Connecting rod and combustion engine

Abstract

Connecting rod (10) for an internal combustion engine with adjustable compression ratio, with a crank bearing eye (11) for connecting it to a crankshaft and a connecting rod bearing eye (12) for connecting it to a cylinder piston, an eccentric adjusting device (13) for adjusting an effective connecting rod length, wherein the eccentric adjusting device (13) has an eccentric (36) cooperating with an eccentric lever (14) and eccentric rods (15, 16), wherein the eccentric rods (15, 16) engage with a first end in an articulated manner on the eccentric lever (14) and with a second end in an articulated manner on pistons (20, 21) displaceably guided in hydraulic chambers (22, 23) of the connecting rod, and wherein the eccentric (36) is received in a connecting rod bearing eye bore of the connecting rod bearing eye (12), which comprises an eccentric bore for receiving a cylinder piston pin, characterized in that a center point (18) of the eccentric bore is selected such that an axis (37) extending through the center point (18) of the eccentric bore and a center point (17) of the connecting rod bearing eye bore encloses a first angle (γ) between 80° and 100° with a direction of movement (38) of the cylinder piston in a center position of the eccentric adjusting device (13), wherein the center position of the eccentric adjusting device (13) is the position of the eccentric adjusting device (13) which lies in the center of the adjustment range of the eccentric adjusting device (13) and thus in the center of the adjustment range of the connecting rod (10), and an engagement point (39) of a first eccentric rod (16) on the eccentric lever (14) is selected such that a movement axis (40) of the piston (20) engaging the first eccentric rod (16) and an axis extending through this engagement point (39) and the center point (17) of the connecting rod bearing eye bore enclose a second angle (α) between 80° and 100° in the center position of the eccentric adjusting device (13), and an engagement point (42) of a second eccentric rod (15) on the eccentric lever (14) is selected such that a movement axis (43) of the piston (21) which engages the second eccentric rod (15) and an axis (44) extending through this engagement point (42) and the center point (17) of the connecting rod bearing eye bore enclose a third angle (β) between 80° and 100° in the center position of the eccentric adjusting device (13).

Description

[0001] The invention relates to a connecting rod for an internal combustion engine and an internal combustion engine.

[0002] Fig. Figure 1 shows a connecting rod of an internal combustion engine with an adjustable compression ratio, as known from DE 10 2010 016 037 A1. Thus, the connecting rod 10 has a pin bearing eye 11 and a connecting rod bearing eye 12, with the pin bearing eye 11 connecting the connecting rod 10 to a Fig. 1 not shown crankshaft and the connecting rod bearing eye 12 of the connection of the connecting rod 10 to a Fig. 1 not shown cylinder piston of the internal combustion engine. The connecting rod 10 is assigned an eccentric adjusting device 13, which Fig. 1, an eccentric lever 14, and eccentric rods 15, 16. The eccentric has a bore arranged eccentrically to a center point 17 of a connecting rod bearing eye bore with a center point 18, wherein the bore in the eccentric accommodates a cylinder piston pin. The eccentric adjustment device 13 serves to adjust an effective connecting rod length l eff , where the connecting rod length is the distance from the center point 18 of the bore in the eccentric to a center point 19 of the pin bearing eye 11. To rotate the eccentric lever 14 and thus to change the effective connecting rod length l effThe eccentric rods 15, 16 are movable. Each eccentric rod 15, 16 is assigned a piston 20, 21, which is displaceably guided in a hydraulic chamber 22, 23 of the connecting rod. Hydraulic pressure prevails in the hydraulic chambers 22, 23, which acts on the pistons 20, 21 assigned to the eccentric rods 15, 16. Depending on the amount of oil in the hydraulic chambers, the displacement of the eccentric rods 15, 16 may or may not be possible.

