EP0970297B1 - Electromagnetic control device - Google Patents

Description

The invention relates to an electromagnetic actuating device with the features the preamble of claim 1.

Electromagnetic actuators with these features are e.g. from the DE 3920976 A1 known. You will e.g. for actuating valves from Internal combustion engines used. The anchor is without the two spring forces Excitation of an electromagnet in an intermediate, in particular middle position brought. The excitation of one of the electromagnets brings the anchor into the associated end position, which means e.g. the valve is fully open. The control the other electromagnet then closes the valve.

To save energy, permanent magnets are provided, which without the armature Can capture excitement in the end positions.

It is also known from DE 35 00 530 C2 to use permanent magnets instead of the two electromagnets for the armature movement and to render the effect of one of the permanent magnets ineffective by a field of an electromagnet during an armature movement. Here, too, the armature is held in the end positions only by the permanent magnets. In DE 35 46 513 C 2, the current for holding the armature in the end position is clocked at a low level.
The invention is based on the object of providing an electromagnetic actuating device which manages with low power in operation.

This object is achieved by the features of claim 1.

The solution according to the invention with the features of claim 1 brings a considerable reduction in the required energy, because the use of permanent magnets an increased air gap by their thickness results in the working stroke (Valve movement) requires increased excitation (= power). The rest system on the other hand, only needs little energy. The size is also with the solution according to the invention cheaper. In addition, the so-called Adhesive forces in the presence of a small air gap, which is made possible by the catch is, not or only slightly present.

Compared to the prior art given by DE 35 46 513 C2 it in the invention to a lower thermal load on the windings and it no special measures for cooling are necessary. The System according to the invention needs a lower drive power, and it comes to a greater acceleration of the armature, because when switching, the full one Magnetic force must be reduced.

An actuating electromagnet is known from DE utility model 17 83 823, which is a rest position and one by switching on the actuating magnet has reached the working position of the anchor. In this position, the anchor locked by engaging elements and despite switching off the Actuation magnets held. An auxiliary magnet unlocks on one corresponding command the latching and the anchor goes into the rest position back.

The locking system preferably has an electromagnetic Actuator on, but there are other electrical Actuators (e.g. piezoelectric) possible. It should preferably be at single or double pole electromagnets are used.

Figure description

Embodiments of the invention and their Functions explained in more detail.

Fig. 1 ein erstes Ausführungsbeispiel

Fig. 2 das zugehörige Ansteuerprogramm

Fig. 3 ein abgeändertes Ansteuerungsprogramm

Fig. 4 ein anderes Ausführungsbeispiel

Fig. 5 das dazugehörige Ansteuerprogramm

Fig. 6 ein weiteres Ausführungsbeispiel

Fig. 7 bis 11 Diagramme zur Funktionserläuterung

Fig. 12 ein dabei unterstellter Anker

Show it:

Fig. 1 shows a first embodiment

Fig. 2 shows the associated control program

Fig. 3 shows a modified control program

Fig. 4 shows another embodiment

Fig. 5 shows the associated control program

Fig. 6 shows another embodiment

Fig. 7 to 11 diagrams for functional explanation

Fig. 12 is an underlying anchor

1 two opposing two-pole electromagnets 1 and 2 with their cores 3 and 4, their control windings 5 and 6 and the pole faces 7 and 8 are shown. An armature 9 is located between the pole faces and is supported by means of two leaf springs 10 and 11. An actuating rod 12 is rotatably attached to the anchor. They actuate, for example, a valve tappet 13 when the armature moves. This is pressed upwards by a spring 14 when the actuating rod 12 permits this and is pressed down by the actuating rod 12 against the force of the spring 14.
In the end positions of the armature 9, the locking system 15 is used, the locking slide 16 of which is then pressed by the force of a spring 17 above or below the armature and holds it in place even when the electromagnet 1 or 2 is not energized. An electromagnet 18 can pull the locking slide 16 back when its winding is excited.
2, the operation of the actuator including the locking system 15 is explained. It is assumed that the armature 9 of the actuator rests on the pole faces 7 of the electromagnet 1 and the locking slide 16 holds the armature there. At T ₁ , the current i _{18 of} the locking magnet 18 is switched on. At T ₂ the locking system 15 sets in motion with its locking slide 16 (S _RM ) and reaches its end position at T ₃ . This process is reflected in the current profile i _{18 of} the locking magnet. A predetermined time after T ₁ , the current i _{2 of} the electromagnet 2 is switched on at T ₄ . This sets the armature 9 in motion at T ₃ (s _v ); the final position is reached at T ₅ . At this point, the locking system 15 also snaps back in (S _RM ). Before the current i _{18 of} the rest system had been switched off. From T ₆ the entire process is repeated with the reverse direction of movement of the armature 9. The times T ₆ , T ₇ , T ₈ , T ₉ and T ₁₀ correspond to the times T ₁ to T ₅ .

