Valve drive, in particular for internal combustion engines

Abstract

The invention relates to a valve drive, in particular for an internal combustion engine (11), having at least one camshaft (12), at least one cam unit (13) which is mounted axially displaceably on the camshaft (12), and at least one actuator unit (14) which has at least one actuator (15) for displacing the cam unit (13) on the camshaft (12), wherein the actuator (15) is periodically mechanically forced apart during operation.

Description

Technical Field

[0001] The present invention relates to a valve train, particularly for internal combustion engines, and a motor vehicle having an internal combustion engine including the valve train. Background Technology

[0002] DE 10 2016 012 194 discloses a valve train, particularly for internal combustion engines, having at least one camshaft, at least one cam unit axially movably mounted on the camshaft, and at least one actuator unit having at least one actuator for moving the cam unit on the camshaft. DE 10 2016012 194 also includes a safety device (locking device) configured to trigger the switching process of the switching unit only in a permissible state. If the safety device fails and the actuator of the switching unit therefore attempts to perform a switch at an incorrect time, it can do so. Thus, the cam unit may be moved at an incorrect time, potentially damaging the valve train.

[0003] A valve train is also disclosed in JPS 60062613A. According to JP 60062613, a mechanism should be used to prevent the cam from moving at the wrong time (especially when the valve is being actuated). This mechanism must be designed to be very rigid because it must block the large moving force generated by the actuator.

[0004] DE 10 2007 042 932 also discloses a valve train. Here, if switching is not required, there is no interaction between the switching component and the switching unit during normal operation. Safety devices are in place to prevent unplanned interaction. When switching is required, interaction between the switching component and the switching unit must first be established. This process takes a certain amount of time, particularly approximately one-quarter of a camshaft rotation. If the switching command is given too late, it is necessary to wait almost a full camshaft rotation before the engagement process can occur. Especially at low engine speeds, the driver therefore experiences an uncomfortable delay under load demands. In vehicle sport mode, higher speeds or continuous large valve lift must be maintained to ensure instantaneous response. Both result in higher energy consumption. Summary of the Invention

[0005] This invention is particularly based on the objective of providing an advantageous, safe, and structurally simple valve train. This objective is accomplished through the design of this invention. The invention also includes various improvements.

[0006] This invention is based on a valve train, particularly for internal combustion engines, having at least one camshaft, at least one cam unit axially movably mounted on the camshaft, and at least one actuator unit having at least one actuator having an electric motor and a main shaft and for moving the cam unit on the camshaft, wherein, by rotating the main shaft using the electric motor, a switching element can be moved axially along the main shaft and relative to the camshaft, wherein the actuator is periodically mechanically forced to disengage during operation and periodically temporarily disengaged from the cam unit relative to the rotation angle of the camshaft, the cam unit having an actuating element and engaging with the actuator unit by means of the actuating element, wherein when at least one valve is actuated by means of the cam unit, the switching element of the actuator is always disengaged from the actuating element, the actuating element being partially intermittent along the circumference of the cam unit, and the actuator temporarily disengaging from the actuating element during operation.

[0007] It is proposed here that the actuator is periodically mechanically forced to disengage during operation. Preferably, the valve train is specifically configured to establish effective engagement (operational connection) between the actuator and the cam unit at the correct angular position with each revolution of the camshaft, independent of the switching process to be performed. This, in particular, provides a highly reliable valve train. It is advantageous to provide a valve train that does not allow switching at incorrect times, thus making the valve train highly reliable. With the design of the present invention, a relatively large and robust mechanism—which must block the movement force generated by the switching unit—can be abandoned. In particular, a valve train can be provided in which, when switching is possible (which occurs particularly with each half-revolution of the camshaft), the actuator is always effectively engaged with the cam unit. Therefore, the actuator can fulfill each switching request without delay. In particular, for example, the process of waiting for the pin to engage with the guide groove can be eliminated. Furthermore, for example, the process of detecting and confirming the pin engagement with the guide groove is no longer necessary.

