Hydraulic Transmission Mode Switching for Smooth Low-Speed Torque Control
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Solution Overview
Problem
Agricultural and earth-moving machinery with hydraulic transmissions face challenges in efficiently switching between low-speed, high-torque 'Turtle' mode and high-speed 'Rabbit' mode due to the lack of control over hydraulic motor displacement, leading to discomforting jerks during mode transitions.
Innovation Solution
Implementing an automatic switching method that activates 'Turtle' mode when the accelerator signal is below a threshold and vehicle speed is low, and switches to 'Rabbit' mode when the vehicle speed exceeds a predetermined threshold, with instantaneous displacement reduction and linear displacement control proportional to the motor's revolution speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the hydraulic motor is forced to maximum displacement to perform low-speed operations, then low speed and high torque are achieved, but the transition between modes produces jerks and discomfort
Solution Approach 1:
The patent applies dynamics by making the hydraulic motor displacement variable rather than fixed. The motor transitions from forced maximum displacement in Turtle mode to load-dependent variable displacement in Rabbit mode, allowing smooth adaptation between operating conditions without abrupt jerks during mode transitions.
Solution Approach 2:
The patent changes the displacement parameter of the hydraulic motor dynamically. In Turtle mode, displacement is forced to maximum; in Rabbit mode, displacement varies continuously based on load conditions, enabling smooth parameter transitions that eliminate jerks during mode switching.
2Power
If the hydraulic motor displacement is forced to maximum in Turtle mode, then high transmission ratio is achieved, but the control system complexity increases
Solution Approach 1:
The patent applies self-service by enabling the hydraulic motor to automatically adjust its own displacement based on operating mode. In Rabbit mode, the motor self-regulates displacement according to load conditions without external intervention, simplifying the overall control system while maintaining high transmission ratio capability in Turtle mode.
3Speed
If the vehicle operates in Rabbit mode with variable displacement, then high speed is achieved, but torque control precision decreases
Solution Approach 1:
The patent applies feedback by making the hydraulic motor displacement depend on the load perceived by the wheel. The system continuously monitors load conditions and adjusts displacement accordingly, maintaining precise torque control even at high speeds in Rabbit mode through closed-loop feedback mechanisms.
Data Source
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AI summary
Control method of a hydraulic transmission of an agricultural vehicle or an earth-moving machine, comprising a variable displacement hydraulic motor (HM), in which the displacement is variable and a function of a load applied to the wheel, defining a first operating and fixed mode at a relative maximum displacement value due to the activation of a control signal, defining a second operating mode, the method providing for automatically activating said control signal when an accelerator signal is lower than a predetermined threshold (AC_TH) and the vehicle speed is lower than a first speed threshold (SP_TH1) or the accelerator signal is higher than said predetermined threshold (AC_TH) and the vehicle speed is lower than a second speed threshold (SP_TH2) lower than the first speed threshold (SP_TH1) and to automatically deactivate said command signal in the opposite conditions.