EP1979598B1 - Device for switching inductive fuel injection valves - Google Patents

Abstract

Disclosed are a method and a device for more rapidly switching inductive fuel injection valves. According to the invention, the magnetic retaining forces generated by remanence in a bistable valve comprising an opening and closing coil or by eddy currents in a standard valve comprising an opening coil and a closing spring are eliminated with the aid of a negative current that flows through the coil in a direction running counter to the direction of the operating current. Additionally, the magnetic yoke and armature that are used are made of materials having different conductivities in order to be able to close the valve even more quickly.

Description

The invention relates to a device for switching inductive fuel injection valves according to claim 1 or 6.

Stricter emission regulations and the need for ever better fuel efficiency have driven the introduction of high-pressure direct injection systems for diesel and gasoline engines in recent years, as this significantly improves the quality of the mixture preparation.

Features of these systems are very high fuel injection pressures up to over 2000 bar (diesel) and over 100 bar (gas), as well as the supply of fuel in several injections per injection.

By adapting the fuel metering to the dynamics of the combustion process, a wealth of functional improvements can be achieved: at the petrol engine: better efficiency, less raw emissions; with the diesel engine: less engine noise (knocking), less soot particles, lower NOx production, better cold start behavior.

In some diesel engines fuel is injected at periodic intervals even in the exhaust stroke to achieve about the regeneration of a particulate filter in the exhaust system by burning the soot particles.

The abundance of these functions, which are possible with modern direct injection systems, have in the episode an enormous Tightening of the requirements for precision and dynamics of the injection valves entailed. Thus, now valve switching times of 100 to 500μs are required in order to inject at the high system pressures even the smallest amounts of fuel down to a few micrograms with high accuracy and high temporal precision.

This has finally allowed piezotechnology breakthrough, allowing much faster and more precise valve actuation compared to traditional solenoid technology. It has meanwhile become standard for diesel passenger car engines.

Since the piezoceramic used here reacts spontaneously to a change in the control voltage with a change in volume of the injected fuel quantity, a very fast, almost instantaneous actuation of the injection valves is possible. In contrast, in the classic solenoid valve, a current flow must first be built up in the inductance-excited exciter winding, which then, but only after reaching a certain current value, can actuate the valve.

However, the benefits of piezo technology for high pressure injectors are associated with significant costs, so there is an urgent need to continue to use solenoid injectors for less demanding high pressure direct injection systems.

A typical example of this is large-volume, slow-running diesel truck engines, such as 9-liter 6-cylinder engines with maximum operating speeds of about 1800 rpm. In addition to the low engine speed, the requirements for the smallest injection quantities are also reduced because of the large displacement. Also, the number of injection pulses per injection process is lower because, for example, a pre-injection to reduce the diesel-typical "nailing" can be omitted because of the already quite high running noise of the truck engine.

Investigations have shown that solenoid injectors are in principle suitable for such applications, but require some further development. Thus, for use in direct injection systems with standard solenoid valves having a coil (winding) for the magnetic opening and a spring for closing the valve, the closing delay must be reduced.

The main obstacle in closing such a standard solenoid valve are the eddy currents in the magnetic material of the valve, which slowly decay after switching off the actuating current and prevent rapid closing of the valve. This behavior defines the minimum valve opening time and thus increases the smallest possible fuel injection quantity.

In the case of bi-stable injectors with two windings and fixation of the valve in the respective end position by means of remanence forces, a reduction of both the switch-on time for opening the valve and the switch-off time for closing the valve is required.

In FIG. 1 a known, basic circuit arrangement for operating a coil of a fuel injection valve with PWM (pulse width modulation) operation is shown. There, the one terminal of the coil L1 is connected by means of a first switching transistor T1 to the positive pole V + of a supply voltage source V and the other terminal by means of a second switching transistor T2 to reference potential GND. The source terminal of the first switching transistor T1 is connected to one terminal of the coil L1, its drain terminal to the positive terminal V +. The source terminal of the second switching transistor T2 is connected to reference potential GND and its drain terminal to the other terminal of the coil L1. In addition, a freewheeling diode D1 of the reference potential GND is arranged to conduct current to one terminal of the coil L1 and a Rekuperationsdiode D2 from the other terminal the coil L1 current-conducting to the positive pole V + of the supply voltage source arranged.

The circuit after FIG. 1 works as follows: before the start of a switch-on both switching transistors T1, T2 are non-conductive. When switching on (opening signal EO, rising edge) both switching transistors T1, T2 are switched electrically conductive. As a result, the supply voltage V is applied to the coil inductance, for example V = 48V. A current flows through the coil L1, which rises rapidly.

Upon reaching a predetermined upper current setpoint at which the valve opens, switching transistor T1 is switched off by means of the PWM unit PWM and the coil current now flows through the coil L1 via the freewheeling diode D1 and switching transistor T2, wherein it slowly drops. If the current now reaches a lower predetermined desired value, switching transistor T1 is again turned on, whereupon the coil current increases again.

By repeated Leitend- and Nichtleitend switching transistor T1 so the coil current can be maintained during the duty cycle of the valve to an approximately constant value. At the end of the switch-on period (falling edge of the opening signal EO), both switching transistors T1 and T2 are simultaneously switched nonconducting (with a standard valve with closing spring), whereupon the coil L1 is connected to the supply voltage source via the freewheeling diode D1 and the recuperation diode D2 V discharges and the valve closes.

