RU2778596C2 - Adjustable valve drive with system of cams with adjustable position for internal combustion engine - Google Patents

Abstract

FIELD: engine building.

SUBSTANCE: invention can be used in internal combustion engines of vehicles. An adjustable valve drive is intended for an internal combustion engine with the first valve of a gas distribution mechanism, in particular an exhaust valve, and the second valve of the gas distribution mechanism, in particular an exhaust valve. The valve drive includes system (26) of cams with an adjustable position. System (26) of cams contains base (34) for cams with the possibility of axial displacement, equipped with first cam (40) for the first valve of the gas distribution mechanism, second cam (42) made with the possibility of displacement relatively to the first one along the axis, third cam (44) for the second valve of the gas distribution mechanism, and fourth cam (46) made with the possibility of displacement relatively to the third one along the axis. A position of first cam (40) installed with the possibility of actuation of the first valve of the gas distribution mechanism and third cam (44) installed with the possibility of actuation of the second valve of the gas distribution mechanism, or a position of second cam (42) installed with the possibility of actuation of the first valve of the gas distribution mechanism and fourth cam (46) installed with the possibility of actuation of the second valve of the gas distribution mechanism is set depending on the axial position of base (34). First cam (40), second cam (42), third cam (44), and fourth cam (46) are made different compared to a cam of zero move. First cam (40) and third cam (44) are made the same. Second cam (42) and fourth cam (46) are made different. A vehicle is disclosed.

EFFECT: provision of the expansion of functionality of an adjustable valve drive without an increase in a number of cams of a base in a system of cams with an adjustable position.

15 cl, 7 dwg

Description

The invention relates to a variable valve actuator with a variable position cam system for an internal combustion engine.

According to the state of the art, cam systems with adjustable position are known, in which, depending on the axial position of the cam base, a kinematic connection is created between different cams of the base and the valve of the gas distribution mechanism.

From DE 10 2015 008722 A1, a mode of internal heating of the engine by increasing the load is known, activated by means of a cam profile change mechanism by switching to another cam.

From DE 10 2011 052912 A1, for example, an adjustable cam system is known. This cam system comprises one variable position cam or cam base respectively with three cam profiles or cam contours respectively for each of the two intake valves.

A disadvantage of the known design may be the presence of a separate cam or, accordingly, a separate cam profile on the base for each required operating mode of the engine. Switching between more than two cam profiles for a single valve can be expensive in terms of design and control.

In more general terms, it is an object of the present invention to provide an alternative and/or improved variable valve actuator that overcomes the disadvantages of known designs. In particular, the extended functionality of the variable valve actuator must be provided without increasing the number of base cams in the variable position cam system.

In a more specific aspect, it is an object of the present invention to provide an alternative and/or improved variable valve actuator that allows the engine to operate in more than two modes, in particular with no more than two cams per valve. In particular, it must be possible to implement the modes of normal engine operation, engine braking and/or increase in exhaust gas temperature.

The tasks are solved due to the characteristics of the independent claim. Preferred additional embodiments of the invention are listed in the dependent claims and in the description.

The variable valve actuator is designed for an internal combustion engine with a first valve timing mechanism, in particular an exhaust valve, and a second valve timing mechanism (for example, the same type (intake or exhaust valve) as the first), in particular an exhaust valve. The variable valve actuator includes a variable position cam system. The variable position cam system includes an axially displaceable cam base (eg, axially displaceable and/or non-rotatable on the shaft). The cam base includes a first cam for the first timing valve and a second cam axially offset relative to it (eg, directly adjacent along the axis). The cam base includes a third cam for a second timing valve and a fourth cam axially offset relative to it (eg, directly adjacent axially). Depending on the axial position of the base for the cams, the position of either the first cam for actuating the first valve timing mechanism and (in particular, simultaneously) the third cam for actuating the second valve timing mechanism, or the second cam for actuating the first valve timing mechanism and (particularly concurrently) a fourth cam for actuating the second timing valve. In other words, if the first cam actuates the first camshaft valve, then the third cam also actuates the second camshaft valve, and if the second cam actuates the first camshaft valve, then the fourth cam also actuates the second camshaft valve. The first cam, second cam, third cam, and fourth cam may be different from the (imaginary) zero stroke cam (eg, their contour includes at least one bulge and/or one recess). The first cam and the third cam are (mostly) the same. The second cam and the fourth cam are made different.

More generally, this variable valve actuator allows the first and third cams to be used for a first mode of operation, such as normal mode of operation. The second and fourth cams, on the other hand, are different, so that different functions can be realized with these two cams using different valves of the timing mechanism, in particular of the same type (inlet valve or exhaust valve). The different functions may, for example, interact with each other in an advantageous manner, or be entirely separate functions.

