WO2000070198A1

WO2000070198A1 - Method for operating an electromagnetic valve gear for actuating a gas exchange valve in a piston internal combustion engine

Info

Publication number: WO2000070198A1
Application number: PCT/EP2000/004464
Authority: WO
Inventors: Günter Schmitz; Christian Boie; Jürgen Hagen
Original assignee: Fev Motorentechnik Gmbh
Priority date: 1999-05-19
Filing date: 2000-05-17
Publication date: 2000-11-23
Also published as: EP1099044A1; DE10081312D2; JP2002544434A; DE19922969A1

Abstract

The invention relates to a method for operating an electromagnetic valve gear for actuating a gas exchange valve in a piston internal combustion engine. The supply of current to the valve gear is controlled by a motor. The method is characterised in that the control and adjustment parameters are continuously modified to suit the corresponding operating states of the piston internal combustion engine, by determining the respective actual state and/or by using performance characteristics which are stored in the motor control and/or by using continuous measurements. The corresponding current is thus supplied in such a way, that the armature of the electromagnetic valve gear impacts with the lowest possible speed.

Description

Description Method for operating an electromagnetic valve train for actuating a gas exchange valve on a piston internal combustion engine

description

The energization of an electromagnetic valve train for actuating a gas exchange valve on a piston internal combustion engine must be regulated in such a way that the impact speed of the armature is kept very low. With changing operating conditions (speed and especially load, temperature etc.) it is almost impossible to design a controller, since the settings of the controller parameters have to be changed depending on the respective operating state.

Another problem with the electromagnetic valve train is that, due to the sticking times of the armature on the pole face, it is not possible to set arbitrarily short control times.

For an electromagnetic actuator for actuating a gas exchange valve on a piston internal combustion engine, which has an armature which is operatively connected to the gas exchange valve and which is guided back and forth between the two electromagnets against the force of at least one return spring, the energization of which is controlled by a motor control. It is provided as a method according to the invention to solve these problems that a continuous adaptation of the control and / or regulating parameters to the respective operating states of the piston internal combustion engine by recording the respective actual conditions and / or via stored characteristic maps in the engine control and / or ongoing measurements are carried out and that the current is supplied in such a way that the armature of the electromagnetic valve drive strikes at the lowest possible speed. According to the method according to the invention, the controller parameters, such as the P component of a PID controller, are set depending on the operating state. At least one piece of information from the engine control system about the current operating state is used for this. This information can either be transmitted directly to the controller in the form of load information, speed information or the like, which then adjusts its parameters accordingly. Or the respective controller parameters for the current operating status are stored in the engine control, for example in the form of a map, and are transmitted to the controller.

Certain data can also be determined in the controller unit itself. For example, information on the sensor value (travel signal) in the end position, that is to say when the armature is present, can be determined from the travel signal of at least one of the preceding switching cycles. This enables self-calibration. It is also possible to determine an asymmetrical parameterization of the controller for opening and closing from the determination of the rest position of the armature if the rest position of the armature is not exactly in the middle between the two pole faces. This saves an exact adjustment of the middle position. This is important for a reduction in service intervals.

It can also be adapted to different valve clearance. The valve clearance is recorded by means of a measurement, or a required parameter variation is derived from the findings of the previous work cycles.

The "knowledge" of the controller can also be used to control the detachment process ie the start of the armature / valve movement. So far, different waste delay times (T ^ times) have been accepted or attempts have been made to compensate for them through specifications from the engine control. Such different "sticking" times are, on the one hand, a consequence of back pressure fluctuations caused by the cyclical fluctuations gen of the internal combustion engine or different load conditions. On the other hand, they also depend on the magnetic conditions of the actuator and are therefore dependent on the type variation. It may also be necessary to change the current switch-off time depending on the expected flight time. The control unit can determine all these influences by observation and compensate accordingly in the next cycle by correcting the switch-off time.

By observing the waste delay time, for example in the event of the outlet opening event, it is possible to draw conclusions about the current cylinder counterpressure and to draw conclusions about cyclical fluctuations from this. The possibility of such an observation can be supported by the current being switched off by the make coil so early that the valve is still held in the closed position by the exhaust gas back pressure. It is possible, also taking into account the valve clearance, then by measuring the voltage curve when detaching or simply by detecting the time of detachment and from the piston position (crank angle) available at this point in time to determine the pressure curve and its change compared to the previous cycles.

