Variable Turbocharger Hydraulic Servo Drive for Precise Nozzle Control
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Solution Overview
Problem
Existing variable geometry turbochargers face challenges in precise control due to hysteresis and load drift issues, particularly with pneumatic and hydraulic servo actuators, which affect the accuracy of nozzle opening degree adjustments.
Innovation Solution
A hydraulic servo drive system with a pilot spool and servo piston configuration that uses pilot pressure to control the movement of the servo piston, reducing hysteresis and load drift, and allowing for precise control of the nozzle opening degree without transmitting drive load to the pilot spool, thereby enhancing control characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a pneumatic actuator with coil spring balance method is used to drive the slide mechanism, then the device complexity is reduced, but hysteresis increases and control precision deteriorates
Solution Approach 1:
The patent introduces a pilot spool as an intermediary element that mediates between the solenoid valve and the servo piston. The pilot spool controls the supply of pressure oil to the servo piston through pilot pressure, isolating the pilot spool from the drive load while maintaining precise control capability. This intermediary mechanism resolves the contradiction by enabling precise control without requiring the pilot spool to directly bear the drive load.
Solution Approach 2:
The patent employs a hydraulic servo actuator system using pressure oil to drive the servo piston, replacing the pneumatic actuator with coil spring balance method. The hydraulic system provides more precise control characteristics with reduced hysteresis and load drift, while the pilot spool controlled by solenoid valve maintains manageable device complexity through efficient pressure control.
2Measurement precision
If a hydraulic servo actuator with solenoid valve and spool is used to improve control precision, then measurement precision improves, but device complexity increases due to additional components
Solution Approach 1:
The patent implements a nested structure where the pilot spool is housed within the servo piston, and the solenoid valve controls the pilot spool which in turn controls the servo piston. This nested arrangement integrates multiple control functions into a compact configuration, reducing the space required for separate components and simplifying the overall hydraulic circuit while maintaining precise control capability.
Solution Approach 2:
The patent segments the control function into two independent levels: the solenoid valve controls the pilot spool through pilot pressure, and the pilot spool controls the servo piston through pressure oil supply. This segmentation allows each component to be optimized independently, with the pilot spool focused on precise position control and the servo piston focused on drive force delivery, thereby reducing overall system complexity.
3Measurement precision
If the solenoid thrust is increased to increase the spring load for better spool control, then measurement precision improves, but the solenoid size increases requiring more space
Solution Approach 1:
The patent employs dynamic pressure control where the pilot spool is actuated by variable pilot pressure from the solenoid valve rather than relying on static spring load balance. The pilot pressure can be dynamically adjusted to achieve precise spool position control without requiring excessive solenoid thrust, allowing the solenoid to maintain a compact size while achieving high control precision through dynamic pressure modulation.
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 achieves improved hysteresis and load drift characteristics, enabling precise control of the nozzle opening degree with reduced size and complexity, allowing for more accurate and reliable operation of the variable geometry turbocharger.
Implementation Method 1
a pilot spool that is housed in a center hole of the servo piston and slides by pilot pressure
Implementation Method 2
a hydraulic servo drive device that drives the slide mechanism
Implementation Method 3
a servo piston slidably housed in the housing and connected to the slide mechanism via the opening
Implementation Method 4
the gap between the exhaust inlet walls is reduced to increase a flow speed of exhaust gas flowing into the exhaust turbine
Data Source
AI summary
A hydraulic servo drive device for driving a slide mechanism of a variable geometry turbocharger includes a servo piston connected to a driveshaft of the slide mechanism and a pilot spool that is accommodated in a center hole of the servo piton and slides by pilot pressure. A first hydraulic chamber and a second hydraulic chamber to and from which pressure oil flows are provided in a housing. The servo piston separately includes a pressure port for introducing pressure oil from an outside, a first piston port for intercommunicating the center hole and the first hydraulic chamber, a second piston port for intercommunicating the center hole and the second hydraulic chamber, and a return port for exiting pressure oil.