CN110799739B

CN110799739B - Length-adjustable connecting rod having a cylinder-piston unit with an anti-rotation part

Info

Publication number: CN110799739B
Application number: CN201880024271.7A
Authority: CN
Inventors: 斯蒂芬尼·雷姆; 凯·阿伦斯; 麦特·黑勒; 佐尔坦·里巴
Original assignee: AVL List GmbH; Evis Engine Systems Co ltd
Current assignee: AVL List GmbH; Evis Engine Systems Co ltd
Priority date: 2017-04-10
Filing date: 2018-04-10
Publication date: 2021-08-31
Anticipated expiration: 2038-04-10
Also published as: AT519799B1; WO2018188789A1; CN110799739A; DE102017107706A1; AT519799A3; AT519799A2

Abstract

The invention relates to a length-adjustable connecting rod for an internal combustion engine, having a first connecting rod part, a second connecting rod part and at least one cylinder-piston unit in order to adjust the first connecting rod part relative to the second connecting rod part. The cylinder-piston unit includes: the device comprises a housing with a cylinder bore, an adjusting piston arranged in the cylinder bore so as to be longitudinally movable, and at least one pressure chamber and a rotation prevention element which are arranged in the cylinder bore. The anti-rotation device is arranged on the first connecting rod part for fixing the rotational angle orientation of the piston pin relative to the crankshaft journal and extends with at least one first locking arm in the longitudinal direction along a guide on the second connecting rod part. The invention further relates to an internal combustion engine having such a length-adjustable connecting rod and to the use of such a cylinder-piston unit for a length-adjustable connecting rod of an internal combustion engine.

Description

Length-adjustable connecting rod having a cylinder-piston unit with an anti-rotation part

Technical Field

The invention relates to a length-adjustable connecting rod for an internal combustion engine, having a first connecting rod section, a second connecting rod section and at least one cylinder-piston unit for adjusting the first connecting rod section relative to the second connecting rod section, wherein the cylinder-piston unit comprises: the device comprises a housing with a cylinder bore, an adjusting piston arranged in the cylinder bore so as to be longitudinally movable, at least one pressure chamber arranged in the cylinder bore, and an anti-rotation element. The invention further relates to an internal combustion engine having such a length-adjustable connecting rod and to the use of a cylinder-piston unit for a length-adjustable connecting rod of an internal combustion engine.

Background

The thermal efficiency of internal combustion engines, in particular gasoline engines, depends on the compression ratio epsilon, i.e. the ratio of the total volume before compression to the compression volume (epsilon ═ working volume Vh + compression volume Vc)/compression volume Vc. The heat efficiency increases as the compression ratio increases. The thermal efficiency is decreasing with increasing compression ratio, but is of course still relatively significant in the range of values common today (e 10 … 14).

In practice, the compression ratio cannot be arbitrarily increased, because an excessively high compression ratio leads to accidental self-ignition of the internal combustion engine due to a pressure increase and a temperature increase. This premature combustion not only leads to jerks in the case of unstable operation and so-called gasoline engines, but also to possible damage to the engine components. The risk of self-ignition in the partial load range, which is dependent on the operating point of the engine in addition to the influence of ambient temperature and pressure, is low. Correspondingly, higher compression ratios can be achieved in the partial load range. In the development of modern internal combustion engines, therefore, efforts are made to match the compression ratio to the respective operating point of the engine.

Different solutions exist for achieving Variable Compression Ratios (VCR) with which the position of the crankshaft journal of the crankshaft or the position of the piston pin of the engine piston is changed, or the effective length of the connecting rod is changed. Solutions for continuous and discontinuous component adjustment exist here, respectively. Continuous regulation realizes CO₂Optimal reduction of emissions and fuel consumption, since the compression ratio is adjustable for each operating point. The discontinuous adjustment using two steps of the end stop designed for the adjustment movement, however, achieves advantages in terms of construction and operating technology and still significant savings in fuel consumption and CO compared to conventional crank mechanisms₂The emission is reduced.

Document US 2,217,721 describes an internal combustion engine with a length-adjustable connecting rod with two telescopically movable rod parts which mutually nest and form together a high-pressure chamber. In order to fill and drain the high-pressure chamber with engine oil and thus to vary the length of the connecting rod, an actuating mechanism is provided with a control valve having a spring-biased closure element which can be moved into an open position by the pressure of the engine oil.

EP 1426584 a1 shows a discontinuous adjustment of the compression ratio for an internal combustion engine, wherein an eccentric connected to a piston pin effects the adjustment of the compression ratio. The fastening of the eccentric in one or the other end position in the pivot region is thereby effected by means of a mechanical lock. The working of a length-adjustable connecting rod is also known from DE 102005055199 a1, with which different compression ratios can be achieved. The different compression ratios are also achieved here by means of an eccentric in a small connecting rod eye, which is fixed in its position by means of two hydraulic cylinders with variable resistance.

WO 2013/092364 a1 describes a length-adjustable connecting rod for an internal combustion engine, with two telescopically movable rod parts, one of which forms a cylinder and the second forms a length-adjustable piston element. A high-pressure chamber is formed between the control piston of the first rod part and the cylinder of the second rod part, said chamber being supplied with engine oil via a hydraulic control mechanism via an oil channel and a valve dependent on the oil pressure.

