Tractor Creep Gear Train Layout for High Reduction in Compact Housings
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Solution Overview
Problem
Conventional travel power transmission systems for tractors require large gear diameters for high deceleration ratios, leading to increased transmission case size, and the braking system applies reaction force to the axle case, making it heavy and costly. Additionally, existing systems struggle to achieve a high braking force without increasing the axle case's weight and cost.
Innovation Solution
The system employs a gear transmission with an output shaft and a creep speed changing apparatus using four pairs of gears to achieve higher deceleration ratios without enlarging the transmission case, and integrates the brake apparatus within the transmission case to distribute the braking reaction force, allowing for a strong yet lightweight axle case.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If large gear diameters are used to increase deceleration ratio in creep speed changing apparatus, then deceleration ratio is improved, but transmission case size increases
Solution Approach 1:
The creep speed changing apparatus is divided into multiple independent gear pairs (first creep gear pair, second creep gear pair, third creep gear pair) arranged in sequence. Each gear pair provides a portion of the total deceleration ratio, allowing the system to achieve high overall deceleration without requiring any single gear to have an excessively large diameter. This segmentation enables compact gear design while maintaining the required power transmission capability.
Solution Approach 2:
The patent utilizes the axial dimension by arranging multiple gear pairs in series along the power transmission path. Instead of increasing gear diameters in the radial plane, the solution extends the transmission train axially, allowing each gear pair to contribute incrementally to the total deceleration ratio. This dimensional approach enables high deceleration ratios within a compact transmission case volume.
2Force
If brake apparatus is integrated into transmission case, then braking reaction force is distributed, but device complexity increases
Solution Approach 1:
The brake apparatus is merged with the transmission case by utilizing the transmission case as the brake disc receiver. The brake disc is rotatably coupled to the output shaft, and the transmission case itself serves as the stationary receiver that receives braking reaction forces. This integration eliminates the need for a separate brake housing or mounting structure, reducing overall device complexity while achieving effective force distribution to the transmission case.
Data Source
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AI summary
Regarding a travel power transmission apparatus for a tractor, in which a creep speed changing apparatus is housed in a transmission case, the present invention increases a deceleration ratio throughout the creep speed change while suppressing an increase in the size of the transmission case. A creep speed changing apparatus 60 includes: a first power transmission gear 66 that is provided on an output shaft gear 54b of a gear transmission 40; a first deceleration gear 62 that is supported by a relay shaft 61 so as to be rotatable relative to the relay shaft 61, in a state of meshing with the first power transmission gear 66; a second power transmission gear 67 that is provided on the first deceleration gear 62; a second deceleration gear 63 that is supported by an output shaft 43 of the gear transmission 40 so as to be rotatable relative to the output shaft 43, in a state of meshing with the second power transmission gear 67; a third power transmission gear 68 that is provided on the second deceleration gear 63; a third deceleration gear 64 that is supported by the relay shaft 61 so as not to be rotatable relative to the relay shaft 61, in a state of meshing with the third power transmission gear 68; and a pair of deceleration gears 65 that are provided so as to span the relay shaft 61 and the output shaft 43, and decelerate power from the relay shaft 61 and transmit the resulting power to the output shaft 43.