Method and device for controlling the glow behavior of a glow plug of an internal combustion engine used in a hybrid vehicle

Abstract

Method for controlling the glow behavior of a glow plug of an internal combustion engine which is used in a hybrid vehicle and in which the glow plug (2a to 2n) is activated before the internal combustion engine (12) is started in order to assist the ignition of a fuel-air mixture, characterized in that after the internal combustion engine (12) is switched off in order to restart the internal combustion engine (12) in the current driving cycle of the hybrid vehicle, in which the hybrid vehicle is operated by an additional motor (13), the glow plug (2a to 2n) is operated as a function of an operating parameter of the hybrid vehicle.

Description

State of the art

[0001] The invention relates to a method for controlling the glow behavior of a glow plug of an internal combustion engine which is used in a hybrid vehicle and in which the glow plug is activated before the start of the internal combustion engine in order to support the ignition of a fuel-air mixture, as well as to a device for carrying out the method.

[0002] To improve starting performance in a motor vehicle with an internal combustion engine, especially a diesel engine, glow plugs are installed in the cylinders of the internal combustion engine. These glow plugs are preheated by applying a glow voltage before the engine starts. This use of glow plugs not only improves the ignition behavior of the internal combustion engine, but also reduces fuel consumption and pollutant emissions. To correctly determine the voltage applied to the glow plug, a control sequence in the form of a state graph is calculated.

[0003] Such a state graph, implemented as software in an engine control unit or a glow plug control unit of a motor vehicle, currently does not take into account the use of the internal combustion engine in a hybrid vehicle. In such a hybrid vehicle, in addition to the internal combustion engine, an additional motor, preferably an electric motor, is provided, which drives the hybrid vehicle when the internal combustion engine is switched off. In hybrid applications, the internal combustion engine starts several times while the hybrid vehicle is driving. This operating state has not yet been provided for in the state graph. This results in problems in the clear detection and assignment of these states of the internal combustion engine, which has a detrimental effect on the voltage control of the glow plug, since this depends on the detected operating states of the internal combustion engine.

[0004] DE 10 2006 021 285 A1 describes a method for operating glow plugs, which have a housing and a glow element protruding beyond the housing, in a diesel engine. The glow plug control unit cooperates with an engine control unit and a glow plug control unit. Following a preheating phase, the glow plug control unit controls the electrical power supplied to the glow plugs depending on a command received from the engine control unit. The engine control unit determines a variable that is a measure of the temperature that should occur at the glow element and transmits this variable as a target to the glow plug control unit, which implements this target using an algorithm stored in the glow plug control unit and taking into account characteristic values ​​stored in the glow plug control unit.

[0005] DE 10 2007 014 677 A1 discloses a power supply control device for a glow plug of an internal combustion engine, which includes a post-start glow section for controlling the power supply of a resistance heater of the glow plug from a battery after the internal combustion engine has started. The post-start glow section is configured to evaluate the stability of the rotational behavior of the internal combustion engine and control the power supply of the resistance heater according to a first control pattern when the stability of the rotational speed of the internal combustion engine is greater than or equal to a threshold level, and to control the power supply of the resistance heater according to a second control pattern that achieves a higher temperature of the shell heater than the first control pattern when the stability of the engine rotational speed is lower than the threshold level.

[0006] DE 10 2008 024 863 A1 describes a hybrid drive system for a vehicle comprising a vehicle drive battery, an internal combustion engine, and an electric drive. The internal combustion engine and the electric drive provide traction drives and are configured for operative and selective connection to a transmission. The internal combustion engine includes a heater for preheating a selected portion of the internal combustion engine. The vehicle drive battery is connected to the heater and configured to supply the heater with electrical energy while the traction drives are off.