A similar length adjustable connecting rod with a telescopically movable connecting rod portion for an internal combustion engine is shown in WO 2015/055582 a 2. The adjustable connecting rod length affects the compression volume in the combustion chamber, wherein the working volume is defined by the position of the crankshaft journal and the cylinder bore. Short connecting rod lengths result in lower compression ratios than long connecting rod lengths when other geometries, such as piston, cylinder head, crankshaft, valve control, etc., are the same. In known length adjustable links, the link length is hydraulically changed between two positions. The entire connecting rod is designed in multiple parts, wherein the length change is achieved by a telescopic mechanism, which is adjustable by a double-acting cylinder. A small connecting rod eye, which is usually used to receive a piston pin, is connected to the piston rod (telescopic connecting rod part). The associated adjusting piston is guided in a cylinder, which is arranged in a connecting rod section with a large connecting rod eye, which is usually used to receive a crankshaft journal. The regulating piston divides the cylinder into two pressure chambers, an upper pressure chamber and a lower pressure chamber. The two pressure chambers are supplied with engine oil by a hydraulic pressure adjusting structure, wherein the supply of engine oil to the pressure chambers is realized by a lubricating oil supply portion of the connecting rod. For this purpose, oil communication is required from the crankshaft journal via the connecting rod bearing to the connecting rod and here via the check valve of the regulating mechanism to the pressure chamber.

If the connecting rod is in the long position, there is no engine oil in the upper pressure chamber. The lower pressure chamber is then completely filled with engine oil. During operation, the connecting rods are alternately subjected to tensile and compressive loads due to the gas forces and inertial forces. In the long position of the connecting rod, the tensile force is absorbed by mechanical contact with the upper stop of the adjusting piston. The link length is therefore unchanged. The active pressure is transmitted via the piston face to a lower pressure chamber filled with engine oil. Since the check valve of this pressure chamber prevents the return flow of the engine oil, the pressure of the engine oil rises, wherein a very high dynamic pressure of significantly more than 1000 bar can occur in the lower pressure chamber. The link length does not change. The connecting rod is hydraulically locked in this direction by the system pressure.

In the short position of the connecting rod the relationship is reversed. The lower pressure chamber is empty and the upper pressure chamber is filled with engine oil. The pulling force causes the pressure in the upper pressure chamber to rise. The pressure is taken up by a mechanical stop.

By emptying one of the two pressure chambers, the connecting rod can be adjusted in two stages. For this purpose, the adjusting mechanism bridges one of the two non-return valves in the inflow or opens the respective return channel. Through this return channel, the engine oil can flow out into the crankcase independently of the pressure difference between the pressure chamber and the supply device. The respective check valve is correspondingly inoperative. Both return channels are opened and closed by means of a control valve, wherein always only one return channel is open and the other return channel is closed. The actuator for switching the two return channels is hydraulically controlled by the supply pressure.

The installation space for this connecting rod is limited in the axial and radial directions. Along the crankshaft direction, the installation space is limited by the bearing width and the distance of the counterweights. In the axial direction, only installation space and a possible adjustment stroke of the connecting rod always exists between the small connecting rod eye for supporting the piston pin and the large connecting rod eye for supporting the crankshaft journal.

The forces that should be transmitted by the connecting rod in an internal combustion engine are significant, and therefore the pressure in the pressure chamber of the cylinder-piston unit may also be significant. In view of the high internal pressures in the case of the cylinder-piston unit and the associated hydraulic actuating mechanism, the fatigue strength of the materials used is problematic, and the construction and loadability of the components and the incorporation of the engine oil supply are also problematic with regard to low installation space.

Patent document AT 516387B 1 relates to a length-adjustable connecting rod for an internal combustion engine, having two telescopically movable connecting rod parts which are nested one inside the other. The pressure chamber formed by the cylinder-piston unit is here formed at least partially by two bellows connected to one of the connecting rod sections. In order to ensure the proper operation of the length-adjustable connecting rod, an anti-rotation device is further provided, which fixes the angular rotation position of the axis of the piston pin arranged in the small connecting rod eye and the axis of the crankshaft journal arranged in the large connecting rod eye, wherein the two axes are generally parallel to each other. The rotation prevention means is designed here as a screw which passes through a bore in the housing of the cylinder-piston unit and in the fixing sleeve of the upper bellows and engages into the long bore of the first telescopic link part and is thus prevented from rotating. The locking screw thereby extends through the housing into the cylinder bore and must be sealed in order to withstand extremely high pressures, depending on the configuration of the pressure chamber in the region of the housing.

Although piston-connecting rod mechanisms are known in many technical fields and reciprocating piston engines are constantly being optimized, improved and expanded in the automotive industry, the hydraulic control and supply mechanisms for the cylinder-piston units of length-adjustable connecting rods, despite extensive development and research efforts, are still subject to further improvement, in particular with regard to the necessary life and functional safety of the length-adjustable connecting rods with respect to the overall life of the internal combustion engine. In addition to simple anti-rotation by means of a locking screw extending through the housing of the cylinder-piston unit, in conventional cylinder-piston units of length-adjustable connecting rods, anti-rotation is achieved by the non-circular cross-section of the piston and cylinder. In addition to a simple oval cross section, a cross-sectional contour with a single or a plurality of star-shaped guides is also present here. Regardless of the cross-sectional profile of the piston and cylinder, such anti-rotation has the disadvantage of high production costs and expensive sealing of the cylinder bore.

Disclosure of Invention

The task of the invention is therefore to: a connecting rod with an adjustable length of the cylinder-piston unit is provided, which achieves a simple and reliable anti-rotation of the rotational angular orientation of the piston pin and the crankshaft journal.

This object is achieved according to the invention in that the rotation prevention means has a disk-shaped locking profile and at least one locking arm arranged on the disk-shaped locking profile, wherein the disk-shaped locking profile is arranged on the first link part in a rotationally fixed manner and the locking arm extends along a guide on the second link part in a manner displaceable in the longitudinal direction of the length-adjustable link. Such a rotation prevention means not only avoids the openings in the housing of the cylinder-piston unit and the corresponding necessary sealing of the housing bore, but also the complex special cross-sectional profile of the cylinder bore of the control piston. The adjusting piston and the cylinder bore can therefore be produced inexpensively as a cylinder despite the provision of the rotation prevention. The use of such an anti-rotation element also makes it possible to avoid additional sealing of the pressure chamber in the cylinder bore. The disc-shaped locking profile can be produced inexpensively separately from the further components of the cylinder-piston unit and is fastened to the first connecting rod part with a correspondingly simple construction (for example, a form-fitting arrangement). The locking arms arranged on the locking profiles can be moved in the longitudinal direction along the guides on the second link part, i.e. in the telescoping direction of the first link part and the second link part, which are movable relative to one another, while the locking arms are prevented from twisting relative to one another by the guides. Preferably, at least two locking arms can be provided on the disk-shaped locking profile in order to minimize the residual play of the rotational angular orientation of the piston pin relative to the crankshaft journal. The locking arms are arranged as uniformly as possible on the circumference of the disk-shaped locking profile.

