DE102015204037A1 - Method for controlling a common-rail injection system - Google Patents

Abstract

The present invention relates to a method for controlling at least one injector (1, 2) of a common rail injection system of an internal combustion engine, in particular of a motor vehicle, for injecting fuel into at least one combustion chamber of the internal combustion engine, wherein the at least one injector by means of an armature space (5 ) and a control chamber (8) having switching valve (1) is operated, and wherein it is provided in particular for at least one injection causing actuation of the at least one injector (1, 2) at least one additional control (410) is performed with a drive time by which the fuel pressure in the control chamber (8) of the switching valve (1) is lowered only so far, so that due to the additional control no injection of fuel into the combustion chamber of the internal combustion engine, but a damping of pressure oscillations in the armature chamber (5) of the switching valve (1).

Description

The invention relates to a method for controlling injectors of a common rail injection system of an internal combustion engine, in particular of a motor vehicle, according to the preamble of claim 1. Subject of the present invention are also a computer program, a machine-readable data storage medium for storing the computer program and an electronic control unit of which the inventive method is feasible.

State of the art

A common rail (CR) injection system concerned here comprises injectors which have a control or switching valve, by means of which fuel is injected in a controlled manner into a combustion chamber of an internal combustion engine affected here.

So goes out of the EP 1 316 719 A1 Such a common rail injector (CRI) with a solenoid valve for controlling an injection valve, in which the opening and closing position of a nozzle needle are controlled by the solenoid valve, so that injection holes for injecting fuel can be opened. With such an injector, a main injection and a pilot injection can be realized with very short injection times.

The solenoid valve of such an injector has a movable armature which lifts when energized, the magnetic group of the solenoid valve from a valve seat in a lower armature space. This valve seat is in turn via one or more (throttle) holes in fluid communication with a control (pressure) chamber of the injection valve. When the valve seat is opened, the pressure in the control chamber of the injection valve is reduced, whereby fluid (pressure medium) flows via the bores in the direction of the valve seat and from there into the lower armature space. At a decreasing pressure in the control chamber, the nozzle needle of the injection valve, which is constantly exposed to an acting in the opening direction of high-pressure fuel, set in motion, whereby the injection holes are opened and the injector can inject fuel.

Said injectors also have a leading to the lower armature space return bore through which leakage quantities from various portions of the solenoid valve and injector are returned to the lower armature space. If the solenoid valve is no longer energized, the armature moves by means of a return spring down and closes the valve seat leading to a throttle. As a result, the pressure in the control chamber increases again, so that the nozzle needle is moved down and the injection holes are closed.

Disclosure of the invention

The invention is based on the recognition that undesirable injections (so-called "ghost injections") may occur in the case of injectors having a switching valve at the beginning, the cause of which is an increased armature bounce of the switching valve, which is caused by reflections of fuel pressure waves in a low-pressure region, e.g. in a low-pressure rail, the CR injection system is triggered. These unwanted injections are from operating variables of the CR injection system, such as e.g. depends on the current fuel pressure in the rail, the injection scenario or the mean pressure level in the low pressure range.

The invention is based on the idea between conventional injections, i. e.g. mentioned preinjections and main injections to perform additional activations of an injector affected here to influence the pressure conditions in a control or switching valve affected here so that said unwanted injections are effectively avoided.

According to the method according to the invention, at least one additional control of an affected here, a switching valve with an armature space and a control chamber having injector with a suitable drive time, the fuel pressure in the control chamber of the switching valve is sufficiently high, so that no injection of fuel into a combustion chamber of the internal combustion engine takes place, however, a damping of said pressure oscillations in the armature space of the switching valve takes place (so-called "blankshot"). Such an activation effectively prevents said unwanted injections ("ghost injections").

In the method according to the invention, the technical effect is based on the fact that the pressure level in the armature chamber of the switching valve is lowered by the at least one additional control with a suitable control period so that unwanted injections are avoided, since on the one hand the largest possible amount of fuel through the switching valve in a said return is retracted, and on the other hand, the fuel pressure in the control room still remains sufficiently high, so that no additional injection is triggered by the additional control.

According to the invention, the technique of additional actuators known per se in the field of CR injection systems for rapid pressure reduction in the high-pressure rail system is used here for targeted lowering or preconditioning of the return backpressure immediately before a switching valve control in which valve bounce is expected.

