Method and device for operating a motor vehicle

Abstract

Method for operating a motor vehicle in which, during driving operation, a power transmission between a vehicle engine (100) and a vehicle transmission (102) is interrupted and the vehicle engine (100) is switched off, comprising the steps: Output (S1) of a shift request by means of a control unit (105) of the vehicle transmission (102) in response to an action of the vehicle user; Driving (S2) an oil pump (104) of the vehicle engine (100) to generate oil pressure required for a shifting operation of the vehicle transmission (102) or for actuating the clutch to restore power transmission by means of a drive unit (106); and Performing (S3) at least one shifting operation by means of the vehicle transmission (102) in response to the shifting request of the control unit (105) of the vehicle transmission (102), wherein, in the event of an interruption of the power transmission between the vehicle engine (100) and the vehicle transmission (102) by opening a clutch (101), a gear change is carried out in response to a shifting request from the control unit (105) of the vehicle transmission (102) by disengaging a currently engaged gear and engaging a desired gear, When the vehicle speed decreases, the control unit (105) of the vehicle transmission (102) issues a shift request to engage a lower gear compared to the currently engaged gear, depending on the vehicle speed, in which the vehicle engine (100) has a speed at which at least 60%, preferably at least 80%, of the maximum torque of the vehicle engine (100) is available.

Description

[0001] The present invention relates to a method and a device for operating a motor vehicle.

[0002] In vehicles equipped with a belt starter generator or crankshaft starter generator and an automatic transmission or dual-clutch transmission with an oil pump located on the transmission input side, it is possible to drive the oil pump by towing the combustion engine with the belt starter generator or crankshaft starter generator when the combustion engine is switched off. This allows the individual gears to be engaged and the clutch to be actuated. In transmissions operated by oil pressure, where the oil pressure is built up via a mechanical pump at the transmission input, engaging the gears and clutches is not possible when the combustion engine is switched off, as no oil pressure is available.

[0003] From the publication DE 10 2008 011 898 A1 it is known to generate the oil pressure for releasing a parking lock via a starter generator, which drives the combustion engine and thus also a hydraulic pump.

[0004] DE 10 2011 114 407 A1 discloses a method for operating a motor vehicle in a start-stop mode, in which a drive unit is switched off during a stop mode, comprising the following steps: issuing a start or stop request by means of a control unit in response to an action of the motor vehicle user; driving an oil pump to generate oil pressure to keep clutch circuits filled; performing a start or stop process in response to the request of the control unit.

[0005] DE 10 2010 024 045 A1 discloses a method for gear selection of a transmission in a traction phase after a sailing phase.

[0006] Against this background, it is an object of the present invention to provide an improved method and an improved device for operating a motor vehicle.

[0007] This object is achieved by a method having the features of patent claim 1, by a method having the features of patent claim 2, by a method having the features of patent claim 4, by a method having the features of patent claim 5 and by a device having the features of patent claim 13.

[0008] The invention accordingly provides a method for operating a motor vehicle in which, during driving operation, a power connection between a vehicle engine and a vehicle transmission is interrupted and the vehicle engine is switched off. The method comprises issuing a gearshift request by a control unit of the vehicle transmission, driving an oil pump of the vehicle engine to generate an oil pressure required for a gearshift of the vehicle transmission, and performing at least one gearshift of the vehicle transmission in response to the gearshift request of the control unit of the vehicle transmission. By driving the oil pump of the vehicle engine to generate oil pressure, the corresponding gears of the vehicle transmission can be engaged and the power connection between the vehicle engine and the vehicle transmission is restored. The coupling takes place without operating the internal combustion engine, which is then subsequently started.

[0009] According to patent claim 1, if the power connection between the vehicle engine and the vehicle transmission is interrupted due to the disengagement of a clutch, a gear change is carried out in response to the shift request of the vehicle transmission control unit by disengaging a currently engaged gear and engaging a desired gear. During coasting operation of the motor vehicle, i.e., when the power connection between the vehicle engine and the vehicle transmission is interrupted and the combustion engine is switched off, a high gear may be engaged, for example. The driver then brakes to a standstill. Shortly before the standstill is reached, a low gear should be engaged for rapid acceleration.By requesting the control unit of the vehicle transmission to carry out a gear change by disengaging the currently engaged gear and engaging the desired gear, a quick start can be made possible after engaging the desired gear.

