EP1655473B1 - method for mounting a system with camshaft and camshaft receiving part - Google Patents

Description

The invention relates to a method for assembling a system comprising a camshaft having at least two bearing points, a two-part camshaft receptacle having at least two incorporated in narrow webs bearing saddles for receiving the camshaft in a lower part and at least two bearing lids corresponding to the bearing caps in an upper part To store the camshaft with their bearings in the bearing saddles and bearing caps, and bearing shells, each two bearing shells together with a bearing forming a radial plain bearing.

A system of the type mentioned above, for example, in the DE 197 47 244 A1 described and used in an internal combustion engine of a motor vehicle to control the charge exchange. The working method of a four-stroke internal combustion engine comprises not only the compression of the fuel-air mixture or the combustion air and the expansion due to the combustion taking place in the combustion chamber, but also the charge exchange. In the context of the charge exchange, the exhaust of the combustion gases via the exhaust valves and the filling of the combustion chamber with fresh mixture or fresh air via the intake valves takes place. For controlling the charge cycle, four-stroke engines use almost exclusively globe valves which perform an oscillating stroke movement during operation of the internal combustion engine and in this way carry out the opening and closing operation of the inlet and outlet openings.

The required actuating mechanism including the valves is referred to as a valvetrain. It is the task of the valve train to open the intake and exhaust ports of the combustion chamber in time or close, with a quick release of the largest possible flow cross sections is sought.

According to the prior art, a valve is used for this purpose, which is movable along its longitudinal axis between a valve closed position and a valve open position to release an intake or exhaust port of a combustion chamber of the internal combustion engine or to block. For actuation of the valve valve spring means are provided on the one hand to bias the valve in the direction of valve closing position, and on the other hand valve actuators used to open the valve against the biasing force of the valve spring means.

The valve actuating device comprises a camshaft on which a plurality of cams is arranged and which - for example by means of a chain drive - is rotated by the crankshaft in such a way that the cam shaft rotates and with this the cams at half the crankshaft speed.

Basically, a distinction is made between an underlying camshaft and an overhead camshaft.

Bottom camshafts are suitable for the operation of so-called standing valves, but also with the aid of bumpers and levers, such as rocker arms or rocker arms, for the operation of hanging valves.

On the other hand, overhead camshafts are used exclusively for the actuation of suspended valves, with an overhead camshaft valve drive having as another valve drive component a rocker arm, a rocker arm or a plunger. An advantage of using overhead camshafts that in particular by the elimination of the bumper, the moving mass of the valve gear is reduced and the valve gear rigid d. H. less elastic. The present invention relates to overhead camshaft systems.

When using a plunger, the plunger is placed on the combustion chamber remote from the end of the lift valve, so that the plunger participates in the oscillatory lifting movement of the valve when the cam is in engagement with the plunger.

According to the prior art overhead camshafts are mounted in two-part so-called camshaft shots. For this purpose, the camshaft has at least two bearing points. The camshaft receiving comprises a lower part and an upper part, wherein in the lower part so-called bearing saddles and in the upper part so-called bearing caps are provided. In the assembled state - d. H. When the lower and upper parts of the camshaft mount are joined together, a bearing saddle and a bearing cover each form a bore for receiving and supporting the camshaft. The camshaft with its bearings is directly - d. H. without introducing any intermediate elements - added and stored in the bearing saddles and bearing caps. The holes are usually supplied with lubricating oil, so that ideally forms between the inner surface of the bore and the bearing points with rotating camshaft - similar to a plain bearing - a lubricating film.

Often, the two parts of a camshaft receiving castings, which are reworked in further manufacturing steps. The bearing saddles are incorporated into narrow webs, which are provided in the lower part of the receptacle. These webs and consequently also the bearing saddles machined out of the webs are very narrow, for example of the order of 1.5 to 3 millimeters. The reason for this is to be seen in the fact that between the webs so-called pockets or chambers must be provided, are used by the plunger during assembly. The bearing caps, however, are incorporated as part of a post-processing in the upper part of the camshaft receiving and can be much wider, for example, in the order of 12 to 14 millimeters, running.

