EP3405660B1 - Cooling system after engine shut-down, cylinder head, and method for operating a cooling system after engine shut-down - Google Patents

Description

The invention relates to an after-run cooling system, a cylinder head for an internal combustion engine of a motor vehicle and a method for operating an after-run cooling system.

Modern internal combustion engines with direct fuel injection must be operated as hot as possible for reasons of fuel efficiency in order to reduce internal engine friction. However, this means that the high-pressure fuel pump, which is operated, for example, with the exhaust camshaft, is also heated, since it is provided in the area of the internal combustion engine. For example, the high-pressure fuel pump can be arranged directly on the cylinder head of the internal combustion engine via a holder.

Under certain circumstances, it can happen that the high-pressure fuel pump heats up very strongly, as a result of which, when the internal combustion engine is switched off hot, very hot areas can occur locally, which lead to the fuel evaporating in the high-pressure fuel pump. This occurs particularly in the case of highly volatile petrol winter fuels, which boil at around 100 ° C at fuel pressures of around 5 to 6 bar. When the fuel evaporates, bubbles then occur which impair the fuel delivery of the high-pressure fuel pump and lead to insufficient fuel pressure and / or fuel delivery volume on the high-pressure side of the high-pressure fuel pump when the internal combustion engine attempts to start again. This can mean that the engine does not start immediately or dies shortly after starting and can only be started and operated again successfully when the system has cooled down and the fuel in the low-pressure area of the fuel system is again sufficiently liquid , so that the high-pressure fuel pump can again deliver liquid fuel to a sufficient extent and thus build up high-pressure fuel again in the high-pressure area of the fuel system.

Cost-intensive measures are known from the prior art in order to solve the above-mentioned problem. For example, the pre-delivery pressure is increased so that the boiling point of the fuel is raised in the low-pressure area of the fuel system. To do this, the fuel system must be set to higher Pressures are designed accordingly, which causes higher costs. An alternative option is to use active water cooling, which actively cools the high-pressure fuel pump. Here, too, high costs arise because additional components are installed which also require space which is usually not present in an engine compartment of a motor vehicle.

From the US 4,728,306 A a post-cooling system with a pump is known which pumps coolant through a fuel pump of the internal combustion engine after an internal combustion engine has been switched off.

In the EP 1923 548 A2 an internal combustion engine with turbocharger after-cooling is shown.

The object of the present invention is to cool a fuel pump in a simple manner, inexpensively and efficiently.

The object is achieved according to the invention by an after-run cooling system with a pump, a coolant channel for a coolant and at least one component to be cooled, the coolant channel being assigned to a fuel pump. Here, the coolant channel extends through a bracket of the fuel pump. This prevents heat from migrating from the engine block or cylinder head through the bracket to the fuel pump. The advantage of this is that the fuel pump can be changed in a simple manner without having to interrupt a cooling circuit and to make it again.

The basic idea of the invention is to design an aftercooling system in such a way that the already existing aftercooling system is used to prevent the fuel pump from overheating if the motor vehicle is parked hot. Accordingly, there are no additional costs for two separate cooling systems, since not every individual component of the internal combustion engine is cooled with a separately designed after-cooling system, but at least two components share a common after-cooling system. It has been found that the cooling capacity is sufficiently high that several components can be cooled by a common cooling system. The fuel pump is, for example, a high-pressure fuel pump.

In particular, the at least one component to be cooled is an exhaust gas turbocharger. In addition to the fuel pump, the exhaust gas turbocharger chilled. The exhaust gas turbocharger is usually cooled with a water-glycol mixture as a coolant. The cooling system used to cool the exhaust gas turbocharger can be modified in such a way that it simultaneously cools the fuel pump to ensure that the fuel does not evaporate.

The at least one component to be cooled can be a cylinder head. The cylinder head is directly or indirectly connected to the fuel pump. As a result, components of the cylinder head can be cooled at the same time.

Especially when cooling the exhaust gas turbocharger, it must be ensured that the cooling of the exhaust gas turbocharger is maintained even when the engine is switched off to prevent temperature damage to the exhaust gas turbocharger. This after-cooling can be used accordingly for the fuel pump, so that the fuel is prevented from evaporating even when the internal combustion engine is switched off hot.

The after-cooling is realized in that a pump, in particular an electric main water pump or a separate electric auxiliary pump, is provided, which conveys the coolant through the coolant channel, which the fuel pump and the exhaust gas turbocharger and / or the cylinder head as components to be cooled or as to be cooled Component is assigned.

Alternatively or in addition, other components of the internal combustion engine, which are cooled afterwards, can be part of the after-cooling system and share a common coolant channel and a pump.

