JP2002122037A - Abnormal cylinder detecting device for multi-cylinder internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a failed injector among injectors 2 of each cylinder of a multi-cylinder internal combustion engine by accurately determining slightly affected state of the load noise, even during the traveling of a vehicle. SOLUTION: During one cycle of the combustion of each cylinder of a multi- cylinder internal combustion engine, when the undulation of a rotational fluctuations of one cycle period is determined to be more than the prescribed value; and an inter-cycle deviation is determined within the predetermined range by an inter-cycle deviation detecting means, even during the traveling of a vehicle, a state of small influence of the load noise is accurately determined, and high possibility of a functional failure in an injector 2 is determined. After obtaining such a result of determination, permission for carrying out the failed injector specifying processing for specifying the injector 2, in which a functional failure is generated, is performed by a permitting means to surely specify the failed injector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal cylinder detecting device for a multi-cylinder internal combustion engine which detects or specifies an abnormal cylinder or an abnormal cylinder of a multi-cylinder internal combustion engine mounted on a vehicle such as an automobile. An injector failure detection device for a diesel engine that determines whether at least one or more injectors among a plurality of injectors installed corresponding to each cylinder of a diesel engine having a plurality of cylinders have a functional failure. Get involved.

[0002]

2. Description of the Related Art A multi-cylinder internal combustion engine, for example, a diesel engine having a plurality of cylinders, operates by injecting high-pressure fuel into a cylinder from an injector. In particular, an injector for a diesel engine used in a pressure-accumulating fuel injection control system for an electronically controlled four-cylinder diesel engine generally has a top dead center (TDC) based on the outputs of a crank angle sensor and a cam angle sensor. ) Inject high-pressure fuel at a position near the cylinder pressure where it is maximum. The fuel injection amount is desirably uniform for each cylinder, and if there is an uneven injection amount between the cylinders, that is, if there is a variation in the fuel injection amount between the cylinders, the deviation in the rotational speed of each cylinder for each explosion stroke is deviated ( Increase / decrease), which adversely affects the driving state of the vehicle or the operating state of the internal combustion engine such as drivability, noise, vibration, and emission.

Usually, a plurality of injectors that inject fuel for each cylinder have individual differences in the injection amount. In other words, there are fuel passages and injection holes that are relatively large and inject a relatively large amount of fuel, and fuel passages and injection holes that are relatively small and those that inject a relatively small amount of fuel. In the case of a four-cylinder engine, the fuel injection amount injected into the cylinder may be different for all four cylinders. For this reason, the individual correction of the injection amount of the injector is relatively easy to handle the sensor signal from the crank angle sensor and is not easily affected by road surface noise or the like. Rotational speed fluctuations in each explosion stroke are detected, and the detected value of the rotation speed fluctuations in each cylinder in the explosion stroke is compared with the average value of the rotation speed fluctuations in all cylinders. Is carried out.

Here, the non-injection failure of the injector does not increase the in-cylinder pressure due to combustion due to the failure to inject fuel into the cylinder. Therefore, the fluctuation of the rotational speed of the abnormal cylinder is greatly reduced. The correction amount by the above unequal amount compensation control corrects the fuel injection amount to the abnormal cylinder so that the rotational speed fluctuation of the abnormal cylinder is smoothed with the rotational speed fluctuation of the other cylinders. The correction amount greatly increases. Therefore, at the time of the non-injection failure of the injector, the failure information of the specific cylinder is continuously output. Then, when the failure information of the same cylinder continues for a predetermined cycle, an abnormal cylinder detection device for a diesel engine that identifies the cylinder as an abnormal cylinder (for example, Japanese Patent Publication No. 6-9700).
No. 8 publication).

[0005]

However, in the conventional abnormal cylinder detecting device for a diesel engine, when a no-injection failure occurs in one cylinder, the cylinder having the largest deviation from the average rotational speed of the four cylinders is the abnormal cylinder. I try to diagnose that there is. Here, FIG. 3 shows actual rotational speed fluctuations during running of the diesel engine when no-injection failure occurs in only one cylinder. From FIG. 3, it is a no-injection failure of only one cylinder, and the four cylinders show different rotation speed fluctuations even though the other three cylinders are normally injecting.

In particular, a diesel engine has a large compression ratio and uses a flywheel heavier than a gasoline engine to stably operate the engine. For this reason, a diesel engine has a large inertia, and the non-injection of the one-cylinder injector has a small effect on the rotation speed.
Therefore, if the cylinder having the largest deviation from the average rotational speed of the four cylinders is diagnosed as an abnormal cylinder in the above-described known technique, there is a possibility that the injector of the normal cylinder may be erroneously detected as a malfunction depending on the operating conditions. was there.

Further, in order to eliminate engine vibrations caused by fluctuations in rotation speed due to variations in explosive force between cylinders, fluctuations in rotation speed for each cylinder are detected and smoothed as in the above-described known technique. As described above, when the unequal amount compensation control (injection amount correction control between the cylinders) for individually adjusting the optimum fuel injection amount for each cylinder is performed, the injector of one cylinder always performs the injection without the injection amount. The correction amount does not converge. Alternatively, there is a problem that it takes time to converge the correction amount of the fuel injection amount. Particularly, while the vehicle is running, the correction amount of the fuel injection amount directly affects the output of the diesel engine. If the convergence of the correction amount of the fuel injection amount is poor, there is a problem that the rotational speed fluctuation of each cylinder greatly changes, and as a result, the drivability deteriorates. Therefore, there is a problem that the above-described known technique cannot be used during running of the vehicle.

