Servo Valve Nozzle Assembly for Easier Axial Calibration
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Solution Overview
Problem
The tight interference fit of nozzles in servo valves makes calibration difficult and increases manufacturing costs due to strict tolerances, as it is challenging to move the nozzle axially within the housing while maintaining a secure fit across varying temperatures.
Innovation Solution
The nozzle design features an annular groove axially spaced from the fluid inlet and outlet, with vent passages and a threaded portion for calibration, and a setting material is used in aligned grooves within the nozzle and housing to secure the nozzle in place, allowing for a loose fit during calibration and maintaining position across operating temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tight interference fit is used to secure the nozzle in the housing, then the nozzle remains in the correct position across operating temperatures, but it becomes difficult to move the nozzle axially for calibration and requires strict manufacturing tolerances
Solution Approach 1:
The nozzle is divided into two functional zones: an upper calibration zone with a loose fit allowing axial movement, and a lower securing zone with an interference fit providing stable positioning. The annular groove separates these zones, enabling the nozzle to be moved during calibration while maintaining position during operation.
Solution Approach 2:
The calibration process is performed before the final interference fit is established. The nozzle is initially positioned in a loose-fit state, calibrated to the correct axial position, and then secured with setting material that creates the interference fit. This preliminary calibration action resolves the contradiction by establishing position before securing.
2Reliability
If a tight interference fit is used to secure the nozzle in the housing, then the nozzle remains in the correct position, but manufacturing costs increase due to strict tolerances
Solution Approach 1:
The fit between nozzle and housing is segmented into two zones: a loose-fit upper zone that requires minimal tolerances and facilitates assembly, and a secure lower zone that provides stable positioning. This segmentation allows relaxed manufacturing tolerances overall while maintaining reliability.
Solution Approach 2:
Setting material acts as an intermediary substance that fills the interference fit zone between the nozzle and housing. It provides the securing function while accommodating minor dimensional variations, thereby reducing the need for strict manufacturing tolerances and lowering manufacturing costs.
3Ease of operation
If a loose fit is used to allow nozzle movement for calibration, then calibration becomes easier, but the nozzle may not remain securely positioned across operating temperatures
Solution Approach 1:
The nozzle-housing interface is segmented into a loose-fit calibration zone and a secure interference-fit zone. The loose zone enables easy axial movement for calibration, while the interference-fit zone with setting material ensures stable positioning during operation, resolving the contradiction between ease of calibration and position stability.
Solution Approach 2:
The nozzle is calibrated in a loose-fit state where movement is easy, then the interference fit is established afterward to secure the calibrated position. This preliminary calibration action allows the loose fit to serve its calibration purpose without compromising final position stability.
Data Source
AI summary
A nozzle for a servo valve comprises an annular body defining an outer circumferential surface and an inner circumferential surface of the nozzle. An annular groove is disposed around the circumference of the annular body in the outer circumferential surface. A nozzle assembly (N) for a servo valve comprises the nozzle and a nozzle housing having a nozzle cavity defined by an inner circumferential cavity surface. The nozzle housing has an annular groove disposed around the circumference of the nozzle cavity in the inner circumferential cavity surface. The nozzle is received within the nozzle cavity such that the annular grooves in the nozzle and the nozzle housing are in fluid communication with each other.