Abstract:
The invention relates to a method and to a device for opening and closing a valve of an internal combustion engine. The aim of the invention is to reduce the energy required for opening and closing a valve of an internal combustion engine, especially one that is provided with an electromagnetic valve control. To this end, the kinetic energy of the valve is transferred to a mass and temporarily stored in a mass.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Applicants claim priority under 35 U.S.C. §119 of German Application No. 199 19 734.2 filed Apr. 30, 1999. Applicants also claim priority under 35 U.S.C. §120 of PCT/EP00/02996 filed Apr. 5, 2000. The international application under PCT article 21(2) was not published in English. 
    
    
     The invention relates to a method and to a device for opening and closing a valve of an internal combustion engine. 
     Known are the camshaft-controlled valve actuation, the electromagnetic control and the hydraulic valve control. The invention is principally based on the electromagnetic valve control (EMVC). However, it can be applied in connection with other valve controls as well, for example such as the hydraulic or the pneumatic valve control. 
     The EMVC has been structured until now in the form of an oscillator comprising one mass, whereby an armature is oscillating back and forth between two magnetic coils. The armature is connected with the valve. In the currentless condition, the armature is located in about the center between the two magnetic coils. Because of the large gap in the idle position and the poor efficiency connected therewith, a relatively high expenditure of energy is required during acceleration, which per se makes the feasibility of the electromagnetic valve control questionable in series applications, to begin with. 
     For reducing the energy requirement and in particular for the purpose of minimizing the so-called armature thumping and thus the noise, DE 197 23 405 A1 discloses a method by which a defined rate of impact of the armature can be adjusted when the valve is closing. 
     A drawback has to be seen in the fact that valve niches have to be worked into the piston in order to safely prevent the valve from coming into contact with the piston, or that the wall of the combustion chamber has to be recessed in the cylinder head. In terms of combustion technology, such measures represent a negative influence on the combustion chamber. 
     Therefore, the invention is dealing with the problem of reducing the use of energy in connection with electromagnetic or hydraulic valve controls and to avoid any negative influence on the combustion process exerted on the cylinder head by valve niches or recessed walls of the combustion chamber. 
     SUMMARY OF THE INVENTION 
     Said problem is solved in connection with methods of the type specified above by the characterizing features specified in claim  1 . In conjunction with devices of the type specified above, the problem is solved by the characterizing features specified in claim  4  or  5 . Advantageous further developments of the invention are the objects of the dependent claims. 
     The basic idea of the invention is to transmit the kinetic energy, and possibly of a mass component connected with the valve, such energy being contained in the valve at the end of the closing process, to a body of mass, and to store such energy there intermediately, so that this energy is available for the next opening stroke of the valve. In such a process, the pulse or mechanical pulse can be transmitted in each case directly between the bodies of mass, or passed on via at least one intermediate member, whereby the intermediate member is either arranged stationary to the greatest possible extent, or connected with one of the two masses. If the body of mass is to be retained, for example, by a magnet, the energy is intermediately stored in a spring, as a rule that exerts a resetting force on the body of mass. 
     Physically speaking, the known EMVC represents a pendulum comprising one mass, whereas the invention can be described as a pendulum comprising two masses with energy transmission. 
     The known one-mass oscillation of the EMVC is divided in this connection in two semi-oscillations with two masses. At the end of each semi-oscillation, the kinetic energy is transferred to the second oscillating mass by a shock pulse. Through suitable coordination, for example via the spring rate, the basic duration of the oscillation of the valve is adjusted at the ratio of “three cycles closed” to “one cycle opened”. 
     Therefore, a variation of the oscillation times can be realized by adjusting the initial tension of the spring and/or the stiffness of the spring, on the one hand, and with the help of known means such as magnetic retention in the end positions on the other. 
     The following advantages are obtained as compared to the known EMVC: 
     The valve remains closed without external energy feed because the energetic zero-position is present in the closed condition. If necessary, the valve can be pressed also into the valve seat by spring force. 
     Undefined operating points are avoided because a clear idle position is available in the cycle of the valve movement. 
     The swing-in takes place in a controlled manner; contact of the valve with the piston can be excluded. This means that the combustion chamber can be designed in an optimal manner, especially without valve niches. 
     Due to the pulse-like transmission it is possible to realize very steep opening flanks, or very rapid opening of the valve is made possible. 
