Abstract:
A device for controlling an electromechanical regulator, including a controller ( 3   a ) that controls the current through a coil ( 113 ) and which, for that purpose, generates control signals for a power regulator ( 5   a ). The control signals are determined with the coil ( 113 ) operating in the free-running operating state. The control signals depend, during the movement of the armature, on the current and the time differential of the current through the coil ( 113 ).

Description:
FIELD OF THE INVENTION 
     The invention concerns a device for controlling an electromechanical regulator provided in particular for controlling an internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     A known regulator (DE 195 26 683 A1) has an actuator designed as a gas shuttle valve and an actuating drive. The actuating drive has two electromagnets, between which an armature plate can be moved against the force of a return mechanism by switching off the coil current on the holding electromagnet and switching on the coil current on the capturing electromagnet. The coil current of the capturing electromagnet is kept constant by a preset capture value for a preset length of time and is then adjusted to a holding value by a two-position hysteresis controller. 
     Increasingly strict legal limits on the noise levels produced by a motor vehicle and demands for a quiet running internal combustion engine require that minimal noise be produced by the regulator for useful mass production. The regulator must also be guaranteed to be long lasting for useful mass production. 
     BRIEF SUMMARY OF THE INVENTION 
     It is the task of this invention to create a device for controlling an electromechanical regulator which minimizes the noise produced when an armature plate contacts an electromagnet and also guarantees that the regulator will last a long time. 
     This problem is solved by the features of claim 1. Advantageous configurations of the invention are found in the subclaims. 
     In a coil through which a current flows and with which a moving plate of the armature is associated, there is, with an unsaturated magnetic circuit and a negligible stray flux, a clear connection between current I through the coil, the time differential of current dI/dt, air gap length l and velocity v of the armature. In the case of dominating magnetic resistance of the air gap to the remaining magnetic circuit, the following relationship can be found:                     I          t       =     -     [         2                   P     v   ,     e                 1            l         AIN   2          μ   o         +     Iv   l       ]               (G1)                                
     in which: 
     A is the bearing surface of the core of the electromagnet on which the armature plate is seated, 
     N is the number of windings in the coil, 
     P v,el  is the dissipated electrical power, and 
     μ 0  is the air permeability. 
     The invention is based on the recognition that the first summand of relationship (G 1 ) is negligible compared with the second summands of equation (G 1 ) if the ratio of dissipated electrical power P v,el  and current I is low. The ratio of dissipated electrical power P v,el  and current I is almost zero when the coil is operated in the free-running operating state. Thus, in this case, the relationship                  I   .     I     =     -     v   l               (G2)                                
     results roughly from relationship (G 1 ). 
     Thus gentle impact with v approximately zero can be achieved as a function of the time differential of current dI/dt and current I through the coil with air gap length  1  at zero without a position sensor having to be provided to detect the present position of the armature in each case. Long life is guaranteed since the regulator is only lightly mechanically stressed due to the soft impact of the armature plate on the core. 
     The control signals of the controller are determined with the coil in the free-running operating state. In the free-running operating state, the coil is short-circuited via a free-running circuit of the power regulator. In the free running state, the current I through the coil can be detected almost without loss. Thus the approximation of relationship (G 1 ) given by relationship (G 2 ) is highly accurate. 
     When there is a deviation from the desired relationship of the time differential of current dI/dt and current I through the coil in the free run, depending on the polarity sign of the deviation, electrical energy is preferably supplied to the actuator coil or removed from the actuator coil for a limited time. The free-running operation is stopped and the coil is applied to the distribution voltage (energy supply) or the stored energy is drained from the distribution voltage (energy drain). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Examples of embodiment of the invention arc illustrated in more detail by means of the schematic diagrams: 
     FIG. 1 shows a regulator arrangement in an internal combustion engine, 
     FIG. 2 shows a block diagram of a controller in the control device and an attached power element, 
     FIG. 3 shows a flow chart of a program that is run by a logic unit of the controller, 
     FIG. 4 shows a second embodiment of the controller, 
     FIG. 5 shows a block diagram of the logic unit of the controller in FIG. 4, 
     FIGS. 6 a  through  6   c  show signals of current I through the coil, position X of the coil and velocity V of the armature plate plotted over time t. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Elements of the same construction and function are provided with the same reference numbers from figure to figure. 
     Regulator  1  (FIG. 1) comprises actuating drive  11  and actuator  12  which is designed, for example, as a gas shuttle valve and has shaft  121  and a disk. Actuating drive  11  has housing  111  in which first and second electromagnets are arranged. The first electromagnet has core  112  into which coil  113  is embedded in a ring-shaped groove. 
     The second electromagnet has  114  into which coil  115  is embedded in another ring-shaped groove. An armature is provided with armature plate  116  being arranged in housing  111  to be moved between core  112  and core  114 . The armature also comprises armature shaft  117  that is guided by recesses in the first and second cores and which can be mechanically coupled with shaft  121  of the valve. Spring  115   a  and spring  115   b  pretension armature plate  116  to preset rest position R. 
