JPH06264795A - Fuel injection control device - Google Patents

Abstract

PURPOSE:To correct flow rate difference of each injector by detecting the flow rate difference of the injector in a fuel injection control device. CONSTITUTION:A fuel injection control means M1 controls a fuel amount injected by a plural number of injectors M3 to each cylinder of a multiple cylinder internal combustion engine M2. An injection amount variable means M4 varies a fuel injection amount of one injector of a plural number of the injectors M3 at a specified ratio. An air fuel ratio variation amount detection means M5 detects variation of the air fuel ratio detected by an air fuel ratio detection means 6 by variation of the fuel injection amount carried out by the injection amount variable means M4. A flow ratio detection means 7 detects respective flow ratios of a plural number of the injectors from a, variable amount of the fuel injection amount and variation of the air fuel ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device, and more particularly to a fuel injection control device for controlling the amount of fuel injected into each cylinder of a multi-cylinder internal combustion engine by a plurality of injectors.

[0002]

2. Description of the Related Art Conventionally, as described in Japanese Utility Model Laid-Open No. 60-90942, it is detected that the air-fuel ratio at the exhaust top dead center of each cylinder is reversed between rich and lean, and the abnormality of the injector of each cylinder is detected. There is a fuel injection control device that detects fuel supply and stops the supply of fuel when an abnormality is detected.

[0003]

In the above-mentioned conventional device, it is possible to judge whether the flow rate of the injector of each cylinder is too large or too small, but it cannot be judged how much it is too large or too small. There is a problem that it is not possible to detect and correct the flow rate difference between the injectors of the cylinders.

The present invention has been made in view of the above points,
By changing the fuel injection amount of each injector at a predetermined rate and detecting the amount of change in the air-fuel ratio, it is possible to detect the flow rate difference of each injector, and thus a fuel injection control device that can correct the flow rate difference of each injector is provided. The purpose is to provide.

Further, the fuel injection amount of each injector is increased or decreased from the injection amount of the feedback control to detect the increase or decrease of the fuel injection amount of the feedback control. It is an object of the present invention to provide a fuel injection control device capable of detecting the flow rate ratio of each injector and correcting the flow rate difference of each injector.

[0006]

FIGS. 1A and 1B show the principle of the present invention.

In FIG. 1A, fuel injection control means M
1 controls the amount of fuel injected into each cylinder of the multi-cylinder internal combustion engine M2 by a plurality of injectors M3.

The injection amount changing means M4 changes the fuel injection amount of one of the plurality of injectors M3 at a predetermined rate.

The air-fuel ratio change amount detecting means M5 detects the change amount of the air-fuel ratio quantitatively detected by the air-fuel ratio detecting means M6 by changing the fuel injection amount performed by the injection amount changing means.

The flow rate ratio detecting means M7 detects the flow rate ratio of each of the plurality of injectors from the variable amount of the fuel injection amount and the change amount of the air-fuel ratio.

In FIG. 1B, the air-fuel ratio detecting means M1
0 detects the air-fuel ratio.

The feedback control means M11 feedback-controls the fuel injection amount so that the air-fuel ratio becomes the stoichiometric air-fuel ratio.

The injection amount increasing / decreasing means M12 selects one of the plurality of injectors during the feedback control.
The fuel injection amount of one injector is increased by a predetermined amount from the injection amount of the feedback control, and the fuel injection amount of the remaining injectors is decreased by a predetermined amount from the injection amount of the feedback control to obtain a new injection amount of the feedback control.

The flow rate ratio detecting means M13 sequentially switches the selection of the injectors for increasing the predetermined amount by the injection amount increasing / decreasing means, and based on the increase / decrease amount of the fuel injection amount of the new feedback control at each selection, the injectors of the plurality of injectors are selected. Detect the flow rate ratio.

[0015]

In the present invention, the fuel injection amount of each injector is varied at a predetermined rate, and the flow rate ratio of each injector is detected by detecting the change amount of the air-fuel ratio during that period. It is possible to detect the flow rate difference between them, and further it is possible to correct the injection amount of each injector in the direction in which this flow rate difference disappears.

