WO1987005075A1

WO1987005075A1 - Method and circuit for driving electromagnetic consumers

Info

Publication number: WO1987005075A1
Application number: PCT/DE1987/000053
Authority: WO
Inventors: Konrad Eckert; Edwin Fauser; Hans Kubach; Fridolin Piwonka; Helmut Rembold; Günter Schirmer; Bernhard Sprenger
Original assignee: Robert Bosch Gmbh
Priority date: 1986-02-18
Filing date: 1987-02-16
Publication date: 1987-08-27
Also published as: DE3702680A1; JPH01501649A; KR950013066B1; KR880700893A

Abstract

In a method for driving electromagnetic consumers comprising at least one magnetic coil, particularly of magnetically actuatable injecting valves, through at least one controllable switch, there is used an inductive energy available, after an electromagnetic consumer has been switched off, in the magnetic coil of the latter (10, 10a) through which the current circulates, for switching on an electromagnetic consumer. Furthermore, a circuit for implementing such method is characterized in that at least one capacitor (17, 17a, 17') connected to an electromagnetic consumer is used to temporarily store the inductive energy available in the magnetic coil (10, 10a) of an electromagnetic consumer upon its switching off.

Description

Method and circuit for controlling electromagnetic consumers

State of the art

The invention relates to a method for controlling electromagnetic consumers with at least one magnetic coil in accordance with the preamble of the main claim and a circuit for carrying out the method in accordance with the preamble of claim 10.

The current flowing through a magnetic coil cannot change as quickly as desired. The rate of change is limited by the inductance of the coil. During the switch-on process, the current increases following an e-function and asymptotically approaches a static end value. The current cannot change abruptly when switching off. If a switch is opened in the coil circuit, ent there is a high inductive voltage peak if overvoltages are not avoided by suitable measures. A generally known possibility is to connect a freewheeling diode parallel to the magnetic coil, which is arranged in such a way that the current flowing in the coil can flow back into the power supply, for example, after the coil has been switched off. The entire inductive energy of the magnet coil is dissipated via this current path, so that heat is generated partly in the current source and partly in the free-wheeling diode without special precautions. The on and off times of the electromagnetic consumer are long. In this circuit arrangement, the time required to build up and break down the magnetic field is essentially determined by the inductance and the operating voltage.

In order to shorten the switch-on time, the operating voltage is transformed to higher values in a known method. This technology is used in particular in battery-operated circuits, since the operating voltage is specified here. The disadvantage of this method is the increased circuit complexity and the additional upload time.

Advantages of the invention

In contrast, the method and the circuit according to the invention have the advantage that the energy balance is improved and the switch-on time is shortened by a rapid magnetic field build-up. This is achieved in that the existing inductive after switching off an electromagnetic consumer Energy of the current-carrying magnet coil is used for switching on an electromagnetic consumer. This reduces the power loss in the circuit and thus reduces the cooling effort. The reduced thermal load also increases operational safety.

The switch-on process is shortened in that the magnetic field build-up is accelerated by a voltage surge, with few additional electronic components being required.

With these properties, the method according to the invention and the associated circuit are particularly suitable for fast electromagnetic signal boxes, as are used in particular in single-coil or multi-coil solenoid valves.

In a particularly preferred embodiment of the method, the inductive energy is temporarily stored in a capacitor as capacitive energy. The free choice of capacitance makes it possible to choose an optimum between minimal power loss and excessive voltage to accelerate the magnetic field build-up.

In a further preferred embodiment of the method, a controllable switch is used in connection with the capacitor. It is then possible to freely select the switch-on time of the magnet coil whose magnetic field structure is to be supported with the capacitive energy. Furthermore, one is then free to choose the coil to be switched on, in particular it can be the same coil whose inductive energy was previously in the capacitor was saved.

A further energy saving and an additional increase in the switching speed of the electromagnetic consumer or of the electromagnetic signal box are obtained in a further preferred embodiment of the method by the switching operation, in which different current levels of the current flowing through the magnetic coil can be set by switching the controllable switches on and off are. The mean value of the current can be adapted to the operating states of the electromagnetic consumer in switching operation. Also in this switching operation, the use of the capacitor has advantages in that a part of the inductive energy is stored as capacitive energy after each switching operation.

