Clutch schedule for a four-speed Ravigneaux transmission
Simscape / Driveline / Transmissions
The 4-Speed Ravigneaux block consists of one Ravigneaux gear set and five clutches. The follower shaft connects to the ring gear of the Ravigneaux set. Three of the clutches determine the gears that the base shaft connects to for power transfer. The other two clutches serve as brakes, grounding various gears of the Ravigneaux set to the transmission housing.
This diagram shows a four-speed Ravigneaux gear transmission. The labels for the gear components are superimposed on the input and output gears. The table lists the gear and clutch components that are labeled in the diagram.
|C||Planet gear carrier|
|SL||Large sun gear|
|SS||Small sun gear|
|A–C||Forward clutches that control the power flow path|
|D–E||Forward, braking clutches|
Drive Ratios, Clutch Schedule, and Power Flow
The drive ratio between the transmission input and output shafts follows from the elementary gear ratios specified for the gear blocks. The elementary gear ratios are
NR is the number of teeth in the Ravigneaux ring gear.
NSL is the number of teeth in the Ravigneaux large sun gear.
NSS is the number of teeth in the Ravigneaux small sun gear.
The table shows the clutch schedule, drive-ratio expressions, drive-ratio default values, and the power-flow diagrams for each gear of the 4-Speed Ravigneaux block.
The letters in the clutch schedule columns denote the brakes and clutches. A value
1 denotes a locked state and a value of
an unlocked state. The clutch schedule generates these signals based on the Gear
port input signal. The signals are scaled through a Gain block and used as actuation
inputs in the clutch blocks.
The power-flow diagrams show the power flow paths between input and output shafts for each gear setting. Power flow is shown in orange. Connections to the transmission housing (a mechanical ground) are shown in black.
|Gear||Clutch Schedule||Drive Ratio Equation||Default Ratio||Power Flow|
Gear — Numerical input for the gear
Specify -1 for reverse, 0 for neutral, and 1–4 for the forward gears.
B — Base interface
Conserving port associated with the base shaft.
F — Follower interface
Conserving port associated with the follower shaft.
Initial gear — Gear state at the beginning of simulation
Neutral (default) |
Sets the initial engagement or disengagement of the clutches using the clutch schedule. When the transmission is in neutral, there is no power flow from the base shaft to the follower shaft.