In the diagrams i ₁ and i ₂ , alternatively usable excitation pulses for the electromagnets 1 and 2 are shown starting at the times T ₁ and T ₆ . These pulses serve to relieve the connection between the armature 9 and the locking slide 16 and to reduce the friction during the unlatching.

The excitation i ₁ or i ₂ from T ₁ or T ₆ is switched off when the locking system 15 has reached its end position (at T ₃ or T ₈ ). This point in time can be derived from the current sale i _{18 of} the locking system or can be obtained by means of an anchor travel sensor.

It would also be conceivable to design the locking system 15 such that the locking slide 16 is brought into the locking position by the electromagnet 18 and a spring brings the locking slide into the other end position. Here the locking magnet should be excited over the opening and closing times of the valve (T ₅ to T ₇ ).

With regard to the switching times specified above, this must be taken into account. that these times do not take into account the switch-on and switch-off delays. One on Switching speed-optimized system will work with lead control. i.e. the The current is switched on or off before the switching times.

The diagram in FIG. 3 shows a slightly different control sequence. After unlocking begins at T _2, the detent magnet 18 is energized until a position sensor (not shown) for the armature position signals the end position of the valve at T ₅ (see Sig.). After a high current value at the beginning, the current is reduced to a lower holding current in order to become 0 at T ₅ . At the same time, a magnetizing current is applied to magnet 2 to T ₁₁ from T ₄ '. The detent slide 16 now engages (at T ₁₁ ) without a load. The same thing happens at M ₁₀ . This process offers less mechanical stress.

T₁:

Sperrschieber ist noch wirksam; die Elektromagnete 1,2 und 18 werden angeschaltet

T₂:

Anker bewegt sich; Sperrschieber wird herausgezogen; i₁₈ wird abgeschaltet

T₃ bis T₅.

Anker bewegt sich in nächste Endlage

T₄':

Elektromagnet 2 wird auf Halteerregung geschaltet bis der nicht mehr erregte Sperrschieber 16 des Rastsystems einrastet

T₁₁ :

Nach der Einrastung des Sperrschiebers wird der Elektromagnet 2 völlig abgeschaltet und der Anker kommt auf dem Sperrschieber zur Anlage

The sequence is as follows:

T ₁ :

Gate valve is still effective; the electromagnets 1, 2 and 18 are switched on

T ₂ :

Anchor moves; Gate valve is pulled out; i ₁₈ is switched off

M ₃ to M ₅ .

Anker moves to the next end position

T ₄ ':

Electromagnet 2 is switched to holding excitation until the locking slide 16 of the locking system no longer excites

M ₁₁ :

After the locking slide engages, the electromagnet 2 is switched off completely and the armature comes to rest on the locking slide

