Hydrostatic Transmission Control for Downhill Speed and Torque
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Solution Overview
Problem
Existing work vehicles with hydraulically controlled motors experience uncontrolled acceleration downhill, low deceleration, and insufficient torque during high-load conditions due to limitations in traditional hydraulic transmission systems.
Innovation Solution
A hydrostatic transmission system with an electronically-controlled variable displacement hydraulic motor, coupled with pressure and speed sensors, and an electronic control unit that adjusts motor displacement based on pressure and speed measurements to enhance control and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a purely hydraulically controlled motor is used, then the system is simple to operate, but the vehicle accelerates uncontrollably when moving downhill
Solution Approach 1:
The patent implements an electronic control system that continuously monitors vehicle speed via a speed sensor and hydraulic circuit pressure via pressure sensors. The ECU processes this feedback information and dynamically adjusts the hydraulic motor displacement to maintain controlled vehicle speed, particularly preventing uncontrolled acceleration when moving downhill while preserving the simplicity of hydraulic operation.
2Device complexity
If traditional hydraulic transmission is used, then the system structure is simple, but deceleration and acceleration levels are low
Solution Approach 1:
The patent employs a variable displacement hydraulic motor whose displacement can be dynamically adjusted by the electronic control system. This dynamic adjustment capability allows the system to optimize motor displacement based on real-time operating conditions, enabling faster acceleration and deceleration responses while maintaining a relatively simple transmission structure compared to mechanical multi-speed systems.
3Speed
If hydraulic motor displacement is reduced for speed control, then vehicle speed is controlled, but torque becomes insufficient during high-load conditions
Solution Approach 1:
The patent utilizes an electronic control system that dynamically changes the displacement parameter of the hydraulic motor based on real-time sensor feedback. The ECU processes speed and pressure signals to determine optimal motor displacement, increasing displacement when high torque is needed during high-load conditions while maintaining speed control when appropriate, thus resolving the trade-off between speed control and torque availability.
4Force
If pressure-based control is used, then torque is improved during high-load conditions, but speed control precision decreases
Solution Approach 1:
The patent implements a dual-feedback control system that simultaneously monitors both hydraulic circuit pressure (for torque management) and vehicle speed (for speed control precision) through dedicated sensors. The ECU integrates both feedback signals to make balanced control decisions, ensuring that pressure-based torque improvement does not compromise speed control precision by continuously adjusting motor displacement based on the combined information from both sensor inputs.
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 solution provides improved controllability, acceleration, and torque management, preventing uncontrolled movements and ensuring better performance during uphill and high-load operations.
Implementation Method 1
a hydraulic pump arranged to be mechanically coupled to an internal combustion engine of the vehicle; the hydraulic pump and the hydraulic motor are hydraulically connected to each other to define a closed hydraulic circuit
Implementation Method 2
an electronically-controlled variable displacement hydraulic motor arranged to be mechanically connected at least to driving wheels of the vehicle
Implementation Method 3
a first pressure sensor arranged to measure the pressure on a forward line of the hydraulic circuit and to provide a signal representative of such pressure to the electronic control unit; a second pressure sensor arranged to measure the pressure on a rearward line of the hydraulic circuit
Implementation Method 4
a speed sensor arranged to measure the travel speed of the work vehicle and to provide a signal representative of such speed to the electronic control unit
Data Source
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AI summary
The hydrostatic transmission (100) for a work vehicle (10) comprises: a hydraulic pump (30) coupled to an internal combustion engine (28) and an electronically controlled variable displacement hydraulic motor (32) connected to driving wheels (16), jointly defining a closed hydraulic circuit (1); a first pressure sensor (111), a second pressure sensor (112) and a speed sensor (113) to sense, respectively, the pressure (pf) on a forward line (101), the pressure (pb) on a rearward line (102) and the speed (uv) of the vehicle (10); and an electronic control unit (ECU) configured to set a commanded displacement (Vcmd) of the hydraulic motor (32) equal to the greater of a first displacement (Vp) and a second displacement (Vv); wherein the first displacement (Vp) is a function of the pressure (pf) on the forward line (101) if the vehicle (10) is moving forward, or the pressure (pb) on the rearward line (102) if the vehicle (10) is moving rearward; and wherein the second displacement (Vv) is a function of the speed (uv) of the vehicle (10).