Connecting rod for internal combustion engine for changing compression ratio

Abstract

The invention relates to a connecting rod for changing the compression ratio of an internal combustion engine. The connecting rod according to the invention has a device for changing the compression ratio of an internal combustion engine, comprising a connecting rod head and a connecting rod pin, which is supported by an eccentric of the connecting rod in a variable distance from the connecting rod head, and a locking device, wherein the connecting rod head or the connecting rod pin comprises a fluid chamber and the eccentric has a protrusion which extends into the fluid chamber, or the eccentric comprises or delimits the fluid chamber and the connecting rod head or the eccentric has a protrusion which extends into the fluid chamber, such that a fluid pressure in the fluid chamber exerts a force onto the protrusion to change an eccentric position of the eccentric, the locking device prevents a twisting of the eccentric relative to the connecting rod head in a locked position, the locking device is releasably configured, and the connecting rod comprises a hydraulic circuit, which has a first sub-circuit for controlling the fluid chamber and a second sub-circuit for controlling the locking device, which is decoupled from the first sub-circuit.

Description

Technical Field

[0001] This invention relates to a connecting rod for changing the compression ratio of an internal combustion engine. Background Technology

[0002] A linkage having a device for changing the compression ratio of an internal combustion engine is known from DE102019103998A1, wherein a releasable locking device is provided in at least one switching position. Summary of the Invention

[0003] The connecting rod according to the invention, having a device for changing the compression ratio of an internal combustion engine, comprises: a connecting rod head, a connecting rod pin, and a locking device. The connecting rod pin is supported by an eccentric wheel of the connecting rod in a manner that allows for a variable distance from the connecting rod head. The connecting rod head or connecting rod pin includes a fluid chamber, and the eccentric wheel has a protrusion extending into the fluid chamber; alternatively, the eccentric wheel includes or confines the fluid chamber, and the connecting rod head or eccentric wheel has a protrusion extending into the fluid chamber, such that fluid pressure in the fluid chamber applies a force to the protrusion to change the eccentric wheel position. In the locked position, the locking device prevents the eccentric wheel from twisting relative to the connecting rod head. The locking device is releasable. The connecting rod includes a hydraulic circuit having a first sub-circuit for controlling the fluid chamber and a second sub-circuit decoupled from the first sub-circuit for controlling the fluid chamber.

[0004] The second sub-circuit is decoupled from the first sub-circuit, thereby enabling the invention to safely seal the locking device. Without decoupling the first and second sub-circuits, a significant amount of air could be trapped in the second sub-circuit, potentially leading to accidental unlocking of the locking device.

[0005] Preferably, a hydraulic resistance element is provided to decouple the first sub-circuit and the second sub-circuit. For example, the first and / or second sub-circuit includes a baffle or a throttle valve.

[0006] Preferably, the locking device includes two stop pins and a receiving portion, such that the first stop pin engages with the receiving portion in a first position of the eccentric wheel, and the second stop pin engages with the receiving portion in a second position. Thus, the present invention achieves the ability to reliably set high and low compression ratios.

[0007] The locking device preferably includes a spring for closing. Particularly preferably, the locking device is connected to a hydraulic circuit for unlocking, such that the pressure of the hydraulic fluid counteracts the force of the spring and unlocks the locking device. To avoid or at least reduce unwanted forces in the hydraulic circuit, the locking device preferably includes a venting device to allow air to escape from a second sub-circuit. Particularly preferably, to close the locking device, the connection between the locking device and the hydraulic circuit is disabled, allowing hydraulic oil to drain, the pressure of the hydraulic fluid to decrease, and the spring to close the locking device again.

[0008] Preferably, the connecting rod head includes two fluid chambers, and the eccentric wheel includes two protrusions extending into the fluid chambers, such that the connecting rod includes four hydraulic chambers. When a high compression ratio is set, one hydraulic chamber in each fluid chamber is in an expanded state. When a low compression ratio is set, the other hydraulic chamber in each fluid chamber is in an expanded state.

[0009] Particularly preferably, the first sub-circuit includes at least one flushing line, which ensures a continuous supply of hydraulic fluid to the fluid chamber and avoids or at least reduces the amount of air trapped inside.

[0010] The hydraulic circuit preferably includes a switching valve configured as a directional valve with two switching positions and seven flow paths. By configuring the switching valve as a 7 / 2 directional valve, the present invention achieves decoupling between the first and second sub-circuits in a compact manner. Due to the compact structure, the hydraulic circuit can be integrated into the connecting rod in a manner that is easy to maintain.