Further, during actual running of the vehicle, road surface noise (road noise, vehicle interior noise) is generated when the vehicle runs on a rough road surface. In addition, road noise
It may be accompanied by very fine vibration. Therefore, when the vehicle is actually running, road noise caused by the road surface condition is added to the rotation speed fluctuation of each cylinder for each explosion stroke. And the diesel engine, as mentioned above,
Since the flywheel is heavier than the gasoline engine, the inertia is large, so that when the injector of one cylinder has no injection failure, the deviation of the rotational speed fluctuation between the abnormal cylinder and the other normal cylinder is small. . Therefore, when the influence of road noise is added to the rotation speed fluctuation of each cylinder for each explosion stroke, the above-described known technology fails to detect the failure only with the maximum value of the correction amount of the fuel injection amount, which is erroneously detected. was there. In particular, there are two types of injector failures: "no-injection failure in which fuel is not injected into the cylinder" and "excessive injection failure in which fuel keeps blowing in the cylinder". Therefore, it is very important to detect the failure of the injector while the vehicle is running.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to accurately detect a faulty injector from a plurality of injectors by accurately judging a state in which the influence of road noise is small even when the vehicle is running. It is an object of the present invention to provide an abnormal cylinder detecting device for a multi-cylinder internal combustion engine, which can detect abnormal cylinders.

[0010]

According to the first aspect of the present invention, there is provided an injector having a function such as "no injection failure in which fuel is not injected into a cylinder" or "excessive injection failure in which fuel keeps being injected into a cylinder". It is determined that a functional failure has occurred when the following determination result is obtained. That is, in one cycle in which the combustion of each cylinder of the multi-cylinder internal combustion engine makes one cycle, it is determined that the rotation fluctuation swell of this one cycle period is equal to or greater than a predetermined value, and the inter-cycle deviation is detected by the inter-cycle deviation detection means. This is when it is determined that it is within the predetermined value.

When such a permission judgment is obtained,
Even while the vehicle is running, it is possible to accurately determine that the state is less affected by road noise, and to determine that there is a high possibility that a malfunction has occurred in the injector. In other words, if the rotation fluctuation undulation in one cycle period is equal to or greater than a predetermined value, it is determined that the possibility that the above-described functional failure has occurred in a certain injector is high. This is because it is determined that the situation is such that the influence of the noise is not added to the rotation fluctuation of the engine. Therefore, after the determination result is obtained, the permission of the failure injector specifying process for specifying the injector in which the functional failure has occurred is permitted by the permission means, so that the faulty injector can be specified reliably.

According to the second aspect of the present invention, the one-cycle swell detecting means detects the maximum rotation speed or the minimum rotation speed in one cycle in the same cylinder continuously for a predetermined cycle. Since it is detected that the swell of the cycle rotation fluctuation has occurred, it is possible to reliably detect the swell of the rotation fluctuation of one cycle cycle.

According to the third aspect of the invention, the one-cycle swell detecting means in the permission means detects one
The determination that the rotation fluctuation waviness of the cycle period is equal to or greater than a predetermined value is determined by detecting an intra-cycle deviation which is a deviation between both the maximum rotation speed and the minimum rotation speed in each cylinder in one cycle, and determining the deviation within the cycle. This is performed by being equal to or more than a predetermined value. This makes it possible to reliably detect the presence of an injector having a functional failure.

According to the fourth aspect of the present invention, the permitting means determines that the inter-cycle deviation detected by the inter-cycle deviation detecting means is within a predetermined value and that the inter-cycle deviation is within the predetermined value. When detected, the execution of the malfunction injector specifying process is permitted. Therefore, since it is detected that the inter-cycle deviation is within the predetermined value continuously for the predetermined cycle, it is possible to reliably eliminate a state in which the influence of the road noise is added to the rotation fluctuation of the engine. Can be determined with higher accuracy, and in that state, it is possible to shift to the fault injector identification process.

According to the fifth aspect of the present invention, the inter-cycle deviation detecting means includes the maximum rotational speed of each cylinder in one cycle, the minimum rotational speed of each cylinder in one cycle, or the one in one cycle. Average rotation speed,
Alternatively, the inter-cycle deviation is detected based on the rotation speed at a predetermined crank angle in one cycle. Therefore, the inter-cycle deviation can be detected by using any of these rotational speeds, so that it is possible to reliably determine whether or not road noise is added to engine rotational fluctuations.

According to the present invention, by measuring the elapsed time between the predetermined convex teeth detected by the crank angle sensor, the rotational speed of each cylinder of the multi-cylinder internal combustion engine for each explosion stroke is measured. The fluctuation is detected as a time change. That is, since the rotation speed fluctuation of each cylinder can be detected using the sensor signal of the existing crank angle sensor, the rotation speed fluctuation of each cylinder can be detected relatively easily.

According to the seventh aspect of the present invention, when the permission means permits the execution of the malfunction injector specifying process, the rotation speed of each cylinder in the explosion stroke in one cycle, or the rotation speed in one cycle, By comparing means for comparing the combustion energy of each cylinder in the explosion stroke of each cylinder or the deviation of the generated torque of each cylinder within one cycle between the cylinders, it is determined that the injector of the cylinder with the largest deviation or the smallest deviation is the failed injector. I try to be specific. Accordingly, when the deviation of the rotation speed fluctuation of each cylinder in each cycle of the explosion stroke in one cycle or the deviation of the combustion energy of each cylinder in each cycle of the explosion stroke within one cycle is used, a plurality of injectors are used. It is possible to specify a malfunctioning injector having a functional malfunction with high accuracy.

Further, when the deviation of the generated torque of each cylinder within one cycle is used, the actual torque of each cylinder can be detected. The detection of the injector can be executed with higher accuracy than in the case of using the rotation speed fluctuation and the deviation of the combustion energy.

According to the present invention, when it is determined whether or not a malfunction has occurred in the injector provided in each cylinder, each cylinder is smoothed so as to smooth the rotational speed fluctuation between the cylinders. The injection amount correction control between cylinders for individually adjusting the injection amount for each cylinder is prohibited. As a result, erroneous detection of a functional failure of the injector can be prevented, so that detection accuracy of a functional failure of the injector can be improved.

According to the ninth aspect of the present invention, the multi-cylinder internal combustion engine operates normally by providing a display means for visually or audibly displaying that a malfunction has occurred in the injector provided in each cylinder. It is possible to promptly inform the driver or the like of an abnormal operating state or an abnormal operating state.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings. FIGS. 1 to 9 show a first embodiment of the present invention. FIG. 1 is a diagram showing the overall configuration of a pressure accumulating fuel injection system for a diesel engine.

