EP2133518B1 - Valve control for a gas exchange valve in a combustion engine - Google Patents

Abstract

The valve control (10) has a valve which comprises a valve disc (18) and a valve stem (22) that is movable in an actuation direction to open and close one of the openings. A fixing device is adapted to fix the valve stem relative to a cylinder head (14). A spring unit for is configured for preloading valve in an end position. A movable insert (34) moves in the cylinder head and supports the spring unit for preloading the valve. An actuation device moves the insert in the actuation direction between an end position near the valve disc and an end position that is remote from the valve disc.

Description

The invention relates to a valve control for a gas exchange valve in an internal combustion engine, with at least one spring element biasing the valve in at least one end position, and a fixing device for releasably fixing the valve.

From the prior art, a variety of valve controls for gas exchange valves in internal combustion engines are known. In general, a distinction can be made between mechanical, hydraulic or electric valve controls.

In purely mechanical valve controls, the adjusting movement of the gas exchange valve is controlled by a cam whose adjusting movement by suitable mechanical transmission elements, such as bumpers, drag or rocker arms, rocker arms and the like, are transmitted. A disadvantage of these purely mechanical valve controls that the adjusting movement of the gas exchange valve is directly coupled to the operation of the engine and an adjustment of the opening time or the travel of the gas exchange valve is possibly possible with great technical effort.

In purely hydraulic and electric valve controls, the adjusting movement of the gas exchange valve is performed by means of hydraulic or electrical adjusting devices which act directly or indirectly on the gas exchange valve. Opening times, opening speeds and travel ranges of the gas exchange valve can be selectively adjusted by appropriate actuation of the actuating devices and varied depending on the operating parameters of the internal combustion engine, such as the rotational speed, the torque, the exhaust gas values or the operating temperature of the internal combustion engine.

An example of a hydraulic valve control shows the DE 38 36 725 C1 in which the gas exchange valve is guided by means of a piston section in a hydraulic adjusting chamber and mechanically by two counteracting compression springs is clamped. The piston portion divides the actuating chamber into two chamber sections, which communicate with a hydraulic supply, so that the piston section is hydraulically clamped. To adjust the gas exchange valve, the two chamber sections are each selectively filled with a hydraulic fluid or discharged from one or the two chamber sections, wherein the adjusting movement is supported by the two compression springs.

From the DE 195 44 473 A1 is a hydraulic valve control is known in which the shaft of the gas exchange valve is mechanically clamped by two opposing compression springs, wherein in the rest position the valve plate near compression spring biases the gas exchange valve in its closed end position. To adjust the gas exchange valve, a hydraulic adjusting device is provided at the end facing away from the valve plate, with the support of the other, valve plate remote compression spring against the force of the valve plate near spring, the gas exchange valve can be opened. Furthermore, a likewise hydraulically operated fixing device is provided with which the gas exchange valve can be releasably fixed or secured in its closed end position, an intermediate position and a fully open position.

A disadvantage of this from the DE 195 44 473 A1 known hydraulic valve control is that the valve control while provides a comparison with purely mechanical valve controls improved adjustability and variability of Offnungszeitpunkte, the opening times and the travel paths of the gas exchange valves, but due to the spring arrangements comparatively high hydraulic forces must be generated to adjust the gas exchange valve.

Based on this prior art, it is an object of the invention to provide a valve control, which is improved over the prior art.

The invention solves the problem by a valve control with the features of claim 1 and in particular by supporting one or more spring elements for biasing the valve in a movable insert, said movable insert by means of an adjusting device in the direction of the valve between a valve close and a valve plate remote end position for adjusting the bias acting on the valve by the spring element (s) and, preferably, being secured in the adjusted position.

Contrary to the usual procedure for hydraulic valve controls, the valve control according to the invention therefore does not move the valve itself but the insert serving as an abutment for the spring elements, in which the gas exchange valve is suspended, with the aid of the adjusting device.

