Method for assessing a mode of operation of an injection valve in the event of an activation voltage being applied, and corresponding evaluation device

[0001] The invention relates to a method for assessing how an injection valve operates when applying an activation voltage. Furthermore, the invention relates to an analyzing device for assessing how the injection valve operates when applying the activation voltage.

[0002] DE 102006013166 describes a method and a control device for determining the opening voltage of an injector with a piezoelectric actuator. Injector opening is detected, the flow being interrupted at a stopping voltage, and then the voltage change on the piezoelectric actuator is measured and compared with the comparative voltage increase.

[0003] Furthermore, EP 1146 216 A describes a method for controlling the exhaust gas temperature. To this end, the target value of the engine operating parameter is calculated based on the air-fuel ratio and engine speed. Based on this target value of the engine operating parameter, the guide value for the regulator, in particular the throttle, is calculated.

[0004] Most often, an injection valve, for example a Common-Rail injector (CRI - Common-Rail-Injector), includes at least one actuator. The at least one actuator may for example be a piezoelectric actuator. In this case, for injecting fuel into the internal combustion engine, at least one actuator is subjected to an activation voltage. At least one actuator expands due to the applied activation voltage and at the same time exerts some pressure on the control chain attached to the at least one actuator, which, for example, includes a hydraulic coupler. The control valve located behind the control chain, or the hydraulic servo valve, is thus moved to the open position. When the valve

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The control is in its open position, the fuel from the fuel tank can flow to the internal combustion engine. [0005] For accurate metering of fuel injected into an internal combustion engine, the control voltage should be selected so that the control valve is moved to the open position with some excess force. It should be noted that the control voltage for moving the valve to its open position depends on the pressure of the injection rail.

[0006] Often, the activation voltage for the manufacture of injectors is set individually for each injection valve. The control voltage characteristic determined for opening the injection valve depending on the given pressure of the injection rail is then stored in the control device for controlling the injection valve. We are also talking about individual injector voltage regulation (ISA).

[0007] However, drift occurs in at least one actuator as well as in the control chain during their lifetime. This also, during the operation of the injection valve in the vehicle, leads to deviations of the control voltage needed to open the injection valve from the original characteristic curve.

[0008] It is therefore advantageous if the characteristics of the activation voltage needed in particular for opening the injection valve are checked during the operation of the injection valve. checking should be carried out taking into account the given pressure of the injection rail. However, the state of the art does not know how to carry out verifications without degrading driver comfort, for example due to noise or a significant impact on the behavior of the vehicle while driving.

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[0009] The invention provides a method having the features of claim 1. 1 and an analyzing device having the features of claim 1. 10.

[0010] The basis of the method according to the invention is based on the knowledge that the number and volume of noise generated when assessing the manner of operation of the injection valve when applying the activation voltage can be significantly reduced when a given activation voltage is applied to at least one injection valve actuator during injection developing torque. This non-torque injection is also often referred to as delayed injection.

[0011] According to the method according to the invention, the noise as almost without injection is almost absent. Similarly, during the implementation of the method according to the invention, there is almost no effect on the behavior of the vehicle while driving. The method according to the invention can thus be carried out during regular driving without compromising the driver's comfort.

[0012] Furthermore, the method according to the invention is based on the observation that non-torque injection by means of rotational detection is possible to a conventionally installed sensor in the vehicle for determining the fuel content of the exhaust system. Therefore, it is not necessary to install an additional sensor device in the combustion engine or exhaust system to carry out the process. This saves costs and space for another sensor device. The measured fuel content can be expressed as the air / fuel ratio or the amount of fuel in the exhaust system. Therefore, the non-torque injection can also be detected after the engine has ignited.

[0013] It is preferred that applying the activation voltage to the at least one actuator does not result

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- opening the injection valve if the predetermined fuel content is less than the reference value, and that applying an activation voltage to the at least one actuator causes the injection valve to open if the predetermined fuel content is greater than the reference value. In this way, it is easy to determine if there is drift of at least one actuator or control chain at the injection valve.

In a preferred embodiment of the method, the fuel content of the exhaust system is determined by means of a lambda probe. Traditionally, almost all vehicles weighing more than 1500 kilograms are equipped with a lambda probe to ensure compliance with the specified emission limits. This lambda probe enables reliable detection of the occurrence of non-torque injection.

[0015] Preferably, the activation voltage is applied to the at least one actuator in a piston position in which no torque is released when the fuel is eventually injected into the engine. Thanks to this, noise generation during the process can be eliminated almost completely.

