CN105317575B

CN105317575B - Method for controlling multiple injections in a fuel injection system, in particular of an internal combustion engine

Info

Publication number: CN105317575B
Application number: CN201510298195.7A
Authority: CN
Inventors: H.朗
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-06-04
Filing date: 2015-06-03
Publication date: 2020-02-18
Anticipated expiration: 2035-06-03
Also published as: FR3022002B1; DE102014210561A1; FR3022002A1; CN105317575A

Abstract

The invention relates to a method for controlling a plurality of injections in an injection system, in particular in a common rail injection system for injecting fuel in an internal combustion engine, wherein at least two partial injections that follow one another in time are injected by means of at least one injector having a nozzle needle, and wherein it is provided, in particular, that a closing time (300) of the at least one nozzle needle is detected, and that an occurrence (310) of an operating state in which a continuous supply of fuel is carried out between the at least two partial injections is detected as a function of the detected closing time of the at least one nozzle needle.

Description

Method for controlling multiple injections in a fuel injection system, in particular of an internal combustion engine

Technical Field

The invention relates to a method for controlling multiple injections in a fuel system, in particular in a common rail injection system of an internal combustion engine, according to the preamble of claim 1. The invention further relates to a computer program, a machine-readable data carrier for storing the computer program, and an electronic control unit, by means of which the method according to the invention can be executed.

Background

It is known for "common rail" injection systems for injecting fuel in internal combustion engines to vary the time interval between the injections or the duration of the injections in order to influence the combustion process taking place in the combustion chamber of the internal combustion engine. As is known, the injection process is carried out by means of an injector which is actuated by means of a nozzle needle.

It is known that "continuous delivery" (Durchförderung) of fuel occurs if the time interval between injections is too short, i.e. at least two individual injections are gradually switched over to one another and act like a single longer injection.

Disclosure of Invention

The invention is based on the following recognition: the mentioned continuous delivery of fuel also leads to the following results: the closing time of the nozzle needle mentioned for the respective injector is generated or shifted back in a delayed manner. This effect is exploited according to the invention-that is to say in the reverse sense-in the following way: the "continuous feed" in a plurality of injections that follow one another in time, in particular in two single injections or partial injections that follow one another in time, is indirectly detected or monitored by detecting the precise closing times of the injection needle concerned. The mentioned detection of the closing time of the nozzle needle can be carried out in a manner known per se by means of a needle closing sensor.

If a change in the closing time of the needle is detected and/or a time delay of the closing process of the needle is detected, the existence of a continuous conveying state is inferred, which is linked to a significant increase in the injection quantity according to a law. The continuous conveying state thus identified can be effectively addressed, preferably by adjusting or changing the time interval between the at least two partial injections and/or the actuation duration of the at least two partial injections, or such an operating state, which is undesirable per se, can be cancelled or ended.

In the event of a detection of a continuous conveying state, the time interval between the at least two partial injections can therefore be increased by a corresponding previously empirically determined correction value and/or the actuation duration of the at least two partial injections can be reduced by a corresponding previously empirically determined correction value. Suitable correction values can be determined for the individual injector characteristics from a correction value table or the like, in which, for example, correction values for all the injectors of one or more internal combustion engines are stored. The method can thus be advantageously used in the entire injection system.

The detection and evaluation of the mentioned change in the needle closing time can advantageously be carried out by means of threshold monitoring, wherein a suitable first threshold value, in particular the mentioned temporally delayed needle closing time, is empirically determined in the preparation phase. It can only be reliably assumed that a continuous delivery of fuel between the two injections occurs if there is a specific delay in the needle closing time.

Furthermore, by precise detection or monitoring of the closing time, the smallest possible injection interval in terms of hydraulics can be achieved, and even precise adjustment or readjustment/readjustment of the injection state can be carried out in the continuous operation of the injection system or the internal combustion engine on which it is based.

In addition, the method according to the invention can also be used to effectively compensate for any possible operating chain tolerances or manufacturing tolerances, in particular the corresponding tolerances of the nozzles or injection valves involved here, with the readjustment (control loop) mentioned during continuous operation.

The method according to the invention can be carried out only after the detection of the presence of two partial injections that follow one another in time, as a result of which system capacity or system resources can be saved. In addition, it can be checked whether the time interval between two partial injections falls below a second empirically predefined threshold value. The mentioned continuous delivery of fuel can only be completely achieved below the second threshold value.

