Abstract:
The present invention relates to a high-speed controlling device, suitable for displacing a switching element between two positions with very short switching times. Said device comprises two switchable electromagnets, between which an armature, with a driven coupling to the switching element, is arranged. According to the invention, said armature contacts the first electromagnet in the first position of the switching element and contacts the other electromagnet in the second position of the switching element. In order to obtain particularly short switching times for the switching element, the armature can be firmly secured to a shaft, which is rotatably mounted about its longitudinal axis and to which said switching element is also fixed in an axially offset manner in relation to the armature.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   Applicants claim priority under 35 U.S.C. §119 of German Application No. 101 40 706.8 filed Aug. 18, 2001. Applicants also claim priority under 35 U.S.C. §365 of PCT/DE02/02992 filed Aug. 16, 2002. The International application under PCT article 21(2) was not published in English. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a high-speed actuating device suitable for actuating a switching device between two switch positions in very short switching times, having the features of the preamble of Claim  1 . 
   2. The Prior Art 
   In certain applications, a mechanical switching device must be actuated between two switch positions within an extremely short switching time. For example, German Patent DE 37 37 824 A1 describes a method of operating an internal combustion engine. This internal combustion engine has an intake channel leading to at least one combustion chamber of the engine, at least one intake valve which is situated between the intake channel and each combustion chamber and determines the start of intake and the conclusion of intake into the combustion chamber and an additional valve situated upstream from the intake valve. According to the known operating method, this additional valve is opened when the intake valve is opened and is closed temporarily during a period of time that maintains an interval from the beginning of intake to the end of intake. Due to this procedure, dynamic effects in the intake stroke of the piston being actuated in the respective combustion chamber can be utilized to increase the loading of the combustion chamber with fresh air. In addition, definitely shorter opening times, in particular a plurality of opening times, can be implemented within the opening period of the intake valve through appropriate operation of the additional valve, and these opening times can also be shifted toward “early” or “late” relatively arbitrarily within said opening period. To this extent, with the help of the additional valve, which can be operated appropriately, it is possible to implement variable valve control units even if the actual valve control, e.g., by means of a camshaft, is invariant per se. 
   To open and close the additional valve during the opening time of the intake valve(s) once or more, very short switching times must be implemented for the additional valve. The switching times required to accomplish this amount to about 2 ms in this specific embodiment. Switching times of about 10 ms can be achieved with traditional electric motors. 
   International Patent WO 98/42953 discloses a high-speed actuating device having two switchable electromagnets between which is arranged an armature that is drive-coupled to the switching device, which is designed as an intake valve or exhaust valve of an internal combustion engine. In the first switch position of the valve, the armature is in contact with the one electromagnet, while in the second switch position, it comes to rest against the other electromagnet. The armature here is connected by way of a connecting part to a rotating rod, which is rigidly clamped on a stationary component of the actuating device. An operating element is mounted on the armature, cooperating with the valve for at least an opening stroke. The known high-speed actuating device serves here as a valve drive in an engine with which variable control times for the respective valve can be implemented. At a high rotational speed of the internal combustion engine, actuating times of approximately 3 ms can be achieved with the help of such a high-speed actuating device. 
   However, there is a demand for a high-speed actuating device with the help of which it is possible to implement even shorter switching times. For the other type of application mentioned above for operation of an additional valve, this means, for example, shortening the switching times by at least 30%. 
   U.S. Pat. No. 5,131,365 describes a high-speed actuating device of the type defined in the preamble, which is suitable for adjusting a switching element designed as a switching flap between two switch positions with very short switching times. The switching valve is situated in a gas-carrying line, namely in an intake channel of an internal combustion engine upstream from an intake valve; in a first switch position, it can close off the line cross section, and in the second switch position, it can open the line cross section. With the known high-speed switching device, the switching flap is prestressed in its closed position with the help of a prestressing spring. An electromagnet is provided, holding the switching flap in its closed position, so that in the filling stroke of the piston, a vacuum pulse can be built up on the cylinder end. As soon as the electromagnet releases the switching flap, the vacuum on the cylinder end causes the switching flap to open. As soon as the pressure on the switching flap is equalized, the restoring spring can adjust the switching flap back into its closed position in which it can then be held again by the electromagnet. The known high-speed actuating device thus operates passively, namely as a function of the piston movement. However, it would be desirable to have a high-speed adjusting device which can be used much more flexibly and nevertheless permits extremely short switching times. 
