EP1001143B1 - Valve control for intake and exhaust valves in internal combustion engines - Google Patents

Description

The invention relates to a valve control for intake and exhaust valves of internal combustion engines according to the preamble of claim 1.

In conventional internal combustion engines, the control of the strokes of the intake and exhaust valves by a driven by the crankshaft in the speed ratio 2: 1 camshaft. The lift curve of the valve is proportional to the course of the cam over the entire area of the characteristic diagram and thus unchangeable. The closing point of the intake valve is due to different flow velocity in the intake manifold, not optimally placed. The inlet or opening point can also not be set optimally. The values for best possible filling of the combustion chamber at high speeds and the cylinder exhaust gas content at low speeds and idling are diametrically opposed. The opening point or outlet beginning is therefore usually chosen so that the Ausschiebeverluste are minimized and the gas is able to do maximum work.

In order to avoid the aforementioned adjustments, which are always compromises, valve controls have been developed in order to influence and be able to change control times, lift characteristics of the intake and exhaust valves as a function of the engine speed, the load and other influencing variables. The course of the valve lift can thus be influenced or changed by variations in the phase position, the valve lift or the valve opening duration. Such measures can be used individually or in combination, on the one hand to reduce fuel consumption and emissions on the gasoline engine and on the other hand to improve the torque curve and to increase the maximum power. Another advantage arises from the ability to influence the intake air volume by changing the valve opening cross-section and thus to allow a throttle-free load control without throttle.

In multi-valve technology, such a circuit can be made that the sucked charge flows only through an inlet valve and thus their amount is affected. A cylinder deactivation by influencing the intake and exhaust valves can also be realized, wherein the fired cylinders can work in the best efficiency range by hiding injections and combustion air. With modern engine electronics, the cylinder deactivation can cyclically (selectively) change to avoid the cooling of the cylinder wall.

The aforementioned possibilities for influencing and changing parameters are summarized under the term "variable valve timing". According to the type of valve actuation, a distinction is made between directly and indirectly actuated systems.

In the indirectly actuated systems, two solutions are known, namely the use of a variable camshaft or a variable intermediate element. In directly operated systems basically three ways are known in which the actuation of the valve is hydraulic, pneumatic or electric. A camshaft is omitted in these cases.

In the hydraulic system, the energy is stored similar to the so-called common rail system and fed by fast solenoid or servo valves the control piston surfaces or discharged from them, with which in turn the intake and exhaust valves are actuated. Such systems are known for use in slow-running diesel engines.

In a known valve control of the generic type (Abstracts JP-A 60-113008), the inlet / outlet valves are always over with the same stroke two solenoid valves open. With the one solenoid valve, the supply of the pressure medium from the tank is controlled to the actuating piston, with which the on / off valve is opened. The other solenoid valve closes the tank line. If the inlet / outlet valve is to be closed again, the pressure line is closed with one solenoid valve and the other solenoid valve is opened. The pressure medium located in front of the actuating piston can then enter the tank line via the opened solenoid valve. The solenoid valves must always be kept energized so that the intake / exhaust valve does not move to the open position where the piston in the combustion chamber could damage the intake / exhaust valve.

The invention has for its object to form a valve control of this kind so that while avoiding a complex servo valve a simple and reliable operation at high switching frequencies is possible, so that the valve control can also be used for high-speed internal combustion engines.

This object is achieved according to the invention in the generic valve control with the characterizing features of claim 1.

In the valve control according to the invention piezoelectric actuators are used as adjusting elements. With them, low-mass valve elements are actuated, which control the inflow and outflow of the pressure medium to and from the control piston, through the stroke of the inlet and outlet valves of the engine are opened and closed. Piezoelectric actuators convert electrical voltages directly into paths and forces. The conversion of the electrical input into a mechanical output is extremely fast. Adjustment strokes of, for example, 40 μm (0.04 mm) can be carried out in a positioning time of 50 μs (0.000.05 sec). The resolution of the travel is possible with suitable electrical control in the nanometer range (0.0001 mm). Actuating forces are achieved in the kilonewton range, ie actuators with very high mechanical rigidity. Since the two piezo elements act as opener and closer, a variable stroke of the inlet / outlet valve can be easily achieved.

This also prevents that in case of power failure, the inlet / outlet valve moves into the open position.

In the highly dynamic range, on the one hand, the availability of suitable power amplifiers is an essential prerequisite for synchronizing the control curve and the response of the intake and exhaust valves. On the other hand, the flow area at the seat valve is to be dimensioned correspondingly large. This is done in an advantageous embodiment of the valve control according to the invention by increasing the stroke to a value for which the available travel of the piezoelectric transducer is insufficient. It is therefore Stellwegvergrößerer used, which advantageously operate on the lever principle and can increase the usable travel of the valve element, for example, up to a factor of ü = 10.

