Hybrid Construction Machine Governor Control for Engine Stall Prevention
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Solution Overview
Problem
Existing hybrid construction machinery faces issues with continuous engine operation at maximum power, leading to inefficient energy use and improper power distribution between the engine and motor generator, resulting in potential engine overload, stall, and improper charging of the electrical storage apparatus.
Innovation Solution
The implementation of a hybrid construction machinery system with a controller that utilizes a governor characteristic with droop characteristics to regulate engine speed based on load torque, combined with a motor generator control unit that adjusts power distribution to maintain optimal engine operation and electrical storage levels, ensuring proper power management and preventing engine stall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the engine operates continuously at maximum power corresponding to the accelerator signal, then the power required for hydraulic pumps is satisfied, but energy consumption increases and fuel is injected at maximum continuously
Solution Approach 1:
The governor characteristic is made dynamically adjustable through the governor characteristic changing unit. Instead of operating at fixed maximum power, the engine's governor characteristic (relationship between rotational speed and load torque) is dynamically changed based on the operation state detected by the operation state detector. This allows the engine to adapt its power output to actual workload requirements, reducing energy consumption during light work while maintaining sufficient power during heavy work.
2Power
If the engine operates at maximum power continuously, then power demand is met, but the electrical storage apparatus becomes overcharged during light work or overdischarged during heavy work
Solution Approach 1:
The operation state detector continuously monitors the actual operation state of the hydraulic pump, and this feedback is used by the governor characteristic changing unit to adjust the governor characteristic. This closed-loop feedback mechanism ensures that the engine power output matches the actual power demand, preventing excessive charging during light work and excessive discharging during heavy work, thereby maintaining electrical storage apparatus within safe operating limits.
3Ease of operation
If power distribution is based on estimated pump requiring power, then power can be allocated between engine and motor generator, but engine overload and stall may occur when true requiring power is unknown
Solution Approach 1:
Instead of relying solely on power estimation, the system changes the governor characteristic parameter (the relationship between rotational speed and load torque) based on detected operation state. This parameter change approach allows the engine to automatically adapt to varying load conditions, maintaining stable operation even when precise power requirements are difficult to predict, thereby preventing engine overload and stall.
Data Source
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AI summary
The purpose of the present invention is to operate an engine in a proper operation state while keeping the remaining amount in an electrical storage apparatus within a proper range. Hybrid construction machinery according to the present invention is provided with a controller for controlling an engine according to a governor characteristic having a predetermined inclination that defines a relationship between load torque and rotational speed so that the rotational speed decreases with an increase in the load torque. In the controller, a target engine power calculating unit (2-5) calculates a first target engine power that increases and decreases according to increases and decreases in output values of a load power calculating unit (2-1) and a charge/discharge request calculating unit (2-3), and a target rotational speed calculating unit (2-6) calculates, as a command value for a target rotational speed of a motor generator, a rotational speed at the intersection point of a governor characteristic line changed by a governor characteristic changing unit (2-4) and an equal power line dependent on the first target engine power on a rotating speed-torque characteristic line diagram.