DE2753563A1 - Variable stroke reciprocating piston IC engine - has resilient connecting rod formed by spring=loaded hydraulic arm - Google Patents

Abstract

The piston type internal-combustion engine has a connecting rod between piston and crankshaft resilient in the lengthwise direction. The rod (7) is in the form of a hydraulic ram, spring-loaded in the extension direction, and having a sleeve (8) in which a shank (9), is guided. By shutting off the oil chamber the rim is locked in position at least at the time of ignition, dependent on the crankshaft position. The sleeve can be on the crankshaft and of the rod, while the shank can be thrust towards the maximum-extension position by a packet of leaf springs (11), accommodated in a bore in the sleeve.

Description

Daimler-Benz Aktiengesellschaft

Stuttgart-Untertürkheim daim ti 285/4

Reciprocating internal combustion engine

The invention relates to a reciprocating internal combustion engine the support of the piston against the crankshaft, which includes a connecting rod, is resilient in the longitudinal direction of the connecting rod is yielding.

In a known construction of this type (DT-PS 487 13 8) there is a spring support between the connecting rod and the piston pin arranged, the hardness of which is designed so that it responds only to peak pressures, so maximum combustion pressures and is compressed. It should thereby reduce the severity of the burns and in a corresponding manner Way, the mechanical stress on the engine parts can be reduced.

In contrast, the invention is based on the object of providing a reciprocating internal combustion engine of the type mentioned at the outset to design that regardless of the load condition, and thus the degree of filling, always an essentially the same Compression pressure is reached.

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According to the invention, this is achieved by designing the connecting rod as a hydraulic cylinder spring-loaded towards its maximum extension length, the hydraulic cylinder having a jacket and a shaft guided in this and, depending on the crankshaft position, at least around the ignition point by shutting off its oil chamber can be blocked. In the solution according to the invention is between the piston and crankshaft during the area of the ignition and combustion phase, in which pressures higher than the maximum permissible compression pressure prevail, given an unyielding support of the piston against the crankshaft. the In contrast, the compliance provided according to the invention enables a design in the compression phase which the maximum compression pressure can still be achieved with minimum filling, while conversely this compression pressure is not exceeded with maximum filling, since in this respect due to the compression of the resilient Support an enlargement of the combustion chamber analogous to the higher degree of filling can be achieved. In the case of the solution according to the invention, it is therefore an objective when the filling is low there is a smaller combustion chamber than with a high filling. This change in the effective combustion chamber volume in adaptation on the degree of filling enables the internal combustion engine to be operated at the maximum possible from the design point of view Compression and thus optimal efficiency. This avoids the compression differences that otherwise occur depending on the load and thus the degree of filling, which result if compression is below the maximum compression according to the design result in poor engine efficiency. as

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There is an additional effect in the embodiment according to the invention, that while the piston is being pushed out, the piston is always in the combustion chamber due to the relaxation of the spring reduced to a constructive minimum, with the result,

what is achieved is that an optimal expulsion of the gases consumed / and so that a very small amount of residual gas remains in the cylinder. Especially in the idle and partial load range This results in a particularly favorable ratio between the relatively small ones in relation to the full load range the amount of fresh gas drawn in and the amount of residual gas.

In an embodiment of the invention, it turns out to be more constructive View as useful if the jacket of the cylinder forms the part of the connecting rod on the crankshaft side, while the shaft is used as the piston-side part of the connecting rod. In principle, however, it is also the other way round Arrangement possible within the scope of the invention. The first-mentioned solution proves to be particularly advantageous, as this results in the proportion of the rotating mass assigned to the crankshaft compared to the oscillating mass on the piston Mass can be relatively large. The latter proves to be particularly important at higher speeds.

With regard to the smallest possible size, it is advantageous if the shaft over leaf spring assemblies in the direction is supported on its maximum extension length, wherein the leaf spring assemblies are preferably arranged in the casing bore are.

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The oil supply of the hydraulic cylinder required according to the invention is carried out in the simplest way via the crankshaft, a direct connection to the engine oil circuit can be made here. The supply itself can be controlled in a simple manner via the crankshaft, so that a simple synchronization between the necessary blocking around the top dead center and the crankshaft rotation is possible. Appropriately For this purpose, a supply bore can be assigned to the jacket, which cooperates with a circumferential supply and control groove assigned to the connecting rod bearing of the crankshaft, with a solution in which the Supply groove only extends over part of the scope of the bearing.

