JP2921202B2 - Fuel control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquefied petroleum gas (LP)
Relates to combustion engine inner Ru using G) or the like as fuel, and more particularly to a fuel control apparatus which performs the fuel control.

[0002]

2. Description of the Related Art Conventionally, for example, an LPG internal combustion engine has been known in which an LPG fuel is supplied through a fuel passage to a venturi formed upstream of a throttle valve in an intake passage. In this LPG internal combustion engine, fuel and intake air are mixed by the venturi and supplied to each cylinder as a mixture.
In addition, there is provided a control valve which is opened and closed by using a step motor or the like as a driving source in the middle of the fuel passage, and the control valve is opened and closed to control the fuel supply amount.

[0003] In the above-described LPG internal combustion engine, when the throttle valve is fully opened, air column vibration increases due to the effect of the intake inertia effect in the intake passage. For this reason, even if the fuel passage area is kept constant by the fuel passage control valve, the fuel amount fluctuates due to the difference in engine speed due to the air column vibration near the throttle valve fully open, and the mixing supplied to each cylinder There is a problem that the air-fuel ratio of the gas greatly changes and adversely affects the air-fuel ratio control.

Accordingly, for example, Japanese Patent Application Laid-Open No. 56-154156 discloses
In Japanese Patent Application Publication No. JP-A-2006-115, there is disclosed a technique for selecting the size of a fuel passage in response to air column vibration of an intake passage. That is, in the technique of this publication, the ratio of the length of the intake passage to the length of the fuel passage is set to a value of "0.5,
-2.0 times ". As a result, the air column vibration of the LPG is generated also in the fuel passage, and the air column vibration in the intake passage and the fuel passage is adjusted to equivalent vibration, thereby suppressing the change in the air-fuel ratio.

[0005]

However, even in the prior art, when the intake passage is long and complicated, the effect of the intake inertia is enhanced. Fluctuations in the air-fuel ratio due to vibration could not be suppressed, and there was a limit to the correction of the air-fuel ratio. Further, the behavior and characteristics of air column vibration may be caused by a change in pressure in the intake passage and a change in intake pulsation due to a change in opening / closing speed of each cylinder intake valve correlated to the engine speed. I know it. Therefore, it has been difficult to accurately correct the fluctuation of the air-fuel ratio due to the vibration of the air column by setting the length of the fuel passage.

The present invention has been made in view of the above circumstances, and has as its object to provide an internal combustion engine capable of accurately correcting a change in air-fuel ratio due to air column vibration in an intake passage. An object of the present invention is to provide an engine fuel control device.

[0007]

To achieve the above object, according to the solution to ## in the present invention, as shown in FIG. 1, to supply the fuel gas to the intake passage M2 internal combustion engine M1, the fuel gas
Scan and the inner combustion engine as the air-fuel mixture by mixing the intake air M1
A fuel mixing means M3 supplied to a driving state detecting means M4 for the intake pressure detecting the operating condition of including the combustion engine M1 engine speed and the intake passage M2 internal combustion engine M1, the driving state detecting means M4 Supply amount calculating means M5 for calculating a fuel supply amount to be supplied to the intake passage M2 based on the detection result of
The fuel control system of combustion engine and a supply control means M6 for controlling the fuel supply of the intake passage M2 by the fuel mixing means M3 based on the calculation result of the supply amount calculation means M5, by the operating state detecting means M4 Running condition detected
It is determined from the state whether the air column is in an excessive vibration state in the intake passage M2.
Air column vibration state determination means M8 and its air column vibration state determination
It is determined by the means M8 that the air column is in an excessive vibration state.
At this time, the supply amount calculating means M depends on the air column vibration state.
Air column vibration correcting means M9 for correcting the calculation result by 5
And

[0008]

SUMMARY OF] According to the arrangement, as shown in FIG. 1, during operation of the internal combustion engine M1, including the intake pressure of the engine speed and the intake passage M2 operating state detecting means M4 inner combustion engine M1 An operation state of the internal combustion engine M1 is detected. The supply amount calculating means M5 calculates the amount of fuel to be supplied to the intake passage M2 based on the detection result. Further, based on the calculation result, the supply control means M6 controls the supply of fuel to the intake passage M2 by the fuel mixing means M3. From this, the mixture of air-fuel ratio in accordance with the fuel supply amount is supplied to the inner combustion engine M1, it is subjected to combustion.

At this time, the air column vibration state determination means M8
Absorption from the operation state detected by the operation state detection means M4.
It is determined whether or not the air column is in an excessive vibration state in the air passage M2. The air column vibration correcting means M9 is provided with an air column vibration state detecting means M
When it is determined that the air column is in an over-oscillation state according to 8,
The calculation result by the supply amount calculation means M5 is increased or decreased according to the air column vibration state .

Here, the behavior and characteristics of air column vibration in the intake passage M2 are determined by operating conditions such as a change in pressure in the intake passage M2 and a change in intake pulsation due to a difference in engine speed.
It is known to change depending on the state . Therefore, even when the amount of fuel actually supplied to the intake passage M2 fluctuates due to the air column vibration, the above-described air column vibration correction means M9 performs the above-described correction of the increase / decrease of the fuel supply amount . the amount of fuel to be a mixture supplied to the internal combustion engine M1 and the air-fuel ratio of the aim is supplied.