In the valve control according to the invention, the opening and closing times for the intake / exhaust valves, the duration of the opening times can be determined as needed in accordance with the engine management in an advantageous manner.

Further features of the invention will become apparent from the other claims, the description and the drawings.

Fig. 1 bis 3

jeweils in schematischer Darstellung verschiedene Ausführungsformen von erfindungsgemäßen Ventilsteuerungen, die mit variablem Hub arbeiten,

Fig. 4

eine Draufsicht auf eine erfindungsgemäße Ventilsteuerung mit Wirkprinzip entsprechend Fig. 1, jedoch mit zusätzlicher Hebelübersetzung,

Fig. 5

einen Schnitt längs der Linie V-V in Fig. 4,

Fig. 6

einen Schnitt längs der Linie VI-VI in Fig. 4,

Fig. 7 und 8

jeweils in vergrößerter Darstellung einen Teil der Ventilsteuerung gem. Fig. 5,

Fig. 9 bis 12

verschiedene Diagramme, die die Möglichkeit der Variierung des Ventilhubs, der Öffnungsdauer, der Phasenlage und der Kombination dieser Parameter zeigen.

The invention will be explained in more detail with reference to some illustrated in the drawings embodiments. Show it

Fig. 1 to 3

in a schematic representation different embodiments of valve controls according to the invention, which operate with variable stroke,

Fig. 4

a plan view of a valve control according to the invention with the operating principle according to FIG. 1, but with additional leverage,

Fig. 5

a section along the line VV in Fig. 4,

Fig. 6

a section along the line VI-VI in Fig. 4,

FIGS. 7 and 8

each in an enlarged view a part of the valve control acc. Fig. 5,

Fig. 9 to 12

various diagrams showing the possibility of varying the valve lift, the opening duration, the phase angle and the combination of these parameters.

With reference to FIGS. 1 to 3, different embodiments of valve controls will be described in their mode of action. FIGS. 4 to 12 then show concrete embodiments of such valve controls and associated characteristic curves.

The valve controls described below allow high control frequencies, so that these valve controls can also be used in high-revving internal combustion engines.

Figs. 1 and 4 to 12 show an embodiment in which the stroke of an intake / exhaust valve 30 can be changed. The valve control has two piezo elements 1, 1 a, with which two plungers 2, 2 a can be actuated in order to displace two valve elements 3, 3 a 2 of two seat valves 9, 9 a. The two valve elements 3, 3a are each under the force of at least one compression spring 6, 6a. In a valve chamber 4a of the seat valve 9a opens a pressure line 7. In electroless piezoelectric element 1a, the pressure line 7 is separated via the closed valve element 3a from a supply line 10 for hydraulic medium, which opens into a pressure chamber 14 which is provided in a valve housing 5 and in the an adjusting piston 15 is located, whose one end face 16 can be acted upon by the hydraulic medium.

From the supply line 10 branches off a connecting line 63, which opens into a valve chamber 4 of the seat valve 9. When not energized piezoelectric element 1, the valve chamber 4 is connected to a tank line 12.

On the opposite side of the pressure chamber 14 is a cylinder chamber 17 which is connected via at least one opening 18 to the atmosphere. In the cylinder chamber 17 protrudes a plunger 19 which cooperates with a tappet 20. He is under the force of at least one compression spring 21, which loads the bucket tappet 20 and thus the bolt-shaped plunger 19 in the direction of the actuating piston 15 via a valve stem 22. The tappet 20 is located on the valve stem 22, which is provided at the free end with a valve plate 23. With him an inlet or outlet opening 24 of a combustion chamber 25 of an internal combustion engine 26 of a motor vehicle is opened and closed.

In the position shown in Fig. 1, the piezoelectric elements 1, 1a are de-energized, so that the inlet / outlet valves 30 are closed. If the inlet / outlet valve 30 to perform the maximum opening stroke (normal and overstroke), both piezo elements 1, 1a are energized. As a result, the two plungers 2, 2a are moved. With the plunger 2, the valve element 3 is moved against the force of the spring 6 in its closed position in which it closes the tank line 12. With the plunger 2a, the valve element 3a is moved to an open position, so that the hydraulic medium via the pressure line 7 and the valve chamber 4a can flow into the supply line 10. The hydraulic medium thereby passes into the pressure chamber 14 and displaces the actuating piston 15 downwards. About the plunger 19 and the tappet 20, the valve stem 22 is moved against the force of the compression spring 21 and opened in this way the inlet / outlet valve 30. The actuating piston 15 is displaced until it comes to rest on the bottom 29 of the cylinder chamber 17. Thus, the stroke of the actuating piston 15 and thus of the valve 30 corresponds to the normal stroke plus an overstroke.

