Actuating device for switching valves of an internal combustion engine and internal combustion engine

Abstract

Actuating device (11) for changeover valves (10) of an internal combustion engine with adjustable compression ratio, wherein each changeover valve (10) serves to control a hydraulic oil flow in hydraulic chambers of an eccentric adjusting device of a respective connecting rod (1) of the internal combustion engine, wherein each changeover valve (10) has a tap (12) which can be actuated by the actuating device (11), wherein the actuating device (11) has a switching fork (13) for each switching valve (10) and thus for each tappet (12) to be actuated, which are fastened to a support structure (14), wherein the support structure (14) comprises a mounting frame (15) made up of mounting rails (26, 27) running parallel to one another and a displacement element (16) made up of displacement rails (17, 18) running parallel to one another, which can be displaced relative to the mounting frame (15), wherein the shift forks (13) are fastened to the displacement rails (17, 18) of the displacement element (16) and are longitudinally displaceable relative to the mounting frame (15) via the respective displacement rail (17, 18), characterized in that on the mounting frame (15) in the region of a single mounting rail (27) of the mounting rails (26, 27) on several sections of the same guide elements (29, 30) are formed, which guide the respective displacement rail (18) on both sides in the respective section of the mounting rail (27) having the guide elements (29, 30), seen transversely to the direction of displacement thereof, namely in a guide region (Y2) which is determined by the width of the displacement rail (18) which is guided on the mounting rail (27) having the guide elements (29, 30).

Description

[0001] The invention relates to an actuating device for changeover valves of an internal combustion engine with a variable compression ratio and to an internal combustion engine with a variable compression ratio.

[0002] In internal combustion engines, a high compression ratio has a positive effect on efficiency. The compression ratio is the ratio of the total cylinder space before compression to the remaining cylinder space after compression. In internal combustion engines with spark ignition, such as gasoline engines, which generally have a fixed compression ratio, the compression ratio may only be selected high enough to avoid knocking during full-load operation. However, for the much more common partial load range of the internal combustion engine, i.e., when the cylinder is low, a higher compression ratio could be selected without knocking occurring. The important partial load range of an internal combustion engine can be improved if the compression ratio can be variably adjusted.

[0003] DE 10 2010 016 037 A1 discloses an internal combustion engine with an adjustable compression ratio. Connecting rods, which have a pin bearing eye and a connecting rod bearing eye, can be connected to a crankshaft via the pin bearing eye and to a respective cylinder piston of the internal combustion engine via the connecting rod bearing eye. Each connecting rod is assigned an eccentric adjustment device comprising an eccentric body and eccentric rods.

[0004] The eccentric known from DE 10 2010 016 037 A1 has a piston pin bore arranged eccentrically to a center point of the connecting rod bearing eye, with a center point, wherein the piston pin bore accommodates a piston pin. The eccentric adjustment device serves to adjust an effective connecting rod length leff, whereby the connecting rod length is understood to be the distance from the center point of the piston pin bore to a center point of the pin bearing eye. To rotate the eccentric body and thus change the effective connecting rod length leff, the eccentric rods of the eccentric adjustment device are displaceable. Each eccentric rod is assigned a piston that is displaceably mounted or guided in a hydraulic chamber. A hydraulic pressure prevails in the hydraulic chambers, which acts on the pistons assigned to the eccentric rods. Depending on the amount of oil in the hydraulic chambers, the displacement of the eccentric rods may or may not be possible.

[0005] The adjustment of the eccentric adjustment device is initiated by the inertia and load forces of the combustion engine, which act on the eccentric adjustment device during a power stroke of the combustion engine. During a power stroke, the directions of action of the forces acting on the eccentric adjustment device constantly change. The adjustment movement is supported by the pistons pressurized with hydraulic oil, which act on the eccentric rods. The pistons prevent the eccentric adjustment device from resetting due to the varying directions of the forces acting on the eccentric adjustment device. The eccentric rods, which interact with the pistons, are connected to the eccentric body on both sides.

[0006] The hydraulic chambers, in which the pistons are guided, can be filled with hydraulic oil via hydraulic oil supply lines from the pin bearing eye. Check valves prevent the hydraulic oil from flowing back into the hydraulic oil supply lines. A changeover valve is housed in a bore in each connecting rod. The hydraulic chambers are in contact with the bore containing the changeover valve via hydraulic oil drain lines. The switching position of the changeover valve determines which of the hydraulic chambers is filled with hydraulic oil and which of the hydraulic chambers is emptied, whereby the adjustment direction or rotation direction of the eccentric adjustment device depends on this.