FIG. 2 As described above, in the upper track, the voltage waveform and, in the lower track, the current waveform in the opening coil L1 during the opening period of a standard fuel injection valve.

FIG. 3 shows the principle of a bistable fuel injector. The valve needle 1 is mounted displaceably in a housing 4 and shown in the "OPEN" position. It lies on the left iron yoke 2. The left iron yoke 2 encloses the opening coil AB (rectangles A and B with bevel). By a previous actuation current in the opening coil AB, the left iron yoke was magnetized, so that now, when the current subsides, it holds the valve needle 1 in the "OPEN" position.

In this position, the way is clear for the fuel under high pressure from the inlet a (in the arrow direction) to the outlets b and c and on to the valve nozzles, not shown, which are opened thereby. In the following, the term "fuel" may also be a "hydraulic medium", wherein instead of a fuel circuit, a hydraulic circuit may be provided, by means of which a fuel injection valve is controlled with hydraulic pressure boosting.

To close the valve, an actuating current is now passed through the closing coil C-D, so that the valve needle 1 moves to the right iron yoke 3. After switching off the closing current, the valve needle 1 is held in the "CLOSED" position by the magnetization of the right-hand iron return key 3.

This blocks the path from the inlet a to the outlets b and c. At the same time, the outlets b and c are connected to the return lines r, which are designed as a ring line, which reduce the fuel pressure between the outlets b, c and the valve nozzles, not shown, whereby the valve is closed.

Since a bistable valve has two coils, namely an opening and a closing coil, the circuit arrangement is after FIG. 1 twice per valve: once to operate the opening coil AB (L1 in FIG. 1 ) and once to operate the closing coil CD.

Out DE 100 18 175 A1 a circuit arrangement for the operation of a Hubanker actuator for a gas exchange valve is known, in which at the end of the actuation operation, a direction opposite to the actuating current current is sent through the coil to initiate a faster change of the switching state.

Such methods are for example also off DE 199 21 938 A1 . DE 195 26 681 A1 and DE 40 16 816 A1 known.

• bei bistabilen Ventilen die Öffnungs- und die Schließverzögerung, und
• bei Standard-Solenoidventilen (mit Schließfeder) die Schließverzögerung

verringert.The object of the invention is to provide an improved device for accelerated switching of inductive fuel injection valves, which

• for bistable valves, the opening and closing delay, and
• for standard solenoid valves (with closing spring) the closing delay

reduced.

This object is achieved by a device according to the features of claim 1 or 6.

Advantageous developments of the invention can be found in the dependent claims.

The valve switching times are known to be reduced when in a bistable valve, the magnetic holding forces are eliminated when activating a coil by deliberately clearing the remanence of the other coil, and in a standard valve (with closing spring) - induced by the decaying eddy currents - magnetic holding forces Disabling the coil can be eliminated.

In both cases, the impression of a negative current pulse is required in the respective coil, whose Current level and time course must correspond as closely as possible to the magnetic requirements of the valve.

Embodiments of the invention are explained below with reference to a schematic drawing.

Figur 1:

eine bekannte, prinzipielle Schaltungsanordnung zum PWM-Betrieb eines induktiven Kraftstoff-Ein- spritzventils,

Figur 2:

die Spannungs- und Stromverläufe bei PWM-Betrieb des Kraftstoff-Einspritzventils nach Figur 1,

Figur 3:

die Detailansicht eines bistabilen Kraftstoff-Ein- spritzventils,

Figur 4:

eine erfindungsgemäße Schaltungsanordnung zum PWM- Betrieb eines induktiven Kraftstoff-Ein- spritzventils,

Figur 5a:

Spannungs- und Stromverlauf am Stromspiegel der er- findungsgemäßen Schaltungsanordnung,

Figur 5b:

den zeitlichen Verlauf von Betriebsstrom und nega- tivem Strom beim Öffnen und Schließen eines bistabilen Ventils.

Figur 6:

eine Steuerungseinrichtung für den negativen Strom bei einem bistabilen Kraftstoff-Einspritzventil,

Figur 7:

eine Steuerungseinrichtung für den negativen Strom bei einem Standard-Einspritzventil mit Öffnungs- spule und Schließfeder,

Figur 8:

eine erfindungsgemäße Schaltungsanordnung zum Be- trieb mehrerer Ventilspulen,

Figur 9:

den zeitlichen Verlauf der Ventilschaltbewegungen, ohne (9a) und mit Entmagnetisierungsstrom (9b),

Figur 10:

eine weitere Schaltungsanordnung,

Figur 11:

eine Steuerungseinheit zur Schaltungsanordnung nach Figur 10,

Figur 12:

die Signalverläufe in dieser Steuerungseinheit,

Figur 13:

eine Steuerungseinheit zur Schaltungsanordnung nach Figur 10.

Figur 14:

eine prinzipielle Darstellung eines Standard- Solenoid-Einspritzventils, und

Figur 15:

die Entstehung vorübergehender, entgegengesetzter Feldrichtungen.

In the drawing show:

FIG. 1:

a known, basic circuit arrangement for the PWM operation of an inductive fuel injection valve,

FIG. 2:

the voltage and current waveforms in PWM operation of the fuel injector after FIG. 1 .

