EP0931604A1 - Method and apparatus for manufacturing composite camshafts - Google Patents

Abstract

The probe (13) has a pressure fluid feed channel (14) connected to a fluid high pressure production unit. A sealing arrangement (24,25) for the hollow shaft (7) is provided on the section (21) of the cam (4) to be joined and in the area (19) of a bearing point. The sealing arrangement contains two sealing bodies (24,25) arranged axially spaced apart and around the probe. The sealing bodies limit the areas (19,21) of the hollow shaft to be widened, axially on both sides with support on the inside (27) of the hollow shaft. The sealing arrangement for the bearing point (20) contains a support tool, which in the usage position locates rigidly on the outside of the hollow shaft, leaving free the area of the hollow shaft to be widened, thereby covering the sealing bodies (24,25). Tools are provided for alignment, positioning and retention of the cam (4),

Description

The invention relates to a method for producing built Camshafts and a device for performing the same.

In the case of conventionally built camshafts, the dimensions may be different the outer diameter of the bearing shells does not fall below a certain level so that the rigidity of the Overall camshaft and the wear resistance of the bearings the camshaft is guaranteed. At the same time the tube outer diameter the bore diameter of the cam pushed onto the hollow shaft. Because the cam is one predefined defined extension in the transverse direction to the hollow shaft has to function the operation of the gas exchange valves the cam belt, i.e. the cam section, which forms the so-called base circle of the cam, um the thinner the larger the tube outer diameter of the hollow shaft. If the cam belt falls below a certain thickness, can achieving a durable joining of the cam on the hollow shaft a press fit between the hollow shaft and the cam can no longer be achieved because the cam does not have sufficient rigidity has more to absorb the joining tension. So is for the production of the camshaft an average pipe outside diameter to be observed, on the one hand the camshaft and the Bearing point has sufficient rigidity and the bearing point there is sufficient wear resistance and on the other hand the cam belt is still strong enough to hold up of the cam to ensure the joining tension. This is constructively feasible. However, this is motor Counter bearing for the bearing points of the camshaft, the bearing shells, for reasons of installation space in some engines due to the specific design of the engine arranged in one position in which the camshaft is spaced from it at its bearing point is. Bridging the spacing will be like EP 0 328 010 A1 can be seen, for example, in which in remaining the joining of the cams under high pressure done by a lance inserted into the hollow shaft, in all Usually by attaching bearing sleeves to the camshaft reached at the position of the bearing points. The bearing sleeves have however, to the disadvantage that it is an independent one Are component and therefore require a separate production. In addition, they are more complex and significantly increase costs Way to obtain a high quality Finishing the surface and turning it on the hollow shaft to attach. On the other hand, the bearing sleeves are sometimes only allowed be very thin (approx. 1mm), which makes it durable the hollow shaft is practically not given under load during engine operation is.

A built camshaft is known from DE 37 04 092 C1, at which a bearing from the hollow shaft by means of expanding High pressure forming is formed. Here, the hollow shaft together with the cams to be joined on it in a hollow receptacle an internal high-pressure forming tool consisting of at least two dies introduced and positioned there, what with closed tool and applying a fluidic Internal high pressure in the hollow shaft this is expanded and Place the cam with these is pressed. Be at the same time the bearing points according to the distance to be bridged Counter bearing expanded. The disadvantage here is the complex Device with a press that the total locking force for the hydroforming tool or for the projected area of the workpiece. Material also flows the hollow shaft when expanding due to internal high pressure in the area the inserted cams in the direction of the joints between Tool and cam, which accordingly on both sides of the End faces of the cam in the transition from the cam end face to the hollow shaft material jams pushing radially outwards in the Form the hollow shaft. This build-up is in the cam Tension peaks are generated, leading to increased wear the cam track. Also works in engine operation Load change is a dynamic moment of force in axial and radial Direction of the build-up, causing the cam to loosen leads on the wave. Overall, the known method or the device for producing a built camshaft due of the aforementioned problems, if any, only to a limited extent Suitable for use in vehicles.

The invention is based, a method and a task Show device for producing a built camshaft, by means of which the operational safety in a simple manner the camshaft in every engine operation is and the camshaft on due to the individual Motor design differently positioned counter bearing can be adjusted.

The task is according to the invention by the features of the claim 1 regarding the procedure and the features of claim 6 with respect to the device.

