AT522503B1 - Length-adjustable connecting rod with multi-part control slide - Google Patents

Abstract

The present invention relates to a length-adjustable connecting rod (1) for a piston engine, the connecting rod (1) having a hydraulic control device (21) for adjusting the effective length of the length-adjustable connecting rod (1) and the hydraulic control device (21) having a hydraulic control valve (34) with a control cylinder (36), a control slide (35) and at least one drain valve (41, 42) which can be actuated by the control slide (35), the control slide (35) having a hydraulic control pressure which is guided in the control cylinder (36) and can be subjected to a hydraulic control pressure Control piston (37) and a slide tappet (39), the control slide (35) having two control slide parts (35a, 35b) which can be manufactured separately and are fixedly joined together when the control slide (35) is used as intended, a first control slide part (35a) being arranged on the end face Control piston (37) followed by a first slide tappet portion (39a) and adjoining this is a second control slide part (35b) with a second slide tappet section (39b), the second control slide part (35b) having at least one switching contour (54) which is rotationally symmetrical to the control slide axis (AS) and with which the at least one discharge valve (41, 42) is actuated. The invention also relates to such a control slide (35) for the hydraulic control valve (34) of a length-adjustable connecting rod (1), as well as a piston motor with a length-adjustable connecting rod (1).

Description

description

LENGTH ADJUSTABLE CONNECTING ROD WITH MULTI-PIECE CONTROL VALVE

The present invention relates to an adjustable-length connecting rod for a piston engine, the connecting rod having a hydraulic control device for adjusting the effective length of the adjustable-length connecting rod and the control device having a hydraulic control valve with a control cylinder, a control slide and at least one drain valve actuated by the control slide, wherein the control slide comprises a control piston, which can be displaced in the control cylinder and can be acted upon by a hydraulic control pressure, and a slide tappet, the control slide having two control slide parts that can be manufactured separately and are firmly joined together when the control slide is used as intended. The invention further relates to a control slide for the hydraulic control valve of a length-adjustable connecting rod and a piston motor with a length-adjustable connecting rod.

In internal combustion engines with reciprocating pistons, there are efforts to change the compression ratio during operation and to adapt it to the respective operating state of the engine in order to improve the thermal efficiency of the internal combustion engine. The thermal efficiency increases as the compression ratio rises, but an excessively high compression ratio can lead to unintended auto-ignition of the piston engine. Such an early combustion of the fuel not only leads to uneven running and the so-called knocking of the engine, but can also lead to component damage on the engine. In the partial load range, the risk of self-ignition is lower, so that a higher compression ratio is possible.

To realize a variable compression ratio ("variable compression ratio" - VCR) there are different solutions with which the position of the crank pin of the crankshaft or the piston pin of the reciprocating piston is changed or the effective length of the connecting rod is varied. There are solutions for continuous and discontinuous adjustment of the components. A continuous length adjustment of the distance between the piston pin and the crankshaft journal enables the compression ratio to be adjusted smoothly to the respective operating point and thus an optimal efficiency of the internal combustion engine. On the other hand, a discontinuous adjustment of the connecting rod length with a few steps results in structural and operational advantages; in comparison to a conventional piston engine, a significant improvement in efficiency and corresponding savings in consumption and pollutant emissions are nevertheless made possible.

A discontinuous adjustment of the compression ratio for a piston engine is described in EP 1 426 584 A1, in which an eccentric connected to the piston pin of the reciprocating piston enables the compression ratio to be adjusted, the eccentric being fixed in the respective end positions of the pivoting range by means of a mechanical lock he follows. In contrast, DE 10 2005 055 199 A1 discloses a length-adjustable connecting rod with which different compression ratios can be achieved, the eccentric being fixed in its position by two cylinder-piston units and the hydraulic pressure difference of the supplied engine oil.

WO 2015/055582 A-2 shows a length-adjustable connecting rod with connecting rod parts that can be telescoped into one another, the adjusting piston provided on the first connecting rod part dividing the cylinder of the second connecting rod part into two pressure chambers. The two pressure chambers of this cylinder-piston unit are supplied with engine oil via check valves, with engine oil under pressure in only one pressure chamber. If the length-adjustable connecting rod is in the long position, there is no engine oil in the upper pressure chamber, while the lower pressure chamber is completely filled with engine oil. During operation, a tensile force is then absorbed by the mechanical contact with the upper stop of the adjusting piston. A compressive force is exerted over the piston surface on the engine oil-filled

transfer lower pressure chamber. Since the check valve in this chamber prevents the return of the engine oil, the pressure of the engine oil rises, so that the connecting rod is hydraulically blocked in this direction. In the short position of the length-adjustable connecting rod, the situation in the cylinder-piston unit is reversed. The lower pressure chamber is empty, while the upper pressure chamber is filled with engine oil. Correspondingly, a tensile force causes a pressure increase in the upper chamber and a hydraulic locking of the length-adjustable connecting rod, while a pressure force is absorbed by the mechanical stop of the adjusting piston.

The connecting rod length of this length-adjustable connecting rod can be adjusted in two stages, one of the two pressure chambers being emptied by bridging the associated check valve in the inlet channel via a corresponding return channel. Engine oil flows through these return channels between the pressure chamber and the engine oil supply, whereby the respective check valve loses its effect. The two return channels are opened and closed by a hydraulic control device, with a maximum of one return channel always being open and the other being closed. The actuator for switching the two return ducts is controlled hydraulically by the supply pressure of the engine oil, which is supplied via corresponding hydraulic fluid ducts in the connecting rod and the bearing of the crankshaft journal in the second connecting rod part. The connecting rod length is then actively adjusted by deliberately emptying the pressure chamber filled with engine oil using the gas and inertia forces acting on the connecting rod, the other pressure chamber being simultaneously supplied with engine oil via the associated check valve and hydraulically blocked.

