Automatic transmission start-up device

[0001] The present invention relates to the field of start-up elements for automatic transmissions.

[0002] As a rule, start-up elements for automatic transmissions are arranged in the drive train behind the engine and in front of the transmission, in order to accommodate the speed difference between the lowest operational speed of the engine and the stationary gearbox input shaft, which occurs upon the start-up of the vehicle from the stopped position. Force-locked clutches are typically used as start-up elements in manual transmissions, and hydrodynamic torque converters are employed with automatic transmissions.

[0003] The use of a brake at the sun gear of the incoming gear set of an automatic transmission, as a start-up element, is known from the publication “Getriebe in Fahrzeugen 2001” [“Transmissions in Vehicles 2001”] P. 461 p., Image 6, VDI-Berichte 1610 [VDI Reports 1610]. However, if a slip of the start-up element is required or desired in all gear selections, for example, for the purpose of an acoustic improvement, the brake at the sun gear described in this publication is not suitable as a start-up element, because it does not support torque transfer in its highest gear.

[0004] Wet start-up clutches have been recommended as start-up elements as well; however their structure is highly complex.

[0005] It is an object of the present invention to provide a start-up element for an automatic transmission that avoids various disadvantages of the state-of-the-art. In particular, a start-up element is provided having low structural complexity, and which allows slip in all gear positions.

[0006] In addition, the start-up element according to the present invention is compact, in order to provide the required space for additional components of the drive train, such as, for example, a crankshaft-mounted starter generator between the engine and the transmission. In particular, the overall length of the start-up element is preferably no longer than a conventional torque converter.

[0007] Accordingly, the present invention provides a startup clutch arranged within a cover that is flanged to the pump for circulating the operating fluid, preferably as a multiple disc clutch. The front pump support and the front gear seal are integrated in the cover. Preferably, the pump remains coupled to the engine side.

[0008] According to the present invention, channels present at a converter gear for opening and closing of the converter clutch are preferably used for controlling the start-up clutch, or for the cooling oil supply of the disc packet of the starter clutch.

[0014] According to FIG. 1, a start-up clutch 1 is arranged within a housing or cover 3 flanged to a pump 2 for pumping the operating fluid. On the gear side, the pump 3 has a fixed connection to a centering plate 15, which forms a front gear housing wall, and typically includes several channels for distributing the operating fluid. Preferably, the start-up clutch 1 is designed as a multi disc clutch with a disc packet 4 that contains inner discs 5 and outer discs 6. According to the present invention, the cylinder 7 and the piston 8 of the start-up clutch 1 are preferably coupled to the engine side via a tappet 9. The pump 2 is coupled to the engine side as well; in the Figures, the pump tappet is shown as reference number 10.

[0015] This design allows for fast filling of the reservoir 12, which includes a retaining disc 11, and thus ensures a rapid build-up of the hydrodynamic pressure equalization. For better flow through the disc packet, it is particularly advantageous to design the outer discs 6 as grooved padded discs and the inner discs 5 as steel discs.

[0016] FIG. 2 presents an additional advantageous embodiment of the present invention. The inner disc carrier 13 of the disc packet 4 is coupled to the engine side, while the servo components 7, 8 of the clutch are connected to the gearbox input shaft 14. In this manner, the inner disc carrier that rotates at the engine speed transports the cooling oil into the disc packet 4.

[0017] In the context of a third embodiment, which is shown in FIG. 3, the servo component of the start-up clutch 1 and the inner disc carrier 13 of the start-up clutch 1 are coupled to the engine side. This design achieves rapid filling of the reservoir 12 and thus a quick build-up of the hydrodynamic pressure equalization. At the same time, the inner disc carrier that rotates at the engine speed transports the cooling oil very effectively into the disc packet 4.

[0018] FIG. 4 shows a variation of the embodiment of FIG. 3, where the elements of the inner disc carrier 13, the retaining disc 11, the disc packet 4 and the piston 8 are arranged in a mirrored manner, while retaining the advantages mentioned above.

[0019] Due to the arrangement according to embodiments of the present invention, there is no need for a torque converter or converter transmission; furthermore, it is possible to install a crankshaft-mounted starter generator, as well as additional components of the drive train, such as a dual-mass flywheel, because the overall space is optimally utilized.

[0020] An additional advantage of the present invention relies on the fact that the channels, which are present at a converter transmission for opening and closing the converter clutch, are used, according to embodiments of the present invention, to control the start-up clutch or for the cooling oil supply of the disc packet of the start-up clutch. In this manner, a typical torque converter that is used as the start-up element can be replaced at the transmission by the start-up element described above, preferably without significant additional cost.

[0021] The start-up clutch described herein can also be employed in an automatic transmission with an external pump for supplying fluid pressure to the automatic transmission. With this embodiment, the cover 3, with the start-up clutch arranged inside cover 3, is flanged directly to the centering plate 15 that has an integrated pump solidly connected to it in accordance with the embodiments described in the Figures above, instead of to the pump housing. Principal advantages of the present invention are retained in this arrangement as well.

[0022] While the above detailed description has shown, described and pointed out the fundamental novel features of the invention as applied to various embodiments, it will be understood that various omissions and substitutions and changes in the form and details of the system and method illustrated may be made by those skilled in the art, without departing from the spirit of the invention. Consequently, the full scope of the invention should be ascertained by the appended claims.