Thanks to the invention, the hollow shaft outer diameter of the undeformed Output shaft largely independent of the bearing diameter be selected, whereby with a suitable choice of the outer diameter the hollow shaft is so large that a sufficient bending stiffness for every engine operating situation the hollow shaft is guaranteed, and at the same time so small is dimensioned that the cam due to a sufficient cam belt thickness still has so much rigidity that it has the joining stresses with the joining high pressure application of the Hollow shaft on the one hand and on the other hand in engine operation take whatever load without suffering damage can. Due to the independence of the bearing diameter from the dimensions of the remaining hollow output shaft, which is due to a targeted widening of the bearing of the Hollow shaft by means of a lance-shaped introduced into the hollow shaft Probe generated internal high pressure adjustable as desired is, modern motors can be of almost any design can be equipped with a single type of camshaft. Only the bearing point has to be shaped differently be what is due to the variability of manufacturing by hydroforming however can be easily achieved. The camshaft is thus easy to the structural Constraints on the counter bearing almost arbitrary adaptable and dimensioned to be reliable without being dependent on education the depository more or less useful compromise solutions have to be accepted. By now achieved Possibility with different engines essentially Using the same camshafts will make them - over seen the previous variety of versions of shaft dimensions - largely simplified, what the apparatus outlay and significantly reduced costs. In terms of Use of bearing sleeves can be used on the separate component of the Bearing sleeve can be completely dispensed with, as it is quasi from the Hollow shaft is formed. This saves further costs and the effort to fix them on the hollow shaft in a rotationally fixed manner. Such an attachment is particularly difficult in that that the manufacture of separate components usually tolerances which will be taken into account later when joining have to. Here, after the final grinding process Cam and the bearings the already small wall thickness of the Bearing sleeve should be reduced so far that a reliable joining or fastening the bearing sleeve to the hollow shaft can be made possible. Furthermore, there is the inventive Training the depository does not pose a risk Detachment in engine operation. Because of the use of the lance-shaped Probe for the joining of the cam as well as for the training of the depository, with the targeted without total load the hollow shaft with internal high pressure formings or widenings the hollow shaft can be reached on a die with the associated immense expenditure on equipment become. There is only one clamping for the hollow shaft and support tools for the cams and the bearings. Due to the targeted use of internal high pressure can in contrast to using a die in immediate Connections to the cams which form Hollow shaft, which loosens the respective cam during engine operation have to be avoided, which is essential to operational safety the camshaft contributes to engine operation.

Fig. 1 eine erfindungsgemäße Vorrichtung zur Herstellung gebauter Nockenwellen in einer perspektivischen Ansicht,

Fig. 2 in einem seitlichen Längsschnitt eine Hohlwelle in ihrer Ausgangsform mit aufgeschobenem Nocken und eingeführter Sonde,

Fig. 3a in einem seitlichen Längsschnitt eine Lagerstelle der Hohlwelle aus Fig. 2 in Kalibrierform mit umgebenden Abstützwerkzeug,

Fig. 3b die Hohlwelle aus Fig. 3a in einem Schnitt entlang der Linie IIIb-IIIb,

Fig. 4a in einem seitlichen Längsschnitt eine Lagerstelle der Hohlwelle aus Fig. 2 in einer aufgeweiteten Form der Lagerstelle mit umgebenden Abstützwerkzeug,

Fig. 4b die Hohlwelle aus Fig. 4a in einem Schnitt entlang der Linie IVb-IVb,

Fig. 5 in einem seitlichen Längsschnitt eine Endform der erfindungsgemäß ausgebildeten Nockenwelle mit eingeführter Sonde.

Expedient embodiments of the invention can be found in the subclaims; otherwise the invention is explained in more detail below with reference to two exemplary embodiments shown in the drawings; shows:

1 shows a device according to the invention for producing built camshafts in a perspective view,

2 shows, in a lateral longitudinal section, a hollow shaft in its initial form with a cam pushed on and an inserted probe,

3a in a lateral longitudinal section a bearing point of the hollow shaft from FIG. 2 in calibration form with surrounding support tool,

3b, the hollow shaft from Fig. 3a in a section along the line IIIb-IIIb,

4a in a lateral longitudinal section a bearing point of the hollow shaft from FIG. 2 in an expanded form of the bearing point with surrounding support tool,

4b, the hollow shaft from FIG. 4a in a section along the line IVb-IVb,

Fig. 5 in a lateral longitudinal section an end shape of the camshaft designed according to the invention with an inserted probe.

