Method for operating a motor vehicle and propulsion system of a motor vehicle

Abstract

Method for operating a motor vehicle with a drive engine designed as an internal combustion engine, wherein the vehicle's speed and the actuation of a speed control device are detected and a driving mode is automatically selected, wherein above a minimum speed of a sailing mode, the sailing mode is selected if the speed control device is not actuated, characterized in that above a maximum speed of the sailing mode, which is in a range of 40 to 90 km / h, a coasting mode is selected if the speed control device is not actuated.

Description

[0001] The invention relates to a method for operating a motor vehicle with a drive motor designed as an internal combustion engine and to a drive system of such a motor vehicle.

[0002] The primary function of a motor vehicle's engine is to generate motive power, which is transmitted to at least one drive wheel to propel the vehicle. This engine is typically an internal combustion engine, such as a gasoline or diesel engine. Since an internal combustion engine consumes fuel even when running, without generating motive power, various methods have been proposed to reduce fuel consumption in driving situations where no motive power is required.

[0003] For example, WO 2010 / 121861 A1 discloses the ability to operate a vehicle in a driving mode, depending on the result of a plausibility check of an automatic speed or distance control function and / or other current vehicle operating or driving condition data. In this mode, the power transmission in the drivetrain is interrupted and the drive motor is operated at idle speed or even switched off. DE 102 21 701 A1 describes a "coasting mode" in which the vehicle drives or rolls in a disengaged state and the engine speed is approximately or exactly equal to the idle speed; the engine can be switched off if necessary. The coasting mode is selected when neither the accelerator nor the brake pedal is pressed; pressing the brake and / or accelerator pedal ends the coasting mode. However, the aforementioned methods are not optimal in all driving situations.

[0004] To decelerate a motor vehicle, particularly when driving downhill, the energy-consuming effect of the engine can be utilized when it is driven via the frictional connection with the drive wheels. Automated methods of this type are known, for example, from DE 603 ​​06 411 T2 and WO 2005 / 084995 A1. These methods are also not suitable for all driving situations, such as those that occur when a motor vehicle is coasting, depending on its speed.

[0005] The engine of a motor vehicle is typically also required to supply the vehicle's electrical systems with electrical energy via a generator. To ensure a continuous electrical power supply even when the engine is switched off while driving, a suitably adapted power supply system is necessary, which may include, for example, a larger battery and sophisticated control systems. This results in increased costs, added weight, and greater complexity.

[0006] The aforementioned processes can result in an increased time delay between a request for drive power and its provision by the drive system, or between this delay and a noticeable acceleration of the vehicle. This delay arises, for example, from the reaction times of sensors and actuators, the processing time of signals in processors, and data transmission. A significant contribution to this delay is due to the time required to restart the combustion engine after it has been switched off, particularly for establishing a connection between the starter motor and the combustion engine, for the starter and combustion engine to begin running, and for torque to build up. Depending on the magnitude of the delay and the driving situation, such a delay can irritate the driver.A related decline in responsiveness is not always acceptable.

[0007] The object of the present invention is to provide a method for operating a motor vehicle with a drive engine designed as an internal combustion engine, as well as a drive system for such a motor vehicle, whereby the aforementioned disadvantages are avoided as far as possible. In particular, it is the object of the present invention to provide a method and such a drive system in which fuel consumption is reduced without the need for complex adaptation of the energy supply system and without a significant deterioration in the response behavior of the drive system.

[0008] This problem is solved by a method and a drive system as specified in the independent claims.

[0009] According to the invention, a motor vehicle has a drive motor designed as an internal combustion engine. The drive system of the motor vehicle further comprises a drive train for transmitting the drive force generated by the internal combustion engine to at least one drive wheel, wherein the drive train has means for controlled establishment and interruption of the power transmission between the drive motor and the drive wheel, in particular an automatically actuated clutch. The drive train can also include a transmission, which can be designed as a manual or automatic transmission.

[0010] According to the invention, the current speed of the motor vehicle is detected. Furthermore, the actuation of at least one speed control device is detected, which may be, in particular, an accelerator pedal or a brake pedal, but also, for example, a control element of a cruise control system. Preferably, actuation of the accelerator pedal and actuation of the brake pedal are detected. In this way, the absence of actuation of the speed control device is also detected; that is, it is also detected when the driver of the motor vehicle does not actuate the accelerator and / or the brake pedal.

