JPH06249034A - Air-fuel ratio measuring deivice, method for evaluating internal combustion engine and judging device - Google Patents

Abstract

PURPOSE:To provide an air-fuel ratio measuring device which calculates the moment-by-moment air-fuel ratio in an internal combustion engine having a fuel injector and can obtain respective air-fuel ratios of a plurality of cylinders with good accuracy. CONSTITUTION:A pressure measuring means 14 to detect the pressure value in a suction tube at the timing of closing an intake valve in synchronisation with the action of the intake valve of a cylinder 12, and a time measuring means 13 to obtain the integrated value of the fuel injection time of a fuel injector 11 during the period from the preceding closing of the intake valve to this time closing in synchronization of the intake valve of the cylinder 12 are provided, and in addition, a computing means 15 to compute the air-fuel ratio in the combustion immediately after this time closing of the intake valve based on the ratio of the pressure value divided by the integrated value is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to (1) an air-fuel ratio measuring device for calculating the air-fuel ratio in an internal combustion engine equipped with a fuel injector, and (2) an internal combustion engine for controlling the injection time of the fuel injector by a microcomputer. The method of evaluating an internal combustion engine that determines whether the air-fuel ratio control is possible, and (3) is installed in the internal combustion engine that controls the fuel injector by measuring the pressure value in the intake pipe, and determines the availability of this control state. Regarding a determination device.

[0002]

BACKGROUND OF THE INVENTION Many applications of conventional carburetor gasoline engines are now being replaced by gasoline and diesel engines using fuel injectors. In an internal combustion engine using a fuel injector, the amount of fuel supplied in each cylinder in each cycle can be adjusted very precisely, so that the air-fuel ratio can be controlled relatively easily. Therefore, it is possible to precisely follow the operating state of the internal combustion engine with the fuel supply amount, stabilize the output state, and simultaneously save the total fuel consumption amount.

Further, a gasoline engine using a fuel injector can efficiently remove hydrocarbons, carbon monoxide, and nitrogen oxides in exhaust gas at the same time by combining with an exhaust gas purifying device using a three-way catalyst. Therefore, active development research has been carried out for the purpose of clearing exhaust gas regulations, and has been put to practical use in recent years.

An internal combustion engine equipped with a fuel injector, especially a gasoline engine combined with an exhaust gas purifying device using a three-way catalyst, is usually equipped with a large number of sensors and an engine control microcomputer. The operating time of the fuel injector is calculated on the basis of the output of the sensor, and the fuel injector is operated according to the calculation result to control the air-fuel ratio within a limited fixed range regardless of the output state of the internal combustion engine. ing.

FIG. 7 is an illustration of an example of a gasoline engine equipped with a fuel injector. Here, a pressure sensor is provided on the cylinder side of the intake pipe to estimate the air intake amount of the cylinder, and the operating time of the fuel injector capable of keeping the air-fuel ratio constant based on the intake amount is calculated.

In FIG. 7, the engine body has a plurality of cylinders 51 arranged in a direction perpendicular to the plane of the drawing, and a water cooling jacket 5 for cooling the engine is provided on the outer periphery of the cylinders 51.
2 is placed. An intake valve 54 is provided above the cylinder 51.
Through the exhaust valve 53 and the exhaust pipe 57 through the exhaust valve 53.
Are connected respectively. In the intake pipe 56, the fuel injector 5
8. A throttle valve 55 is arranged.

ECU (Electronic Control Unit) 50
Controls the fuel injector 58 in real time by calculating the fuel injection time that can keep the air-fuel ratio substantially constant based on the output states of the multiple sensors 61 to 67. The intake pipe 56 has a vacuum sensor 62 and a supply air temperature sensor 63.
However, the exhaust pipe 57 has an oxygen sensor 64 and an exhaust temperature sensor 6
5, the water cooling jacket 52 is provided with a water temperature sensor 66, and the throttle valve 55 is provided with an opening sensor 61.