FIG. 1 shows a lower part of a camshaft holder 100 according to the prior art. The illustrated camshaft receptacle 100 has two bearing saddles 110, which are incorporated in two webs 120 provided in the lower part of the camshaft receptacle 100. Right and left of the webs 120 four circular pockets or chambers 130 are provided, which serve to provide a passage for the insertion of the plunger during assembly. The cramped space or the need for the arrangement of the chambers 130 ultimately leads to the formation of very narrow bearing saddles.

A disadvantage of the small width of the bearing saddles, which serve to support the camshaft, in particular, the low load capacity. Between a bearing saddle and a shaft shoulder, a lubricating film is formed with a rotating camshaft - similar to a plain bearing. The carrying capacity of this lubricating film is significantly influenced by the width of the plain bearing or the bearing saddle.

As the bearing forces increase, the thickness of the lubricating film decreases. As the lubricating film thickness decreases, the area of fluid friction will leave when the surface roughness of the sliding surfaces exceeds the lubricating film thickness. There is mixed friction. If the bearing load increases further, the proportion of solid-state friction increases. It can destroy the camp d. H. the camshaft and the camshaft mount come.

Favorable in view of the small width of the bearing saddles affects the generally one-sided load of the camshaft during operation of the internal combustion engine. Namely, the camshaft is mainly loaded in such a way that it is pressed or pressed into or against the bearing caps.

Thus, the valve spring means act on the valves in the direction of the valve closing position. Thus, forces are exerted by the valve spring means on the valve stem and the cam on the camshaft, wherein an overhead camshaft is pressed into the bearing cap. In particular, during deflection of the valves during the charge cycle, the restoring forces of the valve spring means are large. These biasing forces are intended to prevent lifting of the cam from the plunger.

However, if the camshaft is additionally used to actuate a fuel pump, stresses on the camshaft that push the camshaft into the narrow bearing saddles result. Because of space reasons, the fuel pump is arranged above the camshaft and actuated by means of an additional arranged on the camshaft control cam. The case of the fuel pump on the - during the actuation of the pump - control forces exerted upward control cam are directed downward towards bearing saddles.

The load on the bearing saddles increases, so that concepts must be developed that ensure sufficient bearing capacity of the lubricating film in the camshaft bearing and reduce the specific surface pressure in the camp.

It is the object of the present invention to provide a method according to the preamble of claim 1.

• ■ eine Nockenwelle mit mindestens zwei Lagerstellen,
• ■ eine zweiteilige Nockenwellenaufnahme, die zur Aufnahme der Nockenwelle in einem unteren Teil mindestens zwei in schmalen Stegen eingearbeitete Lagersättel und in einem oberen Teil mindestens zwei zu den Lagersätteln korrespondierende Lagerdeckel aufweist, um die Nockenwelle mit ihren Lagerstellen in den Lagersätteln und Lagerdeckeln zu lagern, und
• ■ Lagerhalbschalen, wobei jeweils zwei Lagerhalbschalen zusammen mit einer Lagerstelle ein Radialgleitlager ausbilden,
  bei dem
• ■ die Nockenwelle zusammen mit den Lagerhalbschalen, von denen jeweils zwei paarweise auf einer Lagerstelle der Nockenwelle mittels eines Halteelementes fixiert sind, als vormontierte Baugruppe in den unteren Teil der Nockenwellenaufnahme in der Art eingebracht wird, daß die dem unteren Teil der Aufnahme zugewandten Lagerhalbschalen in den Lagersätteln platziert werden, und
• ■ der obere Teil der Nockenwellenaufnahme in der Art mit dem unteren Teil zur Anlage gebracht wird, daß die dem oberen Teil der Nockenwellenaufnahme zugewandten Lagerhalbschalen in den Lagerdeckeln angeordnet werden.