Another length-adjustable connecting rod is known, for example, from WO 2016/203047 A1. To adjust the effective length of the connecting rod, a control slide with a centrally arranged control piston is used there, which is pretensioned in one direction by a control slide spring. The control slide comprises a control piston that can be acted upon by a hydraulic control pressure and a slide rod that is fixedly connected to the control piston and protrudes on both sides and has a conical control tip at the respective ends in order to open the associated drainage valves.

WO 2018/060457 A1 shows another such length-adjustable connecting rod in which a first valve can be adjusted along a first adjusting axis and a second valve can be adjusted along a second adjusting axis, the adjusting axes being different from one another.

When used in a piston engine, a length-adjustable connecting rod is naturally exposed to very high acceleration forces, which must also be taken into account in the design of the hydraulic control device. Correspondingly, the hydraulic control valves are designed and manufactured for the respective application of the length-adjustable connecting rod and the respective performance of the piston engine in order to achieve a reliable setting of the effective length of the length-adjustable connecting rod.

In the development of modern piston engines, in addition to the safe functionality of the individual components, there is also the requirement to achieve a significant improvement in efficiency and corresponding savings in consumption and pollutant emissions. At the same time, inexpensive production of the components and the assembly of the piston engine must also be ensured. The installation space for such connecting rods in modern piston engines is limited both axially in the longitudinal direction of the connecting rod and radially, which must be taken into account when designing the hydraulic control device and in particular when designing the hydraulic control valve.

It is therefore the object of the present invention to optimize a length-adjustable connecting rod of the type mentioned in such a way that the hydraulic control valve can be produced safely and inexpensively and can be used in a simple manner in a generic length-adjustable connecting rod.

This object is achieved according to the invention in that a first control slide part surrounds the control piston arranged at the end, followed by a first slide tappet section.

and a second control slide part adjoins it with a second slide tappet section, the second control slide part having at least one switching contour that is rotationally symmetrical to the control slide axis and with which the at least one discharge valve can be actuated.

In conventional length-adjustable connecting rods, control slides made of titanium or ceramic materials are used in the hydraulic control valves, which are often not constructed to be rotationally symmetrical. Both the production and the assembly of such control slides in the hydraulic control valve of conventional length-adjustable connecting rods are correspondingly complex and expensive. Such control slides have a relatively thin slide tappet with corresponding switching contours and a control piston with a significantly larger diameter, on which the control pressure of the hydraulic medium and a restoring force act.

With regard to the necessary tolerances for a reliable function of the hydraulic control valve and the large differences in diameter, such control slides are made in one piece for conventional length-adjustable connecting rods. In an embodiment of the control slide according to the invention, the provision of second control slide parts enables significantly simpler and more cost-effective manufacture without negatively affecting the function of the control slide or its displaceable guide in the control cylinder. By manufacturing the control slide parts as separate components, they can be used in different combinations for different engine types and thus manufactured in larger numbers. Furthermore, due to their separate production, the machining volume is significantly reduced, which means that the consumption of expensive raw materials is reduced. By providing the rotationally symmetrical switching contour, simple actuation of the drain valve or drain valves can be ensured.

The first control slide part and / or the second control slide part are advantageously designed to be rotationally symmetrical. This enables quick and easy production.

It is advantageous if the control slide parts are made of different materials, preferably the first control slide part consists at least predominantly of a material that has a lower density than the material from which the second control slide part is at least predominantly made. In this way, production can be further optimized and the control slide can be designed to suit the function.

The control slide parts are favorably connected to one another via a force-fit and / or a form-fit connection. This means that the control slide parts can be non-positively connected, e.g. screwed or pressed together, and alternatively or additionally a positive connection, e.g. gluing, welding or some other connection can be provided. These types of connection are established and can be carried out quickly and have a high level of durability.

In a variant, the control piston is arranged at one end of the first control slide part and a stop flange is arranged at the opposite end of the first control slide part, preferably at the end of the first slide tappet section, in the direction of the control slide axis. If the control slide is used to operate two drain valves, the stop flange can be used to define one of the switching positions.

Advantageously, an additional constricting annular groove can further be provided between the stop flange and the control piston. As a result, this area between the switching contour of the slide tappet and the control piston can also be mass-optimized. Such a construction of the control slide enables simple assembly in a correspondingly shaped bore in the assembled state of the control slide, without the use of receiving bushings or intermediate pieces. Only the control pressure space formed by the control piston has to be sealed by a corresponding closure, which at the same time can also form a stop for the control piston. In order to further reduce the weight of the control slide, a longitudinal bore running parallel to the control slide axis is expediently made within the first control slide part, which is at least part of the front.

preferably extends over the entire length of the first control slide part. The longitudinal bore is preferably designed to run from the end of the first control slide part opposite the control piston in the direction of the control piston, either as a blind hole or as a through bore.

