Method for operating a drive system of a plug-in hybrid vehicle

Abstract

Method for operating a drive system (1) of a plug-in hybrid vehicle, wherein the drive system (1) - an internal combustion engine (2), - an electric machine (17), - an electrochemical storage device (3) designed to supply the electric machine (17) with electrical energy, as well as - a conditioning system (4) configured for preconditioning the electrochemical storage device (3) and comprising an electric heating element (5), wherein a preconditioning function of the internal combustion engine (2) is activated before starting a journey and a coolant of the internal combustion engine (2) is preheated by a time-controlled activation of the electric heating element (5), characterized in that the activation of the preconditioning function of the internal combustion engine (2) is coupled with a fuel input model by means of which a fuel input into the internal combustion engine (2) is modeled, wherein the preconditioning function of the internal combustion engine (2) is activated at each restart or at a fixed or to be fixed number of starts of the internal combustion engine (2) if a fuel input threshold is exceeded in this fuel input model.

Description

[0001] The present invention relates to a method for operating a drive system of a plug-in hybrid vehicle, wherein the drive system comprises an internal combustion engine, an electric machine, an electrochemical storage device configured to supply the electric machine with electrical energy, and a conditioning system configured to precondition the electrochemical storage device and comprising an electric heating element, and wherein a preconditioning function of the internal combustion engine is activated before driving begins and a coolant of the internal combustion engine is preheated by a time-controlled activation of the electric heating element.

[0002] It is known from the prior art that internal combustion engines, particularly those powered by fossil fuels, introduce a certain amount of fuel into the engine oil during cold start phases. In conventional motor vehicles that rely solely on an internal combustion engine as their propulsion system, this fuel is largely expelled again during longer journeys once the engine reaches its operating temperature.

[0003] Furthermore, plug-in hybrid electric vehicles (PHEVs) are also known from the prior art. These vehicles have an electric motor in addition to the internal combustion engine as a secondary drive system. In intensive short-distance operation, particularly in such plug-in hybrid vehicles, which by design operate purely electrically for part of the journey or only require the internal combustion engine for short periods (so-called boost function), the internal combustion engine does not reach its target operating temperature on a significant number of journeys. This results in an increasing amount of fuel accumulating in the engine oil. This can trigger a low-level warning message, such as "Oil level too high," for the driver. Moreover, an excessive amount of fuel in the engine oil also leads to a deterioration of the engine oil's lubricating properties.This can, under certain circumstances, result in permanent damage to the internal combustion engine due to insufficient lubrication.

[0004] A method for operating a drive system of a plug-in hybrid vehicle is known, for example, from DE 10 2008 021 424 A1.

[0005] German patent application DE 10 2017 116 817 A1 discloses a method for operating a drive system of a plug-in hybrid vehicle, which aims to remove impurities from the engine fluid of the plug-in hybrid vehicle's internal combustion engine by heating it. The thermal energy levels in the internal combustion engine and the engine fluid increase due to the operation of the engine. If the thermal energy levels remain above a threshold temperature for a certain period of time, impurities in the engine fluid are burned off, thus ensuring the quality of the engine fluid. When the engine is not in operation, the thermal energy levels in the engine and the engine fluid do not increase. Over time, impurities can accumulate in the engine fluid if the thermal energy levels in the engine fluid do not increase.During the procedure, calculations are performed to determine, among other things, whether the combustion engine was operated to raise the engine fluid temperature to or above a threshold temperature for a specified period. If the engine fluid temperature does not reach or exceed the threshold for the specified period, the cold start counter is incremented by one. The system also determines whether the cold start counter reading is above a threshold cold start counter reading and whether the engine fluid temperature within the engine fluid reservoir is below a threshold temperature. If so, the plug-in hybrid vehicle enters fluid maintenance mode. While in this mode, the plug-in hybrid vehicle's combustion engine is operated to heat the engine fluid during a driving cycle.Furthermore, the fluid is heated before the driving cycle if the vehicle is in fluid maintenance mode and is electrically connected to a mains power source.

[0006] The invention aims to provide a method for operating a drive system of a plug-in hybrid vehicle of the type mentioned above, which can specifically reduce the amount of fuel entering the engine oil of the internal combustion engine of the plug-in hybrid vehicle.

[0007] The solution to this problem is provided by a method for operating a drive system of a plug-in hybrid vehicle with the features of the characterizing part of claim 1. The dependent claims relate to advantageous further developments of the invention.

[0008] In an inventive method for operating a drive system of a plug-in hybrid vehicle, wherein the drive system comprises an internal combustion engine, an electric machine, an electrochemical storage device configured to supply the electric machine with electrical energy, and a conditioning system designed to precondition the electrochemical storage device and comprising an electric heating element, and wherein a preconditioning function of the internal combustion engine is activated before driving begins and a coolant of the internal combustion engine is preheated by a time-controlled activation of the electric heating element, it is provided according to the invention that the activation of the preconditioning function of the internal combustion engine is coupled with a fuel input model by means of which a fuel input into the internal combustion engine is modeled.wherein the preconditioning function of the internal combustion engine is activated at each restart or after a fixed or definable number of starts of the internal combustion engine when a fuel entry threshold is exceeded in this fuel entry model. The method according to the invention advantageously enables preconditioning of the internal combustion engine of the plug-in hybrid vehicle by preheating the coolant, so that increased fuel entry into the engine oil of the internal combustion engine can be avoided and thereby potentially inadequate lubrication of moving parts of the internal combustion engine can be effectively prevented.

