The invention pertains to a stator for a hydrodynamic torque converter according to the introductory clause of Claim 1.
A stator for a hydrodynamic torque converter is known from DE 195 33 151 A1, which is located between a pump wheel and a turbine wheel and has stator elements in the form of a stator hub with stator vanes mounted thereon. The vanes are connected to each other in the radially outward area by a stator rim. The vanes have the effect of feeding the fluid arriving at the turbine wheel to the pump wheel at the desired angle.
A stator of this type can be produced in various ways. For cost reasons, an injection-molding process is preferred in which the molds are drawn in the axial direction. The molds have cavities, into which material is introduced during the injection-molding process. After this material has cooled, the molds are pulled apart in the axial direction to release the stator. Aluminum is the material which is usually used for an injection molding process of this type. Because of its low viscosity in the heated state, however, the material can escape through the contact zone between the molds, which results in undesirable fins on the vanes. To remove these fins, a chisel is pushed in the axial direction between the flow outlet of a first vane and the flow inlet of the second vane. While the fins are being cut away, forces act on the inserted chisel and threaten to fracture it, since the blade of the chisel is very narrow in the circumferential direction. As a result, the blade of a chisel of this type usually has a minimum width of about 4 mm. As a result of this, however, a corresponding offset equivalent to the width of the chisel is created between the flow outlet of the one vane and the flow inlet of the other vane in the circumferential direction. This has the effect of reducing the length of the vane which is available to guide the flow, which leads in turn in lower efficiency and to an inferior characteristic. As a result, the transmission ratio of the converter is reduced.
Because of these disadvantages, stators are often made of a thermoset plastic. According to this approach, a thermoset powder is introduced into a compression mold and consolidated into a stator under the effects of temperature and pressure. Although the stator has a smooth surface, the necessary admixture of glass fibers or carbon fibers means that it cannot be cut by machine, because this would cause cracks to form. The contact between these cracked surfaces and another material such as steel has the effect of roughening the surface of this other material, and this results in considerable wear.
These types of thermoset plastic stators are preferably drawn in the radial direction. Although it is possible in this way to obtain vanes with the optimal shape, the production method is very expensive, because, after the thermoset powder has been “baked”, the molds, the number of which is equivalent to the number of vanes, must be pulled away in the radially outward direction.
The invention is based on the task of designing a stator in such a way that it can be produced at low cost and will not fracture, whereas it can also offer good efficiency and a good characteristic at the same time.
This task is accomplished according to the invention by the features given in the characterizing clause of Claim 1.
Through the use of a blank for the various groups of stator elements, i.e., the stator hub segments, the stator vanes, and the stator rim segments, the particular advantage is obtained that a considerable amount of design freedom is obtained for each group of stator elements. Thus each group of stator elements can be shaped in the best possible way to achieve optimal operating results. Of essential importance here is the design of the vane group of stator elements, because these affect the efficiency and the characteristic of the hydrodynamic torque converter. By properly laying out the geometry of the areas on the blank which will later form the vanes, it is easy to create the basis for a system of stator vanes in which the individual vanes overlap each other to the maximum possible extent, which promotes efficiency. In the case of the group of hub segment elements and the group of rim segment elements, however, the dimensionally stable support which they give to the vanes and their ability to keep the vanes properly oriented in the desired planes is probably the more important aspect, which means that the hub segments and the rim segments must offer sufficient strength after all the elements have been connected together to form a unit.
The individual groups of stator elements can be freed from each other in the blank by a separation process. The phrase “freed from each other” has been chosen to emphasize that the intention is not to separate the individual stator element groups completely from each other but rather to separate them only just enough so that these groups, which remain connected to each other at predetermined points, can be moved by a deformation process such as plastic metal working out of the original plane of the blank into new planes of extension deviating from the original plane, so that ultimately the desired 3-dimensional stator can be formed out of the original 2-dimensional blank. The deformation processes are not limited to changes in the relative positions of the stator element groups with respect to each other but can also include the plastic deformation of the individual components of each group of stator elements. This type of plastic deformation appears to be especially important for the formation of the vanes in particular, because a considerable effect can be exerted on the operating behavior and efficiency of the hydrodynamic torque converter by manipulating the profile of the vanes. It is also true that the other groups of stator elements can be subjected advantageously to plastic deformation in order to orient them, for example, along lines of curvature, so that both the hub segments and the rim segments extend around the center axis of the stator. It is easy to see here that the lines of curvature of the hub segments will differ from those of the rim segments because the distances which separate the two groups from the previously mentioned center axis are different.