   British Patent 1,572,299 discloses another high-speed actuating device with the help of which a deflector plate can be switched between two end positions. This deflector plate works as a shunt in a conveyor zone for bulk printed matter or the like and is drive-connected via a shaft to an armature. This armature is rotatably adjustable about the longitudinal axis between two electromagnets. 
   SUMMARY OF THE INVENTION 
   The present invention is concerned with the problem of providing an embodiment for a high-speed actuating device of the type defined in the preamble, so that particularly short switching times can be implemented. In addition, the high-speed actuating device should have a compact design, in particular to thereby make it possible to accommodate the high-speed actuating device in the engine space of a motor vehicle. 
   This problem is solved according to this invention by a high-speed actuating device having the features of claim  1 . 
   This invention is based on the general idea of designing the high-speed actuating device as a rotational drive in which the armature drives the switching device to execute pivoting adjustments as directly as possible. This is achieved by a rotatably mounted shaft on which both the armature and the switching device are fixedly mounted. Thus, in this design, the switching device is designed to be rotationally adjustable between its two switch positions by rotating about the longitudinal axis of this shaft. Due to the design according to this invention, the masses to be moved by the high-speed actuating device are relatively close to the rotational center of the actuating movement, so that relatively low moments of inertia are achieved on the whole. Smaller moments of inertia promote faster switching times, and at the same time the energy demand for implementation of the short switching times is reduced. The high-speed actuating device can therefore be designed to be compact. 
   According to an especially advantageous embodiment, each electromagnet may have a yoke on which is provided a stop surface for the armature against which the armature comes to rest in one of its switch positions. The yoke should be interrupted in the area of the stop surface by a gap which is bridged by the armature when the armature is in contact with the stop surface. Due to this measure, there is a controlled shaping of the magnetic field created by the yoke in the area of the stop surface, so as to achieve an extreme increase in the magnetic attractive forces acting on the armature. Whereas the magnetic field lines run essentially inside the yoke up to the gap, a convex curve is obtained for bridging the gap, extending toward the armature, where it creates a corresponding polarization. 
   The smaller the gap width of the gap, the more pronounced is the curvature of the magnetic field lines. An embodiment in which the opening width of the gap is smaller than the thickness of the armature is preferred, the thickness being measured across the radial extent of the armature and across the axial extent of the armature. 
   In a special refinement, the yoke may have a cross section which tapers toward the gap at least in an end section which ends at the gap. As a result of this measure, there is a concentration of the magnetic field lines toward the stop surface in the end section having the tapered cross section, so that the bulging of the magnetic field lines toward the armature can be additionally increased. Thus, this measure also results in an increase in the magnetic attractive forces acting on the armature. 
   According to an advantageous refinement, a spring element may be coupled to the shaft, with this coupling taking place in such a manner that in the two switch positions of the switching device, the spring element initiates a restoring torque into the shaft, driving the switching device in the direction of the other switch position, and the spring element does not initiate any restoring torque into the shaft in a middle position of the switching device. Due to this design, the spring element acts more or less as a storage device for potential energy which is fully loaded in both switch positions and manifests its maximum power output to accelerate the armature in switching the electromagnets at the beginning of the rotational adjustment, i.e., at a point in time when the magnetic field must be built up. 
   A particularly compact design is obtained when the shaft is designed as a hollow shaft and the spring element is designed as a torsion rod, which extends coaxially in the hollow shaft and is connected to the hollow shaft in a rotationally fixed manner at one end and to a stationary component of the high-speed actuating device in a rotationally fixed manner at the other end. In other words, the torsion rod is rigidly clamped with the end which leads out of the hollow shaft. This design also has the advantage that the torsion rod has a minimum moment of inertia due to its central arrangement in the hollow shaft and thereby maximum accelerations are supported. 