[0011]

EXAMPLES Hereinafter, it will be described in detail based on an embodiment embodying the fuel control device of the internal combustion engine that put the present invention in FIGS. 2 16.

FIG. 2 is a schematic configuration diagram showing an engine system to which a fuel control device for an LPG internal combustion engine in this embodiment is applied. LPG internal combustion engine using liquefied petroleum gas (LPG) as fuel (hereinafter referred to as "LPG engine")
Reference numeral 1 denotes a plurality of cylinders (only one cylinder is shown in FIG. 2), and the engine 1 includes an air cleaner 3 through an intake passage 2.
It is connected to the. Venturi 4 in the middle of intake passage 2
Is provided. A throttle valve 5 that opens and closes in response to operation of an accelerator pedal (not shown) is provided downstream of the venturi 4 in the intake passage 2. When the throttle valve 5 is opened and closed, the amount of intake air from the air cleaner 3 to the intake passage 2 is adjusted. Each cylinder of the LPG engine 1 is provided with a spark plug 6. On the other hand, in the middle of the exhaust passage 7 communicating with the LPG engine 1, a three-way catalyst 8 is provided.
Is provided. Further, a well-known exhaust gas recirculation device 9 is provided between the exhaust passage 7 and the intake passage 2.

An ignition signal distributed by a distributor 10 is applied to an ignition plug 6 provided for each cylinder of the LPG engine 1. The distributor 10 distributes the high voltage output from the igniter 11 to each spark plug 6 in synchronization with the crank angle of the LPG engine 1. The ignition timing of each ignition plug 6 is determined by the high voltage output timing from the igniter 11. The distributor 10 is provided with a rotation speed sensor 31 for detecting the rotation speed (engine speed) NE of the LPG engine 1 from the rotation of the rotor.

The venturi 4 of the intake passage 2 has an LP
One end of a main fuel passage 12 for supplying G as a main fuel is in communication. The other end of the main fuel passage 12 is connected to an LPG regulator 1 for adjusting LPG vaporization.
3 is communicated.

A fuel throttle valve 15 driven by a step motor 14 is provided in the main fuel passage 12.
The fuel mixing means is constituted by the main fuel passage 12 and the fuel throttle valve 15. The opening of the main fuel passage 12 is adjusted by controlling the drive of the fuel throttle valve 15. The amount of main fuel supplied to the engine 1 is adjusted.

On the upstream side of the fuel throttle valve 15, the base end of the main fuel passage 12 is connected to a secondary pressure reducing chamber 13 b of the LPG regulator 13. Also, the main fuel passage 12
In the vicinity of the base end of the LPG regulator 13, there is provided a slow fuel passage 16 that communicates with the primary pressure reducing chamber 13 a of the LPG regulator 13 and supplies the slow fuel for idling. In the middle of the slow fuel passage 16, near the junction with the main fuel passage 12, an idle adjust screw 13 c for slow fuel adjustment is provided.

During operation of the LPG engine 1,
Outside air is sucked from the air cleaner 3 through the intake passage 2. Also, at the time of inhalation of the outside air, Venturi 4 has LP
The main fuel from the G regulator 13 is led out through the main fuel passage 12, and the main fuel is mixed with the intake air.
The mixture is taken into the LPG engine 1. still,
The intake amount of the main fuel mixture in the LPG engine 1 is determined by the opening of the throttle valve 5.

On the other hand, at the downstream side of the throttle valve 5, an injector 17 for auxiliary fuel injection is provided.
Is provided. The injector 17 is connected to an auxiliary fuel passage 18 communicating with the slow fuel passage 16. Then, the injector 17 injects a part of the idle slow fuel sent from the primary pressure reducing chamber 13a of the LPG regulator 13 via the auxiliary fuel passage 18 into the intake passage 2 as auxiliary fuel. The injected auxiliary fuel and intake air are taken into the LPG engine 1. The LPG regulator 13 has a slow fuel passage 1.
A slow lock valve 20 driven by a solenoid 19 is provided to open and close the valve 6. The opening / closing of the slow lock valve 20 is controlled to perform a fuel cut or the like at the time of deceleration.

Accordingly, the LPG engine 1 takes in the main fuel mixture or the auxiliary fuel, explodes and burns to obtain a driving force, and then discharges the exhaust gas to the exhaust passage 7. Exhaust gas discharged from the LPG engine 1 to the exhaust passage 7 is purified while passing through the three-way catalyst 8, and is discharged to the outside. At the same time, part of the exhaust gas passing through the exhaust passage 7 is recirculated to the intake system by the exhaust gas recirculation device 9.

As an operating state detecting means for detecting the operating state of the LPG engine 1 and the like, in addition to the rotational speed sensor 31, the temperature THA of the outside air (intake temperature) drawn into the intake passage 2 from the air cleaner 3 is detected. An intake air temperature sensor 32 is provided. A throttle sensor 33 for detecting the opening (throttle opening) VL is provided near the throttle valve 5. Similarly, intake passage 2
Is provided with an intake pressure sensor 34 for detecting the pressure (intake pressure) PM of the intake air. The intake pressure sensor 34 also serves as an atmospheric pressure detecting means for detecting the intake pressure PM under a certain condition as the atmospheric pressure PA while detecting the intake pressure PM. Further, the LPG engine 1 is provided with a water temperature sensor 35 for detecting the cooling water temperature THW. On the other hand, the exhaust passage 7 is provided with an oxygen sensor 36 that detects the air-fuel ratio of the LPG engine 1 from the oxygen concentration in the exhaust gas discharged from the passage 7. Similarly, the exhaust passage 7 is provided with an exhaust gas temperature sensor 37 for detecting the temperature of the exhaust gas (exhaust gas temperature).