[0011] The switching valve is configured to initiate a switching process from high compression ratio to low compression ratio or from low compression ratio to high compression ratio by changing the switching position. Simultaneously, the switching process controls the locking and unlocking of the locking device.

[0012] Other advantageous embodiments of the invention are described below. Attached Figure Description

[0013] Preferred embodiments are illustrated in detail with reference to the following figures. They are shown here:

[0014] Figure 1 An embodiment of a connecting rod having a device for changing the compression ratio of an internal combustion engine is shown.

[0015] Figure 2 A cross-sectional view is shown of one embodiment of a connecting rod having a device for changing the compression ratio of an internal combustion engine.

[0016] Figure 3 Another cross-sectional view shows an embodiment of a connecting rod having a device for changing the compression ratio of an internal combustion engine.

[0017] Figure 4 An embodiment of a hydraulic circuit with a linkage for changing the compression ratio of an internal combustion engine is shown.

[0018] Figure 5 An alternative embodiment of a hydraulic circuit for a linkage with a device for changing the compression ratio of an internal combustion engine is shown.

[0019] Figure 6 An alternative embodiment of a hydraulic circuit for a linkage with a device for changing the compression ratio of an internal combustion engine is shown, and

[0020] Figure 7 An embodiment of a hydraulic module with a linkage for changing the compression ratio of an internal combustion engine is shown. Detailed Implementation

[0021] Figure 1 A connecting rod 1 with a device for changing the compression ratio of an internal combustion engine is shown. The connecting rod 1 includes a connecting rod head 2, a connecting rod shaft 21, and a large connecting rod bore 20. A hydraulic switching module 19 is disposed below the large connecting rod bore 20.

[0022] Figure 2 A cross-sectional view of link 1 is shown. The link includes a link pin 3, which is supported by an eccentric wheel 4 of link 1 at a variable distance from the link head 2.

[0023] During the operation of the internal combustion engine, connecting rod 1 experiences alternating tension and pressure with each engine revolution. The pressure is caused by combustion pressure, while the tension is caused by the inertial force of the piston during its reverse motion. Connecting rod 1 is connected to the piston via connecting rod pin 3. The pressure generates a counterclockwise torque on the eccentric wheel 4, which tends to adjust towards a lower compression ratio. The tension generates a clockwise torque, which tends to adjust towards a higher compression ratio.

[0024] The connecting rod head includes two fluid chambers 6 and 7, and the eccentric wheel 4 has two protrusions 8. The protrusions 8 extend into each of the two fluid chambers 6 and 7, such that the fluid pressure in the fluid chambers 6 and 7 applies a force to the protrusions 8 to change the eccentric wheel position of the eccentric wheel 4. Through the two protrusions 8, each fluid chamber 6 and 7 is divided into two hydraulic chambers 25, 26, 27, and 28.

[0025] Hydraulic chambers 25 and 27 expand when moving towards a small compression ratio adjustment link 1. During the adjustment towards a high compression ratio, hydraulic chambers 25 and 27 compress. Hydraulic chambers 26 and 28 expand when moving towards a high compression ratio adjustment link 1, and compress during the adjustment towards a small compression ratio.

[0026] Linkage 1 includes two locking devices 5 that prevent the eccentric wheel 4 from twisting relative to the link head in a locked position. The locking devices 5 are releasable and each includes stop pins 22 and 23, which can engage with a receiving portion 24. Stop pin 22 locks the eccentric wheel 4 in a high compression ratio position by engaging with the receiving portion 24, and stop pin 23 locks the eccentric wheel 4 in a low compression ratio position by engaging with the receiving portion 24.

[0027] Figure 3Another cross-sectional view of link 1 is shown. Link 1 includes a hydraulic circuit 9. The hydraulic circuit includes oil and is configured to supply oil to hydraulic chambers 25, 26, 27, 28 and stop pins 22, 23, such that the eccentric wheel 4 engages and locks in a desired position at a low or high compression ratio.

[0028] Figure 4 A schematic diagram of a hydraulic circuit 9 is shown, comprising a first sub-circuit 10 (dotted line) and a second sub-circuit 11 (dashed line). Oil is supplied to hydraulic chambers 25, 26, 27, and 28 via the first sub-circuit 10. Oil is supplied to stop pins 22 and 23 via the second sub-circuit 11. The hydraulic circuit 9 is configured to be controllable by a switching valve 12. The switching valve is configured as a directional valve with two switching positions and seven flow paths.

[0029] The oil in hydraulic circuit 9 is cleaned by being fed from connecting rod bearing 29 to filter unit 30. A portion of the oil is fed into first sub-circuit 10, and another portion into second sub-circuit 11.