If the engine management requires it, the actuator piston 15 and thus also the valve 30 can only be adjusted by the normal or any other stroke. For this purpose, both piezo elements 1, 1a are energized and the piezoelectric element 1 a made de-energized after a stroke-determining time, so that the valve element 3 a is moved by the force of the compression spring 6 a in its closed position. As a result, the pressure line 7 of the Feed line 10 separated. At the same time the piezoelectric element 1 remains energized, thereby closing the valve 3 and the chamber chambered in the pressure chamber 14. The now compared to the previous process lower fluid volume of the hydraulic medium flowing into the pressure chamber thus determines the stroke of the actuating piston 15 and thus also the stroke of the inlet / outlet valve 30, since the piezoelectric element 1 continues to be energized and thereby the line 63 to the tank 12 remains closed , The fluid volume located in the pressure chamber 14 thereby remains enclosed (chambered), the valve 30 is less widely opened, so that a correspondingly smaller amount of fuel-air mixture enters the combustion chamber of the internal combustion engine.

If the inlet / outlet valve 30 are closed, the piezoelectric element 1 is de-energized. The compression spring 6 lifts the valve element 3 from its valve seat 66, whereby the hydraulic medium in the pressure chamber 14 can be displaced via the supply line 10 and the open valve chamber 4 into the tank line 12.

As shown in FIGS. 7 and 8, the valve element 3 and the compression spring 6 are in a bushing 64, which is pressed into an installation space 65 of the valve housing 5. The provided for the valve element 3 valve seat 66 is provided on an insert 43. The compression spring 6 holds the valve element 3 at nichtvorromtem piezoelectric element 1 in the open position, which is shown in Fig. 8, the insert 43 is axially secured by the flanged end 67 of the sleeve 64. A central axial bore 68 of the Einsatzstükkes 43 is closed by a closure element 69, preferably a ball.

The valve element 3a is also received in a bushing 70 (FIG. 7) whose lower end 71 is flanged. The valve element 3a is pressed by the compression spring 6a up against a valve seat 72, which the plunger 2a penetrates axially and thus generates an annular surface 81 required for the flow.

The two seat valves 9, 9a are on both sides of the actuating piston 15 and axially parallel to him. As a result, the valve housing 5 has only a small axial height.

The cylinder chamber 17 is, as shown in FIG. 5, connected via the vent line 18 to the atmosphere, so that the actuating piston 15 can be moved to open the on / off valve 30 reliably.

To open the inlet / outlet valve 30, both piezo elements 1, 1a are energized. The size of the stroke of the actuating piston 15 and thus of the inlet / outlet valve 30 depends on the time from the beginning of the opening, the piezoelectric element 1a is no longer energized and thus no hydraulic medium can flow into the pressure chamber 14. As a function of the energization time of the piezoelectric element 1a, the stroke of the inlet / outlet valve 30 can thus be steplessly controlled.

For the closing movement of the inlet / outlet valve 30 may be provided a damping. For this purpose, both end faces 16, 28 of the actuating piston 15 are provided with a throttle cross-section, which is an example diametrically extending, in cross-section triangular depression. The throttle cross-sections cooperate with control edges when the actuator piston 15 is moved. When driving over the respective control edge, a pressure builds up in the medium due to the constantly decreasing flow area for the hydraulic medium, which counteracts the movement of the actuating piston 15 and thus causes the damping by reducing speed.

In the described embodiments, in contrast to a camshaft control, the phase position with respect to the opening and closing of the intake / exhaust valves 30 can be changed. This is possible by virtue of the fact that the piezoelements assigned to the intake / exhaust valves 30 are energized or out-flowed at the desired time. In the embodiment according to FIGS. 1 and 4 to 8, the size of the opening stroke of the inlet / outlet valve 30 can additionally be varied in the described manner.

Fig. 9 shows stroke characteristics of the manner described with reference to the embodiment of FIGS. 1 and 5 to 8, the opening stroke of the inlet / outlet valve 30 to vary.

Fig. 10 shows by means of characteristics that the opening duration of the inlet / outlet valve 30 can be changed in the manner described. From the characteristics in Fig. 11 shows that in addition, the phase angle can be adjusted in the manner described. Finally, FIG. 12 shows characteristic curves for the exemplary embodiment according to FIGS. 1 and 4 to 8, in which the three adjustment possibilities according to FIGS. 9 to 11 can be used in combination. The valve lift, the opening duration and the phase position can be changed. This embodiment represents a fully variable control of the intake / exhaust valves 30.