In order to be able to realize the advantages according to the invention independently of the speed, it proves to be expedient if at in the direction of their maximum extension length spring-loaded connecting rod that can be shortened in the opposite direction the piston connected to the connecting rod via the piston pin is assigned a counterweight which is longitudinally displaceable in the connecting rod direction and which is supported by a lever with respect to the piston-side connecting rod part whose bearing has a fixed radial distance from the crankshaft. This results in a compensation of the loads that occur as a function of centrifugal force, which could lead to a situation in which at high speeds solely due to the given Centrifugal forces at full load the compression pressure is too high.

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In general, it can be stated about the solution according to the invention that this increases the magnitude of the mechanical losses of the internal combustion engine remains essentially unaffected by the operation of the internal combustion engine with almost unchanged

internal

sealing across all load ranges but a significant improvement in efficiency is achieved. In particular, the resilient support does not require any in the solution according to the invention Power loss, since the compression work is released again during the expansion stroke after falling below the maximum compression pressure.

The invention is explained in more detail below with further details on the basis of exemplary embodiments. Show it:

Fig. 1 is a schematic sectional view of a reciprocating internal combustion engine according to the invention, wherein a crankshaft position adjacent to the top dead center - shortly before ignition - is given and for this crankshaft position the different piston positions for work at low part load, high part load and full load are indicated,

FIG. 2 shows a sectional illustration corresponding to FIG. 1 with a maximum combustion pressure corresponding crankshaft position, again showing the different piston positions for low part load, high part load and full load are shown,

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3 shows a sectional view corresponding to FIGS. 1 and 2 through a reciprocating piston internal combustion engine, the piston position for one of the top dead center in the exhaust stroke corresponding crankshaft position is shown,

4 shows a sectional view corresponding to FIGS. 1 to 3

darstellnng by a reciprocating internal combustion engine according to the invention, wherein a Piston position is shown, which corresponds to the crankshaft position at bottom dead center at the end of the intake stroke,

5 shows a further, schematic sectional illustration through a reciprocating piston internal combustion engine according to the invention, wherein a weight relief is provided for the piston and

6-8 sections according to lines VI-VI, VII-VII and VIII-VIII in Fig. 5.

In the figures, a reciprocating piston internal combustion engine 1 is shown schematically, in which the gas exchange takes place via an intake channel 2 and an outlet channel 3, wherein the intake channel 2 is assigned a throttle element in the intake path in a manner not shown here, via which the sucked-in mixture or .Air volume is controlled depending on the load. According to the different ones for different load conditions Positions of the throttle element, so z. B. a throttle valve result for the combustion chamber 4 of the machine, which is essentially through the Zvlhderkopf 5 on the one hand and the piston

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/ ro

on the other hand is limited, different filling quantities, based on a combustion chamber of the same size for all Load conditions would result in different compression pressures.

Depending on the load condition, different levels of compression of the fuel-air mixture influence the efficiency (Fuel consumption) of the machine negative, as this is an optimal range in terms of its efficiency only for a certain compression. But the lower the compression, the worse it gets Efficiency of the internal combustion engine. Accordingly, the solution according to the invention corresponds to the filling of the cylinder in the intake stroke realized a variable volume for the combustion chamber 4 in order to with the different Load conditions, and thus always achieve an approximately equally high compression with the different degrees of filling. This corresponds to the maximum compression, which is why a small combustion chamber with a low filling and a high filling there must be a large combustion chamber.

This change in the volume of the combustion chamber 4 is achieved in the solution according to the invention in that the Connecting rod 7 is designed to be longitudinally flexible at least for the compression stroke and at least following the Compression stroke around top dead center can be blocked in its longitudinal flexibility.

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For this purpose, the connecting rod 7 is a hydraulic cylinder in the embodiment illustrated in the exemplary embodiments formed, which has a jacket 8 and a shaft 9 guided in this, the jacket 8 forming the part of the connecting rod 7 on the crankshaft side and being mounted in the usual way on a corresponding pin 1o of the crankshaft.