The fuel injection time in the ECU 50 is calculated as follows: (1) The value obtained by multiplying the volume of the cylinder 51 by the pressure value in the cylinder is proportional to the weight of air, and (2) when the intake valve 54 is opened. It is based on the principle that the pressure value downstream of the throttle valve 55 substantially matches the pressure value in the cylinder. That is, the pressure value measured by the vacuum sensor 62 is regarded as the pressure value in the cylinder, and the cylinder 51 is set to this pressure value.
To calculate the supply air amount by correcting the temperature and the density, and to calculate the fuel required amount for which the air-fuel ratio becomes, for example, 14.6 with respect to this supply air amount, and to perform fuel injection that satisfies this fuel required amount. The operating time of the device 58 is obtained.

Further, if the throttle valve 55 is suddenly opened, the increase in the supply air amount cannot keep up with the increase in the supply air amount, and the response to the engine operation deteriorates. 6
1 is provided, and the ECU 50 uses the throttle valve 55
The fuel supply amount is predicted and increased / decreased in conjunction with the opening / closing operation of.

Here, the plurality of cylinders 51 arranged in the direction perpendicular to the plane of the drawing each have their own fuel injectors 58, but the plurality of fuel injectors 58 are irrespective of whether the intake valves 54 are open or closed. Instead, the crankshafts are operated simultaneously and under the same conditions at one specific timing for two rotations of the crankshaft (see FIG. 3).

Therefore, in the cylinder 51 in which the intake valve 54 is closed at the time of fuel injection, fuel (steam of the fuel) stays on the intake valve and in the pipe, and this fuel is stored in the cylinder 51 by the air flow accompanying the next valve opening. Is washed away.

Further, the calculation of the operating time of the fuel injector in the ECU 50 is not based on the control for keeping the air-fuel ratio of each cylinder 51 constant, but is based on the pressure value measured by the vacuum sensor 62 at short time intervals. Thus, the control is a control for obtaining a preferable fuel amount as a whole of the plurality of cylinders 51. In other words, the plurality of cylinders 51 are uniform through the arithmetic processing in the ECU 50.
It is handled on average.

[0013]

In an internal combustion engine using a fuel injector, since there is no autonomic adjustment function of the fuel supply amount that follows the air supply amount, unlike a carburetor, the cylinders corresponding to the opening and closing of the throttle valve are not operated. It is necessary to accurately estimate the air supply amount and increase or decrease the fuel supply amount in real time according to the air supply amount to forcibly maintain an appropriate air-fuel ratio.

Now, for the purpose of improving fuel efficiency and preventing pollution, the operating time of the fuel injector is precisely corrected by taking into account various variables that have not been used so far, and the air-fuel ratio is controlled within a very narrow range. There is. Therefore, a large number of sensors for measuring various correction variables such as the water temperature in the water cooling jacket and the oxygen concentration in the exhaust gas are arranged in the engine body, and an arithmetic unit (microcomputer for controlling the operating time of the fuel injector is provided. ) Will be connected to a number of these sensors.

However, in such an internal combustion engine which has been made into a precision machine, precise and proper control is guaranteed on the premise of the normal operation of a large number of sensors. The fuel ratio is not normal. If the air-fuel ratio becomes abnormal, the output decreases, the engine stops, the concentration of nitric oxide in the exhaust gas rises, etc. on the lean fuel side. On the other hand, on the excessive fuel side, wear of the cylinder due to incomplete combustion, deterioration of fuel consumption, increase of carbon monoxide concentration in exhaust gas, and the like occur.

Further, the air-fuel ratio may become abnormal temporarily or intermittently in a form following the vibration of the vehicle body due to poor contact of the sensor wiring or instantaneous noise generation. However, as long as the driver stays in a minor degree, it is easy to overlook the occurrence of these abnormalities, and even if he / she notices the abnormalities, it is quite difficult to pinpoint the cause and perform proper repair.

Further, in the internal combustion engine which uniformly treats a plurality of cylinders through the arithmetic processing for controlling the fuel injector as shown in FIG. 7, a normal air-fuel ratio is guaranteed for each cylinder. It doesn't mean that. Therefore, even if the air-fuel ratio abnormality is detected from the output of the oxygen sensor or the like, it is not always the case that the air-fuel ratio is abnormal in the entire plurality of cylinders, and it is possible to accurately determine whether the operating time of the fuel injection device is appropriate. Can not.

