Arrangement and a control method of an engine cooling system

Abstract

An engine cooling system in a vehicle comprises a first coolant circuit and a second coolant circuit connecting an engine to a radiator. A thermostat is arranged in the first coolant circuit and is arranged to be closed during engine warm-up, to prevent flow through the first coolant circuit. The cooling system further comprises a bypass circuit connecting the thermostat to the second coolant circuit and at least one parallel circuit. Each parallel circuit is connected to the second coolant circuit upstream of the bypass circuit, wherein a partial coolant flow is directed from the bypass circuit and upstream through the second coolant circuit into the at least one parallel circuit during engine warm-up. The disclosure further relates to a method for controlling such an engine cooling system.

Claims

1. An engine cooling system for a vehicle having an engine, the cooling system comprising: a first coolant circuit for connecting a coolant outlet of the engine to a radiator; a thermostat arrangeable in the first coolant circuit, the thermostat configured to be opened when a predetermined first coolant temperature is reached; a second coolant circuit for connecting the radiator to a coolant inlet of the engine; a coolant pump for circulating coolant through the cooling system; a bypass circuit for connecting the thermostat to the second coolant circuit; at least one parallel circuit comprising a heat exchanger, wherein each parallel circuit is configured to be connected to the second coolant circuit upstream of the bypass circuit relative to a normal direction of coolant flow when the thermostat is open; a flow controlling device arrangeable to direct a reversed partial coolant flow from the bypass circuit into the at least one parallel circuit, such that the reversed partial coolant flow is directed from the bypass circuit and upstream through the second coolant circuit into the at least one parallel circuit when the thermostat is closed during engine warm-up.

2. The engine cooling system according to claim 1 wherein at least one parallel circuit comprises a fixed flow or controllable flow throttle valve.

3. The engine cooling system according to claim 1 wherein the flow controlling device is a flow restricting device arrangeable to limit flow rate in the second coolant circuit downstream of the bypass circuit.

4. The engine cooling system according to claim 3 wherein the flow restricting device is a fixed flow or controllable flow throttle valve.

5. The engine cooling system according to claim 3 wherein the flow restricting device is provided with a bypass circuit comprising a controllable valve.

6. The engine cooling system according to claim 4 wherein the flow restricting device is provided with a bypass circuit comprising a controllable valve.

7. The engine cooling system according to claim 1 wherein the flow controlling device is a second coolant pump arrangeable upstream of the bypass circuit.

8. The engine cooling system according to claim 1 wherein the thermostat is controllable in between its open and closed positions and is configured to be partially opened when a predetermined second coolant temperature is reached, which second coolant temperature is lower than the first coolant temperature.

9. The engine cooling system according to claim 1 wherein the flow controlling device comprises a controllable valve with a reduced flow bypass circuit, which controllable valve is configured to be opened when a predetermined operation condition is fulfilled.

10. A method for controlling an engine cooling system, wherein the engine cooling system comprises a first coolant circuit connecting a coolant outlet of an engine to a radiator, a thermostat arranged in the first coolant circuit and configured to be closed if coolant temperature is below a predetermined limit, a second coolant circuit connecting the radiator to a coolant inlet of the engine, and a coolant pump for circulating coolant through the cooling system, the method comprising, during engine warm-up: maintaining the thermostat in a closed position, wherein the thermostat is configured to be opened when a predetermined first coolant temperature is reached; supplying coolant flow through a bypass circuit when the thermostat is closed, wherein the bypass circuit connects the thermostat to the second coolant circuit; maintaining a partial coolant flow from the bypass circuit and downstream through the second coolant circuit; and when the thermostat is closed, maintaining a reversed partial coolant flow directed from the bypass circuit and upstream through the second coolant circuit into at least one parallel circuit comprising a heat exchanger, the at least one parallel circuit being connected to the second coolant circuit upstream of the bypass circuit relative to a normal direction of coolant flow when the thermostat is open.

11. The method according to claim 10 wherein maintaining the partial coolant flow directed into the at least one parallel circuit comprises using a flow restricting device arranged to limit flow rate downstream of the bypass circuit.

12. The method according to claim 10 wherein maintaining the partial coolant flow directed into the at least one parallel circuit comprises using a second coolant pump upstream of the bypass circuit.

13. The method according to claim 10 further comprising controlling the thermostat by partially opening it when a predetermined second coolant temperature is reached, which second coolant temperature is lower than the first coolant temperature.