In a preferred embodiment of the circuit, the capacitor and the controllable switch connected to it can be dispensed with. In this circuit, the excessive voltage occurs at a resistor arranged in parallel with the magnetic coil of the electromagnetic consumer.

Further details and advantageous developments of the method according to the invention and the associated circuitry result from the measures characterized in the subclaims.

drawing

The invention is explained below with reference to the drawing. Show it: Figure 1 shows a first embodiment of the circuit;

Figure 2 is a timing diagram of the circuit of Figure 1;

Figures 3 and 4 further embodiments of the circuit;

Figure 5 is a timing diagram of the circuit of Figure 4;

Figure 7 shows another embodiment of the circuit;

Figures 7 and 8 circuit diagrams of the circuit according to Fi gur 6 and

Figure 9 shows another embodiment of the scarf device.

Description of the execution examples

FIG. 1 shows a magnetic coil 10 with a first and second magnetic coil connection 11 and 12. The second magnetic coil connection 12 can be connected to a first power supply connection 14 by means of a first controllable switch 13. The first magnetic coil connection 11 is connected to a second power supply connection 15 via a first diode 16. A second diode 18 is connected to a first connection 19 of a first capacitor 17, the second connection 20 of which is connected to the first power supply connection 14. The first connection 19 of the first capacitor 17 can be connected to the first magnetic coil connection 11 via a second controllable switch 21 The first and second power supply connections 14 and 15 are bridged by a second capacitor 22. A control circuit 25 is provided which actuates the two controllable switches 13, 21 via two control lines 23, 24.

FIG. 2 shows switching positions S ₁ and S _{2 of} the first and second controllable switches 13, 21, the current i flowing through the magnet coil 10 and the voltage u across the first capacitor 17 as functions of the time t.

Figure 3 shows a further embodiment of the circuit according to the invention, in which two solenoids 10, 10a are driven in push-pull. The circuit is composed of two assemblies which are constructed in accordance with the arrangement shown in FIG. 1. One difference is that the connection 19 of the first capacitor 17 via the second controllable switch 21 with the first magnet coil connection 11a of the magnet coil 10a, or the first connection 19a of the first capacitor 17a via a second controllable switch 21a with the first connection 11 Solenoid 10 is connected. A control circuit 40 is provided, which controls the two first controllable switches 13 and 13a and the two second controllable switches 21 and 21a via four control lines 41 to 44.

FIG. 4 shows a further exemplary embodiment of the circuit which was developed from the circuit shown in FIG. 3. Reference is therefore made to the comments on FIG. 3. A control circuit 50 controls the controllable switches 13, 13a, 21 and 21a via control lines 51, 52, 53, 54. In contrast to the circuit according to FIG. 3, the capacitors 17 and 17a separately assigned to each magnetic coil 10 or 10a were replaced by a capacitor 17 ', the first connection 19' of which is connected to the second power supply connection 15 via a diode 50 and the second connection 20 'of which is connected to the second first power supply connection 14 is connected.

FIG. 5 shows a time diagram of the circuit according to FIG. 4, from which the time profile of the currents i ₁ and i ₂ flowing through the magnetic coils 10 and 10a and the voltage u _C dropping across the capacitor 17 'can be seen.

Figure 6 shows an embodiment of a circuit which differs from the circuit of Figure 3 only in that the controllable switches 21, 21a are omitted or bridged by wire. A second diode 18 connects the second magnetic coil connection 12 of the magnetic coil 10 directly to the first magnetic coil connection 11a of the magnetic coil 10a. Correspondingly, the second diode 18a connects the second magnet coil connection 12a of the magnet coil 10a directly to the first magnet coil connection 11 of the magnet coil 10. A control circuit 55 controls the two controllable switches 13 and 13a via its two control lines 56, 57.

FIGS. 7 and 8 show the course of the currents i ₁ and i ₂ flowing through the magnetic coils 10, 10a with different types of control.

