DE60122657T2 - Device and method for diagnosing a fuel supply system - Google Patents

Description

The The present invention relates to a device and to a method for Diagnosing a fuel supply system of an internal combustion engine, by compensating a command value of a fuel supply amount to the engine according to a Compensation amount is regulated based on a deviation an actual operating state of the engine with respect to a desired Operating state of the engine is determined so that the engine in the desired one Operating state is operated.

JP-B2-2907001 discloses a device that for one lean burn of a lean-burn gasoline engine and set up to diagnose the engine in terms of abnormality so that every cylinder of the engine is in terms of its Combustion state by detecting a change in a rotational speed of the engine is diagnosed, and the fuel supply to each cylinder This compensates for the fuel concentration in each cylinder at a good combustion state, and at the fuel concentration in each cylinder to increase in a bad combustion state. This Device is furthermore set up to check if the compensation of the Air / fuel ratio an air / fuel mixture for increasing the fuel concentration has been implemented with more than a predetermined number, and though for any cylinder of the engine, and to determine that Fuel supply system or an ignition system is defective, and for everyone Cylinder in which the compensation with more than the predetermined Number has been implemented.

The The known device described above is therefore adapted to determine that a given cylinder of the engine is defective, in which the fuel supply amount This cylinder can not be regulated. According to this device is included in a cylinder in which the fuel supply due to a jamming a fuel injection valve in its closed position completely stopped is the command value of the fuel supply amount of this cylinder continuously compensated so as to increase the air / fuel ratio increase, so that this cylinder is diagnosed as defective. on the other hand In some specific operating conditions, the regulation can be used Engine for example while the engine is idling, a normal fuel supply allow a given cylinder, its fuel injector at a leakage of the fuel due to poor placement of his valve body or due to a deterioration of its function for setting its opening time suffers from an increased Sliding resistance of the valve body is caused. In operating conditions of the engine except the specific operating conditions (for example, during the Idling of the engine), however, has the inadequate opening time the fuel injection valve has a strong influence on the amount the fuel supply to the cylinder, and the scheme can not normal fuel supply to this cylinder depending allow the operating condition of the engine. In this case can the device do not determine that the cylinder is defective while the fuel delivery system for this cylinder indeed is defective.

If the compensation of the air / fuel ratio for increasing the Fuel concentration at a given cylinder implemented thereby was that its fuel injector with more than the predetermined Number during the idling of the engine is adjusted, the regulation can for reflecting the amount of compensation which occurred during the Idling of the engine is obtained, a normal fuel supply to this cylinder even in the operating states of the engine except the enable some specific operating conditions, such as the Idling of the engine, if the opening and closing operations of Fuel injection valve are normal.

As As described above, the known apparatus can control the fuel supply system an abnormality or a defect does not diagnose exactly what is not just one Danger of continued operation of the engine at a causes bad combustion state, in which the fuel supply system is in a broken state, and where the fuel economy as well as the exhaust emissions are worsening and other problems but also a risk of a faulty diagnosis that the normally functioning fuel supply system is defective, wherein the faulty diagnosis normal operation of the engine prevented.

US-5 058 547 discloses a generic apparatus and method for diagnosing a fuel supply system of an internal combustion engine, comprising control means for determining a compensation amount for compensating a command value of a fuel injection amount by the fuel supply system to the engine on the basis of a deviation of an actual operating condition of the internal combustion engine of a desired operating state thereof, and for controlling the fuel supply system by means of a control by compensating the command value according to the compensation amount, so that the actual speed coincides with the desired speed.

DE 195 40 826 discloses another method for diagnosing a fuel delivery system of an internal combustion engine.

It The object of the present invention is a device and a A method of diagnosing a fuel delivery system for an internal combustion engine provide an accurate diagnosis of a fuel delivery system enable the internal combustion engine.

These Task is performed by the device with the features of claim 1 and by the method with the Characteristics of claim 10 solved. The invention is further defined as defined in the dependent claims is.

The The above object can according to a first aspect of this Be achieved invention, which is a device for diagnosing a Fuel supply system for one Internal combustion engine provides, with a control device for determining a compensation amount for compensating a Command value of a fuel injection amount by the fuel supply system in the internal combustion engine on the basis of a deviation of a Actual operating state of the internal combustion engine with respect to a desired operating state thereof, and for controlling the fuel supply system by regulation by compensating the command value according to the compensation amount, such that the internal combustion engine is operated in the desired operating state being, the device being a diagnostic device for diagnosing the fuel supply system by forcibly effecting a diagnosis setting of an operating state of the Fuel supply system when the compensation amount is outside a predetermined one Reference range falls.

The above object can be achieved according to another aspect of this invention, which provides a method for diagnosing a fuel supply system for an internal combustion engine, wherein the fuel supply system is controlled so that the internal combustion engine is operated in a desired operating state, and it is through the following steps characterized:
Calculating a deviation of a change amount of an actual operation condition with a desired change amount thereof;
Determining a compensation amount for compensating a command value of a fuel injection amount by the fuel supply system in the internal combustion engine of each cylinder of the internal combustion engine on the basis of the above deviation;
Determining whether the determined compensation amount falls outside a predetermined reference range; and
Diagnosing the fuel delivery system by suspending a control of the fuel delivery system and forcibly effecting a diagnostic adjustment of an operating condition of the fuel supply system when the determined compensation amount falls outside the predetermined reference range.

The diagnostic device and methods described above are not intended for Diagnosing the fuel supply system only in dependence which is set up by the regulation of the fuel supply system used compensation amount outside the predetermined reference range falls. Instead, the diagnostic device and methods adapted to diagnose the operating condition of the fuel supply system forcibly cause, if the compensation amount outside of the predetermined reference range, so that the fuel supply system is diagnosed on the basis of a result of the diagnosis setting. The current one An arrangement for effecting the diagnostic operation setting of the fuel supply system allows an accurate diagnosis of the fuel delivery system not only at a clamping defect of a fuel injection valve in the fuel supply system, but also for other abnormalities with regard to the opening and closing operations of Fuel injection valve, such as deterioration its function to set its opening time. Furthermore, the Diagnostic setting then causes the compensation amount outside of the reference range, that is, if a high probability is that the fuel supply system is defective is. This arrangement allows a further improvement in the accuracy of the diagnosis of the fuel supply system.

Of Further prevents the diagnosis setting of the operating state the fuel supply system, which is only effected when the compensation amount is outside of the predetermined reference range is an unnecessary change the combustion state of the internal combustion engine, and it minimized the deterioration of fuel economy and exhaust emissions the engine, and it minimizes the vibrations of the engine due to a change their operating condition.

According to a preferred embodiment of the present invention, the control means detects a change amount of the actual operation It calculates the deviation of the amount of change of the actual operating state in the idle state with respect to a desired amount of change thereof, it determines the compensation amount for each cylinder of the internal combustion engine on the basis of the aforementioned deviation, and compensates for this Command value of the fuel injection amount by the fuel supply system in each cylinder according to the determined compensation amount, so that the internal combustion engine is operated in the desired operating state.

While that Fuel supply system for each Cylinder of the engine regulated by the control device which has just been described causes the diagnostic device the diagnosis setting of the operating state of the fuel supply system, if the compensation amount based on the deviation between the actual operating state and the desired one Amount of change the operating state of the fuel supply system is determined, outside of the predetermined reference range, so that the fuel supply system diagnosed on the basis of a result of the diagnosis setting becomes.

The The arrangement described above allows an accurate diagnosis of the fuel supply system for each Cylinder of the engine. The accuracy of the diagnosis is further improved, since the diagnosis setting is only effected if the compensation amount for every cylinder outside of the reference range, that is, only if a high There is a likelihood that the fuel delivery system is defective.

Additionally prevented the diagnosis setting of the operating state of the fuel supply system, which is effected only when the compensation amount for each Cylinder outside of Reference range is an unnecessary change of combustion state the internal combustion engine, it minimizes the deterioration of fuel economy and the exhaust emissions of the engine, and it minimizes the Vibrations of the engine due to a change in its operating state.

at a first advantageous arrangement of the device according to the above preferred embodiment According to the invention, the diagnostic device is operable when the compensation amount of one of the cylinders outside the predetermined reference range falls to an operation of the control device to end and the diagnosis setting of the operating state of the fuel supply system for the mentioned above to cause any cylinder.

The just described diagnostic device is adapted to the End control operation by the control device and the diagnosis setting of the fuel supply system for that one Cylinder cause its compensation amount outside of the reference range. This arrangement allows efficient and accurate Diagnosis of the fuel supply system.

at a second advantageous arrangement of the device according to the above preferred embodiment According to the invention, the diagnostic device is operable when the compensation amount of one of the cylinders outside of the predetermined reference range falls to an operation of the control device and the diagnostic settings of the operating states of the Fuel supply systems for selected cylinders cause the internal combustion engine, wherein the selected cylinder The above-mentioned any have a cylinder.

The just described diagnostic device is adapted to the Control mode by the control device to stop and the diagnostic settings the fuel supply systems for the chosen Causing cylinders containing that cylinder, its compensation amount outside of the reference range. According to this Arrangement will be only those fuel supply systems for the selected cylinders, the fuel delivery system which is relatively likely to be defective by effect the diagnostic settings of those fuel delivery systems diagnosed. Accordingly, the present arrangement allows not only the efficient and accurate diagnosis, but it also prevents in Effectively an unnecessary change the combustion state of the internal combustion engine while the Deterioration of fuel economy and exhaust emissions the engine are minimized and the vibrations of the engine due to a change their operating state are minimized.

In the apparatus and method according to the aforementioned preferred embodiment of the invention, the diagnostic device may be configured to be operable to effectuate a forced increase or decrease of the compensation amount for diagnosis of each of the at least one selected cylinder of the internal combustion engine, and the fuel supply system is diagnosed for each selected cylinder based on a change in the actual operating state of the internal combustion engine, which is caused by the forced increase or reduction of the compensation amount for the Di agnose is caused.

at the device just described becomes the fuel delivery system for each the selected one Cylinder of the engine on the basis of change the actual operating state of the engine diagnosed by the compulsory increase or reduction of the amount of compensation for the diagnosis by the diagnostic device is caused. This arrangement allows a higher efficiency and a higher one Accuracy in the diagnosis.

at the device and the method just described, the diagnostic device be arranged to be operable to the fuel supply system for each chosen Cylinder as normal to diagnose when the actual operating condition the internal combustion engine according to the compulsory increase or reduction of the compensation amount is changed for diagnosis, and as a defect or abnormal when the actual operating state according to the compulsory Increase or Reduction of the compensation amount for the diagnosis is not changed.

