WO2017102470A1

WO2017102470A1 - Connecting rod for variable compression of an internal combustion engine

Info

Publication number: WO2017102470A1
Application number: PCT/EP2016/079978
Authority: WO
Inventors: Stefanie Hutzelmann; Alexander MUDRA; Dietmar Schulze
Original assignee: ECO Holding 1 GmbH
Priority date: 2015-12-14
Filing date: 2016-12-07
Publication date: 2017-06-22
Also published as: DE102016107967A1

Abstract

The invention relates to a connecting rod (20) for an internal combustion engine having variable compression, comprising an eccentric adjusting device (22) for adjusting an effective connecting rod length, wherein the eccentric adjusting device (22) has at least one cylinder (1) having a piston (2), which is movably guided in a cylinder bore (4) and is connected to a support rod (3), wherein a supply line (5) for feeding hydraulic fluid from an oil circuit of the internal combustion engine into the cylinder (1) and a removal line (6) for discharging hydraulic fluid from the cylinder (1) into an oil circuit of the internal combustion engine are provided. According to the invention, means (9, 11) for end-position damping of the piston (2) are provided.

Description

Connecting rod for a variable compression of an internal combustion engine

Technical area

The invention relates to a connecting rod for a variable compression of an internal combustion engine with an eccentric adjusting device for adjusting an effective connecting rod length, wherein the eccentric adjusting device has at least one cylinder with a piston which is displaceably guided in a cylinder bore and connected to a support rod, wherein a Supply line for supplying hydraulic fluid from an oil circuit of the internal combustion engine in the cylinder and a drain line for discharging hydraulic fluid from the cylinder are provided in an oil circuit of the internal combustion engine.

State of the art

In internal combustion engines, a high compression ratio has a positive effect on the efficiency of the internal combustion engine. Under compression ratio is generally understood the ratio of the entire cylinder space before compression to the remaining cylinder space after compression. However, in internal combustion engines with spark ignition, in particular gasoline engines, which have a fixed compression ratio, the compression ratio may only be selected so high that a so-called "knocking" of the internal combustion engine is avoided at full-load operation low cylinder filling, the compression ratio with higher values are selected without a "knocking" would occur. The important part load range of an internal combustion engine can be improved if the compression ratio is variably adjustable. To adjust the compression ratio, for example, systems with variable connecting rod length known, which actuate by means of hydraulic switching valves an eccentric adjusting device of a connecting rod.

Disclosure of the invention

The components of such a system, in particular the pistons, are sometimes subject to very high loads. It is therefore an object of the invention to reduce the component load of the piston.

The above object is achieved with the features of the independent claim.

Favorable embodiments and advantages of the invention will become apparent from the other claims, the description and the drawings.

It is proposed a connecting rod for an internal combustion engine with variable compression, which is equipped with an eccentric adjusting device for adjusting an effective connecting rod length, wherein the eccentric adjusting device comprises at least one cylinder with a piston which is guided displaceably in a cylinder bore and connected to a support rod is, wherein a supply line for supplying hydraulic fluid from an oil circuit of the internal combustion engine in the cylinder and a drain line for discharging hydraulic fluid from the cylinder are provided in an oil circuit of the internal combustion engine. In this case, means for cushioning the piston are provided.

Advantageously, the piston speed can be reduced by the end position damping. The piston can be moved quickly without it hitting the bottom of the cylinder bore with high kinetic energy. The load on the components is reduced. The adjustment speed of the connecting rod can be almost constant over almost the entire adjustment range, because the end position damping takes place shortly before reaching the end position. The connecting rod is provided in particular for a variable compression of an internal combustion engine with an eccentric adjusting device for adjusting an effective connecting rod length.

Optionally, a per se known throttling can be combined by means of oil drilling cross sections in the Abiaufbohrung with the end position damping. According to a favorable embodiment of the connecting rod, the means for cushioning the end can be designed such that shortly before reaching a cylinder-side end position of the piston, the discharge of hydraulic fluid takes place only by a leakage between the piston and the cylinder. This allows a high and almost constant adjustment speed of the piston over almost the entire adjustment range, since the end position damping takes effect shortly before reaching the end position.

