Liquid Ejection Head Temperature Sensor Arrangement
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Solution Overview
Problem
Existing liquid ejection heads, such as ink jet recording heads, face challenges in accurately measuring the temperature of the liquid being discharged due to temperature differences between the ambient temperature and the actual ink temperature, leading to suboptimal discharge characteristics.
Innovation Solution
A liquid ejection head with a temperature sensor arranged on the flow path formation substrate, where one lead wiring is connected to the liquid storing portion, allowing direct temperature measurement through a conductive wiring layer, ensuring accurate reflection of the liquid's actual temperature and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thermistor is arranged on the circuit substrate to measure ambient temperature, then the temperature measurement is simple and the device structure is simple, but the temperature measurement accuracy is low due to large temperature difference between ambient temperature and actual liquid temperature
Solution Approach 1:
The patent uses the flow path formation substrate as an intermediary thermal conductor between the liquid and the temperature sensor. The substrate conducts heat from the liquid to the sensor, allowing indirect measurement of liquid temperature while maintaining electrical insulation and structural integrity.
Solution Approach 2:
The temperature sensor is positioned on the back surface of the flow path formation substrate, perpendicular to the liquid flow direction. This spatial arrangement allows the sensor to measure temperature through the substrate thickness dimension, achieving accurate liquid temperature measurement without direct contact.
2Measurement precision
If the temperature sensor is embedded in the heat generation substrate with direct contact to ink, then the temperature measurement accuracy is improved, but the insulation of electrodes and other components is not ensured
Solution Approach 1:
The patent employs the thin flow path formation substrate as a flexible thermal conductor that physically separates the temperature sensor from the liquid-containing chambers. This thin film structure provides both thermal coupling for accurate measurement and physical isolation for electrical insulation protection.
Solution Approach 2:
The flow path formation substrate is divided into distinct functional regions: a sensor contact region on the back surface for temperature measurement, and sealed chamber regions on the front surface for liquid storage. This segmentation allows the sensor to be thermally coupled to the liquid through the substrate while maintaining physical and electrical isolation.
3Reliability
If the temperature detection sensor is arranged on the upper surface of the insulating film with insulation from the lower electrode, then the electrode insulation is ensured, but the configuration becomes complicated and the temperature measuring accuracy is lowered due to measurement through multiple layers
Solution Approach 1:
Instead of placing the temperature sensor on the liquid-facing side or through multiple insulating layers, the patent inverts the approach by positioning the sensor on the back surface of the flow path formation substrate. This allows direct thermal coupling to the liquid through the substrate material itself, eliminating the need to measure through insulating films and electrodes.
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 enables high-accuracy temperature measurement of the liquid, allowing for the selection of an appropriate drive waveform based on the liquid's viscosity, thereby enhancing the discharge characteristics and improving the quality of printed materials.
Implementation Method 1
a temperature sensor is arranged on a surface of the flow path formation substrate at an opposite side to the nozzle opening... one lead wiring of the temperature sensor is connected to a wiring which is formed on the surface of the flow path formation substrate in a state where one end of the wiring faces the liquid storing portion
Data Source
AI summary
A liquid ejection head includes a nozzle plate on which nozzle openings for ejecting liquid are provided, a flow path formation substrate on which pressure generation chambers communicating with the nozzle openings are provided, communicating portions in which the liquid to be supplied to the pressure generation chambers is stored, and piezoelectric elements which generate pressure change in the liquid in the pressure generation chambers. In the liquid ejection head, a thermistor is arranged on a surface of the flow path formation substrate at an opposite side to the nozzle openings and one lead wiring of the thermistor is connected to wiring layers which are formed on the surface of the flow path formation substrate in a state where one side ends of the wiring layers face to the communicating portions.