A suitable embodiment provides that the at least one locking arm is connected elastically to the disc-shaped locking profile, preferably in one piece to the disc-shaped detent contour. The elastic locking arm particularly facilitates a simple and quick installation of the torsion prevention means, but also avoids damage to the torsion prevention means as a result of static and dynamic loading of the length-adjustable connecting rod in the internal combustion engine. In this case, the at least one locking arm can itself be designed to be elastic and/or can be connected elastically to the disk-shaped locking profile.

One interesting embodiment provides that: the disc-shaped locking profile has a profiled opening, wherein the profiled opening engages in a complementary profile on the first lever part. In addition to the cost-effective production, such profiled openings, for example with a non-circular, polygonal or toothed profile, also allow simple arrangement of the disc-shaped locking profiles on the complementary profile on the first lever part and withstand high torsional forces. In one possible refinement, the profiled opening in the disk-shaped locking profile can be configured open on one side. This enables a very rapid subsequent mounting of the locking profile at the complementary contour of the first connecting rod part after the final assembly of the connecting rod. Alternatively, the profiled opening can be closed in order to improve the anti-rotation arrangement, but this requires the first connecting rod part to be guided through the profiled opening when the disc-shaped locking profile is installed.

Another embodiment provides that: the first rod part has a piston rod, wherein the piston rod has at least one, preferably both, flat groove in which a profiled opening of a disk-shaped locking profile is arranged in a rotationally fixed manner. A piston rod, which is arranged on the end side of the adjusting piston, extends through the pressure chamber of the cylinder-piston unit and through a rod bore in the housing cover into the crankcase of the internal combustion engine, achieves a simple conversion of the movement of the adjusting piston in the cylinder bore into a relative length adjustment between the first connecting rod part and the second connecting rod part. The piston rod allows simple creation of a complementary profile for arranging the profiled opening of the disc-shaped locking profile, but also allows the piston rod to pass through the opening designed as closed. At the same time, such a piston rod achieves a reliable sealing of the pressure chamber by means of a rod seal between the piston rod and the rod bore in the housing cover.

In order to produce a length-adjustable connecting rod as inexpensively as possible, the disk-shaped locking profile can be designed as a stamped and bent part. The punch-bending element is produced very inexpensively from a relatively thin disk-shaped profile, wherein the latching profile can be designed in the form of a ring or flange and the corresponding latching arm can also be formed and shaped simultaneously in the punch-bending process.

One interesting embodiment provides that: the guide on the second link part is designed as a groove extending in the longitudinal direction. Such grooves on the outside of the housing of the cylinder-piston unit can easily be introduced later on and can also be provided with grooves without undercuts at the time of manufacture of the housing. Alternatively, the guide may be provided as a hole in the housing or simply as a flat on the housing.

A preferred embodiment provides that: the cylinder-piston unit has a cover covering a cylinder bore, wherein at least one locking arm arranged on the disk-shaped locking profile laterally surrounds the cover in the longitudinal direction and extends along a guide provided on the housing. In addition to sealing the cylinder bore, the cover also delimits an adjoining pressure chamber in the cylinder bore. Since the at least one locking arm of the rotation prevention element laterally surrounds the housing cover, corresponding recesses for the arrangement of the locking arms can be dispensed with, so that the cover only has to be designed and produced for sealing the cylinder bore and accommodating the piston rod in its function.

A preferred embodiment of the length-adjustable connecting rod provides for: a sealing device is arranged between the outer device wall of the adjusting piston and the inner device wall of the cylinder hole. The sealing arrangement prevents the adjusting piston from being pushed into the first or second pressure chamber, which is filled with engine oil, even at high system pressures, and thus achieves a reliable and durable implementation of the function of the length-adjustable connecting rod according to the invention. The sealing arrangement between the outer wall of the control piston and the inner wall of the cylinder bore prevents the control piston from being pushed into the respective pressure chamber even when a high force is exerted on the control piston, in particular during the compression and combustion process in the respective cylinder of the internal combustion engine, as a result of which a variable compression ratio in the cylinder is achieved and the improvement in the efficiency of the internal combustion engine achieved without the control piston being pushed into the respective pressure chamber is reduced. As a sealing device, a gap seal with a certain leakage on the mechanism can be used, but a contact piston seal which almost avoids leakage but is expensive in construction and susceptible to function can also be used. In view of the high system pressures in the pressure chamber of the cylinder-piston unit, which are significantly higher than 1000 bar, the amount of play of the gap seal should be at most 20 μm, in particular at most 10 μm, preferably even less. In view of such a small amount of clearance, in addition to the sealing device, an oil filter and/or oil wiper should be provided, which prevents large soot particles and debris from being introduced from the engine oil into the pressure chamber and from the pressure chamber into the clearance of the clearance seal between the sealing surfaces of the piston seal. It is thereby possible to prevent particles present in the engine oil from being introduced into the sealing device as a result of the high system pressure and the movement of the regulating piston in the cylinder bore. Thus, wear on the inner vessel wall of the cylinder bore and the outer vessel wall of the adjusting piston or on the sealing surfaces of the one or more piston seals may be prevented or significantly reduced, in order to finally prevent damage and failure of the cylinder-piston unit.