4a shows an embodiment of the invention. Two two-pole electromagnets 21 and 22 are provided here. between which an anchor is movable. The armature 29 is spring-loaded here by means of a torsion bar or a rotating tube 27, which can rotate about the axis 28. At the front end, the torsion bar preferably has a bearing, not shown, for example a needle bearing, or it is ball-bearing there.
30 with a connecting part, a so-called cage, between torsion bar and anchor 29 is designated. On the armature 29 or on the connecting part 30, an actuating rod 32 is pivoted, which, when the armature is actuated, presses a valve 33 downward against the force of a spring 34 and can open the valve 33, but which closes the valve 33 by the force of the spring 34 can allow appropriate excitement. The forces of the spring 34 and the torsion bar in its initial position are coordinated with one another in such a way that the two spring forces hold the armature in the center position shown without excitation of one of the electromagnets 21 and 22.
The latching system 35 here contains a rocker 37 which can be tilted about the axis 36 and which is pulled in one direction by a spring 38 and is pulled in the other direction by a latching electromagnet 39 when the winding 26 is excited. The magnetic circuit of the electromagnet 39 is partially formed by the core 24 of the electromagnet 22, its winding and the shunt 37 and 41. Alternatively, a separate winding 40 can also be provided for the locking magnet, as indicated in FIG. 1a.
The actual locking element here is a ball-bearing locking roller 42 attached to the end of the rocker 37. The locking roller here is the ball-bearing shaft 42 ', which is shown drawn out in FIG. 4b.
This rolls with a small diameter on a locking plate 43. The rolling bearing has a larger diameter because of the necessary basic load rating. In Fig. 4c the locking position is shown with "valve open". The locking roller 42 'is locked here above the locking plate 43 and prevents movement of the armature in the direction of the arrow (44), which would like to bring about the restoring force of the spring.

5, the function of the arrangement of FIG. 4a is explained, it being assumed that the armature 29 does not rest on the pole faces of the electromagnet 22, but is held there by the latching roller 42 with a small air gap. The valve is closed. If the valve 33 is to be opened, the winding 26 of the locking magnet 39 is first excited at T ₁ . This excitation causes force to be exerted on the locking roller 42 and the rocker 37 is tilted from T2 and the locking roller 42 is pulled out of the locking position. This happened at T ₃ (see path diagram S _{RM of} the locking magnet). Now the excitation of the electromagnet 22 is switched off after a fixed time. The spring forces move the armature 29 together with the locking plate 43 downward. At T ₄ the electromagnet 21 was energized, which pulls the armature 29 downward. The valve opens and is fully open at T ₅ . The locking roller can then snap in again as a result of the spring force and hold the armature in the second end position.
If the valve 33 is to be closed again, the winding 25 of the electromagnet 22 is activated at T ₉ . First, the detent magnet 39 takes effect after switching on the current i ₂₂ , which pulls the detent roller 42 from the armature 29 (from T ₇ ). The action of the spring forces and the electromagnet 22 brings the armature 29 back into the "valve closed" position and the locking roller is brought back into the locking position by the action of the spring 38 (T ₁₀ ); the excitation of the electromagnet 22 can be switched off .
The design described can only be used if the excitation of at least the electromagnet 22 takes place only over a partial region of the stroke, since the latching electromagnet must be ineffective when the end position is reached.
The solution just described requires a very low control power, since the locking magnet does not require any excitation power in the end position and the switching magnets are not activated here.
As a result, the known problems of sticking times for large magnets are not relevant. Since the full spring restoring force acts immediately after unlocking or disengaging, the system accelerates faster and is not dampened by a decaying magnetic force. The support of the locking roller on the locking plate 43 must take into account both the angular position in the end position and a stop in both directions. The locking plate can be rotated slightly (Fig. 4c) so that the locking roller rests over its full length and experiences a portable surface pressure.

Above, the detent magnet 39 was actuated by the winding 26 of the electromagnet 22. Alternatively, this can also be done by means of an additional winding 40, with the winding 26 or 25 also advantageously being briefly actuated when the winding 40 is activated, in order to relieve the locking and thus reduce the required force of the locking magnet.
If the winding 26 is used as a winding for the locking magnet, this happens automatically.

