RU2757699C2 - Method for stopping internal combustion engine and adjustable valve drive - Google Patents

Abstract

FIELD: internal combustion engines.SUBSTANCE: method for stopping an internal combustion engine is to initiate the stopping process. Reducing the vibration of the internal combustion engine during the stopping is carried out by switching a drive of first exhaust valve (20) of the internal combustion engine by means of cam system (11) with an adjustable position for opening or holding in the open position at the compression and exhaust stroke. And/or switching to an engine braking mode is performed, in which first exhaust valve (20) of the internal combustion engine is first kept in the closed position during the compression and/or exhaust stroke for air compression, and before a piston reaches the upper dead center, is opened to release compressed air. An adjustable valve drive for the internal combustion engine of a vehicle and a vehicle with an adjustable valve drive are disclosed.EFFECT: reducing vibrations during the stopping process.15 cl, 9 dwg

Description

The invention relates to a method for stopping an internal combustion engine and to a variable valve drive.

WO 2014/100185 A1 discloses an engine valve control device for decompressing an engine cylinder when the engine is stopped. The system may include a rocker arm pivotally secured to an axle. Additionally, the system may have a structure that is adjacent to the rocker arm and is fixed motionlessly relative to the rocker arm. The blocking piston can be slidably disposed between the rocker arm and said structure. The locking piston can be selectively extended to engage both the rocker arm and the structure to restrict swing movement of the rocker arm and keep the engine valves open during engine shutdown.

The object of the present invention is to provide an alternative or improved method for stopping an internal combustion engine to reduce vibrations during stopping, and a device for this.

The task is achieved by a method and device according to the independent claims. Preferred embodiments of the invention are listed in the dependent claims and description.

The method for stopping an internal combustion engine involves initiating a stopping process. In addition, the method provides for reducing vibration of the internal combustion engine during stopping by switching the actuator of the first exhaust valve of the internal combustion engine by means of a variable position cam system for opening or holding open during the compression and exhaust strokes. Alternatively or additionally, the method involves switching to the engine braking mode, in which the first exhaust valve of the internal combustion engine during the compression and / or exhaust stroke for compressing air is first held closed, and before the piston reaches top dead center, it is opened to release the compressed air.

By opening the first exhaust valve, in particular during the compression stroke during engine shutdown, it is possible to prevent or reduce the swinging (oscillation in different directions) of the internal combustion engine. This leads to a reduction in the noise level during shutdown. The variable position cam system provides a reliable and fast shifting method. If a switch is made to the engine braking mode, then this makes it possible to abandon the creation of a new device for actuating the first exhaust valve during the stop process and use the system for switching in the engine braking mode. This allows the same system to be used for both braking the motors and stopping the motor.

Of course, no fuel is supplied to the cylinders during engine shutdown. The operation of the intake valves can, in particular, remain unchanged.

In a more preferred embodiment of the invention, a variable valve drive, in particular a variable position cam system, of the internal combustion engine is used to switch over to engine braking.

In another preferred additional embodiment, the variable position cam system has a cam base mounted on the camshaft of an internal combustion engine, rotatable and axially displaceable, with a first cam for normal operation and a second cam that is located on longitudinally offset camshaft and is responsible for operating in engine braking mode and / or for actuating the first exhaust valve when the engine is stopped. The variable position cam system optionally creates a kinematic relationship between the first cam and the first exhaust valve, or creates a kinematic relationship between the second cam and the first exhaust valve.

Preferably, in normal operation, the first exhaust valve is only opened at the exhaust stroke.

In one embodiment of the invention, the method further comprises switching from the first cam to the second cam using the variable position cam system at the start of the stopping process. During the stopping process, the first exhaust valve is driven by the second cam.

Preferably, the second cam opens the first exhaust valve during the compression stroke and the exhaust stroke, or keeps the first exhaust valve open during the compression stroke and exhaust stroke. Alternatively or additionally, the second cam first holds the first exhaust valve closed during the compression stroke and / or the exhaust stroke, and opens it before the piston reaches top dead center.

In another embodiment of the invention, the first exhaust valve opens between 100 ° and 60 ° crankshaft angle before reaching top dead center. Alternatively or additionally, the first exhaust valve is closed after opening at the exhaust stroke in the range from top dead center to 30 ° crankshaft angle after top dead center. Alternatively or additionally, the first exhaust valve is closed after opening on the compression stroke in the range from bottom dead center to 30 ° crankshaft angle after bottom dead center. This can, on the one hand, improve the efficiency of the engine braking mode and, on the other hand, reduce vibration during stopping of the combustion engine.