The shaft 9, which is axially guided in the jacket 8, is supported coaxially to the jacket 8 via leaf spring assemblies 11 with regard to the longitudinal flexibility of the connecting rod 7, the support being directly opposite the jacket 8 or also opposite the crankshaft journal 1o can be done. This latter embodiment is illustrated in Figs. 1 and 2, in which the leaf spring assemblies 11, which are axially guided in a corresponding bore 12 of the shell 8, are supported on a support ring 13, which is in a crankshaft side Extension of the bore 12 is located and is supported directly on the Zap-4n 1o of the crankshaft or the bearing shell 14 assigned to it. The support ring 13 and the central point Shank 9 oil holes 15, 16 on, of which the oil hole 16 in the shaft 9 via a throttle bore 17 with a small cross-section on the piston-side bearing eye 18 of the connecting rod or of the shaft 9 which receives the piston pin 19.

Via a supply bore, not shown here, assigned to the crankshaft, and an adjoining one Radial bore 2o in the crankshaft journal 1o is a control

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Nut 21 connected to the oil supply of the machine. Upper this control groove 21 is used to connect the hydraulic cylinder serving as the connecting rod 7 to the oil supply of the Machine. The control groove 21 extends in the illustrated embodiment over an angular range between about 18o to 27o degrees, preferably about 21o, with reference to the top dead center position of the Piston corresponding position of the crank pin 1o extends approximately over its lower region and further related to their on the direction of rotation 22 of the crankshaft rear edge 23 opposite the vertical radial plane of the crank pin 1o is offset in the direction of rotation 22 in its top dead center position. In the circumferential direction, the size corresponds to this Offset at an angle of about 15 to 2o degrees, so that the oil hole 15 is in the area of the top dead center of the crankshaft journal completed and accordingly the cylinder space, which is essentially through the bores 12, 15 and 16 is formed, is locked. The barrier remains in place until the front edge 24 in relation to the direction of rotation

the control groove 21 the oil bore 15 is reached, so that the connection to the control groove 21 is restored. In the exemplary embodiment shown, the release takes place about $ o after TDC.

Solarge the hydraulic cylinder serving as the connecting rod 7 is disconnected from the oil supply. he practically blocks, so that further retraction is not possible. The connecting rod 7 thus behaves in the said area around the

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top dead center as if rigid. Accordingly, in the solution according to the invention, the volume of the combustion chamber 4 can indeed change during the compression phase in such a way that it is independent depending on the load condition, and thus also on the respective degree of filling, the maximum compression ratio is achieved is when, according to the invention, the leaf spring assemblies in relation are designed accordingly for their supporting force, a further compression following the compression phase and thus under the influence of the much higher combustion pressures but is excluded.

Different sizes of the volume of the combustion chamber 4, which depend on the respective load condition, and thus also The uppermost piston position 25, symbolized by a solid line, is the position of the piston 6 towards the end of the compression phase at low partial load, and thus at lower Filling shows. In relation to the same crankshaft position, the dash-dotted line 26 symbolizes the corresponding position of the piston at high partial load, while the line 27 - dashed - shows the corresponding position of the piston at full load.

The different, load-dependent, d. H. that is to say, piston positions that adjust depending on the degree of filling correspond in each case to corresponding effective lengths of the connecting rod 7, and it becomes these connecting rod lengths during the combustion phase, at least after the top dead center area

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maintained, since, as FIG. 2 shows, the connecting rod length by disengaging the hydraulic cylinder forming the connecting rod 7 is fixed during this phase. Accordingly, also during the said combustion phase, as can be seen from FIG. 2, depending on the respective load condition, and thus on the respective filling level based on the same crankshaft position in turn, given different pin positions for the piston 6 are indicated in Fig. 2 analogously to the representation according to FIG. 1 with 25 ', 26 * and 27'.

