WO2009095125A1

WO2009095125A1 - Method for controlling solenoid valves

Info

Publication number: WO2009095125A1
Application number: PCT/EP2008/066395
Authority: WO
Inventors: Holger Rapp; Thomas Gann; Ralf Schulte
Original assignee: Robert Bosch Gmbh
Priority date: 2008-01-30
Filing date: 2008-11-28
Publication date: 2009-08-06
Also published as: DE102008006706A1

Abstract

The invention relates to a method and a control device for controlling solenoid valves. In order to detect a stroke stop, a current for detecting a transition into a passive switching state is built up, wherein energy which is still inherently stored in a magnetic field of the solenoid valve is used in order to build up the current.

Description

description

title

Method for controlling solenoid valves

The invention relates to a method and a control device for driving solenoid valves and a computer program and a computer program product.

State of the art

Solenoid valves are used, for example, for the control of fuel injection pumps. In these, it is necessary to comply with the opening and closing timing and the opening end of the valve needle as closely as possible in order to accurately determine the amount of fuel supplied.

For solenoid valves, the movement of the valve element affects the relationship between current and voltage of the excitation coil such solenoid valves. It can be drawn from the course of a coil current at a constant voltage or from the course of the coil voltage at a constant coil current conclusions on the stroke profile of the valve element. In particular, rapid changes in speed of the valve element can be detected well. These rapid speed changes occur when the stroke stop is reached for the active switching state of the valve and when the sealing seat is reached, usually during the transition to the passive switching state of the valve.

Methods for detecting such impact events are known. In the document DE 36 09 599 Al is, for example, a method for controlling the de-energizing of electromagnetic devices, in particular of electromagnetic valves in internal combustion engines, known. In this method, it is provided that the excitation current of the electromagnetic device, starting from a holding current corresponding high Value is at least temporarily reduced within the duration of a time provided for the opening of the valve to a lower but positive value below the holding current level.

It should be noted that upon reaching a stop in the active switching state, the coil of the valve is energized anyway and upon reaching the stop for the passive switching state, this stop forms the sealing seat of the valve, the coil is normally de-energized.

In order to be able to detect the impact event, therefore, a coil current must again be actively set up in all known methods before the impact event. This is done either by briefly applying a voltage, for example, from the vehicle battery or a capacitor, or by impressing a current or voltage via a linearly controlled output stage. In any case, the renewed structure of the current is accompanied by an energy withdrawal from the control unit and the current profile or the current level achieved depends on the accuracy of the control voltages provided by the control unit.

It is therefore desirable to achieve the structure of the current for detecting the stroke stop in the passive switching state of the valve without any energy extraction from the control unit.

Disclosure of the invention

The inventive method is used to control solenoid valves and thereby for detecting a stroke stop of a solenoid valve, wherein a current for detecting a

Transition is built into a passive switching state, wherein in a magnetic field of the solenoid valve is still used inherently stored energy to build the current.

The presented method thus utilizes the fact that at the time of extinction of the coil current at the end of the drive, the magnetic field in the valve has not yet extinguished.

Rather, the rapid current reduction in the coil causes build up in the core material and the armature of the solenoid valve eddy currents, which are directed so that they counteract a degradation of the original existing magnetic field. Due to the ohmic resistance The eddy current paths is now induced in the coil at a coil current zero, a negative voltage, which causes both a decay of the eddy currents and a decay of the still existing magnetic field.

In a refinement, it is provided that, after a short pause of the current, the coil or sensor current is switched to the "freewheeling" switching state, so that the coil voltage can no longer be negative, instead the zero voltage is applied to the coil a large part of the core and armature eddy currents are fed back into the coil, and the coil current level achieved in this way results from the magnetic field still present in the solenoid valve at the time of switching

"Zero Voltage" is a simplification, since in reality the negative voltage drop at the wiring harness and at the freewheeling path of the controller still rests against the coil. But this is an unavoidable, unwanted effect.

Since only the voltage zero is applied by the control unit, there is no renewed

Supply of energy into the solenoid valve and therefore no renewed increase in magnetic force. To build up the coil or sensor current only the energy still inherently stored in the magnetic field of the solenoid valve is used. Due to the fact that only the switching state "freewheeling" is used to build the sensor current, the current build-up is independent of the supply voltage or the voltage of a storage capacitor in the control unit.

It can be provided that the current pause is set to zero or negative between extinction of the drive current and switching to the freewheel. In the first case, zero is switched to the freewheel immediately upon reaching the coil current. In another case, the freewheel is switched to freewheel already before the drive current is completely extinguished and switched from the falling drive current edge to the sensor current course.

If the eddy currents in the magnetic circuit diminish too quickly, their decay can be slowed down by the targeted introduction of eddy current paths into the magnetic circuit. For this purpose, the design of the anchor end face can be taken into account. But it can also targeted a shorted secondary coil or a shorted ring in the coil window of - A -

Solenoid valve are inserted. It is thus achieved that the magnetic field present at the time of the sensor current build-up and the level of the sensor current increase.

