Tractor Creep Gear Train for High Reduction in a Compact Case
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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 conventional brake systems for large tractors require strong, heavy axle cases to handle large braking forces, increasing costs and weight.
Innovation Solution
The system employs a gear transmission with an output shaft and switchable output shaft gear for power transmission, and a creep speed changing apparatus with multiple pairs of gears to achieve higher deceleration ratios without increasing transmission case size, and integrates the brake apparatus within the transmission case to apply braking force directly to the transmission case, reducing the load on the axle case.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gears with large gear diameter are used to increase deceleration ratio throughout creep speed change, then the deceleration ratio is improved, but the 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) that operate 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 deceleration performance.
2Force
If the axle case is made strong enough to bear large braking reaction force, then the braking force capability is improved, but the axle case cost and weight increase
Solution Approach 1:
The brake apparatus is extracted from the axle case and relocated to the transmission case. The braking function is separated from the axle case structure, allowing the axle case to be designed without the need to withstand large braking reaction forces. This extraction enables the axle case to be lighter and less expensive while the braking capability is maintained through the separately located brake apparatus that transmits braking forces to the transmission case instead.
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 configuration allows for higher deceleration ratios and reduced transmission case size while providing a strong, cost-effective braking system that does not increase the weight or cost of the axle case, enabling efficient low-speed travel and robust braking.
Implementation Method 1
a first deceleration gear that is supported by the relay shaft so as to be rotatable relative to the relay shaft, in a state of meshing with the first power transmission gear, and rotates at a lower speed than the first power transmission gear; a second deceleration gear that is supported by the output shaft so as to be rotatable relative to the output shaft, in a state of meshing with the second power transmission gear, and rotates at a lower speed than the second power transmission gear; a third deceleration gear that is supported by the relay shaft so as not to be rotatable relative to the relay shaft, in a state of meshing with the third power transmission gear, and rotates at a lower speed than the third power transmission gear; and a pair of deceleration gears that are provided so as to span the relay shaft and the output shaft
Implementation Method 2
a brake apparatus that includes a brake disc, a disc receiver, and a rotating cam that presses the brake disc against the disc receiver, and performs a braking action on the axle
Data Source
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 includes: a first power transmission gear that is provided on an output shaft gear of a gear transmission; a first deceleration gear that is supported by a relay shaft so as to be rotatable relative to the relay shaft, in a state of meshing with the first power transmission gear; a second power transmission gear that is provided on the first deceleration gear; a second deceleration gear that is supported by an output shaft of the gear transmission so as to be rotatable relative to the output shaft, in a state of meshing with the second power transmission gear; a third power transmission gear that is provided on the second deceleration gear; a third deceleration gear that is supported by the relay shaft so as not to be rotatable relative to the relay shaft, in a state of meshing with the third power transmission gear; and a pair of deceleration gears that are provided so as to span the relay shaft and the output shaft, and decelerate power from the relay shaft and transmit the resulting power to the output shaft.