In the method according to the invention may be provided in particular that the pressure level in the armature chamber of the switching valve is lowered so far that the largest possible amount of fuel is diverted through the switching valve in a return and the fuel pressure in the control chamber is sufficiently high, so by the additional control still no injection is triggered. By this measure, the formation of said fuel pressure waves is particularly efficiently prevented.

In the method according to the invention, it can further be provided that by means of the additional control, a targeted preconditioning of the return backpressure occurs immediately before an activation of the switching valve causing an injection, in which an excessive valve bounce is expected. By means of said preconditioning, the formation of said fuel pressure waves can be prevented even more efficiently, since the conditions mentioned can even more easily be met regarding the fuel pressure in the control chamber of the switching valve and the damping of said pressure oscillations in the armature space of the switching valve.

The activation duration of the additional control is preferably a value in the range of 0.05 to 0.4 ms. The time interval between the additional control and a subsequent injection effecting an injection is preferably 0.1 to 2 ms. These measures can be used to ensure that the conditions mentioned can be met by the fuel quantity through the switching valve and the fuel pressure in the control chamber, irrespective of the operating state of the injection system or of the internal combustion engine.

The additional control can advantageously take place in a torque-effective operating point of the injection system, so that a suitable time for such additional activation can be selected essentially without any restrictions and the method can thereby be implemented more simply in a control unit of an injection system affected here.

In the method according to the invention can also be provided that a said additional control as a preventive measure against unwanted injections, preferably with a fixed time interval to a subsequent control, is applied. As a result, a technically particularly simple and therefore cost-effective implementation of the method is made possible.

The invention can in particular be used in a common-rail injection system with magnetically actuated or solenoid-controlled injectors (MV injectors) or corresponding control valves. In this case, the method according to the invention can advantageously be implemented in an existing CR system or corresponding control unit, without any changes to mechanical or electrical components of the CR system or of the internal combustion engine being required.

The computer program according to the invention is set up to carry out each step of the method, in particular if it runs on a computing device or a control device. It allows the implementation of the method according to the invention on an electronic control unit, without having to make structural changes to this. For this purpose, the machine-readable data carrier is provided on which the computer program according to the invention is stored. By applying the computer program according to the invention to an electronic control unit, the electronic control unit according to the invention is obtained, which is set up to control a common-rail injection system affected here by means of the method according to the invention.

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 particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

1 shows the upper part of an injector with solenoid valve and the upper part of the injection valve,

2 shows the lower part of an in 1 shown injector.

3a -D show typical courses of drive current, armature stroke, armature space pressure and nozzle needle lift of an injector concerned here in a single injection and a multiple injection in comparison, to illustrate a chain of action in the formation of unwanted injections.

4a -D show the 3a - 3d corresponding courses in the case of an inventive additional control to avoid unwanted injections.

Description of exemplary embodiments

1 shows the usual construction of a solenoid valve 1 and injection valve 2 existing injector, as used in particular for fuel injection in common rail systems. In the sketch, only the injector parts essential for the invention are indicated. The one-piece anchor 3 is achieved by energizing the solenoid valve 1 against the spring force of the armature spring 11 pulled up. The anchor 3 runs in the anchor guide 12 and is not energized solenoid valve 1 on the valve seat 4 of the injection valve 2 on. In this state, the fluid connection to the control (pressure) space 8th of the injection valve 2 over the A-throttle 6 and the hole 7 interrupted. When energizing the solenoid valve, however, opens the A-throttle 6 and the pressure in the control room 8th sinks because fluid is now from the control room 8th in the lower anchor space 5 can flow. The inlet to the control room 8th is limited by the so-called Z-throttle (not shown), whereas the nozzle needle 17 (see. 2 ) is constantly exposed to an acting in the opening direction high fuel pressure. Because the pressure in the control room 8th with open A-throttle 6 less than that at the nozzle needle 17 pending high-pressure fuel, the push rod sits down 13 in motion and pulls the nozzle needle 17 in the opening direction, whereby the injection holes are opened and the injector can inject fuel.

2 shows the lower part of the injector associated with the injector 2 , whereby also here only some parts are designated. With the push rod 13 out 1 is the nozzle needle 17 connected. The lower nozzle needle space is with 16 designated. At various points of the injector leak quantities occur, via the return bore 9 in the lower anchor space 5 to be led back. These leakage quantities occur at the sealing of the valve piece to the injector body with the 14 designated place, in the place 15 between push rod 13 and valve piece as well as in the place 18 between nozzle and nozzle holder (see. 1 and 2 ). In addition to the leakage amount, the control amount becomes the A-throttle 6 through the hole of the anchor guide 12 about the total return 10 returned from the injector in a (not shown) tank.

