EP3546722B1 - Connecting rod for a combustion engine with variable compression - Google Patents

Description

Technical area

The invention relates to a connecting rod for an internal combustion engine with variable compression, as well as an internal combustion engine with variable compression with a connecting rod.

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, systems with variable connecting rod lengths are known, for example, which actuate an adjusting device of a connecting rod with the aid of hydraulic switching valves.

A switching valve is, for example, from the DE 10 2012 112 461 A1 refer to. The switching valve is designed as a cartridge solution. This has the advantage that the switching valve is independent of the connecting rod arrangement in which the switching valve is installed, can be checked for leaks. The switching valve is pressed into the connecting rod body.

A connecting rod of the generic type is from DE 10 2015 202 050 A1 known. The switching valve of the connecting rod is axially secured in a bore of the connecting rod by means of a collar and a locking ring.

The registrations DE 10 2010 016 037 A1 , DE 10 2015 202 538 A1 , DE 10 2016 211 999 A1 further configurations of the axial securing of the switching valve can be found.

The WO 2017/162425 A1 describes a check valve for a connecting rod which is screwed into the connecting rod body.

Disclosure of the invention

One object of the invention is to create an improved and cost-effective connecting rod for an internal combustion engine with variable compression which can be reliably produced.

Another object is to provide a variable compression internal combustion engine with such a connecting rod.

The aforementioned objects are achieved according to one aspect of the invention with the features of the independent claims.

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

A connecting rod for an internal combustion engine with variable compression is proposed, with an adjusting device for adjusting an effective connecting rod length, an adjustment path of the adjusting device by means of a Switching valve is adjustable. A valve housing of the changeover valve is provided in a bore of the connecting rod in an axially secured manner with respect to a valve axis of the changeover valve.

The connecting rod comprises a connecting rod body and a connecting rod cover arranged thereon, which enclose a pin bearing eye. At the opposite end of the connecting rod body, for example, a connecting rod bearing eye with the eccentric adjusting device can be arranged. The distance between a central axis of the pin bearing eye and a central axis of the connecting rod eye is defined as the connecting rod length.

For the structural implementation of the hydraulic circuit diagram of a connecting rod for an internal combustion engine with variable compression, it is advantageous to incorporate changeover valves in the connecting rod body. It is common to use interference fits in which valves with a cylindrical outer geometry, for example turned parts, are pressed into bores transversely to a connecting rod center plane. In order to cope with the high loads on the connecting rod, the valves must be positioned in such a way that the bores are exposed to the lowest possible loads, which can lead to oval deformation, but which can occur during engine operation. On the one hand, strong deformations in weak interference fits lead to leakage and reduce the axial holding force of the interference fit so that the valve can exit axially from the bore. On the other hand, an interference fit can only be designed with as much excess as the structural mechanics of the connecting rod and the valve allow due to assembly stresses. Furthermore, the valves can rotate axially if the interference fit is weak and the friction is too low. The orientation of the switching valve in the bore can, however, be of decisive importance for the functioning of the valve if, for example, the tap of the valve is not arranged in the valve axis. This results in a conflict of objectives for the interference fit design: sufficient axial holding force, position fixation and low leakage against impermissibly high assembly tension superimposed by operating voltages.

In order to meet the conflicting requirements, very close Tolerance ranges for the interference fits can be selected. However, with this measure, the production costs increase significantly, so that series production is no longer economical.

The valve housing of the changeover valve is provided axially secured in the bore of the connecting rod body. As a result, the valve housing cannot loosen and move or twist out of its intended position in the connecting rod body.

In this way, the upper limit of the interference fit valve housing in the connecting rod body can be adapted to the maximum permissible assembly stresses and the lower limit can be shifted towards economical production. The risk of an axial displacement or rotation of the changeover valve in the connecting rod during engine operation can advantageously be reduced with the aid of the axial securing of the valve housing in the connecting rod on the end face described here.

A simple axial securing can take place via a weld seam or weld points between the valve housing and the connecting rod body or connecting rod cover. An adhesive or a front-side coating, for example paint, can also be used as a backup.

According to the invention, the connecting rod or the valve housing has one or more axial countersunk bores, the protrusions of which are formed into one or more end-face recesses in the valve housing or the connecting rod to axially secure the switch valve.