[0016] In a preferred embodiment, the application of the activation voltage to the at least one actuator takes place in a piston position in which ignition of the fuel possibly injected into the engine no longer occurs. This prevents ignition noise or heat during the process. This embodiment of the method is therefore particularly well suited to being carried out while driving.

[0017] In addition, the injection rail pressure can be measured and the injection valve function evaluated depending on the injection rail pressure. The method therefore also takes into account the relationship between voltage

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6 activation needed to open the injection valve and the current pressure of the injection rail [0018] In another embodiment of the method, an initial value of the activation voltage is given at the beginning of the method. Such an initial value may be, for example, the activation voltage set by the manufacturer at the current pressure of the injection rail for the newly manufactured injection valve.

[0019] In a preferred other embodiment, if the obtained fuel content is less than the reference value, the activation voltage is increased by the first set voltage difference and the procedure is performed at least once again to obtain the activation voltage as a newly defined activation voltage, the application of which to at least one actuator opens the injection valve. The method can therefore be used not only to determine if there is drift of at least one actuator or injection valve control chain. In addition, whenever such a situation is detected, the activation voltage suitable for opening the injection valve can be determined again.

[0020] Similarly, if the calculated fuel content is greater than the reference value, the activation voltage can be reduced by a second preset voltage difference, the procedure can be repeated at least once again, and then the lowest activation voltage can be determined as the newly determined control voltage, at which application to at least one actuator, an injection valve opening is detected. The second voltage difference can be chosen much lower than the first voltage difference. This allows you to relatively accurately determine the lowest activation voltage that causes the injection valve to open. IN

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In the context of the present invention, in this way, after a prolonged operation of the injection valve, the activation voltage can be redefined, which must be applied to the actuator for safe injection in normal driving mode. The activation voltage to be applied to a given actuator can be determined again depending on the pressure of the injection rail. The determined correction values ​​can then be saved individually in the equalizer correction characteristics field.

[0021] In another embodiment of the method, the characteristic for the optimal activation voltage is determined based on the injection rail pressure based on the newly determined activation voltage. At the same time, when using the injection valve, a number of idle points are determined that allow sufficiently unambiguous identification of the actuator. To check the installed actuators while ensuring the appropriate freedom parameters, which are, for example, the value of the injection rail pressure, exhaust gas temperature or other steady states, idle points are measured in succession with their activation voltage deviations. After measuring all the idle points of the actuator, the fingerprint obtained in this way is compared with the minimum voltage demand values ​​originally stored for this actuator and placed in the characteristic field. These characteristic field values ​​are then made available for the correction of voltage control of the individual actuators.

[0022] The advantages of the method according to the invention detailed above also apply to the respective analyzing device. Drift corrections can also be made with this analyzing device

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- 8 actuators installed on the injection valve, which ensures correct operation of the actuators during the whole operation.

[0023] Further applicability and advantages of the invention result from the following descriptions of embodiments which are illustrated in the drawings. The figures of the drawings show:

Fig. 1: a flowchart of a first embodiment of a method for assessing how an injection valve operates by applying an activation voltage;

Fig. 2: a flowchart of a second embodiment of the method; and Fig. 3: a structure diagram illustrating the functions of the analyzing device for evaluating the operation of the injection valve when applying the activation voltage.

[0024] Fig. 1 is a flowchart of a first embodiment of a method for assessing how an injection valve operates by applying an activation voltage.

[0025] Before the actual start of the process, a reference value R0 is set for the fuel content in the exhaust system (step S0). The reference value R0 is, for example, the amount of fuel or the fuel / air ratio. At the same time, the reference value R0 corresponds to the fuel content in the exhaust system after the non-generating fuel injection in the associated internal combustion engine.

[0026] Preferably, step S0 is performed before the injection valve is actuated by the manufacturer. The injection valve is then mounted on the vehicle.

[0027] In step S1, for example when the vehicle is moving, the activation voltage U is applied to effect non-torque injection, to which

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- 9 at least one injection valve actuator. In a preferred embodiment, the at least one actuator is a piezoelectric actuator. The activation voltage U is applied, for example, with the pistons in such a way that no torque is released during the combustion of any fuel injected into the engine. Preferably, this arrangement of pistons can be selected such that any fuel injected into the engine no longer ignites.

[0028] The activation voltage U is, for example, the activation voltage given by the injection valve manufacturer at the current rail pressure p. In addition, the activation voltage U can also be selected in terms of the current flue gas temperature.

[0029] In a further step S2, after applying the activation voltage U to the at least one actuator, the fuel R (U) content in the exhaust system is determined. The fuel R (U) content can be, for example, the amount of fuel or the air / fuel ratio in the exhaust system.