Further, in the internal combustion engine which detects the opening / closing of the throttle valve and predictably increases / decreases the fuel supply amount as shown in FIG. 7, it is difficult to accurately perform the predictive correction of the fuel supply amount. is there. Since it is not possible to separately understand the opening / closing speed of the throttle valve, the injection timing for correction, the injection duration, the effect of the corrected injection amount on each cylinder, etc. Compared with the case of operation at the rotational speed, during acceleration / deceleration, operation with a considerably rough air-fuel ratio is temporarily required.

If the air-fuel ratio can be independently measured for each of the plurality of cylinders of the internal combustion engine, these problems can be solved. However, currently possible methods are: (1) Separate the exhaust pipes of multiple cylinders, install oxygen sensors and hydrocarbon sensors in each, and measure the exhaust gas amount at each explosion, It is only a method of calculating the air-fuel ratio from the exhaust composition, and (2) observing the emission color at the time of explosion by making a hole in the cylinder outer wall of the internal combustion engine and inserting glass. And these methods require a major modification of the internal combustion engine for implementation,
Due to the complexity of the necessary measurement and arithmetic processing, it is impossible to measure the air-fuel ratio accurately in real time.

The present invention provides (1) an air-fuel ratio measuring device capable of accurately determining the air-fuel ratio in each of a plurality of cylinders, and (2) an internal combustion engine capable of precisely determining whether or not the air-fuel ratio control of the internal combustion engine is accurate. It is an object of the present invention to provide an evaluation method and (3) a determination device that can accurately determine whether or not air-fuel ratio control can be performed by directly using a pressure sensor originally provided in the intake pipe.

[0021]

FIG. 1 is an explanatory diagram of the basic configuration of the present invention. In FIG. 1, the air-fuel ratio measuring apparatus according to claim 1 is connected to an internal combustion engine 10 including a fuel injector 11 to calculate an air-fuel ratio of one cycle in at least one of a plurality of cylinders 12 of the internal combustion engine 10. In a possible air-fuel ratio measuring device, in synchronization with the operation of the intake valve of the cylinder 12, the pressure measuring means 14 for detecting the pressure value in the intake pipe at the timing before the closing of the intake valve, and the intake air of the cylinder 12. In synchronization with the operation of the valve, the time measuring means 13 for obtaining an integrated value of the fuel injection time of the fuel injector 11 in the period from the last closing of the intake valve to the current closing of the intake valve.
And a calculation means 15 for calculating an air-fuel ratio in combustion immediately after the current valve closing based on a value obtained by dividing the pressure value by the integrated value.

The limited aspect of the invention of claim 1 is connected to an internal combustion engine 10 equipped with a fuel injector 11, and calculates the air-fuel ratio in every cylinder 12 of the internal combustion engine 10 every moment. In the air-fuel ratio measuring device, in synchronization with the operation of each intake valve of the plurality of cylinders 12, pressure measuring means 14 for detecting the pressure value in the intake pipe at the timing before the closing of each intake valve, In synchronization with the operation of each intake valve of the plurality of cylinders 12, the integrated value of the fuel injection time of the fuel injector 11 in each period from the previous closing of the intake valve to the present closing is obtained. For each of the time measuring means 13 and the plurality of cylinders 12, an air-fuel ratio in one cycle of combustion is calculated based on a value obtained by dividing the pressure value by the integrated value, A calculating means for calculating the average of the air-fuel ratio of the cylinder 12, and has a.

According to a second aspect of the present invention, there is provided a method for evaluating an internal combustion engine, comprising: a fuel injector provided in an air supply path for a plurality of cylinders; a measuring means for measuring the amount of intake air of the cylinder through the air path; An internal combustion engine having a control means for calculating an operating time of the fuel injector based on an air amount, in an internal combustion engine evaluation method for determining adequacy of the calculation, the cylinder side of a throttle valve of the air supply path. The pressure value output by the pressure sensor placed in the cylinder is measured at the timing before closing of the intake valve of each cylinder, and for each cylinder, the above value in the period from the previous closing of the intake valve to the current closing of the intake valve is measured. The integrated value of the operating time of the fuel injector is calculated, and one cycle of combustion is calculated for each cylinder based on the value obtained by dividing the pressure value by the integrated value. It calculates the definitive air, a method of temporal change of the air-fuel ratio to generate a warning signal when exceeding the allowable range.

