SE542236C2

SE542236C2 - A cooling system for a water retarder

Info

Publication number: SE542236C2
Application number: SE1750482A
Authority: SE
Inventors: Lukas Schimke; Mikael Sannelius; Per Arnelöf
Original assignee: Scania Cv Ab
Priority date: 2017-04-24
Filing date: 2017-04-24
Publication date: 2020-03-17
Also published as: DE102018003101B4; CN108730380A; SE1750482A1; DE102018003101A1

Abstract

Cooling system for a water retarder (6). The cooling system comprises a control valve (12) configured to direct coolant, via a retarder line (13), to the water retarder (6) or past the water retarder (6) via a retarder bypass line (14), a supply line (11) direct coolant to the control valve (12) which is arranged at a downstream end (11b) of the supply line (11) and a return line (17) configured to receive coolant from the retarder line (13) and the retarder bypass line (14) at an upstream end (17a). The cooling system comprises a second retarder bypass line (19) configured to receive coolant from a position (1 lc) of the supply line (11) located at a distance from its downstream end (11b) and to deliver coolant to a position (17c) of the return line (17) located at a distance from its upstream end (17a).

Description

A cooling system for a water retarder BACKGROUND OF THE INVENTION AND PRIOR ART The present invention relates to a cooling system for a water retarder according to the preamble of claim 1.

Heavy vehicles are often equipped with one or several supplementary brakes in order to reduce wear on the ordinary wheel brakes of the vehicle. Such a supplementary brake may be a hydraulic retarder. Primary hydraulic retarders are connected to a component in the powertrain located upstream of the gearbox and secondary hydraulic retarders are connected to a component in the driveline located downstream of the gearbox. One kind of hydraulic retarder, commonly referred to as a water retarder, uses coolant as cooling medium as well as working medium.

A secondary water retarder is usually arranged in a position on a rear side of the gear box. The coolant lines directing coolant to and from the water retarder must often be bent and restricted due to lack of space in the area around the gearbox. Usually, the coolant flow obtains relatively large pressure drops in that area which place high demands on the coolant pump. Consequently, the coolant pump has to provide a high pumping work for circulation of the coolant through a cooling system comprising a secondary water retarder. Due to this fact, coolant pumps of a relatively high pump capacity has to be used. The operation of such pumps effects on the fuel consumption of the combustion engine. The existence of long coolant lines to the water retarder results in that a large amount of coolant has to circulate through the cooling system. After a cold start, it takes a relatively long time to heat such a large amount of coolant to an operating temperature.

DE 196 03 184 shows a cooling system for a combustion engine and a water retarder. The water retarder is engaged by means of a clutch by which a rotor of the retarder is releasably connected to an outlet shaft of a gearbox. The cooling system comprises a retarder bypass line and a check valve. When the retarder is not engaged, an increased pressure is obtained in the cooling system in an area adjacent to the retarder which opens the check valve and allows a coolant flow through the retarder bypass line.

US 4,538,553 shows a cooling system for a combustion engine and a water retarder. The cooling system comprises a 2/2 way valve which in an open position allows a coolant flow to the water retarder and in a closed position prevent a coolant flow to the water retarder. The cooling system comprises a retarder bypass line arranged at a distance from the 2/2 way valve. When the 2/2 way valve is set in the closed position, the coolant flow is directed through the retarder bypass line.

SUMMARY OF THE INVENTION The object of the present invention is to provide a cooling system cooling for a water retarder having a design ensuring relatively low flow losses during operating conditions when the retarder is not activated.

This object is achieved by the features defined in the characterizing portion of claim 1. When the control valve is switched from a retarder on position to a retarder off position, it stops the coolant flow to the retarder and the coolant flow is directed to the first retarder bypass line. It is important that the control valve is arranged very close to the retarder such that the coolant supply to the retarder is stopped immediately when the control valve is set in the retarder off position. It is also important that the first retarder bypass line is arranged close to the control valve, in order to minimize the creation of pressure shocks and standing waves which may arise when the control valve is switched between said two positions. In case the retarder is arranged at a relatively long distance from the radiator, there is a risk that the supply line leading coolant to the water retarder and the return line leading the coolant back from the retarder obtain a high flow resistance.

According to the invention, when the control valve is set in the retarder off position, the existence of the second retarder bypass line makes it possible for a part of the coolant flow to take an alternative shorter flow path than the ordinary flow path via the first bypass line. The distribution of coolant flow through the two bypass lines is related to the flow resistance in the two alternative flow paths. It is usually no problem to arrange the second retarder bypass line in a position in which it creates an alternative flow path with a significantly lower flow resistance than the ordinary flow path defined by the first retarder bypass line. The application of such a second bypass line results in that a main part of the coolant flow will be directed via the second bypass line when the control valve is in the retarder off position. Consequently, the existence of the second bypass line may significantly reduce the flow losses in the cooling system during operating conditions when the retarder is not activated.