[0007] The changeover valve known from DE 10 2010 016 037 A1 comprises an actuating element, a return spring and a control piston.

[0008] As stated, the hydraulic oil, which acts on the pistons of the eccentric rods guided in the hydraulic chambers, is supplied to the hydraulic chambers from the crank bearing eye via the hydraulic oil supply lines, wherein the respective connecting rod engages the crankshaft with the crank bearing eye in such a way that a connecting rod bearing shell is arranged between the crankshaft, namely a crankshaft bearing journal thereof, and the crank bearing eye.

[0009] The hydraulic chambers can be vented via the hydraulic oil drain lines depending on the switching position of the changeover valve. This determines the adjustment direction or rotation direction of the eccentric adjustment device.

[0010] DE 10 2012 112 461 A1 describes another internal combustion engine with an adjustable compression ratio, in which the connecting rod length is variably adjustable. A changeover valve, which includes a tappet, is housed in a bore of the respective connecting rod. The respective changeover valve can be actuated via the tappet, namely via an actuating device acting on the tappet.

[0011] The subsequently published DE 10 2015 104 762 A1 discloses an actuating device for changeover valves of an internal combustion engine according to the preamble of claim 1.

[0012] DE 10 2015 106 315 A1 and DE 10 2014 118 728 A1 disclose further subsequently published prior art.

[0013] WO 2014 / 019 684 A1 also discloses an actuating device for switching valves of an internal combustion engine

[0014] There is a need for an actuating device for the changeover valves of an internal combustion engine with adjustable compression ratio, which allows reliable actuation of the changeover valves of an internal combustion engine with a simple design.

[0015] The object of the invention is to provide a novel actuating device for the switching valves of an internal combustion engine with adjustable compression ratio and an internal combustion engine with such an actuating device.

[0016] This object is achieved by an actuating device according to patent claim 1. According to the invention, guide elements are formed on the mounting frame in the region of a single mounting rail of the mounting rails on several sections of the same, which guide elements guide the respective displacement rail on both sides in the respective section of the mounting rail having the guide elements, viewed transversely to the direction of displacement, namely in a guide region determined by the width of the displacement rail guided on the mounting rail having the guide elements. The actuating device for the changeover valves of an internal combustion engine with an adjustable compression ratio has a simple design and allows reliable actuation of the changeover valves of an internal combustion engine. There is no risk of incorrect positioning between the mounting frame and the displacement element.

[0017] The internal combustion engine according to the invention with an adjustable compression ratio is defined in claim 5.

[0018] Preferably, the actuating device is mounted on a crankcase in such a way that, relative to a rotational direction of the connecting rod, the mounting rail on which the guide elements are formed, which guide the respective displacement rail on both sides transverse to the direction of displacement of the connecting rod, is arranged at a position at which a component of the movement direction of the respective connecting rod attempts to move the displacement element away from the mounting frame. With a simple design of the actuating device, there is no risk of misalignment between the mounting frame and the displacement element.

[0019] 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 with eccentric adjustment device and changeover valve; Fig. 2 a perspective view of an actuating device according to the prior art; Fig. 3 a plan view of the actuating device of the Fig. 2; Fig. 4 a perspective view of an actuating device according to the invention; Fig. 5 a plan view of the actuating device of the Fig. 4; and Fig. 6 a partial cross-section through an internal combustion engine.

[0020] Fig. Figure 1 shows a connecting rod 1 of an internal combustion engine with an adjustable compression ratio. The connecting rod 1 has a connecting rod base body 7 with a connecting rod bearing eye 2 and a pin bearing eye 3.

[0021] The connecting rod bearing eye 2 serves to connect the respective connecting rod 1 to a cylinder piston 23 ( Fig. 6) of a respective cylinder of the combustion engine. The crankshaft bearing eye 3 serves to connect the respective connecting rod 1 to a crankshaft 24 ( Fig. 6) of the combustion engine.