According to a favorable embodiment of the connecting rod, the means for cushioning the end can be designed such that shortly before reaching a cylinder-side end position of the piston at least a portion of the piston and at least a portion of the cylinder bore include a damping volume. By means of the damping volume and the size of the leakage, the damping properties of the connecting rod can be specified and determined for boundary conditions in use.

According to a favorable embodiment of the connecting rod, a hydraulic resistance of the leakage from the damping volume relative to the hydraulic resistance of the discharge line can be at least doubled. The condition can be realized with conventional connecting rods with reasonable effort.

According to a favorable embodiment of the connecting rod hydraulic fluid may be included in a damping volume in the state of the end position damping between a bottom of the cylinder bore and the piston. This allows a simple construction of piston and cylinder for adjusting the end position damping.

After a favorable embodiment of the connecting rod, the drain line can open into the cylinder bore such that the piston passes over the drain line before reaching the cylinder-side end position. The damping volume can be reliably separated from the drain line as soon as the piston overflows the drain line.

According to a favorable embodiment of the connecting rod, the mouth of the drain line in the cylinder bore may be spaced from a bottom of the cylinder bore. In particular, the piston may have a circumferential chamfer whose height is less than the distance. The size of the damping volume can be easily specified in this way. The chamfer allows a smooth transition from the open state of the drain line to the shut-off state of the drain line.

According to a favorable embodiment of the connecting rod hydraulic fluid in the damping volume between the bottom of the cylinder bore and the piston may be included as soon as the piston has passed over the drain line with its chamfer. The construction is reliable and robust.

According to a favorable alternative embodiment of the connecting rod, the piston support rod side a first, large diameter and cylinder side have a second, small diameter and be provided at the bottom of the cylinder bore a shoulder, which is adapted in diameter to the second diameter of the piston, so that after the Dipping the second diameter of the piston in the shoulder of the cylinder bore hydraulic fluid is enclosed in a damping volume, from which the hydraulic fluid is displaced only by a leakage between the piston and the cylinder.

According to a favorable embodiment of the connecting rod Abiaufbohrung can open at the bottom of the paragraph in the cylinder bore, so that after immersing the second diameter of the piston in the shoulder of the cylinder bore hydraulic fluid is enclosed in a damping volume between the second diameter of the piston and the cylinder bore. This allows an alternative design of the damping volume.

According to a favorable embodiment of the connecting rod can be enclosed in the shoulder of the cylinder bore hydraulic fluid in a damping volume above the heel between the second diameter of the piston and the cylinder bore after immersing the second diameter of the piston. The size of the damping volume can be determined over the axial extent of the second diameter region.

Brief description of the drawings

Further advantages emerge from the following description of the drawing. In the drawings, embodiments of the invention are shown schematically. The drawings, the description and the claims contain numerous features in combination. Of the A person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Showing:

1 shows a connecting rod with double-sided eccentric lever and an eccentric

Adjusting device with cushioning;

2 shows a section through a cylinder, support rod and piston of a connecting rod according to a first embodiment of the invention, in a first phase with a

Drilling in cylinder in open condition;

Fig. 3 shows a section through the cylinder of the connecting rod in Fig. 1 in a further phase in which the piston has just run over the Abiaufbohrung and piston and

Cylinder include a damping volume;

4 shows a section through the cylinder of the connecting rod in Figure 1 with the piston in its cylinder-side end position.

5 shows a section through a cylinder, support rod and piston of a connecting rod according to a further embodiment of the invention, in a first phase with a

Drilling in cylinder in open condition;

6 shows a section through the cylinder of the connecting rod in Figure 5 in a further phase in which the piston with a second diameter in a paragraph in the cylinder just dips and piston and paragraph include a damping volume. and

Fig. 7 shows a section through the cylinder of the connecting rod in Fig. 5 with the piston in its cylinder-side end position.

Embodiments of the invention

In the figures, the same or similar components are numbered with the same reference numerals. The figures are merely examples and are not intended to be limiting.

