EP3267011A1 - Device for changing a compression ratio of a reciprocating piston combustion engine - Google Patents

Abstract

Device for changing a compression ratio of a reciprocating internal combustion engine with a crank mechanism with a crankshaft with at least one both sides rotatably mounted crank pin, which is operatively connected to a connecting rod and a piston in a cylinder of the reciprocating internal combustion engine piston arranged to convert a rotational movement of the crankshaft in a bidirectional, translational movement of the piston with a defined lifting height, between the crank pin and a connecting rod of the connecting rod a rotatable externally toothed eccentric is arranged to change the lifting height of the piston, wherein an externally toothed first gear is provided for rotating the eccentric, the axially is rotatably connected to a second gear via a shaft arranged parallel to the crankshaft, which is arranged on a, rotatable by an actuating element third gear meshing, wherein the shaft parallel and radia l is arranged spaced from a rotational axis of the crankshaft.

Due to the inventive design, the device can be integrated to save space, without major changes in a conventional crankcase.

Description

The invention relates to a device for changing a compression ratio of a reciprocating internal combustion engine having the features of the preamble of patent claim 1.

A variable compression ratio opens up consumption and performance potentials by adapting it to the load condition of the internal combustion engine, which remain unused with a fixed compression ratio.

Also known is the use of an eccentric bearing shell in the large connecting rod to represent a variable compression ratio or compression ratio, which rotates in the same direction at half crankshaft speed. The compression ratio is then adjustable by adjusting the phase angle of the bearing shell.

From the WO 2011/006537 A1 is a generic device for changing the compression ratio of a reciprocating internal combustion engine with a crank mechanism known. The crank mechanism has a crankshaft, with both sides rotatably mounted crank pin, each with a connecting rod and a sliding in a cylinder of the reciprocating internal combustion engine arranged piston in Active compound stand. This results in the conversion of the rotational movement of the crankshaft into a bidirectional translational movement of the pistons in the cylinders with a defined lifting height. Between the crank pin and the connecting rod of the connecting rod in each case a rotatable, externally toothed eccentric is arranged, with the aid of which the lifting height of the piston adjustable, and the compression ratio is variable. Here, an externally toothed first gear is provided for rotating the eccentric, which is rotatably connected axially with a second gear via a shaft arranged parallel to the crankshaft. This gear interacts with an internally toothed gear, which is rotatable by a worm. By the rotation of the internally toothed gear thus the compression ratio of the reciprocating internal combustion engine is variable or adjustable.

A disadvantage of this configuration is a significant weakening of the load-bearing structure of the crankshaft, in particular in the region of the main bearing, by the necessary for Phasenwinkel-, or compression adjustment synchronization transmission from the crankcase to the eccentric bearing shells. This leads to a reduction in the achievable increased efficiency of the internal combustion engine associated with the compression adjustment and to an increase in the frictional losses due to increased bearing diameters, whereby essential parts of the achievable potential are again consumed by the variable compression ratio of the internal combustion engine.

Next is from the European patent application EP 0 184 042 , from which the present invention proceeds, an apparatus for varying a compression ratio of a reciprocating internal combustion engine known. The reciprocating internal combustion engine has a crank mechanism with a crankshaft with at least one crank pin rotatably mounted on both sides, with a connecting rod and a piston movably movably arranged in a cylinder of the reciprocating internal combustion engine Active connection stands up to the conversion of a rotational movement of the crankshaft in a bidirectional, translational movement of the piston with a defined lifting height. Between the crank pin and the connecting rod eye of the connecting rod, a rotatable, externally toothed eccentric is arranged to change the lifting height of the piston, wherein an externally toothed first gear is provided for rotating the eccentric axially parallel with a second gear via a crankshaft and with her circumferentially arranged shaft is rotatably connected, which is arranged on a meshing, rotatable by an actuating element third gear, wherein the shaft is arranged parallel and radially spaced from the crankshaft.

A disadvantage of this configuration is the frontal adjustment of the compression ratio, which requires a lot of space. Furthermore, this device can not be integrated into an existing crankcase.

The object of the present invention is o. G. To avoid disadvantages.

This object is achieved by the feature in the characterizing part of patent claim 1.

It is inventively proposed a device (a synchronization gear) for changing the compression ratio of a reciprocating internal combustion engine, which acts around the load-bearing crankshaft structures outside and at the same time ensures the necessary speed ratios. Here, the rotatably mounted in the crankcase gears (third and fourth gear) move only in the adjustment of the compression ratio, but not constantly due to the rotation of the crankshaft. The device itself is stored here to save space rotatably mounted in the crankcase.

The proposed device according to claim 1 is suitable for a single-cylinder reciprocating internal combustion engine.