14. The method according to claim 10 wherein the engine cooling system comprises a flow controlling device configured to enable the partial coolant flow from the bypass circuit into the at least one parallel circuit, wherein the flow controlling device comprises a controllable valve with a reduced flow bypass circuit, and wherein the controllable valve is opened when a predetermined operation condition is fulfilled.

15. The method according to claim 10 further comprising controlling the coolant flow in at least one parallel circuit using a fixed flow or controllable flow throttle valve.

16. A vehicle comprising: an engine having a coolant inlet and a coolant outlet; a radiator; and an engine cooling system comprising: a first coolant circuit that connects the coolant outlet of the engine to the radiator; a thermostat arranged in the first coolant circuit and configured to be opened when a predetermined first coolant temperature is reached; a second coolant circuit that connects the radiator to the coolant inlet of the engine; a coolant pump for circulating coolant through the cooling system; a bypass circuit connected to the thermostat and the second coolant circuit; at least one parallel circuit, each parallel circuit comprising a heat exchanger and being connected to the second coolant circuit upstream of the bypass circuit relative to a normal direction of coolant flow when the thermostat is open; and a flow controlling device arranged to direct a reversed partial coolant flow from the bypass circuit into the at least one parallel circuit, such that the reverse partial coolant flow is directed from the bypass circuit and upstream through the second coolant circuit into the at least one parallel circuit when the thermostat is closed during engine warm-up.

17. The vehicle according to claim 16 wherein at least one parallel circuit of the at least one parallel circuit comprises a fixed flow or controllable flow throttle valve.

18. The vehicle according to claim 16 wherein the flow controlling device of the engine cooling system is a flow restricting device arranged to limit flow rate in the second coolant circuit downstream of the bypass circuit.

19. The vehicle according to claim 18 wherein the flow restricting device is a fixed flow or controllable flow throttle valve.

20. The vehicle according to claim 18 wherein the flow restricting device is provided with a bypass circuit comprising a controllable valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) With reference to the appended drawings, below follows a more detailed description of embodiments according to the disclosure cited as examples. In the drawings:

(2) FIG. 1 shows a schematically illustrated vehicle provided with an engine cooling system according to the disclosure;

(3) FIG. 2A shows a schematically illustrated engine cooling system according to the disclosure;

(4) FIG. 2B shows an alternative version of the engine cooling system in FIG. 2A;

(5) FIG. 3 shows a schematically illustrated first alternative example of an engine cooling system according to the disclosure;

(6) FIG. 4 shows a schematically illustrated second alternative example of an engine cooling system according to the disclosure;

(7) FIG. 5 shows a schematically illustrated third alternative example of an engine cooling system according to the disclosure; and

(8) FIG. 6 shows a schematically illustrated third alternative example of an engine cooling system according to the disclosure.

DETAILED DESCRIPTION

(9) As required, detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary and that various and alternative forms may be employed. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art.

(10) FIG. 1 shows a schematically illustrated vehicle provided with an engine cooling system according to the disclosure. The figure shows a vehicle 10 provided with an internal combustion engine 11, connected to a radiator 12.

(11) FIG. 2A shows a first schematically illustrated engine cooling system 20. The engine cooling system 20 comprises a first coolant circuit 21 connecting a coolant outlet of an engine 30 to a radiator 31, a thermostat 32 arranged in the first coolant circuit 21, which thermostat 32 is arranged to be closed during engine warm-up, thereby preventing flow through the first coolant circuit, and a second coolant circuit 22 connecting the radiator to a coolant inlet of the engine 30. Throughout the figure, the direction of flow is indicated by arrows. A coolant pump 33 is provided for circulating coolant through the cooling system 20. The coolant pump 33 is arranged in the second coolant circuit 22 and is driven directly by the engine 30, for instance, electric or hydraulic means (not shown). In this context, the terms “circuit” and “coolant circuit” are used to describe suitable means for conveying coolant through an engine or a powertrain cooling system.

(12) The cooling system further comprises a bypass circuit 24 connecting the thermostat to the second coolant circuit 22 upstream of a first throttle valve 34. In this example the thermostat 32 is closed during an engine warm-up mode, i.e., when starting a cold engine, wherein the coolant flow supplied by the coolant pump 33 flows through the bypass circuit 24. This will prevent cooling of the coolant in the radiator 31 during the engine warm-up mode. When the engine 30 is started, the coolant temperature will immediately begin to increase as the coolant flowing through the engine 30 is heated by the heat generated in the combustion chambers.

(13) The thermostat 32 is a low temperature thermostat that will open at a relatively lower temperature. In a conventional cooling system the thermostat will open at approximately 90° C., whereby the coolant flow will pass from the engine and directly into a main coolant circuit to be cooled in the radiator. In this case, the low temperature thermostat 32 opens at a temperature of 75-80° C.

