Method for diagnosing a water injection system of an internal combustion engine of a hybrid electric vehicle and hybrid electric vehicle

Abstract

The present invention relates to a method for diagnosing a water injection system (3) of an internal combustion engine (2) of a hybrid electric vehicle (100), comprising: providing water at a defined test water pressure by means of a water supply device (3.3), closing a shut-off valve (3.4) when water at the defined test water pressure is provided, injecting a defined target quantity of water into an intake manifold (2.2) of the internal combustion engine (2) via the injection nozzle (3.1), and determining a pressure after injection in a section of the water line (3.4) located between the injection nozzle (3.1) and the shut-off valve (3.4).2) remaining residual water pressure, wherein a current engine load of the internal combustion engine (2) is determined before injection, wherein the determined current engine load is compared with a load threshold value, and wherein the internal combustion engine (2) is subjected to an additional load by operating an electric traction motor (1) of the hybrid electric vehicle (100) in generator mode if the determined current engine load is less than the load threshold value. The present invention further relates to a hybrid electric vehicle (100) with a diagnostic unit (4) which is configured to carry out a method according to the invention.

Description

[0001] The present invention relates to a method for diagnosing a water injection system of an internal combustion engine of a hybrid electric vehicle and to a hybrid electric vehicle.

[0002] From DE 10 2023 106 197 B3 a method for diagnosing a water injection system of an internal combustion engine is known.

[0003] German patent application DE 10 2017 116 332 A1 discloses a method for controlling a water injection system of an internal combustion engine of a hybrid electric vehicle, as well as a hybrid electric vehicle itself. It describes how, in response to a change in driver demand, the system switches between different water injection states if this improves efficiency by more than a defined threshold. The water injection states differ, in particular, in that different target quantities of water are injected via injection nozzles, for example, into the intake manifold of an internal combustion engine of the hybrid electric vehicle. It further describes how an electric traction motor of the hybrid electric vehicle can be operated as a generator to supply the internal combustion engine with an additional load.

[0004] The present invention is based on the objective of enabling a reliable diagnosis of a water injection system of an internal combustion engine of a hybrid electric vehicle.

[0005] This problem is solved according to the invention by a method for diagnosing a water injection system of an internal combustion engine of a hybrid electric vehicle with the features of claim 1 and by a hybrid electric vehicle with the features of claim 6.

[0006] The inventive method for diagnosing a water injection system of an internal combustion engine of a hybrid electric vehicle checks whether an injection nozzle of the water injection system, which is designed to inject water into an intake manifold of the internal combustion engine, enables a desired water flow or whether it is dirty or clogged.

[0007] For this purpose, in the method according to the invention, water at a defined test water pressure is supplied in a section of a water line located between the injection nozzle and a shut-off valve by means of a water supply device. The water supply device typically comprises a water tank and a pump to deliver water from the water tank to the injection nozzle via water lines. The water supply device is configured in a generally known manner to supply water at a defined water pressure to the injection nozzle.

[0008] When water with the desired defined test water pressure is provided in the area of ​​the water line located between the injection nozzle and a shut-off valve, the shut-off valve is closed, thereby enclosing a defined volume of water exhibiting the test water pressure in the area of ​​the water line located between the injection nozzle and the shut-off valve.

[0009] With the shut-off valve closed, a defined target quantity of water is injected via the injection nozzle into an intake manifold of the internal combustion engine, thereby reducing the water volume and consequently the water pressure in the area of ​​the water line located between the injection nozzle and the shut-off valve.

[0010] After injection, the residual water pressure remaining in the section of the water line between the injection nozzle and the shut-off valve is measured and compared to a reference water pressure that would be expected for a reduction in the enclosed water volume by the target water quantity. Excessive residual water pressure indicates that too little water was extracted from the enclosed water volume and is therefore an indicator of a dirty or clogged injection nozzle.

[0011] Since injecting water into the intake manifold affects, and specifically delays, the combustion of the internal combustion engine, misfires can be caused by injecting water at relatively low engine loads.

[0012] According to the invention, therefore, before the water is injected into the intake manifold, the current engine load of the internal combustion engine is determined in a generally known manner and the determined current engine load is compared with a load threshold value.

[0013] If the determined current engine load is less than the load threshold, then an electric traction motor of the hybrid electric vehicle is operated in generator mode, in which a motor rotor of the electric traction motor is driven by the combustion engine, in order to supply the combustion engine with an additional load. The electric traction motor is controlled in such a way that the total load resulting from the sum of the determined current engine load and the additional load is greater than or equal to, preferably approximately equal to, the load threshold.