3 shows the internal combustion engine explained with reference to FIGS. 1 and 2 in their top dead center position at the end of the exhaust stroke. As in the position according to FIG. 2, this is the case Connecting rod 7 cut off from the oil supply and thus blocked in its length. This blocking is so far but without Significance, since the exhaust stroke corresponds to the compression pressure Back pressure is not given, so that the connecting rod is already under the influence of the exhaust stroke Spring force was extended to its maximum length, in which it is now (Fig. 3) blocked around the top dead center. Through this, that there is no significant back pressure during the exhaust stroke, and accordingly the maximum extension length for the connecting rod is achieved, a minimum combustion chamber volume can be achieved in this work phase for the internal combustion engine shown realize, with the result that only a very small amount of fuel gas remains in the combustion chamber 4. The consequence is that about the Residual gases only insignificantly contaminated the fresh gases drawn in in the subsequent intake phase, which is essential in order to ensure regular ignition, especially at low partial loads and when idling is.

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The intake stroke in Tig. 4, runs practically without changes in the machine designed according to the invention compared to comparable internal combustion engines with a fixed piston rod length. That during the suction phase of the the hydraulic cylinder forming the connecting rod 7 is in turn connected to the oil supply, remains without influence the process, since the maximum length of the connecting rod has already been set during the exhaust stroke, that too is maintained during the intake stroke.

The invention thus makes it a reciprocating internal combustion engine created, which without substantial complication of their structure in a wide variety of load conditions has constant compression, and which therefore leads to better efficiency - lower fuel consumption - and leads to better exhaust gas composition. In this sense, it is also advantageous that the residual gas content in the solution according to the invention, as explained with reference to FIG. 3, can be kept particularly small, whereby misfires can be largely avoided and whereby a lower idle speed is also possible.

Opposite to the gas pressure forces in the compression phase act on it, the piston will through towards the end of the compression phase, especially at higher speeds applied to him acting mass forces. These can earth so high that they at least partially absorb the gas pressure forces Compensate, so that compression can be too high, especially in the full load range.

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To counter this, according to the invention in connection with the one provided here, spring-loaded in the direction of its maximum extension length and shortenable in the opposite direction Connecting rod 1o7 a relief device can be provided, in which deru over the piston pin 119 with the Connecting rod 1o7 connected piston 1o6 is assigned a counterweight, which is in the longitudinal direction of the divided connecting rod 1o7 is longitudinally displaceable and is supported by lever 129 with respect to the piston-side connecting rod part 1o9 is, the bearing 13o a fixed radial distance to the crankshaft, or the connecting rod 1o7 supporting Has crank pin 11o.

In detail, the crankshaft-side is also in this embodiment Connecting rod part 1o8 designed like a jacket and takes the leaf spring assemblies 111 in its jacket bore on. In the above-mentioned bore 112, a support ring 113 is in turn arranged adjacent to the crank pin 11 o, the

is screwed against the jacket 1o8 and on which the leaf spring assemblies 111 are supported on the crankshaft side. In the opposite direction, the leaf spring assemblies act on the piston-like guide end located in the bore 112 / the piston-side connecting rod part 1o9, which has a sleeve-shaped extension 132 against the crankshaft, which centrally penetrates the leaf spring assemblies and is additionally guided in a guide bore 133 of the support ring 113.

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The crankshaft side and essentially through a jacket The connecting rod part 1o8 formed has a collar 134 protruding into the bore 112 at its end facing the piston which limits the extension length of the piston-side connecting rod part 1o9 and serves as a stop for the guide piston 131. At its end facing the piston 1o6, the connecting rod part 1o8 on the crankshaft side is also provided with two nozzles 135, the axes of which are parallel to one another and to the crankshaft axis and which are parallel to one another with respect to the axis 136 of the connecting rod 1o7 are diametrically opposite, lying in a common plane perpendicular to the axis 136. Above the eyelets are 135 attached to the connecting rod part 1o8 on the crankshaft side, as shown in particular in FIG. As FIG. 7 shows, the bearing bores 138 have bearing journals 139 assigned to the levers 129. Opposite the eyelets 135 are the tabs 137 are fixed by screws 14o inserted into the eyelet eyes.