[0010] According to claim 1, it is further provided that when the driving speed decreases, the control unit of the vehicle transmission issues a shift request to engage a lower gear than the currently engaged gear, depending on the driving speed, in which the vehicle engine has a speed at which at least 60% of the maximum torque, preferably at least 80% of the maximum torque of the vehicle engine, is present. Because the vehicle engine is in the range of maximum torque when the lower gear is engaged, rapid starting of the motor vehicle is possible.

[0011] According to a further preferred embodiment, when the driving speed decreases, the control unit of the vehicle transmission issues a shift request to engage a lower gear than the currently engaged gear. This enables rapid starting in the lower gear.

[0012] According to claim 2, if the power transmission between the vehicle engine and the vehicle transmission is interrupted due to a disengaged gear of the vehicle transmission, a desired gear is engaged in response to the shift request from the vehicle transmission control unit. During coasting operation of the motor vehicle with the combustion engine switched off, the gears can be disengaged to reduce transmission losses. Thus, when the driver requests acceleration, the shift request can be issued, and a desired gear can be engaged in response to the shift request from the vehicle transmission control unit.

[0013] According to claim 2, it is further provided that when the driving speed decreases, the control unit of the vehicle transmission issues a shift request to engage a gear, depending on the driving speed, in which the vehicle engine has a speed at which at least 60% of the maximum torque, preferably at least 80% of the maximum torque, is present. Because the vehicle engine is in the range of maximum torque when the lower gear is engaged, a rapid start is possible.

[0014] According to a further preferred embodiment, when the driving speed decreases, the control unit of the vehicle transmission issues a shift request to engage a desired gear shortly before the vehicle reaches a standstill. When the driver requests acceleration, a gear can be engaged sufficiently quickly during the engine start-up to a tethering speed. This is not the case when the vehicle is stationary, since the tethering speed is significantly lower and is reached more quickly. For this reason, a low gear is engaged shortly before the vehicle reaches a standstill to enable rapid acceleration.

[0015] Preferably, it is further provided that the reduction in driving speed is achieved by applying a vehicle brake or by the vehicle's driving resistance. The coasting mode of the motor vehicle is thus maintained until the driver requests acceleration or the motor vehicle is close to reaching a standstill.

[0016] According to a further preferred embodiment, the action of the motor vehicle user that causes the shift request to be issued by the control unit of the vehicle transmission is performed by the motor vehicle user pressing an accelerator pedal. The coasting operation of the motor vehicle is thus terminated by the motor vehicle user pressing the accelerator pedal.

[0017] According to patent claims 4 and 5, the vehicle engine's oil pump is driven to achieve the oil pressure required for a gearshift or clutch actuation of the vehicle transmission by driving the vehicle engine. Driving the vehicle engine by the belt starter generator or the crankshaft starter generator thus drives the oil pump to generate the oil pressure required for a gearshift of the vehicle transmission.

[0018] According to claim 4, the drive unit drives the vehicle engine to a connecting speed for connecting the vehicle transmission to the vehicle engine, at which the speed of the vehicle engine essentially corresponds to the speed of an associated transmission shaft. This allows for a convenient reconnection of the vehicle transmission to the vehicle engine.

[0019] According to claim 5, it is further provided that a determination is made as to whether an energy storage device of the motor vehicle has sufficient energy to drive the vehicle engine with the drive unit for a predetermined duration. If sufficient energy is available, a torque is applied to the crankshaft by the belt starter generator or the crankshaft starter generator to bring the internal combustion engine to a speed sufficient to provide the required oil pressure.

[0020] According to a further preferred embodiment, the drive unit is formed by a belt starter generator or a crankshaft starter generator. The belt starter generator is preferably connected to a crankshaft of the motor vehicle via a V-belt of the motor vehicle. The oil pump, in turn, is connected to the crankshaft of the vehicle engine.