[0011] Based on the detected vehicle speed, whether or not the cruise control is engaged, and potentially other parameters, a driving mode is automatically selected for the vehicle. If the vehicle speed is below a maximum speed for a stationary mode, the stationary mode is selected, in which the vehicle's engine is stopped. In stationary mode, the power transmission between the engine and the drive wheels is interrupted, primarily by opening the automatically actuated clutch; in the case of an automatic transmission with a torque converter, the clutch in the drivetrain may also be engaged. The maximum speed for stationary mode can be zero, meaning that stationary mode is only activated when the vehicle is completely stopped.The maximum speed of the stationary mode can also be different from 0, for example, around 5 km / h, so that even at very slow speeds the vehicle is in stationary mode if the drive power of the engine is not needed to generate or maintain the vehicle's movement. This can be the case regardless of whether a brake pedal is pressed.

[0012] If the vehicle speed exceeds the minimum speed of a coasting mode, the coasting mode is selected if the cruise control is not engaged. In coasting mode, the internal combustion engine is idled, i.e., at least approximately at idle speed; the power transmission in the drivetrain is interrupted, in particular, the automatically actuated clutch is disengaged. The internal combustion engine can also be operated, at least temporarily, at a speed corresponding to the speed of an engine-side drive shaft of a transmission, thus enabling a smooth transition to a driving mode with the power transmission engaged. The minimum speed of the coasting mode is greater than the maximum speed of the stationary mode; for example, the minimum speed of the coasting mode is greater than approximately 8 km / h or, preferably, greater than approximately 15 km / h.

[0013] According to the invention, when the vehicle speed exceeds a maximum speed of the coasting mode and the cruise control is not engaged, i.e., in particular when the driver is neither pressing the accelerator nor the brake pedal, a coasting mode is selected. A minimum coasting speed is therefore, in particular, equal to the maximum speed of the coasting mode. The maximum coasting speed can be, for example, approximately 40 to 90 km / h, preferably approximately 50 km / h, but can also be, for example, 108 km / h. In coasting mode, the power transmission between the vehicle's drive motor and the drive wheel(s) is interrupted; the drive motor is stopped in coasting mode.

[0014] The method according to the invention can be advantageously used when a motor vehicle is coasting from an initial speed to a lower final speed or to a standstill. The method is also advantageous when driving downhill from a standstill or from an initial speed to a higher final speed. The method according to the invention can likewise be advantageously used when coasting downhill or, for example, in other driving situations where the accelerator pedal is not pressed.

[0015] In order to save fuel, it would be advantageous to switch off the combustion engine as often and for as long as possible; however, this would increase the time delay between a demand for driving power, for example by pressing the accelerator pedal, and a noticeable acceleration of the vehicle to a frequently unacceptable level.

[0016] According to the invention, it has been found that fuel-efficient operation of the motor vehicle can be achieved without a noticeable deterioration in responsiveness if the coasting mode is used in a speed range above the maximum speed of the sailing mode. This ensures that the drive motor is completely switched off in the upper speed range, while in the middle speed range the drive motor operates at idle. It has been found that in the upper speed range a time delay between a demand for drive power and the provision of the drive power can be tolerated to a greater extent than in the middle speed range.

[0017] For example, at speeds below approximately 80 km / h, a time delay of less than 100 ms is acceptable, while at speeds above approximately 150 km / h, a time delay of more than 300 ms can be tolerated without noticeably impairing responsiveness. At a standstill, a time delay of approximately 400 ms is acceptable. According to the invention, the time delay in a medium speed range is minimized by operating the drive motor in idle mode in this range. Therefore, no time is required to start the motor and bring it up to idle speed after a demand for drive power, for example, by pressing the accelerator pedal. Furthermore, the coasting mode in the medium speed range achieves fuel-efficient operation of the vehicle, while the rolling mode in the upper speed range achieves fuel-optimized operation.

[0018] According to the invention, the response behavior of the vehicle's drive system is optimized to promote fuel-efficient driving. Furthermore, in many cases, the electrical power supply remains unchanged, eliminating the need for complex modifications to the vehicle's electrical system. Thus, coasting and downhill driving are controlled in such a way that even with limited adjustments to the electrical system, a particularly fuel-efficient driving style is enabled without any significant impairment of the response behavior.

