EP1967706A2 - Valve gear - Google Patents

Abstract

The drive has with an operating element (21) e.g. piston, which is movably supported in an operating cylinder (20), where the operating element is provided for driving a valve (22). A fluid conduit is provided on a side of the operating element in the operating cylinder. Non-return valves (30, 31) for controlling the fluid flow are connected in series or in parallel to an actively operable control valve (29). The operating element is hydraulically and/or pneumatically operated.

Description

The present invention relates to a valve drive, in particular for gas exchange valves of internal combustion engines, with a movably mounted in a cylinder actuator, in particular pistons, for driving a valve, wherein in the working cylinder on one side of the actuating element at least one at least a first fluid line with at least one pressure accumulator for Fluid is provided in the associated working volume, wherein an at least two Fluidieitungen switching, actively actuated control valve is disposed in the first fluid line and in particular an internal combustion engine with such a valve drive.

Generic valve actuators are for example from the EP 1215369 A2 known. One speaks also of fully variable valve drives. These are predominantly based on the concept of a free oscillator and follow the basic idea to recover energy when braking the valve or the valve drive and store in the form of pressure to this pressure for driving the valve in a subsequent stroke, especially at the counter stroke again to use for the acceleration of the valve. The basic idea is therefore to create particularly energy-saving valve drives for the opening and / or closing movement of a valve in the form of quasi-free oscillators.

In the systems known from the prior art, it is necessary, during an opening and closing stroke cycle of the valve drive, to shade several electrically switched or pressure-controlled or travel-controlled actively actuable control valves, if necessary several times. This leads to very complex structures.

The object of the invention is to minimize the number of required active actuated control valves and the number of switching operations per cycle.

This is achieved according to the invention in that at least one passive switching element for controlling a fluid flow, preferably a check valve, is connected in series or in parallel to the control valve.

By passive switching elements is meant in particular switching elements which are switched by means of the fluid flowing through them. You do not need an additional actuator, as is provided for actively operable control valves for switching. Frequently used, passive switching elements are for example check valves. The inventive use of passive switching elements favorably only a single actively actuated control valve is needed. Moreover, it is also possible that this actively actuated control valve only has to be moved back and forth between two positions during an opening and closing cycle of the valve to be switched.

Favorable embodiments provide that the working volume is a first working volume and the pressure accumulator is a first pressure accumulator and at least one second working volume in the working cylinder in communication with at least one second fluid line with at least one second pressure accumulator for fluid on a side of the actuating element opposite the first working volume is, wherein the actively actuable control valve is arranged in the first and / or in the second fluid line. But it is also possible instead of the second working volume and the second pressure accumulator to switch to this side of the actuating element, a spring or a constant back pressure.

Particularly simple, inventive embodiments provide that the valve drive has exactly one actively actuated control valve. As the embodiments explained below, it is advantageous if at least, preferably exactly, two passive switching elements for controlling a fluid flow to the actively actuated control valve are connected in series and / or in parallel. In the case of a series connection, the passive switching element (s) are arranged to control a fluid flow in the first and / or the second fluid line, preferably on the side of the actively actuable control valve facing the respective working volume. In the case of a parallel connection may be provided in a favorable manner that the passive switching elements or, preferably in each case in at least one leading around the actively actuable control valve bypass line of the first and / or the second fluid conduit are arranged. In the case of the valve drives according to the invention, the actuating elements can be actuated hydraulically and / or pneumatically. A general one But it is an advantage if the valve actuators are designed such that preferably during braking, kinetic energy of the valve drive, preferably the valve, by pressure build-up in the first pressure accumulator and / or in the second pressure accumulator for a subsequent stroke of the valve is temporarily stored.

The valve actuators described so far can be used particularly well for opening and closing valves in which approximately the same counterforce acts on the valve during the opening as well as during the closing stroke. This is the case, for example, with intake valves for combustion chambers of internal combustion engines. However, the situation is different for example in exhaust valves of combustion chambers, where in the prior art, a significant additional power consumption is created by the so-called gas counterforce in the combustion chamber. This gas counterforce results from a residual pressure, which is still present when opening the exhaust valve from the previous cycle of the combustion chamber. Depending on the driving style and opening time, this residual pressure varies in size. But it can make up to 10 bars and more on the order of magnitude. Against this pressure, the outlet valve must be opened. This gas counterforce is only available during the opening stroke and not during the closing stroke. This results in an imbalance, which has a negative effect, especially in the above-mentioned energy-saving valve drives. To achieve an improvement here, see particularly preferred, for example, for the operation of exhaust valves of internal combustion engines usable, valve actuators before a Zusatzaktuator, which supports the actuator at the more force-requiring stroke, at least in sections.

