EP1041252A2 - Valve with electromagnetic actuator - Google Patents

Abstract

The gas changing valve has a valve element (1) acted on by a closure spring (3) and an electromagnetic actuator (5) with 2 electromagnets (6,7) positioned with their pole faces (8) towards one another, so that a magnetic armature (9) with attached gui bolts (10,11) is displaced between them. One guide bolt cooperates with an opening spring (12), the other guide bolt cooperating with the valve element, with a valve play gap between the guide bolt and the valve element. The armature mass is at least double mass of the valve element.

Description

In addition to mechanical valve drives, piston internal combustion engines are also used with camshaft and hydraulic valve drives electromagnetic actuators, such as those used, for example are known from DE 195 18 056-A.

An electromagnetically actuated gas exchange valve arrangement for a piston internal combustion engine consists essentially of a valve body connected to a closing spring and one electromagnetic actuator of two electromagnets has whose pole faces are aligned with each other and with Are spaced from each other, and the one between the pole faces are guided back and forth with anchor bolts has at one end with the valve body and are connected to an opening spring at the other end, being between the guide pin and the valve body there is a valve clearance.

Such a gas exchange valve arrangement forms an oscillatory one Spring-mass system, the total mass of which is essentially through the anchor with its guide bolts and is formed by the valve body and its "spring" by the opening and closing springs are formed. The order is usually made so that the two return springs are equally designed.

The basic idea of this gas exchange valve arrangement is that to reduce the electrical necessary for operation Energy the natural vibratory capacity of this spring-mass system is exploited so that in principle the catcher and electromagnet holding for the opening or closing time only has to be energized so much that the armature in each case when its center position overshoots from the magnetic field of the catching magnet is attracted, but otherwise the kinetic Energy of the total mass for a substantial part the movement is exploited.

Since each time the armature approaches the pole face of the energized catching magnets the spring force of the opposite direction acting spring only increases linearly, in contrast with constant current supply to the capturing electromagnet magnetic forces acting on the approaching armature progressively rise and already with a view to safe catching the increase in the spring force acting in the opposite direction are a number of regulatory procedures the current supply has been developed by means of a withdrawal the current level during the approach of the armature to the Pole surface of the catching electromagnet also on the armature acting magnetic force is withdrawn, so a gentle Impact of the armature on the pole face and to avoid annoying bouncing processes.

To regulate the current supply to the magnet in question it is necessary to also face the respective position of the anchor the pole face and / or the speed of the armature to be recorded in the proximity area. Methods have been developed for this been the repercussions of itself in the magnetic field moving armature on current and voltage of the power supply capture and from this the necessary signals for influencing derive the current.

In addition, control systems have been developed in which over Sensors the respective anchor position and / or the respective Anchor speed directly over the anchor as a signal is tapped. Since the anchor for design reasons with its guide pin and the essentially Valve plate and valve stem not existing valve body can be formed in one piece, inevitably results between the free end of the valve stem on the one hand and the associated end of the guide pin on the other hand a valve clearance that changes due to changing temperature influences during the operation of a piston internal combustion engine changes.

By usually hydraulic means for valve clearance compensation So far, care has been taken to ensure that the company due to an inserted between guide pin and valve stem this distance can be filled with oil as was bridged with a "rigid" intermediate layer, whereby the arrangement is such that changing valve lashes were balanced. Such valve clearance compensation systems are technically complex to manufacture on the possibilities of fully variable electromagnetic Valve train, it would be desirable to allow valve clearance, to take appropriate measures in the control of the current supply Avoid problems with valve movement. Here is the detection of the armature movement and / or the anchor speed is important in the first phase of movement, where the derivative of a signal is just above the detection of the respective anchor position and the anchor speed is advantageous.

However, due to the presence of valve clearance, this is vibratory spring-mass system formed by the overall arrangement divided into two temporarily decoupled subsystems. As a result, especially at the beginning of the Opening process, but also at the end of the closing process the armature supported on the opening spring with its guide pin compared to that supported on the closing spring Valve body can perform own movements. By hitting the guide bolt of the anchor on the shaft of the The gas return valve becomes the two return springs on the one hand and the armature mass and the valve mass on the other hand spring-mass system formed by the impact of the anchor mass excited to a resonance oscillation on the valve stem, which does not subside until the armature hits the opening magnet. This overlaps the flight movement of the anchor the back and forth movement of the resonance oscillation Anchor complicates the difficult approach of the anchor to the pole face of the catching opening magnet with a impact speed as low as possible, so that despite a targeted guidance of the anchor movement by an appropriate Regulation of the catching current are adverse bouncing processes cannot be avoided.

