This application claims the benefit of International Application PCT/EP2021/086829, filed Dec. 20, 2021, which claims priority to German Application 10 2021 202 655.9, filed Mar. 18, 2021. The disclosures of the above applications are incorporated herein by reference.
The disclosure relates to a method and a device for diagnosing an internal combustion engine of a powertrain, where the powertrain has the internal combustion engine and a transmission unit, and the diagnosis is carried out using a running irregularity signal.
In modern internal combustion engines, a running irregularity signal is formed for each cylinder, that is to say cylinder-specifically, on the basis of engine speed information. This cylinder-specific signal reflects a torque contribution of the cylinder in question to the overall torque power of the internal combustion engine and to the torque profile of the internal combustion engine.
A closed powertrain of a vehicle acts on these signals as disturbance variable. The closed powertrain is then present, for example, if a coupling of the powertrain is closed, and accordingly the torque of the internal combustion engine is transferred to the drive axle or to the drive wheels. Accordingly, roadway unevenness or other disturbance variables, which act on the drive wheels and accordingly on the drive axle, would act against rearwards the torque direction as far as the internal combustion engine. Accordingly, these signals act on the running irregularity signal in the case of the closed powertrain as disturbance variables. Such disturbance variables are of high frequency under most operating conditions of the internal combustion engine or the entire powertrain. In conventional internal combustion engines and in the case of a conventional running irregularity signal evaluation, high-frequency disturbance variables of this kind are effectively filtered out using a corresponding signal conditioning.
However, with certain transmission ratios, a low-frequency oscillation effect may occur as disturbance variable.
For diagnosis of the individual cylinders of the internal combustion engine, the filtered running irregularity signal is used in the engine control to identify differences between the individual cylinders in relation to the air/fuel mixture. Here, each cylinder is made leaner progressively in succession (an injection volume is reduced). The corresponding running irregularity signal thus deteriorates on account of the leaning of the particular cylinder. For diagnosis of the cylinder in question, a ratio between leaning and change or deterioration of the corresponding running irregularity signal can then be formed in order to assess the cylinder in question and correct it if necessary. If the diagnosis of the particular cylinder exceeds or drops below a predefined threshold value, a fault memory entry can be input in an engine control unit, which in turn can be displayed to a driver of the vehicle, showing that a vehicle repair is necessary.
With certain transmission ratios of a transmission unit of the powertrain, the low-frequency oscillation effect superimposes this ratio formation and thus increases the inaccuracy of the results of the diagnosis. This increase in the inaccuracy may mean that fault-free cylinders are classified as faulty, and accordingly an unauthorized fault store entry may be input in the engine control unit although the system and the powertrain are not defective.
One aspect of the disclosure provides a method for diagnosing an internal combustion engine of a powertrain having the steps listed below. The powertrain has an internal combustion engine and a transmission unit. The internal combustion engine is configured to provide the torque to the powertrain, and the transmission unit is configured to provide the desired ratio to a drive axle of the powertrain, so that the torque or the speed can be transferred as desired to the drive axle or the drive wheels. The diagnosis of the internal combustion engine is carried out using a running irregularity signal. The running irregularity signal reflects a torque contribution of various cylinders to the overall torque of the internal combustion engine, whereby an assessment or the diagnosis of the internal combustion engine or the individual cylinders of the internal combustion engine is possible using this running irregularity signal.
In some examples, the method includes ascertaining a diagnostic value of the internal combustion engine during operation using the running irregularity signal of the internal combustion engine, where the powertrain is operated using a diagnostic gear of the transmission unit. According to this first-mentioned step, the diagnostic value which diagnoses the internal combustion engine is ascertained during operation of the internal combustion engine on the basis of the running irregularity signal. During operation of the internal combustion engine, an arbitrary gear of the transmission unit is engaged. Accordingly, the transmission unit is operated with this arbitrary gear, the diagnostic gear. If, for example, the transmission unit has five, six or seven different gears, which each offer a different ratio, the gear that is engaged in the transmission unit when the diagnostic value of the internal combustion engine is ascertained is the diagnostic gear. Accordingly, the diagnostic gear can differ according to the moment in time or time period or operating mode of the internal combustion engine or the powertrain.