In a specific aspect, the variable valve actuator allows the second and fourth cams to implement the engine braking mode due to mutual overlap, while the second and fourth cams present, for example, different components of the engine braking mode. As a result, the first valve timing mechanism implements the first component of the engine braking mode, while the second valve timing mechanism implements the second component of the engine braking mode.

In the mode of braking by the engine, ignition of the working mixture in the cylinder belonging to the first and second valves of the gas distribution mechanism does not expediently occur.

In one of the preferred embodiments of the invention, the adjustable valve actuator further includes a separate force transmission mechanism (for example, pushers, rockers, rocker arms) to provide a kinematic connection between the first and second cams and the first valve of the gas distribution mechanism, as well as to provide a kinematic connection between the third and fourth cams and the second valve of the gas distribution mechanism. Thus, these force transmission mechanisms make it possible to actuate the first and second valves of the timing mechanism separately from each other.

For example, a variable valve actuator may include a first force transfer mechanism (eg, pushrod, rocker arm, rocker arm) that, depending on the axial position of the cam base, provides the first valve of the timing mechanism with the first or second cams. Alternatively or additionally, the variable valve actuator may include a second force transfer mechanism (e.g. pushrod, rocker arm, rocker arm) which, depending on the axial position of the cam base, kinematically couples the second timing valve to the third or fourth cams. The first and second force transfer mechanisms may be separate from each other and/or may not be kinematically connected to each other.

In one exemplary embodiment of the invention, the first force transmission mechanism and/or the second force transmission mechanism includes, in particular, a plug-in corrective device for changing the transmission of the kinematically linked cam profile. This makes it possible, for example, to increase, decrease and/or shift the valve timing curve.

In the most preferred embodiment of the invention, the first force transmission mechanism and/or the second force transmission mechanism include, in particular, a plug-in freewheel for at least partial compensation, in particular for complete compensation of the profile transmission of the kinematically linked cam.

In particular, the first force transmission mechanism (by way of example only) may include a freewheel. The freewheel device can be designed to compensate for the profile of the second cam, in particular for full compensation.

The freewheel can expediently be placed on the side of the valves or on the side of the camshaft of the power transmission mechanism.

For example, the freewheel device may include a movable control piston, which can be locked, for example, hydraulically to implement a freewheel function, for example, at least one control piston.

It is possible that the first force transmission mechanism, the second force transmission mechanism, the corrective device and/or the freewheel device may include a hydraulic element 54 for adjusting the valve clearance.

In a further embodiment of the invention, the first cam and the third cam are conventional exhaust valve cams. Alternatively or additionally, the first cam and the third cam are configured to hold the first camshaft valve and the second camshaft valve open during the exhaust stroke. For example, the first cam and the third cam may hold the first and second timing valves closed during the remainder of the control cycle.

In one of the embodiments of the invention, the second cam is designed to hold closed and then open the first valve of the gas distribution mechanism on the compression stroke in order to decompress the gas. This means that the first camshaft valve on the compression stroke is first held closed and then opened again on the compression stroke. Alternatively or additionally, the second cam is designed to at least temporarily hold the first valve of the gas distribution mechanism in the open state during the stroke of the power stroke in order to admit gas. Thus, on the first valve of the gas distribution mechanism with the help of the second cam, the first component of the engine braking mode with gas decompression on the compression stroke and subsequent gas inlet on the power stroke can be implemented.

In a further embodiment of the invention, the fourth cam is configured to hold closed and then open the second valve timing mechanism on the exhaust stroke to decompress the gas. This means that the second camshaft valve on the exhaust stroke is first held closed and then opened again on the exhaust stroke. Thus, the second component of the engine braking mode with gas decompression on the compression stroke can be implemented on the second valve of the gas distribution mechanism using the fourth cam. Additionally, on the second valve of the gas distribution mechanism, using the fourth cam, a mode of increasing the temperature of the exhaust gases can be implemented, when the working mixture is ignited in the cylinder, and the profile of the second cam is compensated in some way, for example, using a freewheel device. The increase in temperature occurs, in particular, due to a significant increase in work in the circuit for changing the working mixture in the indicator diagram.

In the mode of increasing the temperature of the exhaust gases, it is advisable to ignite the working mixture in the cylinder associated with the first and second valves of the gas distribution mechanism.

In a preferred embodiment of the invention, the phases of the second cam and the fourth cam overlap to implement the engine braking mode, in particular by first gas decompression on the compression stroke, gas intake on the power stroke and/or second gas decompression on the exhaust stroke.