One variant uses a countersink hole in the connecting rod and face millings in the valve. The counterbores serve as centering for a forming tool, for example with a hard spherical head that presses the protrusion of the counterbore into the milled recess of the valve in order to secure the valve axially and against rotation. Likewise, a counterbore can be assigned to several milled recesses of different valves. The Axial locking can be selected regardless of the valve position in the connecting rod. Several millings or forming processes can also be set up.

Countersunk bores, which are arranged in the connecting rod sufficiently close to the bore in the connecting rod to accommodate the switching valve, can have a sufficiently thin wall thickness towards the bore as a protrusion so that the material of these protrusions can be displaced towards the bore by mechanical pressure. If the valve housing has frontal recesses at this point, the material of the protrusions can be pushed into these recesses. As a result, there is a toothing between the connecting rod body or connecting rod cover and valve housing. In this way, the valve housing is secured against axial displacement in the bore. If the recesses in the valve housing are not arranged circumferentially, but rather over a limited angular range, then the valve housing and thus the switching valve can also be secured against twisting in the bore.

According to an alternative according to the invention of the connecting rod, the valve housing can have axial countersunk bores, the protrusions of which are formed into one or more end-face recesses of the connecting rod to axially secure the switchover valve. The countersunk bores can also be arranged in the valve and the end millings in the connecting rod body. The axial securing of the valve housing in the bore of the connecting rod can thus be achieved in the same way when the material of the protrusions is displaced.

According to an advantageous embodiment of the connecting rod, the protrusions of the countersunk bores can be pressed into the recesses by means of a forming tool. The material of the protrusions can be pressed into the recesses by the action of a mechanical pressure, such as can be generated, for example, by means of a forming tool. In this way, the desired interlocking between connecting rod body or connecting rod cover and valve housing can be achieved in a suitable manner.

According to an advantageous embodiment of the connecting rod, balls can be pressed into the countersunk bores, whereby the protrusions are pressed into the recesses. A variant of this technical solution is to press a ball into the counterbore. When the ball is pressed into the counterbore, the protrusion is deformed to such an extent that an axial and anti-rotation lock is created, but the ball is also prevented from loosening. As a result, the desired interlocking between the connecting rod body or connecting rod cover and valve housing can be achieved in a suitable manner. In a similar manner, conical or frustoconical bodies could also be pressed into the counterbores in order to achieve the desired effect.

According to an advantageous embodiment of the connecting rod, the recesses can be provided as a bevel running around an outer edge of the valve housing. A simple design of the recesses in the valve housing can be achieved in the form of a bevel running around the outer edge of the valve housing. As a result, the changeover valve can be secured axially in the bore of the connecting rod. If the material of the protrusions is pressed into the bevel and against the valve housing with a suitable pressure, then it can also be used to secure against twisting of the valve housing in the bore.

According to a further aspect of the invention, an internal combustion engine with at least one connecting rod is proposed. In this case, a connecting rod as described above can advantageously be used in order to implement an adjusting device in a favorable manner and to implement an advantageous combustion process and thus fuel consumption in the internal combustion engine.

Brief description of the drawings

Further advantages emerge from the following description of the drawings. An exemplary embodiment of the invention is shown schematically in the drawings.

It shows as an example:

Fig. 1

a side view of a connecting rod according to the invention in a first position with the sectional plane E-E drawn;

Fig. 2

an enlarged section of the connecting rod in the section plane EE according to Fig. 1 ;

Fig. 3

a top view of a in the connecting rod after Figure 1 built-in switch valve with countersunk bores according to an embodiment of the invention with the drawn section plane AA;

Fig. 4

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

Fig. 5

a top view of a in the connecting rod after Figure 1 built-in changeover valve with a shoulder and a locking ring according to an example not according to the invention with the drawn section plane AA;

Fig. 6

a longitudinal section through the switch valve in the section plane AA according to Fig. 5 ;

Fig. 7

an isometric view of a locking ring for a switch valve according to an example not according to the invention;

Fig. 8

a schematic plan view of a in the connecting rod according to Figure 1 built-in switch valve with grain sizes in the valve housing according to a further embodiment;

Fig. 9

a schematic plan view of a in the connecting rod according to Figure 1 built-in changeover valve with grain sizes in the connecting rod cover according to another example not according to the invention and

Fig. 10

a schematic plan view of a in the connecting rod according to Figure 1 built-in switching valve with safety elements according to a further example not according to the invention.