Figure 9 shows a further embodiment of the circuit according to the invention. This differs from that shown in Figure 3 in that the two first capacitors 17 and 17a and the two second controllable switches 21 and 21a are omitted. The second diode 18 connects the second magnet coil connection 12 of the magnet coil 10 directly to the first magnet coil connection 11a of the magnet coil 10a; the second diode 18a connects the second magnetic coil connection 12a of the magnetic coil 10a directly to the first magnetic coil connection 11 of the magnetic coil 10. In parallel with the two magnetic coils 10 and 10a there is in each case a series circuit which consists of a resistor 62, 62d and a third diode 64, 64a . A control circuit 70 controls the two controllable switches 13 and 13a via its two control lines 72 and 74.

The circuit according to FIG. 1 is explained on the basis of the diagrams in FIG. 2. The magnet coil 10 with its first and second magnet coil connections 11 and 12 is part of an electromagnetic consumer, e.g. an electromagnetic signal box, which preferably knows two stable switching states. One application in which fast switching is required is, for example, in the case of fuel injection valves, by means of which fuel is metered in internal combustion engines.

As an initial state it is assumed that the first controllable switch 13 is open and no current i ₁ flows in the magnet coil 10. At a time t ₁ , the first controllable switch 13 receives a closing signal generated by the control circuit 25 via the control line 23. The switch 13 is a semiconductor component that can be switched on and off, for example a transistor. With the controllable second switch 21 open, a current i ₁ begins in the magnetic coil 10 via the first diode 16 and the closed to flow its transistor 13. The forward direction of the first diode 16 is determined such that current flows through it when the potential at the second power supply connection 15, that is to say at the anode of the diode 16, is higher than at the first magnet coil connection 11, that is to say at the cathode of the diode 16. The rise time is dependent on the ohmic resistance of this circuit, on the internal resistance of the current source lying between the first and second power supply connections 14 and 15, on the inductance L ₁ and the resistance R _{1 of} the magnet coil 10 and the operating voltage U _b . The final value of the current is given by the ohmic resistance of the series circuit, consisting of the first diode 16, the solenoid 10 and the closed transistor 13. At the time t ₂ , the transistor 13 receives a device 23 from the control circuit 25 via the control 1 issued opening signal. The current i ₁ in the magnetic coil 10 cannot change abruptly. It therefore continues to flow through the second diode 18 into the first capacitor 17. The forward direction of the second diode 18 is determined such that current can flow through it if the potential at the second magnet coil connection 12, that is to say at the anode of the diode 18, is higher than at the first connection 19 of the first capacitor 17, that is to say the cathode of the diode 18 The capacitor 17 collects the charge and a voltage u is produced, the height of which is given by the capacitance of the first capacitor 17 and the amount of charge introduced. The value from which the voltage u across the capacitor 17 increases after the time t ₂ is slightly below the operating voltage U _b . When the current i ₁ through the solenoid 10 has dropped to zero, the voltage u on the first capacitor 17 has reached its maximum value. At time t ₃ , the transistor 13 and simultaneously the second controllable switch 21 are closed via the control lines 23 and 24. In this switch-on process, in contrast to the switch-on process at time t ₁ , a higher voltage is available at the first magnet coil connection 11, which voltage is equal to the voltage u at the first capacitor. The higher voltage on the magnetic coil 11 results in a rapid current rise which continues until the charge has flowed from the first capacitor 17 via the closed second controllable switch 21, ie u has assumed approximately the value of U. During this process, the first magnetic coil connection 11 is separated from the second power supply connection 15 by the first diode 16 which is acted on in the reverse direction. After the capacitor has been charged, the current in the magnet coil 10 changes, starting from the instantaneous value, in accordance with the time constant available at the time t ₁ . If the coil current has not yet reached a stationary end value during the capacitor discharge, it rises again after the capacitor 17 has discharged with the slower time constant based on U _b . If, as shown in FIG. 2, the current value overshoots during capacitor discharge, the current drops to a stationary value after the discharge. For fast switching behavior, overshoot 1 is desirable. The first capacitor 17 discharges to a voltage value which is given by the operating voltage U _b minus the lock voltage of the first diode 16.

If a thyristor is provided for the second controllable switch 21, the switch 21 opens without another control signal in the zero current crossing. Is a second controllable switch 21 Transistor provided, then this is supplied via the control line 24 from the control circuit 25, an opening signal. The second capacitor 22 parallel to the power supply between the first and second power supply connections 14 and 15 has the task of keeping the internal resistance of the power source low at the moment of switching on t ₁ and t ₃ .