According to a third aspect of the present invention, there is provided a determination device that includes a fuel injector provided in an air supply path for a plurality of cylinders, a pressure sensor provided on a cylinder side of a throttle valve in the air path, and a pressure output by the pressure sensor. Is attached to an internal combustion engine having a control means for calculating the intake air amounts of a plurality of cylinders from the values and calculating the operation time of the fuel injector based on the air amounts, and determining the suitability of the calculation. In the determination device, the pressure value output by the pressure sensor is measured at a timing before closing of the intake valve of each cylinder, and the measuring means for measuring the pressure value in the period from the previous closing of the intake valve to the current closing of the intake valve. Integrating means for obtaining the integrated value of the operating time of the fuel injector for each cylinder,
An air-fuel ratio for one cycle in each cylinder is calculated based on a value obtained by dividing the pressure value by the integrated value, and a warning is issued when the difference between the individual air-fuel ratios with respect to the average value of the air-fuel ratio exceeds an allowable range. And a control means for generating a signal.

[0025]

In FIG. 1, in the air-fuel ratio measuring apparatus according to claim 1, at least one of the plurality of cylinders 12 of the internal combustion engine 10 is
The actual air-fuel ratio for one cycle in one cycle can be calculated predictively based on the data acquired before the ignition explosion.

The fuel injector 11 directly supplies into the cylinder 12 the liquid or gaseous fuel in an amount that is expected in advance to give an air-fuel ratio that is substantially appropriate for the amount of air supplied to the cylinder 12. Alternatively, the fuel is injected into the air supply path via the intake valve. However, this amount cannot always achieve an appropriate air-fuel ratio after the fact due to the operating state of the internal combustion engine 10, the delay in the control calculation of the fuel injector 11, the malfunction of the sensor, and the like.

The fuel injector 11 may be shared by all of the plurality of cylinders 12 or by each group of two to three intake pipes, but one fuel injector 11 may be arranged for each of the plurality of cylinders 12.

The calculation principle of the air-fuel ratio by the calculation means 15 is as follows.
As in the case of FIG. 5, (1) the pressure in the intake pipe matches the pressure in the cylinder 12 when the intake valve is open, and (2) the pressure in the cylinder 12 is proportional to the air supply amount of one cycle,
Based on that. However, (3) the pressure measuring means 14 captures the pressure value at the timing before the valve closing of the specific cylinder 12 to independently obtain the pressure in the specific cylinder 12, and (4)
The time measuring means 13 independently obtains the integrated value of the operating time of the fuel injector 11 in the period from the last closing of the intake valve of the specific cylinder 12 to the present closing, and (5) the calculating means 1
5 independently calculates the air-fuel ratio based on these unique pressure value and integrated value. By combining the respective features, the unique air-fuel ratio which is not averaged in each of the plurality of cylinders 12 is calculated. Makes it possible.

Here, the peculiar air-fuel ratio is independently calculated for one or more of the plurality of cylinders 12. Also, the pressure value is captured in synchronization with the operation of the intake valve,
The synchronization signals for dividing the operating time of the fuel injector 11 into the current time and the next time are the operation of the intake valve itself, the operation of the drive cam,
The rotation phase angle of the crankshaft or the like may be detected and generated.

When a pressure sensor is previously arranged in the intake pipe as shown in FIG. 5, the pressure measuring means 14 detects the timing immediately before the closing operation of the intake valve from the output of the rotation phase sensor of the crankshaft, for example. It is configured by combining an existing pressure sensor with the circuit. The pressure value taken at the timing immediately before the valve closing operation serves as a basis for obtaining the air supply amount in one cycle immediately after the valve closing of the cylinder.

The amount of fuel for one cycle for calculating the air-fuel ratio is regarded as the fuel injection amount being substantially proportional to the operating time of the fuel injector 11, and the valve closing time from the previous closing time to the current closing time is considered. It is represented by the total operating time to the valve. Therefore, when one of the plurality of cylinders 12 approaches the valve closing period during the operation of the fuel injector 11, the injection amount before the valve closing is used for the calculation of the air-fuel ratio in one cycle after the valve closing this time. However, the remaining injection amount after the valve is closed is used for calculating the air-fuel ratio in one cycle after the next valve close.