FIG. 3:

the detailed view of a bistable fuel injection valve,

FIG. 4:

an inventive circuit arrangement for the PWM operation of an inductive fuel injection valve,

FIG. 5a

Voltage and current profile at the current mirror of the circuit arrangement according to the invention,

FIG. 5b:

the time course of operating current and negative current when opening and closing a bistable valve.

FIG. 6:

a negative current control means in a bistable fuel injection valve,

FIG. 7:

a control device for the negative current in a standard injection valve with opening coil and closing spring,

FIG. 8:

a circuit arrangement according to the invention for operating a plurality of valve coils,

FIG. 9:

the time course of the valve switching movements, without (9a) and with degaussing (9b),

FIG. 10:

another circuit arrangement,

FIG. 11:

a control unit according to the circuit arrangement FIG. 10 .

FIG. 12:

the signal curves in this control unit,

FIG. 13:

a control unit according to the circuit arrangement FIG. 10 ,

FIG. 14:

a schematic representation of a standard solenoid injector, and

FIG. 15:

the emergence of temporary, opposite field directions.

FIG. 4 shows a circuit arrangement according to the invention for the PWM operation of a coil, for example, the opening coil L1 of an inductive fuel injection valve. The circuit part (T1, T2, D1, D2) used to control the valve operating current is included in the description FIG. 1 already executed.

As described therein, the one terminal of the coil L1, for example, the opening coil of the valve by means of the first switching transistor T1 to the positive terminal V + of the supply voltage source V and the other terminal connected by means of the second switching transistor T2 to reference potential GND. The source terminal of the first switching transistor T1 is connected to one terminal of the coil L1 - its drain terminal to the positive terminal V +. The source terminal of the second switching transistor T2 is connected to reference potential GND, its drain terminal to the other terminal of the coil L1.

The freewheeling diode D1 is arranged to conduct current from the reference potential GND to one terminal of the coil L1 and the recuperation diode D2 is arranged to conduct current from the other terminal of the coil L1 to the positive pole V + of the supply voltage source.

In addition, the circuit is extended by five transistors T3 to T7, five resistors R1 to R5, a capacitor C1 and a diode D3, as well as the inclusion of the on-board vehicle voltage source Vbat.

The third transistor T3 is connected in parallel with the freewheeling diode D1: its source terminal is connected to reference potential GND, its drain terminal to the connection point of freewheeling diode D1 and the one terminal of the coil L1. It serves to connect in the current-conducting state connected to the first switching transistor T1 terminal of the coil L1 with reference potential GND.

Transistors T4 to T6, together with resistors R2 to R4, form a complementary Darlington current mirror which provides a negative current. This current mirror T4-T6 is connected via a first resistor R1 to the positive pole V + of the supply voltage V. The source terminal of the fourth transistor T4 is connected to the other terminal of the coil L1, while the source terminal of the sixth transistor T6 is connected via the series circuit of the seventh transistor T7 and the fifth resistor R5 to reference potential GND. The gate terminals of the third transistor T3 and the seventh transistor T7 are connected to each other and to the output of a control device, which in FIG. 6 7 and 7, respectively, for generating a negative current control negative current control NSC.

Between the connected to the current mirror T4-T6 terminal of the first resistor R1 and reference potential GND. a capacitor C1 is connected, which is charged by the on-board voltage source Vbat via a protective diode D3 and the current mirror T4-T6 is energized, which is controlled by the seventh transistor T7 connected as a current source.

As long as the control signal NSC at the gate terminal of the third transistor T3 has low level (0V), this transistor T3 and also the seventh transistor T7 is non-conducting, so that at the output of the current mirror, through the source terminal of the fourth transistor T4 is formed, too no electricity flows. The circuit is inactive, through the coil L1 no current flows in the negative direction (in the direction from transistor T4 to transistor T3).

If the control signal NSC jumps to high level (for example + 5V), the third transistor T3 is turned on and connects one terminal of the coil L1 to reference potential GND. At the same time begins to flow through the seventh transistor T7, a current whose magnitude by the value of the fifth resistor R5 and the base voltage (+ 5V) of the seventh transistor T7 minus its base-emitter voltage (5V-0.7V ≈ 4.3V) is determined.

Furthermore, this current also flows through the sixth transistor T6 and the third resistor R3, at which it generates a voltage drop. According to the principle of operation of a current mirror with emitter resistors (for negative current feedback), the same voltage drop will develop between the base terminal of the fifth transistor T5 and the second resistor R2. If one now chooses the value of resistor R2 much lower than the value of R3, a correspondingly higher current through R3 is required for this: $${\mathrm{I}}_{\mathrm{R}\mathrm{2}}\mathrm{/}{\mathrm{I}}_{\mathrm{R}\mathrm{3}}\mathrm{=}\mathrm{R}\mathrm{3}\mathrm{/}\mathrm{R}\mathrm{2}$$

The fifth transistor T5 forms, together with the fourth transistor T4, a complementary Darlington transistor. Accordingly, the main portion of the current I _R2 flowing through the second resistor R2 will flow through the fourth transistor T4.

