Chapter Operating Principles

Table of Contents

2.1 OVERVIEW 2-1

2.2 PRINTER MECHANISM OPERATING PRINCIPLES_2-1

2.2.1 Printing Operation Principles 2-1

2.2.2 Printer Mechanism 2-3

2.2.3 Carriage Drive Mechanism 2-4

2.2.4 Paper Feed Mechanism 2-5

2.2.4.1 Auto Sheet Feeder Mechanism 2-6

2.2.4.2 Push Tractor Mechanism 2-7

2.2.4.3 Manual Feed Mechanism 2-7

2.2.5 Platen Gap Adjust Mechanism 2-8

2.2.6 Ink System 2-9

2.2.7 Pump Mechanism 2-10

2.2.8 Cap Mechanism 2-13

2.2.9 Wiping Mechanism 2-13

2.3 ELECTRICAL CIRCUIT OPERATING PRINCIPLES_2-14

2.3.1 Power Supply Circuit Operating Principles 2-14

2.3.2 Main Control Circuit Operating Principles 2-16

2.3.2.1 Reset Circuits 2-17

2.3.2.2 Sensor Circuits 2-17

2.3.2.3 Carriage Motor Driver Circuit 2-19

2.3.2.4 Paper Feed Motor Driver Circuit 2-20

2.3.2.5 Printhead Driver Circuit 2-21

2.4 INK SYSTEM MANAGEMENT_2-25

2.4.1 Ink Operations 2-25

2.4.2 Counters 2-27

List of Figures

Figure 2-1. Black Printhead Structure 2-1

Figure 2-2. Color Printhead Structure 2-1

Figure 2-3. Printing Operation States 2-2

Figure 2-4. Printer Mechanism Block Diagram 2-3

Figure 2-5. Carriage Movement Mechanism 2-4

Figure 2-6. Paper Feed Mechanism 2-6

Figure 2-7. ASF Mechanism 2-6

Figure 2-8. Tractor Paper Advance Mechanism 2-7

Figure 2-9. Platen Gap Adjust Mechanism 2-8

Figure 2-10. Ink System Block Diagram 2-9

Figure 2-11. Release Cam Set 2-10

Figure 2-12. Pump Mechanism Function 2-10

Figure 2-13. Release Cam Reset 2-11

Figure 2-14. Paper Feed Mechanism Function 2-11

Figure 2-15. Pump Operation 2-12

Figure 2-16. Cap Mechanism 2-13

Figure 2-17. Wiping Mechanism 2-13

Figure 2-18. Electrical Circuit Block Diagram 2-14

Figure 2-19. Power Supply Circuit Diagram 2-15

Figure 2-20. Main Control Circuit Block Diagram 2-16

Figure 2-21. Reset Circuit Block Diagram 2-17

Figure 2-22. Sensor Circuit Block Diagram 2-17

Figure 2-23. Carriage Motor Driver Circuit Block Diagram 2-19

Figure 2-24. Paper Feed Motor Driver Circuit Block Diagram 2-20

Figure 2-25. Printhead Driver Circuit Block Diagram 2-21

Figure 2-26. Normal Dot Data Transmission Timing 2-22

Figure 2-27. Color Upgrade Kit Connector Pin Alignment 2-23

Figure 2-28. Color Data Transmission Timing 2-23

Figure 2-29. EPSON Micro Dot Printing Driver Waveform 2-24

List of Tables

Table 2-1. Carriage Motor Specifications 2-4

Table 2-2. Drive Terms (Carriage Drive Mechanism) 2-4

Table 2-3. Paper Feed Motor Specifications 2-5

Table 2-4. Drive Terms (Paper Feed Drive Mechanism) 2-5

Table 2-5. Platen Gap Adjust Lever Positions 2-8

Table 2-6. Pump Mechanism Operation 2-12

Table 2-7. DC Voltage Distribution 2-14

Table 2-8. Black Ink-Out Sensing Mode 2-18

2.1 OVERVIEW

This section describes the operating principles of the Stylus 1500 printer mechanism and electrical circuits.

