DE102022101751A1 - Intake air heating system for a vehicle engine - Google Patents

Abstract

Intake air heating system for a vehicle engine (10), having an air supply (11) for supplying air to the vehicle engine (10). A discharge branch (15) and a return branch (16) are formed in the air supply (11), the discharge branch (15) having a controllable bypass valve (13) and between the discharge branch (15) and the return branch (16) a bypass - Line (41) is formed, in which a heating device (45) is arranged. The heating device (45) is designed to heat an air flow in the bypass line (41), and a control unit (60) is provided which is designed to activate the bypass valve (13) in order to heat an air flow in of the air supply (11) at least partially through the bypass line (41).

Description

The invention relates to an intake air heating system for a vehicle engine, having an air supply for supplying air to the vehicle engine. In particular, the heating system in the air supply has a compressor unit for compressing the air and an intercooler, which is located behind the compressor unit in the direction of flow, for cooling the compressed air before it is supplied to the vehicle engine.

Such intake air systems in the intake tract for vehicle engines are known, with a charge air cooler as a heat exchanger reducing the temperature of the combustion air supplied to the engine. It is installed in the intake tract between a compressor and the vehicle engine, with the compressor typically being a turbocharger. The intercooler dissipates some of the heat generated by compressing the air in the compressor. The goal is to increase the power and efficiency of the engine.

However, in order to achieve the lowest possible emissions from the vehicle engine, even with such intake systems, it is necessary to take various measures to reduce emissions. This is particularly the case for the cold start behavior when, for example, low emission limit values are to be maintained even at sub-zero temperatures. Compliance with emission limit values after take-off is also desirable.

For example, measures such as the use of electrically heated exhaust gas catalytic converters, cold-start NOx storage catalytic converters (LNTs - lean NOx traps), air-insulated exhaust gas components, suitable engine combustion modes for low FG-NOx, increased heat flow and engine power limitation and accelerated aftertreatment shutdown are known for this from the prior art. However, these measures are often not sufficient to control the cold start behavior of any type of engine application and drive scenario. There is therefore a need for new solutions to improve the cold start behavior of vehicle engines without adversely affecting CO ₂ emissions, with heating of the intake air before combustion in the engine being a particular option. Various solutions from the prior art are already known for this.

For example, the DE 100 07 158 A1 describe an intake air heating system for engines, in which high-temperature combustion gas from a combustor is supplied to the intake side of an engine to heat air supplied to the engine. This is intended to improve the startability of the engine. For this purpose, intake air is branched off, for example, behind an intercooler or behind a turbo compressor, heated by the burner and fed back to the intake air in front of the engine.

The DE 10 2011 087 260 A1 discloses an arrangement for recirculating exhaust gas and supplying cooled charge air to an internal combustion engine, in which fresh air is compressed and cooled as so-called charge air via two different turbochargers and subsequent charge air coolers before it is fed to an internal combustion engine. In front of the second intercooler there is a bypass, via which charge air can be supplied to a heater, which heats the charge air flowing through the bypass by additional heating. This heater can be electronically controlled and electrically operated. As a result of this additional heating in the area of the bypass of the charge air cooler, heated charge air can be admixed with the cooled charge air in such a way that the final temperature of the charge air can be adjusted in a targeted manner.

From the U.S. 5,855,192 A a diesel engine with air preheating is known, which uses a carburetor that vaporizes the fuel supplied by means of a heating element. The heating element is, for example, a glow plug or a ceramic grid, which can be energized. As a result, the ceramic element heats up and vaporizes a fuel.

The U.S. 6,564,545 B1 discloses the combination of a three-way catalyst and a heat exchanger for preheating fresh air prior to delivery to an engine. The fresh air is heated by the heat generated when the exhaust gas from the engine reacts with the catalytic converter.

The CN 201 606 168 U discloses heating for the combustion air of a vehicle engine, in which a ceramic PTC element (positive temperature coefficient heating) is used.

From the US 2008 / 0 060 619 A1 however, a fuel atomizer is known which is electrically heated. The fuel vapor generated by the atomizer is directed into the airflow in an intake manifold to form a gaseous fuel/air mixture there. The fuel atomizer is preferably activated prior to a vehicle starting event. For example, this is initiated by turning a key in the ignition or by opening a vehicle door on the driver's side.

