REGENERATION OF A PARTICULATE FILTER

Abstract

A method for regenerating a particulate filter (30) that is arranged in the exhaust train of an internal combustion engine (12) of a vehicle. The vehicle has a drive train (10) with the internal combustion engine (12) and a clutch unit (18), and the clutch unit (18) connects the internal combustion engine (12) in a separable manner to a transmission (20). The method includes switching off the internal combustion engine (12), and closing the clutch unit (18) with a slip.

Claims

1. A method for regenerating a particulate filter that is arranged in the exhaust train of an internal combustion engine of a vehicle, the vehicle having a drive train with the internal combustion engine and a clutch unit, and the clutch unit connects the internal combustion engine in a separable manner to a transmission, the method comprising the steps switching off the internal combustion engine, and closing the clutch unit with a slip.

2. The method of claim 1, further comprising an additional step for activating the internal combustion engine to carry out a temperature increase in the particulate filter before the internal combustion engine is switched off.

3. The method of claim 1, further comprising checking a temperature of the particulate filter before the internal combustion engine is switched off, wherein the step of closing the clutch unit with a slip takes place depending on the temperature of the particulate filter.

4. The method of claim 1, wherein the step for closing the clutch unit with a slip comprises closing the clutch unit for transmitting 10% of 90% of a torque of the drive train to the internal combustion engine.

5. The method of claim 1, further comprising a step for bite point adaptation of the clutch unit.

6. The method of claim 1, further comprising monitoring an engine rotational speed and opening the clutch unit when an idling rotational speed is reached or when the internal combustion engine is at a standstill.

7. A vehicle comprising: a drive train comprising an internal combustion engine and a clutch unit to connect the internal combustion engine to a transmission, and a particulate filter arranged in the exhaust train of the internal combustion engine, and a control unit for activating the internal combustion engine and the clutch unit, wherein the control unit is configured for closing the clutch unit with a slip when turning off the internal combustion engine.

8. The vehicle of claim 7, further comprising a measuring device for measuring a temperature of the particulate filter, wherein the measuring device is connected to the control unit to transmit the temperature to the control unit.

9. The vehicle of claim 8, characterized in that the drive train additionally has an electric motor between the internal combustion engine and the transmission, and the clutch unit being arranged between the internal combustion engine and the electric motor.

10. The vehicle of claim 9, wherein the drive train further has a start-stop-on-the-move device between the internal combustion engine and the transmission, and the clutch unit is between the internal combustion engine and the start-stop-on-the-move device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a schematic illustration of a drive train with an internal combustion engine, an electric motor and a clutch unit arranged in between, according to a first preferred embodiment, together with a particulate filter of the internal combustion engine and a control unit for activating the internal combustion engine.

[0028] FIG. 2 shows a flow diagram for carrying out a method for regenerating the particulate filter.

[0029] FIG. 3 shows various rotational speed profiles of the internal combustion engine from FIG. 1.

[0030] FIG. 4 shows various torque profiles of the clutch unit of FIG. 1 with the rotational speed profiles of the internal combustion engine of FIG. 2.

DETAILED DESCRIPTION

[0031] FIG. 1 shows a drive train 10 according to a first embodiment. The drive train 10 drives one or more axles of a vehicle.

[0032] The drive train 10 comprises an internal combustion engine 12 and an electric motor 14, which are arranged in order to transmit force to a driveshaft 16. The internal combustion engine 12 here is a gasoline engine for burning fuel after production of an ignition spark.

[0033] A clutch unit 18 is arranged between the internal combustion engine 12 and the electric motor 14. The force of the driveshaft 16 is converted via a transmission 20 and distributed.

[0034] The clutch unit 18 is designed to connect or to separate the internal combustion engine 12 to or from the electric motor 14 and the transmission 20 depending on actuation, with separation of the clutch unit 18 meaning an interruption to the force transmission. The clutch unit 18 is designed in such a manner that the force transmission can take place with a slip, and therefore only a partial force transmission takes place. The clutch unit 18 is designed here by way of example as a frictionally locking separating clutch, as a transmission clutch or as a viscous clutch.

[0035] The drive train 10 additionally comprises a vibration damper 22 and a starting element 24, which are arranged on the driveshaft 16. The vibration damper 22 is arranged between the internal combustion engine 12 and the clutch unit 18, while the starting element 24 is positioned between the electric motor 14 and the transmission 20.

[0036] The starting element 24 is a component which, in mechanical drives, sits in the torque flux between the motor/engine or the motors/engines and the transmission 20. The starting element 24 permits the transmission of torque at different rotational speeds. The starting element 24 can be designed as a classic disk clutch.

[0037] FIG. 1 additionally shows two starter devices 26, 28, of which a first starter device 26 acts directly on the internal combustion engine 12, and a second starter device 28 acts on the vibration damper 22.

[0038] A particulate filter 36 which is illustrated in FIG. 1 is connected downstream of the internal combustion engine 12. The particulate filter 30 is arranged in an exhaust train of the internal combustion engine 12. The particulate filter 30 is a gasoline particulate filter. Particulates are understood here as essentially meaning soot particulates which are based on carbon and are formed during the combustion of fuel in the internal combustion engine 12 and are subsequently filtered out of an exhaust gas flow in the particulate filter 30.