[0019] Advantageously, an electric starter can be connected to the vehicle's internal combustion engine while stationary and / or coasting, for example, by engaging a starter clutch or a starter motor. This means the electric starter is already engaged with the drive motor before switching to another driving mode, such as by pressing the accelerator pedal. Therefore, no time is required to connect the starter to the internal combustion engine when needed. This further improves the responsiveness of the drive system.

[0020] The maximum speed of the stationary mode can be equal to a minimum speed of the coasting mode, above which the coasting mode is selected if the speed control device is not activated. According to a preferred embodiment of the method according to the invention, however, the minimum speed of the coasting mode is greater than the maximum speed of the stationary mode, and a creep mode is selected at a driving speed above the maximum speed of the stationary mode and below a minimum speed of the coasting mode. In creep mode, there is a power transmission between the drive motor and the drive wheel(s) of the vehicle. Therefore, the drive motor runs in this mode, but at a speed corresponding to the low speed, which may also depend on the gear ratio of a transmission and, if applicable, on the slippage of a torque converter in an automatic transmission and the accelerator pedal position.This results in a particularly favorable throttle response.

[0021] As an alternative to engaging creep mode, according to a further embodiment of the inventive method, roll mode can also be selected at a driving speed above the maximum speed of stand mode and below a minimum speed of sailing mode, provided the speed control device is not activated. This results in a particularly fuel-efficient driving style.

[0022] According to a particularly preferred embodiment of the method according to the invention, a passive deceleration mode is selected when the vehicle speed is above the maximum speed of the stationary mode and below a minimum speed of the coasting mode, provided the cruise control is not engaged. In the passive deceleration mode, there is a power transmission between the drive motor and the drive wheel(s) of the vehicle; the fuel supply to the drive motor is interrupted. The drive motor runs at a speed above its idle speed. In this mode, the drive motor itself is used to decelerate the vehicle. Such a mode is known, for example, as "engine braking with overrun cut-off." The clutch of the electric starter is disengaged. The maximum speed of the passive deceleration mode can be, for example, approximately 30 to 70 km / h.The passive deceleration mode allows for a braking effect to be achieved in a simple and gentle manner, especially when the driver is not using either the accelerator or brake pedal.

[0023] The maximum speed of the stationary mode can be equal to the minimum speed of the passive deceleration mode. Advantageously, however, the minimum speed of the passive deceleration mode can be greater than the maximum speed of the stationary mode; in this case, the creep mode can be engaged when the driving speed is between the minimum speed of the passive deceleration mode and the maximum speed of the stationary mode.

[0024] Preferably, the speed control device includes a brake pedal, wherein an additional driving mode is selected when the brake pedal is pressed. This additional driving mode enables a particularly fuel-efficient driving style, even during deceleration initiated or supported by pressing the brake pedal, without requiring complex adjustments to the vehicle's electrical system. If a maximum speed is specified for the coasting mode, this also applies, in particular, to driving speeds above this speed.

[0025] In a particularly preferred configuration, the further driving mode is an active deceleration mode. In such a driving mode, the power transmission between the vehicle's drive engine and the drive wheel(s) is closed, and the fuel supply to the drive engine is interrupted. This driving mode therefore corresponds to the passive deceleration mode, except that the brake pedal is applied. The active deceleration mode can also be initiated by applying the brake pedal and then remain active until another driving mode is engaged, without the brake pedal being applied further.

[0026] Alternatively, the subsequent driving mode can also be configured such that the power transmission between the drive motor and the drive wheel(s) of the vehicle is interrupted and the drive motor is stopped. This corresponds to the coasting mode, except that the brake pedal is now applied, or, if the subsequent driving mode is initiated by applying the brake pedal, has already been applied. Preferably, the starter clutch of the electric starter is closed in this driving mode, so that the electric starter is connected to the drive motor and, when drive power is required, for example when the accelerator pedal is pressed, a particularly rapid start of the drive motor is enabled.