[0021] According to a further preferred embodiment, the vehicle transmission is embodied as an automatic transmission or a dual-clutch transmission. Both the automatic transmission and the dual-clutch transmission are oil-pressure actuated transmissions. Thus, with both of the aforementioned transmission variants, gears can be engaged and disengaged, as well as the clutch can be engaged, while the combustion engine is switched off.

[0022] The invention further provides a device for operating a motor vehicle according to the method according to the invention, which device is suitable, when the power connection between a vehicle engine and a vehicle transmission is interrupted during driving operation and the vehicle engine is switched off, for outputting a gearshift request by means of a control unit of the vehicle transmission in response to an action of the motor vehicle user, for driving an oil pump of the vehicle engine by means of a drive unit to generate an oil pressure required for a gearshift operation of the vehicle transmission; and for carrying out at least one gearshift operation by means of the vehicle transmission in response to the gearshift request of the control unit of the vehicle transmission.

[0023] Embodiments of the invention are illustrated in the figures of the drawings and explained in more detail in the following description.

[0024] It illustrates: Fig. 1 a flowchart of the method according to the invention for operating a motor vehicle; and Fig. 2 a block diagram of the device according to the invention for operating a motor vehicle.

[0025] Fig. 1 shows a flowchart of the method according to the invention for operating a motor vehicle. The method begins with step S1, in which a shift request is output by a control unit 105 of a vehicle transmission 102. In step S1A, it is determined whether an energy storage device of the motor vehicle has sufficient energy to drive the vehicle engine 100 with the drive unit 106 for a predetermined duration. If this is not the case, the method returns to the beginning. If necessary, a message can be generated that the energy storage device of the motor vehicle does not have sufficient energy to drive the vehicle engine with the drive unit for a predetermined duration. If it is determined that the energy storage device of the motor vehicle has sufficient energy to drive the vehicle engine 100 with the drive unit 106 for a predetermined duration, the method proceeds to step S2.

[0026] In step S2, an oil pump 104 of the vehicle engine 100 is driven to generate the oil pressure required for a shifting operation of the vehicle transmission 102. In step S2A, it is determined whether the required oil pressure has been reached. If it is determined in step S2A that the required oil pressure has not yet been reached, the method returns to step S2, and the oil pump 104 of the vehicle engine 100 continues to be driven. If it is determined that the required oil pressure is present, the method proceeds to step S3, and the oil pump continues to be driven.

[0027] In step S3, at least one shift operation of the vehicle transmission 102 is performed in response to the shift request from the control unit 105 of the vehicle transmission 102. The shift operation of the vehicle transmission 102 can occur, for example, by engaging or disengaging a gear. The oil pump is now no longer driven separately.

[0028] Fig. 2 shows a block diagram of the device according to the invention for operating a motor vehicle. Fig. Figure 2 shows the vehicle engine 100 and the vehicle transmission 102, which can be non-positively connected by means of a clutch 101, or the non-positive connection between the vehicle engine 100 and the vehicle transmission 102 can be interrupted by the clutch 101. The vehicle engine 100 is further connected to an oil pump 104. The oil pump 104 is driven by a drive unit 106 formed by a belt starter generator.

[0029] The vehicle transmission 102 is connected to a control unit 105 for controlling the vehicle transmission 102. The control unit 105 is further connected to the drive unit 106. In the present embodiment, the control unit 105 is directly connected to the drive unit 106. Alternatively, the connection between the control unit 105 and the drive unit 106 can also be established indirectly, i.e., via another control device.

[0030] The drive unit 106 is suitable for driving the vehicle engine 100, which is preferably embodied by an internal combustion engine, by means of a V-belt. This also drives the pump 104 arranged on the engine side, which is embodied by a mechanical oil pump. By driving the oil pump 104, the required oil pressure can be provided, which is needed for shifting the gears and for actuating the clutch of the vehicle transmission 102. Thus, gears can be engaged or disengaged or the clutch can be actuated. This can be necessary, for example, when the vehicle is coasting, i.e. with interrupted power transmission between the vehicle engine 100 and the vehicle transmission 102 and with the internal combustion engine switched off, and is braked from a high speed with a high gear engaged or with gears disengaged down to a standstill, and a low gear is to be engaged for a quick start.In this case, the control unit 105 of the vehicle transmission 102 outputs a shift request, which causes the oil pump 104 of the vehicle engine 100 to be driven to generate an oil pressure required for a shift operation of the vehicle transmission 102 and to perform at least one shift operation of the vehicle transmission 102 in response to the shift request of the control unit 105 of the vehicle transmission 102.

