Branched Transmission with Planetary Summing Unit
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Solution Overview
Problem
Existing continuously variable power-split transmissions for vehicles and work machines are costly and space-intensive due to the need for multiple hollow shafts and clutches designed for high torque, which complicates pilot oil supply and limits design flexibility.
Innovation Solution
A simplified design featuring a single four-shaft planetary gear summation transmission with reduced components, where clutches are only designed for lower input torque and mechanical power paths can route through either the sun gear or ring gear, allowing for direct coaxial input and output shafts and easier pressure oil supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If multiple hollow shafts and high-torque clutches are used in existing transmissions, then torque handling capability is improved, but device complexity and installation space increase
Solution Approach 1:
The transmission is divided into two distinct torque paths: a mechanical power path for high-torque direct transmission and a hydrostatic path for variable ratio transmission. This segmentation allows each path to be optimized independently, with the mechanical path handling peak torques through simple gear connections and the hydrostatic path handling variable speed requirements through the variator, thereby reducing overall complexity while maintaining torque capability
Solution Approach 2:
A coupling device acts as an intermediary between the mechanical and hydrostatic power paths, selectively connecting or disconnecting them based on operating conditions. This intermediary allows the system to switch between high-torque mechanical transmission and variable-ratio hydrostatic transmission, enabling torque handling capability without requiring the entire transmission system to be designed for maximum torque in all configurations
2Force
If multiple hollow shafts are used in existing transmissions, then torque handling capability is improved, but manufacturing cost and assembly difficulty increase
Solution Approach 1:
The transmission system is segmented into separate mechanical and hydrostatic modules that can be manufactured and assembled independently. The mechanical power path uses standard gear components that are easier to manufacture than complex hollow shaft assemblies, while the hydrostatic path uses the variator and coupling device as separate manufacturable units, reducing overall manufacturing complexity and cost
3Power
If clutches are arranged in the power flow between the variator and summing transmission, then power splitting is achieved, but installation space and hydraulic supply complexity increase
Solution Approach 1:
The coupling device merges the mechanical and hydrostatic power paths into a single integrated transmission system, eliminating the need for separate clutch assemblies distributed throughout the power flow. This consolidation achieves power splitting functionality while reducing the total installation space required and simplifying hydraulic supply requirements
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 design achieves a cost-effective, space-saving, and more flexible transmission with reduced component complexity, enabling direct through-drive and efficient power splitting with fewer hollow shafts and simplified clutch arrangements.
Implementation Method 1
a variator (2) which supplies a portion of the power to the summing transmission (4) with an output speed continuously controllable between maximum speeds in both directions of rotation
Implementation Method 2
the summing transmission is a four-shaft planetary gear set comprising a first sun gear as the first central gear, a second central gear, a ring gear and a number of planet gears mounted on a carrier (also called a web)
Implementation Method 3
a planetary gear set with two ring gears and is connected to the output-side clutches via two further hollow shafts
Data Source
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AI summary
A continuously variable transmission (CVT) for powering vehicles with an internal combustion engine comprises a variator, a summing unit, and several clutches. Multiple ranges can be synchronized at synchronization points, with the clutches (C0, C1; B0, B1) grouped together in an input unit (E) located upstream of the summing unit (SG1) in the power flow.In order to achieve high functionality with the simplest possible design, the summing transmission (SG1) has meshing first (P1) and second (P2) planet gears (P1, P2) mounted on a common planet carrier (St1), the first sun gear (S1) or the first ring gear (H1) is driven by the internal combustion engine (V) and the second central gear (S2; H2) by the variator (V), wherein the first sun gear (S1) or the first ring gear (H1) is alternately connected to the internal combustion engine (V) via the input unit (E) at a synchronization point when transitioning from one range to the next, and the carrier (St1) is connected to the vehicle's drive.