[0009] In an advantageous embodiment, it is proposed that before activating the preconditioning function of the internal combustion engine, a plurality of state data, in particular a current operating temperature of the internal combustion engine, an outside temperature threshold, a standby time of the plug-in hybrid vehicle and an oil level threshold of the internal combustion engine, are queried and processed, and that the activation of the preconditioning function is controlled on the basis of these state data.

[0010] Preferably, the preconditioning function of the internal combustion engine can be activated by querying an activation means, in particular a calendar memory, a set departure timer or a learned pattern obtainable by an artificial intelligence method.

[0011] In an advantageous embodiment, it is proposed that the preconditioning function of the internal combustion engine be activated during a charging process of the electrochemical storage device. In this case, the preheating advantageously has no effect on the range of the plug-in hybrid vehicle. Likewise, in another embodiment, it is also possible to heat the coolant autonomously using the electric heating element if this is connected to a power supply unit that is not intended for charging the electrochemical energy storage device.

[0012] Further features and advantages of the present invention will become clear from the following description of a preferred embodiment with reference to the enclosed Fig. Figure 1, which shows a schematically simplified representation of a drive system 1 of a plug-in hybrid vehicle, on the basis of which details of a method for operating such a drive system 1 are to be explained in more detail.

[0013] The drive system 1 of the plug-in hybrid vehicle comprises an internal combustion engine 2, which burns fossil fuels in a combustion process, and an electric machine 17, which enables the plug-in hybrid vehicle to be operated purely electrically for at least part of the journey. The drive system 1 also comprises an electrochemical energy storage device 3, which is designed using high-voltage technology and is configured to supply the electric machine 17 of the drive system 1 of the plug-in hybrid vehicle with electrical energy during operation.

[0014] The internal combustion engine (engine 2) always requires a certain operating time to reach its target operating temperature. During cold start phases, when the target operating temperature of the engine 2 has not yet been reached, a certain amount of fuel is introduced into the engine oil of the engine 2. In the case of intensive short-distance driving, the engine 2 of such a plug-in hybrid vehicle will not reach its target operating temperature on a significant number of journeys. As a result, an increasing amount of fuel can accumulate in the engine oil. This can lead to the driver receiving a low-level warning message, such as "Oil level too high." Furthermore, an excessive amount of fuel in the engine oil also leads to a deterioration of the engine oil's lubricating properties.This can, under certain circumstances, result in permanent damage to the internal combustion engine 2 due to insufficient lubrication.

[0015] The following describes a method and a system that are capable of achieving a targeted reduction of fuel entry into the engine oil of the internal combustion engine 2.

[0016] The drive system 1 of the plug-in hybrid vehicle includes a conditioning system 4, which is designed to condition the electrochemical energy storage device 3 appropriately by heating and, if necessary, also to heat the interior of the plug-in hybrid vehicle via an interior heating device 10. It is proposed to functionally extend and further develop this conditioning system 4 as described below so that it can also be used specifically for preconditioning a coolant of the internal combustion engine 2.

[0017] The conditioning system 4 has an electric heating element 5, which is preferably self-regulating and, in this embodiment, is designed as a PTC heating element (PTC resistor). The electric heating element 5 can be connected to a power supply. This was in Fig. 1 is symbolized by a corresponding electrical connection cable 6. This electrical connection cable 6 can, for example, be the charging cable by means of which the electrochemical energy storage device 3 of the drive system 1 of the plug-in hybrid vehicle can be connected to a power grid or a charging station for charging purposes. However, a separate connection cable 6 can also be provided to operate the electric heating element 5 independently and thus without simultaneously charging the electrochemical energy storage device 3.

[0018] The conditioning system 4 comprises a high-temperature island circuit 7, into which the electric heating element 5 is integrated to heat a coolant flowing through the high-temperature island circuit 7. The conditioning system 4 further comprises several valve elements 8a, 8b, 8c, and at least one pump device 9, which are also integrated into the high-temperature island circuit 7. A first fluid supply line 11 of the high-temperature island circuit 7 leads to the internal combustion engine 2 and can be selectively opened and subsequently closed again by means of a first valve element 8a for preconditioning the internal combustion engine 2. A second fluid supply line 12 leads to the electrochemical energy storage device 3 and can be selectively opened and subsequently closed by means of a second valve element 8b for conditioning the electrochemical energy storage device 3.Finally, in the embodiment shown here, a third fluid supply line 13 is provided, which leads to the interior heating device 10 and can be selectively opened or closed by means of the third valve means 8c, so that it is also possible to heat the interior of the plug-in hybrid vehicle.