Further, in the present invention, since the fuel injection amount of each injector is increased / decreased from the injection amount of feedback control to detect the increase / decrease amount of the fuel injection amount of feedback control, the air-fuel ratio detecting means makes a quantitative measurement. It is not necessary to be able to perform, and it suffices if rich / lean detection necessary for feedback control can be detected.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 2 is a block diagram of an embodiment of the present invention. In the figure, the present embodiment shows an example in which the present invention is applied to a 4-cylinder 4-cycle spark ignition type internal combustion engine (engine) as the internal combustion engine 11. The engine 31 is controlled by the microcomputer 21 described later.

In FIG. 2, a surge tank 23 is provided downstream of the air cleaner 22 via a throttle valve 19. An intake air temperature sensor 24 that detects the intake air temperature is attached near the air cleaner 22, and a throttle opening sensor 25 that detects the opening of the throttle valve 19 is attached to the throttle valve 19. A diaphragm-type pressure sensor 26 is attached to the surge tank 23.

The surge tank 23 is connected to a combustion chamber 32 of an engine 31 via an intake manifold 29 and an intake port 30. An injector 20 is provided for each cylinder so that a part thereof projects into the intake manifold 29, and the injector 20 injects fuel into the air flow passing through the intake manifold 29.

The combustion chamber 32 is connected to a catalyst device 35 via an exhaust port 33 and an exhaust manifold 34. Further, reference numeral 36 is an ignition plug, which is provided so as to partially project into the combustion chamber 32. Further, 37 is a piston, which reciprocates vertically in the drawing.

The igniter 38 generates a high voltage and the distributor 39 distributes and supplies the high voltage to the ignition plug 36 of each cylinder. The rotation drive sensor 40 detects rotation of the shaft of the distributor 39 and detects, for example, 30
Microcomputer 21 outputs the engine rotation signal every ° C
Output to.

A water temperature sensor 41 is provided so as to penetrate the engine block 42 and partially project into the water jacket 42. The water temperature sensor 41 detects the water temperature of the engine cooling water and outputs a water temperature sensor signal (THW). Is output. Further, 43 is an oxygen concentration detection sensor (O ₂ sensor), which is arranged so as to project through the exhaust manifold 34 at the collecting portion of each cylinder or downstream thereof, and the oxygen concentration in the exhaust gas before entering the catalyst device 35. To detect.

The microcomputer 21 for controlling the operation of this embodiment has a hardware configuration as shown in FIG. 2, those parts which are the same as those corresponding parts in FIG. 2 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 3, the microcomputer 21 includes a central processing unit (MPU) 53 and a read only memory (ROM) 5 storing a processing program.
4. A random access memory (RAM) 55 used as a work area, a backup RAM 56 that retains data even after the engine is stopped, and a clock generator 57 that supplies the master clock to the MPU 53. The input / output port 59, the input port 60, and the output port 6 are connected to each other via the bus line 58.
1 and 62 are connected to each other.

Further, the microcomputer 21 outputs a pressure detection signal from the pressure sensor 26 taken out via the filter 65 and the buffer 66 in series, and an intake temperature detection signal from the intake temperature sensor 24 taken out via the buffer 67, The water temperature sensor signal (THW) taken out via the buffer 68 and the throttle opening signal from the throttle opening sensor 25 taken out via the buffer 79 are selectively output by the multiplexer 70, which outputs the A / D converter 71.
After being converted into a digital signal by, the signal is sent to the bus line 58 via the input / output port 59. The filter 65 is a filter for removing the pulsating component of the intake pipe pressure included in the output detection signal of the pressure sensor 26.

Thus, each input detection signal of the multiplexer 70 is sequentially selected and output by the multiplexer 70 under the control of the MPU 53, converted into a digital signal by the A / D converter 71, and then stored in the RAM 55. .