(14) The cooling system 20 further comprises a number of parallel circuits 25, 26, 27, 2n, each comprising a throttle valve 35, 36, 37, 3n and a heat exchanger 45, 46, 47, 4n, respectively. Each parallel circuit 25, 26, 27, 2n is connected to the second coolant circuit 22 at a common location upstream of the bypass circuit 24 and downstream of the first throttle valve 34. While the thermostat is closed, a partial coolant flow is directed from the bypass circuit 24 and upstream through the second coolant circuit 22 into the parallel circuits 25, 26, 27, 2n during engine warm-up. The throttle valve 34 in the secondary circuit 22 will restrict the coolant flow from the bypass circuit 24 and force a part of the coolant flow through the parallel circuits 25, 26, 27, 2n. This arrangement causes a reverse flow over a portion of the second coolant circuit 22, between the connection with the bypass circuit 24 and the connection of the parallel circuits 25, 26, 27, 2n. This counter flow prevents cold coolant in the second coolant circuit 22 in or downstream of the radiator 31 and upstream of the parallel circuits 25, 26, 27, 2n from being drawn towards the coolant pump 33 and the engine 30. The coolant flow in the second coolant circuit 22 and the parallel circuits 25, 26, 27 during engine warm-up is indicated with dashed lines in the respective circuit. The coolant flowing through the parallel circuits 25, 26, 27, 2n is returned to the second coolant circuit 22 downstream of the first throttle valve 34.

(15) Each parallel circuit 25, 26, 27, 2n is provided with a heat exchanger 45, 46, 47, 4n that is arranged for selectively heating or cooling a powertrain component (not shown). According this example, a first parallel circuit 25 comprises an exhaust gas recirculation EGR heat exchanger 45. A second parallel circuit 26 comprises a catalytic converter heat exchanger 46 for heating e.g., a selective catalytic reduction (SCR) device. A third parallel circuit 27 comprises a transmission oil heat exchanger 47. The parallel circuit 27 comprising the transmission oil heat exchanger 47 also comprises a controllable valve 38. This valve 38 is open while the thermostat 32 is closed, in order to assist in heating the transmission, and is closed when the thermostat 32 opens, in order to stop cold coolant from the radiator 31 to cool the transmission unnecessarily. By heating the transmission oil friction is reduced and gearshift quality and fuel economy is improved. During engine warm-up, the active heating of the transmission will have a greater effect of the fuel consumption than the heating of the engine itself.

(16) A cooling system 20 according to the disclosure can comprise further parallel circuits 2n comprising a throttle valve 3n and a heat exchanger 4n, as indicated by dashed lines in FIG. 2A.

(17) The cooling system 20 further comprises a third coolant circuit 23 connecting the coolant pump 33 to an engine oil heat exchanger 39, often termed oil cooler. In addition, a fourth coolant circuit 28 is provided for connecting the engine oil cooler 39 to the second coolant circuit 22 upstream of the first throttle valve 34 and downstream of the parallel circuits 25, 26, 27, as shown. Alternatively the fourth coolant circuit 28 can be connected upstream of the bypass circuit 24 and downstream of the parallel circuits 25, 26, 27. The third coolant circuit 23 comprises a controllable valve 40. This controllable valve 40 is open while the thermostat 32 is closed, in order to assist in heating the engine oil, and is closed when the thermostat 32 opens, in order to increase the oil temperature towards a desired operating temperature. By heating the engine oil, friction in the engine is reduced, fuel economy is improved and oil dilution, i.e., fuel and combustion products leaking past the piston rings, is reduced. For diesel engines it is also possible to speed up the diesel oxidation catalyst (DOC) light-off. The DOC promotes oxidation of several exhaust gas components by oxygen, which is present in diesel exhaust. When passed over an oxidation catalyst, diesel pollutants, such as carbon monoxide (CO), gas phase hydrocarbons (HC) and organic fraction of diesel particulates (SOF) can be oxidized to harmless products.

(18) As described above, each parallel circuit is provided with a heat exchanger and a throttle valve. In FIG. 2A all throttle valves are shown as fixed flow valves pre-set to balance the coolant flow through the first throttle valve 34 and through each parallel circuit 25, 26, 27. The flow rate is determined by the heating and cooling requirements for each respective component connected to a respective heat exchanger 45, 46, 47 in a parallel circuit.