According to the invention, cooling system is also configured to cool a combustion engine, and the supply line is a supply line receiving coolant which has cooled the combustion engine. It is customary to use a common cooling system for the combustion engine and the water retarder. The existence of the second bypass line reduces the required amount of coolant which has to flow through the cooling system when the water retarder is shut off. This results in a faster heating of the coolant to a desired operating temperature of the combustion engine after a cold start.

According to the invention, the second retarder bypass line comprises a flow member allowing a coolant flow from the supply line to the return line but preventing a coolant flow in the opposite direction. In any event, it is necessary to prevent a coolant flow in wrong direction through the second retarder bypass line. A flow member in the form of a check valve is used in the second retarder bypass line. Such a flow member is the only component which needs to be arranged in the second retarder bypass line. Thus, the second retarder bypass line may have a very simple design.

According to an embodiment of the invention, the second retarder bypass line receives coolant from the supply line in a position located at a smaller flow distance from its upstream end than from its downstream. In order to minimize the length of flow path defined the second retarder bypass line, it is suitable to arrange an inlet of the second retarder bypass line relatively close to its upstream end.

According to an embodiment of the invention, the cooling system comprises a control unit configured to control the control valve by means of information from a brake activating member. The brake activating member may be a brake pedal or another kind of brake activating member by which a driver or a vehicle control system indicates activation of the retarder.

According to an embodiment of the invention, the control valve is a solenoid valve switchable to a retarder on position in which it directs the coolant flow to the retarder and to a retarder off position in which it directs the coolant flow to the first retarder bypass line. It is of course possible to use other kinds of valves which control the activation of the retarder.

According to an embodiment of the invention, the retarder line comprises a flow member arranged in a position downstream of the retarder configured to prevent a backward coolant flow in the retarder line towards the retarder. Such a flow member may be a check valve. Furthermore, the retarder line may comprise a pressure control valve.

According to an embodiment of the invention, the supply line receives coolant at an upstream end which is arranged on the side of combustion engine located at the longest distance from the radiator. Usually coolant enters the combustion engine via an inlet line arranged relatively close to the radiator and it leaves the combustion engine via an outlet line arranged at an opposite side of the combustion engine.

According to an embodiment of the invention, the combustion engine is connected to a gearbox, and that the control valve and the water retarder are arranged in a position located at a longer distance from the radiator than from the gearbox. The cooling system may be arranged in a vehicle and that a rotor unit of the water retarder is connected, via a motion transmitting mechanism, to a part of the powertrain of the vehicle. In case the water retarder is a secondary retarder, a rotor unit of the water retarder is connected, via a motion transmitting mechanism, to a component of the powertrain of the vehicle located downstream of the gearbox. The component of the powertrain may be an output shaft of the gearbox. In this case, the supply line and the return line are to be long. Furthermore, said coolant lines must often be bent and restricted due to lack of space in the area around the gearbox. In this case, the use of a second retarder bypass line will be very favorable in order to reduce flow losses in the cooling system during operating conditions when the retarder is not activated.

The invention is also related to a water retarder comprising a cooling system according to the above. The invention is also related to a vehicle comprises a water retarder according to the above.

BRIEF DESCRIPTION OF THE DRAWING In the following a preferred embodiment of the invention is described, as an example, with reference to the attached drawing, in which: Fig. 1 shows a cooling system according to an embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Fig. 1 shows a schematically indicated vehicle 1 which may be a heavy vehicle. The vehicle 1 is driven by a combustion engine 2. The combustion engine 2 may be an Otto engine or a diesel engine. The vehicle 1 comprises a powertrain, which in addition to the combustion engine 2, comprises a clutch mechanism 3, a gearbox 4 and a gearbox output shaft 5. The combustion engine 2 comprises an engine front side 2a and an engine rear side 2b which is located at a longer distance from a radiator 23 than the engine front side 2a. The gearbox 4 comprises a gearbox front side 4a and a gearbox rear side 4b which is located at a longer distance from a radiator 23 than the gearbox front side 4b. The vehicle 1 is equipped with a water retarder 6 comprising a rotor unit 6a and a stator unit 6b. The rotor unit 6a and a stator unit 6b define a toroidal space for receiving coolant. The rotor unit 6a and the stator unit 6b each have a plurality of vanes situated in the toroidal space. The stator unit 6b is stationary arranged in the vehicle. The rotor unit 6a is, via a motion transmitting mechanism 7, connected to the powertrain of the vehicle 1 via the gearbox outlet shaft 5. Thus, the rotor unit 6a is rotated by a speed defined by the speed of the gearbox outlet shaft 5 and the gear ratio in the motion transmitting mechanism 7. A control unit 8 is adapted to activate the retarder 6 by means of information from a brake activating member 8a, which may be a brake pedal.