   According to a particularly clever design, on the end of the torsion rod which is assigned to the switching device, the torsion rod may be mounted on the end of the hollow shaft assigned to the armature, while the hollow shaft is radially supported directly or indirectly on the torsion rod. This design simplifies the mounting of the hollow shaft in the area of the rigidly clamped end of the torsion rod. 
   The problem on which the present invention is based is also solved by an application according to claim  18 . 
   Additional important features and advantages of this invention are derived from the subclaims, the drawings and the respective description of the figures on the basis of the drawings. 
   It is self-evident that the features mentioned above and also to be explained in greater detail below can be used not only in the combination given here but also in any other combinations or even alone without going beyond the scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred exemplary embodiments of this invention are illustrated in the drawings and are explained in greater detail in the following description, where the same reference notation is used to refer to the same or functionally same or similar components. 
     The drawings show the following in schematic diagrams: 
       FIGS. 1A–1C  basic diagrams of a particular application of the present invention in various positions of a switching device; 
       FIG. 2  a longitudinal section through an inventive high-speed actuating device; 
       FIG. 3  a cross section according to the sectional lines III in  FIG. 2  through the high-speed actuating device; 
       FIG. 4  a highly simplified cross section like that in  FIG. 3  but in another embodiment; and 
       FIG. 5  a circuit configuration for connecting an electromagnet of the high-speed actuating device. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   According to  FIGS. 1A through 1C , an engine (not shown in detail), in particular in a motor vehicle, has an intake channel  1  which may also be referred to below as a fresh air supply line. The engine may be designed as a diesel engine or an internal combustion engine as well as an aspirating engine or a supercharged engine. The intake channel  1  leads to at least one combustion chamber  2  of the engine, which is provided in a cylinder  3  in which a piston  4  is mounted so that it has an adjustable stroke. An intake channel  5  is situated at the transition between the intake channel  1  and the combustion chamber  2 ; likewise, embodiments having a plurality of intake valves  5  are also possible. Upstream from this intake valve  5 , an additional valve  6 , which is provided in the intake channel  1 , may also be referred to below as a switching device. This additional valve or switching device  6  is designed here as a switching flap  7  and may be used, for example, to improve the filling of the combustion chamber  2  with fresh air in that dynamic flow effects are utilized in the process of filling the combustion chamber  2  through targeted switch operation of the additional valve  6 . The intake channel or the fresh air supply line  1  thus forms a gas-carrying line in the application illustrated here, its line cross section optionally being opened or closed with the help of the switching device  6 . 
   For operation of the additional valve or the switching device  6 , a high-speed actuating device  8  is provided and is drive-connected to the additional valve  6  in a suitable manner. The drive connection is represented symbolically by a dotted-line arrow  9  in  FIGS. 1A through 1C . A suitable controller  10  is provided for controlling the high-speed actuating device  8 . 
   With the help of the high-speed actuating device  8 , the switching device  6  is adjustable between a first switch position, which is illustrated in  FIG. 1  and in which the switching device  6  closes off the line cross section of the intake channel  1 , to a middle position shown in  FIG. 1D  and then to a second switch position shown in  FIG. 1C , where the switching device  6  opens (maximally) the line cross section of the intake channel  1 . In the preferred embodiment shown here, the switching flap  7  is arranged in the line cross section in such a way that its pivot axis  11  is essentially perpendicular to a longitudinal central axis  12  of the intake channel  1 . According to the representation selected here, this pivot axis  11  is thus perpendicular to the plane of the drawing. In addition, the switching flap  7  is dimensioned and positioned in such a way that in its first switch position according to  FIG. 1A , it runs at an angle α to a plane  13 , which is perpendicular to the longitudinal axis  12  of the intake channel  1  and/or in which the line cross section of the intake channel  1  is situated. In the embodiment shown here, this angle α is 45°. This arrangement yields a reduction in the actuation path or actuation angle which is necessary to pivot the switch flap  7  between its two switch positions according to  FIG. 1A  and  FIG. 1C , because in the second switch position according to  FIG. 1C , the switch flap  7  runs essentially parallel to the line axis  12  to achieve a maximum degree of opening so that the angle of rotation by which the switch flap  7  must be pivoted between its switch positions according to  FIGS. 1A and 1C  is only 45°. It is clear that the switching times necessary to adjust the switch flap  7  are thereby reduced accordingly. 