The method according to the invention has the advantage, at least in some of the listed embodiments, that an energy transfer from the control unit to the solenoid valve is not required to build up the coil current required for the stop detection. Consequently, no energy is drawn from a storage capacitor with limited energy content. The course of the sensor current is independent of the battery voltage or of the voltage of a storage capacitor.

Furthermore, since no energy is transmitted from the controller to the solenoid valve, the structure of the sensor current also causes no increase in the magnetic force in the solenoid valve. Since the sensor current is not actively established by the controller, control of the sensor current build-up by the controller is not required.

The control unit according to the invention is used to control solenoid valves and is designed to build a coil current before reaching a stop for a passive switching state, is switched to build the coil current in a switching state freewheel, so that the voltage across the coil is zero.

The invention further relates to a computer program with program code means to perform all the steps of a described method, when the computer program is executed on a computer or a corresponding computing unit, in particular in a presented device.

The computer program product according to the invention with program code means which are stored on a computer-readable data carrier is designed to carry out all the steps of a described method when the computer program is executed on a computer or a corresponding computing unit, in particular in a presented device.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings. It is understood that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations or alone, without departing from the scope of the present invention.

Brief description of the drawings

Figure 1 shows a schematic representation of a circuit of a control unit output stage according to the prior art.

FIG. 2 shows in a graph the course of the sensor current.

FIG. 3 shows, in an equivalent circuit diagram, the magnetic circuit of a high-speed solenoid valve.

FIG. 4 shows the course of the sensor current in a sensor current configuration according to the invention.

Embodiments of the invention

1 shows a circuit 10 of a conventional control unit power amplifier with a connected solenoid valve (shown here by the coil 26) and the current paths that occur in the various switching states shown. The circuit comprises a DC / DC converter 12, a storage capacitor C _B oos 14, a semiconductor valve which can be switched on and off, for example a FET or IGBT, T _B oos 16, a diode D _B oos 18, a transistor T _LS 20, a diode D _Fr 22, a transistor T _H s 24 and a coil 26. The storage capacitor C _B oos

14 is charged to the voltage U _BO os 34.

The reduction of the drive current to the end of the valve control is usually done by switching to the switching state "snow erase". In this switching state, the current flow takes place via a terminal 28 of a battery voltage U _BA τ 30 via the transistor T _H s 24, the coil

26, the diode D _BO os 18, the storage capacitor C _B oos 14 to ground 32. In this case, only the transistor T _H s 24 is conductive, all other transistors are blocked. The voltage U _BAT - U _B oos is then applied to the coil. Alternatively, all the transistors can be extinguished during snow erase be locked. The current flow then takes place from the ground point 32 via the diode D _Fr 22, the coil 26, the diode D _B oos 18 and the storage capacitor C _B oos 14 back to the ground point 32. At the coil 26 in this case the voltage -U _B oos at.

In topologies without the storage capacitor C _B oos 14 eliminates the transistor T _BOOS 16 and the diode D _B oos 18 is instead connected to the positive pole of the storage capacitor 14 to the positive terminal 28 of the power supply of the controller. The structure of the sensor current required for the stop detection is usually carried out by short-term application of the capacitor voltage (switching state "Boosters") or the battery voltage (switching state "driving") to the coil 26 of the solenoid valve. In the first case this is the

Booster capacitor C _B oos 14 additional energy removed, which must be redelivered via the DC / DC converter 12 again and this therefore additionally charged.

Relevant switching states are thus:

Driving T _H s 24, T _LS 20 are conductive; u = U _BA ττ

Boosters T _BO os 16, T _LS 20 conductive; u = U _BO os

Quick reset T _H s 24 conductive; u = U _BA ττ - U _BO os <0 as long as i> 0 then blocks D _BO os 18

Freewheel T _LS 20 conductive; u = 0 as long as i> 0 then locks D _Fr

Quick delete 2 all transistors disabled, u = -U _BO os <0, as long as i> 0, then lock D _BO os 18 and D _Fr 22

A typical course of the sensor current from t ~ 65 μs in this procedure is shown in FIG. In this illustration, at an ordinate 50, the current versus time (abscissa

52). The accuracy of the set sensor current in the case of boosting depends on the accuracy of the booster voltage and on the accuracy with which the control unit terminates the switching state "booster" again when a switch-off threshold is reached. moreover With the construction of the sensor current, a renewed increase in the magnetic force of the valve takes place, which leads to a slight delay in the closing operation of the valve.

The illustration shows in a first region 54 a snow erase, in which the measuring range of the voltage is exceeded. A renewed booster in a second area 56 serves to build up the sensor current, wherein the measuring range of the voltage is exceeded. There is an energy extraction from the booster capacitor C _B oos 14, a very fast current increase and a renewed increase in magnetic force. In a third area 58, a kink in the course of the current can be seen, which indicates the closing time.

