EP3502436A1 - Connecting rod for a combustion engine with variable compression with a switching valve - Google Patents

Abstract

The invention relates to a connecting rod (1) for an internal combustion engine with variable compression with an eccentric adjusting device (6) in Pleuelkörper (29) for adjusting an effective connecting rod length, wherein a displacement of the eccentric adjusting device (6) by means of a switching valve (11). is adjustable, wherein a valve housing (12) of the changeover valve (11) by means of one or more securing elements axially in a bore (23) of the connecting rod (1) is provided secured.

Description

Technical area

The invention relates to a connecting rod with a switching valve for controlling a hydraulic fluid flow.

State of the art

In internal combustion engines, a high compression ratio has a positive effect on the efficiency of the internal combustion engine. Under compression ratio is generally understood the ratio of the entire cylinder space before compression to the remaining cylinder space after compression. In internal combustion engines with spark ignition, in particular gasoline engines, which have a fixed compression ratio, the compression ratio, however, may only be selected so high that a so-called "knocking" of the internal combustion engine is avoided during full load operation. However, for the much more frequently occurring partial load range of the internal combustion engine, that is to say with low cylinder filling, the compression ratio could be selected with higher values without "knocking" occurring. The important part load range of an internal combustion engine can be improved if the compression ratio is variably adjustable. To adjust the compression ratio For example, systems with variable connecting rod length known which operate by means of hydraulically or mechanically actuated changeover valves an eccentric adjustment of a connecting rod.

A generic connecting rod is for example from the DE 10 2012 112 461 A1 refer to. A tapping element of the switching element described therein can be locked by means of a detent ball and a spring in two switching positions, wherein the detent ball cooperates with two locking grooves formed in the tapping element. The structure of the known switching valve is considered to be expensive and therefore expensive.

Disclosure of the invention

An object of the invention is to provide a connecting rod with an improved changeover valve.

The above object is achieved with the features of the independent claim.

Favorable embodiments and advantages of the invention will become apparent from the other claims, the description and the drawings.

According to one aspect of the invention, a connecting rod for an internal combustion engine with variable compression is proposed, with an eccentric adjusting device in the connecting rod cover for adjusting an effective connecting rod length. An adjustment of the eccentric adjusting device is adjustable by means of a switching valve. In this case, a valve housing of the changeover valve is provided secured by means of one or more securing elements axially in a bore of the connecting rod.

The securing of the changeover valve according to the invention by means of one or more securing elements axially in a bore of the connecting rod proves to be advantageous compared to the prior art, in which it is customary to press a change-over valve in a parallel to Pleuelaugen introduced bore in the connecting rod. The interference fit seals external grooves and bores on the changeover valve from each other and prevents a hydraulic short circuit. In addition, the press fit secures the switching valve against falling out in the axial direction. The press fit must be designed so that there is always a sufficiently large press-in force for all tolerances, wherein the press-in force is approximately equal to the extrusion force, and the material load limits are not exceeded. The maximum insertion force is additionally reduced by the material load during operation. It is best to install the changeover valve in a low loaded area, such as above conrod bolts, but this is not always possible due to the geometry of the engine.

For reasons of construction of the crank mechanism, the changeover valve may be arranged, for example, centrally below the connecting rod in the connecting rod cover. By tensile forces it comes at this point to strong deformations, which can also deform the bore for the switching valve oval. Excessively high insertion forces could lead to material fatigue and thus cause plastic deformation, which weakens the press fit over the service life. In the worst case, it may lead to breakage of the changeover valve or the changeover valve may fall out of the bore. In both cases, an engine failure would result. Another negative effect with excessive combined load could be that the deformation clamps the tapping element, which is very tight due to low leakage, and higher loads occur during the switching process.

According to the invention, therefore, a transition fit or very small interference fit can be used in combination with a positive connection between the valve housing and the connecting rod. In a transitional fit, it is advantageous if play and thus leakage between the valve housing and connecting rod is possible. This can be kept as low as possible, but can conveniently due to the Leakage of Tap element to valve housing have a relatively small impact on the system behavior.