Additionally, the method also includes detecting the diagnostic gear which is engaged in the transmission unit while ascertaining the diagnostic value. According to this method step, the diagnostic gear is detected that was available in the transmission unit when ascertaining the diagnostic value, whereby the corresponding ratio was provided.
Additionally, the method also includes comparing the ascertained diagnostic value with a predefined diagnostic threshold value and comparing the diagnostic gear of the transmission unit with at least one predefined gear of the transmission unit. According to this method step, the ascertained diagnostic value is firstly compared with a predefined diagnostic threshold value. For example, it is examined here whether the diagnostic value exceeds or drops below the diagnostic threshold value. It is also conceivable that the diagnostic threshold value is a limit band, and the diagnostic value is compared to ascertain whether the diagnostic value breaks out from the limit band of the diagnostic threshold value. According to this method step, it is then compared, where an order is irrelevant, however, whether the diagnostic gear of the transmission unit that was engaged whilst ascertaining the diagnostic value corresponds to a predefined gear of the transmission unit. It is examined here whether or not the diagnostic gear matches at least one of the predefined gears of the transmission unit. The diagnostic threshold value and the predefined gear of the transmission unit can be determined, for example, during the development of the powertrain and stored in a memory, where they are used accordingly for the comparison according to this method step.
Additionally, the method also includes identifying that the diagnosis of the internal combustion engine is reliable and there is a fault of the internal combustion engine if the ascertained diagnostic value exceeds the predefined diagnostic threshold value and at the same time the diagnostic gear of the transmission unit differs from all of the predefined gears of the transmission unit. The comparison of the ascertained diagnostic value with the predefined diagnostic threshold value accordingly delivers a result as to whether there is a fault of the internal combustion engine. The comparison of the diagnostic gear of the transmission unit with the at least one predefined gear accordingly delivers a result as to whether or not the ascertained diagnosis is reliable. Accordingly, if the diagnostic gear of the transmission unit is different from all of the predefined gears of the transmission unit, i.e., a different gear from the predefined gears, then the diagnosis of the internal combustion engine is reliable, and the ascertained fault of the internal combustion engine corresponds to an actual, existing fault case. Accordingly, a fault entry may be made.
Additionally, the method also includes identifying that the diagnosis of the internal combustion engine is unreliable if the ascertained diagnostic value exceeds the predefined diagnostic threshold value and at the same time the diagnostic gear of the transmission unit corresponds to one of the predefined gears of the transmission unit. According to this case, it is identified that the diagnosis of the internal combustion engine is implausible if the ascertained diagnostic value exceeds the predefined diagnostic threshold value, thus correspondingly there is potentially a fault, but at the same time the diagnostic gear of the transmission unit corresponds to one of the predefined gears of the transmission unit, thus during the ascertainment of the diagnostic value a gear was engaged in the transmission unit which corresponds to one of the predefined gears. By way of the two last-mentioned method steps, a plausibility check of the ascertained diagnostic value is accordingly carried out by examining which gear of the transmission unit was engaged during the ascertainment of the diagnostic value. If the ascertained diagnostic value exceeds the predefined diagnostic threshold value, it is then examined accordingly whether the gear that was engaged in the transmission unit during the determination of the diagnostic value corresponds to one of the gears that were excluded for the ascertainment of the diagnostic value.
The disclosure provides a method and a device with which a reliable diagnosis of an internal combustion engine of a powertrain is possible.
In some implementations, a fault entry is only made if the diagnosis of the internal combustion engine is reliable and a diagnosed fault is thus most likely actually due to a fault in the internal combustion engine. Accordingly, the low-frequency oscillation effects which occur more frequently with the predefined gears of the transmission unit and which would lead to a false diagnosis can be excluded, whereby overall the diagnosis of the internal combustion engine can be carried out in an advantageously robust and reliable manner.
