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Method to Control Engine Torque and RPM in a Hybrid Electric Powertrain

IP.com Disclosure Number: IPCOM000123534D
Publication Date: 2005-Apr-05
Document File: 1 page(s) / 26K

Publishing Venue

The IP.com Prior Art Database

Abstract

When the throttle is not controllable, it is released to a spring-neutral position of roughly 8 degrees, which provides a limited amount of airflow. When the hybrid system needs more power than the engine can provide at the current RPM, it raises RPM. When the throttle in limp-home position, raising the RPM beyond 2000RPM will actually decrease the amount of power the engine delivers. Above 3000 RPM, the engine is being pushed by the hybrid system, draining power from the system. This condition quickly results in a drained hybrid battery and no power available to move the vehicle. The problem is solved by tightly constraining the RPM that the hybrid system is allowed to turn the engine when the ETC is in limp-home mode. The RPM range is optimized for peak power delivery when the ETC is near 8 degrees. The requested torque is set to the indicated torque as inferred from airflow. Using the electric machine to control engine RPM to a confined region on a hybrid electric vehicle during time that the throttle is uncontrollable.

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Method to Control Engine Torque and RPM in a Hybrid Electric Powertrain

Problem

When the throttle is not controllable, it is released to a spring-neutral position of roughly 8 degrees, which provides a limited amount of airflow.  When the hybrid system needs more power than the engine can provide at the current RPM, it raises RPM.  When the throttle in limp-home position, raising the RPM beyond 2000RPM will actually decrease the amount of power the engine delivers.  Above 3000 RPM, the engine is being pushed by the hybrid system, draining power from the system.  This condition quickly results in a drained hybrid battery and no power available to move the vehicle.

Solution

The problem is solved by tightly constraining the RPM that the hybrid system is allowed to turn the engine when the ETC is in limp-home mode.  The RPM range is optimized for peak power delivery when the ETC is near 8 degrees. The requested torque is set to the indicated torque as inferred from airflow. 

Using the electric machine to control engine RPM to a confined region on a hybrid electric vehicle during time that the throttle is uncontrollable.

Figure 1.  Logic Diagram for proposed engine speed limiting

Submitted Anonymously