An energy saving compared to conventional circuits with free 1 aufdi edens results from intermediate storage of the inductive energy present immediately after the magnetic coil 10 is switched off in the first capacitor 17. This energy is used again for the next switch-on process or for the reconstruction of the magnetic field during the switch-on process . The transistor 13 is subjected to less stress during the switch-on process, since its switch-on process is also accelerated due to the faster current rise in the magnet coil 10.

The circuit for a single-coil signal box according to FIG. 1 can be expanded according to FIG. 3 for a two- or multi-coil signal box. With this circuit too, the inductive energy present when the magnet coil 10 is switched on is stored in the first capacitor 17 after the magnet coil 10 has started to be switched off. This energy is used to rapidly build up the magnetic field in the other magnet coil 10a. For this purpose, the first connection 19 of the first capacitor 17 is connected to the first coil connection 11a via the first controllable switch 21 during the switching-on process of the other magnet coil 10a. Analogously, the magnetic energy is stored in the other first capacitor 17a after the start of the shutdown process of the other magnet coil 10a. It then becomes a quick one Magnetic field structure used in the magnetic coil 10. For this purpose, the first connection 19a of the other first capacitor 17a is connected via the other second controllable switch 21a to the first coil connection 11 of the magnet coil 10 during its switch-on process. The solenoids 10 and 10a are switched on and off alternately, for example in push-pull. If the greatest possible energy saving is dispensed with, this circuit can also be used in “overlapping” operation, ie a current flows in both magnet coils 10 and 10a during short periods of time. The control circuit 40 here has four control lines 41 to 44, which are used to control the four controllable switches 13, 13a, 21 and 21a. The two second controllable switches 21 and 21a can be thyristors which only require a switch-on pulse and switch off at the next current zero crossing without a switch-off pulse. Semiconductor components that can be switched on or off, such as transistors or thyristors that can be switched on and off, can also be used here, with which, in overlapping operation, a defined separation of the two magnet coil circuits results.

The circuit according to FIG. 4 is explained using the time diagram shown in FIG. 5. The aim of the circuit is to reduce the current i ₂ flowing through the magnet coil 10a as quickly as possible to i ₂ = 0 at time t ₁ in FIG. 5 and to increase the current i ₁ through the magnet coil 10 to i ₁ = i _max . It is assumed here that the capacitor 17 'is charged to a voltage of U _{C soll} > U _b by one or more preceding switching operations at the time t t t ₁ , as shown in FIG. 2 for t t t ₃ . The controllable switches 13 and 21a are closed at the time t ₁ t t t t ₃ . The capacitor 17 'is thus discharged via the solenoid 10. The rise of i ₁ is very fast, especially with U _C >> U _b . Neglecting the voltage drop at the controllable switches for the current rise, the following equation applies:

where R ₁ denotes the resistance and L ₁ the inductance of the magnetic coil 10 and u _C denotes the voltage stored in the capacitor 17 '. The current i ₁ approaches the value u _C / R asymptotically.

At the time t ₁ ≤ t ≤ t ₂ , the diodes 16a and 18a are conductive. The capacitor 17 'is charged via it with the current i ₂ as long as i ₂ > i ₁ . The voltage u _C across the capacitor 17 'therefore rises for a short time

Time to values u _C > U _{C should} . If the voltages dropping across the diodes 16a and 18a are neglected, the rate of decrease for i _{2 is}

R ₂ denoting the resistance and L ₂ denoting the inductance of the magnetic coil 10a.

The value i ₂ = 0 is reached quickly at time t = t ₂ and is then maintained because then the diodes 16a and 18a block. It can be seen from FIG. 5 that i ₁ and i _{2 reach} their target values very quickly. Therefore should the armature of the electromagnetic consumer will also fly in the time range t ₁ ≤ t ≤ t ₂ .

At time t = t ₃ , i _{1 has reached} the lower setpoint of i _max ; the voltage u _{C of} the capacitor

17 'is significantly reduced. The sum of the energies is also reduced due to the losses occurring in the components at the time t ₃ compared to the time t ₁ , the following equation applying to the energy:

To be able to carry out the next switching process at the same speed, u _C must therefore be increased again. For this reason, the controllable switch 21a is blocked for the period t ₃ ≤ t t t ₄ and a current is passed through the magnet coil 10 via the diode 16. The rate of increase di ₁ / dt of current i ₁ is reduced compared to t ₁ ; the asymptote is now U _b / R. The lower rate of increase can be seen in FIG. 5. During this period, energy is withdrawn from the voltage source and input into the magnetic coil as inductive energy.