In some examples, the ascertainment of the diagnostic value is repeated if a gear change has been performed by way of the transmission unit, and where it is identified that the diagnosis of the internal combustion engine is reliable and there is a fault if the diagnostic value ascertained during the repetition exceeds the predefined diagnostic threshold value and at the same time the diagnosis of the transmission unit differs from all of the predefined gears of the transmission unit. For example, if a diagnosis is increasingly performed and it is identified that the diagnosis is unreliable or unreliable because the diagnostic gear of the transmission unit present during this diagnosis matches one of the predefined gears of the transmission unit, then the ascertainment of the diagnostic value is repeated when a gear change has been performed, for example due to a change in operation of the drive unit or due to a change in speed. The thus newly determined diagnostic value is then examined again here to determine whether it is reliable and whether a fault actually exists by comparing the ascertained diagnostic value with the predefined diagnostic threshold value, where it is identified that a fault exists if the ascertained diagnostic value exceeds the predefined diagnostic threshold value and at the same time the diagnostic gear of the transmission unit differs from all of the predefined gears of the transmission unit. Accordingly, due to the gear change, this new diagnostic gear differs from the diagnostic gear that was engaged during the previous ascertainment of the diagnostic value. Accordingly, by performing a second ascertainment of the diagnostic value, it can be identified whether there is actually a fault of the internal combustion engine. In some examples, the identification that the diagnosis of the internal combustion engine is unreliable can be used by performing the diagnosis again when a different gear is present in the transmission unit. Accordingly, if the diagnosis now performed is reliable, and the diagnostic value ascertained exceeds the predefined diagnostic threshold value, then an internal combustion engine fault is indeed present, and a corresponding fault entry is justified. According to this example, the diagnosis of the internal combustion engine can be performed reliably and robustly.
In some implementations, a gear change request is actively sent to the transmission unit if the ascertained diagnostic value exceeds the predefined diagnostic threshold value and at the same time the diagnostic gear of the transmission unit corresponds to one of the predefined gears of the transmission unit. Accordingly, an unreliable result or a diagnosis not performed under reliable conditions because the diagnostic gear of the transmission unit corresponds to one of the predefined gears of the transmission unit is used by identifying that there is potentially a fault case. However, to turn the unreliable result into a reliable one, a gear change is requested in order to investigate whether the ascertained diagnostic value continues to exceed the predefined diagnostic threshold value even if the gear is different, whereupon it is identified that the diagnosis is reliable and, accordingly, that a fault is indeed present. The request for the active gear change may be requested, for example, from an engine control unit to a transmission control unit. Provided that such a gear change can be performed without traction interruption or without noticeable changes to the powertrain that the driver might possibly detect, the corresponding gear change can then be performed immediately by the transmission unit, whereby the diagnosis can be checked for plausibility as to whether the diagnostic value actually exceeds the predefined diagnostic threshold value and a fault is actually present. According to this example, a new diagnosis can be carried out relatively quickly by way of the active gear change, whereby it is advantageously quickly recognized whether or not there is actually a fault.
In some implementations, the predefined gears are blocked by way of the transmission unit until the ascertainment of the diagnostic value is completed in a gear different from the predefined gears. According to this example, the predefined gears are blocked by way of the transmission control unit of the transmission unit so that the transmission unit cannot be operated in the corresponding gears, in other words, the corresponding gears cannot be engaged until the diagnostic value is ascertained. Due to the fact that the predefined gears cannot be engaged, the ascertained diagnosis is reliable, so that, if the diagnostic value is exceeded by the corresponding predefined diagnostic threshold value, the result is reliable and accordingly a fault is actually present. According to this example, a reliable diagnosis of the internal combustion engine can accordingly be performed comparatively easily and quickly.
In some implementations, the gear change and/or the gear block of the transmission unit are performed in dependence on the driver requirements or the powertrain requirements. For example, if the driver requests a corresponding load change, for example due to a desired strong acceleration, then it may be necessary for the transmission unit to be operated in corresponding gears that actually correspond to the predefined gears. Accordingly, the execution of the diagnosis can be stopped when a gear is engaged that corresponds to the predefined gears of the transmission unit. However, provided that the driver requirements again permit a change to gears of the transmission unit that do not correspond to the predefined gears, the diagnosis can be continued, thus allowing a reliable diagnosis to be performed.
