Xerox DocuColor 12/DCCS50, Service Manual

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1/05
10-72 DocuColor 12/DCCS50
Image Sensing (Digital Copier & Copier/Printer Con-
Reissue
Principles of Operation
Figure 4 Xenon Lamp Interrupted Drive Waveform
Carriage Motor and Drive
The Carriage Motor is a high-torque five-phase stepping motor driven by five magnetic control
lines: A through E. These lines are +24 VDC outputs of the Motor/Fan/Lamp Driver PWBA
which is under the control of the CPU on the Pre-IPS PWBA. +24 VDC is applied to all lines
when the motor is locked in one position.
The motor uses rubber dampers to isolate vibrations from the rest of the IIT. It also uses mag-
netic damping to maintain a constant speed.
The motor emits a pulse ever 0.72 degrees of rotation. This is equivalent to 500 pulses per one
complete motor revolution. These pulses are routed back to the Motor/Fan/Lamp Driver PWBA.
This assembly uses the interval between the pulses to determine if the carriage speed is cor-
rect and the cumulative number of pulses to determine the current location of the carriage.
Full and Half-Rate Carriages
The Xenon Lamp is mounted in the Full-Rate Carriage ( Figure 1 ). Reflected light from the orig-
inal document is passed via mirrors through a stationary lens to a CCD PWBA. To maintain a
constant image size, the distance between the original document and CCD (known as the con-
jugate) must remain constant. Therefore, an additional Half-Rate Carriage, traveling at half the
speed of the Full-Rate Carriage, is used.
Figure 5 shows the carriages and their relative
motion.
• T is the distance which the Half-Rate Carriage Moves
• 2T is the distance which the Full-Rate Carriage moves
• A is the distance from the original document to the mirror on the Full-Rate Carriage. This
distance is constant
• B is the minimum distance between the Full-Rate Carriage mirror and the top mirror on
the Half-Rate Carriage. This occurs when the two carriages are at the start of their travel.
During carriage travel, this distance increases to a maximum of B + 2T - T=B + T.
• C is the distance between the mirrors on the Half-Rate Carriage, and is constant
• D is the maximum distance between the bottom Half-Rate Carriage mirror and the station-
ary mirror in front of the CCD PWBA. This occurs when the two carriages are at the start
of their travels. During carriage travel, this distance decreases to a minimum of D - T.
At the start of carriage travel, the conjugate is A + B + C + D. At the end of carriage travel, the
distance is A + (B + 2T - T) + C + (D - T) = A + B + C + D.
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