The plungers 2, 2a can be actuated directly by the piezo elements 1, 1a, as shown schematically in FIG. But it is also possible between the plunger 2, 2a and the piezoelectric element 1, 1a each have a transmission lever 59, 59a provided to increase the opening and closing of the valve element 3, 3a at a given piezohub. In the schematically illustrated embodiment of FIG. 2, the transmission lever 59, 59a one-armed lever. At a distance 60 from the pivot axis 61, 61a of the lever 59, 59a attacks on them the plunger 58, 58a. At the free end of the lever 59, 59 a, which is located at a distance 62 from the respective pivot axis 61, 61 a, engages the plunger 2, 2 a. The plungers 2, 58 and 2a, 58a lie on opposite sides of the lever 59, 59a. About the ratio of the distances 60 and 62 to each other, the gear ratio can be determined.

In the embodiment according to FIG. 3, the levers 33, 33a are two-armed levers which have differently long lever arms 86, 87. At the shorter lever arm 87, the plunger 58, 58a of the piezo elements 1, 1 a engage. On the same side of the levers 33, 33a engage at the free ends of the longer lever arms 86, the plunger 2, 2a. About the ratio of the length of the lever arms to each other can also set the gear ratio.

Since in the embodiment of Figure 3, the two plunger 2, 58; 2a, 58a are on the same side of the levers 33, 33a, results in a low overall height 73. The two-armed levers 33, 33a are, as explained with reference to the embodiment of FIGS. 4 to 8 in detail, spatially offset from each other, so that the valve housing 5 has only correspondingly small dimensions.

In the embodiment of Fig. 2, the overall height is greater than in the embodiment of FIG. 3, because the piezo elements 1, 1a with their plungers 58, 58a on one side and the plunger 2, 2a with the valves 9, 9a on the other side the lever 59, 59a sit. In Fig. 2, the height of the piezo elements 1, 1a with the plungers 58, 58a with 74 and the height of the seat valves 9, 9a with the plungers 2, 2a and the pivot levers 59, 59a denoted by 75. It can be seen that the overall height 74, 75 is about twice as large as the overall height 73 in the embodiment of FIG. 3rd

In the embodiment according to FIGS. 1 and 4 to 8, the two two-armed levers 33, 33a in the housing space 34, which is closed by a housing cover 76. The two levers 33, 33a are arranged offset to one another and are each at an acute angle to a longitudinal center plane 77 of the valve housing 5. Seen in side view, the two levers 33, 33a overlap one another at a small distance one behind the other. The pivot axes 36, 36a are parallel to each other. At the free end of the shorter lever arm, the plunger 58, 58 a of the two piezo elements 1, 1 a engage. At the free ends of the longer lever arms are the plunger 2, 2 a, with which the valve elements 3, 3 a are actuated in the manner described.

The two piezoelectric elements 1, 1a lie in separate housing spaces 78, 79 (FIG. 6). In the area between the two housing chambers 78, 79 is the cylinder chamber 17 with the piston 15. By the ratio of the length the lever arms of the respective lever 33, 33 a, the gear ratio is determined. In this way, the small path of movement of the piezoseitigen plunger 58, 58a can be translated into the required adjustment of the plunger 2, 2a very simply to move the respective valve element 3, 3a reliably with the required stroke in the corresponding open or closed position.

Claims (24)