Here, the ratio of the amount of air to be charged (pre-valve closing pressure) to the operating time of the fuel injector 11 is equal for combustion in each of the plurality of cylinders 12 or each time combustion in one cylinder 12. For example, since it is considered that the air-fuel ratio of combustion is also equal, the subsequent factors (for example, the temperature difference between the cylinders 12 and the abnormality of the plug) cannot be separated. However, for example, when the oxygen concentration of the exhaust gas is measured and incomplete combustion is detected even though the air-fuel ratio is proper, the cause is the ratio of the amount of air to be filled and the operating time of the fuel injector 11. Will be automatically narrowed down to the subsequent factors that may make the air-fuel ratio abnormal, even if
Elucidation of the cause and re-evaluation after repair can be performed very easily.

In the limited aspect of the invention of claim 1, the average value is obtained from the air-fuel ratio uniquely obtained for each of the plurality of cylinders 12. In the normal internal combustion engine 10, the plurality of cylinders 12 have the same volume, and the ignition-combustion process is expected to proceed in the same manner in the plurality of cylinders 12. Therefore, the average value of the air-fuel ratio is 10
It reflects the exhaust gas composition and oxygen concentration.

In the method for evaluating an internal combustion engine according to the second aspect of the present invention, a unique air-fuel ratio is calculated for each of the plurality of cylinders, and a warning is issued when the temporal change in the calculated air-fuel ratio greatly exceeds the allowable range. The signal is output. The temporal changes referred to here are: (1) Abnormality detection in multiple explosions in the sequence that make up one cycle of the internal combustion engine ( Calculation), (2) difference of the average value (or individual air-fuel ratios) of the air-fuel ratios of a plurality of cylinders with respect to a temporal change of a predetermined air-fuel ratio characteristic, (3) a certain number of cycles from the present (for example, 50 It can be obtained by comparing the average value of the air-fuel ratios of a plurality of cylinders (or the individual air-fuel ratios) obtained for 100 cycles of the cycle) with the difference between the individual air-fuel ratios of this cycle.

In a preferred evaluation method, among the air-fuel ratios sequentially calculated for a plurality of cylinders in accordance with the rotation of the internal combustion engine, a plurality of the latest consecutive air-fuel ratios (preferably the number of cylinders) including the latest air-fuel ratio. The average value is obtained from the air-fuel ratio, the latest air-fuel ratio is compared with this average value, and a warning signal is generated when the difference exceeds the allowable range. That is, the range that should be judged to be normal is gradually changed by following the operating state of the internal combustion engine.

In the control device for the fuel injector, the fuel supply may be increased to set a low air-fuel ratio immediately after starting or when the outside air is extremely cold. In such a case, a low air-fuel ratio should be judged to be normal, and if an evaluation method that gradually changes the range to be judged to be normal is adopted, the generation of a warning signal due to a wrong judgment can be avoided.

In the determination device of the third aspect, like the engine of FIG. 5, the pressure sensor is arranged in the air supply path, and the operating time of the fuel injector is calculated in accordance with the pressure value obtained by the pressure sensor. It is mounted on an internal combustion engine that determines the accuracy of the arithmetic operation of the control means of the internal combustion engine. For example, the output is partially borrowed from the pressure sensor on the internal combustion engine side, the drive coil of the fuel injector, and the phase sensor of the crankshaft. Basically, based on these three, the empty space for one cycle in each cylinder is calculated. The fuel ratio is calculated to obtain an average value of the air-fuel ratios of the plurality of cylinders, and a warning signal is generated when at least one of the individual air-fuel ratios has a difference exceeding the allowable range with respect to the average value.

When signals are obtained from these existing elements provided in the internal combustion engine, the determination device may be configured as a program stored in the microcomputer itself which controls the fuel injector of the internal combustion engine. The microcomputer handles a plurality of cylinders on an average basis to calculate the operating time of the fuel injector, and at the same time identifies in real time whether or not the operating time achieves an appropriate air-fuel ratio in each of the plurality of cylinders. .

Identification of the air-fuel ratio in each of the plurality of cylinders requires considerably less both the number of data and the number of calculation steps involved in the calculation, as compared with the normal calculation of the operating time of the fuel injector. New programs can be added without compromising the computing power of the microcomputer.

