EP0839990B1 - Assembled camshaft - Google Patents

Abstract

The camshaft has a shaft body (12) on which separately produced cams (3) are fixed. The body is produced by casting or forging. All its functional parts, such as chain wheel accommodation (16), axial bearing (17) with shoulder (18) and position indicator (19) are of one-piece construction. The shaft body is externally (22) and-or internally profiled. It comprises metallic or non-metallic material, particularly iron-carbon material, alloyed or non-alloyed iron, lamella or ball graphite iron or steel casting, injection moulding or similar material usable in the interior space of an internal combustion engine.

Description

The invention relates to a built camshaft, in particular for internal combustion engines, with a shaft body, on which separately manufactured cams are fixed are. Built camshafts, for example with a steel tube as the shaft body, can have various attached or attached parts, namely cams, sprocket mount, Thrust bearings, thrust bearing shoulder, signal transmitter, sprocket or the like.

A camshaft is said to be "built" if the shaft body and the Cams manufactured in a separate manner and the essentially finished Cams on the shaft body, e.g. by being attached. Such built Camshafts and their assembly are described in DE 41 21 951 C1 and in DE 195 20 306 A1.

In the prior art, there are also manufactured in one piece, that is, with molded cams Camshafts, e.g. are cast from iron. Be camshafts traditionally for this very reason, i.e. with the cams, cast because the one-piece molding of the cams during casting is a very economical method of manufacture is. For example, cast iron can also be used when the camshaft to be cast entirely from a single part (i.e. with the cams); it reference is made to US-A-52 998 81. There it is stated, among other things, that the one-piece cast with the cam shaft body by a multi-part Steel shaft body must be replaced to save costs.

The one-piece camshafts can also be produced as hollow bodies; in this connection reference is made to GB-PS 15 96 442, GB-PS 11 91 202, JP-A-619 959, EP 0 154 787 B1 and EP 0 272 471 B1. Cast camshafts are usually made so that they the cams and other functional parts embrace in one piece when pouring.

In modern internal combustion engines, for the camshafts described here are preferably provided, are not straight with the help of the cams, as before Tappet, but lever operated with attached small rollers. The roles start the cam. Cams are used, not only can be machined very precisely (accuracy on the order of micrometers), but also at least one because of the kinematics of the lever linkage require concave area in circumference. Under a "concave" area is in In this sense, a circumferential cam section with over two geometric turning points decreasing and increasing radius of the cam. The lever roller runs through the concave peripheral section like a car wheel a bump. Of course, the concave circumferential area should also be exact how the other parts of the cam circumference are machined. The inventor recognized that these accuracy regulations only with economically justifiable means for individually manufactured cams, e.g. can be achieved by sintering. If lever linkage to be operated by the cams, practically only come built Camshafts in question.

In the prior art cited in DE 23 262 41 A, castings are cast with cams Waves revealed. To the camshaft "in the material optimally to the specific Adapt operating conditions "and still be able to manufacture economically, is the known camshaft from a solid or hollow profile or Round shaft exist to be pushed onto the separately manufactured control elements are. The well-known profile shaft itself is to be made of steel.

DE 25 46 802 A quotes a built camshaft whose (separately manufactured) Components (shaft body and cams) consist of solid material. Doing so considered it disadvantageous "that the same material expenditure as with a cast Camshaft is required ". It follows that the shaft body is straight should not be poured.

Means for setting separately manufactured cams on non-cast iron existing shaft bodies are described in DE 195 00 621 A1, US-A-47 83 898, DE 352 10 06 A and DE 33 01 749 A.

In practice, camshafts of internal combustion engines are already based on vibration technology Aspects balanced by shaping the shaft, so that if possible optimal running smoothness at all possible speeds is present. Such balancing comes from one, for example starting from of a steel tube, camshaft built is not really out of the question since one Steel pipe with economically and safety-related means as well as with that cannot balance the required micrometer accuracy. So optimal Balanced camshafts are only available in cast iron stores. With these However, camshafts (see above) cannot be used with the cam itself the accuracy required by modern technology.