The step motor 14 of the fuel throttle valve 15, the solenoid 19 of the slow lock valve 20,
The injector 17 and the igniter 11 are electrically connected to an electronic control unit (hereinafter simply referred to as “ECU”) 38 that constitutes a supply amount calculation unit, a supply control unit, a pressure difference calculation unit, and an air column vibration correction unit. Also, this ECU 3
8, a rotation speed sensor 31, an intake air temperature sensor 32, a throttle sensor 33, an intake pressure sensor 34, a water temperature sensor 35,
The oxygen sensor 36 and the exhaust gas temperature sensor 37 are connected to each other. Then, the ECU 38 detects each of these sensors 31
37, the step motor 14, the solenoid 19, the injector 17, the igniter 11, and the like are suitably controlled.

Next, the configuration of the ECU 38 will be described with reference to the block diagram of FIG. The ECU 38 includes a central processing unit (CPU) 41, a read-only memory (ROM) 42 in which a predetermined control program and the like are stored in advance, and a random access memory (R) that temporarily stores calculation results of the CPU 41 and the like.
AM) 43, a backup RAM 44 for storing data stored in advance, and the like, and a logical operation circuit in which these components are connected to an external input circuit 45, an external output circuit 46, and the like via a bus 47.

The external input circuit 45 includes a rotational speed sensor 31, an intake air temperature sensor 32, a throttle sensor 33,
An intake pressure sensor 34, a water temperature sensor 35, an oxygen sensor 36, an exhaust temperature sensor 37, and the like are connected to each other. Then, the CPU 41 transmits each sensor 3 via the external input circuit 45.
The detection signals output from 1 to 37 are read as input values. The CPU 41 suitably controls the igniter 11, the step motor 14, the injector 17, the solenoid 19, and the like connected to the external output circuit 46 based on these input values.

Next, the processing operation of the air-fuel ratio control of the LPG engine 1 executed by the aforementioned ECU 38 will be described with reference to the flowcharts shown in FIGS. FIG. 4 is a flowchart showing a "main routine" process related to the opening / closing control of the fuel throttle valve 15 and the opening / closing control of the injector 17 among the processes executed by the ECU 38. Be executed.

When the process proceeds to this routine, first, at step 100, the process of the "ST calculation routine" for calculating the target number ST of the step motor 14 in the fuel throttle valve 15 is executed.

Next, at step 200, a "FAF calculation routine" for calculating an air-fuel ratio correction coefficient FAF for air-fuel ratio feedback control is executed.
Subsequently, in step 300, a process of a “learning routine” for further improving the control accuracy to the stoichiometric air-fuel ratio is executed.

Further, in step 400, the processing of a "TAU calculation routine" for calculating the injection time TAU of the injector 17 is executed, and thereafter the processing of the "main routine" is temporarily terminated.

Next, the processing of steps 100, 200, 300, and 400 in the aforementioned "main routine" will be described in detail. First, step 100
Of the “ST calculation routine” in step 10
The subroutine is called at 0 and executed, as shown in the flowchart of FIG.

When this processing is started, first, in step 1
At 10, the basic step number S of the step motor 14 in the fuel throttle valve 15 is calculated. The basic step number S is obtained by referring to a three-dimensional map (not shown) stored in the ROM 42 in advance based on the engine speed NE and the intake pressure PM obtained by the detection of the rotation speed sensor 31 and the intake pressure sensor 34. The basic step number S of the three-dimensional map is set in advance so that the main fuel supplied through the main fuel passage 12 is on the lean side.

Next, at step 120, the column vibration correction step number SV for correcting the basic step number S
Load L. This air column vibration correction step number SVL
Is a value for correcting a change in the air-fuel ratio due to air column vibration in the intake passage 2, and is calculated according to the flowchart of the "SVL calculation routine" shown in FIG.

Here, the flowchart of the "SVL calculation routine" will be described. When the processing of this routine is started, first, in step 181, the atmospheric pressure PA, the intake pressure PM, and the engine speed NE are loaded based on the detected values of the intake pressure sensor 34 and the rotation speed sensor 31, respectively.

Next, at step 182, the difference between the loaded atmospheric pressure PA and the intake pressure PM is calculated, and the calculation result is set as the pressure difference PX. Subsequently, at step 183, the calculated pressure difference P
It is determined whether X is larger than a predetermined reference value α. If the pressure difference PX is larger than the reference value α, in step 184, the number of air column vibration correction steps SVL is calculated from the pressure difference PX and the engine speed NE, and the subsequent processing is temporarily terminated.