mit U_GS(T4) = Gate-Source-Spannung des vierten Transistors T4 und I_R3 = Strom durch den dritten Widerstand R3, dann fließen durch die beiden Transistoren T5 und T6 annähernd gleiche Ströme. Dies verbessert die Genauigkeit des Stromübersetzungsverhältnisses I_R2/I_R3 beim Stromspiegel soweit, dass auch große Übersetzungen von beispielsweise >1000:1 stabil und reproduzierbar dargestellt werden können. Im ausgeführten Beispiel wird mit einem Steuerstrom von beispielsweise 2mA durch Transistor T7 ein Ausgangsstrom von 2A durch Transistor T4 kontrolliert. Die Versorgung des Stromspiegels erfolgt aus dem Kondensator C1.For static control of the fourth transistor T4, which is designed as a MOS-Fet, no current flow is required, but it must be set to the drain current and the control characteristic corresponding gate-source voltage. If one chooses the value of the fourth resistor R4 such that I _{D (T4)} = I _R2 (drain current through T4 = current through the second resistor R2) the condition is: $${\mathrm{U}}_{\mathrm{GS}\left(\mathrm{T}\mathrm{4}\right)}\mathrm{/}\mathrm{R}\mathrm{4}\mathrm{=}{\mathrm{I}}_{\mathrm{R}\mathrm{3}}\mathrm{.}$$

with U _{GS (T4)} = gate-source voltage of the fourth transistor T4 and I _R3 = current through the third resistor R3, then flow through the two transistors T5 and T6 approximately equal currents. This improves the accuracy of the current transmission ratio I _R2 / I _R3 in the current mirror to the extent that even large translations of, for example> 1000: 1 can be represented stable and reproducible. In the example shown, with a control current of, for example, 2 mA through transistor T7, an output current of 2A is controlled by transistor T4. The current mirror is supplied from the capacitor C1.

At the beginning of a negative current pulse introduced by the signal NSC, capacitor C1 is charged by means of the first resistor R1 to the potential of the supply voltage V + (for example + 48V). As a negative current here is a current through the opening or closing coil defined in the direction of the actuating current opposite direction.

The value of R1 is selected to be so high that its current flow is substantially lower than the negative current flowing through the second resistor R2 and the fourth transistor T4. However, the value of R1 must be small enough to allow the capacitor C1 to be charged to the potential V + during the pauses between two consecutive negative current pulses.

By the current flowing through the second resistor R2 and the fourth transistor T4 through the coil L1 and the third transistor T3 (negative) current capacitor C1 is now discharged and its voltage is smaller than the on-board voltage Vbat. As a result, the protection diode D3 becomes conductive and capacitor C1 clamped to the on-board voltage Vbat. This ensures that at the beginning of a negative current pulse, the high supply voltage V + allows a fast current build-up in the coil L1 and low enough in the further course, to prevent unnecessary power loss in the fourth transistor T4 arise.

FIG. 5a shows the voltage and current waveform at the current mirror T4-T6, wherein the upper trace shows the voltage U _C1 at the capacitor C1. With increasing negative current pulse I _L1 , the voltage U _C1 drops until it is clamped at approx. 11.3V. After completion of the negative current pulse, the voltage U _C1 rises again to V +. The lower trace shows the negative current pulse I _L1 . The setpoint of 2A is already reached after 38μs.

For bistable valves, it has been found that the duration of the negative current pulse should be set to the amount of time that the current in the other coil requires to reach its operating value. As a result, the control signal NSC can be obtained in a simple manner. It is sufficient a flip-flop, which can be set at the beginning of the valve activation and in turn can be reset at the first reaching the operating current.

FIG. 6 shows a circuit of such a control device in a bistable valve for the negative current through the one coil, for example, the opening coil L1, by the closing signal of the other coil, for example, the closing coil.

This circuit consists only of a flip-flop IC1A. With the rising edge of, for example, the closing signal ES for the closing coil, not shown, the flip-flop IC1A (terminal CLK) is set so that its output Q, at which the signal NSC appears, assumes high level.

The output of the PWM unit PWM connected to terminal CLR-not of the flip-flop IC1A (see Figures 2 and 4 ) is getting high level at this time. If the current through the closing coil reaches its operating value, then this output switches to low level and thus also deletes the flip-flop IC1A, so that its output signal NSC at the output Q jumps back to low level. Thus, the signal NSC supplied to the base terminal of the transistors T3 and T7 of the circuit for the opening coil L1 has high level as long as the current through the closing coil requires until the first time it reaches its operating value.

For a bistable valve is for generating the negative current for both the opening and the closing coil depending on a circuit after FIG. 4 and FIG. 6 required. It should be noted that the PWM unit associated with opening the valve controls the negative current pulse in the valve closing coil and the PWM unit associated with closing the valve controls the negative current pulse in the valve opening coil. The time course of operating current and negative current for opening and closing a bistable valve is in FIG. 5b shown schematically.

For a standard valve with opening coil and closing spring, the control of the negative current of the single coil L1 must be at the end of the opening signal EO, as in FIG. 7 shown, done.

At the control unit after FIG. 7 the negative current is used to cancel the eddy currents, which continue to flow in the magnetic circuit of the standard valve after the current in the opening coil has been switched off and faded off. For this purpose, a negative current should be passed through the opening coil L1 immediately after completion of the valve activation (falling edge of the actuation (opening) signal EO.
The circuit after FIG. 7 contains a timer (monoflop IC2) to determine the duration of the negative current pulse through the coil L1 which is triggered by the falling edge of the signal EO inverted by means of an inverter IC4.