This energy is then stored as capacitive energy in the capacitor 17 ', a distinction being made in the following two cases:

In case 1 i reaches at time t. the upper value of i _max so that the maximum energy is reached. This case is also shown in FIG. 5

In case 2, i ₁ does not reach the upper value of i _max

For example, because the energy stored in the capacitor 17 'from previous switching operations was not sufficient for sufficient current increase in the solenoid 10.

The voltage in the capacitor 17 'is now increased in that the controllable switch 13 is switched off for t ₄ t t t t ₅ . In this case, the diodes 16 and 18 are in the conductive state, so that the capacitor 17 'is charged with i ₁ , i ₁ starting from i _max in case 1 and from an underlying value in case 2 and to a holding current i _H falls off. The holding current i _H is selected so that the electromagnetic consumer remains in the activated state despite the reduction in the current i ₁ flowing through the magnetic coil 10. It can be seen from FIG. 5 that a maximum limit value i _{H max} and a minimum limit value i _{H min are} specified for i _H.

In case 1, the value U _c set given for the capacitor voltage _is reached before i _{1 has} dropped to i _{H min} . In the time interval t ₅ t t t t ₆ , the controllable switch 21a is therefore switched on, so that the inductive energy is reduced practically without external voltage via the resistor R _{1 of} the magnetic coil 10, via the switch 21a and the diode 18 and not further into the Capacitor 17 'is stored. The voltage u _C therefore remains during this

Period unchanged at U _{C sol l} . When the current i _{1 reaches} the value i _{H min} , the controllable

Switch 21a off and switch 13 switched on, so that i ₁ increases again. At time t ₇ , i ₂ again reaches the value i _{H max} , so that current i ₁ is reduced again by switching on switch 21a and switching off switch 13. In this way, i _{1 is} always kept at a predetermined value i _{H min} i i ₁ i i _{H max} . In case 2, in which i _l has not reached the value i _max at the time t ₄ , the switch 13 is switched on instead of the switch 21 a in the time range t ₅ t t t t ₆ , so that new energy is drawn from the voltage source, which then can be fed into the capacitor 17 'until finally the required total energy is reached.

The controllable switch 13 is also turned on in case 1 when the current i _l drops to i _{H min} before u _{C has reached} the value U _{C soll} . This increases i _l again. In a next cycle, i _l is then reduced again and the inductive energy is fed to the capacitor 17 '.

In case 2, both controllable switches 13 and 21a are opened at time t ₆ , so that u _{C is increased} via diodes 16 and 18.

It can be seen that i _l and u _C can be set to any desired value of u _C or mean value for i _l by suitable control of switches 13 and 21a.

At time to, for example, the solenoid 10 is switched off and the solenoid 10a is switched on by a signal generated outside the control circuit, ie the current i _l is to be reduced as quickly as possible to i _l = 0 and the current i _{2 is} as fast as possible to the value i ₂ = i _{max can be} increased. For this purpose, the controllable switches 13 and 21a are opened and the switches 13a and 21 are closed, so that the charging of the capacitor 17 'is available for a rapid increase in i ₂ . The diode 60 connected to the power supply and to the capacitor 17 'is arranged such that the capacitor 17' is charged to U _b immediately after the power supply is switched on, so that the transistors used as controllable switches 13 and 13a do not have an inverse voltage which is too high be charged. For this purpose, the anode of the diode 60 is connected to the second power supply termination 15 and the cathode of the diode 60 to the first connection 19 'of the capacitor 17'.

Another embodiment of the circuit is shown in Figure 6. It is explained in more detail with reference to FIGS. 7 and 8.

In this case, the control of the circuit should take place in such a way that the currents flowing through the magnet coils 10 and 10a assume an upper holding current i _HO or a lower holding current i _HU . The holding currents are selected so that the armatures of the solenoids 10 and 10a do not fall back when the current is reduced from i = i _max to i = i _HO or when the current increases from i = zero or one

Do not tighten the value i <i _HU to i = i _HU . In figure

7 is a value of i _HO <i _max for i _HO and in FIG

8 the value i _HO = i _{max has been} selected for i _HO .