[0030] Then, in step S3, the fuel content R (U) is compared with the reference value R0. In this way, it is determined whether, when the activation voltage U is applied to at least one actuator, the injection valve opens and the fuel is injected into the internal combustion engine.

[0031] If the measured fuel content R (U) is less than the reference value R0, then in step S4 it is checked whether applying the activation voltage U to at least one actuator does not open the injection valve. If the injection valve does not open when applying the U activation voltage, this indicates the probable drift of at least one actuator or control chain. In this case, it is necessary to redefine the activation voltage U

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Necessary to open the injection valve, so that the desired injection quantities are reliably kept during the further operation of the injection valve. An appropriate message is then given.

[0032] If the measured fuel content R (U) is greater than the reference value R0, supplying the activation voltage U to the actuator opens the injection valve, thereby fuel injection into the internal combustion engine. This is done in step S5. Also in this case an appropriate message is given.

[0033] Fig. 2 is a flowchart of a second embodiment of a method for assessing how an injection valve operates when applying an activation voltage.

[0034] In the step S10 preceding the method, the activation output voltage U0, the voltage difference Δυ and the reference value R0 for the fuel content in the exhaust system are already described. In a preferred embodiment, this step S10 is performed by the injection valve manufacturer prior to its activation.

[0035] The output activation voltage U0 is, for example, a control voltage suitable for opening a new injection valve, which is specified by the manufacturer specifically for this injection valve. The voltage difference Δυ is discussed in more detail below.

[0036] During the movement of the vehicle, the method is started at step S11a to examine at least one actuator and injection valve control chain from the point of view of possible drift. The current p rail pressure is measured here. Depending on the current pressure p of the injection rail, the activation voltage υ is selected from the prepared output activation voltages υ0 (step S11).

[0037] In a further step S12, the activation voltage υ is supplied for the non-torque injection into

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- 11 at least one injection valve actuator. It is particularly advantageous if the activation voltage U is applied to the at least one injection valve actuator only when the pistons are in a position in which any fuel injected into the engine can no longer ignite. Alternatively, the following fuel injection into the engine has little effect on engine operation. In the case of delayed injection, possible changes in noise, e.g. engine noise or combustion noise, are avoided. Similarly, no torque change is caused, so that the method can also be used during normal operation.

[0038] In next step S13, the fuel content R (U) is determined, for example the amount of fuel or the fuel / air ratio in the exhaust system. In a preferred embodiment, the fuel content R (U) is determined in such a way that the fuel / air ratio in the exhaust system is measured with a lambda probe and then compared with the measured value of the amount of air meter placed in the air supply line. Since the air quantity meter and lambda probe are traditionally already installed in many vehicles, it is possible to perform this embodiment according to step S13 in this form without having to install an additional sensor in the vehicle.

[0039] In a further step S14, the determined fuel content R (U) is compared with the reference value R0. If the fuel R (U) content is less than the reference R0 value, then it is stated that when the activation voltage U is applied to at least one actuator, the injection valve does not open. This indicates the drift of at least one actuator or injection valve control chain. That's why it's beneficial

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- 12 is if in this situation the activation U voltage for opening of the injection valve is determined again.

[0040] In the next step S15 of the method, the activation voltage U is increased by the voltage difference AU. Then, process steps S12 to S14 are again carried out for the newly determined activation voltage U. If the obtained R (U) content of the fuel is also lower than the reference value R0 this time, process steps S15 and S12 to S14 are repeated. This continues until the fuel content R (U) is higher than the reference R0 value.

[0041] With a fuel content R (U) higher than the reference value R0, it is checked whether the injection valve opens when the activation voltage U is applied to at least one actuator (not shown in Fig. 2). In the next method step S16, the lowest activation voltage U, at which the fuel content R (U) greater than the reference value R (0) is obtained, is taken as the newly determined activation voltage Un (p). Based on this newly determined activation voltage Un (p), a fingerprint can then be determined for a given drift of at least one activator and / or control chain. Then, based on this fingerprint, a new activation voltage characteristic U can be determined for opening the control valve depending on the given pressure p of the injection rail. [0042] In a further embodiment of the method, after step S14, if the measured fuel content is greater than the reference value R0, the activation voltage U may be reduced by a given minimum voltage difference. This minimum voltage difference is preferably considerably smaller than the voltage AU difference. Steps S12 to S14 are then carried out until the fuel R (U) content is again measured below the reference R0 value. IN

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- this way you can determine the lowest activation voltage U, at which the fuel content R (U) is higher than the reference value R0. This type of iterative step can be carried out to more accurately determine the activation voltage Un (p). The newly determined activation voltage Un (p) can then, as described above, be analyzed and / or used when operating the injection valve. Of course, it is also possible to omit this type of iteration step for accurate determination of the newly determined activation voltage Un (p), which is because, for example, a relatively small voltage difference Δυ is given.