By attaching the individual segments of the stator hub to each other, which can be done, for example, by welding, brazing, or bonding them together with an adhesive at their abutting ends, a segmented stator hub is obtained which can be set onto a base body hub, which acts as a carrier. The two components together, i.e., the segmented hub and the base body hub, are thus ultimately able to form the complete stator hub.
It is possible to dimension the original blank in such a way that, after the individual hub segments have been lined up in the circumferential direction and connected to each other, a single segmented stator hub is obtained, which can be drawn onto the base body hub and then completed simply by connecting the two abutting ends, which are now facing each other. But it is also equally possible to provide shorter blanks and to produce two or more segmented hub sections. These shorter sections are then connected to each other after they have been fastened to the base body hub. A segmented hub formed in this way must, of course, will be fastened to the base body hub in such a way that no relative movement is possible between the segmented hub and the base body hub in either the axial direction or the circumferential direction. To reduce the number of connecting points, it can be preferable to provide a retaining device between the segmented hub and the base body hub. This retaining device acts in the circumferential direction and/or in the axial direction and fastens the segmented hub to the base body hub so that the two parts cannot move relative each other. To form the retaining device, a profiled channel, for example, can be machined into the base body hub. The segmented hub is given a mating shape, which can fit into the channel. The positive connection between the base body hub and the segmented hub prevents any movement between these two components in the circumferential and/or axial direction. A permanent connection can also be provided for safety reasons between the the base body hub and the segmented hub in the form of individual spot welds, although the two components can also be brazed together or bonded together with an adhesive, which can also be done in a spotwise manner.
In contrast to the hub segments, which must be attached to each other at their abutting ends, the rim segments can be joined together without any additional connecting measures in that, on the blank, a shroud is provided, at which the blank is not interrupted by separation processes, in contrast to the other groups of stator elements. During the deformation processes which are to be performed, therefore, the stator rim segments can, together with the shroud, obtain the curvature which is required for the rim to surround the center axis.
Ideally, the blanks consist of a metallic material which ensures that the finished stator has the necessary stability and which at the same time offers good ductility so that the necessary deformation process, preferably a cold working process such as deep-drawing or die forming, can be successfully performed. As a result, by the use of appropriately shaped tool carriers, it is possible not only to orient the individual groups of elements properly with respect to each other without material problems but also to carry out the plastic deformations which are also required for the individual stator element groups such as adjusting the curvature of the vanes.
Additional special design features of the individual groups of stator elements are described in the claims. By interaction with each other, these features improve the stability of the stator and increase its efficiency even more.
The invention is illustrated in the attached drawing and is explained in greater detail below:
a shows a special design of the radially outside surface of the base body hub;
b shows a cross-sectional view along line VIIIb-VIIIb of
The pump shell 1 shown in
The previously mentioned pump shell 1 is attached in its radially inner area to a pump hub 6, which extends toward the power takeoff. Axially between the pump wheel 2 and the turbine wheel 3 there is a stator 7, which is mounted by way of a first axial bearing 8 between the turbine hub 4 and a freewheel 9 and by way of a second axial bearing 10 between the freewheel 9 and the pump hub 6. The two axial bearings 8 and 10 are each provided with grooves 11, 12 for the hydraulic fluid with which the converter circuit is supplied, especially via the grooves 11 in the axial bearing 8.
The axial bearing 8 is formed as a single piece with a stator hub 15, illustrated only schematically, on the circumferential area of which vanes 17 are provided. The radially outer ends of these vanes are connected to each other by a rim 19. The freewheel 9, on which the stator 7 is mounted, has an outer freewheel ring 23, which is guided by clamping bodies 25 on an inner freewheel ring 27, which is connected nonrotatably by a set of teeth 29 to a power takeoff element (not shown). Fluid for supplying the converter circuit via the groove 11 can be guided radially between this power takeoff element and the power takeoff shaft connected nonrotatably to the turbine hub 4.
