Construction Machine Protection Mode Control
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Solution Overview
Problem
Conventional construction machines, such as hydraulic excavators, face the risk of engine stall when the engine output is lowered due to protection mode operation, leading to an inability to move to a repair location if the operator inadvertently switches to high-speed travel, causing an overload state.
Innovation Solution
A control device with an output lowering determination unit and low-speed control unit is implemented, which determines if the engine output is reduced and automatically switches the vehicle to a low-speed state, even if the operator selects high-speed travel, thereby maintaining a low load on the engine and preventing stall. Additionally, a motor displacement control mechanism and small displacement holding unit for the hydraulic pump are used to limit the flow rate and maintain a low speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine output is lowered in protection mode operation, then the engine is protected from serious damage, but the traveling speed increases causing engine overload and potential stall
Solution Approach 1:
The control device continuously monitors the operating state of the engine and automatically adjusts the traveling speed based on real-time feedback. When the engine enters protection mode, the control device detects this state and automatically limits the traveling speed to a predetermined value, creating a closed-loop control system that prevents engine overload while maintaining protection mode operation
Solution Approach 2:
The system changes the operating parameters dynamically based on engine condition. When protection mode is activated, the control device modifies the traveling speed parameter from its normal variable state to a fixed predetermined value, thereby adapting the system's behavior to the degraded engine performance while preventing stall
2Reliability
If the traveling speed is automatically limited in protection mode, then engine stall is prevented, but the operator's ability to control traveling speed is reduced
Solution Approach 1:
The control device automatically manages the traveling speed without requiring operator intervention when protection mode is detected. The system serves itself by autonomously adjusting the speed parameter based on engine state, eliminating the need for the operator to manually compensate for reduced engine output and preventing stall conditions
3Reliability
If the fuel injection amount is limited in protection mode, then the engine output is reduced to protect the engine, but the load on the engine increases potentially causing stall
Solution Approach 1:
The control device takes preliminary action by automatically limiting the traveling speed before the engine can enter an overloaded state. When protection mode is detected, the speed limitation is applied in advance to prevent the situation where reduced engine output would be overwhelmed by high traveling demands, thus preventing stall before it occurs
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 allows the construction machine to self-move to a repair location at a low speed, even when the engine output is reduced, preventing engine stall and ensuring maintenance can be performed without interruption.
Implementation Method 1
a hydraulic pump which is driven by the engine and sucks an oil liquid in a tank and delivers a pressurized oil
Implementation Method 2
a hydraulic motor for traveling which is driven by the pressurized oil delivered from the hydraulic pump
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An engine (10) electronically controlled by a control device (33), a hydraulic motor (24) for traveling which is driven by a pressurized oil delivered from a hydraulic pump (13), and a traveling speed switching member (29) which switches a traveling speed by the hydraulic motor (24) at least in two stages of a low speed and a high speed. The control device (33) includes an output lowering determination unit for determining whether or not a fuel injection amount to be supplied to the engine (10) is limited and an engine output is in a lowered state and a low-speed control unit in which, when the engine (10) output is in a lowered state, a traveling speed is controlled to a low speed state kept lower than a high speed even if the traveling speed switching member (29) has been switched to the high speed side.