For a standard valve is only one circuit after each FIG. 4 and FIG. 7 required.

In a further advantageous embodiment of the circuit according to FIG. 4 can diode D1 omitted, the substrate diode of transistor T3 their function, the freewheel, takes over.

• es ergibt sich eine zeitlich variable Versorgungsspannung, wodurch die Verlustleistung in der Stromquelle gering gehalten werden kann;
• die Versorgung des Darlington-Stromspiegels erfolgt aus einem Kondensator, der zunächst auf das Potential der Versorgungsspannung V+ aufgeladen wird, um einen raschen Stromanstieg in der Spuleninduktivität zu erreichen.

The advantages of the circuit according to the invention FIG. 4 are the following:

• This results in a time-varying supply voltage, whereby the power loss in the power source can be kept low;
• the supply of the Darlington current mirror is made of a capacitor which is first charged to the potential of the supply voltage V + to achieve a rapid increase in current in the coil inductance.

For bistable valves with two actuating windings, the negative current is controlled by a signal from the drive electronics, which controls the current flow in the opposite coil.

For standard valves with closing spring, the negative current is controlled by the falling edge of the actuation (opening) signal.

In the course of the negative current is a clamping of the capacitor voltage to the on-board voltage Vbat.

In a further advantageous embodiment, the energy required for demagnetization can also be acted upon accelerated. This is useful if the fastest possible start of the valve movement is required. To the negative current is not at a predetermined, largely constant value for a certain period of time, such as FIG. 5a but set as an approximately triangular current pulse with a predetermined maximum value ( FIG. 9b ).

The speed of the current increase is determined by the inductance of the coil and the supply voltage V. Also, the peak value of the current is higher than in the first embodiment because the demagnetizing energy is provided in a shorter time.

• die obere Spur: den Entmagnetisierungsstrom,
• die mittlere Spur: die Ventilbewegung, und
• die untere Spur: das Steuersignal (fallende Flanke).

In FIG. 9 are the valve switching times without ( Figur9a ) and with degaussing current ( FIG. 9b ) compared with each other. There each show:

• the upper track: the degaussing current,
• the middle lane: the valve movement, and
• the lower track: the control signal (falling edge).

A circuit diagram for such a circuit arrangement is shown in FIG. The circuit essentially corresponds to the embodiment FIG. 4 , but eliminates resistor R1, capacitor C1, diode D3 and the connection to the on-board voltage source Vbat. Also, the resistors R2 and R3 are directly connected to the positive pole V + of the supply voltage, and a resistor R7 is inserted between the source terminal of the transistor T3 and the ground terminal GND.

Furthermore, the current source T4-T6 is now designed by selecting the value ratio of the resistors R2 and R3 for a much higher constant current - for example 8A.

When the signal Negative-Strom-Control NSC is activated by the closing signal, it will - as with FIG. 4 described - the opening coil associated transistor T3 turned on, at the same time by means of transistor T7, the current source T4 to T6. According to the inductance of the coil L1 (opening coil) the current through them will now increase in time ( FIG. 9b , upper lane). This current is observable at the resistor R7 as the voltage negative current sense NSS. If this voltage NSS has reached a predetermined value, then the signal negative current control NSC is controlled to 0V and the current flow is terminated.

In a measured embodiment of the circuit according to FIG. 10 determined valve switching time is for example from 620μs (without degaussing, FIG. 9a ) to 504μs (with degaussing current, FIG. 9b ) shortened.
The current source T4-6 also has a protective function, since in case of a short circuit of the right terminal of the coil L1 to reference potential of the current from T6 is limited.

The valve coils are located in the injection valve, not shown, on the engine block of the internal combustion engine outside of the electronic control unit, and a short circuit of the leads to vehicle ground is a common mistake. However, this must not lead to damage to the electronics.

The evaluation of the voltage Negative Current Sense NSS as well as the control of the signal Negative Current Control NSC takes place with a suitable control unit, which in FIG. 11 is described.

The control unit designed for a bistable injector FIG. 11 includes a monoflop IC2, a flip-flop IC1A, a comparator Comp1 and an AND gate IC3A with three inputs. The closing signal ES is connected to the trigger input Ck of the monoflop IC2, to an input of the AND gate IC3A and to the reset input CLR-not of the flip-flop IG1A.

The resistor R7 in FIG. 10 tapped signal NSS (negative current sense) is with the noninverting input the comparator Comp1 whose inverting input a reference voltage Vref is supplied. The output of the comparator Comp1 is connected to the trigger input CLK of the flip-flop IC1A.

The output Q of the monoflop IC2 is connected to a second input of the AND gate whose third input is connected to the inverting Q-not output of the flip-flop IC1A.

At the output of the AND gate IC3A the signal NSC (negative current control) appears, and at the non-inverting output Q of the flip-flop IC1A appears a signal NSD (negative current diagnosis).

This in FIG. 6 Control signal already described, for example, the closing signal ES also controls the switching on of the negative current for the opening coil L1. But the negative current is now switched off when a predetermined current value is reached, but which must be less than the setpoint value of the current of the current source T4-6.

