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Automatic Transmission Power Flow, Basic Function - GF27.10-P-1002A

Model all with transmission 725 

Overview 

This document contains information on:

General 

The designation "force flux" refers to the transmission paths of torques. The torque is transferred to the wheels through the mechanical-hydraulic connection between the combustion engine, electric machine (integrated starter alternator/hybrid vehicle electric motor), torque converter or wet clutch, downstream automatic transmission and the differential.

Function requirements 

Function 

Power transmission on transmissions with torque converter 

Power is transferred in the torque converter via the driven impeller by diverting hydraulic fluid to the turbine wheel which is connected to the drive shaft. When the torque converter lockup clutch is engaged, the force flux is transmitted via this mechanical connection. The gear wheels of the individual planetary gear sets forward the torques generated by the torque converter to the output shaft with the help of the multidisk clutches and multidisk brakes to match the transmission ratio and actuated shift elements. A reduction of the output speed in lower gears results in lower vehicle speeds with simultaneously higher tractive forces and torques at the wheels.

IMPORTANT All planetary gear sets consist of the following elements: sun gear, planetary gears, planet carrier and annulus gear.

Power transmission on transmissions with wet clutch 

Power transmission in the wet clutch ensues through the non-positive connection of the internal and external plates, which are pressed together by the clutch piston. The pressure in the clutch piston is regulated via the wet clutch control solenoid valve. The torques generated by the wet clutch are forwarded onto the main shaft through the gear wheels of the individual planetary gear sets with the help of the multidisk clutches and multidisk brakes to match the transmission ratio and actuated shift elements. A reduction of the output speed in lower gears results in lower vehicle speeds with simultaneously higher tractive forces and torques at the wheels.

IMPORTANT All planetary gear sets consist of the following elements: sun gear, planetary gears, planet carrier and annulus gear.

Force flux in each gear range 

The function sequence is described in the following subfunctions:

Schematic diagram of involved components, force flux in automatic transmission 725.0/1 

G14472049Courtesy of MERCEDES-BENZ USA

Schematic diagram of force flux in 1st gear 

G14472050Courtesy of MERCEDES-BENZ USA

Force flux in 1st gear 

The following multidisk brakes and multidisk clutches are engaged:

The force flux in 1st gear passes through the following gear sets:

The sun gear (2) of planetary gear set P1 (P1) is part of the drive shaft (1) and is driven by this. The planet carrier (6) of planetary gear set P1 (P1) is connected via multiplate clutch K38 (E) to the ring gear (11) of planetary gear set P2 (P2). Multidisk brake B05 (B) brakes the sun gear (3) of planetary gear set P2 (P2). As a result, the torque increases and the rotational speed is decreased. The ring gear (11) of planetary gear set P2 (P2) has a mechanical connection to the sun gear (4) of planetary gear set P3 (P3). The planetary gears roll in the ring gear (12), stalled by multidisk brake B06 (C), of planetary gear set P3 (P3) and the planet carrier (8) of planetary gear set P3 (P3) transfers the resulting increased torque and reduced engine speed to the output shaft (14). As a result, the output shaft (14) rotates at a reduced input speed in the direction of engine rotation.

Schematic diagram of force flux in 2nd gear 

G14472051Courtesy of MERCEDES-BENZ USA

Force flux in 2nd gear 

The following multidisk brakes and multidisk clutches are engaged:

The force flux in 2nd gear passes through the following gear sets:

The sun gear (2) of planetary gear set P1 (P1) is part of the drive shaft (1) and is driven by this. Multiplate clutch K81 (D) connects the drive shaft (1) to the planet carrier (6) of planetary gear set P1 (P1) so that these revolve in the block. Multiplate clutch K38 (E) makes a mechanical connection to the sun gear (4) of planetary gear set P3 (P3). Multidisk brake B06 (C) brakes the ring gear (12) of planetary gear set P3 (P3). The planet carrier (8) of planetary gear set P3 (P3) transfers the resulting increased torque and reduced engine speed to the output shaft (14). As a result, the output shaft (14) rotates at a reduced input speed in the direction of engine rotation.