(19) Alternatively, at least one throttle valve is a controllable flow valve arranged to balance the coolant flow through the first throttle valve and the at least one parallel circuit. In this case, the first throttle valve in the second coolant circuit and/or each throttle valve in a parallel circuit can be adjusted in steps or continuously to adapt the flow rate for the first throttle valve and each individual heat exchanger dependent on the current heating or cooling requirements for each respective component connected to a heat exchanger.

(20) The cooling system 20 shown in FIG. 2A further comprises a heater 51 for the passenger compartment. Coolant can be directed from the engine 30, through a controllable valve 52 to the heater 51, before being returned to the second coolant circuit 22 upstream of the coolant pump 33 and downstream of the first throttle valve 34. A portion of the coolant drawn from the engine 30 towards the heater 51 can be passed through a de-gassing unit 53 and be returned to the second coolant circuit 22 upstream of the coolant pump 33 and downstream of the return flow from the heater 51.

(21) FIG. 2B shows an alternative version of the engine cooling system in FIG. 2A. The engine cooling system in FIG. 2B substantially identical to the example described in FIG. 2A and uses the same reference numerals for corresponding components.

(22) As in the cooling system shown in FIG. 2A, the cooling system 20 in FIG. 2B comprises a number of parallel circuits 25, 26, 27, 2n, each comprising a heat exchanger 45, 46, 47, 4n, respectively, arranged for selectively heating or cooling a powertrain component (not shown). Each parallel circuit 25, 26, 27, 2n is connected to the second coolant circuit 22 at a common location upstream of the bypass circuit 24 and downstream of the first throttle valve 34. While the thermostat is closed, a partial coolant flow is directed from the bypass circuit 24 and upstream through the second coolant circuit 22 into the parallel circuits 25, 26, 27, 2n during engine warm-up. The throttle valve 34 in the secondary circuit 22 will restrict the coolant flow from the bypass circuit 24 and force a part of the coolant flow through the parallel circuits 25, 26, 27, 2n. This arrangement causes a reverse flow over a portion of the second coolant circuit 22, between the connection with the bypass circuit 24 and the connection of the parallel circuits 25, 26, 27, 2n. This counter flow prevents cold coolant in the second coolant circuit 22 in or downstream of the radiator 31 and upstream of the parallel circuits 25, 26, 27, 2n from being drawn towards the coolant pump 33 and the engine 30. The coolant flow in the second coolant circuit 22 and the parallel circuits 25, 26, 27 during engine warm-up is indicated with dashed lines in the respective circuit. The coolant flowing through the parallel circuits 25, 26, 27, 2n is returned to the second coolant circuit 22 downstream of the first throttle valve 34.

(23) The cooling system 20 in FIG. 2B differs from the cooling system in FIG. 2A in that, each parallel circuit is provided with a heat exchanger without an associated throttle valve (see FIG. 2A; “35, 36, 37, 3n”). Instead of using throttle valves, the dimensions of each parallel circuit 25, 26, 27 is selected to balance the coolant flow through the second coolant circuit 22 upstream of the bypass circuit and the parallel circuits 25, 26, 27. For instance, if a heat exchanger 45 in a first parallel circuit 25 requires a greater coolant flow than the heat exchangers 46, 47 in the other parallel circuits 26, 27 then the conduit making up the first parallel circuit 25 is given a larger cross-section to allow a greater flow rate through that parallel circuit. In this way, the cross-section of the conduits in each parallel circuit can be dimensioned to the requirements of each associated heat exchanger. This arrangement allows for increased heating of the heat exchangers during start-up while providing increased cooling after the thermostat has opened. An advantage of the system shown in FIG. 2B is that the flow resistance through the parallel circuits can be reduced.

(24) FIG. 3 shows a schematically illustrated first alternative example of an engine cooling system according to the disclosure. The engine cooling system in FIG. 3 substantially identical to the example described in FIG. 2A and uses the same reference numerals for corresponding components.

(25) The first alternative example differs from the engine cooling system described in FIG. 2A in that it further comprises a second coolant pump 60 arranged to control the coolant flow through the at least one parallel circuit 25, 26, 27. The second coolant pump 60 is a controllable pump located in the inlet of the at least one parallel circuit 25, 26, 27 adjacent the connection of the parallel circuit 25, 26, 27 to the second coolant circuit 22. In this way the flow rate through each parallel circuit 25, 26, 27 is controllable by a throttle valve 35, 36, 37 in the respective parallel circuit and by controlling the second coolant pump 60. The provision of a coolant pump for the at least one parallel circuit makes the first throttle valve 34 (indicated in dashed lines) in the second coolant circuit 22 optional.