By adjusting the insert, the bias voltage with which the spring element biases the gas exchange valve in at least one of its end positions can be adjusted. In this case, the gas exchange valve by means of the fixing device, which removably fixes or secures the gas exchange valve, be kept in its biased position. Once the fixing device releases the gas exchange valve, the gas exchange valve moves due to the previously set biasing force of the spring elements in the direction of its opposite end position in which it can be fixed again by the fixing to hold the gas exchange valve, for example in its open or closed position. In this case, advantageously introduced by the movement of the gas exchange valve in the spring element energy stored as soon as the fixing device fixes the gas exchange valve, for example, at the dead center of the reversal movement of the gas exchange valve. When the fixing device releases the gas exchange valve again, this energy stored in the spring element is released again, wherein the biasing force of the spring element can also be changed and adjusted here by adjusting the insert. In this way, the necessary energy for valve control can be reduced.

By the valve control according to the invention, the gas exchange valve of the internal combustion engine can be actuated very quickly independently of other gas exchange valves. Furthermore, a significant advantage of a valve control according to an embodiment of the present invention is that a large part of the kinetic energy released during the adjustment of the gas exchange valve is stored or recovered again by the spring element, so that the energy to be introduced by the adjusting device only the Corresponds to energy lost due to friction in the overall system.

Another advantage of the adjustability of the insert is that the required stroke movement of the spring element itself may be less than the valve lift, whereby a particularly rapid opening of the gas exchange valve is possible. In this case, the time between the actual positioning movements of the gas exchange valve can be used to selectively bias the spring element by means of the insert, so that the biasing of the spring element is not essential in otherwise known valve timing short valve lift time. The adjusting movement of the gas exchange valve is ultimately triggered by the fixing device, which fixes or secures the gas exchange valve in its biased position until the valve lift is triggered. The actual movement of the gas exchange valve is, unlike purely hydraulic valve controls, not by the actuator itself, but by the or the biased spring elements.

Another significant advantage of a valve control according to an embodiment of the present invention is that by adjusting the insert different bias of the system in the direction of the strokes can be specified so that then the maximum opening stroke of the gas exchange valve can be varied continuously. In addition, the fixing device offers the possibility to fix the gas exchange valve in half or partially open positions. Furthermore, an overlapping movement of the insert and the gas exchange valve can be made possible for time-critical movements. If several gas exchange valves of a cylinder equipped with the valve control according to the invention, a single control of the gas exchange valves is given in a simple manner, by which a variation of the charge stratification by temporally offset movement of the gas exchange valves is possible.

Further advantageous developments of the invention are disclosed in the following description, the drawings and the subclaims.

Thus, it is proposed in a particularly preferred embodiment of the valve control according to the invention that the valve is biased by at least two mutually acting compression springs, which are both supported in the insert in the respective end positions. By using two or more compression springs, the one compression spring is elastically biased by compressing when the other compression spring relaxes when the valve lift, since the kinetic energy of the valve by the free suspension of the valve between the two springs when swinging through the equilibrium position, the counteracting the movement of the compression spring biased and so the previously released energy is stored again. The compression springs can be identical. However, it is also conceivable that the compression springs have different spring constants and / or travel ranges.

As a setting device for use preferably a hydraulic adjusting device is used, since this allows a relatively low energy input and high speed precise adjustment of the insert and the hydraulic fluid simultaneously reduces due to their damping properties resulting vibrations in the valve control.

When using a hydraulic adjusting device, this is preferably equipped with a parking chamber in which the insert is guided and hydraulically clamped. The hydraulic clamping of the insert ensures that the insert can be positioned very accurately, at the same time an undesirable displacement of the insert is prevented.

Alternatively, however, it is also conceivable to use as adjusting device an electrical adjusting device, for example a servomotor, which is coupled to the insert via corresponding mechanical couplings, for example a toothed rack and pinion arrangement. Also electromagnetic, pneumatic other control devices are possible.