According to one aspect, the coolant channel extends through the fuel pump, for example through its housing. This ensures that the fuel pump and the fuel therein are cooled essentially directly, since the coolant flows directly through the fuel pump, in particular through a housing area of the fuel pump. Any heat transfer losses can be minimized in this way.

According to one aspect, a coolant cooler is provided in the after-run cooling system at least in part parallel to or in series with the coolant channel. This makes it possible to achieve particularly effective cooling, in particular the Fuel pump and the components to be cooled. The coolant cooler produces an even higher cooling effect.

In particular, a fan can be assigned to the after-cooling system. The fan can be used to further increase the additional cooling effect of the coolant cooler.

The object of the invention is also achieved by a cylinder head for an internal combustion engine, through which a part of the coolant channel of a post-cooling system of the aforementioned type extends. The fuel pump is attached to the cylinder head by means of a holder, the coolant channel being located in the vicinity of the area in which the holder for the fuel pump is arranged on the cylinder head. The cylinder head thus includes an area of the coolant channel, so that the cylinder head serves to cool components to be cooled and / or the fuel pump. This ensures that the fuel pump is cooled in an indirect manner, since the coolant flows directly in the connection area of the fuel pump through the cylinder head which is formed separately from it. "Indirect cooling" means that heat transfer from a hot component to the fuel pump is prevented. The fuel pump can be changed in a simple manner, since no coolant lines run through the fuel pump itself. Furthermore, a uniform interface is created for different fuel pumps, via which the correspondingly connected fuel pump can be cooled.

Furthermore, the invention provides a method for operating an after-cooling system of the type mentioned above, in which the pump of the after-cooling system is operated on the basis of a determined, needs-based control. This makes it possible to optimize the cooling by means of the after-cooling system, since this takes place as required. For this purpose, the after-cooling system can meet the greatest individual cooling requirement of the respective components to be cooled. As a result, the energy consumption required by the after-cooling system can be minimized as required.

One aspect provides that the activation of the pump is determined from known variables of an engine control unit, in particular via software for determining the minimum cooling requirement of the at least one component to be cooled and the fuel pump. It is thus possible in a simple manner to control the pump as required, since no additional values need to be determined beforehand.

Furthermore, the after-cooling system can comprise a fan, the operation of which is based on a determined control. The fan has an influence on the cooling capacity, which is why different control of the fan can cause a correspondingly different cooling capacity.

In particular, the control of the fan is determined from known variables of an engine control unit, in particular via software for determining the minimum cooling requirement of the at least one component to be cooled and the fuel pump. It is thus possible in a simple manner to implement the fan control as required, since no additional values have to be determined beforehand.

The known variables for determining the control of the pump and / or the fan are, for example, variables of the current engine operation, for. B. current coolant temperature, current oil temperature, current engine power averaged over a certain period of time and / or current ambient temperature.

According to a further aspect, the after-cooling system is assigned at least one switchable actuator which is switched during operation of the after-cooling system in such a way that the best possible cooling effect is achieved for the at least one component to be cooled and / or the fuel pump. This makes it possible to switch the cooling capacity as required.

• Figur 1 eine Perspektivansicht eines Verbrennungsmotors mit einem erfindungsgemäßen Zylinderkopf,
• Figur 2 eine Schnittdarstellung eines Teils des Verbrennungsmotors aus Figur 1,
• Figur 3 eine schematische Übersicht eines erfindungsgemäßen Nachlaufkühlsystems bei einem Verbrennungsmotor gemäß einer ersten Ausführungsform, und
• Figur 4 eine schematische Übersicht eines erfindungsgemäßen Nachlaufkühlsystems bei einem Verbrennungsmotor gemäß einer zweiten Ausführungsform.

Further advantages and properties of the invention result from the following description and the drawings to which reference is made. The drawings show:

• Figure 1 1 shows a perspective view of an internal combustion engine with a cylinder head according to the invention,
• Figure 2 a sectional view of a part of the internal combustion engine Figure 1 ,
• Figure 3 2 shows a schematic overview of an after-run cooling system according to the invention in an internal combustion engine according to a first embodiment, and
• Figure 4 is a schematic overview of an after-cooling system according to the invention in an internal combustion engine according to a second embodiment.

In Figure 1 An internal combustion engine 10 is shown that has an engine block 12 and a cylinder head 14 that is coupled to the engine block 12.

The internal combustion engine 10 also includes a fuel pump 16, which in the embodiment shown is attached to the cylinder head 14 via a holder 18 in the form of a pump bracket. The fuel pump 16 can be a high-pressure fuel pump. In addition, the internal combustion engine 10 has an exhaust gas turbocharger 20, which is a component of the internal combustion engine 10 to be cooled.

The internal combustion engine 10 also has an after-run cooling system 22 with which, among other things, the exhaust gas turbocharger 20 and the fuel pump 16 are cooled, as will be explained below.

