Fluid cooling system of a combustion engine charged by a turbocharger and method for cooling a turbine housing of a turbocharger   

This application claims priority to German Patent Application No. 10 2010 005 824.6, filed Jan. 27, 2010, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The technical field relates to a fluid cooling system of a combustion engine charged by a turbocharger, more preferably of a motor vehicle. Additionally, it relates to a method for cooling a turbine housing of a turbocharger.

Combustion engines, more preferably spark ignition and diesel engines have a complex fluid cooling system that is subjected to varying requirements at different operating conditions. The engine block, for example, is to be effectively cooled in full load operation, while for example during a cold start heat supply to the engine block would be desirable in order to reduce the fuel consumption. In addition to the engine block, further components are also cooled for example the turbine bearing housing of a turbocharger.

From U.S. Pat. No. 6,553,762 B2 it is known to design the turbine housing of a turbocharger in a double-walled design and cool it with the help of a coolant. However, no comments are made as to how the supply and discharge of coolant is to take place.

Accordingly, at least one object is to provide a fluid cooling system of a combustion engine charged by a turbocharger with which improved thermal management particularly also during warming-up of the engine is achieved. In addition, it is at least one object to provide an efficient method for cooling a turbine housing of a turbocharger. Furthermore, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.

SUMMARY

A fluid cooling system of a combustion engine charged by a turbocharger comprises a first cooling circuit operable by a coolant pump, which coolant circuit runs through an engine block cooling jacket and a second cooling circuit branched off from the first cooling circuit, which runs through a cooling jacket formed between an inner wall and an outer wall of a double-walled turbine housing of the turbocharger.

Thus, cooling of the turbine housing of the turbocharger is provided which in addition to the heat removal and the unloading of the turbine housing connected with this also makes possible utilization of the removed heat in that the cooling of the turbine housing in an intelligent manner is incorporated in the entire fluid cooling system. To this end, an exchange of coolant and thus also an exchange of heat takes place between the first and the second coolant circuit.

This fluid system has the advantage that it makes possible transport of heat from the turbine housing of the turbocharger to the engine block, which is advantageous particularly during a cold start. For as analyses have shown, the turbine housing is a particularly fast-heating component. It thus makes available heat particularly soon after starting, which can be utilized for heating the engine and thus for lowering the fuel consumption.

In an embodiment, the second cooling circuit comprises a branch-off to the turbine bearing housing of the turbocharger upstream of the cooling jacket of the turbine housing, so that cooling of the turbine bearing housing subjected to major thermal load within the fluid cooling system is also possible.

In an embodiment a temperature sensor is provided in the second cooling circuit which for example can be arranged upstream of the cooling jacket of the turbine housing.

In an embodiment a switching valve activatable by an engine control is provided in the second cooling circuit upstream of the cooling jacket of the turbine housing. This embodiment has the advantage that through the control by the engine control, thermal management optimally adapted to the current operating conditions can take place in the fluid cooling system. To this end, the engine control receives as input quantities for activating the switching valve a temperature signal of the temperature sensor, a temperature signal of a further temperature sensor, which is arranged in a first cooling circuit upstream of an engine block cooling jacket, the current engine rotational speed and the current engine rotational moment.

In an embodiment the switching valve is arranged between the branch-off to the turbine bearing housing of the turbocharger and the cooling jacket of the turbine housing. Because of this it is achieved that the cooling of the turbine bearing housing takes place in the known manner, while intelligent cooling of the turbine housing is additionally implemented.

In an embodiment a switchable coolant pump is provided in the first cooling circuit which controls the coolant inflow to the engine block cooling jacket. With a fluid cooling system of this type heat can be optimally distributed as follows: the turbine housing constitutes a heat reservoir which can make available larger quantities of heat even very quickly after the engine start. A measure for the heat removable from this reservoir and feedable to the engine block for heating is the difference of the temperatures measured by the temperature sensor and the additional temperature sensor. If this difference is large, there is a large potential for heating the engine block by feeding-in heat from the turbine housing of the turbocharger. Accordingly, in this case, the switching valve in the second cooling circuit is for instance opened in a pulse width modulated manner on the one hand such that the volumetric flow of coolant in the second cooling circuit is increased. Thus, effective removal of heat from the turbine housing is made possible. In order to feed this heat to the engine block, the switchable coolant pump is operated in such a manner that it pushes the heated coolant into the engine block cooling jacket.

If the difference of the temperatures measured by the temperature sensor and the additional temperature sensor is small, either sufficient heat for heating the engine block is not yet available at the turbine housing shortly after the start or the engine block itself is already heated to a high operating temperature. In both cases additional heating of the engine block through waste heat of the turbine housing is not possible or desirable. However, cooling of the turbine housing through the cooling jacket is then possible, which protects said turbine housing from excessively high thermal loads and which can be controlled by the engine control through the activatable switching valve.

The linking of the cooling of the engine block and the turbine housing of the turbocharger, which is controlled through the engine control in an intelligent manner, thus makes possible favorable distribution, which is removal and redistribution of the generated heat in any operating state of the combustion engine. In this manner, not only the thermal loading of individual components can be reduced but in particular also the fuel consumption can be lowered during a cold start.

In an embodiment the double-walled turbine housing is designed of sheet metal and for example produced through deep-drawing and/or welding. Compared with the otherwise usual use of castings this has the advantage that the turbine housing is relatively light. In addition, good heat conduction of the turbine housing is realized.

The fluid cooling system is more preferably suitable for use with combustion engines, for example spark-ignition or diesel engines of a motor vehicle.

