# US 2023/0264682 A1 · Method for Operating a Motor Vehicle Drive Train and Electronic Control Unit for Carrying Out Said Method

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- Number: US 2023/0264682 A1
- Document ID: US20230264682A1
- Status: Published application
- Kind: A1
- Application number: 17/922,035
- Filed: 2021-04-29
- Published: 2023-08-24
- Earliest claimed: 2020-04-29
- Assignees: ZF Friedrichshafen AG; Bayerische Motoren Werke Aktiengesellschaft (Bmw)
- Applicants: ZF Friedrichshafen AG; Bayerische Motoren Werke AG (BMW)
- Inventors: Roland Neubaur; Florian Hannemann; Markus Pfisterer; Wolfgang Fickler
- Web page: https://patentgrep.com/patent/US20230264682A1

## CPC

- B60W 20/40: Controlling the engagement or disengagement of prime movers, e.g. for transition between prime movers {(power-up or power-down of the driveline B60W30/192)}
- B60K 6/48: Parallel type
- B60W 10/02: including control of driveline clutches
- B60W 10/06: including control of combustion engines
- B60W 10/08: including control of electric propulsion units, e.g. motors or generators
- B60W 20/15: Control strategies specially adapted for achieving a particular effect
- B60W 30/18027: {Drive off, accelerating from standstill}
- B60W 30/186: excessive wear or burn out of friction elements, e.g. clutches
- F02N 11/0851: {characterised by means for controlling the engagement or disengagement between engine and starter, e.g. meshing of pinion and engine gear}
- B60W 2710/025: Clutch slip, i.e. difference between input and output speeds
- B60W 2710/0644: Engine speed
- Y02T 10/62: Hybrid vehicles
- B60W: CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60K: ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
- F02N: STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A method for operating a drive train having a starting component between an electric machine and an output shaft of a transmission, and a separating clutch between an internal combustion engine and the electric machine, with a rotor of the electric machine being coupled to the input shaft of the transmission, where the method initially drives a motor vehicle solely by the electric machine while the starting component is engaged or slipping and the separating clutch is disengaged. The method then engages the separating clutch to crank the internal combustion engine. The method disengages the separating clutch after cranking, with an output-side rotational speed of the separating clutch being lower than an idling speed of the internal combustion engine. Subsequently, the method engages the separating clutch to drive the motor vehicle with the internal combustion engine when a target drive torque reaches or exceeds a limit.

## Claims

### Claim at position 1

1-12: (canceled)

### Claim 13

A method for operating a drive train of a motor vehicle, the drive train comprising an internal combustion engine (VM), an electric machine (EM) having a rotor (R), a transmission (G) for providing different gear speed ratios between an input shaft (GW1) and an output shaft (GW2) of the transmission (G), a starting component (WK, SCI, DC1, DC2) in power flow between the electric machine (EM) and the output shaft (GW2), and a separating clutch (K0) in power flow between the internal combustion engine (VM) and the electric machine (EM), with the rotor (R) of the electric machine (EM) being coupled to the input shaft (GW1), the method comprising:
driving the motor vehicle solely by the electric machine (EM) during a first stage of an electric starting process while the starting component (WK, SCI, DC1, DC2) is engaged or in a slip state, and while the separating clutch (K0) is disengaged;
engaging the separating clutch (K0) during a second stage of the electric starting process to crank the internal combustion engine (VM) using the electric machine (EM), the second stage being subsequent to the first stage;
disengaging the separating clutch (K0) and continuing driving the motor vehicle solely by the electric machine (EM) after the cranking of the internal combustion engine (VM), with an output-side rotational speed (n_EM) of the separating clutch (K0) being lower than an idling speed (n_VM_LL) of the internal combustion engine (VM); and
engaging the separating clutch (K0) to support driving the motor vehicle by the internal combustion engine (VM) only when a target drive torque (M_soll) of the motor vehicle reaches or exceeds a limit value (M_lim).

### Claim 14 (depends on 13)

The method of claim 13, wherein the output-side rotational speed (n_EM) of the separating clutch (K0) remains lower than the idling speed (n_VM_LL) of the internal combustion engine (VM) after the cranking of the internal combustion engine (VM) at least until the target drive torque (M_soll) of the motor vehicle reaches or exceeds the limit value (M_lim).

### Claim 15 (depends on 13)

The method of claim 13, further comprising operating the starting component (WK, SCI, DC1, DC2) in the slip state during the cranking of the internal combustion engine (VM), wherein a slip at the starting component (WK, SCI, DC1, DC2) is reduced after the separating clutch (K0) is disengaged after the cranking of the internal combustion engine (VM).

### Claim 16 (depends on 15)

The method of claim 15, wherein the slip at the starting component (WK, SCI, DC1, DC2) is reduced to zero after the separating clutch (K0) is disengaged after the cranking of the internal combustion engine (VM).

### Claim 17 (depends on 13)

The method of claim 13, wherein a slip at the starting component (WK, SCI, DC1, DC2) is enlarged when the target drive torque (M_soll) of the motor vehicle reaches or exceeds the limit value (M_lim) to minimize a differential speed at the separating clutch (K0) while engaging of the separating clutch (K0).

### Claim 18 (depends on 13)

The method of claim 13, wherein a slip at the starting component (WK, SCI, DC1, DC2) remains unchanged when the target drive torque (M_soll) of the motor vehicle reaches or exceeds the limit value (M_lim) so that the separating clutch (K0) is engaged during a continuous slip operation of the separating clutch (K0).

### Claim 19 (depends on 13)

The method of claim 13, further comprising operating the starting component (WK, SCI, DC1, DC2) in the slip state and the separating clutch (K0) in a slip state when the target drive torque (M_soll) of the motor vehicle reaches or exceeds the limit value (M_lim).

### Claim 20 (depends on 13)

The method of claim 13, further comprising selecting a slip at the starting component (WK, SCI, DC1, DC2) based at least in part on a magnitude of the target drive torque (M_soll) when the target drive torque (M_soll) of the motor vehicle reaches or exceeds the limit value (M_lim).

### Claim 21 (depends on 13)

The method of claim 13, further comprising:
actively operating the internal combustion engine (VM) after the cranking of the internal combustion engine (VM); and
coupling the internal combustion engine (VM) to the transmission (G) after the cranking of the internal combustion engine (VM) only when the target drive torque (M_soll) of the motor vehicle reaches or exceeds the limit value (M_lim).

### Claim 22 (depends on 21)

The method of claim 21, further comprising operating the internal combustion engine (VM) in a speed-controlled manner after the cranking of the internal combustion engine (VM) until the internal combustion engine (VM) is coupled to the transmission (G).

### Claim 23 (depends on 22)

The method of claim 22, wherein operating the internal combustion engine (VM) in the speed-controlled manner comprises operating the internal combustion engine (VM) at a target rotational speed, the target rotational speed being dependent on the target drive torque (M_soll).

### Claim 24 (depends on 13)

An electronic control unit (ECU) for open-loop and closed-loop control of a motor vehicle drive train, the electronic control unit (ECU) performing the method of claim 13.