The fixing device can also be controlled hydraulically, pneumatically and / or electrically. For this purpose, the fixing device is equipped, for example, with a hydraulic or electric actuator, which engages with a locking mechanism with the gas exchange valve, preferably its valve stem, and secures it in the respective desired position. For this purpose, the locking mechanism can be designed as a clamping mechanism which fixes or secures the gas exchange valve in the respectively desired position by appropriately clamping the valve stem. Furthermore, it is possible to provide depressions on the gas exchange valve, preferably on the valve stem, for example circumferential grooves which engage with a form element of the locking mechanism, for example, a preferably elastically biased ball, for fixing or securing the gas exchange valve in order to predefine the holding position or to prevent a displacement of the gas exchange valve in the held state.

It is particularly advantageous if the position of the insert is detected along its travel with the aid of a displacement transducer designed for this purpose, for example an induction sensor, whereby a very exact positioning of the insert during operation of the valve control becomes possible. For this purpose, the displacement sensor is preferably coupled to a management system or a motor control of the internal combustion engine, in which based on the current engine parameters, the bias of the spring element can be readjusted.

Further, it is advantageous if the position of the valve, preferably the valve stem, is detected along its travel to ensure accurate positioning, in particular opening and closing of the gas exchange valve. For this purpose, preferably also a displacement sensor is provided in the valve control, which is coupled to the management system of the internal combustion engine. Furthermore, it can be monitored whether the gas exchange valve is stuck.

The combined use of such displacement transducer for use and the valve can advantageously be detected opening position and positioning speed during the adjusting movement of the gas exchange valve. As a result, a controlled and possibly regulated opening and closing of the gas exchange valve in a simple manner possible.

In order to achieve an optimum adjustment of the gas changes to the internal combustion engine, it is also proposed to couple both the fixing device and the adjusting device with the engine control or control (engine management) of the internal combustion engine. The engine control then actuates correspondingly detected engine parameters, such as the rotational speed, the torque, the engine temperature, the exhaust gas values and the like, the fixing device and the setting device in accordance with predetermined rules, for example in such a way that predetermined optimum operating parameters are maintained.

Furthermore, in a particularly preferred embodiment of the valve control according to the invention is proposed to form the shaft of the valve in two parts, wherein a first shaft portion is received and guided in the insert, while a second shaft portion guided in a valve guide immediately adjacent to the valve seat and the first shaft portion by a Coupling is detachably connected. As a result, the actual valve control forms an independent structural unit, which can be easily and quickly mounted or released during maintenance.

It should be noted that only by the controlled fixing of the valve in the end position no reliable bias of the valve seat is achieved in the closed position. The closing force is achieved in particular by the entire clamping mechanism is moved axially by a hydraulic cylinder. After the closed position is reached very precisely by the electronic path control and / or mechanical positioning systems, the mechanical stroke of the preload cylinder is vanishingly small (very low energy requirement). Nevertheless, there is a small movement in the direction of the closed position of the valve during each closing process. Therefore, the biasing cylinder must be hydraulically relieved each time the clamping mechanism from the closed position and thereby moved back by a spring in a defined starting position.

In particular, the rotationally symmetrical use by hydraulic or mechanical measures can be designed so that with each stroke movement takes place a minimum rotation and thus the valve seat is not taken unilaterally.

Fig. 1

eine Seitenansicht einer Ventilsteuerung eines Gaswechselventils nach einer Ausführung der vorliegenden Erfindung;

Fig. 2a bis c

die Ventilsteuerung aus Fig. 1 in einer Ausgangsposition, bei- spielsweise unmittelbar nach der Montage;

Fig. 3a bis d

die Ventilsteuerung aus Fig. 1 beim Öffnen des Gaswechselven- tils; und

Fig. 4a bis d

die Ventilsteuerung aus Fig. 1 beim Schließen des Gaswechsel- ventils.

