Wheel Loader HST Pump Control for Precise Engine Speed Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The wheel loader disclosed in Patent Literature 1 lacks fine adjustment of engine rotational speed according to the operation state of the working device, leading to potential vehicle speed being slower than necessary, thus impacting work efficiency.
Innovation Solution
A loading vehicle equipped with a variable displacement traveling hydraulic pump, a traveling hydraulic motor, a loading hydraulic pump, and a discharge pressure sensor, where a controller adjusts the input torque of the traveling hydraulic pump based on the discharge pressure of the loading hydraulic pump to optimize engine rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the engine rotational speed is controlled to a predetermined rotational speed when a lifting operation is detected, then the discharge flow rate of the loading hydraulic pump is increased to suppress decrease in lifting operation speed, but the vehicle speed becomes slower than necessary with respect to the operation state of the working device
Solution Approach 1:
The patent applies dynamics by making the HST pump displacement volume adjustable and variable based on real-time operating conditions. Instead of fixed displacement, the system dynamically modifies the pump's displacement volume according to the loading hydraulic pump's torque demand, allowing the vehicle speed to adapt flexibly to different working states while maintaining high lifting operation speed when needed.
Solution Approach 2:
The patent changes the parameter of HST pump displacement volume based on the operating state. By calculating the required displacement volume from the loading hydraulic pump's torque demand and using this to control the HST pump, the system optimizes the balance between vehicle speed and working device speed, improving work efficiency without unnecessarily reducing vehicle speed.
2Productivity
If the input torque of the HST pump is controlled to a characteristic at lifting operation when eco mode is selected, then the matching rotational speed of the engine is increased, but the adjustment of engine rotational speed cannot be performed finely in accordance with the operation state of the working device
Solution Approach 1:
The patent implements feedback by calculating the input torque of the loading hydraulic pump based on discharge pressure detected by a pressure sensor, and using this feedback information to determine the appropriate HST pump displacement volume. This closed-loop control enables fine adjustment of engine rotational speed according to the actual operation state of the working device, rather than using fixed predetermined characteristics.
3Power
If the HST pump and loading hydraulic pump are driven by the same engine, then the sum of input torques becomes the engine output torque, but this creates a conflict in torque allocation between traveling and working operations
Solution Approach 1:
The patent resolves the torque allocation conflict by making the HST pump displacement volume dynamic and adjustable. Based on the calculated torque demand of the loading hydraulic pump, the system dynamically sets the HST pump displacement to optimize the division of engine output torque between the two pumps, allowing flexible adaptation to different operating conditions.
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 precise adjustment of engine rotational speed, enhancing work efficiency by balancing vehicle speed and working device speed, thereby improving overall operational efficiency.
Implementation Method 1
a solenoid proportional valve configured to generate control pressure for controlling displacement volume of the traveling hydraulic pump based on a control signal output from the controller
Implementation Method 2
a discharge pressure sensor that detects discharge pressure of the loading hydraulic pump
Implementation Method 3
a traveling hydraulic motor that is connected to the traveling hydraulic pump through a closed circuit and transmits drive force of the engine to the plurality of wheels
Data Source
AI summary
A loading vehicle is capable of improving work efficiency by adjusting engine rotational speed with high accuracy in accordance with an operation state of the working device. An HST traveling driven wheel loader has an electrically controlled HST pump. A controller is configured to control input torque of the HST pump 31 and solenoid proportional pressure reducing valve is configured to generate control pressure for controlling displacement volume of the pump based on a control signal from the controller. The controller is configured to calculate the displacement volume q of the HST pump based on discharge pressure Pf of a loading hydraulic pump so that maximum input torque Thst of the HST pump decreases as the discharge pressure Pf or input torque of the loading hydraulic pump increases, and output a control signal corresponding to the calculated displacement volume q to the solenoid proportional pressure reducing valve.