Hybrid Vehicle Catalyst Warm-Up Control During EV-HEV Switching
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Solution Overview
Problem
In hybrid vehicles, unnecessary catalyst warm-up can occur when the engine is started due to a rapid increase in driver-required torque during EV travel, leading to poor fuel efficiency.
Innovation Solution
A control device that calculates a warm-up completion period and a catalyst performance maintaining period to determine if a catalyst warm-up is necessary, prohibiting unnecessary warm-ups by switching between EV and HEV modes based on predicted arrival times and driver torque requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is started in response to a rapid increase in driver required torque during EV traveling to the destination point, then the catalyst warm-up is released and the engine operation continues, but fuel efficiency becomes worse due to unnecessary catalyst warm-up
Solution Approach 1:
The control device calculates the arrival period of time (time to reach start prediction point) and compares it with the catalyst warm-up efficient period of time (warm-up completion period + catalyst performance maintaining period) in advance. This preliminary calculation determines whether catalyst warm-up should be prohibited before the engine start event occurs, preventing unnecessary warm-up operations that would waste fuel.
Solution Approach 2:
The system dynamically adjusts the catalyst warm-up control strategy based on real-time conditions. When the arrival period is equal to or longer than the warm-up efficient period, the system prohibits catalyst warm-up control. When the arrival period is shorter, the system allows catalyst warm-up control. This dynamic adjustment optimizes fuel efficiency while ensuring catalyst performance when needed.
2Reliability
If the engine operation is continued for catalyst warm-up after the driver required torque decreases, then the catalyst temperature is maintained, but fuel consumption increases due to unnecessary engine operation
Solution Approach 1:
The system performs preliminary calculation of the catalyst performance maintaining period of time, which is the time for catalyst temperature to drop from warm-up completion temperature to lower limit temperature with engine stopped. This allows the system to predict whether the catalyst will maintain sufficient temperature without continuous engine operation, enabling early termination of unnecessary warm-up operations.
Solution Approach 2:
The catalyst retains heat from the warm-up operation and maintains its temperature for a certain period (catalyst performance maintaining period) without requiring continuous engine operation. The system exploits this thermal inertia to allow engine stop during EV traveling, letting the catalyst serve itself by maintaining temperature through retained heat.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively avoids unnecessary catalyst warm-ups, thereby improving fuel efficiency in hybrid vehicles by optimizing engine operation and catalyst warm-up timing.
Implementation Method 1
a catalyst to purify an exhaust gas from the engine
Implementation Method 2
operating the engine to warm-up the catalyst
Data Source
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AI summary
[Object] It is to provide a control device of a hybrid vehicle capable of avoiding an unnecessary catalyst warm-up to thereby improve a fuel efficiency performance. [Solution] An ECU performs a catalyst warm-up control, a switching control, and a calculation, the switching control being of switching between an EV mode and an HEV mode based on a driver required torque, the calculation being of calculating a start prediction point at which an engine is predicted to be started, and an arrival period of time t(D) to arrive at the start prediction point. The ECU, when starting the engine based on the driver required torque (at step S2), calculates a warm-up completion period, a catalyst performance maintaining period, and a catalyst warm-up efficient period when the catalyst warm-up control is to be performed. The ECU stops the engine to thereby prohibit the catalyst warm-up control (at step S6) if a condition for switching to the EV mode based on the driver required torque is established ("YES" at step S5) when the arrival period is equal to or longer than the catalyst warm-up efficient period ("YES" at step S4).