the engine has reached operating temperature, the potential flow paths are as illustrated in Fig. 3. A conventional flow path is provided via the flow conduit 16, radiator 12, and return conduits 17a, 17b; the bypass conduit 20 is substantially or completely closed. If cooling of the auxiliary device 31 is required, the auxiliary pump 33 facilitates coolant flow through the auxiliary conduit 32. The auxiliary pump is typically electric and responsive to a temperature sensor of the auxiliary device; the auxiliary pump may have a variable speed/flow rate.

The baffle 34 provides that vertical flow through the radiator is substantially divided, so that in Fig. 4 the finned tubes 15a to the left of the baffle (as illustrated) may be considered distinct from those tubes 15b to the right. By virtue of the additional flow restriction provided by the components in the auxiliary conduit 32, vertical coolant flow from the upper tank 13 through the right-hand tubes 15b may be relatively slow as compared with that flowing through the left hand tubes 15a, so that coolant flowing into the initial portion 35 of the auxiliary conduit from the lower tank 14, may be cooler than that flowing from the lower tank 14 into the return conduit 17a. This phenomenon may be used to achieve a greater cooling effect by adjusting the speed S of the auxiliary pump 33, so as to control the rate of flow of coolant to achieve optimum cooling of the auxiliary device.

Accordingly, coolant flow direction is as indicated by the arrows of Fig. 3, with substantially no flow in the bypass conduit 20.

If the engine has not reached normal operating temperature, but is running, the bypass conduit 20 is open and the upstream portion 17a of the return conduit is closed by the valve 19. Coolant circulates in a closed path, as illustrated in Fig. 4, and no flow passes from the engine 11 through the radiator 12. In this condition the auxiliary device 31 cannot be conventionally cooled because there is no coolant flow through the radiator as a result of operation of the pump 18.

However in this condition, activation of the pump 33 causes reverse coolant flow through the upstream portion 17a of the return conduit, and then vertically upward through the left side iSa of the radiator to the upper tank 13. Flow is then downwardly through the right side 15b of the radiator to the auxiliary outlet of the lower tank 14 and into the conduit portion 35; the baffle 34 prevents or substantially prevents direct flow through the lower tank from the conduit 17a to the conduit portion 35. Coolant circulates through a second closed path, as indicated by the arrows of Fig. 4. It will be observed that there is no flow in the flow conduit 16 downstream of the connection of the bypass conduit 20, or in the return conduit immediately upstream of the valve 19.

It will be understood that the two flow circuits of Fig. 4 are isolated by portions of the forward conduit and return conduit in which flow is substantially or completely ceased.

If the engine of Fig. 4 ceases to run, or has not been started, coolant flow in the circuit of the pump 18 ceases or does not occur. Nevertheless coolant flow in the circuit of pump 33 can occur on demand.

In case of the dual circuit flow of Fig. 4, the engine (if running) will eventually reach operating temperature, and flow in the bypass conduit 20 will be restricted by the valve 19. In this condition flow in the left side of the radiator will revert to the normal downward direction, and the flow paths will be as illustrated in Fig. 3.

Fig. 5 illustrates a variant of the circuit of Figs. 2-4, in which two auxiliary devices are S provided downstream of the secondary outlet of the radiator 12.

A first auxiliary device, for example an integrated electric motor/generator 41 associated with an electric vehicle drive system is cooled directly. The motor/generator 41 includes a coolant jacket through which engine coolant is passed via an inlet branch 42 and an outlet branch 43. A fluid restrictor 44 allows some coolant to pass directly between the branches 42, 43.

Downstream of the outlet branch 43 is a second auxiliary device 45, for example a liquid/liquid heat exchanger for lubricating oil of a vehicle transmission 46. In this case lubricating oil is pumped through the heat exchanger 45 via a pump incorporated within the transmission via flow and return conduits 47, 48; however an independent pump may also be provided. The transmission in this example is cooled indirectly.