The invention will be explained in more detail with reference to an embodiment with reference to the drawing. In it shows, partially schematized:

Fig. 1

a side view of a valve control of a gas exchange valve according to an embodiment of the present invention;

Fig. 2a to c

the valve control off Fig. 1 in a starting position, for example immediately after assembly;

Fig. 3a to d

the valve control off Fig. 1 when opening the gas exchange valve; and

Fig. 4a to d

the valve control off Fig. 1 when closing the gas exchange valve.

Fig. 1 shows in side view a valve control 10 for a gas exchange valve 12 in an internal combustion engine according to an embodiment of the present invention. For clarity, only a small portion of the cylinder head 14 and the cylinder 16 is indicated by the internal combustion engine.

The valve 12 has a valve plate 18 protruding into the cylinder 16, which protrudes in a known manner through an inlet or outlet opening of the cylinder 16 and between a first end position, in which the valve plate 18 for closing the inlet or outlet opening on a valve seat 20th comes to rest (see. Fig. 3a ), and an opened second end position (see. Fig. 4a ) is movable, in which the inlet or outlet opening is released.

The shaft 22 of the valve 12 is formed in two parts and has a first, integrally formed with the valve plate 18 shaft portion 24 and a detachably connected thereto via a coupling 26 second shaft portion 28. The coupling 26 is designed so that the valve control 10 can be released from the first shaft portion 24, for example for maintenance purposes.

The first shaft portion 24 protrudes through the inlet or outlet opening and is guided in a valve guide 30 such that the valve plate 18 sealingly comes to rest on the valve seat 20 when the valve 12 is moved to its closed end position.

The second shaft section 28 projects through an insert 34 of an adjusting device 36 accommodated in a housing 32 of the valve control 10 and by a fixing device 38 arranged near its valve disk distal end. As will be explained in detail later, the two devices 36 and 38 are provided with a control device 40 the engine management of the internal combustion engine and are actuated by this.

The insert 34 is guided longitudinally displaceably and sealingly in a positioning chamber 42 of the adjusting device 36 in the direction of adjustment of the valve 12. Inside the insert 34, a valve plate remote first compression spring 44 and a valve plate near second compression spring 46 are added. The compression springs 44 and 46 counteract each other and are supported on the one hand on the inner sides of the insert 34 and on the other hand on a collar 48 of the valve 12, which protrudes in the radial direction from the second shaft portion 28.

At its outer periphery of the insert 34 is provided with a circumferential sealing collar 50 which is in sealing contact with the inner wall of the adjusting chamber 42 and the adjusting chamber 40 in a valve plate remote first chamber portion 52 and a valve chamber near second chamber portion 54 divided. Each chamber portion 52 and 54 is connected via a channel 56 and 58 with a not shown hydraulic supply of the adjusting device 36 in such a way that the insert 34 is hydraulically clamped between the two filled with hydraulic fluid chamber portions 52 and 54 and defined by changing the volumes of Valve seat 20 away (up in Fig. 1 ) or valve seat 20 (down in Fig. 1 ) and can be secured in the set position. The position of the insert 34 is thereby detected by a side of the insert 34 arranged first displacement sensor 60, which, like the hydraulic supply of the adjusting device 36, is connected to the control device 40 of the engine management.

The fixing device 38 has a likewise hydraulically actuated actuator 62, which is coupled to a clamping mechanism 64 for the second shaft section 28. The fixing device 38 is likewise connected to the control device 40 of the engine management system and generates with its clamping mechanism 64 such high clamping forces, that the valve 12 is fixed or secured against the forces caused by the two compression springs 44 and 46 in the respective adjusted position with the clamping mechanism 64 closed. The position of the valve 12 is detected by a second displacement sensor 66, which is arranged adjacent to the fixing device 38 and is also in communication with the control device 40.

Hereinafter, the operation of the valve control 10 according to the invention on hand of the Fig. 2a to 2c . 3a to 3d and 4a to 4d explained in more detail.