The adjusting piston of the cylinder-piston unit may preferably be designed as a double-acting adjusting piston, wherein the adjusting piston arranged longitudinally movably in the cylinder bore delimits a first pressure chamber on a first end side and delimits a second pressure chamber on a second end side. The double-acting control piston achieves the fixation of the piston rod in the direction of increasing compression ratio and in the direction of decreasing compression ratio in a single cylinder-piston unit. Thus, unlike DE 102005055199 a1, the same adjusting piston is used for the bidirectional adjustment of the piston stroke or compression ratio. A stepped piston can be used here, which, via its larger end face, holds the piston rod in its extended position when pressure is applied correspondingly. Due to the mainly acting force relationships in internal combustion engines, a smaller end face is generally sufficient for fastening in the opposite direction.

For a simple construction of the length-adjustable connecting rod, the first connecting rod part can be connected to the adjusting piston of the cylinder-piston unit, and the second connecting rod part can have the cylinder bore of the cylinder-piston unit.

The invention further relates to the use of a cylinder-piston unit having a rotation prevention element for a length-adjustable connecting rod of an internal combustion engine, the connecting rod having a first connecting rod part and a second connecting rod part, which are adjusted by means of the cylinder-piston unit. The cylinder-piston unit includes: a housing with a cylinder bore; an adjusting piston arranged so as to be longitudinally movable in the cylinder bore; and at least one first and second pressure chamber for receiving engine oil in the cylinder bore, which are delimited on one side by a longitudinally movable adjusting piston; and a cap for sealing the cylinder hole. Such a cylinder-piston unit for a length-adjustable connecting rod of an internal combustion engine makes it possible to utilize engine oil in the hydraulic actuating mechanism, despite the small dimensions of the cylinder-piston unit and the extremely high system pressures. The operation of the cylinder-piston unit is effected here by the gas and inertial forces of the internal combustion engine acting on the connecting rod part, while the positioning of the connecting rod part is locked by the engine oil present in the respective pressure chamber. Furthermore, the disk-shaped locking profile and the laterally extending locking arms enable rotationally symmetrical components to be used for the cylinder-piston unit and the connecting rod with adjustable overall length, which has the advantage of using a small installation space and having low material and production costs.

In another aspect, the invention relates to an internal combustion engine with: at least one reciprocating piston, at least one compression ratio adjustable within a cylinder, and a length adjustable connecting rod according to the previous embodiment connected to the reciprocating piston. Preferably, all reciprocating pistons of an internal combustion engine are equipped with such a connecting rod of adjustable length, but this is not required. The fuel economy of the internal combustion engine can be significant when the compression ratio is adjusted accordingly depending on the respective operating state. Suitably, the cylinder-piston unit of the length-adjustable connecting rod may be coupled to an engine oil hydraulic device of the internal combustion engine. Thus, the pressure existing in the engine oil circuit may be used to control the hydraulic adjustment mechanism. The presence of soot particles and debris in the engine oil is to be taken into account, which requires that the hydraulic control mechanism and the associated sealing arrangement are insensitive. The less dirt particles are introduced from the engine oil, the more safe the operation of the cylinder-piston unit can be ensured. The use of the anti-rotation device with the disk-shaped locking profile and the at least one locking arm achieves a correct operation of the length-adjustable connecting rod by a reliable parallel arrangement of the piston pin axis and the crankshaft journal axis.

Another modification provides for: the system pressure of the engine oil in the first pressure chamber or the second pressure chamber of the cylinder-piston unit is between 1000 bar and 3000 bar, preferably between 2000 bar and 2500 bar. The limitation of the system pressure enables a safe design of the inner diameter of the cylinder bore and the wall thickness of the cylinder, and thus of the length-adjustable connecting rod according to the invention.

According to a further refinement, a timing drive with at least one timing chain, tensioning rail and/or guide rail and/or chain tensioner can be provided, which connects the crankshaft with at least one camshaft of the internal combustion engine. The timing drive is important because it has a great influence on the dynamic load of the engine and therefore also on the length-adjustable connecting rod. Preferably, this timing drive is designed such that no excessively high dynamic forces are introduced by the timing drive. Alternatively, the timing drive can also be designed with spur gear toothing or a drive belt, for example a toothed belt, which is pretensioned by a tensioning device with a tensioning roller.

Drawings

The embodiments are explained in detail below with reference to the drawings. The figures are as follows:

FIG. 1 shows a schematic cross section of an internal combustion engine, an

Figure 2 shows in a partially cut-away illustration a schematic representation of the length-adjustable connecting rod of figure 1,

fig. 3a shows a perspective view of a part of the length-adjustable connecting rod in fig. 2, with an anti-twist part,

figure 3b shows a perspective view of the disc-shaped locking profile of the anti-twist part in figure 3a,

fig. 4a shows a perspective view of a portion of the length adjustable connecting rod of fig. 2, with another embodiment of the anti-twist portion of fig. 3a,

figure 4b shows a perspective view of the disc-shaped locking profile of the anti-twist part in figure 4a,

fig. 5a shows a perspective view of a part of the length-adjustable connecting rod of fig. 2, with a further anti-twist part,

figure 5b shows a perspective view of the disc-shaped locking profile of the anti-twist part in figure 5a,

FIG. 6a shows a perspective view of a portion of the length adjustable connecting rod of FIG. 2 with another embodiment of the anti-twist portion of FIG. 5a, an

Fig. 6b shows a perspective view of the disc-shaped locking profile of the rotation prevention element in fig. 6 a.

