EP3502436B1 - Connecting rod for a combustion engine with variable compression with a switching valve - Google Patents

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. The compression ratio is generally understood to mean 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 Otto engines that have a fixed compression ratio, the compression ratio may only be selected so high that so-called "knocking" of the internal combustion engine is avoided when operating at full load. However, for the part-load range of the internal combustion engine that occurs much more frequently, that is to say with a low cylinder charge, the compression ratio could be selected with higher values without "knocking" occurring. The important partial load range of an internal combustion engine can be improved if the compression ratio can be set variably. To adjust the compression ratio are For example, systems with a variable connecting rod length are known which actuate an eccentric adjusting device of a connecting rod with the aid of hydraulically or mechanically actuated switchover valves.

A connecting rod of the generic type is, for example, from DE 10 2012 112 461 A1 refer to. A pick-up element of the switchover element described therein can be locked in two switching positions by means of a locking ball and a spring, the locking ball cooperating with two locking grooves formed in the pick-up element. The construction of the known switchover valve is viewed as complex and therefore costly.

Disclosure of the invention

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

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

Favorable configurations and advantages of the invention emerge from the further claims, the description and the drawing.

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 path of the eccentric adjustment device can be adjusted by means of a switchover valve. A valve housing of the changeover valve is provided axially secured in a bore of the connecting rod by means of one or more securing elements.

The inventive securing of the switching valve by means of one or more securing elements axially in a bore of the connecting rod has proven to be advantageous compared to the prior art, in which it is customary to press a changeover valve into a bore in the connecting rod that is made parallel to the connecting rod eyes. The interference fit seals external grooves and bores on the switching valve from one another and prevents a hydraulic short circuit. In addition, the interference fit secures the changeover valve against falling out in the axial direction. The interference fit must be designed in such a way that there is always a sufficiently large press-in force with all tolerances, the press-in force being approximately equal to the press-out force, and the material load limits not being exceeded. The maximum press-in force is also reduced by the material stress during operation. It is best to mount the switchover valve in an area with low loads, such as above connecting rod bolts, but this is not always possible due to the engine geometry.

For reasons of the construction of the crank drive, the changeover valve can be arranged, for example, centrally below the connecting rod in the connecting rod cover. Tensile forces cause severe deformations at this point, which can also deform the hole for the switchover valve into an oval shape. Press-in forces that are too high could lead to material fatigue and thus cause plastic deformations that weaken the interference fit over its service life. In the worst case, the changeover valve can break or the changeover valve can fall out of the bore. In both cases, engine damage would be the result. Another negative effect if the combined load is too great could be that the deformation jams the pick-up element, which is guided very closely because of the low leakage, and higher loads occur in the switching process.

According to the invention, a transition fit or a very small interference fit can therefore be used in combination with a form fit between the valve housing and the connecting rod. In the case of a transition fit, it is advantageous if play, and thus leakage, is possible between the valve housing and the connecting rod. This can be kept as low as possible, but can be beneficial due to the Leakage points from the tapping element to the valve housing have a relatively minor influence on the system behavior.

Therefore, for example, a locking pin can advantageously be pressed together as a securing element through the connecting rod cover and the valve housing. There is advantageously 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 are obtained in the valve housing at this point and tolerances with regard to the concentricity of the bores can be compensated for.

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

According to an advantageous embodiment, the switchover valve can be designed as described above and preferably inserted in the connecting rod cover without a seal. The interference fit can seal external grooves and bores on the changeover valve with one another and prevent a hydraulic short circuit. The installation in the interference fit means that an additional seal is not required.

According to the invention, the locking pin is also provided as a locking pin to axially secure the switch valve in the connecting rod.

This advantageously avoids providing an additional locking pin, which simplifies the manufacture and assembly of the connecting rod.

According to an advantageous embodiment, a bore can be provided in the connecting rod cover for mounting the latching element in the valve housing of the switchover valve. This allows the locking element through the hole in the connecting rod cover in a simple manner Way to be mounted in the valve housing or the tapping element of the switching valve.