The invention can be used in particular in the common rail injection systems mentioned, but can in principle also be used in other injection systems in which a plurality of injections follow one another in time, for example in injection systems in which an aqueous urea solution (HWL) is injected for the purpose of exhaust gas aftertreatment or for reducing nitrogen oxides formed during the combustion of fuel.

The computer program according to the invention is set up to carry out each step of the method, in particular when it is executed on a computer or a controller. It is possible to carry out the method according to the invention on an electronic control unit without having to make structural modifications to the electronic control unit. For this purpose, the machine-readable data carrier is provided, on which the computer program according to the invention is stored. The electronic control unit according to the invention is obtained by loading the computer program according to the invention on an electronic control unit which is set up to control a plurality of injections in an injection system by means of the method according to the invention.

Further advantages and embodiments of the invention emerge from the following description and the drawings.

It goes without saying 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 leaving the scope of the invention.

Drawings

Fig. 1a-c schematically show a device or sensor device known from the prior art for detecting the closing time of a nozzle needle of a common rail injection valve;

fig. 2a-c show the measured injector current level, injection rate and nozzle needle movement curves on a common rail injection system, and more precisely compare the situation according to the prior art with the situation using the method according to the invention; and is

Fig. 3 shows an embodiment of the method according to the invention by means of a flow chart.

Detailed Description

Fig. 1a shows a sensor device known from EP 1961952 a1 for detecting or detecting an injector needle closing in a common rail injection system of an internal combustion engine. The sensor device comprises a sensor 405 for detecting an opening and/or closing movement of a nozzle needle (not shown here) of the respective injection valve or injector, in particular for detecting a closing and/or opening time of the nozzle needle. In the present exemplary embodiment, sensor 405 is designed as a piezoelectric or micromechanical acceleration sensor and is used to detect mechanical vibrations caused by the movement of the nozzle needle.

Furthermore, the device shown in fig. 1a comprises a sensor module 400 for determining the amount of fuel to be injected by the respective injector into the respective combustion chamber of the internal combustion engine (not shown). The sensor module 400 comprises, in particular, the mentioned vibration sensor 405, which is designed here as a piezoelectric acceleration sensor, for detecting the closing time of the nozzle needle of the injector. Furthermore, a microprocessor 410 for editing the measurement data is provided. The sensor module 400 additionally comprises a temperature sensor 415 with which the fuel temperature in the injector or in the injector supply line in the immediate vicinity of the injector can be measured. Furthermore, a data memory 420 is provided, in which injector-specific compensation variables are stored and which can be queried by the control unit of the internal combustion engine. The

electronic components

405, 410, 415, 420 of the sensor module 400 are arranged on a circuit mount 430 of a circuit board, which is embodied in this exemplary embodiment as ceramic.

An alternative device or sensor device for detecting the closing times of the nozzle needles referred to here is known from WO 2011085867 a1, with which the closing times of the nozzle needles and thus the operating phases of the fuel injection system can be detected particularly precisely. The device is based on the following principle: when the nozzle needle is closed or opened, a characteristic pressure change occurs, which can be detected very precisely. The following recognition is used in particular: the control chamber pressure, which can be detected by means of a pressure measuring device, changes significantly at the beginning and at the end of the injection phase of the fuel injector.

Fig. 1b shows a partial axial section of the fuel injector referred to here, shown in WO 2011085867 a1, with a high-pressure chamber 2 and a low-pressure chamber 3 in the interior of the injector body 1. The two pressure chambers are separated from each other by a valve element 4. The high-pressure chamber 2 communicates with a common rail, not shown, for example, via an inlet channel 5. The low-pressure chamber 3 is connected to the fuel tank via a return line 21.

