Work Machine Drivetrain Downshift Using Dual-Motor Clutch Handover
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Solution Overview
Problem
Electrically driven mobile machines face difficulties in rotational speed synchronization during shifting operations, particularly in traction downshifts, due to the higher moment of inertia and rotational speed spectrum of electric motors, leading to increased clutch size and weight, higher costs, and greater drag torques and friction losses.
Innovation Solution
A method where the first electric motor drives the propulsion drive via a clutch during shifting, allowing the second electric motor to rapidly increase its rotational speed without power interruption, using the first motor to maintain traction force and synchronize clutch elements, thus reducing the need for large, heavy clutches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rotational speed synchronizing is performed during shifting operation in electrically driven mobile machines, then power transmission continuity is maintained, but clutch size and weight must be increased to handle higher differential rotational speeds
Solution Approach 1:
The system dynamically switches between two clutch configurations: a first clutch for normal power transmission and a second clutch specifically for rotational speed synchronizing during shifting operations. This dynamic reconfiguration allows the system to handle high differential rotational speeds only when necessary, enabling the use of a smaller second clutch that would not need to continuously handle the full torque load.
Solution Approach 2:
The clutch system is segmented into two separate clutches with distinct functions: the first clutch handles normal power transmission from the internal combustion engine, while the second clutch is dedicated to rotational speed synchronizing during shifts. This segmentation allows each clutch to be optimized for its specific function, with the second clutch being smaller since it only needs to handle synchronizing torque rather than full power transmission.
2Reliability
If larger clutches are used to handle higher differential rotational speeds during shifting, then rotational speed synchronization is achieved, but installation space requirement and production costs increase
Solution Approach 1:
The clutch system is divided into two separate clutches with distinct functions. The second clutch is specifically designed for rotational speed synchronizing during shifting operations, allowing it to be smaller in size since it only needs to handle the torque required for synchronization rather than full power transmission. This segmentation reduces the installation space requirement compared to a single large clutch design.
3Productivity
If larger clutches are used to handle higher differential rotational speeds, then shifting under power is enabled, but drag torques and friction losses increase
Solution Approach 1:
The system dynamically engages the second clutch only during the brief period when rotational speed synchronizing is needed during shifting operations. After synchronization is complete, the second clutch is disengaged and normal power transmission resumes through the first clutch. This dynamic operation minimizes the time that friction and drag torques are present in the second clutch, reducing overall energy losses.
Solution Approach 2:
The second clutch is designed to provide exactly the amount of torque capacity needed for rotational speed synchronizing, no more. This partial action approach allows the clutch to be smaller and generate less friction and drag torques during its brief period of engagement, compared to a larger clutch that would continuously handle full power transmission.
4Power
If electric motors with greater moment of inertia are used, then power output is increased, but rotational speed synchronization during shifting becomes more difficult
Solution Approach 1:
The rotational speed synchronizing function is extracted from the normal power transmission path by introducing a separate second clutch specifically dedicated to this function. This allows the electric motor's greater moment of inertia to be fully utilized for power output without compromising synchronization capability, as the second clutch can independently manage the synchronizing process during shifting operations.
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
Enables seamless power-shift capability without traction interruption, using smaller, less expensive clutches and maintaining power output during shifting, while ensuring continuous operation of the working drive and efficient rotational speed adaptation.
Implementation Method 1
comparatively greater drag torques and friction losses
Data Source
AI summary
A method for operating a drive train for a mobile machine, including a first electric motor driving a working drive of the mobile machine via a first transmission arrangement, and a second electric motor driving a propulsion drive of the mobile machine via a second transmission arrangement, wherein a rotational speed of the second electric motor increases during a shifting operation of the second transmission arrangement out of a higher gear stage into a lower gear stage, and wherein during the shifting operation, a drive connection is established via a first clutch between the first electric motor and the propulsion drive, such that the propulsion drive is driven by the first electric motor during the shifting operation.