AUTOMATIC TRANSMISSION FOR AUTOMOTIVE VEHICLES

Abstract

An automatic transmission is provided comprising a transmission case, a first shaft housed in and rotationally supported by said transmission case, and capable of receiving torque from an engine, a first shifting gear mechanism arranged coaxially with the first shaft, and a second shifting gear mechanism including a second planetary gear set. The second planetary gear set is housed within the transmission case and arranged coaxially with the first shaft, one of its sun and ring gears is capable of rotating together with the input shaft, and the other of the sun and ring gears is fixed to the transmission case. The automatic transmission further comprises first and second frictional elements arranged at least partly overlapped with the second planetary gear set in the axial direction between the planetary gear set and the transmission case in the radial direction. Accordingly, the plurality of frictional elements may be arranged on a shorter shaft without excessively increasing the radial size of the automatic transmission.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by reading an example of embodiments in which the above aspects are used to advantage, referred to herein as the Detailed Description, with reference to the drawings wherein:

FIG. 1 is a sectional view of transaxle including an automatic transmission for an automotive vehicle in accordance with an embodiment of the present description;

FIG. 2 is a side explanatory diagram of the transaxle of the embodiment;

FIG. 3 is a sectional view of the automatic transmission of the embodiment;

FIG. 4 is a skeleton diagram schematically showing rotational elements and frictional elements of the automatic transmission of the embodiment;

FIG. 5 is a table showing engaged frictional elements at respective speed gears;

FIG. 6 is an enlarged sectional view of an automatic transmission in accordance with another embodiment of the present description, showing a neighborhood of an output gear.

Claims

1. An automatic transmission comprising: a transmission case;a first shaft housed in and rotationally supported by said transmission case, and capable of receiving torque from an engine;a first shifting gear mechanism arranged coaxially with said first shaft;a second shifting gear mechanism including a second planetary gear set, said second planetary gear set being housed within said transmission case and arranged coaxially with said first shaft, one of its sun and ring gears being capable of rotating together with said input shaft, and the other of said sun and ring gears being fixed to said transmission case; andfirst and second frictional elements, each of which is arranged at least partly overlapped with said second planetary gear set in the axial direction and between said second planetary gear set and said transmission case in the radial direction.

2. The automatic transmission as described in claim 1, further comprising a torque converter capable of transmitting torque from said engine to one axial end region of said first shaft, and wherein first shifting gear mechanism is arranged between said torque converter and said second planetary gear set in the radial direction.

3. The automatic transmission as described in claim 2, further comprising: an output gear arranged coaxially on said first shaft between said second planetary gear set and said torque converter in the axial direction;a second shaft arranged in parallel to said first shaft;a driven gear coaxially arranged on said second shaft and engaging with said output gear; anda final gear coaxially arranged on said second shaft between said torque converter and said driven gear in the axial direction, and capable of transmitting torque from said driven gear to a vehicle driving wheel.

4. The automatic transmission as described in claim 2, wherein said sun gear of said second planetary gear set is fixed to said transmission casing.

5. The automatic transmission as described in claim 4, wherein said ring gear of said second planetary gear set is connected to said first shaft at a first side of said second planetary gear set that faces to said torque converter.

6. The automatic transmission as described in claim 5, wherein a planetary carrier of said second planetary gear set is connected to said first frictional element at a second side of said second planetary gear set that is opposite to said first side.

7. The automatic transmission as described in claim 5, wherein said first frictional element is connected to one of rotational elements of said first shifting gear mechanism at said first side of said second planetary gear set.

8. The automatic transmission as described in claim 7, further comprising a hydraulic piston capable of axially moving and selectively engaging said first or second frictional element, said hydraulic piston being arranged at said second side of said second planetary gear set.

9. The automatic transmission as described in claim 8, wherein said second frictional element is arranged between said first frictional element and said transmission case in the radial direction and connected to one of rotational elements of said first shifting gear mechanism at said first side of said second planetary gear set.

10. The automatic transmission as described in claim 2, wherein said one of said sun and ring gears of said second planetary gear set is connected to said first shaft at a first side of said second planetary gear set that faces to said torque converter.

11. The automatic transmission as described in claim 10, wherein said first frictional element is connected to one of rotational elements of said first shifting gear mechanism at said first side of said second planetary gear set.

12. The automatic transmission as described in claim 10, further comprising a hydraulic piston capable of axially moving and selectively engaging said first or second frictional element, said hydraulic piston being arranged at a second side of said second planetary gear set that is opposite to said first side.

13. The automatic transmission as described in claim 12, wherein said second frictional element is arranged between said first frictional element and said transmission case in the radial direction and connected to one of rotational elements of said first shifting gear mechanism at said first side of said second planetary gear set.

14. The automatic transmission as described in claim 1, wherein said first frictional element is a clutch, and said second frictional element is a brake arranged between said clutch and said transmission case in the radial direction.

15. The automatic transmission as described in claim 14, wherein said clutch and brake are connected to a single rotational element of said first shifting gear mechanism.

16. The automatic transmission as described in claim 14, wherein said transmission case directly supports a one side of said brake so that it does not rotate.

17. The automatic transmission as described in claim 1, further comprising a third frictional element arranged overlapped with a planetary gear set consisting of a part of said first shifting gear mechanism and is arranged next to said second planetary gear set in the axial direction.

18. An automatic transmission comprising: a transmission case;a first shaft housed in and rotationally supported by said transmission case, and capable of receiving torque from an engine;a first shifting gear mechanism arranged coaxially with said first shaft;a second shifting gear mechanism including a second planetary gear set, said second planetary gear set being housed within said transmission case and arranged coaxially with said first shaft, its ring gear being connected to said input shaft, its sun gear being fixed to said transmission case, and torque being transmitted from said first shaft through some of rotational elements of said first and second shifting gear mechanism;a frictional brake arranged at least partly overlapped with said planetary gear in the axial direction, and arranged between said planetary gear set and said transmission case in the radial direction; anda frictional clutch arranged at least partly overlapped with said planetary gear and said frictional brake in the axial direction, and arranged between said planetary gear set and said frictional brake in the radial direction.

19. The automatic transmission as described in claim 18, wherein said frictional clutch is connected to a planetary carrier of said second planetary gears.

20. The automatic transmission as described in claim 19, wherein one of rotational elements of said first shifting gear mechanism is connected to said frictional brake and said frictional clutch.