The transfer of parameters to the controller described at the beginning results in better controllability of the entire piston internal combustion engine in addition to the advantage mentioned above. For this purpose, the controller from the engine control system is informed of the need, small valve opening times (small

Load at high speed). So that a correspondingly small valve opening time is not prevented by an excessively long adhesive time, the controller is controlled so that the armature is not pulled up to the pole face, but rather "floats" shortly before it. From this state, the closing movement can be initiated without delay be reduced or switched off by the current flow through the opening coil.

Various types of influences to be taken into account when adapting parameters can be given as examples: namely, on the one hand, rapidly changing influences, such as the counterpressure when the valve is opened, which fluctuates cyclically. Furthermore, medium-fast influences, such as temperature changes, coil resistance, friction, valve clearance, sensor offset (for example, a drift of the sensor due to temperature influences, mechanical influences). Finally, long-term changes (middle position = rest position of the armature, stroke, valve mass, friction)

In the long-term parameters, of course, no quick adjustments to the model may be made, since correspondingly quick changes cannot occur and it must therefore be an artifact. Even in the case of medium-fast changes, the speed of adaptation to the newly determined values must be limited. This can be done by averaging (e.g. moving averaging) or low-pass filtering. A plausibility check must also be carried out. If a determined model parameter lies outside a reasonable range, or would show a change that was too strong compared to the previous one, the newly determined value is discarded.

Should a valve "fail", i.e. If the current setting of the model parameters does not arrive at the anchor, an uncritical basic setting for the model parameters is selected for the "restart" of the valve, in which case the impact speed may be greater, but the operational safety is then guaranteed again.

Such an uncritical basic setting can also be made after a component replacement or another workshop intervention. Even when starting the engine, it makes sense to take some of the parameters (medium-term) from an uncritical basic setting.

The invention is explained in more detail with reference to schematic drawings. Show it:

1 shows an electromagnetic actuator with gas exchange valves, an idealized stroke curve as a function of time,

Fig. 2 shows an idealized course of

Stroke in the form of a voltage signal,

Fig. 3 shows an idealized course of

Stroke as a function of time,

4 shows an idealized course of the speed as a function of the path,

5 shows a realistic course of the path as a function of time,

6 shows a realistic course of the speed as a function of the path,

7 shows a complete stroke curve for a normal opening and closing movement of a gas exchange valve,

8 shows a stroke course for a so-called free flight,

Fig. 9 shows a stroke course with holding the armature in the floating position. To explain the invention, a schematic drawing in FIG. 1 shows an electromagnetic actuator that can be controlled via a motor control for actuating a gas exchange valve.

An electromagnetic actuator 1 for actuating a gas exchange valve 2 consists essentially of a closing magnet 3 and an opening magnet 4, which are arranged at a distance from one another and between which an armature 5 back and forth against the force of return springs, namely an opening spring 7 and a closing spring 8 is movably guided. In the drawing the arrangement is shown in the closed position, specifically in the "classic" arrangement of the opening spring and the closing spring. In this arrangement, the closing spring 8 acts directly via a spring plate 2.2 connected to the shaft 2.1 of the gas exchange valve 2. The guide rod 11 of the electromagnetic actuator is separated from the shaft 2.1, usually a gap in the form of the so-called valve clearance VS is present here in the closed position. The opening spring 7 is in turn supported on a spring plate 11.1 on the guide rod 11, so that the guide rod 11 is supported on the shaft 2.1 of the gas exchange valve 2 in the central position under the opposing effect of the opening spring 7 and the closing spring 8.

It is also possible to provide only a single restoring spring at the location of the opening spring 7, which is designed such that it builds up a corresponding restoring force each time the armature 5 swings over the central position. A separate closing spring 8 is therefore not required. In such an arrangement, however, the guide rod 11 must be connected to the shaft 2.1 of the gas exchange valve via a corresponding coupling element which transmits the reciprocating movement of the armature to the gas exchange valve 2 in the same way.

The closing spring 8 and the opening spring 7 are now generally designed so that in the rest position, ie when not in use. flowed electromagnets the armature 5 is in the central position between the two pole faces. From this central position, the electromagnetic actuator 2 with its gas exchange valve 2 must then be started in accordance with the above-described method for starting up the associated piston internal combustion engine.

The electromagnets 3 and 4 of the actuator 1 are controlled via an electronic motor control 9 in accordance with the specified control programs and depending on the operating data supplied to the motor control, such as speed, temperature, etc.