     The valve opening duration can be varied without changing the initial tension of the spring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in the following with the help of an exemplified embodiment shown in the drawing, in which: 
     FIG. 1 shows a device as defined by the invention for actuating a valve in the idle position. 
     FIG. 2 shows a flow diagram of a method as defined by the invention. 
    
    
     In FIG. 1, the system is shown in the idle condition. 
     DETAILED DESCRIPTION 
     A valve  1  and a mass  1 ′ connected with the valve by a thread, as well as a mass  2  are capable of exchanging their kinetic energy or their pulse via an intermediate member  3  that is connected with the mass  2  (m 2 ) in a fixed manner. 
     For limiting the movement of the mass  1 ′ or of the valve  1  connected with the mass  1 ′, provision is made for a stop  5  for the valve seat ring  4  with the cylinder head not shown, and for the mass  2 . The position of the stop  5  is fixed or adjustable in such a manner that the valve can be closed under all operating conditions. The initial tensional force of the spring  6  is adjusted with the help of the adjustable support  8  in such a way that it is greater than the force of the spring  7  with the support  9  in order to assure that the valve is safety closed in the idle position. The masses  1 ′ (ml) and  2  (m 2 ) are accelerated, delayed, and retained in the end positions by means of the electromagnets  10  (M 1 ) and  11  (M 2 ). 
     As compared to known electromagnetic actuators for valve controls, no connection exits between the valve  1  and the actuating member for the valve, thus the mass m 2 ; the two elements are separated from each other, with the separation being located as shown in FIG. 1 between the start of the thread of the valve and the intermediate member  3 . 
     FIG. 2 shows a possible sequence of the method as defined by the invention, which has to be read in association with FIG.  1 . 
     Plotted above the time axis t in the upper area are the switch-on times of the electromagnets M 1  and M 2 , and in the lower area the deflections Sm 1  and Sm 2  of the masses m 1  and m 2  caused by the electromagnets. 
     At the t 0 , the magnet M 2  is supplied with current and moves the mass m 2  with acceleration until time t 1  against the force of the spring  7  in the direction of the retaining position (area A). 
     At time t 1 , the delay of the mass m 2  starts, and then ends at t 2  when the mass m 2  has reached the retaining position. Starting at time t 2 , the magnet M 2  retains the mass m 2  until time t 3  (area B). 
     At time t 3 , the mass m 2  is released and, accelerated by the spring  7 , starts the return movement until the transfer point of the energy from m 2  to m 1  at time t 4 . After the energy has been transferred, the pulse of the mass m 2  is almost 0 and the mass m 1  has taken over the pulse of the mass m 2  to the greatest possible extent. 
     The mass m 1  accelerates starting at t 4  and is moved within the time span t 5 , until t 6  (area C) in to the valve opening direction by supplying current to the magnet M 1 . At the same time, the mass m 2  moves by means of spring force into the idle position on the stop  5 , passing in the process through the idle path s. Said movement may takes place in a delayed manner with the help of a damping element. 
     The mass m 1  is retarded during the time span from t 6  until t 7 . 
     The time during which the valve is completely opened (area D) is disposed between t 7  and t 8 , during which time the magnet M 1  retains the valve in the open position. 
     At time t 8 , m 1  is released, the valve closing movement starts, and the kinetic energy is transferred from m 1  to m 2  at time t 9 . 
     The mass m 2  accelerates and is moved in the direction of the retaining position by supplying M 2  with current during the time span E, and fixed in the retaining position by supplying M 2  with current during the time span F. 
     At the same time, starting at t 9 , the mass m 1  starts to move by the force of the spring  6  and moves into its idle position, in which the valve is closed, passing in the process through the idle path s. 
     The feed is current to the magnets M 1  and M 2  thus is interrupted in each case shortly before the deflected position of the associated masses has been reached (time spans t 1  until t 2 , t 6  until t 7 , and t 10  until t 11 ), in order to prevent the associated stops from being impacted excessively hard. 
     From t 0  until t 4 , the valve rests against the valve seat; from t 4  until t 10 , the valve is completely or partially opened. 
     The maximum consumption of electrical power of the electromagnets can be substantially reduced by the valve control as defined by the invention because within the range of large gaps between the magnet and the component attracted by the magnet, re-application of the kinetic energy saves a major portion of the electrical energy required otherwise.