To avoid such bouncing processes, US-A-5,832,883 suggested the anchor fixed to the valve body to connect and one that is also firmly connected to the valve provide hydraulic damper element through which the Lowering speed of the valve on its valve seat reduced shall be. A valve clearance is not provided. The known system can because of the constantly acting damping not operated using the natural vibration capability become. To act through the entire valve movement Damping force, which is a gentle impact of the valve on the valve seat, the anchor may not in the closed position on the pole face to the system come and on the other hand must compensate for the braking effect the damping element designed the closing spring stronger are called the opening spring. This has a higher energy requirement as a result, especially because of the damping element usable natural vibration is missing.

It has proven to be disadvantageous that, in the pursuit of Reduction of the total mass of the vibrating system tried to reduce the anchor mass only, as a reduction the mass of the valve body depends on the material is very limited. The anchor guides during the opening process even with a small valve clearance of 0.1 mm after switching off of the holding current at the closing magnet due to the high Acceleration by the opening spring when it hits such a high energy surge on the stem of the valve body into that formed by the closing spring and valve body Subsystem that on the one hand the anchor against the force of the Opener spring several times overlaid on the opening movement Shrinking movement and the other at the same time also the valve body moving in the opening direction also a vibration movement superimposed on the opening movement executes. Because of the multiple, out of phase opposite movements of anchor on the one hand and Valve body overlaps on both moving systems a vibratory movement that extends well beyond the middle position of the armature between the two pole faces.

One grabs now directly at the anchor over an appropriate Sensors the anchor position and / or anchor speed, so there is no precise signal here, but a through the oscillating movement of the armature causes "washed out" or "noise" signal.

To overcome this disadvantage, according to the invention proposed in a gas exchange valve arrangement with valve clearance the mass of the anchor of the type described above to be dimensioned such that it is at least twice the Has mass of the valve body.

The anchor wetness is defined by the mass of the anchor plate even with the related leadership Anchor bolt and the reduced mass of the opening spring and the mass of the spring bolt assigned to the opening spring. Although the spring bolt is not firmly attached to the anchor bolt connected, however, has been shown to be in operation due to the given geometric assignment between the opening spring, Spring bolts and anchors with anchor bolts opposite the anchors the spring bolt during the swinging movements "Own life" developed.

The mass of the valve body is defined by the Mass of the valve body itself including the valve spring retainer and the reduced mass of the closing spring.

By increasing the anchor mass compared to the mass of the The valve body is the armature movement when hitting the Valve stem stabilized during the opening movement, so that the armature's natural vibrations subside much faster. It is not a disadvantage that the result of the im Ratio lower mass of the valve body the reinforcing, natural vibrations superimposed on the opening movement of the valve body at the moment of impact are larger because these natural vibrations are stabilized by Effect of the anchor mass and those acting on the valve body Damping forces reduce these natural vibrations much earlier leave, so that the overall system much earlier Calm comes. It is important, however, that the natural vibrations of the anchor shortly after hitting the guide pin have subsided on the valve stem, so that thereby a "noise reduction" for one of the armature movement tapped signal is given.

With the interpretation of the mass ratio between anchor mass and valve body mass can now be within a wide range Selections are made. Unless you know about the bouncing process immediately when the anchor hits its guide bolt wants to receive a signal on the valve stem, then it is appropriate if the ratio of the anchor mass to the mass of the valve body is only increased so far that still a clear signal via the existing sensors can be detected. The disadvantage, however, is that that the overlapping vibrations both during the armature movement as well as when the valve body moves later fade away. If this signal is not required, you can use further increase in anchor mass due to the impact Minimize the natural vibration of the anchor mass.

In order to understand the vibration behavior of the Overall system, in particular an increase in energy consumption Avoiding when starting is a reduction in vibrating total mass displayed. This would be through use other lighter materials for the valve body possible. Ceramic materials are suitable for this, for example. But it is also possible to reduce the anchor mass, if the criteria according to the invention for the Mass distribution between anchor mass and valve body mass be adhered to by the opening process Impact of the anchor bolt on the stem of the valve body to at least minimize induced natural vibrations of the anchor mass. A reduction in the total mass of the valve train overall given vibratory spring-mass system then allows the spring constants to be adjusted the springs to the operating conditions of the piston internal combustion engine, with an increase in the spring constants in the conventional valve lashes around 0.15 mm have proven to be advantageous Has.

Another advantage of the configuration according to the invention is in that a so-called valve clearance compensation can be dispensed with because the bouncing processes are shortened and natural vibrations of armature and valve body during the opening movement and a reduction in the amplitudes the natural vibrations of the armature and the valve body the noise level is also reduced.

