Hybrid Shovel Engine Speed Control via Partial Torque Assist
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Solution Overview
Problem
When the engine revolution speed of a hybrid shovel is reduced due to increased load, relying solely on an assist motor to return to the original speed can result in the engine losing power and failing to regain the original torque, leading to reduced fuel efficiency and movement slowness.
Innovation Solution
A control method for a hybrid shovel that assists the engine by electrically driving the motor generator to set a target revolution speed lower than the engine's, allowing the engine to increase its torque and return to the original speed without relying solely on the assist motor's torque, thereby maintaining constant revolution speed control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the assist motor provides entire torque to return engine revolution speed, then the engine revolution speed returns to constant speed, but the engine loses power and cannot regain original torque
Solution Approach 1:
The assist motor provides only partial torque assistance rather than complete torque substitution. The control unit calculates required assist torque based on the difference between target and actual engine torque, ensuring the engine still contributes its own torque output. This partial action allows the engine to maintain and regain its torque capability while still achieving speed recovery.
2Speed
If fuel injection is increased to return engine revolution speed, then the engine revolution speed recovers, but fuel consumption deteriorates
Solution Approach 1:
The assist motor acts as an intermediary energy source that supplements engine output during transient load conditions. By providing electrical torque assistance from the motor generator, the system reduces the need for excessive fuel injection to maintain speed, thereby lowering fuel consumption while still recovering engine revolution speed efficiently.
3Stability of the object's composition
If the assist motor is used to maintain constant revolution speed, then the engine revolution speed is stabilized, but the movement becomes slow due to reduced engine torque
Solution Approach 1:
The system merges the torque output of the engine with the torque output of the assist motor to create a combined power source. This combined torque is transmitted to the hydraulic pump, maintaining both stable engine revolution speed and sufficient movement speed by leveraging the complementary strengths of both power sources simultaneously.
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
Enables the engine to return to its original revolution speed by increasing its own torque, improving fuel efficiency and preventing slowness, while the assist motor's role is limited to suppressing speed decreases, ensuring continuous operation.
Implementation Method 1
an electric motor (assist motor) that outputs a power for driving a hydraulic pump to assist an engine
Implementation Method 2
a hydraulic pump which is driven by the engine to drive a hydraulic actuator with discharged hydraulic fluid
Data Source
Figure 1
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Figure 3
AI summary
A hybrid shovel includes an engine 11 that is controlled at a constant revolution speed, a motor generator 12 that assists the engine 11, a controller 30 that controls a drive of the motor generator 12, and a main pump that is driven by the engine 11. The controller 30 assists the engine 11 by the motor generator 12 when a revolution speed of the engine 11 is lower than said constant revolution speed due to a load of the main pump 14, and decreases an assist output to the engine 11 by the motor generator 12 before the revolution speed of the engine 11 returns to the constant revolution speed.