In one embodiment of the invention, the second cam of the variable-position cam system at the end of the stopping process maintains a kinematic relationship with the first exhaust valve. Alternatively, at the end of the stop process, the variable position cam system switches to the first cam. The state of the variable-position cam system at the end of the stopping process can have a significant effect on the starting process of an internal combustion engine.

In another embodiment of the invention, the method includes recording the temperature of the internal combustion engine and / or the operating time of the internal combustion engine. Switching the drive of the first exhaust valve of an internal combustion engine using a variable position cam system to open or hold open on the compression stroke and on the exhaust stroke and / or switch to engine braking is performed when the detected engine temperature is below or equal to the preset temperature the engine temperature threshold and / or the recorded run time is less than or equal to the predetermined run time threshold. Thus, for example, at low engine temperatures, such (switching) switching can be dispensed with.

In one embodiment, the method further comprises keeping the second exhaust valve of the internal combustion engine closed during shutdown. The second exhaust valve operates on the same cylinder of the combustion engine as the first exhaust valve. This reduces the load on the variable valve drive since not all cylinder outlet valves open against the pressure in the cylinder.

In another preferred additional embodiment, keeping the second exhaust valve closed includes switching to a no-cam portion of the variable-position cam system.

In one embodiment of the invention, the first group of cylinders is opened or held open on the first exhaust valve on the compression stroke and the exhaust stroke by switching the actuator using a variable position cam system and / or the first group of cylinders of the internal combustion engine is switched to the engine braking mode in the process of stopping the engine. In the second group of cylinders, the exhaust valve actuator remains unchanged during stopping. This reduces wear on the switching system.

In particular, the first group and / or the second group may contain no cylinders, one, several or all cylinders.

In a preferred embodiment of the invention, the number of cylinders in the first group and / or in the second group is determined depending on at least one operating parameter of the internal combustion engine, in particular the temperature of the internal combustion engine and / or the operating time of the internal combustion engine. As a result, for example, at low engine temperatures, fewer cylinders can be included in the first group.

In a preferred embodiment of the invention, the attachment to the first and / or to the second group is carried out on a sliding principle, in particular on a sliding principle among successive stopping processes. This allows the wear of the shift system to be uniform across several cylinders.

The invention also relates to a variable valve drive for an internal combustion engine of a vehicle, in particular a commercial vehicle. The variable valve drive has a first exhaust valve, a camshaft and at least one variable position cam system. The variable position cam system has a cam base that is rotatably and axially displaceable on the camshaft and has a first cam and a second cam. The first cam and the second cam are offset along the camshaft. The variable valve actuator has a control unit that is designed to implement the method in accordance with the description provided here.

The term "control unit" refers to electronic devices that, depending on their design, can carry out control and / or regulation functions.

Preferably, the cam base is axially displaceable on the camshaft between the first axial position and the second axial position. The valve drive also has a transmission device. In the first axial position of the cam base, the transmission device is in kinematic relationship between the first cam and the first exhaust valve. In the second axial position of the cam base, the transmission device is in kinematic relationship between the second cam and the first exhaust valve. The first cam is for normal operation of the internal combustion engine, which assumes that the first cam holds the first exhaust valve open during the exhaust stroke. The second cam is designed to operate the combustion engine in a braking mode, which assumes that the second cam first holds the first exhaust valve closed during the compression stroke and / or exhaust stroke, and opens the first exhaust valve before the combustion engine piston reaches top dead center ...

Of course, while the second cam is in engagement with the first transmission device, the intake valve or intake valves only open on the intake stroke. However, the fuel supply and ignition of the mixture does not occur.

The first cam and the second cam may have different profile shapes and / or may be offset relative to each other around the circumference of the cam base.

In one embodiment, the cam base has a third cam that follows the shape of the first cam and has one non-cam portion. The first cam, the second cam, the third cam, and the non-cam portion are disposed on the camshaft with a longitudinal offset. In particular, the first cam is adjacent to the second and the third cam is adjacent to the non-cam area. The integration of the third cam and the non-cam area allows the second exhaust valve to be actuated in a braking and stop mode differently from the first exhaust valve. In normal operation, the second exhaust valve, on the other hand, can be operated as the first exhaust valve, since the third cam and the first cam have the same shape.

The no-cam area is also called zero cam. The non-cam section is in the form of a cylinder without bulges for driving the transmission device.

Preferably, the valve actuator has a second exhaust valve, which in particular operates on the same cylinder as the first exhaust valve and a second transmission device. The second transmission device in the first axial position of the cam base is in a kinematic relationship between the third cam and the second exhaust valve. In the second axial position of the cam base, the second transmission device keeps the second outlet valve closed due to the shape of the non-cam portion. In this case, the section without cams may or may not be in engagement with the second transmission device.