Schematic diagram of force flux in 3rd gear 

G14472052Courtesy of MERCEDES-BENZ USA

Force flux in 3rd gear 

The following multidisk brakes and multidisk clutches are engaged:

The force flux in 3rd gear passes through the following gear sets:

The sun gear (2) of planetary gear set P1 (P1) is part of the drive shaft (1) and is driven by this. Multiplate clutch K81 (D) connects the drive shaft (1) to the planet carrier (6) of planetary gear set P1 (P1) so that these revolve in the block. The ring gear (10) of planetary gear set P1 (P1) is driven by the planet carrier (6) of planetary gear set P1 (P1). In turn, the ring gear (10) drives the planet carrier (7) of planetary gear set P2 (P2). Multidisk brake B05 (B) brakes the sun gear (3) of planetary gear set P2 (P2). As a result, power is transmitted to the sun gear (4) of planetary gear set P3 (P3) via the ring gear (11) of planetary gear set P2 (P2). Multidisk brake B06 (C) brakes the ring gear (12) of planetary gear set P3 (P3). The planet carrier (8) of planetary gear set P3 (P3) transfers the resulting increased torque and reduced engine speed to the output shaft (14). As a result, the output shaft (14) rotates at a reduced input speed in the direction of engine rotation.

Schematic diagram of force flux in 4th gear 

G14472053Courtesy of MERCEDES-BENZ USA

Force flux in 4th gear

The following multidisk brakes and multidisk clutches are engaged:

The force flux in 4th gear passes through the following gear sets:

The sun gear (2) of planetary gear set P1 (P1) is part of the drive shaft (1) and is driven by this. The planet carrier (9) of planetary gear set P4 (P4) is also driven. The sun gear (3) of planetary gear set P2 (P2) is braked by multidisk brake B05 (B). The ring gear (11) of planetary gear set P2 (P2) supports the sun gears (4, 5) of planetary gear sets P3 (P3) and P4 (P4). Multidisk brake B06 (C) brakes the ring gear (12) of planetary gear set P3 (P3). Multiplate clutch K27 (F) is closed and planetary gear set P4 (P4) is switched in. The planet carrier (8) of planetary gear set P3 (P3) and the ring gear (13) of planetary gear set P4 (P4) transfer the resulting increased torque and reduced engine speed to the output shaft (14). As a result, the output shaft (14) rotates at a reduced input speed in the direction of engine rotation.

Schematic diagram of force flux in 5th gear 

G14472054Courtesy of MERCEDES-BENZ USA

Force flux in 5th gear 

The following multidisk brakes and multidisk clutches are engaged:

The force flux in 5th gear passes through the following gear sets:

The sun gear (2) of planetary gear set P1 (P1) is part of the drive shaft (1) and is driven by this. The planet carrier (9) of planetary gear set P4 (P4) is also driven by the drive shaft (1). Multiplate clutch K81 (D) connects the drive shaft (1) to the planet carrier (6) of planetary gear set P1 (P1) so that these revolve in the block. The ring gear (10) of planetary gear set P1 (P1) supports the planet carrier (7) of planetary gear set P2 (P2). Multidisk brake B05 (B) brakes the sun gear (3) of planetary gear set P2 (P2). As a result, the ring gear (11) of planetary gear set P2 (P2) transfers the force to the sun gear (5) of planetary gear set P4 (P4). Via the closed multiplate clutch K27 (F), the ring gear (13) of planetary gear set P4 (P4) transfers the resulting increased torque and reduced engine speed to the output shaft (14). As a result, the output shaft (14) rotates at a reduced input speed in the direction of engine rotation.

Schematic diagram of force flux in 6th gear 

G14472055Courtesy of MERCEDES-BENZ USA

Force flux in 6th gear 

The following multidisk clutches are engaged:

The force flux in 6th gear passes through the following gear sets:

The planet carrier (9) of planetary gear set P4 (P4) is driven by the drive shaft (1). Multiplate clutches K81 (D) and K38 (E) connect the respective elements of planetary gear sets P1 (P1) and P2 (P2). As a result, these revolve in the block and support the sun gear (5) of planetary gear set P4 (P4). Via the closed multiplate clutch K27 (F), the ring gear (13) of planetary gear set P4 (P4) transmits the torque to the output shaft (14). As a result, the output shaft (14) rotates at a reduced input speed in the direction of engine rotation.