In a further preferred embodiment of the invention, the fourth cam and the activated freewheel implement an exhaust gas temperature increase mode to, in particular, completely compensate the profile of the second cam, in particular by decompressing the gas on the exhaust stroke.

In one embodiment of the invention, the fourth cam is configured to open the second valve timing mechanism (in particular, once per control cycle), namely on the exhaust stroke after the first half of the exhaust stroke; in the area between 120° of rotation KV (angle of rotation of the crankshaft) to TDC (top dead center of piston movement in the cylinder) and 40° of rotation of KV to TDC; and / or in the area between 100 ° turn KV to TDC and 60 ° turn KV to TDC; and/or in the region between 90° of the CV to TDC and 70° of the CV to TDC; and/or at (approximately) 80° CV to TDC.

In a further embodiment of the invention, the fourth cam is configured to hold the second camshaft valve open (particularly once per control cycle) for less than 160° CV, 150° CV, 140° CV, and/or 130° turning KV; and/or more than 80° of CV, 90° of CV, 100° of CV and/or 110° of CV; and/or at (approximately) 120° of CV.

In a further embodiment of the invention, the (maximum) valve stroke set by the fourth cam is less than 50%, 40%, 30% and/or 25%; and/or more than 5%, 10%, 15% of the (maximum) valve stroke given by the third cam. Alternatively or additionally set by the fourth cam (maximum) valve travel is less than 5mm, 4mm, 3mm and/or 2.5mm; and/or more than 0.5 mm, 1 mm, 1.5 mm; and/or (approximately) 2 mm.

In one embodiment of the invention, the closing timing of the exhaust valve (generally) remains unchanged compared to the normal closing timing of the exhaust valve (e.g., normal closing timing, for example, at the end of the exhaust stroke or, respectively, at the beginning of the intake stroke) in particular in accordance with the profile of the first and third cams. Alternatively or additionally, the closing timing of the exhaust valve is in the region of TDC (on the exhaust stroke), in particular between TDC and 40° after TDC (on the intake stroke).

In a preferred embodiment of the invention, the operation of the internal combustion engine in the mode of increasing the temperature of the exhaust gases is carried out in the low load range, in particular, at an engine shaft speed of (approximately) less than 1200 rpm in the engine shaft speed range of (approximately) 600 rpm. min to (approximately) 1000 rpm. In particular, under such low load conditions, it was previously difficult to achieve a high exhaust gas temperature, for example, for a reduction reaction in a particulate filter.

In one of the embodiments of the invention, the exhaust gas temperature increase mode is activated when, in particular, direct (for example, by measurement) or indirect (for example, indirectly, by recording parameter values, the state of the switchgear elements, conditions or the operating state of the internal combustion engine) registration of the fact that the current exhaust gas temperature is less than the required exhaust gas temperature (for example, 300 °C for the reduction reaction in the particulate filter or 150 °C for the operation of the selective catalytic reduction catalyst). Alternatively or additionally, the fact is recorded that the current exhaust gas temperature is less than the minimum exhaust gas temperature required for the operation of the exhaust gas aftertreatment system, in particular the selective catalytic reduction catalyst of the internal combustion engine and / or the reduction reaction in the particulate filter, in in particular in the diesel particulate filter (for example, the expiration of a predetermined time or the time the engine has been running since the last reduction reaction, the measurement of the number of particles or similar events). The start of an internal combustion engine, in particular cold start conditions, may also be recorded. Thus, the exhaust gas temperature increase mode can be activated, in particular under conditions where the exhaust gas temperature increase is actually necessary or required.

In an additional embodiment of the invention, the exhaust gas temperature increase mode is activated for the time during which the current exhaust gas temperature is greater than or equal to the required value, which is recorded, in particular directly (for example, by measurement) or indirectly (for example, indirectly, by registering parameter values, state of switchgear elements, conditions or operating state of the internal combustion engine). It is also possible, for example, to record the fact that the current exhaust gas temperature is equal to or higher than the minimum exhaust gas temperature required for the operation of the exhaust gas aftertreatment system, in particular the selective catalytic reduction catalyst, the internal combustion engine, and/or the fact that the reduction reactions in a particulate filter, in particular in a diesel particulate filter. This makes it possible to deactivate the exhaust gas temperature increase mode when the increased exhaust gas temperature is no longer required or, respectively, when the exhaust gas temperature has reached the required value.