In Fig. 1 is a device 1 for producing a built Camshaft 2 shown, which several arranged one behind the other Tools 3 for positioning and holding the cams 4 includes, which is pneumatically aligned in the tools 3 become. These tools 3 are located between one Hollow shaft feed 5 and a clamping tool 6, which Hollow shaft 7 at one end with a gripper 8 in a central Fixed position. The hollow shaft 7 is before the fixation through the feed 5 through the cam holes 9 in the Tools 3 held cams 4 threaded through. On hollow shaft facing away Page 10 of the clamping tool 6 is one with an insertion funnel 11 provided with an insertion funnel 11, by means of which a lance-shaped probe 13 (FIG. 2) can be inserted exactly centered into the clamped hollow shaft 7 is.

The probe 13 consists essentially of a metal rod which a central fluidic with a high-pressure fluid generating system connected pressure fluid guide channel 14. From Pressure fluid guide channel 14 branch axially spaced apart Cross channels 15 and 16, the outlet openings 17 and 18 own in the probe jacket 38. It is conceivable that in the area of Outlet openings 17 and 18 in the probe jacket 38 a circumferential Recess is incorporated, which is an annular pressure chamber open towards the hollow shaft 7. This will make one simultaneous and uniform high pressure application of the respective Widening of the hollow shaft 7 reached, whereby a Uniformity of the expanded point of the hollow shaft 7 achieved becomes. This is favorable for the necessary to be applied Stop of the cam 4 on the hollow shaft 7 due to a same press compound on all sides and for the concentricity of the hollow shaft 7 in the bearing shells arranged on the engine during engine operation. The outlet openings 17 and 18 are in the insertion position of probe 13, of course, to be expanded by high-pressure fluid Area 19 of the bearing 20 of the hollow shaft 7 and on the section 21 of the hollow shaft 7 between the two transverse to their Longitudinal end faces 22,23 of the respective Cam 4 placed.

The expansion area 19 and the section 21 are each by the sealing arrangement for pairs of sealing bodies forming the hollow shaft in the form of two axially spaced ring seals 24, 25 axially bounded on both sides by the probe 13 and for their mounting in the probe jacket 38 each two circumferential Recording grooves 26 are formed. The ring seals 24, 25 are supported radially on the inside 27 of the hollow shaft 7 sealing off. In addition to the sealing body pairs, the Sealing arrangement for the bearing point 20, a support tool 28 (Fig. 3a, b) or 29 (Fig. 4a, b), the outside in the use position the hollow shaft 7 revolving with the release of the to be expanded Area 19 of the hollow shaft 7 rests rigidly and the ring seals 24.25 covers. The support tool 28 and 29 consists of three jaw-like segments 39, 40, 41, the division joints 42 in contact with the hollow shaft 7 offset by approximately 120 ° to one another are arranged.

To manufacture the assembled camshafts 2, the probe 13 inserted into the hollow shaft 7, the probe 13 with the Outlet openings 17, 18 of the transverse channels 15, 16 of the pressure fluid guide channel 14 exactly to the respective expansion area 19 and the section 21 are axially aligned. The hollow shaft 7 can, as already described, through the cam bores 9 the cam 4 are threaded through. Alternatively, however equally the cams 4 on a firmly clamped hollow shaft 7 pushed on and positioned there in the intended relative position become. The cams 4 are now representative of the game characterized by the gap 30 in Fig. 2 - on the Hollow shaft 7 positioned. Then the support tools 28 or 29 move radially to the hollow shaft 7 until it on it issue. The applied to the hollow shaft 7 directly to the Widening area 19 of the hollow shaft 7 adjoining sections 31 of the support tool 28 and 29 are the one to be expanded Bearing 20 spanning section 32 of the tool 28 and 29 are connected to each other. Section 32 jumps compared to the contact surfaces 33 of the tool 28 or 29 so far back that he has an annular with the bearing 20 Includes expansion space 34 (Fig. 4a, b). The depository 20 facing surface 35 of the spanning section 32 of the Tool 28 can be die-engraved for the expansion Bearing 20 be formed and is then to the best possible flow of material during expansion ensure highly polished (Fig. 3a, b). Eventually, over the pressure fluid guide channel 14 and the transverse channels 15 and 16 of the Probe 13 brought a tensioned pressure fluid on the hollow shaft 7, which is due to the high internal pressure in the area 19 and the section 21 expands radially outward, after which on the one hand the press fit between cam 4 and hollow shaft and on the other hand, the distance between the hollow shaft 7 and the counter bearing of the motor bridging bulge 36 of the bearing 20 results. The support tool 28 or 29 is in the position of use rigid, i.e. immovable, arranged and covered in such a way the ring seals 24, 25 that a lifting of the abutting them Hollow shaft material under the high pressure fluid of the ring seals 24, 25 is avoided, what else Loss would result in their sealing effect. Due to the Narrowing of the expansion area to section 21 between the end faces 22, 23 of the respective cam 4 by means of the targeted Placement of the ring seals 24, 25 are for one secure hold of the cam 4 on the hollow shaft 7 damaging material build-up the hollow shaft 7 prevented on both sides of the cam 4. Due to the sealing effect, the sections of the Hollow shaft 7 between the bearing points 20 and the sections 21 the cam 4 is depressurized and thus undeformed.