This object is achieved by a method for assembling a system comprising

• ■ a camshaft with at least two bearing points,
• ■ A two-part camshaft receiving, which has at least two incorporated in narrow webs bearing saddles for receiving the camshaft and in an upper part at least two corresponding to the bearing saddles bearing caps to support the camshaft with their bearings in the bearing saddles and bearing caps, and
• ■ half-shells, with two half-shells forming a radial plain bearing together with one bearing,
  in which
• ■ The camshaft together with the bearing shells, two of which are fixed in pairs on a bearing point of the camshaft by means of a holding element is introduced as a preassembled module in the lower part of the camshaft receptacle in such a way that the lower half of the receptacle facing bearing shells in the Storage saddles are placed, and
• ■ The upper part of the camshaft receptacle is brought into abutment with the lower part in such a way that the bearing shells facing the upper part of the camshaft receptacle are arranged in the bearing caps.

The system comprises half-shells, two of which are arranged in pairs between a bearing and this bearing bearing bearing saddle and bearing cover, so that the bearing shells on the one hand on the bearing saddle or bearing cover supported and on the other two training half shells together with a bearing forming a radial plain bearing.

According to the invention bearing shells are provided for receiving and supporting the camshaft. In this case, a bearing half shell is arranged on each bearing saddle after insertion of the plunger during assembly. For this purpose, a bearing half-shell is selected, the width of which exceeds the width of the narrow bearing saddle, so that the trained between this bearing half shell and the bearing surface of the bearing system of the invention is greater than the trained according to the prior art between the narrow bearing saddle and the bearing surface sliding surface.

As a result, a much more viable bearing is formed in the region of the bearing saddle of the camshaft receiving. The arrangement of the bearing half shell on the web or the bearing saddle can be done separately as part of a single assembly step or - which is preferable - together with the camshaft, with the already arranged on her half shells as a pre-assembled structural unit in a single assembly step is arranged in the lower part of the camshaft holder.

The revolving camshaft is supported by a wide hydrodynamic lubricating oil film, which forms between bearing point and bearing shells. The camshaft bearing according to the invention can absorb higher bearing loads as a result of the wider slide bearing surface in the area of the bearing saddles, without leaving the area of fluid friction. Mixed friction or high solid friction in the bearing surface can be avoided.

As a result, by means of the system according to the invention, in particular a fuel pump arranged above the camshaft can be easily connected via an additional fuel pump arranged on the camshaft control cam can be operated without having to worry that the camshaft runs dry in the region of the bearing saddle.

In each case, the two provided at a bearing bearing half shells with respect to the camshaft are fixed, wherein the two bearing shells are fixed by a holding element at a bearing point, which allows a simple, quick fixation of the bearing shells.

This allows the installation of the camshaft with already arranged on this in the installed position bearing shells as a preassembled structural unit. This reduces in the assembly not only the number of assembly steps, but also the number of items to be kept and managed to be managed and thus the total cost of production.

The bearings are at least fixed in such a way that they do not come loose from the camshaft and are not lost. The fixation can also be made more extensive. Thus, the bearing shells can be axially fixed in such a way that they can not be moved in the direction of the longitudinal axis of the camshaft. This offers advantages, since the bearing shells are then positioned during assembly directly in the storage saddles and bearing caps provided for them, without a readjustment d. H. axial alignment of the shells is required. The bearing shells can also be fixed against rotation, so that the so-called shock, the area in which the two separating surfaces of the half shells face each other comes to lie in the circumferential direction in a predetermined position.

The fixation can - if it does not affect the functioning of the system - remain on the assembled system or be removed after or during assembly. In any case, it must be ensured that the camshaft can rotate or rotate later during operation.

Essential for the proposed method is the knowledge that the provided between the webs of the lower part of the camshaft receiving chambers or pockets can be reduced after insertion of the plunger in the context of assembly in its cross-section or diameter. A widening of the lower half of the bearing in the region of the bearing saddle by introducing a wider bearing shell is harmless after insertion of the plunger.

According to the assembly method according to the invention, the camshaft is inserted together with the bearings arranged on the bearing half shells as a preassembled module after insertion of the plunger in the lower part of the camshaft receiver.

