DE102015217645A1 - Method for operating an injection system - Google Patents

Abstract

The invention relates to a method and an arrangement for operating an injection system of an internal combustion engine with a first injector (10) and at least one second injector (10), wherein the injection system has a high-pressure accumulator, wherein a pressure curve in the region of a high pressure feed line (15) of the first Injector (10) is recorded and evaluated to detect actuation of at least one of the at least one second injector (10).

Description

The invention relates to a method for operating an injection system of an internal combustion engine, in particular a common rail injection system. The method finds particular use in an injection system with piezo injectors.

State of the art

Injection systems in internal combustion engines are used to convey or inject fuel from a tank into the combustion chambers of the internal combustion engine, the cylinders. In a common-rail injection system, the fuel is brought to a high pressure level by means of a high-pressure pump. The pressurized fuel is introduced into a pipeline system, the rail, from which in turn the pressurized fuel injectors for injection is supplied. The common-rail injection principle is characterized by a complete separation of pressure generation and actual injection process. The actual injection takes place via activation of an injector, which is also referred to as an injection valve, for example by triggering with an electrical signal, the activation signal. Depending on the principle of operation, a distinction is made between solenoid valves and piezo injectors that have a piezo actuator.

In order to be able to meet ever higher emission requirements, the injection quantities and the injector function of the injectors must be kept as constant as possible, especially over the lifetime. It should be noted that for the development of a voltage correction function learning over the lifetime of the injector, it is very helpful to know the change in the voltage requirement.

An important factor in achieving this requirement is the accuracy of the amount and timing of the fuel injected via the injectors and the determination of the property of the fuel. In order to be able to determine the point in time and the fuel quantity of the injection over the lifetime, it is known to equip injectors with a sensor with which the time of opening the needle and closing the needle of an injection can be detected.

The publication DE 10 2014 204 746 A1 describes a common rail injector with an injector, in which a high-pressure chamber is formed, which is supplied via a formed in the injector inlet or high pressure bore with pressurized fuel. On the outer surface of the injector, a sensor is provided, with which a pressure drop in the high-pressure bore can be detected as a result of an injection. Also, a pressure increase due to a needle closing or the completion of an injection is detected via this sensor.

It is thus necessary to equip each of the injectors with a pressure sensor, which involves high costs. Furthermore, it should be noted that if one of the sensors fails, the procedure can no longer be carried out.

Disclosure of the invention

Against this background, a method according to claim 1 and an arrangement according to claim 9 are presented. Embodiments emerge from the dependent claims and from the description.

With the method, a pressure profile in the high-pressure feed line of a spatially remote injector is recorded and evaluated by a sensor in order to determine an actuation of this remote injector.

Actuation means an opening and / or closing, in particular a needle opening and / or needle closing.

The proposed method is used in particular in a piezo injector typically in a common rail injection system. The method is applicable to all types of injectors with a sensor on the holding body. In this case, a pressure profile determined in the region of a high-pressure feed line is evaluated. It is important that the sensor of a first injector is used to make a statement about the behavior of at least one second injector.

The presented method utilizes in an embodiment the elastic deformation on the holding body in the area of the high-pressure bore due to the pressure wave in the high-pressure bore of the first injector for detecting the actuation, in particular a needle opening and a needle closing, of other, adjacent injectors of the engine, which possibly have no sensors or their sensors have failed. In this case, a failure also implies such a high signal loss over the runtime, so that an evaluation can no longer be carried out. In addition, the elastic deformation on the holding body in the region of the high-pressure bore due to the pressure wave in the high-pressure bore of a first injector for detecting the needle-opening and / or the needle-closing of the first injector having a sensor can be evaluated.

The method can also be used to monitor sensors and results of plausibility of sensors by other sensors.

Thus, the pressure profile in the high-pressure bore or the high-pressure inlet line of an injector is used to detect the needle-opening and the needle-closing of another injector in the engine in which the sensor has failed or several injectors of the injection system over the running time , In this case, the deformation of the holding body or the conduit can be used as a size to be detected. The required sensor can be attached to the holding body or the supply line and must be installed neither in the high pressure nor in the low pressure of the injector. However, it is basically possible to use a sensor provided in the high-pressure accumulator or rail.

In this way, in case of failure of a sensor, the needle-opening and needle-closing of this injector can be measured by the other injectors and determined by the computing unit of the injection system, for example. The common-rail injection system. Further control of needle opening and needle closing and other functionalities based on the open and close timing detection are thus still possible despite the failure of one or more sensors for the affected injectors where the sensor has failed. Emission and performance requirements can thus be met even after failure of one or more sensors.