In Fig. 2a the valve control 10 is shown in a rest position, as it sets, for example, immediately after installation. The two compression springs 44 and 46 are in equilibrium of forces, so that the collar 48 is arranged centrally in the insert 34. The two chamber sections 52 and 54 are uniformly filled with hydraulic fluid, so that the sealing collar 50 of the insert 34 is arranged centrally in the adjusting chamber 42. The fixing device 38 is opened, so that the valve 12 is held exclusively by the compression springs 44 and 46 and is in this rest position in a slightly open position.

In Fig. 2b For example, the second chamber portion 54 close to the valve plate is filled with hydraulic fluid while hydraulic fluid is discharged from the second chamber portion 56. As a result, the entire insert 34 with the valve 12 suspended therein is moved away from the valve seat 20 in such a way that the valve disk 18 comes into contact with the valve seat 20. As soon as the inlet or outlet opening of the valve disk 18 is closed, the adjusting device 36 is deactivated and the fixing device 38 is activated, which then fixes or secures the valve 12 in the newly set position, as shown in FIG Fig. 2c is shown.

Based on Fig. 3a to 3d the process for opening the valve 12 is explained in more detail. As soon as the control device 40 wishes to open the valve 12 due to the current operating parameters of the internal combustion engine, it activates the adjusting device 36 in such a way that the insert 34 is made of the in Fig. 2c shown position moves toward the valve seat 20, ie in Fig. 2c is lowered. Since the valve 12 is secured by the fixing device 38, however, in its position, the lowering of the insert 34 causes a compression of the first compression spring 44 and at the same time an elongation of the second compression spring 46, whereby in the spring system formed by the compression springs 44 and 46 a predetermined preload is set, the valve secured in the fixing device 38 from the valve seat 20 away (down in Fig. 3a ). As soon as the first displacement transducer 60 detects that the insert 34 is in a position predetermined by the control device 40, the hydraulic supply of the actuating device 36 is deactivated and the supply is switched off interrupted by the channels 56 and 58 so that the insert 34 remains hydraulically clamped in its new position.

In a next step, as he is in Fig. 3b is shown, the fixing device 38 is deactivated so that it opens and the valve 12 releases. After the release of the valve 12, this is accelerated by the two compression springs 44 and 46 away from the valve seat 20, so that the valve 12 opens, as in Fig. 3c shown. In this case, the first compression spring 44 relaxes, while the second compression spring 46 is compressed. Due to inertia, the valve moves beyond the equilibrium point of the spring system until the prestress built up in the compression springs has completely decelerated the valve so that a large part of the energy stored in the first compression spring 44 before the fixing device 38 is opened again by the second compression spring 46 is recorded.

Once the valve 12 has reached its dead center at which the valve 12 would move back toward the valve seat 18 - this is detected by the second transducer 66 - activates the control device 40 based on the signals of the second transducer 66, the fixing device 38, the the valve 12 again clamped and so holds in its open position, as in Fig. 3d shown.

If now the valve 12 to be closed again, this process is in the Fig. 4a to 4d shown, the control device 40 first activates the actuator 36 such that the insert 34 moves away from the valve seat 20, that is raised. As a result, the already precompressed second compression spring 46 is further compressed, while the first compression spring 44 is elongated, as in Fig. 4a is shown. As a result, in particular friction-induced energy losses of the oscillatory spring system can be compensated.

As soon as the first displacement sensor 60 detects that the insert 34 has been raised sufficiently, the adjusting device 36 is deactivated so that the insert 34 is hydraulically clamped in its new position (cf. Fig. 4b ).

Subsequently, the hitherto closed fixing device 38 is opened, so that the valve 12 due to the bias of the two compression springs 44 and 46 returns to its closed position, as in Fig. 4c shown. there The second compression spring 46 relaxes while the first compression spring 44 is compressed again.

As soon as the second displacement sensor 66 detects that the valve 12 is closed, the fixing device 38 is reactivated and the valve 12 is secured in its closed end position, as shown in FIG Fig. 4d is shown.

For re-biasing the insert 34 must now be adjusted again in the direction of the valve seat 20 until the insert 34 again in Fig. 3a shown position occupies.