Schematic diagram of force flux in 7th gear 

G14472056Courtesy of MERCEDES-BENZ USA

Force flux in 7th gear 

The following multidisk brakes and multidisk clutches are engaged:

The force flux in 7th gear passes through the following gear sets:

The sun gear (2) of planetary gear set P1 (P1) is part of the drive shaft (1) and is driven by this. The planet carrier (9) of planetary gear set P4 (P4) is also driven by the drive shaft (1). The ring gear (10) of planetary gear set P1 (P1) supports the planet carrier (7) of planetary gear set P2 (P2). The ring gear (10) of planetary gear set P1 (P1) is driven by the planet carrier (6) of planetary gear set P1 (P1). Multidisk brake B05 (B) brakes the sun gear (3) of planetary gear set P2 (P2). As a result, the ring gear (11) of planetary gear set P2 (P2) transfers the force via the closed multiplate clutch K38 (E) to the sun gear (5) of planetary gear set P4 (P4). Via the closed multiplate clutch K27 (F), the ring gear (13) of planetary gear set P4 (P4) transfers the resulting reduced torque and increased engine speed to the output shaft (14). As a result, the output shaft (14) rotates at an increased input speed in the direction of engine rotation.

Schematic diagram of force flux in 8th gear 

G14472057Courtesy of MERCEDES-BENZ USA

Force flux in 8th gear 

The following multidisk brakes and multidisk clutches are engaged:

The force flux in 8th gear passes through the following gear sets:

The sun gear (2) of planetary gear set P1 (P1) is part of the drive shaft (1) and is driven by this. The planet carrier (9) of planetary gear set P4 (P4) is also driven by the drive shaft (1). The planet carrier (6) of planetary gear set P1 (P1) is braked by actuation of multidisk brake B08 (A). The sun gear (5) of planetary gear set P4 (P4) is connected by actuation of multiplate clutch K38 (E) to the planet carrier (6) of planetary gear set P1 (P1) and also braked. Via the closed multiplate clutch K27 (F), the ring gear (13) of planetary gear set P4 (P4) transfers the resulting reduced torque and increased engine speed to the output shaft (14). As a result, the output shaft (14) rotates at an increased input speed in the direction of engine rotation.

Schematic diagram of force flux in 9th gear 

G14472058Courtesy of MERCEDES-BENZ USA

Force flux in 9th gear 

The following multidisk brakes and multidisk clutches are engaged:

The force flux in 9th gear passes through the following gear sets:

The sun gear (2) of planetary gear set P1 (P1) is part of the drive shaft (1) and is driven by this. The planet carrier (9) of planetary gear set P4 (P4) is also driven by the drive shaft (1). The planet carrier (6) of planetary gear set P1 (P1) is braked by actuation of multidisk brake B08 (A). The force flux is transmitted via the ring gear (10) of planetary gear set P1 (P1) to the planet carrier (7) of planetary gear set P2 (P2). Multidisk brake B05 (B) brakes the sun gear (3) of planetary gear set P2 (P2). The ring gear (11) of planetary gear set P2 (P2) drives the sun gear (5) of planetary gear set P4 (P4). Via the closed multiplate clutch K27 (F), the ring gear (13) of planetary gear set P4 (P4) transfers the resulting reduced torque and increased engine speed to the output shaft (14). As a result, the output shaft (14) rotates at an increased input speed in the direction of engine rotation.

Schematic diagram of force flux in reverse gear 

G14472059Courtesy of MERCEDES-BENZ USA

Power flow in reverse gear 

The following multidisk brakes are engaged:

The force flux in reverse gear passes through the following gear sets:

The sun gear (2) of planetary gear set P1 (P1) is part of the drive shaft (1) and is driven by this. The planet carrier (6) of planetary gear set P1 (P1) is braked by multidisk brake B08 (A). The force flux is transmitted via the ring gear (10) of planetary gear set P1 (P1) to the planet carrier (7) of planetary gear set P2 (P2). The planet carrier (7) of planetary gear set P2 (P2) rolls on the sun gear (3), braked by multidisk brake B05 (B), of the planet carrier (7) of planetary gear set P2 (P2). The ring gear (11) of planetary gear set P2 (P2) drives the sun gear (4) of planetary gear set P3 (P3). Multidisk brake B06 (C) brakes the ring gear (12) of planetary gear set P3 (P3). The planet carrier (8) of planetary gear set P3 (P3) transfers the resulting increased torque and reduced engine speed to the output shaft (14). As a result, the output shaft (14) rotates at a reduced input speed opposite the direction of engine rotation.

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