The invention has for its object an alternatively produced shaft body to be specified for a camshaft.

The solution according to the invention exists for the built-in camshaft with a shaft body on which separately manufactured cams can be fixed in that a manufactured by casting Shaft body is provided.

Accordingly, the invention provides a cast camshaft for receiving a large number of cam parts for producing a composite or built camshaft. This camshaft is said to be according to another invention with the exception of the actual cams, if possible, all of their other functional parts, such as sprocket mount, thrust bearing and position encoder, due to manufacturing or in one piece as a fixed part of the cast body. On the shaft body So in addition to the actual cams, the other functional parts of the Shaft production can be molded in one piece.

The fact that according to the invention including the other functional parts mentioned one-piece "cast" shaft body is used, the conventional (based on a steel tube) built camshafts required Special work to apply or fix the other functional parts mentioned, like sprocket mount, thrust bearing and position transmitter, surprisingly essentially saved. This is because these parts require molding of the shaft body only postprocessing with less accuracy than the cams.

The inventive combination of the manufacturing steps of conventionally built Camshafts and conventionally cast camshafts bring that unexpected technical and economic advantage that the highly precise to be machined Cams can be manufactured separately and those that are less precise to process remaining functional parts together with the shaft body are producible. It can be as precise as a built one Camshaft with about the little effort of a total produce cast camshaft.

A decisive advantage of the invention is that the cast shaft body already in its manufacture in optimally balanced in terms of vibration technology is to be shaped. According to another invention, namely the shaft is beneficial in manufacturing profiled according to the predetermined balancing rules become.

Both massive and hollow come within the scope of the invention Shaft body in question. The shaft body of camshafts can e.g. according to EP 0 272 471 B1 mentioned at the beginning using glass bodies with a through hole, with Pour blind holes and / or internal cavity. It's in the frame the invention, when casting the respective cavity already a profile specified on the inside of the shaft to generate immediately so that the shaft essentially the predetermined in this first production step vibrationally balanced accordingly is manufactured. In addition to or instead of this inner profile comes according to yet another invention, an outer profile - In particular also according to the intended Balancing - in question.

In the context of the present invention, the shaft body can be made of metallic or non-metallic material, in particular from Iron-carbon material, from alloyed or unalloyed iron, made of lamellar or spheroidal graphite iron or cast steel and from injection molding and the like in the engine compartment of internal combustion engines usable materials. The invention relates in the narrower sense only on the one piece with the additional functional parts required for the cams - but without precisely reworked cams - manufactured and if necessary balanced shaft body. The individually produced The cams themselves can be made according to known joining processes (see DE 41 21 951 C1 and DE 195 20 306 A1 mentioned above) after essentially complete preprocessing on the shaft body be fixed.

Fig. 1

eine herkömmlich gebaute Nockenwelle, teilweise im Schnitt;

Fig. 2

eine erfindungsgemäß gebaute Nockenwelle mit gegossenem Wellenkörper;

Fig. 3

das gegossene Rohteil des Wellenkörpers nach Fig. 2; und

Fig. 4

einen Querschnitt durch eine einzelne Nocke.

Details of the invention are explained on the basis of the schematic representation of exemplary embodiments. Show it:

Fig. 1

a conventionally built camshaft, partly in section;

Fig. 2

a camshaft built according to the invention with a cast shaft body;

Fig. 3

the cast blank of the shaft body according to Fig. 2; and

Fig. 4

a cross section through a single cam.

Fig. 1 shows a built camshaft 1 with a shaft body 2, on which separately manufactured cams 3 are fixed. To the Fixing the individual cam 3 can in a collar 4 of the shaft body 2 used, corrugated clamping sleeves 5 serve. On the shaft body 2, which according to FIG. 1 preferably consists of a Steel pipe is required to complete the Camshaft 1 usually a hub or sprocket holder 6, an axial bearing 7 with a shoulder 8 and usually also an asymmetrical one Position transmitter 9 (for the first cylinder dead center detection) be fixed. The receptacle 6 and / or the shoulder 8 can also be designed as a sprocket. The parts 6 to 9 are required to complete a conventionally built 1 can be produced separately.