[0027] Alternatively, in the next driving mode, the power transmission between the drive motor and at least one drive wheel of the vehicle can be interrupted, and the drive motor can operate in neutral, i.e., essentially at idle speed. This corresponds to the coasting mode, except that here the brake pedal is simultaneously applied, or has been applied to initiate the next driving mode.

[0028] Alternatively, the driving mode can be configured such that the power transmission between the vehicle's drive motor and the drive wheel(s) is interrupted, in particular by opening an automatically actuated clutch in the drivetrain, and the drive motor is operated at a speed corresponding to the speed of a motor-side input shaft of the transmission. In this mode, a smooth restoration of the power transmission or a smooth engagement of the clutch is therefore possible.

[0029] Several or all of the aforementioned alternatives can also be executed sequentially, depending on the speed and, if applicable, other parameters. In particular, before re-establishing the power transmission between the drive motor and at least one drive wheel, the drive motor can be operated at a speed corresponding to the speed of a motor-side drive shaft of the transmission. This achieves a smooth transition between a driving mode without power transmission and a driving mode with power transmission between the drive motor and the drive wheel.

[0030] A drive system for a motor vehicle according to the invention comprises a drive motor and a drive train for transmitting a drive force to at least one drive wheel of the motor vehicle, in particular to the two drive wheels or, in the case of all-wheel drive vehicles, to all four drive wheels. The drive train includes an automatically actuated clutch for interrupting and engaging the power transmission between the drive motor and the at least one drive wheel. The drive train may further include a transmission, which may be, for example, a manual transmission, an automatic transmission with predefined gear ratios, or a continuously variable automatic transmission.

[0031] According to the invention, the drive system further comprises a control device for controlling the drive motor and the automatically actuated clutch, which is configured to carry out a method according to one of the preceding claims. For this purpose, the control device has, in particular, signal inputs for acquiring signals representing the vehicle's speed and the actuation of at least one speed control device, for example, an accelerator and / or brake pedal. Such signals are generally acquired for display to the driver or for controlling other systems and are available to the control device. The control device further comprises processor means for determining a driving mode depending on the vehicle speed and the actuation of the at least one speed control device, as well as control means for actuating the automatically actuated clutch, the internal combustion engine, and, if applicable, other systems.of the electric starter and the starter clutch. The control unit can also be integrated as part of the engine control system.

[0032] The invention is explained in more detail below with reference to the drawing. It shows:

[0033] Fig. 1 a compilation of driving strategies according to exemplary embodiments of the method according to the invention.

[0034] In Fig. Figure 1 shows five different driving strategies according to which a motor vehicle can be operated according to the invention and the vehicle's drive system can be controlled accordingly. The current driving speed of the motor vehicle is plotted at the top. The different strategies 1 to 5 are shown to the right, identified by the numbers above the corresponding column.

[0035] In all driving strategies, the drive system is controlled at speeds below v1, and especially when stationary, in such a way as to implement a static start / stop (SSS) mode. Static start / stop mode is characterized by an interrupted power transmission in the drivetrain; in an automatic transmission with a torque converter, the power transmission may be closed via the converter. The internal combustion engine that powers the vehicle is stopped in static mode; the engine's starter may be disconnected by opening the starter clutch. If power is requested by pressing the accelerator pedal, the engine is started by the starter, if necessary after the starter clutch engages, and the open clutch in the drivetrain is closed, or manual engagement of the clutch is enabled.

[0036] According to Strategy 1, above a vehicle speed v1, which corresponds to the maximum speed of stationary mode and the minimum speed of coasting mode, and below a vehicle speed v4, which corresponds to the maximum speed of coasting mode and the minimum speed of rolling mode, coasting mode (SAIL) is selected if neither the brake nor the accelerator pedal is applied. In coasting mode, the power transmission in the drivetrain is interrupted. The drive motor is running, specifically at idle speed. The starter is not connected to the drive motor. Above vehicle speed v4, rolling mode (RSS, "Rolling Start Stop") is engaged if neither the brake nor the accelerator pedal is applied. In rolling mode, the drive system is controlled by the control unit in such a way that the power transmission in the drivetrain is interrupted, for example by opening a clutch, and the drive motor is stopped.The starter can be connected to the drive motor, for example via a closed starter clutch or a geared starter, to start it when needed, such as when the accelerator pedal is pressed. Unlike in coasting mode, the drive motor is stopped in coasting mode. Coasting mode can be used up to a maximum vehicle speed v5. v5 can be the maximum achievable speed of the vehicle, but it can also be lower. There may be a difference between v5 and the maximum speed v. max Further strategies will be applied.