The high-pressure chamber 2 can be connected to a combustion chamber of an internal combustion engine, which is likewise not shown, via a nozzle, which is not shown. The nozzle is controlled in a known manner by means of a nozzle needle, of which only the end remote from the nozzle, embodied as a plunger 6, is shown in fig. 1 b. The plunger 6 is arranged in a control chamber 7 arranged in the valve part 4 in a pressing manner. The control chamber 7 communicates with the high-pressure chamber 2 via an inlet throttle 8 and with the low-pressure chamber 3 via a preferably throttled outlet channel 9, wherein the outlet channel 9 is controlled by means of a control valve arrangement 10. If the outlet channel is isolated by means of the control valve device 10 and the nozzle needle is in its closed position, the same high pressure occurs in the control chamber 7 as in the high pressure chamber 2, with the result that: the plunger 6 is pressed downwards in fig. 1b and the nozzle needle connected thereto is held in a closed position, which closes off the nozzle. If the outlet channel 9 is opened by means of the control valve device 10, a reduced pressure occurs in the control chamber 7 relative to the high pressure in the high pressure chamber 2, and the plunger 6 is moved together with the nozzle needle in the upward direction in fig. 1b, that is to say the nozzle needle is adjusted into its open position, so that fuel is injected through the nozzle into the combustion chamber.

The control valve device 10 has a sleeve-like closing body 11 which is pressed by a locking spring 12, which is embodied as a helical compression spring, against a counter-seat which is concentric with the outlet opening of the outlet channel 9. The sleeve-like closing body 11 is guided in an axially displaceable manner on a guide rod 13 which is coaxial to the longitudinal axis 100 of the injector body 1, wherein an annular gap between the inner circumference of the closing body 11 and the outer circumference of the guide rod 13 acts as a leak-free sealing gap.

If the closing body 11 assumes the closed position shown in fig. 1b, the pressure chamber 14 formed inside the closing body 11, which communicates with the control chamber 7 via the outlet channel 9 and then accordingly has the same fluid pressure as the control chamber 7, is sealed off from the low-pressure chamber 3. A star-shaped armature 15 of an electromagnet arrangement 16 is arranged on the closing body 11, which electromagnet arrangement 16 is provided as an actuator for actuating the control valve arrangement 10. In a manner known per se, this electromagnet arrangement 16 has an electromagnetic coil 17, which is arranged inside the electromagnet arrangement concentric to the guide rod 13 and has an annular outer pole 18 and an annular inner pole 19. If the electromagnetic coil 17 is energized, the armature 15 is magnetically attracted by the

poles

18 and 19, lifting the closure body 11 from its mating seat against the force of the closure spring and opening the control valve device 10.

In the closing phase of the nozzle needle connected to the plunger 6, i.e. when the nozzle is closed, the control valve device 10 is closed and the same fluid pressure is present in the pressure chamber 14 and in the control chamber 7. Just before the closing moment of the nozzle needle, the pressure in the control chamber 7 drops below the high pressure in the inlet channel 5 due to the lower pressure below the nozzle seat of the nozzle needle at this moment and the consequent closing movement of the plunger 6. Immediately after the nozzle needle has closed, a steep rise in pressure occurs in the control chamber 7 due to the now stopped plunger 6, wherein the control chamber pressure rises to the pressure in the inlet channel 5. The pressure in the control chamber 7 and the pressure in the pressure chamber 14, which is virtually identical to the pressure in the control chamber 7, therefore have a prominent minimum at the closing time of the nozzle needle.

Fig. 1c shows an exemplary profile of the nozzle needle lift (diagram a) and of the control chamber pressure (diagram B) for the injector shown in fig. 1B. Since the pressure of the control chamber 7 is also present in the pressure chamber 14 when the closing body 11 is closed, the control rod 13 is always subjected to the pressure of the control chamber on the end face in this valve position inside the closing body 11. The control chamber pressure is transmitted, in particular, by means of the control rod 13 to a pressure sensor 20, which is schematically illustrated in fig. 1b, so that an evaluation circuit, not illustrated, which is connected to the pressure sensor 20 on the inlet side, continuously receives information about the pressure in the control chamber 7 and thus detects, in particular, the closing time of the nozzle needle. The evaluation circuit mentioned can be integrated into the not shown control unit of the internal combustion engine.

The described sensor device for detecting the closing time of the nozzle needle provides a voltage or a voltage change in the range of approximately 1V as a measurement signal. Instead of the piezoelectric sensor device shown in the preceding figures for detecting the closing time, a piezoresistive element can also be considered, which uses the so-called piezoresistive effect, which consists in many materials changing their specific resistance under pressure.

Curves

200, 205 shown in fig. 2a have a relatively small energization time interval between a first injection 210 and an immediately temporally subsequent second injection 215. The injection rate measurement shown in fig. 2b, which is carried out at the mentioned energization, shows that two injections 220 are not sufficiently separated in time. The "not enough separation in time" is caused in particular by: the injection rate between the two injections 220 in the case of energization according to curve 200 does not drop to the original value of approximately 0mV, but only to a significantly higher value of approximately 70 mV.

