Vehicular Drive Control Device Engine Speed Limiting
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Solution Overview
Problem
The durability of coupling devices in vehicular drive systems is compromised when switching between power-cutoff and power-transmitting states, especially with increasing engine torque, due to manual operation in hybrid vehicle drive systems.
Innovation Solution
A control device that includes a differential mechanism, a transmission portion, a coupling device, and a shifting device, where the engine-speed control means limits engine speed to a predetermined value when shifting from a non-drive to a drive position, and electric-motor control places electric motors in a non-load state, reducing engine torque and energy loss, thereby enhancing coupling device durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the shifting device is manually operated from the non-drive position to the drive position with high engine torque, then the power transmitting path is established, but the durability of the coupling device deteriorates
Solution Approach 1:
The control device limits engine speed to a predetermined value before the coupling device is engaged during manual shifting from non-drive to drive position. This preliminary speed limitation prevents excessive engine torque from being transmitted to the coupling device during engagement, thereby protecting the coupling device from durability deterioration while still allowing the power transmitting path to be established.
2Reliability
If the engine speed is limited to a predetermined value during shifting, then the durability of the coupling device is improved, but the engine output is reduced
Solution Approach 1:
The engine speed limitation is applied dynamically only during the specific transient period when the shifting device is being operated from non-drive to drive position. Once the shifting is complete and the power transmitting path is established, the engine speed limitation is released and normal engine operation resumes. This dynamic, time-limited approach protects the coupling device during vulnerable engagement while minimizing impact on overall engine output and performance.
3Loss of energy
If the electric motors are placed in a non-load state, then the energy loss is reduced and fuel economy is improved, but the ability to assist engine torque is reduced
Solution Approach 1:
The electric motors are placed in a non-load state preliminarily during the manual shifting operation from non-drive to drive position. This preliminary disengagement of motor load eliminates energy loss associated with motor operation during the shifting transient. The motors can subsequently be re-engaged to provide torque assistance when needed for vehicle propulsion, thus achieving energy savings during shifting while preserving torque assistance capability during normal operation.
Data Source
AI summary
A control device for a vehicular drive system including (a) a differential portion having a differential mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, and a second electric motor disposed in a power transmitting path between the power transmitting member and a drive wheel of a vehicle, (b) a transmission portion which constitutes a part of the power transmitting path, (c) a coupling device operable to place a power transmitting path between the engine and the drive wheel, selectively in a power-transmitting state or a power-cutoff state, and (d) a shift lever operable between a drive position for the coupling device to select the power-transmitting state, and a non-drive position for the coupling device to select the power-cutoff state, the control device including an engine-speed control device for controlling engine speed NE so as not to exceed a predetermined engine speed value NE′ while the shift lever is placed in the non-drive position, so that the coupling device is engaged while engine torque TE is reduced as a result of an operation of the shift lever from the non-drive position to the drive position, whereby the durability of the coupling device is improved.