[0037] A transition from one driving mode to another can occur by changing the speed, for example, by decelerating while coasting or accelerating downhill. A driving mode can also be ended by pressing the accelerator or brake pedal, or by deactivating eco-driving settings via the vehicle's software or a control switch, such as the start / stop on / off switch. There can be several reasons why the mode might change, such as the activation of the aforementioned control switch, passenger comfort and / or climate settings, battery charge level, emissions control, altitude (above sea level) where the vehicle is operating, ambient temperature, engine temperature, and potentially, what slows down the restart process.

[0038] According to Strategy 2, the maximum speed v1 of the stationary mode corresponds to the minimum speed of the creep mode (CREEP); the maximum speed v2 of the creep mode is the minimum speed of the sailing mode. As shown in Fig. As can be seen from strategy 1, the creep mode is selected according to strategy 2, based on the minimum and maximum speeds of creep mode v1 and v2. In creep mode, the power transmission between the drive motor and the drive wheels is engaged, the drive motor is operating at a corresponding speed, and the starter is disconnected from the drive motor. Above the maximum speed v2 of creep mode, driving strategy 2 corresponds to driving strategy 1.

[0039] According to Strategy 3, if the vehicle speed is greater than the maximum speed v1 of stationary mode but less than the minimum speed v3 of coasting mode, a passive deceleration mode (DFSO passive, "Deceleration Fuel Shut Off") is engaged, provided the driver is not pressing the brake or accelerator pedal. In passive deceleration mode, the power transmission in the drivetrain is established by engaging the corresponding clutch, so that the engine runs at a speed corresponding to the current vehicle speed and the selected gear or drive stage, possibly taking into account the slippage of a torque converter in an automatic transmission. However, the fuel supply to the combustion engine is interrupted, resulting in engine deceleration, which, according to Driving Strategy 3, is used to control coasting and driving downhill.Preferably, the starter is not connected to the drive motor, but it could also be engaged. At a driving speed above v3, driving strategy 3 corresponds to strategy 1.

[0040] How Fig. As shown in Figure 1, strategy 4 corresponds to strategy 3 at a speed above v2. Below v2, which in this case represents the minimum speed of the passive deceleration mode, but above v1, the maximum speed of the stationary mode, strategy 4 selects the creep mode.

[0041] According to strategy 5, the roll mode is used both in the speed range between v1 and v2, i.e. between the maximum speed of the stationary mode and the minimum speed of the sailing mode, and in the speed range above v4, i.e. above the maximum speed of the sailing mode.

[0042] When stationary or at a very low speed of less than 5 km / h, a relatively long time delay between pressing the accelerator pedal and a noticeable acceleration is tolerable, for example, 400 ms. In such a driving situation, if neither the accelerator nor the brake pedal is pressed, the vehicle's engine is switched off and put into standby mode.

[0043] At speeds up to approximately 60 km / h, a time delay of about 70 to 80 ms is acceptable, and at speeds up to approximately 100 km / h, a delay of about 160 ms is acceptable without noticeably impairing the responsiveness of the drive system. In this speed range, it is therefore advantageous for the combustion engine to remain running even when no propulsion power is required. This is achieved through coasting or passive deceleration mode. This results in a restart delay that, in most cases, is no more than approximately 50 to 100 ms longer than the aforementioned values. In this way, fuel consumption is reduced without significantly impairing responsiveness.

[0044] At speeds above approximately 100 km / h, a greater time delay between pressing the accelerator pedal and a noticeable acceleration is tolerated, for example, approximately 260 ms at 150 km / h and 400 ms at 190 km / h. By using coasting mode in this speed range, a fuel-efficient driving style is achieved, while a time delay of up to 450 ms caused by restarting the drive motor is generally acceptable.

[0045] This results in an overall reduction in fuel consumption for the vehicle, without significantly impairing the responsiveness of the drive system. Furthermore, this minimizes the necessary adjustments for ensuring a reliable power supply to the electrical systems.