If the operating state of the fuel supply system such as the opening and closing his Fuel injection valve is normal, then changes the actual operating state of Internal combustion engine according to the increase or reduction of the compensation amount for diagnosis of each selected cylinder. In view of this fact, the diagnostic device can be set up be the fuel supply system to diagnose as normal if the actual operating condition is the Engine according to the forced increase or Reduction of the compensation amount is changed for diagnosis, and as defective or abnormal if the actual operating state of the engine according to the compulsory increase or reduction of the compensation amount for diagnosis is not changed.

Of the Compensation amount can be increased gradually or be reduced if the increase or Reduction for diagnosis is forcibly performed.

Of the Compensation amount may gradually increase his original Return value, after the increase or reduction of the compensation amount for diagnosis forcibly accomplished has been.

SUMMARY THE DRAWINGS

Further Advantages and features as well as the technical meaning of the present The invention will be apparent from the following detailed description of currently preferred exemplary embodiments of the invention, when taken together with the accompanying drawings is considered, wherein:

1 shows a schematic view of a diesel engine of a common rail type and a control system, which is arranged according to a first embodiment of this invention for controlling the diesel engine;

2 FIG. 12 is a flowchart of a routine for controlling a fuel injection amount executed by an ECU of the control system of the first embodiment; FIG.

3 FIG. 12 is a flowchart showing a routine for calculating a cylinder compensation amount executed for each cylinder of the engine, in the first embodiment; FIG.

4 Fig. 10 is an illustration showing an arrangement of an engine speed sensor and a pulser used in the first embodiment;

5 FIG. 10 is a time chart showing a change in the number of revolutions of the common rail diesel engine in the first embodiment; FIG.

6 FIG. 12 is a graph showing a data map used in the routine for calculating the cylinder compensation amount according to FIG 3 is used to calculate an integral compensation amount dgcy based on a speed change DNE (K);

7 FIG. 12 is a flowchart showing a part of a preliminary diagnosis routine executed by the ECU of the control system of the first embodiment to effect a preliminary diagnosis of the fuel supply system; FIG.

8th shows a flowchart of the other part of the preliminary diagnosis routine;

9 FIG. 10 is a flowchart of a part of a main diagnostic routine executed in the first embodiment to effect a main diagnosis of the fuel supply system; FIG.

10 shows a flowchart of the other part of the main diagnostic routine;

11 FIG. 12 is a flowchart of a gradual-reset control routine executed in the first embodiment; FIG.

12 Fig. 10 is a timing chart showing an example of various parameters whose values change during the control effected in the first embodiment;

13 FIG. 10 is a flowchart of a routine for diagnosing a fuel supply system executed in a third embodiment of the present invention; FIG. and

14 FIG. 12 is a flowchart of a gradual-reset control routine executed in the third embodiment. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Under Reference to the accompanying drawings become the present preferred embodiments of this invention described in detail.

With reference to the schematic view in the 1 are initially shown a diesel engine 2 of the common rail type and a control system arranged according to the first embodiment of the present invention to the diesel engine 2 to control. The diesel engine 2 is adapted to be mounted as a drive power source on an automobile.

The diesel engine 2 has a plurality of cylinders, more specifically four cylinders # 1- # 4 in this specific embodiment. In the 1 only one of the four cylinders # 1- # 4 is shown. Each cylinder is equipped with a fuel injection valve 4 provided for injecting fuel into its combustion chamber. The fuel injector 4 is with a solenoid control valve 4a which is opened to allow injection of the fuel through the fuel injector 4a into the corresponding cylinder and closed to prevent fuel injection. Although the present embodiment is described as applying to the four-cylinder diesel engine 2 is applied, the same embodiment is applicable not only to the diesel engine, but also to gasoline engines, and moreover, it is applicable to a six-cylinder diesel or gasoline engine or any number of cylinders other than a four-cylinder engine.

Every fuel injection valve 4 is with a common rail 6 connected, which serves as a common accumulator for the four cylinders # 1- # 4. While the above-mentioned solenoid control valve 4a being kept open, the fluid coming out of the common rail 6 is conveyed into the corresponding cylinder through the corresponding fuel injection valve 4 injected. The common rail 6 is further charged with the pressurized fuel, the pressure being sufficiently high, and allowing fuel injection into each cylinder. To the fuel pressure in the common rail 6 to maintain a desired level is the common rail 6 through a feed pipe 8th with an outlet section 10a a fuel supply pump 10 connected. The fuel supply pump 10 is with a fuel tank 12 through a suction port 10b connected.

A channel that connects the suction port 10b with the fuel tank 12 connects is with a filter 14 Mistake. The fuel supply pump 10 has a plunger reciprocated by a drive cam (not shown) synchronizing with a rotary motion of the diesel engine 2 rotates. Will the fuel supply pump 10 so operated, that of the fuel tank 12 through the filter 14 absorbed fuel through the fuel supply pump 10 pressurized to the desired level, and the thus pressurized fuel becomes the common rail 6 promoted.

The combustion chamber of each cylinder of the diesel engine 2 is with an inlet channel 18 and with an exhaust duct 20 connected, and a throttle valve (not shown) is in the inlet channel 18 intended. The opening angle of this throttle valve becomes dependent on the operating state of the diesel engine 2 controlled to thereby meter a flow of the intake air into the combustion chamber.

The combustion chamber of each cylinder of the diesel engine 2 is with a glow plug 22 which is energized by an electric current flowing in it from a glow plug relay 22a is fed immediately before the diesel engine 2 is started. When the glow plug is energized 22 is a spray of the fuel that goes beyond the glow plug 22 is blown, easily ignited, and the combustion of the fuel is promoted. Thus, the glow plug is used 22 as a device for assisting the starting of the diesel engine 2 ,

To the operating condition of the diesel engine 2 In the present embodiment, the following sensors are provided. It is an accelerator sensor 26 near an accelerator pedal 24 arranged to an operation amount ACCPF of the accelerator pedal 24 and an acceleration OFF switch 28 is near the accelerator sensor 26 is orders to detect that the accelerator pedal 24 rests, that is, it is arranged in its non-actuated position. The diesel engine 2 is also with a starter 30 provided for starting the engine. This starter 30 is with a starter switch 30a provided for detecting its operating state. The diesel engine 2 is also equipped with a water temperature sensor 32 provided on its cylinder block for detecting a temperature THW of cooling water flowing through the cylinder block. The diesel engine 2 has an oil pan (not shown), in which an engine oil is stored, and with an oil temperature sensor 34 for detecting a temperature THO of the engine oil in the oil pan. A return pipe 16 that with the fuel tank 12 , the fuel supply pump 10 and the fuel injection valve 4 is connected to a fuel temperature sensor 36 for detecting a temperature THF of the fuel. The common rail 6 is with a fuel pressure sensor 38 for detecting the pressure of the fuel within the common rail 6 Mistake. The crankshaft (not shown) of the diesel engine 2 is with a pulser 41 provided, and an engine speed sensor 40 for detecting the rotational speed of the engine 2 is near the pulser 41 arranged like this in the 4 is shown.

A rotational movement of the crankshaft is transmitted through a timing belt to a camshaft (not shown) for opening and closing an intake valve 18a and a conductive fixed exhaust valve 20a is provided. This camshaft rotates at a speed that is half the speed of the crankshaft. Near a pulser (not shown) disposed on the camshaft is a cylinder detection sensor 42 arranged. In the first embodiment of this invention, output signals are from the engine speed sensor 40 and the cylinder detection sensor 42 for calculating the rotational speed Ne and a crank angle CA of the diesel engine 2 and a top dead center (TDC) of cylinder # 1. The vehicle has a gearbox 44 that with a shift position sensor 46 for detecting the currently selected operating position of the transmission 44 and with a dispensing speed sensor 48 for detecting the rotational speed of an output shaft of the transmission 44 is provided. The output signal from the output speed sensor 48 is used to calculate a speed SPD of the vehicle. The vehicle also has air conditioning (not shown) by the diesel engine 2 is driven, and by an air conditioner switch 50 switched on and off.

To different controls of the diesel engine 2 to effect is an electronic control unit (ECU) 52 provided, which is arranged according to the present embodiment of the invention. The ECU 52 is for effecting fuel injection control of a glow plug control and other controls of the diesel engine 2 and is further configured to effect diagnostic controls to diagnose the fuel delivery system of each cylinder. The ECU 52 mainly consists of a microcomputer containing the following; a central processing unit (CPU); a read-only memory (ROM) storing various control programs and data maps; random access memory (RAM) for temporarily storing various types of data such as those obtained by arithmetic operations by the CPU; a backup RAM for storing arithmetic operation data and prepared data; Time counter; an input interface; and a delivery interface. With the input interface of the ECU 52 are the above-described accelerator sensor 26 , the water temperature sensor 32 , the oil temperature sensor 34 , the oil temperature sensor 36 , the fuel pressure sensor 38 etc. connected by buffers, multiplexers and A / D converters (not shown). Also with the input interface are the engine speed sensor 50 , the cylinder detection sensor 42 , the output speed sensor 48 etc. connected by waveshaping circuits (not shown). The accelerator OFF switch 28 , the starter switch 30a , the shift position sensor 46 , the air conditioning switch 05 etc. are directly with the input interface of the ECU 52 connected. The input interface of the ECU 52 Further, a signal indicative of a battery electric voltage Vb and a signal indicative of a duty ratio DF of an inverter (not shown) provided for the diesel engine are received 2 intended. The CPU reads the output signals from the sensors and switches described above, which are picked up by the input interface. With the output interface of the ECU 52 are by driving circuits, the above-mentioned solenoid control valve 4a and the glow plug relay 22a and a pressure control valve 10c connected to that for controlling the delivery pressure of the fuel supply pump 10 is provided. The CPU operates to perform arithmetic operations based on the signals picked up by the input interface and suitably controls the solenoid control valve 4a , the pressure control valve 10c , the glow plug relay 22a etc. through the delivery interface.