[0014] The method according to the invention enables, without the risk of misfires, a diagnosis of the water injection system even at relatively low current engine load and thus a continuous and consequently particularly reliable diagnosis of the water injection system of an internal combustion engine of a hybrid electric vehicle.

[0015] The water injection system of multi-cylinder internal combustion engines typically comprises several injectors, specifically a number of injectors corresponding to the number of cylinders, each configured to inject water into the intake manifold of one of the cylinders. Preferably, the previously described method is carried out sequentially for each of the multiple injectors individually in order to test each injector separately. Thus, for each injector, the test water pressure is applied in the section of the water line located upstream of the respective injector, a volume of water is enclosed upstream of the respective injector by closing a shut-off valve, the target quantity of water is injected into the respective intake manifold via the respective injector, and after injection, the respective residual water pressure in the respective enclosed water volume is determined.Preferably, the residual water pressures determined for the individual injectors are compared not only with the reference water pressure but also with each other. This enables a reliable diagnosis of a water injection system with multiple injectors. It is conceivable that all injectors are connected to a single shut-off valve, or that each injector has its own individual shut-off valve.

[0016] Preferably, to inject the defined target water quantity, several individual partial injections are carried out with the respective injection nozzle, in each case in which a partial target water quantity is injected into the intake manifold via the respective injection nozzle, whereby the sum of all partial target water quantities is equal to the defined target water quantity.

[0017] In this case, it is particularly preferred that an equal partial target amount of water is injected into the intake manifold via the respective injection nozzle in each partial injection.

[0018] In order to avoid the occurrence of a relatively low engine load during the diagnostic procedure of the water injection system as much as possible, a fuel cut-off function of the hybrid electric vehicle, designed in a generally known manner, is preferably blocked during the execution of the method according to the invention, i.e., a fuel cut-off of the combustion engine is prevented.

[0019] The hybrid electric vehicle according to the invention comprises an electric traction motor that can be operated in either motor or generator mode in a known manner. In motor mode, electrical energy is supplied to the electric traction motor, typically from a high-voltage battery, also referred to as a traction battery, thereby electromagnetically driving a motor rotor of the electric traction motor. In generator mode, on the other hand, the motor rotor of the electric traction motor is driven mechanically, for example by the internal combustion engine or by the wheels of the hybrid electric vehicle, thereby generating electrical energy in the electric traction motor.

[0020] The hybrid electric vehicle according to the invention further comprises an internal combustion engine with a water injection system. The water injection system comprises at least one injection nozzle, configured as described above, to inject water into an intake manifold of the internal combustion engine. The water injection system further comprises at least one shut-off valve, arranged in a water line leading to the injection nozzle, and configured in a known manner to selectively shut off, i.e., prevent, or allow the flow of water through the water line. The water injection system further comprises a water supply device, configured as described above, for supplying water at a defined water pressure to the at least one injection nozzle.

[0021] The hybrid electric vehicle according to the invention further comprises a diagnostic unit configured to execute a previously described method according to the invention for diagnosing the water injection system of the combustion engine of the hybrid electric vehicle. The diagnostic unit can, for example, be implemented by suitable programming of a control unit of the hybrid electric vehicle. However, it is also conceivable that the diagnostic unit is implemented by a separate hardware component.

[0022] For the reasons described above, the diagnostic unit enables a reliable diagnosis of the water injection system of the combustion engine of the hybrid electric vehicle by carrying out the method according to the invention.

[0023] An embodiment of the present invention is described below with reference to the attached Fig. 1 described, which shows a schematic diagram of a hybrid electric vehicle according to the invention. Fig. Figure 1 shows a hybrid electric vehicle 100 according to the invention comprising an electric traction motor 1, an internal combustion engine 2 with a water injection system 3, and a diagnostic unit 4.

[0024] The internal combustion engine 2 comprises several cylinders 2.1, each of which is connected to an air supply system 2.3 via an intake manifold 2.2, and each of which is connected to an exhaust system 2.5 via an exhaust pipe 2.4.

[0025] The water injection system 3 comprises a number of injection nozzles 3.1 corresponding to the number of cylinders 2.1, each of which is arranged on the intake manifold 2.2 of one of the cylinders 2.1 and which is each configured to inject water supplied via a water line 3.2 into the respective intake manifold 2.2.

[0026] The water injection system 3 comprises a water supply device 3.3 with a pump 3.3.1 and a water tank 3.3.2, wherein the pump 3.3.1 is configured to supply water from the water tank 3.3.2 via the water lines 3.2 at a defined water pressure to the injection nozzles 3.1.

[0027] In the water lines 3.2 leading to the individual injection nozzles 3.1, a shut-off valve 3.4 and a pressure sensor 3.5 are arranged, the pressure sensor 3.5 being arranged downstream of the shut-off valve 3.4.