In some implementations, a cylinder-specific diagnostic value is determined for each individual cylinder of the internal combustion engine by way of a cylinder-specific running irregularity signal. According to this implementation, a cylinder-specific running irregularity signal is provided, whereby a corresponding cylinder-specific diagnostic value can be ascertained. It is possible to provide a cylinder-specific running irregularity signal so that a corresponding diagnosis of the corresponding cylinder of the internal combustion engine can be performed using this corresponding running irregularity signal for the cylinder in question. Accordingly, a diagnosis can be made for each of the individual cylinders of the internal combustion engine using the respective cylinder-specific running irregularity signal, so that a statement can be made accordingly as to which of the cylinders has a fault, if the internal combustion engine as a whole has a fault. Accordingly, in accordance with this example, the diagnosis can additionally be carried out advantageously accurately.
In some examples, during a predefined first time period, one of the cylinders of the internal combustion engine is made leaner in comparison to the other cylinders of the internal combustion engine and the running irregularity signal detected during this first time period is used to ascertain the diagnostic value of the corresponding cylinder. A cylinder is made leaner by successively reducing the fuel supply to the particular cylinder compared to the other cylinders. As a result, this corresponding cylinder makes a smaller torque contribution to the overall torque of the internal combustion engine compared with the other cylinders. This leaning of the corresponding cylinder results in torque fluctuations which can be read out from the corresponding running irregularity signal. A ratio between the corresponding cylinder leaning and a change in the running irregularity signal (for example amplitude increase) is used to evaluate the corresponding cylinder. Accordingly, a cylinder-specific diagnosis, which is advantageously accurate, can be carried out by way of the leaning.
In some implementations, an entry is made in a fault memory if it is identified that the diagnosis of the internal combustion engine is reliable and a fault is present, i.e., the diagnosis value exceeds the predefined diagnostic threshold value, and where the entry is omitted from the fault memory if it is identified that the diagnosis of the internal combustion engine is unreliable, i.e., the diagnosis value exceeds the predefined diagnostic threshold value, but at the same time the diagnostic gear also corresponds to one of the predefined gears.
Another aspect of the disclosure provides a device for diagnosing an internal combustion engine of a powertrain. The powertrain has the internal combustion engine and a transmission unit and the diagnosis is performed by way of a running irregularity signal, The device includes a control unit designed to control one of the aforementioned methods. The device may be a control unit of the powertrain. In some examples, the device is a separate part of a control unit or is provided as an additional control unit for explicit control. For example, the device may be an engine control unit, which is for controlling the internal combustion engine. The device can also be, for example, a combination of the engine control unit and the transmission control unit.
The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
In
In other words, in such a situation with the appropriate transmission ratio, correspondingly the first cylinder would always sweep the first segment 510, the second cylinder would always sweep the second segment 520, the third cylinder would always sweep the third segment 530, and the fourth cylinder would always sweep the fourth segment 540. However, if the overall transmission ratio deviates only slightly from the integral ratio, the assignment of the corresponding segments 510-540 to the drive gear 170 shifts slowly with each revolution. This shift and the fact that, due to tolerances, the assignment is never exactly the same causes the low-frequency oscillation effect. With this low-frequency oscillation effect, the frequency of the oscillation that occurs is directly proportional to the deviation of the transmission ratio from the integral ratio (for example: very slow oscillations at 1:2.01 and very fast oscillations at 1:2.1). The amplitude of these oscillations is amplified if the powertrain has an imbalance, which is amplified, for example, by a poorly balanced drive wheel 170 or due to a loss of balance weights.