A method is provided for cooling a turbine housing of a turbocharger, the flow of coolant through a cooling jacket of the turbine housing is controlled and/or regulated by means of a switching valve activatable by an engine control.

According to an embodiment, the engine control in this case is supplied with the engine speed, the engine rotational moment, a temperature T2 measured downstream of the cooling jacket of the turbine housing and a temperature T1 measured downstream of an engine block cooling jacket as input quantities.

In an embodiment a differential ΔT with ΔT=T2−T1 is used as a control quantity for the activation of the switching valve.

In an embodiment control and/or regulation of the coolant flow through the engine block cooling jacket is carried out through a switchable coolant pump that can be activated by the engine control.

Control and/or regulation of the coolant flow through the engine block cooling jacket can more preferably be carried out as a function of the temperature T1 and/or the temperature T2, more preferably as a function of the temperature differential ΔT=T2−T1.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and:

FIG. 1 schematically shows a cross section through a turbocharger according to an embodiment; and

FIG. 2 schematically shows a circuit diagram of a fluid cooling system according to an embodiment.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description.

The turbocharger 1 according to FIG. 1 comprises a compressor 2, a turbine 4 and a shaft 3 connecting the compressor 2 and the turbine 4. The shaft 3 is mounted in a turbine bearing housing 12 by a turbine bearing 14. In the compressor 2 fresh air fed in through the air inlet 5 is compressed and discharged through the air outlet 13 and made available in the intake section of a combustion engine. For operating the compressor, the energy of the exhaust gas is utilized which enters the turbine 4 through the exhaust inlet 6 where it is expanded and which it leaves again through the exhaust outlet 7.

In operation, the turbine housing 15 is severely heated by the hot exhaust gas. The turbine housing 15 is of a double-walled design with an inner wall 9 and an outer wall 10, wherein between the inner wall 9 and the outer wall 10 a cooling jacket 8 is formed, in which a coolant for example water flows. The turbine housing 15 with the inner wall 9 and the outer wall 10 is designed of sheet metal as deep-drawn part and comprises a number of welded points 11.

The cooling jacket 8 of the turbine housing 15 is connected to a fluid cooling system of a motor vehicle, of which FIG. 2 schematically shows a circuit diagram according to an embodiment.

The fluid cooling system 16 comprises a first cooling circuit 17 designed as engine cooling circuit, which comprises the engine block cooling jacket 18 of an engine block 19. A switchable coolant pump 34 controls or regulates the coolant flow. Furthermore, a temperature sensor 29 which senses the coolant temperature T1 downstream of the engine block cooling jacket 18 is arranged in the first cooling circuit 17.

The fluid cooling system 16 furthermore comprises a second cooling circuit 21 designed as turbocharger circuit branched-off from a first cooling circuit 17, which second cooling circuit comprises the cooling jacket 8 of the turbine housing 15 of a turbocharger 1. Upstream of the cooling jacket 8 of the turbine housing 15 a switching valve 35 is arranged in the second cooling circuit 21, via which the coolant flow to the turbine housing 15 can be controlled or regulated.

Upstream of the switching valve 35 a line 27 branches off at the branch-off 25 which in a known manner cools the turbine bearing housing 12 of the turbocharger 1. The line 27 in the embodiment shown is designed for a lower volumetric flow than the line 26, which supplies the cooling jacket 8 of the turbine housing 15. Downstream of the cooling jacket 8 of the turbine housing 15 a temperature sensor 28 is arranged, which senses the coolant temperature T2 downstream of the turbine housing 15.

The shown fluid cooling system 16 as further component comprises a radiator 20, and engine oil cooler 30, an expansion tank 31, a heater heat exchanger 32 and an additional pump 33. The switchable coolant pump 34 and the switching valve 35 can be activated through the engine control 36. To this end, the engine control 36 receives the temperatures T1, T2 measured by the temperature sensor 28, temperature sensor 29 and values for the current engine rotational speed and the current engine rotational moment as input signals.

In operation, the engine control 36 initiates coolant delivery in the first cooling circuit 17 and in the second cooling circuit 21 in such a manner that thermal management optimally adapted to the prevailing operating conditions can take place. This is explained by means of two special operating states, cold start and full-load operation.

During a cold start the engine block 19 is subjected to severe load through the uneven heating of its components, which results in increased wear. In addition, with some engines, fuel enrichment because of the condensation of fuel in the intake section and in the cylinder is necessary, which results in increased fuel consumption. It is therefore desirable to bring the engine block 19 up to a favorable operating temperature as quickly as possible. To this end, heat from the turbine housing 15 of the turbocharger 1 is utilized with the fluid cooling system 16, since the turbine housing 15 on start-up heats up particularly rapidly, thus making available a larger quantity of heat particularly early on.

If the engine control 36 because of the current values of the engine rotational speed and the engine rotational moments and the coolant temperatures measured by the temperature sensor 28 and temperature sensor 29 determines a cold starting situation, the switching valve 35, which for example is activated in a pulse width modulated manner, is increasingly opened so that the volumetric flow through the cooling jacket 8 of the turbine housing 15 is increased. At the same time, the switchable coolant pump 34 delivers an increased quantity of heated cooling water into the engine block cooling jacket 18 as required.

In full load operation, there is typically no need to feed the engine block 19 with heat from the outside. The temperature T1 measured by the temperature sensor 29 is then also so close to the temperature T2 measured by the temperature sensor 28 that the cooling jacket 8 of the turbine housing 15 no longer constitutes a high-yielding heat reservoir. In this operating state the switching valve 35 is activated with a view to good cooling of the turbine housing, wherein the temperature T2 measured by the temperature sensor 28 can more preferably serve as regulating quantity.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.