A sensor 10 is assigned to the actuator 1, which enables the actuator functions to be recorded. The sensor 10 is shown schematically here. Depending on the design of the sensor, the path of the armature 5 can be detected, for example, so that the respective armature position can be transmitted to the motor controller 9. The armature speed can then optionally also be determined in the motor controller 9 by means of corresponding arithmetic operations, so that the energization of the two electromagnets 3, 4 can be controlled as a function of the armature position and / or as a function of the armature speed.

The sensor 10 does not necessarily have to be assigned to the armature 5 laterally, as shown, but it is also possible to arrange corresponding sensors in the region of the pole face of the respective electromagnet or, as with the sensor 10.1, one with the armature 5 in connection to assign standing push rod 11.1.

As already explained above, the sensor 10 shown in the schematic drawing is not shown in its geometric position. The sensor 10 is part of the overall sensor system of the engine control. The motor controller 9 also has corresponding means for detecting the current and the voltage for the respective electromagnet 3 and 4 and for changing the current profile and the voltage profile. The actuator 1 of the gas exchange valve 2 can then be controlled in a fully variable manner as a function of predefinable operating programs, possibly based on corresponding characteristic maps, for example with regard to the start and end of the opening times. Controls regarding the amount of the opening stroke or the number of opening strokes during a closing time can also be controlled.

Taking the exhaust gas back pressure into account when actuating the gas outlet valve is briefly explained as an example of a quick parameter adaptation:

From the first part of a path course or a speed course over the time of the valve movement and / or the armature movement, it can be estimated how large the counter pressure is. For example, the speed can be compared with a preset value after a certain time. If, for example, the speed is lower than the specified value of a low load point, the corresponding back pressure parameters can be determined from the quotient of the specified value to the measured value using a table. Instead, a table that is filled differently can naturally also receive the difference as an input variable.

Such an estimation of the parameters that change from cycle to cycle makes it possible to use sensors that are partially "blind". 2 shows, for example, the course of the voltage as a sensor signal of a GMR (Giant Magnetic Resistance) sensor, which due to its directional dependence on the magnetic field in the respective end areas of the valve lift (here approx. 0-2mm and 6-8mm) a high Has path sensitivity, but practically none in the middle.

At the start of the movement, the influence of back pressure is determined from the behavior of the armature on the first path. While the sensor does not provide a usable signal, the model of an observer, who is now fed with the information about the estimated gas counter-pressure influence, can estimate the further course of the armature quite accurately and thus provide the controller with very good information about the current course of the path. If the armature then comes into the area of the other end position, the sensor signal again gives very precise information, so that an arrival at a low speed can then be achieved with this additional information.

The parameters that are influenced by the back pressure can be compared and corrected if necessary when using multiple outlet valves. Methods such as averaging or, depending on the version, maximum averaging (for the greatest possible reliability) are possible. If the exhaust valves are not actuated at the same time, the information of the earlier opening valve can already be used for the later opening valve.

The "self-learning ability" of neural networks can also be used to adapt the parameters. In this case, either all parameters or only a part can be adapted; the entire model formation can even be implemented using a neural network.

Fuzzy-based controllers or fuzzy-based algorithms can also be used to adapt the parameters. A corresponding partial or complete implementation in fuzzy technology can also be carried out here

Another way to achieve a smooth impact of the valve and armature in the presence of valve clearance The regulation to a constant low speed is in the range of the expected valve attachment. It is then not necessary to know the exact value of the valve clearance.

3 and 4 show the idealized course of path and speed as a function of time and path. 3 shows the path beginning at "A" and ending at "E", which initially runs according to the usual cosine curve, and then assumes a linear course when approaching the end position. Linear course means constant speed. This can be seen in the representation of the course of the speed in FIG. 4. Here the speed is plotted over the path starting at "A" and ending at "E". With such a

Regardless of whether the valve is placed 0.1mm or, for example, 0.3mm before the armature is attached, the speed of impact is very low.

A realistic course is shown in FIGS. 5 and 6. Even with a non-optimized controller you can see that the speed remains below about 0.2m / s and sometimes also becomes significantly lower.