[0040]

FIG. 2 is an explanatory view of a mounting state of the A / F evaluation device of the embodiment, FIG. 3 is an explanatory view of a relationship between a cycle of each cylinder and fuel injection timing in the gasoline engine of FIG. 2, and FIG. 4 is an embodiment. 5 is an explanatory diagram of the calculation flow of FIG. 5, FIG. 5 is a flowchart of the embodiment, and FIG. 6 is an explanatory diagram of the defect detection flag output. Here, an A / F evaluation device is shown which is mounted on a 4-cylinder 4-cycle gasoline engine having a fuel injector in each cylinder and determines the air-fuel ratio (A / F: Air / Fuel) in each cylinder.

In FIG. 2, a vehicle-mounted gasoline engine 21 has four cylinders C1 to C4.
A dedicated fuel injector 28 is provided in each of the intake pipes 1 to C4. Intake pipe 26 of cylinders C1 to C4
Are grouped together, via the throttle valve,
It is connected to an air cleaner (not shown). On the other hand, the exhaust pipes 27 of the cylinders C1 to C4 are integrated into one and connected to an exhaust gas purification device (not shown).

Like the gasoline engine of FIG. 7, the gasoline engine 21 is provided with a number of sensors, and these sensors are not shown in an ECU (Electronic Control Uni).
t)). The ECU calculates the fuel supply amount corresponding to the preferable air-fuel ratio according to the input state from these sensors every moment, and determines the operating time (number of operations) of the fuel injector 28.

The A / F evaluation device 20 obtains signals from the existing vacuum sensor 32, the crank angle sensor 37, and the signal line of the fuel injector 28 provided in the gasoline engine 21, and receives signals from the respective cylinders C1 to C4. Calculate the air-fuel ratio.

In the A / F evaluation device 20, the timing immediately after the intake valve of each of the cylinders C1 to C4 starts the closing operation is extracted through the crank angle sensor 37, and the pressure value PM of the vacuum sensor 32 is calculated at this timing. It is taken in and the air supply amount in each cylinder C1-C4 is estimated. Further, the crank angle sensor 37 detects the period from the last closing timing to the current closing timing of the intake valves of the cylinders C1 to C4, and the integrated value ΣT of the operating time of the fuel injector 28 corresponding to this period. Calculate _i . Then, through the operation of dividing the pressure value PM by the integrated value ΣT _i and multiplying it by a predetermined constant K,
The air-fuel ratio A / F in each of the cylinders C1 to C4 is calculated.

The A / F evaluation device 20 also obtains signals from the other sensors 21 provided in the gasoline engine 21, and the vacuum sensor 32, the crank angle sensor 37,
When an abnormality is detected in the air-fuel ratio A / F calculated from the operation signal of the fuel injector 28, the program proceeds to a program for identifying the input states of other sensors and locating the abnormal portion.

Referring to FIG. 3, the gasoline engine 2 of FIG.
Cylinder C1 of 1 has a crank angle of 0 to 720 degrees 2
By rotation, four cycles of intake, compression, expansion and exhaust are executed in one cycle. Cylinder C2, Cylinder C3, Cylinder C4
Are 180 degrees, 360 degrees, and
4 strokes of air supply, compression, expansion and exhaust with a delay of 540 degrees 1
Run the cycle.

On the other hand, the four fuel injectors 28 of the gasoline engine 21 start injection all at once slightly before the crank angle of 360 degrees, and the ECU is operated based on the input state of each sensor.
The injection is continued for a corrected time calculated by. The fuel injection times T ₂ and T ₃ executed subsequent to the fuel injection time T ₁ in the figure are the correction amounts due to the sudden opening operation of the throttle valve. Further, the fuel injection time T _4, the fuel injection time T _1, T _2, belongs to a cycle subsequent to a cycle in which belongs T _3, the fuel injection time T _1, the T _2, T ₃ time slightly longer which is the sum of It is being calculated.

The amount of fuel supplied into the cylinders C1 to C4 in the air supply stroke of each of the cylinders C1 to C4 depends on the period from the last valve closing timing of each of the cylinders C1 to C4 to the current valve closing timing. It is calculated as the total injection time ΣT _i .