Often it is sufficient in this case if the additional actuator is designed so that it acts on the valve only a portion, preferably at the beginning of the actuator to be executed by the opening and closing stroke. In this context, it can be provided that a stop is provided for the additional actuator, which it reaches before the valve reaches one of its end positions. It is expediently provided that the additional actuator can not be operated as a driving force with pressure derived from a combustion chamber, preferably an internal combustion engine. This avoids problems with the removal of combustion gases from the combustion chamber, which can lead to failure of such systems due to coking.

The additional actuators which can be used to support the actuating element can be designed in many different ways. Favorable variants provide that they can be driven hydraulically and / or pneumatically and / or electrically and / or piezoelectrically and / or magnetically and / or electromagnetically.

Fig. 1

ein erstes erfindungsgemäßes Ausführungsbeispiel, insbesondere für Einlassventile von Brennkraftmaschinen, mit in Reihe zum Steuerventil geschalteten passiven Schaltelementen,

Fig. 2a, b, c

Verläufe des Öffnungshubes des Ventils, des Druckverlaufs in den Druckspeichern und der Stellung des Steuerventils sowie seiner Ventilkanten während des öffnungs- und Schließzyklus,

Fig. 3

ein zweites erfindungsgemäßes Ausführungsbeispiel, insbesondere für Einlassventile von Brennkraftmaschinen, mit parallel zum Steuerventil geschalteten passiven Schaltelementen,

Fig. 4

das Ausführungsbeispiel aus Fig. 1 ergänzt durch einen Zusatzaktuator, insbesondere für Gasauslassventile,

Fig. 5a, b, c

zu den Fig. 2a bis c analoge Verläufe des Schließ- und Öffnungshubes des Ventils, des Druckverlaufs in den Druckspeichem und der Bewegung des Steuerventils für das Ausführungsbeispiel gemäß Fig. 4,

Fig. 6

ein weiteres Ausführungsbeispiel mit Zusatzaktuator basierend auf dem Ausführungsbeispiel gemäß Fig. 3 und

Fig. 7 und 8

verschiedenen Ausführungsformen von Druckspeichern.

Further details and features and embodiments of the invention will be explained with reference to the following figures. Showing:

Fig. 1

a first embodiment according to the invention, in particular for intake valves of internal combustion engines, with passive switching elements connected in series with the control valve,

Fig. 2a, b, c

Course of the opening stroke of the valve, the pressure profile in the accumulators and the position of the control valve and its valve edges during the opening and closing cycle,

Fig. 3

A second embodiment of the invention, in particular for intake valves of internal combustion engines, with parallel to the control valve switched passive switching elements,

Fig. 4

the embodiment Fig. 1 supplemented by an additional actuator, in particular for gas outlet valves,

Fig. 5a, b, c

to the Fig. 2a to c analogous courses of the closing and opening stroke of the valve, the pressure curve in the Druckspeichem and the movement of the control valve for the embodiment according to Fig. 4 .

Fig. 6

a further embodiment with Zusatzaktuator based on the embodiment according to Fig. 3 and

FIGS. 7 and 8

various embodiments of pressure accumulators.

At the in Fig. 1 shown embodiment, two passive switching elements 30, 31 connected in the form of check valves to the control valve 29 in series. The valve drive shown there serves to carry out the opening and closing stroke of the valve 22. This may be, for example, an inlet valve in a combustion chamber of an internal combustion engine. As in Fig. 1 it can be seen, the shaft of the valve 22 is connected to the actuator 21 formed as a piston of the working cylinder 20. The two pressure accumulators 27 and 28 are connected to the two working chambers 23 and 24 of the working cylinder 20. The second pressure accumulator 28 is on the second Fluid line 26 is directly connected to the second working chamber 24 on the rod side of the working cylinder 20 and thus always acts in the direction of the closing stroke of the valve 22. The first pressure accumulator 27 is connected via the control valve 29 and designed as check valves 30 and 31 passive switching elements with the first Working chamber 23 connected. The two pressure accumulators 27, 28 are brought to system pressure PS before the opening stroke of the valve 22. This is done for the second pressure accumulator 28 via the supply check valve 36 and the first pressure accumulator 27 on the Nachfüllventilkante 37. This also ensures that the valve 22 is closed, the piston-side, first working volume 23 via the Ablassventilkante 38 and the diaphragm or Throttle 54 is drained into tank T.