In addition to the weight reduction, the connection of the control slide parts can also be facilitated: In one variant, the second control slide part has a connection area that can be inserted into the longitudinal bore for joining or connecting the control slide parts, and preferably can be firmly positioned in this. For example, the interior of the longitudinal bore can be provided with an internal thread and the connection area is designed as a corresponding external thread, so that a quick and easy connection is possible. Alternatively, the connection area can also be fixed in the longitudinal bore using a press fit.

In a variant, the control cylinder has a low-pressure section with a first diameter and a high-pressure section with a second diameter, the first diameter preferably being greater than the second diameter. As a result, the actuation of the control slide can be separated from the medium flowing through the drain valves or the two areas can be provided with different pressures. For example, the low-pressure section can be set up for pressures from 1 to 20 bar, while the high-pressure section is suitable for pressures from 100 to 5000 bar.

In order to prevent media from crossing between the pressure areas, the second control slide part favorably at its end facing the first control slide part has a sealing section which, when the control slide is used as intended, partially penetrates the low-pressure section but does not completely leave the high-pressure section at any time during use . In particular, the sealing section can have a diameter corresponding to the diameter of the high pressure area, so that a sealing effect is achieved.

Another variant provides that the slide tappet section and / or the second slide tappet section is designed as a mass-optimized slide tappet section, the mass of the slide tappet section being reduced due to the choice of material for the slide tappet section or due to a contour of the second slide tappet section provided with at least one constriction corresponds to a maximum of 0.93 times, preferably a maximum of 0.85 times, the envelope volume of the contour of the second slide tappet section multiplied by the density of steel (7.85 g / mm®). In order to implement a special control slide design with a suitable control piston for as large a number of different engine types as possible, in accordance with the common parts concept common in the automotive sector, the control slide can be such a mass-optimized control slide. Either light materials and / or material removed in the area of the slide tappet sections can be used to reduce the mass of the control slide. The envelope volume of the switching contours is to be understood as the volume of the switching contour of the slide tappet based on the length of the switching contour and the largest cross section of the switching contour. Compared to this theoretical mass of the envelope volume of the switching contour, corresponding incisions, grooves and depressions in the area of the switching contour and the shaft reduce its actual mass. By reducing the mass of the slide valve, the mass forces acting on the control slide, which are essentially independent of the speed of the internal combustion engine and the specific arrangement of the control slide in the connecting rod, can be reduced.

A useful embodiment provides that the control slide is arranged inclined to the longitudinal direction of the connecting rod and / or inclined to the normal to the longitudinal direction of the connecting rod, preferably at an angle between 15 ° and 75 °. The inclined arrangement of the control slide relative to the longitudinal direction of the connecting rod and / or relative to the normal to the longitudinal direction of the connecting rod can further reduce the negative effects of the inertia of the hydraulic medium in the hydraulic medium channels and in the components of the hydraulic control device if the angle is favorable. Both malfunctions and malfunctions occur

the activation of the control device as well as disruptive influences on the other components of the hydraulic control device can be minimized by the inclined arrangement of the control slide.

A preferred embodiment provides that the hydraulic control device has a return spring to hold the control slide in a first starting position or to return it to the first starting position, wherein the return spring is preferably arranged at least around the first slide tappet portion and is attached to the control piston supports. The return spring makes it possible to provide two different switching positions in the hydraulic control valve without providing an active return mechanism, additional pressure chambers or supply lines. As a result, the manufacturing costs can be kept low, with a simultaneous increase in functional reliability. Furthermore, such a return spring can be easily adapted to different control pressures or applications of the control valve without having to change the entire construction of the hydraulic control device or even the length-adjustable connecting rod. In this case, an arrangement of the return spring around the control slide reduces the installation space required for the control valve and, at the same time, also the manufacturing costs.

An advantageous embodiment provides that at least two drain valves which can be actuated by the control slide are provided, the at least two drain valves preferably being actuatable alternately. Depending on the position of the control slide, a maximum of one of the two drain valves is open so that hydraulic fluid can escape either from the first pressure chamber or the second pressure chamber of the control device, in particular a double-acting cylinder-piston unit of the length-adjustable connecting rod. Meanwhile, the other pressure chamber can be filled with hydraulic fluid at the same time, due to the gas and inertia forces acting in the piston engine during the stroke movement of the connecting rod, which cause the non-return valve assigned to the other pressure chamber to open by means of the resulting suction. With increasing filling of this pressure chamber, hydraulic medium is discharged from the open pressure chamber, so to speak, whereby the effective length of the length-adjustable connecting rod changes. Depending on the configuration of the hydraulic control device and depending on the operating state of the piston engine, several strokes of the connecting rod may be necessary until the change in length of the connecting rod is complete. The drain valves advantageously have spring-loaded valve bodies, preferably valve balls, which are moved against the spring tension in the direction of the stroke axis of the valve body via a suitable transmission element, for example transmission pins or transmission balls, in order to open the drain valve.

For a reliable function and a simple structure of the drain valves, the at least two drain valves can be arranged inclined to the control slide axis, preferably perpendicular to the control slide axis. The arrangement of the drain valves relates to the opening direction of the valve bodies in the drain valves. This inclined arrangement of the discharge valves enables, in addition to a simple construction of the hydraulic control valve, overall small dimensions of the connecting rod with a corresponding reduction in mass.

An embodiment of the length-adjustable connecting rod provides that at least two connecting rod parts are provided, the first connecting rod part having the first connecting rod eye and the second connecting rod part having the second connecting rod eye, and the first connecting rod part being movable relative to the second connecting rod part in the longitudinal direction of the connecting rod, is preferably telescopic to adjust the distance between the piston pin and the crankshaft journal. In contrast to connecting rods with eccentrics, two connecting rod parts that can be moved relative to one another in the longitudinal direction of the connecting rod enable a stable structure as well as safe and permanent operation of the length-adjustable connecting rod.