It goes without saying that the second transmission device in the second axial position of the base for the cams is not in kinematic connection with any other cam of the base.

The advantage of this design is that only the first outlet valve is used for braking and stopping. The second exhaust valve, when the first exhaust valve is engaged in engine braking, remains closed throughout the entire cycle. This reduces the load on the variable valve drive. In particular, when the exhaust valve is opened against the pressure in the cylinder, a large pressure is generated on the surface between the cam and the contact plane of the transfer device. In designs where both exhaust valves are actuated during braking, the variable valve actuator must be adequately dimensioned.

In an alternative embodiment of the invention, the valve actuator further comprises a second exhaust valve, which in particular operates on the same cylinder as the first exhaust valve. The first transmission device in the first axial position of the cam base is additionally in a kinematic connection between the first cam and the second exhaust valve, and in the second axial position is additionally in a kinematic connection between the second cam and the second exhaust valve.

The first cam and the third cam may have the same profile shape and / or may be aligned (coaxially) with each other around the circumference of the cam base.

The advantage of this design is the use of two exhaust valves for engine braking. Both exhaust valves are driven by the same transmission device and the same cams.

In one embodiment of the invention, the cam base has a first working portion for axially displacing the cam base in a first direction. The first working section has, in particular, a spiral shape.

The first working section is designed to move the cam base axially by engaging with the actuator, for example, from a first axial position to a second axial position or from a second axial position to a first axial position.

In a more preferred embodiment of the invention, the first working area is located in the area without cams. In other words, the first working area is located in the zero cam.

The advantage of this design is, firstly, the use of a section without cams for axial movement. Second, the non-cam section prevents the second exhaust valve from opening during engine braking and during engine shutdown. The integration of functions reduces the space required to install the cam base.

In another embodiment of the invention, the first working portion and / or the non-cam portion is located between the first and third cams or at the end of the cam base. The arrangement of the cams, the no-cam section and the first working section can be adapted to the respective requirements.

In one embodiment of the invention, the cam base has a second working portion for axially displacing the cam base in a second direction opposite to the first direction. The second working area is located between the first and third cams or at the end of the cam base. The second working section can be made, in particular, in the form of a spiral.

The second working section is designed to move the cam base axially by engaging with the actuator, for example, from a first axial position to a second axial position or from a second axial position to a first axial position. The first and second working sections provide reliable movement of the cam base.

In another embodiment of the invention, the variable valve actuator includes a first actuator for selectively engaging the first actuator and moving the cam base in a first direction. Alternatively or additionally, the variable valve actuator includes a second actuator for selectively engaging the second actuator and moving the cam base in a second direction.

Preferably, the camshaft has a resilient pre-stressed member that engages a first cam base recess at a first cam base axial position and a second cam base recess at a second cam base axial position.

The advantage of the stopper is the ability to lock the cam base in the first and second axial positions. This prevents the cam base from accidentally moving along the camshaft.

In another embodiment of the invention, the first transmission device and / or the second transmission device are designed as a lever, in particular as a rocker arm or a rocker arm or a pusher. The rocker arm can be used, for example, for the upper camshaft. The rocker arm can be used, for example, for the lower camshaft.

In another embodiment, the camshaft can be top or bottom. Alternatively or additionally, the camshaft is part of a dual camshaft timing system that has an additional camshaft for actuating at least one intake valve.

In another embodiment of the invention, the camshaft for the exhaust valve or exhaust valves and / or the auxiliary camshaft for the intake valve or intake valves may have a variable valve timing device. The variable valve timing device is designed to change the angle of rotation of the camshaft relative to the angle of rotation of the crankshaft. Thus, the variable valve timing device makes it possible to change the valve timing for the respective valves. The variable valve timing device can be, for example, hydraulic, in particular, it can have the form of a variable valve timing device with a hydraulically controlled clutch. An advantage of such an embodiment of the invention is the increased flexibility of the system due to the combination with a movable cam base.

In another embodiment, the second cam is shaped to provide a greater opening stroke for the first exhaust valve on the compression stroke than when opening on the exhaust stroke. Alternatively or additionally, the second cam is shaped so that the opening stroke of the first exhaust valve is shorter than that of the first cam. The presence of a multi-stage valve stroke that is reduced in comparison with the usual mode reduces the load on the valve actuator. In particular, when the exhaust valve is opened against the pressure in the cylinder, a large load is applied to the valve actuator.