The signal curves of in FIG. 11 shown control unit are off FIG. 12 refer to. At the beginning, the closing signal ES has low levels. This level is also applied to the reset input CLR-not of the flip-flop IC1A, so that at its non-inverting output Q is applied a signal negative-current diagnosis NSD with low level. Accordingly, the inverting output Q-not of flip-flop IC1A has high level.

The rising edge of the control signal ES clocks the monoflop IC2 whose output Q now assumes high levels for the duration of the monoflop time. The AND gate IC3A combines the signals ES, Q of IC2 and Q-not of IC1A. Since all of these signals are now high, signal NSC at the output of AND gate IC3A goes high with the rising edge of the control signal ES also high level on. The negative current starts to increase.

As a result, the transistors T3 and T4 ( FIGS. 9b and 10 ), so that a current through the coil L1 ( Figur10 ) begins to flow. This current also flows through resistor R7, resulting in a corresponding voltage drop, signal Negative Current Sense NSS. Comparator Comp1 now compares this voltage NSS with the reference voltage Vref.

If NSS <Vref, the output of the comparator Comp1 has low level. If the value of NSS exceeds that of Vref, the output of the comparator Comp1 jumps to high level and sets the downstream flip-flop IC1A. Its inverting output Q-Not jumps to low level and switches via the AND gate IC3A the signal NSC to low level, whereby the negative current in the opening coil L1 is turned off. Similarly, the signal NSD jumps to non-inverting output Q to high level.

By observing the time when or if this voltage jump occurs, a possible malfunction can be detected. Likewise, the nature of the error can be detected. If there is a short circuit to the reference potential at one of the supply lines of the coils, then no current will flow through resistor R7 and the signal NSD remains at low level. This also applies to a line break.

It is therefore sufficient to query the signal NSD immediately before switching on the opening signal EO or closing signal ES.

The time constant of the monoflop IC2 is chosen so that the desired value of the negative current is safely achieved, but a thermal overload of the power transistor T4 of the power source is avoided in case of short circuit to reference potential.

If the signal NSS (negative current sense) has not exceeded the value of Vref until the time constant has expired, then the downstream flip-flop IC1A is not triggered. The signal NSD at the non-inverting output Q remains at low level. The output Q of the monoflop IC2 goes back to low level and blocks the AND gate IC3A, so that its output signal NSC goes to low level.

In the case of a bistable valve, once again a circuit is created for the opening coil and for the closing coil FIG. 10 and FIG. 11 needed.

For a standard valve with recoil spring, whose control unit is in Figur13 is shown, the control unit is after FIG. 11 added thereto that the opening signal EO before it is the monoflop IC2, the AND gate IC3A and the flip-flop IC1A is inverted by means of an inverter IC4, so that the monoflop IC2 is triggered only by the falling edge of the signal EO ,

As in FIG. 8 for a circuit arrangement according to FIG. 4 shown, in a further advantageous embodiment of the invention, the circuit arrangement according to FIG. 4 or FIG. 10 for the operation of multiple valves, ie, all (for example, four or six) fuel injectors of an internal combustion engine can be extended without having to increase the number of circuits proportionally. This is achieved by adding additional diodes D7 to D10 in series with the drain of the third transistor T3, additional diodes D4a to D6a and D4b to D6b in series with the source of the transistor T4, and / or another transistor T3b, or another current mirror T4b-T7b, R2b-R5b.

However, an additional, not shown, selection circuit is required, which is the respectively desired Current path selected by appropriate control of T3, T3b, T7, T7b.

The main obstacle when closing are, as already stated, the eddy currents in the magnetic material of the valve, which decay slowly after switching off the actuating current and prevent rapid closing of the valve. As a rule, steel with a low electrical conductance is used.

In order to further reduce the closing delay in standard solenoid valves, in addition to the use of a negative current pulse, use is also made of the different decay times of eddy currents in magnetic materials having different electrical conductivities.

FIG. 14 shows a schematic representation of a standard solenoid injector with coil S4 and closing spring S3. The coil S4 is surrounded by the iron yoke S5. The valve needle S7 and its associated armature S6 is pressed by the closing spring S3 against a valve seat, not shown, and thus blocks the valve opening, not shown. When the coil S4 is energized, the armature S6 is attracted against the force of the closing spring S3 and thus the valve is opened.

According to the invention, contrary to the rule described above, a material with the highest possible electrical conductance is selected for the armature S6 in order to let the eddy currents decay as slowly as possible in the armature. However, the iron yoke S5 still consists of material with a low electrical conductance.

This makes it possible, when closing the valve with a negative current pulse to the coil S4 in the iron yoke S5 to achieve a temporary field reversal, while the original excitation field in the anchor S6 has not quite decayed.

This results in the gap between iron yoke and armature temporarily a repulsive force between iron yoke S5 and armature S6, which significantly accelerates the beginning of the closing movement and the closing of the valve.

In FIG. 14 are the solid field lines 14a (left) with the valve open and the dashed lines 14b (right) shown in the closing process in the temporarily arising field reversal.

FIG. 15 shows in principle the formation of temporary, opposite field directions between iron yoke S5 and anchor S6.