[0030] Connecting rod 1 is positioned at a high compression ratio. Hydraulic chambers 26 and 28 have the largest volume and are connected to hydraulic circuit 9 for oil supply. Hydraulic chambers 26 and 28 are completely filled with oil. Any system leakage will be replenished into hydraulic chambers 26 and 28 unimpeded from connecting rod bearing 29 via first sub-circuit 10.

[0031] Simultaneously, hydraulic fluid is supplied from the connecting rod bearing 29 to the hydraulic chambers 25 and 27, which have the smallest chamber volume, via the first hydraulic circuit 10. This portion of the first hydraulic circuit 10 undergoes a continuous flushing effect via the flushing line 16, thereby preventing the pipes from emptying and avoiding: significant air intake in the first sub-circuit 10 and unacceptably high dynamics during switching. The flushing line 16 includes a hydraulic resistance element 18 configured as a baffle to set a favorable pressure in the hydraulic chambers 25 and 27.

[0032] Meanwhile, a continuous oil supply is provided to the stop pin 23 via the second sub-circuit 11, causing the stop pin 23 to unlock. The stop pin 22 is separated from the oil supply device, allowing for reset by spring force, and preventing undesirable pressure dynamics caused by the inertial force acting on the oil during engine operation from unlocking the stop pin 22. By separating the stop pin 22 from the oil supply device, oil can be discharged from the corresponding pipe into the oil pan 31. To regulate and prevent backflow, a check valve 37 is provided in the pipeline between the switching valve 12 and the oil pan 31.

[0033] The necessary piping system for hydraulic circuit 9 is introduced into the connecting rod base, i.e., connecting rod shaft 21 and (not shown) bearing cap, and connected to the hydraulic switching module 19. The hydraulic switching module 19 includes a switching valve 12, a filter unit 30, a flushing line 16, a baffle 18, a check valve 37, and sections of the first sub-circuit 10 and the second sub-circuit 11, especially the sections related to wiring.

[0034] If the switching valve 12 is in the low compression ratio position, the stop pin 23 is first connected to the second sub-circuit 11. Pressure builds up in the corresponding piping system, causing the stop pin 23 to unlock. This is achieved by a defined ventilation device: air can escape from the stop pin 23.

[0035] Simultaneously, the oil supply from the stop pin 22 is reduced, causing a reset by spring force that results in locking. However, geometrically, the locking process of the stop pin 22 is prevented because it cannot engage with the receiving portion 24 provided for it in the eccentric wheel 4. Therefore, the rotational movement of the eccentric wheel 4 is released, and the switching process towards a lower compression ratio is initiated.

[0036] Here, oil is squeezed out of hydraulic chambers 26 and 28 during the current pressure phase and flows into chambers 25 and 27 via hydraulic module 19. During this period, the fluid passes through hydraulic resistance element 17, which is configured as a baffle in flushing line 15. This achieves a damping effect on the rotation of eccentric wheel 4. Check valve 14 and switching valve 12 are configured as backflow cut-off sections to hold eccentric wheel 4 in its position during the tension phase. This process is repeated until the final position of low compression ratio is reached after several cycles. To switch from low compression ratio to high compression ratio, the same process is performed, and check valve 13 is accordingly configured as a backflow cut-off section to hold eccentric wheel 4 in its position during the pressure phase.

[0037] Figure 5 The connecting rod 1 is shown in the low compression ratio position. A stop pin 23 engages with a provided receiving portion 24. To prevent accidental unlocking, the oil in the line leading to the stop pin 23 is reduced to prevent pressure increases due to inertia. Such pressure increases could lead to an undesirable unlocking process. Therefore, the dimensions of the baffle 17 are determined such that the duration of the switching process matches the reduction of oil in the line leading to the stop pin 23. Similarly, the dimensions of the baffle 18 are determined such that the duration of the switching process from a low compression ratio to a high compression ratio matches the reduction of oil in the line leading to the stop pin 22.

[0038] Figure 6An alternative embodiment of connecting rod 1 in a low compression ratio position is shown. A sub-circuit 10 includes a first relief line 39 and a second relief line 40 having a first hydraulic resistance element 41 and a second hydraulic resistance element 42. The first relief line 39 is configured to connect hydraulic chambers 26, 28 to the oil pan 31. The second relief line 40 is configured to connect hydraulic chambers 25, 27 to the oil pan 31. For pressure regulation in hydraulic chambers 25, 26, 27, 28, the first hydraulic resistance element 41 and the second hydraulic resistance element 42 are configured as overpressure valves. Therefore, the first relief line 39 and the second relief line 40 achieve pressure regulation in hydraulic chambers 25, 26, 27, 28. When connecting rod 1 is in a low compression ratio position... Figure 6 In the positions shown, overpressure in hydraulic chambers 25 and 27 is avoided or at least reduced.