1. Valve control for intake and exhaust valves (30) of combustion engines with setting elements (1, 1a), with which the intake/exhaust valve (30) is opened and closed and with which respectively a valve element (3, 3a) is actuated, which control the inflow and outflow of a pressurized medium and of at least one setting piston (15), displacable via the pressurized medium for opening and closing the intake/exhaust valve (30), whereby the one valve element (3a) connects in one position a pressure line (7) with a pressure chamber (14) in front of the setting piston (15) and the other valve element (3) closes a tank line (12), whereby the intake/exhaust valve (30) is adjustable in its closed position by a force independent from the pressurisation of the setting piston (15), whereby the one valve element (3a) adjusts into its position closing the pressure line (7) and the pressurized medium which is within the pressure chamber (14) in front of the setting piston (15) is being displaced into a tank line (12),
   characterised in that the setting elements (1, 1a) are piezoelectric elements and that both the valve elements (3, 3a) work in an opposite direction and control the inflow to a common supply line (10) for the pressurized medium, which flows to the pressure chamber (14) and that the two piezoelectric elements (1, 1a) for adjustment of the course of the intake/exhaust valve (30) are actuable independently from one another and that the one piezoelectric element (1) is effective as a shutter for the tank line and the other piezoelectric element (1a) is effective as an opener for the pressure line.
2. Valve control according to claim 1,
   characterised in that both valve elements (3, 3a) are parts of seat valves (9, 9a), which control the inflow of the pressurized medium from the pressure line (7) to the setting piston (15).
3. Valve control according to claim 2,
   characterised in that both seat valves (9, 9a) are connected to the common supply line (10).
4. Valve control according to claim 2 or 3,
   characterised in that with piezoelectric elements (1, 1a) being non-electric the one seat valve (9) is opened and the other seat valve (9a) is closed.
5. Valve control according to one of the claims 1 to 4,
   characterised in that the setting piston (15) acts via a pestle (19) in combination with a valve stem (22) of the intake/exhaust valve (30), advantageously cooperating via a bucket tappet (20) with the pestle (19).
6. Valve control according to one of the claims 1 to 5,
   characterised in that the both piezoelectric elements (1, 1a) act in combination respectively via a pestle (2, 2a) with the valve element (3, 3a).
7. Valve control according to one of the claims 4 to 6,
   characterised in that the valve element (3) of the opened seat valve (9) is adjustable by the pestle (2) of the one piezoelectric element (1) at its current feed to its closing position, in which the supply line (10) is separated from the tank line (12) .
8. Valve control according to one of the claims 4 to 7,
   characterised in that the valve element (3a) of the closed seat valve (9a) is adjustable by the pestle (2a) of the further piezoelectric element (1a) at its current feed into its open position, in which the pressure line (7) is connected with the supply line (10), flowing to the pressure chamber (14).
9. Valve control according to one of the claims 1 to 8,
   characterised in that at chronological sufficient current feed of both piezoelectric elements (1, 1a) the setting piston (15) and with it the driven intake/exhaust valve (30) executes its maximum lift and can be held there.
10. Valve control according to one of the claims 2 to 9,
    characterised in that for holding the setting piston (15) in the maximum open position both seat valves (9, 9a) are closed.
11. Valve control according to one of the claims 2 to 10,
    characterised in that for holding the setting piston (15) in the maximum open position the one seat valve (9) is closed and the other seat valve (9a) is opened.
12. Valve control according to one of the claims 2 to 11,
    characterised in that at chronological shorter current feed of both piezoelectric elements (1, 1a) the setting piston (15) executes a smaller lift in comparison with the maximum lift.
13. Valve control according to claim 12,
    characterised in that for holding the setting piston (15) at reduced opening lift both seat valves (9, 9a) are closed.
14. Valve control according to one of the claims 1 to 13,
    characterised in that both piezoelectric elements (1, 1a) act in combination via a transmitter (33, 33a), preferably a lever with two branches, with the pestle (2, 2a).
15. Valve control according to claim 14,
    characterised in that both transmitters (33, 33a) are arranged overlapping one another, seen in direction of its pivoting axe (36, 36a).
16. Valve control according to claim 14 or 15,
       characterised in that both transmitters (33, 33a) are diposed in line.
17. Valve control according to one of the claims 14 to 16,
    characterised in that both transmitters (33, 33a) are diposed parallel to one another and advantageously at an acute angle to a longitudinal midplane (77) of a valve case (5).
18. Valve control according to one of the claims 1 to 17,
    characterised in that the valve element (3, 3a), advantageously manufactured out of a ball comprises a seat means (83), from which protrudes an appendix (84), smaller in the cross-section.
19. Valve control according to claim 18,
    characterised in that the compression spring (6, 6a) is put onto the appendix (84) of the valve element (3, 3a), advantageously widening itself conically from the seat means (83) on.
20. Valve control according to claim 18 or 19,
    characterised in that at the transition from the appendix (84) to the seat means (83) the difference in diameter corresponds to the double wire gauge of the compression spring (6, 6a).
21. Valve control according to one of the claims 18 to 20,
    characterised in that at the free end of the appendix (84) a further seat means (85) is provided, preferably partially spherically or conically formed.
22. Valve control according to claim 21,
    characterised in that the further seat means (85) comprises a smaller diameter of the seat than the other seat means (83).
23. Valve control according to one of the claims 14 to 22,
    characterised in that the both pestles (2, 2a) are situated at the same side of the two transmitters (33, 33a).
24. Valve control according to one of the claims 14 to 23,
    characterised in that the both transmitters (33, 33a) are disposed spatially offset to each other.

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