With reference to the flowchart in the 2 First, a routine for controlling a fuel injection represented by the ECU 52 is performed. This routine for controlling the fuel injection is repeated as an interrupt routine having a cycle time corresponding to a predetermined change amount of the crank angle CA of the engine 2 more specifically, with a cycle time corresponding to a change in the crank angle CA by 180 ° in the present embodiment in which the engine 2 which has four cylinders. In the routine for controlling the fuel injection according to the 2 and other routines that will be described, steps for performing various control operations are identified by a respective step number preceded by the letter "S".

The routine for controlling the fuel injection according to the 2 is started at a step S110 to calculate a command value QFIN of a fuel injection amount Q based on the engine speed NE and the accelerator operation amount ACCPF and a predetermined equation. The step S110 is followed by a step S120 in which the command value QFIN of the fuel injection amount is compensated according to the following equation (1) based on a cylinder compensation amount qcy [K] calculated in a routine for calculating the cylinder compensation amount (described with reference to FIG on the flowchart in the 3 for a currently selected cylinder #K in which the fuel is to be injected. QFIN ← QFIN + qcy [K] (1)

Then, the control flow goes to a step S130 at which the opening time of the solenoid control valve 4a of the fuel injection valve 4 set for the currently selected cylinder #K is set on the basis of the thus compensated command value QFIN of the fuel injection amount. Thus, one cycle of execution of the routine is according to 2 completed.

When the routine for controlling the fuel injection according to 2 is repeatedly executed, then appropriate fuel injection quantities sequentially from the fuel injection valves 4 injected into the respective individual cylinders which are sequentially supplied with the fuel in a predetermined order. Thus, the amounts of the fuel supplied to the cylinder are appropriately controlled depending on the specific operating condition of the vehicle.

Now, the above-mentioned routine for calculating the cylinder compensation amount will be described with reference to the flowchart in FIG 3 described. As with the routine for controlling the fuel injection according to the 2 For example, the present routine is repeatedly executed as an interrupt routine having a cycle time corresponding to the predetermined change amount of the crank angle CA, more specifically, a cycle time corresponding to a change in the crank angle CA by 180 degrees in the present embodiment in which the engine 2 which has four cylinders. The routine for calculating the cylinder compensation amount in accordance with 3 is started at a step S200 to determine whether a calculation permission flag Xqcy is in an ON state. If the flag Xqcy is in an OFF state, that is, if a negative decision (NO) is obtained in step S200, an execution cycle of the routine is ended.

If the flag Xqcy is in the ON state, that is, if an affirmative decision (YES) is obtained in step S200, the control flow proceeds to step S210 to determine whether the diesel engine 2 is in a stable idle state. The stable idle state of the diesel engine 2 is interpreted as meaning an idle state in which the vehicle speed SPD is 0 km / h, and in which the idling speed of the diesel engine 2 stabilized when a sufficiently long time elapses after the accelerator pedal 24 has returned to its fully released or non-actuated position (where the actuation amount ACCPF is 0, and the accelerator OFF switch) 28 in the ON state).

If the diesel engine 2 is not in the stable idling state, that is, if a negative decision (NO) is obtained in step S210, an execution cycle of the routine is executed in accordance with 3 completed. If the diesel engine 2 is in the stable idle state, that is, if an affirmative decision (YES) is obtained in step S210, the control flow proceeds to step S220 to determine whether the currently detected engine speed NE is substantially equal to a desired idling speed NF, namely, whether the Istkraftmaschinenleerlauflaufzahl NE is maintained within a predetermined reference range, which is determined by the desired idle speed NF. This step S220 is implemented for the purpose of determining whether an external device by the diesel engine 2 is driving, such as a compressor of the air conditioning, which has just been turned on or off. If the external device has just been turned on or off, the actual engine speed NE changes to a value outside the predetermined reference value rich, which includes the desired idle speed NF, that is, the Istkraftmaschinendrehzahl NE is not stabilized. The actual engine speed NE is stabilized while being kept within the predetermined reference range, unless the external device has just been turned on or off.

If the actual engine speed NE is not substantially equal to the desired idle speed NF, that is, if a negative decision (NO) is obtained in step S220, one execution cycle of the current routine is ended. On the other hand, if the actual engine speed NE is substantially equal to the desired idle speed NF, that is if an affirmative decision (YES) is obtained in step S220, the control flow proceeds to step S230 to determine a speed change DNE [K] of the currently selected one Cylinder #K (into which the fuel is to be injected) according to the following equation: DNE [K] ← TNH [K] - TNH [K-1] (2)

In the above equation (2), TNH [K] represents a value depending on the maximum speed of the currently selected cylinder #K (hereinafter referred to as a "maximum cylinder speed"), and TNH [K-1] sets a value accordingly of the maximum speed of the cylinder # K-1 of the combustion stroke, which takes one stroke before the stroke of the currently selected cylinder #K The values TNH [K] and TNH [K-1], which will be described in detail later, are reversed or reciprocally proportional to the rotational speed NE of the diesel engine 2 ,

Namely, the value TNH represents a period of time during which a predetermined number of successive pulse signals are detected by the engine speed sensor 40 in cooperation with the pulser 41 is generated in the 4 is shown. Described in more detail, the engine speed sensor is 40 including an electromagnetic pickup coil in the toothed outer peripheral surface of the wheel of the pulser 41 arranged on the crankshaft of the diesel engine 2 is appropriate. The engine speed sensor 40 generates a pulse signal each time a tooth is attached to the wheel of the pulser 41 is formed, the engine speed sensor 40 happens during a rotation of the crankshaft. The ECU 52 calculates the rotational speed NE of the diesel engine 2 based on the pulse signals generated by the engine speed sensor 40 be generated. The wheel of the pulser 41 has in total 36 Teeth which are positioned in the circumferential direction at an angular interval of 10 ° evenly spaced from each other. However, the wheel of the pulser has 41 a total of 34 teeth, wherein teeth are missing at two consecutive positions of the 36 teeth, that is, in the presence of a non-toothed peripheral portion 41a according to the two consecutive tooth positions. During an operation of the diesel engine 2 is at a change in the crank angle CA by 10 ° and per tooth of the pulser 41 That is, the pulse signals are generated by the engine speed sensor 40 at an angle interval of 10 ° of the teeth of the pulser 41 generated as in the 5 in which the pulse signals are shown after having formed their waveforms. It should be noted that the pulse-to-pulse interval at the non-toothed section 41a 30 °, and this comparatively large pulse-to-pulse interval, the non-toothed section 41a corresponds to, appears at each change in the crank angle CA by 360 °, that is, every full revolution of the crankshaft. The cylinder detection sensor 42 is configured to detect a reference angular position of the camshaft corresponding to the top dead center (TDC) of the cylinder # 1 on the basis of the pulse signals generated by the engine speed sensor 40 and the cylinder detection sensor 42 are generated as described above, and the crank angle CA is obtained with respect to the detected top dead center of the cylinder # 1.

Since the value TNH [K] represents the time duration during which the predetermined number of consecutive pulse signals by the engine speed sensor 40 is generated, the value TNH [K] is smaller than the value TNH [K-1] when the maximum rotational speed of the currently selected cylinder #K is larger than that of the cylinder # K-1. In this case, therefore, the speed change DNE [K] calculated according to the aforementioned equation (2) is a negative value. On the other hand, if the maximum speed of the currently selected cylinder #K is smaller than that of the cylinder # K-1, then the value TNH [K] is greater than the value TNH [K-1]. In this case, the speed change DNE [K] is therefore a positive value.

More specifically, the maximum rotational speed of each cylinder is represented by the time duration TNH of the predetermined number of consecutive pulse signals, namely the specific example of FIG 5 three pulse signals. This time TNH of the three pulse signals is a time interval between the times of increasing the first and fourth pulses of four consecutive pulse signals including the above-mentioned three pulse signals and the one by the engine speed sensor 40 be generated at four different crank angles CA (different four angular positions of the crankshaft), which are equally spaced from each other. Namely, these four pulse signals are generated at the respective crank angles CA corresponding to the maximum rotational speed of each cylinder, as shown in the graph of FIG 5 is specified. Accordingly, the value DNE [K] calculated according to the above equation (2) represents a difference between the maximum rotational speeds of the two cylinders #K and # K-1, that is, a speed change of the currently selected cylinder #K with respect to the speed of the preceding cylinder # K-1.

After the speed change DNE [K] has been calculated as described above, the control flow goes to a step S240 to calculate an integral compensation amount dgcy on the basis of the speed change DNE [K] and in a graph shown in FIG 6 is shown. This graph represents a relationship between the integral compensation amount dgcy and the rotational speed change DNE [K], and is formulated such that the integral compensation amount dgcy increases as the rotational speed change DNE [K] increases.

The control flow then proceeds to a step S250 at which the cylinder compensation amount qcy [K] is updated on the basis of the thus calculated integral compensation amount dgcy and the following equation (3): qcy [K] ← qcy [K] + dgcy (3)

Thus, the integral compensation amount dgcy is added to the cylinder compensation qcy [K] when the speed change of the consecutive two cylinders #K and # K-1 of the diesel engine 2 and the thus-updated cylinder compensation amount qcy [K] at the step S120 of the routine according to the 2 for controlling the fuel injection to compensate the command value QFIN of the fuel injection amount of each of the four cylinders, so as to change the speed of the diesel engine 2 to eliminate, so that the fuel supply system is regulated, so as to change the speed of the diesel engine 2 to minimize.

When the rotational speed change DNE [K] of the currently selected cylinder #K is a negative value, that is, when the rotational speed of the diesel engine 2 due to combustion of the currently selected cylinder #K is greater than a result of combustion of the preceding cylinder # K-1, then the integral compensation amount dgcy is a negative value, so that the cylinder compensation amount qcy [K] is reduced by the integral compensation amount dgcy. Consequently, the command value of the fuel injection amount QFIN for the currently selected cylinder #K is reduced by the compensation in step S120.

When the speed change DNE [K] of the cylinder #K is a positive value, that is, when the speed of the diesel engine 2 due to combustion of the present cylinder #K is less than a result of combustion in the preceding cylinder # K-1, then the integral compensation amount dgcy is a positive value, so that the cylinder compensation amount qcy [K] is increased by the integral compensation amount dgcy. Consequently, the command value for the fuel injection amount QFIN for the current cylinder #K is increased by the compensation at step S120.

If the absolute value of the speed change DNE [K] is comparatively small, that is when the speed in a row a combustion in the present Cylinder #K and the speed due to combustion in the previous one Cylinder # K-1 approximately are equal to each other, then the integral compensation amount is dgcy approximately 0, and the cylinder compensation amount qcy [K] remains substantially unchanged, so that the command value QFIN the fuel injection amount of the current cylinder #K remains essentially constant.