In view of the prior art shown, the area of preheating However, intake air of a vehicle engine still has room for improvement. The invention is based on the object of providing an intake air heating system for a vehicle engine, which can be activated in various situations and enables a heating system to be switched on and off as quickly as possible.

According to the invention, the object is achieved by an intake air heating system having the features of claim 1. Further, particularly advantageous configurations of the invention are disclosed in the dependent subclaims.

It should be pointed out that the features and measures listed individually in the following description can be combined with one another in any technically meaningful way and show further refinements of the invention. The description additionally characterizes and specifies the invention, in particular in connection with the figures.

The intake air heating system for a vehicle engine according to the invention has an air supply for supplying air to the vehicle engine. Parallel to this air supply, an air heating system is designed, which is operated in a bypass. A discharge branch and a return branch are formed in the air supply, the discharge branch has a controllable bypass valve and a bypass line is formed between the discharge branch and the return branch, in which a heating device is arranged. The heating device is designed to heat an air flow in the bypass line. The air flow within the bypass line is thus heated by the heating device and fed back into the air supply at the return branch. Furthermore, a control unit is provided, which is designed to activate the bypass valve in order to direct an air flow in the air supply at least partially through the bypass line.

A compressor unit for compressing the air and an intercooler, which is located downstream of the compressor unit in the direction of flow, are preferably provided within the air supply for cooling the compressed air before it is supplied to the vehicle engine. The compressor unit is typically a turbocharger and the charge air cooler can be designed in various ways. For example, a water-cooled intercooler is used here.

The air heating system is then configured parallel to the charge air cooler and, as already described, is operated in a bypass to the charge air cooler. The air heating system again includes a heating device for preheating the combustion air before it is fed to the vehicle engine, with the air being branched off and heated in particular before the intercooler. For this purpose, a discharge branch between the compressor unit and the charge air cooler and a return branch between the charge air cooler and the vehicle engine are formed in the air supply. The discharge branch has the controllable bypass valve and the bypass line is formed between the discharge branch and the return branch. The heating device, which is designed to heat an air flow in the bypass line, is arranged in this bypass line. The system also has a control unit which is designed to activate the bypass valve in order to direct an air flow in the air supply at least partially through the bypass line. Within the bypass line, this air flow is heated by the heating device and fed back into the air supply at the return branch, this taking place behind the charge air cooler in the direction of flow. The control unit preferably controls the bypass valve in such a way that an air flow is guided completely through the bypass line, so that the intercooler is completely bypassed.

The heating device can be designed in various ways, in one embodiment of the invention having a catalyst element and a vapor generator element designed to generate a fuel vapor. The heating device is designed to supply fuel vapor generated with the steam generator element to the catalytic converter element, as a result of which its exothermic chemical reactions generate heat, with which an air flow in the bypass line can be heated. The steam generator element generates, for example, fuel vapor from a diesel fuel, which is supplied to the steam generator element. For this purpose, the steam generator element has, for example, a ceramic structure which can be heated by supplying electrical energy, as a result of which fuel applied to the structure can be vaporized. The fuel is supplied to the steam generator element under pressure or without pressure.

The steam generator element uses in particular a PTC heating element with a ceramic structure, which uses the "positive temperature coefficient - PTC". It is a ceramic-based electrical component with a temperature-dependent resistance that is used as a heating element. Such a PTC element is usually composed of one or more ceramic plates.

The catalytic converter element is designed, for example, as a diesel oxidation catalytic converter. The Catalyst element is preferably designed to be relatively small. The steam generator element and the catalyst element are heated together or separately from one another by an additional heating device, which is operated electrically, for example. Due to the small size of the catalytic converter element and a corresponding design of the entire heating device, very rapid changes in the operating state of the catalytic converter element are possible. On the one hand, the catalytic converter element can be rapidly exposed to fuel vapor. On the other hand, it can also be switched off and deactivated again quickly. The entire air heating system is designed to increase the temperature of the combustion air as quickly as possible during a cold start.

The intake air heating system is preferably activated for a cold start of the vehicle, with the control unit directing the air flow through the bypass line based on various signals. However, the heating system can also be activated in other situations, such as when driving downhill and the intake tract “cools down” as a result. The control unit then controls the bypass valve of the discharge branch and the heating device. The bypass valve is controlled to direct the air flow partially or completely through the bypass line to the heater and the evaporator element is heated to generate the fuel vapor. This is initiated, for example, by starting the associated vehicle, which generates a signal for the control unit. However, this is preferably done before the starting process.

