GB2282646A

GB2282646A - Oil sump for an infinitely-variable belt-driven transmission

Info

Publication number: GB2282646A
Application number: GB9419884A
Authority: GB
Inventors: Romanus Scholz; Paulus Heidemeyer
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1993-10-09
Filing date: 1994-10-03
Publication date: 1995-04-12
Anticipated expiration: 2014-10-03
Also published as: GB2282646B; FR2710958B1; GB9419884D0; FR2710958A1; JPH07167263A

Abstract

Below an upper set of conical pulleys (2) is a main oil sump (14) and below the lower set of conical pulleys (3) is a secondary oil sump (15). A separating rib (17) extends through the transmission housing (1) between the two centres of rotation (2, 3) and separates the main oil sump (14) of the upper set of conical pulleys from the region of rotation of the lower set of conical pulleys. The conical pulley (6), fixed on the output shaft (9), of the lower set of conical pulleys (3) is provided with conveying elements (12) by which the oil accumulating in the secondary oil sump (15) may be conveyed into the main oil sump (14). <IMAGE>

Description

DESCRIPTION AN INFINITELY VARIABLE BELT-DRIVEN TRANSMISSION The present invention relates to an infinitely variable belt-driven transmission.

In automatic transmissions, it is known that the clutches and lubrication points are supplied with pressure oil during operation. Infinitely variable belt-driven transmissions having only two centres of rotation, such as are known from, for example, DE-OS 42 22 115, therefore require below the first centre of rotation, formed by the first set of conical pulleys and the transmission input shaft, an oil sump of sufficient volume from which an operating-oil pump may draw the oil required for lubrication of the transmission. The second centre of rotation, formed by the second set of conical pulleys and the transmission output shaft, is kept free from oil on account of the rotating parts which otherwise would be immersed and would impair the efficiency of the transmission. Nevertheless, a slight flow of leakage oil towards the second set of conical pulleys, that is the set of conical output pulleys, cannot be avoided during operation of a transmission of this kind.

In the interests of optimum efficiency of the transmission, it is desirable for the level of operating oil to be as low as possible in the region of the lower set of conical pulleys. The aim of the present invention is to provide a transmission in which the operating oil accumulating in the region of the lower set of conical pulleys may be returned to the main oil sump of the upper set of conical pulleys without incurring great structural expense.

According to the present invention there is provided an infinitely variable belt-driven transmission having a sump oil conveying device and comprising a transmission housing, transmission input and output shafts journalled therein, two sets of conical pulleys each having a conical pulley fixed on the respective transmission shaft and an axially displaceable pulley, and a flexible drive element embracing the two sets of conical pulleys, wherein the first set of conical pulleys, connected to the transmission input shaft, forms a first, upper centre of rotation in the transmission housing, while the second set of conical pulleys, connected to the transmission output shaft, constitutes a second, lower centre of rotation in the transmission housing, a region disposed below the first set of conical pulleys forming a main oil sump, in the transmission housing, and, a region below the second set of conical pulleys forming a secondary oil sump, a separating rib extending through the transmission housing outside the region of the flexible drive element between the two sets of conical pulleys, said separating rib separating the main oil sump of the first set of conical pulleys from the rotation space of the second set of conical pulleys, the conical pulley fixed on the output shaft of the second set of conical pulleys being provided with conveying elements by which oil accumulating in the secondary oil sump may be conveyed into the main oil sump.

Accordingly, in accordance with the present invention, a separating rib passes through the housing of the transmission of the generic type and is disposed substantially vertically between the two centres of rotation and separates the main oil sump associated with the upper centre of rotation from the lower centre of rotation and the secondary oil sump formed there. Furthermore, in accordance with the invention, for the purpose of pumping out the leakage oil collecting in the secondary oil sump, the conical pulley, fixed on the output shaft, of the lower set of conical pulleys is provided with conveying elements by which the oil accumulating in the secondary oil sump may be conveyed into the main oil sump.

