GB2366365A

GB2366365A - Engine Cooling system

Info

Publication number: GB2366365A
Application number: GB0021012A
Authority: GB
Inventors: William Richard Hutchins
Original assignee: Land Rover Group Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2000-08-26
Filing date: 2000-08-26
Publication date: 2002-03-06
Anticipated expiration: 2020-08-26
Also published as: GB0021012D0; GB2366365B

Abstract

An engine cooling system for an internal combustion engine 11 comprises an engine coolant delivery passage 12 and an engine coolant return passage 13 for the return of the coolant to the engine 11. A primary heat exchanger 15 for cooling the engine coolant is connected to the engine delivery passage 12 and to a return passage 16. A bypass passage 19 is connected to the engine delivery passage 12 through a thermostat valve means 18. The engine cooling system also has an auxiliary heat exchanger 33 connected into the return passage 16 through a feed connection 31 and a return connection 32 so that a proportion of the cooled coolant return flow from the primary heat exchanger 15 can flow through the auxiliary heat exchanger 33 . The cooling system also has a control valve 17 in the return passage 16 between the feed connection 31 and the return connection 32. The control valve 17 restricts the coolant flow in the return passage 16 and enhances the coolant flow through the auxiliary heat exchanger 33. The control valve 17 may be a spring loaded valve. The auxiliary heat exchanger 33 may be a transmission oil cooler or an engine oil cooler or a fuel cooler.

Description

<Desc/Clms Page number 1> EnLyine Cooling Svstems The invention relates to cooling systems for internal combustion engines and in particular to those employing a liquid coolant, a primary heat exchanger to remove excess heat from the coolant and an auxiliary heat exchanger for other cooling purposes, e.g., cooling transmission oil in a motor vehicle. In some installations, for example as shown in WO-A-97/33078, the auxiliary heat exchanger is in its own sub-circuit and uses a separately cooled now.

It is also possible to use the cooled return flow from the primary heat exchanger for the auxiliary heat exchanger. See, for example, EP-A-0 544 522 where the auxiliary heat exchanger is connected into the heat exchanger return passage through a feed connection and a return connection, there being a restrictor in the return passage to induce flow through the auxiliary heat exchanger. Whilst the restrictor is of a variable diameter to allow extra flow when the engine speed is high, this document does not address the particular problems which can arise when there is a bypass passage which can circulate coolant between an engine coolant delivery passage which delivers a hot output flow of coolant from the engine and an engine coolant return passage for the return of coolant to the engine without the coolant passing through the primary heat exchanger. Flow in the bypass passage is under the control of thermostat valve means which is operative to distribute the proportions of the output flow as between the cooled return flow from the primary heat exchanger and the bypass flow in the bypass passage so that the engine can be maintained at its optimum operating temperature. The problems with this arrangement can arise because the auxiliary heat exchanger is required to dissipate a significant amount of heat compared to the amount of heat from the engine which is dissipated by the primary heat exchanger.

In the particular case of a diesel engined road vehicle with automatic transmission running under ordinary road conditions in a temperate atmosphere, the primary heat exchanger or radiator may receive only 5% of the coolant flow through the engine whereas the bypass receives 95%. At such low engine speeds and powers, the flow through the radiator may be insufficient to create any perceptible circulation through the auxiliary heat exchanger, particularly if, because of installation constraints, the auxiliary heat exchanger is positioned above the heat exchanger return passage. This is because the heated coolant in the auxiliary heat exchanger is less dense than the cold coolant in the heat exchanger return passage. The effect is analogous to an inverted U-tube manometer, the hot, less dense, coolant being in the upper bend of the inverted U. An appreciable pressure difference is thus required to displace the hot coolant and initiate flow through the auxiliary heat exchanger.

The present invention provides an engine cooling system in which the above problems are alleviated.

According to one aspect of the present invention there is provided A cooling system for an internal combustion engine and comprising a coolant delivery passage for the delivery of a hot output flow of coolant from the engine, a coolant return passage for the return of coolant to the engine, a primary heat exchanger connected to the coolant delivery passage and having a heat exchanger return passage connected thereto such that a proportion of the output flow can be passed through the primary heat exchanger and the heat exchanger return passage before being returned to the engine as a cooled return flow through the coolant return passage, a bypass passage connected to the coolant delivery passage and to the coolant return passage to enable another proportion of the output flow to be returned to the engine as a bypass flow without passing through the primary heat exchanger, thermostat valve means connected to the bypass passage, the heat

exchanger return passage and the coolant return passage and operative to distribute the proportions of the output flow as between the cooled return flow and the bypass flow, an auxiliary heat exchanger connected into the heat exchanger return passage through a feed connection and a return connection so that a proportion of the cooled return flow can flow through the auxiliary heat exchanger and a flow control valve in the heat exchanger return passage between the feed connection and the return connection to restrict the flow in the heat exchanger return passage between said connections and enhance the flow through the auxiliary heat exchanger.

