Transmission unit for motor vehicles

Abstract: Transmission unit consisting of a continuously variable transmission (1); a hydraulic cylinder/piston unit (3) to set the transmission ratio of the continuously variable transmission (2); a pressure compensation chamber (4) working in conjunction with the cylinder/piston unit (3); and a passage organ (5) having at least one passage way (6) connecting the pressure compensation chamber (4) with the piston chamber (7) of said cylinder/piston unit (3), characterized in that the passage way (6) stretches at least partially along the outer surface of the passage organ (5).

Description: The present invention concerns a transmission unit for motor vehicles, in particular of the type whereby the transmission ratio is regulated steplessly by means of a continuously variable transmission. It is known that such transmission units, apart from the actual transmission, are provided with a hydraulic cylinder/piston unit to set the transmission ratio of the continuously variable transmission. It is also known that such transmission units can be equipped with a pressure compensation chamber to compensate increases of pressure in the piston chamber of the cylinder/piston unit resulting from centrifugal forces, whereby this pressure compensation chamber is connected with said piston chamber via a filler port. It is also known that this filler port can be provided with a passage organ having a passage opening with very precise dimensions, for example as described in Dutch patent application No 8302089 (EP-A-0 128 611). The known passage organs are composed of different parts, which may considerably increase the risk of manufacturing faults as well as the total cost of production. Moreover, the passage openings in these existing passage organs are mainly situated centrally and thus can only be made by drilling, punching or such. Technically, it is very difficult to make the small passage openings in accordance with the required tolerances. This may result in frequent disturbances during the working of the transmission unit. Another possibility for providing a passage has been proposed in EP-A-0.329.205 from which the features defined in the first part of claim 1 are known, whereby said passage is formed by one or more calibrated openings between the piston and the wall of the cylinder. This technique however shows that the passage is delimited by parts which are moving along each other. The present invention aims to further develop the above-mentioned device. To this aim the invention concerns a transmission unit consisting of the features as defined in claim 1. By providing the passage opening on the outer surface of a plug-shaped passage organ, it is possible to obtain a relatively big accuracy by means of relatively simple operations. For in this case the passage opening can be made through grinding or by already providing this opening as the passage organ is still being moulded. The simplicity of the passage organ according to the invention makes it possible to manufacture it through moulding without even one finishing process Deing required. Moreover, this process makes it possible to simultaneously mould in a filter gauze without any extra manufacturing stages being required. In order to better explain the characteristics according to the invention, the following preferred embodiment is described by way of example only and without being limitative in any way with reference to the accompanying drawings, where: figure 1 shows a section of a part of a transmission unit according to the invention; figure 2 shows a view to a larger scale of the part indicated in figure 1 by F2; figures 3, 4 and 5 are sections according to lines III-III, IV-IV and V-V in figure 2. As shown in figures 1 and 2 the invention concerns a transmission unit 1 which mainly consists of a continuously variable transmission 2; a hydraulic cylinder/piston unit 3 to set the transmission ratio of the continuously variable transmission 2; a pressure compensation chamber 4 working in conjunction with the cylinder/piston unit 3; and a passage organ 5 having at least one passage way 6 connecting the pressure compensation chamber 4 with the piston chamber 7 of the above-mentioned cylinder/piston unit 3. As shown in figure 1, the continuously variable transmission 2 has an endless transmission element, such as a V-belt 8, which works in conjunction with at least one V-shaped pulley 9 of which at least one pulley half 10 can be moved. In the example shown the transmission 2 also has a fixed pulley half 11 forming one whole with a shaft 12. The axially moveable pulley half 10 forms one whole with a bush 13 which can be shifted over the shaft 12. To this end, the shaft 12 is provided with a ball track 14 at the height of the moveable pulley half 10. The bush 13 has an axial groove 15 on the inside which works in conjunction with the above-mentioned ball track 14 in such a manner that only a movement in the axial direction over the shaft 12 is possible. The walls of the pulley halves 10 and 11 pointing towards each other are cone-shaped, such that their V-shaped section corresponds with the V-shape of the belt 8. A spring 16 provides a certain bias with which the zero position of the belt 8 is determined. The cylinder/piston unit 3 and the pressure compensation chamber 4 are mainly composed of two cylinder-shaped parts 17 and 18. The first cylinder-shaped part 17 is fixed at one end 19 to the pulley half 10 and stretches parallel to the bush 13 so that, at the height of the end of this bush 13, it first bends slantwise and then perpendicular towards it, whereby a certain distance is kept between the second end 20 and the bush 13. The second cylinder-shaped part 18 is fixed to the shaft 12 at one end 21 outside the cylinder-shaped part 17. The wall of the part 18 stretches out perpendicular with regard to the shaft 12 and subsequently parallel to it and ends via the space between the cylinder-shaped part 17 and the bush 13 in the cylinder-shaped part 17. Here, the wall of the part 18 first forms a seating 22 for the spring 16 to subsequently run in the shape of a perpendicular wall 23 towards the inside of the first cylinder-shaped part 17. The second end 24 of the cylinder-shaped part 18 makes contact with the inside of the cylinder-shaped part 17 by means of a sealing ring 25. It is clear that the cylinder-shaped parts 17 and 18 work in conjunction with one another in such a way that a piston chamber 7 on the one hand and a pressure compensation chamber 4 on the other hand as mentioned above are formed. The hydraulic fluid can reach the piston chamber 7 via successively an axial bore hole 26, a radial bore hole 27 and a recess 28 in the shaft 12 and a passage 29 in the bush 13. The supply of fluid in the piston chamber 7 results in an increase of pressure therein, as a result of which the moveable pulley half 10 is pushed towards the axially fixed pulley half 11. As soon as the whole starts rotating around the shaft 12, there will be an increase of pressure in the piston chamber 7 due to centrifugal forces acting on the fluid. This increase of pressure can be compensated by letting fluid flow from the piston chamber 7 to the above-mentioned pressure compensation chamber 4, from where the excess fluid can flow out via an opening 30. To this end a filler port 31 has been provided in the wall 23 of the second cylinder-shaped part 18, which is better visible in figure 2. In this filler port 31, the above-mentioned passage organ 5 has been provided, with a passage way 6 for the correct dosing of the hydraulic fluid. The present invention is special in that, in order to achieve the aims mentioned in the introduction, the passage way 6 is situated at least partly on the outer surface of the passage organ 5, whereby this part determines the passage and in other words the flow characteristics of the passage organ. Preferably, the passage organ 5 mainly consists of a plug-shaped body 32 and a collar 33 whose diameter is considerably bigger than that of the body 32. The collar 33 fits in a seating 34. Preferably, the passage way 6 is built as shown in figures 2 to 5. Through the collar 33, an axial opening 35 has been provided whose side 36 which is closest to the axis 37 of the passage organ 5, is situated at a distance from the axis 37 which is equal to the radius of the plug-shaped body 32. On the underside of the collar 33 there is a concentric groove 38 whose smallest diameter is equal to the diameter of the plug-shaped body 32 and whose biggest diameter is at least smaller than the diameter of the collar 33. Together with the inside of the seating 34, the concentric groove 38 forms a duct in which the axial bore hole 35 ends, which in turn ends in a concentric room 39 formed by a bevel at the edge of the seating 34 and the filler port 31. A groove running around the entire circumference of the plug-shaped body 32 forms, together with the inside of the filler port 31, a second concentric room 40. The rooms 39 and 40 are connected by means of a first passage opening 41, whereas the room 40 is interconnected to the pressure compensation chamber 4 via a second passage opening 42. The passage openings 41 and 42 each stretch over half the length of the plug-shaped body 32 and are shifted 180 degrees with regard to one another. The bore hole 36, the groove 38, the room 39, the first passage opening 41, the room 40 and the second passage opening 42 together form the passage way 6. Hereby, it is essential that according to the invention, the passage openings 41 and 42 which determine the flow are situated at the outer surface or the outside of the passage organ 5, as a result of which they can be made in a relatively simple manner with very precise tolerances. The passage organ 5 preferably consists of a moulding, whereby the passage way 6, or at least the passage openings 41 and 42 are made through moulding. As shown in figure 2, a filter gauze 43 can be moulded in the collar 33 such that at least the opening 35 is entirely covered by the filter gauze 43.