The reduction in the value of i _HO according to FIG. 7 leads to an energy saving.

At time t ₁ , the magnet coil 10 is to be excited in FIGS. 7 and 8. For this purpose, the controllable switch 13 is closed and the switch 13a is opened. For the time t <t ₁ , the currents i ₁ and i ₂ flow in the magnet coils 10, 10a. After the switches have been activated, the current i _{1 flows} via the controllable switches 13 and i ₂ via the diodes for t <t ₁ 16a and 18a. As long as i ₂ > i ₁ , the capacitor 17 is charged to a value u _C > U _b since the diode 16 blocks. If a small capacitance is selected for the capacitor 17, u _C becomes particularly large.

As already explained with reference to FIG. 5, i ₂ falls very quickly, while i ₁ increases rapidly. Due to the rapid change in current and the resulting change in force in the time interval t ₁ ≤ t ≤ t ₂ , the armature lifts off the stop. The forces increase during the movement without any further increase in current.

At time t ₃ , the sensible maximum current i _{max is} reached for i ₁ in _FIGS . 7 and 8. The controllable switch 13 is opened, the switch 13a remains open. As a result, i ₁ decreases, while i ₂ increases again due to the energy transfer. Finally, the currents reach the desired holding values i _HO or i _HU , i _HO <i _max in FIG. 7 and i _HO = i _max in FIG. Due to the hysteresis, an "overshoot" takes place. At time t = t ₄ , switch 13 is closed so that i ₁ rises again while i ₂ decreases. By opening switch 13 for t = t ₅ , i ₁ decreases again, while i ₂ increases. Due to the clocked control, the holding currents can be set to any desired value 0 ≤ i ≤ i _max

Provided that the timing with ideally switched diodes and transistors as controllable switches does not generate any losses, the following equation applies to the lower mean holding current:

with T ₁ = t _{13 a} / t _tot , where t ₁₃ denotes the time that the switch

13 in the switched-on state, and t _{tot stands} for the entire clocked period.

The following equation applies to the upper mean holding current i _HO :

i _HO = i _HU / (1-T ₁ ).

The circuit is only effective when i _HO / i _HU > O. A practical value is i _HO / i _HU = 4. From this, T _{1 is} calculated as T ₁ = 0.75

While, in the operation shown in Figure 8 tvorgang a Umschal at time t ₆ can be immediately initiated, it is necessary in accordance with Figure 7 before switching at time t _7, the current i ₁ in the period t ₆ ≤ t ≤ t ₇ in driving can be increased to i _max , so that

Switching enough energy is available.

This period t ₆ ≤ t A t ₇ in FIG. 7 must, however, be given before each switchover. An advantage of this control, however, is that the effects of the clocking have decayed at time t ₇ and cannot adversely affect the switching of the solenoids 10 and 10a.

Another embodiment of the circuit according to the invention is shown in FIG. This circuit is particularly suitable for a two-coil signal box. Compared to the circuit according to FIG. 3, the two first capacitors 17, 17a and the two second controllable switches 21, 21a have been omitted. The switch-on time of one coil after switching off the other coil can therefore no longer be freely selected. For this purpose, the circuit according to FIG lines consisting of a resistor 62, 62a and a third diode 64, 64a supplemented, which are parallel to the two solenoids 10, 10a. A simplification results with respect to the control circuit 70, which need only have two control lines 72, 74, via which the two controllable switches 13, 13a are actuated. As a result of the elimination of the first two capacitors 17, 17a, the inductive energy can no longer be stored temporarily, but is instead used directly to build up the magnetic field in the other magnet coil.