   According to  FIGS. 2 and 3 , the high-speed actuating device  8  according to this invention has two electromagnets  14  and  15 , which are arranged in a V shape in cross section according to  FIG. 3 . Each electromagnet  14 ,  15  has a coil  16  and a yoke  17  which surrounds one half of the coil  16  in a ring shape except for a gap  18 . The yokes  17  are usually made of a relatively easily magnetizable iron or steel, and in particular the yokes  17  are made of sheet metal in a sandwich structure. The electromagnets  14 ,  15  are thus designed to be switchable. For simplified production, it is expedient to assemble the yokes  17  of at least two individual parts, whereby the coil  16 , which has already been completely wound in advance simultaneously with the assembly of the yokes, can be used and/or the unwound coil  16  can be used and can be wound relatively easily. 
   Between the electromagnets  14  and  15  there is an armature  19 , which is adjustably mounted so it can rotate about a pivot axis  20 . To this end, the armature  19  is connected to a shaft  21  in a rotationally fixed manner. The armature  19  may be welded to the shaft  2 , for example, or it may be manufactured in one piece with it. In the two-part variant, it is possible to manufacture the shaft  21  and the armature  19  from different materials. The armature  19  is preferably made of an easily magnetizable iron or steel, but it may be advantageous for the shaft  21  to be made of an iron or steel that is difficult or impossible to magnetize, e.g., austenitic steel. The shaft  21  is mounted in radial bearings  22  and  23  on both sides of the armature  19  so it can be adjusted by rotation. 
   According to  FIG. 2 , the switching device  6 , which is designed here as an elliptical switching flap  7 , is also rotationally fixedly connected to the shaft  21 . The switching device  6  here is axially offset from the armature  19  on the shaft  21 . It is expedient for the switching flap  7  to be made essentially of an extremely lightweight material, in particular CFK or GFK plastic cloth, whereby the switching flap  7  has a sleeve  24 , preferably metallic in the exemplary embodiment shown here, this sleeve being tied into the lightweight construction material of the other switching flap  7 . The sleeve  24  is rotationally fixedly connected to the shaft  21 , particular by welding or gluing. Since the switching valve  7  is mounted on the same shaft  21  as the armature  19 , the swivel axis  11  of the switching valve  7  coincides with the swivel axis  20  of the armature  19 . 
   According to  FIG. 2 , the high-speed actuating device  8  is designed as a module, which can be inserted into the intake channel  1  according to  FIGS. 1A through 1C , for example, whereby the high-speed actuating device  8  comprises a corresponding channel section  24  in which the switching device  6  is situated. 
   According to the preferred embodiment shown here, the shaft  21  is designed as a hollow shaft in which a torsion rod  26  extends coaxially. On its end  27  which is assigned to the armature  19  and is shown at the left in  FIG. 2 , this torsion rod  26  is rotationally fixedly connected to the end  42  of the shaft  21  there. For example, radial gear teeth with teeth running axially may be provided in the area of these ends  27 ,  42 . The torsion rod  26  is rigidly clamped on its end  28 , which is assigned to the switching device  6  and is shown at the right of  FIG. 2 . To this end, this right end  28  is rotationally fixedly connected to an immovable component  29  of the high-speed actuating device  8 , e.g., again by way of multiple gear teeth. This component  29  may form, for example, a part of a housing of the high-speed actuating device  8 . 
   The shaft  21  is mounted in the area of the switching device  6 , because the shaft  21  is rotationally supported by the sleeve  24  on its end  30 , which faces way from the armature  19 , and by a bushing  31  on the torsion rod  26 . This support is provided essentially radially, thus achieving centering of the shaft  21  due to an appropriate contouring of the bushing  31 . 
   The central position of the armature  19  shown in  FIGS. 2 and 3  correlates with the central position of the switching device  6  shown in  FIG. 1B . In this central position of the armature  19  and/or the switching device  6 , the tension on the torsion rod  26  is released, i.e., it does not initiate any restoring torque into the shaft  21 . 