At least one cylinder-piston unit hydraulically connected to the hydraulic control device can be provided to move the first connecting rod part relative to the second connecting rod part, the first connecting rod part being connected to an adjusting piston of the cylinder-piston unit and the second Connecting rod part on a cylinder bore of the cylinder-piston unit

shows. In addition to a very robust construction of the length-adjustable connecting rod, this also enables simple and inexpensive connecting rod parts, the adjusting piston of the first connecting rod part preferably being connected directly to the piston rod and the connecting rod head to the first connecting rod eye and the second connecting rod part having a housing in which, in addition to the cylinder bore, also the hydraulic control device is provided.

Furthermore, the invention relates to a built control slide for a length-adjustable connecting rod according to the above-described embodiments with a first control slide part with a control piston, which can be displaced in a control cylinder and can be acted upon by a hydraulic control pressure, and a first slide tappet section of a slide tappet, as well with a separately manufactured second control slide part with a second slide tappet section of a slide tappet. In accordance with the general concept of identical parts, such a control slide enables the use of different control slide parts produced in large numbers. At the same time, a number of different motor types can be supplied with a specifically adapted control slide at low manufacturing costs by means of a corresponding adaptation of the mass of the individual control slide parts by means of the concept of the same slide tappets.

In a further aspect, the invention relates to a piston engine with at least one engine cylinder, a reciprocating piston moving in the engine cylinder and at least one adjustable compression ratio in the engine cylinder, as well as with at least one adjustable length connected to the reciprocating piston Connecting rod according to the embodiments described above. Preferably, all of the reciprocating pistons of the piston engine are equipped with such a length-adjustable connecting rod and the control device of the length-adjustable connecting rod is connected to the engine oil hydraulics of the piston engine. The fuel savings of such a piston engine can be considerable if the compression ratio is set accordingly as a function of the respective operating state. A cost-effective and robust control of the length-adjustable connecting rod is made possible by means of the hydraulic control device and the control slide with separately manufactured control slide parts.

In the following, non-limiting embodiments of the invention are explained in more detail with reference to exemplary drawings. Show it:

1 shows a top view of a length-adjustable connecting rod according to the invention,

FIG. 2 shows a schematic view of the partially cut-open length-adjustable connecting rod from FIG. 1,

3 shows a schematic view of the length-adjustable connecting rod from FIG. 1 with a schematic representation of the hydraulic control valve,

4 shows an enlarged sectional view of the length-adjustable connecting rod

from Fig. 1 along the line IV,

[0037] FIG. 3 a shows a perspective illustration of a control slide in the assembled state;

[0038] FIGS. 5b and 5c show a second control slide part and a first control slide part in the separated state; and

6 shows a sectional view of the control slide from FIG. 5a along a control slide axis.

The length-adjustable connecting rod 1 shown in Fig. 1 comprises two telescopic mutually movable connecting rod parts 2, 3. The lower connecting rod part 2 arranged at the bottom in the illustration of the length-adjustable connecting rod 1 in FIG. 1 has a large connecting rod eye 4 with which the length-adjustable Connecting rod 1 is mounted on the crankshaft (not shown) of the piston engine. For this purpose, a bearing shell 5 is further arranged on the lower connecting rod part 2, which together

men with the also bearing shell-like lower area of the lower connecting rod 2 forms the large connecting rod eye 4. The bearing shell 5 and the lower connecting rod part 2 are connected to one another by means of connecting rod bolts 43. The upper connecting rod part 3 has a connecting rod head 6 with a small connecting rod eye 7 which receives the piston pin (not shown) of the reciprocating piston in the piston engine.

As can be clearly seen in FIG. 2, the connecting rod head 6 is connected to a piston rod 8 and, via the piston rod 8, to an adjusting piston 9 of an adjusting device of the length-adjustable connecting rod 1, designed here as a cylinder-piston unit 10. In the illustrated embodiment, the connecting rod head 6 is screwed or welded to the piston rod 8, while the adjusting piston 9 and the piston rod 8 are formed in one piece. This enables a cylinder cover 15 of the cylinder-piston unit 10, a rod seal 16 on the piston rod 8 and piston seals 17, 18 on the adjusting piston 9 to be arranged easily and without damage before the upper connecting rod part 3 is assembled. In an exemplary embodiment (not shown), the piston rod 8 and the connecting rod head 6 are made in one piece, while the adjusting piston 9 is screwed onto the piston rod 8.

The upper connecting rod 3 is telescopically guided via the adjusting piston 9 in the lower connecting rod 2 in order to adjust the distance between the piston pin of the reciprocating piston received in the small connecting rod eye 7 and the crankshaft of the piston engine received in the large connecting rod eye 4, thus adjusting the compression ratio of the piston engine to the respective operating condition. This makes it possible to operate the piston engine in the partial load range with a higher compression ratio than under full load and thus to increase the efficiency of the engine.