[0003] The adjustment of the eccentric adjustment device 13 is initiated by the action of mass and load forces of the internal combustion engine, which act on the eccentric adjustment device 13 during a power stroke of the internal combustion engine. During a power stroke, the directions of action of the forces acting on the eccentric adjustment device 13 constantly change. The adjustment movement is supported by the pistons 20, 21, which are pressurized with hydraulic oil and act on the eccentric rods 15, 16. The pistons 20, 21 prevent the eccentric adjustment device 13 from resetting due to varying directions of the forces acting on the eccentric adjustment device 13. The eccentric rods 15, 16, which interact with the pistons 20, 21, are connected to the eccentric lever 14 on both sides thereof.The hydraulic chambers 22 and 23, in which the pistons 20, 21 are guided, can be supplied with hydraulic oil via hydraulic oil lines 24 and 25 from the pin bearing eye 11. Check valves 26 and 27 prevent the hydraulic oil from flowing back from the hydraulic chambers 23 and 24 into the hydraulic lines 24 and 25. A changeover valve 29 is accommodated in a bore 28 of the connecting rod 10. The switching position of the changeover valve 29 determines which of the hydraulic chambers 22 and 23 is filled with hydraulic oil and which of the hydraulic chambers 22 and 23 is emptied, the adjustment direction or rotation direction of the eccentric adjustment device 13 depending on this. The hydraulic chambers 22 and 23 are in contact with the bore 28, which accommodates the changeover valve 29, via fluid lines 30 and 31, respectively. From the changeover valve 29 are in . Fig. 1 an actuating means 32, a spring device 33 and a control piston 34 are shown schematically, the function of these components of the changeover valve 29 already being known from DE 10 2010 016 037 A1.

[0004] From DE 10 2013 111 617 A1, another switching valve of a connecting rod of an internal combustion engine with an adjustable compression ratio is known.

[0005] As stated above, the hydraulic oil acting on the pistons 20, 21 guided in the hydraulic chambers 22, 23 is supplied to the hydraulic chambers 22, 23 from the pin bearing eye 11 via hydraulic lines 24 and 25, whereby the connecting rod 10 is connected to the pin bearing eye 11 at the Fig. 1 not shown crankshaft, that a connecting rod bearing shell 35 is arranged between the crankshaft, namely a crankshaft bearing journal thereof, and the crank bearing eye.

[0006] Each of the eccentric rods 15, 16 engages with a first end in an articulated manner on one of the pistons 20, 21 and with a second end in an articulated manner on the eccentric lever 14. Since, when adjusting the connecting rod, the effective lever arm lengths for forces acting on the connecting rod or the eccentric adjustment device 13 change over the adjustment travel of the connecting rod or the eccentric adjustment device 13, a significant variance in adjustment speeds as well as adjustment forces or adjustment torques can be observed in connecting rods known from the prior art over the adjustment range of the connecting rod. This is disadvantageous.

[0007] WO 2014 / 019 683 A1 and JP 2015 - 014 286 A disclose further prior art.

[0008] The object of the invention is to create a novel connecting rod with a lower variance of the adjustment speeds and adjustment forces or adjustment moments as well as an internal combustion engine with such a connecting rod.

[0009] This object is achieved by a connecting rod for an internal combustion engine with adjustable compression ratio according to claim 1.

[0010] According to the invention, a center point of the eccentric bore is selected such that an axis extending through the center point of the eccentric bore and a center point of the connecting rod bearing eye bore encloses a first angle between 80° and 100° with a direction of movement of the cylinder piston located near the top dead center in a center position of the eccentric adjusting device. In addition, a first point of engagement of a first eccentric rod on a first section of the eccentric lever is selected such that a movement axis of the piston that engages this first eccentric rod and an axis extending through the first point of engagement and the center point of the connecting rod bearing eye bore enclose a second angle between 80° and 100° in the center position of the eccentric adjusting device.Additionally, a second engagement point of a second eccentric rod on a second section of the eccentric lever is selected such that a movement axis of the piston engaging this second eccentric rod and an axis extending through the second engagement point and the center of the connecting rod bearing eye bore enclose a third angle of between 80° and 100° in the center position of the eccentric adjustment device. This design of the connecting rod ensures more uniform adjustment speeds as well as adjustment forces and torques across the entire adjustment range of the connecting rod.

[0011] Preferably, in the center position of the eccentric adjustment device, the first angle and / or the second angle and / or the third angle is 90°±7°, preferably 90°±6°, particularly preferably 90°±5°. These angular ranges are particularly preferred for providing uniform adjustment speeds as well as uniform adjustment forces or adjustment moments across the adjustment range of the connecting rod or the eccentric adjustment device.

[0012] The internal combustion engine is defined in claim 5.

