Heating Resistor Defect Detection in Inkjet Printers
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Solution Overview
Problem
Inkjet printers face challenges in accurately determining defective heating resistors, which can lead to artifacts in printed images due to electrical malfunctions, and existing methods are inefficient or require expensive amplifiers.
Innovation Solution
A method and apparatus that utilize a variable power supply to switch between operating and test voltage levels, inserting a reference resistor in series with the heating resistor and capacitor, and digitizing the voltage at their junction to determine if the heating resistor is defective, without the need for expensive amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If expensive amplifiers are used to determine defective heating resistors, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive amplifiers with inexpensive components including a variable power supply, reference resistor, capacitor, and analog-to-digital converter. These cheaper components achieve the same measurement function without requiring complex amplifier circuitry, directly resolving the contradiction between measurement precision and device complexity/cost
Solution Approach 2:
The patent substitutes the electrical measurement system by replacing analog amplifier-based detection with a digital voltage measurement approach. By measuring voltage across the reference resistor and using an analog-to-digital converter, the system achieves accurate resistor detection without mechanical or complex analog amplifier systems
2Productivity
If the capacitor remains connected during testing, then the circuit operates continuously, but measurement precision deteriorates due to capacitor interference
Solution Approach 1:
The patent makes the capacitor connection dynamic by using a switch to isolate the capacitor during test mode. The system transitions from a static continuously-connected capacitor to a dynamic configuration where the capacitor is connected during operation but isolated during testing, allowing both continuous operation capability and accurate measurement
Solution Approach 2:
The patent segments the circuit operation into distinct modes (operation mode and test mode) with different circuit configurations. During operation mode, the capacitor remains connected for continuous operation; during test mode, the capacitor is isolated by opening a switch to enable precise resistor measurement without capacitor interference
3Measurement precision
If the reference resistor is always inserted in series, then measurement precision is maintained, but power consumption increases
Solution Approach 1:
The patent makes the reference resistor insertion dynamic by using a switch to insert it only during test mode. The reference resistor remains out of the circuit during normal operation to minimize power consumption, and is inserted only when needed for measurements, achieving both measurement precision and energy efficiency
Solution Approach 2:
The patent implements periodic testing where the reference resistor is inserted intermittently rather than continuously. The system alternates between operation mode (resistor out, low power consumption) and test mode (resistor in, measurement taken), achieving accurate measurements while minimizing overall power consumption through periodic rather than continuous resistor insertion
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
Effectively identifies open-circuited or improperly resistant heating resistors, ensuring accurate determination without the use of expensive amplifiers, thereby improving the reliability of inkjet printer operations.
Implementation Method 1
providing a variable power supply effective in a first condition to produce a first operating DC voltage Vo and, in a second condition, to produce a second known test DC voltage Vt
Implementation Method 2
Each inkjet has a heating resistor that, in response to current, produces heat that causes the ejection of ink droplets
Implementation Method 3
an analog to digital circuit electrically connected to the junction of the heating resistor Ri and the known reference resistor Rr for digitizing the junction voltage
Data Source
AI summary
A method and apparatus for determining defective heating resistors Ri in each of a plurality of inkjets in an inkjet printer, wherein each heating resistor Ri is connected in parallel with a common capacitor, the method for each heating resistor Ri includes providing a variable power supply effective in a first condition to produce a first operating DC voltage and, in a second condition, to produce a second known test DC voltage Vt, and inserting a known reference resistor Rr in series with the heating resistor Ri and capacitor and also open circuiting the capacitor in response to sensing that the power supply has changed from the first condition to the second condition. The method and apparatus further include digitizing the voltage Vi at the electrical junction between the heating resistor Ri and the reference resistor Rr, and using the digitized voltage to determine if the heating resistor Ri is defective.