[0007] JP 2009-035226 A discloses a hybrid vehicle equipped with an engine with an exhaust gas purification device, a motor generator, and a battery, and configured to include an electric heater for heating all portions of the engine, including the exhaust gas purification device, by consuming generation power from a motor generator or storage power from a battery. The hybrid vehicle also has a control device that, when operation of the engine is necessary based on the required driving power of the vehicle and the remaining capacity of the battery, performs conduction control of the electric heater before and after the engine start, and controls the drive and power generation of the engine and the motor generator based on the required driving power of the vehicle and the remaining capacity and the temperature state of each portion of the engine. Disclosure of the invention

[0008] The invention is therefore based on the object of specifying a method and a device for controlling the glow behavior of a glow plug of an internal combustion engine in a hybrid vehicle, in which all conceivable operating states of the internal combustion engine in a hybrid vehicle are correctly taken into account when controlling the voltage of the glow plug.

[0009] According to the invention, this problem is solved by operating the glow plug depending on an operating parameter of the hybrid vehicle after the internal combustion engine is shut down to restart the internal combustion engine during the ongoing driving cycle of the hybrid vehicle, in which the hybrid vehicle is powered by an auxiliary engine. Checking the operating parameters ensures that the glow plugs always have an operating state that ensures stable combustion of the fuel-air mixture when the internal combustion engine is restarted.

[0010] Advantageously, the operating parameter is a vehicle speed and / or a battery condition and / or a cooling water temperature of the combustion engine. Based on at least one of these operating parameters, a reliable estimate can be made of when it is necessary to restart the combustion engine and thus activate the glow plugs.

[0011] In one embodiment, after the combustion engine is shut down and the hybrid vehicle is driven solely by the auxiliary motor, preferably an electric motor, the glow plug enters a first standby state in which the glow plug is deactivated and in which a decision is made as to whether the glow plug should be activated. In this state, no glow voltage is generated to control the glow plug, thus reducing the load on the vehicle battery.

[0012] In one embodiment, the glow plug remains switched off after the immediate restart of the combustion engine or enters an afterglow mode. The decision as to whether the glow plug remains switched off or enters an afterglow mode after the immediate restart of the combustion engine depends on the operating parameters of the hybrid vehicle.

[0013] In one variant, after the combustion engine is shut down and the hybrid vehicle is powered solely by an auxiliary motor, the glow plug enters a second standby state, in which it remains activated for a specified period of time. During this specified time, a defined voltage is applied to the glow plug to ensure that the glow plug is preheated when the combustion engine is restarted, thus immediately initiating stable combustion of the fuel-air mixture.

[0014] In one embodiment, when the combustion engine is restarted within the specified time period, the glow plug enters afterglow or is deactivated. Here, too, the current operating parameters of the hybrid vehicle determine whether afterglow is necessary or whether the glow plug remains deactivated.

[0015] The glow plug is advantageously operated when a restart of the combustion engine is expected. The restart time is determined by the engine control unit or the glow time control unit, which also controls the activation of the glow plug with the glow voltage. The glow plug is heated up so that at the time the combustion engine restarts, it has the correct temperature, which reliably initiates the combustion process of the fuel-air mixture.

[0016] A further development of the invention relates to a method for controlling the glow behavior of a glow plug of an internal combustion engine used in a hybrid vehicle, in which the glow plug is activated before the internal combustion engine starts in order to assist the ignition of a fuel-air mixture. In order to take all conceivable operating states of the hybrid vehicle into account when controlling the voltage of the glow plug, after the internal combustion engine is switched off and simultaneously disconnected from a drive train for the immediate restart of the internal combustion engine during the ongoing driving cycle of the hybrid vehicle, in which the hybrid vehicle is powered by an auxiliary engine, the glow plug is placed in a state intended for start-stop operation of the internal combustion engine.The state of the rolling hybrid vehicle, in which the combustion engine is switched off and simultaneously decoupled from the hybrid vehicle's drivetrain, is equated with the state of the combustion engine when the vehicle is stopped, for example, at a traffic light. In both of these states, it is assumed that the combustion engine will be restarted as quickly as possible. The start-stop state of the glow plug is thus applied not only when stopping the combustion engine when the vehicle is stationary, but also when stopping the combustion engine when the vehicle is moving.