As shown in
The blank 32 has stator hub segments 36 on the side designated by the letter U in
Each hub segment 36 of the stator has a first bending line 74, which forms the boundary between it and a vane 17, which for its own part has a second bending line 76, which forms the boundary between it and a stator rim segment 38, where all of the rim segments 38 of the blank 32 are formed as integral parts of a common shroud 39, which extends along the side of the blank 32 marked with the symbol 0 in
After the blank 32 has been laid in a workpiece carrier designed in the usual way (and therefore not shown) with a flat receiving area for the blank 32, the blank is subjected to separating operations by means of a stamping tool, also of the conventional type, by means of which the individual segments 33 of the blank are freed from each other and unneeded or even interfering areas of the blank are completely removed. The areas which are removed from the blank include both the cutouts 53 in the area of the hub segments 36 on side U of the blank 32 and also the compensating cutouts 70 between the hub segments 36 and the adjacent vanes 17. For the sake of clarity, the lines along which one of the blank segments 33 is cut during the process of separating it from the two adjacent blank segments 33 are emphasized in
The blank 32 is now transferred to a different workpiece carrier 90, the basic design of which can be derived from
The results of these deformation operations is illustrated in
During the course of the previously mentioned deformation operations, the hub segments 36 as well as the rim segments 38 opposite the vanes 17 are bent in such a way around the bending lines 74, 76 shown in
Because of the new orientation produced during the course of the deformation operations, the hub segments 36 arrive in positions relative to each other in which, as
To return to
Formed in this way, the hub segments 36 can be connected to each other by welding or possibly by brazing or adhesive bonding at the contact points located between the engaging projections 72 and the compensating openings 70 and at the circumferential ends of the adjacent circumferential trailing lips 66, so that the previously mentioned segmented stator hub 58 is obtained. Because the rim segments 38 are connected to each other in any case by the shroud 39 and cooperate with the segmented stator hub 58 to hold the vanes 17 in their predetermined, defined positions, the vane area 96 of the stator 7 is thus also obtained in finished form. If the original blank 32 was dimensioned in such a way that the vane area 96 completely encloses the outer circumference 100 of a base body hub 60, shown schematically in
Even better conditions with respect to fabrication are obtained when the vane area 96 extends not over an angle of 360° but rather over only a portion thereof, such as for example over an angle of 120°. The individual vane areas 96 are thus easier to fabricate and can then be connected to each other when the segmented hub is attached to the base body hub 60, for which purpose, in the previously described manner, both the abutting ends 65, 67 of the individual sections of the segmented stator hub 58 and also the abutting ends 62, 64 of the individual sections of the stator rim 19 are connected to each other by welds 99 (or by brazing or adhesive bonding) and also by welds 98 (or by brazing or adhesive bonding) to the base body hub 60.
a shows a view of the base body hub 60 radially from the outside, without the mounted vane area 96. In contrast to the design according to
1 pump shell
2 pump wheel
3 turbine wheel
4 turbine hub
5 set of teeth
6 pump hub
7 stator
8 first axial bearing
9 freewheel
10 second axial bearing
11, 12 groove
15 stator hub
17 stator vanes
19 stator rim
23 outer ring of the freewheel
25 clamping body
27 inner ring of the freewheel
29 set of teeth
30 stator elements
32 blank
33 segments of the blank
34 groups of stator elements
36 stator hub segments
38 stator rim segments
39 shroud
40 original plane of the blank
42, 44, 46 new plane of extension
48 center axis
50, 52 lines of curvature
53 openings
54, 56 abutting ends of the stator hub segments
58 segmented stator hub
60 base body hub
61 retaining device
62, 64 abutting ends of the stator rim
65, 67 abutting ends of the segmented stator hub
66 circumferential trailing lip
68 receiving area
70 compensating opening
72 engaging projection
74 first bending line
76 second bending line
78 separation line
79 support
80 overlap area
81 flow inlet
82 flow inlet edge
83 flow outlet
84 flow outlet edge
86, 88 metal-forming tools
90 workpiece carrier
92 receiving bed
94 ram
96 vane area
98, 99 spot welds
100 outside circumference
102 profiled groove
104 axial edges
106 converter circuit
108, 110 closed edges of the segmented hub
112, 114 circumferential ends
Number | Date | Country | Kind |
---|---|---|---|
102 59 412.0 | Dec 2002 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP03/14104 | 12/12/2003 | WO | 3/17/2005 |