[0022] The connecting rod 1 of the Fig. 1 has a preferably hydraulically adjustable eccentric adjustment device 6 arranged at least in sections in the connecting rod bearing eye 2. The eccentric adjustment device 6 has a piston pin bore arranged eccentrically to a central axis 8 of the connecting rod bearing eye 2, with a central axis which has a piston pin 22 ( Fig. 6). The respective connecting rod 1 is coupled to the cylinder piston 23 of the respective cylinder via the piston pin 22.

[0023] The eccentric adjustment device 6 serves to adjust an effective connecting rod length leff of the connecting rod 1. Rotation of the adjustable eccentric adjustment device 6 is initiated by the action of mass and load forces of the internal combustion engine, which act on the eccentric device 6 during a power stroke of the internal combustion engine. During a power stroke, the directions of action of the forces acting on the eccentric device 6 change continuously. The rotational movement or adjustment movement is supported by pistons pressurized with hydraulic fluid, in particular engine oil, which are integrated in the connecting rod arrangement 1 and guided in hydraulic chambers. The pistons prevent the eccentric adjustment device 6 from resetting due to varying directions of action of the forces acting on the eccentric adjustment device 6.

[0024] The pistons of the eccentric adjustment device 6 are operatively connected to an eccentric body 9 of the eccentric adjustment device 6 by means of eccentric rods 4, 5 on both sides. The eccentric adjustment device 6 can have the pistons, the eccentric rods 4, 5 and the eccentric body 9. The pistons of the eccentric adjustment device 6 are Fig. 1 not shown hydraulic fluid lines from the pin bearing eye 3 with hydraulic fluid via in Fig. 1 check valves (not shown). The check valves prevent the hydraulic fluid from flowing back from the piston volumes into the hydraulic fluid lines in the interior of the combustion engine.

[0025] A changeover valve 10 is accommodated in a bore of the respective connecting rod 1.

[0026] The hydraulic chambers of the eccentric adjustment device 6 of the respective connecting rod 1 are in contact with the bore via hydraulic fluid lines, which accommodates the switching valve 10. The switching position of the switching valve 10 determines which of the hydraulic chambers is filled with hydraulic oil and which of the hydraulic chambers is emptied, whereby the adjustment direction or rotation direction of the eccentric adjustment device 6 depends on this.

[0027] The respective switching valve 10 of the respective connecting rod 1 has a tappet 12. The respective switching valve 10 can be actuated via the tappet 12, namely via an actuating device 11 acting on the tappet 12. Details of the switching valve 10 of the respective connecting rod 1 and the tappet 12 of the respective switching valve 10 are familiar to the person skilled in the art, for example, from DE 10 2012 112 461 A1.

[0028] The present invention relates to details of the actuating device 11 for such an internal combustion engine with a variably adjustable compression ratio, namely an actuating device 11 which serves to actuate the tappets 12 of the changeover valves 10 of a plurality of connecting rods 1.

[0029] An actuating device 11 for actuating a plurality of switching valves 10 of an internal combustion engine with an adjustable compression ratio has a plurality of shift forks 13, each of the shift forks 13 interacting with a respective tappet 12 of a respective switching valve 10 to be actuated. All shift forks 13 are preferably attached to a common support structure 14.

[0030] The support structure 14 of the actuating device 11 has a mounting frame 15 and at least one displacement element 16, preferably one common to all shift forks 13, which is displaceable relative to the mounting frame 15. The displacement element 16 preferably has two parallel displacement rails 17, 18 which are firmly connected to one another via a connecting web 19. Several shift forks 13 are fastened to each displacement rail 17, 18 of the displacement element 16. The entire actuating device 11 is mounted on the crankcase 25 ( Fig. 6) of the combustion engine, namely via mounting screws (not shown) which extend through mounting openings 20 in the mounting frame 15.

[0031] The displacement element 16 of the actuating device 11, to which the shift forks 13 are fastened, is displaceable relative to the mounting frame 15, namely in the direction of the double arrow 21. The mounting frame 15 has a mounting rail 26 and 27 for each displacement rail 17 and 18 of the displacement element 16, which in turn run parallel to one another, are firmly connected to one another via connecting webs 28 and extend below the displacement rails 17 and 18. The mounting openings 20 are formed in the region of the ends of the connecting webs 28. Due to the relative movement of the shift forks 13 of the actuating device 11 orof the displacement element 16 carrying the shift forks 13 relative to the mounting frame 15, when the changeover valve 10 integrated into the respective connecting rod 1 of the respective cylinder has moved into the area of ​​the respective shift fork 13 of the actuating device 11 during a working stroke of a cylinder, the tappet 12 of the respective changeover valve 10 can be actuated to actuate the same.