Detailed Description

An internal combustion engine (gasoline engine) 1 is schematically illustrated in fig. 1. The internal combustion engine 1 has three cylinders 2.1, 2.2 and 2.3, in each of which a reciprocating piston 3.1, 3.2, 3.3 moves up and down. The internal combustion engine 1 furthermore comprises a crankshaft 4, which crankshaft 4 is rotatably mounted by means of crankshaft bearings 5.1, 5.2, 5.3, 5.4. The crankshaft 4 is connected to the associated reciprocating pistons 3.1, 3.2 and 3.3 via connecting rods 6.1, 6.2 and 6.3, respectively. The crankshaft 4 has eccentrically arranged crankshaft journals 7.1, 7.2 and 7.3 for each connecting rod 6.1, 6.2 and 6.3. The large connecting rod eye 8.1, 8.2 and 8.3 of the connecting rod 6.1, 6.2, 6.3 is supported on the associated crankshaft journal 7.1, 7.2 and 7.3, respectively. The small connecting rod eye 9.1, 9.2 and 9.3 of the connecting rod 6.1, 6.2, 6.3 is supported on the piston pin 10.1, 10.2 and 10.3, respectively, and is thus pivotably connected to the associated reciprocating piston 3.1, 3.2 and 3.3. The terms small connecting rod eye 9.1, 9.2 and 9.3 and large connecting rod eye 8.1, 8.2 and 8.3 are understood here to mean neither absolute nor relative size relationships, but rather they are used merely to distinguish components and relationships relative to the internal combustion engine shown in fig. 1. Correspondingly, the diameter dimension of the small connecting rod eye 9.1, 9.2, 9.3 may be smaller, equal or larger than the diameter dimension of the large connecting rod eye 8.1, 8.2, 8.3.

The crankshaft 4 is provided with a crankshaft sprocket 11, and is coupled with a camshaft sprocket 13 by a timing chain 12. The camshaft sprocket 13 drives a camshaft 14 with its associated cams to actuate the inlet and exhaust valves (not shown in detail) of each cylinder 2.1, 2.2 and 2.3. The slack side of the timing chain 12 is tensioned by means of a pivotably arranged tensioning rail 15, which tensioning rail 15 is pressed onto by means of a chain tensioner 16. The drive side of the timing chain 12 may slide along the guide rails. The basic functional manner of timing drive and fuel injection and ignition by a spark plug is not explained in more detail and is considered to be known. The eccentricity of the crankshaft journals 7.1, 7.2 and 7.3 decisively defines the stroke H_KIn particular, in the present case, the crankshaft 4 is arranged exactly centrally below the cylinders 2.1, 2.2 and 2.3. In fig. 1 the shuttle piston 3.1 is shown in its lowest position, while the shuttle piston 3.2 is shown in its highest position. In this case, the difference defines the stroke H_K. Height H of remaining_C(see cylinder 2.2) gives the remaining compression height inside cylinder 2.2. Combined with the diameter of the reciprocating piston 3.1, 3.2 or 3.3 or of the associated cylinder 2.1, 2.2 and 2.3, from stroke H_KTo obtain a working volume V_hAnd compressing the height H from the remainder_CCalculating the compressed volume V_C. Of course, the compressed volume V_CDepending crucially on the construction of the cylinder head. From volume V_hAnd V_CThe compression ratio epsilon is obtained. In detail, the working volume V_hAnd the sum of the compressed volume Vc divided by the compressed volume V_cThe compression ratio epsilon is calculated. Currently, for gasoline engines, the compression ratio epsilon is typically between 10 and 14.

In order to be able to adjust the compression ratio epsilon as a function of the operating point of the internal combustion engine 1 (speed n, temperature T, throttle position), the connecting rods 6.1, 6.2 and 6.3 are configured to be adjustable in length according to the invention. Thereby, the vehicle can travel in the partial load range at a higher compression ratio than in the full load range.

In fig. 2, a length-adjustable connecting rod 6.1 is illustrated by way of example, said connecting rod 6.1 being constructed identically to the connecting rods 6.2 and 6.3. Therefore, the description also applies correspondingly. The connecting rod 6.1 has a connecting rod head 17.1 with the mentioned small connecting rod eye 9.1 and a first connecting rod part 18.1 which is guided telescopically in a second connecting rod part 19.1. The relative movement of the first connecting rod part 18.1 in the longitudinal direction with respect to the second connecting rod part 19.1 takes place by means of a cylinder-piston unit 20.1, which cylinder-piston unit 20.1 has an adjusting piston 21.1 and a cylinder bore 22.1 and a sealing device 23.1 between the adjusting piston 21.1 and the cylinder bore 22.1. A lower bearing shell 19b.1 is arranged on the second connecting rod part 19.1, which lower bearing shell 19b.1 surrounds the large connecting rod eye 8.1 together with a lower region of the second connecting rod part 19.1. The lower bearing shell 19b.1 and the second connecting rod part 19.1 are connected to each other in the usual manner by fastening means. The piston rod 18a.1 at the lower end of the first connecting rod part 18.1 is connected to an adjusting piston 21.1, which adjusting piston 21.1 is guided displaceably in the cylinder bore 22.1 of the second connecting rod part 19.1. On the upper end, the second shaft part 19.1 has a cap 19a.1, through which cap 19a.1 the piston rod 18a.1 of the first shaft part 18.1 is guided and sealed. The cover 19a.1 thus seals the cylinder bore 22.1 overall. The adjusting piston 21.1 is designed as a stepped piston. A first pressure chamber 24.1 with a circular cross section is formed below the control piston 21.1, and a second annular pressure chamber 25.1 is formed above the control piston 21.1. In order to change the connecting rod length by means of the movement of the adjusting piston 21.1 in the cylinder bore 22.1, a hydraulic adjusting mechanism 26.1 is provided. A hydraulic circuit, which will be described in detail below, which leads to a flow of engine oil into and out of the pressure chambers 24.1 and 25.1, respectively, and thus a fixing of the adjusting piston 21.1, which is actuated by means of a force acting on the connecting rod 6.1, belongs to the adjusting mechanism 26.1.

In the present exemplary embodiment, the section of the second connecting rod part 19.1 in the region of the pressure chambers 24.1 and 25.1 and the adjusting piston 21.1 is designed in cross section as a circular ring (in addition to the hydraulic lines that may be present). Additional geometries are also contemplated. Accordingly, the wall thickness D of the housing in the region of the cylinder bore 22.1_WFrom the associated outer radius r of the upper section of the second connecting rod part 19.1_aMinus the inner radius r of the cylinder bore 22.1_iThus obtaining the product. In this symmetrical configuration, the wall thickness D at the periphery of the second connecting rod 19.1_WThe thickness is uniform and the stress in the material of the second connecting rod 19.1 is uniformly small, so that the maximum system pressure generated in the connecting rod 6.1 is within manageable limits due to the relatively large piston diameter with which the piston 21.1 is adjusted.