In a preferred arrangement, the flow control valve comprises a housing, an inlet port and an outlet port each forming part of the heat exchanger return passage, an orifice in the housing between the inlet port and the outlet port and a spring loaded valve member arranged to at least partially obstruct the orifice and to be movable against the spring loading by a pressure drop between the coolant flowing in through the inlet port and flowing out through the outlet port, movement of the valve member against the spring loading reducing the obstruction of the orifice.

The housing may include a feed port upstream of the orifice and which provides said feed connection into the heat exchanger return passage and a return port downstream of the orifice and which provides said return connection into the heater return passage.

Preferably the inlet and outlet ports are arranged substantially in line with each other. This reduces the restriction when high flows are required and allows for easier installation into an existing cooling system arrangement.

Conveniently, the valve member comprises a head portion for obstruction of the orifice and-a guide portion to guide the valve member axially away from the orifice. The guide portion may comprise a plurality of axially extending radial fins.

The valve member may be spring biased towards the orifice by a helical compression spring. Conveniently, the spring is guided for axial movement by the housing and the valve member is guided for axial movement by the helical compression spring.

An abutment member may be provided in the housing to limit axial movement of the valve member away from the orifice. Such an abutment member may be in the outlet port and may provide an abutment for the said helical compression spring. Furthermore, the abutment member may comprise at least one transverse cross member having ends which each extend into a respective window in the housing. The windows may be sealed by a connecting hose. This can also serve to locate the cross member positively.

The invention also provides, according to a second aspect thereof, a flow control valve for use in a cooling system according to said one aspect.

The invention will now be described by way of example and with reference to the accompanying drawings, of which:- Fig.1 is a diagram of a cooling system for an internal combustion engine according to the invention; Fig.2 is a cross-section through a flow control valve assembly shown in Fig. 1; Fig. 3 is a section on the line III-III in Fig.2; Fig.4 is a side elevation of a valve member shown in Figs.2 and 3; Fig.5 is a view on arrow A in Fig.4; and

Fig.6 is graph showing flow through the primary heat exchanger and the auxiliary heat exchanger.

Referring initially to Fig. 1, a cooling system for an internal combustion engine 11 includes an engine coolant delivery passage 12 for the delivery of a hot output flow of coolant from the engine and an engine coolant return passage 13 for the return of coolant to the engine through a pump 14. A primary heat exchanger in the form of an air cooled radiator 15 is connected to the engine delivery passage 12 and has a heat exchanger or radiator return passage 16 connected to it.

A bypass passage 19 is connected to the engine delivery passage 12 through thermostat valve means in the form of a thermostat and bypass control valve assembly 18. This may be as described in EP-A-0 794 327 which is hereby incorporated by reference. The thermostat and bypass valve assembly 18 is connected to the radiator return passage 16 and to the engine return passage 13 so that in use a proportion of the output flow of coolant from the engine 11 passes through the radiator 15 and another proportion passes through the bypass passage 19, these proportions being controlled according to the temperature of the coolant being returned through the engine return passage 13.

An expansion tank 21 is included to provide for expansion of the liquid coolant in the cooling system and to allow the removal of gasses and vapours. A relatively small flow of coolant circulates through the expansion tank passages 22 and 23 which are connected to the delivery passage 12 and the engine return passage 13 respectively. Typically, for use of a motor vehicle, a heater matrix 24 is also provided. This receives a supply of hot coolant through a heater supply passage 25 connected to the engine delivery passage 12 and a heater return passage 26 connected to the engine return passage 13.

A flow control valve assembly 17 is in the radiator return passage 16 and in effect divides the radiator return passage 16 into an upstream section 45 and a downstream section 46. The flow control valve assembly 17 incorporates a feed connection 31 into the upstream section 45 and a return connection 32 into the downstream section 46 of the radiator return passage 16. The feed connection 31 and the return connection 32 connect the flow control valve assembly 17 through a cooler feed passage 34 and a cooler return passage 35 to an auxiliary heat exchanger in the form of a transmission oil cooler 33. The transmission oil cooler also includes an oil inlet port 36 and an oil outlet port 37 for the circulation of oil from ## ; -.. automatic transmission assembly (not shown) driven by the engine 11. With further reference to Figs.2 to 5, it can be seen that the flow control valve assembly 17 comprises a housing 41 having a stepped through passage 42 which forms part of the radiator return passage 16. A circular orifice 43 is formed at a step 44 in the through passage 42 at the intersection of the upstream section 45 of the radiator return passage 16 and the downstream section 46. The housing 17 has an inlet connection 47 at an inlet port 48 and this is connected to the radiator 15 through a hose 49 of an elastomeric material and which forms part of the passage upstream section 45. Similarly, an outlet connection 51 at an outlet port 52 is connected to another hose 53 of an elastomeric material and which forms part of the passage downstream section 46. The outlet port 52 forms part of a downstream portion 54 of the stepped through passage 42. A valve member 55 is situated in the passage downstream portion 54 and is spring loaded by a helical compression spring 56 towards and into abutment with the step 44. The valve member 55 comprises four axially extending radial fins 57 which form a guide portion of the valve member and a disc-like head portion 58. When the valve assembly 17 is in an "at rest" condition as shown in Fig.2, the head portion 58 is immediately adjacent the orifice 43 so as