The accumulator type fuel injection system for a diesel engine according to the present embodiment is generally called a common rail system. For example, the operating state of a four-cylinder diesel engine 1 mounted on a vehicle such as an automobile, the running state of the vehicle, and the like. An electronic control system control unit (hereinafter referred to as E) constituting an abnormal cylinder detection device of a multi-cylinder internal combustion engine by detecting an operation amount (will) of a driver (driver) by various sensors.
CU) 9 to calculate the optimal fuel injection amount and fuel injection timing based on sensor signals from various sensors,
It is configured to instruct a plurality (four in this example) of injectors (electromagnetic fuel injection valves) 2 and a fuel pressure pump 3 for controlling each of them.

The diesel engine 1 corresponds to the multi-cylinder internal combustion engine of the present invention, and is a four-cycle four-cylinder engine including a cylinder block, a cylinder head, an oil pan, and the like. The four cylinders 10 of the diesel engine 1 are formed by a cylinder block, a cylinder head, and the like. And each cylinder 10
The intake port is opened and closed by an intake valve (intake valve) 11, and the exhaust port is opened and closed by an exhaust valve (exhaust valve) 12. In each cylinder 10, a piston 14 connected to the crankshaft 13 via a connecting rod is slidably provided.

The plurality of injectors 2 are mounted on the cylinder block of the diesel engine 1 (corresponding to each of the cylinders # 1 to # 4), and the cylinders 10 for each cylinder are provided.
An electromagnetic fuel injection valve includes a fuel injection nozzle for injecting high-pressure fuel into the inside thereof, and an actuator (not shown) such as an electromagnetic valve for driving a valve body of the fuel injection nozzle. The longer the valve opening time (injection period) of the valve body of the injector 2, the greater the amount of fuel injected into the cylinder 10 for each cylinder, and the longer the valve opening time (injection period) of the valve body of the injector 2. Is shorter, the fuel injection amount injected into the cylinder 10 for each cylinder is smaller.

The fuel pressure pump 3 is a high pressure supply pump incorporating a feed pump 16 for pumping fuel from the fuel tank 15 and an actuator (not shown) such as a solenoid valve for adjusting the pressure of the high pressure fuel to the common rail 17. is there. The fuel pump 3 sucks fuel from the fuel tank 15 and pressurizes the fuel, and pumps the fuel amount commanded by the ECU 9 to the common rail 17. This common rail 1
The fuel pressure stored in the fuel cell 7 is measured by a fuel pressure sensor 18 as fuel pressure detecting means, and a pump driving command and a driving command for the injector 2 are calculated by the ECU 9. In the fuel tank 15, a liquid level sensor 19 for measuring the liquid level of the fuel in the fuel tank 15 is provided.

The common rail 17 is a kind of surge tank for storing high-pressure fuel of a relatively high pressure (common rail pressure). The common rail 17 is connected to a plurality of injectors 2 attached to each cylinder via a fuel pipe 20. ing.
Here, in the present embodiment, a return pipe 21 for returning fuel from the common rail 17 to the fuel tank 15 is provided. Then, the common rail 17 opens the valve of the pressure limiter 22 so that the common rail pressure does not exceed the limit pressure accumulation pressure, passes through the fuel passage in the pressure limiter 22 and the return pipe 21, and passes through the common rail 17. It is configured so that pressure can be released.

The ECU 9 includes a control unit, a CPU including an operation unit and a register unit, a memory (RAM, PROM or ROM) for storing a control program and various data,
A well-known microcomputer configured to include functions such as an I / O port (input / output circuit) for inputting and outputting signals to and from various sensors and actuators is provided. Then, sensor signals from various sensors are A / D converted by an A / D converter, and then input to a microcomputer.

The ECU 9 is configured to output a crankshaft rotation pulse and a camshaft from the crankshaft angle sensor 4 attached to the crankshaft (crankshaft) 13 and the camshaft angle sensor 5 attached to the camshaft (camshaft) 23. The common rail pressure is maintained at a predetermined pressure value by determining the fuel injection timing of the injector 2 and the fuel pumping period of the fuel pump 3 based on the signal of the rotation pulse.

Here, the crank angle sensor 4 corresponds to the rotational speed detecting means of the present invention, and includes a timing rotor (signal rotor) 24 made of a magnetic material and fixed to the crankshaft 13 of the diesel engine 1. The rotation angle of the crankshaft 13 is detected by an electromagnetic rotation sensor composed of an electromagnetic pickup coil 25 arranged to face the peripheral surface of the rotor 24 and a permanent magnet (magnet) for generating a magnetic flux. The ECU 9
Detects the engine rotation speed (NE) by measuring the interval time between crank angle signals (NE pulse signals).

The timing rotor 24 has a plurality of convex teeth 26 formed at predetermined angles (for example, 10 °).
Therefore, when the timing rotor 24 rotates, the protruding teeth 26 move toward and away from the electromagnetic pickup coil 25, so that the electromagnetic pickup coil 2
5 outputs a crank angle signal (NE pulse signal). In this embodiment, 36-2 = 34 teeth are formed with the two teeth of the timing rotor 24 being missing teeth. By detecting this missing tooth, one rotation of the timing rotor 24 can be detected.

That is, in the case of the 4-cycle 4-cylinder diesel engine 1, one cycle of the diesel engine 1 (1 cycle: intake stroke, compression stroke, explosion stroke, exhaust stroke), that is, the crankshaft 13 rotates twice (720 °) CA)
During the operation, 68 crank angle signals (10 ° per pulse)
CA) occurs on the outer peripheral surface of the timing rotor 24 every 10 ° (corresponding to 20 ° CA).
Are provided as described above.

Then, by calculating the interval time of the crank angle signal of the crank angle sensor 4, the instantaneous rotational speed of each cylinder for each explosion stroke is calculated, and the BTDC 90 ° CA
The maximum value of the interval time of the crank angle signal between ＡＴATDC 90 ° CA is read as the minimum rotation speed of the instantaneous rotation speed of this cylinder. BTDC90 ° CA to ATDC90
The minimum value of the interval time of the crank angle signal between ° CA is read as the maximum rotation speed of the instantaneous rotation speed of this cylinder.