In the housing 11 formed by the lower connecting rod part 2, a cylinder 12 is formed in the upper region as a cylinder bore or cylinder sleeve of the lower connecting rod part 2. The adjusting piston 9 of the upper connecting rod part 3 is arranged in the cylinder 12 so as to be movable in the longitudinal direction A of the connecting rod 1 in order to form the cylinder-piston unit 10 together with the cylinder 12 and the cylinder cover 15. The adjusting piston 9 is shown in a central position in FIG. 2, in which the adjusting piston 9 divides the cylinder 12 into two pressure chambers 13 and 14. The piston rod 8 extends from the adjusting piston 9 through the upper pressure chamber 14 and through the cylinder cover 15, which delimits the housing 11 and the cylinder 12 towards the top. The rod seal 16 is provided on the cylinder cover 15 and is held by a locking ring 19 at the transition between the piston rod 8 and the cylinder cover 15. The rod seal 16 surrounds the piston rod 8 and seals the upper pressure chamber 14 from the environment. The two piston seals 17, 18 arranged on the adjusting piston 9 seal the adjusting piston 9 from the cylinder 12 and thus also the pressure chambers 13, 14 from one another. The locking ring 19 together with the cylinder cover 15 forms an upper stop against which the adjusting piston 9 rests in the upper position, the long position of the length-adjustable connecting rod 1, while in the lower position (short position) of the length-adjustable connecting rod 1, the adjusting piston 9 rests the lower stop formed by the cylinder base 20 rests.

In the following, the hydraulic interconnection of a control device 21 for supplying the adjustment device formed by the cylinder-piston unit 10 is explained in more detail with reference to FIG. The two pressure chambers 13, 14 are each connected to the engine oil circuit of the piston engine via separate hydraulic medium lines 22, 23 and separate check valves 24, 25 and a common oil supply channel 26 which opens into the large connecting rod eye 4. If the length-adjustable connecting rod 1 is in the long position, there is no engine oil in the upper pressure chamber 14, while the lower pressure chamber 13, on the other hand, is completely filled with engine oil. During operation, the connecting rod 1 is alternately subjected to tension and compression due to the inertia and gas forces.

In the long position, the tensile force is absorbed by the mechanical contact of the adjusting piston 9 with the locking ring 19, the length of the connecting rod 1 not changing any further. An applied compressive force is applied to the engine oil via the piston surface

Filled lower pressure chamber 13 transferred. Since the check valve 25 assigned to the lower pressure chamber 13 prevents the engine oil from flowing out, the pressure of the engine oil rises sharply and prevents the connecting rod length from changing, as a result of which the length-adjustable connecting rod 1 is hydraulically locked in this direction of movement.

In the short version of the length-adjustable connecting rod 1, the situation is reversed. The lower pressure chamber 13 is empty and a compressive force is absorbed by the mechanical stop of the adjusting piston 9 on the cylinder base 20 (see FIG. 2), while the upper pressure chamber 14 is filled with engine oil, so that a tensile force on the length-adjustable connecting rod 1 causes a pressure increase in the causes upper pressure chamber 14 and a hydraulic lock.

The connecting rod length of the length-adjustable connecting rod 1 shown here can be adjusted in two stages by emptying one of the two pressure chambers 13, 14 and filling the other pressure chamber 13, 14 with engine oil. For this purpose, one of the check valves 24, 25 is bridged in the hydraulic control device 21 so that the engine oil can flow out of the previously filled pressure chamber 13, 14. The respective check valve 24, 25 thus loses its effect. For this purpose, the hydraulic control device 21 comprises a 3/2-way valve 27, the two switchable connections 30 of which are each connected via a throttle 28, 29 to a hydraulic medium line 22, 23 of the pressure chambers 13, 14. A first connection 30 is assigned to the lower pressure chamber 13 and a second connection 30 is assigned to the upper pressure chamber 14.

The 3/2-way valve 27 is actuated via the pressure of the engine oil which is supplied to the 3/2-way valve 27 via a control pressure line 31 connected to the oil supply channel 26. The 3/2-way valve 27 is reset by a return spring 32. The two switchable connections 30 of the 3/2-way valve 27 are connected to an outflow channel 33 which releases the engine oil discharged from the pressure chambers 13, 14 to the oil supply channel 26, from where it is available for filling the respective other pressure chamber 14, 13 or can be delivered to the engine oil circuit of the piston engine and / or the environment via the large connecting rod eye 4.

In a variant not shown, the outflow channel 33 can also lead directly into the vicinity of the connecting rod 1, wherein a throttle and / or a check valve opening in the direction of the environment can be arranged in front of the exit into the environment. In the preferred position of the 3/2-way valve 27 shown in FIG. 3, the upper pressure chamber 14 is open.

In the 3/2-way valve 27, one of the switchable connections 30 is open, so that the associated pressure chamber 13, 14 is emptied, while the other connection 30 is closed. When the switching position of the 3/2-way valve 27 changes, when a higher control pressure is applied via the control pressure line 31 or when the control pressure is reset via the return spring 32, the previously open port 30 is closed and the previously closed port 30 is opened . As a result, the engine oil, which was previously filled with engine oil, flows from the pressure chamber 13, 14, which was previously filled with engine oil, via the respective hydraulic medium line 22, 23 and the associated throttle 28, 29 through the open connection 30 of the 3/2-way valve 27 and the outflow channel 33 into the Oil supply channel 26.