In one embodiment of the invention, the second cam is configured to open the first valve of the gas distribution mechanism (in particular, once per control cycle), namely on the compression stroke after the first half of the compression stroke; and / or in the area between 120 ° turn KV to TDC and 40 ° turn KV to TDC; and / or in the area between 100 ° turn KV to TDC and 60 ° turn KV to TDC; and/or in the region between 90° of the CV to TDC and 70° of the CV to TDC; and/or at (approximately) 80° CV to TDC.

In a further embodiment of the invention, the second cam is configured to hold the first valve timing valve open (particularly once per control cycle) for less than 400° CV, 350° CV, 330° CV, and/or 310° turning KV; and/or more than 200° CV, 250° CV, 270° CV and/or 290° CV; and/or (approximately) 300° of CV rotation.

Additionally, the invention relates to a vehicle, in particular to a utility vehicle (eg bus or truck) with a variable valve drive as described herein.

It is also possible to apply the device described here to passenger cars, high power engines, off-road vehicles, stationary engines, marine engines, etc.

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

Fig. 1 Schematic representation of an internal combustion engine cylinder;

Fig. 2 An example of a variable position cam system according to this disclosure;

Fig. 3 An example of a corrective device according to this disclosure;

Fig. 4 An additional example of a corrective device according to this disclosure;

Fig. 5 Timing diagram for exhaust valves in normal operation;

Fig. 6 Timing diagram for exhaust and intake valves in engine braking mode with corresponding cylinder pressure curve; and

Fig. 7 Timing diagram for one exhaust valve and intake valves in exhaust gas temperature boost mode with corresponding cylinder pressure curve.

The embodiments of the invention shown in the figures coincide at least partially, so that similar or identical parts are indicated by the same reference numbers and, as explanations, reference is made to the description of other embodiments or, accordingly, to other figures in order to avoid repetition.

In FIG. 1 shows a cylinder 12 of an internal combustion engine 10. The internal combustion engine 10 is a four-stroke internal combustion engine, specifically a four-stroke diesel internal combustion engine or a four-stroke gasoline internal combustion engine. Preferably, the internal combustion engine 10 is part of a utility vehicle, such as a truck or bus, and is used to drive the utility vehicle.

An exemplary cylinder 12 includes two intake valves 14 (only one is shown in FIG. 1) and two exhaust valves 16 (only one is shown in FIG. 1). The cylinder 12 further includes a combustion chamber 18 and a piston 20. The internal combustion engine 10 may include a number of cylinders 12.

The intake valves 14 connect the combustion chamber 18 to the air supply system of the internal combustion engine 10 to deliver combustion air to the combustion chamber 18. Exhaust valves 16 connect the combustion chamber 18 to the exhaust path of the internal combustion engine 10 to remove exhaust gases.

The exhaust valves 16 are connected to a variable valve actuator 22. For each exhaust valve 16, the variable valve actuator 22 has a separate force transfer mechanism 24 (only one is shown in FIG. 1). Variable valve actuator 22 further includes a variable position cam system 26 . The force transmission mechanism 24 may establish a kinematic relationship between the variable position cam system 26 and the exhaust valves 16. The force transmission mechanisms 24 may be pushrods, rockers or rockers, for example. Acting as copiers, force transmission mechanisms 24 may include, for example, a roller or a slider. One of the force transfer mechanisms 24 includes, for example, a corrective device 28 made in the form of a freewheel (idle) device. The corrective device 28 is designed to change the transmission of the cam profile, repeated or, respectively, reproduced by the force transmission mechanism 24, to the exhaust valve 16. The corrective device 28 can be integrated into the force transmission mechanism 24 in any position. For example, the corrective device 28 may be placed on the side of the valves or on the side of the camshaft of the power transmission mechanism 24.

The piston 20 is installed in the cylinder 12 in a known manner with the possibility of reciprocating motion and is connected to the crankshaft 30.

One or more aftertreatment devices 32 may be installed in the exhaust path, for example, a particulate filter, in particular a diesel particulate filter, an oxidation catalyst, in particular a diesel engine oxidation catalyst, and/or a selective catalytic reduction (SCR) catalyst.

In FIG. 2 is an external view of an exemplary variable position cam system 26.

The variable position cam system 26 includes one (adjustable position) cam base 34 . The base 34, which is axially displaceable and non-rotatable, is located on the (camshaft) shaft 36. The axial displacement of the base 34 can take place, for example, by actuating elements not shown, which can engage with the helical working sections 38 to displace the base. 34.