[0031] A gearshift request is also issued, for example, when driving with the combustion engine switched off, the clutch disengaged, and a gear engaged, if a specific gear is engaged when entering coasting mode with the combustion engine switched off. The driver then brakes slowly or the speed is reduced due to driving resistance. The optimal gear should be engaged at all times for comfortable reconnection and / or rapid acceleration after the vehicle transmission 102 is reconnected to the vehicle engine 100, i.e., the gears are tracked during coasting mode of the vehicle engine 100 with the vehicle engine 100 switched off.

[0032] A shift request is also issued if the motor vehicle's gears are disengaged during coasting with the combustion engine 100 switched off, and the driver desires to accelerate. When the driver desires to accelerate, a gear can be shifted sufficiently quickly during engine start-up while the engine is accelerating to the tethering speed. This is not the case at standstill, as the tethering speed is significantly lower and is reached more quickly. For this reason, a low gear is engaged shortly before reaching a standstill for rapid acceleration.

[0033] The invention is not limited to the above embodiments. Within the scope of the invention, the method for operating a motor vehicle according to the invention and the device for operating a motor vehicle according to the invention may also take on embodiments other than those specifically described above.

Claims

[1] Method for operating a motor vehicle, in which during driving operation a power connection between a vehicle engine (100) and a vehicle transmission (102) is interrupted and the vehicle engine (100) is switched off, comprising the steps: Outputting (S1) a shift request by means of a control unit (105) of the vehicle transmission (102) in response to an action of the motor vehicle user; Driving (S2) an oil pump (104) of the vehicle engine (100) to generate an oil pressure required for a shifting operation of the vehicle transmission (102) or for actuating the clutch to restore the power connection by means of a drive unit (106); and Carrying out (S3) at least one shifting operation by means of the vehicle transmission (102) in response to the shifting request of the control unit (105) of the vehicle transmission (102), wherein, in the event of an interruption of the power connection between the vehicle engine (100) and the vehicle transmission (102) by opening a clutch (101), a gear change is carried out in response to a shift request from the control unit (105) of the vehicle transmission (102) by disengaging a currently engaged gear and engaging a desired gear, when the driving speed is reduced, the control unit (105) of the vehicle transmission (102) issues the shift request to engage a lower gear compared to the currently engaged gear, depending on the driving speed, in which gear the vehicle engine (100) has a speed at which at least 60% of the maximum torque, preferably at least 80% of the maximum torque of the vehicle engine (100) is present. [2] A method for operating a motor vehicle, in which, during driving operation, a power connection between a vehicle engine (100) and a vehicle transmission (102) is interrupted and the vehicle engine (100) is switched off, comprising the steps: Outputting (S1) a shift request by means of a control unit (105) of the vehicle transmission (102) in response to an action of the motor vehicle user; Driving (S2) an oil pump (104) of the vehicle engine (100) to generate an oil pressure required for a shifting operation of the vehicle transmission (102) or for actuating the clutch to restore the power connection by means of a drive unit (106); and Carrying out (S3) at least one shifting operation by means of the vehicle transmission (102) in response to the shifting request of the control unit (105) of the vehicle transmission (102), wherein, in the event of an interruption of the power connection between the vehicle engine (100) and the vehicle transmission (102) by a disengaged gear of the vehicle transmission (102), a desired gear is engaged in response to the shift request of the control unit (105) of the vehicle transmission (102), wherein, when the driving speed is reduced, the control unit (105) of the vehicle transmission (102) issues the shift request to engage a gear depending on the driving speed, in which gear the vehicle engine (100) has a speed at which at least 60% of the maximum torque, preferably at least 80% of the maximum torque, is present. [3] Method according to claim 2, characterized by that when the driving speed is reduced, the control unit (105) of the vehicle transmission (102) issues the shift request to engage a desired gear shortly before the motor vehicle comes to a standstill. [4] A method for operating a motor vehicle, in which, during driving operation, a power connection between a vehicle engine (100) and a vehicle transmission (102) is interrupted and the