As a result, the object underlying the invention is achieved, namely to show a method for assembling a system with camshaft and camshaft recording.

Further advantages of the method according to the invention are discussed in connection with the embodiments according to the subclaims.

Advantageous embodiments of the method in which the holding elements are removed after placing the camshaft in the lower part of the camshaft receiving.

Embodiments of the method in which the holding element is a ring are advantageous. A built-up of an elastic material ring can be pushed laterally over the arranged on the shaft shoulder bearing shells. The restoring forces of the ring then press the shells onto the shaft shoulder like a spring.

Embodiments of the method in which the holding element is a clamp-shaped clip with a pincer-shaped opening are advantageous. In contrast to the ring described above, this clip is guided radially over the shells, with a fixation is given as soon as the clip engages.

Embodiments of the method in which the holding element is formed from a strip-shaped material are advantageous. The strip-shaped material can be, for example, an adhesive strip which is provided as an endless belt and from which a piece is wound around the bearing shells for fixing purposes. A wire or a plastic cord are just two more examples of a holding element formed from a strip-shaped material.

Embodiments of the method in which the holding element is connected in a material-locking manner to the bearing half-shells, preferably by means of an adhesive connection, are advantageous. An unintentional release of the holding means, whereby the fixation of the bearing shells would be repealed, can be prevented in this way.

Embodiments of the method in which the bearing shells have a recess in the circumferential direction for receiving the retaining element on their outer circumferential surface facing the camshaft receptacle are advantageous.

Embodiments of the method in which the holding element is completely embedded in the recess are advantageous. This embodiment is advantageous because the retaining elements then do not need to be removed during assembly, but can remain in the bearing shells. An additional assembly step can be avoided. Due to the fact that the holding elements are completely absorbed in the recess, they do not hinder the joining process ie the introduction of the camshaft and the half shells in the camshaft receiver. A slipping of the bearing shells when removing the retaining means thus also eliminated.

However, embodiments of the method in which the holding element is partially embedded in the recess and partially protrudes from the recess are also advantageous.

The protruding part of the holding means can assume different functions. For example, this part can be used to fix the shells in the bearing saddle or bearing cap, to prevent in this way an unwanted movement of the shells - in the axial direction or in the circumferential direction - with rotating camshaft. But they are also suitable as an assembly aid to arrange the bearings in the intended position.

For this reason, embodiments of the method are advantageous in which the camshaft receptacle in each case in the region of the bearing cap and / or the bearing saddle has a recess for receiving the retaining element. Attaches the holding means on the one hand in the recess of the bearing shell and on the other hand in the recess of the bearing cap and / or the bearing saddle, the shells are fixed in position relative to the camshaft receiving.

Embodiments of the method in which at least one bearing half shell of the two bearing half shells forming a radial sliding bearing are provided with means for axial fixing on their outer circumferential surface facing the camshaft receptacle are advantageous.

A means for axial fixation, for example, the holding means - as in the previously described embodiment - be. On the outer circumferential surface of the bearing shell but also a nose or the like may be provided for axial fixation.

Embodiments of the method in which a first recess is provided in the outer circumferential surface of the at least one bearing half shell for axial fixing are advantageous, in which a fixing element is arranged, which engages in a second recess provided in the camshaft receptacle.

Embodiments of the method in which the two bearing half shells forming a radial plain bearing are connected to one another are advantageous. Such a connection of the bearing shells can replace the above-mentioned holding means. On the other hand, the compound can be considered as such as a holding means.

Embodiments of the method in which the two bearing half shells forming a radial sliding bearing are connected to one another in a material-locking manner are advantageous. A cohesive connection can be generated by a welded connection, in particular by means of laser welding, but also designed as an adhesive connection.

Embodiments of the method in which the two bearing half shells forming a radial sliding bearing are positively connected with one another are also advantageous. A positive connection can be formed for example by a so-called latching of the bearing shells. The dividing surfaces of the shells are profiled in such a way that engage in the joint hook-shaped elements.

