Method for controlling an oil supply during driving of a motor vehicle and a drive train for a motor vehicle

Abstract

Method for controlling a drive train during driving of a motor vehicle with a switched-off internal combustion engine for an automatic transmission or an automated transmission having a hydraulic switching arrangement, wherein in a first step (2) a request to switch off the internal combustion engine is sent to a control unit, in a second step (8) a frictional connection is interrupted by means of a hydraulically actuated clutch arrangement between the internal combustion engine and the transmission, in a third step (2) the internal combustion engine is switched off and the motor vehicle is operated with the internal combustion engine switched off, that is to say in coasting mode, in a fourth step (14) a request to switch on the internal combustion engine is sent to the control unit,in a fifth step (24) the internal combustion engine is started and in a sixth step (28) the power connection is established by means of the clutch arrangement between the internal combustion engine and the transmission, characterized in that in the second step (10) in the control unit based on vehicle data (6), such as gradient, speed, rolling resistance, driving resistance, etc., drive train data, such as gear ratio, speeds, etc., route information, such as altitude, driving line, etc., at least one coasting gear is calculated and this is engaged after the interruption of the power flow by means of the circuit arrangement.

Description

[0001] The invention relates to a method for controlling a drive train during driving of a motor vehicle with a switched-off internal combustion engine for an automatic transmission or an automated transmission having a hydraulic switching arrangement, wherein in a first step a request to switch off the internal combustion engine is sent to a control unit, in a second step a frictional connection is interrupted by means of a hydraulically actuated clutch arrangement between the internal combustion engine and the transmission, in a third step the internal combustion engine is switched off and the motor vehicle is operated with the internal combustion engine switched off, that is to say in coasting mode, in a fourth step a request to switch on the internal combustion engine is sent to the control unit,In a fifth step, the internal combustion engine is started and in a sixth step, the power connection is established by means of the clutch arrangement between the internal combustion engine and the transmission.

[0002] Furthermore, the invention relates to a drive train for a motor vehicle with an internal combustion engine with an automatic transmission or an automated transmission having a hydraulic switching arrangement, with a hydraulically actuated clutch arrangement and with a control unit which controls the driving operation of a motor vehicle with the internal combustion engine switched off.

[0003] To save fuel, the power transmission can be opened during normal driving conditions—for example, when driving in a convoy, downhill, at a constant speed, or while the vehicle is rolling—to decouple the engine's gas exchange losses from the vehicle. This technique is well known and is referred to below as coasting. For this purpose, all power-carrying clutches are opened in both automatic and automated transmissions. Due to the reduced thrust torque of the combustion engine, or the electric drive motor in an electrically powered vehicle, the vehicle continues to roll with minimal losses and low deceleration values.

[0004] To further optimize consumption, it is also known to switch off the internal combustion engine while coasting, as is known, for example, from DE 10 2010 024 045 A1, in order to also save idle consumption. However, this poses the problem that a transmission oil pump driven by the internal combustion engine, which is used to supply oil to the hydraulic circuit arrangement, the hydraulically actuated clutch arrangement, and to lubricate and cool the clutch arrangement, can no longer provide the necessary pressurized oil in the individual circuits. DE 10 2005 013 137 A1 or US 2012 / 0135841 A1 therefore disclose the use of an electrically driven auxiliary oil pump, which is intended to ensure the supply of pressurized oil even when the internal combustion engine is switched off. However, the use of such an auxiliary oil pump is expensive and complex in terms of design.Furthermore, such a solution requires complex cabling with sealing systems, which poses assembly challenges, especially in confined spaces. Furthermore, DE 10 2010 039 173 A1 discloses monitoring the supply status of the gearbox with lubricating oil and / or cooling oil and changing the operating mode in the event of an insufficient supply. This solution also requires considerable control effort and additional monitoring resources. Furthermore, changing the operating mode can be disruptive to the user.

[0005] The invention is therefore based on the object of providing a method for controlling an oil supply during driving of a motor vehicle and a drive train for a motor vehicle, whereby the above-mentioned disadvantages are avoided.

[0006] This problem is solved by a method for controlling an oil supply. In a second step, the control unit calculates at least one coasting gear based on vehicle data such as gradient, speed, rolling resistance, driving resistance, etc., drive train data such as gear ratio, engine speeds, etc., and route information such as altitude, driving line, etc., and this is engaged by the circuit arrangement after the power flow has been interrupted. Although this causes a slightly small drag torque, the advantage of the performance when restoring the power connection outweighs this, which means that an additional electric pump can be easily dispensed with. In principle, the journey can be continued with the coasting gear engaged even after the combustion engine has been switched on.Advantageously, a quick and convenient restoration of the traction from sailing operation without a combustion engine is therefore necessary, even without an additional pump.