With reference to the flowcharts in FIGS 7 to 10 Next, a preliminary diagnostic routine and a main diagnostic routine will be described. The preliminary diagnostic routine is in the flowcharts of 7 and 8th shown. The routine is repeatedly executed when the crank angle CA changes by 180 °.

The preliminary diagnostic routine is started at a step S310 to determine whether the diesel engine 2 is in the stable idle state. This step S310 is identical to the step S210 in the routine of FIG 3 for calculating the cylinder compensation amount. If the diesel engine 2 is in the stable idle state, that is, if an affirmative decision (YES) is obtained in step S 310, the control flow proceeds to step S320 to determine whether the detected engine speed NE is substantially equal to the desired idling speed NF. This step S320 is identical to the step S 220 of the routine according to FIG 2 for calculating the cylinder compensation amount.

If a negative decision (NO) is obtained in step S310 or step S320, then the control flow goes to step S330 to reset a delay counter Dcnt. If both steps S310, S320 an affirmative decision (YES) is obtained, then the control flow goes to a step S340 to increment the delay counter Dcnt. Thus, the content of the delay counter Dcnt represents a time period during which the diesel engine 2 was in the stable idle state, with their rotational speed NE was kept substantially equal to the desired idling state NF. More specifically, the content of the deceleration counter Dcnt represents a cumulative number of revolutions of the crankshaft while the diesel engine 2 is kept in the stable idle state while maintaining its rotational speed NE substantially equal to the desired idle state NF.

Steps S330 and S340 are followed by a step S350 to determine whether the content of the delay counter Dcnt is greater than a threshold value Td. This threshold value Td provides a period of time required to obtain the cylinder compensation amounts qcy [K] of all four cylinders in which steps S230 to S250 in the routine of FIG 3 to be repeatedly implemented for calculating the cylinder compensation amount.

While the content of the delay counter Dcnt is equal to or smaller than the threshold value Td, namely, if a negative decision (NO) is obtained in step S350, then the control flow advances to step S370. In step S370, a cylinder identification value "k" is set to 1. "k" identifies the cylinder whose compensation amount qcy [K] is to be diagnosed. In this case, one execution cycle of the routine is completed. When the content of the delay counter Dcnt has exceeded the threshold Td due to repeated increments of the delay counter Dcnt while the diesel engine 2 is maintained in the stable idle state with its rotational speed substantially equal to the desired idle state NF, that is, if an affirmative decision (YES) is obtained in step S350 as a result of repeated increments of the counter Dcnt after the positive decisions (YES) In steps S310 and S320, the control flow proceeds to step S380 to determine whether a sub-diagnostic flag Xtst is in an OFF state. Since this flag Xtst is initially set in the OFF state, that is, an affirmative decision (YES) is obtained in step S380 at the first execution cycle of the present provisional diagnosis routine, the control flow proceeds to step S390 to determine whether the cylinder compensation amount qcy [K], which is the step S250 of the routine according to 3 for calculating the cylinder compensation amount equal to or greater than zero. Since the cylinder identification value "k" is initially set to "1", the compensation value qcy [1] of the cylinder # 1 is checked.

If the cylinder compensation amount qcy [K] is equal to or greater than Zero is, that is if an affirmative decision (YES) is obtained in step S390 is the control flow proceeds to a step S400 to a Sign flag explus [k] set to an ON state. In which first cycle is the sign flag explus [1] in the ON state set. If the zpb qcy [1] is less than zero, if at a negative decision (NO) is obtained in step S390, the control flow goes to a step S410 to get the flag Explus [1] in an OFF state.

Steps S400 and S410 are followed by a step S420 to determine whether the absolute value of the cylinder compensation amount qcy [K] is equal to or smaller than a provisional diagnosis threshold value A. If the absolute value of the compensation amount qcy [1] is equal to or smaller than the threshold value A, namely, if an affirmative decision (YES) is obtained in step S420, the control flow proceeds to a step S430 to increment the cylinder identification value "k". In the first execution cycle of the routine in the 7 and 8th the cylinder identification value "k" is incremented to "2".

If the absolute value of the compensation amount qcy [1] greater than the threshold A is, if indeed get a negative decision (NO) at step S420 is the control flow proceeds to a step S440 to the sub-diagnostic flag in to set the ON state. Step S440 is taken from a step S430 is followed to increment the cylinder identification value "k".

The step S430 is followed by a step S450 to determine whether the cylinder identification value "k" is equal to or less than "4". It should be noted that the diesel engine 2 which has four cylinders # 1- # 4. Since the cylinder identification value "k" is now equal to "2", an affirmative decision (YES) is obtained in step S450, and the control flow returns to step S390. The steps S390 to S450 are repeated to check the compensation amount qcy [2] of the cylinder # 2 (identified by the value "k" = 2) whose combustion stroke takes place after the stroke of the cylinder # 1 (which is the value "K" = 1 is identified). After repeating steps S390 to S450 for the compensation amount qcy [2], these steps for the compensation amounts qcy [3] and qcy [4] are further repeated at the following cylinders # 3 and # 4.

When the cylinder identification value "k" is on "5" is incremented, namely, if a negative decision (NO) is obtained in step S450, the control flow proceeds to step S470 to determine whether the sub-diagnostic flag Xtst is now set in the ON state. If the flag Xtst is set in the OFF state, that is, if a negative decision (NO) is obtained in step S470, the control flow goes to step S475 to reset the delay flag Dcnt to "0", and one execution cycle of FIG Routine is finished. The sub-diagnostic flag Xtst in the OFF state indicates that the values | qcy [k] | of all four cylinders are equal to or smaller than the threshold value A, that is, an affirmative decision (YES) has been obtained for all four cylinders in step S420. In this case, the delay counter Dcnt is reset to " 0 ", and the provisional diagnosis routine according to the 7 to 8th will be executed again.

If the marker Xtst of the preliminary Diagnosis in the ON state is offset, that is if an affirmative decision (YES) is obtained in step S470 This indicates that the absolute value of the compensation amount gcy [k] is larger as the threshold A for at least one of the four cylinders # 1- # 4. In this case, the control flow goes to a step S480, to reset an addition-subtraction term dtst to "0". The term dtst is described below. Then, a step S490 implemented to the present obtained cylinder compensation amounts qcy [1], qcy [2], qcy [3] and qcy [4] as different variables gcyorg [1], gcyorg [2], gcyorg [3] and gcyorg [4], and is one execution cycle of the routine completed.

at the next execution cycle the routine after the steps S470 to S490 is at the step S380 received a negative decision (NO) because of the sub-diagnostic flag Xtst is set to the ON state, and this cycle is ended. As long as the flag Xtst is kept in the ON state Steps S390 through S490 are not implemented, even if the positive Decision (YES) at steps S310, S320 and S350 becomes.

With reference to the flowchart of 9 and 10 the main diagnostic routine will now be described. This routine is also executed with a cycle time corresponding to a change of the crank angle CA by 180 °. The current main diagnostic routine is started at a step S500 to determine whether a gradual toggle flag Xret is set in the OFF state. Since this flag is initially set in the OFF state, an affirmative decision (YES) is obtained in the first execution cycle of the routine, and the control flow goes to a step S510 to determine whether the diesel engine 2 is in the stable idle state. This step S510 is identical to the step S210 in the routine of FIG 3 for calculating the cylinder compensation amount. If the diesel engine 2 is in the stable idle state, that is, if an affirmative decision (YES) is obtained in step S510, the control flow proceeds to step S520 to determine whether the detected engine speed NE is substantially equal to the desired idle state NF. This step S520 is identical to the step S220 in the routine of FIG 3 for calculating the cylinder compensation amount.

If a negative decision (NO) is obtained in step S510 or S520, the control flow goes to step S525 to set the sub-diagnostic flag Xtst to the OFF state, and then proceeds to step S526 to The step S526 is followed by a step S530 to set the calculation permission flag Xqcy to the ON state, and from a step S540 to increment a cylinder identification value "m", namely the step S540 Set value "m" to "1" in the first execution cycle of the routine. Thus, one execution cycle of the routine is completed. In this case, in which the flag Xtst is set in the OFF state, in the provisional diagnosis routine in step S380, in accordance with 7 and 8th get an affirmative decision (YES), and steps S390 to S490 can be implemented. Further, since the flag Xqcy is set in the ON state, in the step S200, the routine according to FIG 3 for calculating the cylinder compensation amount, an affirmative decision (YES) is obtained, and the cylinder compensation amount qcy [K] may be updated at step S240.

If the diesel engine 2 is in the stable idling state with its rotational speed NE substantially equal to the desired idle rotational speed, that is, if an affirmative decision (YES) is obtained in steps S510 and S520, the control flow proceeds to a step S550 to determine whether sub-throttle Diagnostic Flag Xtst is in the ON state. If the flag Xtst is in the OFF state, that is, if a negative decision (NO) is obtained in step S550, the control flow proceeds to step S530 to set the calculation permission flag Xqcy to the ON state. The step S530 is followed by a step S540 to set the value "m" to "1", and one execution cycle of the routine is ended.

If the flag Xtst is in the ON state, that is, if an affirmative decision (YES) is obtained in step S550, the control proceeds flow to a step S560 to set the calculation permission flag Xqcy in the OFF state. In this case, the negative decision (NO) at the step S200 in the routine according to 3 for calculating the cylinder compensation amount, so that the cylinder compensation amount qcy [K] of each cylinder in the routine of FIG 3 not updated.

Then, step S570 is implemented to calculate the addition-subtraction term dtst according to the following equation (4): dtst ← dtst + dq (4)

In In the above-mentioned equation (4), "dq" represents the gradual change value thereto provided that the addition-subtraction value dtst is gradually increased.

Then, the control flow goes to a step S580 to determine whether the flag explus [m] is in the ON state. In the first execution cycle of the routine, the value "m" is equal to "1", and it is determined whether the sign flag explus [1] is in the ON state. If the flag explus [1] is in the ON state, that is, if an affirmative decision (YES) is obtained in step S580, the control flow goes to a step S590 to obtain the cylinder compensation amount qcy [m] according to the following equation ( 5) to update: qcy [m] ← qcyorg [m] - dtst (5)

If the flag explus [m] is in the OFF state, that is, if a negative decision (NO) is obtained in step S580, the control flow advances to step S600 to obtain the cylinder compensation amount qcy [m] according to the following equation ( 6) to update: qcy [m] ← qcyorg [m] + dtst (6)

If the cylinder compensation amount qcy [m] is equal to or greater than Is zero, this amount qcy [m] thus becomes by the gradually increasing addition-subtraction term dtst reduced so that the actual fuel injection amount gradually reduced becomes. When the cylinder compensation amount qcy [m] is less than zero is, then this amount qcy [m] by the gradually increasing addition-subtraction term dtst so elevated, that the actual fuel injection amount is gradually increased.