Fig. 1

den unteren Teil einer Nockenwellenaufnahme nach dem Stand der Technik in der Seitenansicht und teilweise geschnitten,

Fig. 2a

schematisch eine Nockenwelle nach dem Stand der Technik in der Seitenansicht und teilweise geschnitten,

Fig. 2b

schematisch eine Nockenwelle einer ersten Ausführungsform des Systems in der Seitenansicht und teilweise geschnitten,

Fig. 2c

die in Figur 2b kenntlich gemachte Einzelheit Y,

Fig. 3a

schematisch eine zweite Ausführungsform des Systems in der Seitenansicht und teilweise geschnitten, und

Fig. 3b

die in Figur 3a kenntlich gemachte Einzelheit X.

In the following the invention is based on two embodiments according to the Figures 1 to 3b described in more detail. Hereby shows:

Fig. 1

the lower part of a camshaft receiver according to the prior art in side view and partially cut,

Fig. 2a

schematically a camshaft according to the prior art in the side view and partially cut,

Fig. 2b

schematically a camshaft of a first embodiment of the system in side view and partially cut,

Fig. 2c

in the FIG. 2b marked detail Y,

Fig. 3a

schematically a second embodiment of the system in side view and partially cut, and

Fig. 3b

in the FIG. 3a marked detail X.

FIG. 1 was already discussed in the introduction to the description.

FIG. 2a schematically shows a portion of a camshaft 140 according to the prior art in the side view and partially cut.

The illustrated portion of the camshaft 140 has two cams 150, between which a thickened shaft shoulder 160 is provided. This shaft shoulder 160 serves to support the camshaft 140 in the camshaft receptacle and is for this purpose in the lower part of the recording in a narrow bearing saddle (see also FIG. 1 ) and received in the upper part of the receptacle in a bearing cap (not shown).

FIG. 2b schematically shows a portion of a camshaft 1 of a first embodiment of the system in side view and partially cut.

In the illustrated section, the camshaft 1 has two cams 2 and a shaft shoulder 3 arranged between these cams 2, which serves as a bearing point 3. On the shaft shoulder 3, two bearing shells 5 are arranged, which are fixed by means of a holding element 6 on the shaft shoulder 3.

The two bearing half-shells 5 are each provided on their outer lateral surface with a recess 4,12 which extends in the circumferential direction.

The recesses serve to receive the retaining element 6, wherein in the in FIG. 2b illustrated embodiment, the holding element 6 is completely embedded in the recesses 4,12 and not only partially protruding. For this reason, the support member 6 need not be removed during assembly and, since it does not hinder the assembly process, remain in the recesses 4,12.

So that the nominal diameter of the shaft shoulder 3 ie the storage compared to the conventional system (see FIG. 2a ) is not changed, in particular not increased, a groove 7 for receiving the bearing shells 5 is provided in the shaft shoulder 3.

Figure 2c shows the in FIG. 2b indicated detail Y in an enlargement.

The bearing half shell 5 is positioned in a groove 7 in the shaft shoulder 3. The holding element 6, with which the bearing half-shell 5 is fixed on the shaft shoulder 3, is completely embedded in a recess 12 incorporated in the bearing shell 5.

FIG. 3a schematically shows a second embodiment of the system in side view and partially cut. It should only the differences to the in the FIGS. 2b and 2c For that reason, reference is made to FIGS FIGS. 2b and 2c , The same reference numerals have been used for the same components.

In contrast to the first embodiment, the in FIG. 3a illustrated second embodiment, characterized in that the holding element 6 is only partially embedded in the recesses 4,12 of the bearing half-shells 5 and partially protruding from the recesses 4,12. The protruding part of the retaining element 6 engages in the camshaft receptacle. For this purpose, the camshaft receiving in the region of the bearing cap 8 and the bearing saddle 9 is in each case equipped with a recess 10,11 for receiving the retaining element 6.

For this reason, the holding element 6 is used after mounting the camshaft 1 in the camshaft receiving simultaneously as a fixing member 13 against axial displacement.

