Wheel Loader Speed Control via Lift Arm Pressure Detection
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Solution Overview
Problem
In wheel loaders, erroneous determination of lift arm raising operations leads to sudden changes in vehicle speed, causing vibrations and impacts due to the reliance on bottom pressure of the lift arm cylinder, which is prone to errors from load presence and uneven road surfaces.
Innovation Solution
A wheel loader equipped with a travel state sensor and pressure sensor, along with a controller that adjusts the displacement volume of the hydraulic pump or motor based on the detected travel state and discharge pressure to limit vehicle speed during lift arm raising operations, thereby reducing erroneous speed changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the bottom pressure of the lift arm cylinder is used to detect raising operation, then the detection method is simple, but erroneous determination occurs when load exists in bucket or on uneven road surfaces
Solution Approach 1:
The patent introduces an intermediary detection mechanism (detecting means for lift arm raising operation) that directly monitors the lift arm's motion state rather than relying on bottom pressure. This intermediary detection method acts as a mediator between the hydraulic system and control system, providing accurate raising operation detection without being influenced by load conditions or road surface variations that affect bottom pressure readings.
2Speed
If engine rotational speed is increased when raising operation is detected, then the lift arm raising speed is maintained, but sudden vehicle speed changes occur due to erroneous detection
Solution Approach 1:
The patent implements a feedback control mechanism where the control unit continuously monitors the actual lift arm raising operation status and adjusts engine rotational speed accordingly. The feedback loop ensures that engine speed changes only occur when genuine raising operations are detected, preventing sudden vehicle speed changes caused by erroneous detection while maintaining adequate lift arm raising speed during legitimate operations.
3Productivity
If the control system responds to pressure variations, then the lift arm operation response is fast, but false responses occur due to vibrations on uneven road surfaces
Solution Approach 1:
The patent employs a dynamic detection approach that distinguishes between genuine lift arm raising operations and false signals caused by vibrations. The detection means dynamically evaluates the motion characteristics of the lift arm, identifying true raising operations based on their distinctive motion patterns rather than merely responding to pressure variations. This dynamic differentiation maintains fast response to legitimate operations while filtering out false signals from road surface vibrations.
Data Source
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AI summary
A wheel loader configured to reduce a sudden change in vehicle speed caused by an erroneous determination of a raising operation of a lift arm is provided. A wheel loader 1 includes an engine 3, a variable displacement type HST pump 41, a variable displacement type HST motor 42 coupled to the HST pump 41 in a closed circuit, a hydraulic pump for working device 43, a forward/reverse selector switch 62 for switching a forward movement and a backward movement of a vehicle body, a depression amount sensor 610 that detects a depression amount of an accelerator pedal 61, a pressure sensor 73 that detects a discharge pressure Pa of the hydraulic pump for working device 43, and a controller 5. The controller 5 determines whether a specific condition to identify an upward movement of a lift arm 21 during a forward travel of the vehicle body based on a forward/reverse switching signal, the depression amount of the accelerator pedal 61, and the discharge pressure Pa detected by the pressure sensor 73. When the specific condition is satisfied, the controller 5 controls a displacement volume of the HST motor 42 according to an increase of the discharge pressure Pa, so as to limit the vehicle speed.