The circuit according to FIG. 9 works as follows: First, the first controllable switch 13, preferably a transistor, is closed. A current i ₁ then flows in the magnetic coil 10. After the transistor 13 has received an opening signal from the control circuit 70 via the control line 72, the current i ₁ in the magnet coil 10 no longer flows via the transistor 13 to the first power supply connection 14 but now via the second diode 18 directly to the first magnet coil connection 11 a of the magnet coil 10a, which is still currentless at this point in time, although the second controllable switch 13a, also preferably a transistor, has received a closing signal from the control circuit 70 via the control line 74 at the same time as the opening signal for the switch 13. The current i ₁ originating from the magnetic coil 10 can only flow via the current path consisting of the resistor 62a and the third diode 64a when the transistor 13a is switched on. The forward direction of the third diode 62, 62a is determined such that current flows through it when the potential at the first magnet coil connection 11, 11a, that is to say at the anode of the diode 62, 62a, is higher than at the second magnet coil connection 12 or at the cathode the diode 62, 62a. According to Ohm's law, a voltage increase results as the product of the resistance value of the resistor 64a and the current i ₁ flowing through the resistor 64a. This excessive voltage leads to an accelerated current build-up in the magnet coil 10a. In the stationary, switched-on state of the magnet coil 10a, no current flows through the resistor 62a and the third diode 64a, since in general the voltage drop across the magnet coil 10a is below the lock voltage of the third diode 64a and thus blocks it. The current ip through the magnetic coil 10a then flows through the first diode 16a, which had blocked at the resistor 62a during the voltage surge.

If the transistor 13a now receives an opening signal and at the same time the transistor 13 receives a closing signal, the magnetic field build-up in the magnetic coil 10 takes place again in the manner described, the inductive energy of the magnetic coil 10a being used for the switching-on process of the magnetic coil 10.

The resistance value of the two resistors 62, 62a is dimensioned in such a way that the excess voltage cannot assume too high values. In one embodiment, it was 100 Ω, which resulted in a voltage surge of about 200 V when the coil current was in the steady state of 2 A.

A further improvement in the switching behavior, ie a further energy saving and time reduction, is obtained in clocked operation. The exemplary embodiments of circuits 1, 3, 4 and 6 are particularly suitable for this. As already mentioned above, clocked operation means that the first controllable switch 13 or the first two controllable switches 13 and 13a can also be switched on or off in the stationary operating states of the electromagnetic consumer. If the clock frequency is sufficiently high, a certain average value of the current through the magnet coil 10, 10a is set depending on the ratio of the switch-on to the switch-off period. The capacitor 17, 17 'or the two capacitors 17 and 17a are charged somewhat after the start of each switch-off process. This switching operation makes it possible to assign different current and thus force levels of the electromagnets to the different operating states, namely stroke to one position, holding state in this position, return stroke to the other position and holding state in the other position, with electromagnetic manipulated values. As already described, the current in the magnet coil 10 or in the magnet coils 10, 10a is completely switched on or off during the stroke and return stroke phases. In the stationary operating state, an average current i _HU is then set in the switching position that corresponds to the de-energized state so that the switching function is still guaranteed. Switching to the other position, which corresponds to the strora flow case, is then possible in a short time by overcoming a minimal force. If this position is then reached, the average current is reduced from i _max to the value i = i _HO , that is, to such an extent that the switching function in this position is also just just guaranteed. A return to the previous position is then also quickly possible by overcoming a small force. This example is a system in which the current has four different levels: zero, holding current i _HU for one position, maximum value i _max and holding current i _HO for the other position. The clocked activation of the controllable switches 13, 13a also makes it possible to compensate for the predetermined holding current values or the value of i _max even with changes in the voltage supply that occur during the driving operation of a motor vehicle by a suitable change in the clock ratio. For example, the clock ratio is varied in the range of 0.75 t t ₁ 1 1.

With the method according to the invention of using the inductive energy of a switched-on current-carrying magnet coil after the start of its switch-off process to build up current in a magnet coil, a switching arrangement according to FIG. 3 resulted in a reduction in the switching time of a double solenoid valve from 0.31 ms to 0.24 ms in clocked operation. The magnet coils 10, 10a each had a nominal current of 20 A and had an inductance of 300 μH. The capacitance of the first two capacitors 17 and 17a was 20 μ F each.

Claims

EXPECTATIONS

1. A method for controlling electromagnetic consumers with at least one magnetic coil, in particular magnetically actuated injection valves, via at least one controllable switch, characterized in that the inductive energy of the current-carrying magnetic coil (10, 10a) of the electromagnetic consumer after switching off an electromagnetic consumer for the switching on of an electromagnetic consumer is used.