In one embodiment of the invention, the control unit is designed, for example, to activate the bypass valve in the discharge branch and/or the heating device upon receipt of a signal, which is triggered by detecting the opening of a vehicle door or the presence of a vehicle key in a defined area of the vehicle. Consequently, opening a vehicle door or recognizing a vehicle key in the area of the vehicle generates a signal for the control unit. In the case of keyless entry systems, any other type of driver recognition can also generate a corresponding signal for the control unit.

The bypass valve in the shunt manifold regulates the flow between the main air supply to the charge cooler and the bypass line, for example under cold start conditions. In particular, the bypass valve in the diverter branch regulates the flow between the main air supply to the charge cooler and the bypass line. The bypass valve preferably opens the bypass line completely and closes the main line, in particular the main line to the intercooler. At the same time, for example, the ceramic structure of the steam generator element is wetted with fuel. The ceramic structure and the diesel oxidation catalytic converter are then heated, although one or both components can also be heated earlier when the respective driver is detected. When the vehicle engine is started, the generated fuel vapor is supplied to the catalyst element. The exothermic chemical reactions within the catalyst element significantly increase the temperature in the bypass line airflow. As soon as these exothermic reactions have started, the heating of the catalyst element can be stopped.

The heated bypass air is then routed back into the air supply via the recirculation manifold and fed to the vehicle engine. The increased air temperature leads to NOx-optimized combustion with low HC/CO values. In addition, the exhaust gas temperature increases, which contributes to accelerated heating of the exhaust gas aftertreatment components. This enables quicker activation of exhaust aftertreatment components and lower tailpipe emissions. At least the bypass valve in the discharge branch is activated during the warm-up of the vehicle engine in order to ensure the required inlet temperatures. Here, the mixing temperature of the air is regulated by the bypass line/heating device and the intercooler.

However, a signal for the control unit can also be generated independently of a key or driver recognition. For example, the required fuel vapor can also be generated as a function of temperature. This is the case, for example, when the cooling water temperature or the outside temperature falls below a specific limit temperature, which would make improved cold start behavior necessary when starting the vehicle. For this situation, the fuel vapor can already be generated with a corresponding drop in temperature, so that it is already available when the vehicle is started. In one embodiment of the invention, it is therefore provided that the control unit is designed to activate the bypass valve in the diversion branch, a further bypass valve in the return branch and/or the heating device upon receipt of a signal which is triggered by the drop in temperature below a defined limit temperature, the bypass valve in the diversion branch and a bypass valve in the return branch being closed and the steam generator element being supplied with fuel. At the temperature acts it is, for example, the temperature of the cooling water or the outside temperature. The bypass line is completely closed by the two valves so that the fuel vapor generated cannot escape from the bypass line.

However, any other temperatures can also be monitored and used to generate a signal if it can be concluded from their level that activation of the heating system is advantageous. For example, the temperature in front of the exhaust gas components or modeled catalyst material temperatures could also be used here. If the temperature falls below a certain limit, this can also initiate the activation of the heating system. This temperature limit is, for example, around 200° C. (light-off value).

A signal as described above then triggers heating of the catalytic converter element, to which the already generated fuel vapor is then supplied, so that the processes described can take place.

Further advantageous embodiments of the invention are in the dependent claims and the following description of the figures 1 disclosed.

The principle of operation of the intake air heating system according to the invention is based on the schematic representation of the 1 explained.

The essential components are located in the intake tract for a vehicle engine 10. This intake tract includes an air supply 11 for supplying air to a vehicle engine 10, this supply of air being denoted by a horizontal arrow. Another horizontal arrow indicates the removal of exhaust gas via an exhaust gas discharge 12. Components for fuel supply are in the simplified representation of FIG 1 not shown and may be constructed and arranged in any known manner. Furthermore, the invention is explained below with reference to a vehicle engine 10 in which combustion air is precompressed by a compressor or a turbocharger (engine supercharging). However, the invention can also be used with a naturally aspirated engine without supercharging.