[0043] Alternatively to the fuel / air ratio, the fuel content can also be determined as the air / fuel ratio. In this case, the injection valve opening can be determined if the determined air / fuel ratio is less than the set reference value. The non-opening of the injection valve despite the application of the activation voltage is then detected if the detected air / fuel ratio is greater than the set reference value. However, this is not shown in Figures 1 and 2.

[0044] Fig. 3 is a diagram of the structure illustrating the operation of the analysis device for assessing how the injection valve operates by applying an activation voltage to the injection valve actuator.

[0045] The tested injection valve 10 is located between the fuel tank 12 and the combustion engine 14. If the injection valve 10 is open, the fuel from the fuel tank 12 is injected into the combustion engine 14.

[0046] The internal combustion engine 14 is also connected to an air supply 16. Inside lead 16

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An air volume meter 18 is arranged which measures the amount of air introduced into the internal combustion engine 14 and provides the corresponding first sensor signal 20.

[0047] In addition, the internal combustion engine 14 has an outlet to the exhaust system 22. Inside the exhaust system 22 there is a lambda sensor 24. The lambda sensor 24 is adapted to determine the fuel / air ratio in the exhaust system 22 and to provide a second sensor signal 26.

[0048] In addition, a sensor assembly 28 is arranged on the combustion engine 14, by means of which it is possible to determine the position of the pistons. The third sensor signal 30 generated by the sensor assembly 28 determines the angle behind the top dead center and is transmitted to the injection control device 32.

[0049] The injection control device 32 is adapted to, that after receiving the third sensor signal 30 having an angle behind the upper dead center from the sensor assembly 28, it controls the injection valve 10 by means of a voltage signal 34 applied to at least one actuator (not shown), in such a way that the injection valve 10 is opened or closed at a certain angle behind the upper dead center 30.

[0050] The following explains how the analyzing device 36 operates to evaluate how the injection valve 10 operates by applying an activation voltage U:

the analyzing device 36 receives via the receiving device 36a a fourth sensor signal 40, with the injection rail pressure p determined by the vehicle pressure sensor 38. The output device 36b of the analyzing device 36 then sends to the injection control device 32 as a control signal 42 a voltage U

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- 15 activations, corresponding to the p rail pressure of the injection rail. The injection control device 32 is controlled by a control signal 42 such that a voltage signal 34 corresponding to the activation voltage U at the non-torque injection is applied to the actuator of the injection valve 10. For example, the injection control device 32 waits for an angle behind the top dead center at which the fuel injected into the internal combustion engine 14 no longer ignites.

[0051] In an alternative embodiment, the sensor assembly 28 may provide the third output sensor signal 30, with a predetermined angle behind the top dead center, also to the analyzing device 36. In this case, the analyzing device 36 provides the control signal 42 to the injection control device 32 only at a certain angle after the top dead center.

[0052] The analyzing device 36 receives a second sensor signal 26 from the lambda sensor 24, with a measured fuel / air ratio in the exhaust system 22. Additionally, the analyzing device 36 receives from the air quantity meter 18 the first sensor signal 20 with the amount of air supplied to the internal combustion engine 14. The comparator device 36c of the analyzing device 36 then determines from this data the amount of fuel supplied to the internal combustion engine 14. Then the calculated amount of fuel is compared with the reference value R0. If the amount of fuel injected into the internal combustion engine 14 is greater than the reference value R0, then the analyzing device 36 recognizes that when applying a given activation voltage U to at least one actuator, the injection valve 10 is opened.

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[0053] If, on the other hand, the calculated amount of fuel is less than the reference value R0, then the analyzing device 36 recognizes that applying the activation voltage U to at least one injection valve actuator 10 does not open the injection valve

10. Thus, the given activation voltage U for opening the injection valve 10 is not suitable. If this activation voltage U corresponds to the manufacturer's preset value for the new injection valve 10, there is drift of at least one actuator and / or control chain.

[0054] Then, it is possible to determine the minimum necessary voltage by the analyzing device 36 by repeating the measurement voltage U described by the alternating voltages.

the minimum required activation voltage U for injection is then stored individually for the cylinders in the characteristic fields, and therefore remains available for compensation of actuator drift.

Robert Bosch GmbH

Proxy:

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