1 shows an isometric view of an inventive connecting rod 20 for an internal combustion engine with variable compression, with an eccentric adjusting device 22 for adjusting an effective connecting rod length. As effective connecting rod length, the distance of the central axis of the Hublagerauges (large connecting rod eye) to the center axis of the Piston pin bore (small connecting rod eye) called. The eccentric adjusting device 22 may have an eccentric 23 cooperating with a one-part or multi-part eccentric lever 24. An adjustment of the eccentric adjusting device 22 is adjustable by means of a switching valve 25. In the exemplary embodiment, the eccentric 23 has a double-sided eccentric lever 24. Alternatively, the eccentric lever 24 may be formed on one side.

A rotation of the adjustable eccentric adjusting device 22 is initiated by the action of mass and load forces of the internal combustion engine, which act on the eccentric adjusting device 22 during a power stroke of the internal combustion engine. During a power stroke, the directions of action of the force acting on the eccentric adjusting forces change continuously. The rotary movement or adjusting movement is assisted by one or more of hydraulic fluid, in particular motor oil acted on, integrated in the connecting rod 20, not visible in the figure piston 2, or prevent the pistons 2 a Rücksteilen the eccentric adjusting device 22 due to varying force action directions on the eccentric adjusting 22 acting forces. The piston 2 in the eccentric adjusting device 22 shown on the right in the figure is in its cylinder-side end position.

Fig. 2 shows a schematic representation of a cylinder 1 of a connecting rod 20 according to the invention (Figure 1). As can be seen in FIG. 2, the piston 2 is displaceably guided in a cylinder bore 4 of the cylinder 1 and connected to a support rod 3. The cylinder 1 can be provided as a separate component or integrally with a connecting rod body of the connecting rod 20 (FIG. 1).

Further, a supply line 5 for supplying hydraulic fluid from an oil circuit of the internal combustion engine in a cylinder formed by the cylinder bore 4 hydraulic chamber 7 and a drain line 6 for discharging hydraulic fluid from the hydraulic chamber 7 in an oil circuit of the internal combustion engine are provided.

In the supply line 5, a check valve 8 is arranged, which prevents a backflow from the hydraulic chamber 7 in the supply line 5, however, a subsequent sucking of hydraulic fluid into the hydraulic chamber 7 allows.

In order to reduce the load on the piston 2, means for cushioning the piston 2 are provided according to the invention. According to the embodiment shown in FIGS. 2 to 4, the means for cushioning are designed such that shortly before reaching a cylinder-side end position of the piston 2, the discharge of hydraulic fluid takes place only by a leakage between the piston 2 and the cylinder 1. This can advantageously be achieved in that the drain line 6 opens into the cylinder bore 4 such that the piston 2 passes over the drain line 6 before reaching the cylinder-side end position, which is shown in Fig. 4.

From Fig. 2 it can be seen that the mouth of the drain line 6 in the cylinder bore 4 has a distance h from a bottom 10 of the cylinder bore 4. At the same time, the piston 2, for example, a circumferential bevel 9, the height L is less than the distance h. As soon as the piston 2 with its chamfer 9 has run over the drain line 6, hydraulic fluid is enclosed in a damping volume 13 between the bottom 10 and the piston 2, from which the hydraulic fluid can be displaced only by leakage between the piston 2 and the cylinder 1 in Fig. 3 is shown.

In this way, a cushioning of the piston 2 can be achieved in a simple manner, wherein the damping takes place shortly before reaching the end position. The damping therefore has almost no effect on the adjustment speed of the connecting rod 20 (Figure 1), and the load on the piston 2 can be effectively reduced.

A second advantageous embodiment of the invention provides - as shown in FIGS. 5 to 7 - before, that the piston 2 support rod side has a first, large diameter D1 and the cylinder side, a second, small diameter D2. As can be seen, the piston 2 is guided with its first diameter D1 in the cylinder bore 4. At the bottom 10 of the cylinder bore 4, a shoulder 1 1 is provided, which is adapted in diameter to the second diameter D 2 of the piston 2 and in which the piston 2 can dip with its second diameter D 2. The Abiaufbohrung 6 opens at the bottom 12 of the paragraph 1 1 in the cylinder bore 4 so that - as shown in Fig. 6 can be seen - after immersing the area with the second diameter D2 of the piston 2 in paragraph 1 1 of the cylinder bore 4 hydraulic fluid in a damping volume 13 is enclosed above the shoulder 1 1 between the second diameter D2 of the piston 2 and the cylinder bore 4, from which the hydraulic fluid can be displaced only by a leakage between the piston 2 and the cylinder 1. Also, the second embodiment allows in a simple way a cushioning of the piston 2, wherein the damping takes place shortly before reaching the end position. The damping therefore has almost no effect on the adjustment speed of the connecting rod and the load on the piston 2 can be effectively reduced.