Thus, it is sufficient to equip a motor with only one injector, which is equipped, for example, with a sensor on the holding body. In one embodiment, it is provided that some injectors are equipped with a sensor. The number is less than the number of injectors in a system, eg. B. two injectors with sensor in a V6 engine. The sensor can also be mounted on the rail or other point in the system. This point should be hydraulically coupled to all injectors. In a V6 engine with two rails, two sensors, i. E. H. one sensor per rail, be provided. The advantage is thus the saving of sensors on injectors. This leads to a cost saving for the entire system.

In the presented method is thus provided in an embodiment, the needle-opening and the needle-closing of one or more injectors in which the sensor has failed to determine or measure the remaining functioning sensors of the other injectors on the engine. It can also be provided to detect the needle opening and the needle closing of all injectors on an internal combustion engine via one or several sensors. Consequently, the number of sensors is less than the number of injectors.

So far, on the other hand, it has been provided to install a separate sensor for each injector in the case of upcoming common rail injectors with piezo control, which detects the needle opening and the needle closing of the respective injector.

In an embodiment, the presented method enables the detection of the needle opening and the needle closing of one or more adjacent injectors with a sensor in the system. Furthermore, it allows the detection of needle opening and needle closing of one or more adjacent injectors with a few sensors, d. H. their number is smaller than the number of injectors in the system. A plausibility check and / or check of the adjacent injectors with one or a few sensors can be carried out. A takeover of the function of one or more failed sensors by the or still functioning sensors is also possible.

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 an embodiment of an injector for carrying out the method described.

2 shows in four graphs gradients of sizes.

3 shows a section through a holding body of an injector.

4 shows in a graph the correlation between injector voltage demand and rail pressure.

5 shows a sensor signal on a cylinder

Embodiments of the invention

The invention is schematically illustrated by means of embodiments in the drawings and will be described in detail below with reference to the drawings.

1 shows an embodiment of an injector, in total with the reference numeral 10 is designated. The illustration shows a switching valve 12 , one Switching valve chamber 14 , a throttle plate 16 , a drain throttle 18 , an inlet throttle 20 , a control room 22 , a control chamber sleeve 24 and a nozzle needle 26 ,

Furthermore, the illustration shows a high-pressure feed line 15 leading to a high pressure bore 17 leads, in whose area a holding body 19 is arranged. At this holding body 19 is a piezo element 21 arranged, which serves as a sensor and a deformation of the holding body 19 , In particular, the course of deformation of the holding body 19 , picks up.

In the illustrated injector 10 is achieved by switching the servohydraulic switching valve 12 the pressure in the control room 22 changed. The control room 22 is located directly above the nozzle needle 26 , To open the injector 10 is due to the flow of the drain throttle 18 and the inlet throttle 20 the pressure in the control room 22 so far lowered until the balance of power at the nozzle needle 26 is reached and this opens. There is the switching valve 12 the space behind the drain throttle 18 to the low pressure area freely, so that functionally the tax amount from the control room 22 over the drain throttle 18 can drain into the low pressure area. As long as the switching valve 12 is open, the tax amount flows off.

Opening the switching valve 12 leads to a pressure drop in the high-pressure feed line 15 and the high pressure bore 17 , The pressure drop in the high pressure bore 17 leads to an elastic deformation of the high-pressure bore 17 and also to an elastic deformation of the holding body 19 passing over the piezo element 21 , which serves as a piezo sensor element, is measured and converted by this sensor into electrical signals and a control unit 23 via electrical lines 25 is transmitted.

In the presented method now the elastic deformation of the high-pressure bore 17 and also the elastic deformation of the holding body 19 , which is effected by the actuation of another injector, recorded and evaluated. Since the injectors are hydraulically connected to each other, the operation of one of the other injectors also affects the pressure curve in the high-pressure feed line 15 the other injectors. Although there is a delay due to the duration of the pressure wave. However, this can be determined, for example, with the aid of a temperature model. If the injection duration, ie the period between needle opening and needle closing, is to be determined, then the running time can be disregarded.

Alternatively or additionally, a sensor, for example a piezoelectric element, can be connected to the high-pressure feed line 15 be arranged.