According to an advantageous embodiment, the bores can be provided as blind bores, which is advantageous with regard to residual dirt. Furthermore, the press-in process can be simplified in that the press-in process can take place in blocks and no longer has to be monitored with regard to the path.

According to an advantageous embodiment, the bores can have a clearance fit, in which the one or more locking pins can be secured against falling out by reshaping. This enables the locking pins to be secured in a simple manner. Reshaping can take place, for example, by flanging the ends of the locking pins or similar suitable processes.

Brief description of the drawings

Further advantages emerge from the following description of the drawings. Exemplary embodiments of the invention are shown in the drawings. 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 useful further combinations.

It shows as an example:

Fig. 1

a longitudinal section through an example of a connecting rod not according to the invention;

Fig. 2

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

Fig. 3

an example not according to the invention, plan view of the switch valve according to a section planes A-A and B-B drawn in;

Fig. 4

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

Fig. 5

a further longitudinal section through the switching valve in the sectional plane BB according to FIG 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

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

Fig. 9

a further side view of the switching valve according to Fig. 3 with the drawn section plane CC;

Fig. 10

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

Fig. 11

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

Fig. 12

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

Fig. 13

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

Fig. 14

an enlarged detail 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 drawn section plane AA; and

Fig. 17

a longitudinal section through the switch valve in the section plane AA according to Fig. 16 .

Embodiments of the invention

Identical or similar components are numbered with the same reference symbols in the figures. The figures show only examples and are not to be understood as restrictive.

The Figures 2 to 12 show different views and sections of a first example of a switchover valve 11, or of individual parts of the switchover valve 11 of a non-inventive, in Figure 1 connecting rod shown 1.

The in Figure 1 The connecting rod 1 shown has a connecting rod 34, comprising a connecting rod body 29 and a connecting rod cover 30, and an adjustable eccentric adjusting device 6 arranged at least in sections in a connecting rod bearing eye 2 an eccentric 10. The eccentric adjusting device 6 is used to adjust an effective connecting rod length. The distance between a central axis of a pin bearing eye 3 and a central axis of the connecting rod eye 2 is defined as the connecting rod length.

A rotation of the adjustable eccentric adjusting device 6 is initiated by the action of inertia and load forces of the internal combustion engine, which act on the eccentric adjusting device 6 during a working cycle of the internal combustion engine. During a work cycle, the directions of action of the forces acting on the eccentric adjusting device 6 change continuously. The rotary movement or adjustment movement is supported by pistons 4, 5 that are loaded with hydraulic fluid, in particular with engine oil, and are integrated in the connecting rod 1. The pistons 4, 5 prevent the eccentric adjusting device 6 from being reset due to varying directions of force action of the forces acting on the eccentric adjusting device 6.

The pistons 4, 5 are operatively connected to a lever 9 of the eccentric adjusting device 6 on both sides by means of eccentric rods 7, 8. The pistons 4, 5 are arranged displaceably in hydraulic chambers and acted upon by hydraulic fluid via hydraulic fluid lines (not shown) via non-return valves (not shown). The check valves prevent the hydraulic fluid from flowing back from the hydraulic chambers back into the hydraulic fluid lines and enable hydraulic fluid to be sucked into the hydraulic chambers.
The check valves can advantageously be integrated into the switchover valve 11, for example as ball or plate check valves or as band check valves. When designed as a band check valve, for example, a position lock such as a bolt or the like. be provided. The hydraulic fluid lines connected to the hydraulic chambers all or at least partially interact with the switchover valve 11. In a first switching position S1 of the switchover valve 11, which corresponds to a high compression position of the connecting rod 1 (shown in FIG Figure 1 ), the first hydraulic chamber is with a relief line, not shown, and in a second switching position S2 of the switchover valve 11, which corresponds to a low compression position of the connecting rod 1, the second hydraulic chamber is connected to the relief line. The relief line represents the connection to a supply of the connecting rod 1 with hydraulic fluid, for example via a groove in the pin bearing eye 3 of the connecting rod 1.