[0017] In another embodiment, the glow plug is deactivated despite the immediate restart of the combustion engine or enters afterglow mode. The activation or deactivation of the glow plug is determined depending on the operating parameters of the hybrid vehicle.

[0018] Another development of the invention relates to a device for controlling the glow behavior of a glow plug of an internal combustion engine used in a hybrid vehicle, in which the glow plug is activated before the internal combustion engine starts to assist the ignition of a fuel-air mixture. In order to always be able to control the internal combustion engine with a correct glow voltage to generate a required ignition temperature for the fuel-air mixture under all conceivable operating conditions, means are provided which, after the internal combustion engine has been switched off, operate the glow plug depending on an operating parameter of the hybrid vehicle in order to restart the internal combustion engine during the ongoing driving cycle of the hybrid vehicle, in which the hybrid vehicle is powered by an auxiliary motor.This timely preheating of the glow plug ensures reliable combustion of the fuel-air mixture when the combustion engine starts.

[0019] A further development of the invention relates to a device for controlling the glow behavior of the glow plug of an internal combustion engine used in a hybrid vehicle, in which the glow plug is activated before the internal combustion engine is started in order to assist the ignition of a fuel-air mixture. In order to always be able to control the glow plug with the required glow voltage in all conceivable operating states of the hybrid vehicle, means are provided which, after the internal combustion engine has been switched off and simultaneously disconnected from a drive train in order to restart the internal combustion engine during the ongoing driving cycle of the hybrid vehicle in which the hybrid vehicle is operated by an additional engine, place the glow plug into a state which is provided for start-stop operation of the internal combustion engine, in which the glow plug is preferably deactivated.The vehicle condition in which the combustion engine is switched off and, in contrast to the condition known as coasting, the drivetrain is also disengaged as soon as the driver releases the accelerator pedal, is referred to as "sailing." Ancillary units such as the power steering, brake booster, and the like are operated purely electrically in this "sailing" driving condition. Taking this "sailing" vehicle condition into account covers the possible need for glow plug operation.

[0020] The invention permits numerous embodiments. One of these will be explained in more detail with reference to the figures shown in the drawing.

[0021] It shows: Fig. 1: Schematic diagram of a glow system in a hybrid vehicle Fig. 2: a sequence control for a control unit of a hybrid vehicle for glow time control.

[0022] Cold internal combustion engines, especially diesel engines, require starting assistance at ambient temperatures below 40°C to ignite the fuel-air mixture introduced into the combustion engine. Glow systems are used as starting aids. These consist of glow plugs, a glow-time control unit, and glow-time software stored in an engine control unit or the glow-time control unit. Glow systems are also used to improve hybrid vehicle emissions. Other applications for glow systems include burner exhaust systems, auxiliary heating, fuel preheating (flex-fuel), and coolant preheating.

[0023] Fig. Figure 1 shows such a glow system 1 for a hybrid vehicle, which is connected via an engine control unit 7 to the internal combustion engine 12 and the auxiliary motor 13, which is designed as an electric motor. The glow system 1 has several glow plugs 2a to 2n, each of which extends into a cylinder of a combustion chamber (not shown) of the internal combustion engine 12. The glow plugs 2a to 2n are identically constructed and represent conventional low-voltage glow plugs. Fig. 1, the glow plugs 2a to 2n are shown as equivalent resistance for the sake of simplicity, which leads to the mass 3 of the combustion engine 12.

[0024] The glow plugs 2a to 2n are connected to the glow time control unit 4, which has a power semiconductor 5a to 5n for each glow plug 2a to 2n. The glow time control unit 4 comprises a microcontroller and / or ASIC 4a for processing incoming and outgoing signals. Furthermore, an on-board power supply 6 is connected to the glow time control unit 4, which supplies the glow plugs 2a to 2n with the required effective voltage via the power semiconductors 5a to 5n. The glow time control unit 4 leads to the engine control unit 7, which is connected to the combustion engine 12 and the auxiliary motor 13, which is designed as an electric motor. The engine control unit 7 and the glow time control unit 4 have an interface. This interface can consist of either a single-wire or a two-wire connection 10, 11.Data is exchanged between the engine control unit 7 and the glow plug control unit 4 via this interface, which is used for both the control of the glow plug control unit 4 and diagnostic communication. The glow plug control unit 4 transmits a pulse-width modulated output signal to the glow plugs 2a to 2n via the power semiconductors 5a to 5n. This output signal sets the required glow plug control voltage at the respective glow plug 2a to 2n.