In a vehicle engine 10 with precompression, the air supply 11 contains a compressor 20, which is typically a compressor of a turbocharger. Furthermore, there is an intercooler 30 between the compressor 20 and the vehicle engine 10. When the vehicle engine 10 is in operation, the compressor 20 first compresses the combustion air, as a result of which it heats up. The intercooler 30 cools the combustion air down again before it is fed to the vehicle engine 10 .

An air heating system 40 is connected in parallel with the intercooler 30, with which the air or the combustion air can be heated if necessary. This air heating system 40 includes a bypass line 41 and a heating device 45 connected thereto. A second recirculation junction 16 is formed between the charge air cooler 30 and the vehicle engine 10 . Both branches are each designed with a bypass valve 13,14. The bypass valves 13, 14 can in particular be flaps which open and close the air flow to the bypass line 41. The bypass duct 41 extends between the discharge branch 15 and the return branch 16, the bypass airflow through this bypass duct 41 being shown with two curved arrows.

The heating device 45 has several components. A first component is a steam generating element 42 which may be, for example, a ceramic structure in the form of a PCT heating element. Another component is a catalyst element 43, which is, for example, a diesel oxidation catalyst. Furthermore, an electrical heater 44 is provided, with which both the steam generator element and the catalyst element 43 can be heated. In addition, the steam generator element 42, a fuel 50 can be supplied, which in the 1 is indicated schematically by an arrow with which the reference number 50 is indicated. The fuel 50 is a diesel fuel, for example. The mode of operation of the heating device 45 formed in this way includes the introduction of fuel 50 into the steam generator element 42, with the ceramic structure being wetted with the fuel, for example. The ceramic structure is heated by means of the electrical heating 44 in such a way that the fuel evaporates and a fuel vapor 51 is generated. The catalyst element 43 is also heated by the electric heater 44 and the fuel vapor 51 is supplied to the catalyst element 43 .

The exothermic chemical reactions within the catalytic converter element 43 generate heat, which heats the combustion air in the bypass line 41 . Devices for this heat transfer are in the 1 not explicitly shown, but can be formed in a known manner. For example, the airflow can do that Flow around catalyst element 43 and absorb its heat. Alternatively, the air flow can also be passed through the catalyst element 43 and thereby absorb its heat, as is shown schematically in FIG 1 is indicated. Furthermore, any other type of heat transfer from the catalytic converter element 43 to the air flow in the bypass line 41 is possible.

To control the entire air heating system 40, this is connected to a control unit 60. This control unit 60 and its connection to the air heating system 40 are in FIG 1 again shown only schematically and are only intended to clarify the basic functionality of this control unit 60 . The control unit 60 can be integrated into a general control system of a vehicle and is not only in communication with the air heating system 40 but also with other components of the vehicle that are not shown. In particular, these are door opener systems, starter systems and sensors. The control unit 60 receives associated signals from these systems, which are triggered when a corresponding event occurs in the vehicle and make an approaching cold start of the vehicle probable. Upon receipt of such a signal, the control unit 60 partially or fully operates the air heating system 40 .

If the control unit 60 receives a signal from a door opening system, for example, that the driver's door has been opened, it controls the bypass valve 13 in such a way that the air flow from the air supply 11 is routed completely into the bypass line 41 . The flow of air to the intercooler 30 is prevented as a result. The electric heater 44 heats the ceramic structure of the steam generator element 42 and the catalyst element 43. The fuel 50 evaporates on the ceramic structure of the steam generator element 42 and when the fuel vapor 51 is fed to the catalyst element 43, this generates heat, which in turn is transferred to the air flow in the bypass line 41. The bypass valve 14 is opened at the latest when the vehicle engine 11 is started. The heated bypass air flow is thus fed back to the air supply 11 via the return branch 16 . The heated air flow then reaches the vehicle engine 10 via this air supply.

Other events can also be used as a signal for initiating this air heating. For example, recognizing a vehicle key in a specific area of the vehicle or, in the case of keyless entry systems, detecting a driver can also trigger a corresponding signal. In an alternative embodiment, the initiation of the air heating is temperature-controlled. If, for example, the cooling water temperature and/or the outside temperature of the vehicle falls below a specific limit value, fuel vapor 51 can already be generated within the air heating system 40 . This remains within the system in that the two bypass valves 13 and 14 are controlled in such a way that the branches 15 and 16 to the bypass line 41 are closed. As soon as the control unit 60 receives a signal which makes an approaching cold start of the vehicle probable, the catalytic converter element 43 is also heated by the electrical heating 44 so that the exothermic chemical reactions in the catalytic converter element 43 can take place with the fuel vapor 51 . The bypass valves 13 and 14 are opened so that air can flow through the bypass line 41 and be heated.

