Hydrostatic Transmission Speed Control via Drag Torque
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Solution Overview
Problem
Existing speed control systems for hydrostatic drives with insufficient engine braking power fail to automatically adjust speed and maximize drag torque utilization, and cannot exceed engine braking capabilities without operator input.
Innovation Solution
A speed control system for hydrostatic transmissions that uses a microcontroller connected to sensors and high pressure relief valves to automatically adjust pump and motor displacement, allowing for maximum drag torque utilization and exceeding engine braking capabilities by converting excess energy to heat through a high pressure relief valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If existing speed control systems are used with insufficient engine braking power, then the system can provide basic speed control, but the engine braking capability is insufficient to limit engine over-speed or provide adequate braking
Solution Approach 1:
The patent introduces a hydrostatic transmission system as an intermediary between the engine and the load, incorporating pressure reducing valves and flow control mechanisms that mediate the power transmission. This intermediary system enables automatic speed control and braking assistance without requiring the engine itself to provide sufficient braking power, thus resolving the contradiction between limited engine braking capability and the need for reliable engine over-speed limitation.
Solution Approach 2:
The patent replaces reliance on pure mechanical engine braking with a hydraulic control system that uses pressure reducing valves and electronic control units to manage speed and braking. This substitution allows the system to achieve reliable engine over-speed limitation and adequate braking performance through hydraulic and electronic mechanisms rather than depending solely on engine mechanical braking capability.
2Ease of operation
If manual operator input is required for brake control, then the system can provide braking control, but the response time is delayed and cannot immediately maximize drag torque utilization
Solution Approach 1:
The patent implements electronic control units and sensors that continuously monitor system parameters such as engine speed, hydraulic pressure, and vehicle velocity. This feedback mechanism enables the system to automatically adjust pressure reducing valves and hydrostatic transmission parameters in real-time, eliminating the delay associated with manual operator input and immediately maximizing drag torque utilization when braking is required.
Solution Approach 2:
The system is designed to automatically control braking and speed regulation without requiring continuous manual intervention. The electronic control units process sensor data and automatically adjust hydraulic valves and transmission parameters, enabling the system to serve itself by immediately responding to braking demands and maximizing drag torque utilization without waiting for operator input.
3Speed
If pressure reduction occurs inline between pump and motor, then the system can control speed, but the flow path causes pressure relief to consume portion of transmitted flow bypassing the pump rotating kit
Solution Approach 1:
The patent segments the hydraulic circuit into distinct flow paths, separating the pressure reduction function from the main power transmission path. By positioning pressure reducing valves in a configuration that allows independent flow management, the system achieves speed control while minimizing the loss of transmitted flow through the pump rotating kit, thus reducing energy loss associated with flow bypass.
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
The system effectively provides automatic speed adjustment and maximizes braking power by utilizing available drag torque, ensuring vehicle braking exceeds engine capabilities without operator input, while protecting the engine from overspeed and efficiently converting excess energy to heat.
Implementation Method 1
converting excess energy to heat through a high pressure relief valve
Implementation Method 2
At least one hydrostatic motor is connected to the pump in a closed circuit by a flow line
Implementation Method 3
maximum and immediate utilization of available drag torque
Data Source
AI summary
A speed control system for a hydrostatic transmission includes an engine having a drive shaft connected to a hydraulic pump. At least one hydrostatic motor is connected to the pump in a closed circuit by a flow line. Connected to the motor via a system shaft is a vehicle system. A controller is connected to a plurality of sensors and a high pressure relief valve that is connected to the flow line between the pump and the motor. Based on information received from the sensors, the controller sets the pump and motor displacements to limit the pressure to a value that will not overspeed the engine and allow the system to automatically provide braking beyond the engine's capability. This may be accomplished through the use of various algorithms.