In the Fig. 2a the path x (t) of the valve 22 during the opening and closing stroke are shown. Fig. 2b shows the course p _{z2 of} the pressure in the second pressure accumulator 28 and the course p _{z1 of} the. pressure in the first accumulator 27. The stroke of the control valve, together with the opening phases of the individual valve edges 37, 38 and 39 Ober a duty cycle in Fig. 2c shown. The solid line shows the course of the position of the control valve 29. The dashed line shows the course of the connection 1 to 2, so the opening and closing course of the main valve edge 39. In addition, the course of the connection 1 to 3 for the main valve edge 39 is shown dotted , The dot-dashed lines show the opening and closing curves for the Nachfüllventilkante 37 and the Ablassventilkante 38, ie for the compounds 4 to 5 and 9 to 10.

To trigger the movement will, as from the Fig. 1 and 2a to c seen, the control valve 29 switched. In this opening movement, the refill valve edge 37 and the discharge valve edge 38 and thus the connections 4 according to FIGS. 5 and 9 are closed as shown in FIG. Furthermore, the connection 1 to 3 from the piston-side first working volume 23 via the check valve 31 (second passive switching element) to the first pressure accumulator 27 at the main valve edge 39 is closed. After complete closure of this connection, the connection 1 to 2 from the first pressure accumulator 27 via the check valve 30 (first passive switching element) to the piston-side first working volume 23 of the main valve edge 39 is opened. In this case, the fluid flows into the first working volume 23, the pressure acting on the first pressure surface 40 accelerates the valve 22 in the opening direction so down, since the second pressure surface 41 of the actuating element 21 is smaller than that first pressure surface 40 is. During the _stroke movement of the valve 22, the pressure p _z2 in the second pressure accumulator 28 increases. The pressure p _z1 in the first pressure accumulator 27 drops during this stroke movement, 1m point x _{max of} the maximum opening of the valve 22, the flow direction over the main valve edge 39 wants to reverse. However, the first passive switching element in the form of the check valve 30 prevents backflow of the fluid, so that the valve 22 remains in the open position. The time T _s for opening and closing the valve 22 corresponds to half the period of a free oscillator. For the system to be energy efficient, the in Fig. 2c shown closing movement of the control valve 29 to be tuned to this time T _s . The closing movement of the control valve 29 (see Fig. 2c ) should be about twice as long as T _s .

The closing stroke of the valve 22 does not begin until the control valve 29 has closed the connection 1 according to FIG. 2 at the main valve edge 39 and the connection 1 according to FIG. 3 opens again. As a result, the fluid can flow back into the first pressure accumulator 27 via the check valve 31 from the piston-side first working volume 23. Due to dissipative effects, the valve 22 no longer reaches its home position and the lack of energy must be returned to the system. This is done on the one hand via the refilling of the first pressure accumulator 27 via the Nachfüllventilkante 37 and the second pressure accumulator 28 via the supply check valve 36. Far the piston-side first working volume 23 is placed on the tank T via the Ablaßventilkante 38. This can be guaranteed that the valve 22 is closed safely. As described above, the control valve 29 thus has only once from the closed in the in. During the entire cycle of the opening and closing stroke of the valve 22 Fig. 2c with 1 defined open position and moved back to the closed position (= 0). It is not a sudden, but rather a gradual opening and closing of the individual valve edges, as is the case Fig. 2c evident. The valve edges 37, 38 and 39 are physically designed accordingly.