Claims

claims

1 . Connecting rod (20) for an internal combustion engine with variable compression with an eccentric adjusting device (22) for adjusting an effective connecting rod length, wherein the eccentric adjusting device (22) has at least one cylinder (1) with a piston (2) in a Cylinder bore (4) slidably guided and connected to a support rod (3), wherein a feed line (5) for supplying hydraulic fluid from an oil circuit of the internal combustion engine in the cylinder (1) and a drain line (6) for discharging hydraulic fluid from the cylinder (1) are provided in an oil circuit of the internal combustion engine, characterized in that means (9, 1 1) for cushioning the piston (2) are provided.

2. Connecting rod according to claim 1, characterized in that the means (9, 1 1) are designed for cushioning such that shortly before reaching a cylinder-side end position of the piston (2) the discharge of hydraulic fluid only by a leakage between the piston (2 ) and the cylinder (1).

3. Connecting rod according to claim 1 or 2, characterized in that the means (9, 1 1) are designed for cushioning such that shortly before reaching a cylinder-side end position of the piston (2) at least a portion of the piston (2) and at least one Area of the cylinder bore (4) include a damping volume (13).

4. connecting rod according to claim 3, characterized in that a hydraulic resistance of the leakage from the damping volume (13) relative to the hydraulic resistance of the drain line (6) is at least doubled.

5. Connecting rod according to one of the preceding claims, characterized in that in the state of the end position damping between a bottom (10) of the cylinder bore (4) and the piston (2) hydraulic fluid in a damping volume (13) is included.

6. Connecting rod according to one of the preceding claims, characterized in that the drain line (6) opens into the cylinder bore (4) such that the piston (2) passes over the drain line (6) before reaching the cylinder-side end position.

7. Connecting rod according to one of the preceding claims, characterized in that the mouth of the drain line (6) in the cylinder bore (4) has a distance (h) from a bottom (10) of the cylinder bore (4).

8. connecting rod according to claim 7, characterized in that the piston (2) has a circumferential chamfer (9) whose height (L) is less than the distance (h).

9. Connecting rod according to one of claims 3 to 8, characterized in that hydraulic fluid in the damping volume (13) between the bottom (10) of the cylinder bore (4) and the piston (2) is included as soon as the piston (2) with its chamfer (9) has run over the drain line (6).

10. connecting rod according to one of claims 2 to 5, characterized in that the piston (2) support rod side has a first, large diameter (D1) and the cylinder side a second, small diameter (D2) and at the bottom (10) of the cylinder bore (4 ) a shoulder (11) is provided, which is adapted in diameter to the second diameter (D2) of the piston (2), so that after immersion of the second diameter (D2) of the piston (2) in the paragraph (1 ) of the cylinder bore (4) hydraulic fluid in a damping volume (14) is enclosed, from which the hydraulic fluid can be displaced only by a leakage between the piston (2) and the cylinder (1).

1 1. Connecting rod according to claim 10, characterized in that the Abiaufbohrung (6) at the bottom (12) of the shoulder (1 1) in the cylinder bore (4) opens, so that after immersing the second diameter (D2) of the piston (2) in the shoulder (1 1) of the cylinder bore (4) hydraulic fluid in a damping volume (13) between the second diameter (D2) of the piston (2) and the cylinder bore (4) is included.

12. Connecting rod according to claim 1 1, characterized in that after the immersion of the second diameter (D2) of the piston (2) in the paragraph (1 1) of the cylinder bore (4) hydraulic fluid in a damping volume (13) above the paragraph (1 1) between the second diameter (D2) of the piston (2) and the cylinder bore (4) is included.