[0008] Here, "internal combustion engine" should specifically refer to the engine of motor vehicles and / or commercial vehicles, which provides driving power to drive the corresponding motor vehicles and / or commercial vehicles by burning fuel such as gasoline or diesel. Here, "camshaft" should specifically refer to a shaft that is provided with multiple valves for actuating the internal combustion engine and has at least one cam profile for actuating the valves. It is conceivable that the camshaft is designed not only as an intake camshaft and provided for actuating the intake valves, but also as an exhaust camshaft and provided for actuating the exhaust valves. In principle, it is also conceivable that the camshaft is provided for actuating both the intake and exhaust valves. "Cam profile" should specifically refer to a region extending on the circumferential surface of the camshaft, preferably on the circumferential surface of the cam unit, which forms a valve actuation curve for valve actuation and / or defines valve actuation. "Cam unit" should specifically refer to a unit that is anti-rotationally and preferably axially movable on the camshaft and is provided for actuating the valves by directly or indirectly applying at least one valve lift to the respective valve. "Modifiable cam unit" here should particularly refer to a cam unit that is axially mounted on a camshaft and has at least two different cam profiles for actuated valves, said cam profiles preferably having different cam profiles. "Switching unit" should particularly refer to a unit configured to axially move the cam unit on the camshaft so that the different cam profiles of the cam unit engage corresponding valves. The switching unit preferably has an actuator and a connecting component connected to the actuator and the cam unit to be moved. "Actuator" should particularly refer to an electromechanical component configured to convert electrical and / or electronic signals into motion, especially rotational and / or linear motion. Here, the actuator is preferably designed as a spindle drive mechanism, a pneumatic piston, a hydraulic piston, or other actuators deemed meaningful by a technician. Thus, the switching unit is particularly configured to move the axial position of the cam unit. Here, the switching unit is preferably controlled by a control and / or adjustment unit to move or adjust the axial position. "Configuration" should particularly refer to something specifically designed, equipped, and / or arranged. "Control and / or adjustment unit" should particularly refer to a unit having at least one electronic controller. The electronic "controller" should specifically refer to a unit having a processing unit and a storage unit, as well as operating programs stored in the storage unit. In principle, the control and / or regulation unit can have multiple interconnected controllers, preferably configured for communication with each other via a bus system, particularly a CAN bus system. Depending on other designs, the control and / or regulation unit may also have hydraulic and / or pneumatic components, particularly valves. Relatedly, "the actuator is periodically mechanically forced to disengage during operation" should specifically refer to the periodic automatic mechanical disconnection of the effective engagement between the actuator and the cam unit during operation. Preferably, this disengagement is performed mechanically without intervention from the control unit.Particularly preferably, in the forced disengagement state, the actuation of the cam unit, or the switching process by means of the actuator, is technically impossible due to the lack of effective engagement. Here, "periodic" should specifically refer to periodicity, where the period can be related to the camshaft speed. In particular, the period can vary with the camshaft speed. Particularly preferably, this should specifically refer to the periodic change of the rotation angle and / or angular position relative to the camshaft. "Switching process" should specifically refer to the process of switching from one cam profile engaged with the corresponding valve to another cam profile and engaging it with the valve. Here, during the switching process, the cam unit having two switchable cam profiles moves axially on the camshaft. "Permissible state" should specifically refer to the state of the valve train and / or internal combustion engine in which valve lift switching can be performed reliably by switching from one engaged cam profile to another.

[0009] It is also proposed that, during operation, the actuator periodically and temporarily disengages from the cam unit relative to the camshaft rotational speed. Preferably, during operation, the actuator is periodically and forcibly disengaged from the cam unit due to the rotational angle of the camshaft. Preferably, the actuator is temporarily and forcibly disengaged from the cam unit whenever the cam unit should not be moved, i.e., especially when at least one valve is actuated by means of the cam unit. Thus, it is advantageous to provide a valve train that is structurally non-disallowing for switching at incorrect times, thereby allowing for a highly reliable valve train design. In particular, it is possible to provide a valve train in which the actuator is always effectively engaged with the cam unit when switching is possible.

[0010] Furthermore, the cam unit has an actuating element, through which the cam unit engages with the actuator unit. Preferably, the actuator and the actuating element are in direct and effective engagement in at least one operating state. Preferably, the actuator is configured to transmit a moving force to the cam unit via the actuating element. This, in particular, ensures reliable transmission of the moving force to the cam unit. It provides an advantageous mechanical force transmission. Relatedly, "actuating element" specifically refers to a protrusion extending at least partially in the circumferential direction of the cam unit, which is in direct and effective engagement with the actuator in at least one operating state. Preferably, the actuating element is composed of ribs at least partially surrounding the circumferential direction of the cam unit.

