Die Cushion Hydraulic Circuit for Fast Stable Pressure Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing die cushion devices face issues with slow pressure increase, pressure fluctuations, and complex control mechanisms, leading to inadequate die cushion pressure maintenance, especially near bottom dead center, and potential malfunctions due to noise interference in control systems.
Innovation Solution
A die cushion device with a hydraulic closed circuit including a pilot-operated logic valve, a pressure generator, and a controller that adjusts pilot pressure to achieve precise control of die cushion pressure, allowing independent control of die cushion force and position, reducing the need for a hydraulic pump and minimizing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a pilot relief valve is used to generate pilot pressure in a hydraulic closed circuit without a hydraulic pump, then the device complexity is reduced and cost is lowered, but the pressure increase speed becomes slow and the time to reach predetermined pressure increases
Solution Approach 1:
The system pre-charges the hydraulic closed circuit with hydraulic fluid at a predetermined pressure before the die cushioning action. This preliminary pressurization allows the pilot-operated logic valve to respond more quickly when activated, as the hydraulic fluid is already under pressure and can immediately actuate the cushion pad, eliminating the slow pressure buildup associated with conventional pilot relief valve systems.
Solution Approach 2:
The invention replaces the conventional pilot relief valve mechanism with a pilot-operated logic valve that is actuated by a pilot pressure source. This substitution changes the control mechanism from a pressure-dependent relief system to an actively controlled logic valve system, enabling faster and more precise control of the die cushion pressure while maintaining the pumpless hydraulic closed circuit architecture.
2Device complexity
If a pilot relief valve is used to control die cushion pressure, then the device structure is simplified, but pressure fluctuations occur due to flow rate characteristics and the velocity of the die cushion cylinder
Solution Approach 1:
The system incorporates a pressure sensor that continuously monitors the die cushion pressure and provides feedback to the control unit. The control unit adjusts the pilot pressure applied to the pilot-operated logic valve based on this feedback, maintaining the die cushion pressure within a predetermined range despite variations in cylinder velocity or flow rate, thereby eliminating the pressure fluctuations inherent in pilot relief valve systems.
Solution Approach 2:
The pilot-operated logic valve is designed with dynamic control capabilities, allowing its opening degree to be adjusted in real-time based on operational conditions. This dynamic adjustment enables the valve to maintain stable die cushion pressure across varying flow rates and cylinder velocities, unlike fixed-characteristic pilot relief valves that exhibit pressure fluctuations under changing operating conditions.
3Measurement precision
If a hydraulic pump and servomotor are used to control die cushion pressure, then precise pressure control is achieved, but the device size and cost increase
Solution Approach 1:
The invention extracts and eliminates the hydraulic pump and servomotor from the die cushion pressure control system, retaining only the essential pilot-operated logic valve and pressure sensor. This extraction achieves precise pressure control through the logic valve's pilot pressure mechanism while dramatically reducing device size and cost compared to full hydraulic servo systems.
Solution Approach 2:
The system uses the hydraulic fluid already present in the closed circuit and the force generated by the cushion pad itself to control the pressure. The pilot-operated logic valve utilizes the system's own hydraulic fluid under pressure to actuate, eliminating the need for external hydraulic power sources and reducing overall system size while maintaining precise control capability.
4Measurement precision
If multiple control mechanisms (proportional valve and servomotor) are used to control die cushion pressure, then pressure control capability is enhanced, but noise interference increases and may cause malfunction
Solution Approach 1:
The invention removes the servomotor and proportional valve from the control system, retaining only the pilot-operated logic valve and pressure sensor. This extraction eliminates the primary noise sources associated with electromagnetic motors and complex valve actuation, reducing noise interference that could cause malfunction while preserving essential pressure control capability through the simplified logic valve mechanism.
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
The solution enables rapid pressure increase, stable die cushion pressure maintenance, and simplified control, reducing costs and complexity while enhancing the die cushion device's responsiveness and reliability.
Implementation Method 1
a hydraulic closed circuit including a die cushion pressure generation line connected to a lower chamber of a hydraulic cylinder, a system pressure line to which an accumulator in which hydraulic fluid having a system pressure is connected
Implementation Method 2
a pilot-operated logic valve which has a port connected to the die cushion pressure generation line and a B port connected to the system pressure line, and a pressure generator configured to generate a pilot pressure to act on a pilot port of the logic valve
Implementation Method 3
an accumulator in which hydraulic fluid having a system pressure is connected
Data Source
AI summary
The die cushion device includes a first hydraulic cylinder for supporting a cushion pad, and a first hydraulic circuit for driving the first hydraulic cylinder. The first hydraulic circuit is a hydraulic closed circuit including a logic valve connected between a die cushion pressure generation line and a system pressure line, and a hydraulic pump driven by a first servomotor for applying a pilot pressure to the logic valve. The first controller controls the first servomotor (pilot pressure) based on a first pressure command corresponding to the die cushion force and the pressure detected by the first pressure detector to control the pressure in a lower chamber of the first hydraulic cylinder so that the pressure is equal to a pressure corresponding to the first pressure command.