(26) FIG. 4 shows a schematically illustrated second alternative example of an engine cooling system according to the disclosure. The engine cooling system in FIG. 4 substantially identical to the example described in FIG. 3 and uses the same reference numerals for corresponding components.

(27) The second alternative example differs from the engine cooling system described in FIG. 3 in that it further comprises a controllable thermostat 42 in the first coolant circuit 21 connecting the coolant outlet of the engine to the radiator 31. As the temperature of the coolant leaving the engine 30 increases towards a desired coolant temperature, the thermostat 42 is be partially opened to provide a leakage flow through the radiator 31. This will provide the EGR heat exchanger 45 with cold coolant from the relatively cold portion of the coolant circuit comprising the first coolant circuit 21, the radiator 31 and the portion of the second coolant circuit 22 upstream of the parallel circuits 25, 26, 27. In this way the NOx-emissions from the engine exhaust can be reduced when the engine 30 approaches its normal operating temperature. The controllable thermostat 42 will subsequently be gradually opened as the coolant temperature increases, until it is fully open at its predetermined set temperature. The set temperature of the thermostat can later be adjusted up or down dependent on current cooling requirements.

(28) This second example is preferably, but not necessarily, combined with a second coolant pump 42 as described in the first alternative example in FIG. 3. The provision of a second coolant pump 42 allows the flow rate through the EGR heat exchanger 45 to be controlled accurately.

(29) FIG. 5 shows a schematically illustrated third alternative example of an engine cooling system according to the disclosure. The engine cooling system in FIG. 5 substantially identical to the example described in FIG. 3 and uses the same reference numerals for corresponding components.

(30) The third alternative example differs from the engine cooling system described in FIG. 3 in that it further comprises a an alternative coolant return circuit 51, 52, 53. The alternative coolant return circuit 51, 52, 53 comprises a first return circuit 51 connected to the parallel circuits 25, 26, 27 downstream of the respective heat exchanger 45, 46, 47, a controllable valve 52, and a second return circuit 52 connected to the first coolant circuit 21 downstream of the thermostat 32 and upstream of the radiator 31. The coolant return circuit 51, 52, 53 bypasses the second coolant circuit 22 and the coolant pump 33 and returns a partial coolant flow from the parallel circuits 25, 26, 27 to the first coolant circuit 21. The controllable valve 52 can be opened prior to the opening of the thermostat to provide a leakage flow through the radiator 31 towards the parallel circuits 25, 26, 27. The valve 52 can be either a fixed flow valve or a controllable flow valve. This will provide the EGR heat exchanger 45 with cold coolant from the relatively cold portion of the coolant circuit comprising the first coolant circuit 21, the radiator 31 and the portion of the second coolant circuit 22 upstream of the parallel circuits 25, 26, 27. In this way the NOx-emissions from the engine exhaust can be reduced when the engine 30 approaches its normal operating temperature. This third example shown in FIG. 5 provides an alternative to the second alternative example shown in FIG. 4, wherein the alternative coolant return circuit 51, 52, 53 replaces a controllable thermostat 42.

(31) FIG. 6 shows a schematically illustrated third alternative example of an engine cooling system according to the disclosure. The engine cooling system in FIG. 6 substantially identical to the example described in FIG. 2A and uses the same reference numerals for corresponding components.

(32) The third alternative example differs from the engine cooling system described in FIG. 2A in that it comprises an alternative flow controlling device 61, 62, 63, replacing the first throttle valve 34 in the second coolant circuit 22 downstream of the bypass circuit 24. The alternative flow controlling device 61, 62, 63 comprises a controllable valve 61 with a reduced flow bypass circuit 62. During a cold start, the controllable valve is closed and a partial coolant flow is directed through the reduced flow bypass circuit, which circuit has the same function as the first throttle valve 34 described in FIG. 2A above. The flow restriction function can be achieved either by the use of a throttle valve 63 (shown in dashed lines) or by a conduit having a reduced cross-sectional area suitable for reducing the flow rate in the bypass circuit 62. In operation, when the engine 30 reaches its desired operating temperature, when the thermostat 32 opens, and/or when a predetermined operation condition is fulfilled, the valve can be opened to allow full flow of coolant through the second coolant circuit 22.

(33) This fourth example can be combined with a second coolant pump 60 (shown in dashed lines) as described in the first alternative example shown in FIG. 3. The provision of a second coolant pump 60 allows at least a minimum flow rate through at least the EGR heat exchanger 45 to be maintained even if the valve 61 in the second coolant circuit 22 is fully open.

(34) It is to be understood that the present disclosure is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims. Additionally, the features of various implementing embodiments may be combined to form further embodiments of according to the disclosure.