[0032] The shift forks 13 of the actuating device 11 can therefore be displaced together with the aid of the displacement element 16 of the support structure 14, which is preferably common to all shift forks and to which the shift forks 13 are fastened, relative to the mounting frame 15 of the support structure 14 and thus relative to the tappets 12 of the changeover valves 10, namely between a first switching position and a second switching position of the shift forks 13. A defined switching position of the changeover valves 10 of the connecting rods 1 of the internal combustion engine with an adjustable compression ratio can be set in the respective switching position via the shift forks 13 of the actuating device 11.

[0033] It is already known from the state of the art (see Fig. 2 and Fig. 3) that the displacement element 16, namely the displacement rails 17 and 18 of the displacement element 16, are guided on the mounting frame 15, namely on the mounting rails 26 and 27 of the mounting frame 15, namely longitudinally displaceable in the direction of the double arrow 21, for which purpose guide elements 29 are formed on the two mounting rails 26 and 27 of the mounting frame 15. These guide elements 29 are according to Fig. 2 and Fig. 3 on an outer edge of the mounting rail 26 and an outer edge of the mounting rail 27 of the mounting frame 15 at lateral ends of the mounting rails 26 and 27, as seen in the direction of displacement 21, which thus form a guide area with the width Y1 for the displacement element 16. The outer edges of the mounting rails 26, 27, on which the guide elements 29 are formed, face away from each other. As seen in the direction of displacement 21 of the displacement element 16, the width of the displacement element 16 is adapted to the width Y1 of the guide area defined by the guide elements 29, specifically with a defined clearance.

[0034] For weight and functional reasons, the mounting frame 15 is made of aluminum, and the displacement element 16 is made of steel. These different materials have different thermal expansion coefficients, so the clearance between the displacement element 16 and the mounting frame 17 varies depending on the current temperature of the combustion engine in the area of ​​the actuating device 11. Excessive clearance can result in misalignment between the displacement element 16 and the mounting frame 15; insufficient clearance can result in excessive friction between the displacement element 16 and the mounting frame 15.

[0035] In order to avoid the disadvantages of the actuating device 11 known from the prior art, the invention proposes an actuating device 11 (see Fig. 4 and Fig. 5), in which in the area of ​​a single mounting rail 27 of the mounting frame 15, guide elements 29, 30 are formed on several sections of the same, which guide the respective displacement rail 18 on both sides in the respective section of the respective mounting rail 27, transversely to the displacement direction 21 of the same. As a result, a guide area Y2 is spanned, which is determined by the width of a displacement rail 18 and not by the width of the entire displacement element 16. Therefore, changes in the dimensions of the mounting frame 15 and displacement element 16 caused by differing thermal expansion coefficients have a less pronounced effect, so that the actuating device 11 according to the invention of the Fig. 4 and Fig. 5 is guided with greater precision than the actuating device 11 of the prior art according to Fig. 2 and Fig. 3.

[0036] In the actuating device 11 according to the invention (see Fig. 4 and Fig. 5) In the area of ​​a single mounting rail 27, guide elements 29 and 30 are formed on several sections thereof, preferably on opposite end sections thereof, which guide the respective displacement rail 18 on both sides in the respective section, in particular in the respective end section, of the mounting rail 27, transversely to the displacement direction 21 of the same, as seen from the side. Due to the inventive design of the actuating device 11, the different thermal expansion coefficients of the mounting frame 15 and the displacement element 16 have a less pronounced effect on the guide area Y2 of the actuating device 11, so that the risk of misalignment between the displacement element 16 and the mounting frame 15 is reduced.

[0037] Fig. 6 shows a section of an internal combustion engine 1 in the area of ​​a connecting rod 1, which is connected via its connecting rod bearing eye 2 to the cylinder piston 23 and via its stroke position eye 3 to the crankshaft 24, as well as in the area of ​​the actuating device 11, of which only the shift fork 13 is shown, which interacts with the tappet 12 of the changeover valve 10 of the connecting rod 1 shown.

