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Power-on downshift control for a hybrid electric vehicle powertrain

  • US 7,517,298 B2
  • Filed: 09/05/2006
  • Issued: 04/14/2009
  • Est. Priority Date: 09/05/2006
  • Status: Expired due to Fees
First Claim
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1. A method for controlling power distribution in a hybrid electric vehicle powertrain, the powertrain comprising an engine, a multiple-ratio transmission having a power delivery member drivably connected to the engine for developing a mechanical driving power flow path to vehicle traction wheels, a first electric machine coupled to the engine and a second electric machine in an electrical power flow path to the vehicle traction wheels, the transmission having selectively engageable friction elements for establishing at least two forward drive transmission ratios, one friction element being released as a second friction element is engaged to effect a power-on downshift, the method comprising:

  • increasing torque output of the second electric machine in a first operating mode at the beginning of the power-on downshift following a shift request;

    maintaining torque delivered through the mechanical driving power flow path at approximately its pre-shift level as the first friction element is slipping and the second friction element is engaging in a second operating mode;

    maintaining torque output of the second electric machine during the second operating mode;

    decreasing the torque output of the second electric machine in a third operating mode at the end of the power-on downshift; and

    increasing torque delivered through the mechanical power flow path to fully engage the second friction element in the third operating mode as the torque output of the second electric machine returns to approximately its pre-shift level whereby a fast response to a request for an increase in traction wheel torque is achieved.

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