Hydraulic Pump Startup Control to Prevent Cold-Fluid Cavitation
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Solution Overview
Problem
Electric working machines with electric motors experience cavitation in hydraulic pumps when started at low hydraulic fluid temperatures, leading to premature wear and reduced service life due to sudden increases in rotation speed.
Innovation Solution
Incorporating a controller that gradually increases the electric motor's rotation speed to a target speed over a longer time when the hydraulic fluid temperature is low, using a fluid temperature detector and rotation speed detector to adjust the delay time and control data for stable motor operation, preventing sudden suction negative pressure and cavitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electric motor rotation speed is increased to target speed all at once when started, then the response speed and productivity are improved, but cavitation occurs in the hydraulic pump when hydraulic fluid temperature is low, reducing reliability
Solution Approach 1:
The patent applies dynamics by making the motor rotation speed increase profile variable based on hydraulic fluid temperature. When temperature is low, the rotation speed increases gradually over a longer period; when temperature is high, the rotation speed increases more quickly. This dynamic adjustment resolves the contradiction between fast response and preventing cavitation-induced wear.
Solution Approach 2:
The patent changes the parameter of rotation speed increase rate based on temperature conditions. By detecting hydraulic fluid temperature and adjusting the speed increase profile accordingly, the system prevents cavitation at low temperatures while maintaining fast response at high temperatures, resolving the reliability-speed contradiction.
2Reliability
If the electric motor rotation speed is increased gradually to prevent cavitation, then the reliability of hydraulic pump is improved, but the time to reach target speed increases, reducing productivity
Solution Approach 1:
The system dynamically adjusts the speed increase profile based on real-time temperature detection. At low temperatures, gradual speed increase protects the hydraulic pump; at high temperatures, faster speed increase maintains productivity. This dynamic behavior resolves the contradiction between reliability and productivity.
Solution Approach 2:
The rotation speed increase rate parameter is changed based on temperature conditions. The controller selects different speed profiles (gradual vs. rapid) depending on detected temperature, allowing the system to maintain high productivity when conditions permit while ensuring reliability when conditions require protection.
3Ease of operation
If the electric motor is started with high rotation speed immediately, then the ease of operation is improved, but sudden actuation of hydraulic pump causes suction negative pressure increase and cavitation
Solution Approach 1:
The system performs preliminary detection of hydraulic fluid temperature before starting the motor. Based on this preliminary information, the controller pre-determines the appropriate speed increase profile. This preliminary action prevents cavitation by preparing the appropriate protection strategy before the motor starts, while still allowing simple operator input.
Solution Approach 2:
The system uses feedback from temperature detection to automatically adjust the motor starting behavior. The controller continuously monitors temperature and uses this feedback to select the appropriate speed increase profile, eliminating the need for manual operator adjustment while protecting against cavitation.
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 reduces or prevents cavitation in hydraulic pumps, thereby extending their service life and ensuring stable operation by gradually increasing the motor speed, even at low temperatures.
Implementation Method 1
a fluid temperature detector to detect a temperature of the hydraulic fluid
Implementation Method 2
a rotation speed detector to detect a rotation speed of the electric motor
Implementation Method 3
the controller is configured or programmed to gradually increase the rotation speed of the electric motor such that the rotation speed of the electric motor reaches a target rotation speed in a longer time when the electric motor is started in a state in which the temperature of the hydraulic fluid detected by the fluid temperature detector is lower than or equal to a predetermined temperature
Data Source
AI summary
An electric working machine includes an electric motor to use electric power received from a battery via an inverter to drive a hydraulic pump to deliver hydraulic fluid to actuate a hydraulic device. A controller to control driving of the inverter and the electric motor is configured or programmed to gradually increase a rotation speed of the electric motor such that the rotation speed of the electric motor reaches a target rotation speed in a longer time when the electric motor is started in a state in which a temperature of hydraulic fluid detected by a fluid temperature detector is lower than or equal to a predetermined temperature than when the electric motor is started in a state in which the temperature of hydraulic fluid is higher than the predetermined temperature.