In embodiments of the invention where the second cam is used to inter alia actuate the second exhaust valve, the embodiments that relate to the action of the second cam on the first exhaust valve are equally suitable for the second exhaust valve. In embodiments of the invention where a third cam is used to actuate the second exhaust valve, the embodiments that relate to the action of the first cam on the first exhaust valve are equally suitable for the third cam and the second exhaust valve.

In addition, the invention relates to a vehicle, in particular, to a commercial vehicle with variable valve drive as described herein. A commercial vehicle can be, for example, a minibus or a commercial vehicle.

The above described preferred embodiments of the invention and the features of the invention can be combined with each other in any combination. Other details and advantages of the present invention are described below with reference to the accompanying drawings. They show:

FIG. 1 Axonometric view of an exemplary variable valve actuator;

FIG. 2 Additional perspective view of an exemplary variable valve actuator;

FIG. 3 Top view of the camshaft of an exemplary variable valve drive;

FIG. 4 View of the camshaft shown in FIG. 3, in longitudinal section along the line A-A;

FIG. 5 Exemplary timing diagram with variable valve drive;

FIG. 6A A first view of the camshaft shown in FIG. 4, in cross-section along the line B-B;

FIG. 6B A second view of the camshaft shown in FIG. 4 in cross-section along the line C-C;

FIG. 7 Exemplary method for stopping an internal combustion engine according to the present disclosure; and

FIG. 8 Diagram showing the variation of the engine, turbine and boost pressure curves over time.

The illustrated embodiments of the invention overlap at least in part, so that like or identical parts are designated with the same reference numerals and are explained by reference to descriptions of other embodiments of the invention, or to other figures, respectively, in order to avoid repetition.

Below, using the example of FIG. 1-6B, the most preferred variable valve drive embodiment is first described, which is suitable for both the method of stopping an internal combustion engine disclosed herein and the engine braking mode. The internal combustion engine can be installed, in particular, in a vehicle, preferably in a commercial vehicle, for example a minivan or a commercial vehicle. Then, using the example of FIG. 7 and 8 describe, in particular, a method for stopping an internal combustion engine. This method can use a variable valve actuator disclosed herein or another variable valve actuator, in particular with a modified variable position cam system.

FIG. 1 and 2 show a variable valve actuator 10. The variable valve actuator 10 has one camshaft 12 and one cam base 14. Additionally, variable valve actuator 10 has first and second transmission devices 16 and 18, as well as first and second exhaust valves 20 and 22. In addition, variable valve actuator 10 has a first actuator 24 and a second actuator 26. Cam base 14, transmission the devices 16 and 18, as well as the actuators 24 and 26, form a cam system 11 with an adjustable position.

Camshaft 12 is in the form of an exhaust camshaft that drives exhaust valves 20 and 22. Camshaft 12 is part of a dual camshaft timing system (not shown in detail) that further includes one intake camshaft (not shown) for actuation of one or more intake valves. Camshaft 12 together with the intake camshaft are the overhead camshafts. Thus, the camshaft 12 and the intake camshaft form the so-called DOHC system (English double overhead camshaft - two overhead camshafts). Alternatively, the camshaft 12 can also have the form of the so-called SOHC system (English single overhead camshaft - one overhead camshaft). In other embodiments, the camshaft 12 may also be a lower camshaft.

On the camshaft 12, there is a base 14 for cams without the possibility of rotation. The cam base 14 is further axially displaceable along the longitudinal axis of the camshaft 12. The cam base 14 is axially displaceable between the first stop 28 and the second stop 30.

In the example of FIG. 1-4, the cam base 14 is described below. The cam base 14 has three cams 32, 34 and 36, which are offset longitudinally relative to each other on the cam base 14 and camshaft 12. The first cam 32 is located at the first end of the cam base 14 and is designed to operate normally. mode, as will be described in detail below with an example. The second cam 34 is adjacent to the first cam 32 and is designed to operate in the engine braking mode, as will also be described in detail below by way of example. The engine braking mode can be used to slow down and / or brake the vehicle while driving downhill. The engine braking mode can additionally be used to reduce the vibration of the combustion engine during stopping. The third cam 36 is spaced from the second cam 34 and from the second end of the cam base 14. The third cam 36 is designed for normal operation. The third cam 36 has the same shape as the first cam 32.

In addition, the cam base 14 has a first section 38 without cams and a second section 40 without cams. The first non-cam portion 38 is located at the second end of the cam base 14. The second section 40 without cams is located between the second cam 34 and the third cam 36. In the first section 38 without cams in the form of a spiral around the longitudinal axis of the base 14 for the cams, the first working section (shift rocker) 42 extends. In the second section 40 without cams in the form of a spiral around the longitudinal axis of the base 14 for the cams there is a second working section (shift rocker) 44.