Steps S590 and S600 are followed by step S610 to calculate the speed change DNE [m] according to the following equation (7): DNE [m] ← TNH [m] - TNH [m-1] (7)

The Calculation according to the above Equation (7) is equal to the calculation used in step S230 according to the equation (2) is effected.

The step S610 is followed by a step S620 to determine whether the absolute value of the speed change DNE [m] is greater than a threshold B. If the value | DNE [m] | is equal to or smaller than the threshold B, that is, if a negative decision (NO) is obtained in step S620, the control flow proceeds to step S630 to determine whether the addition-subtraction term dtst is greater than a threshold value D is. If the value dtst is equal to or smaller than the threshold value D, that is, if a negative decision (NO) is obtained in step S630, an execution cycle of the current routine is ended. Accordingly, the cylinder compensation amount qcy [m] is gradually changed as long as the absolute value of the speed change DNE [m] is equal to or smaller than the threshold value D and the addition-subtraction term dtst is equal to or smaller than the threshold value D, that is, so long as the negative decision (NO) is obtained in steps S620 and S630 while the fuel injection amount is gradually increased or reduced by implementing steps S590 and S600. In other words, the command value QFIN of the fuel injection amount of each cylinder is gradually increased or reduced by gradually increasing or decreasing the cylinder compensation amount qcy [K], which is the same as that of the step S120 in the routine of FIG 2 for controlling the fuel injection, and which is calculated according to the aforementioned equation (1).

If the value | DNE [m] | greater than the threshold value B became, before the term dtst became greater than the threshold value D, this means if an affirmative decision (YES) is obtained in step S620, before obtaining an affirmative decision (YES) at step S630 is, with the speed change DNE [m] as a result of the gradual change of the cylinder compensation amount qcy [m], it means that the speed change DNE [m] as expected due to a change of the cylinder compensation amount qcy [m] based on the addition-subtraction term dtst increased Has. In this case, therefore, the control flow goes to a step S640 to diagnose that the fuel delivery system for the Cylinder #m is normal. Step S640 is taken from a step S650 followed to increment the cylinder identification value "m". If the fuel supply system for the Cylinder # 1 was diagnosed as normal, the value "m" is incremented to "2".

Of the Step S650 is followed by a step S660 to determine whether the cylinder identification value "m" is equal to or less than "4". Since the value "m" is now equal to "2", in the Step S660 receives an affirmative decision (YES), and the control flow goes to a step S670 to the addition-subtraction term dtst to reset to "0". Step S680 is then implemented to perform the gradual ZuZurücksetzungsmerker Xret is set to the ON state, and one execution cycle is the routine completed.

In the next execution cycle of the routine in the 9 and 10 the flag Xret is set to the ON state, that is, a negative decision (NO) is obtained at the step S500, whereby practically no operation is performed.

In In this case, a routine for controlling a gradual reset (which will be described) executed, by the cylinder compensation amount qcy [1] gradually to the original one Value qcyorg [1] reset.

After this the cylinder compensation amount qcy [1] to the original one Value qcyorg [1] reset became, is the gradual ZuZurücksetzungsmerker Xret on the off state at the routine for controlling the gradual reset reset so that the positive decision (YES) is obtained in step S500 becomes. Accordingly, the above-described operation for the cylinder # 2 repeated. In further detail, the compensation amount qcy [2] for the cylinder # 2 at steps S590, S600 depending on the state of the sign flag explus [2] gradually increases or decreases, and it becomes determines whether the absolute value of the speed change DNE [2] is greater than step B is at step S620.

If the value | DNE [2] | got bigger as the threshold B before the term dtst became greater than the threshold D, this means, if the affirmative decision (YES) is obtained in step S620 before the affirmative decision (YES) is made in step S630 is obtained, wherein the speed change DNE [2] as a result of gradual change of the cylinder compensation amount qcy [2], it means that the speed change DNE [2] as expected due to a change of the cylinder compensation amount qcy [2] based on the addition-subtraction term dtst increased Has. In this case, therefore, the control flow goes to a step S640 to diagnose that the fuel delivery system for the Cylinder # 2 is normal. Step S640 is followed by step S650, to increment the cylinder identification value "m" to "3". Since the value "m" is not equal to "3", in the Step S660 receives an affirmative decision (YES), and the control flow goes to a step S670 to the addition-subtraction term dtst to reset to "0". Step S680 is then implemented to set the gradual toggle flag in the ON state, and is an execution cycle of the routine completed.

In the next execution cycle of the routine according to 9 and 10 the flag Xret is set in the ON state, that is, at the step S500, the negative decision (NO) is obtained, so that practically no operation is performed. In this case, the gradual reset control routine (to be described) is executed to gradually reset the cylinder compensation amount qcy [2] to the original value qcyorg [2].

After this the cylinder compensation amount qcy [2] to the original one Value qcyorg [2] reset became, is the gradual ZuZurücksetzungsmerker Xret in the OFF state at the routine to control the gradual reset reset so that the affirmative decision (YES) is obtained at step S500 becomes. Accordingly, the above-described operation for the cylinder # 3 repeated. In further detail, the compensation amount qcy [3] for the cylinder # 3 at steps S590, S600 depending on the state of the sign flag explus [3] gradually increases or decreases, and the Determination is made to step S620 as to whether the absolute value of the Speed change DNE [3] bigger than that Threshold B is.

If the value | DNE [3] | got bigger as the threshold B, that is if the affirmative decision (YES) is obtained in step S620 becomes the fuel supply system for the Cylinder # 3 diagnosed as normal, and the compensation amount qcy [3] for the cylinder # 3 is gradually to the original one Value qcyorg [3] reset. Then, the compensation amount qcy [4] for the cylinder # 4 in the steps S590, S600 depending on the state of the sign flag explus [4] gradually increases or decreases, and at In step S620, it is determined whether the absolute value of the speed change DNE [4] greater than the threshold B is.

If the value | DNE [4] | becomes larger than the threshold B, that is, if the affirmative decision (YES) is obtained in step S620, the fuel supply system for the cylinder # 4 is diagnosed to be normal. Then, the cylinder identification value "m" is incremented to "5" at step S650, so that a negative decision (NO) is obtained at step S660. The gradual Reset flag Xret is then set to the ON state at step S680, and one execution cycle of the routine is ended. Accordingly, the compensation amount qcy [4] for the cylinder #Q is gradually reset to the original value qcyorg [4] in the routine for controlling the gradual reset.

When the compensation amount qcy [4] has returned to the original value qcyorg [4], the calculation allowance flag Xqcy is set to the ON state in the gradual reset control routine, and the sub-diagnostic flag Xtst is set in the OFF state. State set. Since the flag Xqcy is in the ON state, the compensation amount calculation according to the calculation routine of FIG 3 be effected practically. Since the flag Xtst is in the OFF state, the provisional diagnosis may be made according to the routine of FIG 7 and 8th be started while the main diagnosis according to the routine in the 9 and 4 practically is not effected.

With reference to the flowchart in the 11 Next, the routine for controlling the gradual reset will be described. This routine is executed with a cycle time corresponding to a change of the crank angle CA by 180 °. The routine is started at a step S810 to determine whether the gradual reset flag Xret is set in the ON state. If the flag Xret is in the ON state, that is, if a negative decision (YES) is obtained in step S810, one execution cycle of the routine is ended.

If the gradual reset flag Xret at the step 5680 in the main diagnostic routine according to the 9 and 10 is set to the ON state, an affirmative decision (YES) is obtained in step S810, and the control flow advances to step S820 to determine whether the sign flag explus (m-1) is set to an ON state , For example, if the cylinder # 1 fuel supply system is the main diagnostic routine in step S620 in FIG 9 and 10 is diagnosed as normal, wherein the affirmative decision (YES) is obtained in step S620, the affirmative decision (YES) is obtained in step S680. At this moment, the cylinder identification value "m" is set to "2".

If the value "m" is equal to "2", the determination in step S820 as to whether the sign flag explus [m-1] is in the ON state is a determination of whether the sign flag explus [1] in the ON State is. If the sign flag explus [m-1] is in the ON state, that is, if an affirmative decision (YES) is obtained in step S820, the control flow advances to step S830 to obtain the cylinder compensation amount qcy [m-1] to update the following equation (8): qcy [m-1] ← qcy [m-1] + dret (8)

at In the above equation (8), the value dret is a gradual reset value gradual Reset to default of the cylinder compensation amount qcy [m-1]. The gradual reset amount dret can be equal to the gradual change value "dq" according to the above Be description.

If the cylinder compensation amount qcy [m-1] at the step S590 in the main diagnostic routine according to 9 and 10 has been gradually reduced, the cylinder compensation amount qcy [m-1] is increased by the gradual reset value dret so that the amount qcy [m-1] gradually returns to the original value.

Then the control flow goes to a step S840 to determine whether the cylinder compensation amount qcy [m-1] is equal to or greater than the variable is qcyorg [m-1], which is the original value. If the Cylinder compensation amount qcy [m-1] smaller than the variable qcyorg [m-1] if there is a negative decision (NO) in step S840 is obtained, it means that the cylinder compensation amount qcy [m-1] not to the original value qcyorg [m-1] returned is. In this case, one execution cycle of the routine is completed.

If the explus [m-1] is in the OFF state, that is, if the negative decision (NO) is obtained in step S820, the control flow goes to step S850 to obtain the cylinder compensation amount qcy [m-1] according to FIG to update the following equation (9): qcy [m-1] ← qcy [m-1] - dret (9):

Of the gradual Reset value The above equation (9) has been described above described.

If the cylinder compensation amount qcy [m-1] at the step S600 in the main diagnostic routine according to 9 and 10 is gradually increased, the cylinder compensation amount qcy [m-1] is reduced by the gradual reset value dret so that the amount qcy [m-1] gradually returns to the original value.