In Fig. 3 is an implementation example with two parallel passive switching elements 30, 31 - also formed in the form of check valves - shown. The passive switching elements 30, 31 are arranged in the bypass line 32, 33, which lead around the control valve 29, whereby the passive switching elements are connected in parallel to the control valve 29. This realization is similar to the one before detailed system. The main differences are in the mentioned parallel arrangements of the two check valves 30 and 31 to the control valve 29 and in the circuit of the connection to the second pressure accumulator 28 via the control valve 29 (connection 11 and 12). To trigger the opening stroke, the control valve 29 is switched. Before the main valve edge 39 is opened, the refill valve edge 37 (connection 4 of FIG. 5) and the discharge valve edge 38 (connection 9 of FIG. 10) are closed. When the main valve edge 39 (connection 1 to 2) opens, the opening stroke of the valve 22 begins. When the majority of the stroke is reached, the main valve edge reaches its end position and thus closes the connection 11 to 12. Only a very small part of the volume flow must thus flow over the check valve 31. As soon as the valve 22 reaches the maximum stroke and wants to swing back again, the check valve 31 closes. The valve 22 is held in its open position.

The return movement of the valve 22 is triggered by the closing movement of the control valve 29. As soon as the connection 11 to 12 is opened, the valve 22 begins to move back in the form of the closing stroke. Next, the valve edge 39 is closed and the fluid flows over the check valve 30. Shortly before the point of reversal, the refill valve edge 37 opens (connection 4 of FIG. 5) and the discharge valve edge 38 (connection 9 of FIG. 10). By means of the aperture 54, the impact speed can be adjusted at the seat.

In the variant according to Fig. 1 the main valve edge is always operated in series with one of the two check valves 30 and 31, which leads to slightly higher losses and thus to a slightly higher drive power. In the variant according to Fig. 3 This loss is reduced because the phases in which the volume flow must flow through a check valve and a valve edge are significantly reduced.

In Fig. 3 In addition, a cushioning is realized at the connection between the second working volume 24 and the second fluid line 26. This serves to decelerate the valve 22 when it reaches one of its end positions, in particular its open end position. For this purpose vain choke or aperture 42 is provided, via which the fluid flows from the second working volume 24 into the second fluid line 26, when the actuating element 21 carries out the residual stroke between X _max and X _maxmachine . The check valve 43 is provided for the return flow of the fluid.

This type of end position damping can be provided especially when the valve drive is designed for asymmetrical force distribution or gas counterforce. Mostly it is only used when, for example, by a misfire in the combustion chamber of the internal combustion engine no gas counterforce is built up, in which case the valve 22 can be intercepted by the Endlagendämpfung.

In the embodiments according to Fig. 4 and 6 is for actuation of the valve 22 in addition to the actuating element 21 in each case also a Zusatzaktuator 34 is provided. This is particularly favorable in internal combustion engines when the valve 22 has to be opened against a high backpressure in the combustion chamber. This is especially the case with exhaust valves. In most cases, it is sufficient if the support of the additional actuator 34 at the beginning of the opening movement is thus provided only for a partial stroke hp. The additional force required at the outlet valve to overcome the counter gas forces during the opening stroke or the work done is lost and can not be recovered.

Since the force required to open the outlet valve 22, against the high back pressure, already in the range of opening and closing forces and thus no longer plays a minor role, it is beneficial to separate the drive for the lifting movement and the opening against the gas power ,

This is for example in Fig. 4 shown. The structure largely corresponds to that of the valve drive according to Fig. 1 , One difference, however, is that an auxiliary actuator 34 can exert a force on the valve rod 45 with a limited stroke plunger 44. A spring 46 ensures a defined initial position of the plunger 44. The supply of the plunger chamber 47 via an additional 3/2-way valve edge 48 on the control valve 29. In the initial position, the plunger chamber 47 is connected to tank T. When opening the control valve 29, the tank connection is closed and the plunger chamber 47 connected to high pressure (see Fig. 5 ). The plunger 44 thus acts on the actuators and supports the opening movement of the actuating element 21 and thus the valve 22. However, the force acts only until the plunger 44 has performed the stroke hp and is braked at the stop 35. The valve rod 45 then lifts off the plunger 44 and is only moved by the working cylinder 20 or actuating element 21.

During the return stroke, the plunger chamber 47 is again connected to tank T and the plunger 44 is pushed back by the spring 46 to its starting position.