To move the cam base 14 between stops 28 and 30, actuating elements 24 and 26 (Figs. 1 and 2) with retractable elements (not shown in detail) can selectively engage with the working sections 42, 44. In particular, the first actuator 24 may selectively engage with the first operating portion 42 to bias the cam base 14 from one axial position to another axial position. In the first axial position, the cam base 14 bears against the second stop 30. In the second axial position, the cam base 14 bears against the first stop 28. In FIG. 1-4 show the base for the cams in the first axial position. The second actuator 26, in turn, can selectively engage with the second actuating section 44. The cam base 14 is thereby moved from the first axial position to the second axial position. The first actuator 24 and the second actuator 26 are actuated by a control unit 27 (FIGS. 1 and 2), which is shown schematically.

The displacement process is initiated by the fixed attachment of the extended portion of the corresponding actuator 24, 26 relative to the axial direction of the camshaft 12. As a result, the movable cam base 14 moves along the camshaft 12 due to the spiral shape of the working sections 42, 44 when the extended portion engages with the corresponding working section 42, 44. At the end of the displacement process, the movable part of the corresponding actuator 24, 26 is directed to the opposite side of the corresponding working section 42, 44, and thus retracts. The movable part of the respective actuator 24, 26 is disengaged with the corresponding operating section 42, 44.

The first transfer device 16 and the second transfer device 18 (FIGS. 1 and 2) establish a kinematic connection between the cam base 14 and the exhaust valves 20, 22. The first exhaust valve 20 is activated (opened) when the first cam 32 or the second cam 34 press on the first transfer device 16 and move it down. The second exhaust valve 22 is activated (opened) when the third cam 36 pushes against the second transmission device 18 and moves it downward.

If the cam base 14 is in the first axial position (as shown in FIGS. 1-4), then the first transmission device 16 establishes a kinematic connection between the first cam 32 and the first exhaust valve 20. In other words, the first transmission device 16 is in the first axial position the cam base 14 is not kinematically connected between the second cam 34 and the first exhaust valve 20. The first exhaust valve 20 is driven by the circuitry of the first cam 32. In the second axial position of the cam base 14, the first transfer device 16 is in kinematic relationship between the second cam 34 and the first exhaust valve 20. The first exhaust valve 20 is driven by the circuit of the second cam 34.

In the first axial position of the cam base 14, the second transmission device 18 is kinematically connected between the third cam 36 and the second exhaust valve 22. The second outlet valve 22 is driven by the circuitry of the third cam 36. In the second axial position of the cam base 14, the second transmission device 18 does not operate the second exhaust valve 22. In the second axial position of the cam base 14, the contact area 18A of the second transmission 18 is in the same axial position with respect to the camshaft 12 as the first non-cam portion 38. The first non-cam portion 38 does not have bumps for driving the second transmission device 18. If the cam base 14 is in the second axial position, then the second exhaust valve 22 is not activated.

Thus, the first section 38 without cams has two functions. On the one hand, in the first section 38 without cams, there is a first operating section 42. On the other hand, the first section 38 without cams serves to prevent the second exhaust valve 22 from being actuated in the second axial position of the cam base 14. advantageous for reasons of space saving.

In the illustrated embodiment, the first transfer device 16 and the second transfer device 18 are in the form of rocker arms. In other embodiments of the invention, the transmission devices 16 and 18 may be in the form of a rocker arm or a pusher. In some embodiments of the invention, the transfer devices 16 and 18 may have different forms of the pusher member, for example, the form of rotating rollers.

FIG. 4 shows a stopper 46. Stopper 46 has a resilient element 48 and a locking element 50. The resilient element 48 is located in a blind hole in the camshaft 12. The resilient element 48 presses the locking element 50 against the cam base 14. Along the inner circumference of the cam base 14 are first and second recesses 52 and 54. To secure the cam base 14, the locking member 50 is pressed into the first recess 52 when the cam base 14 is in the first axial position. In the second axial position of the cam base 14, the locking member 50 is pressed into the second recess 54.

In the example of FIG. 5 below describes the control of the first exhaust valve 20, as well as its effect on the pressure in the cylinder. FIG. 5 shows a complete cycle of four strokes: compression, travel, exhaust and inlet.

Curve A describes the dynamics of pressure change in the cylinder during engine braking operation when the second cam 34 is in kinematic connection with the first exhaust valve 20. Curve B describes the stroke of the first exhaust valve 20 when the first cam 32 is connected to the first exhaust valve 20 (t I.e. in normal operation). The third curve C describes the intake valve travel for both normal operation and engine braking. Curve D describes the travel of the first exhaust valve 20 when the second cam 34 is in kinematic communication with the first exhaust valve 20 (i.e., in engine braking mode).

