Efficient eight speed automatic transmission
View Patent ↗The present invention provides an eight speed automatic transmission for motor vehicles having three planetary gear sets, four friction clutches, a friction brake, a band brake and an optional overrunning clutch. The eight speed transmission according to the present invention exhibits good gear ratio progression and high efficiency due to its excellent gear mesh efficiency, low spin losses and low pinion speeds.
1. A multiple speed automatic transmission comprising;
a housing, an input member and an output member,
a first planetary gear assembly having a first sun gear, a first planet carrier and a first ring gear,
a second planetary gear assembly having a second sun gear, a second planet carrier and a second ring gear,
a third planetary gear assembly having a third sun gear, a third planet carrier and a third ring gear,
a first brake selectively connecting said housing and said third ring gear,
a first clutch selectively connecting said third ring gear and said first planet carrier,
a second clutch selectively connecting said third planet carrier and said first ring gear and said second sun gear,
a third clutch selectively connecting said third planet carrier and said second planet carrier,
a fourth clutch selectively connecting said third sun gear and said second planet carrier, and
a second brake selectively connecting said second planet carrier and said housing.
2. The multiple speed automatic transmission of claim 1 wherein said first brake is a friction brake and said second brake is a band brake.
3. The multiple speed automatic transmission of claim 1 wherein said input member is coupled to said third sun gear and said fourth clutch.
4. The multiple speed automatic transmission of claim 1 wherein said output member is coupled to said second ring gear.
5. The multiple speed automatic transmission of claim 1 further including a freewheeling clutch selectively connecting said second planet carrier and said first sun gear and said housing.
6. The multiple speed automatic transmission of claim 1 wherein said clutches include a plurality of interleaved plates.
7. The multiple speed automatic transmission of claim 1 wherein each of said planet carriers rotatably support a plurality of planet gears.
8. An eight speed automatic transmission comprising;
a housing rotatably supporting an input member and an output member,
a first planetary gear assembly having a first sun gear, a first planet carrier and a first ring gear,
a second planetary gear assembly having a second sun gear, a second planet carrier and a second ring gear,
a third planetary gear assembly having a third sun gear, a third planet carrier and a third ring gear,
a first torque transmitting device selectively connecting said housing and said third ring gear,
a second torque transmitting device selectively connecting said third ring gear and said first planet carrier,
a third torque transmitting device selectively connecting said third planet carrier and said first ring gear and said second sun gear,
a fourth torque transmitting device selectively connecting said third planet carrier and said second planet carrier,
a fifth torque transmitting device selectively connecting said third sun gear and said second planet carrier, and
a sixth torque transmitting device selectively connecting said second planet carrier and said housing.
9. The eight speed transmission of claim 8 wherein said first and sixth torque transmitting devices are brakes and said second, third, fourth and fifth torque transmitting device are clutches.
10. The eight speed transmission of claim 8 wherein said input member is coupled to said third sun gear and said fifth torque transmitting device.
11. The eight speed transmission of claim 8 wherein said output member is coupled to said second ring gear.
12. The eight speed automatic transmission of claim 8 wherein each of said planet carriers rotatably support a plurality of planet gears.
13. The eight speed automatic transmission of claim 8 further including a freewheeling clutch selectively connecting said second planet carrier and said first sun gear and said housing.
14. The eight speed automatic transmission of claim 8 wherein said sixth torque transmitting device is a band brake.
15. An eight speed automatic transmission comprising;
a housing,
a first planetary gear assembly having a first sun gear, a first planet carrier and a first ring gear,
a second planetary gear assembly having a second sun gear, a second planet carrier and a second ring gear,
a third planetary gear assembly having a third sun gear, a third planet carrier and a third ring gear,
a first torque transmitting device selectively connecting said housing and said third ring gear,
a second torque transmitting device selectively connecting said third ring gear and said first planet carrier,
a third torque transmitting device selectively connecting said third planet carrier and said first ring gear and said second sun gear,
a fourth torque transmitting device selectively connecting said third planet carrier and said second planet carrier,
a fifth torque transmitting device selectively connecting said third sun gear and said second planet carrier, and
a sixth torque transmitting device selectively connecting said second planet carrier and said housing.
16. The eight speed automatic transmission of claim 15 further including an input member coupled to said third sun gear and said fifth torque transmitting device.
17. The eight speed automatic transmission of claim 15 further including an output member coupled to said second ring gear.
18. The eight speed automatic transmission of claim 15 wherein said first and sixth torque transmitting devices are brakes and said second, third, fourth and fifth torque transmitting device are clutches.
19. The eight speed automatic transmission of claim 15 further including a seventh torque transmitting device selectively connecting said second planet carrier and said first sun gear.
20. The eight speed automatic transmission of claim 15 further including a seventh torque transmitting device selectively connecting said second planet carrier and said first sun gear and said housing.