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 1 and 2 show a connecting rod 1 according to the invention for variable compression of an internal combustion engine, wherein Figure 1 a side view of the Connecting rod 1 and Figure 2 shows an enlarged section through the connecting rod cover 10. The connecting rod 1 has a connecting rod body 2 and an adjustable eccentric adjusting device 6 with an eccentric 4, which is arranged at least in sections in a connecting rod bearing eye 3. At the opposite end of the connecting rod body 2 is a Hub bearing eye 5 is arranged, which is closed with the connecting rod cover 10. The eccentric adjusting device 6 is used to adjust an effective connecting rod length. The distance between a central axis of the pin bearing eye 5 and a central axis of the connecting rod eye 3 is defined as the connecting rod length. In principle, different types of adjusting devices for adjusting an effective connecting rod length are also conceivable within the scope of the invention, so that the invention is not limited to this specific embodiment.

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 integrated in the connecting rod 1, acted upon by hydraulic fluid, in particular with engine oil. The pistons prevent resetting of the eccentric adjusting device 6 due to varying directions of force action of the forces acting on the eccentric adjusting device 6.

The pistons are operatively connected to a lever 9 of the eccentric device 6 on both sides by means of eccentric rods 7, 8. The pistons are arranged displaceably in hydraulic chambers and are acted upon by hydraulic fluid via hydraulic fluid lines (not shown) via non-return valves which are not visible. These 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 hydraulic fluid lines connected to the hydraulic chambers all or at least partially interact with a switchover valve 11.

The switching valve 11, which in Figure 2 is shown in an enlarged detail in the sectional plane EE, arranged in a valve housing 12 tapping element 13, which can be shifted in an axial direction optionally in a first switching position or a second switching position can be displaced and optionally locked in the first or the second switching position by means of a spring-loaded latching element.

For the structural implementation of a hydraulic circuit diagram of the connecting rod 1, it is necessary to incorporate a switching valve 11 into the connecting rod body 2 or the connecting rod cover 10. A common possibility is the use of interference fits, in which changeover valves 11 with circular external geometry (turned parts) are pressed into bores 23 transversely to the connecting rod center plane. In order to cope with the high loads on the connecting rod 1, the switchover valves 11 must be positioned in such a way that the bores 23 are exposed to the lowest possible loads that arise during engine operation and can cause oval deformation. On the one hand, strong deformations in weak interference fits lead to leakage and reduce the axial holding force of the interference fit, so that the switchover valve 11 can exit axially from the bore 23. On the other hand, an interference fit can only be designed with as much oversize as the structural mechanics of the connecting rod 1 and the switchover valve 11 allow due to assembly stresses. In addition, the switching valves 11 can rotate axially in the case of weak interference fits and too little friction. The orientation of the switchover valve 11 in the bore 23 can, however, be important if, for example, the gripper is introduced into the switchover valve outside of an axis. This results in a conflict of objectives for the interference fit design, namely sufficient axial holding force, position fixation and low leakage against an inadmissibly high assembly tension superimposed by operating voltages.

In order to meet the conflicting requirements, very narrow tolerance ranges can be selected for the interference fits. However, with this measure, the manufacturing costs increase significantly, which makes them less attractive for series applications.

According to the invention, the valve housing 12 of the switching valve 11 is therefore provided axially secured in a bore 23 of the connecting rod 1.

As in particular in the plan view in Figure 3 and in the corresponding section in Figure 4 As can be seen, the connecting rod 1 or the connecting rod cover 10, according to an exemplary embodiment, can have one or more axial countersunk bores 14, the protrusions 15 of which are directed towards the valve housing 12 and are formed into one or more end-face recesses 16 of the valve housing 12 to axially secure the switch valve 11 will. Alternatively, it is also possible to provide the axial countersunk bores 14 in the valve housing 12 and the recesses 16 in the connecting rod.

The protrusions 15 of the countersunk bores 14 are pressed into the recesses 16 by means of a forming tool. The countersunk bores 14 serve as a centering for the forming tool, for example for a hard ball head, which deforms the protrusions 15 and presses them into the recesses 16, so that the valve housing 12 is axially secured in the bore of the connecting rod 1 and fixed against rotation.

An embodiment not shown provides that balls are pressed into the countersunk bores 14 of the connecting rod 1, whereby the protrusions 15 are pressed into the recesses 16.

In a further embodiment, not shown, the recesses 16 can be provided as a bevel running around an outer edge 30 of the valve housing 12. In this case, too, if the protrusions 15 of the countersunk bores 14 are pressed sufficiently firmly, an axial securing as well as an anti-twist locking of the valve housing 12 in the connecting rod 1 can be achieved.