Here, the number of air column vibration correction steps SV
L is experimentally determined in advance in accordance with the relationship between the pressure difference PX and the engine speed NE as shown in FIG.
2 with reference to a map stored in advance. In this map, as the pressure difference PX is smaller, that is, when the atmospheric pressure PA and the intake pressure PM are equal, the correction amount of the column vibration correction step number SVL increases, and as the pressure difference PX increases, the column vibration correction increases. The correction amount of the step number SVL is set to be small. In FIG. 7, "PX = 0"
And the case of “PX = 40”.
Further, as can be seen from FIG. 7, the air column vibration correction step number SVL is set as a correction amount on the plus side or the minus side depending on the region of the engine speed NE. This is because the behavior and characteristics of air column vibration in the intake passage 2 are caused by a change in pressure in the intake passage 2 and a change in intake pulsation due to a change in the opening / closing speed of each cylinder intake valve correlated to the engine speed NE. This is a setting made in view of the fact that

On the other hand, in step 183, the pressure difference P
If X is not greater than the reference value α, step 18
In 5, the number of air column vibration correction steps SVL is set to "0", and the subsequent processing is temporarily terminated.

The atmospheric pressure PA used in the "SVL calculation routine" is calculated according to the flowchart of the "PA calculation routine" shown in FIG.
When the processing of this routine is started, first, in step 19
1, the intake pressure sensor 34, the throttle sensor 33
Pressure PM, throttle opening VL based on the detected values of
To load. Then, in step 192, the throttle opening VL is set to a predetermined value (“50 °” in this embodiment).
It is determined whether or not the intake pressure PM is larger than the atmospheric pressure PA, and the intake pressure PM is set as the atmospheric pressure PA in step 193, and the subsequent processing is temporarily terminated.

As described above, the air column vibration correction step number SVL is obtained. Returning to the description of the “ST calculation routine” in FIG. 5 again, in step 130, the intake temperature correction coefficient FTHA is calculated. This calculation is
Based on the intake air temperature THA obtained by the detection of the intake air temperature sensor 32, the process is performed by referring to a two-dimensional map stored in the ROM 42 in advance.

In step 140, a water temperature correction coefficient FTHW is calculated. This calculation is based on the cooling water temperature THW obtained by the detection of the
2 with reference to a two-dimensional map stored in advance.

Further, in step 150, a feedback correction coefficient FAFST for performing feedback control of the step motor 14 of the fuel throttle valve 15 is loaded. This feedback correction coefficient FAFST is obtained in the processing of the “FAF calculation routine” described later.

Subsequently, in step 160, a learning correction value KG for correcting the basic step number S is loaded. This learning correction value KG is obtained in the processing of a “learning routine” described later.

In step 170, the intake temperature correction coefficient FTHA, the water temperature correction coefficient FTHW, and the sum of the basic step number S and the air column vibration correction step number SVL are calculated.
Feedback correction coefficient FAFST and learning correction value KG
Are respectively multiplied to correct the basic step number S.
Further, the calculation result is set as the target step number ST for the step motor 14, and the subsequent processing is temporarily ended.

Next, the processing of the "FAF calculation routine" will be described. This “FAF calculation routine” is a process that is executed by being called as a subroutine in step 200, and is shown in the flowcharts of FIGS.

First, in step 201, it is determined whether a feedback (F / B) control condition is satisfied. In this embodiment, it is determined based on the detection signals of the water temperature sensor 35 and the rotation speed sensor 31 whether or not the condition that the cooling water temperature THW is sufficiently high and the engine rotation speed NE is not higher than necessary is satisfied. Is done.

Here, if the condition of the feedback control is satisfied, in step 202, the oxygen sensor 3
It is determined whether the air-fuel ratio (A / F) is rich based on the detection signal of No. 6. Then, when the air-fuel ratio is rich, the processing of the following steps 203 to 208 is executed.

That is, in step 203, when the process of the "FAF calculation routine" is executed in the previous control cycle, it is determined whether or not the air-fuel ratio is lean by the air-fuel ratio flag YOX. Here, the air-fuel ratio flag Y
If OX is “0”, the process proceeds to step 204 assuming that the air-fuel ratio has changed from lean to rich based on the determinations in steps 202 and 203.

In step 204, the average air-fuel ratio correction coefficient FA during the air-fuel ratio feedback control is determined.
Calculate FAV. This average air-fuel ratio correction coefficient FAFAV
Is calculated based on the current air-fuel ratio correction coefficient FAF and the old air-fuel ratio correction coefficient FAF obtained when the previous time was changed from rich to lean.
This is performed by calculating an arithmetic mean with zero.

Next, at step 205, the air-fuel ratio correction coefficient FAF is set as the previous old air-fuel ratio correction coefficient FAF0. Subsequently, in step 206, a result obtained by subtracting the predetermined skip amount a from the air-fuel ratio correction coefficient FAF is set as a new air-fuel ratio correction coefficient FAF.

In step 207, since the current air-fuel ratio is rich, the learning timing flag YK
Set G to "1". This learning timing flag Y
KG is used to determine whether or not it is time to learn the learning correction value KG, which will be described later.

Further, in step 208, the air-fuel ratio is rich, so that the air-fuel ratio flag YOX is set to "1". On the other hand, when the air-fuel ratio flag YOX is “1” in step 203, the processing of steps 209 to 211 is executed. Here, when the process proceeds to step 209 according to the determination in steps 202 and 203, it indicates that the air-fuel ratio is maintaining a rich state.

That is, in step 209, it is determined whether or not the timer counter CNT1 exceeds a constant c.
The timer counter CNT1 is a value that has a shorter cycle than the processing of the “FAF calculation routine” and is added in the processing of a “compare interrupt routine” described later. here,
If the timer counter CNT1 exceeds the constant c, in step 210, the result obtained by subtracting the constant b from the air-fuel ratio correction coefficient FAF is set as a new air-fuel ratio correction coefficient FAF.