Curve B shows that the exhaust valve is open normally on the exhaust stroke. Curve C shows that the intake valve is open during normal operation and during braking on the intake stroke.

Curve D shows that the exhaust valve is slightly open at the end of the compression stroke at top dead center by about 60-100 ° crankshaft angle to top dead center. The outlet valve opens more at top dead center and closes at approximately bottom dead center at the end of its travel. Opening the exhaust valve at the end of the compression stroke causes compressed air to be pushed out of the cylinder through the open exhaust valve and into the exhaust system by a piston that moves to top dead center. Previously perfect compression work brakes the crankshaft and thus the combustion engine. The pressure in the cylinder during the compression stroke first increases, but then decreases as a result of the opening of the exhaust valve, even before the piston reaches top dead center (cf. curve A). Opening the exhaust valve during the stroke cycle causes air from the exhaust pipes to be sucked back into the cylinder. At the end of the stroke, the cylinder is largely filled with air from the exhaust system.

In addition, curve D shows that the exhaust valve initially remains closed after the piston reaches bottom dead center at the end of its travel. At the end of the exhaust stroke, the exhaust valve opens at top dead center. Opening, in turn, occurs approximately in the range of 60-100 ° crankshaft angle to top dead center. The closed state of the exhaust valve on the exhaust stroke causes the air that was drawn in during the stroke stroke to be compressed to perform work. The cylinder pressure rises (curve A). Perfect work brakes the crankshaft and thus the combustion engine. Opening the exhaust valve at the end of the exhaust stroke forces air through the open exhaust valve into the exhaust system. On the intake stroke, the cylinder is again filled with air through the open or open intake valve (s) (curve C). The cycle starts over.

As described above, by using the second cam to control the exhaust valve, it is compressed twice, followed by decompression, thereby providing engine braking. In addition, when the engine braking mode is turned off during the stopping of the internal combustion engine, the vibration of the internal combustion engine is reduced, since the swinging of the internal combustion engine during the compression stroke is reduced due to the opening of the exhaust valve until the piston reaches top dead center.

As you can see from the comparison of curves B and D, the travel of the exhaust valve in braking mode (curve D) is less than in normal mode (curve B). In addition, the opening stroke of the exhaust valve on the compression stroke and the stroke is performed in two stages. These measures reduce the load on the variable valve drive in deceleration mode, since the opening of the exhaust valve against the pressure in the cylinder can cause high loads on the valve drive.

FIG. 6A is a cross-sectional view of the second cam 34. In FIG. 6B shows a cross section of the first cam 32.

The second cam 34 is designed to produce the curve D shown in FIG. 5. To this end, the second cam 34 in particular has a first bump 34A, a second bump 34B and a third bump 34C. The first, second and third protuberances 34A-34C are located around the circumference of the second cam 34 with an offset. The first bulge 34A causes the exhaust valve to open at the end of the compression stroke. The second bulge 34B, which extends from the first bulge 34A, causes the exhaust valve to open wider on the stroke. The third bulge 34C causes the exhaust valve to open at the end of the exhaust stroke.

The first bulge 34A has the lowest height of all, 34A to 34C when measured in the radial direction of the camshaft 12. The second bulge 34B has the highest height of all, 34A to 34C, when measured in the radial direction of the camshaft 12. The third bulge 34C is smaller than second bulge 34B and larger than first bulge 34A. The different heights of the bumps 34A – 34C provide a corresponding difference in valve travel (cf. FIG. 5).

The first, second and third protuberances 34A-34C are disposed around the circumference, respectively, with an offset from the bulge 32A of the first cam 32. The first cam 32 is intended to obtain the curve B shown in FIG. 5. The bulge 32A of the first cam 32 causes the exhaust valve to open on the exhaust stroke. Bump 32A, measured in the radial direction of camshaft 12, is higher than bumps 34A – 34C. The valve travel provided by the 32A bump is greater than the travel provided by the 34A – 34C bumps.

In addition, in FIG. 6B shows a stopper 46 with a resilient member 48, a locking member 50 and a first recess 52.

Further, using the example of FIG. 7 and 8 describe an exemplary method for stopping an internal combustion engine.

In step S100, the stop process is initiated. This can be done, for example, by turning the key in the ignition lock or by pressing the engine stop button.

Immediately after the stopping process has been initiated, engine braking can be activated. For this, in step S102, a switch to the second cam 34 can be performed (see, for example, FIG. 1). It is possible that switching occurs on all cylinders of the internal combustion engine or only on some of the cylinders.