The invention utilizes the fact that at the time of extinction of the coil current at the end of the drive, the magnetic field in the valve is not yet extinguished. Rather, the rapid power reduction in the coil causes build up in the core material and the armature of the solenoid valve eddy currents, which are directed so that they counteract degradation of the original existing magnetic field. Due to the ohmic resistance of the eddy current paths, a negative voltage is now induced in the coil at coil current zero, which causes both a decay of the eddy currents and a decay of the still existing magnetic field.

A simplified equivalent circuit of the magnetic circuit in consideration of this

Eddy current paths is shown in FIG. The illustration shows a first current path 60, which comprises a coil 62, whose inductance L is determined as a function of the variable air gap s of the magnetic circuit, and a series resistance Rs 64. The magnetic flux linkage ψ describes the behavior of the coil 62. Furthermore, an eddy current path 66 can be seen, which in turn comprises the coil 62, a leakage inductance L _σ * 68 and a scattering resistance Rw * - for a

Blowing all transistors or all transistors except T _H s 24 (not shown in Figure 3) are disabled, so that the current i 72 quickly assumes the value 0.

According to the invention, the switching state "freewheeling" is now switched to build up the sensor current after a short pause of the current.The coil voltage u _{m (} j 70) can thus no longer be negative, but the voltage zero is applied to the coil, as a result of which a large commutator commutes Part of the eddy currents of core and armature back into the coil 62. The case achieved coil current level resulting from the time of switching in the solenoid valve yet existing magnetic field. Since only the zero voltage is applied by the control unit, there is no renewed feed of energy into the solenoid valve and consequently no renewed increase in magnetic force. To build up the sensor current, only the energy still inherently stored in the magnetic field of the solenoid valve is used. Because only the "freewheeling" switching state is used to build up the sensor current, the current build-up is absolutely independent of the supply voltage or the voltage of a storage capacitor in the control unit, and no energy is taken from a voltage source in the control unit.

The pause between extinction of the drive current and switching into the circuit may also be set to zero or negative. In the first case, zero is switched directly to the freewheel when reaching the coil current, in the other case is already switched to freewheel before the complete extinction of the drive current and switched from the falling Ansteuerstromflanke in the sensor current waveform. If the eddy currents in the magnetic circuit diminish too quickly, their decay can be reduced by the targeted introduction of eddy current paths into the magnetic field

Slowed down magnetic circuit. For this purpose, the design of the anchor end face can be used, but it can also be selectively inserted a short-circuited secondary coil or a short-circuited ring in the coil window of the solenoid valve. This increases the magnetic field present at the time of the sensor current build-up and the level of the sensor current.

FIG. 4 shows the course of the coil current from t.about.65 μs and the coil voltage when the sensor current is generated according to the invention. Here, the current at an ordinate 80 is plotted against time (abscissa 82). The illustration shows the course of the sensor current by switching to the "freewheeling" switching state.

Here, too, a snow erasure can be recognized in a first region 84, with the measuring range of the voltage being exceeded. In a second area 86, for example between 25 and 50 μs, all current paths in the control unit are blocked. Decaying eddy currents induce a negative coil voltage. The measuring range of the voltage is exceeded most of the time. To a

Time 88 is a switch to freewheel to build the sensor current. The sensor current structure is driven by the eddy currents in the magnetic circuit. There is no new energy input into the magnetic circuit and no renewed magnetic force increase. There is no dependence of the sensor current on voltages in the control unit.

At a point in time 90, a bend in the course of the current can be seen, which indicates the closing time.

Claims

claims

1. A method for controlling solenoid valves, wherein for detecting a stroke stop of a solenoid valve, a current for detecting a transition is built into a passive switching state, wherein in a magnetic field of the solenoid valve nor inherently stored energy is used to build up the current.

2. The method of claim 1, wherein the construction of the stream is switched to a switching state "freewheeling" after a short pause.

3. The method of claim 2, wherein the current pause is set to zero.

4. The method of claim 2, wherein the current pause is set to a negative value.

5. The method according to any one of claims 1 to 4, wherein the design of an anchor end face is used.

6. The method according to any one of claims 1 to 5, wherein a short-circuited secondary coil is inserted into the coil window of the solenoid valve.

7. The method according to any one of claims 1 to 6, wherein a short-circuited ring is inserted into the coil window of the solenoid valve.

8. Control unit for controlling solenoid valves, which is designed to build up before reaching a stop for a passive switching state, a coil current, wherein the construction of the coil current is switched to a switching state freewheel, so that the voltage across the coil is zero.

9. Computer program with program code means to perform all the steps of a method according to any one of claims 1 to 7, when the computer program on a computer or a corresponding processing unit, in particular in the control device according to claim 8, is executed.

10. Computer program product with program code means which are stored on a computer-readable medium to perform all the steps of a method according to any one of claims 1 to 7, when the computer program on a computer or a corresponding processing unit, in particular in a control device according to claim 8, is executed.