[0025] In Fig.2 shows a control sequence for determining correct glow plug activation of the glow plugs 2a to 2n, which is also referred to as a state graph. Such a state graph is contained either in the engine control unit 7 or in the glow time control unit 4. The state graph is divided into two groups, with group 14 containing all states that do not require glow plugs 2a to 2n to glow, while group 15 includes all states of the internal combustion engine 12 that require glow plugs 2a to 2n to glow. In an initialization step 40, the activation process of the glow plugs 2a to 2n is started. In step 50, the system waits for information about the temperature of the internal combustion engine 12.If the initialization is triggered by signals that do not directly intervene in the ignition electronics of the motor vehicle, such as the opening of the vehicle door or the occupancy of a vehicle seat, the system proceeds from step 50 to step 60 in group 15, where a predetermined period of time is waited before the preheating of the glow plugs 2a to 2n is started in step 70.

[0026] If, after a predetermined time has elapsed since preheating began in step 70, the internal combustion engine 12 has not yet started, the system proceeds to a standby glow in step 80. If the internal combustion engine 12 does not start, the standby glow is aborted in step 90. The standby glow in step 80 is a standby function that enables immediate starting of the internal combustion engine 12. After a certain time has elapsed, during which the internal combustion engine 12 has not been started, the system proceeds to a non-preheating state in step 90, which is located in group 14, where the control of the glow plugs 2a to 2n is interrupted.

[0027] However, if the internal combustion engine 12 is started, the process proceeds from subgroup 100, which comprises steps 60, 70 and 80, to step 150 of group 15 for afterglow or to step 160 of group 14 for deactivating the glow plugs 2a to 2n. From this point on, the combustion of the fuel-air mixture in the internal combustion engine 12 takes place. However, if the internal combustion engine 12 that has already been started is switched off again, a distinction is made in group 14 as to whether the switching off of the internal combustion engine 12 occurs due to the motor vehicle coming to a stop, for example at a traffic light, which is taken into account in step 120, or whether it is due to a sudden "stalling" of the internal combustion engine 12, which is taken into account in step 130 of group 15.Both after stopping at the traffic light in step 120 and after the sudden stalling of the internal combustion engine 12 in step 130, it is assumed that the internal combustion engine 12 will be restarted as quickly as possible.

[0028] However, it is also possible to proceed from step 130 to step 110, in which no afterglow activities of the glow plugs 2a...2n take place, or to step 50, in which preheating of the glow plugs 2a...2n is started depending on the cooling water temperature of the internal combustion engine 12.

[0029] In step 110 of group 14, it is provided that no afterglow activities of the glow plugs 2a to 2n occur when the internal combustion engine 12 is stopped. This step 110 leads to step 50, where the temperature of the internal combustion engine 12 is determined, depending on which temperature the control sequence of the glow plugs 2a to 2n is tracked in the manner explained.

[0030] Based on steps 70, 80, or 120, a decision is made as to whether post-glow of the glow plugs 2a to 2n is necessary, which is provided in step 150 of group 15, or whether such post-glow can be omitted in step 160 of group 14. Depending on the current operating state of the internal combustion engine 12, it is then determined whether step 150 or step 160 is implemented.

[0031] If the internal combustion engine 12 is in an operating state in which no start is performed, which is provided in step 190 and thus does not require afterglow, after a certain time has elapsed, the afterglow interruption is switched to a complete shutdown of the glow state of the glow plugs 2a to 2n in step 160 of group 14. The afterglow time has thus expired and the sequence control of the glow plugs 2a to 2n is completed.