6 shows a valve 51 with a valve stem 52 in the valve block 53. A spring 54 pushes the valve 1 upwards.
A two-pole electromagnetic drive is shown at the top, which has two electromagnets 55 and 56 and an armature 57 located between them. The armature 57 is mounted by means of a torsion spring 58. An actuating rod 59 is articulated on the armature 57 and its length can be changed by a screw 60. The screw 60 stands on the valve stem 52. The torsion spring 58 is biased so that it keeps the armature 57 in the middle position shown together with the spring 54 without energizing the electromagnets 55 and 56. A connecting part 61 connects the armature 57 to the torsion spring 58. A locking system 62 is shown on the right on the electromagnet 56. It consists of a rocker 64 which can be tilted about the axis 63. At the lower end of the rocker, a locking roller 65 is shown, which in the end positions of the armature 57, into which it is driven by the force of the electromagnets 55 and 56 and by the action of the springs 54 or 58 is brought, engages above or below the locking plate, and holds the anchor 57. The locking roller 65 is ball-bearing to reduce the friction. It is formed by a shaft 65a between two ball bearings. A latching electromagnet 67 is accommodated in the core of the electromagnet 56, the rocker 64 included in the magnetic circuit of the latching magnet 67 being actuated when it is excited. As a result, the latched locking roller 65a is pulled out of the locked positions. The shaft 65a rolls during the deflection of the armature 57 on a locking plate connected to the armature 57. 6 shows a valve travel sensor 68 and an armature travel sensor 69. Both sensors work, for example, on the basis of a linear Hall barrier. Inductive sensors 68a can also be used. To simplify the illustration, this is only drawn on one side. The closed position of the valve 57 is detected via the valve travel sensor. The anchor travel sensor 69 detects the total stroke.
During the working stroke, the measurement results of both sensors are the same. Only when the valve closes does the armature travel sensor continue to run an amount. Preferably, a sensor for the stroke end area is also provided with great accuracy.
In the end position of the armature 57 shown in dash-dotted lines, the valve 51 is closed and valve clearance of approximately 0.1 to 0.3 mm occurs between the actuating rod 59 and the stem 52 of the valve.

7 to 12, the adjustment of the armature to the desired position described below.

