Construction Machine Engine Control for Malfunction Stall Prevention
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Solution Overview
Problem
Construction machines with electronically controlled engines and exhaust gas purifying devices face issues with engine stall and excessive particulate matter deposition when in a malfunction state, leading to potential inability to self-propel and move to service sites.
Innovation Solution
A control system that determines malfunctions in the engine or exhaust gas purifying device, limits the engine's highest rotational speed and maximum fuel injection quantity, and includes features to prevent excessive operation, such as automatic shutdown or prohibition of engine start after a specified number of stops, to protect the engine and allow stable movement to service sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protection mode operation is performed by limiting fuel injection quantity to lower engine output, then engine and exhaust gas purifying device are protected from malfunction deterioration, but engine enters overload state and may stall
Solution Approach 1:
The control device changes the engine speed parameter to a second rotational speed higher than the first rotational speed when malfunction is detected. This parameter change allows the engine to operate at higher RPM where the torque characteristic curve provides sufficient torque even with limited fuel injection quantity, preventing engine stall while maintaining protection mode operation.
Solution Approach 2:
The control device dynamically adjusts the target engine speed based on the malfunction state. Instead of maintaining a fixed speed limit, the system adapts the engine operating point to the second rotational speed which is dynamically determined to be higher than the first rotational speed, allowing the engine to deliver adequate torque for self-propelled movement while still operating in protection mode.
2Stability of the object's composition
If highest rotational speed is limited to prevent engine stall, then engine stability is improved, but maximum torque output is reduced
Solution Approach 1:
The control device changes the engine speed parameter to a second rotational speed that is higher than the first rotational speed. This parameter change shifts the operating point on the torque characteristic curve to a position where the engine can deliver adequate torque for self-propelled movement while maintaining stability through controlled speed limitation.
3Duration of action of stationary object
If engine speed is reduced to protect exhaust gas purifying device, then device durability is improved, but engine may not produce sufficient torque for continuous operation
Solution Approach 1:
The control device changes the engine speed to a second rotational speed higher than the first rotational speed, allowing the engine to operate in a regime where sufficient torque is available for continuous operation. This speed parameter change enables the engine to maintain adequate power output while still operating in protection mode to preserve exhaust gas purifying device durability.
Data Source
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AI summary
During an operation, a control device (38) for performing output control of an engine (10) determines whether or not the engine (10) and/or an exhaust gas purifying device (18) has a malfunction. If it is determined that the engine (10) and/or the exhaust gas purifying device (18) has a malfunction, a highest rotational speed of the engine (10) is controlled to a second rotational speed (Nt) higher by a predetermined amount (α) than a first rotational speed (Ns) at which an engine maximum torque (Tm) before the malfunction can be outputted. In this case, a maximum fuel injection quantity of the engine (10) is limited so that a rated torque (Tr) before the malfunction can be outputted at the first rotational speed (Ns).