[0046] The speeds v1 to v5 do not have to be the same for all strategies. They can also depend on other parameters that characterize the specific driving situation. Each strategy can be designed so that when the driving speed equals a maximum or minimum speed, the driving mode corresponding to the lower or higher speed is selected. The speed at which a different driving mode is selected can also differ between the transition to a higher speed and the transition to a lower speed.

[0047] Each time the brake pedal is pressed, one of the following can occur: Fig. One driving mode (not shown) can be selected, for example, an active deceleration mode, which corresponds to the passive deceleration mode but includes additional braking action via the service brake. The selected driving mode can also depend on the current speed and, if applicable, on other vehicle parameters and the driving situation. Furthermore, the driver can switch to the mode shown, particularly by pressing the accelerator pedal. Fig. 1. Normal driving operation, which is also not shown, in which the motor vehicle is accelerated or kept at a constant driving speed, for example by a driving force generated according to the accelerator pedal position. QUOTES INCLUDED IN THE DESCRIPTION

[0048] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0049] WO 2010 / 121861 A1

[0003] DE 10221701 A1

[0003] DE 60306411 T2

[0004] WO 2005 / 084995 A1

[0004]

Claims

[1] Method for operating a motor vehicle with a drive engine designed as an internal combustion engine, wherein a driving speed of the motor vehicle and an actuation of a speed control device are detected and a driving mode is automatically selected, wherein above a minimum speed of a sailing mode, the sailing mode is selected if the speed control device is not actuated, thereby characterized t that above a maximum speed of the sailing mode, a roll mode is selected if the speed control device is not activated. [2] Method according to claim 1, characterized in that the stand mode is selected below a maximum speed of a stand mode. [3] Method according to claim 1 or 2, characterized in that an electric starter is connected to the internal combustion engine in stationary mode and / or in rolling mode. [4] Method according to one of the preceding claims, characterized in that above the maximum speed of the stationary mode and below a minimum speed of the sailing mode a creep mode is selected in which a force transmission exists between the drive motor and at least one drive wheel of the motor vehicle, or the rolling mode is selected. [5] Method according to one of the preceding claims, characterized in that above the maximum speed of the stationary mode and below a minimum speed of the sailing mode, when the speed control means is not actuated, a passive deceleration mode is selected in which there is a force transmission between the drive motor and at least one drive wheel of the motor vehicle and the fuel supply to the drive motor is interrupted. [6] Method according to one of the preceding claims, characterized in that below a minimum speed of the sailing mode, when the speed control means is not actuated, a passive deceleration mode is selected in which there is a frictional connection between the drive motor and at least one drive wheel of the motor vehicle and the fuel supply to the drive motor is interrupted, and that below a minimum speed of the passive deceleration mode and above the maximum speed of the stationary mode, a creep mode is selected in which there is a frictional connection between the drive motor and at least one drive wheel of the motor vehicle. [7] Method according to one of the preceding claims, characterized in that the speed control means comprises a brake pedal and that when the brake pedal is actuated, a further driving mode is selected. [8] Method according to the preceding claim, characterized in that the further driving mode is an active deceleration mode in which there is a force transmission between the drive motor and at least one drive wheel of the motor vehicle and the fuel supply to the drive motor is interrupted. [9] Method according to claim 7, characterized in that in the further driving mode a power transmission between the drive motor and at least one drive wheel of the motor vehicle is interrupted and the drive motor is stopped. [10] Method according to the preceding claim, characterized in that in the further driving mode an electric starter is connected to the internal combustion engine. [11] Method according to claim 7, characterized in that in the further driving mode a power transmission between the drive motor and at least one drive wheel of the motor vehicle is interrupted and the drive motor is operated in neutral. [12] Method according to claim 7, characterized in that in the further driving mode a power transmission between the drive motor and at least one drive wheel of the motor vehicle is interrupted and the drive motor is operated at a speed that corresponds to the speed of a motor-side drive shaft of a transmission. [13] Drive system of a motor vehicle, comprising a drive motor, a drive train for transmitting a drive force to at least one drive wheel of the motor vehicle, wherein the drive train has an automatically actuated clutch, and a control device for controlling the drive motor and the automatically actuated clutch, characterized in that the control device is configured to carry out a method according to one of the preceding claims.

Images