[0019] Furthermore, the conditioning system 4 comprises a temperature control device 14, which is configured to control the electric heating element 5 (designed here as a PTC heating element), the valve elements 8a, 8b, 8c, and the at least one pump device 9. The preferably self-regulating electric heating element 5 allows, for example, electrical energy from the charging station to be introduced into the coolant of the high-temperature island circuit 7 during the charging process of the electrochemical energy storage device 3.

[0020] By selectively opening and closing the valve means 8a, 8b, 8c, the coolant flow to the internal combustion engine 2, the electrochemical energy storage device 3, and the interior heating device 10 can be controlled as desired. This allows for preconditioning of the internal combustion engine 2 and / or preconditioning of the electrochemical energy storage device 3 and / or heating of the interior of the plug-in hybrid vehicle.

[0021] The drive system 1 further comprises a central control unit 15, which is configured to control the operation of the internal combustion engine 2 and the electric machine 17 of the plug-in hybrid vehicle. In particular, the central control unit 15 activates or deactivates the internal combustion engine 2 and the electric machine 17. Furthermore, the central control unit 15 also controls the conditioning system 4 at a higher level.

[0022] The central control unit 15 incorporates a control logic that, among other things, determines a suitable timing to achieve the maximum effect when the internal combustion engine 2 is switched on. Switching on the internal combustion engine 2 does not necessarily have to occur immediately after disconnecting the electrical connection cable 6 from the external power supply unit, but can also occur after the plug-in hybrid vehicle has traveled a certain distance in purely electric mode. The control logic for preconditioning the internal combustion engine 2 is thus the responsibility of the central control unit 15, which then provides corresponding control signals to the temperature control unit 14.

[0023] Activating the preconditioning function of the internal combustion engine 2 includes, in particular, determining the current operating temperature of the internal combustion engine 2, which is detected using a coolant sensor, an outside temperature threshold, which is detected using an outside temperature sensor, a standby time of the plug-in hybrid vehicle and an oil level threshold of the internal combustion engine 2, and processing this and, if necessary, further data accordingly.

[0024] Preferably, the activation of the preconditioning function of the internal combustion engine 2 can also be coupled with a fuel input model, by means of which fuel input into the internal combustion engine 2 is modeled. If a fuel input threshold is exceeded in this fuel input model, the preconditioning is activated at each restart or after a fixed or definable number of starts of the internal combustion engine 2.

[0025] The frequency of activation of the preconditioning function can be determined from a query of an activation means coupled with the central control unit 15 of the plug-in hybrid vehicle, in particular a calendar memory 16, a set departure timer 18 or a learned pattern 19, which can take into account different usage patterns of the plug-in hybrid vehicle (daily commute on weekdays and different user behavior on weekends) and can be obtained, for example, by an artificial intelligence method, in particular by a trained artificial neural network.

[0026] Furthermore, in the case of critical values ​​of the fuel input model and a sufficient state of charge of the electrochemical energy storage device 3, activation of the preconditioning function of the internal combustion engine 2 is also conceivable independently of the charging operation of the electrochemical energy storage device 3.

[0027] The method presented here advantageously enables preconditioning of the internal combustion engine 2 of the plug-in hybrid vehicle by preheating the coolant, so that increased fuel entry into the engine oil of the internal combustion engine 2 can be effectively prevented and thus potentially inadequate lubrication of moving parts of the internal combustion engine 2 can be effectively prevented.

Claims

[1] Method for operating a drive system (1) of a plug-in hybrid vehicle, wherein the drive system (1) - an internal combustion engine (2), - an electric machine (17), - an electrochemical storage device (3) designed to supply the electric machine (17) with electrical energy, as well as - a conditioning system (4) designed for preconditioning the electrochemical storage device (3) and comprising an electric heating element (5), wherein a preconditioning function of the internal combustion engine (2) is activated before starting a journey and a coolant of the internal combustion engine (2) is preheated by a time-controlled activation of the electric heating element (5), characterized by, that the activation of the preconditioning function of the internal combustion engine (2) is coupled with a fuel input model by means of which a fuel input into the internal combustion engine (2) is modeled, wherein the preconditioning function of the internal combustion engine (2) is activated at each restart or at a fixed or to be fixed number of starts of the internal combustion engine (2) if a fuel input threshold is exceeded in this fuel input model. [2] Method according to claim 1, characterized by, that before activating the preconditioning function of the internal combustion engine (2), a plurality of state data, in particular a current operating temperature of the internal combustion engine (2), an outside temperature threshold, a standby time of the plug-in hybrid vehicle and an oil level threshold of the internal combustion engine (2), is queried and processed and the activation of the preconditioning function is controlled on the basis of these state data. [3] Method according to one of claims 1 or 2, characterized by , that the preconditioning function of the internal combustion engine (2) is activated by querying an activation means, in particular a calendar memory (16), a set departure timer (18) or a learned pattern (19) obtainable by an artificial intelligence method. [4] Method according to any one of claims 1 to 3, characterized by, that the preconditioning function of the internal combustion engine (2) is activated during a charging process of the electrochemical storage device (3).

Images