2 and 3 in total designated 11 according to the invention Camshaft with shaft body 12 made of cast iron sees externally essentially the same as the completely built one 1. In particular, the cams 3 can be applied practically the same way with collar 4 and adapter sleeve 5 as in Fig. 1. There is a significant difference in that the receptacle 16, the thrust bearing 17, the shoulder 18 and the (asymmetrical) signal transmitter 19 already in one piece on the shaft body 11 during the production of the raw body 20 3 arise. Of course, the cast one Raw body 20 before further processing, especially before Applying the cams 3 to be processed on its surface; for example, an outer layer 21 can be removed, so that the contour according to Fig. 2 is formed. When removing the Outer layer 21 can also the bundles 4 on the for the cams 3 intended positions can be generated.

There is a significant advantage of the camshaft according to the invention in that the shaft body 12 already in its shape as a green body 20 (Fig. 3) by casting in the after vibration engineering Viewpoint optimally balanced manufactured can be. With this in mind, even when pouring on the Surface of the green body 20 indentations 22 at certain Make the surface be provided. For example the shaft body 12 in the area between two cams 3, where no bearings 23 are required, an oval, rectangular or similar non-circular cross-section, to achieve the desired balance. The deformation for the purpose of balancing should be done so that the cams 3 is not hindered; Bulges of the outer surface are therefore usually not permitted.

According to the profiling described by the outer surface of the shaft body also reached balancing or additionally by profiling a hollow cast (or otherwise hollow) camshaft can be achieved. If, for example, within the cast Shaft body 12 or the body 20 a sack-shaped cavity 24 according to Fig. 2 or 3, e.g. by inserting a quartz core, is formed - with the appropriate shape of the core - profiling already when casting on the inner surface manufactured with bulges 25 or indentations 26 that the shaft according to predetermined, e.g. calculated, Rules is already balanced as a raw body.

Fig. 4 shows an example of the cross section of an inventive on the shaft body 12 to be attached cam 3 which a point of their tread, ie their circumference 27, one has concave region 28 with two turning points 29. By the way can the inner surface 30 of the cam 3 with a wave profile fitted to the shaft profile of the clamping sleeve 5 (Fig. 1 and 2) become.

It becomes a built-up camshaft with a shaft body the separately manufactured cams are fixed, described. To achieve that the individual cams with the greatest accuracy and also with concave peripheral areas or treads are to be produced and at the same time the shaft body in one optimally balance vibrational aspects is one by pouring manufactured shaft body provided. On the shaft body apart from the cams, all of its functional parts, like Sprocket mount, axial bearing and position encoder, due to manufacturing reasons be molded in one piece.

Reference list

1 = camshaft (Fig. 1)

2 = shaft body (Fig. 1)

3 = cam

4 = federal government

5 = adapter sleeve

6 = sprocket mount

7 = thrust bearing

8 = shoulder (7)

9 = signal generator

11 = camshaft (Fig. 2 and 3)

12 = shaft body (Fig. 2 and 3)

16 = sprocket holder (Fig. 2)

17 = thrust bearing (Fig. 2)

18 = shoulder of 17 (Fig. 2)

19 = signal generator

20 = raw body

21 = outer layer (20)

22 = indentation

23 = warehouse

24 = cavity

25 = bulge (24)

26 = indentation (24)

27 = scope (3)

28 = concave area (27)

29 = turning point (28)

30 = inner surface (3)

Claims (3)

1. Constructed camshaft, in particular for internal combustion engines, with a shaft member on which separately produced cams (3) are fixed, characterised in that a shaft member (12) produced by casting is provided.
2. Camshaft according to claim 1, characterised in that apart from the cams (3), all the functioning parts such as sprocket wheel retainer (16), thrust bearing (17) with shoulder (18) and locator (19) are moulded on in one piece on the shaft member (12) in accordance with production conditions.
3. Camshaft according to claim 1 or 2, characterised in that the shaft member (12) is profiled outside (22) and/or inside (25, 26).

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