At the same time, the mass and gas forces acting during the stroke movement of the connecting rod 1 in the previously empty pressure chamber 14, 13 create a suction effect through which the associated check valve 24, 25 opens, so that the previously empty pressure chamber 14, 13 opens fills with engine oil. With increasing filling of this pressure chamber 14, 13, the engine oil is increasingly discharged from the other pressure chamber 13, 14 via the opened connection 30, as a result of which the length of the connecting rod 1 changes. Depending on the configuration of the length-adjustable connecting rod 1 and the hydraulic control device 21 and the operating state of the piston engine, several strokes of the connecting rod 1 may be required until the pressure chamber 14, 13 blocked by the hydraulic control device 21 is completely filled with engine oil and the other open pressure chamber 13, 14 is completely emptied and so the maximum possible change in length of the connecting rod 1 is reached.

2 shows a hydraulic control valve 34 as an embodiment of the described 3/2-way valve 27, the control valve 34 being designed as a slide valve with a control cylinder 36 and a mushroom-shaped control slide 35 slidably arranged in the control cylinder 36.

The control slide 35 has a control piston 37 which is arranged on the front side and which, together with the control cylinder 36, forms a control pressure chamber 38 arranged on the front side of the control slide 35. The control cylinder 36 is designed as a stepped bore inclined with respect to the longitudinal axis A of the connecting rod 1 and also with respect to the normal to the longitudinal axis A of the connecting rod 1 in the housing 11 of the lower connecting rod part 2. At the open end of the control cylinder 36, a closure cap 46 is provided which seals the control pressure chamber 38 from the environment. The control pressure chamber 38 is supplied with a hydraulic medium under control pressure from the oil supply channel 26 (see FIG. 3) via the control pressure line 31. On the back of the front control piston 37 facing away from the control pressure chamber 38, a slide tappet 39 extends into the lower end of the control cylinder 36 designed as a high pressure chamber 45, which is why a contacting or contactless seal is provided between the front control piston 37 and the control cylinder 36. As can also be seen in FIG. 4, on an upper section of the slide tappet 39 facing the control piston 37, the return spring 32 is arranged around the slide tappet 39, while a switching contour 54 is formed at the lower end of the slide tappet 39 for opening and closing the drain valves 41, 42 is to lift the respective valve body 49 from the valve seat 50 of the first and second drain valve 41, 42 evenly with the least possible effort and to open the respective drain valve 41, 42.

In the following, the structure and the function of the hydraulic control valve 34 for a connecting rod 1 according to the invention will be explained in more detail with reference to FIGS. 4 and 5a, 5b, 5c and 6.

4 shows an enlarged sectional view of the hydraulic control valve 34 along the section line IV shown in FIGS. 1 and 2. Here, a two-part control slide 35 with a slide tappet 39 is shown with a first control slide part 35a and one in the longitudinal direction along the control slide axis A : adjoining second control slide part 35b. The head of this mushroom-shaped control slide 35 on the side of the first control slide part 35a is designed as a cup-shaped control piston 37, followed by a first slide tappet section 39a. This is followed by the second control slide part 35b with the second slide tappet section 39b. The control slide axis As is essentially normal to the axis A «of the crankshaft (not shown). The two control slide parts 35a, 35b can be manufactured separately but, when used as intended, are firmly joined together as shown.

The first slide tappet section 39a of the first control slide part 35a has a section with a larger diameter in the upper region, around which the return spring 32 is arranged.

In the lower region of the second slide tappet section 39b, the switching contour 54 is also provided, which, in addition to guiding the control slide 35, also engages the two drain valves 41, 42 in order to open the associated pressure chambers 13, 14 alternately from the closed state . Both drain valves 41 and 42 have the same structure, which is why the associated elements will only be described with reference to the first drain valve 41. The drain valve 41 comprises a screw plug 47 which is screwed into a corresponding receiving opening provided with a thread in the housing 11 of the lower connecting rod part 2. A valve spring 48, which acts on the spherical valve body 49, is arranged in the screw plug 47. The spherical valve body 49 interacts with a conical valve seat 50 which opens into a valve opening 51. A likewise spherical closing body 52 is arranged in the valve opening 51. The first drain valve 41 is shown in FIG. 4 in the closed position and the second drain valve 42 in the open position. Between the second slide tappet section 39b of the control slide 35 and the control cylinder 36, the valve

pressure chamber 45, via which the hydraulic medium flowing out of the upper pressure chamber 14 via the opened second drain valve 42 is discharged to the oil supply channel 26, among other things in order to provide the outflowing engine oil directly for filling the lower pressure chamber 13.

According to the function, the control cylinder 36 has two areas: the low-pressure section 36a is located on the side of the control pressure chamber 38 and the high-pressure section 36B is located in the high-pressure chamber 45, where the oil is supplied from the pressure chambers 13, 14.

The two sections 36a, 36b have different diameters: The low-pressure section 36a has a first diameter D1 which is greater than the second diameter D2 of the high-pressure section 36b.

Sections 36a, 36b are sealed against one another in that the second control slide part 35b has a sealing section 58 at its end facing the first control slide part 35a, which when the control slide 35 is used as intended partially penetrates into the low-pressure section 36a, but the high-pressure section 36b at no point completely leaves the use. The diameter of the second control slide part 35b in the area of the sealing section 58 corresponds essentially to the second diameter D2, so that a sealing effect is achieved.

The discharge valves 41 and 42 are actuated by means of the control slide 35. The control slide 35 is hydraulically connected to the engine oil circuit via the control pressure line 31. An increase in the control pressure in the engine oil circuit acts on the front side on the control pressure surface 40 of the control piston 37. As a result, the control piston 37 is moved against the action of the return spring 32 in the direction of the valve pressure chamber 45. The slide tappet 39 has a flange 56 in the area of the first slide tappet section 39a, which defines the second position.