The switchover 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 device of the connecting rod can be designed with a so-called swivel motor system.

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

As in Figure 2 can be seen, the switching valve 11 is arranged axially in a bore 23 of the connecting rod 1, for example, pressed. In order to mount the switching valve 11 without a seal in the connecting rod 34 or a connecting rod body 29 or connecting rod cover 30, the valve housing 12 of the switching valve 11 can be provided 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 Figure 2 not to be taken, because the locking pin is arranged in a different cutting plane.

To accommodate the securing pin, not shown, the connecting rod 1 has bores 32, which in the second exemplary embodiment are shown in FIG Figure 14 can be seen, while the valve housing 12 has corresponding bores 27 (in Figure 9 shown), in which a locking pin can be provided pressed. The bores 32 of the connecting rod 1 are designed, for example, as through bores for easy production.

In cross section in Figure 2 the valve housing 12 of the changeover valve, which is pressed into the bore 23 of the connecting rod cover 30, with the pick-off element 13 guided in the interior can be seen. The locking pin 18 is arranged in the bores 20, 21 transversely to the axis of the valve housing 12.

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

The switchover valve 11 has a pick-off element 13 which is arranged in a valve housing 12 and which extends in an axial direction L (see FIG Figure 4 ) can be shifted optionally into a first switching position S1 or a second switching position S2 and can be locked in the first or the second switching position S1, S2 by means of a spring-loaded latching element 14. For this purpose, the latching element 14 has a spring element 15 arranged in a latching sleeve 33. In the first switching position S1, a first hydraulic connection 22 of the switchover valve 11 is connected to a relief connection 26 and in the second switching position S2 a second hydraulic connection 24 is connected to the relief connection 26, in particular Figure 4 can be found.

The pick-off element 13 arranged in the valve housing 12 can optionally be locked in the first switch position S1 or the second switch position S2. For this purpose, the latching element 14 and the spring element 15 arranged in the latching element 14 are at least partially arranged in a transverse recess 16 of the pick-off element 13. The valve housing 12 has this in the axial Direction L has an axially delimited first groove 17, in which the latching element 14 to limit the switching path and to prevent rotation of the pick-off element 13 is arranged axially displaceably. 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 switchover valves. The tendency to tilt and self-locking can be reduced and safe reaching of the end positions can be improved by one's own strength. In addition, the spring design of the spring element 15 is not critical because of the greater installation length compared to the prior art.

The latching element 14 also serves as a stop element which limits a displacement path of the pick-up element 13 in the valve housing 12. This means that the stop element can be omitted as an additional component. The latching element 14 is provided axially displaceably together with the tapping element 13. The latching element 14 interacts with a latching pin 18 which is arranged in the valve housing 12 in the area of the first groove 17.

In order to lock the switchover 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, enables two latching positions for the latching element 14. As Figure 4 As can be seen, when the pick-up element 13 is axially displaced, the latching element 14 can latch with its latching contour 19 on both sides of the latching pin 18.

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

As Figure 6 As can be seen, the valve housing 12 has bores 20, 21 in the region of the first groove 17, into which the latching pin 18 is intended to be pressed. The relief connection 26 can also be seen.

The side view in Figure 7 shows the arrangement of the two hydraulic connections 22, 24 while Figure 8 shows the relief connection 26 as an elongated hole.

To receive a locking pin, the connecting rod 1 has bores 32, as in the exemplary embodiment in FIG Figure 14 shown, while the valve housing 12 has corresponding holes 27 (in Figure 9 shown), in which a locking pin can be provided pressed. The bores 32 of the connecting rod 1 are designed, for example, as through bores for easy production.

A hole in the connecting rod 1 could alternatively be designed as a blind hole, whereby residual dirt can advantageously be avoided. Furthermore, the press-in process can be simplified in that the press-in process no longer has to be monitored with regard to the path.

In Figure 9 The locking pin 18 can also be seen through the groove 17.