to partially obstruct it. The spring 56 is guided for axial movement by five axial ribs 61 in the downstream passage section 54 and abuts with a preload a ladder- shaped abutment member 63 extending transversely across the outlet port 52. The valve member 55 is itself guided for axial movement by the spring 56 on the outer edges of the fins 57, the fins each having a step 59 to abut the spring and receive the axial spring load.

The abutment member 63 comprises two parallel cross members 64 and 65 which extend into generally rectangular windows or apertures 66 in the outlet connection 51, the cross members 64 and 65 being linked by two parallel link members 67 and 68. The abutment member 63 is assembled into the housing 41 by being inserted into the outlet port 52 at an angle so that one end of each of the cross members 64 and 65 can extend through two of the windows 66 to such an extent that the other end of each of the cross members can enter the port and be aligned with the other two windows 66. The abutment member 63 can then be slid transversely so that these other ends of the cross members 64 and 65 can then enter their respective windows. The tips of the cross members 64 and 65 then lie flush with the outer surface of the outlet connection 51. Each window 66 is wider (in the axial direction of the outlet port 52) than the ends of the cross members 64 and 65 to allow the abutment member 63 to tilt as described. Conveniently, the face of the abutment member which faces outwards from the outlet port 52 is stepped so that the spring 56 will keep it centralised in the outlet port 52. In use, the hose 53 seals the windows 66 and provides a positive location for the abutment, member 63 and the valve assembly 17 can be supplied to an engine assembly line or to a vehicle assembly line with the hose 53 already in place.

The feed connection 31 for the cooler feed passage 34 opens into the stepped through passage 42 upstream of the orifice 43 and the return connection 32 for the

cooler return passage 35 is connected into the downstream section 54 of the stepped through passage 42 downstream of the orifice 43.

In use, flow through the valve assembly 17 between the inlet port 48 and the outlet port 52 creates a pressure drop across the orifice 43 to induce a parallel flow through the transmission oil cooler 33. If the engine 11 is operating at or near maximum power, then the orifice 43 would in itself create sufficient pressure drop to allow for an adequate flow of coolant through the oil cooler 33. Typically, the transmission oil cooler 33 takes just 10% of the radiator flow, the remaining 90% passing through the orifice 43. However, typical open road cruising at 80 to 120 kilometres per hour can result in the radiatw flow being only a small proportion of the hot output flow from the engine 11.

In the case of a diesel engine in particular, the cruising conditions just described equate to an engine speed of approximately 2500 rpm. Under these conditions, the division of flow between the bypass passage 19 and the radiator return passage 16 is typically such that 95% of the flow is in the bypass passage 19 and only 5% of flow is in the radiator return passage 16. It has been found that if a fixed restrictor 43 is used (without the valve member 55) and is of a size which gives an appropriate flow of coolant through the oil cooler at maximum engine power, the flow at the cruising conditions just described may be only 0.5% of the engine output flow. This is quite insufficient, despite the relatively low engine speed and power, because the transmission may have to dissipate up to 30% of the engine heat output through the transmission oil cooler 33.

The problem outline immediately above is overcome by making the effective area of the orifice 43 variable by partially obstructing it with the valve member head portion 58. At the low radiator flows just described, the valve member 55 is in abutment with the step 44 to maximise the restriction across the orifice 43

whereas at higher engine powers which require a greater flow through the radiator 15 the valve member 55 can move against the preload of the spring 56 to reduce the obstruction of the orifice 43. Movement of the valve member 55 against the spring 56 is limited by the abutment member 63.