A cooling system with a circulating coolant is configured to cool the combustion engine 2 and the water retarder 6. The cooling system comprises a coolant pump 9 circulating coolant in the cooling system. The coolant pump 9 is arranged in an engine inlet line 10 at the engine front side 2a. The coolant leaving the engine inlet line 10 circulates through cooling channels in the combustion engine. The coolant leaves the combustion engine 1 and enters a supply line 11 directing coolant to the retarder 6. The supply line 11 leads the coolant from a downstream end 11a which is connected to the rear side of the combustion engine 2b to an upstream end 11b which is connected to a control valve 12. The flow control valve 12 is switchable to a retarder on position in which it directs the coolant to the retarder 6 via a retarder line 13 and to a retarder off position in which it directs the coolant past the retarder 6 via a first retarder bypass line 14.

The retarder line 13 comprises a pressure control valve 15 and a second check valve 16 which are arranged in a downstream position of the retarder 6. The coolant leaving the retarder line 13 enters an upstream end of a return line 17. The return line 17 directs the coolant to a thermostat 18 arranged at a downstream end 17b of the return line 17. The coolant leaving the first retarder bypass line 14 also enters the return line 17 via the upstream end 17a. The cooling system also comprises a second retarder bypass line 19 which directs coolant past the retarder 6 at a distance from the first bypass line 14. The second retarder bypass line 19 receives coolant in a position 1 lc of the supply line 1 1 located at a relatively long distance from its downstream end 11b. The second retarder bypass line 19 delivers coolant to a position 17c of the return line 17 located at a relatively long distance from its upstream end 17a. The second retarder bypass line 19 comprises a first check valve 20 which allows a coolant flow from the supply line 1 1 to the return line 17 and prevents a coolant flow in the opposite direction.

Thus, the thermostat 18 receives coolant from the return line 17. The thermostat 18 directs the coolant to a radiator bypass line 21 when the coolant has a lower temperature than a regulating temperature of the thermostat 18. The radiator bypass line 21 leads the coolant to the engine inlet line 10. The thermostat 18 directs the coolant to a radiator line 22 comprising a radiator 23 when the coolant has a higher temperature than its regulating temperature. The coolant is cooled in the radiator 23 by a cooling air flow forced through the radiator 23 by ram air and a radiator fan 24. The coolant which has been cooled in the radiator 23 is directed to the engine inlet line 10.

The coolant pump 9 starts the circulation of coolant through the cooling system as soon as the combustion engine is activated 2. During operating conditions when the control unit 8 receives information from the brake control unit 8a indicating that the retarder 6 is not to be activated, it sets the flow control valve 12 in the retarder off position. In this position, a first part of the coolant flow in the supply line 11 is directed to the first retarder bypass line 14 and a second part of the coolant flow is directed to the second retarder bypass line 19. The ratio between said parts of the coolant flow is related to the flow resistance in the flow paths defined by the respective retarder bypass lines 14, 19. The flow path defined by the first retarder bypass line 14 is longer than the flow path defined by the second retarder bypass line 19.

Furthermore, there is usually lack of space in vicinity of the gearbox 4 which may complicate the line routing and increase the flow resistance in the supply line 11 and the return line 17 in this area. In view of these facts, the coolant flow through the second retarder bypass line 19 will be considerably higher than the coolant flow through the first retarder bypass line 14. Consequently, the existence of the second retarder bypass line 19 reduces the flow losses in the cooling system considerably during operating conditions when the water retarder 6 is not in operation.

Furthermore, the shorter flow path defined by second retarder bypass line 19 results in circulation of a smaller amount of coolant in the cooling system when the water retarder 6 is not in operation. In view of that fact, the coolant in the cooling system receives a faster heating to a desired operating temperature after a cold start when the retarder is not in operation.

During operating conditions when the control unit 8 receives information from the brake control unit 8a indicating that the water retarder 6 has to be activated, it switches the flow control valve 12 to the retarder on position. The activated retarder 6 works like a pump and it sucks coolant from the supply line 11 to the retarder 6. In this case, the coolant flow to the second retarder bypass line 19 will be substantially eliminated. Substantially the entire coolant flow in the supply line 11 is directed to the water retarder 6, which ensures an efficient braking action of the water retarder 6, via the movement transmission mechanism 7, on the gearbox outlet shaft 5 and the powertrain of the vehicle 1. Thus, the existence of the second bypass line 19 does not at all influence on the efficiency of the water retarder 6 when the control valve 12 is in the retarder on position.

