BMW 3: Emergency braking function
Regenerative braking with help of the drivetrain only effects the rear axle. The brake force on the rear axle must not exceed a specific value in proportion to that on the front axle. This would otherwise compromise driving stability. This is also why there is a limit to the maximum deceleration that can be achieved through brake energy regeneration (maximum 0.07 g).
The maximum permissible brake force by brake energy recovery is subject to stability monitoring of slip, lateral accelerations and stability control processes. In this way it is guaranteed that the vehicle constantly remains in a stable driving condition also during brake energy regeneration.
If the DSC control unit identifies an unstable driving condition, regenerative braking is cancelled and the DSC control unit intervenes with stabilizing measures.
When the driver operates the brake pedal, a direct mechanical connection is established to the brake booster and thus to the hydraulic brake system. Activation is therefore the same as in a conventional vehicle.
Distribution of hydraulically and regenerative brake force
The following diagram summarizes how the entire brake force is distributed into the hydraulic and regenerative shares. In the diagram it is presupposed that there is no unstable driving condition and the high-voltage battery unit is able to use electrical energy.
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G20 PHEV, diagram for distributing the brake force
- Brake force at the wheels
- Brake pedal travel
- Accelerator pedal angle
- Total brake force
- Hydraulically generated brake force of the front axle
- Hydraulically generated brake force of the rear axle
- Regenerative generated brake force
- Free travel at the brake pedal
- Artificial extension of the brake pedal free travel by the DSC function
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Voltage supply
The 12 V vehicle electrical system of the G20 PHEV is essentially the same as
the electrical system of
the G20. The main difference lies in the fact that the power supply is no longer
by the al
Start-up system
Starter motor
The combustion engine B46 can be started via the conventional starter motor
and the electrical
machine.
The following table shows when and under which conditions the respective start
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ECO PRO
The HYBRID ECO PRO driving mode rigorously supports a driving style that
reduces consumption
and its attribute corresponds to the combination of ECO PRO and Auto eDrive of
the predecessor
model. In this driving mode the G20 PHEV has its maximum overall range.
Essentially the follow
Fuel high-pressure pump
The single-piston high pressure pump by Bosch, well-known from the B46
engine, is used. The high
pressure pump HDP6 is driven by a triple cam which is attached to the exhaust
camshaft. To be able
to accommodate a fuel system pressure of 350 bar (5076 psi), the pump piston and
tappet have bee