The embodiment according to claim 2 is suitable for a multi-cylinder reciprocating internal combustion engine.

The embodiment according to claim 3 is particularly compact.

The drives of the third or fourth gear according to claim 4 are particularly preferred embodiments.

The arrangement acc. Claim 5 is particularly compact and can be integrated with only minor changes in an existing crankcase.

The embodiment according to claim 6 is a variant.

Fig. 1

zeigt schematisch eine erfindungsgemäße Vorrichtung zum Verändern eines Kompressionsverhältnisses für eine Hubkolben-Brennkraftmaschine mit zwei Zylindern.

Fig. 2

zeigt schematisch eine zweite erfindungsgemäße Vorrichtung zum Verändern des Kompressionsverhältnisses einer Hubkolben-Brennkraftmaschine mit sechs Zylindern.

Fig. 3

zeigt schematisch eine Stirnansicht einer erfindungsgemäßen Vorrichtung zum Verändern des Kompressionsverhältnisses einer Hubkolben-Brennkraftmaschine für ein erstes konkretes Ausführungsbeispiel.

Fig. 4

zeigt schematisch eine Stirnansicht einer erfindungsgemäßen Vorrichtung zum Verändern des Kompressionsverhältnisses einer Hubkolben-Brennkraftmaschine für ein zweites konkretes Ausführungsbeispiel.

Fig. 5

zeigt eine technische Ausführung der erfindungsgemäßen Vorrichtung zum Verändern des Kompressionsverhältnisses einer Hubkolben-Brennkraftmaschine, wobei die Kurbelwelle nicht dargestellt ist.

The invention is explained in more detail below with reference to three exemplary embodiments in five figures.

Fig. 1

schematically shows a device according to the invention for varying a compression ratio for a reciprocating internal combustion engine with two cylinders.

Fig. 2

schematically shows a second device according to the invention for varying the compression ratio of a reciprocating internal combustion engine with six cylinders.

Fig. 3

schematically shows an end view of a device according to the invention for changing the compression ratio of a reciprocating internal combustion engine for a first specific embodiment.

Fig. 4

shows schematically an end view of a device according to the invention for varying the compression ratio of a reciprocating internal combustion engine for a second specific embodiment.

Fig. 5

shows a technical embodiment of the inventive device for varying the compression ratio of a reciprocating internal combustion engine, wherein the crankshaft is not shown.

The following apply to the same components in the FIGS. 1 to 5 the same reference numbers.

Fig. 1 schematically shows an inventive device for varying a compression ratio of a reciprocating internal combustion engine with two cylinders.

mit

• V_H = Hubraum (Kolbenhub * Kolbenfläche)
• V_K = Kompressionsvolumen

The compression ratio ε is the ratio of an entire cylinder space of an internal combustion engine before compression to the remaining space after compression. $$\epsilon =\frac{V_H+V_K}{V_K}$$

With

• V _H = displacement (piston stroke * piston area)
• V _K = compression volume

The reciprocating internal combustion engine has a crank mechanism 1, with a dashed crankshaft 2 with two mutually rotatably mounted crank pins 3, 3 ', each with a connecting rod 4, 4' and one in a cylinder 5, 5 'of the reciprocating internal combustion engine Bidirectionally sliding movably arranged pistons 6, 6 'are in operative connection. A crankshaft axis is numbered 2 '. This part of the device is used to convert a rotational movement of the crankshaft 2 in a bidirectional, translational movement of the piston 6, 6 'with a defined lifting height. Between the crank pins 3, 3 'and non-numbered connecting rods of the connecting rods 4, 4' is in each case a rotatable, externally toothed eccentric 7, 7 'arranged to change the lifting height of the piston 6, 6'. To rotate the eccentric 7, an externally toothed first gear 8 is provided, which is axially connected in rotation with a second gear via a parallel to the crankshaft 2 arranged Weller10. The second gear 9 is rotatably connected in this embodiment via the third gear 12 with a fourth gear 13 having a larger outer diameter than the revolving second gear 9. The fourth gear 13 is rotatably adjustable in this embodiment via an actuating element 11. The third and fourth gear 12, 13 are rotatably mounted in a crankcase of the reciprocating internal combustion engine. By adjusting the fourth gear 13, as already mentioned, the eccentric 7 is rotated and thus changes the compression ratio of the internal combustion engine. According to the invention, the shaft 10 is arranged parallel to and radially outwardly spaced from the crankshaft 2. In this case, the rotational movement of the crankshaft 2 and the adjusting movement of the fourth gear 13 can take place simultaneously and at different speeds.

This basic adjustment mechanism or this device for changing the compression ratio of the reciprocating internal combustion engine can be used for a reciprocating internal combustion engine with a cylinder.