Further, the microcomputer 21 inputs the oxygen concentration detection signal from the O ₂ sensor 43 to the comparator 73 via the buffer 72, shapes the waveform here and supplies it to the input port 60, and the waveform shaping circuit 74. A signal obtained by waveform-shaping the detection signal from the rotation angle sensor 40 is supplied to the input port 60.

Further, the microcomputer 21 has drive circuits 75 and 76, supplies a signal from the output port 61 to the igniter 38 via the drive circuit 75, and has a down counter for the signal from the output port 62. It is configured to supply the injector 20 via the driving circuit 76.

Next, a first embodiment of the fuel injection control process executed by the microcomputer 21 will be described with reference to FIG. The fuel injection control process of FIG. 4 is part of the main routine.

In FIG. 4, in step 101, it is judged whether or not the O ₂ sensor 43 is activated, and if it is activated, in step 102 it is in a steady state in which there is little change in the rotational speed, or in the idle state. Determine if there is. Here, if it is a steady state or an idle state, step 10
At 3, it is determined whether the value of the counter T is greater than or equal to the predetermined value Tc. The predetermined value Tc is a value corresponding to, for example, one week or one month.

If T <Tc, step 104
Then, the counter T is incremented and the process ends. T
If ≧ Tc, the air-fuel ratio feedback control is stopped in step 105, the flow rate difference detection correction process described below is executed in step 106, and then the counter T is reset to 0 in step 107 and the process ends. .

That is, the flow rate difference detection correction process is performed in the steady state or idle state in which the O ₂ sensor is activated.
It is executed weekly or monthly.

FIG. 5 shows a flow chart of the first embodiment of the flow rate difference detection and correction processing executed in step 106. In the figure, in step 201, the cylinder number n is set to 1,
Reset the timer t to 0. Next, in step 202, n
The fuel injection amount of the No. cylinder is reduced by a predetermined minute amount, and in step 203, the value of the timer t is, for example, a predetermined value Δ of about 1 sec.
determines whether t ₀ or more, in the case of t <Delta] t ₀ injection amount returns to step 202 through step 205 described later is reduced in predetermined proportions physician. Step 2 if t ≧ Δt ₀
At 04, the detection signal of the O ₂ sensor 43 is read and stored in A _(n) , and the routine proceeds to step 202. When t <Δt _0, the routine proceeds to step 205, where it is judged whether or not the value of the timer t is equal to or more than the sum of a predetermined value Δt ₁ and Δt _{0 of} about several seconds, and t <
If Δt ₁ + Δt ₀ , the process proceeds to step 202, where t ≧ Δ
If t ₁ + Δt ₀ , the process proceeds to step 206.

In step 206, the detection signal of the O ₂ sensor 43 is read and stored in B _(n) . Then step 207
Then, the difference between B _(n) and A _(n) is calculated and stored in ΔO _(n) .
Then, in step 208, the difference ΔO _(n) is divided by the predetermined value Δt ₁ to calculate the slope K _(n) . After this, step 20
At step 9, the reduction of the nth cylinder is finished, and at step 210, it is confirmed that the detection signal of the O ₂ sensor 43 matches the target air-fuel ratio of the feedback control, and at step 211, the cylinder number is incremented and the timer t is set to 0. Reset to.

Next, at step 212, it is judged if the cylinder number n exceeds 4, and if n ≦ 4, the process returns to step 202 and steps 202 to 211 are repeated. As a result, as shown in FIG. 6, the predetermined time Δt of the injector of each cylinder is
₁ O ₂ sensor output change amount O ₍₁₎ ~O ₍₄₎ is obtained in a further variation of the O ₂ sensor output per unit time slope K ₍₁₎ ~K ₍₄₎ is calculated .

If n> 4 in step 212, step
Slope K at 213₍₁₎~ K_(Four)Calculate the average value of K_AVeThe case
Pay. After this, in step 214, the inclination K of each cylinder₍₁₎
~ K _(Four)Average slope K of each_AVeRatio to₍₁₎~ R
_(Four)Is obtained, and the process ends. This ratio R₍₁₎~ R_(Four)husband
Shows the flow rate ratio of the injector of each cylinder, and the ratio R
_(n)The larger the value, the larger the capacity of the injector.
It represents.