[0039] Combustion gases flow through the particulate filter 30 during the normal operation of the internal combustion engine 12. When the internal combustion engine 12 is switched off, the generation of a combustion mixture in the internal combustion engine 12, and the combustion of said combustion mixture are stopped. The internal combustion engine 12 peters out without active braking in a spinning movement. The petering out of the internal combustion engine 12 therefore relates to a passive mode without combustion, in which kinetic energy of the internal combustion engine 12 or of that part of the drive train 10 which is fixedly connected to the internal combustion engine 12 moves the cylinders thereof.

[0040] FIG. 1 furthermore shows a measuring device 32 for measuring a temperature of the particulate filter 30, which measuring device is designed here as a temperature sensor. The measuring device 32 is connected to a control unit 34 in order to transmit the measured temperature of the particulate filter 30 to said control unit. The control unit 34 here controls the internal combustion engine 12 and the clutch unit 18. Furthermore, the control unit 34 can also control the transmission 20 and the starting element 24.

[0041] A method for regenerating the particulate filter 30 will be described below with reference to FIG. 2. Individual method steps can be carried out here in different sequences, as emerges from the description below.

[0042] The method begins at step S100 with checking of the temperature of the particulate filter 30. The temperature is determined with the measuring device 32 and transmitted to the control unit 34.

[0043] In step S110, the internal combustion engine 12 is activated in order to carry out a temperature increase in the particulate filter 30. The control unit 34 has received a command to switch off the internal combustion engine 12 or determines itself that the internal combustion engine 12 should be switched off. Depending on the temperature of the particulate filter 30 that is determined in step S100, the control unit 34 determines whether the exhaust gases of the internal combustion engine 12 in the preceding operation have sufficiently heated the particulate filter 30 in order to carry out a regeneration in the particulate filter 30. Otherwise, the internal combustion engine 12 is activated, for example with lambda-split, a rich operation of the internal combustion engine 12, or other measures in order to adapt the combustion and to increase the temperature in the particulate filter 30.

[0044] In step S120, the internal combustion engine 12 is switched off at a time t0. A mixture is not prepared in the cylinders of the internal combustion engine 12, and generation of ignition sparks is stopped. During rotation of the driveshaft 16, air from the internal combustion engine 12 is conveyed to the particulate filter 30. The internal combustion engine 12 begins to coast to a stop.

[0045] In step S130, the clutch unit 18 is closed with a slip. The partial closing of the clutch unit also takes place at the time t0. In the present case, the slip results in a transmission of approximately 20% to 30% of the torque of the drive train 10 to the internal combustion engine 12. Instead of completely opening the clutch unit 18 in order not to transmit kinetic energy of the vehicle to the internal combustion engine 12, the internal combustion engine 12 is partially coupled up.

[0046] The same is illustrated in FIG. 3 in comparison to coasting of the internal combustion engine 12 to a stop without a slip, i.e. with the clutch unit 18 open. A resulting first rotational speed profile 40 corresponds to coasting of the internal combustion engine 12 to a stop with the clutch unit 18 completely open if, for example, the temperature of the particulate filter 30 is too low for regeneration. The rotational speed relatively rapidly drops after the time t0 in comparison with a second and third rotational speed profile 42, 44, in which the clutch unit 18 is in each case closed with a slip. The corresponding actuation of the clutch unit 18 emerges from FIG. 4. A first clutch actuating curve 50 shows that the clutch unit 18 is completely closed before the time t0 in accordance with the first rotational speed profile 40 and is then completely open. In accordance with the second and third rotational speed profiles 42, 44, the clutch unit 18 is completely closed before the time t0 and is then closed with a slip. This is shown in a second and third clutch actuating curve 52, 54 in FIG. 4.

[0047] While the internal combustion engine 12 is coasting to a stop, air is conveyed by the cylinders into the particulate filter 30, as a result of which the latter is regenerated. The ventilation of the particulate filter 30 is carried out here to meet requirements by adjusting the slip and depending on the temperature of the particulate filter 30. When more torque of the drive train 10 is transmitted to the internal combustion engine 12, the internal combustion engine 12 will peter out over a longer period and will supply air to the particulate filter 30.

[0048] Step S140 relates to monitoring of the engine rotational speed and to opening of the clutch unit 18 when an idling rotational speed or a standstill of the internal combustion engine 12 is reached. This differentiates the second and third rotational speed profiles 42, 44. The second rotational speed profile 42 shows the internal combustion engine 12 coasting as far as a standstill, while the third rotational speed profile 42 shows that, when an idling rotational speed is reached at a time t1 of the internal combustion engine 12, the clutch unit 18 is completely open, as the corresponding profiles of the second and third clutch actuating curve 52, 54 show.

LIST OF REFERENCE SIGNS

[0049] Drive train 10 [0050] Internal combustion engine 12 [0051] Electric motor 14 [0052] Driveshaft 16 [0053] Clutch unit 18 [0054] Transmission 20 [0055] Vibration damper 22 [0056] Starting element 24 [0057] First starter device 26 [0058] Second starter device 28 [0059] Particulate filter 30 [0060] Temperature sensor 32 [0061] Control unit 34 [0062] First rotational speed profile 40 [0063] Second rotational speed profile 42 [0064] Third rotational speed profile 44 [0065] First clutch actuating curve 50 [0066] Second clutch actuating curve 52 [0067] Third clutch actuating curve 54