The lower diagram shows the time course of the applied to the coil negative current pulse during the closing of the injector.

The upper diagram shows the field strengths or holding forces resulting from eddy currents. The respective value of the eddy current is associated with a magnetic field strength and thus a holding force.

The upper curve 15a shows the course of the field strength in the armature S6, which consists of material with the highest possible electrical conductance, while the lower curve 15b represents the course of the effective field strength in the iron yoke S5 made of material with a low electrical conductance.

In addition, the line 15c is still shown, which represents the holding force of the closing spring S3.

At the moment in which the field strength influenced by the negative current pulse - curve 15b - becomes negative and thus reverses its direction, the repulsive force between iron yoke S5 and armature S6 begins to act. At the point indicated by a double arrow, this force is greatest.

Thus, the combination of negative current pulse at the end of the excitation current and proper choice of magnetic material properties results in a substantial reduction in the turn-off delay for standard solenoid valves.

Claims (11)

1. Device for switching inductive fuel injection valves,
   wherein, in the case of a bistable fuel injection valve (with opening and closing coil), the magnetic holding forces induced by remanence which hold the valve needle (1) firmly in the closed position are eliminated by means of a negative current generated in the closing coil in order to accelerate the opening of the valve, and which hold the valve needle (1) firmly in the open position are eliminated by means of a negative current generated in the opening coil in order to accelerate the closing of the valve; and
   wherein, in the case of a standard fuel injection valve (with opening coil and closing spring), the eddy currents in the magnetic material of the opening coil (L1) which are induced after the actuation signal (EO) has been turned off and which decay only slowly are eliminated by means of a negative current generated in the opening coil,
   wherein a current through the opening or closing coil in the opposite direction to the direction of the actuation current is defined as the negative current,
   having a circuit arrangement which has a coil (L1) of a fuel injection valve, which coil is controlled by a switching signal (Enable Open EO, Enable Close ES) via a pulse width modulation unit (PWM),
   one terminal of which is connected to the positive pole (V+) of a supply voltage source (V) by means of a first switching transistor (T1) and the other terminal of which is connected to reference potential (GND) by means of a second switching transistor (T2),
   wherein the source terminal of the first switching transistor (T1) is connected to one terminal of the coil (L1), its drain terminal to the positive pole (V+) of the supply voltage source (V), and its gate terminal to the output of the PWM unit (PWM),
   wherein the source terminal of the second switching transistor (T2) is connected to reference potential (GND) and its drain terminal to the other terminal of the coil (L1),
   wherein a freewheeling diode (D1) is arranged to conduct current from reference potential (GND) to one terminal of the coil (L1) and a recuperation diode (D2) is arranged to conduct current from the other terminal of the coil (L1) to the positive pole (V+) of the supply voltage source (V),
   characterised in that
   a third transistor (T3) connected in parallel with the freewheeling diode (D1) is provided whose source terminal is connected to reference potential (GND) and whose drain terminal is connected to the connecting point of the freewheeling diode (D1) and one terminal of the coil (L1),
   a complementary Darlington current mirror (transistors T4 to T6, resistors R2 to R4) is provided which is connected to the positive pole (V+) of the supply voltage source (V) via a first resistor (R1),
   wherein the source terminal of the fourth transistor (T4) is connected to the other terminal of the coil (L1), and the source terminal of the sixth transistor (T6) is connected to reference potential (GND) via the series circuit of a seventh transistor (T7) and a fifth resistor (R5),
   the gate terminals of the third transistor (T3) and the seventh transistor (T7) are connected to one another, to which a negative current control signal (NSC) can be supplied,
   a capacitor (C1) is connected into the circuit in parallel with the series circuit consisting of sixth transistor (T6), seventh transistor (T7) and fifth resistor (R5), and
   a series circuit is arranged in parallel with the capacitor (C1), said series circuit consisting of a vehicle onboard voltage source (Vbat) connected to reference potential (GND) on one side and of a protection diode conducting current towards the capacitor (C1).
2. Device according to claim 1, characterised in that in the case of a bistable fuel injection valve a control device is provided for the purpose of generating the negative current control signal (NSC), said control device having a flip-flop (IC1A) which is set by the opening or closing signal (EO, ES) of the opening or closing coil and is reset by the closing signal of the PWM unit (PWM) assigned to said coil, wherein between the setting and resetting of the flip-flop (IC1A) the negative current control signal (NSC) appears at its non-inverting output (Q) and is supplied to the circuit arrangement of the other coil in each case.
3. Device according to claim 1 or 2, characterised in that a circuit arrangement according to claim 1 and a control device according to claim 2 are provided in each case both for the opening coil (L1) and for the closing coil for the purpose of controlling a bistable fuel injection valve.
4. Device according to claim 1, characterised in that in the case of a standard fuel injection valve a control device is provided for the purpose of generating a negative current control signal (NSC), said control device having a series circuit of an inverter (IC4) and a monoflop (IC2), wherein the opening or closing signal (EO, ES) inverted by the inverter (IC4) sets the monoflop (IC2), at whose non-inverting output (Q) the negative current control signal (NSC) appears during the holding time of the monoflop (IC2) and is supplied to the circuit arrangement of the other coil in each case.