2 shows in three graphs respectively waveforms over a corresponding period. A first graph 30 shows the course of the drive voltage 32 over time. A second graph 40 shows the pressure curve 42 in the high pressure feed line over time. A third graph 50 shows a filtered voltage signal 52 at the control unit input of the piezoelectric element, which is arranged on the holding body in the region of the high-pressure feed line.

In the first graph 30 is a drive time 34 marked, starting at a first time 35 until a second time 36 at which the triggering of the injector ends. One point 38 on the course 32 indicates the value of the driving voltage to be controlled by one embodiment of the described method.

When the switching valve is opened and the amount of control discharged as a result, there is a pressure drop in the high-pressure feed line at a third point in time 44 , This pressure drop leads to a mechanical relief of the holding body on the circumference of the high-pressure bore, ie at the bevel on which the sensor sits. If, for example, a piezoelectric element is used as the sensor, this relief leads to a relief of the prestressed piezoelectric element and can be measured as a voltage change at this point.

When opening the nozzle needle, there is a further pressure drop in the high pressure line at a fourth time 46 , This pressure drop leads to a further mechanical relief of the holding body on the circumference of the high-pressure bore or on the bevel on which the sensor sits.

This discharge leads to a further relief of the biased piezoelectric element and can be measured as a voltage change at this. The fourth time 46 can be defined or recognized by a gradient change of the voltage change of the sensor.

When needle closing a pressure wave or a pressure increase in the high-pressure bore at a fifth time 48 triggered. This pressure increase leads to a further bias of the sensor element and can be measured as a voltage change at this.

When opening an injector needle, it also leads to a pressure drop in the high pressure holes of the other injectors in a common rail injection system, as the injectors hydraulically via the rail and the HD lines are coupled. Due to the longer hydraulic distance, this pressure drop arrives laterally with respect to the top dead center of the injecting injector in the case of the other injectors.

In case of failure of one or more sensors on one or more injectors, the needle-opening of this or these injectors and the pressure drop caused thereby from the other injectors, which still have a working sensor on the high-pressure bore and the deformation of the holding body due to the pressure drop in a convert electrical size and forward this signal the arithmetic unit of the common rail injection system, detected and determined.

This pressure drop can thus also be detected and determined by the other injectors, which have a sensor on the high pressure bore and the deformation of the holder body due to the pressure drop into an electrical variable and forward this signal to the arithmetic unit of the common rail injection system.

The same applies to the needle closing. When the needle is closed by the injection injector, a pressure wave, namely an increase in pressure, is triggered in the high-pressure bore (fifth time 48 ). This pressure increase also leads to a rise in pressure in the high-pressure bores of the other injectors in the injection system since the injectors are hydraulically coupled via the high-pressure accumulator, the rail, and the high-pressure lines. Due to the longer, hydraulic path, this pressure increase is offset in time with respect to the top dead center of the injecting injector with the other injectors.

This pressure increase can thus also be detected and determined by the other injectors, which have a sensor on the high-pressure bore and the deformation of the holder body due to the pressure increase into an electrical variable and forward this signal of the arithmetic unit of the common rail injection system.

In the event of a failure of one or more sensors on one or more injectors, the needle closing of this or these injectors and the resulting pressure increase from the other injectors, which still have a working sensor on the high pressure bore and the deformation of the holding body due to the pressure drop in a convert electrical variable and this signal of the arithmetic unit of the common-rail injection system, which is typically integrated in a control unit and represents the arrangement described herein, pass, detected and determined.

In the presented method, the course 42 in the second graph 40 and the course 52 in the third graph 50 between the third time 44 and the fourth time 46 recorded and evaluated. Thus, the period between these two times, which is, for example, 200 .mu.s, and the gradient in this period, allow important conclusions about the function of the injector, which can be taken into account in the control.

In this way, the required Injektorspezifische drive voltage for opening the switching valve can be detected by the sensor and used for a "closed loop" voltage regulation in the vehicle over the term and possibly in the testing and coding in the factory.

Too high voltage reserve, which is currently held partially, is therefore no longer necessary. Each injector gets through the voltage control exactly the required drive voltage for him to ensure the injector function. The control unit in the vehicle is thus not unnecessarily burdened. Furthermore, this can limit the production, d. H. electrical sizes of the injector to comply with the control unit load within the permitted range, increases and the yield can be increased thereby.

By the method can be further waived the existing in the factory testing the voltage requirements and its coding on the injector and the corresponding reading at the customer on the vehicle.