[0013] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 a connecting rod of an internal combustion engine known from the prior art; Fig. 2 a detail of a connecting rod according to the invention with adjustable compression ratio in a central position of an eccentric adjusting device; Fig. 3 the detail of the Fig. 2 in a first end position of the eccentric adjustment device; Fig. 4 the detail of the Fig. 2 in a second end position of the eccentric adjustment device; and Fig. 5 to 7 diagrams to illustrate the functional principle of the connecting rod according to the invention.

[0014] An internal combustion engine with an adjustable compression ratio has at least one, preferably several, cylinders.

[0015] Each cylinder of an internal combustion engine with an adjustable compression ratio has a cylinder piston connected to a crankshaft of the internal combustion engine via a connecting rod 10. Each connecting rod 10 has a connecting rod bearing eye 12 at one end and a crankshaft bearing eye 11 at the opposite end. The respective connecting rod 10 engages a crankshaft bearing journal of the crankshaft with its crankshaft bearing eye 11 and the respective cylinder piston of the internal combustion engine with its crankshaft bearing eye 12.

[0016] An internal combustion engine with adjustable compression ratio has an eccentric adjusting device 13 in the area of each connecting rod 10 for adjusting the effective connecting rod length l eff the respective connecting rod 10.

[0017] The eccentric adjustment device 13 has an eccentric 36, an eccentric lever 14, and eccentric rods 15, 16, which can be displaced to adjust the compression ratio depending on the hydraulic pressure prevailing in the hydraulic chambers 22, 23 interacting with the eccentric rods 15, 16. The hydraulic chambers 22, 23 are integrated into the connecting rod 10. The eccentric rods 15, 16 engage, with their first ends, in an articulated manner with pistons 20, 21 displaceably guided in the hydraulic chambers 22, 23, with the eccentric rods 15, 16 engaging, with their opposite second ends, in an articulated manner with the eccentric lever 14.

[0018] A bore in the connecting rod bearing eye 12, also referred to as the connecting rod bearing eye bore, accommodates the eccentric 36. The eccentric 36 is connected to the eccentric lever 14. The eccentric 36 has an eccentric bore that accommodates a cylinder piston pin, via which the eccentric 36 engages the cylinder piston of the respective cylinder of the internal combustion engine.

[0019] A center point of the connecting rod bearing eye bore is in Fig. 1 is marked with the reference number 17, wherein a center point of the bore in the eccentric 36, i.e. a center point of the eccentric bore, is marked with the reference number 18.

[0020] In the sense of the present invention, it is proposed that the center point 18 of the eccentric bore is selected such that an axis 37 extending through the center point 18 of the eccentric bore and the center point 17 of the connecting rod bearing eye bore is aligned with a direction of movement of the cylinder piston located near the top dead center, which in Fig. 2 is visualized by an arrow 38, in a central position of the eccentric adjusting device 13 and thus in a central position of the connecting rod, enclose a first angle γ between 80° and 100°.

[0021] In addition, a first point of engagement 39 of a first eccentric rod 16 on a first section of the eccentric lever 14 is selected such that an axis of movement of the piston 20 which engages this first eccentric rod 16 and an axis 41 extending through the first point of engagement 39 and the center point 17 of the connecting rod bearing eye bore enclose a second angle α between 80° and 100° in the center position of the eccentric adjusting device 13 and thus in the center position of the connecting rod.

[0022] In addition, a second point of engagement 42 of a second eccentric rod 15 on an opposite second section of the eccentric lever 14 is selected such that a movement axis 43 of the piston 21 which engages this second eccentric rod 15 and an axis 44 extending through the second point of engagement 42 and the center point 17 of the connecting rod bearing eye bore enclose a third angle β between 80° and 100° in the center position of the eccentric adjusting device 13 and thus in the center position of the connecting rod.

[0023] The above angles α, β and γ therefore each refer to the center position of the eccentric adjusting device, whereby the center position of the eccentric adjusting device 13 is understood to be the position of the eccentric adjusting device 13 which is in the center of the adjustment range of the eccentric adjusting device 13 and thus in the center of the adjustment range of the connecting rod 10. Fig. 2 shows the eccentric adjustment device 13 and thus the connecting rod in this middle position M, whereas Fig. 3 and Fig. 4 show the eccentric adjustment device 13 and thus the connecting rod 10 in its two end positions, whereby the end position E1 of the Fig. 3 providing a high compression ratio and the end position E2 of the Fig. 4 serves to provide a low compression ratio. If the eccentric 36 can be rotated by a total of 60° between the two end positions E1 and E2, for example, the middle position M of the Fig. 2 by the position which the eccentric 36 assumes when it has been rotated by 30° in the direction of the other end position, either starting from the end position E1 or starting from the end position E2.

