DE10338353A1 - Switching arrangement for combined spark plug/ injection valve unit e.g. for combustion engine, has discharge current circuit of capacitive actuator/control connected to primary winding of ignition transformer - Google Patents

Abstract

A switching arrangement for a combined spark plug /injection valve unit has a capacitive actuator/control (2) for the injection valve and the discharge current circuit (23) of the capacitive actuator/control (2) is joined to a primary winding (14) of an ignition transformer assigned to the spark plug (10).

Description

The The invention relates to a switching arrangement for a combined Zündkerze- / injector unit with the features of the preamble of claim 1.

A corresponding unit is from the EP 861 371 B1 known. The two electrodes of the spark plug are arranged off-center and at a certain distance from the fuel outlet opening. In particular, with lean fuel-air mixtures can thereby ignition problems arise under widely varying operating conditions.

The High voltage supply done via a on the outside the injection valve arranged high voltage terminal. from that result especially in thin Injectors isolation problems, as the high voltage line within the injector near the fuel.

Further Problems arise from the operation of the capacitive actuator for the Injector. This usually consists of a piezo material. For his Effect, it is necessary, each power stroke one performance which amounts to about 100 mJoule (mJ). These Performance must be constant applied and the applied charge carriers must be removed again. Insufficient charge discharge leads to malfunctions of the Actuator. To make matters worse, the different cycle times added, which are due to the speed range of the internal combustion engine. This can be a maximum of about 18,000 rpm and above.

Of the Invention is based on the object, a switching arrangement of to create the type mentioned in the beginning, under all operating conditions a functional and fail-safe Operation of spark plug / injector unit guaranteed.

The Invention solves This object with the means of claim 1.

Now the charge applied to the capacitive actuator is dissipated via the primary winding of the ignition transformer. This gives two advantages:
On the one hand, the application and the removal of the charge carriers are synchronous across all rotational speeds, since one ignition spark is generated per injection stroke.
On the other hand, the amount of charge required for the operation of the actuator is at least approximately equal to the power that must be applied in the primary circuit for the production of the spark.

advantageous Embodiments of the invention are specified in the further claims and will be further explained with reference to the drawing.

Show

1 for example, a spark plug / injector unit and

2 a circuit arrangement according to the invention for the operation of the unit of 1 ,

The fuel injection valve unit shown in the drawing 1 has a piezoelectric actuator 2 in a metal case 3 is arranged. The housing 3 serves to screw in and to dissipate the heat absorbed by the fuel combustion.

The actuator 2 expands upon application of a voltage (not shown) and moves a cylindrical valve body 4 in a fixed valve sleeve 5 against the action of a spring 6 and thus controls the escape of fuel through an opening 7 starting from a high-pressure pump, not shown, starting in a jacket region 8th of the housing 2 fed and within the valve 1 in another coat area 9 between valve sleeve 5 and valve body 4 is transferred. The fuel flows around the valve body 4 ,

Within the unit 1 is a spark plug 10 integrated. It has a high voltage electrode 11 that of a ceramic serving as an insulator 12 is surrounded. The ceramic is located inside the valve sleeve and closes with this towards the combustion chamber (not shown) flush. As earth electrode of the spark plug 10 serve the valve body made of metal 4 and the likewise metal valve sleeve 5 Both are at ground potential. The spark plug 10 generated in the area of the opening 13 between the high voltage electrode 11 and the valve body 4 a spark.

An ignition transformer is used for this purpose 14 with a primary winding 15 and a secondary winding 16 , which are arranged concentrically with each other in the housing. The two windings sit on concentric bobbins 17 and 18 , The bobbin 18 has a core 19 Made of soft iron material and sits on a shaft 20 that is between the actuator 2 and the valve body 4 located.

When applying a voltage of, for example, 12 V to the primary winding 14 via an outgoing lead 21 increases the current in this winding during the charging time to the desired primary current. Accordingly, this increases in the ignition transformer 14 ' stored electrical energy. If the primary current is interrupted by an external switch (not shown), it will be in the secondary winding 15 induced a high voltage, which leads to a spark by arc and / or glow discharge and ignited the fuel-air mixture in the combustion chamber (not shown).

The ignition transformer 14 generates the high voltage directly at the spark plug 10 , This eliminates the insulation problem, as it would otherwise with a high voltage line passing through the valve 1 is performed, would occur.

In the 2 shown switching arrangement is used to operate the spark plug / injector unit 1, the essential components with the same reference numerals as in 1 are provided. The switching arrangement includes an external drive part 22 , with the speed correct, the excitation charge for the actuator 2 is applied.

Further, a discharge circuit 23 for the actuator 2 provided, which is essentially a switching element 24 , a rectifier 25 As well as not shown contains a capacitor in the switching element 24 is integrated. In the discharge circuit is also the primary winding 14 of the ignition transformer 14 ' and another switch which controls the discharge of the capacitor.

Synchronous speed is the actuator 2 through the control part 22 excited. For this purpose, a charge amount of about 100mJ is applied. The actuator 2 opens the injector as described above. To close the injector, the amount of charge on the discharge circuit 23 dissipated. For this purpose, an electrical connection to the capacitor is made in the switching element and the capacitor charged with it. The above-mentioned further switch prevents the discharge through the primary winding 14 ,

For generating the spark for the spark plug 10 After the closing of the further switch, the capacitor is discharged via the primary winding and the current flow is interrupted by opening this switch. In the secondary winding 15 A high ignition voltage is generated which acts as a spark over the spark plug 10 discharges.

The timing of the spark is also speed synchronized. The respective ignition timing is determined by a map. This and a corresponding characteristic map for the control of the actuator are stored externally and are used to the control part 22 and the switching element 24 to control.

The illustrated switching arrangement according to the invention enables trouble-free operation of the unit 1 over all speeds.

Claims (4)

Switching arrangement for a combined spark plug / injection valve unit with a capacitive actuator for the injection valve of an internal combustion engine, characterized in that the discharge circuit ( 23 ) of the capacitive actuator ( 2 ) with a primary winding ( 14 ) one of the spark plug ( 10 ) associated ignition transformer ( 14 ' ) connected is. Switching arrangement according to claim 1, characterized in that the primary and the secondary winding ( 14 . 15 ) of the ignition transformer within the unit ( 1 ) are arranged. Switching arrangement according to Claim 1 or 2, characterized by a switch (switching element) arranged in the discharge circuit 24 ). Switching arrangement according to one of claims 1 to 3, characterized by a arranged in the discharge circuit Capacitor.