3 shows a section through a holding body, the reference numeral 70 is designated. The illustration shows a high-pressure bore 72 , a piezo element 74 , which serves as a piezo sensor element, a bracing ring 76 which is as stiff as possible, and a strain area 78 at the polished section of the holding body 70 ,

A deformation of the high pressure bore 72 due to a pressure wave causes a deformation of the holding body 70 , in turn, with the piezo element 74 is recorded. In particular, the temporal course of the deformation is recorded and evaluated.

4 shows in a graph 80 a course 82 which is given by a rising straight line and a correlation between a voltage requirement of the injector, the ordinate 84 is applied, and the rail pressure, the abscissa 86 is applied.

The course illustrates a linear relationship between the voltage requirement and the rail pressure. The higher the rail pressure, the higher the voltage required by the injector.

This correlation can be taken into account in the presented method, in particular in the control of the drive voltage. Thus required drive voltages can be determined for some, for example at two or three, rail pressures. The required drive voltage at a further rail pressure can then be determined by interpolation or extrapolation.

5 shows the signal of a sensor on the injector in cylinder 1. It is a 4-cylinder engine. It can be clearly seen the characteristics of the needle-opening and the needle-closing of the other injectors in cylinders 2, 3 and 4 on the sensor signal of the injector in cylinder 1.

The illustration shows with reference numeral 100 the energizing cylinder 1, with reference numeral 102 the energizing cylinder 3, with reference numeral 104 the energizing cylinder 4, with reference numeral 106 the energizing cylinder 2 and with reference numeral 108 the energizing cylinder 1. With reference numeral 110 is the outflow cylinder 1, with reference numeral 112 the outflow cylinder 3, with reference number 114 the outflow cylinder 4, with reference number 116 the outflow cylinder 2 and with reference numeral 118 the outflow cylinder 1 is displayed.

Furthermore, the illustration shows a sensor signal 130 , which results from the recorded pressure curve. Significant points in the course of the sensor signal 130 are marked with reference numbers.

With reference number 140 the voltage drop due to the needle opening of the cylinder 1 is characterized. numeral 142 indicates the voltage increase due to the needle closing cylinder 1. numeral 144 shows the voltage drop due to needle-opening cylinder 3, reference numeral 146 shows the voltage increase due to needle closing cylinder 3, reference numeral 148 the voltage drop due to needle-opening cylinder 4, reference numeral 150 the voltage increase due to needle closing cylinder 4, reference numeral 152 the voltage drop due to needle-opening cylinder 2, reference numeral 154 the voltage increase due to needle closing cylinder 2, reference numeral 156 the voltage drop due to needle opening cylinder 1 and reference numeral 158 the voltage increase due to needle closing cylinder 1.

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

• DE 102014204746 A1 [0005]

Claims (10)

Method for operating an injection system of an internal combustion engine with a first injector ( 10 ) and at least one second injector ( 10 ), wherein the injection system has a high-pressure accumulator, wherein a pressure curve in the region of a high-pressure feed line ( 15 ) of the first injector ( 10 ) is received and evaluated in order to actuate at least one of the at least one second injector ( 10 ) to recognize. Method according to Claim 1, in which a deformation of the high-pressure feed line ( 15 ) of the first injector ( 10 ) is detected. Method according to Claim 1 or 2, in which a deformation of a holding body ( 19 . 70 ) in the area of a high-pressure bore ( 17 . 72 ) of the first injector ( 10 ) is detected. Method according to Claim 2 or 3, in which a deformation of a piezoelement ( 21 . 74 ) is detected. Method according to Claim 1, in which the pressure profile in the region of a high-pressure feed line of a first injector ( 10 ) via a sensor having a pressure curve in the high-pressure accumulator ( 15 ) is recorded. Method according to one of claims 1 to 5, wherein monitoring at least one sensor of at least one of the at least one second injectors ( 10 ) is made. Method according to one of claims 1 to 6, which is for determining an injection start of an injection from at least one of the at least one second injector ( 10 ) is used is used.  Method according to Claim 7, which is carried out with the aid of a temperature model for determining a transit time. Arrangement for operating an injection system of an internal combustion engine, which has a first injector ( 10 ), at least one second injector ( 10 ) and a high-pressure accumulator, wherein the arrangement is adapted to a pressure curve in the region of a high-pressure feed line ( 15 ) of the first injector ( 10 ) in order to actuate at least one of the at least one second injector ( 10 ) to recognize. Arrangement according to Claim 9, which is provided in a control unit ( 23 ) is integrated.

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