[0024] In Fig. 2, lever arm lengths L1, L2 and L3 are shown, namely the lever arm length L1 is the length of the lever arm between the point of application 39 of the eccentric rod 16 relative to the center point 17 of the connecting rod bearing eye bore, the lever arm L2 is the length of the lever arm between the point of application 42 of the eccentric rod 15 to the center point 17 of the connecting rod bearing eye bore and the lever arm L3 is the length of the lever arm of the cylinder piston to the center point 17 of the connecting rod bearing bore or the force acting on the piston pin.

[0025] Then, when, as in Fig. 2, in the middle position M all three angles α, β and γ described above are selected so that they are each 90° in the middle position M, then effective lever arm lengths L1eff, L2eff and L3eff correspond to the lever arm lengths L1, L2 and L3.

[0026] In the end positions E1 and E2 of the Fig. 3 and Fig. 4, however, the effective lever arm lengths L1eff, L2eff and L3eff differ from the lever arm lengths L1, L2 and L3.

[0027] The lever arm lengths L1, L2, L3 correspond for L1 to the distance between the point of application 39 of the eccentric rod 16 and the center point 17 of the connecting rod bearing eye bore, for L2 to the distance between the point of application 42 of the eccentric rod 15 and the center point 17 of the connecting rod bearing eye bore, and for L3 to the distance between the centers 17, 18 of the connecting rod bearing eye bore or the eccentric bore, in each case in the direction of the axes 41, 44 and 37 extending through them.

[0028] The effective lever arm lengths L1eff, L2eff and L3eff are the respective projections of the lever arm lengths L1, L2 and L3 in the direction of movement of the respective piston 20, 21 or the cylinder piston.

[0029] For L1eff, the projection of L1 is in the direction of movement of the piston 20, for L2eff, the projection of L2 is in the direction of movement of the piston 21, and for L3eff, the projection of L3 is in the direction of movement of the cylinder piston.

[0030] Due to the inventive selection of the center point 18 of the eccentric bore and / or at least one of the two points of engagement 39, 42 on the eccentric lever 14 in such a way that in the center position M of the eccentric adjusting device 13 and thus in the center position of the connecting rod 10, the respective directions of movement 38, 40 and 43 of the cylinder piston and the pistons 20, 21 with the axes 37, 41 and 44 extending through the center point 17 of the connecting rod bearing eye bore enclose the defined angles α, β and γ, a homogenization of the adjustment speeds as well as adjustment forces or adjustment moments can be ensured over the adjustment path of the eccentric adjusting device 13 or over the adjustment range thereof.

[0031] So in Fig. 5, Fig. 6 and Fig. 7 over the adjustment range of the eccentric adjustment device 13 and thus over the adjustment range of the respective connecting rod 10, which is defined by the two end positions E1 and E2, the effective lever arm lengths L1eff, L2eff and L3eff are plotted, whereby in the ideal case of 90° the solid lines 45, 46 and 47 of the Fig. 5, Fig. 6 and 7 respectively, with a corresponding inventive design of the first point of engagement 39, the second point of engagement 42 and the center point 18 of the eccentric bore, whereas the dashed lines 48, 49 and 50 of the Fig. 5, Fig. 6 and Fig. 7 correspond to the course of the effective lever arm lengths L1eff, L2eff and L3eff according to the state of the art.

[0032] Fig.5 shows that when the first point of application 37 of the eccentric rod 16 on the eccentric lever 14 is selected such that the movement axis 40 of the piston 20 encloses the defined second angle α=90°±10° with the straight line 41, the effective lever arm length L1eff changes uniformly starting from the center position M for both possible adjustment directions in the direction of the end position E1 and in the direction of the end position E2, whereby uniformly changing adjustment speeds as well as adjustment forces or adjustment moments are ensured.

[0033] The same applies to the effective lever arm lengths L2eff and L3eff with a corresponding inventive design of the second point of application 42 of the eccentric rod 15 on the eccentric lever 14 or with a corresponding inventive design of the center point 18 of the eccentric bore, so that the movement axis 43 of the piston 41 then encloses the defined third angle β=90°±10° with the straight line 44 or the movement direction 38 of the cylinder piston with the axis 37 encloses the defined first angle γ=90°±10°.