7a shows the path / time curve (s over t) of the magnet armature 57 or the valve 51/52 during the valve opening in FIG. 7a, FIG. 7b shows the time curve of the forces and FIG. 7c shows the movement of the Locking roller 65. At time T ₀ , the armature movement begins and after a short distance Δs _v (valve clearance), the adjusting screw 60 hits the valve stem 52 and takes the valve 51/52 with it. The force jump shown occurs when it hits the valve when its valve spring becomes effective. Due to the spring and magnetic forces, the moving path shown in FIG. 4a illustrates a that brings in the ideal case exactly the armature 57 in the desired position s _to which is remote by a distance from the end stop .DELTA.s. The dash-dotted and dashed lines show deviations from the set course, namely that the setpoint is undershot in the dashed line and exceeded in the dash-dotted line, the armature 57 hitting the end stop here. The setpoint can be defined by the locking roller or the distance from the end stop.
In Fig. 7b with F _F the resulting force of the springs 54 and 58 is superimposed by the forces of two further springs, not shown, which are active in the vicinity of the end positions (left and right of the kink). These additional springs cause a large acceleration of the armature 57 from the end positions. F _M denotes the force of the magnet 55. Here, a shape of the armature 57 'and the magnetic poles is assumed, as shown in FIG. 9. This design enables a high initial force, which is particularly favorable for the exhaust valve, since the gas force must also be overcome here. In order to take into account the dead times of the signal processing, the electromagnet 55 is switched on by the time t ₀₁ before T ₀ . After unlocking the locking system at T ₀ , this magnetic force becomes effective at T ₀ . It acts over a relatively short period of time T _s . The sum of the forces F _F and F _{M shown} acts on the armature and the valve and accelerates them. After switching off the excitation current after T _s , the magnetic force decays over t _v . The sum of the forces brings the anchor to the other end position. For a simplified representation, the friction and gas forces are not taken into account. The deviation from the target position is determined by the anchor travel sensor 69. From the determination of the storage (+ Δs, -Δs), a computer (not shown) determines a correction value -ΔT or + ΔT for switching on the electromagnet 55 in the next cycle. 4c shows the movement sequence of the detent roller 65. The detent magnet is switched on according to the dead and delay times by t ₀₂ before T ₀ . At T ₀ , the locking roller 65 has moved over the edge of the locking plate and releases the armature 57. The sum of the forces can be effective and accelerate the armature including the valve. After some time T _RR , the locking magnet is switched off. The locking roller 65 is pressed by the force of the spring 66 onto the locking plate and rolls on it. When the end position is reached, the locking roller 65 engages again and holds the armature in the end position. A magnetic holding force is not necessary. This also eliminates annoying sticking times in the following reversal of the valve: the system according to the invention can accelerate faster. Additional damping measures are not necessary.
If the - Δs deviation is too large so that the locking roller cannot engage, the electromagnet 55 is actuated again briefly at T _x . This can be optimized if, in addition to the anchor path, the anchor speed is also evaluated or the distance covered is determined at a specific point in time or the distance covered is evaluated at the point in time.
The magnet can be switched on again at time TX if the stroke is below the setpoint curve. The same applies to FIG. 8.
Fig. 8 shows the curves corresponding to Fig. 7 for the closing of the valve.
At T ₀ the locking roller 65 releases the armature 57 and the armature and valve move in the direction of the closed position by the force of the springs F _F. F _M would be the course of the magnetic force F _M if the electromagnet 56 were switched on. In fact, this is only switched on for a relatively short time T ₆ after the intermediate position has been exceeded (F _F = 0). The magnetic force is already great with this distance or the remaining air gap to the magnetic pole. The influence of the spring force shows the sum F _M and F _F. In the ideal course, the anchor gets into the
Position s _{should be} Δs away from the end stop.
The force curve F _{M of} the stronger electromagnet 56 is similar to a hyperbolic curve. He was elected. In order to avoid the usual start-up of the system after starting the engine and to be able to close the valve immediately in the normal control process in the event of a greater setpoint deviation, since a corresponding excess force is provided in relation to the spring. This is not necessary for the weaker electromagnet 55 for reasons of cost and weight, since in the limit case the motor function is also possible with the valve half open.
The control is carried out analogously to FIG. 7, in that the deviation from the desired position is determined and the actuation time T ₆ is varied by a time - ΔT or + ΔT for the following closing operation. The locking roller 65 also has the same effect as in FIG. 7.
Here, too, the electromagnet can be switched on again at T _{x in} accordance with FIG. 7 in order to ensure a secure engagement. A latching switch can be provided to monitor the latching function. The latching can also be derived from the current profile of the latching magnet.
9 shows the start of the stroke for opening with high resolution. This shows a phase shift in the path of armature S _M and valve s _V. With a total stroke of approximately 8 mm, a valve clearance of approximately 0.1 to 0.3 mm must be taken into account. The valve lift sensor therefore only has to evaluate this area.
Fig. 10 shows an enlarged view of the states at the end of the stroke during the closing process. The S _RR engages before the S _SHOULD and the valve closes before the engaging. The magnet system and the end stops are locked accordingly. This is ensured in one unit. After assembly, the valve clearance is then adjusted. This can be monitored by evaluating s _V and s _M in the control process, as well as when adjusting the valve clearance in the factory or service.
11 shows the valve stroke movement in relation to the piston movement with key values OT and UT.

The solenoid system is controlled in a motor-specific and speed-dependent manner. Via the freely selectable time offset t _s (system time), the control is based on the described T ₀ . Speed, depending also defining an opening time T _and a valve closing time T is carried _to. The above parameters are part of the motor control, which specifies the specifications t _s , T _auf , T _for the magnetic control system.
Accordingly, a correspondingly fast microprocessor with, for example, DSP is necessary for the fast arithmetic operations, since a large number of fast real-time processes have to be calculated.

By regulating the target positions near the poles, damping and thus low noise are automatically given. There are no temperature influences as they occur with hydraulic damping. The electromagnets are housed in a dry environment. The overall structure is extremely low-friction, so that little energy has to be supplied in the lifting phase.
A large part of the kinetic energy is stored in springs and not like in the hydr. Damping wasted.

The electromagnetic drive described above can be used to drive a gas exchange valve or another comparable valve. It can also be used to drive a pump, the valve tappet being replaced by a pump piston.
But it can also be used in gearboxes, because fast switching from one position to the other with high force is also desired there.
The invention can also be used in other applications with similar requirements.