Therefore, regarding the cylinders C1 and C2,
Since the current valve closing timing has passed, the total of the fuel injection times T ₁ , T ₂ , and T ₃ of this time, together with the pressure value immediately before each valve closing of the next time, calculates the air-fuel ratio of the next cycle. Used for. Further, regarding the cylinder C3, since the current fuel injection time T ₁ is in time for the current valve closing, the total of the current fuel injection times T ₂ , T ₃ and the portion before the dotted line of the next fuel injection time T ₄ is the sum. , Is used for the calculation of the air-fuel ratio in the next cycle together with the pressure value immediately before the next valve closing.
For the cylinder C4, the fuel injection times T ₁ , T ₂ , T
The sum of ₃ is used in the calculation of the air-fuel ratio of this cycle, together with the pressure value immediately before each closing of this cycle.

Referring to FIG. 4, in the A / F evaluation device of FIG. 2, each cylinder C1 is detected from the injection signals of the crank angle sensor 37, the vacuum sensor 32, and the fuel injector 28.
The air-fuel ratio A / F at C4 is calculated one after another. Then, the upper and lower limits of the judgment level are set for the average value obtained from the latest four consecutive air-fuel ratios A / F including the latest air-fuel ratio A / F, and the upper and lower limits of the judgment level are set. The latest air-fuel ratio A / F is compared and the latest air-fuel ratio A / F is compared.
If is out of the range from the upper limit to the lower limit of the determination level, the malfunction trigger signal is output.

In this way, the air-fuel ratios A / F of the cylinders C1 to C4 are, in order, the four most recent air-fuel ratios A / F.
As long as the gasoline engine 21 continues to rotate, the calculation of the air-fuel ratio A / F and the determination of suitability are repeatedly executed indefinitely, and as a result, the four cylinders C1 to C4 are continuously connected. The air-fuel ratio A / F is calculated and appropriateness is determined for all the explosions that are repeatedly repeated.

In FIG. 5, at step 41, the timing immediately after the intake valves of the cylinders C1 to C4 start the closing operation is extracted, and the pressure value PM of the vacuum sensor 32 is taken in only at this timing. Therefore, in the air-fuel ratio A / F determination program, four pressure values P per two revolutions of the crankshaft of the gasoline engine 21 are set.
Only M is taken in, and the number of data to be handled is small compared to a normal fuel injector control program executed by taking in the pressure value of the vacuum sensor 32 at a sampling interval much shorter than this. Gasoline engine 2 even if a relatively small arithmetic element is used
High-speed processing capable of following the high-speed rotation of 1 is possible.

At step 42, the upper limit AF of the determination level is set.
The air-fuel ratio A / F is compared with H and the lower limit AFL.
Then, if the output level of the determination level deviates from the upper limit AFH to the lower limit AFL, the output state of the defect detection flag is set to 1 in step 44, and if it is within the range, the output state of the defect detection flag is set to 0 in step 43. .

In FIG. 6, E of the gasoline engine 21
Immediately after starting the gasoline engine 21 at time 0, the CU performs fuel supply in a slightly rich manner and executes the operation at a low air-fuel ratio A / F, but with a rise in the temperature of the cooling water and the cylinders C1 to C. Then, the fuel supply is gradually narrowed down, and the operation is shifted to the normal air-fuel ratio A / F. During this period, the absolute value of the air-fuel ratio A / F changes as shown in FIG. 6, but the upper limit judgment level AFH and the lower limit judgment level AFL also change accordingly, so that no malfunction detection flag is output.

However, if some disturbance occurs in the ECU of the gasoline engine 21 and an abnormal fuel injection time is calculated and executed, at least four combustion strokes before and after are performed.
The air-fuel ratio A / F is affected, and a protrusion 45 of the air-fuel ratio A / F is generated. At this time, the defect detection flag outputs 1.

[0056]

According to the air-fuel ratio measuring device of the first aspect, the independent air-fuel ratio can be accurately obtained for each of the plurality of cylinders of the internal combustion engine. Further, since the air-fuel ratio is calculated with a small number of data and a simple arithmetic operation, the air-fuel ratio can be obtained for each cycle of all cylinders of the internal combustion engine even with a relatively low speed arithmetic device. It can follow in real time even when the engine is rotating at high speed.

Further, since the state of the air-fuel ratio can be observed in real time and the influence of each parameter on the air-fuel ratio can be confirmed one by one, the necessary fine adjustment of the mutually influencing parameters of the internal combustion engine can be carried out. Even an inexperienced operator can make accurate adjustments in a short time.