The after-cooling system 22 is designed in particular in such a way that the components or components of the internal combustion engine 10 to be cooled are still cooled even when the internal combustion engine 10 is switched off hot.

For this purpose, the after-cooling system 22 has its own pump 24, which in the embodiment shown is designed as an electrical auxiliary pump (see Figure 3 ). Alternatively, a non-electric pump can be provided. Furthermore, the after-cooling system 22 includes a coolant channel 26 for a coolant, which extends from the pump 24 through the cylinder head 14 to the exhaust gas turbocharger 20.

The coolant channel 26 accordingly has a coolant supply 28, which extends from the pump 24 to the cylinder head 14. Starting from the coolant flow 28, the coolant channel 26 runs along a region 29 within the cylinder head 14, which is assigned to the holder 18 of the fuel pump 16. The coolant (K) flowing through the coolant channel 26, which is represented by the arrow, reduces the heat (W) transmitted from the internal combustion engine 10 to the holder 18, which is also represented by corresponding arrows. The heat input of the internal combustion engine 10 into the holder 18 and the fuel pump 16 connected to it is therefore significantly reduced, which is why that in FIG Fuel pump 16 existing fuel is not heated so much that it could boil.

After the coolant has flowed through the cylinder head 14, the coolant flows into an exhaust gas turbocharger feed line 30, which in the embodiment shown is located on the side of the engine block 12 and leads to an inlet 32 of the exhaust gas turbocharger 20. The exhaust gas turbocharger 20 is accordingly cooled by the same coolant that has previously cooled the fuel pump 16.

In addition, the internal combustion engine 10 includes a mechanically driven water pump 34, for example.

Because of the pump 24 provided, an after-run cooling system is created which is also still active when the internal combustion engine 10 is switched off or is still running after a hot shutdown. Accordingly, the coolant is still conveyed through the coolant channel 26 in a hot-switched-off internal combustion engine in order to cool the fuel pump 16 and the exhaust gas turbocharger 20. In the case of an electric pump as a pump 24, the after-cooling can accordingly take place independently of the operation of the internal combustion engine.

The coolant used to cool the exhaust gas turbocharger 20 is thus first diverted into the cylinder head 14, so that the coolant cools the cylinder head 14 or reduces the heat input, in particular into the area 29 where the holder 18 with the fuel pump 16 is arranged. In this respect, the fuel pump 16 and the fuel contained therein are cooled indirectly, thereby effectively preventing the fuel from evaporating and forming vapor bubbles, which can lead to poor starting behavior of the internal combustion engine 10. After cooling the fuel pump 16, the exhaust gas turbocharger 20 is cooled by the same coolant.

As an alternative to the embodiment shown, in which the coolant channel 26 indirectly cools the fuel pump 16, it can also be provided that the fuel pump 16 has an interface in its housing to which the coolant channel 26 can be connected, so that the coolant channel 26 at least partially through the Fuel pump 16 would run itself.

A particularly effective cooling of the components described is achieved if a coolant cooler 40, for example in the form of an air-coolant heat exchanger, is arranged in series or at least in parts in parallel in the after-cooling system 22 is integrated into the coolant channel 16 and at least a partial volume flow of the coolant flows through it (see Figure 4 ).

The additional cooling effect of the coolant cooler 40 on the coolant and thus also on the components to be cooled can be increased, for example, by operating a fan 41, in particular an electrical fan, after the internal combustion engine 10 has been switched off hot. Through the operation of the pump 24, at least a partial volume flow of the coolant is pumped through the coolant cooler 40, which is additionally cooled by the operation of the fan 41 and thus enables more effective cooling of the components to be cooled, in particular the fuel pump 16 and the exhaust gas turbocharger 20 and / or the cylinder head 14.

The order in which the components to be cooled are flowed through by the coolant is only shown here as an example and can be chosen as desired. For example, in the Figures 2 to 4 schematically, with the help of the arrows flow direction of the coolant can also be reversed in the opposite direction, so that, for. B. starting from the pump 24, the exhaust gas turbocharger 20 and then the fuel pump 16 is cooled.

Since no additional components are required, the after-cooling system 22, with which the fuel pump 16 and the exhaust gas turbocharger 20 are cooled, is designed to be particularly cost-effective, since only components that have already been used are used, which are used for after-cooling the exhaust gas turbocharger 20.

In addition, no additional electronic components are required, since the existing electronic components only have to be adapted to the after-cooling of the exhaust gas turbocharger 20.

In addition, complex venting measures can be dispensed with in the after-cooling system 22, since the fuel pump 16 is above the components of the after-cooling system 22 when the internal combustion engine 10 is installed, as a result of which siphon formation in the after-cooling system 22 is avoided.

Furthermore, in the after-cooling system 22 or the cylinder head 14, an additional cooling function is created for areas of the cylinder head 14 which are subject to high thermal stress, for example exhaust valve webs.

