Systems and methods for controlling an engine start in a hybrid vehicle

Patent metadata

Field	Value
Publication number	US-2018244262-A1
Application number	US-201715671333-A
Country	US
Kind code	A1
Filing date	Aug 8, 2017
Priority date	Feb 24, 2017
Publication date	Aug 30, 2018
Grant date	—

Abstract

Methods and systems are provided for operating a driveline of a hybrid vehicle that includes an internal combustion engine, an electric machine, and a transmission, where the transmission is downstream of the engine, and where the electric machine is downstream of the transmission. In one example, responsive to a driver-demanded wheel torque that exceeds a capacity of the electric machine, a vehicle acceleration plateau is avoided by transiently connecting a crankshaft of the engine to a low speed input shaft of the transmission while the engine is accelerating to a target speed.

First claim

1 . A driveline operating method, comprising:
controlling a first target input shaft of a dual clutch transmission to a first speed, while controlling a second non-target input shaft of the dual clutch transmission to a second speed; and transmitting torque to driven vehicle wheels via an engine configured to propel the vehicle by connecting an engine crankshaft to the second non-target input shaft while the engine is increasing speed to the first speed.

2 . The method of claim 1 , wherein the first speed is greater than the second speed.

3 . The method of claim 1 , further comprising propelling the vehicle solely via an electric machine positioned downstream of the dual clutch transmission while the engine is off under conditions where a wheel torque demand can be met solely via the electric machine; and
wherein transmitting torque to the one or more driven wheels by connecting the engine crankshaft to the second non-target input shaft while the engine is increasing speed occurs responsive to a driveline torque request exceeding a capability of the electric machine that results in an engine startup event to deliver additional torque to the driveline.

4 . The method of claim 1 , wherein controlling the first target input shaft to the first speed includes engaging a first target gear with the first target input shaft, and wherein controlling the second non-target input shaft to the second speed includes engaging a second non-target gear with the second non-target input shaft; and
wherein engaging the first target gear with the first target input shaft and engaging the second non-target gear with the second non-target input shaft occur either while the engine is off and the vehicle is being propelled solely via the electric machine, or subsequent to the engine startup event to deliver additional torque to the driveline.

5 . The method of claim 3 , further comprising increasing torque provided to the driven wheels via controlling torque of the electric machine to an electric machine maximum torque limit responsive to the driveline torque request exceeding the capability of the electric machine, the maximum torque limit determined based on one or more of at least a state of charge of an onboard energy storage device, and a temperature of the electric machine.

6 . The method of claim 1 , further comprising fully disconnecting the engine crankshaft from the second non-target input shaft and connecting the engine crankshaft to the first target input shaft responsive to engine speed being synchronized with the first speed.

7 . The method of claim 6 , wherein the engine crankshaft is connected to the first target input shaft via a first target clutch, and wherein connecting and fully disconnecting the engine crankshaft from the second non-target input shaft is via a second non-target clutch.

8 . A driveline operating method, comprising:
propelling a vehicle solely via an electric machine while an engine of the vehicle is not connected to a dual clutch transmission, the electric machine positioned in the driveline downstream of the dual clutch transmission; starting the engine from rest responsive to a driveline torque request exceeding a torque capability of the electric machine, to deliver additional torque to the driveline; controlling a first target input shaft of the dual clutch transmission to a first speed via engaging a first target gear, controlling a second non-target input shaft of the dual clutch transmission to a second speed via engaging a second non-target gear, where the first speed is higher than the second speed; and transmitting torque to one or more driven wheels of the vehicle via the engine by partially connecting an engine crankshaft to the second non-target input shaft via a second clutch while the engine is increasing speed to the first speed.

9 . The method of claim 8 , further comprising pre-engaging the first target gear and the second non-target gear while the vehicle is being propelled solely via the electric machine.

10 . The method of claim 8 , further comprising shifting one or more gears of the dual clutch transmission to engage the first target gear and the second non-target gear responsive to the driveline torque request exceeding the capability of the electric machine.

11 . The method of claim 8 , further comprising fully disconnecting the engine crankshaft from the second non-target input shaft and connecting the engine crankshaft to the first target input shaft responsive to engine speed being synchronized with the first speed.

12 . The method of claim 11 , wherein a first target clutch connects the engine crankshaft to the first target input shaft, and wherein a second non-target clutch partially connects and fully disconnects the engine crankshaft from the second non-target input shaft.

13 . The method of claim 12 , further comprising linearly increasing torque to the driveline via the second non-target clutch at a rate slower than a rate at which engine torque is increasing while the engine is increasing speed to the first speed.

14 . The method of claim 12 , further comprising continuously commanding engine torque to a maximum value while the engine is increasing speed to the first speed; and
absorbing excess torque via the second non-target clutch to transmit engine torque to the driveline and control engine speed to the first speed.

15 . The method of claim 12 , further comprising modulating engine torque to reach the first speed while the engine is increasing speed to the first speed; and
in parallel, absorbing excess torque via the second non-target clutch to transmit engine torque to the driveline and control engine speed to the first speed.

16 . The method of claim 12 , further comprising modulating engine torque to reach the first speed while the engine is increasing speed to the first speed; and
in parallel, absorbing excess torque via the second non-target clutch to transmit engine torque to the driveline to cross lash prior to connecting the engine crankshaft to the first target input shaft.

17 . The method of claim 12 , further comprising modulating engine torque to reach the first speed while the engine is increasing speed to the first speed; and
in parallel, absorbing excess torque via the second non-target clutch to transmit engine torque to the driveline to preload the engine to increase engine response when the first target clutch connects the engine crankshaft to the first target input shaft when engine speed is synchronized with the first speed.

18 . A system, comprising:
an engine including a crankshaft; an integrated starter/generator coupled to the engine; a dual clutch transmission coupled to the engine including a first target clutch, a second non-target clutch, a first target input shaft, and a second non-target input shaft; an electric machine coupled to the dual clutch transmission downstream of the dual clutch transmission; and a controller storing executable instructions in non-transitory memory that, when executed, cause the controller to start the engine from rest via the integrated starter/generator responsive to a driveline torque request exceeding a torque capability of the electric machine; command the electric machine torque to an electric machine maximum torque limit; control the first target input shaft to a first target speed and control the second non-target input shaft to a second non-target speed, the first target speed higher than the second non-target speed; and transmit torque from the engine through the transmission via the second non-target in

Assignees

• Ford Global Tech Llc

Inventors

• Ruybal Kevin Ray
• Meyer Jason
• Doering Jeffrey Allen
• Wang Xiaoyong

Classifications

• B60W2710/0644

  Engine speed · CPC title

• B60W2710/083

  Torque · CPC title

• B60K6/387

  Actuated clutches, i.e. clutches engaged or disengaged by electric, hydraulic or mechanical actuating means · CPC title

• F02D29/02

  peculiar to engines driving vehicles; peculiar to engines driving variable pitch propellers · CPC title

• B60K2006/4825

  Electric machine connected or connectable to gearbox input shaft · CPC title