FIG. 7 shows a flowchart of the fuel injection process. This process is interrupted and executed at a predetermined crank angle for each cylinder. In the figure, in step 301, the pressure sensor 26
The basic injection amount Ta is calculated on the basis of the intake pipe pressure PM from the rotational speed NE, the rotational speed NE from the rotational angle sensor 40, and the like. Next, at step 302, the fuel injection time TAU is calculated by the following equation. TAU = Ta * Ka / R _(n) + Tv Here, Ka is a correction coefficient according to the operating state, R _(n) is the ratio of each cylinder obtained in step 214, and Tv is the invalid injection time.

The amount of fuel commensurate with the fuel injection time TAU calculated in the next step 303 is injected, and this processing ends.

In this way, the fuel injection amount of each injector is varied at a predetermined rate, and the flow rate ratio of each injector is detected by detecting the change amount of the air-fuel ratio during that period. The flow rate difference can be detected, and the injection amount of each injector can be corrected in the direction in which this flow rate difference disappears, and emission can be improved.

In the first embodiment, step 202
However, the fuel injection amount of each cylinder is reduced, but this may be increased.

Next, a second embodiment of the fuel injection control process executed by the microcomputer 21 will be described with reference to FIG. The fuel injection control process of FIG. 8 is part of the main routine.

In FIG. 4, in step 401, it is judged whether or not the O ₂ sensor 43 is activated, and if it is activated, in step 402 it is in a steady state in which there is little change in the rotational speed, or in the idle state. Determine if there is. Here, if it is a steady state or an idle state, step 40
At 3, it is determined whether the value of the counter T is greater than or equal to the predetermined value Td. The predetermined value Td is, for example, a value corresponding to several tens of minutes.

If T <Tc, step 404.
Then, the counter T is incremented and the process ends. T
If ≧ Tc, the flow rate difference detection correction process described later is executed in step 406, and thereafter, the counter T is detected in step 407.
Is reset to 0 and the processing ends.

That is, the flow rate difference detection correction process is executed every tens of minutes in the steady state or the idle state in which the O ₂ sensor is activated.

FIG. 9 shows a flowchart of the second embodiment of the flow rate difference detection / correction processing executed in step 406. In the figure, in step 501, the pattern number m is set to 1, and the timer t is reset to 0. Then step 502
Then, among the patterns 1 to 4 shown in FIG. 10A, the pattern designated by the pattern number m is selected to select each cylinder # 1 to #.
4 Increase or decrease the fuel injection time TAU. In the pattern 1, the TAUs of all the cylinders # 1 to # 4 are not increased or decreased, and in the pattern 2, the TAU of the first cylinder # 1 is increased by 3% and the TAU of the second cylinder # 2 is decreased by 3%. In each of the patterns 3 and 4, the TAU of the first cylinder is increased by 3% and the TAU of the third or fourth cylinder is decreased by 3% as in the pattern 2.

Next, at step 503, O₂Sensor 43
The stoichiometric air-fuel ratio
Then, in step S504, the feedback control is performed.
Read the fuel injection amount TAU. After this, step 505
And the value of the timer t is the predetermined time t ₀(T₀Is more than a few seconds)
Whether t <t₀If yes, go to step 502
Repeat steps 502-505, t ≧ t₀In the case of
Go to step 506.

In step 506, the average value of the fuel injection time TAU read during the time t ₀ is calculated, and this average value is set as the fuel injection time TAUm in the pattern m. Next, at step 507, the pattern number m is incremented by 1 and the timer t is reset to zero. Thereafter, in step 508, it is determined whether the pattern number m is 4 or more, and m ≦
If 4, then go to step 502 and steps 502-5
08 is repeated. As a result, TAU1 to TAU4 are obtained as shown in FIG. If m> 4, in step 509, each of TAU1 to TAU4 is divided by TAU1, and as shown in FIG. 10C, the flow rates of the injectors of the second to fourth cylinders based on the injector of the first cylinder. The ratios R (1) to R (4) are calculated, and the process ends.

