Epson Stylus Pro 7400, Service Manual

Page: 152 / 428

EPSON Stylus Pro 7400/7800/9400/9800 Revision B
Operating Principles Print Mechanism Components 152
CARRIAGE MOVING UNIT
The carriage is installed on the square pipe - CR shaft (guide rail) made of extruded
aluminum via roller type bearings as the previous model; Stylus Pro 7600/9600. The
bearings contact/run on/across the CR shaft via steel rails incorporated on the CR shaft.
This reduces the vibration and friction produced while moving the carriage and
improves durability of the carriage mechanism.
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CR Motor
A DC motor moves the carriage across the CR shaft. The movement speed is
controlled by the control circuit on the main board. It receives carriage position
signals detected by the encoder sensor on the carriage and compares them with the
logical values to reflect the difference in the carriage control. The encoder sensor
sends the carriage position signals each time it detect the slits on the CR scale
(timing fence) which is attached parallel to the CR guide rail (Linear encoder
system). This feedback control ensures high printing accuracy.
To transmit the CR motor drive to the carriage, an easy-to-maintain, durable
timing belt is used.
The sensors used in the carriage moving unit are described below.
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CR HP Sensor (Carriage Home Position)
This is a transmissive photosensor which is mounted on the right end of the printer
mechanism and detects the entry position of the flag (projection) provided on the
carriage as the carriage moving home position. Outputs from this sensor are
“OFF” in the HP range and “ON” outside the HP range.
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CR Encoder Sensor (Linear Encoder)
This encoder is mounted on the back of the carriage and outputs pulses (2
channels) corresponding to the position of the slit on the CR scale (timing fence)
that is incorporated into the CR guide rail which are used for CR motor servo
control and PTS (Print Timing Signal) generation. The resolution is 1/180 inch.
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Ink Mark Sensor
This is a diffuse reflectance photosensor which functions in the same way as the
multi sensor used on the previous models; Stylus Pro 4000/4400/4800. The sensor
located on the rear of the carriage unit performs emitting light and responding to
the reflected light one at a time. Its white LED emits light against the paper or
dedicated print pattern printed on paper and the photoreceiver (PTR1) of the
sensor reads the reflected light. According to the reflected light read by the sensor,
the printer performs corrective actions as necessary.
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Ink Mark Sensor Functions
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Auto Bi-D Adjustment
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Auto Uni-D Adjustment
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Missing dots detection (Auto Nozzle Check)
C A U T I O N
Do not remove the carriage and the screws that secure the CR shaft
(guide rails). These are adjusted and assembled to the nearest 1/100
mm at the factory.