[0028] The diagnostic unit 4 is set up to control the pump 3.3.1 in such a way that water with a defined test water pressure is provided in the water lines 3.2.

[0029] The diagnostic unit 4 is further configured to close the shut-off valves 3.4 while water with the defined test water pressure is provided in the water lines 3.2, so that a volume of water having the defined test water pressure is enclosed in a section of the water lines 3.2 located between the respective injection nozzle 3.1 and the respective shut-off valve 3.4.

[0030] The diagnostic unit 4 is further equipped to control each of the injectors 3.1 individually in such a way that a defined target quantity of water is injected into the respective intake manifold 2.2 via the respective injector 3.1.

[0031] The diagnostic unit 4 is specifically designed to perform several individual partial injections to inject the defined target amount of water via the respective injection nozzle 3.1, in each of which an equal partial target amount of water is injected into the respective intake manifold 2.2 via the respective injection nozzle 3.1.

[0032] The diagnostic unit 4 is further equipped to determine, after injection, the residual water pressure remaining in the area of ​​the respective water line 3.2 located between the respective injection nozzle 3.1 and the respective shut-off valve 3.4 by means of the respective pressure sensor 3.5.

[0033] The diagnostic unit 4 is further equipped to compare the residual water pressures determined in this way for the individual injectors 3.1 with each other and with a reference water pressure.

[0034] The diagnostic unit 4 is configured to determine the current engine load of the internal combustion engine 2 in a generally known manner before injection, to compare the determined current engine load with a load threshold value, and to subject the internal combustion engine 2 to an additional load by operating the electric traction motor 1 in generator mode if the determined current engine load is less than the load threshold value.

[0035] The diagnostic unit 4 is further equipped to disable a fuel cut-off function of the hybrid electric vehicle 100, designed in a generally known manner, during the execution of the steps described above. Reference symbol list 100 hybrid electric vehicles 1 electric traction motor 2 Internal combustion engine 2.1 cylinders 2.2 Intake manifolds 2.3 Air supply system 2.4 Exhaust pipes 2.5 Exhaust system 3 Water injection system 3.1 Fuel injectors 3.2 Water pipes 3.3 Water supply system 3.3.1 Pump 3.3.2 Water tank 3.4 Shut-off valves 3.5 Pressure sensors 4 Diagnostic Unit

Claims

[1] Method for diagnosing a water injection system (3) of an internal combustion engine (2) of a hybrid electric vehicle (100), comprising: Providing water at a defined test water pressure in a section of a water line (3.2) located between an injection nozzle (3.1) and a shut-off valve (3.4) by means of a water supply device (3.3), Closing the shut-off valve (3.4) with water supplied at the defined test water pressure, Injecting a defined target quantity of water into an intake manifold (2.2) of the internal combustion engine (2) via the injection nozzle (3.1), and Determining the residual water pressure remaining after injection in the area of ​​the water line (3.2) located between the injection nozzle (3.1) and the shut-off valve (3.4), wherein, prior to injection, the current engine load of the internal combustion engine (2) is determined and the determined current engine load is compared with a load threshold value, and wherein the combustion engine (2) is subjected to an additional load by operating an electric traction motor (1) of the hybrid electric vehicle (100) in generator mode when the determined current engine load is less than the load threshold. [2] Method according to claim 1, wherein the water injection system (3) comprises several injection nozzles (3.1), and wherein the method according to claim 1 is carried out successively with each of the several injection nozzles (3.1) individually. [3] Method according to one of the preceding claims, wherein several individual partial injections are carried out to inject the defined target quantity of water, in each case in which a partial target quantity of water is injected via the injection nozzle (3.1) into the intake manifold (2.2). [4] Method according to claim 3, wherein in each partial injection an equal partial target water quantity is injected via the injection nozzle (3.1) into the intake manifold (2.2). [5] Method according to one of the preceding claims, wherein a fuel cut-off function of the hybrid electric vehicle (100) is blocked during the execution of the method. [6] Hybrid electric vehicle (100) comprising an electric traction motor (1), an internal combustion engine (2) with a water injection system (3), and a diagnostic unit (4), wherein the water injection system (3) comprises: at least one injection nozzle (3.1) configured to inject water into an intake manifold (2.2) of the internal combustion engine (2), a shut-off valve (3.4) arranged in a water line (3.2) leading to the injection nozzle (3.1), and a water supply device (3.3) for providing water at a defined water pressure to the at least one injection nozzle (3.1), and wherein the diagnostic unit (4) is configured to carry out a method according to one of the preceding claims.

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