In this case, R (1) = 1 because the first cylinder is the reference. The flow rate ratios R (1) to R (4) are reflected in the subsequent calculation of the fuel injection amount TAU of each cylinder,
And write it in the learning section. By the way, the reference cylinder need not be limited to the first cylinder, and the rate of increase or decrease in TAU is 3
Not limited to%, it may be set to, for example, 5%, which may be appropriately changed according to the engine model and operating conditions. Further, when the flow rate ratios R (1) to R (4) exceed a predetermined value (for example, ± 15%), the emission etc. may be adversely affected, so an alarm may be issued.

FIG. 11 shows a flow chart of a modification of the flow rate difference detection / correction processing executed in step 406. In the figure, the fuel injection amount TAU is calculated in step 600, the pattern number m is set to 1 in step 601, and the timer t is set.
Is reset to 0. Next, in step 602, as shown in FIG.
The pattern designated by the pattern number m is selected from the patterns 1 to 4 shown in (A) to increase or decrease the fuel injection time TAU of each of the cylinders # 1 to # 4. In Pattern 1, the TAU of No. 1 cylinder # 1 was increased by 3%, and No. 2, 3, and 4 cylinders # 2, #
Reduce TAU of # 3 and # 4 by 1%. In Pattern 2, the TAU of No. 2 cylinder # 2 was increased by 3%, and No. 1, 3, 4 cylinder #
Reduce the TAUs of # 1, # 3 and # 4 by 1%. In pattern 3, the TAU of # 3 is increased by 3% and the TAUs of the other # 1, # 2 and # 4 are decreased by 1%. Pattern 4 TA # 4
U is increased by 3%, and TAUs of the other # 1, # 2, and # 3 are decreased by 1%.

Next, at step 603, O₂Sensor 43
The stoichiometric air-fuel ratio
Then, in step S604, the feedback control is performed.
Read the fuel injection amount TAU. After this, step 605
And the value of the timer t is the predetermined time t ₀(T₀Is more than a few seconds)
Whether t <t₀If yes, go to step 602
Repeat steps 602-605, t ≧ t₀In the case of
Go to step 606.

In step 606, the average value of the fuel injection time TAU read during the time t ₀ is calculated, and this average value is set as the fuel injection time TAUm in the pattern m. Next, at step 607, the pattern number m is incremented by 1 and the timer t is reset to zero. Thereafter, in step 608, it is determined whether the pattern number m is 4 or more, and m ≦
If it is 4, the process proceeds to step 602 and steps 602 to 6
08 is repeated, and if m> 4, the process proceeds to step 609.

In step 609, the flow rate ratio R is calculated by the following equation.
(1) to R (4) are calculated.

(1 + 3/100) .K1 + (1-1 / 100) .K2 + (1-1 / 100) .K3 + (1-1 / 100) .K4 = 1 / TAU1 (1) (1- 1/100) ・ K1 + (1 + 3/100) ・ K2 + (1-1 / 100) ・ K3 + (1-1 / 100) ・ K4 = 1 / TAU2 ・ ・ ・ (2) (1-1 / 100) ・ K1 + (1-1 / 100) ・ K2 + (1 + 3/100) ・ K3 + (1-1 / 100) ・ K4 = 1 / TAU3 (3) (1-1 / 100) ・ K1 + (1-1 / 100) ) ・ K2 + (1-1 / 100) ・ K3 + (1 + 3/100) ・ K4 = 1 / TAU4 (4) From the above equations (1) to (4), the ratio of K1, K2, K3, K4 is Can be calculated. From this, the flow rate ratio R (m)
Is calculated.

R (m) = Km / {(K1 + K2 + K3 + K4) / 4} (5) However, Km is K1, K2, K3, K4.

After obtaining R (m) in step 609, the process ends.