The restrictor 44 is sized to permit a sufficient volume of coolant to be apportioned to the devices 41, 45, so that adequate cooling can be provided in use. The restrictor 44 may be variable, and adjusted to suit flow requirements according to normal control parameters and sensitive to coolant demands of the devices 41, 45.

The baffle 34 is illustrated schematically in Figs. 2-5, but in Fig. 6 is illustrated an example consisting of a planar barrier 51 situated in the lower tank 14, and having a small aperture 52 to permit communication between the primary and secondary outlets. The aperture may be used to allow a slight fluid flow and/or to equalize pressure. The baffle may be a separate component retained by ribs of the lower tank or by adhesive, or may be integrally moulded in a lower tank of plastics material.

Variations to the invention are possible within the scope of the claims appended hereto.

Features of the invention will be apparent from the numbered aspects that follow: 1. A cooling system of a liquid cooled internal combustion engine, said system including a coolant circuit having: an air liquid heat exchanger, a primary coolant pump, and S a thermostatically controlled valve for determining the proportion of liquid coolant flowing through said heat exchanger, said heat exchanger having an inlet for hot coolant, a primary outlet for relatively cool coolant and wherein said valve is in the outlet path from said primary outlet, said heat exchanger further comprising a secondary outlet spaced from said primary outlet, an auxiliary device downstream of said secondary outlet, and a secondary coolant pump downstream of said secondary outlet and upstream of said valve, said secondary pump being operable to direct coolant from said secondary outlet to said primary outlet whilst said valve substantially prevents coolant flow through said heat exchanger.

2. A system according to aspect 1 wherein said secondary coolant pump is downstream of said auxiliary device.

3. A system according to aspect 1 and comprising a plurality of said secondary devices.

4. A system according to aspect 3 wherein said plurality of auxiliary devices are provided in series upstream of said secondary pump.

5. A system according to aspect 4 wherein said devices include an electric motor upstream of an oil cooler of a transmission.

6. A system according to aspect 5 wherein said oil cooler receives transmission oil directly.

7. A system according to aspect 5 wherein said electric motor includes a coolant bypass having a flow restrictor therein.

8. A system according to aspect 4 wherein one of said devices receives full coolant flow therethrough.

9. A system according to aspect 4 wherein one of said devices receives a S proportion of full coolant flow therethrough.

10. A system according to aspect 1 wherein said heat exchanger is a multi-tube finned radiator having at opposite ends of the tubes an elongate inlet tank and an elongate outlet tank, the primary and secondary outlets being at opposite sides of said outlet tank.

11. A system according to aspect 10 wherein said outlet tank includes one or more baffles to substantially prevent direct liquid flow from the primary outlet to the secondary outlet.

12. A system according to aspect 1 wherein said primary pump is in the outlet path of the heat exchanger, downstream of said valve.

13. A system according to aspect 1 wherein said valve is responsive to coolant temperature in the inlet path of said heat exchanger.

14. A system according to aspect 1 wherein said valve comprises a first inflow path from said inlet path, a second inflow path from said outlet path, an outflow path, and a movable valve element to determine the proportion of inflow from said first and second inflow paths.

15. A system according to aspect 1 wherein the auxiliary device is a heat transfer device of one of a vehicle transmission and an electric motor.

16. A system according to aspect 1 wherein the auxiliary device is one of a vehicle transmission and an electric motor.

17. A vehicle having an internal combustion engine and incorporating the cooling system of aspect 1.

18. A vehicle according to aspect 17, being a hybrid having an electric battery and an electric traction motor.

19. A method of using the liquid coolant of an internal combustion engine to cool S an auxiliary device when coolant flow through a heat exchanger of said circuit is substantially blocked by a thermostatically controlled valve in the outlet path from a primary outlet of said heat exchanger, the method comprising: providing a secondary outlet of said heat exchanger; locating said auxiliary device downstream of said secondary outlet; providing a pump downstream of said secondary outlet and upstream of said valve; and activating said pump to provide a reverse flow coolant circuit from the secondary outlet to the primary outlet and via said heat exchanger to the secondary outlet.