Then, in step 211, after clearing the timer counter CNT1 to "0", the process proceeds to step 212. If it is determined in step 209 that the timer counter CNT1 is equal to or smaller than the constant c, the process directly proceeds to step 212. That is, step 209
In the processing of Step 211, the value of the air-fuel ratio correction coefficient FAF is subtracted by a constant b every predetermined time.

After step 208, step 209 or step 211, in step 212, it is determined whether or not the injector feedback determination flag YFBINJ is "1". This flag YFBIN
J indicates whether or not the feedback control of the injector 17 should be executed, and “JFBI” shown in FIG.
NJ calculation routine ".

Here, the flowchart of the "YFBINJ calculation routine" will be described first. When the processing of this routine is started, first, in step 251, a predetermined constant j is subtracted from a predetermined pressure PMVL indicating the intake pressure when the opening of the throttle valve 5 is large, and the result of the subtraction is referred to as a high load determination pressure PMG. Set as

Next, in step 252, it is determined whether or not the throttle opening VL detected by the throttle sensor 33 is larger than a predetermined value ("50 °" in this embodiment). Here, if the throttle opening VL is not larger than the predetermined value, the process directly proceeds to step 254.

If the throttle opening VL is larger than the predetermined value in step 252,
3, the intake pressure P detected by the intake pressure sensor 34
M is set as the next predetermined pressure PMVL, and step 2
Move to 54.

Then, step 252 or step 25
In step 254 after shifting from 3, it is determined whether or not the intake pressure PM detected by the intake pressure sensor 34 is smaller than the previously calculated high load determination pressure PMG. That is,
It is determined whether the load is not high. If the intake pressure PM is smaller than the high load determination pressure PMG, the process proceeds to step 255 on the assumption that the load is not the high load state but the medium light load state. Then, in step 255,
The injector feedback determination flag YFBINJ is set to “1”, and the subsequent processing is temporarily terminated.

On the other hand, if the intake pressure PM is not smaller than the high load determination pressure PMG in step 254, it is determined that the load is high, and in step 257, the injector feedback determination flag YFBI is determined.
NJ is reset to "0", and the subsequent processing is temporarily ended.

Returning again to the processing of the "FAF calculation routine" in FIG. 9, if it is determined in step 212 that the injector feedback determination flag YFBINJ is "1",
Assuming that the load is in the middle to light state, the process proceeds to step 213 in order to execute the feedback control of the injector 17. In step 213, the feedback correction coefficient FA for the step motor 14 of the fuel throttle valve 15
Set the value of FST to "1.0".

In step 214, the air-fuel ratio correction coefficient FAF calculated in step 206 or step 210 is set as a feedback correction coefficient FAFINJ for the injector 17, and the subsequent processing is temporarily terminated.

On the other hand, if it is determined in step 212 that the injector feedback determination flag YFBINJ is not "1", that is, if the load is high, step 2
Move to 15. In step 215, the air-fuel ratio correction coefficient FAF calculated in step 206 or step 210 is set as a feedback correction coefficient FAFST for the step motor 14 of the fuel throttle valve 15.

In step 216, the feedback correction coefficient FAFINJ for the injector 17 is set to "1.0", and the subsequent processing is temporarily terminated. Note that the processing in steps 203 to 211 described above is processing when the air-fuel ratio is rich, and is processing for reducing the air-fuel ratio correction coefficient FAF. In contrast to this processing, the processing in steps 221 to 229 shown in the flowchart of FIG. 10 is a processing when the air-fuel ratio is lean, and is a processing for increasing the air-fuel ratio correction coefficient FAF.

That is, if the air-fuel ratio is lean in step 202, the process proceeds to step 221. In step 221, the air-fuel ratio flag YOX is set to "1".
Is determined. Air-fuel ratio flag YOX is "1"
In the case of, the process proceeds to step 222 assuming that the air-fuel ratio has switched from rich to lean,
In the same manner as in the processing in step 204 described above, the average air-fuel ratio correction coefficient F during the air-fuel ratio feedback control
Calculate AFAV.

Subsequently, at step 223, the value of the air-fuel ratio correction coefficient FAF is set as the old air-fuel ratio correction coefficient FAF0. In step 224, the result of adding the skip amount a to the air-fuel ratio correction coefficient FAF is set as a new air-fuel ratio correction coefficient FAF.

In step 225, the learning timing flag YKG is set to "1". And
In step 226, it is determined that the air-fuel ratio is lean, and the air-fuel ratio flag YOX is reset to “0”.
Is performed.

If it is determined in step 221 that the air-fuel ratio flag YOX is "0", the processing in steps 227 to 229 is executed. Here, step 2
When the process proceeds from step 21 to step 227, it indicates that the air-fuel ratio is maintaining a lean state.

At step 227, it is determined whether or not the above-mentioned timer counter CNT1 exceeds a constant c.
Here, when the timer counter CNT1 exceeds the constant c, in step 228, the air-fuel ratio correction coefficient FAF
The result of adding the constant b to the air-fuel ratio correction coefficient FAF
Set as

Then, in step 229, after clearing the timer counter CNT1 to "0", the process proceeds to step 212, and the processing of steps 212 to 216 is executed.