In the combustion chamber closed by the outlet valve 22, misfiring may occur. Only a very small gas back pressure occurs without misfiring. To protect the valve drive from damage, an additional end position damping is also integrated here. The construction is also in Fig. 4 shown. If the maximum stroke x _{max is} exceeded, the supply line or discharge line 49 is closed and the fluid can only escape through the diaphragm or restrictor 42. This increases the pressure in the rod-side second working volume 24 and brakes the valve 22. In order to prevent cavitation during the return stroke, an additional check valve 43 is in turn integrated.

In the Fig. 5a, 5b and 5c are essentially the same diagrams as in the Fig. 2a, 2b and 2c shown. Additionally are in Fig. 5c still the movement of the control valve 29 additionally realized 3/2-way valve edge 48 located. This serves to act on the plunger chamber 47 and opens and closes the connection 7 according to FIGS. 6 and 6 according to FIG.

The additional actuator can - as in Fig. 4 shown - hydraulically realized. In addition, however, there are also possibilities of pneumatic, electrical, piezoelectric and / or magnetic and / or electromagnetic drive of Zusatzaktuators 34. Such drives are known per se and therefore need not be explained again in detail. As in Fig. 4 shown, the additional actuator 34 as well as the actuator 21 can be operated hydraulically and / or pneumatically and fed from a common system pressure source pS.

An electrical realization, however, is in Fig. 6 shown. The actuation of the actuating element 21 corresponds in this embodiment to Fig. 3 described. In contrast, new is the additional electric actuator 34. This supports the actuator 21 at the beginning of the opening stroke and is then moved back, for example via a spring or electrically to its original position. Also in this embodiment is thus provided that the additional actuator 34 engages supportive only on a partial stroke.

The systems shown in the various embodiments with energy recovery by intermediate storage can be performed both pneumatically and hydraulically. In hydraulic vibrators, the compression of the fluid is preferably used. It can be dispensed with additional external memory. The disadvantage of this variant, however, is that the pressure accumulators 27 and 28 have a relatively large space requirement. If this is not desired, such as for mobile drives, but can also be using external storage 27 and / or 28, such as gas storage, work to build the actuator itself as small as possible. It is beneficial to resort to memory with a long service life and compact design. Conventional diaphragm accumulators often do not meet these requirements. In the FIGS. 7 and 8 show two implementation possibilities of gas storage, which are favorable for use according to the invention. The gas 51 is thereby separated from the fluid 53 by the membrane 52. In order to set the life as high as possible, conveniently steel membranes are used.

As shown in the embodiments, the control valve 29 consists of several stages or valve edges. It thus switches at least two or more fluid lines. In order to set the energy efficiency of the overall system as high as possible, especially at the main valve edge 39, attention must be paid to favorable nominal volume flows. The pressure loss in this generally designed as a 3/2-way valve main valve edge should be kept as low as possible. At the additional valve edges 37, 38 and 48 pressure losses are not so crucial. The main advantage of the multi-stage control valve 29 is that only a single valve or only a single slider is needed. This has a positive effect on both the cost and the reliability of the system.

In the embodiments shown, the control valve 29 has a hydraulic feedforward control, since with this the timing of the control valve 29 is particularly easy to implement.

As check valves favorably fast variants are used, which cause the lowest possible pressure loss.

The embodiment variants according to the invention described above have a great advantage, above all with regard to robustness and simple construction. In addition, these forms of realization have a high energy-saving potential, which is in the range of 50 percent. Another advantage is the automatic valve clearance compensation. A valve clearance compensation, especially for large engines, must be able to compensate for several millimeters - on the order of 4 mm. In this system, one can accommodate this change in length in the piston-side first working volume 23 of the working cylinder 20. This volume change is very small compared to the volumes of the accumulators 27 and 28. As a result, the switching sides and the stroke of the actuator do not change noticeably. When using a Zusatzaktuators 34 could also be installed in the actuator 21 a valve clearance compensation.

Although the valve actuators according to the invention in the embodiments shown focus on the application of gas inlet or outlet valves of internal combustion engines, so embodiments of the invention but also for large valve spool in hydraulics, compressor valves or drives of punching machines u. Like. Used to name just a few examples.

