Hydrostatic Auxiliary Drive Control Without Valves
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Solution Overview
Problem
Current control systems for vehicles with hydrostatic auxiliary drives, such as motor graders, face high technical and financial expenses due to the need for complex valve systems, energy losses, and limited adjustability, especially during motion and varying operating conditions, which affects traction and steering performance.
Innovation Solution
A control arrangement that connects the hydraulic pump directly to the hydraulic motors via parallel hydraulic lines without valves, using rotary sensors to control the displacement volume of each motor based on their rotational speed signals, allowing continuous adjustment and self-compensation of volume flow rates, enabling connection or disconnection during motion without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a volume flow divider valve and nozzle are used to control the hydraulic motors, then the synchronous run of wheels is achieved, but major energy losses are generated
Solution Approach 1:
The patent removes the volume flow divider valve and nozzle from the hydraulic circuit, eliminating the source of energy losses. Instead of using these passive flow control components, the invention employs active electronic control of variable displacement hydraulic motors to achieve wheel synchronization without throttling losses.
Solution Approach 2:
The patent implements an electronic control system with sensors that detect wheel speeds and provide feedback to the control unit. The control unit processes this information and adjusts the hydraulic motor displacement volumes accordingly, creating a closed-loop feedback system that achieves synchronization without energy-wasting mechanical flow dividers.
2Speed
If the feed volume is adjusted by a proportional solenoid valve, then the rotational speed of hydraulic motors is controlled, but the system can only be connected or disconnected at standstill with high technical expense
Solution Approach 1:
The patent replaces the mechanical proportional solenoid valve system with an electronic control system that directly adjusts the displacement volume of variable displacement hydraulic motors. This substitution eliminates the need for complex valve mechanisms and enables dynamic connection and disconnection during motion through electronic control signals.
Solution Approach 2:
The patent employs variable displacement hydraulic motors whose displacement volumes can be dynamically adjusted during operation. This dynamic capability allows the system to be connected or disconnected at any speed, not just at standstill, providing operational flexibility that static valve-based systems cannot achieve.
3Device complexity
If radial piston motors with constant volumetric flow rate are used, then the drive system is simplified, but continuous adjustment to operating conditions is limited especially in the higher speed range
Solution Approach 1:
The patent uses variable displacement hydraulic motors where the displacement volume parameter can be continuously changed during operation. This allows the motors to adapt to different operating conditions and speed ranges by adjusting their displacement, providing versatility that constant displacement radial piston motors cannot achieve.
Solution Approach 2:
The variable displacement hydraulic motors serve multiple functions: they can operate across a wide speed range, provide continuous adjustment capability, enable dynamic connection and disconnection, and adapt to varying load conditions. This multi-functionality replaces the need for multiple fixed-displacement motors or complex valve systems.
4Manufacturing precision
If a volume flow divider valve is used to distribute pump feed to two hydraulic motors, then uniform distribution is achieved, but inherent risk of loss and rotational speed deviation occurs
Solution Approach 1:
The patent employs electronic sensors on each wheel that provide feedback signals to the control unit. The control unit independently adjusts the displacement volume of each hydraulic motor based on its specific speed feedback, eliminating the need for mechanical flow division and preventing speed deviations caused by unequal pressure losses in the circuit.
Solution Approach 2:
The control system applies local control to each hydraulic motor independently, adjusting each motor's displacement volume based on its own speed sensor feedback. This localized control approach allows each motor to be optimized for its specific operating conditions, achieving better synchronization than a centralized mechanical flow divider can provide.
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 reduces technical and financial expenses, minimizes energy losses, and improves traction and steering performance by eliminating the need for valves and clutches, allowing for automatic calibration and efficient traction distribution across wheels.
Implementation Method 1
A control arrangement is proposed which provides both a hydraulic pump (12) and the hydraulic motors (8, 9) with an electrical control and is characterized in that the hydraulic pump (12) is connected via hydraulic lines (10, 11) in parallel and without valve directly to the hydraulic motors (8, 9)
Data Source
AI summary
The invention relates to a control arrangement for vehicles having a hydrostatic auxiliary drive for one or more axles, in particular for motor graders, having a drive engine, driven rear wheels coupled to the drive engine, further wheels which can be activated by associated hydraulic motors and can be operated by a hydraulic pump coupled to the drive engine and which has an adjustable feed volume, wherein each wheel is connected to a hydraulic motor without a clutch. The hydraulic pump and the hydraulic motors can be activated electrically and adjusted in a continuously variable fashion and the hydraulic pump is connected directly, without valves, to the hydraulic motors in parallel by hydraulic lines. The control device controls the respective displacement volume of the hydraulic motors only as a function of the rotational speed signals of the sensors.