Claims

Claims 1. A cooling system of a liquid cooled internal combustion engine, said system including a coolant circuit having: S an air liquid heat exchanger, a primary coolant pump, and a thermostatically controlled valve for determining the proportion of liquid coolant flowing through said heat exchanger, said heat exchanger having an inlet for hot coolant, a primary outlet for relatively cool coolant and wherein said valve is in the outlet path from said primary outlet, said heat exchanger further comprising a secondary outlet spaced from said primary outlet, an auxiliary device downstream of said secondary outlet, and a secondary coolant pump downstream of said secondary outlet and upstream of said valve, said secondary pump being operable to direct coolant from said secondary outlet to said primary outlet whilst said valve substantially prevents coolant flow through said heat exchanger.
2. A system according to claim 1 wherein said secondary coolant pump is downstream of said auxiliary device.
3. A system according to claim 1 or claim 2 and comprising a plurality of said secondary devices.
4. A system according to claim 3 wherein said plurality of auxiliary devices are provided in series upstream of said secondary pump.
5. A system according to claim 4 wherein said devices include an electric motor upstream of an oil cooler of a transmission.
6. A system according to claim 5 wherein said oil cooler receives transmission oil directly.
7. A system according to claim 5 or claim 6 wherein said electric motor includes a coolant bypass having a flow restrictor therein.
8. A system according to claim 4 wherein one of said devices receives full coolant flow therethrough.
9. A system according to claim 4 wherein one of said devices receives a proportion of full coolant flow therethrough.
10. A system according to any preceding claim wherein said heat exchanger is a multi-tube finned radiator having at opposite ends of the tubes an elongate inlet tank and an elongate outlet tank, the primary and secondary outlets being at opposite sides of said outlet tank.
11. A system according to claim 10 wherein said outlet tank includes one or more baffles to substantially prevent direct liquid flow from the primary outlet to the secondary outlet.
12. A system according to any preceding claim wherein said primary pump is in the outlet path of the heat exchanger, downstream of said valve.
13. A system according to any preceding claim wherein said valve is responsive to coolant temperature in the inlet path of said heat exchanger.
14. A system according to any preceding claim wherein said valve comprises a first inflow path from said inlet path, a second inflow path from said outlet path, an outflow path, and a movable valve element to determine the proportion of inflow from said first and second inflow paths.
15. A system according to any preceding claim wherein the auxiliary device is a heat transfer device of one of a vehicle transmission and an electric motor.
16. A system according to any of claims 1-15 wherein the auxiliary device is one of a vehicle transmission and an electric motor.
17. A vehicle having a liquid cooled internal combustion engine and incorporating the cooling system of any of claims 1-16.
18. A vehicle according to claim 17, and comprising a hybrid incorporating a traction battery and electric traction motor.
19. A method of using the liquid coolant of an internal combustion engine to cool S an auxiliary device when coolant flow through a heat exchanger of said circuit is substantially blocked by a thermostatically controlled valve in the outlet path from a primary outlet of said heat exchanger, the method comprising: providing a secondary outlet of said heat exchanger; locating said auxiliary device downstream of said secondary outlet; providing a pump downstream of said secondary outlet and upstream of said valve; and activating said pump to provide a reverse flow coolant circuit from the secondary outlet to the primary outlet and via said heat exchanger to the secondary outlet.
20. A cooling system substantially as described herein with reference to Figs. 2-5 of the accompanying drawings.
21. A hybrid vehicle substantially as described herein with reference to Figs. 2-5 of the accompanying drawings.
22. A method of cooling an auxiliary device of a vehicle, substantially as described herein with reference to Figs. 2-5 of the accompanying drawings.