Then, the control flow goes to a step S860 to determine whether the cylinder compensation amount qcy [m-1] is equal to or smaller than the variable qcyorg [m-1] which is the original value. If the cylinder compensation amount qcy [m-1] is larger than the variable qcyorg [m-1], that is, if a negative decision (NO) is obtained in step S860, it means that the cylinder compensation amount qcy [m-1] is not returned to the original value qcyorg [m-1]. In this case, one execution cycle of the routine is completed.

If the cylinder compensation amount qcy [m-1] to the original one Value qcyorg [m-1] returned and an affirmative decision (YES) at step S840 or S860 as a result of a repeated implementation of step S830 or S850, the control flow goes to step S870, by the variable qcyorg [m-1] as the cylinder compensation amount qcy [m-1], and it proceeds to step S880 to take the gradual Reset flag Put Xret in the OFF state.

Then, the control flow goes to a step S890 to determine whether the value "m-1" is "4". Since the value "m" is now equal to "2", a negative decision (NO) is obtained in a step S890, and an execution cycle of the routine is ended. In the next execution cycle, the flag Xret is in the OFF state, and the negative decision (NO) is obtained in step S810, so that in the routine of FIG 11 virtually no operation is performed to control the gradual reset. On the other hand, the affirmative decision (YES) at the step S500 in the main diagnosis routine is made in accordance with 9 and 10 since the flag Xret is set in the OFF state, so that the fuel supply system for the cylinder # 2 is diagnosed as described above, since the value "m" is now equal to "2".

If the fuel supply system for cylinder # 2 is normal for the main diagnostic routine according to the 9 and 10 is diagnosed, the gradual reset flag Xret is set in the ON state at the step S680, and the routine according to 11 for controlling the gradual reset is performed for the cylinder # 3 in the same manner as described above. Then, the fuel supply for the cylinder # 3 is diagnosed as described above. If the fuel supply system for the cylinder # 3 is diagnosed to be normal, the routine according to the 11 for controlling the gradual reset for the cylinder # 4 in the same manner as described above. Then, the fuel supply system for the cylinder # 4 is diagnosed, and if the fuel supply system for the cylinder # 4 is diagnosed to be normal, the routine according to the 11 to control the gradual reset, setting the value "m" to "5".

In the routine according to the 11 for controlling the gradual reset with the value "m" set to "5", the compensation amount qcy [4] is reset to the original value qcyorg [4] at step S870, and the flag Xret is turned to at step S880 in FIG set the OFF state. Then, the step S820 is implemented to determine whether the value "m-1" is equal to "4", and the affirmative decision (YES) is obtained in the step S890. As a result, the calculation permission flag Xqcy is set to the ON state at step S900, and the sub-diagnostic flag Xtst is set to the OFF state at step S910. Then, the delay counter Dcnt is reset at a step S911, and an execution cycle of the routine according to FIG 11 is finished.

In the next execution cycle of the routine according to 11 For controlling the gradual reset, the flag Xret is set in the OFF state, and practically no operation is performed. Since the flag Xqcy is set in the ON state, the compensation amount calculation according to the calculation routine in FIG 3 be effected practically. Since the flag Xtst is in the OFF state, the provisional diagnosis according to the routine in FIG 7 and 8th while the main diagnosis according to the routine of 9 and 10 practically is not effected.

If the fuel supply system for one of the four cylinders is not diagnosed as being defective as described above, the routine according to FIG 3 for calculating the cylinder compensation amount and the routine according to FIGS 7 and 8th the preliminary diagnosis in the same manner as described above.

The timing diagram in the 12 shows an example in which the fuel supply system for any cylinder is diagnosed as defective. In this timing diagram, the delay counter Dcnt has exceeded the threshold value Td, and in the preliminary diagnosis routine in step S350, in accordance with 7 and 8th As a result, the absolute value of the compensation amount qcy [2] is larger than the threshold value A, and at step S420, the negative decision is obtained (YES) at a time "t1" and steps S390-S450 Decision (NO) is obtained, so that the sub-diagnostic flag Xtst is set to the ON state at step S440.

The calculation permission flag Xqcy is set in step S560 in the main diagnostic routine according to 9 and 10 is set in the OFF state, and the compensation amount qcy [1] for the cylinder # 1 is gradually reduced during a period of time between the times "t1" and "t2", and it is made during a period of time between the times "t2" and " t3 "gradually increases because the amount qcy [1] is equal to or greater than zero. Since the compensation amount qcy [1] for the cylinder # 1 is diagnosed to be normal, the compensation amount qcy [2] for the cylinder # 2 is gradually reduced during a time period between the times "t3" and "t3", and it is during a Time period between times "t4" and "t5" gradually increased because the amount qcy [2] is equal to or greater than zero. Since the compensation amount qcy [2] for the cylinder # 2 is also diagnosed to be normal, the compensation amount qcy [3] for the cylinder # 3 is gradually increased during a period of time between time points "t5" and "t6" and becomes during one Time period between times "t6" and "t7" gradually reduced because the amount qcy [3] is less than zero. Since the compensation amount qcy [3] for the cylinder # 3 is also diagnosed to be normal, the compensation amount qcy [4] for the cylinder # 4 is gradually reduced during a period of time between time points "t7" and "t8" and becomes during a Time period between times "t8" and "t9" gradually increased because the amount qcy [4] is equal to or greater than zero. Since the compensation amount qcy [4] for the cylinder # 4 is also diagnosed to be normal, the gradual reset flag Xret is set to the OFF state at step S880, and the calculation allowance flag Xqcy is set to the ON state at step S900, while the sub-diagnostic flag Xtst is reset to the OFF state. Accordingly, the compensation amount calculation according to the routine of FIG 3 for calculating the cylinder compensation amount and the preliminary diagnosis according to the preliminary diagnosis routine in the 7 and 8th practically started while the main diagnosis according to the main diagnostic routine in the 9 and 10 practically is not effected.

For example, if the fuel injector 4 is defective for the cylinder # 2 in its function to set the fuel injection amount due to deterioration of the function of its solenoid control valve 4a For setting its opening time during execution of the above-described routines, the time duration TNH [2] of the cylinder # 2 is longer than the time duration TNH [1] of the cylinder # 1, for example. Accordingly, the speed change DNE [2] calculated in the aforementioned equation (2) at the step S230 is a positive value, and the positive integral compensation amount dgcy at the step S240 shown in the graph in FIG 6 is determined so that this integral compensation amount dgcy is added to the compensation amount qcy [2] in step S250. If at the step S420 in the provisional diagnosis routine in the 7 and 8th it is determined that the compensation amount qcy [2] becomes larger than the threshold value A, that is, if the negative decision (NO) is obtained in step S420, as a result of adding the integral compensation amount dqcy to the compensation amount qcy [2], At step S440, the sub-diagnostic flag Xtst is set to the ON state.

When the flag Xtst is in the ON state, the main diagnosis according to the routine in FIG 9 and 10 is practically started, and the fuel supply system for the cylinder # 1 is initially diagnosed by gradually changing the amount of fuel coming out of the fuel injection valve 4 for the cylinder # 1 is to inject. In the absence of a defect of the fuel supply system for the cylinder # 1, the absolute value of the rotational speed change DNE [1] exceeds the threshold value B before the addition-subtraction term dtst exceeds the threshold value D, that is, the affirmative decision (YES) becomes Step S620 is obtained before the affirmative decision (YES) is obtained in step S630. Accordingly, the cylinder # 1 fuel supply system is diagnosed to be normal at step S640. After the compensation amount qcy [1] has returned to the original value, the main diagnosis of the fuel supply system for the cylinder # 2 according to the routine in FIG 9 and 10 started. In this specific example, where the solenoid control valve 4a is deteriorated for the cylinder # 2 in its function for setting its opening time, the amount of fuel injection into the cylinder # 2 is not really changed according to the command applied to the solenoid control valve 4a is applied to the corresponding fuel injection valve, even if the command value for the from the fuel injection valve 4 is gradually reduced, that is, even when the commanded opening time of the solenoid control valve is to be injected into the cylinder # 2 4a from this fuel injector 4 is gradually reduced by gradually increasing the addition-subtraction term dtst at step S590.

Accordingly, the addition-subtraction term dtst exceeds the threshold value D before the speed change DNE [2] exceeds the threshold value B, that is, the affirmative decision (YES) is obtained at step S630 before the affirmative decision (YES) at step S630 S620 is obtained. This in the 12 indicated by a dashed line, where "ta" indicates a time, in which the addition-subtraction term dtst exceeds the threshold value D.

Accordingly, the fuel supply system for the cylinder # 2 is diagnosed to be defective at step S690, and a suitable recovery operation becomes at one step 5700 performed to treat the defect. The normal control of the diesel engine 2 Namely, it is interrupted, and the recovery operation such as "limp home processing" is started, step S700 is followed by step S710 to set the sub-diagnostic flag Xtst to the OFF state, and an execution cycle the routine is over.

In the first embodiment of this invention described above, the routine according to FIG 3 for calculating the cylinder compensation amount of a controller for controlling the fuel supply system while the preliminary diagnostic routine according to 7 and 8th , the main diagnostic routine according to the 9 and 10 and the routine for controlling the gradual reset according to the 11 a diagnostic device for diagnosing the fuel supply system for each cylinder.

• (1) Die Hauptdiagnoseroutine gemäß den 9 und 10 und die Routine zum Steuern des allmählichen Rücksetzens gemäß der 11 sind so formuliert, dass eine Einstellung des Betriebszustandes des Kraftstoffzuführungssystems für jeden Zylinder durchgeführt wird, um dadurch das Kraftstoffzuführungssystem zu diagnostizieren. Somit wird das Kraftstoffzuführungssystem nicht nur auf der Grundlage des Zylinderkompensationsbetrages qcy[K] diagnostiziert, der bei der Routine gemäß der 3 zum Berechnen des Zylinderkompensationsbetrages berechnet wird. Das gegenwärtige Diagnosegerät ermöglicht eine genaue Diagnose des Kraftstoffzuführungssystems nicht nur für einen Klemmdefekt des Elektromagnetsteuerventils 4a des Kraftstoffeinspritzventils 4, sondern auch von anderen Anomalitäten bezüglich der Öffnungs- und Schließvorgänge des Ventils 4a, wie zum Beispiel eine Verschlechterung seiner Funktion zum Einstellen seiner Öffnungszeit.