The intake air amount may be corrected by the intake air temperature, as is done by the ECU of the gasoline engine of FIG. However, in order to more effectively utilize the feature that the number of data to be processed is narrowed down and the individual air-fuel ratios of all the explosions can be obtained for all of the plurality of cylinders, rather than correction of the absolute value by correction, Rather, it is preferable to choose a relative value comparison as done in the examples.

According to the internal combustion engine evaluation method of claim 2,
Whether or not the control state of the fuel injector in the internal combustion engine is appropriate can be identified in real time. Therefore, it is less likely that an abnormal state is overlooked and left unattended to damage the internal combustion engine. Further, even in an internal combustion engine in which a large number of sensors are complicatedly affected, the cause analysis of an abnormal state and the evaluation after repair can be accurately performed in a short time.

According to the determination device of the third aspect, since the air-fuel ratio is determined by using the pressure sensor originally installed in the internal combustion engine, it is possible to minimize the modification of the internal combustion engine and the addition of the sensor accompanying the mounting.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the invention of claim 1.

FIG. 2 is an explanatory view of a mounted state of the A / F evaluation device of the embodiment.

FIG. 3 is an explanatory diagram of a relationship between a cycle of each cylinder and fuel injection timing.

FIG. 4 is an explanatory diagram of a calculation flow of the embodiment,

FIG. 5 is a flowchart of an embodiment.

FIG. 6 is an explanatory diagram of a defect detection flag output.

FIG. 7 is an explanatory diagram of a configuration of a gasoline engine including a fuel injector.

[Explanation of symbols]

 10 Internal Combustion Engine 11 Fuel Injector 12 Cylinder 13 Time Measuring Means 14 Pressure Measuring Means 15 Computing Means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location F02D 41/36 A 8011-3G 45/00 368 F 7536-3G

Claims (3)

[Claims] 1. An air-fuel ratio for one cycle in at least one of a plurality of cylinders (12) of an internal combustion engine (10) connected to an internal combustion engine (10) having a fuel injector (11) can be calculated. In another air-fuel ratio measuring device, a pressure measuring unit (14) for detecting a pressure value in an intake pipe at a timing before closing of the intake valve in synchronization with the operation of the intake valve of the cylinder (12); In synchronization with the operation of the intake valve of (12), a time measuring means for obtaining an integrated value of the fuel injection time of the fuel injector (11) in the period from the previous closing of the intake valve to the current closing of the intake valve ( 13) and a value obtained by dividing the pressure value by the integrated value, the calculating means (1) for calculating the air-fuel ratio in the combustion immediately after the current valve closing.
5) An air-fuel ratio measuring device comprising: 2. A fuel injector provided in an air supply path for a plurality of cylinders, measuring means for measuring the amount of air sucked into the cylinder through the air path, and the fuel injector based on the measured air quantity. An internal combustion engine having a control means for calculating the operation time of, a method for evaluating the internal combustion engine for determining the suitability of the calculation, wherein the pressure output by a pressure sensor arranged on the cylinder side of the throttle valve in the air supply path is output. The value is measured at the timing before closing the intake valve of each cylinder, and for each cylinder, the cumulative value of the operating time of the fuel injector in the period from the previous closing of the intake valve to the current closing For each cylinder, the air-fuel ratio in one cycle of combustion is calculated based on a value obtained by dividing the pressure value by the integrated value, Evaluation method for an internal combustion engine, characterized in that temporal variation of the ratio is to generate a warning signal when exceeding the allowable range. 3. A fuel injector provided in an air supply path for a plurality of cylinders, a pressure sensor provided on a cylinder side of a throttle valve in the air path, and a plurality of cylinders based on a pressure value output by the pressure sensor. A determination device that is mounted on an internal combustion engine having a control unit that calculates an intake air amount and calculates an operation time of the fuel injector based on the air amount, and determines whether the calculation is appropriate. Measuring means for measuring the pressure value output by the sensor at the timing before closing the intake valve of each cylinder, and the operating time of the fuel injector in the period from the previous closing of the intake valve to the current closing Of the air-fuel for one cycle based on the value obtained by dividing the pressure value by the integrated value. Calculates a, and having a control means for generating a warning signal when the difference between the individual air-fuel ratio to the average value of the air-fuel ratio has exceeded the allowable range determining unit.