In one embodiment of the present invention, the conveying elements, preferably disposed on the end face of the fixed conical pulley, are in the form of sheet metal plates or teeth which are aligned parallel to the axis of rotation of the transmission output shaft. The dimensions of the conveying elements are preferably such that the conveying elements move past the interior wall of the transmission housing, or past a housing rib formed or mounted thereon, at a short distance therefrom. Preferably, this housing rib projects from the lowest point of the secondary oil sump to above the vertex of the lower set of conical pulleys.

For the purpose of increasing the conveying performance of the conveying elements, the housing rib may be of L-shaped or U-shaped configuration.

Moreover, this housing rib may be formed on, or secured to, the inside of the cover of the transmission housing.

In a modified embodiment of the present invention, an annular sheet metal plate having vane surfaces is secured to the end face of the fixed conical pulley of the second set of conical pulley, instead of individual conveying elements previously mentioned.

In a further embodiment, teeth formed on the fixed conical pulley may be used as conveying elements for the purpose of measuring the rotational speed of the transmission output shaft.

For the purpose of collecting the oil conveyed from the secondary oil sump by the conveying elements, the housing rib separating the main oil sump from the second set of conical pulleys may have, in the region of the conveying elements, an oil-collecting and oilguiding rib which is guided towards the axis of rotation of the transmission output shaft and by which the secondary sump oil conveyed is conducted into the main oil sump.

Finally, in a further advantageous development of the present invention, the transmission housing may have a depression which forms the secondary oil sump and into which the housing rib extends.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic cross section through a twin-shaft, conical pulley belt-driven transmission, constructed according to the present invention; Fig. 2 is a diagrammatic end elevation of the two centres of rotation of the transmission of Fig. 1; Fig. 3 is a detailed view of a modified embodiment of the present invention having a U-shaped housing rib; and Fig. 4 shows a modification of the conveying elements for use in the embodiment of Fig. 3.

Only the part, essential for explaining the invention, of the infinitely variable belt-driven transmission with a twin-shaft structure, known per se from DE-OS 42 22 115 already cited, is shown diagrammatically in the embodiment of Fig. 1. A transmission input shaft 8 and a transmission output shaft 9 are journalled in a transmission housing 1. A set of conical pulleys 2 is disposed on the transmission input shaft 8, and a lower set of conical pulleys 3 is disposed on the transmission output shaft 9. Each of these sets of conical pulleys comprises a fixed conical pulley 4,6 and a conical pulley 5, 7 which is displaceable, preferably hydraulically, coaxially to the respective transmission shafts. The two sets of conical pulleys 2, 3 are embraced by a flexible drive element 11.

The end face 10, acing the transmission housing 1, of the fixed conical pulley 6 of the lower set of conical pulleys 3 has conveying elements 12 which are movable past, and at a short distance from, a housing rib 13 formed on, or secured to, the transmission housing 1. In the embodiment shown in Fig. 1, the housing rib 13 is formed as an J.-shaped structure which, in this embodiment, is an integral component part of the cast structure of a cover 25 of the transmission housing 1. The distance between the conveying elements 12 and the housing rib 13 must be kept as small as possible or the purpose of making possible a high conveying performance. Preferably, a distance of 0.2 mm has to be provided.

The detailed view of Fig. 3 shows a different embodiment wherein, a U-shaped housing rib 21 surrounds the conveying elements 12 for the purpose of further increasing the conveying performance. A modified construction of the conveying elements is shown in the detail of Fig. 4. In this variant, the individual vane surfaces 27 are disposed on an annular sheet metal plate 26 which is secured to the end face 10 of the conical pulley 6.

The end elevation illustrated in Fig. 2, taken approximately on the sectional line A-A in fig. 1, shows the transmission housing 1 with the two sets of conical pulleys 2, 3 located therein. A separating rib 17 in accordance with the present invention is disposed substantially vertically between the two sets of conical pulleys in the transmission housing 1 and separates a main oil sump 14 located below the first set of conical pulleys 2 from the largely dry rotation space 28 below the second set of conical pulleys 3.

A secondary oil sump 15 is formed in the region of a housing depression 22 which will be seen in the lower part of the rotation space 28. The housing rib 13 connected to the transmission housing 1 has a profiled part 23 extending into the secondary oil sump, which in this embodiment, has a run-in contour 23 which extends into the housing depression 22 as an L-shaped transmission housing component beyond the vertex 16 of the second set of conical pulleys 3.