FIG. 3b shows the in FIG. 3a indicated detail X in an enlargement. It is apparent how the holding element 6 engages both in the recess 12 of the bearing shell 5 and in the recess 11 of the bearing saddle 9.

reference numeral

1

camshaft

2

cam

3

Bearing point, thickened shaft shoulder

4

recess

5

Half bearing

6

retaining element

7

groove

8th

bearing cap

9

bearing saddle

10

recess

11

recess

12

recess

13

fixing

20

system

100

lower part of a camshaft holder

110

bearing saddle

120

web

130

Pocket, chamber

140

camshaft

150

cam

160

Bearing point , shaft shoulder

Claims (15)

1. Method for assembling a system (20), comprising

   ■ a camshaft (1) with at least two bearing points (3),

   ■ a two-part camshaft receptacle which, for receiving the camshaft (1), has, in a lower part, at least two bearing saddles (9) incorporated in narrow webs and, in an upper part, at least two bearing covers (8) corresponding to the bearing saddles (9), in order to mount the camshaft (1) with its bearing points (3) in the bearing saddles (9) and bearing covers (8), and
   characterized in that

   ■ bearing half shells (5) in each case two bearing half shells (5), together with a bearing point (3), forming a radial plain bearing,
   in which

   ■ the camshaft (1), together with the bearing half shells (5), of which in each case two are fixed in pairs on a bearing point (3) of the camshaft (1) by means of a holding element (6), is introduced as a preassembled subunit into the lower part of the camshaft receptacle, in such a way that the bearing half shells (5) facing the lower part of the receptacle are placed in the bearing saddles (9), and

   ■ the upper part of the camshaft receptacle is brought to bear with the lower part in such a way that the bearing half shells (5) facing the upper part of the camshaft receptacle are arranged in the bearing covers (8).
2. Method according to Claim 1,
   characterized in that
   the holding elements (6) are removed after the camshaft (1) has been placed in the lower part of the camshaft receptacle
3. Method according to Claim 1 or 2,
   characterized in that
   the holding element (6) is a ring.
4. Method according to Claim 1 or 2,
   characterized in that
   the holding element (6) is a staple-shaped clip with a tong-like aperture.
5. Method according to Claim 1 or 2,
   characterized in that
   the holding element (6) is produced from a strip-shaped material.
6. Method according to one of the preceding claims,
   characterized in that
   the holding element (6) is connected to the bearing half shells (5) in a materially integral manner, preferably by means of an adhesive bond.
7. Method according to one of the preceding claims,
   characterized in that
   the bearing half shells (5) have, on their outer surface area facing the camshaft receptacle, a recess (4, 12) in the circumferential direction for the reception of the holding element (6).
8. Method according to Claim 7,
   characterized in that
   the holding element (6) is embedded completely in the recess (4, 12).
9. Method according to Claim 7,
   characterized in that
   the holding element (6) is embedded partially in the recess (4, 12) and projects partially out of the recess (4, 12).
10. Method according to one of the preceding claims,
    characterized in that
    the camshaft receptacle has in each case in the region of the bearing cover (8) and/or of the bearing saddle (9) a recess (10, 11) for the reception of the holding element (6).
11. Method according to one of the preceding claims,
    characterized in that
    at least one bearing half shell (5) of the two bearing half shells (5) forming a radial plain bearing has, on its outer surface area facing the camshaft receptacle, means (6, 13) for axial fixing.
12. Method according to Claim 11,
    characterized in that,
    for axial fixing, a first recess (4, 12) in the outer surface area of the at least one bearing half shell (5) is provided, in which is arranged a fixing element (13) which engages into a second recess (10, 11) provided in the camshaft receptacle.
13. Method according to one of the preceding claims,
    characterized in that
    the two bearing half shells (5) forming a radial plain bearing are connected to one another.
14. Method according to Claim 13,
    characterized in that
    the two bearing half shells (5) forming a radial plain bearing are connected to one another in a materially integral manner.
15. Method according to Claim 13,
    characterized in that
    the two bearing half shells (5) forming a radial plain bearing are connected positively to one another.

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