[0007] Advantageously, however, a new gear can be calculated before the fifth step, and the gearshift arrangement and / or the clutch arrangement can be hydraulically filled by means of a starting or revving process, and the gear can be engaged after the fifth step if necessary. In this case, the gear is optimally adapted to the new driving situation and ensures maximum comfort when restarting the internal combustion engine and thus, in particular, during the subsequent renewed power connection via the clutch arrangement between the internal combustion engine and the transmission. To shorten the reconnection time when the engine is started, the valves of the hydraulic control unit are electrically controlled before or during starting, so that the first pumped oil is diverted to the corresponding actuators.

[0008] Advantageously, the clutch(es) are flooded with a cooling oil volume flow pulse before the third step in order to ensure optimal initial lubrication of the clutch plates before sailing operation.

[0009] Particularly advantageously, the automated transmission is designed as a dual-clutch transmission, with one and / or two gears of the dual-clutch transmission being calculated and engaged as coasting gear(s). This provides the greatest possible flexibility for reconnecting the internal combustion engine. Depending on the driving situation and speed, one or two gears can be engaged.

[0010] Advantageously, the drive gear can be synchronized before the sixth step by briefly actuating the clutch assembly. This allows a free drive shaft to be accelerated toward the engine speed.

[0011] The object is also achieved by a drive train for a motor vehicle, wherein the control unit has means which calculate a coasting gear based on vehicle data, such as gradient, speed, rolling resistance, driving resistance, etc., drive train data, such as gear ratio, speeds, etc., route information, such as altitude, driving line, etc.

[0012] In a particularly advantageous manner, the automated transmission is designed as a dual-clutch transmission. Furthermore, in dual-clutch transmissions without oil chamber separation or in automated transmissions with splash lubrication, it is advantageous to provide oil collection pockets, a splash lubrication system, or mechanically driven wheel-side lubricating oil pumps for splash oil supply.

[0013] The invention is explained in more detail below with reference to the drawing. Herein: Fig. 1 a flow diagram for controlling a drive train when driving a motor vehicle with the internal combustion engine switched off, and Fig. 2 a diagram of the speed of the transmission shaft and the internal combustion engine over time.

[0014] To save fuel, a vehicle's internal combustion engine can be switched off during normal driving, for example, when coasting or driving downhill. To do this, all power-carrying clutches must be disengaged in vehicles with automatic transmissions or automated transmissions, including dual-clutch transmissions. The transmission has a hydraulic shifting arrangement, and the respective clutch is also hydraulically actuated.

[0015] The flow chart of the Fig. 1 shows the method according to the invention. Upon a driver request or a control unit specification, a request to shut down the internal combustion engine is sent to the control unit via an operation block 2. In a decision block 4, the fundamental decision is then made as to whether to initiate coasting mode or to continue driving with the internal combustion engine switched on. In the following, it is assumed that coasting mode should be initiated. Based on vehicle data 6, such as the current gradient, the current speed, the existing rolling resistance, and the existing driving resistance, as well as drivetrain data, such as gear ratio, possible engine speeds, etc., and available route information, such as elevation, route line, etc., the control unit calculates the desired value for the desired value., a coasting gear is calculated, which is engaged (identified by block 10) after the interruption of a power connection by means of the hydraulically actuated clutch arrangement between the internal combustion engine and the clutch arrangement (represented by block 8). Then, in a third step (identified by block 12), the internal combustion engine is switched off and the vehicle is operated in coasting mode. If the driver or the control unit now sends a request to switch on the internal combustion engine to the control unit (as represented by block 14), the coasting mode can generally be exited using decision block 16, as shown.

[0016] In the present exemplary embodiment, a driving gear is advantageously calculated, indicated by block 18, which, depending on the driving situation, can correspond to the previous coasting gear or a new gear to be engaged. The internal combustion engine is then to be started with this driving gear in a later step. Data such as a shifting strategy, vehicle data, drivetrain data, or even route information can also be stored in the control unit for calculating the driving gear; here, this data is indicated by data block 20.

[0017] Advantageously, when the internal combustion engine is switched off, the clutch or clutches in a dual-clutch transmission can also be flooded by a cooling oil volume flow pulse in order to ensure optimal initial lubrication of the clutch plates.