The conveying elements 12 are mounted on the end face 10, only shown diagrammatically in this manner of representation, of the fixed conical pulley 6 and extend into the L-shaped contour of the housing rib 13.

Upon rotation of the conical pulley 6 in the direction of rotation 24, the conveying elements 12 enter the secondary oil sump 5 and, with the aid of housing rib 13 functioning as a pump housing bottom, to convey the oil beyond the vertex 16 of the conical pulley 6. The oil th's conveyed above the level of fluid in the main oi sump 4 is then either centrifuged directly into the main oil sump 14 or is conducted to the main oil sump i4 by an oil-collecting and oil-guiding rib IS mounted on the separating rib 17, preferably in the region cf the conveying elements 12.

In a further advantageous embodiment, the conveying elements 12 of the present invention can be used for sensing the rotational speed of the transmission output shaft. For this purpose, there may be provided in the transmission housing an opening 19 through which is inserted a rotational speed sensor which, for example, operates capacitively, and which receives rotational speed pulses from the conveying elements moving past. It is also possible to convey oil from the secondary sump 15 by using teeth, provided on the end face of the conical pulley 6 fixed on the transmission output shaft, for ascertaining the rotational speed.

Claims

1. An infinitely variable belt-driven transmission having a sump oil conveying device and comprising a transmission housing, transmission input and output shafts journalled therein, two sets of conical pulleys each having a conical pulley fixed on the respective transmission shaft and an axially displaceable pulley, and a flexible drive element embracing the two sets of conical pulleys, wherein the first set of conical pulleys, connected to the transmission input shaft, forms a first, upper centre of rotation in the transmission housing, while the second set of conical pulleys, connected to the transmission output shaft, constitutes a second, lower centre of rotation in the transmission housing, a region disposed below the first set of conical pulleys forming a main oil sump, in the transmission housing, and, a region below the second set of conical pulleys forming a secondary oil sump, a separating rib extending through the transmission housing outside the region of the flexible drive element between the two sets of conical pulleys, said separating rib separating the main oil sump of the first set of conical pulleys from the rotation space of the second set of conical pulleys, the conical pulley fixed on the output shaft of the second set of conical pulleys being provided with conveying elements by which oil accumulating in the secondary oil sump may be conveyed into the main oil sump.

2. A transmission as claimed in claim 1, in which the conveying elements are formed as sheet metal plates or teeth on the end face of the fixed conical pulley and their longitudinal extents are aligned parallel to the axis of the transmission output shaft.

3. A transmission as claimed in claim 1 and claim 2, in which teeth formed on the fixed conical pulley for the purpose of rotational speed measurement, are used as conveying elements.

4. A transmission as claimed in any one of claims 1 to 3, in which the dimensions of the conveying elements are such that the conveying elements move past the interior wall of the transmission housing, or past a housing rib formed or mounted thereon, at a short distance therefrom.

5. A transmission as claimed in claim 4, in which the housing rib extends from the lowest point of the secondary sump to above the vertex of the second set of conical pulleys.

6. A transmission as claimed in claim 4 and claim 5, in which the housing rib is formed in an Lshaped or U-shape.

7. A transmission as claimed in claims 4 to 6, in which the housing rib is formed on, or secured to, the inside of a transmission housing cover forming part of the transmission housing.

8. A transmission as claimed in any one of the preceding claims, in which an oil-collecting and oilconducting rib guided towards the transmission output shaft is formed on the separating rib in the region of the conveying elements of the second set of conical pulleys, by which oil-collecting and oil-conducting rib oil conveyed by the conveying elements over the vertex of the second set of conical pulleys can be guided into the main oil sump.

9. A transmission as claimed in any one of the preceding claims, in which the transmission housing has a depression forming the secondary oil sump.

10. A transmission as claimed in any one of the preceding claims, in which an annular sheet metal plate having vane surfaces is secured to the fixed conical pulley to said vanes forming said conveying elements.

11. An infinitely variable belt-driven transmission, constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.