After performing these calculations for each cylinder, as shown in FIGS. 2 and 3, the rotational speed difference between the maximum rotational speed for each cylinder and the minimum rotational speed for each cylinder is calculated. By doing so, fluctuations in the rotational speed of each cylinder, which occur in synchronization with the fuel injection of each cylinder, for each explosion stroke are detected or calculated. Here, FIG. 2 is a diagram showing the behavior of the rotational speed fluctuation of each cylinder of the diesel engine in every cylinder during the explosion stroke when all the cylinders are normal at the time of running at low load and low rotation, and FIG. 3 shows the first cylinder # 1. FIG. 9 is a diagram illustrating a behavior of a rotation speed fluctuation of each cylinder for each explosion stroke when a no-injection failure occurs.

The cam angle sensor 5 is a timing rotor (signal rotor) 27 made of a magnetic material and fixed to the cam shaft 23 of the diesel engine 1, and an electromagnetic sensor arranged to face the peripheral surface of the timing rotor 27. The rotation angle of the camshaft 23 is detected by an electromagnetic rotation sensor including a pickup coil 28 and a permanent magnet (magnet) that generates a magnetic flux. Timing rotor 27
, A plurality of convex teeth 29 are arranged at predetermined angles.

The ECU 9 also includes an accelerator opening sensor 3 for measuring the amount of depression of the accelerator pedal (accelerator opening).
0 and a cooling water temperature sensor 31 for detecting the cooling water temperature of the diesel engine 1 and the like. The ECU 9 detects the accelerator opening (ACCP), which is a value detected by the accelerator opening sensor 30, the engine rotation speed (NE) detected (calculated) from the crank angle signal from the crank angle sensor 4, and the detection of the cooling water temperature sensor 31. To calculate the fuel injection amount from the cooling water temperature (THW), which is a value, and to achieve the calculated fuel injection amount,
Each injector 2 is driven by an opening / closing command calculated from the fuel pressure in the common rail 17 for each operation state. As a result, the diesel engine 1 is operated.

The ECU 9 is configured to receive a vehicle speed signal from a vehicle speed sensor 32 for measuring the running speed (vehicle speed) of the vehicle. Here, injector 2
The fuel used to open the valve is returned to the fuel tank 15 via a return pipe 33 as a relief pipe. A fuel temperature sensor 34 for measuring a fuel temperature is mounted on the return pipe 33. It is desirable that the fuel temperature sensor 34 be mounted at a position as close as possible to the gathering portion of the return pipes 33 of each injector 2 in order to increase the detection accuracy.

Exhaust gas burned in the cylinder 10 during operation of the diesel engine 1 passes through an exhaust pipe 35 and becomes a driving source of a turbine of a variable nozzle turbo (VNT) 36, and then a catalyst (not shown). And discharged through a muffler (not shown). The control of the variable nozzle turbo 36 is performed based on the signal of the intake pressure sensor 47 and the signal of the VNT drive amount sensor 37. The supercharged intake air is introduced into the cylinder 10 through the intake pipe 38. A throttle valve (throttle valve) 39 is provided in the middle of the intake pipe 38.
Is adjusted by an actuator 40 operated by a signal from the ECU 9.

The intake pipe 38 of the present embodiment has an exhaust gas recirculation gas (EGR) which is a part of the exhaust gas flowing through the exhaust pipe 35.
An exhaust gas recirculation pipe 41 for guiding the gas to the intake pipe 38 is connected. An exhaust gas recirculation device valve (EGR valve) 42 is installed at the entrance of the exhaust gas recirculation pipe 41, and an EGR gas cooler 43 for cooling the EGR gas is installed in the exhaust gas recirculation pipe 41. Have been.
Therefore, the opening degree of the EGR valve 42 is controlled so that the intake air sucked into the cylinder 10 becomes the exhaust gas recirculation amount (EGR amount) set for each operation state in order to reduce the emission, and the exhaust pipe 35 Will be mixed with the exhaust gas. The EGR amount is
Feedback control is performed by signals from the intake air amount sensor 44, the intake air temperature sensor 45, and the EGR valve opening degree sensor 46 so that a predetermined value can be maintained.

[Failure Detection Method of First Embodiment] Next, a method of detecting an injector failure of the diesel engine 1 of the present embodiment will be briefly described with reference to FIGS. Here, FIGS. 4 and 5 are flowcharts showing a method for detecting an injector failure of the diesel engine 1. FIG.

When the ignition switch is turned on (IG / O
N), and when the diesel engine 1 starts, FIG.
Is started. Then, first, in step S1, it is determined whether the operation state of the diesel engine 1 is an idle state. The idle speed is
For example, it is about 850 rpm. If it is determined that the vehicle is in the idle state, the process proceeds to step S2, where it is determined whether or not the vehicle speed is "0", and it is determined whether or not the vehicle is in a stopped state.

If the vehicle speed is "0" in step S2, the process proceeds to step S3, in which the injection amount for each cylinder is individually adjusted so as to smooth the rotational speed fluctuation between cylinders. Injection amount correction control (unequal amount compensation control) is performed. In the injection amount correction control between the cylinders, the diesel engine 1
Of the rotation speed of each cylinder in each explosion stroke, and compares the average value of the rotation speed fluctuations of all the cylinders with the detected value of the rotation speed fluctuation of each cylinder. Correct the amount.

Next, the routine proceeds to step S4, where it is determined whether or not the correction amount of the fuel injection amount to each cylinder in the inter-cylinder injection amount correction control executed in step S3 is within a predetermined range. If this determination result is NO, that is, if the correction amount is within the predetermined range, the process returns to step S1 again.

On the other hand, if the decision result in the step S4 is YES
In other words, if the correction amount is out of the predetermined range, the process proceeds to step S5, which is to detect the failed cylinder of the injector. In step S5, a cylinder to which the correction amount determined to be outside the predetermined range set in advance in step S4 is applied is detected as an abnormal cylinder. By the above steps,
It is determined that the injector 2 of this abnormal cylinder has a functional failure such as a no-injection failure or an excessive injection failure, and this routine ends.

