Piezoelectric Liquid Ejecting Head Aspect Ratio Optimization
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Solution Overview
Problem
In liquid ejecting heads with high nozzle density, the ratio of pressure chamber length to width is excessively high, impeding displacement portion movement and reducing expelled volume, while increasing chamber length complicates size reduction and limits piezoelectric element capability.
Innovation Solution
A liquid ejecting head with a pressure chamber-forming member and piezoelectric element configuration where the ratio of the displacement portion-side opening length to width is between 4.3 and 6.0, and a second electrode covers the piezoelectric body layer, functioning as a protective layer to reduce thickness and enhance displacement efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pressure chamber length is increased to secure larger capacity and opening area, then the expelled volume can be increased, but the displacement portion movement is impeded and the head size increases
Solution Approach 1:
The patent optimizes the aspect ratio parameter of the pressure chamber opening (length/width ratio between 4.3 and 6.0) to achieve optimal displacement efficiency. This parameter change allows the displacement portion to move effectively without requiring excessive chamber length, thereby resolving the contradiction between expelled volume and chamber dimensions.
Solution Approach 2:
The patent transitions from optimizing only the length dimension to optimizing the aspect ratio (length/width relationship). By controlling the opening shape in both length and width dimensions, the patent achieves better displacement efficiency without proportionally increasing the overall chamber length, thus resolving the contradiction.
2Quantity of substance
If the pressure chamber length is increased to secure larger capacity, then the expelled volume can be increased, but the head size reduction becomes complicated
Solution Approach 1:
The patent changes the geometric parameters of the pressure chamber, specifically optimizing the opening aspect ratio to achieve high displacement efficiency in a compact configuration. This allows sufficient expelled volume without proportionally increasing the overall head volume.
Solution Approach 2:
The patent employs a flexible displacement portion (vibration plate) that can effectively move to displace liquid. This flexible structure achieves high displacement efficiency without requiring large chamber dimensions, thereby enabling compact head design while maintaining sufficient expelled volume.
3Quantity of substance
If the piezoelectric element displacement is increased to improve expelled volume, then the liquid ejection efficiency is improved, but the electrode structure becomes more complex
Solution Approach 1:
The patent merges the upper electrode with the insulation film structure, creating an integrated component that serves both electrical and insulating functions. This reduces the number of separate layers and simplifies the overall electrode structure while maintaining effective piezoelectric element displacement for high expelled volume.
Solution Approach 2:
The upper electrode structure serves multiple functions: it provides electrical connection to the piezoelectric element, acts as an insulation barrier, and contributes to the mechanical structure of the vibration plate. This multi-functionality reduces the need for additional separate components, simplifying the overall device complexity.
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
This configuration improves displacement efficiency and increases expelled volume while reducing the size of the liquid ejecting head, allowing for smaller pressure chamber capacity and head size, and enhances piezoelectric element displacement without electrode destruction.
Implementation Method 1
a piezoelectric element in which a lower electrode film at a side nearer to the pressure chamber, a piezoelectric body layer of lead zirconium titanate (PZT), etc., and an upper electrode film are stacked... portions sandwiched between the upper and lower electrodes are active portions that deform when voltage is applied between the upper and lower electrodes
Data Source
AI summary
Piezoelectric elements each have a configuration in which a lower electrode film, a piezoelectric body layer, and an upper electrode film are stacked in order from a side relatively near to a displacement portion that defines a pressure chamber by tightly closing a portion of a pressure chamber space that forms the pressure chamber. The lower electrode film is provided individually for each pressure chamber. The upper electrode film covers the lower electrode film and the piezoelectric body layer, and is common to the piezoelectric elements. The ratio of a length (L) of a displacement portion-side opening of each pressure chamber space in a direction orthogonal to a pressure chamber space juxtaposition direction to a width (W) of the displacement portion-side opening in the pressure chamber space juxtaposition direction is greater than or equal to 4.3 and less than or equal to 6.0.