From the fourth diagram 600, it can be seen that at a certain point in time the diagnostic value 630 exceeds the diagnostic threshold value 640. Once the diagnostic value 630 exceeds the diagnostic threshold value 640, a check is made to determine which gear in the transmission unit 150 (not shown) was engaged during the diagnosis. If it is identified that the gear in the transmission unit 150 which triggers the low-frequency oscillation effects was engaged, then a blocking of the function in eighth gear 670 is requested in the transmission unit. This blocking is shown in the fourth diagram 600 by way of the profile 670. It can be seen here that the eighth gear is blocked as soon as the diagnostic value 630 exceeds the diagnostic threshold value 640. There is no immediate gear change according to this example, since the driving commands of a driver do not allow this. The dynamics of the powertrain or the driver's request are shown in the fourth diagram 600 in the profile 660. It can be seen here that as soon as the driver's wish requests acceleration (evident from the local peak in the profile 660), then a corresponding request for a gear change occurs. This request for a gear change is shown in the fourth diagram 600 with the profile 680. This request to the transmission unit 150 to change the corresponding gear is sent, for example, from an engine control unit to a transmission control unit. Accordingly, the transmission circuit is activated to change gear. This activation of the transmission circuit is shown in the fourth diagram 600 in the profile 650. Once the transmission control unit has performed the gear change, the diagnosis of the internal combustion engine 110 may be performed again. This release is shown in the fourth diagram 600 with the reference sign 690. In this regard, it can be seen from the corresponding course of the diagnostic value 630 that the corresponding diagnostic value 630 after release 690 is below the diagnostic threshold value 640, so that it is identified that the internal combustion engine 110 does not have a fault. Overall, according to the present disclosure, the influence of the low-frequency oscillation effects on the diagnosis of the internal combustion engine 110 can be avoided by only performing an active diagnosis and can lead to a corresponding fault entry if the transmission unit 150 has a diagnostic gear that does not correspond to the predefined gears.
If the diagnostic value 630 exceeds the diagnostic threshold value 640 and the diagnostic gear does not correspond to one of the specified gears, the cycle counter is increased. This increase of the cycle counter causes the next diagnostic cycle to be started. This increase of the cycle counter is shown in the block diagram 700 with block 725 and block 730. As soon as the cycle counter has reached the maximum, i.e., as soon as the diagnosis has been carried out completely, the gear shift request from the motor control unit to the transmission control unit is withdrawn. This reset is shown schematically in the block diagram 700 with block 755. The transmission control unit then switches back to the normal program. This switch-back is shown in the block diagram 700 with block 760. Subsequently, it is checked whether the result of the diagnosis is above an error threshold. This error threshold can, for example, be somewhat higher than the diagnostic threshold value 640 in order to reproduce tolerances or other deviations, for example. This comparison is shown in the block diagram 700 with block 765. Provided that the diagnostic value is above this error threshold, an error has been identified by way of the diagnosis, and processing of this error follows. For example, an error entry may be made in the engine control unit, whereupon, for example, the vehicle is to be taken to the workshop for inspection and rectification of the error. This error identification is shown in the block diagram 700 with block 775. Accordingly, provided that the diagnostic value is not above the fault threshold, there is no fault in the internal combustion engine, and therefore the internal combustion engine can continue to be operated without restriction. This identification is shown schematically in the block diagram 700 with block 770. The method ends with the evaluation of whether the diagnostic value is above the fault threshold value. Overall, according to this example, a diagnosis of the internal combustion engine 110 and in particular a diagnosis of the respective cylinders of the internal combustion engine 110 can be performed depending in each case on the gear present in the transmission unit 150 during the diagnosis. As a result, the low-frequency oscillation effects can be filtered out during the diagnosis of the internal combustion engine 110. Overall, according to this example, the operating range of the internal combustion engine 110 during which the diagnosis of the internal combustion engine 110 is performed can be increased considerably compared to conventional diagnoses, since a gear change can be actively requested in order to complete the diagnosis, whereas this is not possible with conventional internal combustion engines.
A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.
Number | Date | Country | Kind |
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10 2021 202 655.9 | Mar 2021 | DE | national |
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Entry |
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International Search Report and Written Opinion dated Apr. 20, 2022 from corresponding International Patent Application No. PCT/EP2021/086829. |
German Office Action dated Sep. 2, 2021 for corresponding German Patent Application No. 10 2021 202 655.9. |
Number | Date | Country | |
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20240003311 A1 | Jan 2024 | US |
Number | Date | Country | |
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Parent | PCT/EP2021/086829 | Dec 2021 | WO |
Child | 18468842 | US |