Advantageously, therefore, for example, a locking pin can be pressed together as a fuse element through the connecting rod cover and the valve housing. Advantageously, there is only one interference fit in the valve housing, while the locking pin in the connecting rod cover has minimal play. As a result, no additional stresses in the valve housing and tolerances with respect to concentricity of the holes can be compensated at this point.

According to an advantageous embodiment of the connecting rod and the valve housing may have bores in which one or more locking pins are provided as a fuse elements are provided. The pressing of one or more locking pins as securing elements, preferably transversely to a press-in direction of the changeover valve, can ensure in a favorable manner that the changeover valve is secured against falling out of the connecting rod cover.

According to an advantageous embodiment, the switching valve may be formed as described above and preferably be used sealless in the connecting rod cover. The interference fit can thereby seal out external grooves and bores on the changeover valve and prevent a hydraulic short circuit. By mounting in the press fit can be dispensed with an additional seal.

According to an advantageous embodiment, the locking pin can be additionally provided as a locking pin as axial securing the switching valve in the connecting rod. This can be conveniently avoided to provide an additional locking pin, which simplifies the manufacture and installation of the connecting rod.

According to an advantageous embodiment, a bore in the connecting rod cover for mounting the locking element may be provided in the valve housing of the changeover valve. This allows the locking element through the hole in the connecting rod in a simple Way are mounted in the valve housing and the tap element of the changeover valve.

According to an advantageous embodiment, the holes may be provided as blind holes, which is advantageous in terms of residual dirt. Furthermore, the pressing-in process can be simplified in that the pressing-in process can take place in a block and no longer has to be monitored with respect to the path.

According to an advantageous embodiment, the holes may have a clearance in which the one or more locking pins can be secured by forming against falling out. As a result, a backup of the locking pins is possible in a simple manner. Forming can be done, for example, by crimping the ends of the locking pins or similar suitable processes.

According to an advantageous embodiment, the valve housing can be fixed by means of a frontal weld as a securing element to the connecting rod cover. Conveniently, a transition fit can be provided for the press-in operation of the change-over valve in the connecting rod cover. A weld on one or both end sides of the changeover valve and the connecting rod cover permanently fixes the changeover valve in the connecting rod cover.

Brief description of the drawings

Further advantages emerge from the following description of the drawing. In the drawings, embodiments of the invention are shown. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

They show by way of example:

Fig. 1

a longitudinal section through a first embodiment of a connecting rod according to the invention;

Fig. 2

an enlarged section Z of the longitudinal section according to Fig. 1 with focus on the switching valve in a cross section;

Fig. 3

a plan view of the switching valve according to an embodiment of the invention with marked sectional planes A-A and B-B;

Fig. 4

a longitudinal section through the switching valve in the sectional plane AA according to Fig. 3 ;

Fig. 5

a further longitudinal section through the switching valve in the sectional plane BB according to Fig. 3 ;

Fig. 6

an isometric view of the switching valve according to Fig. 3 ;

Fig. 7

a side view of the switching valve according to Fig. 3 ;

Fig. 8

another side view of the switching valve according to Fig. 3 ;

Fig. 9

another side view of the switching valve according to Fig. 3 with marked section plane CC;

Fig. 10

a cross section through the switching valve in the sectional plane CC according to Fig. 9 ;

Fig. 11

a further isometric view of the switching valve according to Fig. 3 ;

Fig. 12

a plan view of the switching valve according to Fig. 3 ;

Fig. 13

a longitudinal section through a further embodiment of a connecting rod according to the invention;

Fig. 14

an enlarged section Z of the longitudinal section according to Fig. 13 with focus on the switching valve in a cross section;

Fig. 15

an isometric view of the switching valve according to Fig. 13 ;

Fig. 16

a plan view of the switching valve according to Fig. 13 with marked section plane AA; and

Fig. 17

a longitudinal section through the switching valve in the sectional plane AA according to Fig. 16 ,

Embodiments of the invention

In the figures, the same or similar components are numbered with the same reference numerals. The figures are merely examples and are not intended to be limiting.

The FIGS. 2 to 12 show various views and sections of a first embodiment of a switching valve 11, or of individual parts of the switching valve 11 of an inventive, in FIG. 1 shown connecting rod 1.