5. Device according to claim 1 or 4, characterised in that a circuit arrangement according to claim 1 and a control device according to claim 4 are provided in each case for the purpose of controlling a standard fuel injection valve.
6. Device for switching inductive fuel injection valves,
   wherein, in the case of a bistable fuel injection valve (with opening and closing coil), the magnetic holding forces induced by remanence which hold the valve needle (1) firmly in the closed position are eliminated by means of a negative current generated in the closing coil in order to accelerate the opening of the valve, and which hold the valve needle (1) firmly in the open position are eliminated by means of a negative current generated in the opening coil in order to accelerate the closing of the valve; and
   wherein, in the case of a standard fuel injection valve (with opening coil and closing spring), the eddy currents in the magnetic material of the opening coil (L1) which are induced after the actuation signal (EO) has been turned off and which decay only slowly are eliminated by means of a negative current generated in the opening coil,
   wherein a current through the opening or closing coil in the opposite direction to the direction of the actuation current is defined as the negative current,
   having a circuit arrangement which has a coil (L1) of a fuel injection valve, which coil is controlled by a switching signal (Enable Open EO, Enable Close ES) via a pulse width modulation unit (PWM),
   one terminal of which is connected to the positive pole (V+) of a supply voltage source (V) by means of a first switching transistor (T1) and the other terminal of which is connected to reference potential (GND) by means of a second switching transistor (T2),
   wherein the source terminal of the first switching transistor (T1) is connected to one terminal of the coil (L1), its drain terminal to the positive pole (V+) of the supply voltage source (V), and its gate terminal to the output of the PWM unit (PWM),
   wherein the source terminal of the second switching transistor (T2) is connected to reference potential (GND) and its drain terminal to the other terminal of the coil (L1),
   wherein a freewheeling diode (D1) is arranged to conduct current from reference potential (GND) to one terminal of the coil (L1) and a recuperation diode (D2) is arranged to conduct current from the other terminal of the coil (L1) to the positive pole (V+) of the supply voltage source (V),
   characterised in that
   a third transistor (T3) connected in parallel with the freewheeling diode (D1) is provided whose source terminal is connected to reference potential (GND) via a seventh resistor (R7) and whose drain terminal is connected to the connecting point of the freewheeling diode (D1) and one terminal of the coil (L1),
   a complementary Darlington current mirror (transistors T4 to T6, resistors R2 to R4) is provided,
   wherein the source terminal of the fourth transistor (T4) is connected to the other terminal of the coil (L1), the source terminal of the sixth transistor (T6) is connected to reference potential (GND) via the series circuit of a seventh transistor (T7) and a fifth resistor (R5), and the drain terminals of the fourth and sixth transistors (T4, T6) are each connected to the positive pole (V+) of the supply voltage source (V) via a resistor (R2, R3),
   the gate terminals of the third transistor (T3) and the seventh transistor (T7) are connected to one another, to which the negative current control signal (NSC) can be supplied, and
   a negative current sense signal (NSS) can be tapped at the seventh resistor (R7).
7. Device according to claim 6, characterised in that
   in the case of a bistable fuel injection valve a control device is provided for the purpose of generating the negative current control signal (NSC), said control device containing a comparator (Comp1) to whose non-inverting input the negative current sense signal (NSS) can be supplied and to whose inverting input a reference voltage (Vref) can be supplied,
   a flip-flop (IC1A) is provided whose set input (CLK) is connected to the output of the comparator (Comp1), at whose non-inverting output (Q) a negative current diagnosis signal (NSD) can be tapped,
   a monoflop (IC2) and an AND element having three inputs (IC3A) are provided, wherein
   the closing signal (ES) or the opening signal (EO) can be supplied to an input of the AND element (IC3A), the trigger input (Ck) of the monoflop (IC2) and the reset input of the flip-flop (IC1A),
   a second input of the AND element (IC3A) is connected to the inverting output (Q-Not) of the flip-flop (IC1A) and
   a third input of the AND element (IC3A) is connected to the output (Q) of the monoflop (IC2), and the negative current control signal (NSC) can be tapped at the output of the AND element (IC3A).
8. Device according to claim 6, characterised in that in the case of a standard fuel injection valve a control device according to claim 12 is provided for the purpose of generating the negative current control signal (NSC), with an inverter (IC4) additionally being provided in which the closing signal (ES) is inverted before it is supplied to an input of the AND element (IC3A), the trigger input (Ck) of the monoflop (IC2) and the reset input of the flip-flop (IC1A) .
9. Device according to claim 7 or 8, characterised in that

   - the negative current diagnosis signal (NSD) of the opening coil (L1) has low level prior to the turning-on of the opening signal (EO) or

   - the negative current diagnosis signal (NSD) of the closing coil has low level prior to the turning-on of the closing signal (ES)
   if the negative current flowing through the opening or closing coil

   - does not reach its predefined value before the monoflop holding time expires, or

   - a shorting to reference potential (GND) or a line break occurs in one of the feed lines to the coils.
10. Device according to one of claims 1 or 4 to 8, characterised in that in the case of a standard fuel injection valve the magnetic yoke (S5) of the coil (S4) and the armature (S6) are manufactured from materials having different electrical conductances.
11. Device according to claim 10, characterised in that the armature (S6) consists of material having the highest possible electrical conductance and the magnetic yoke (S5) consists of material having low electrical conductance.

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