At one in the 1 and 2 shown injector now occurs in certain injection scenarios an unwanted injection ("ghost injection"). The occurrence of such unwanted injections depends on several factors, eg the rail pressure or the return backpressure. Trigger or cause of this malfunction of the injector are in a previously described return system 10 occurring pressure oscillations, which cause excessive valve bounce or anchor bounce. Such reinforced anchor bumpers cause, in particular in the case of short actuation periods, due to the renewed depressurization caused thereby in a described control chamber 8th of the injector or solenoid valve 1 an at least temporary reopening of an already (nearly) closed valve needle or nozzle needle 17 ,

The emergence of said unwanted injections is based on the figures 3a to 3d or illustrated by the chain of action shown there. 3a shows qualitatively exemplary current waveforms in two successive drives 300 . 305 a solenoid valve affected here 1 and 3b also only qualitatively corresponding, with these controls 300 . 305 resulting anchor lift curves 310 . 315 , each over time t. The 3c shows the at the controls 300 . 305 resulting pressure curves or pressure waveforms 320 . 325 in the anchor space, and that compares to a single injection 320 . 325 and a multiple injection 320 . 330 , again over time t. In 3d are the results of a single injection nozzle needle lift course 350 in a single injection and one in the control 305 a multiple injection resulting unwanted injection 355 shown over time t.

Based on 3a to 3d Now the mentioned chain of action for the development of unwanted injections ("ghost injections") is described. You can see in 3c when opening the solenoid valve by the so-called bubble collapse in a present in this example low-pressure (ND) rail pressure peaks (pressure peaks) 340 . 343 the said pressure waveforms 320 . 325 , In 3c are also the pressure values resulting during the respective closing operation 335 located in the anchor room.

The first of the two pressure peaks 340 caused, schematically indicated pressure wave is running 340 in the case of a single injection by the ND-Rail and is reflected at one end of the rail 341 , Thereafter, the pressure wave reflected there runs back 345 and lifts it in the armature space of the solenoid valve 1 and at one said valve seat 4 surrounding valve cup present pressure accordingly 325 , This results in combination with the pressure increase 330 due to the second control 305 . 315 to a significant increase of anchor bounce and thus in a multiple injection ultimately to a named in 3d shown unwanted injection.

Like from the 3c furthermore, the pressure curve in the armature space is immediately before the second activation 305 by the from the previous control 300 the switching valve 1 resulting, returning pressure wave significantly increased 325 , This initial state at the beginning of yet another control favors the mentioned excessive valve bounce and thereby leads to a nozzle needle stroke course which ultimately causes the unwanted injection 355 ,

The with the 3a to 3d corresponding 4a to 4d show an embodiment of the method according to the invention for the prevention of unwanted injections ("ghost injections") by lowering the pressure level in the armature space by means of inventive additional controls, but without taking place injections (hereinafter "BS control").

In a presently adopted injection system with adjuster design, i. with a fuel metering unit (ZME), but no pressure control valve (DRV), an artificial leakage of excess fuel is generated by the injectors in the overrun operation of the internal combustion engine by said BS controls. By this leakage discharge, on the one hand, the permanent leakage of the metering unit is removed and the metering unit thereby given leeway for the rail pressure control.

In the BS control, the control period is selected so that on the one hand the largest possible amount of fuel per BS control is controlled by the switching valve in the return, on the other hand, the pressure in the control chamber at selected drive time is sufficiently high, so that no injection takes place ,

As in the 4a to 4d Based on a main injection (HE) and a subsequent secondary injection (NE) illustrated in the field of CR injection systems for rapid pressure reduction in the high-pressure rail system known per se technique of BS control presently for targeted reduction or preconditioning of the return back pressure immediately before Switching valve control, in which excessive valve bounce is expected applied. This invention BS control can also be used in injection systems with multi-valve concepts, eg in injection systems with a fuel metering unit (ZME) and a pressure control valve (DRV).