The in FIG. 1 shown connecting rod 1 has a connecting rod 34, comprising a Pleuelkörper 29 and a connecting rod cover 30, and arranged at least partially in a Pleuellagerauge 2 adjustable eccentric adjustment device 6 with an eccentric 10. The eccentric adjusting device 6 is used to adjust an effective connecting rod length. As the connecting rod length of the distance of a central axis of a Hublagerauges 3 is defined to a central axis of the Pleuellagerauges 2.

A rotation of the adjustable eccentric adjusting device 6 is initiated by the action of mass and load forces of the internal combustion engine, which act on the eccentric adjusting device 6 at a power stroke of the internal combustion engine. During a working cycle, the directions of action of the forces acting on the eccentric adjusting device 6 change continuously. The rotary movement or adjustment is supported by hydraulic fluid, in particular engine oil, acted upon in the connecting rod 1 integrated piston 4, 5. The pistons 4, 5 thereby prevent the eccentric adjusting device 6 from being reset due to varying directions of force acting on the eccentric adjusting device 6.

The pistons 4, 5 are operatively connected by means of eccentric rods 7, 8 on both sides with a lever 9 of the eccentric adjusting device 6. The pistons 4, 5 are arranged displaceably in hydraulic chambers and are acted upon by hydraulic fluid, not shown, with hydraulic fluid via non-visible check valves. The check valves prevent a backflow of the hydraulic fluid from the hydraulic chambers back into the hydraulic fluid lines and allow a Nachsaugen hydraulic fluid in the hydraulic chambers.
The check valves may advantageously be integrated into the changeover valve 11, for example as ball or disc check valves or as band check valves. In the execution as a band check valves, for example, a position securing such as a bolt o.ä. be provided. The hydraulic fluid conduits connected to the hydraulic chambers all or at least partially interact with the switching valve 11. In a first switching position S1 of the switching valve 11, which corresponds to a position of high compression of the connecting rod 1 (shown in FIG FIG. 1 ), is the first hydraulic chamber with a discharge line, not shown, and in a second switching position S2 of the changeover valve 11, which corresponds to a position of low compression of the connecting rod 1, the second hydraulic chamber connected to the discharge line. The discharge line is the connection to a supply of the connecting rod 1 with hydraulic fluid, for example via a groove in the Hublagerauge 3 of the connecting rod 1.

However, the reversing valve 11 described in more detail below can also be provided for any other connecting rod for an internal combustion engine with variable compression, which has an eccentric adjusting device for adjusting an effective connecting rod length and at least one hydraulic chamber. For example, the eccentric adjusting the connecting rod may be formed with a so-called swing motor system.

The switching valve 11 is in FIG. 2 shown in an enlarged section Z of the connecting rod 1 in a cross section. FIG. 3 shows a plan view of the switching valve 11 with drawn sectional planes AA and BB. Figure 4 shows a longitudinal section through the switching valve 11 in the sectional plane AA, while FIG. 5 represents a longitudinal section in the sectional plane BB.

As in FIG. 2 to recognize the changeover valve 11 is arranged axially in a bore 23 of the connecting rod 1, for example, pressed. In order to seallessly mount the changeover valve 11 in the connecting rod 34 or a connecting rod 29 or connecting rod cover 30, the valve housing 12 of the changeover valve 11 may be axially secured in the bore 23 of the connecting rod 1 by means of one or more locking pins. The one or more locking pins are in the cut in FIG. 2 not to be seen, since the locking pin is arranged in a different cutting plane.

For receiving the locking pin, not shown, the connecting rod 1 holes 32, which in the second embodiment in FIG. 14 can be seen while the valve housing 12 corresponding thereto respectively bores 27 (in FIG. 9 shown), in which a locking pin can be provided pressed. The holes 32 of the connecting rod 1 are designed for ease of manufacture, for example, as through holes.

In cross section in FIG. 2 is the in the bore 23 of the connecting rod cover 30 pressed valve housing 12 of the switching valve with the guided inside the tap element 13 can be seen. Transverse to the axis of the valve housing 12 of the latching pin 18 is disposed in the bores 20, 21.

