Working Vehicle Drive Control for Engine Downsizing
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Solution Overview
Problem
Downsizing engines while maintaining output is challenging due to increased parts and costs, with reduced output torque in low rotation regions and difficulty in securing output torque compared to engines with higher displacement.
Innovation Solution
A drive system control device for working vehicles with an engine and common rail fuel injection system, limiting engine speed to two levels, using a continuously variable transmission to maintain vehicle speed and adjust gear ratios, and optimizing fuel injection to reduce fuel consumption and secure higher output horsepower without the need for a supercharger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If engine displacement is reduced to achieve downsizing, then vehicle compactness and fuel consumption improve, but output torque in low rotation region decreases and parts cost increases
Solution Approach 1:
The patent changes the operating parameters of the engine by limiting rotation speed to two specific ranges (first rotation speed range and second rotation speed range higher than the first). This parameter change allows the engine to operate efficiently in high rotation regions while maintaining adequate torque through transmission ratio adjustments, achieving downsizing without superchargers while preserving fuel economy and acceptable power output.
Solution Approach 2:
The patent dynamically adjusts the transmission ratio of the continuously variable transmission based on the engine's rotation speed range. When the engine operates in the first rotation speed range, the transmission provides a first ratio, and when in the second range, it provides a second ratio. This dynamic adjustment compensates for torque variations and maintains vehicle performance across different operating conditions.
2Weight of moving object
If engine displacement is reduced, then vehicle weight decreases, but output torque in low rotation region becomes insufficient
Solution Approach 1:
The patent achieves downsizing by changing engine displacement parameters while compensating for torque loss through rotational speed management. The engine is designed to operate primarily in higher rotation speed ranges where a smaller displacement engine can maintain adequate power output, eliminating the need for torque-boosting devices like superchargers.
Solution Approach 2:
The continuously variable transmission acts as an intermediary between the downsized engine and the wheels. By providing appropriate ratio adjustments, it compensates for the reduced torque output of the smaller engine, ensuring sufficient wheel torque is delivered across various vehicle operating conditions.
3Power
If rotation speed is limited to two kinds, then output horsepower increases and downsizing is achieved, but vehicle speed stability may be affected
Solution Approach 1:
The patent dynamically adjusts the transmission ratio in response to engine rotation speed changes. When the engine switches between the first and second rotation speed ranges, the transmission ratio is simultaneously adjusted to compensate, thereby maintaining stable vehicle speed despite the bimodal engine operation.
Solution Approach 2:
The control system monitors engine rotation speed and transmission ratio, and adjusts the transmission ratio based on feedback from the engine's operating state. This feedback mechanism ensures that vehicle speed remains stable by compensating for power fluctuations when the engine operates in different rotation speed ranges.
Data Source
AI summary
In a working vehicle, it is possible to achieve a downsizing of an engine by securing an output torque in a low rotating region of the engine without using any supercharger. In the working vehicle having the engine mounted to a travel machine body, a common rail type fuel injection device which injects fuel to the engine, and a continuously variable transmission which shifts power from the engine, a rotating speed N of the engine is limited to two kinds, N#1 and N#2. Further, a change gear ratio of the continuously variable transmission is changed and regulated in such a manner as not to change a vehicle speed of the travel machine body before and after changing the rotation speed N whichever of the two kinds N#1 and N#2 the rotating speed N of the engine is changed to.