If NO is determined in steps S1 and S2, it is determined that the vehicle is running, and the process proceeds to step S6, in which the cylinder-to-cylinder injection amount correction control executed in step S3 is performed. To stop. In this case, the calculation of the correction amount between the cylinders may be continued.

Then, the process proceeds to a step S7, wherein it is determined whether or not the vehicle is traveling normally. This determination is, for example,
The determination is made by detecting whether or not the accelerator opening (ACCP), which is a sensor value of the accelerator opening sensor 30, continues at a predetermined value. If it is determined in step S7 that the vehicle is not traveling normally, the process returns to step S1.

If it is determined in step S7 that the vehicle is traveling in a steady state, the process proceeds to step S7 in FIG.
It is determined whether or not a functional failure of the injector 2 has occurred by the processing of Steps S8 to S14, and when it is determined that a functional failure of the injector 2 has occurred, which injector of the plurality of injectors 2 has been determined. Permission is given to a malfunction injector identification process for identifying whether or not the malfunction 2 has occurred.

In this embodiment, in step S8, first, the maximum rotation speed and the minimum rotation speed of each cylinder of the diesel engine 1 for each explosion stroke are detected. As shown in FIG. 2, this corresponds to the maximum rotation speeds max1 to max4 and the minimum rotation speeds mi of the first cylinder # 1 to the fourth cylinder # 4 for each explosion stroke.
n1 to min4 are detected using output values from the crank angle sensor 4. The subscript of each rotation speed indicates a cylinder number.

Next, the process proceeds to step S9, where the maximum rotational speeds (max1 to m1) for each cylinder obtained in step S8 are determined.
ax4), one of the cylinders that showed the maximum in one cycle
The cycle maximum rotation speed Maxi is detected (calculated). At the same time, the one-cycle minimum rotation speed Mini of the cylinder showing the minimum within one cycle is detected (calculated) from the minimum rotation speeds (min1 to min4) for each cylinder obtained in step S8. Here, the subscript i of Maxi and Mini indicates the i-th cycle. In the present embodiment, one cycle refers to 720 ° CA in which a four-cylinder four-cycle engine is employed and combustion of each of the first to fourth cylinders is completed. The explosion order is, for example, as shown in FIG. 2, # 1 → # 3 → # 4 → # 2.

Next, the above-mentioned Maxi and Mini are specifically detected by selecting the maximum value of the following equation 1 and the minimum value of the following equation 2.

(Equation 1) In the cycle shown in FIG. 3, the maximum rotation speed max2 of the second cylinder is selected as Maxi.

(Equation 2) In the cycle shown in FIG. 3, the minimum rotation speed min3 of the third cylinder is selected for Mini.

Then, the process proceeds to step S10,
Using either the one-cycle maximum rotation speed Maxi or the one-cycle minimum rotation speed Mini detected in step 9, the cylinder showing Maxi (or Mini) is continuously operated for a predetermined cycle (for example, three cycles) in the same cylinder. Detect if there is. If this determination is NO, the process returns to step S1.

On the other hand, if it is detected in step S10 that the cylinders indicating Maxi (or Mini) are the same cylinders for a predetermined cycle, step S11 is executed.
Proceed to. Here, when it is determined as YES in step S10, Maxi (or Min.
Since i) is continuously detected for a predetermined cycle, it can be determined that the rotation fluctuation of the engine has a fluctuation of one cycle (720 ° CA).

Next, in step S11, an inter-cycle deviation ΔMi is calculated using Maxi (or Mini) detected in step S9. Specifically, this cycle (the i-th cycle) is calculated using the calculation formula of the following equation (3).
By calculating the deviation between the maximum rotation speed Maxi in one cycle in the cycle (1) and the maximum rotation speed Maxi-1 in the previous cycle (the (i-1) th cycle),
The above ΔMi is calculated.

(Equation 3)

Note that ΔMi is the minimum rotation speed M in one cycle.
When calculating using ini, the minimum rotation speed of one cycle in the current and previous cycles may be used as in the calculation formula of the following equation (4).

(Equation 4)

Then, the process proceeds to step S12, and it is determined whether or not this ΔMi is within a predetermined value (for example, 10 rpm) continuously for a predetermined cycle using the inter-cycle deviation ΔMi calculated in step S11. If the result of this determination is NO, the process returns to step S1 again.

On the other hand, if it is detected that ΔMi is within the predetermined value continuously for the predetermined cycle, the process proceeds to step S13. Here, when YES is determined in step S12, a state in which the inter-cycle deviation ΔMi is within a predetermined value is detected continuously for a predetermined cycle, so that
The influence of road noise generated by road surface vibrations and the like is added to the rotation fluctuation of the engine, so that it is possible to determine that a long-cycle fluctuation component over several cycles is not superimposed.

Further, in the state where YES is determined in both the steps S10 and S12, Max
It is a state that the cylinders indicating i (or Mini) are the same for a predetermined cycle and that ΔMi is within a predetermined value for a predetermined cycle. It can be determined that the swell of one cycle (720 ° CA), which is extremely small due to the noise, has occurred.

In step S13, one cycle maximum rotation speed Maxi and one cycle minimum rotation speed Mini in one cycle detected in step S9 are performed.
From this, the intra-cycle deviation Δi in this cycle is calculated by the following equation (5).

(Equation 5)

Then, in the next step S14, it is determined whether or not the intra-cycle deviation Δi calculated in step S13 is equal to or more than a predetermined value (for example, 10 rpm).
If the determination is NO, no significant rotation fluctuation deviation occurs within one cycle, so it is determined that no functional failure of the injector 2 has occurred, and the process returns to step S1.

On the other hand, if it is determined in step S14 that Δi is equal to or greater than the predetermined value, a no-injection failure or a continuous injection failure of the injector 2 in a certain cylinder has occurred within one cycle. It can be determined that there is a possibility. In addition, as described above, step S1
0 and S12 are established, and it is determined that the swell of one cycle (720 ° CA) that is extremely small due to the road noise is caused by the engine speed fluctuation. In this state, in step S14, When it is determined that Δi is equal to or greater than a predetermined value, it can be determined that the swell of the one cycle period is equal to or greater than a predetermined value. Therefore, a functional failure of the injector 2 (for example, no injection failure)
Can be determined with certainty.