If it is determined in step 227 that the timer counter CNT1 is equal to or smaller than the constant c, the flow directly proceeds to step 212. That is, the processing in steps 227 to 229 is the opposite of the processing in steps 209 to 211 described above, and is a processing for increasing the value of the air-fuel ratio correction coefficient FAF by a constant b every predetermined time.

As shown in FIG. 9, when the condition of the feedback control is not satisfied in step 201, the process proceeds to step 230. Then, in step 230, the values of the air-fuel ratio correction coefficient FAF and the old air-fuel ratio correction coefficient FAF0 are set to "1". Thereafter, the process proceeds to step 212, and in the processing of steps 212 to 216, the feedback correction coefficient FAFST for the step motor 14 or the feedback correction coefficient FAFINJ for the injector 17 is determined using the air-fuel ratio correction coefficient FAF.

Next, a "learning routine" executed in step 300 in the processing of the "main routine" described above.
Will be described with reference to the flowchart of FIG. The process of the “learning routine” is executed by calling a subroutine in step 300.

When the processing of this routine is started, first, at step 310, the learning timing flag YKG
Is determined to be “1”. If the learning timing flag YKG is not "1", the process directly proceeds to step 320, where the learning timing flag YKG is set to "0", and the subsequent processing is temporarily terminated. That is, the following process is executed only when the learning timing flag YKG is “1”, that is, only when the air-fuel ratio is switched from rich to lean or from lean to rich.

If the learning timing flag YKG is "1" in step 310,
At 30, it is determined whether or not the injector feedback determination flag YFBINJ is "1", that is, whether or not the vehicle is in a medium / light load state. Here, the determination flag YFB
If INJ is “1”, the process proceeds to step 340 assuming that the vehicle is in the medium / light load state, and
0, 360, and 320 are executed.

That is, in step 340, “FA
The magnitude of the value of the average air-fuel ratio correction coefficient FAFAV obtained in the processing of the “F calculation routine” is determined. And
In step 340, the average air-fuel ratio correction coefficient FA
If the FAV is "1", it is assumed that the actual air-fuel ratio is the stoichiometric air-fuel ratio, and the learning timing flag YKG is reset to "0" at step 320, and the subsequent processing is temporarily terminated.

If it is determined in step 340 that the average air-fuel ratio correction coefficient FAFAV is greater than "1", then in step 350, a learning correction value KG corresponding to the intake pressure PM at that time is added by a constant i. Then, in step 320, the learning timing flag YKG is reset to "0", and the subsequent processing is temporarily terminated.

Further, when the average air-fuel ratio correction coefficient FAFAV is smaller than "1" in step 340,
In step 360, a constant i is subtracted from the learning correction value KG. Then, in step 320, the learning timing flag YKG is reset to "0", and the subsequent processing is temporarily terminated.

As described above, steps 340, 3
By executing a series of processes in 50, 360, and 320 each time the air-fuel ratio switches between lean and rich, the learning correction value KG is increased or decreased by a constant i, and eventually becomes an optimal value for the intake pressure PM at that time. . Then, by using the learning correction value KG, in step 170 of the “ST calculation routine”, the target step number ST in a medium / light load state, that is, during normal operation or the like is calculated, and the “TAU calculation routine” described later is performed. In step 460, the target injection time TAU in idle operation or the like is calculated.

On the other hand, if the injector feedback determination flag YFBINJ is not "1" in step 330, that is, if the load is high, the process directly proceeds to step 320 without calculating the learning correction value KG. At 320, the learning timing flag YKG is reset to "0", and the subsequent processing is temporarily terminated.

Next, the processing of the “TAU calculation routine” executed in step 400 in the processing of the aforementioned “main routine” will be described. The processing of the “TAU calculation routine” is a processing that is executed by a subroutine call in step 400, and is shown in the flowchart of FIG.

When the processing of this routine is started, first, at step 410, a basic injection time TAUBSE is calculated. The basic injection time TAUBSE is obtained by referring to a three-dimensional map stored in the ROM 42 in advance based on the values of the engine speed NE and the intake pressure PM detected by the rotation speed sensor 31 and the intake pressure sensor 34.

Next, at step 420, the feedback correction coefficient FAFINJ for the injector 17 calculated in the above-mentioned "FAF calculation routine".
To load.

In step 430, the ROM 42 is determined based on the intake air temperature THA detected by the intake air temperature sensor 32.
The intake air temperature correction coefficient FTHAI is calculated with reference to the two-dimensional map stored in advance in FIG.

Further, at step 440, based on the cooling water temperature THW detected by the water temperature sensor 35, the ROM 4
2, a water temperature correction coefficient FTHWI is calculated with reference to a two-dimensional map stored in advance.

Subsequently, at step 450, the learning correction value K obtained by the above-described "learning routine" processing.
Load G. Then, in step 460,
The intake temperature correction coefficient FTHAI, the water temperature correction coefficient FTHWI, and the feedback correction coefficient FAF for the injector 17 are added to the previously calculated basic injection time TAUBSE.
The basic injection time TAUBSE is corrected by multiplying each of the INJ and the learning correction value KG, and the calculation result is set as a target injection time TAU for opening / closing control of the injector 17. Then, after executing the processing of step 460, the processing of this routine is temporarily terminated.

