Powershift Transmission Layout for More Gear Variants in Compact Tractors
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Solution Overview
Problem
Existing powershift transmissions for agricultural machines are costly to manufacture and lack versatility, particularly in not allowing for a crawling speed mode, with limited gear shift variants and requiring a large number of clutches, which complicates design and increases size.
Innovation Solution
A powershift transmission design featuring two range units and a reduction gear unit with multiple gear wheel pairs and shifted states, allowing for a high number of gear shift variants while minimizing the number of clutches and maintaining a compact size, achieved through a parallel offset auxiliary shaft unit and hydraulic actuation arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional two-stage powershift transmission is used, then the transmission can be operated in through-connected drive mode and gear reduction mode, but it is costly in terms of fabrication technology and does not permit further operating modes such as crawling speed mode
Solution Approach 1:
The transmission is divided into two independent range units (front-mounted and rear-mounted), each capable of providing multiple gear ratios. This segmentation allows each unit to be optimized independently and provides versatility through combination of different range unit configurations, enabling crawling speed mode and other operating modes without requiring a completely new transmission design.
Solution Approach 2:
The range units are designed with universal applicability across different operating modes. The same range unit configuration can serve multiple functions including through-connected drive mode, gear reduction mode, and crawling speed mode by varying the engagement of gear wheel pairs and clutches, eliminating the need for mode-specific transmission designs.
2Adaptability or versatility
If multiple clutches are added to increase gear shift variants, then more operating modes become available, but the device complexity and size increase
Solution Approach 1:
The clutch system is segmented into two independent range units, each with its own set of clutches. This allows the clutches in one range unit to be optimized independently of the other, reducing the overall complexity by dividing the control system into manageable modules rather than requiring a single complex clutch arrangement for all gear shifts.
Solution Approach 2:
The transmission utilizes dynamic engagement and disengagement of gear wheel pairs within each range unit to create multiple gear shift variants. By dynamically reconfiguring which gear wheels are engaged rather than relying solely on additional clutches, the system achieves high versatility with a limited number of clutch actuators.
3Volume of moving object
If the auxiliary shaft unit is arranged with parallel offset between input shaft and output shaft, then a compact size is achieved, but the torque transmission path becomes more complex
Solution Approach 1:
The auxiliary shaft unit is positioned with a parallel offset between the input and output shafts, utilizing the radial dimension rather than extending the axial length. This three-dimensional arrangement achieves compact transmission size by stacking gear components radially rather than arranging them linearly, reducing the overall footprint of the transmission housing.
Solution Approach 2:
The gear wheel pairs and shafts are arranged in a nested configuration where the auxiliary shaft unit is positioned within the space between the input and output shafts. This nesting approach allows multiple torque transmission paths to coexist in a compact volume, with gear components from different range units interlocking in a space-efficient manner.
Data Source
AI summary
A powershift transmission for an agricultural machine includes a transmission housing, an input shaft unit and an output shaft, wherein the input shaft unit and the output shaft extend at least in sections within the transmission housing. An auxiliary shaft is arranged parallel to but offset between the input shaft unit and the output shaft. The input shaft unit and the auxiliary shaft are connected to one another via a front-mounted range unit, and the auxiliary shaft and the output shaft are connected to one another via a rear-mounted range unit. The front-mounted and rear mounted range units each includes at least two gear wheel pairs, the at least two gear wheel pairs being individually coupled or decoupled. The auxiliary shaft unit includes a first auxiliary shaft and a second auxiliary shaft, where the first and second auxiliary shafts are coupled to one another via a reduction gear unit.