Claims (24)

1. Electromagnetic actuator device have two electromagnets whose pole faces in particular at least partly face one another and having a displaceably mounted armature which can be moved to and from between the pole faces by the electromagnets and which, without the electromagnet energised, is held in an intermediate position by two oppositely directed forces from springs and which after reaching an end position is held immobile at least in the vicinity of the pole faces of one electromagnet even when the electromagnet is switched off, characterised in that a latching system (35, 62) hold the armature (29, 57) or a part connected to it mechanically immobile in the two end positions and in that the latching system (35, 62) has for both end positions an electrically operated device, and in particular an electromagnet (39), which releases the latched position.
2. Electromagnetic actuator device according to claim 1, characterised in that the armature (29, 57) is spring mounted (torsion springs 27, 58).
3. Electromagnetic actuator device according to claim 1 or 2, characterised in that the latching-in is effected non-electrically by means of spring force (38, 66).
4. Electromagnetic actuator device according to claim 1 or 2, characterised in that the latching-in takes place in opposition to a spring force as a result of the electromagnet being actuated.
5. Electromagnetic actuator device according to any of claim 1 to 4, characterised in that the latching system has a sliding latching element (42a, 65a).
6. Electromagnetic actuator device according to claim 5, characterised in that the latching element (42') has a low-friction mounting (rolling bearings 47).
7. Electromagnetic actuator device according to claim 5 or 6, characterised in that the latching element is a latching roller (42) of small diameter and is mounted by means of rolling bearings (47) of larger diameter.
8. Electromagnetic actuator device according to any of claims 1 to 7, characterised in that at least one stop is provided for the latching element (42') to limit its travel.
9. Electromagnetic actuator device according to claim 8, characterised in that the stop is formed by a rotatable abutment plate.
10. Electromagnetic actuator device according to any of claims 1 to 9, characterised in that the electromagnet assigned to the particular end position of the armature is energised briefly at the time of unlatching to relieve the load on the latching system.
11. Electromagnetic actuator device according to claim 10, characterised in that the energisation time is brought to an end by a signal (sensor 69) triggered by the movement of the armature (57)
12. Electromagnetic actuator device according to claim 11, characterised in that the signal is a signal from a switch.
13. Electromagnetic actuator device according to claim 11, characterised in that the signal is obtained from the curve followed by the current to the latching magnet (35).
14. Electromagnetic actuator device according to claims 1 to 13, characterised in that the magnetic circuit of the latching system is partly integrated into the magnetic circuit of one of the electromagnets.
15. Electromagnetic actuator device according to claims 1 to 14, characterised in that signals from an armature travel sensor for the end positions are made use of to control the actuator.
16. Electromagnetic actuator device according to any of claims 1 to 15, characterised in that desired positions s_soll for the armature (57) are defined in the neighbourhood of each of the pole faces and these positions are monitored by a sensor (69), in that the electromagnets (55, 56) are energised by a current pulse to go to one of the desired positions s_soll and in that the length of the current pulse in the next cycle is varied if the armature (57) deviates from the desired position s_soll.
17. Electromagnetic actuator device according to claim 16, characterised by its use as an actuator of a valve (51, 52) in an internal combustion engine, in which case a spring force (54) acts on the valve in the "valve closed" direction and at least part of this spring force is one of the spring forces which set the valve to the intermediate position.
18. Electromagnetic actuator device according to claim 17, characterised in that the current pulse to open the valve (51, 52) comes into action at the beginning of the opening process (at T₀) .
19. Electromagnetic actuator device according to claim 16 or 17, characterised in that the current pulse to close the valve (51, 52) comes into action in the second half of the valve travel.
20. Electromagnetic actuator device according to claim 18, characterised in that the current pulse is switched on prior to the unlatching of the armature (7).
21. Electromagnetic actuator device according to any of claim 16 to 21, characterised in that an armature travel sensor (69) is provided to detect setting values.
22. Electromagnetic actuator device according to claim 21, characterised in that the armature travel sensor (69) is provided for the full travel and a valve travel sensor (68) with a small sensing range is provided.
23. Electromagnetic actuator device according to claim 22, characterised in that the sensor or sensors are used to sense the valve clearance.
24. Electromagnetic actuator device according to any of claims 16 to 23, characterised in that additional energisation is applied to the associated electromagnet (55 or 56) (at TX) when the desired position (s_soll ) is not approached sufficiently closely.

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