CONTROL FUNCTIONS (CONT’D)

Engine Control - General (Cont’d)

Torque curve and engine regulation

Standard engine torque curves are outlined in [Figure 10-40-15] and [Figure 10-40-16]. The figure is an image. Details of the curves vary depending on the engine models. When the engine load or speed is changed instantaneously, there is some delay until the engine speed is set to the specified regulations.

For the Eco-governor, engine regulations are available in the following variations:

•Isochroous

The engine speed is constant, regardless of the load (regulation 0%).

•Virtual droop (torque curve of base engine)

Approx. 7% regulation regardless of the engine speed. The engine speed is kept until a torque equivalent to a load factor of approx. 30% is reached, in order that the idling (non load) speed does not fluctuate even if installation of the engine on a machine causes some power loss. Even when virtual droop is active, it is possible that the engine speed does not decrease to lower than the low-idling speed (optional)

CONTROL FUNCTIONS (CONT’D)

Engine Control - General (Cont’d)

Figure 10-40-16

②Virtual Droop（Const. regulation:7%）

①Iso-chronous

Engine Speed

For the NV2 Eco optional engine, torque curve and engine regulation are set to the same specification as a standard mechanical governor specification engine.

Switching between "isochroous" and "virtual droop" can be done with an external switch or through CAN communication, while the engine is running. Selection of either one as default is allowed on customer's request. Whichever is set as default, the high idle speed on application is the high idle speed at droop.

Switching between "isochroous" and "virtual droop" can be done even while the engine is running. Switching between "isochroous" and "virtual droop" while the engine is running can change the engine speed.

The Isochroous-Virtual droop switching by external switch connection diagram is shown in [Figure 10-40-17]

CONTROL FUNCTIONS (CONT’D)

Engine Control - General (Cont’d)

Speed control

The target engine speed is defined by input signals from the accelerator sensor or through CAN communication. [Figure 10-40-18] shows the flow of defining the target engine speed. Elements and optional settings in the flow will be described later.

The accelerator input selection feature allows certain accelerator sensors to be selected as input source among others depending on the setting and status of accelerator sensors. [See "Accelerator input selection" on page 10-40-22] for details.

The engine speed selection feature allows the target speed to be changed depending on the status of external switches APP-IP3/IP4/IP6. [See "Speed selection" on page 10-40-30] for details.

The idling speed up feature allows the low idling speed of the engine to be raised depending on the coolant temperature. [See "Idling speed up" on page 10-40-39] for details.

The blue and white smoke suppression feature allows the high idling speed of the engine to be reduced depending on the coolant temperature. [See "Blue and white smoke suppression" on page 10-40-41] for details.

The governor control feature calculates the target engine speed for virtual droop. [See "Torque curve and engine regulation" on page 10-40-13] for details.

The accelerator filter suppresses fluctuations in target engine speed, minimizing overshoot or undershoot. [See "Accelerator filter" on page 10-40-42] for details.

The low/high idling speed limiting feature checks if the target engine speed is in the range of the low idling speed to the high idling speed and adjusts it if required.

CONTROL FUNCTIONS (CONT’D)

Engine Control - General (Cont’d)

[Figure 10-40-19] shows the engine speed control block diagram.

•Speed control

The deviation of the actual engine speed (Nrpm) from the target engine speed (Nset) is used to determine the target rack position (Rset) with PID control. The target rack position is the basis for providing torque limitation or rack motion delay adjustment for transition control (described later).

•Rack position control

The deviation of the actual rack position (Ract) from the target rack position (Rset) is used to determine the target current (Iset) with PID control. To check that the control system of the Eco-governor works properly, use the engine diagnosis tool to make sure that Ract is approximately equal to Rset while the engine is running.

CONTROL FUNCTIONS (CONT’D)

Engine Control - General (Cont’d)

Transition control

The Eco-governor delays the rack motion at engine start or during acceleration in order to minimize the emission of black smoke. See [Figure 10-40-20]. Surplus fuel injection control during acceleration is adopted only in the supercharged engines.

CONTROL FUNCTIONS (CONT’D)

Engine Control - General (Cont’d)

EGR control

The Eco-governor uses an electronic-controlled EGR valve to reduce the emission of NOx from the rated power 37 kW or more engines.

The EGR valve is driven by a stepping motor. The opening (0 ~ 54 steps) of the EGR valve is adjusted depending on the engine speed and load factor so as to control recirculation of exhaust gas. [Figure 10-40-21] outlines the relationship between the number of steps and the flow rate.

The EGR valve does not open when the coolant temperature is lower than 60°C. This is because low temperature corrosion due to condensation of exhaust gas components must be prevented.

CONTROL FUNCTIONS (CONT’D)

Engine Control - General (Cont’d)

CSD control

The fuel injection pump (MP pump) has a CSD valve mechanism that allows the fuel injection timing to advance, thereby improving the cold start performance of the engine.

The Eco-governor has a solenoid valve CSD where the CSD can be opened or closed with a solenoid. The E-ECU opens the CSD valve when the coolant temperature sensor detects that the coolant temperature is 5°C or lower in case of the NV2 engine and 10°C or lower in case of the NV3 engine at cold start. The CSD stops when the coolant temperature is 5°C or higher in case of the NV2 engine and 10°C or higher in case of the NV3, or five minutes have elapsed. Once the CSD is stopped from the actuation state, it doesn’t re-actuate until the temperature is reduced by 5°C from the above-mentioned actuation stop temperature.

In the Eco-governor, the engine speed is increased 50min-1 in case of the NV2 engine and 75min-1 in case of the NV3 engine during CSD actuation in order to check the CSD actuation.However, the high idling speed isn’t exceeded during CSD actuation. After the completion of CSD actuation, the engine speed is automatically reduced to the normal speed.

When the idling speed up feature (described later) is used, the added value of the idling speed up speed increase and the CSD actuation speed increase to the speed command from the accelerator become the target speed.

Target speed = speed command from the accelerator + idling speed up speed increase + the CSD actuation speed increase. The CSD control action is summarized in the table below.

CONTROL FUNCTIONS (CONT’D)

Engine Control - General (Cont’d)

Calculation of load factor

The load factor of the engine is determined as a percentage from the rack position at idling (Ridl), maximum rack position (Rmax), minimum rack position (Rmin) and actual rack position relative to Rmin (Ract) [Figure 10-40-22].

The calculated load factor is delivered as a PWM signal from an E-ECU terminal or through CAN communication.

Figure 10-40-22