The expansion of section 21 and area 19 of the depository 20 can be done simultaneously, but by the in contrast, faster contact of the cam 4 with the hollow shaft 7 to achieve the desired final shape of the bearing 20 on the cams 4 due to the larger expansion axial tensile stresses act, resulting in a reduction in transferable Torques can lead to the cam 4 in engine operation. This can in turn be reduced by the fact that due to the Support by the tool 28 or 29, the hollow shaft 7 such is pinched that the hollow shaft material to expand the Bearing 20 not free from the length of the hollow shaft 7 but is obtained only from the area 19, so that the wall thickness the bearing 20 in its final form compared to its original form is reduced. The reduced wall thickness of the bearing 20 is their wear resistance and rigidity detrimental. A free flow of the hollow shaft material also acts from the length of the hollow shaft 7 negative to the Positioning of the cams 4 on the hollow shaft 7, since the Hollow shaft 7 is shortened after the forming, so that repositioning the cam 4 is necessary or a complex Stockpiling of material is required, resulting in a larger one Output hollow wavelength leads. The latter also works with one complex prepositioning that deviates from the end position the cam 4 hand in hand.

Alternatively, the formation of the bearing point can be provided in a favorable manner 20 and the joining process of the cam 4 on the hollow shaft 7 done sequentially, the bearing 20 being formed first becomes. For this purpose, a pressure relief valve is in the transverse channel 15 to the cam 4 37 arranged, which blocks the transverse channel 15, if the bearing 20 is subjected to high internal pressure. The respective cam 4 is placed on the hollow shaft 7 in a provisional Joint position pushed or takes when threading the hollow shaft 7 in the cams 4 a provisional joining position on. Now the bearing 20 is as desired according to FIG. 4a, b in a simple manner in the form of a bulge 36 by about 1-2 mm expanded. Accordingly, the counter bearing must be formed dome-shaped on the engine, which in turn some Effort means.

When the surface 35 facing the bearing 20 is formed the tool section 32 in the manner of a die engraving can Bearing 20, however, when expanding after the hollow shaft material has been applied assume a cylindrical shape on the engraving, which simplifies the formation of the counter bearing of the engine will (Fig. 3a, b). The section reproduced from a die engraving 32 can also be one of the support tool (28) separate tool shape can be formed. To be precise To achieve contouring of the bearing point 20, the bearing point 20 with a comparatively substantial for expansion printing higher pressure can be calibrated. After the formation of the bearings 20, which are freely formed from the length of the hollow shaft 7 and thus largely the same wall thickness in the final shape have as in the initial form of the hollow shaft 7, the Shortening of the hollow shaft 7 occurring during the forming Compliance with the distances of the bearing points 20 from each other Provision of material by using a longer hollow shaft 7 or by gradually expanding the individual storage locations 20 can be countered, the cams 4 between the Bearing positions 20 positioned in their final joining position. Then the cross channel 15 is released and section 21 of the Hollow shaft 7 in a second forming process with one opposite the expansion pressure described above for the bearing 20, in particular the internal pressure, which is much lower than the calibration pressure acted upon, with the expansion of the Hollow shaft 7 of the cams 4 to form a press fit it is added. The shortening of the hollow shaft 7 in this Second forming is of no importance since the hollow shaft 7 only widens there by about 0.2 mm. Using of the support tool 29, it is useful for a further expansion to avoid during the joining process, in the transverse channel 16 also to provide a pressure relief valve that this locks when joining. After the forming operations the hollow shaft 7 becomes the desired camshaft 2, as from Fig. 5 can be seen. The pressure fluid is released, the Support tools 28 and 29 removed and the probe 13 from the Camshaft 2 pulled out. Then the clamping is released and removed the finished camshaft 2 for further installation.

