Piezo Injector Hydraulic Coupling Thermal Compensation
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Solution Overview
Problem
Piezo injectors in internal combustion engines face challenges in maintaining a backlash-free coupling due to thermal changes in length, leading to issues with nozzle needle closure and increased control energy requirements, which are costly to address through material and geometric selection.
Innovation Solution
A piezo injector design featuring a hydraulic coupling between the piezo actuator and nozzle needle, with a control piston and leakage pin system that compensates for thermal changes and wear, allowing for the use of any material and reducing manufacturing costs and energy requirements, while maintaining injection stability and minimizing pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the idle stroke between the piezo actuator and the nozzle needle is reduced to maintain complete nozzle needle closure, then the nozzle needle can close completely, but the coupling becomes sensitive to thermal changes and wear
Solution Approach 1:
The control piston serves as an intermediary element between the piezo actuator and the nozzle needle. It receives the actuator stroke through a drive connection and translates it to the nozzle needle via a control connection, allowing the idle stroke to be optimized for reliability while the control piston compensates for thermal changes and wear through its stroke translation mechanism
Solution Approach 2:
The control piston enables dynamic adjustment of the coupling parameters through its movable position and stroke translation capability. By changing the effective stroke length and positioning, the system compensates for thermal expansion and wear without requiring a fixed, overly tight idle stroke, thus maintaining reliable nozzle closure while reducing sensitivity to environmental changes
2Reliability
If the idle stroke between the piezo actuator and the nozzle needle is increased to accommodate thermal changes and wear, then thermal compensation is improved, but the control energy required increases
Solution Approach 1:
The hydraulic connection replaces a purely mechanical rigid coupling with a fluid-based transmission system. The control piston translates the actuator stroke hydraulically to the nozzle needle, providing thermal compensation through the compliant hydraulic medium while requiring less control energy than a rigid mechanical system with large clearances
Solution Approach 2:
The control piston acts as a mediator that decouples the actuator from the nozzle needle, allowing thermal compensation through controlled stroke translation without directly increasing the idle stroke. This intermediary mechanism achieves thermal adaptation with minimal additional control energy by optimizing the translation ratio
3Reliability
If material and geometry are selected to compensate for thermal changes in length, then thermal compensation is achieved, but manufacturing costs increase and design freedom is restricted
Solution Approach 1:
Instead of relying on special materials with specific thermal expansion properties, the invention compensates for thermal changes by dynamically adjusting geometric parameters through the control piston stroke translation. This allows the use of standard, easily manufacturable materials while achieving thermal compensation through controlled parameter changes during operation
Solution Approach 2:
The control piston serves as an intermediary that decouples the thermal compensation function from the structural materials. By using the control piston to absorb and compensate for thermal length changes, the system can be manufactured from conventional materials without requiring expensive special alloys or complex thermal compensation geometries
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 design effectively compensates for thermal changes and wear, reducing manufacturing costs and energy needed for control, while enhancing injection stability and minimizing pressure loss, allowing for a compact and cost-effective piezo injector with improved dynamic operation.
Implementation Method 1
a piezo actuator for axial adjustment of the nozzle needle
Implementation Method 2
A hydraulic transmission unit is provided between the actuator and the nozzle needle. The deflection of the actuator is translated into a corresponding deflection of the nozzle needle
Implementation Method 3
a spring arranged in a spring chamber which acts on the control piston with a force acting in the direction of the first control chamber
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a piezo injector with an actuator chamber (170), in which a piezo actuator (180) is arranged. The piezo injector comprises an upper section, the injector body (150) and a lower section, the nozzle body (140). The piezo injector also has a control piston bore (200), which is formed in the nozzle body, wherein a control sleeve (220), in which a control piston (340) is received, is arranged in the control piston bore (200). The control sleeve (220) seals against an intermediate plate (260) with a first front face (240) facing the piezo actuator (180). The control piston (340) has a first side (360) facing the piezo actuator (180), wherein the first front face (360) of the control piston (340) and the section of the control sleeve (220) facing the piezo actuator (180) form a first control chamber (380).