Hydrostatic CVT Swashplate Control for Smooth Tractor Braking
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Solution Overview
Problem
Existing tractor designs with hydrostatic continuously variable transmissions face challenges in stabilizing behavior, especially under increased load and during braking, due to speed-shift shocks and inadequate engagement of compound planetary transmission units.
Innovation Solution
A working vehicle equipped with a swashplate-controlled hydraulic pump, a variable-speed traveling motor, angle and rotation speed detectors, and a controller that adjusts the swashplate angle to stabilize transmission behavior, improves travelability by reducing rotation speed and angle deviations, and strategically engages/disengages clutch mechanisms during braking and acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the hydrostatic continuously variable transmission unit transmits power to the compound planetary transmission unit, then power transmission is achieved, but speed-shift shock becomes large when speed shift is performed
Solution Approach 1:
The clutch mechanism is engaged in advance before the speed shift is completed, so that when the speed shift finishes, the power transmission path is already established. This preliminary engagement prevents sudden shock during the transition. Specifically, the controller engages the clutch mechanism before the rotation speed deviation between the continuously variable transmission unit and planetary transmission unit becomes too large, ensuring smooth power transfer.
Solution Approach 2:
The clutch mechanism acts as an intermediary element between the continuously variable transmission unit and the planetary transmission unit. It provides a buffer that allows gradual engagement and disengagement, mediating the shock that would otherwise occur during direct power transmission during speed shifts.
2Stability of the object's composition
If the rotation speed of the hydraulic motor is made constant by controlling the swashplate angle, then stable operation is achieved, but when load increases it becomes difficult to stabilize the behavior of the continuously variable transmission
Solution Approach 1:
The control system dynamically adjusts the swashplate angle based on real-time rotation speed feedback. When load increases causing rotation speed deviation, the controller modifies the swashplate angle to compensate, maintaining stable operation while adapting to changing load conditions. This dynamic control allows the system to maintain stability across varying operational demands.
3Device complexity
If the compound planetary transmission unit is not engaged during braking, then the transmission structure remains simple, but the behavior (traveling) of the tractor at braking may be changed
Solution Approach 1:
The clutch mechanism is engaged in advance before braking occurs, preparing the power transmission path. This preliminary engagement ensures that during braking, the power from the hydraulic motor can be properly transmitted through the planetary transmission unit, providing predictable and controllable braking behavior without complicating the overall transmission structure.
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 stabilizes the continuously variable transmission, enhances travelability by minimizing speed-shift shocks, and improves braking performance by adjusting power output and clutch engagement, resulting in smoother operation and reduced deviations during load changes and braking.
Implementation Method 1
a hydraulic pump including a swashplate configured to change an output of the hydraulic pump according to a swashplate angle
Implementation Method 2
a traveling motor including an output shaft having a rotation speed variable according to the output of the hydraulic pump and capable of transmitting power of the output shaft to the traveling device
Data Source
AI summary
A working vehicle includes: a vehicle body provided with a traveling device; a hydraulic pump including a swashplate configured to change an output of the hydraulic pump according to a swashplate angle; a traveling motor including an output shaft having a rotation speed variable according to the output of the hydraulic pump and capable of transmitting power of the output shaft to the traveling device; an angle detector configured to detect the swashplate angle that is an angle of the swashplate; and a swashplate control unit configured to control the swashplate angle on the basis of control information relating to control of the swashplate angle and an actual swashplate angle that is the swashplate angle detected by the angle detector.