As can also be seen from the injection rate measurement according to fig. 2b, two clearly separated injections 225 are produced according to curve 205 with a large current supply interval between first injection 210 and second injection 215.

According to the invention, the missing or insufficient temporal separation of the two injections 220 also causes a temporal shift or delay in the closing process of the nozzle needle. The measurement curves of the injector

nozzle needle movements

230, 235 generated during the energization according to the

curves

200, 205 shown in fig. 2c illustrate this connection, since the measurement curve 230 generated from the earlier energization 210 is shifted significantly back in time relative to the measurement curve 235 generated from the later energization 205, and more precisely in the present exemplary embodiment by approximately 0.05 ms.

It is to be noted that the respective scaling of the X-axis and Y-axis of the measurement curves shown in fig. 2a to 2c merely shows the results of the test examples obtained on the measuring table or test bed, and therefore the particular measured values shown for the present invention should not be understood in any way as limiting.

According to the exemplary embodiment of the method according to the invention, which is illustrated in fig. 3, the time and/or the magnitude of the closing operation of the needle or of the corresponding voltage value mentioned, i.e., the voltage value, is first detected 300. On the basis of the detected voltage value, it is checked 305 whether the needle closing time, which is also detected here, is greater than an empirically predefined threshold value, i.e. shifted backwards in time. If this condition is not met, the needle closing operation is checked again, since if this condition is not met 305, it is assumed according to the invention that the previously described situation of continuous fuel delivery, together with the mentioned disadvantageous consequences, does not occur for the combustion operation.

If, however, the check 305 indicates that the condition mentioned is fulfilled, it is assumed or recognized 310 that a continuous fuel supply between the respective two injections is present, and in a subsequent step 315 the time interval between the current supply curves of the two injections is adjusted, in particular increased, in order to cope with the mentioned continuous fuel supply or to suppress or end this.

It should be noted that the routine shown in fig. 3 is preferably only started if two injections that follow one another in time are detected or present.

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

Claims

1. Method for controlling a plurality of injections in an injection system, wherein at least two partial injections that follow one another in time are performed by means of at least one injector having a nozzle needle, characterized in that a closing time of the at least one nozzle needle is detected (300), and the presence of an operating state in which a continuous supply of fuel is carried out between the at least two partial injections is detected (310) as a function of the detected closing time of the at least one nozzle needle.

2. Method according to claim 1, characterized in that the detection of the closing time of the at least one nozzle needle is carried out by means of a needle closing sensor device.

3. Method according to claim 1 or 2, characterized in that the detected closing time is compared (305) with a first threshold value and a situation in which a continuous feed state is present between the at least two partial injections is only concluded (310) if the first threshold value is exceeded.

4. The method according to claim 1 or 2, characterized in that the time interval for the actuation of the at least two partial injections and/or the actuation duration of the at least two partial injections are changed (315) if a continuous feed state between the at least two partial injections is detected.

5. The method as claimed in claim 4, characterized in that the time interval for the actuation of the at least two partial injections is increased by a first correction value determined empirically beforehand and/or the duration of the actuation of the at least two partial injections is decreased by a second correction value determined empirically beforehand.

6. The method according to claim 5, characterized in that a correction value table is provided, in which correction values specific to the injectors are stored, wherein the correction values mentioned are retrieved from the correction value table.

7. Method according to claim 1 or 2, characterized in that the mentioned steps according to one or more of the preceding claims are carried out only if two partial injections are detected which follow one another in time.

8. Method according to claim 7, characterized in that the time interval between the two partial injections is compared with a second threshold value and the mentioned steps are carried out only if the second threshold value is undershot.

9. Method according to claim 1 or 2, characterized in that the injection system is a common rail injection system for injecting fuel in an internal combustion engine.

10. Method according to claim 1 or 2, characterized in that, if a continuous transport state between at least two partial injections is detected, the time interval between the activation of the at least two partial injections is increased and/or the activation duration of the at least two partial injections is reduced.

11. Machine-readable data carrier, on which a computer program is stored, which computer program is set up to carry out each step of a method.

12. An electronic control unit which is set up to control a plurality of injections in an injection system by means of a method as claimed in any one of claims 1 to 10.