Press Die Cushion Hydraulics for High-Speed Force Control
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Solution Overview
Problem
Conventional die cushion devices for press machines face limitations in responding to high-speed operations due to the maximum rotation speed of servo motors and increased costs associated with enhancing their capacity, while also having complex control systems that require extensive man-hours and maintenance.
Innovation Solution
A die cushion device that incorporates a hydraulic cylinder, a throttle part, and a hydraulic pump/motor connected in parallel with an electric motor, where the control unit adjusts the electric motor's torque to manage die cushion force without altering the throttle opening, allowing the device to switch between motor and pump modes to handle varying slide speeds without increasing the motor's capacity or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the capacity of the servo motor is increased to improve the maximum rotation speed, then the response capability to high-speed press machine operation is improved, but the manufacturing cost increases
Solution Approach 1:
The patent divides the oil discharge function into two separate paths: one through the hydraulic pump/motor and another through a dedicated discharge valve. This segmentation allows the servo motor to operate within its speed limits while the discharge valve handles the additional flow requirements for high-speed operation, avoiding the need to oversize the motor.
Solution Approach 2:
The discharge valve acts as an intermediary component that assists the hydraulic pump/motor in discharging oil during high-speed operation. By introducing this intermediate element, the system can achieve high-speed response without requiring the servo motor to exceed its maximum rotation speed, thus avoiding increased manufacturing costs.
2Speed
If a hydraulic proportion flow control valve or servo valve is added to enable high-speed operation, then the response capability is improved, but the control system becomes complicated and maintenance becomes difficult
Solution Approach 1:
The patent extracts the flow control function from the servo valve/proportion flow control valve and implements it through a simple discharge valve with fixed or manually adjustable opening. This removes the complex electronic control system while maintaining the ability to discharge excess oil during high-speed operation.
Solution Approach 2:
The patent replaces expensive, complex servo valves or proportion flow control valves with a simpler, more robust discharge valve that has fewer moving parts and control mechanisms. This simpler valve is easier to maintain and less prone to failure, aligning with the principle of using simpler components when adequate performance can be achieved.
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 die cushion device to respond to increased slide speeds without raising manufacturing costs or complicating the control system, maintaining consistent die cushion pressure and reducing surge pressure through the use of a throttle part and electric motor torque control.
Implementation Method 1
a rotation direction of the electric motor controlled in torque by the control unit switches from a first rotation direction in which the hydraulic pump/motor serves as a hydraulic motor
Implementation Method 2
a rotation direction of the electric motor controlled in torque by the control unit switches from a first rotation direction in which the hydraulic pump/motor serves as a hydraulic motor to a second rotation direction in which the hydraulic pump/motor serves as a hydraulic pump
Implementation Method 3
a throttle part and a hydraulic pump/motor that are connected to each other in parallel between a lower chamber of the hydraulic cylinder and a low-pressure source
Data Source
AI summary
A die cushion device of a press machine includes a hydraulic cylinder that supports a cushion pad and generates die cushion force when a slide of the press machine descends, an orifice and a hydraulic pump/motor that are connected to each other in in parallel between a lower chamber of the hydraulic cylinder and a tank, a servo motor connected to a rotating shaft of the hydraulic pump/motor, and a control unit that controls torque of the servo motor to control the die cushion force, wherein a rotation direction of the servo motor switches from a first rotation direction in which the hydraulic pump/motor serves as a hydraulic motor to a second rotation direction in which the hydraulic pump/motor serves as a hydraulic pump, during generation of the die cushion force.