To delimit the control pressure chamber 38 defined by the control piston 37, a closure cap 46 is provided. In the area of the second slide tappet section 39b, the control slide 35 has switching contours 54 with two cross-sectionally diamond-shaped elevations (section plane parallel to the control slide axis As), which each act on the associated closing body 52, which then moves the associated valve body 49. In the position of the control slide 35 shown in FIG. 4, there is sufficient play between the slide valve 39, or the switching contour 54 and the closing body 52 of the first drain valve 41, so that the valve body 49 is securely seated on the valve seat 50. The closing body 52 assigned in the second drain valve 42 has a raised position in the position of the control slide 35 shown in FIG. 4. The closing body 52 thus acts on the valve body 49 of the second drain valve 42 and lifts the valve body 49 and the associated valve spring 48 out of the valve seat 50. The second drain valve 42 is thereby opened. Accordingly, the engine oil can flow out of the upper pressure chamber 14, while the lower pressure chamber 13 is blocked.

If the control slide 35 moves due to the increasing control pressure of the engine oil in the control pressure chamber 38 in the direction of the valve pressure chamber 45, the closing body 52 of the second drain valve 42 slides down the switching contour 54 into a relaxed position and releases the associated valve body 49, so that the valve spring 48 presses the valve body 49 onto the valve seat 50. The closing body 52 of the first drain valve 41 then slides upward on the switching contour 54, as a result of which the associated valve body 49 is pushed away from the axis A: of the control slide 35. At the same time, the associated valve spring 48 compresses and the valve body 49 lifts off the valve seat 50. As a result, the control valve 34 is pressed into the second valve position, which results in the short position of the length-adjustable connecting rod 1.

On the slide tappet 39 of the control slide 35 shown in FIG. 4, specifically the second slide tappet section 39b, various measures for optimizing the mass of the slide tappet 39 can be provided. In the middle area of the second slide valve

Switching contour 54 provided in section 39b, a trapezoidal constriction 55 is provided, which is arranged between the two raised areas of the switching contour 54, which are related to the two drain valves 41, 42 and enable the control slide 35 to be guided in the control cylinder 36. In addition, the upper section of the slide tappet 39, especially the first slide tappet section 39a, can be provided with a smaller diameter in the area of the return spring 32. Because of these weight and volume reductions made specifically for this slide tappet 39, the mass of the slide tappet 39 can be reduced very significantly, so that the control slide 35 of the hydraulic control valve 34 can be adjusted to a wide variety of applications.

The acceleration forces acting on the control slide 35 are dependent on the respective design of the length-adjustable connecting rod 1 and the hydraulic control device 21, but also on the respective piston motor. Due to the total mass of the control slide 35, considerable forces can act on the control slide 35 and on the return spring 32 via the acceleration forces, which is why the mass of the control slide 35 should be kept as small as possible and designed for the respective application in order to optimally adapt to the respective piston engine to enable.

This situation, as well as the adaptability to various requirements, is made possible by the design of the control slide 35 described below with two control slide parts 35a, 35b.

5a shows a perspective illustration of a control slide 35 in the assembled state. The control slide 35 is designed to be rotationally symmetrical throughout. The stop flange 56 is shown between the area with the switching contours 54 and the control piston 37. The sealing section 58 is located on the side of the stop flange facing away from the control piston 37. It can be seen that the diameter of the slide tappet 39 is smaller on one side of the stop flange 56 than on the other side facing the control piston 37. This has to do in particular with the design of the high-pressure section 36b of the control cylinder 36.

5b shows the second control slide part 35b with the switching contours 54 and the sealing section 58. In FIG. 5c, the first control slide part 35a with the control piston 37 and the stop flange 56 is shown. The two parts 35a, 35b can be made of different materials, which allows further weight optimization. The first control slide part 35a is preferably made of a lighter material that has a lower density than the material, or predominantly of such a material if one or both parts 35a, 35b consist of several materials.

In Fig. 6 it can be seen on the basis of a sectional view of the control slide 35 that the two control slide parts 35a, 35b are plugged into one another, the second control slide part 35b having a connecting area 35b 'which is inserted into a longitudinal bore 53 made within the first control slide part 35a is. The longitudinal bore 53 extends over at least part of the first control slide part 35a, but is designed as a through bore in the present exemplary embodiment.

The connection of the control slide parts 35a, 35b can take place via a non-positive connection if, for example, the interior of the longitudinal bore 53 is provided with an internal thread and the connection area 35b ‘of the second control slide part 35b has an external thread. It is also possible to provide a press fit or, in addition, to carry out a form-fitting connection - gluing, welding or soldering.