Switching to the second cam 34 causes the first exhaust valve 20 to be initially held closed during the compression and exhaust strokes, and before the piston reaches top dead center, it is opened to release the compressed air.

FIG. 8 depicts the deflection movement (vibration) l of the internal combustion engine over time t during stopping in the normal mode (dotted line E) and in the mode according to this disclosure (solid line F). First, the internal combustion engine is idling in the t1 region. At time T1, the stop process is initiated. In the region t2, the actual stopping process itself is shown.

In the normal shutdown mode, the combustion engine rocking occurs immediately at the beginning of the shutdown process. Undesirable swinging is caused by the fact that the cylinders, on the one hand, are at different strokes, and, on the other hand, all the valves on the compression stroke are closed.

During the stopping process according to the present disclosure, the rocking of the internal combustion engine can be reduced or eliminated. By switching to the second cam 34, the first exhaust valve 20 is opened on the compression stroke until the piston reaches top dead center. That is, during the compression stroke, not all valves are closed, so swinging is at least reduced. This is qualitatively shown by the solid line in FIG. 8. Residual fluctuations are due to the energy of the inertial mass of the internal combustion engine and the inertia of the system.

The first exhaust valve 20 may be driven by the second cam 34 prior to stopping the internal combustion engine. Here, it is also possible that, for example, if the predetermined engine speed threshold is not reached (step S106), at the end of the stopping process, the first cam 32 is switched again (step S108). The state of the variable position cam system 11 at the end of the stopping process can affect the starting of the internal combustion engine.

The method disclosed here for stopping an internal combustion engine can be modified and / or supplemented in various ways.

For example, it is possible to switch a system of 11 cams with an adjustable position of several cylinders to engine braking during a stop. The more cylinders are operated in engine braking mode, the more efficiently swinging of the combustion engine is prevented or reduced.

The number of variable position cam systems 11 that switch to engine braking during stopping can be determined depending on at least one operating parameter of the internal combustion engine. This operating parameter can be, in particular, the temperature of the internal combustion engine and / or the operating time of the internal combustion engine. Thus, for example, at a relatively low temperature of the internal combustion engine and a short operating time of the internal combustion engine, (slight) rocking of the internal combustion engine can be taken into account. It is also possible that, depending on the low temperature of the internal combustion engine and / or the short operating time of the internal combustion engine, no variable position cam system 11 switches to engine braking.

In embodiments of the invention, where one group of cylinders switches to the engine braking mode during stopping, and the second group of cylinders does not switch, the inclusion in the groups can occur on a sliding principle. The sliding grouping principle can be applied during stopping or, preferably, between different stopping processes. This makes it possible to make the wear rate of the variable-position cam system 11 uniform for several cylinders.

As described above, the method may involve using a variable position cam system 11 to stop the internal combustion engine. In particular, the control unit 27 can operate the actuators 24 and 26 (see FIG. 1) in accordance with the method disclosed herein for stopping an internal combustion engine. However, this method can be used with another variable position cam system, which involves switching between the first cam for normal mode and the second cam for stop mode. The second cam, for example, can be specially shaped to stop the engine and, in particular, to keep at least one exhaust valve of the cylinder open, at least during the compression and exhaust strokes.

This invention is not limited to the preferred embodiments of the invention that have been described above. Moreover, many variations and modifications are possible in which the idea of the present invention will also be used, and therefore such variations will fall within the scope of legal protection. In particular, the present invention claims to protect the subject matter and features from the dependent claims, regardless of the reference to the corresponding claims.

Item number list

10 Variable valve actuator

11 Adjustable cam system

12 Camshaft

14 Cam base

16 First transfer device (first rocker arm)

18 Second transfer device (second rocker arm)

18A Contact area

20 First outlet valve

22 Second outlet valve

24 First actuator

26 Second actuator

27 Control unit

28 First stop

30 Second stop

32 First cam

32A Bulge

34 Second cam

34A – 34C Bulges

36 Third cam

38 First section without cams

40 Second section without cams

42 First work area

44 Second working area

46 Stopper

48 Elastic element

50 Fixing element

52 First recess

54 Second recess

A Cylinder pressure

B Exhaust valve opening period curve

C Intake valve opening period curve

D Exhaust valve opening period curve

t Time axis

T1 Stop initiation moment

t1 First area (engine idle)

t2 Second area (stopping process)

l Deflection / vibration

E Vibration during normal stop

F Vibration when stopped according to the disclosed method.