In longitudinal section of the switching valve 11 in FIG. 4 are further the two hydraulic connections 22, 24, which are each assigned to the supply of the hydraulic chambers of the connecting rod 1 on the mass force side (MKS), or gas power side (GKS) of the eccentric adjusting device 6 of the connecting rod 1 and the switching positions S1 and S2 correspond. In cross section in FIG. 5 the relief ports 26 can be seen, which are connected to the hydraulic supply P.

The switching valve 11 has a tap body 12 disposed in a tap member 13, which in an axial direction L (see FIG. 4 ) displaceable either in a first switching position S1 or a second switching position S2 displaceable and by means of a spring-loaded locking element 14 either in the first or the second switching position S1, S2 can be locked. For this purpose, the latching element 14 has a spring element 15 arranged in a latching sleeve 33. In the first shift position S1, a first hydraulic port 22 of the changeover valve 11 with a discharge port 26 and in the second shift position S2, a second hydraulic port 24 is connected to the discharge port 26, in particular FIG. 4 can be seen.

The arranged in the valve housing 12 tap element 13 is selectively locked in the first switching position S1 or the second switching position S2. For this purpose, the latching element 14 and arranged in the latching element 14 spring element 15 are at least partially disposed in a transverse recess 16 of the tap element 13. The valve housing 12 has to in the axial Direction L to an axially limited first groove 17, in which the locking element 14 is arranged axially displaceable for limiting the switching path and for preventing rotation of the tapping element 13. The at least partial arrangement of the latching element 14 in the recess 16 is advantageous, since the guide length of the movable latching element 14 can be significantly increased in comparison to the known switching valves. The canting tendency and self-locking tendency can be reduced and a safe achievement of the end positions can be improved on their own. In addition, the spring design of the spring element 15 is not critical because of greater installation length compared to the prior art.

The locking element 14 additionally serves as a stop element, which limits a displacement path of the tapping element 13 in the valve housing 12. As a result, the stop element can be omitted as an additional component. The locking element 14 is provided with the tapping element 13 axially displaceable together. The latching element 14 cooperates with a latching pin 18, which is arranged in the valve housing 12 in the region of the first groove 17.

In order to lock the reversing valve 11 in the two switching positions S1 and S2, the latching element 14 has a latching contour 19 which, in interaction with the latching pin 18, allows two latching positions for the latching element 14. As FIG. 4 can be seen, the latching element 14 can engage with its catch contour 19 on both sides of the locking pin 18 during axial displacement of the tapping element 13.

FIG. 6 shows an isometric view of the switching valve 11 according to FIG. 3 while in the FIGS. 7, 8, 9 different side views of the switching valve 11 are shown. In FIG. 9 is a sectional plane CC drawn, the cross section of the switching valve 11 in FIG. 10 is shown. FIG. 11 shows a further isometric view of the switching valve 11 and FIG. 12 a plan view of the switching valve 11th

As FIG. 6 can be seen, the valve housing 12 in the region of the first groove 17 holes 20, 21, in which the locking pin 18 is provided pressed. Also, the discharge port 26 can be seen.

The side view in FIG. 7 shows the arrangement of the two hydraulic ports 22, 24, while FIG. 8 shows the discharge port 26 as a slot.

For receiving a locking pin, the connecting rod 1 holes 32, as in the embodiment in FIG. 14 shown, while the valve housing 12 corresponding thereto respectively bores 27 (in FIG. 9 shown), in which a locking pin can be provided pressed. The holes 32 of the connecting rod 1 are designed for ease of manufacture, for example, as through holes.

A bore of the connecting rod 1 could alternatively be formed as a blind hole, whereby advantageous residual dirt can be avoided. Furthermore, the pressing-in process can be simplified in that the pressing-in process no longer has to be monitored with respect to the path.

In FIG. 9 is further recognized by the groove 17 of the locking pin 18.

The FIGS. 13 to 17 shows a further embodiment of a connecting rod 1 according to the invention, which differs in that the locking pin 18 additionally serves as a locking pin. The locking pin 18 as a locking pin is provided as axial securing the switching valve 11 in the connecting rod 1.

FIG. 13 shows a longitudinal section through the connecting rod 1, while in FIG. 14 an enlarged section Z of the longitudinal section according to FIG. 13 is shown with a focus on the switching valve 11 in a cross section.