   The switch positions shown in  FIGS. 1A and 1C  each correspond to a maximum deflection or rotational adjustment of the armature  19  about the angle α in one direction of rotation or the other. The armature  19  then comes to rest with a corresponding stop surface  32  of the respective yoke  17  over a large area. In this switch position the torsion rod  26  is maximally rotated, storing up potential energy and initiating a maximum restoring torque into the shaft  21  which attempts to drive the armature  19  into the other switch position. In order for the armature  19  to remain in the particular switch position, the corresponding retaining forces must be introduced into the armature  19  via the electromagnets  14  and  15 . 
   The gap  18  in the yoke  17  through which the magnetic field lines are deflected in the direction of the armature  19  serves to generate these relatively high retaining forces. The narrower this gap  18 , the more pronounced is the bulging of the field lines. The opening width of this gap  18  is expediently dimensioned to be smaller than a thickness  43  of the yoke  17 , which is measured next to the stop surface  32 , across the axial extent of the yoke  17  and across the stop surface  32 . In the present case, the opening width of the gap  18  is even smaller than a thickness  33  of the armature  19 , as measured across the radial extent of the armature  19  and across the axial extent of the armature  19 . As an additional measure to influence the field lines in the case of a yoke  17 , an end section  34  adjacent to the gap  18  is provided with a cross section which decreases down to an end  35  of the yoke  17  situated in the gap  18 , causing the field lines to be concentrated in the direction of the stop surface  32 . In addition, the gap  18  is positioned so that it is approximately at the center of the armature  19  when the armature  19  is adjacent to the stop surface  32 , so that the armature  19  can bridge the field lines between the opposite ends  35  and  36  of the yoke  17  in the gap  18 . The measures described here for influencing the magnetic field lines increase the magnetic attractive forces in effect in the armature  19 , so that the available power can be converted to torque on the shaft  21  in a particularly advantageous manner. 
   To be able to implement particularly rapid switching times, the masses to be moved in the present invention are also kept as small as possible, so that in particular minimum moments of inertia are the goal. To this end, the armature  19  is designed to be relatively short with regard to its radial extent from the pivot axis  20 . According to  FIG. 3 , the armature  19  is designed in this radial direction at least to be much smaller than a side  37  of the yoke  17  having the stop surface  32  facing the armature  19 . The center of gravity is therefore shifted in the direction of the pivot axis  20 . To be able to implement an armature  19  which is short in the radial direction, the yokes  17  are situated very close the shaft  21 . The yokes  17  and the shaft  21  are preferably adjacent to one another without coming in contact. In the embodiment shown here, on each yoke  17  one corner  38  is chamfered to thereby position the shaft  21  closer to or virtually inside the interspace between the yokes  17 . 
   As an additional measure to reduce the masses to be moved, the cross section of the armature  19  through which the magnetic field lines flow, i.e., the cross section of the armature  19  which extends over the thickness  33  in the axial direction, is designed to be much smaller than the cross section of the yoke  17  through which the magnetic field lines flow outside of the stop surface  32  and/or outside of the tapered end section  34 . In the embodiment shown here, the cross section of the armature  19  through which the magnetic field lines flow is approximately half as large as the cross section of the yokes  17  through which the magnetic field lines flow. 
   To be able to transmit sufficiently large forces to the armature  19 , it is considerably longer in the axial direction of the shaft  21  than in the radial direction (see  FIG. 2 ). Preferably the extent of the armature  19  in the axial direction is at least two or three times greater than that in the radial direction. In the exemplary embodiment shown here, the axial extent of the armature  19  is more than four times greater than its radial extent. It is clear that the electromagnets  14  and  15  and/or their coils  16  and yokes  17  accordingly have a corresponding axial extent to be able to introduce the desired forces into the armature over the entire axial length of the armature  19 . 
   According to  FIG. 4 , as an additional measure for reducing the moving masses, an end  39  of the armature  19  at a distance from the swivel axis  20  may have beveled flanks  40 , in which case then the stop surfaces  32  will have a complementary stop flank  41 . In addition, the orientation of the field lines in the direction of the armature  19  can also be influenced by these stop flanks  41 , thus yielding an additional reinforcement of the attractive or repulsive effect. 