[0032] In a state occurring outside the normal control sequence of the internal combustion engine 12, the generator is started in step 170 by increasing the load. In this case, a high electrical power is drawn from the battery 6 for the operation of the internal combustion engine 12, which is why intermediate glowing of the glow plugs 2a to 2n is necessary. In step 180, the glowing of the glow plugs 2a to 2n is considered when the internal combustion engine 12 is in overrun mode. If necessary, the program returns to step 170 when the internal combustion engine 12 is restarted, where intermediate glowing of the glow plugs 2a to 2n takes place.

[0033] The following considers the hybrid vehicle, which is powered by the internal combustion engine 12 and / or the auxiliary motor 13 in only one driving cycle. A driving cycle is understood to be the period from the start of the hybrid vehicle to the shutdown of the hybrid vehicle. If the internal combustion engine 12 is stopped during the current driving cycle, a first standby state is first assumed in step 200 in group 15. In step 200, it is assumed that the hybrid vehicle will now continue to be powered solely by the auxiliary motor 13 and that the driving cycle, once begun, will be continued. In this step 200, a defined glow voltage is applied to the glow plugs 2a to 2n for a predetermined time so that the internal combustion engine 12 can be restarted with warm glow plugs 2a to 2n.

[0034] If the internal combustion engine 12 is restarted in the same driving cycle without this defined, predefined time having elapsed, the system proceeds to step 160 of group 14, where the glow plugs 2a to 2n are not heated before the internal combustion engine 12 begins to rotate. Alternatively, the system can also proceed to step 150, where the glow plugs 2a to 2n are post-heated. Once the time has elapsed, a transition to a second standby state occurs in step 210 in group 14. In this step, the glow plugs 2a to 2n are deactivated.

[0035] Alternatively, it is also possible, after stopping the internal combustion engine 12 and driving the motor vehicle only with the aid of the auxiliary motor 13, to immediately transition to the second standby state in step 210 of group 14, wherein the glow plugs 2a to 2n are immediately deactivated. If the internal combustion engine 12 is now restarted from step 210, the process proceeds to step 160, in which no glow process of the glow plugs 2a to 2n takes place, or to step 150 of group 15, where afterglow takes place. The decision as to whether to proceed to step 150 or step 160 is made depending on the current operating parameters of the hybrid vehicle. These operating parameters include, for example, the charge state of a high-voltage battery (not shown in detail), by means of which the auxiliary motor 13 designed as an electric motor is operated.If the charge level is too low, the hybrid vehicle must be driven by the internal combustion engine 12 for a foreseeable period of time. Since the combustion of the fuel-air mixture must be stable when the internal combustion engine 12 restarts, the glow plugs 2a to 2n are reheated in step 150. If, when checking the current operating parameters, it is determined that the hybrid vehicle can be driven by the auxiliary engine 13 for a foreseeable period of time, the system proceeds to step 160, where the glow plugs 2a to 2n are deactivated.

[0036] In addition to the state of charge of the high-voltage battery, the vehicle speed or the cooling water temperature of the combustion engine 12 can be used as operating parameters as decision criteria.

[0037] If the engine control unit 7, which controls both the internal combustion engine 12 and the auxiliary engine 13, reports that the internal combustion engine 12 will be started in the near future, assuming a period of approximately 12 seconds, a transition to subgroup 100 for preheating the glow plugs 2a to 2n occurs immediately. In step 70 of subgroup 100, the glow plugs 2a to 2n are heated so that the correct temperature of the glow plugs 2a to 2n is present when the internal combustion engine 12 is restarted.

[0038] The case in which, during an ongoing driving cycle of the hybrid vehicle, not only the combustion engine 12 is stopped but also disconnected from the drive train is referred to as the "sailing" vehicle state. Once the hybrid vehicle has assumed this driving state, it proceeds to step 120 in group 14. As already explained, starting from step 120, a decision is made as to whether post-glow of the glow plugs 2a to 2n is necessary, which is provided for in step 150 of group 15, or whether such post-glow can be omitted in step 160 of group 14.