If the result of the determination in step S14 is YES, the flow proceeds to the fault injector identification processing in step S15 in FIG. That is, the above steps S8 to S1
If it is determined by the injector malfunction detection process in step 4 that a malfunction has occurred in the injector 2, the execution of the malfunction injector identification process in step S15 is permitted.

Here, for example, when the injector of one cylinder has no injection failure and a misfire occurs in that cylinder, the rotation speed fluctuation synchronized with the fuel injection in each cylinder, that is, the rotation speed fluctuation in each cylinder for each explosion stroke Then, a swell of one cycle period represented by 720 ° CA occurs (see FIG. 7). Further, it is known from the results of our experiments that, when affected by road noise, a larger swell of 10 Hz or less is added to the rotation speed fluctuation (see FIG. 6).

That is, if one cycle cycle swell represented by 720 ° CA is observed, and it is observed that the one cycle cycle swell does not fluctuate between cycles, one injector malfunctions. We have found through intensive studies that it is very likely that there will be no (eg no injection) and road noise effects.

Then, the above-described undulation of one cycle period does not change between cycles, that is, the state of the injector 2
The state in which the functional failure has occurred is shown in step S8 in FIG.
This can be determined by the injector function failure detection processing in steps S14 to S14.

Next, when it is determined in the injector functional failure detection processing that a functional failure has occurred in the injector 2, as described above, the execution of the failure injector identification processing in step S15 of FIG. 4 is performed. Allowed.
This failure injector identification processing is performed by the following calculation /
An abnormal cylinder provided with a failed injector may be specified by the comparison process. For example, when the rotational speed fluctuation deviation of each cylinder for each explosion stroke is larger or smaller than a predetermined value than the rotation speed fluctuation deviation of each cylinder for each explosion stroke, the cylinder is identified as an abnormal cylinder. Or, when the deviation of the maximum or minimum value of the instantaneous rotational speed of a certain cylinder is larger than or smaller than the deviation of the maximum or minimum value of the instantaneous rotational speed of another cylinder by a predetermined value or more, the cylinder is identified as an abnormal cylinder. I do.

That is, the combustion energy for each cylinder is obtained from the difference between the maximum value and the minimum value of the rotational speed fluctuation generated in synchronization with the fuel injection into each cylinder, and the difference is the largest among the cylinders. Alternatively, a small cylinder is specified as an abnormal cylinder.
Here, as a method of diagnosing the failure of the injector 2, it is needless to say that a cylinder that has performed the calculation but is not actually controlled and has the largest injection amount correction amount may be diagnosed as an abnormal cylinder.

[Characteristics of the first embodiment] Here, when the amount of fuel injected into the cylinder 10 of each cylinder of the diesel engine 1 is the same, the rotation speed fluctuation of each cylinder for each power stroke is shown in FIG. Shows the same behavior. That is, the deviation (rotational speed fluctuation) between the maximum value and the minimum value of the instantaneous rotational speed of each cylinder shows the same behavior.

However, if there is a faulty injector having a non-injection failure among a plurality of injectors 2, fuel is not injected into an abnormal cylinder (failure cylinder) having a non-injection failure. No combustion occurs, and the cylinder pressure does not increase. Therefore, as shown in FIG. 3, the rotation speed fluctuation of each cylinder in each cycle during the explosion stroke corresponds to the maximum rotation speed (Maxi in cylinder # 2 in FIG. 3) indicating the maximum rotation speed in one cycle. ) And 1
The cylinder showing the minimum rotational speed in the cycle (cylinder # in FIG. 3)
In-cycle deviation Δ from minimum rotation speed (Mini) in 3)
The behavior of Mi is large. Further, when the influence of the road noise is superimposed on the rotation fluctuation of the internal combustion engine, a rotation fluctuation of a large frequency of 10 Hz or more as shown in FIG. 6 is added.

The inventor of the present invention has found that when no injection failure occurs in the injector 2 of one cylinder in the absence of road noise, a swell of 720 ° CA with no cycle-to-cycle deviation occurs in the rotation speed fluctuation. That is, the relationship between the rotational speeds corresponding to the crank angles (CA) is continuous (see FIG. 7). If this undulating rotation speed fluctuation of 720 ° CA cycle can be continuously observed,
It can be predicted that the influence of road noise is extremely small. Then, an in-cycle deviation Δi between the minimum rotation speed (Mini) and the maximum rotation speed (Maxi) in one cycle is calculated, and this Δi is set to a predetermined value (for example, 10r
pm) or more, there is a high possibility that a functional failure of the injector 2 (no injection failure or excessive injection failure, etc.), combustion failure, or failure of the injection amount control system has occurred. Can be determined.

The maximum rotation speed (Max) within one cycle
i) or a cylinder showing the minimum rotation speed (Mini) is detected, and it is detected that the cylinder is the same cylinder continuously for a predetermined cycle, and the maximum rotation speed (Max) between the cycles is detected.
If it is detected that i) or the inter-cycle deviation ΔMi of the minimum rotation speed (Mini) is within a predetermined value (for example, 10 rpm), it can be predicted that a stable swell of one cycle period is caused by the rotation speed fluctuation. Therefore, it can be determined that there is no or very little influence of road noise even when a vehicle such as an automobile is running.

As described above, when the above three conditions continue for a predetermined cycle, it can be predicted that there is no influence of road noise and there is a high possibility that a functional failure of the injector 2 has occurred. When the above three conditions are satisfied, the abnormal cylinder is specified from among the plurality of cylinders, so that the abnormal cylinder ( (Failed cylinder) can be detected. not to mention,,
, May be changed, and all three conditions must be satisfied.

Here, when it is detected that a stable swell of one cycle period has occurred in the rotation speed fluctuation,
Rotational speed fluctuations of each cylinder for each explosion stroke can be detected by frequency analysis. However, the frequency analysis is not realistic because the calculation load on the ECU 9 is large.
For this purpose, the present embodiment proposes a method for easily detecting that a stable swell of one cycle period is generated in the rotation speed fluctuation with a small calculation load.

