Hybrid Vehicle Deceleration Control With Lower Engine Speed Target
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Solution Overview
Problem
In hybrid vehicles, restricting fuel cut to maintain deceleration can lead to excessive rotational speed of the first motor, increasing power consumption, and during deceleration due to downshift, the power consumption further rises.
Innovation Solution
A hybrid vehicle system that includes an engine, first and second motors, and a control device to execute a decrease process by restricting fuel cut and an increase process by power running torque of the first motor, with the target rotational speed set to a lower value during the increase process, especially when battery charge is low or coolant temperature is low.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fuel cut is restricted to maintain deceleration, then deceleration performance is improved, but rotational speed of the first motor becomes excessively high and power consumption increases
Solution Approach 1:
The patent applies dynamics by making the target rotational speed variable rather than fixed. During the decrease process, the target rotational speed is set to a lower value than the standard target rotational speed. This dynamic adjustment allows the first motor to achieve necessary deceleration while operating at lower rotational speeds, thereby reducing power consumption.
Solution Approach 2:
The patent changes the parameter of target rotational speed based on operational conditions. When the decrease process is detected, the control device sets the target rotational speed to a lower value. This parameter change enables the system to maintain deceleration performance while reducing the rotational speed and corresponding power consumption of the first motor.
2Speed
If increase process is executed during decrease process, then engine rotational speed reaches target speed, but power consumption of the first motor and vehicle increases
Solution Approach 1:
The patent applies dynamics by adjusting the target rotational speed based on the operational state. When the decrease process is detected during the increase process, the target rotational speed is set to a lower value. This prevents excessive rotational speed and associated power consumption while still achieving the necessary engine speed for deceleration control.
Solution Approach 2:
The patent uses feedback by detecting whether the decrease process is being executed and adjusting the target rotational speed accordingly. The control device continuously monitors the operational state and modifies the target rotational speed parameter based on this feedback, preventing unnecessary power consumption during the increase process.
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
Suppresses electric power consumption and prevents battery undercharging by setting a lower target rotational speed during the increase process, thereby maintaining efficient deceleration and reducing power consumption.
Implementation Method 1
a first motor that rotates the engine
Implementation Method 2
a second motor coupled to the drive shaft
Data Source
AI summary
The hybrid vehicle includes an engine coupled to a drive shaft, a first motor that rotates the engine a second motor coupled to the drive shaft, a transmission interposed between the engine and the first motor, and the second motor, and a control device configured to execute a decrease process and an increase process. The decrease process is a process for decreasing deceleration of the hybrid vehicle by restricting fuel cut in the engine. The increase process is a process for increasing a rotational speed of the engine to a target rotational speed by power running torque of the first motor during deceleration by downshift of the transmission. The target rotational speed in the increase process is set to a lower value during execution of the decrease process than during stop of the decrease process.