Using the target number of steps ST and the target injection time TAU obtained as described above, how to drive and control the step motor 14 and the injector 17 will be described with reference to the flowcharts of FIGS. Will be described.

FIG. 14 shows a "capture interrupt routine".
This is the process. When the process of this routine is started, first, at step 500, the engine speed NE is calculated based on the detection signal of the speed sensor 31.

Next, at step 510, the injector 17 is operated based on the calculated engine speed NE.
It is determined whether or not it is the injection timing. Here, if it is not the injection timing of the injector 17, the subsequent processing is once ended as it is.

If it is determined in step 510 that the injection timing of the injector 17 has been reached, step 52
At 0, energization of the injector 17 is started to open the injector 17.

Further, in step 530, based on the target injection time TAU described above, the power supply end time of the injector 17 is set, and the subsequent processing is temporarily terminated. FIG. 15 shows the processing of the "compare interrupt routine", which is executed at a relatively short predetermined time interval.

When the processing of this routine is started, first, in step 600, it is determined whether or not it is the timing of the energization end time set in step 530 in the processing of the aforementioned “capture interrupt routine”. Here, if it is not the timing, the process directly proceeds to step 620.

If it is determined in step 600 that the current is the end time of the energization, in step 610, the energization of the injector 17 is terminated, the injector 17 is closed, and the routine proceeds to step 620.

In step 620 after shifting from step 600 or step 610, it is determined whether or not it is the control timing of the step motor 14 determined in the processing described later. Here, if the control timing is not reached, the subsequent processing is once ended as it is.

On the other hand, if it is the control timing of the step motor 14, in step 630, the processing of the "step motor control routine" is executed. The processing of this "step motor control routine" is shown in the flowchart of FIG. 16, and is executed by calling a subroutine in step 630. When the processing of this routine is started, first, in step 631, the current step number SNOW representing the current step number of the step motor 14 is loaded. This current step number SNO
W is a value written to the backup RAM 44 when the CPU 41 outputs a rotation command value to the step motor 14 via the external output circuit 46.

In step 632, "ST
Target step number ST obtained in the process of "calculation routine"
To load. Then, in step 633, the loaded current step number SNOW and the target step number ST
Compare with. In steps 633 to 637, a process of converging the current step number SNOW indicating the step number of the step motor 14 to the target step number ST is performed.

That is, if the target step number ST and the current step number SNOW are equal in step 633, there is no need to drive the step motor 14, and the subsequent processing is once ended as it is.

If the target step number ST is larger than the current step number SNOW in step 633, a forward rotation command is output to the step motor 14 to increase the step number of the step motor 14 in step 634. Then, the motor 14 is rotated forward by one step.

Subsequently, in step 635, the current step number SNOW is incremented by "1", and the subsequent processing is temporarily terminated. Further, in step 633, if the target step number ST is smaller than the current step number SNOW, in step 636, a reverse rotation command is output to the step motor 14 to reduce the step number of the step motor 14, and 14 is rotated in reverse by one step.

Subsequently, in step 637, the current step number SNOW is decremented by "1", and the subsequent processing is temporarily terminated. Then, by repeatedly executing the series of steps 633 to 637 described above, the number of steps of the step motor 14 is made to converge to the target number of steps ST.

After the processing of the "step motor control routine" is completed as described above, the processing returns to the flowchart of FIG. 15, and in step 640, the next control timing is set. This control timing is determined in step 6
20 is used for the determination, for example, a time obtained by adding a certain time to the current time.

Thereafter, at step 650, the value of the timer counter CNT1 is incremented by "1", and the subsequent processing is temporarily terminated. As described in detail above, according to the fuel control apparatus for an LPG internal combustion engine in this embodiment, in the processing of the “SVL calculation routine” shown in FIG. 6, the pressure difference P between the atmospheric pressure PA and the intake pressure PM is obtained.
The air column vibration correction step number SVL is calculated from the relationship between X and the engine speed NE. Then, in the processing of the "ST calculation routine" shown in FIG. 5, the sum of the air column vibration correction step number SVL and the basic step number S is added to the intake air temperature correction coefficient FTHA, the water temperature correction coefficient FTHW, the feedback correction coefficient FAFST, and the learning. The basic step number S is corrected by multiplying each of the correction values KG,
A target step number ST for controlling the drive of the step motor 14 is set. Here, the number of air column vibration correction steps SVL is a value for correcting the fluctuation of the air-fuel ratio due to the air column vibration in the intake passage 2, and in consideration of the behavior of the air column vibration and its characteristics, the pressure difference PX and the pressure difference PX It is experimentally determined according to the relationship with the engine speed NE. That is, the number of air column vibration correction steps SVL is appropriately set in accordance with the characteristics of air column vibration caused by a change in pressure in the intake passage 2 and a change in intake pulsation correlated with the engine speed NE. .

Therefore, even if the air column vibration changes due to the difference in the engine speed NE, the target step number ST is appropriately corrected by the air column vibration correction step number SVL corresponding to the change, and the stepping motor 14 is controlled. can do. As a result, the fuel throttle valve 15 is properly opened, and the main fuel passage 12 supplies the intake passage 2 with an appropriate amount of main fuel corrected in accordance with the fluctuation of the air column vibration.
To each cylinder.