The diagnostic apparatus according to the first embodiment described above has the following advantages:

• (1) The main diagnostic routine according to the 9 and 10 and the routine for controlling the gradual reset according to the 11 are formulated such that adjustment of the operating state of the fuel supply system is performed for each cylinder to thereby diagnose the fuel supply system. Thus, the fuel supply system is diagnosed not only based on the cylinder compensation amount qcy [K] used in the routine of FIG 3 for calculating the cylinder compensation amount. The present diagnostic apparatus enables accurate diagnosis of the fuel supply system not only for a clamping failure of the solenoid control valve 4a of the fuel injection valve 4 , but also of other abnormalities in the opening and closing operations of the valve 4a such as deterioration of its function for setting its opening time.

The main diagnostic routine according to the 9 and 10 and the routine according to 11 for controlling the gradual reset are then executed when the absolute value of the cylinder compensation amount qcy [K], which according to the routine in FIG 3 for calculating the cylinder compensation amount becomes larger than the threshold value A. Namely, when the cylinder compensation amount qcy [K] is out of the predetermined reference range, there is a high possibility that the fuel supply system is defective. In this case, the main diagnostic routine will be according to the 9 and 10 and the routine according to 11 to perform gradual reset. This arrangement ensures improved accuracy of abnormal diagnosis of the fuel supply system.

• (2) Gemäß der Hauptdiagnoseroutine in den 9 und 10 und der Routine gemäß der 11 zum Steuern des allmählichen Zurücksetzens wird die Ausführung der Routine gemäß der 3 zum Berechnen des Zylinderkompensationsbetrages beendet, wenn der Zylinderkompensationsbetrag qcy[K] außerhalb des Referenzbereiches fällt. Dann wird der Kompensationsbetrag qcy[K] für den gegenwärtig ausgewählten einen Zylinder zum Zwecke der Diagnose erhöht oder reduziert. Auf der Grundlage der Drehzahländerung der Dieselkraftmaschine 2, die durch die Erhöhung oder die Reduzierung des Kompensationsbetrages qcy[K] verursacht wird, wird das Kraftstoffzuführungssystem für den gegenwärtig ausgewählten Zylinder #K als anomal diagnostiziert.

Further, only if the cylinder compensation amount qcy [K] is out of the reference range, the diagnosis setting of the operating state of the fuel supply system prevents an unnecessary change in the combustion state of each cylinder and prevents deterioration of the fuel economy and the exhaust emissions of the diesel engine 2 , and it minimizes the vibrations of the diesel engine 2 due to a change in their speed.

• (2) According to the main diagnostic routine in the 9 and 10 and the routine according to 11 For controlling the gradual reset, the execution of the routine according to the 3 for calculating the cylinder compensation amount when the cylinder compensation amount qcy [K] falls outside the reference range. Then, the compensation amount qcy [K] for the currently selected one cylinder is increased or reduced for the purpose of diagnosis. Based on the speed change of the diesel engine 2 caused by the increase or decrease of the compensation amount qcy [K], the fuel supply system for the currently selected cylinder #K is abnormally diagnosed.

• (3) Die zwangsweise Erhöhung oder Reduzierung des Zylinderkompensationsbetrages qcy[K] bei der Diagnose wird allmählich implementiert. Diese allmähliche Erhöhung oder Reduzierung des Zylinderkompensationsbetrages qcy[K] ist zum Minimieren der Schwingungen der Dieselkraftmaschine 2 aufgrund ihrer Drehzahländerung wirksam, die durch die Erhöhung oder Reduzierung bei der Diagnose verursacht werden. Des Weiteren wird der Zylinderkompensationsbetrag qcy[K] allmählich zu dem ursprünglichen Wert zurückgesetzt, bevor die allmähliche Erhöhung oder Reduzierung der Diagnose bewirkt wird. Dieses allmähliche Zurücksetzen ist außerdem zum Minimieren der Schwingungen der Dieselkraftmaschine 2 aufgrund ihrer Drehzahländerung wirksam, die durch die rückwärtsläufige Änderung des Zylinderkompensationsbetrages verursacht werden.

The main diagnostic routine according to the 9 and 10 is configured to diagnose the fuel supply system for the currently selected cylinder so that the fuel delivery system is normal if the speed of the diesel engine 2 according to the increase or reduction of the compensation amount qcy [K] of the diagnosis changes, and that it is defective if the rotational speed does not change according to the increase or decrease of the compensation amount qcy [K] of the diagnosis. This arrangement enables efficient and even more accurate diagnosis of the fuel delivery system.

• (3) Forcibly increasing or decreasing the cylinder compensation amount qcy [K] in the diagnosis is gradually implemented. This gradual increase or decrease of the cylinder compensation amount qcy [K] is to minimize the vibration of the diesel engine 2 effective due to their speed change, which are caused by the increase or decrease in the diagnosis. Further, the cylinder compensation amount qcy [K] is gradually reset to the original value before the gradual increase or decrease of the diagnosis is effected. This gradual reset is also to minimize the vibration of the diesel engine 2 due to their speed change caused by the backward change of the cylinder compensation amount.

Second Embodiment

In the first embodiment of this invention which has been described, the main diagnostic routine according to FIGS 9 and 10 and the routine according to 11 for controlling the gradual reset for all cylinders when the compensation amount qcy [K] for any of the cylinders falls outside the predetermined reference range. This defective state of the fuel supply system for a given cylinder tends to have a great influence on the compensation amounts qcy [K] of those cylinders whose combustion strokes take place before or after the combustion stroke of the cylinder whose fuel supply system is defective. In view of this tendency, the main diagnostic routine can be performed according to the 9 and 10 and the routine according to 11 for controlling the gradual reset only for one of the three above-mentioned cylinders, namely for that cylinder whose compensation amount qcy [K] falls outside the reference range, and for the two cylinders whose combustion strokes precede and follow the combustion stroke of the cylinder, its compensation amount outside the reference range. Thus, the diagnosis can be limited to the cylinders, which are relatively likely to be defective. This arrangement makes it possible to minimize the time required to execute the main diagnostic routine according to the 9 and 10 and the routine according to 11 is required for controlling the gradual reset, which accordingly leads to a reduced influence of the diagnosis on the vibrations and the exhaust emissions of the diesel engine 2 leads.

[Third Embodiment]

The main diagnostic routine according to the 9 and 10 In the first embodiment, it is so formulated that the step S690 of diagnosing a given cylinder fuel supply system when the affirmative decision (YES) is obtained in the step S630 is followed by the step S700 in which a suitable recovery operation is performed is going to treat the defect. In this case, the diagnosis of the other cylinder or cylinders is not effected. However, the main diagnostic routine according to the 9 be modified as shown in the flow chart of 13 that is shown 10 equivalent. In this modified routine, the control flow proceeds to step S650 when the fuel supply system for a given cylinder is diagnosed to be defective at step S690 based on the affirmative decision (YES) at step S630. Thus, the fuel delivery systems for all cylinders are diagnosed according to this modified routine so that all cylinders may be identified whose fuel delivery systems are defective, with the fuel delivery systems for two or more cylinders being defective. The third embodiment is further configured to execute a routine for controlling a gradual reset, which is shown in the flowchart of FIG 14 is shown, instead of the routine according to the 11 for controlling the gradual reset used in the first embodiment, when the fuel supply system of any one of the cylinders is diagnosed as being defective. According to the routine in the 14 For controlling the gradual reset, steps S900-S911 are implemented when the value "m-1" becomes "4", that is, when the affirmative decision (YES) is obtained in step S890, and they are followed by step S912 to determine if the fuel delivery system of any of the cylinders is defective. If none of the fuel supply systems of all the cylinders is defective, that is, if a negative decision (NO) is obtained in step S912, one execution cycle of the routine is ended. If the fuel supply system for any one of the cylinders is defective, that is, if an affirmative decision (YES) is obtained in step S912, the control flow goes to step S914, where the appropriate recovery operation is performed to deal with the defect. In step S912, the normal operation of the diesel engine becomes 2 The limp home processing is an operation for storing data with software to minimize problems caused by the problem defective fuel supply system would be caused.

[Fourth Embodiment]

In the first embodiment, the change of the cylinder compensation amount qcy [K] for the diagnosis is effected only once, and the fuel supply system for a given cylinder is diagnosed as defective if the Speed of the engine does not change according to the change of the compensation amount qcy for the diagnosis of the cylinder. However, the accuracy of the diagnosis can be improved by causing two or more gradual changes of the compensation amount qcy [K] for the diagnosis for each cylinder. In this case, the fuel supply system for a given cylinder is diagnosed to be defective only if the engine speed does not change according to all of the two or more gradual changes of the compensation amount qcy [K] for the diagnosis. Alternatively, the diagnosis may be effected depending on the number of gradual changes for the diagnosis in which the engine speed changes accordingly and the number of gradual changes for the diagnosis in which the engine speed does not change accordingly. Still alternatively, the fuel delivery system may be diagnosed as defective if the engine speed does not change according to any of the two or more gradual changes for the diagnosis. The fourth embodiment of this invention employs one of the alternative diagnostic methods described above.

• (1) Ein Gerät zum Diagnostizieren eines Kraftstoffzuführungssystems für eine Brennkraftmaschine, das mit einer Regeleinrichtung zum Bestimmen eines Kompensationsbetrages auf der Grundlage einer Abweichung eines Istbetriebszustandes der Brennkraftmaschine bezüglich ihres gewünschten Betriebszustandes versehen ist, und zum Steuern des Kraftstoffzuführungssystems mittels einer Regelung durch Kompensieren eines Befehlswertes einer Kraftstoffeinspritzmenge durch Kraftstoffzuführungssystem in die Brennkraftmaschine gemäß dem Kompensationsbetrag, so dass die Brennkraftmaschine in dem gewünschten Betriebszustand betrieben wird, charakterisiert durch eine Diagnoseeinrichtung zum Diagnostizieren des Kraftstoffzuführungssystems durch Bewirken einer Diagnoseeinstellung eines Betriebszustandes des Kraftstoffzuführungssystems.
• (2) Das Gerät ist dadurch charakterisiert, dass die vorstehend angegebene Diagnoseeinrichtung zum Diagnostizieren des Kraftstoffzuführungssystems durch Bewirken der Diagnoseeinstellung des Betriebszustandes des Kraftstoffzuführungssystems dazu eingerichtet ist, die Regelung durch die Regeleinrichtung zu beenden oder zu unterbinden, wenn der Kompensationsbetrag für irgendeinen der Zylinder der Brennkraftmaschine außerhalb des vorbestimmten Referenzbereiches fällt, und es ist des Weiteren dazu eingerichtet, Diagnoseeinstellungen der Betriebszustände der Kraftstoffzuführungssysteme für die vorstehend angegebenen einen Zylinder und die beiden Zylinder zu bewirken, deren Verbrennungshübe einen Hub vor und nach dem Verbrennungshub des vorstehend angegebenen einen Zylinders stattfinden, so dass jene Kraftstoffzuführungssysteme auf der Grundlage eines Ergebnisses der Diagnoseeinstellungen diagnostiziert werden.
• (3) Das Gerät ist dadurch charakterisiert, dass die vorstehend angegebene Diagnoseeinrichtung dazu eingerichtet ist, eine Erhöhung oder Reduzierung des Kompensationsbetrages von jedem des zumindest einen ausgewählten Zylinders der Brennkraftmaschine für eine Diagnose zu bewirken, und zum Diagnostizieren des Kraftstoffzuführungssystems für jeden ausgewählten Zylinder als normal, wenn ein Änderungsbetrag der Drehzahl der Brennkraftmaschine, der durch die Erhöhung oder Reduzierung des Kompensationsbetrages für die Diagnose verursacht wird, größer als ein vorbestimmter Schwellwert ist, und als Defekt, wenn der Änderungsbetrag nicht größer als der vorbestimmte Schwellwert ist.