The invention can be used particularly advantageously when the internal combustion engine or the vehicle has stood still for a long time and a cold start has to be carried out. It is within the meaning of the invention that activation of the air heating can be omitted if the internal combustion engine is not started with a cold start, which can be the case, for example, after a longer operating phase, e.g. after a brief stop at traffic lights or the like, or after the vehicle has been parked for a short time. Furthermore, it might be necessary to activate the heating system again if the flue gas temperature falls below the light-off value (e.g. 200°C).

Reference List

10

Vehicle engine, internal combustion engine

11

air supply

12

exhaust gas discharge

13:14

bypass valve

15

drain branch

16

feedback branch

20

Compressor unit, turbocharger

30

intercooler

40

air heating system

41

bypass line

42

steam generator element

43

catalyst element

44

Heating, electric

45

heating device

50

fuel

51

fuel vapor

60

control unit

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 10007158 A1 [0005]
• DE 102011087260 A1 [0006]
• US5855192A [0007]
• US6564545B1 [0008]
• CN201606168U[0009]
• US20080060619A1[0010]

Claims (10)

Intake air heating system for a vehicle engine (10), having an air supply (11) for supplying air to the vehicle engine (10), wherein a discharge branch (15) and a return branch (16) are formed in the air supply (11), and the discharge branch (15) has a controllable bypass valve (13) and between the discharge branch (15) and the return branch (16) a bypass line ung (41), in which a heating device (45) is arranged, which is designed to heat an air flow in the bypass line (41), and a control unit (60) is provided, which is designed to activate the bypass valve (13) in order to conduct an air flow in the air supply (11) at least partially through the bypass line (41). Intake air heating system after claim 1 , characterized in that it has a compressor unit (20) in the air supply (11) for compressing the air and a charge air cooler (30) located downstream of the compressor unit (20) in the direction of flow, the discharge branch (15) being formed between the compressor unit (20) and the charge air cooler (30) and the return branch (16) being formed between the charge air cooler (30) and the vehicle engine (10). Intake air heating system after claim 1 or 2 , characterized in that the control unit (60) is designed to activate the bypass valve (13) in order to conduct an air flow in the air supply (11) completely through the bypass line (41). Intake air heating system according to any of the preceding Claims 1 until 3 , characterized in that the heating device (45) has a catalyst element (43) and a steam generator element (42) designed to generate fuel vapor (42), the heating device (45) being designed to supply fuel vapor (51) generated with the steam generator element (42) to the catalyst element (43), as a result of which its exothermic chemical reactions generate heat with which an air flow in the bypass line (41) can be heated. Intake air heating system according to any of the preceding Claims 1 until 4 , characterized in that the steam generator element (42) has a ceramic structure which can be heated by supplying electrical energy, whereby fuel applied to the ceramic structure can be vaporized. Intake air heating system according to any of the preceding Claims 1 until 5 , characterized in that the catalyst element (43) is a diesel oxidation catalyst. Intake air heating system according to any of the preceding Claims 1 until 6 , characterized in that the return branch (16) is provided with a bypass valve (14). Intake air heating system according to any of the preceding Claims 1 until 7 , characterized in that the control unit (60) is designed to activate the bypass valve (13) and/or the heating device (45) upon receipt of a signal which is triggered by recognizing the opening of a vehicle door or the presence of a vehicle key in a defined area of the vehicle. Intake air heating system according to any of the preceding Claims 1 until 8th , characterized in that the control unit (60) is adapted to open a bypass valve (14) in the return branch (16) when it receives a signal which is triggered by the starting of the vehicle engine (10). Intake air heating system according to any of the preceding Claims 1 until 9 , characterized in that the control unit (60) is designed to activate the bypass valve (13) in the discharge branch (15), a bypass valve (14) in the return branch (16) and/or the heating device (45) upon receipt of a signal which is triggered by the drop in temperature below a defined limit temperature, the bypass valve (13) in the discharge branch (15) and the bypass valve (14) in the return branch (16) is closed and the steam generator element (42) is charged with fuel.

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