Carriage Motor Control/Drive Circuit - Epson DFX-8000 Service Manual

2.3.10 Carriage Motor Control/Drive Circuit

Figure 2-26 shows a block diagram of the carriage motor control/drive circuit.
The carriage motor is a DC servo motor driven using bipolar drive, and can operate in any of the following
modes.
a. Forward rotation "RUN" mode:
b. Forward rotation "BRAKE" mode:
c. Reverse rotation "RUN" mode:
d. Reverse rotation "BRAKE" mode:
e. Halt mode:
The phase signals (CRA to CRD) are inverted by the predrive circuit, and transmitted to the driver board.
The relationship between the modes and phase signals is shown in Table 2-24.
The carriage motor speed is controlled using either PRC (Period Control) or PWM (Pulse Width
Modulation) control. PRC control is used for high and middle speeds, and PWM control is used for middle
and low speeds. The PRC/PWM switching signal is output from port P32 of the CPU to port PWM of
the E05A38NA, and the E05A38NA changes the control sequence.
Torque switching corresponding to the rotational speed is executed by changing the current applied
to motor driver STK6885H, which is the same principle used for the paper feed motor speed control.
The drive current switching signals (CRI 1 to CR13) are output from the E05A16GA.
The VREF port of the STK6885H, which sets the reference voltage of the internal chopper controller,
is set to the output voltage level of the drive current select circuit. The drive current select circuit
switches the output voltage in accordance with the drive current switching signal (CRI 1, CR12, or CR13).
The drive voltage is a constant 36.5 VDC from the VP3 line. An interlock mechanism is installed in the
motor common line, so that the drive current is cut when the case is open.
Carriage motor control is performed using the carriage home position sensor (CHP sensor) and the
encoder signal. The CHP sensor determines the reference position for carriage operation during
initialization (home position seek) when the printer is reset. If the CRHP signal is not detected during
home position seeking, it is regarded as a carriage error.
The encoder signal is input to the ENC port of the E05A38NA, and feeds back the following:
Number of pulses counted, which is the distance the carriage has moved
Interval between the pulse edges, which is the speed of the carriage
Pulse edge of the detected A-/B-phase, which is the direction the carriage is moving
When the encoder signal is input to the ENC port of the E05A38NA, the encoder pulse interval is
output as is from the EN CAB port to the CPU. The CPU generates the print timing upon receiving
the signal at the INT 1 port.
Since the encoder signal must be output continuously while the motor is operating, it is regarded
as a carriage error if the signal is not detected. Since the home position is outside the20printable
area, it is also a carriage error if the CRHP signal is detected during printing.
Driven state. The carriage moves from left to right.
Non-driven state. The carriage is slowed down.
Driven state. The carriage moves from right to left.
Non-driven state. The cariage is slowed down.
Driven state. The carriage is held at any position.
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