vehicle engine (100) is switched off, comprising the steps: Outputting (S1) a shift request by means of a control unit (105) of the vehicle transmission (102) in response to an action of the motor vehicle user; Driving (S2) an oil pump (104) of the vehicle engine (100) to generate an oil pressure required for a shifting operation of the vehicle transmission (102) or for actuating the clutch to restore the power connection by means of a drive unit (106); and Carrying out (S3) at least one shifting operation by means of the vehicle transmission (102) in response to the shifting request of the control unit (105) of the vehicle transmission (102), wherein the driving of the oil pump (104) of the vehicle engine (100) for generating an oil pressure required for a shifting operation of the vehicle transmission (102) is carried out by driving the vehicle engine (100), wherein the drive unit (106) drives the vehicle engine (100) to a connecting speed for connecting the vehicle transmission (102) to the vehicle engine (100), at which the speed of the vehicle engine (100) substantially corresponds to a speed of an associated transmission shaft. [5] Method for operating a motor vehicle, in which during driving operation a power connection between a vehicle engine (100) and a vehicle transmission (102) is interrupted and the vehicle engine (100) is switched off, comprising the steps: Outputting (S1) a shift request by means of a control unit (105) of the vehicle transmission (102) in response to an action of the motor vehicle user; Driving (S2) an oil pump (104) of the vehicle engine (100) to generate an oil pressure required for a shifting operation of the vehicle transmission (102) or for actuating the clutch to restore the power connection by means of a drive unit (106); and Carrying out (S3) at least one shifting operation by means of the vehicle transmission (102) in response to the shifting request of the control unit (105) of the vehicle transmission (102), wherein the driving of the oil pump (104) of the vehicle engine (100) for generating an oil pressure required for a shifting operation of the vehicle transmission (102) is carried out by driving the vehicle engine (100), wherein a determination (S1A) is made as to whether an energy storage device of the motor vehicle has sufficient energy to drive the vehicle engine (100) with the drive unit (106) for a predetermined period. [6] Method according to one of claims 1 to 3, characterized bythat the reduction in driving speed is carried out by actuating a vehicle brake or a driving resistance of the motor vehicle. [7] Method according to one of the preceding claims, characterized by that the action of the motor vehicle user which causes the output (S1) of the shift request by means of the control unit (105) of the vehicle transmission (102) is carried out by actuation of an accelerator pedal by the motor vehicle user. [8] Method according to one of the preceding claims 1 to 3, characterized by that the driving of the oil pump (104) of the vehicle engine (100) for generating an oil pressure required for a shifting operation of the vehicle transmission (102) is carried out by driving the vehicle engine (100). [9] Method according to claim 8, characterized bythat the drive unit (106) drives the vehicle engine (100) to a connecting speed for connecting the vehicle transmission (102) to the vehicle engine (100), at which the speed of the vehicle engine (100) substantially corresponds to a speed of an associated transmission shaft. [10] Method according to one of claims 8 or 9, characterized by that the drive unit (106) is formed by a belt starter generator. [11] Method according to one of the preceding claims, characterized by that the vehicle transmission (102) is formed by an automatic transmission or a dual-clutch transmission. [12] Method according to one of claims 8 to 11, characterized by that a determination (S1A) is carried out as to whether an energy storage device of the motor vehicle has sufficient energy to drive the vehicle engine (100) with the drive unit (106) for a predetermined period. [13] A device for operating a motor vehicle according to the method according to one of the preceding claims, which, when the power connection between a vehicle engine (100) and a vehicle transmission (102) is interrupted during driving operation and the vehicle engine (100) is switched off, is suitable for issuing a gearshift request by means of a control unit (105) of the vehicle transmission (102) in response to an action of the motor vehicle user, for driving an oil pump (104) of the vehicle engine (100) by means of a drive unit (106) to generate an oil pressure required for a gearshift operation of the vehicle transmission (102); and for carrying out at least one gearshift operation by means of the vehicle transmission (102) in response to the gearshift request of the control unit (105) of the vehicle transmission (102).

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