The levers 129, which are designed as two-armed levers, are arranged symmetrically to a plane containing the axis 136, in turn, however, not symmetrical about their axis of rotation. Rather, the lever arm assigned to the counterweight is larger than that piston-side connecting rod part assigned, so that the counterweight is designed to be lighter in accordance with the transmission ratio can be. The piston-side connecting rod part 1o9 on the one hand and the counterweight 128 on the other hand are recesses 143, for the arms of the lever assigned, the recesses 143 in the counterweight and the recesses 144 in the piston rod side Connecting rod part 1o9 are provided. The recesses

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extend as substantially semi-cylindrical recesses parallel to the axes of rotation 142 of the levers, which, in the case of the basic shape of the remnant, are replaced by parallel and cylindrical parts adjoining one another are formed in the transverse direction via a constriction.

The counterweight 128 is in the solution according to the invention both with respect to the piston 1o6 as well as with respect to the connecting rod part 1o9 on the kibensei side in the longitudinal direction of the Connecting rod Io7 displaceable, whereby it is opposite to the piston-side Connecting rod part is guided. The guide is designed as a slide guide, with the counterweight with a corresponding shoulder 145 in each case in a receiving groove 146 of the piston rod-side connecting rod part 1o9. Rei U-shaped, to one the axis of the piston pin 110 and the axis 136 of the connecting rod 1o7 containing plane of symmetrical design of the counterweight 128 results such an exact guidance in the longitudinal direction of the connecting rod, the recesses 143 for the lever 129 near the free ends of the U-shaped counterweight 12S lie.

The basic function and the basic structure of a connecting rod 5 to 8 corresponds to what has been explained with reference to FIGS. 1 to 4. In addition, in the embodiment according to FIGS. 5 to 8 only achieve a speed-dependent mode of operation, since the inertia forces that take effect on the piston 1o6 compensated through the intermediary of the lever 129 via the counterweight 128 and thus directly on the crank

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so shaft / supported that the levers over the tabs 137 and the connecting rod part 1o8 on the crankshaft side are directly connected to the crankshaft.

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Claims (9)

Daimler-Benz Aktiengesellschaft Stuttgart-Untertürkheim Daim 11 285/4 Expectations .) Reciprocating internal combustion engine in which the one connecting rod comprehensive support of the piston against the crankshaft in the longitudinal direction of the connecting rod is resilient, characterized by the design of the connecting rod (7, 1o7) as in the direction of its maximum Extension length of spring-loaded hydraulic cylinder, which has a jacket (8) and a shaft (9) guided in this and as a function of the crankshaft position at least around the ignition point by shutting off its oil chamber can be blocked. 2. Reciprocating internal combustion engine according to claim 1, characterized in that the jacket (8) forms the part of the connecting rod (7) on the crankshaft side. 3. Reciprocating internal combustion engine according to claim 1 or 2, characterized in that the Shank (9) over / fifa <tfeiTTpakete towards its maximum Extension length is supported. 909823/0199 - 2 - Daim 11 285/4 2763563 4. Reciprocating internal combustion engine according to claim 3, characterized in that the Springs (11) are arranged in a bore (12) of the jacket (8). 5. Reciprocating internal combustion engine according to one of the preceding claims, characterized in that that the hydraulic cylinder (connecting rod 7) via the crankshaft to an oil circuit, in particular the Motovölkreislauf is connected. 6. Reciprocating internal combustion engine according to one of the preceding Claims, characterized in that the jacket (8) assigned to the crankshaft a supply bore (15) is assigned, which is assigned to a circumferential, the connecting rod bearing of the crankshaft Supply and control groove (21) cooperates. 7. Reciprocating internal combustion engine according to claim 6, characterized in that the control groove (21) only extends over part of the scope of the warehouse. 8. Reciprocating internal combustion engine, in particular after a of the preceding claims, characterized in that when in the direction of their Maximum extension length of spring-loaded connecting rod (1o7) that can be shortened in the opposite direction dem A counterweight (128) is assigned to the piston (1o6) connected to the connecting rod (1o7) via the piston pin (119) which is longitudinally displaceable in the connecting rod direction and which is opposite to the piston-side connecting rod 909873/0199 ~ ³ - Daim 11 285/4 27Ö3563 Rod part (1o9) supported by at least one lever (129 ") is, whose bearing is held in a fixed radial distance to the crankshaft. 9. Reciprocating internal combustion engine according to claim 8, characterized in that the storage of the two-armed reversing lever (129) is assigned to the crankshaft-side part (1o8) of the connecting rod (1o7). 90982V 0199