[0039] In another embodiment (not shown), two stop pins are used for locking in one or both positions of the eccentric wheel 4. In another embodiment, the two stop pins 22, 23 are configured to lock in one position of the eccentric wheel 4. In the other position of the eccentric wheel 4, locking is not performed.

[0040] Figure 7 An embodiment of a hydraulic switching module 19 is shown, comprising a cylinder 40, two threaded caps 41, a switching valve 12, check valves 13 and 14, and a partition 38 for decoupling a first sub-circuit from a second sub-circuit 11. The stop of the switching valve 12 within the cylinder 40 is mechanically implemented via a locking ball. In an alternative embodiment, additive manufacturing is used to optimize the cylinder 40 and the switching valve 12 to reduce flow losses.

[0041] The hydraulic switching module 19 is integrated here within the large connecting rod bore 20. In an alternative embodiment, the hydraulic switching module 19 is housed in the connecting rod shaft 21 to accommodate separate structural space requirements.

[0042] The switching valve 12 is mechanically operated here. In an alternative embodiment, the switching valve 12 is configured to be hydraulically or electromagnetically operated.

[0043] The switching axis of the switching valve 12 is positioned parallel to the crankshaft axis of the internal combustion engine to reduce the effect of acceleration force on the switching axis. Check valves 13, 14, and 37 are oriented along the crankshaft axis to prevent inertial effects during valve opening and / or closing.

[0044] In alternative embodiments, a pressure relief port or overpressure valve is provided instead of check valve 37 to reduce the oil pressure in stop pins 22, 23, which are separate from the hydraulic circuit.

Claims

1. A connecting rod (1) having a device for changing the compression ratio of an internal combustion engine, the connecting rod comprising: The connecting rod head (2) and connecting rod pin (3), the connecting rod pin being supported by an eccentric wheel (4) of the connecting rod (1) in a manner that allows for a changeable distance from the connecting rod head (2); and a locking device (5), wherein... - The connecting rod head (2) or the connecting rod pin (3) includes a fluid chamber (6, 7), and the eccentric wheel (4) has a protrusion (8) extending into the fluid chamber (6, 7), or the eccentric wheel (4) includes or confines a fluid chamber (6, 7), and the connecting rod head (2) or the eccentric wheel (4) has a protrusion (8) extending into the fluid chamber (6, 7), such that the fluid pressure in the fluid chamber (6, 7) applies a force to the protrusion (8) to change the eccentric wheel position of the eccentric wheel (4). - The locking device (5) prevents the eccentric wheel (4) from twisting relative to the connecting rod head (2) in the locked position. - The locking device (5) is configured to be releasable, and - The connecting rod (1) includes a hydraulic circuit (9) having a first sub-circuit (10) for controlling the fluid chambers (6, 7) and a second sub-circuit (11) decoupled from the first sub-circuit (10) for controlling the locking device (5).

2. The connecting rod (1) according to claim 1, wherein the hydraulic circuit (9) includes a switching valve (12) configured as a directional valve having two switching positions and seven flow paths.

3. The connecting rod (1) according to claim 1 or 2, wherein the hydraulic circuit (9) includes a hydraulic return cut-off section (13, 14, 37).

4. The linkage (1) according to any one of the preceding claims, wherein the first sub-circuit (10) includes flushing lines (15, 16) for flushing the fluid chambers (6, 7).

5. The connecting rod (1) according to claim 4, wherein the flushing conduit (15, 16) includes hydraulic resistance elements (17, 18).

6. The connecting rod (1) according to any one of the preceding claims, wherein the connecting rod (1) includes a hydraulic switching module (19), and wherein the hydraulic switching module (19) includes a cylinder and a section of the hydraulic circuit having a switching valve (12) and a hydraulic backflow cutoff portion (13, 14).

7. The connecting rod (1) according to claim 6, wherein the hydraulic switching module (19) is disposed in the large connecting rod hole (20) or in the shaft (21) of the connecting rod (1).

8. The linkage (1) according to any one of the preceding claims, wherein the locking device (5) includes a stop pin (22, 23) configured to engage with a receiving portion (24).

9. The linkage (1) according to claim 2 or 6, wherein the switching valve (12) is configured to be operated mechanically, hydraulically or electromagnetically.

10. The connecting rod (1) according to any one of the preceding claims, wherein the first sub-circuit (10) includes a pressure relief line (39) having hydraulic resistance elements (41, 42).

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