The base 34 includes a first cam 40, a second cam 42, a third cam 44, and a fourth cam 46. Depending on the axial position of the base 34, either the first cam 40 or the second cam 42 actuates the first exhaust valve 16 via an appropriate force transmission mechanism 24 (see FIG. . one). Likewise, the second exhaust valve 16 is actuated through the appropriate force transfer mechanism 24 (see FIG. 1) either by the third cam 44 or the fourth cam 46. The cams 40-46 are arranged so that the exhaust valves 16 (see FIG. 1 ) are driven either by the first cam 40 and the third cam 44, or by the second cam 42 and the fourth cam 46. The first cam 40 has the same shape as the third cam 44. The second cam 42 is different from the fourth cam 44. All cams 40-46 are not zero cold cams, i.e. all cams 40, 46 have a profile that actuates the corresponding exhaust valve 16.

In FIG. 3 and 4 show examples of corrective devices 28.

In FIG. 3 shows the corrective device 28 in the seat 48 of the mechanism 24 for transmitting force from the valve side. Correction device 28 includes a control piston 50, two blocking pistons 52, a hydraulic valve clearance adjustment element 54, and a contact element 56.

Control piston 50 is axially movable in seat 48 along the longitudinal axis of seat 48. In particular, control piston 50 is axially movable between a first position, as shown in FIG. 3 and the second position. In the one shown in FIG. In the operating state of the corrective device 28, the movement of the control piston 50 from the first position to the second position is blocked by the blocking piston 52. There is no change in the transmission of the cam profile reproduced by the mechanism 24. The control piston 50 in the direction of the first position can be subjected to a preliminary axial force generated by the elastic element, as shown in FIG.

The blocking pistons 52 are mounted and guided in the control piston 50 in a radially movable direction with respect to the longitudinal axis of the seat 48. In the shown in FIG. In the 3 position, the blocking pistons 52 rest on the protrusion of the annular groove 58. Such support of the blocking pistons 52 results in blocking the movement of the control piston 50. The elastic element can abut the blocking pistons 52 against each other in the direction of the annular groove 58. The blocking pistons 52 can be subjected to hydraulic pressure control environment. The control medium may be supplied through a supply channel (not shown) connected to the annular groove 58. The supply of the control medium causes the blocking pistons 52 to move towards each other. As soon as the blocking pistons 52 are no longer supported by the protrusion of the annular groove 58, the movement of the control piston 50 from the first position to the second position is released (no longer blocked).

In this way, the cam profile transmission can be changed by means of the correcting device 28 if the blocking pistons 52 are retracted, that is, the movement of the control piston 50 is released. In particular, the control piston 50 can completely produce a free stroke L, by the length of which the cam profile transmitted during operation to the exhaust valve 16 is reduced.

The hydraulic valve clearance adjusting element 54 may be in the form of a conventional hydraulic valve clearance adjusting element (so-called hydraulic valve actuator element), so its principle of compensating for the changing clearance between the ball joint and the ball seat of the contact element 56 is not described in detail here.

As shown in FIG. 4, it is also, for example, possible for the correcting device 28 to be provided without a hydraulic valve clearance adjusting element.

The advantage shown in Fig. 3 and 4 of the correction device 28 is that these devices are two-stage versions, in which the hydraulic chamber can be structurally adapted to the stroke or to the gear ratio, whereby, in turn, the volume and flow of the working fluid can be small.

It is additionally possible for the correction device to have a different design and/or a different arrangement to the extent that it is possible to change the transmission of the reproducible cam profile to the timing valve, in particular in the form of a controlled activation of the freewheel.

A variable valve actuator 22 with a variable position cam system 26 and a corrective device 28 allows the internal combustion engine 10 or its exhaust valves 16 to be controlled in three different modes of operation. These three modes of operation are described with reference to FIG. 1–7.

In FIG. 5 shows a first mode of operation with respect to the valve timing of the exhaust valves 16. This first mode of operation corresponds to the normal mode of operation. In normal operation, the exhaust valves 16 are driven so that they are open on the exhaust stroke (see curve A). In particular, the profiles of the first cam 40 and the third cam 44 are made in accordance with the valve timing curve A. In normal operation, the first and second exhaust valves 16 open at the end of their stroke and close at the end of the exhaust stroke or the beginning of the intake stroke, respectively. In normal operation, an air-fuel mixture is supplied to the cylinders 12 of the internal combustion engine 10, which ignites in these cylinders 12.

The cylinder 12 can operate normally if the base 34 is in such an axial position that the first cam 40 and the third cam 44 are kinematically connected to the first and second exhaust valves 16. Additionally, the corrective device 28 cannot be activated.