2.2 PRINTER MECHANISM OPERATING PRINCIPLES 2.2.1 Printing Operation Principles

This printer mechanism uses a drop-on-demand ink jet system similar to the one used on all other EPSON ink jet printers. However, the printhead in this system is completely redesigned to make it more compact and to ensure a high level of reliability. The printer has two printheads: monochrome (black ink) and color (yellow, cyan, and magenta ink).

1. Monochrome Printhead

The figure below shows the structure of the monochrome printhead, which consists of the nozzle, nozzle plate, piezo elements, cavities, and printhead driver board.

For Ink Cartridge

For Ink Cartridge

Figure 2-1. Black Printhead Structure

2. Color Printhead

The figure below shows the structure of the color printhead. Its structure is different from the monochrome printhead. The color printhead consists of the nozzle plates, two rows of nozzles, piezo elements, and cavities for each of the three colors.

Nozzle

Figure 2-2. Color Printhead Structure

Nozzle

Figure 2-2. Color Printhead Structure

The printhead operates in one of two states to eject ink from each nozzle:

No electrical charge is applied to the piezoelectric element attached to the back of the cavity, and pressure inside the cavity is kept at a constant level.

□ Ejecting state

The head data signal is applied to a specific nozzle control line to select the active nozzle for printing, and the piezoelectric element is gradually charged by the drive voltage. Charging the piezoelectric element bends the vibration plate to compress the cavity. Ink is then ejected from the nozzle.

Piezo

Nozzle

Normal State

Ejecting State

Piezo

Nozzle

Vibration Plate

Figure 2-3. Printing Operation States

Vibration Plate

Figure 2-3. Printing Operation States

When the ink charge or printhead cleaning operation is performed, ink in the cavity is vacuumed out with a pump mechanism. During printing, the ink is simultaneously supplied from the ink cartridge and ejected from the nozzle, depending on changes in the volume of the cavity.

A thermistor is attached to the side of the black ink printhead driver board to monitor the temperature, because the viscosity of the ink varies depending on the temperature. The detected temperature level is fed back to the printhead driver voltage control circuit to change the time of the Tc pulse.

3. EPSON Micro Dot Printing Mode

The Stylus 1500 has a special black ink printing mode called EPSON Micro Dot Printing Mode. This mode can be selected when using a special paper type (such as glossy or transparency). Selecting this printing mode via the printer driver can improve output quality because it eliminates banding that can sometimes occur in normal mode. In normal dot printing mode, the print dot consists of two ink dots combined into a single dot. In EPSON Micro Dot Printing Mode, the print dot consists of a single ink dot only. Using this mode, the ink dot size is smaller than the normal dot and the graded representation is larger than normal dot printing. This mode is effective for 720 dpi printing on normal paper.

2.2.2 Printer Mechanism

The Stylus 1500 printer mechanism is composed of the printhead unit; paper feed, carriage drive, pump, and push tractor feed mechanisms; and various sensors. The figure below shows a functional block diagram of the printer mechanism. Depending on the position of the carriage unit, the paper feed motor torque is transmitted to the paper feed, auto sheet feeding, push tractor feed, or pump mechanisms via a disengage mechanism.

Release Lever

Release Lever

Figure 2-4. Printer Mechanism Block Diagram

2.2.3 Carriage Drive Mechanism

The timing belt attached to the base of the carriage unit is driven by the carriage motor, causing the carriage unit to move along the carriage guide shaft from left to right or vice versa. The carriage drive motor in this printer is a 4-phase, 96-pole, hybrid-type stepping motor, allowing the printer to stop the carriage or change the carriage movement at any position. The carriage position is recognized by the home position (HP) sensor, and position information is fed back to the CPU. This carriage motor is driven by the SLA7043M motor driver IC.

Table 2-1. Carriage Motor Specifications

Item

Description

Motor type

4-phase / 96-pole hybrid-type stepping motor

Drive voltage

+42 VDC ± 5%

Coil resistance

5 W ± 7 %

Drive frequency

480 - 9600 Hz

Excitation mode

Constant current unipolar drive

Minimum step

□ 0.106 mm (at 1-2 phase)

Table 2-2. Drive Terms (Carriage Drive Mechanism)

Print Mode

Print Speed (cps)

Current Value (A / Phase)

+

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