[0034] The ratios L1 eff / L2eff and L1 eff / L3eff and L2eff / L3eff are constant or approximately constant in the inventive configuration of the three above-mentioned design parameters. This ensures a constant transmission behavior of the external gas and inertia forces acting via the cylinder piston onto the eccentric 36 via the lever arm L3, and a constant transmission behavior of the oil pressures acting via the pistons 20, 21 onto the eccentric 36 via the lever arms L1 and L2, in each case over the adjustment range of the eccentric adjustment device 13 and thus over the adjustment range of the connecting rod 10.

[0035] Particularly preferred is an embodiment of the invention in which, in the central position of the eccentric adjusting device 13, the first angle γ and the second angle α and the third angle β are each 90°±7°, preferably 90°±6°, particularly preferably 90°±5°.

[0036] As already explained, both the center point 18 of the eccentric bore and both points of application 39, 42 of the eccentric rods 15, 16 are selected such that in the center position of the eccentric adjusting device 13 the first angle γ and the second angle α and the third angle β are each between 80° and 100°, i.e. 90°±10°, in particular 90°±7°, preferably 90°±6°, particularly preferably 90°±5°.

[0037] In the optimal case, all three angles α, β and γ are 90° in the middle position of the eccentric adjustment device 13.

[0038] With the invention, it is possible to ensure uniform adjustment forces or adjustment moments as well as adjustment speeds of the eccentric adjustment device 13 and thus of the connecting rod 10 having the eccentric adjustment device 13 over the adjustment range thereof.

Claims

[1] Connecting rod (10) for an internal combustion engine with adjustable compression ratio, with a crank bearing eye (11) for connecting it to a crankshaft and a connecting rod bearing eye (12) for connecting it to a cylinder piston, an eccentric adjusting device (13) for adjusting an effective connecting rod length, wherein the eccentric adjusting device (13) has an eccentric (36) cooperating with an eccentric lever (14) and eccentric rods (15, 16), wherein the eccentric rods (15, 16) engage the eccentric lever (14) in an articulated manner with a first end and engage pistons (20, 21) displaceably guided in hydraulic chambers (22, 23) of the connecting rod in an articulated manner with a second end, and wherein the eccentric (36) is received in a connecting rod bearing eye bore of the connecting rod bearing eye (12), which comprises an eccentric bore for receiving a cylinder piston pin, characterized by , that a center point (18) of the eccentric bore is selected such that an axis (37) extending through the center point (18) of the eccentric bore and a center point (17) of the connecting rod bearing eye bore encloses a first angle (γ) between 80° and 100° with a direction of movement (38) of the cylinder piston in a center position of the eccentric adjusting device (13), wherein the center position of the eccentric adjusting device (13) is the position of the eccentric adjusting device (13) which lies in the center of the adjustment range of the eccentric adjusting device (13) and thus in the center of the adjustment range of the connecting rod (10), and an engagement point (39) of a first eccentric rod (16) on the eccentric lever (14) is selected such that a movement axis (40) of the piston (20) engaging the first eccentric rod (16) and an axis extending through this engagement point (39) and the center point (17) of the connecting rod bearing eye bore enclose a second angle (α) between 80° and 100° in the center position of the eccentric adjusting device (13), and an engagement point (42) of a second eccentric rod (15) on the eccentric lever (14) is selected such that a movement axis (43) of the piston (21) which engages the second eccentric rod (15) and an axis (44) extending through this engagement point (42) and the center point (17) of the connecting rod bearing eye bore enclose a third angle (β) between 80° and 100° in the center position of the eccentric adjusting device (13). [2] Connecting rod according to claim 1, characterized bythat in the middle position of the eccentric adjusting device (13) the first angle (γ), the second angle (α) and the third angle (β) are each 90°±7°. [3] Connecting rod according to claim 2, characterized by that in the middle position of the eccentric adjusting device (13) the first angle (γ), the second angle (α) and the third angle (β) are each 90°±6°. [4] Connecting rod according to claim 3, characterized by that in the middle position of the eccentric adjusting device (13) the first angle (γ), the second angle (α) and the third angle (β) are each 90°±5°. [5] Internal combustion engine having an adjustable compression ratio, with at least one cylinder and with a crankshaft to which at least one connecting rod (10) engages, characterized by that the or each connecting rod (10) is designed according to one or more of claims 1 to 4.

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