According to an embodiment not according to the invention, which in the plan view in Figure 5 and in the corresponding section in Figure 6 is shown, the switching valve 11 can have an axial stop in the form of a shoulder 17 on a first end face 20, which on the connecting rod 1 and in the Figures 5 and 6 embodiment shown on the connecting rod cover 10 comes to rest. On a second End face 21, valve housing 12 has an axial protrusion 18, with protrusion 18 being fixed with a locking ring 19 to axially secure changeover valve 11.

The securing ring 19 can, for example, be pressed onto the protrusion 18, welded or fastened by means of a thread. Other fastening options are also conceivable within the scope of the invention. According to an embodiment not shown, the securing ring 19 can engage in a groove in the valve housing 12 and be fixed therein.

The locking ring 19 can, as in the isometric illustration in Figure 7 shown, additionally have a rotation lock 26. For example, retaining tabs 25 which engage in corresponding recesses in the connecting rod 1 are conceivable. The anti-rotation device 26 can have at least one of the locking ring 19 radially include outwardly protruding tab 25 which is fixed to the connecting rod 1, in particular to the connecting rod cover 10. The example not according to the invention in Figure 7 has two mutually opposite, radially outwardly projecting tabs 25. The tabs 25 can engage in corresponding recesses in the connecting rod 1 and thus represent an effective anti-rotation device 26.

Figure 8 shows a schematic plan view of a in the connecting rod 1 according to Figure 1 built-in switching valve 11 with grain sizes 22 on one end face 20, 21 of the valve housing 12 according to a further example not according to the invention. Through the grain sizes 22, material of the valve housing 12 is displaced into a bore gap 27 between the valve housing 12 and the connecting rod 1 by means of a forming tool in order to axially secure the switching valve 11. The arrow directions 24 in Figure 8 show the deformation directions of the displaced material. The material is displaced radially outward from the grain size 22 into the bore gap 27, whereby the valve housing 12 is effectively fixed in the bore gap 27 of the connecting rod cover 10 and is thus both axially secured and secured against rotation. The end faces 20, 21 of the valve housing 12 end with the end faces 28, 29 of the connecting rod cover 10.

In Figure 9 is shown as an alternative example not according to the invention, a switch valve 11 with grain sizes 22 in the connecting rod cover 10. In this case, the material of the connecting rod cover 10 is shifted radially inward into the bore gap 27 in order to axially secure the switchover valve 11 in accordance with the deformation direction 24 shown.

Another possibility, not according to the invention, is to use a securing element 31, for example a feather key, a cone, or a wedge, which can be designed as a DIN standard part, for example, and which is driven at the end between the valve housing 12 and the bore. This can also be welded, glued or joined in a similar way.

Figure 10 shows in a schematic plan view a in the connecting rod 1 according to Figure 1 built-in switching valve 11 with such securing elements 31 according to a further example not according to the invention. In this example there is at least one, in Figure 10 three securing elements 31 for axially securing the switchover valve 11 in the bore gap 27 between the valve housing 12 and the connecting rod 1.

Claims (5)

1. Connecting rod (1) for an internal combustion engine with variable compression, having an adjusting device (6) for adjusting an effective connecting-rod length, wherein an adjustment travel of the adjusting device (6) is adjustable by means of a switching valve (11), wherein a valve housing (12) of the switching valve (11) is provided in a bore (23) of the connecting rod (1) so as to be axially secured in relation to a valve axis of the switching valve (11),
   characterized in that the connecting rod (1) or the valve housing (12) respectively has one or more axial countersink bores (14), the protrusions (15) of which are, for the purposes of axially securing the switching valve (11), deformed into one or more end-side recesses (16) of the valve housing (12) or of the connecting rod (1) respectively.
2. Connecting rod according to Claim 1, characterized in that the protrusions (15) of the countersink bores (14) are pressed into the recesses (16) by means of a deforming tool.
3. Connecting rod according to Claim 1, characterized in that balls are pressed into the countersink bores (14), whereby the protrusions (15) are pressed into the recesses (16).
4. Connecting rod according to any of the preceding claims, characterized in that the recesses (16) are provided as bevels running in encircling fashion on an outer edge (30) of the valve housing (12).
5. Internal combustion engine having at least one connecting rod (1) according to any of the preceding claims.

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