However, since in the present embodiment, a reciprocating internal combustion engine is shown with two cylinders, engages in the outer toothing of the eccentric 7, a fifth gear 14 which rotatably on a parallel to the crankshaft axis 2 'arranged second Shaft 15 rotatably connected to a sixth gear 14 ', which transmits the adjustment of the fifth gear 14 to an outer toothing of the second eccentric 7'.

In a further embodiment, the fourth gear 13 can be omitted and the actuator 11 acts directly on the third gear 12 a.

In the embodiment in Fig. 1 is the second shaft 14 disposed in an axial through hole of the crankshaft 2 coaxial with the crankshaft 2, which allows a very space-saving design. In other embodiments, the third or fourth gear 12, 13 may be rotated by the actuator 11 via a seventh gear or a rack or a worm or a slider.

Fig. 2 shows a device for varying the compression ratio of a reciprocating internal combustion engine with six cylinders. The two middle cylinders again show the same kinematics as Fig. 1 however, adjacent to the two middle cylinders on each side there are two further non-numbered cylinders with the same crank mechanism, each having a drive-through with a second shaft 15, for varying the compression ratio of the four other non-numbered cylinders.

In the in Fig. 2 illustrated embodiment, the cylinder 6 of the reciprocating internal combustion engine, a high compression 16 and the cylinder 6 'has a low compression 17.

Fig. 3 schematically shows an end view of the inventive device for varying the compression ratio of a reciprocating internal combustion engine for a specific embodiment, as shown in the FIGS. 1 and 2 can be used. In this real working embodiment, the gears have the following numbers of teeth: Eccentric 7: 55 teeth First gear 8: 15 teeth Second gear 9 36 teeth Third gear 12: 66 teeth Fourth gear 13: 148 teeth

The directions of rotation of the individual gears to a larger compression ratio out are indicated schematically by arrows. The cylinder direction is upwards, d. H. in the direction of the crank pin, and the eccentric third

Fig. 4 shows schematically an end view of a device according to the invention for varying the compression ratio of a reciprocating internal combustion engine for a second specific embodiment. It essentially applies to Fig. 3 said, but in this second embodiment between the first gear 8 and the fifth gear 14, an intermediate gear 19 is arranged, which consists in this embodiment of only a single gear.

The directions of rotation of the individual gears to a larger compression ratio are again shown schematically by arrows.

Fig. 5 shows a technical embodiment of the inventive device for varying the compression ratio of a reciprocating internal combustion engine. The crankshaft 2 and a crankcase are not shown. In Fig. 5 are three storage rollers 20 for the fourth gear 13 can be seen, with which the fourth gear 13 is rotatably mounted radially outwardly relative to the crankcase of the reciprocating internal combustion engine. Preferably, three storage rollers 20 are provided for a statically determined storage. As in Fig. 5 further recognizable, is the device Space-saving between two cylinders 5, 5 'of the reciprocating internal combustion engine arranged, whereby they can be integrated into an existing crankcase without much rework.

In other words, in summary:

It is thus proposed a synchronization gear, which acts around the load-bearing crankshaft structures outside and ensures the necessary speed ratios. Here, the mounted in the crankcase gears 12, 13 move only during the adjustment of the compression ratio, but not constantly due to the rotation of the crankshaft 2. Between two cranks of the crankshaft synchronization takes place through the center of the journal pin of the crankshaft 2, as this often hollow, because at this point the crankshaft hardly a load is transmitted.

Thus, a system is proposed which generates no friction disadvantages by a larger crankshaft diameter.

With a suitable dimensioning of the plain bearings inside and outside on the eccentric bearing shell (width x diameter ³ are approximately the same inside and outside), these rotate by themselves with half the crankshaft speed, so that on average no drive energy is obtained. The sum of the friction of the two in each case crank pin connected in series sliding bearing can be even lower than that of an original Hubzapfenschleitlager from the prior art, namely, if the sum of the two bearing clearance can remain greater than that of the original one sliding bearing (the friction is proportional to the relative speed squared divided by the bearing clearance).

Since the position of the crankcase-side control element 11 clearly reflects the set compression ratio (in contrast to known systems which have only one stop and the system can adjust itself under the acting forces), a valve lift adjustment device (eg BMW Valvetronic) can mechanically couple valve lift or phase angle of the valve lift with the compression ratio. An example of the combination of a variable compression ratio with a variable valve train, for example, from the German patent application DE 10 2006 015 887 A1 known. Thus, since low compression is generally combined with high valve strokes and low valve overlap and vice versa at high load, valve freeances in the piston can thus be minimized, opening up further thermodynamic fuel economy potentials through a more favorable combustion chamber shape.