In the following, the function of the link 6.1 is explained in more detail according to fig. 2. The adjusting piston 21.1 of the cylinder-piston unit 20.1 is designed as a double-acting piston. In general, a double-acting piston is understood to be a piston having differently oriented active surfaces. The first end side 27.1 is designed as a ring-shaped part of the first pressure chamber 24.1. The second end side 28.1 is also designed as a circular ring and is associated with the second pressure chamber 25.1, wherein the first end side 27.1 and the second end side 28.1 can have the same or different areas. The cylinder-piston unit 20.1 is operated with engine oil. For this purpose, the oil supply channel 29.1 is connected to the large rod eye 8.1, with which the engine oil can be supplied to the hydraulic control device 26.1 or, in alternative lines, the engine oil can also flow out of the control device 26.1, if necessary. Subsequently, a control valve 30.1 is provided on the oil supply channel 29.1. The engine oil, which is supplied by means of the gas and inertial forces of the internal combustion engine 1 acting on the connecting rod parts 18.1 and 19.1, passes from the control valve 30.1 via the first oil duct 31.1 into the first pressure chamber 24.1 and via the second oil duct 32.1 into the second pressure chamber. In the flow direction of the inflowing engine oil, a check valve and optionally an oil filter are arranged in the first oil channel 31.1, and the first oil channel 31.1 then opens into the first pressure chamber 24.1. Between the non-return valve and the first oil duct 31.1 into the first pressure chamber 24.1, a branch of a discharge duct (not shown) is provided, which opens out on the outside of the second connecting rod part 19.1 into the crankcase of the internal combustion engine 1. The discharge channel is fitted with a discharge valve which is closed when the engine oil flows into the first pressure chamber 24.1 via the first oil channel 31.1. The second oil channel 32.1 is formed in accordance with the first oil channel 31.1 and, in the inflow direction of the engine oil into the second pressure chamber 25.1, has a check valve, a branch of the outlet channel with an outlet valve (not shown) and a selective oil filter downstream of the check valve 30.1, after which the second oil channel 30.2 opens into the second pressure chamber 25.1.

When the engine oil flows from the control valve 30.1 into the first pressure chamber 24.1 or into the second pressure chamber 25.1 via the second oil channel 32.1 under the control of the gas force and the inertia force, the entire inflowing engine oil can be guided via an oil filter, in which larger soot particles and debris are filtered out of the engine oil and fixed. As a result, the engine oil flowing into the pressure chambers 24.1 and 25.1 of the cylinder bore 22.1 is only slightly contaminated, so that the sealing device 23.1 between the outer wall of the control piston 21.1 and the inner wall of the cylinder bore 22.1 is correspondingly only slightly subject to wear. This prevents the risk of damaging the surface of the sealing device 23.1 even more, and increases the necessary service life of the length-adjustable connecting rod 6.1.

The control valve 30.1 of the hydraulic control device 26.1 of the length-adjustable connecting rod 6.1 actively controls the outlet valves assigned to the first oil channel 31.1 and the second oil channel 32.1 in the branched outlet channel, so that the position of the connecting rod 6.1 can be adjusted by a fixed length, while the admission of the engine oil driven by the gas and inertia forces into the first oil channel 31.1 and the second oil channel 32.1 takes place only passively via the control valve 30.1. When opening the first oil duct 31.1 or the second oil duct 32.1 and allowing the engine oil to flow into the first pressure chamber 24.1 or the second pressure chamber 25.1, the outlet valve in the other branch of the hydraulic control mechanism 26.1, i.e. in the first oil duct 31.1 or the second oil duct 32.1, must be opened at the same time in order to achieve a controlled outflow of the engine oil from the respective other pressure chamber, i.e. the second pressure chamber 25.1 or the first pressure chamber 24.1, and to achieve a displacement of the control piston 21.1 into the second pressure chamber 25.1 or the first pressure chamber 24.1. The actuation of the control valve 30.1 is preferably carried out with the pressure of the engine oil present in the oil supply channel 29.1, whereby an additional alternative, but also possible, electrical, electronic, magnetic or mechanical actuation of the control valve 30.1 or the outlet valve can also be avoided.

In the connecting rod 6.1 shown in fig. 2, a rotation prevention means 33.1 is further provided, which rotation prevention means 33.1 is connected in a rotation-proof manner to the piston rod 18a.1 of the first connecting rod part 18.1. The rotation prevention element 33.1 comprises a disk-shaped locking profile 34.1 with which the rotation prevention element 33.1 rests on the piston rod 18a.1, and the rotation prevention element 33.1 further comprises two locking arms 35.1, which locking arms 35.1 extend from the disk-shaped protective profile 34.1 in the longitudinal direction of the connecting rod 6.1, i.e. parallel to the longitudinal axis of the connecting rod 6.1 in the direction of the second connecting rod part 19.1. On the outer circumference of the second connecting rod part 19.1, the two locking arms 35.1 rest on suitable guides 36.1 or engage in said guides 36.1, which guides 36.1 extend in the longitudinal direction of the connecting rod 6.1 in accordance with the locking arms 35.1, in order to prevent a rotation of the large connecting rod eye 8.1 in relation to the small connecting rod eye 9.1 (in accordance with the rotational angular orientation of the piston pin 10.1 in relation to the crankshaft journal 7.1) by means of the rotation prevention 33.1 during a longitudinal movement of the first connecting rod part 18.1 in relation to the second connecting rod part 19.1. The locking arm 35.1 arranged in the disk-shaped locking profile 34.1 is guided in the longitudinal direction laterally next to the cover 19a.1 of the cylinder-piston unit 20.1 without intersecting the maximum radial contour of the cover 19 a.1.