If required, the head portion 58 of the abutment member 55 may be shaped so as to provide a lower resistance to flow when the flow through the radiator 15 is at a maximum. In any event, minimal flow resistance at maximum engine power is helped by having the inlet port 48 and the outlet port 52 in line with each other. It will be appreciated that instead of the auxiliary heat exchanger being a transmission oil cooler 33 it may also take the form of an engine oil cooler- or a fuel cooler. The radial fins 57 also provide for a low resistance to now when the flow through the radiator 15 is at a maximum, as does the ladder shaped abutment member 65. If required, there may be only three fins on the valve member or a greater number, e.g. five.

By having a flow control valve in the radiator return passage 16 with careful control of the flow through the oil cooler 33 as described above, it is possible to avoid the use of a thermostat to control the flow of coolant through the oil cooler. For some arrangements of cooling system it may be advantageous for the valve member head portion 58 to be of equal or larger area than the orifice 43 so as to completely obscure the orifice when the valve assembly 17 is in the at rest condition as shown in Fig.2. This will force all of the flow in the radiator return passage 16 through the oil cooler 33 at very low engine outputs. However, in a typical installation it has been found that a valve member head portion 58 with a diameter of 20 mm works satisfactorily in an orifice of diameter 24 mm.

The effect of the flow control valve is illustrated in Fig.6 which shows in line "a" the radiator flow Q as a function of engine power P. Without the valve member

55, the flow in the oil cooler 33 is represented by the curve "b". It can be seen that the thermo-syphon effect of having the oil cooler 33 above the radiator return passage 16 results in there being no flow until a power P1 has been reached and that thereafter the flow is approximately 10% of the radiator flow. With the valve member 55 in place, flow through the oil cooler 33 is enhanced at low engine speeds as shown by the curve "c".

Claims

CLAIMS 1. A cooling system for an internal combustion engine and comprising a coolant delivery passage for the delivery of a hot output flow of coolant from the engine, a coolant return passage for the return of coolant to the engine, a primary heat exchanger connected to the coolant delivery passage and having a heat exchanger return passage connected thereto such that a proportion of the output flow can be passed through the primary heat exchanger and the heat exchanger return passage before being returned to the engine as a cooled return flow through the coolant return passage, a bypass passage connected to the coolant delivery passage and to the coolant return passage to enable another proportion of the output flow to be returned to the engine as a bypass flow without passing through the primary heat exchanger, thermostat valve means connected to the bypass passage, the heat exchanger return passage and the coolant return passage and operative to distribute the proportions of the output flow as between the cooled return flow and the bypass flow, an auxiliary heat exchanger connected into the heat exchanger return passage through a feed connection and a return connection so that a proportion of the cooled return flow can flow through the auxiliary heat exchanger and a flow control valve in the heat exchanger return passage between the feed connection and the return connection to restrict the flow in the heat exchanger return passage between said connections and enhance the flow through the auxiliary heat exchanger.
2. A cooling system according to claim 1 wherein the flow control valve comprises a housing, an inlet port and an outlet port each forming part of the heat exchanger return passage, an orifice in the housing between the inlet port and the outlet port and a spring loaded valve member arranged to at least partially obstruct the orifice and to be movable against the spring

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loading by a pressure drop between the coolant flowing in through the inlet port and flowing out through the outlet port, movement of the valve member against the spring loading reducing the obstruction of the orifice.
3. A cooling system according to claim 2 wherein the housing includes a feed port upstream of the oriflce and which provides said feed connection into the heat exchanger return passage and a return port downstream of the orifice and which provides said return connection into the heater return passage.
4. A cooling system according to claim 2 or claim 3 wherein the inlet and outlet ports are arranged substantially in line with each other.
5. A cooling system according to any of claims 2 to 4 wherein the valve member comprises a head portion for obstruction of the orifice and a guide portion to guide the valve member axially away from the orifize.
6. A cooling system according to claim 5 wherein the guide portion comprises a plurality of axially extending radial fins.
7. A cooling system according to any of claims 2 to 6 wherein the valve member is spring biased towards the oriflce by a helical compression spring.
8. A cooling system according to claim 7 wherein the spring is guided for axial movement by the housing and the valve member is guided for axial movement by the helical compression spring.
9. A cooling system according to any of claims 2 to 8 wherein an abutment member is provided in the housing to limit axial movement of the valve member away from the orifice.

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10. A cooling system according to claim 9 wherein the abutment member is in the outlet port.
11. A cooling system according to claim 9 or claim 10 when either is dependent upon claim 7 wherein the abutment member provides an abutment for the spring.
12. A cooling system according to any of claims 9 to 11 wherein the abutment member comprises at least one transverse cross member having ends which each extend into a respective window in the housing.
13. A cooling system according to claim 12 wherein the windows are sealed by a connecting hose.
14. A cooling system substantially as described herein with reference to Figs. 1 to 5 of the accompanying drawings.
15. A flow control valve for use in a cooling system according to any preceding claim.