[0011] It is also proposed that the actuating element is partially interrupted along the circumference of the cam unit. The actuating element preferably has at least one interruption. Preferably, the at least one interruption extends through at least 5%, preferably at least 15%, and particularly preferably at least 25% of the circumference of the cam unit. Particularly preferably, the interruption is arranged such that when the interruption faces the actuator, the cam unit actuates just one valve. That is, preferably, the interruption always faces the actuator whenever the cam unit should not be moved, i.e., especially when at least one valve is actuated by means of the cam unit. Preferably, the interruption, in its position facing the actuator, causes forced separation of the actuator. Preferably, the cam unit does not contact the actuating element in the region of the interruption. This provides, in particular, a valve train that advantageously, in a simple form, does not allow switching at incorrect times, thus making the valve train highly reliable. It also provides, in particular, a valve train in which the actuator is always effectively engaged with the cam unit when switching is possible (this occurs particularly when the camshaft rotates half a revolution).

[0012] It is also proposed that the actuator temporarily disengages from the actuating element during operation. Preferably, the actuator always disengages from the actuating element whenever the cam unit should not be moved, i.e., especially when at least one valve is actuated by means of the cam unit. Preferably, the actuator is not moved to disengage from the actuating element. This provides, in particular, a valve train that preferably does not allow switching at incorrect times in a structurally simple manner, thus making the valve train highly reliable. In particular, a valve train can be provided in which the actuator is always effectively engaged with the cam unit when switching is possible (this occurs especially when the camshaft rotates half a revolution). Because the valve train does not block incorrect movement as according to SdT, but rather prevents movement force from being generated at incorrect times, the actuator unit can be designed to be very lightweight. Incorrect switching is reliably prevented.

[0013] It is also proposed that the actuating element is composed of sickle-shaped ribs. This provides an actuating element with an intermittent portion, which is particularly advantageous. It also provides an actuating element with a simple structure and ease of manufacture. "Sickle-shaped ribs" specifically refers to ribs that have a cross-section, at least substantially sickle-shaped, and especially crescent-shaped, in a section perpendicular to the camshaft's rotation axis. The ribs preferably have a radial height that continuously decreases to zero from the center of the rib towards both rotational directions.

[0014] The present invention is also based on a motor vehicle having an internal combustion engine, the internal combustion engine including the valve train. Attached Figure Description

[0015] Other advantages can be seen from the following description of the accompanying drawings. One embodiment of the invention is illustrated in the drawings. The drawings, description, and claims contain many combinations of features. Those skilled in the art can also appropriately view these features individually and combine them into other meaningful combinations. In the drawings:

[0016] Figure 1 A schematic diagram of a motor vehicle having an internal combustion engine and a multi-stage transmission is shown, the internal combustion engine including a valve train according to the invention;

[0017] Figure 2 A schematic diagram of the valve train of the present invention is shown, which includes a camshaft, a cam unit, and an actuator unit;

[0018] Figure 3 The valve train of the present invention is shown in a cross-sectional view along section line III-III, which includes a camshaft, a cam unit and an actuator unit. Detailed Implementation

[0019] Figure 1 A motor vehicle 17 is schematically shown. The motor vehicle 17 includes a powertrain to drive drive wheels 18 (not further shown) of the motor vehicle 17. The powertrain includes an internal combustion engine 11. The internal combustion engine 11 is a combustion engine. Additionally, the motor vehicle 17 has a multi-stage transmission 19. The internal combustion engine 11 has a driven crankshaft connected to the transmission input of the multi-stage transmission 19. The multi-stage transmission 19 is a motor vehicle transmission. The multi-stage transmission 19 forms part of the powertrain of the motor vehicle 17. The internal combustion engine 11 includes at least one valve train 10. Preferably, the internal combustion engine 11 includes multiple valve trains 10. The internal combustion engine 11 is designed as a motor vehicle internal combustion engine, configured to convert chemical energy into kinetic energy, particularly for the traction of the motor vehicle 17. The internal combustion engine 11 here has multiple cylinders, each cylinder having multiple valves 20, 20'. The internal combustion engine 11 has two valves 20 and 20' for each cylinder, which serve as intake valves, and two valves for each cylinder, which serve as exhaust valves. It is also conceivable that the internal combustion engine 11 could have other numbers of valves 20 and 20'. The valves 20 and 20' are described here... Figure 2 It is schematically shown by its plane of motion.

[0020] The valve train 10 is equipped with valves 20 and 20' for actuating the internal combustion engine 11. The valve train 10 includes a camshaft 12. Figure 2Only the portion of camshaft 12 that corresponds to a cylinder not shown in detail is shown. Furthermore, valve train 10 has another camshaft not shown in detail. The camshaft 12 shown is, for example, designed as an intake camshaft, while the camshaft not shown in detail is designed as an exhaust camshaft. Hereinafter, only the portion of camshaft 12 will be described in detail. Figure 2 and Figure 3 The following description applies to the undescribed portions of camshaft 12 and the undescribed portions of the camshaft itself.