It is to be noted that the control valve 12 and the first retarder bypass line 14 are mounted in positions closed to the water retarder 6. Such a mounting positioning of the flow control valve 12 makes it possible to subsequently immediately shut off the coolant supply to the water retarder 6 and to finish the braking process when the control valve 12 has switched from the retarder on position to the retarder off position. The amount of coolant to be separated in the retarder 6 during said switching process will be relatively small and thereby the subsequently formed amount of steam in the retarder. It is important to minimize the amount of steam in the water retarder 6 in order to reduce drag losses when the water retarder 6 is not in operation. It is also suitable to minimize the amount of steam in the cooling system by other reasons. It is, for example, difficult to design a cooling system which are adaptable to receive large volumes of steam. Furthermore, it is important to arrange the first bypass line 14 close the control valve 12 in order to reduce pressure shocks from the control valve 12 when it is switched between said two positions.

Consequently, it is suitable to arrange the control valve 12 close to the retarder 6 in order to minimize the formation of steam in the water retarder 6. Further, it is suitable to arrange a first bypass valve 14 in a position close to the control valve 12 in order to reduce pressure shocks from the control valve 12. Finally, it is suitable to arrange a second retarder bypass line 19 at a distance from the first retarder bypass line allowing a flow path of the coolant with low flow losses when the water retarder 6 is not in operation.

The invention is not restricted to the described embodiment but may be varied freely within the scope of the claims. The control valve 12 may, for example, be arranged in in other positions than in a downstream position of the supply line 11.

Claims

1. Cooling system for a combustion engine (2) and a water retarder (6), wherein the cooling system comprises a coolant pump (9) configured to circulate coolant through the cooling system, a radiator (23) in which the coolant is cooled, a radiator bypass line (21) in which the coolant flows past the radiator (23), a supply line (11) configured to direct coolant towards the water retarder (6), a control valve (12) configured to direct coolant to a retarder line (13) comprising the water retarder (6) or to a first retarder bypass line (14) leading coolant past the water retarder (6), a return line (17) configured to receive coolant from the retarder line (13) and the first retarder bypass line (14) at an upstream end (17a) and direct it towards the radiator (23) and the radiator bypass line (21), a second retarder bypass line (19) configured to receive coolant from a position (1 lc) of the supply line (11) located at a distance from the downstream end (11b) of the supply line (11) and to deliver coolant to a position (17c) of the return line (17) located at a distance from the upstream end (17a) of the return line (17), wherein the supply line is a supply line (11) receiving coolant which has cooled the combustion engine (2), characterized in that the second retarder bypass line (19) comprises a check valve (20) configured to allow a coolant flow from the supply line (11) to the return line (17) and to prevent a coolant flow in the opposite direction.

2. Cooling system according to claim 1, characterized in that the second retarder bypass line (19) receives coolant from the supply line (11) in a position (lie) located at a longer flow distance from its downstream end (11b) than from its upstream end (11a).

3. Cooling system according to claim 1 or 2, characterized in that that the cooling system comprises a control unit (8) configured to control the control valve (12) by means of information from a brake activating member (8a).

4. Cooling system according to any one of the preceding claims, characterized in that the control valve (12) is a solenoid valve switchable to a retarder on position in which it directs the coolant flow to the water retarder (6) and to a retarder off position in which it directs the coolant flow to the first retarder bypass line (14).

5. Cooling system according to any one of the preceding claims, characterized in that the retarder line (13) comprises a flow member (16) arranged in a position downstream of the water retarder (6) configured to prevent a backward coolant flow from the return line (17) towards the retarder (6).

6. Cooling system according to any one of the preceding claims, characterized in that the retarder line (13) comprises a pressure control valve (15).

7. Cooling system according to any one of the preceding claims, characterized in that the supply line (11) receives coolant at an upstream end (11a) which is arranged on the side (2b) of combustion engine (2) located at the longest distance from the radiator (23).

8. Cooling system according to any one of the preceding claims, characterized in that the combustion engine (2) is connected to a gearbox (4), and that the control valve (12) and the water retarder (6) are arranged in a position located at a longer distance from the radiator (23) than from the gearbox (4).

9. Cooling system according to any one of the preceding claims, characterized in that the cooling system is arranged in a vehicle (1) and that a rotor unit (6a) of the water retarder (6) is connected, via a motion transmitting mechanism (7), to a part (5) of the powertrain of the vehicle (1).

10. A water retarder comprising a cooling system according to any of the preceding claims 1-9.

11. A vehicle comprising a water retarder according to claim 10.