Hydraulic Pump Torque Control for Electric Motor Power Reduction
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Solution Overview
Problem
The existing hydraulic drive systems for electrically-operated hydraulic work machines, such as excavators, face issues with high horsepower consumption and short operating times due to the use of fixed displacement hydraulic pumps, leading to rapid battery exhaustion and the need for high-output electric motors.
Innovation Solution
A hydraulic drive system that incorporates an electric motor rotation speed control system and a torque control device to manage the delivery pressure of the hydraulic pump, using a variable displacement pump and a torque control regulator to limit absorption torque, thereby reducing the delivery rate and electrical power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed displacement hydraulic pump is used with load sensing control by controlling electric motor rotation speed, then the system can be easily mounted without complex variable displacement pumps, but the horsepower consumption increases to maximum when delivery pressure is maximized, causing rapid battery exhaustion and short operating time
Solution Approach 1:
The patent applies dynamics by making the hydraulic pump displacement variable rather than fixed. The variable displacement pump adjusts its displacement according to operating conditions, allowing the system to maintain load sensing control while optimizing power consumption. This resolves the contradiction by enabling easy mounting (like fixed displacement) while adding dynamic adjustment capability to extend operating time.
Solution Approach 2:
The patent changes the displacement parameter of the hydraulic pump dynamically. By adjusting the pump displacement based on delivery pressure and load conditions, the system optimizes the relationship between pressure and flow rate, preventing maximum horsepower consumption during normal operations and extending battery life and operating time.
2Productivity
If a fixed displacement hydraulic pump is used with maximum delivery pressure, then the delivery rate is maximized, but the horsepower consumption increases to the product of maximum delivery pressure and maximum delivery rate, requiring a high-output electric motor
Solution Approach 1:
The variable displacement pump enables dynamic adjustment of delivery rate based on actual load requirements. Instead of maintaining maximum delivery rate at all times, the pump adjusts displacement to match demand, thereby reducing power consumption while maintaining necessary productivity when needed.
Solution Approach 2:
The patent changes the displacement parameter of the pump to optimize the power-delivery rate relationship. By adjusting displacement according to delivery pressure and load conditions, the system achieves maximum productivity only when necessary, reducing overall power requirements and allowing for a smaller electric motor.
3Speed
If the electric motor rotation speed is controlled to maximum level due to load sensing, then the delivery rate of the hydraulic pump is maximized, but the electrical power consumption increases, causing the battery to rapidly become exhausted
Solution Approach 1:
The system uses dynamic coordination between variable displacement pump and electric motor rotation speed control. The pump displacement is adjusted based on delivery pressure, and motor speed is controlled accordingly, preventing simultaneous maximization of both parameters and thus reducing electrical power consumption and battery exhaustion.
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 extends the operating time of the hydraulic work machine, reduces the size and power consumption of the electric motor, and conserves space by using a smaller hydraulic pump, while maintaining effective load sensing control.
Implementation Method 1
a hydraulic pump driven by the electric motor, a plurality of actuators driven by a hydraulic fluid discharged from the hydraulic pump
Implementation Method 2
a plurality of flow control valves for controlling the flow rate of the hydraulic fluid supplied from the hydraulic pump to the actuators
Data Source
AI summary
An electrically-operated hydraulic work machine drives an actuator with a hydraulic pump driven by an electric motor and exercises load sensing control by controlling the rotation speed of the electric motor. The useful life of an electrical storage device, which is an electrical power source for the electric motor, is increased by suppressing the horsepower consumption of the hydraulic pump. This prolongs the operating time of the electrically-operated hydraulic work machine, and reduces the size of the electric motor. A controller exercises load sensing control over a variable displacement main pump by controlling the rotation speed of the electric motor, and provides the main pump with a torque control device that reduces the delivery rate of the main pump when the delivery pressure of the main pump increases, or provides the controller with a control algorithm that performs the same function as the torque control device.