In FIG. 6 shows the second mode of operation with respect to the (combined) exhaust valve curve 16, intake valve curve 14 and cylinder pressure curve. The second mode of operation corresponds to the braking mode of the internal combustion engine 10 . In the engine braking mode, ignition in the corresponding cylinder 12 does not occur.

Cylinder 12 can be operated under engine braking if base 34 is in such an axial position that second cam 42 and fourth cam 44 are kinematically coupled to first and second exhaust valves 16. Additionally, corrective device 28 cannot be activated.

In the engine braking mode, the intake valves 14 open as in normal operation on the intake stroke, as shown by the dotted line B. The valve timing curve C, indicated by the dashed line, is distributed between the second cam 42 and the fourth cam 46. In particular, the operation of the second cam 42 corresponds to the area C1 of curve C. Outside the section C1, the curve of the second cam 42, in particular, no longer has a rise. The operation of the fourth cam 46 corresponds to section C2 of curve C. Beyond section C2, the curve of fourth cam 46, in particular, no longer has a rise. As a result, exhaust valves 16 are actuated as described below. The first exhaust valve 16 is opened by the action of the second cam 42 at the end of the compression stroke, opens more during the power stroke, and finally closes at the beginning of the exhaust stroke. At this time, the second exhaust valve 16 remains closed due to the lack of a corresponding lift on the fourth cam 46. At the end of the exhaust stroke, the fourth cam 46 opens the second exhaust valve 16 in accordance with the section C2, and then closes it again at the beginning of the intake stroke. At this time, the first exhaust valve 16 remains closed due to the lack of a corresponding lift on the second cam 42.

In particular, the first exhaust valve 16 is opened by the action of the second cam 42 in the range from 120° TC to TDC to 40° TC to TDC, in particular at approximately 80° BTDC on the compression stroke, and then held open, e.g. approximately 300° of CV rotation. The opening of the first exhaust valve 16 by the second cam can be done in two stages, as shown, to, for example, obtain the necessary decompression at the end of the compression stroke by limiting the flow area by partially opening the first exhaust valve 16 and/or to keep the load on the variable valve actuator 22 due to the opening of the first exhaust valve 16 to overcome the pressure in the cylinder at a low level. Then, on the power stroke, the first exhaust valve 16 may be opened further than the compression stroke.

In particular, the second exhaust valve 16 opens under the action of the fourth cam 46 in the range from 120° CV to TDC to 40° CV to TDC, in particular at approximately 80° CV to TDC on the exhaust stroke, and then held open position, for example, approximately 120° of rotation of the CV.

The combined valve timing curve C shows a double decompression of the compressed exhaust gas in the exhaust path, thereby achieving an engine braking effect. The first decompression occurs at the end of the compression stroke by opening the first exhaust valve 16 through which the compressed gas is forced out of the combustion chamber 18 into the exhaust path. During the power stroke, gas is sucked from the exhaust tract into the combustion chamber through the open first exhaust valve 16. The second decompression occurs at the end of the exhaust stroke by opening the second exhaust valve 16, through which the compressed gas is squeezed out of the combustion chamber 18 into the exhaust tract. The double compression followed by decompression is in each case visually depicted by the in-cylinder pressure curve D, which is shown as a solid line.

In FIG. 7 shows the third mode of operation with respect to the curve of the second exhaust valve 16, the curve of the intake valves 14 and the cylinder pressure curve. The third mode of operation corresponds to the mode of increasing the temperature of the exhaust gases in the cylinder 12 of the internal combustion engine 10 . In the exhaust gas temperature increase mode, the corresponding cylinder 12 is ignited. The exhaust gas temperature increase mode is activated when it is necessary to increase the temperature of the exhaust gases.

The exhaust gas temperature increase mode may be required in certain situations during operation of the internal combustion engine 10 . For example, it may be necessary to carry out a reduction reaction in the particulate filter, which may require an exhaust gas temperature in the range of 300 to 350°C. It is also possible that during a cold start of the internal combustion engine 10, a minimum exhaust gas temperature must be reached to ensure the required operation of the selective catalytic reduction catalyst. In particular, at a temperature of 150°C, the conversion of nitrogen oxides in the selective catalytic reduction catalyst may not be sufficient. If the vehicle is operated in the low load range, for example at 600-1000 rpm, then the temperature level of the exhaust gases can generally be relatively low.

The cylinder 12 can operate in the mode of increasing the temperature of the exhaust gases, if the base 34 is in such an axial position in which the second cam 42 and the fourth cam 44 are kinematically connected with the first and second exhaust valves 16. Additionally, a corrective device 28 can be activated.