Claims (19)

Valve drive, in particular for gas exchange valves of internal combustion engines, with a movably mounted in a cylinder actuator, in particular pistons, for driving a valve, wherein in the working cylinder on one side of the actuating element at least one on at least one first fluid line with at least one pressure accumulator for fluid in connection standing working volume wherein an at least two fluid lines switching, actively actuable control valve is arranged in the first fluid line, characterized in that at least one passive switching element (30, 31) for controlling a fluid flow, preferably non-return valve, to the control valve (29) in series or in parallel is switched. Valve drive according to claim 1, characterized in that the working volume is a first working volume (23) and the accumulator is a first pressure accumulator (27) and on a first working volume (23) opposite side of the actuating element (21) at least one at least a second fluid line (26) is provided with at least one second pressure accumulator (27) for fluid-related second working volume (24) in the working cylinder (20), wherein the actively actuable control valve (29) in the first and / or in the second fluid line (25, 26) is arranged. Valve drive according to claim 1 or 2, characterized in that the valve drive has exactly one actively actuable control valve (29). Valve drive according to one of claims 1 to 3, characterized in that at least, preferably exactly, two passive switching elements (30, 31) for controlling a fluid flow to the actively actuated control valve (29) are connected in series and / or in parallel. Valve drive according to one of claims 1 to 4, characterized in that in the case of a series connection, the (the) passive (s) switching element (s) (30, 31) for controlling a fluid flow in the first (and / or the second fluid line ( 25, 26), preferably on the respective working volume (23, 24) facing side of the actively actuated control valve (29) is arranged (are). Valve drive according to one of claims 1 to 4, characterized in that in the case of a parallel connection, the (the) passive (s) switching element (s) (30, 31) for controlling a fluid flow, preferably in each case in at least one of the actively operable control valve (29) bypassing the bypass line (32, 33) of the first (and / or the second fluid line (25, 26) is arranged). Valve drive according to one of claims 1 to 6, characterized in that the actuating element (21) is hydraulically and / or pneumatically actuated, Valve drive according to one of claims 1 to 7, characterized in that , preferably during braking, kinetic energy of the valve drive, preferably the valve (22) by pressure build-up in the first pressure accumulator (27) and / or in the second pressure accumulator (28) for a subsequent Stroke of the valve (22) is cacheable. Valve drive according to one of claims 1 to 8, characterized in that it provides a, preferably hydraulic and / or pneumatic, end position damping for at least a region in which the valve (22) reaches one of its end positions. Valve drive according to one of claims 1 to 9, characterized in that the actuating element (21) for carrying out an opening stroke and a closing stroke of the valve (22) is provided and at least a part of the opening stroke or the closing stroke more force from the actuating element (21) the valve (22) is applied, as at the respective other hub, wherein a Zusatzaktuator (34) is provided which at least partially supports the actuating element (21) in the more force-requiring stroke. Valve drive according to claim 10, characterized in that the additional actuator (34) is not operable with a from a combustion chamber, preferably an internal combustion engine, derived pressure as a driving force. Valve drive according to claim 10 or 11, characterized in that the additional actuator (34) is hydraulically and / or pneumatically and / or electrically and / or piezo-electrically and / or magnetically and / or electro-magnetically driven. Valve drive according to one of claims 10 to 12, characterized in that both the additional actuator (34) and the actuating element (21) are hydraulically and / or pneumatically operable and preferably by a common system pressure source (pS) can be fed. Valve drive according to one of claims 10 to 13, characterized in that the additional actuator (34) supports the actuating element (21) at the more power-requiring stroke during the entire stroke. Valve drive according to one of claims 10 to 13, characterized in that the Zusatzaktuator (34) is formed so that it only on a partial section (h _p ), preferably at the beginning of the Betätigungselemtent (21) to be executed opening or closing stroke on the Valve (22) acts. Valve drive according to one of claims 10 to 13, characterized in that the additional actuator (34) terminates the power supply before the valve (22) reaches one of its end positions. Valve drive according to claim 15 or 16, characterized in that for the additional actuator (34), a stop (35) is provided, which it reaches before the valve (22) reaches one of its end positions. Valve drive according to one of claims 1 to 17, characterized in that the valve drive is provided for a gas outlet valve or a gas inlet valve of an internal combustion engine. Internal combustion engine with a valve drive according to one of claims 1 to 18.

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