In this modification, the deviation ratios K1 to K4 from the reference TAU are obtained and the flow rate ratio R (m) is calculated. This flow rate ratio R (m) is written in the learned value of the two-dimensional map based on the engine load and the rotational speed, and is reflected in the subsequent calculation of the fuel injection amount TAU of each cylinder.

In the first embodiment shown in FIG. 4, in order to obtain the signal waveform shown in FIG. 6, the O ₂ sensor 43 needs to be, for example, of the limiting current type capable of quantitative measurement. However, in the second embodiment shown in FIG. 8, the air-fuel ratio feedback control is performed and the correction amount TAU is obtained from the fuel injection amount TAU.
_{As the 2} sensor 40, for example, a material such as zirconia or titania that cannot be quantitatively measured can be used.

[0057]

As described above, according to the fuel injection control device of the present invention, the fuel injection amount of each injector is varied at a predetermined rate to detect the change amount of the air-fuel ratio, so that the difference in the flow rate of each injector is detected. It is possible to detect and to correct the flow rate difference between the injectors.

Further, since the fuel injection amount of each injector is increased / decreased from the injection amount of the feedback control to detect the increase / decrease amount of the fuel injection amount of the feedback control, the air-fuel ratio detecting means which cannot perform quantitative measurement is used. The flow rate ratio of the ejectors can be detected, and the flow rate difference between the ejectors can be corrected by this, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a block diagram of a microcomputer.

FIG. 4 is a flowchart of a fuel injection control process.

FIG. 5 is a flowchart of flow rate difference detection and correction processing.

FIG. 6 is a waveform diagram of an O ₂ sensor signal.

FIG. 7 is a flowchart of a fuel injection process.

FIG. 8 is a flowchart of a fuel injection control process.

FIG. 9 is a flowchart of flow rate difference detection and correction processing.

FIG. 10 is a diagram for explaining the process of FIG.

FIG. 11 is a flowchart of flow rate difference detection and correction processing.

FIG. 12 is a diagram for explaining the process of FIG. 11.

[Explanation of symbols]

M1 fuel injection control means M2 internal combustion engine M3, 20 injector M4 injection amount variable means M5 air-fuel ratio change amount detection means M6 air-fuel ratio detection means M7 flow ratio detection means 19 throttle valve 20 injector 21 microcomputer 25 throttle opening sensor 26 pressure sensor 36 Spark Plug 31 Engine 38 Igniter 41 Water Temperature Sensor 43 O ₂ Sensor

Claims (2)

[Claims] 1. A fuel injection control device for controlling an amount of fuel injected into each cylinder of a multi-cylinder internal combustion engine by a plurality of injectors, comprising an air-fuel ratio detecting means for quantitatively detecting an air-fuel ratio. Of the fuel injection amount of one of the injectors at a predetermined rate, and a change amount of the air-fuel ratio detected by the air-fuel ratio detecting device by changing the fuel injection amount performed by the injection amount changing means. Fuel injection characterized by having an air-fuel ratio change amount detecting means for detecting, and a flow rate ratio detecting means for detecting a flow rate ratio of each of the plurality of injectors from the variable amount of the fuel injection amount and the change amount of the air-fuel ratio. Control device. 2. An air-fuel ratio detecting means for detecting an air-fuel ratio, and a feedback control means for feedback-controlling a fuel injection amount so that the air-fuel ratio becomes a stoichiometric air-fuel ratio. In the fuel injection control device for controlling the amount of fuel injected by the injector, the fuel injection amount of one injector selected from the plurality of injectors during the feedback control is increased by a predetermined amount from the injection amount by the feedback control, and the remaining fuel injection amount is increased. The fuel injection amount of the injector is reduced by a predetermined amount from the fuel injection amount of the feedback control to obtain a new fuel injection amount of the feedback control, and the selection of the injector for increasing the fuel injection amount by the fuel injection amount increasing / decreasing means is sequentially switched. From the increase / decrease in the fuel injection amount of the new feedback control when selecting The fuel injection control apparatus characterized by comprising a flow rate detection means for detecting the flow rate of the injector respectively.