Activation of the correction device 28 causes the lift of the second cam 42, i.e. section C1 in FIG. 6 is compensated by the free play L. The second cam 42 does not open the first exhaust valve 16 during the entire control cycle. As shown by the valve timing curve E (dashed-dotted line), the second exhaust valve 16 is opened by the fourth cam 44 at the end of the exhaust stroke and closed again at the beginning of the intake stroke in accordance with section C2 in FIG. 6. The pressure in the cylinder 12 with the ignition of the working mixture can, for example, vary in accordance with the curve F (solid line).

The increase in temperature in the mode of increasing the temperature of the exhaust gases occurs due to a significant increase in work in the circuit for changing the working mixture. This increase is due to the initial compression of the exhaust gas in cylinder 12 on the exhaust stroke and subsequent decompression in the TDC region. As a result, on the indicator diagram (diagram of the dependence of pressure p on volume V), a left-hand rotation contour (left-hand process) is formed, reflecting the operation with a negative value and the increase in the temperature of the exhaust gas. At the same time, in the high-pressure circuit, it is necessary to compensate for the additional work to change the working mixture, which leads to an increase in the amount of injected fuel and also to an increase in the temperature of the exhaust gases.

This describes the most preferred embodiment of the invention of a variable valve actuator, which allows the engine to be operated in normal mode, in engine braking mode and in exhaust gas temperature rise mode. It should be noted that the possibility of different valve control schemes of the gas distribution mechanism, in particular, of the same type (for example, exhaust or intake valves), due to different cam profiles of the same base, can be used to implement other engine operating modes. Thus, for example, with the help of the first cam and the third base cam, the normal mode of operation can be realized. By means of the second cam and the fourth cam, a mode of operation different from that mentioned above can be realized, with the respective valves actuated differently by the second and fourth cams. The combination of the cam profiles or their overlaps then makes other operating modes possible. Additionally and as an optional condition, one or more corrective devices can be used, as described, for example, here, to compensate for the profile of, for example, the second cam and/or the fourth cam. This may provide for operation in one or more additional modes, as described herein using the exhaust gas temperature increase mode as an example.

The present invention is not limited to the preferred embodiments that have been described above. Moreover, many variations and modifications are possible in which the idea of this invention will also be used, and therefore such variations will be within the scope of legal protection. In particular, the present invention claims to protect the subject matter and features of the dependent claims, regardless of reference to the respective claims. In particular, the features of the independent claim 1 of the claims can be disclosed independently of each other. Additionally, the features of the dependent claims are disclosed independently of all the features of the independent claim 1 and, for example, regardless of the features regarding the presence and/or configuration of the variable position cam system, the cam base, the first cam, the second cam, the third cam and/or the fourth cam from independent point 1.

Position number list

10 Internal combustion engine

12 Cylinder

14 intake valve

16 Exhaust valve

18 Combustion chamber

20 Piston

22 Variable valve drive

24 Force transfer mechanism

26 Variable cam system

28 Correction device

30 Crankshaft

32 Exhaust gas aftertreatment system

34 Cam base

36 Shaft

38 Work area

40 First cam

42 Second cam

44 Third cam

46 Fourth cam

48 Nest

50 Control piston

52 Blocking piston

54 Hydraulic element for adjusting valve clearance

56 Contact element

58 Ring groove

A - Exhaust valve timing curve (normal operation)

B - Inlet valve timing curve

C - Exhaust valve timing (engine braking mode)

C1 - First section

C2 - Second section

D - Change in cylinder pressure (engine braking mode)

E - Exhaust Valve Timing Curve (Exhaust Gas Temperature Boost Mode)

F - Changing the pressure in the cylinder (exhaust gas temperature increase mode)

L - Free play.

Claims (47)