Thus, according to the invention, consumption advantages for conventional reciprocating internal combustion engines with space-conforming technology are developed at very low adjustment energy. Further, maximum utilization of the potential of the variable compression ratio is achieved by direct, continuous and quick adjustability.

It is further proposed an actuator between two cylinders 5, 5 ', consisting of a rotatable, for the purpose of assembly to the one-piece crankshaft 2 divided adjusting wheel (fourth gear 13), the z. B. is supported by bearing rollers 20 in the crankcase, see Fig. 5 ,

With its inner gear (third gear 12) meshes a gear (second gear 9) mounted in the crankshaft 2, rotating pickup shaft (shaft 10), while the second gear (first gear 8) in the toothing of the adjusted bearing shell (eccentric 7) engages and thus acts directly on one of the synchronized bearing shells (eccentric 7, second eccentric 7 ') speed and phasing.

The numbers of teeth are chosen so that the bearing shell (eccentric 7) with the desired speed around the crank pin 3 of the crankshaft 2 rotates. When the adjusting wheel (fourth gear 13) is stationary, the phase angle of the rotation and thus the compression of the reciprocating internal combustion engine remain constant.

This can be adjusted by turning the same, for example by means of a worm drive and a servomotor acting on it, in the crankcase. This results in a clear relationship between the angle of the setting wheel (fourth gear 13) in the crankcase and the set compression.

LIST OF REFERENCE NUMBERS

1.

crankshaft

Second

crankshaft

2 '

crankshaft axis

Third

crank pins

3 '

second crankpin

4th

pleuel

4 '

second connecting rod

5th

cylinder

5 '

second cylinder

6th

piston

6 '

second piston

7th

eccentric

7 '

second eccentric

8th.

first gear

9th

second gear

10th

wave

11th

actuator

12th

third gear

13th

fourth gear

14th

fifth gear

14 '

sixth gear

15th

second wave

16th

high compression

17th

low compression

18th

Main bearing

19th

intermediate gear

20th

Lagerungsrolle

Claims (6)

Device for modifying a compression ratio of a reciprocating internal combustion engine with a crank mechanism (1) with a crankshaft (2) with at least one crank pin (3) rotatably mounted on both sides and connected to a connecting rod (4) and a cylinder (5) of the piston piston Internal combustion engine sliding movably arranged piston (6) is in operative connection, for converting a rotational movement of the crankshaft (2) in a bidirectional, translational movement of the piston (6) with a defined lifting height, wherein between the crank pin (3) and a connecting rod eye of the connecting rod ( 4) a rotatable, externally toothed eccentric (7) is arranged to change the lifting height of the piston (6), wherein the rotation of the eccentric (7) an externally toothed first gear (8) is provided which axially with a second gear (9) via one to the crankshaft (2) arranged in parallel shaft (10) is rotatably connected, which on one of a control element (11) rotatable d ritten toothed wheel (12) is arranged, wherein the shaft (10) parallel and radially outwardly spaced to a rotation axis crankshaft (2) is arranged, wherein a fourth gear (13) is provided, which is non-rotatably connected to the third gear (12), wherein the fourth gear (13) has a larger outer diameter than the third gear (12) and the fourth gear (13) of the adjusting element (11) is rotatable,
characterized in that the fourth gear (13) is rotatably mounted in an interior of a crankcase of the reciprocating internal combustion engine. Device according to claim 1, wherein the crankshaft (2) has a second crank pin (3 ') which is connected to a second connecting rod (4') and a second piston (6 ') movably movably arranged in a second cylinder (5') of the reciprocating piston engine. ) is in operative connection, for converting the rotational movement of the crankshaft (2) into a bidirectional, translational movement of the second piston (6 ') with a defined lifting height, wherein between the second crank pin (3') and a second connecting rod eye of the second connecting rod ( 4 ') a rotatable, externally toothed second eccentric (7') is arranged to change the lifting height of the second piston (6 '),
characterized in that for the rotation of the second eccentric (7 ') an externally toothed fifth gear (14) is provided, which is rotatably connected to a sixth gear (14') via a parallel to the crankshaft second shaft (15), wherein the sixth gear (13) with the externally toothed eccentric (7) is in operative connection. Device according to claim 2,
characterized in that the second shaft (15) in an axial through hole of the crankshaft (2) is arranged coaxially with the crankshaft (2). Device according to one of the claims 1 to 3,
characterized in that the third or the fourth gear (12, 13) of the adjusting element (11) via a seventh gear or a rack or a worm or a slider is rotatable. Device according to one of the claims 2 to 4,
characterized in that the actuator (11) and the third gear (12) and the fourth gear (13) between the first cylinder (5) and the second cylinder (5 ') are arranged. Device according to one of the claims 1 to 5,
characterized in that between the first gear 8 and the fifth gear 14, an intermediate gear 19 is arranged.

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