Claims (39)

1. A method for stopping an internal combustion engine, including: initiation of the shutdown process; and reducing the vibration of the combustion engine during shutdown by: a) switching the actuator of the first exhaust valve (20) of the internal combustion engine by means of the variable position cam system (11) to open or hold open on the compression and exhaust stroke; and / or b) switching to engine braking, in which the first exhaust valve (20) of the internal combustion engine is first held closed during the compression and / or exhaust stroke for compression of air, and opens to release the compressed air before the piston reaches top dead center. 2. The method according to claim 1, in which the internal combustion engine is switched to the engine braking mode by means of a variable valve drive (10), in particular a variable position cam system (11). 3. A method according to claim 1 or 2, in which the variable position cam system (11) has a cam base (14) mounted on a camshaft (12) of an internal combustion engine without the possibility of rotation and with the possibility of axial displacement, with the first a cam (32), responsible for normal operation, and a second cam (34), which is located on the camshaft (12) with an offset in the longitudinal direction and is responsible for the operation in the engine braking mode and / or for the actuation of the first exhaust valve (20) during stopping, wherein the variable position cam system (11) optionally creates a kinematic relationship between the first cam (32) and the first exhaust valve (20) or creates a kinematic relationship between the second cam (34) and the first exhaust (20) valve. 4. The method according to claim 3, further comprising: switching from the first cam (32) to the second cam (34) by means of the variable position cam system (11) at the beginning of the stopping process; and actuation of the first exhaust valve (20) with the help of the second cam (34) during stopping. 5. The method according to claim 4, wherein: the second cam opens or holds open the first exhaust valve (20) during the compression stroke and the exhaust stroke; and / or the second cam first holds the first exhaust valve (20) closed during the compression stroke and / or the exhaust stroke, and opens it before the piston reaches top dead center. 6. The method according to any of the preceding paragraphs, in which: the first exhaust valve (20) opens in the range from 100 ° to 60 ° of the crankshaft angle of rotation until the top dead center is reached; and / or the first exhaust valve (20) is closed after opening at the exhaust stroke in the range from top dead center to 30 ° crankshaft angle after top dead center; and / or the first exhaust valve (20) closes after opening on the compression stroke in the range from bottom dead center to 30 ° crankshaft angle after bottom dead center. 7. A method according to any of the preceding paragraphs, in which: at the end of the stopping process, the second cam (34) of the variable position cam system (11) maintains a kinematic connection with the first exhaust valve (20); or at the end of the stopping process, the variable position cam system (11) switches to the first cam (32). 8. A method according to any of the preceding claims, further comprising: recording the temperature of the internal combustion engine and / or the operating time of the internal combustion engine; moreover, the switching of the drive of the first exhaust valve (20) of the internal combustion engine by means of the system (11) of cams with a variable position for opening or holding in the open state on the compression and exhaust stroke and / or switching to the engine braking mode is performed under the following conditions: the detected engine temperature is less than or equal to a predetermined engine temperature threshold; and / or the registered run time is less than or equal to the predefined run time threshold. 9. A method according to any of the preceding claims, further comprising: keeping the second exhaust valve (22) of the internal combustion engine in a closed state during stopping, the second exhaust valve (22) operating on the same cylinder of the internal combustion engine as the first exhaust valve (20). 10. A method according to claim 9, wherein keeping the second outlet valve (22) closed comprises switching to a no-cam portion (38) in the variable-position cam system (11). 11. The method according to any of the previous paragraphs, in which in the first group of cylinders, the first exhaust valve (20) is opened or kept open during the compression stroke and the exhaust stroke by switching the drive using the variable position cam system (11) and / or the first group of cylinders of the internal combustion engine switches to engine braking in the process of stopping the engine; and / or in the second group of cylinders, the exhaust valve actuator (20) remains unchanged during stopping. 12. The method according to claim 11, wherein the number of cylinders in the first group and / or in the second group is determined depending on at least one operating parameter of the internal combustion engine, in particular the temperature of the internal combustion engine and / or the operating time of the internal combustion engine. combustion. 13. The method according to claim. 11 or 12, in which the assignment to the first and / or to the second group is performed on a sliding principle, in particular on a sliding principle among successive stopping processes. 14. Variable valve drive (10) for an internal combustion engine of a vehicle, in particular a commercial vehicle, comprising: the first outlet valve (20); the camshaft (12); a system (11) of cams with an adjustable position with a base (14) for the cams, which is mounted on the camshaft (12) without the possibility of rotation and with the possibility of axial displacement, and which has a first cam (32) and a second cam (34) located on the camshaft (12) longitudinally offset; and a control unit (27) installed to implement the method according to any of the preceding claims. 15. A vehicle, in particular a commercial vehicle, comprising a variable valve drive (10) according to claim 14.

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