With the valve control according to the invention, it is possible to set the opening time, the opening duration and the valve lift in a very targeted manner and, unlike mechanical valve controls, completely independent of the actual operation of the internal combustion engine. The adjusting movements of the insert 34, as well as the time of holding the valve 12 by means of the fixing device 36 can be set and specified by the control device 40 based on the operating parameters of the internal combustion engine. It is also possible to let the movement of the insert 34 and the release or closing of the fixing device 36 at the same time, in particular intersecting each other instead of staggered. In addition, the height of the biasing force can be adjusted continuously, with which the compression springs 44 and 46 are biased.

Furthermore, the valve control 10 according to the invention can be provided for one or more valves 12 of a cylinder, so that an independent opening and closing of the individual valves 12 is also possible. The valve control 10 according to the invention is suitable for any type of internal combustion engine, such as gasoline engines and diesel engines, which can be arranged both mobile, for example, in land or sea vehicles, as well as stationary. It should also be noted that the actuation of the adjusting device 34 and the fixing device 36 can also be purely hydraulic. Also, instead of the hydraulically operated actuator 34 and the fixing device 36 electrically operated devices may be used.

Due to the inertia-related swinging through the valve by the rest position of the spring system 44, 46 advantageously only low hydraulic work must be expended for biasing.

LIST OF REFERENCE NUMBERS

10

valve control

12

Gas exchange valve

14

cylinder head

16

cylinder

18

valve disc

20

valve seat

22

shaft

24

first shaft section

26

clutch

28

second shaft portion

30

valve guide

32

casing

34

commitment

36

setting device

38

fixing

40

control device

42

setting chamber

44

valve plate remote first compression spring

46

close to the valve second compression spring

48

Federation

50

sealing collar

52

first chamber section

54

second chamber section

56

channel

58

channel

60

first transducer

62

actuator

64

Clamping mechanism

66

second transducer

Claims (7)

1. A valve control for a gas exchange valve of an internal combustion engine with at least two compression spring elements(44, 46) acting against each other for preloading the valve (12) in end positions opposing each other, and a fixing device (38) for the releasable fixing of the valve (12), characterized in that the spring elements (44, 46) for preloading the valve (12) support themselves in a moveable insert (34) which by means of an hydraulic actuation device (36) in the actuation direction of the valve (12) is adjustable between an end position close to the valve disc and an end position far from the valve disc for adjusting a preload which acts on the valve (12) through the spring elements (44, 46), wherein the insert (34) is guided hydraulically adjustably in an actuation chamber (42) of the actuation device (36), and a travel sensor (60) for sensing the position of the insert (34) along its actuation travel is provided, which is coupled with an engine control of the internal combustion engine through which the preload of the spring elements can be newly adjusted based on the current engine parameter.
2. The valve control according to any one of the preceding claims, characterized in that the fixing device (38) comprises an actuator (62) with an arresting mechanism, more preferably a clamping mechanism (64).
3. The valve control according to claim 5, characterized in that the actuator (62) is hydraulically actuatable.
4. The valve control according to any one of the preceding claims, characterized in that a second travel sensor (66) for sensing the position of the valve (12) preferentially a valve stem (22) is provided along its actuation travel.
5. The valve control according to any one of the preceding claims, characterized in that the fixing device (38) and/or the actuation device (36) can be actuated through an engine control (40) which actuates the fixing device (38) and the actuation device (34) according to sensed engine parameters.
6. The valve control according to any one of the preceding claims, characterized in that a stem (22) of the valve (12) protrudes through the insert (34) and the at least one spring element (44, 46) supports itself axially fixed on the stem, more preferably is permanently connected with the latter.
7. The valve control according to Claim 10, characterized in that the stem (22) of the valve (12) is designed in multiple parts, wherein a first stem section (24) is guided in a valve guide (30), more preferably immediately adjacent to the valve seat (20) and a second stem section (28) is guided in the insert (34), and wherein the second stem section (28) is connected with the first stem section (24) through a coupling (26).

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