[0021] The camshaft 12 is rotatably mounted via a camshaft housing (not shown in detail). The camshaft housing includes multiple supports fixed to a housing, which support the camshaft 12. The camshaft 12 is rotatably mounted here about a rotation axis 21. The rotation axis 21 of the camshaft 12 is oriented substantially parallel to the crankshaft rotation axis of the internal combustion engine 11. The camshaft 12 is driven by the crankshaft via a connecting component (not shown in detail). The valve train 10 has at least one cam unit 13 axially movably mounted on the camshaft 12. The valve train 10 includes one cam unit 13 for each cylinder. Figure 2 An example is shown of a cam unit 13. The cam unit 13 is axially movably arranged on a camshaft 12. Here, the cam unit 13 is anti-rotationally connected to the camshaft 12. The cam unit 13 is connected to the camshaft 12, particularly via a toothed structure 22. The cam unit 13 is configured to actuate valves 20, 20'. For this purpose, the cam unit 13 has one multi-faceted cam 23, 23' for each valve 20, 20'. The cam unit 13 has two multi-faceted cams 23, 23'. Each of the multi-faceted cams 23, 23' has three cam faces 24, 24', 25, 25', 26, 26' respectively. In principle, it is also conceivable that the cam unit 13 has only two or more of three cam faces 24, 24', 25, 25', 26, 26' for each multi-faceted cam 23, 23'. Cam profiles 24, 24', 25, 25', 26, and 26' each have different profiles and therefore actuate valves 20 and 20' with correspondingly different valve lifts. In the first switching position of cam unit 13, the first cam profiles 24 and 24' actuate the corresponding valves 20 and 20'. Valves 20 and 20' are actuated at this time, for example, with a medium lift. In the second switching position of cam unit 13, the second cam profiles 25 and 25' actuate the corresponding valves 20 and 20'. Valves 20 and 20' are actuated at this time, for example, with a large lift. In the third switching position of cam unit 13, the third cam profiles 26 and 26' actuate the corresponding valves 20 and 20'. Figure 2 Valve 20, 20' is actuated at this time, for example, with a small lift. Valve 20, 20' is actuated by cam profiles 24, 24', 25, 25', 26, 26' in a manner known to those skilled in the art.

[0022] Additionally, the valve train 10 includes an actuator unit 14. The valve train 10 has an actuator unit 14 to move the cam unit 13 between three switching positions on the camshaft 12. The actuator unit 14 has an actuator 15. The actuator 15 is composed of a switching actuator. The actuator 15 is configured to move the cam unit 13 on the camshaft 12. The actuator 15 is configured to move the cam unit 13 axially on the camshaft 12 so that the different cam profiles 24, 24', 25, 25', 26, 26' of the multi-faceted cams 23, 23' engage the corresponding valves 20, 20'. The actuator 15 is designed as an electronic control unit. The actuator 15 includes a motor 27 and a spindle 28, which can be driven by the motor 27 in two rotational directions. To convert the rotation of the spindle 28 into linear motion, the actuator 15 has a switching element 29. The switching element 29 is designed in the shape of a nut. The switching element 29 has an internal thread (not shown in detail) and is mounted on the spindle 28. The spindle 28 is rotated by a motor 27, thereby allowing the switching element 29 to move axially along the spindle 28. A support for the switching element 29 can be, for example, a slide rail or a rope device, instead of the spindle 28. The actuator 15 is arranged parallel to and offset from the camshaft 12.

[0023] The cam unit 13 also has an actuator 16. The cam unit 13 engages with the actuator unit 14 via the actuator 16. The cam unit 13 engages with the actuator 15 via the actuator 16. The axially movable switching element 29 of the actuator 15 effectively engages with the actuator 16. The actuator 16 is designed as a narrow, annular rib. The actuator 16 is partially interrupted in the circumferential direction of the cam unit 13. The actuator 16 has an interruption in the circumferential direction of the cam unit 13. Therefore, in the circumferential direction of the cam unit 13, the actuator 16 does not extend completely around the cam unit 13. The actuator 16 is designed as a rib. The actuator 16 is composed of ribs that surround the cam unit 180° in the circumferential direction. The actuator 16 is composed of sickle-shaped ribs. The actuator 16 is designed as a crescent-shaped rib. However, other shapes of the actuator 16 that would be meaningful to a person skilled in the art are also conceivable in principle. Actuator 16 is designed to have no slope in the axial direction and a constant width in the circumferential direction of camshaft 12. Actuator 16 is arranged between the multi-faceted cams 23, 23' of cam unit 13. Switching element 29 is temporarily connected to actuator 16 in a form-fit manner. For this purpose, switching element 29 has a groove into which the rib-shaped actuator 16 is inserted. Actuator 16 forms an engagement for applying an axially acting moving force to cam unit 13. In the illustrated embodiment, the axially acting moving force is applied solely by actuator 15. It is independent of the rotational movement of camshaft 12.