It can be seen in all of these pictures that a "long creep" in the last phase of the movement results in a relatively long movement process. This would be rather annoying at high speeds. However, it is not a matter of such low landing speeds because the rest of the engine noise is already dominant there. For this reason, it makes sense to adapt the control parameters required for this "creeping" control intervention to the operating point, so that faster closing is ensured at high speeds. 7, 8 and 9 show a comparison of conventional valve lifts (FIGS. 7 and 8) for a valve lift in a control according to the method according to the invention (FIG. 9).

FIG. 7 shows a "normal" opening and closing movement of a gas exchange valve, in which the armature comes into contact alternately with the associated pole face of the two electromagnets and is held there for a period of time which can be predetermined by the engine control. If the energization of the electromagnet 3 held in the flow position of the armature 5 is switched off, as shown in FIG. 1, then the armature disengages from the pole face of the electromagnet 3 at time t _λ and moves in the direction of the force of the return spring 7 the pole face of the capturing electromagnet 4. This is energized accordingly, so that the armature 5 comes to rest on the pole face of the now capturing electromagnet 4 at time t ₂ . At time t ₃ , the current supply to the electromagnet 4 is switched off, so that at time t ₄ and the corresponding current supply to the electromagnet 3, the armature 5 again reaches the closed position on the electromagnet 3.

8 shows a control for a so-called "free flight". The armature 5 abuts the closing magnet 3, for example. If the closing magnet 3 is de-energized at time t _x , the armature 5 moves in the opening direction. If the opening magnet 4 is not energized, the armature 5 reverses its movement in the direction of the closing magnet 3 under the action of the closing spring 8 and can be caught again at time t ₅ if the current is applied appropriately. This results in a reduced opening stroke.

In order to minimize or even switch off the adhesive time of the armature 5 on the closing magnet 3 for the opening process, the method according to the invention, as described at the beginning, consists of a corresponding parameterization of the current operating data the possibility to energize the "holding" magnet in such a way that the armature 5 does not come to rest on the pole face on its way to the opening position but "hovers" just before it for the duration of the opening time from t ₂ to t ₃ . Thus, the closing process can be initiated practically without delay by switching off the current supply, so that the valve reaches its closed position again at time t ₄ . This process is shown in Fig. 9.

In a lean operation, which is caused by a leaner fuel supply or an increase in the residual gas content, cyclical fluctuations can occur in the combustion process if the leanness is excessive or the residual gas content is too high. These cyclical fluctuations can no longer be tolerated above a certain level of around 0.1 bar indicated mean pressure, because on the one hand the driver feels the uneven running of the piston internal combustion engine and on the other hand the emissions increase. The presence of cyclical fluctuations can be recognized from the changes in the gas back pressure. The opening time of the gas outlet valve varies depending on the exhaust gas back pressure, because the time of the equilibrium of forces between the decreasing magnetic force and the spring force is influenced by the exhaust gas back pressure that acts on the valve disk. The detection of the fluctuation in the time at which the armature is released and / or the start of movement of the valve when the gas outlet valve is opened now provides the possibility of intervening in a regulating manner via the engine control. If the uneven running is too great, there is too much uncertainty with regard to the required magnetic current due to the exhaust gas back pressures changing too quickly from cycle to cycle. With this measure, the above-described disadvantageous influence is to be avoided when adapting to the regulation and / or control parameter "engine load".

Claims

Expectations

1. Method for operating an electromagnetic actuator for actuating a gas exchange valve on a piston internal combustion engine, which has an armature which is operatively connected to the gas exchange valve and which is guided back and forth between the two electromagnets against the force of at least one return spring, the energization of which is carried out via a Engine control is controlled, characterized in that a continuous adaptation of the control and / or regulating parameters to the respective operating states of the piston internal combustion engine takes place via detection of the respective actual conditions and / or via stored characteristic maps in the engine control and / or via ongoing measurements, and that from this the energization takes place in such a way that the armature of the electromagnetic valve drive strikes at the lowest possible speed.

2. The method according to claim 1, characterized in that the adjustment of the control and / or regulating parameters takes place as a function of the engine load.

3. The method according to claim 1 or 3, characterized in that the adjustment of the control and / or regulating parameters takes place as a function of the engine speed.

4. The method according to any one of claims 1 to 3, characterized in that the acquisition of parameters from previous operating cycles is taken into account when adapting the control and / or regulating parameters.

5. The method according to any one of claims 1 to 4, characterized in that fluctuations in the detachment time of the armature and / or the start of movement of the valve during the opening process of the gas outlet valve are detected and the engine control affects the operating state of the piston internal combustion engine.