BMW 3: Introduction
The automatic transmission GA8P75HZ of the G20 PHEV, which is based on the transmission introduced in the F07 at the end of 2009 (GA8HP70Z), is also manufactured by ZF.
If you have already taken part in the training for the 2nd generation of BMW ActiveHybrid vehicles, you will already be familiar with the GA8P70HZ transmission used there. The structure of the automatic transmission GA8P75HZ of the G20 PHEV is similar.
GA8P75HZ transmission
Structure and function
Overview
In order to satisfy the requirements of a Plug-in Hybrid Electric Vehicle, the automatic transmission was adapted. For this purpose, some existing components have been modified or replaced with other components. A part of the damping system was also extracted from the transmission area and connected to the combustion engine as a dual-mass flywheel with integrated centrifugal pendulum.
The connection to the transmission is effected via a spline.
As a result of the larger electrical machine and the additional torsional vibration damper, the housing of the GA8P75HZ transmission was extended by 30 mm in comparison to the GA8P70HZ transmission.
The hybrid area in the GA8P75HZ transmission can be divided into 5 components:
- Dual-mass flywheel
- Additional torsional vibration damper
- Separation clutch
- Electric motor
- Electrical transmission oil pump for supplying oil pressure when transmission input shaft is idle.
Like on the GA8P70HZ transmission, the multidisc brake B is also reinforced in the GA8P75HZ transmission by increasing the diameter and number of discs and is equipped with actively controllable transmission oil cooling. This is necessary as, in addition to its function as a shift element, it must also enable the vehicle to start-up and crawl.
GA8P75HZ transmission
- Dual-mass flywheel (including torsional vibration damper and centrifugal pendulum)
- Additional torsional vibration damper
- Separation clutch
- Electric motor
- Multidisc brake B
- Electrical transmission oil pump
The transmission power flow of the GA8P75HZ transmission shows how the new components have been integrated in the automatic transmission.
Schematic structure of the GA8P75HZ transmission
- Torsional vibration damper
- Centrifugal pendulum
- Additional torsional vibration damper
- Electric motor
- Gear set 1
- Gear set 2
- Gear set 3
- Gear set 4
- Mechanical transmission oil pump
- Multidisc brake A
- Multidisc brake B
- Multidisc clutch C
- Multidisc clutch D
- Multidisc clutch E
K0. Separation clutch
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Dual-mass flywheel
In order to reduce fuel consumption and CO2 emissions, high-charged engines
are used, the number
of cylinders is reduced and the drivable speeds are lowered.
However, with these measures the torsion
Shift elements
Brakes and clutches are described as shift elements which make possible the
shifting and changing
of all gears. Like in the GA8HP70Z transmission, the following shift elements
are also used in the
G
Oil supply
The basic functions of the oil circuit of the GA8P75HZ transmission
correspond to those of the
GA8HP70Z transmission. The oil has the following tasks:
Lubrication
Control of the shift elements
Co
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Adapted control units
It was necessary to adapt the IHKA to enable activation of the electric A/C
compressor (EKK) in all
operating conditions. The electric A/C compressor control unit communicates with
the IHKA via the
LIN bus.
To be able to show additional displays for driving readiness, electric driving,
brake ene
Dual-mass flywheel
In order to reduce fuel consumption and CO2 emissions, high-charged engines
are used, the number
of cylinders is reduced and the drivable speeds are lowered.
However, with these measures the torsional vibrations of the crankshaft are
increased as a result of
the acceleration during the work cycle