Claims (17)

Claims 1. Length-adjustable connecting rod (1) for a piston engine, the connecting rod (1) having a hydraulic control device (21) for adjusting the effective length of the length-adjustable connecting rod (1) and the hydraulic control device (21) having a hydraulic control valve (34) with a control cylinder (36), a control slide (35) and at least one drain valve (41, 42) which can be actuated by the control slide (35), the control slide (35) having a control piston (37) which is guided in the control cylinder (36) and can be acted upon by a hydraulic control pressure ) and a slide tappet (39), wherein the control slide (35) has two control slide parts (35a, 35b) which can be manufactured separately and are firmly joined together when the control slide (35) is used as intended, characterized in that a first control slide part (35a) is arranged on the end face Control piston (37) followed by a first slide tappet section (39a) and a The second control slide part (35b) is connected to a second slide tappet section (39b), the second control slide part (35b) having at least one switching contour (54) which is rotationally symmetrical to the control slide axis (A;) and with which the at least one drain valve (41, 42) can be actuated . 2. Length-adjustable connecting rod (1) according to claim 1, characterized in that the first control slide part (35a) and / or the second control slide part (35b) are designed to be rotationally symmetrical. 3. Length-adjustable connecting rod (1) according to claim 1 or 2, characterized in that the control slide parts (35a, 35b) are made of different materials, the first control slide part (35a) preferably consisting at least predominantly of a material that has a lower density than the material from which the second control slide part (35b) consists at least predominantly. 4. Length-adjustable connecting rod (1) according to one of claims 1 to 3, characterized in that the control slide parts (35a, 35b) are connected to one another via a non-positive and / or positive connection. 5. Length-adjustable connecting rod (1) according to one of claims 1 to 4, characterized in that the control piston (37) is arranged at one end of the first control slide part (35a) and at the opposite end of the first control slide part (35a), preferably at the end of the first slide tappet section (39a), a stop flange (56) is arranged. 6. Length-adjustable connecting rod (1) according to one of claims 1 to 5, characterized in that within the first control slide part (35a) a parallel to the control slide axis (A; :) extending longitudinal bore (53) is executed, which extends at least over a part, preferably extends over the entire length of the first control slide part (35a). 7. Length-adjustable connecting rod (1) according to claim 6, characterized in that the longitudinal bore (53) from the control piston (37) opposite end of the first control slide part (35a) is designed to run in the direction of the control piston (37), either as a blind hole or as Through hole. 8. Length-adjustable connecting rod (1) according to claim 6 or 7, characterized in that the second control slide part (35b) has a connecting region (35b ‘) which can be inserted into the longitudinal bore (53) for joining the control slide parts (35a, 35b). 9. Length-adjustable connecting rod (1) according to one of claims 1 to 8, characterized in that the control cylinder (36) has a low-pressure section (36a) with a first diameter (D1) and a high-pressure section (36b) with a second diameter (D2) , wherein the first diameter (D1) is preferably greater than the second diameter (D2). 10. Length-adjustable connecting rod (1) according to claim 9, characterized in that the second control slide part (35b) facing the first control slide part (35a) The end has a sealing section (58) which, when the control slide (35) is used as intended, partially penetrates the low-pressure section (36a) but does not leave the high-pressure section (36b) completely at any time during use. 11. Length-adjustable connecting rod (1) according to one of claims 1 to 10, characterized in that the first slide tappet section (39a) and / or the second slide tappet section (39b) is designed as a mass-optimized slide tappet section, the mass of the slide tappet section (39a, 39b) is reduced due to the choice of material of the slide tappet section (39a, 39b) or because of a contour (54) provided with at least one constriction (55) of the second slide tappet section (39b) whose mass is a maximum of 0.93 times, preferably a maximum of 0.85 times. times the envelope volume of the contour (54) of the second slide tappet section (39b) multiplied by the density of steel (7.85 g / mm®). 12. Length-adjustable connecting rod (1) according to one of claims 1 to 11, characterized in that the hydraulic control valve (34) has a return spring (32) to hold the control slide (35) in a first starting position or to reset it to the first starting position , wherein the return spring (32) is preferably arranged at least around the first slide tappet section (39a) and is supported on the control piston (37). 13. Length-adjustable connecting rod (1) according to one of claims 1 to 12, characterized in that the control slide (35) inclined to the longitudinal axis (A) of the connecting rod (1) and / or inclined to the normal to the longitudinal axis (A) of the connecting rod (1 ) is arranged, wherein the control slide axis (As) is preferably arranged at an angle between 15 ° and 75 °. 14. Length-adjustable connecting rod (1) according to one of claims 1 to 13, characterized in that at least two connecting rod parts (2, 3) are provided, the first connecting rod part (3) having a first connecting rod eye (7) for receiving a piston pin and the second Connecting rod part (2) has a second connecting rod eye (4) for receiving a crankshaft journal, and wherein the first connecting rod part (3) can be moved relative to the second connecting rod part (2) in the longitudinal direction (A) of the connecting rod (1), preferably telescoping by the distance between the piston pin and the crankshaft journal. 15. Length-adjustable connecting rod (1) according to claim 14, characterized in that at least one cylinder-piston unit (10) hydraulically connected to the hydraulic control device (21) is provided in order to move the first connecting rod part (3) relative to the second connecting rod part (2 ), the first connecting rod part (3) being connected to an adjusting piston (9) of the cylinder-piston unit (10) and the second connecting rod part (2) having a cylinder bore (12) of the cylinder-piston unit (10) . 16. Assembled control slide (35) for a length-adjustable connecting rod (1) according to one of claims 1 to 15, with a first control slide part (35a) with a control piston (37) which is displaceable in a control cylinder (36) and can be acted upon by a hydraulic control pressure is, and a first slide tappet section (39a) of a slide tappet (39), and with a separately manufactured second control slide part (35b) with a second slide tappet section (39b) of a slide tappet (39). 17. Piston engine with at least one engine cylinder, one reciprocating piston moving in the engine cylinder and at least one adjustable compression ratio in the engine cylinder, as well as with at least one length-adjustable connecting rod (1) according to one of claims 1 to 15 connected to the reciprocating piston . In addition 5 sheets of drawings