[0024] During operation, actuator 15 is periodically mechanically forced to disengage. During operation, the rotational speed of actuator 15 relative to camshaft 12 is periodically and temporarily separated from cam unit 13. During operation, the rotational angle of actuator 15 relative to camshaft 12 is periodically and temporarily forced to disengage from cam unit 13. Furthermore, whenever cam unit 13 should not be moved, especially when valves 20, 20' are just actuated by cam unit 13, actuator 15 is temporarily forced to disengage from cam unit 13. Forced disengagement is performed mechanically by means of actuating element 16. For this purpose, actuating element 16 has an interruption. This interruption is arranged such that when the interruption faces actuator 15, cam unit 13 just actuates valves 20, 20'. That is, whenever cam unit 13 should not be moved, especially when at least valves 20, 20' are just actuated by cam unit 13, the interruption always faces actuator 15. The interruption at the position toward actuator 15 causes forced disengagement of actuator 15. Actuator 15 is thus temporarily disengaged from engagement with actuator 16 during operation. Switching element 29 of actuator 15 is also temporarily disengaged from engagement with actuator 16 during operation. Switching element 29 of actuator 15 is always disengaged from engagement with actuator 16 when cam unit 13 should not be moved.

[0025] During each half-turn of the camshaft (when mechanical switching is always possible), the actuator 16 allows interaction between the actuator 15 and the cam unit 13. However, whenever a switching attempt could potentially cause damage, force engagement between the actuator 15 and the cam unit 13 is not possible. This prevents the cam unit 13 from moving at the wrong time.

[0026] To operate the actuator 15, the valve train 10 has a control and adjustment unit (not shown in detail). This control and adjustment unit is configured to control the electric motor 27 of the actuator 15 and thereby operate the actuator 15. The control and adjustment unit is designed here as part of the engine control unit. Alternatively, it is conceivable that the control and adjustment unit could be designed as a separate control unit. Under the control of the control and adjustment unit, the electric motor 27 of the actuator 15 can be driven in two directions, thereby allowing the switching element 29 to move in two axial directions.

[0027] List of reference numerals

[0028] 10 Valve transmission device

[0029] 11 Internal Combustion Engine

[0030] 12 Camshafts

[0031] 13 Cam Unit

[0032] 14 Actuator Units

[0033] 15 Actuators

[0034] 16. Functional Components

[0035] 17 Motor vehicles

[0036] 18 drive wheels

[0037] 19-stage multi-speed transmission

[0038] 20 valves

[0039] 21. Rotation axis

[0040] 22-tooth structure

[0041] 23 Cam

[0042] 24 Cam profile

[0043] 25 Cam profile

[0044] 26 Cam profile

[0045] 27 Electric motor

[0046] 28 Spindle

[0047] 29 Switching components.

Claims

1. A valve train, comprising: - At least one camshaft (12); - At least one cam unit (13) axially movably mounted on the camshaft (12); and - At least one actuator unit (14) having at least one actuator (15) having a motor (27) and a main shaft (28) for moving the cam unit (13) on the camshaft (12). in, By using the motor to rotate the main shaft, the switching element (29) can move axially along the main shaft and relative to the camshaft. Its characteristic is that the actuator (15) is periodically mechanically forced to separate during operation and is periodically temporarily separated from the cam unit (13) relative to the rotation angle of the camshaft (12), the cam unit (13) having an actuating element (16), the cam unit (13) engaging with the actuator unit (14) by means of the actuating element, and the switching element (29) of the actuator (15) always disengaging from the actuating element (16) when at least one valve is actuated by means of the cam unit (13). The actuating element (16) is partially interrupted along the circumference of the cam unit (13). The actuator (15) is temporarily disengaged from the actuating element (16) during operation.

2. The valve train according to claim 1, characterized in that, The actuating element (16) is formed by sickle-shaped ribs.

3. The valve train according to claim 1, characterized in that, This valve train is used in an internal combustion engine (11).

4. A motor vehicle having an internal combustion engine (11), said internal combustion engine including a valve train (10) according to any one of the preceding claims.

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