     Regulator  1  is rigidly connected to cylinder head  21 . Intake channel  22  and cylinder  23  with piston  24  are attached to cylinder head  21 . Piston  24  is coupled with a crankshaft via connecting rod  25 . Master controller  3  is provided which receives signals from sensors and generates adjustment signals depending on which coil  113  and coil  115  of regulator  1  are driven by power regulator  5   a  and power regulator  5   b . The sensors are designed as current meter  4   a  which detects current through coil  113  or current in the power regulator  5   a , or as current meter  4   a  which detects current through coil  115  or in power regulator  5   b . There may be other sensors in addition to the sensors mentioned. 
     FIG. 2 shows the part of master controller  3  relevant to understanding the invention. Controller  3   a  is provided which generates adjustment signals for power regulator  5   a  as a function of current I through coil  113  as measured by current meter  4   a.    
     Current I is differentiated in differentiator  31 . The ratio of the time differential dI/dt of current I and current I is ascertained in divider  32 . Comparator  33  is provided the input of which is a preset threshold value SW 1  and the output of divider  32 . Output signal KS of comparator  33  is at high level H if the preset threshold value SW 1  is lower than the output of divider  32 . Otherwise, the output signal of the comparator  33  is at a low level. 
     Logic unit  34  is provided which generates the adjustment signals for power regulator  5   a  as a function of the comparator  33  output signal KS, oscillator  35  timing signal TS and other operating parameters. The construction of logic unit  34  is further illustrated below in FIG.  3 . 
     Power regulator  5   a  has transistor T 1 , the gate connection of which is electrically connected to one output of logic unit  34 . Power regulator  5   a  has a second transistor T 2 , the gate connection of which is electrically connected to logic unit  34 . Diode D 1  and a second diode D 2  are provided. Resistor R is also located between the source output of transistor T 2  and the reference potential. Resistor R acts as a multiplier for current meter  4   a.    
     If the high level H is applied at the gate connection of transistor T 1 , the transistor conducts from the drain to the source. If high-level H is also applied to transistor T 2  at the gate side connection, transistor T 2  also conducts. The distribution voltage U v  then drops at the second coil reduced by the voltage drop at resistor R. Current I through the coil then rises. 
     If a low level is then preset at the gate side connection of transistor T 1 , transistor T 1  does not conduct and diode D 2  becomes conductive in the free-running state. The voltage drop at coil  113  is then given by the conducting-state voltage of diode D 2  and transistor T 2  and the voltage drop at resistor R (total of two volts for example). Current I through coil  113  then decreases. 
     If both the levels at the gate side connection of transistors T 1  and T 2  are switched from high to low, then both diode D 1  and diode D 2  become conductive and the current through the first coil is very rapidly decreased—so that decommutation occurs. Power regulator  5   b  is therefore designed analogously to power regulator  5   a.    
     FIG. 3 shows a flow chart of a program as run in logic unit  34 . It does not matter whether the program is hard-wired in or is run by a micro-controller. 
     The program is started in step S 1 . In step S 2 , the constant current through the coil is set, i.e., the current is set to an initial capture value for a preset first time delay TD 1 . A two-position hysteresis controller is provided for this purpose. 
     In step S 4 , transistor T 1  is switched off and transistor T 2  is switched on and the coil is thus operated in the free-running operating state. In step S 5 , there is a delay for a preset second time delay TD 2 . In step  6 , there is a check to see if current I through coil  113  has fallen below a minimum limit current I grenz  in the free-running operating state. If such is not the case, a check is performed in step S 7  to see whether control signal KS from the first comparator  33  is at level H. If this is the case, the armature is too fast and transistors T 1  and T 2  are switched off in step S 8 , i.e., set to “off” and energy is therefore drained. If the condition of step S 7  is not met, the armature is too slow and transistors T 1  and T 2  are switched on in step S 9 , i.e., set to “on” and energy is therefore supplied. In step S 9 , there is a preset third time delay TD 3  and in step S 10  a preset fourth time delay TD 4 . During the delay in steps S 9  and S 10 , the drive of transistors T 1  and T 2  remains unchanged. The program then resumes in step S 4 . 
     If, in step S 6 , the current through the coil is less than the minimum limit current I grenz , the current is adjusted to an increased holding current in steps S 11  and S 12  for a preset fifth time delay TD 5 . This ensures safer capturing of the armature. In step S 13 , the current through the coil is then set to a lower holding current. 
     The program ends in step S 14 . 
     FIG. 4 shows a second embodiment of controller  3   a . Unlike the embodiment in FIG. 2, a second comparator  36  is provided, the output signal of which depends on preset second threshold value SW 2  and the output of divider  32 . A version of logic unit  34  adapted to this embodiment is illustrated in FIG.  5 . 
     D flip-flop  341  generates its output signal at the Q output as a function of oscillator  35  timing signal TS and the output signal of comparator  33 . Another D flip-flop  342  is provided, the output signal of which at its Q output depends on oscillator  35  timing signal TS and the output signal of the second comparator  36 . The input of NOT gate  343  is electrically connected to oscillator  35  and its output is electrically connected to one input of AND gate  344 . The second input to AND gate  344  is electrically connected to the output of D flip-flop  342 . 