[0038] Then, if, as in the preferred embodiment of the Fig. 4 and Fig. 5, the actuating device 11 is designed such that only on a single mounting rail 27 opposing guide elements 29, 30 are formed for guiding the respective displacement rail 18, the actuating device 11 is mounted in a defined manner on the crankcase 25 of the internal combustion engine 1.

[0039] This defined assembly of the actuating device 11 on the crankcase 25 is carried out in such a way that, with respect to a direction of rotation 31 of the crankshaft 24 and thus of the connecting rod 1, that mounting rail 27 on which the guide elements 29, 30 are formed, which guide the respective guide rail 27 on both sides transversely to the direction of displacement 21 of the same, is arranged at a position at which a component of the direction of movement 31 of the respective connecting rod 1 attempts to move the displacement element 16 away from the mounting frame 15, namely in the installation position of the Fig.6 attempts to lift the displacement element 16 from the mounting frame 15. This is the mounting rail that is positioned downstream of the direction of movement 31 of the connecting rod 1. Due to this mounting position of the actuating device 11 on the crankcase 25, there is no risk of the displacement element 16 of the actuating device 11 being lifted from the mounting frame 15 and thus assuming an incorrect position relative to the mounting frame 15. An actuating force acting during switching presses the displacement element 16 against the mounting frame 15. The resulting supporting forces generate friction, which prevents the displacement element 16 from being lifted from the mounting frame 15.

Claims

[1] Actuating device (11) for changeover valves (10) of an internal combustion engine with adjustable compression ratio, wherein each changeover valve (10) serves to control a hydraulic oil flow in hydraulic chambers of an eccentric adjusting device of a respective connecting rod (1) of the internal combustion engine, wherein each changeover valve (10) has a tap (12) which can be actuated by the actuating device (11), wherein the actuating device (11) has a switching fork (13) for each switching valve (10) and thus for each tappet (12) to be actuated, which are fastened to a support structure (14), wherein the support structure (14) comprises a mounting frame (15) made up of mounting rails (26, 27) running parallel to one another and a displacement element (16) made up of displacement rails (17, 18) running parallel to one another, which can be displaced relative to the mounting frame (15), wherein the shift forks (13) are fastened to the displacement rails (17, 18) of the displacement element (16) and are longitudinally displaceable relative to the mounting frame (15) via the respective displacement rail (17, 18), characterized by , that on the mounting frame (15) in the region of a single mounting rail (27) of the mounting rails (26, 27) on several sections of the same guide elements (29, 30) are formed, which guide the respective displacement rail (18) on both sides in the respective section of the mounting rail (27) having the guide elements (29, 30), seen transversely to the direction of displacement thereof, namely in a guide region (Y2) which is determined by the width of the displacement rail (18) which is guided on the mounting rail (27) having the guide elements (29, 30). [2] Actuating device according to claim 1, characterized by that the shift forks (13) are fastened to a displacement element (16) common to all shift forks (13). [3] Actuating device according to claim 1 or 2, characterized by that guide elements (29, 30) are formed on two lateral, opposite end sections of the respective mounting rail (27), which guide the respective displacement rail (18) on both sides in the respective end section of the mounting rail (27) transversely to the direction of displacement thereof. [4] Actuating device according to one of claims 1 to 3, characterized by that the mounting frame (15) consists of an aluminum material and the displacement element (16) consists of a steel material. [5] Internal combustion engine having an adjustable compression ratio, with a plurality of connecting rods (1), each having a hydraulically adjustable eccentric adjusting device (6) arranged in a connecting rod bearing eye (2) and / or a pin bearing eye (3) for adjusting an effective connecting rod length (leff) of the respective connecting rod bearing eye (2), wherein an adjustment path of the eccentric adjusting device (6) is controllable by means of a changeover valve (10), characterized by that the changeover valves (10) can be actuated by an actuating device (11) according to one of claims 1 to 4. [6] Internal combustion engine according to claim 5, characterized bythat the actuating device (11) is mounted on a crankcase (25) in such a way that, with respect to a direction of rotation of the connecting rod (1), that mounting rail (27) on which the guide elements (29, 30) are formed, which guide the respective displacement rail (18) on both sides as seen transversely to the direction of displacement thereof, is arranged at a position at which a component of the direction of movement of the respective connecting rod (1) attempts to move the displacement element (16) away from the mounting frame (15).

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