While the first to fourth embodiments of the present invention are described above, the present invention can cover other embodiments such as the following modifications and changes:

• (1) An apparatus for diagnosing a fuel supply system for an internal combustion engine, which is provided with a control means for determining a compensation amount based on a deviation of an actual operating state of the internal combustion engine with respect to its desired operating state, and for controlling the fuel supply system by means of a control by compensating a command value of a Fuel injection amount by fuel supply system in the internal combustion engine according to the compensation amount, so that the internal combustion engine is operated in the desired operating condition, characterized by a diagnostic device for diagnosing the fuel supply system by effecting a diagnosis setting of an operating state of the fuel supply system.
• (2) The apparatus is characterized in that the above diagnosing means for diagnosing the fuel supply system by effecting the diagnosis setting of the operating state of the fuel supply system is arranged to terminate or inhibit the control by the controller when the compensation amount for any of the cylinders of the internal combustion engine is outside the predetermined reference range, and is further configured to effect diagnosis settings of the operating conditions of the fuel supply systems for the above-mentioned one cylinder and the two cylinders whose combustion strokes take a stroke before and after the combustion stroke of the above-mentioned one cylinder, so that those fuel delivery systems are diagnosed based on a result of the diagnostic settings.
• (3) The apparatus is characterized in that the above diagnosing means is arranged to cause increase or decrease of the compensation amount of each of the at least one selected cylinder of the internal combustion engine for diagnosis, and to diagnose the fuel supply system for each selected cylinder as normal when a change amount of the engine speed caused by the increase or decrease of the compensation amount for the diagnosis is greater than a predetermined threshold, and a failure when the amount of change is not greater than the predetermined threshold.

While the present invention with its presently preferred embodiments is described above, it is obvious that the present Invention not on the details of the preferred embodiments limited is, but that they are diverse Other variations of the illustrated embodiments are executed can, what is attached by the claims is defined.

An apparatus and method for diagnosing a fuel supply system for an internal combustion engine determine a compensation amount (qcy) for each cylinder based on a deviation (DNE) of an actual operating state of the engine with respect to its desired operating state, and the fuel supply system is controlled by setting a command value (QFIN ) of a fuel injection amount is compensated by the fuel supply system to the internal combustion engine according to the compensation amount. The apparatus and method include a diagnostic device ( 52 or a diagnostic step for effecting a forced setting for a diagnosis (at steps S590 and S600) of an operating state of the fuel supply system for each cylinder when the absolute value of the compensation amount (qcy) exceeds a predetermined threshold value (A) (if a step S550 positive decision), and for diagnosing the fuel supply system based on a speed change of the engine caused by the setting is caused.

Claims (15)

Device for diagnosing a fuel supply system for an internal combustion engine ( 2 ), with a control device ( 52 ) for determining a compensation amount (qcy) for compensating a command value (QFIN) of a fuel injection quantity from the fuel supply system to the internal combustion engine ( 2 ) on the basis of a deviation (DNE) of an actual operating state of the internal combustion engine ( 2 ) with respect to a desired operating condition thereof and for controlling the fuel supply system by means of control by compensating the command value (QFIN) according to the compensation amount (qcy) so that an actual rotational speed (NE) coincides with a desired rotational speed, characterized by: a diagnostic device ( 52 ) for diagnosing the fuel supply system by forcibly effecting diagnosis setting of an operating state of the fuel supply system when the compensation amount (qcy) falls outside a predetermined reference range (A). Device according to claim 1, characterized in that the control device ( 52 ) a change amount (TNH) of the actual operating state of the internal combustion engine ( 2 ), while the internal combustion engine ( 2 ) in an idling state, the deviation (DNE) of the change amount (TNH) of the present operation state in the idle state with respect to a desired change amount thereof is calculated, the compensation amount (qcy) of the respective cylinder (# 1- # 4) of the internal combustion engine ( 2 ) is determined based on the deviation (DNE) and the command value (QFIN) of the fuel injection amount from the fuel supply system into the respective cylinder is compensated according to the determined compensation amount (qcy) so that the engine ( 2 ) is operated in the desired operating state. Device according to claim 2, characterized in that the diagnostic device ( 52 ) is operable when the compensation amount (qcy) of any one of the cylinders (# 1- # 4) falls outside the predetermined reference range (A) to prevent operation of the control device (FIG. 52 ) and forcibly effecting the diagnosis setting of the operating state of the fuel supply system for the arbitrary cylinder (# 1- # 4). Device according to claim 2, characterized in that the diagnostic device ( 52 ) is operable when the compensation amount (qcy) of any one of the cylinders (# 1- # 4) falls outside the predetermined reference range (A) to terminate operation of the controller and the diagnostic settings of the operating conditions of the selected cylinder fuel supply systems (# 1 - # 4) of the internal combustion engine ( 2 ), the selected cylinders having the one arbitrary cylinder (# 1- # 4). Device according to claim 3 or 4, characterized in that the diagnostic device ( 52 ) for forcibly causing an increase or decrease in the compensation amount (qcy) of each of the at least one selected cylinder (# 1- # 4) of the internal combustion engine ( 2 ) is operable for diagnosis, and wherein the fuel supply system for each selected cylinder (# 1- # 4) based on a change (DNE) of the actual operating state of the internal combustion engine ( 2 ) caused by forcibly increasing or decreasing the amount of compensation (qcy) for the diagnosis. Device according to claim 5, characterized in that the diagnostic device ( 52 ) is operable to diagnose the fuel delivery system as normal for each selected cylinder (# 1- # 4) when the actual operating condition of the internal combustion engine ( 2 ) according to the forcible increase or decrease of the compensation amount (qcy) for the diagnosis, and as defective if the actual operating state does not change according to the compulsory increase or decrease of the compensation amount (qcy) for the diagnosis. Device according to claim 6, characterized in that the diagnostic device ( 52 ) for effecting a plurality of forced increases or decreases in the compensation amount (qcy) of each of the at least one selected cylinder (# 1- # 4) of the internal combustion engine ( 2 ) is diagnosable, and diagnoses the fuel supply system for the respective cylinder (# 1- # 4) as defective only when the changes (DNE) of the actual operating state of the engine ( 2 ) caused by all the forced increases or reductions from the plurality of forced increases or decreases for the diagnosis indicate that the fuel supply system for each cylinder (# 1- # 4) is defective. Device according to claim 5 or 7, characterized in that the diagnostic device ( 52 ) gradually increases or decreases the compensation amount (qcy) when the increase or decrease is forcibly carried out for diagnosis. Device according to one of claims 5 to 8, characterized in that the diagnostic device ( 52 ) the compensation amount (qcy) to a ur gradually resets the value after forcibly increasing or decreasing the amount of compensation (qcy) for the diagnosis. Method for diagnosing a fuel supply system for an internal combustion engine ( 2 ), wherein the fuel supply system is controlled so that the internal combustion engine ( 2 ) is operated in a desired operating state, comprising the steps of: calculating a deviation (DNE) of a change amount (TNH) of an actual operating state with respect to a desired amount of change thereof; Determining a compensation amount (qcy) for compensating a command value (QFIN) of a fuel injection amount from the fuel supply system to the internal combustion engine ( 2 ) at the respective cylinders (# 1- # 4) of the internal combustion engine ( 2 ) on the basis of the deviation (DNE); and determining whether the determined compensation amount (qcy) falls outside a predetermined reference range (A); and characterized by a step of diagnosing the fuel supply system by suspending a control of the fuel supply system and forcibly effecting a diagnosis setting of an operating state of the fuel supply system when the determined compensation amount (qcy) falls outside the predetermined reference range (A). A method according to claim 10, characterized in that the step of diagnosing the fuel supply system comprises forcibly increasing or decreasing the compensation amount (qcy) of each of at least one selected cylinder (# 1- # 4) of the internal combustion engine ( 2 ) for diagnosing and diagnosing the fuel supply system for each selected cylinder (# 1- # 4) based on a change (DNE) of the actual operating state of the internal combustion engine ( 2 ) caused by forcibly increasing or decreasing the amount of compensation (qcy) for the diagnosis. A method according to claim 11, characterized in that the step of diagnosing the fuel delivery system includes diagnosing the fuel delivery system for each selected cylinder (# 1- # 4) as normal when the actual operating condition of the internal combustion engine ( 2 ) according to the forcible increase or decrease of the compensation amount (qcy) for the diagnosis, and as defective if the actual operating state does not change according to the forced increase or decrease of the compensation amount for the diagnosis. Method according to claim 11 or 12, characterized in that the compensation amount (qcy) gradually elevated or is reduced if the increase or decrease for the diagnosis forcibly accomplished becomes. Method according to claim 11 or 12, characterized in that the compensation amount (qcy) gradually to an original one Value reset will, after the increase or reduction of the compensation amount (qcy) for the diagnosis Forcibly executed has been. Method according to one of claims 10 to 14, characterized in that the amount of change (TNH) of the actual operating state of the internal combustion engine ( 2 ) is detected while the internal combustion engine ( 2 ) is in an idle state.