To reduce the natural vibrations of the system is in particular in connection with the vote according to the invention the anchor mass also for a gas exchange valve arrangement an electromagnetic actuator of the above Art provided that the two return springs are different Have spring characteristics. Because of this "asymmetrical" Spring design This ensures that the given Spring-mass system is "out of tune" and no pronounced resonance frequency exists and so is the impact of the anchor mass on the gas exchange valve after overcoming the Valve play causes vibration excitation and breaks down quickly the anchor practically free of vibrations on the pole face of the catching opening magnet strikes.

Fig. 1

einen schematischen Vertikalschnitt durch eine elektromagnetisch betätigbare Gaswechselventilanordnung,

Fig. 2

das aus Fig. 1 abgeleitete Schwingungssystem,

Fig. 3

den Verlauf der Geschwindigkeiten von Anker und Ventilkörper bei "kleiner" Ankermasse,

Fig. 4

den Verlauf der Geschwindigkeit von Anker und Ventilkörper bei "großer" Ankermasse,

Fig. 5

eine Überlagerung der Kurven der Ankerbewegungen bei einer Auslegung gem. Fig. 3 und Fig. 4,

Fig. 6

eine Anordnung mit "unsymmetrischer" Auslegung der Rückstellfedern.

The invention is explained in more detail with the aid of schematic drawings and diagrams. Show it:

Fig. 1

2 shows a schematic vertical section through an electromagnetically actuated gas exchange valve arrangement,

Fig. 2

the vibration system derived from Fig. 1,

Fig. 3

the course of the speeds of the armature and valve body with a "small" armature mass,

Fig. 4

the course of the speed of the armature and valve body with "large" armature mass,

Fig. 5

a superposition of the curves of the anchor movements in an interpretation acc. 3 and 4,

Fig. 6

an arrangement with "asymmetrical" design of the return springs.

As can be seen from FIG. 1, there is the one to be examined here Gas exchange valve arrangement in a piston internal combustion engine from a valve body 1 with valve stem 2, which with a Closing spring 3 is connected and via a valve plate 4 in Can be held in the closed position.

An electromagnetic one is used to actuate the gas exchange valve Actuator 5 is provided, which consists essentially of a Opening magnet 7 and a closing magnet 6, the Pole faces 8 facing each other and at a distance from each other are arranged. In the space between the two Pole faces 8, an armature 9 is guided to move back and forth, which is firmly connected at one end to an anchor bolt 10 and the other end is via a spring pin 11 on an opening spring 12 supports.

In Fig. 1 the overall arrangement is shown in the closed position, d. H. the armature 9 lies on the pole face of the closing magnet 6 so that the opening spring 12 is compressed by a corresponding amount is. The valve body 1 is by the Closing spring 3 held in the closed position. Between the end the anchor bolt 10 and the end of the valve stem 2 is a Space VS, a so-called valve clearance available, the in practice is in the range of about 0.15 mm. The valve clearance VS can change due to thermal influences, in particular Change in length of valve stem 2 when the temperature rises and / or correspondingly rectified change in length of the cylinder head carrying the electromagnetic actuator 5 change in operation within certain limits.

If the gas exchange valve is to be opened, the current supply of the closing magnet 6 switched off, so that the armature 9 through the opening spring 12 in the direction of the gas exchange valve 1 is accelerated, here after overcoming the valve clearance VS hits the end of the valve stem 2 and the Valve body 1 advances in the opening direction. The opening magnet 7 is depending on the control in the course of the armature movement energized so that the anchor when overshooting its middle position in the influence of the magnetic field building up device and then against the force of the closing spring 3 comes to rest on the pole face 8 of the opening magnet 7. After the stopping time specified by the motor control the opening magnet 7 is de-energized so that the armature 9 can move back into the closed position, captured by the closing magnet and until the next opening process is held. The closing spring 3 and the opening spring 12 form the so-called return springs for the armature 5.

When arranging a so-called valve clearance compensation, through which the valve clearance VS by a corresponding hydraulic Coupling is bridged, there is practically one movement of armature 9 and valve body 1 in the same direction each time the current is switched off on holding magnets. However, if there is valve clearance, the moves at Opening process of the anchor 9 with its anchor bolt 10 and Spring bolts 11 formed guide bolts initially independently under the influence of the accelerating force of the opening spring 12 until the anchor bolt 10 on the free end of the valve stem 2 and then the anchor mass and mass total mass of the valve body is moved.