[0039] Based on the above explanations, the operating conditions that occur in the internal combustion engine 12 when used in a hybrid vehicle are also reliably taken into account when controlling the glow plugs 2a to 2n. In particular, the driving conditions of the hybrid vehicle in which the internal combustion engine 12 is repeatedly restarted within the same driving cycle of the hybrid vehicle are taken into account.

Claims

[1] Method for controlling the glow behavior of a glow plug of an internal combustion engine used in a hybrid vehicle, in which the glow plug (2a to 2n) is activated before the start of the internal combustion engine (12) in order to assist the ignition of a fuel-air mixture, characterized by that after switching off the internal combustion engine (12) for restarting the internal combustion engine (12) in the current driving cycle of the hybrid vehicle, in which the hybrid vehicle is operated by an additional motor (13), the glow plug (2a to 2n) is operated as a function of an operating parameter of the hybrid vehicle. [2] Method according to claim 1 characterized by that the operating parameter is a vehicle speed and / or a battery state and / or a cooling water temperature. [3] Method according to claim 1 or 2, characterized bythat after the internal combustion engine (12) has been switched off and the hybrid vehicle is driven solely by the additional motor (13), preferably an electric motor, the glow plug (2a to 2n) changes into a first standby state in which the glow plug (2a to 2n) is deactivated and in which a decision is made about activating the glow plug (2a to 2n). [4] Method according to claim 3, characterized by that the glow plug (2a to 2n) remains switched off after the combustion engine (12) has been restarted or goes into afterglow. [5] Method according to claim 1 or 2, characterized by that after the internal combustion engine (12) is switched off and the hybrid vehicle is driven solely by the additional motor (13), the glow plug (2a to 2n) changes into a second standby state in which the glow plug (2a to 2n) remains activated for a predetermined period of time. [6] Method according to claim 5, characterized bythat when the internal combustion engine (12) is restarted within the specified period of time, the glow plug (2a to 2n) switches to afterglow or is deactivated. [7] Method according to at least one of the preceding claims, characterized by that the glow plug (2a to 2n) is operated when a restart of the combustion engine (12) is expected. [8] Method for controlling the glow behavior of a glow plug of an internal combustion engine used in a hybrid vehicle, in which the glow plug (2a to 2n) is activated before the start of the internal combustion engine (12) in order to assist the ignition of a fuel-air mixture, characterized bythat after switching off the internal combustion engine (12) and simultaneously disconnecting the internal combustion engine (12) from a drive train for restarting the internal combustion engine (12) in the current driving cycle of the hybrid vehicle, in which the hybrid vehicle is operated by an additional motor (13), the glow plug (2a to 2n) is placed in a state which is provided for in a start-stop operation of the internal combustion engine (12). [9] Method according to claim 8, characterized by that in order to restart the combustion engine (12) the glow plug (2a to 2n) is deactivated or goes into afterglow. [10] Device for controlling the glow behavior of a glow plug of an internal combustion engine used in a hybrid vehicle, in which the glow plug (2a to 2n) is activated before the start of the internal combustion engine (12) in order to assist the ignition of a fuel-air mixture, characterized bythat means (4, 7) are provided which, after the internal combustion engine (12) has been switched off, operate the glow plug (2a to 2n) in dependence on an operating parameter of the hybrid vehicle in order to restart the internal combustion engine (12) in the current driving cycle of the hybrid vehicle, in which the hybrid vehicle is operated by an additional motor (13). [11] Device for controlling the glow behavior of a glow plug of an internal combustion engine used in a hybrid vehicle, in which the glow plug (2a to 2n) is activated before the start of the internal combustion engine (12) in order to assist the ignition of a fuel-air mixture, characterized bythat means (4, 7) are provided which, after the internal combustion engine (12) has been switched off and the internal combustion engine (12) has been simultaneously disconnected from a drive train in order to restart the internal combustion engine (12) in the current driving cycle of the hybrid vehicle, in which the hybrid vehicle is operated by an additional motor (13), put the glow plug (2a to 2n) into a state which is provided for a start-stop operation of the internal combustion engine (12), in which the glow plug (2a to 2n) is preferably deactivated.

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