   The high-speed actuating device  8  according to this invention operates as follows: 
   Starting from the middle position of the armature shown in  FIGS. 2 through 4  and thus also the middle position of the switching device  6 , the armature  19  is first actuated into one of its two switch positions. This is expediently the open position shown in  FIG. 1C . Since the torsion rod  26  is designed for generating extremely high restoring torques, the desired switch position can be approached directly from the middle position only with a very high electric power. Therefore, it is advantageous to have the sequence of a starting procedure prior to operation; in this starting procedure, through a specific sequence of polarity reversal processes, oscillation is induced in the oscillating system formed by the rotating rod  26 , the shaft  21 , the armature  19  and the switching device  6 , with their amplitudes increasing progressively. This “build up” of the oscillating system is continued until the armature  19  comes to rest in the desired switch position on the corresponding yoke  17 . 
   For switching between one switch position and the other switch position, the electromagnets  14  and  15  are turned on in alternation. The armature  19  is accelerated toward the other switch position due to the attractive forces which are then built up and act in opposition. At the same time, the torsion rod  26  can relax, so that the acceleration of the armature  19  is extremely increased precisely in the initial phase of the actuating movement. The pivoting adjustment of the armature  19  over the common shaft  21  at the same time produces a corresponding pivoting adjustment of the switching device  6 . The use of the torsion rod  26  here as a driving means and as an energy storage device is particularly advantageous because the torsion rod  26  itself has only a low moment of inertia and therefore its driving energy can be transmitted to the shaft  21  with virtually no retardation. 
   For operation, i.e., triggering, of the electromagnets  14  and  15 , a circuit configuration  44  according to  FIG. 5  is preferred. Such a circuit configuration  44  uses chopping of the current flow through the coil  16  of the respective electromagnet  14 ,  15 . With regard to high-speed electromagnets  14 ,  15 , this type of triggering offers considerable advantages in comparison with other principles. With the help of this triggering, the three following states of the electromagnets  14 ,  15  must be implemented in particular under all operating conditions: energy supply, energy maintenance and energy dissipation. As a rule a so-called H-bridge is used for this purpose and is also implemented in the circuit configuration  44  in  FIG. 5 , whereby instead of the diodes  45 , corresponding transistors may also be used. An on/off transistor  46  is used for turning the coil  16  of the respective electromagnet  14  or  15  on and off. This on/off transistor  46  is operated by a switch  47 . A chopper current regulator  48  compares an actual current which can be determined with the help of a measurement element  49  with a setpoint current which is predetermined at  50 , e.g., by an engine control unit. The chopper current regulator  48  operates a chopper transistor, i.e., a chopper transistor configuration  51 , as a function of this comparison, to thereby regulate the current flow from a power supply  52  to the coil  16  of the respective electromagnet  14  or  15  at the setpoint level. In addition, two series resistors  53  are provided in the circuit configuration  44 . 
   The measurement element  49  has a definite point of reference due to the arrangement of the measurement element  49  which is selected in the preferred embodiment of the circuit configuration  44  shown here and which is preferably designed as a current sensor or as a measuring shunt on the emitter of the on/off transistor  46 . This makes is possible for the current flow to be reliably detected with the help of the measurement element  49  during the entire period of energization of the coil  16 . In addition, the circuit configuration  44  presented here has the advantage that the chopper transistor  51  can be designed as a so-called high transistor and consequently also the predetermination of the setpoint current has a definite reference point to the actual current. The H-bridge shown in the circuit configuration  44  is characterized in that the measurement element  49  is situated between the on/off transistor  46  and the reference point for the current measurement, with the chopper transistor  51  as the high transistor also being applied to the other pole of the operating voltage. This design has a positive effect on the measurement dynamics and consequently also on the switching frequency of the electromagnets  14 ,  15  that can be achieved with the help of the circuit configuration  44  shown here. In addition, the circuit configuration shown here can also maintain the fluctuations in the chopped current flow with sufficient accuracy while the inductance is variable. 
   Chopping the current flow may be accomplished, for example, as a function of a predetermined chopper frequency. Likewise, it is possible to perform the chopping with the help of predetermined current limits which are selected to be relatively narrow between which the current flow fluctuates during the chopping.