The Figures 13 to 17 an embodiment of a connecting rod 1 according to the invention can be seen, which differs in that the latching pin 18 also serves as a locking pin. The locking pin 18 as a locking pin is provided as an axial lock for the switchover valve 11 in the connecting rod 1.

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

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

As in particular the enlarged section in Figure 14 As can be seen, the locking pin 18 is pressed through the connecting rod cover 30 and the valve housing 12. For this purpose, a bore 32, preferably a through bore, is provided in the connecting rod cover 30, through which the locking pin 18 can be inserted as a securing element and through bores 20, 21 in the valve housing 12. With a sufficient length of the locking pin 18, the locking pin 18 can 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 press 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 are obtained at this point in the valve housing 12 and tolerances with regard to the concentricity of the bores 32 in the connecting rod cover 30 and the bores 20, 21 in the valve housing 12 can be compensated for.

Alternatively, the bores 32 can also be provided as blind bores. The bores 32 can advantageously have a clearance fit in which the one or more locking pins are secured against falling out by reshaping the ends, for example by flanging.

For assembly, the situation arises that the switchover valve 11 can no longer be preassembled since the latching pin 18 is only pressed in after the valve housing 12 has been pressed in. The locking pin 18 is mounted after the valve housing 12 has been pressed into the bore 23 in the connecting rod cap 30. In the connecting rod cap 30, at least one bore 31 is expediently made through which the locking element 14 can be introduced into the valve housing 12. Alternatively, an elongated slot is conceivable.

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

In the isometric representation in Figure 15 the locking pin 18, which is longer than in the previous exemplary embodiment, can be seen, which crosses the groove 17 of the valve housing 12 and projects beyond the valve housing 12 on both sides. The relief connection 26 can also be seen. The length of the locking pin 18 is also shown in the top view in FIG Figure 16 refer to.

Figure 17 shows in longitudinal section the switchover valve, which essentially corresponds to the illustration of the first example in Figure 4 equals. The difference is that no additional bores 27 are necessary for attaching an additional locking pin, so that the manufacture of the valve housing 12 can be simplified.

Claims (6)

1. Connecting rod (1) for an internal combustion engine with variable compression, having an eccentric adjusting device (6) in the connecting-rod body (29) for the purposes of adjusting an effective connecting-rod length, wherein an adjustment travel of the eccentric adjustment device (6) is adjustable by means of a switchover valve (11), wherein a valve housing (12) of the switchover valve (11) is axially secured in a bore (23) of the connecting rod (1) by means of one or more securing elements, and the switchover valve (11) has a pick-off element (13) which is arranged in the valve housing (12) and which is selectively displaceable into a first switching position (S1) or a second switching position (S2) and is selectively lockable in the first or the second switching position (S1, S2), characterized in that the switchover valve (13) is selectively arrestable in the first or the second switching position (S1, S2) by means of a detent element (14) which is acted on by a spring element, wherein the detent element (14), arranged at least partially arranged in a recess (16) of the pick-off element (13), is displaceable with the pick-off element (13) in an axial direction (L) in an axially delimited groove (17) of the valve housing (12) and interacts with a detent pin (18), wherein the detent pin, as a securing pin, is additionally provided as an axial securing means of the switchover valve (11) .
2. Connecting rod (1) according to Claim 1, wherein the connecting rod (1) and the valve housing (12) have bores (32, 37) into which the securing pin is pressed.
3. Connecting rod (1) according to Claim 1 or 2, wherein the switchover valve (11) is inserted without a seal in the connecting-rod cover (30).
4. Connecting rod (1) according to Claim 1, wherein a bore (31) is provided in the connecting-rod cover (30) for the installation of the detent element (14) into the valve housing (12) of the switchover valve (11) .
5. Connecting rod (1) according to any of Claims 2 to 4, wherein the bores (32) are provided as blind bores.
6. Connecting rod (1) according to any of Claims 2 to 5, wherein the bores (32) have a clearance fit in which the securing pin is secured against falling out by deformation.

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