Doosan G643, Руководство по обслуживанию

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G643(E) Service Manual Chapter 5. Engine Management System (EMS) 159
Electronic Throttle System
The electronic throttle system controls engine output
(speed and torque) through electronic control of
mass airflow to the engine. Any DC motor-actuated
or Limited Angle Torquemotor (LAT)-actuated
throttle with less than 5A peak and 2A steady state
can be controlled. The TPS must be directly coupled
to the throttle shaft for direct shaft position
measurement.
A commonly used throttle is the Bosch DV-E5. This
throttle is available in a variety of bore sizes to meet
specific engine needs: 32mm, 40mm, and 54mm are
readily available throttle bore sizes; other sizes are
possible. The Bosch throttle is a fully validated
automotive component incorporating a brushed DC
motor with gear reduction, dual throttle position
sensors, throttle plate, and cast aluminum housing.
In the event of an electrical disconnection or other
related failure, the throttle plate returns to a limp-
home idle position at a no-load engine speed above
curb idle speed. This provides sufficient airflow for
the engine to move the vehicle on level ground. Any
throttle bodies used for MI-07 meet or exceed the
specification for the Bosch throttle bodies.
In terms of response, the throttle is capable of fully
opening and closing in less than 50 msec. Position
resolution and steady state control should be 0.25%
of full travel or better.
MI-07 Electronic Throttle
Conventional throttle systems rely on a mechanical
linkage to control the throttle valve. To meet
fluctuating engine demands a conventional system
will typically include a throttle valve actuator
designed to readjust the throttle opening in response
to engine demand, together with an idle control
actuator or idle air bypass valve.
In contrast, the MI-07 system uses electronic throttle
control (ETC). The SECM controls the throttle valve
based on engine RPM, engine load, and information
received from the foot pedal. Two potentiometers on
the foot pedal assembly monitor accelerator pedal
travel. The electronic throttle used in the MI-07
system is a Bosch 40mm electronic throttle body
DV-E5 (Figure 14). The DV-E5 is a single unit
assembly, which includes the throttle valve, throttle-
valve actuator (DC motor) and two throttle position
sensors (TPS). The SECM calculates the correct
throttle valve opening that corresponds to the
driver’s demand, makes any adjustments needed for
adaptation to the engine’s current operating
conditions and then generates a corresponding
electrical (driver) signal to the throttle-valve actuator.
Figure 14. Bosch Electronic Throttle Body
The MI-07 uses a dual TPS design (TPS1 and
TPS2). The SECM continuously checks and
monitors all sensors and calculations that effect
throttle valve position whenever the engine is
running. If any malfunctions are encountered, the
SECM’s initial response is to revert to redundant
sensors and calculated data. If no redundant signal
is available or calculated data cannot solve the
malfunction, the SECM will drive the system into one
of its limp-home modes or shut the engine down,
storing the appropriate fault information in the SECM.