When a no-injection failure of the injector 2 occurs in a specific cylinder, as shown in FIG. 8, a swell of 720 ° CA cycle occurs in the rotation speed fluctuation. At this time, the cylinder showing the maximum rotation speed or the minimum rotation speed within one cycle should be the same for each cycle. For this reason, when it is continuously detected that the cylinders exhibiting the maximum rotation speed or the minimum rotation speed in one cycle are the same cylinder for a predetermined cycle or more, a swell of 720 ° CA cycle is generated in the rotation speed fluctuation. Can be estimated. This allows
The swell of the 720 ° CA cycle can be easily detected without increasing the calculation load.

If the road noise affects the rotation speed fluctuation, a frequency of 10 Hz or less, that is, a large period of swell is added to the rotation speed fluctuation (see FIG. 6). Whether or not there is an influence of road noise can be detected by detecting the inter-cycle deviation ΔMi of the maximum rotation speed (Maxi) or the minimum rotation speed (Mini) between the cycles. As a detection method, a method of calculating the average value or the integrated value of the rotation speed between cycles and comparing the values between the cycles can be considered, but the method of comparing the average value or the integrated value between the cycles clearly shows a difference. hard. In other words, averaging by adding the rotation speeds of the other normal cylinders may lower the output accuracy.

For this reason, it is clear that the inter-cycle deviation can be accurately detected by using the method of calculating the inter-cycle deviation only with the maximum rotation speed (Maxi) or the minimum rotation speed (Mini). That is, the same cylinder continuously has the maximum rotation speed (Maxi) or the minimum rotation speed (M
By detecting that the inter-cycle deviation at the time of (ini) is equal to or smaller than a predetermined value, it is possible to accurately detect the rotation speed fluctuation in each cycle.

[Effects of the First Embodiment] In the injector failure detection method for the diesel engine 1 of the present embodiment,
By paying attention to the fact that a large swell of 720 ° CA is added to the rotation speed fluctuation when the injector 2 fails, if it can be observed that a stable swell of 720 ° CA occurs in the rotation speed fluctuation, the injector 2 Can be accurately predicted to be in an operating state in which there is always a functional failure (for example, no injection failure or excessive injection failure) and the effect of road noise is likely to be small. At this time, by detecting the functional failure of the injector 2, it is possible to accurately detect the failed injector from the plurality of injectors 2.

Further, by using the output signal (crank angle signal) of the existing crank angle sensor 4 to measure the elapsed time between the specified predetermined convex teeth 26, the rotational speed fluctuation for each cylinder is measured with respect to time. It can be detected as a change. As a result, since the sensor signal of the existing crank angle sensor 4 can be used, it is possible to relatively easily detect the rotational speed fluctuation of each cylinder. Therefore, there is an effect that the logic circuit for detecting the injector failure can be simplified.

Further, when detecting a malfunction of the injector 2, if the injection amount correction control between the cylinders is performed, an erroneous detection will result. Therefore, when detecting a malfunction of the injector 2, the detection accuracy of the malfunction of the injector 2 can be improved by stopping or inhibiting the injection amount correction control between the cylinders. Although the above description has been made with reference to the no-injection failure, it goes without saying that an excessive injection failure due to continuous injection can be similarly detected (see FIG. 9).

The conditions for determining whether or not to detect a malfunction of the injector 2 of an abnormal cylinder, for example, a specific cylinder, have been described above. Next, a method of specifying a further fault injector will be described. In each cylinder 10 of the diesel engine 1, combustion occurs due to fuel injection from each injector 2, but it is generally known that fluctuations in rotation speed largely depend on inertia of a flywheel, a flywheel, and the like.

In particular, the combustion energy of each cylinder is ｛(d
maxi / dθ) ² − (dmini / dθ) ² } (where i = 1, 2, 3, 4 (cylinder number)) (see FIG. 2). Calculate the combustion energy for each cylinder,
By comparing the cylinders, the cylinder having the largest deviation from the other cylinders can be specified as the abnormal cylinder. Then, if the three conditions for determining whether or not to execute the above-described abnormal cylinder identification processing are satisfied, the combustion energy of each cylinder can be detected without the influence of road noise. The failure injector can be detected with high accuracy.

In detecting the combustion energy of each cylinder, cylinder-specific generated torque estimating means for estimating the generated torque of each cylinder, such as an in-cylinder pressure sensor, may be used. In order to estimate the actual torque generated for each cylinder, the failure injector can be detected with high accuracy.

[Second Embodiment] FIGS. 10 and 11 show a second embodiment of the present invention. FIGS. 10 and 11 are flow charts showing a method for detecting an injector failure of the diesel engine 1. FIG.

In this embodiment, as shown in FIG. 11, only the steps S11 and S12 are different from the first embodiment, and a step S1 replacing the steps S11 and S12 is performed.
11, S121 will be described.

In step S111, first, an average rotation speed for one cycle is calculated. Specifically, in the case of a general four-cylinder diesel engine, the time change between 180 ° CA is calculated as the rotation speed for each cylinder, so this rotation speed information is used. Then, the average rotation speed in a cycle is calculated by averaging the rotation speeds of the cylinders calculated in one cycle. Then, a deviation between the average rotational speed in the cycle and the average rotational speed in the cycle calculated in the next cycle is calculated as an inter-cycle deviation ΔM′i.

Next, the process proceeds to a step S121, wherein the Δ
It is determined whether or not M′i is within a predetermined value for a predetermined cycle continuously. In this embodiment, as described above, there is an advantage that a new calculation is not required because an existing engine rotation signal can be used.

[Modification] In this embodiment, an example in which a four-cylinder diesel engine 1 is applied as a multi-cylinder internal combustion engine has been described. You may adopt it. Further, a gasoline engine having two or more cylinders may be employed as the multi-cylinder internal combustion engine. In this case, an electromagnetic fuel injection valve such as an injector is attached to an intake pipe upstream of an intake port of each cylinder.

Further, when it is determined by the above-described injector functional failure detection processing that a functional failure has occurred in the injector 2, a visual display or an audible display for transmitting the occurrence of the failure to a driver or the like is provided. A lamp or buzzer may be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of a pressure accumulating fuel injection system for a diesel engine (first embodiment).