Claims (10)

Method for producing built camshafts (2), wherein on a hollow shaft (7) at least one cam (4) on the Hollow shaft (7) is pushed, after which the hollow shaft (7) between the two transverse to the longitudinal extension of the hollow shaft (7) End faces (22, 23) of the cam (4) and on the respective Bearing (20) by means of a high-pressure fluid, that of a lance-shaped introduced into the hollow shaft (7) Probe (13) is promoted, expanded so that on the one hand a press compound of cams (4) and hollow shaft (7) and on the other a the distance between the hollow shaft (7) and counter bearing bridging bulge (36) of the bearing (20) of the Hollow shaft (7) is formed, the hollow shaft (7) between the expanded areas (20,21) by a sealing arrangement (28; 29 and 24.25) on the probe (13) opposite the expanding one High pressure is sealed. Method according to claim 1,
characterized,
that the respective cam (4) is positioned in the desired relative position of the hollow shaft (7) corresponding to its end position and that thereafter the joint (21) of the hollow shaft (7) with the respective cam (4) between its end faces (22, 23) and the respective bearing point (20) of the hollow shaft (7) is simultaneously subjected to high internal pressure via the probe (13), the hollow shaft (7) at the location of the sealing arrangement (28; 29 and 24, 25) of the probe (13) from the outside in this manner is supported against the internal high pressure that the expansion of the bearing (20) by the internal high pressure takes place exclusively by reducing the wall thickness in the region of the hollow shaft section (19, 21) to be expanded. Method according to claim 1,
characterized,
that the respective cam (4) is pushed onto the hollow shaft (7) in a provisional mounting position, that the bearing point (20) of the hollow shaft (7) is then widened and that the cams (20) of the cams () 4) is positioned in its final joining position and is then added to the hollow shaft (7) there by applying high pressure to the hollow shaft (7). Method according to one of claims 1 to 3,
characterized,
that the sections (20, 21) of the hollow shaft (7) to be expanded are acted upon by fluid pressures of different heights, the bearing point (20) being pressurized with higher pressure than the joint (21) of the cam (4). Method according to one of claims 1 to 3,
characterized,
that the expanded bearing points (20) are finally subjected to a calibration pressure that is substantially higher than the expansion pressure, the respective bearing point (20) being contoured by pressing against a tool mold surrounding it. Device for producing a hollow shaft (7) and at least one camshaft (4) built camshaft (2) with one in the hollow shaft located in an end clamping (7) insertable lance-shaped probe (13), which a fluidly connected to a high-pressure fluid generating system Compressed fluid guide channel (14), the outlet openings (17,18) in the area to be expanded by high-pressure fluid (19) a bearing (20) of the hollow shaft (7) and on the section (21) of the hollow shaft (7) between the two of the Longitudinal end faces (22,23) of the respective Has cam (4), each with a sealing arrangement (28; 29 and 24.25) for the hollow shaft (7) on the section (21) of the cam (4) to be joined and in the area (19) of the bearing point (20), wherein the sealing arrangements (28,29 and 24,25) two sealing bodies (24,25) included, arranged on the probe (13) all around and are axially spaced from each other and die die Areas (19, 21) of the hollow shaft (7) to be expanded axially on both sides with support on the inside (27) of the hollow shaft (7) limit sealing, and wherein the sealing arrangement (28; 29 and 24, 25) includes a support tool (28, 29) for the bearing point (20), the circumferential in the use position on the outside of the hollow shaft (7) with the release of the area to be expanded (19) Hollow shaft (7) rests rigidly and the respective sealing body (24, 25) covers, and with tools (3) for alignment, Positioning and holding the cam (4). Apparatus according to claim 6,
characterized,
that the sections (31) of the supporting tool (28; 29) abutting the hollow shaft (7) are connected to one another by a section (32) spanning the bearing point (20) to be widened, this with the bearing point (20) forming an annular widening space (34 ) includes. Device according to claim 7,
characterized,
that the bearing point (20) facing surface (35) of the spanning section (32) of the support tool (28) is designed in the manner of a die engraving for the bearing point (20) to be expanded. Device according to claim 8,
characterized,
that the shaping surface (35) is polished. Apparatus according to claim 6,
characterized,
that a transverse channel (15, 16) connecting it to the respective outlet opening (17, 18) branches off from the pressure fluid guide channel (14) of the probe (13), the transverse channel (15) leading to the expansion section (21) of the hollow shaft (7) leads on the cam (4), a pressure relief valve (37) is arranged.

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