Work Vehicle Speed Control Clutch Overlap
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Solution Overview
Problem
Existing work vehicles experience speed change shocks during heavy load operations due to incomplete power disconnection when switching between speed stages, affecting the speed change feeling.
Innovation Solution
The work vehicle employs a combination of the high-speed clutch of the Hi-Lo clutch and the first- and fourth-speed clutches of the hydraulic main speed change clutches to ensure continuous power transmission until the switch is complete, and supplies operating oil to the oil chamber of the speed change destination clutch to rapidly increase pressure, thereby suppressing power disconnection and improving the speed change feeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the main speed change clutch and high-low clutch are switched at the same time with complete power disconnection, then the speed change is rapid, but a speed change shock occurs during heavy load work
Solution Approach 1:
The patent applies preliminary action by pre-engaging the destination clutch (e.g., high-speed clutch or main speed change clutch) before completely disengaging the source clutch. This ensures that power transmission is re-established before the old path is fully cut, preventing complete power disconnection and reducing speed change shock during heavy load operations
Solution Approach 2:
The patent uses an intermediary approach by maintaining overlapping engagement of source and destination clutches during the transition period. This overlapping engagement acts as a mediator that smooths the power transmission transition, preventing abrupt shocks while still achieving rapid speed change
2Reliability
If the pressure of the speed change source clutch is kept until the destination clutch reaches predetermined pressure, then power disconnection is suppressed, but the speed change feeling is not optimized during heavy load work
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the pressure control strategy based on the clutch engagement state and load conditions. The control system continuously monitors and adjusts the pressure of source and destination clutches to optimize both power transmission continuity and speed change feeling, rather than using a fixed pressure maintenance approach
Solution Approach 2:
The patent changes parameters by dynamically modifying the pressure levels and engagement timing of clutches based on real-time operating conditions. This includes adjusting the pressure rise rate, engagement duration, and disengagement timing to achieve optimal speed change feeling while maintaining reliable power transmission
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
This approach effectively reduces speed change-induced shocks and enhances the speed change feeling by maintaining power transmission and controlling pressure transitions during shifts from high to low speed stages and vice versa.
Implementation Method 1
a work vehicle configured to change a speed by a combination of a main speed change clutch and a high-low clutch (a Hi-Lo clutch) configured to operate by a hydraulic pressure
Data Source
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AI summary
[Problem] To provide a work vehicle and a method for controlling work vehicle speed change, which can reduce as much as possible a speed change shock during speed change and thus improve a speed change feeling. [Means for Resolution] A work vehicle includes a hydraulic main speed change clutch and a Hi-Lo clutch provided to a power transmission device for transmitting power to drive wheels, and a speed change control device configured to control vehicle speed in multi-stage manner by a combination of the main speed change clutch and the hydraulic Hi-Lo clutch. In shift-up operation for changing the speed from a low speed stage range to a high speed stage range in which a high speed clutch is used, before completion of speed change, the high speed clutch pressure is kept at a first pressure (Pa) higher than the low speed clutch pressure while the pressure of the main speed change clutch, which is a speed change source, is kept, so that the power is transmitted by a combination of the high speed clutch and the main speed change clutch, which is a speed change source.