2. The method according to claim 1, characterized in that the existing after switching off the electromagnetic consumer inductive energy of the current-carrying magnet coil (10, 10a) is used to generate capacitive energy in at least one capacitor (17, 17a, 17 ').

3. The method according to claim 2, characterized in that the energy stored in the capacitor (17, 17a, 17 ') is used for the switching-on process of the electromagnetic consumer switched off immediately before.

4. The method according to claim 2, characterized in that the capacitive energy stored after switching off an electromagnetic consumer in the capacitor (17, 17a, 17 ') is used for switching on at least one other electromagnetic consumer.

5. The method according to any one of claims 1 to 4, characterized in that the energy stored in the capacitor (17, 17a, 17 ') is deliberately delivered via at least one controllable switch (21, 21a) connected to the capacitor for a later switch-on process.

6. The method according to any one of claims 2 to 4, characterized in that the energy stored in the capacitor (17, 17a, 17 ') is set to a predetermined value.

7. The method according to claim 1, characterized in that the inductive energy present after switching off the electromagnetic consumer d e r current-carrying magnet coil (10, 10a) of the consumer is used immediately after the start of the shutdown for the switching-on process of at least one other electromagnetic consumer.

8. The method according to any one of claims 1 to 7, characterized in that the middle through the magnetic coil (10, 10a) of the electromagnetic Current flowing to the consumer is kept at least one value, preferably four different predetermined values, by periodic activation of the consumer.

9. The method according to any one of claims 1 to 8, characterized in that the current flowing through the magnetic coil (10, 10a) of the electromagnetic consumer to be switched off before it is switched off is set to an optimum value for a subsequent switch-on process.

10. Circuit for carrying out the method according to one of claims 1 to 6 and 8 or 9, characterized by at least one capacitor connected to at least one electromagnetic consumer (17, 17a, 17 ') for temporary storage of the electromagnetic consumer in its magnetic coil when the electromagnetic consumer is switched off ( 10, 10a) existing inductive energy.

11. A circuit according to claim 10, characterized in that a capacitor (17, 17a) is assigned to each electromagnetic consumer.

12. Circuit according to Anspru.ch 10, characterized in that a capacitor (17 ') is assigned to several electromagnetic consumers.

13. Circuit according to one of claims 10 to 12, characterized by at least one switch (21, 21a), via which the energy stored in the capacitor (17, 17a, 17 ') can be supplied to at least one electromagnetic consumer for switching it on.

14. Circuit according to claim 13, characterized in that the controllable switch (21, 21a) is a transistor.

15. Circuit according to one of claims 10 to 14, characterized by a diode (18, 18a) arranged between the electromagnetic consumer and the capacitor (17, 17a, 17 ') via which the inductive energy present in the capacitor when the electromagnetic consumer is switched off (17, 17a, 17 ') is fed in and which prevents a current flowing in the opposite direction to the inductive energy.

16. Circuit for carrying out the method according to claim 1 or 7, characterized by a connection of an electromagnetic consumer with at least one further electromagnetic consumer, via which the inductive energy present when the one electromagnetic consumer is switched off is fed directly to the other electromagnetic consumer for switching it on .

17. A circuit according to claim 16, characterized by a series circuit connected in parallel with the electromagnetic consumer, comprising a resistor (62, 62a) and a diode (64, 64a), via which the inductive energy of one of the consumers switched off for generating a switch-on operation of the other Electromagnetic consumer serving voltage is derived, the diode (62, 62a) prevents a current flowing in the opposite direction.

18. Circuit according to one of claims 16 or 17, characterized by a diode arranged in the connection (18, 18a), which prevents a current flowing in the opposite direction to the inductive energy.

19. Circuit according to one of claims 10 to 18, characterized by at least one diode (16, 16a) arranged between the electromagnetic consumer and a voltage source connected to it, which prevents the inductive energy from being dissipated into the voltage source.

20. Circuit according to one of claims 10 to 19, characterized in that the controllable switch (13, 13a) serving to control the electromagnetic consumer is a transistor.

21. Circuit according to one of claims 10 to 19, characterized in that the controllable switch (13, 13a) serving to control the electromagnetic consumer is a thyristor which can be switched on and off.

22. Circuit according to one of claims 10 to 21, characterized by at least one diode (60) via which the capacitor (17, 17a, 17 ') can be connected and charged to the voltage source.