     The output of D flip-flop  341  is electrically connected to the input of a second NOT gate  345 . The output of NOT gate  345  is also connected, like oscillator  35 , to OR gate  346 . The outputs of AND gate  344  and OR gate  346  are led to the gate of transistor T 1  and transistor T 2  respectively. Optionally, a driver may also be located between the outputs of AND gate  344  and OR gate  346  to the gate of transistor T 1  and transistor T 2  respectively. 
     Due to the design of logic unit  34  in FIG. 5, the power regulator is always operated in the free-running operating state when the level of timing signal TS is high. If timing signal TS is at the low level, there is a three-position adjustment, i.e., either transistor T 1  is switched off and transistor T 2  is switched on, i.e., free-running operation, or both transistors are in the conducting mode, i.e., energy supply, or both transistors are not conducting, i.e., energy drain. 
     Instead of threshold values SW 1  and SW 1 , only one threshold value may also be preset, and, in addition, a preset value may be added or subtracted at the pertinent inputs of the first comparators  33  and  36  respectively. 
     In FIG. 6 a , the current through coil  113  is plotted over time t. In FIG. 6 b , position X of armature plate  116  is plotted over time t. In FIG. 6 c , velocity v of armature plate  116  is plotted over time t. At time t 0A , armature plate  116  begins to move from its open position O, i.e., its contact with the second electromagnet, toward its closed position C, i.e., contact with the first electromagnet. Initial capture value I-F 1  for the current through the first coil  113  is preset. 
     The current through coil  113  is adjusted for preset time delay TD 1  (e.g., 2 milliseconds) from the initial capture value I-F 1 . After time to, the current through coil  113  is adjusted by controller  3   a.    
     From time t 0B  to time t 1 , coil  113  is operated in the free-running operating state. The current through coil  113  is measured and the time differential of the current is determined. At time t 1 , the relationship of the time differential dI/dt determined in the free-running state and current I is greater than the preset threshold value SW 1 . Accordingly, both transistor T 1  and transistor T 2  are switched off and the current drops sharply. 
     After time t 2 , coil  113  is again operated in the free-running operating state and current I and its differential dI/dt are determined. At time t 3 , the relationship of the time differential of current I determined in the free-running state and the current is smaller than the preset threshold value SW 1 . Both transistors T 1  and T 2  are switched on and the current through the coil increases until time t 4 . 
     From time t 4  to time t 5 , the coil is again operated in the free-running operating state. From time t 5  to time t 6 , transistors T 1  and T 2  are both switched off, and decommutation therefore occurs again. From time t 6  to time t 7 , the coil is again operated in the free-running state. From time t 7  to time t 8 , transistors T 1  and T 2  are both switched on to conduct and the current rises until time t 8 . From time t 8  to time t 9 , decommutation again occurs. From time t 10  to time t 11 , the coil is operated in the free-running operating state. At time t 11 , current I through the coil in the free-running state becomes lower than a limit value of the current through the coil in the free-running state. The limit value is the value of the current in the free-running state as determined by testing at which the armature plate reaches the first coil. The limit value may be a firmly preset value or may be determined from a characteristic diagram depending on operating parameters. 
     From time t 11  to time t 12 , an increased holding value I-H is preset at a nominal value of the current through the coil and adjusted by the controller (not shown). This ensures a more reliable capturing of the armature plate and softens the impact of the armature plate. 
     This increased holding value is preferably preset for a predetermined length of time until the current through the coil is adjusted by the controller (not shown) to holding value I-H from time t 12  to time t 13 . 
     It can be clearly seen from velocity v of armature plate  116  that the armature plate meets the first electromagnet virtually at a velocity of zero. 
     The invention is not limited to the example of embodiment described. For example, the actuator may be designed as an injection valve. Each coil can also have its own controller. Energy can also be supplied to the coil until the current through the coil ( 113 ) has increased by a preset threshold value, if the ratio of the differential of current I and current I falls below a preset threshold value, and energy can be drained from the coil ( 113 ) until the current through the coil ( 113 ) has dropped by a preset threshold value if the ratio exceeds a preset threshold value. Alternatively, the supply or draining of energy to or from coil  113  may be performed by varying the amount of the voltage drop at coil  113  or by locking coil  113  onto a preset voltage that is different from the distribution voltage. A preset energy may be supplied to or drained from the coil in each case. It is best if the energy to be supplied or drained is estimated by an observer. The observer would estimate the energy, for example, depending on the deviation of the first or second threshold value from the ratio of the current I differential and current I. 
     The first and second threshold values applied to the inputs of the comparator may, alternatively, also be a function of the sizes and pressure in cylinder  23  or other operating parameters of the internal combustion engine or regulator. 
     Alternatively, the current I differential can be compared by the comparator with a threshold value that is a function of current I and/or other operating parameters. 
     There may also be any desired combination of the steps cited. 
     Controller  3   a  may also be designed as a continuous-action, discrete-time, P, PI, PD, PID or other familiar controller.