A particularly advantageous implementation according to the invention is obtained if the components are cooled as required. The after-cooling system 22 must meet the greatest individual cooling requirement of the respective components to be cooled.

Such an individual cooling request consists, for example, of the combination of a control duration and a control intensity, e.g. B. to vary the delivered coolant volume flow, the pump 24, a control duration and control intensity, for. B. to vary the speed, a fan 41 and a control duration and a control signal of possibly further switchable components in the after-cooling system 22, for example an electrically switched actuator 42 (see Figure 4 ).

The determination of the individual cooling requirement of a component can, for. B. an empirical or physical model, for example in the form of a model of the maximum temperature of the component for the time range after a possible shutdown of the internal combustion engine 10, which is stored in the engine control unit.

For example, from sizes of the current engine operation, e.g. B. current coolant temperature, current oil temperature, averaged over a certain period of time current engine power, current ambient temperature, etc., the need and the size of an individual cooling request, for example, the fuel pump 16 or the exhaust gas turbocharger 20 can be determined.

If this results in the need for post-cooling of at least one component, the post-cooling system 22 is activated when the internal combustion engine 10 is switched off and is operated in accordance with the greatest individual cooling requirement of all components to be cooled.

As a result, the energy consumption required by the after-cooling system 22 can be minimized accordingly.

A follow-up cooling system 22 and a cylinder head 14 are thus created in a simple manner, with which active cooling of the fuel pump 16 can be ensured efficiently and inexpensively.

For example, from sizes of the current engine operation, e.g. B. current coolant temperature, current oil temperature, averaged over a certain period of time current engine power, current ambient temperature, etc., the need and the size of an individual cooling request, for example, the fuel pump 16 or the exhaust gas turbocharger 20 can be determined.

If this results in the need for post-cooling of at least one component, the post-cooling system 22 is activated when the internal combustion engine 10 is switched off and is operated in accordance with the greatest individual cooling requirement of all components to be cooled.

As a result, the energy consumption required by the after-cooling system 22 can be minimized accordingly.

A follow-up cooling system 22 and a cylinder head 14 are thus created in a simple manner, with which active cooling of the fuel pump 16 can be ensured efficiently and inexpensively.

Claims (12)

1. An engine-off cooling system (22), with a pump (24), a coolant duct (26) for a coolant and at least one component which is to be cooled, wherein the coolant duct (26) is associated with a fuel pump (16), characterised in that the coolant duct (26) extends through a holding means (18) of the fuel pump (16).
2. An engine-off cooling system (22) according to Claim 1, characterised in that the component which is to be cooled is an exhaust turbocharger (20).
3. An engine-off cooling system (22) according to Claim 1 or Claim 2, characterised in that the component which is to be cooled is a cylinder head (14).
4. An engine-off cooling system (22) according to one of the preceding claims, characterised in that the coolant duct (26) extends through the fuel pump (16).
5. An engine-off cooling system (22) according to one of the preceding claims, characterised in that a coolant cooler (40) is provided in the engine-off cooling system (22) at least piece-wise parallel to or in series with the coolant duct (26).
6. An engine-off cooling system (22) according to one of the preceding claims, characterised in that a fan (41) is associated with the engine-off cooling system (22).
7. A cylinder head assembly with a engine-off cooling system according to one of the preceding claims (14) for an internal combustion engine (10), wherein a coolant duct of the engine-off cooling system extends through the cylinder head assembly, characterised in that the fuel pump (16) is attached to the cylinder head (14) by means of the holding means (18) and in that the coolant duct (26) is located in the vicinity of the region in which the holding means (18) for the fuel pump (16) is connected to the cylinder head (14).
8. A method for operating an engine-off cooling system (22) according to one of Claims 1 to 6, wherein the operation of the pump (24) of the engine-off cooling system (22) takes place using an ascertained control.
9. A method according to Claim 8, characterised in that the control of the pump (24) is ascertained from known variables of an engine control unit, especially by way of software for determining the minimum cooling requirement of the at least one component which is to be cooled and the fuel pump (16).
10. A method according to Claim 8 or Claim 9, characterised in that the engine-off cooling system (22) comprises a fan (41), the operation of which takes place using an ascertained control which is tailored to meet requirements.
11. A method according to Claim 10, characterised in that the control of the fan (41) is ascertained from known variables of an engine control unit, especially by way of software for determining the minimum cooling requirement of the at least one component which is to be cooled and the fuel pump (16).
12. A method according to one of Claims 8 to 11, characterised in that at least one switchable actuating element (42) is associated with the engine-off cooling system (22), which element is switched during operation of the engine-off cooling system (22) such that as good as possible a cooling action for the at least one component which is to be cooled and/or the fuel pump (16) is achieved.

Images