Claims: Transmission unit consisting of a continuously variable transmission (1); a hydraulic cylinder/piston unit (3) having a piston chamber (7) to set the transmission ratio of the continuously variable transmission (2); a pressure compensation chamber (4) working in conjunction with the cylinder/piston unit (3); said pressure compensation chamber (4) and said piston chamber (7) being separated from each other by means of a wall (23); and a passage organ (5) having at least one passage way (6) connecting the pressure compensation chamber (4) with the piston chamber (7) and stretching at least partially along the outer surface of the passage organ (5); characterized in that the passage organ (5) consists of a plug-shaped body (32) which fits in a filler port (31) provided in said wall (23), the outer side of said passage way (6) being delimited by the inner wall of said port (31). Transmission unit according to claim 1, wherein the passage organ (5) is a mould in which the passage way (6) is provided through moulding. Transmission unit according to claim 1 or 2, wherein a filter gauze (43) is provided in the passage way (6). Transmission unit according to claim 3, wherein the filter gauze (43) is moulded in the passage organ (5). Transmission unit according to any of the preceding claims, wherein the plug-shaped body (32) is provided with a collar (33). Transmission unit according to claim 5, wherein the passage organ (5) with its collar (33) is provided in a seating (34) which in turn is provided in said filler port (31). Transmission unit according to claim 5 or 6, wherein the collar (33) has an axial opening (35) which is part of the passage way (6). Transmission unit according to claim 7, wherein said filter gauze (43) is applied in said opening (35). Transmission unit according to claim 7 or 8, wherein a concentric groove (38) is provided in the underside of the collar (33) working in conjunction with the inside of the seating (34) of the passage organ (5). Transmission unit according to claim 7, 8 or 9, wherein the passage way (6) has at least one passage opening (41,42) which is situated on the outside of the plug-shaped body (32). Transmission unit according to any of claims 5 to 10, wherein at the height of the transition between the collar (33) and the plug-shaped body (32) a room (39) in the form of a bevel is provided in the seating (34) of the passage organ (5), such that a passage is formed between the part of the passage way (6) in the collar (33) and the part in the plug-shaped body (32). Transmission unit according to any of claims 5 to 11, wherein the passage way (6) at the height of the plug-shaped body (32) mainly consists of a first passage opening (41) formed as an axial groove in the outer surface of the plug-shaped body (32) from the collar (33) to halfway the plug-shaped body (32), a second passage opening (42) rotated 180 degrees with regard to the first passage opening (41) formed also in as an axial groove running from halfway the plug-shaped body (32) to the end of it, and a concentric groove (40) around the circumference of the plug-shaped body (32) which connects both passage openings (41, 42).

Inventors: ADRIAENSSENS FRANK, ADRIAENSSENS, FRANK
Applicants: VCST NV, VCST, NAAMLOZE VENNOOTSCHAP
Application year: 1992
Main classification: F16H61
IPC codes: F16H61, F16H63