1. Variable valve drive (22) for an internal combustion engine (10) with a first valve of the gas distribution mechanism, in particular the exhaust valve (16), and a second valve of the gas distribution mechanism, in particular the exhaust valve (16), including system (26) of cams with adjustable position, containing a base (34) for cams with the possibility of axial displacement, provided with a first cam (40) for the first valve of the gas distribution mechanism and a second cam (42) made with the possibility of displacement relative to the first along the axis, and a third cam (44) for the second valve of the gas distribution mechanism and fourth cam (46), made with the possibility of displacement relative to the third along the axis, while the position of the first cam (40) mounted to actuate the first valve timing mechanism and the third cam (44) mounted to actuate the second valve timing mechanism, or the position of the second cam (42) mounted to be actuated the first valve of the gas distribution mechanism, and the fourth cam (46), installed with the possibility of actuating the second valve of the gas distribution mechanism, is set depending on the axial position of the base (34); the first cam (40), the second cam (42), the third cam (44) and the fourth cam (46) are different from the zero stroke cam; the first cam (40) and the third cam (44) are identical; and the second cam (42) and the fourth cam (46) are different. 2. Adjustable valve actuator (22) according to claim 1, further comprising a separate mechanism (24) for transmitting force, made with the possibility of kinematic connection of the first cam (40) and the second cam (42) with the first valve of the gas distribution mechanism and made with the possibility of kinematic connection of the third cam (44) and the fourth cam (46) with the second valve of the mechanism gas distribution. 3. Adjustable valve actuator (22) according to claim 1 or 2, in which the first force transmission mechanism (24) and/or the second force transmission mechanism (24) comprises, in particular, a plug-in corrective device (28) configured to change the profile transmission of the kinematically coupled cam. 4. Adjustable valve drive (22) according to one of the previous paragraphs, in which the first force transmission mechanism (24) and/or the second force transmission mechanism (24) comprises, in particular, a freewheel corrective device (28) configured to at least partially compensate, in particular, configured to fully compensate for the transmission of a profile of a kinematically connected cam. 5. Adjustable valve drive (22) according to one of the previous paragraphs, in which the first cam (40) and the third cam (44) are made in the form of conventional exhaust valve cams; and/or the first cam (40) and the third cam (44) are configured to hold the first camshaft valve and the second camshaft valve open during the exhaust stroke. 6. Adjustable valve drive (22) according to one of the previous paragraphs, in which the second cam (42) is made with the possibility of holding in the closed state and then opening the first valve of the gas distribution mechanism on the compression stroke with the possibility of decompressing the gas. 7. Adjustable valve drive (22) according to one of the previous paragraphs, in which the second cam (42) is configured to at least temporarily hold the first valve of the gas distribution mechanism in the open state on the power stroke with the possibility of gas inlet. 8. Adjustable valve actuator (22) according to one of the previous paragraphs, in which the fourth cam (46) is made with the possibility of holding in the closed state and subsequent opening of the second valve of the gas distribution mechanism on the exhaust stroke with the possibility of gas decompression. 9. Adjustable valve drive (22) according to one of the previous paragraphs, in which the phases of the second cam (42) and the fourth cam (46) overlap with the possibility of implementing the engine braking mode, in particular due to the first gas decompression on the compression stroke, the gas intake on the power stroke and/or the second gas decompression on the exhaust stroke. 10. Adjustable valve actuator (22) according to one of the previous paragraphs, in which the fourth cam (46) and the corrective device (28) of the freewheel realize the mode of increasing the temperature of the exhaust gases with the possibility, in particular, of the complete compensation of the profile of the second cam (42), in particular with the possibility of gas decompression on the exhaust stroke. 11. Adjustable valve drive (22) according to one of the previous paragraphs, in which the fourth cam (46) is configured to open the second valve of the gas distribution mechanism, namely on the exhaust stroke after the first half of the exhaust stroke; and/or in the area between 120 ° turn KV to TDC and 40 ° turn KV to TDC; and/or in the area between 100 ° turn KV to TDC and 60 ° turn KV to TDC; and/or in the area between 90° of the CV to TDC and 70° of the CV to TDC; and/or at 80 ° turn KV to TDC. 12. Variable valve actuator (22) according to one of the previous claims, in which the fourth cam (46) is configured to hold open the second valve of the gas distribution mechanism less than 160° of CV, 150° of CV, 140° of CV and/or 130° of CV; and/or for more than 80° of the CV, 90° of the CV, 100° of the CV and/or 110° of the CV; and/or for 120° turn KV. 13. Variable valve actuator (22) according to one of the previous paragraphs, in which the second cam (42) is configured to open the first valve of the gas distribution mechanism, namely on the compression stroke after the first half of the compression stroke; and/or in the area between 120 ° turn KV to TDC and 40 ° turn KV to TDC; and/or in the area between 100 ° turn KV to TDC and 60 ° turn KV to TDC; and/or in the area between 90° of the CV to TDC and 70° of the CV to TDC; and/or at 80 ° turn KV to TDC. 14. Variable valve actuator (22) according to one of the previous paragraphs, in which the second cam (42) is configured to hold open the first valve of the gas distribution mechanism at less than 400° CV, 350° CV, 330° CV and/or 310° CV; and/or for more than 200° CV, 250° CV, 270° CV and/or 290° CV; and/or for 300° rotation KV. 15. A vehicle, in particular a utility vehicle, with an adjustable valve drive (22) according to one of the previous paragraphs.

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