Hydrostatic Transmission Gear Shifting Synchroniser Wear
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing transmission arrangements with hydrostatic and manual gearboxes suffer from significant wear on synchroniser rings due to large rotational speed jumps and inertial stresses, leading to reduced synchroniser lifetime and harsh gear changes.
Innovation Solution
The method involves reducing the output torque of the hydrostatic motor before gear changes, using an electronic control unit to set the rotational speed of the hydrostatic motor above the target speed, and adjusting the gear ratio to minimize synchroniser load, thereby reducing friction and shifting jolt during gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the hydrostatic motor is set to approximately 0 pivoting angle to reduce output torque for load-free gear changing, then the gear changing becomes easier, but large rotational speed jumps cause considerable wear on synchroniser rings and increase shifting jolt
Solution Approach 1:
The patent applies preliminary action by pre-positioning the hydrostatic motor at a first rotational speed corresponding to the gear to be engaged before the actual gear changing occurs. The control unit determines this preliminary speed based on the target gear, and the hydrostatic transmission adjusts the motor speed in advance. When the gear change is initiated, the motor is already near the target speed, minimizing the rotational speed jump that the synchroniser must absorb. This preliminary preparation significantly reduces wear on synchroniser rings while maintaining ease of gear changing.
2Productivity
If the synchroniser rings are applied while the next gear is being engaged, then the gear change is completed, but the suddenly occurring additional moment of the hydraulic motor ensures a considerable shifting jolt
Solution Approach 1:
The patent applies preliminary anti-action by having the hydrostatic transmission counteract the inertial moment of the hydraulic motor before the gear change is completed. The control unit monitors the gear changing process and, upon detecting that the synchroniser rings are being applied, commands the hydrostatic transmission to generate a counteracting torque. This preliminary anti-action neutralizes the suddenly occurring additional moment during gear engagement, significantly reducing the shifting jolt transmitted to the vehicle cabin while ensuring complete gear change.
3Ease of operation
If the rotational speed of the hydrostatic motor is reduced significantly for gear changing, then the gear can be disengaged easily, but the inert mass of the hydraulic motor causes considerable stress on the synchroniser
Solution Approach 1:
The patent applies dynamics by continuously and dynamically adjusting the rotational speed of the hydrostatic motor during the gear changing process, rather than making abrupt speed reductions. The control unit modulates the hydrostatic transmission to gradually reduce the motor speed to match the target gear speed, taking into account the inert mass of the hydraulic motor. This dynamic speed adjustment minimizes the stress impulse on the synchroniser rings while still achieving easy gear disengagement, as the speed reduction is smooth and controlled rather than sudden.
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 reduces synchroniser wear, extends its lifespan, and enables smoother gear changes by minimizing the work required from the synchroniser and reducing inertial stresses.
Implementation Method 1
a hydrostatic transmission (3) having a variable displacement hydraulic motor (9)
Implementation Method 2
the synchroniser, which is present in the downstream manual gearbox, adjusts the actual rotational speed of the hydrostatic motor to the driving situation by reducing the rotational speed of the hydrostatic motor
Data Source
AI summary
The invention concerns a method and a transmission arrangement for changing gears in a transmission with a hydrostatic transmission and a manual gearbox (4) connected downstream from it. First the output torque of a hydrostatic motor (9) is reduced. After the reduction of the output torque of the hydrostatic motor (9), an engaged gear (12, 13) of the manual gearbox (4) which is connected downstream is disengaged. An output rotational speed of the hydrostatic motor (9) corresponding to the gear (13, 12) to be engaged is determined. The gear ratio of the hydrostatic transmission is then adjusted, so that the output rotational speed of the hydrostatic motor (9) is higher than the determined corresponding output rotational speed. After this increased output rotational speed is reached, the gear (13, 12) to be engaged is engaged.