As a result, the fluctuation of the air-fuel ratio due to the air column vibration in the intake passage 2 can be corrected with high accuracy, so that the fluctuation of the air-fuel ratio can be suppressed and the appropriate air-fuel ratio control can be performed. Furthermore, as a result, the output of the LPG engine 1 can be stabilized to improve drivability, and deterioration of exhaust emissions can be prevented.

In this embodiment, the influence of air column vibration can be eliminated by correcting the supply amount of the main fuel based on the air column vibration correction step number SVL obtained by the calculation as described above. 2 and the shape of the main fuel passage 12
There is no need to worry about the selection and setting of dimensions. Therefore, the shape of the intake system including the intake passage 2 and the main fuel passage 12
The degree of freedom in dimension design can be increased. As a result, even in a long and complicated intake system, it is possible to remove the influence of the air column vibration and perform an appropriate air-fuel ratio correction.

Note that the present invention is not limited to the above-described embodiment, and may be implemented as follows by appropriately changing a part of the configuration without departing from the spirit of the invention. (1) In the above embodiment, the intake pressure sensor 34 is also used as the atmospheric pressure detecting means, but a special pressure sensor for detecting the atmospheric pressure may be provided.

(2) In the above-described embodiment, the number of air column vibration correction steps SVL obtained from the relationship between the pressure difference PX between the atmospheric pressure PA and the intake pressure PM and the engine speed NE is added to the basic step number S. Was adjusted to increase or decrease
The air column vibration correction coefficient obtained from the relationship between the pressure difference PX between the atmospheric pressure PA and the intake pressure PM and the engine speed NE may be multiplied by the basic step number S to perform increase / decrease correction. May be appropriately changed.

[0104]

As described in detail above, according to the present invention,
Such as the behavior and the characteristics of the air column vibration in the intake passage, the gas
Since the amount of fuel to be supplied to the intake passage is increased or decreased according to the column vibration state, it is possible to accurately correct fluctuations in the air-fuel ratio due to air column vibration in the intake passage, thereby improving drivability. It is possible to achieve an excellent effect that it is possible to prevent deterioration of exhaust emission.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram illustrating a basic conceptual configuration of the present invention.

FIG. 2 is an LPG according to an embodiment of the present invention;
It is a schematic structure figure showing an engine system.

FIG. 3 is a block diagram illustrating a configuration of an electronic control device according to one embodiment.

FIG. 4 is a flowchart illustrating a “main routine” executed by the electronic control unit in one embodiment.

FIG. 5 is a flowchart illustrating an “ST calculation routine” executed by the electronic control unit in one embodiment.

FIG. 6 is a flowchart illustrating an “SVL calculation routine” executed by the electronic control unit in one embodiment.

FIG. 7 is a diagram illustrating a map experimentally determined in advance according to a relationship between a pressure difference between an atmospheric pressure and an intake pressure and an engine speed in one embodiment.

FIG. 8 is a flowchart illustrating a “PA calculation routine” executed by the electronic control unit in one embodiment.

FIG. 9 is a flowchart illustrating a “FAF calculation routine” executed by the electronic control unit in one embodiment.

FIG. 10 is a flowchart illustrating a “FAF calculation routine” executed by the electronic control unit in one embodiment.

FIG. 11 is a flowchart illustrating a “YFBINJ calculation routine” executed by the electronic control unit in one embodiment.

FIG. 12 is a flowchart illustrating a “learning routine” executed by the electronic control unit in one embodiment.

FIG. 13 is a flowchart illustrating a “TAU calculation routine” executed by the electronic control unit in one embodiment.

FIG. 14 is a flowchart illustrating a “capture interrupt routine” executed by the electronic control unit in one embodiment.

FIG. 15 is a flowchart illustrating a “compare interrupt routine” executed by the electronic control unit in one embodiment.

FIG. 16 is a flowchart illustrating a “step motor control routine” executed by the electronic control unit in one embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... LPG engine, 2 ... Intake passage, 12 ... Main fuel passage, 14 ... Step motor, 15 ... Fuel throttle valve (12,
Reference numeral 15 and the like constitute fuel mixing means), 31: a rotational speed sensor, 33: a throttle sensor, 34: an intake pressure sensor (31, 33, 34, etc. constitute operating state detecting means, and 3
Numeral 4 denotes an atmospheric pressure detecting means), 38... ECUs constituting supply amount calculating means, supply controlling means, pressure difference calculating means and air column vibration correcting means.

Claims (1)

(57) [Claims] 1. A within the fuel gas supplied to the intake passage of the combustion engine, a fuel mixing means supplies before Symbol the combustion engine as a mixture by mixing its fuel gas and intake air, before Symbol in combustion engine operating condition detecting means for detecting the operating state before Symbol in combustion engine comprising an intake pressure of the engine speed and the intake passage, the fuel supply amount to be supplied to the intake passage based on the detection result of said operating condition detecting means a supply amount calculating means for calculating a, the fuel control system of combustion engine and a supply control means for controlling the fuel supply to the intake passage by the fuel mixing means based on the calculation result of the supply amount calculating means, Absorption from the operating state detected by the operating state detecting means
Air column vibration to determine whether the air column is in an excessive vibration state in the air passage
An air column over-vibration state by a state determination unit and the air column vibration state determination unit
It When is determined, the fuel control system of combustion engine and a columnar vibration correcting means increases or decreases for correcting the calculation result of the supply quantity calculating means in accordance with the air column vibration state.