The mechanical system shown in Fig. 1 is now to be resolved as an oscillation system in springs and masses. This resolution is shown in Fig. 2. The anchor mass m _{A *} to be considered here is formed by the mass of the armature 9 with its anchor bolt 10 and by the mass of the spring bolt 11 and the so-called reduced mass of the opening spring 12. In FIG. 2, the mass m _{A *} is a corresponding mass point shown, while the opening spring 12 is symbolized by its spring constant C12 and the anchor bolt 10 is only shown as a mass-free component. Correspondingly, the oscillating valve mass m _{V * is shown} as a mass point, the mass of the valve body 1 and the reduced mass of the closing spring 3 including the valve plate 4 also being taken into account here. The closing spring 3 is only indicated schematically by its spring constant C3, while the valve stem 2 is shown here as a mass-free component.

As indicated by the force arrow P, the excitation force P acts on the armature mass m _{A *} . The spring-mass system in Fig. 2 is shown in the closed position shown in Fig. 1. If one examines the system shown in FIG. 2 with the same valve clearance and with the same spring constants, but with different mass ratios, the result is a mass ratio m A * / m V * = 0.6 the curve 13 shown in FIG. 3 for the armature mass m _{A *} and the curve 14 for the valve mass m _{V *} . It can be seen that in the time from the detachment of the armature 9 from the pole face of the holding closing magnet until the free end of the armature bolt 10 strikes the end of the valve stem 2, the armature speed increases sharply, drops sharply on impact and swings back during this the valve mass moves with increasing speed in the opening direction (position I). Here, the valve clearance "opens" again, so that the armature mass m _{A *} again hits the valve mass m _{V *} (position II) after the movement reverses under the influence of the opening spring 12 (position II), in this case is braked again, the valve mass m _{V *} accelerates and itself swings back towards the pole face of the closing magnet 6. Since these opposing oscillation processes separate the entire system into two subsystems, namely one into the subsystems C12-m _{A *} and C3-m _{V *} , the subsystem C3-m _{V *} also performs its own movement, i.e. after the first acceleration ( Position I) the mass m _{V *} swings back by a small amount, but is then driven again in the opening direction when the anchor mass m _{A *} reappears (position II), as shown in the illustration in accordance with. Fig. 3 can be seen.

3 reveals that the overlapping, sometimes opposing, vibrations of the two partial masses m _{A *} and m _{V *} continue far beyond the apex. It should not be neglected here that the longitudinal elasticities of the anchor bolt 10 on the one hand and the valve stem 2 on the other also play a role, so that when selecting largely inelastic materials at least for the valve stem, such as ceramic materials, which may also be used for the anchor bolt can be used, these bouncing processes can be reduced.

In order to show the limit range, the mass distribution was extremely reversed for the same total mass. In the experiment shown in FIG. 4, the armature mass m _{A * was} significantly increased and the valve mass m _{V * was} significantly reduced, so that a mass ratio m _{A *} / m _{V *} of about 6 resulted, so the mass ratio compared to the experiment Fig. 3 enlarged 10 times. The result of this is that the correspondingly larger armature mass m _{A *} suffers only a slight loss of speed after overcoming the valve clearance when it strikes the stem of the valve body 1, as can be seen in curve 13.1, while the lighter valve body carried out significantly higher natural vibrations. It can be seen, however, that due to the "calming down" due to the larger anchor cup m _{A *} , the valve mass m _{V * also} comes to rest much sooner, which is not least due to the higher damping which is caused by higher friction on the valve body and braking influences of the gas flow can be attributed.

5, the curves 13 and 13.1 for the anchor speed are superimposed in both tests. It can be clearly seen here that by appropriately increasing the mass ratio m _{A *} / m _{V *,} the natural movements of the armature mass can be reduced, although depending on the resolution of the sensor used to detect the armature movement, it is not necessary to determine the mass ratio m _{A *} / m _{V *} to enlarge extremely.

If it is desirable to also detect the impact of the armature on the valve stem via the detection of the armature movement, then the ratio m _{A *} / m _{V * may} only be changed so far with a view to increasing the armature mass that the given sensitivity Sensor technology also the time of impact from the armature movement can still be detected, ie the mass ratio must be specifically changed so that a detectable first rebound of the armature mass m _{A *} takes place.

Using a schematic drawing acc. Fig. 6 becomes a Embodiment with "asymmetrical" spring design closer explained.