The partial perspective view of the length-adjustable connecting rod 6.1 in fig. 3a shows an embodiment of the torsion prevention means 33.1 in the retracted position of the connecting rod 6.1. The locking profile 34.1 is designed in the form of a flange and is provided with two holes 37.1 for the arrangement of two pin-shaped locking arms 35.1. The two locking arms 35.1 arranged on the outer tip of the flange-like locking profile 34.1 are received in groove-shaped guides 36.1 on the outer circumference of the second link part 19.1 and overlap the cover 19a.1 in the longitudinal direction. In the perspective view of the disk-shaped locking profile 34.1 in fig. 3b, in addition to the flange-like contour and the bores 37.1 arranged on the two points, the opening 38.1 for the arrangement of the torsion-prevention means 33.1 on the piston rod 18a.1 can also be seen very well. Opening 38.1 is designed to be closed and accordingly is slipped onto piston rod 18a.1 and fixed, for example by gluing, welding or pressing, before connecting rod 6.1 is finally mounted. The opening 38.1 is designed in this embodiment with two flat sides, but polygonal or hexagonal shapes of the opening 38.1 may also be applied. The anti-rotation element 33.1 is connected to the piston rod 18a.1 in a rotationally fixed manner by the contour of the opening 38.1.

The rotation prevention 33.1 in the perspective view of the part of the connecting rod 6.1 in fig. 4a shows a variant of the flange-shaped locking profile 34.1 in fig. 3a and 3 b. As can be seen clearly from fig. 4b, the disk-shaped locking profile 34.1 is provided with a profile opening 38.1 which is open to one side. The opening 38.1 is again provided with two flat sides. As shown in fig. 4a, this contour opening 38.1, which is open to one side, can be installed in a final installation step after the final installation of the first and second link parts 18.1, 19.1. For this purpose, the disk-shaped locking profile 34.1 with the opening 38.1 open to one side is pushed laterally onto the profile nut 39.1 of the piston rod 18a.1 and is arranged in a rotationally fixed manner. Then, a pin-shaped locking arm 35.1 is fixed in the hole 37.1 of the locking profile 34.1, whereby the locking profile 34.1 is also arranged in a loss-proof manner on the piston rod 18a.1 by means of the guidance of the locking arm 35.1 in the groove-shaped guide 36.1 on the second lever part 19.1.

In fig. 5a, a perspective view of a section of the connecting rod 6 shows a further embodiment of the torsion prevention 33.1 for the length-adjustable connecting rod 6.1 according to the invention. The locking profile 34.1 and the two lateral locking arms 35.1 are designed in one piece as a stamped and bent part. As can be seen well in fig. 5b, the disk-shaped locking profile 34.1 is designed essentially in the form of a ring with two laterally arranged curved locking arms 35.1, which locking arms 35.1 engage in corresponding guides 36.1 on the outer circumference of the second link part 19.1 or rest on the guides 36.1. The locking arm 35.1 can be designed to be elastic in order to be able to easily overlap laterally on the cover 19a.1 when the first link part 18.1 and the second link part 19.1 are mounted and to be reliably guided by the guide 36.1. The profiled opening 38.1 of this locking profile 34.1, which is also shown in detail in fig. 5b, is closed again and is designed with two flat sides. Correspondingly, this locking profile 34.1 is also arranged on the piston rod 18a.1 before final safety and is connected to this piston rod 18a.1 in a rotationally fixed manner.

Alternatively, the profile opening 38.1 of the locking profile 34.1 in fig. 5b can be open to one side, see fig. 6 b. After the final assembly of the connecting rod 6.1, the fastening profile 34.1 can again be pushed onto the corresponding profile groove 39.1 on the piston rod 18a.1, see also fig. 6 a. The locking arm 35.1, which is formed in one piece with the locking profile 34.1, must be easily bent in order to be arranged on the guide 36.1 on the outer circumference of the second connecting rod 19.1 and be positioned accordingly. In an alternative embodiment, the rotation prevention element 33.1 can also have a second locking profile 34.1, which second locking profile 34.1 is arranged opposite the first locking profile 34.1 on the profile groove 39.1 of the piston rod 18a.1 and is preferably connected to the first disc-shaped locking profile 34.1.

List of reference numerals

1 internal combustion engine

2.1, 2.2, 2.3 cylinders

3.1, 3.2, 3.3 reciprocating piston

4 crankshaft

Crankshaft bearing of 5.1, 5.2, 5.3, 5.4

6.1, 6.2, 6.3 connecting rod

7.1, 7.2, 7.3 crankshaft journal

8.1, 8.2, 8.3 big connecting rod eye

9.1, 9.2, 9.3 Small Link eye

10.1, 10.2, 10.3 piston pin

11 crankshaft sprocket

12 timing chain

13 camshaft sprocket

14 camshaft

15 tensioning rail

16 chain tensioner

17.1 connecting rod head

18.1 first Link portion

18a.1 piston rod

19.1 second Link part

19a.1 cover

19b.1 bearing housing

20.1 Cylinder-piston Unit

21.1 regulating piston

22.1 Cylinder bores

23.1 sealing device

24.1 first pressure Chamber

25.1 second pressure Chamber

26.1 Hydraulic adjusting mechanism

27.1 first end side

28.1 second end side

29.1 oil supply channel

30.1 control valve

31.1 first oil passage

32.1 second oil passage

33.1 anti-twist part

34.1 locking section bar

35.1 locking arm

36.1 guide part

37.1 holes

38.1 opening

39.1 Profile trough

D_WWall thickness

V_hWorking volume

V_CCompressed volume

H_CHeight of compression

H_KStroke control

r_iInner diameter

r_aOutside diameter

Amount of S space

Compression ratio of epsilon

n number of revolutions

T temperature.