FIG. 15 shows an isometric view of the switching valve 11 according to FIG. 13 , In FIG. 16 is a plan view of the switching valve 11 with marked Sectional plane AA shown while FIG. 17 shows a longitudinal section through the switching valve 11 in the sectional plane AA.

As in particular the enlarged section in FIG. 14 can be seen, the locking pin 18 is pressed by the connecting rod cover 30 and the valve housing 12. For this purpose, a bore 32, preferably a through hole is provided in the connecting rod cover 30, through which the locking pin 18 are inserted as a securing element and can be passed through holes 20, 21 in the valve housing 12. With sufficient length of the locking pin 18, the locking pin 18 may protrude on both sides over the valve housing 12 so that it is anchored as a securing element in the bore 32 of the connecting rod cover 30. Advantageously, there is only one interference fit in the valve housing 12, while the locking pin 18 in the connecting rod cover 30 has minimal play. As a result, no additional stresses in the valve housing 12 are obtained at this point and tolerances with regard to concentricity of the bores 32 in the connecting rod cover 30 and the bores 20, 21 in the valve housing 12 can be compensated.

Alternatively, the holes 32 may be provided as blind holes. The holes 32 may conveniently have a clearance in which the one or more locking pins is secured by forming the ends, such as flanging, against falling out.

For assembly results in the situation that the switching valve 11 can not be pre-assembled, since the locking pin 18 is pressed only after pressing the valve housing 12. The assembly of the locking pin 18 is thus carried out after pressing the valve housing 12 into the bore 23 in the connecting rod 30. In the connecting rod 30 is therefore advantageously at least one bore 31 is introduced, through which the locking element 14 can be introduced into the valve housing 12. Alternatively, a Langlochnut is conceivable.

As a further alternative embodiment can be provided to mount a temporary locking pin in the valve housing 12, which does not consist of the valve housing 12th protrudes and is pushed out by means of the final locking pin 18 during its assembly. The temporary detent pin may have an interference fit, a transition fit, or a clearance fit.

In an alternative embodiment, however, the valve housing 12 may also be fixed to the connecting rod cover 30 as a securing element by means of a frontal weld.

In the isometric representation in FIG. 15 is the longer than in the previous embodiment formed locking pin 18 can be seen, which passes transversely through the groove 17 of the valve housing 12 and extends beyond the valve housing 12 on both sides. Also, the discharge port 26 can be seen. The length of the locking pin 18 is also the top view in FIG. 16 refer to.

FIG. 17 shows in longitudinal section the switching valve, which is substantially the representation of the first embodiment in FIG. 4 like. The difference is that no additional holes 27 are required for mounting an additional locking pin, so that the manufacture of the valve housing 12 can be simplified.

Claims (8)

Connecting rod (1) for an internal combustion engine with variable compression with an eccentric adjusting device (6) in Pleuelkörper (29) for adjusting an effective connecting rod length, wherein a displacement of the eccentric adjusting device (6) by means of a switching valve (11) is adjustable, wherein a Valve housing (12) of the changeover valve (11) by means of one or more securing elements axially in a bore (23) of the connecting rod (1) is provided secured. Connecting rod (1) according to claim 1, wherein the connecting rod (1) and the valve housing (12) bores (32, 27), in which one or more locking pins are provided as securing elements are provided. Connecting rod (1) according to claim 1 or 2, wherein the switching valve (11) is designed according to one of claims 1 to 6 and is preferably used sealless in the connecting rod cover (30). Connecting rod (1) according to claim 3, wherein the locking pin (18) is additionally provided as a locking pin as axial securing of the changeover valve (11) in the connecting rod (1). Connecting rod (1) according to claim 4, wherein a bore (31) in the connecting rod cover (30) for mounting the locking element (14) in the valve housing (12) of the changeover valve (11) is provided. Connecting rod (1) according to one of the preceding claims 2 to 5, wherein the bores (32) are provided as blind bores. Connecting rod (1) according to one of the preceding claims 2 to 6, wherein the bores (32) have a clearance fit, in which the one or more locking pins is secured by forming against falling out. Connecting rod (1) according to one of the preceding claims 1 to 7, wherein the valve housing (12) is fixed by means of a front-side weld as a securing element on the connecting rod cover (30).

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