As in the 3a to 3d , shows 4a qualitatively exemplary current curves in the two aforementioned drives HE 400 and NE 405 such a solenoid valve 1 . 4b qualitatively corresponding, with these controls 400 . 405 similar to in 3b resulting anchor lifting curves 415 . 420 . 430 . 4c from the controls 400 . 405 resulting pressure waveforms 435 . 455 in the armature space, for comparison both with and without a BS control according to the invention, and 4d the resulting in a multiple injection (HE and NE) affected here Düsennadelhubverlauf 475 ,

In addition to the two controls 400 . 405 takes place shortly before the second activation (NE) 405 a BS control according to the invention 410 , The activation duration of the additional OS activation 410 preferably has a value in the range of 0.05 to 0.4 ms. The time interval between the BS control 410 and a subsequent subsequent or subsequent, an injection-causing control is in the range of 0.1 to 2.0 ms.

This additional control 410 causes, in addition to the two usual Ankerhubverläufen 415 such as 420 . 430 , a relatively small additional armature stroke 425 , the one mentioned lowering or preconditioning of the return back pressure immediately before the second control 405 or the corresponding armature stroke 420 . 430 causes. This will especially the in 3c illustrated increase 325 the pressure curve in the armature space effectively avoided. In contrast, in this embodiment takes place a division of the pressure curve 325 in two parts 450 and 455 , due to which the resulting pressure oscillations in in 1 and 2 shown return according to the dashed lines 460 . 465 reflected at one end of the rail 470 becomes.

In 4c is for comparison, the pressure curve in the armature space without a said BS control 410 shown. In this case, in turn, would result, similar to in 3c , a pressure gradient 440 with an elevation 445 in the initial area, which also present an unwanted injection 485 would effect. According to 4d in contrast, ie in the presence of a BS control 410 , a nozzle needle stroke 480 according to the control 405 the NE, but in this case not the unwanted (post-) injection 485 ,

The mentioned pressure oscillations in the return depend on a number of parameters such as e.g. the average pressure in the ND rail, the fuel temperature in the ND rail, the air content in the fuel, the precise, especially hydraulic structure of the ND rail, etc. from. However, the aforementioned BS control can be applied in critical injection scenarios, in particular independently of the timing of the pressure wave in the armature space, as a preventive measure against unwanted injections, preferably with a fixed time interval to a subsequent control. With such a simplified implementation, the required application or programming effort is relatively low.

The method described can be implemented in the form of a control program for an electronic control unit for controlling an internal combustion engine or in the form of one or more corresponding electronic control units (ECUs).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1316719 A1 [0003]

Claims (11)

Method for controlling at least one injector ( 1 . 2 ) of a common rail injection system of an internal combustion engine, in particular of a motor vehicle, for the injection of fuel into at least one combustion chamber of the internal combustion engine, wherein the at least one injector by means of an armature space ( 5 ) and a control room ( 8th ) having switching valve ( 1 ) is operated, characterized in that for at least one injection causing actuation of the at least one injector ( 1 . 2 ) at least one additional control ( 410 ) is carried out with a control duration, by which the fuel pressure in the control room ( 8th ) of the switching valve ( 1 ) is lowered so far that due to the additional control no injection of fuel into the combustion chamber of the internal combustion engine takes place, however, a damping of pressure oscillations in the armature space ( 5 ) of the switching valve ( 1 ) he follows. A method according to claim 1, characterized in that in the additional control, the pressure level in the armature space ( 5 ) of the switching valve ( 1 ) is lowered so that the largest possible amount of fuel through the switching valve ( 1 ) in a return ( 9 ) and the fuel pressure in the control room ( 8th ) is sufficiently high, so that no additional injection is triggered by the additional control. A method according to claim 2, characterized in that by means of the additional control targeted preconditioning of the return back pressure immediately before an injection causing actuation of the switching valve ( 1 ), in which a valve bounce is expected takes place. Method according to one of the preceding claims, characterized in that the activation duration of the additional activation ( 410 ) has a value in the range of 0.05 to 0.4 ms. Method according to one of the preceding claims, characterized in that the time interval between the additional control ( 410 ) and a subsequent injection effecting injection is 0.1 to 2 ms. Method according to one of the preceding claims, characterized in that the additional control takes place in a torque-effective operating point of the injection system or the internal combustion engine. Method according to one of the preceding claims, characterized in that a said additional control is applied as a preventive measure against unwanted injections. A method according to claim 7, characterized in that said additional control is applied at a fixed time interval to a subsequent drive. A computer program configured to perform each step of a method according to any one of claims 1 to 8. Machine-readable data carrier on which a computer program according to claim 9 is stored. Electronic control unit, which is set up to control a common-rail injection system of an internal combustion engine, in particular of a motor vehicle, by means of a method according to one of claims 1 to 8.

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