FIG. 2 is a diagram showing a behavior of a rotation speed fluctuation of each cylinder of a diesel engine in which all cylinders are normal during an explosion stroke during traveling at a low load and a low rotation speed (first embodiment).

FIG. 3 is a diagram showing a behavior of a rotation speed fluctuation in each cylinder during an explosion stroke when a no-injection failure occurs in a first cylinder # 1 (first embodiment).

FIG. 4 is a flowchart showing a method for detecting an injector failure of a diesel engine (first embodiment).

FIG. 5 is a flowchart showing a method for detecting an injector failure of a diesel engine (first embodiment).

FIG. 6 is a diagram illustrating a behavior in a state in which a large swell caused by road noise is added to a rotation speed variation of each cylinder (first embodiment).

FIG. 7 is a diagram showing a behavior in a state in which a swell of one cycle period is added to a rotation speed fluctuation for each cylinder (first embodiment).

FIG. 8 is a diagram showing a behavior in a state where a swell of 720 ° CA cycle is generated in the rotation speed fluctuation of each cylinder (first embodiment).

FIG. 9 is a diagram showing a behavior of a rotational speed fluctuation of each cylinder of a diesel engine having an abnormal injection cylinder (first embodiment).

FIG. 10 is a flowchart showing a method for detecting an injector failure of a diesel engine (second embodiment).

FIG. 11 is a flowchart illustrating a method for detecting an injector failure of a diesel engine (second embodiment).

[Explanation of symbols]

 Reference Signs List 1 diesel engine (multi-cylinder internal combustion engine) 2 injector 4 crank angle sensor (rotation speed detecting means) 9 ECU (abnormal cylinder detection device of multi-cylinder internal combustion engine) 10 cylinder 13 crankshaft 26 convex teeth

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02D 45/00362 F02D 45 / 00362J

Claims (9)

[Claims] 1. An abnormal cylinder detection device for a multi-cylinder internal combustion engine, to which an injector for injecting fuel for each cylinder is attached, wherein, in one cycle in which combustion of each cylinder of the multi-cylinder internal combustion engine makes one cycle, the one cycle cycle A one-cycle swell detecting means for detecting occurrence of swell of rotation fluctuation of the motor; and an inter-cycle deviation detecting means for detecting an inter-cycle deviation for each cycle. When it is determined that the swell of the rotation fluctuation in one cycle period is equal to or more than a predetermined value, and further, when the inter-cycle deviation detection means determines that the inter-cycle deviation is within a predetermined value,
A permission means is provided for judging that a functional failure has occurred in the injector provided in each of the cylinders, and permitting execution of a failed injector identification process for identifying the injector in which the functional failure has occurred. Abnormal cylinder detection device for a multi-cylinder internal combustion engine. 2. The apparatus according to claim 1, further comprising: a rotation speed detection unit configured to detect a maximum rotation speed or a minimum rotation speed of each of the cylinders for each of the explosion strokes. 2. The method according to claim 1, wherein when the detected maximum rotation speed or minimum rotation speed is detected in the same cylinder continuously for a predetermined cycle, it is detected that the swell of the rotation fluctuation in the one cycle period has occurred. 2. The abnormal cylinder detection device for a multi-cylinder internal combustion engine according to claim 1. 3. An intra-cycle deviation detection for detecting an intra-cycle deviation which is a deviation between a maximum rotation speed and a minimum rotation speed in one cycle from a maximum rotation speed and a minimum rotation speed in each cylinder in the one cycle. Means for permitting, when the in-cycle deviation detected by the in-cycle deviation detection means is equal to or greater than a predetermined value,
3. An abnormal cylinder detecting device for a multi-cylinder internal combustion engine according to claim 1, wherein it is determined that the swell of the rotation fluctuation of one cycle period detected by the cycle swell detecting means is equal to or more than a predetermined value. . 4. When the inter-cycle deviation detected by the inter-cycle deviation detection means is within a predetermined value, and when the inter-cycle deviation is within the predetermined value is detected continuously for a predetermined cycle, The abnormal cylinder detection device for a multi-cylinder internal combustion engine according to any one of claims 1 to 3, wherein execution of the failed injector identification processing is permitted. 5. The cycle-to-cycle deviation detecting means, wherein the maximum rotation speed of each cylinder in the one cycle, the minimum rotation speed of each cylinder in the one cycle, the average rotation speed in the one cycle, or 5. The abnormal cylinder detecting device for a multi-cylinder internal combustion engine according to claim 1, wherein an inter-cycle deviation is detected based on a rotation speed at a predetermined crank angle in the one cycle. 6. The rotation speed detecting means has a crank angle sensor for detecting a rotation angle of a crankshaft of the engine, and measures an elapsed time between predetermined convex teeth detected by the crank angle sensor. The abnormal cylinder detection of the multi-cylinder internal combustion engine according to any one of claims 1 to 5, wherein a rotation speed fluctuation of each cylinder of the multi-cylinder internal combustion engine for each explosion stroke is detected as a time change. apparatus. 7. When the permitting means permits the execution of the malfunction injector identification processing, the malfunction injector identification processing includes a rotation speed fluctuation for each cylinder in an explosion stroke in one cycle, or a rotation speed variation in one cylinder. By comparing means for comparing the combustion energy of each cylinder in the explosion stroke of each cylinder or the deviation of the generated torque of each cylinder within one cycle between the cylinders, it is determined that the injector of the cylinder with the largest deviation or the smallest deviation is the failed injector. The abnormal cylinder detecting device for a multi-cylinder internal combustion engine according to any one of claims 1 to 6, wherein the device is specified. 8. An injection amount correction control between cylinders is prohibited when it is determined whether a malfunction has occurred in an injector provided in each of the cylinders. An abnormal cylinder detection device for a multi-cylinder internal combustion engine according to any one of the above. 9. The display device according to claim 1, further comprising a display unit for visually or audibly displaying that a malfunction has occurred in the injector provided in each of the cylinders. An abnormal cylinder detection device for a multi-cylinder internal combustion engine according to the above.