Claims

1. A length-adjustable connecting rod (6.1) for an internal combustion engine (1), with a first connecting rod portion (18.1) and a second connecting rod portion (19.1), the first connecting rod portion (18.1) being configured for accommodating a piston pin (10.1) and the second connecting rod portion (19.1) being configured for accommodating a crankshaft journal (7.1), wherein the first connecting rod portion (18.1) is movable in a longitudinal direction relative to the second connecting rod portion (19.1) in order to adjust a distance between the piston pin (10.1) and the crankshaft journal (7.1), the length-adjustable connecting rod (6.1) further being provided with at least one cylinder-piston unit (20.1) in order to adjust the first connecting rod portion (18.1) relative to the second connecting rod portion (19.1), the cylinder-piston unit (20.1) comprising: a housing with a cylinder bore (22.1), an adjusting piston (21.1) arranged in the cylinder bore (22.1) so as to be longitudinally movable, wherein the cylinder-piston unit (20.1) has a rotation prevention means (33.1) in order to fix the rotational angular position of the piston pin (10.1) relative to the crankshaft journal (7.1);

it is characterized in that the preparation method is characterized in that,

the torsion-proof section (33.1) has a disc-shaped locking profile (34.1) and at least one locking arm (35.1) arranged on the disc-shaped locking profile (34.1), wherein the disc-shaped locking profile (34.1) is arranged on the first link part (18.1) in a rotationally fixed manner, and the locking arm (35.1) extends in the longitudinal direction of the length-adjustable link (6.1) along a guide (36.1) on the second link part (19.1) in a displaceable manner.

2. The length-adjustable connecting rod (6.1) according to claim 1, characterized in that at least two locking arms (35.1) are provided on the disc-shaped locking profile (34.1).

3. The length-adjustable connecting rod (6.1) according to claim 1 or 2, characterized in that at least one locking arm (35.1) is connected elastically to the disc-shaped locking profile (34.1).

4. The length-adjustable connecting rod (6.1) according to claim 1 or 2, characterized in that the disc-shaped locking profile (34.1) has a profiled opening (38.1), wherein the profiled opening (38.1) engages in a complementary profile on the first connecting rod section (18.1).

5. The length-adjustable connecting rod (6.1) according to claim 4, characterized in that the profiled opening (38.1) on the disc-shaped locking profile (34.1) is open on one side.

6. The length-adjustable connecting rod (6.1) according to claim 4, characterized in that the first connecting rod section (18.1) has a piston rod (18a.1), wherein the piston rod (18a.1) has a groove (39.1) which is flat on one side, wherein the profiled opening (38.1) of the disc-shaped locking profile (34.1) is arranged in the groove (39.1) in a rotationally fixed manner.

7. The length-adjustable connecting rod (6.1) according to claim 1 or 2, characterized in that the disc-shaped locking profile (34.1) is configured as a punch-bend.

8. A length adjustable connecting rod (6.1) according to claim 1 or 2, characterized in that the guide (36.1) on the second connecting rod portion (19.1) is configured as a groove (39.1) extending in the longitudinal direction.

9. The length-adjustable connecting rod (6.1) according to claim 1 or 2, characterized in that the cylinder-piston unit (20.1) has a cover (19a.1) which seals the cylinder bore (22.1), wherein at least one locking arm (35.1) arranged on the disc-shaped locking profile (34.1) laterally surrounds the cover (19a.1) and extends along a guide (36.1) provided on the housing.

10. The length-adjustable connecting rod (6.1) according to claim 1 or 2, characterized in that the first connecting rod portion (18.1) is connected with an adjusting piston (21.1) of the cylinder-piston unit (20.1) and the second connecting rod portion (19.1) has a cylinder bore (22.1) of the cylinder-piston unit (20.1).

11. A length adjustable connecting rod (6.1) according to claim 1, characterized in that the combustion engine (1) is a gasoline engine.

12. The length-adjustable connecting rod (6.1) according to claim 3, characterized in that the at least one locking arm (35.1) is connected in one piece with the disc-shaped locking profile (34.1).

13. The length-adjustable connecting rod (6.1) according to claim 4, characterized in that the first connecting rod section (18.1) has a piston rod (18a.1), wherein the piston rod (18a.1) has a groove (39.1) which is flat on both sides, wherein the profiled opening (38.1) of the disc-shaped locking profile (34.1) is arranged in the groove (39.1) in a rotationally fixed manner.

14. Use of a cylinder-piston unit (20.1) with an anti-twist portion (33.1) for a length-adjustable connecting rod (6.1) of an internal combustion engine (1), the connecting rod (6.1) having a first connecting rod portion (18.1) and a second connecting rod portion (19.1) which are adjustable by means of the cylinder-piston unit (20) in order to move the first connecting rod portion (18.1) relative to the second connecting rod portion (19.1) in the longitudinal direction of the length-adjustable connecting rod (6.1), the cylinder-piston unit (20.1) comprising: a housing with a cylinder bore (22.1), an adjusting piston (21.1) arranged in the cylinder bore (22.1) in a longitudinally movable manner, a first pressure chamber (24.1) and a second pressure chamber (25.1) which are arranged in the cylinder bore (22.1) and are delimited on one side by the movable adjusting piston (21.1), and a cover (19a.1) for sealing the cylinder bore (22.1),

it is characterized in that the preparation method is characterized in that,

the torsion-prevention element (33.1) has a disc-shaped locking profile (34.1) and at least one locking arm (35.1) extending laterally from the disc-shaped locking profile (34.1) in the longitudinal direction of the length-adjustable connecting rod (6.1), wherein the disc-shaped locking profile (34.1) is arranged on the first connecting rod part (18.1) in a rotationally fixed manner, and wherein the locking arm (35.1) laterally surrounds the cover (19a.1) and extends along a guide (36.1) provided on the housing.

15. Internal combustion engine (1) with: -at least one reciprocating piston (3.1, 3.2, 3.3), -at least one compression ratio adjustable in a cylinder (2.1, 2.2, 2.3), and-a length adjustable connecting rod (6.1, 6.2, 6.3) according to any of claims 1 to 13 connected with the reciprocating piston (3.1, 3.2, 3.3).