The modified electromagnetic actuator for actuation of a gas exchange valve 2 consists essentially of FIG. 1 again from a closing magnet 6 and an opening magnet 7, which are arranged at a distance from each other and between which an armature 9 against the force of return springs, namely an opening spring 12 and a closing spring 3 is guided to move back and forth. In the drawing it is Arrangement shown in the closed position in the "Classic" arrangement of the opening spring 12 and the closing spring 3. With this arrangement, the closing spring 3 acts directly via one connected to the stem of the gas exchange valve 2 Spring plate 4 a. The anchor bolt 10 of the electromagnetic Actuator is separated from the valve stem in the Usually there is a gap in the closed position in the form of so-called valve clearance VS available. The opening spring 12 is in turn based on a spring plate 11.1 on the spring bolt 11, so that in the opening movement under the opposing Effect of opening spring 12 and closing spring 3 of the spring bolt 11 on the shaft of the gas exchange valve supports.

The alternating energization of the electromagnets 6 and 7 of the Actuator takes place via a current regulator assigned to it 14.1, which corresponds to an electronic engine control 14 the specified control programs and depending from the operating data supplied to the engine control, such as Speed, temperature, etc. is controlled. So that will be Gas exchange valve specifically in its open position or its Closed position moves. While it's basically possible one for all actuators on a piston internal combustion engine central current controller, it may be appropriate if each actuator is assigned its own current regulator, connected to a central power supply 14.2 and which is controlled by the engine controller 14.

A sensor 15 is assigned to the actuator, which detects which enables actuator functions. The sensor 15 is here shown schematically. Depending on the design of the sensor For example, the path of the armature 5 can be detected that the respective armature position of the motor controller 14 and / or the current controller 14.1 can be transmitted. In the Motor control 14 or the current controller 14.1 can then corresponding arithmetic operations, if necessary, also the anchor speed be determined so that depending on the anchor position and / or depending on the anchor speed controlled the energization of the two electromagnets 6, 7 can be.

Will now stop after switching off the power supply Closing magnet 6 due to the force of the opening spring 12 the armature 5 moves in the direction of the gas exchange valve, so exercises the mass consisting of anchor 5 and guide rod 10, 11 after overcoming the valve clearance VS a bump on the still closed gas exchange valve before as a result of Force action of the opening spring and the magnetic force that is immediately applied of the opening magnet 7 then opens the gas exchange valve becomes. This shock turns the two return springs 3 and 12 and anchor 5, guide rod 10, 11 and Gas exchange valve formed spring-mass system to one that Opening movement superimposed resonance vibration.

To suppress this resonance vibration, are at otherwise unchanged structure for the return springs different Spring characteristics for the opening spring 12 and the closing spring 3 intended. In the embodiment shown here is, for example, the closing spring 3 "harder", d. H. it has a higher spring characteristic than the opening spring 12. Through this measure, the spring-mass system "out of tune" so that due to the impact of the anchor mass after overcoming the valve clearance VS that is forming Vibrations overlapping the opening movement during the Opening movement practically completely degrades because of the system the possibility of a vibration in the natural frequency the different spring design is taken. In the Drawing are the different spring characteristics of the two Return springs 3 and 12 with different line widths identified.

It is useful if the closing spring 3 has the higher spring characteristics has, d. H. so is harder to get one to ensure reliable closing of the gas exchange valve.

The principle of ^" detuning" the two return springs 3 and 12 can also be used by themselves with a normal design of the ratio of armature mass to valve body mass. However, the combination with an interpretation of the mass ratios according to this invention is advantageous.

Claims (4)

Gas exchange valve arrangement on a piston internal combustion engine with a valve body (1) connected to a closing spring (3) and with an electromagnetic actuator (5) which has two electromagnets (6, 7), the pole faces (8) of which are aligned with one another and arranged at a distance from one another and which has an armature (9) which is guided to and fro between the pole faces (8) and has guide bolts (10, 11) which are connected at one end to the valve body (1) and at the other end to an opening spring (12), wherein there is a valve clearance (VS) between the guide pin (10) and the valve body (1), and in which the oscillating mass (m _{A *} ) of the armature (5) is at least twice the oscillating mass (m _{V *} ) of the valve body (1). Gas exchange valve arrangement according to claim 1, characterized in that that the opening spring (12) and the closing spring (3) have the same spring constants and the same masses. Gas exchange valve arrangement according to claim 1 or 2, characterized in that the oscillating mass (m _{A *} ) of the armature (5) is only so much greater than the oscillating mass (m _{V *} ) of the valve body (1) that when the valve is opened the first Impact of the guide pin (10) on the valve body (1) can still be detected as a drop in speed. Gas exchange valve arrangement on a piston internal combustion engine, the one with a gas exchange valve (2) and two at a distance mutually arranged electromagnets (6, 7), between which an anchor (9) against the force of two return springs (3, 12) is guided to move back and forth, in particular Gas exchange valve arrangement according to claims 1 to 3, characterized characterized in that the two return springs (3, 12) have different spring characteristics.

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