Browse Prior Art Database

LOW-MASS THERMAL INK JET PRINTHEAD EMPLOYING HEAT SPREADER

IP.com Disclosure Number: IPCOM000027678D
Original Publication Date: 1998-Oct-31
Included in the Prior Art Database: 2004-Apr-08
Document File: 6 page(s) / 268K

Publishing Venue

Xerox Disclosure Journal

Abstract

As the mechanical efficiency of thermal ink jet printheads is extremely poor, essentially all the heat input to generate drops needs to be taken away by other means: through the ejected ink, thermal transients, and direct heat transfer to ambient (e-g., natural air cooling).

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XEROX DISCLOSURE JOURNAL

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40

LOW-MASS THERMAL INK JET PRINTHEAD EMPLOYING HEAT SPREADER
Mehmet 2. Sengun

Proposed Classification
U. S. CL 347/018 Int. C1. B41j 29/377

Steady-State Heater Temperature vs. Area Coverage for HP 850C-Black and Printer Die with No Heat Sink

. " ~ ' " 1 " ' 1 " ' 1 ' " 1 ' " ~

600 SPI, 12kHz

FIG. 2 Geometry of Single Chamber

HEAT SPREADER

XEROX DISCLOSURE JOURNAL - Vol. 23, No. 5 September/October 1998 205

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J

HP-850C Black XEROX DIE with no heat sink -

' " ~ ' " I ' ' ' I " ' I ' ' ' I ' "

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LOW-MASS THERMAL INK JET PRINTHEAD EMPLOYING HEAT SPREADER (CONT'D)

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Steady-State Heater Temperature vs. Area Coverage for HP 850C-Black Printer and Proposed Hybrid Design

. . . ~ . . . ~ . . ~ ~ ' ' ' I ' ' ' l ~ ' '

600 SPI, 1 2Hz

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40

HP-850C Black -

A XEROX DIE with Hybrid Design -

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FIG. 4 Time History of Heater Temperature Above Ambient for Proposed Hybrid Design with 50% Area Coverage Suddenly Applied

I I I I I

o.moo 0.400oo o.80000 190001 1.60001 2.00001

TIME (seconds) x 10

206 XEROX DISCLOSURE JOURNAL - Vol. 23, No. 5 September/October 1998

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LOW-MASS THERMAL INK JET PRINTHEAD EMPLOYING HEAT SPREADER

(CONT'D)

FIG. 5 Geometry for Two-Chamber Design

50

1°L

0 0

1

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LOW-MASS THERMAL INK JET PRINTHEAD EMPLOYING HEAT SPREADER

(CONT'D)

As the mechanical efficiency of thermal ink jet printheads is extremely poor, essentially all the heat input to generate drops needs to be taken away by other means: through the ejected ink, thermal transients, and direct heat transfer to ambient (e-g., natural air
cooling). A key parameter in thermal management is the thermal efficiency of the drop generator defined as the drop volume divided by the energy input per drop. At a value around 5 pV@, the drop temperature would increase by 50°C if all the heat left with the ink. Commercial printers, such as the Hewlett-Packard 850, follow the design strategy of removing all the heat with the ejected ink. However, heat transfer is accomplished through temperature gradients and the chip temperature may have to be significantly higher than the drop temperature at high area coverages. Therefore, the heat transfer effectiveness from the die to the ink is another key parameter in heat management.

Another printhead design employs a large heat sink that smoothes the transients and cools via natural air convection during breaks in operation. For long print jobs, on the other hand, the temperature rise in the heat sink superimposes to the thermal swings in the chip. This has the potential to degrade and even paralyze the print quality. In addition, a large thermal mass is normally associated with a large mechanical mass which requires a higher motor power.

A low-thermal-mass printhead has a quick transient r...