[0018] After the gear calculation, in the present exemplary embodiment, the gearshift arrangement and the clutch arrangement are hydraulically filled by means of a starting or revving process (block 22), in order to then directly engage the calculated gear after starting the internal combustion engine (block 24), represented by block 26. Finally, when the target speed of the internal combustion engine is reached (block 28), the clutch arrangement is hydraulically actuated, whereby a frictional connection is established between the transmission and the internal combustion engine.

[0019] The drive train according to the invention for a motor vehicle with an internal combustion engine, an automatic transmission or an automated transmission, which has a hydraulic switching arrangement, a hydraulically actuated clutch arrangement, and a control unit that controls the driving operation of a motor vehicle with the internal combustion engine switched off, has, according to the invention, a control unit with means that calculate a coasting gear based on vehicle data, such as gradient, speed, rolling resistance, driving resistance, etc., drive train data, such as gear ratio, speeds, etc., and route information, such as altitude, driving lines, etc. The time sequence when climbing from such a coasting mode is now shown Fig.2. Here, 30 denotes the speed of the internal combustion engine, 32 the speed of a transmission shaft, 34 the engagement process of a shift rod, and 36 the clutch closing process. At time t0, the information for restarting the internal combustion engine is available. Here, the speed of the internal combustion engine is denoted by 30. The speed of the transmission shaft is denoted by 32, and the movement of a shift rod is denoted by 34. Sailing operation was carried out with sailing gear 1. Up to time t1, the internal combustion engine is started, whereby the clutch assembly is hydraulically filled. The filling process of the clutch assembly is denoted by 36. At t SDue to the preloaded clutch assembly, a brief actuation of the clutch assembly, also known as synchronous assistance, takes place, which is completed at t2. Afterward, at t3, the clutch can be opened again until the clutch is closed again at t4 and the transmission shaft, with the engaged gear, has the same speed as the internal combustion engine.

Claims

[1] Method for controlling a drive train during driving of a motor vehicle with a switched-off internal combustion engine for an automatic transmission or an automated transmission having a hydraulic switching arrangement, wherein in a first step (2) a request to switch off the internal combustion engine is sent to a control unit, in a second step (8) a frictional connection is interrupted by means of a hydraulically actuated clutch arrangement between the internal combustion engine and the transmission, in a third step (2) the internal combustion engine is switched off and the motor vehicle is operated with the internal combustion engine switched off, that is to say in a coasting mode, in a fourth step (14) a request to switch on the internal combustion engine is sent to the control unit,in a fifth step (24) the internal combustion engine is started and in a sixth step (28) the frictional connection is established by means of the clutch arrangement between the internal combustion engine and the transmission, , characterized by that in the second step (10) in the control unit at least one sailing gear is calculated on the basis of vehicle data (6), such as gradient, speed, rolling resistance, driving resistance, etc., drive train data, such as gear ratio, speeds, etc., route information, such as altitude, driving line, etc., and this is engaged by means of the circuit arrangement after the interruption of the power flow. [2] Method according to claim 1, characterized bythat before the fifth step (14) a new driving gear is calculated (18), the circuit arrangement and / or the clutch arrangement is hydraulically filled by means of a starting or revving process (22) and after the fifth step the driving gear is engaged if necessary (26). [3] Method according to claim 1 or 2, characterized by that before the third step the clutch or clutches are flooded with a cooling oil volume flow pulse. [4] Method according to one of claims 1-3, characterized by that the automated transmission is designed as a dual-clutch transmission, with one and / or two gears of the dual-clutch transmission being calculated and engaged as sailing gear(s). [5] Method according to one of the preceding claims, characterized by that before the sixth step (28) a synchronization of the driving gear is carried out by a brief actuation of the clutch arrangement. [6] Drive train for a motor vehicle with an internal combustion engine with an automatic transmission or an automated transmission, which has a hydraulic circuit arrangement with a hydraulically actuated clutch arrangement and with a control unit which controls the driving operation of a motor vehicle with the internal combustion engine switched off, characterized by that the control unit has means which calculate a sailing gear based on vehicle data such as gradient, speed, rolling resistance, driving resistance, etc., drive train data such as gear ratio, speeds, etc. route information such as altitude, driving line, etc. [7] Drive train according to claim 6, characterized by that the automated transmission is designed as a dual-clutch transmission. [8] Drive train according to claim 7, characterized bythat in dual-clutch transmissions without oil chamber separation or in automated transmissions with splash lubrication, oil collection pockets, splash lubrication or mechanically wheel-driven lubricating oil pumps are provided for splash oil supply. [9] Drive train according to one of claims 6-8, characterized by that the starter arrangement has a belt starter generator or electric motor for faster revving.

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