JPH0942018A - Fuel injection quantity control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily control the fuel injection quantity even under an engine operating condition where there is no proportionality between the injection time and the injection quantity by pressure-correcting the fuel injection quantity based on the pressure behavior characteristics preset near the nozzle of an injector in a specified engine. SOLUTION: An estimating means 54 for estimating the pressure near the nozzle of an injector 19 provided in an intake passage based on the operating parameter of an engine, is provided in an electronic control device 53. Based on the estimated pressure near the nozzle of the injector 19 estimated by the estimating means 54, a target fuel injection quantity is corrected, and fuel injection is controlled. The first correcting means 54 is especially provided. During a specified period after the engine start, instead of the correction of the target fuel injection quantity based on the estimated pressure, the fuel injection quantity is pressure-corrected by the first correcting means 54 based on the pressure behavior characteristics preset near the nozzle of the injector 19 in a specified engine,. Thus, the most suitable fuel injection quantity can be supplied even during starting the engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control device for an internal combustion engine.

[0002]

2. Description of the Related Art In an electronically controlled fuel injection engine, a fuel injection valve is connected to a delivery pipe, and a pressure regulator is attached to the delivery pipe for adjusting the fuel pressure of the fuel injection valve. 62-1732
It is known as disclosed in No. 3. The pressure regulator is for keeping the difference between the pressure of fuel in the delivery pipe (hereinafter referred to as fuel pressure) and the intake pressure constant and preventing the fuel injection amount from changing with respect to the changing intake pressure. Then, for pressure regulation, the intake pressure is introduced into the back pressure chamber partitioned by the diaphragm of the pressure regulator.

By the way, when the temperature of the fuel in the delivery pipe or the fuel injection valve becomes high, fuel vapor is easily generated.
In such a state, there arises a problem that the startability and the idle stability are remarkably deteriorated especially when the engine is started. In order to solve this problem, an electromagnetic valve is installed in the passage connecting the pressure regulator and the intake pipe, and when the temperature of the fuel in the delivery pipe exceeds a specified value, the electromagnetic valve is activated when the engine is started, and the pressure regulator is activated. The back pressure chamber is open to the atmosphere. By opening the pressure regulator to the atmosphere, the fuel pressure in the delivery pipe and the fuel injection valve is increased as compared with the case where the pressure regulator is connected to the intake passage. As the pressure increases,
Since the vaporization temperature of the fuel rises, the generation of fuel vapor in the delivery pipe and the fuel injection valve is prevented, and the engine startability is improved.

As described above, conventionally, an electromagnetic valve is required for switching the back pressure of the pressure regulator, which causes a problem that the system becomes complicated and the reliability and cost increase.

To solve this problem, the applicant has already proposed the following fuel injection control device in which the solenoid valve is omitted (Japanese Patent Application No. 7-8477). In this fuel injection control device, the back pressure chamber of the pressure regulator is always open to the atmosphere. Then, from the intake air amount GA and the engine speed NE, the air amount GN per revolution (= GA / N
E) is obtained, and the load factor (GN / GNMA) is calculated from this air amount GN per one revolution and the standard intake air amount GNMAX per one revolution when the throttle valve is fully opened. The intake pipe pressure P1 is estimated, and the correction coefficient K is calculated from the estimated intake pipe pressure P1.
The FPC is calculated to correct the fuel injection amount.

[0006]

The intake air amount GA is detected by an air flow meter provided in the intake passage, but the air flow meter is provided much upstream of the injector from the injector. . Therefore, immediately after the engine is started, the intake air amount GA detected by the air flow meter is faster than the negative pressure generated at the tip of the injector. As a result, the intake pipe pressure P1 obtained as described above becomes larger than the actual pressure P at the actual tip of the injector immediately after the engine is started.
It was found that the fuel injection amount corrected by the correction coefficient KFPC becomes larger than the required value.

The object of the present invention is to eliminate the above-mentioned problems of the prior art. The back pressure chamber of the pressure regulator is always open to the atmosphere, and the injection time and the injection amount are not in a proportional relationship. Provided is a fuel injection amount control device for an internal combustion engine, which can easily manage the fuel injection amount even in the engine operating state and can supply the optimum fuel injection amount within a predetermined period from the engine start. Especially.

[0008]

In order to solve the above problems, the invention of claim 1 is based on a pressure regulator for adjusting the fuel pressure of an internal combustion engine to be higher than atmospheric pressure by a constant pressure, and an operating parameter of the engine. Estimating means for estimating the pressure in the vicinity of the injector nozzle provided in the intake passage, and the target fuel injection amount is corrected based on the estimated pressure in the vicinity of the injector nozzle estimated by the estimating means, and fuel injection control is performed with the corrected value. In a fuel injection amount control device for an internal combustion engine, which performs a predetermined fuel injection amount based on the estimated pressure instead of correcting the target fuel injection amount within a predetermined period from engine startup, a preset value is set in the vicinity of the injection port of the injector within the predetermined period. The gist of the fuel injection amount control device for an internal combustion engine is provided with a first correction means for correcting the pressure of the fuel injection amount on the basis of the pressure behavior characteristic described above.

According to a second aspect of the present invention, there is provided a pressure regulator for adjusting the fuel pressure of the internal combustion engine to be higher than the atmospheric pressure by a constant pressure, and a pressure in the vicinity of the injection port of the injector provided in the intake passage based on the intake air amount of the engine. A fuel injection amount control device for an internal combustion engine, which corrects a target fuel injection amount on the basis of an estimation means for estimating and an estimated pressure near the injection port of the injector estimated by the estimation means, and performs fuel injection control with the corrected value. The gist of a fuel injection amount control device for an internal combustion engine is provided with second correction means for correcting the target fuel injection amount based on the estimated pressure so as to be smaller than the pressure correction within a predetermined period from the engine start. There is.

According to a third aspect of the present invention, a pressure regulator for adjusting the fuel pressure of the internal combustion engine to be higher than the atmospheric pressure by a constant pressure, and a pressure in the vicinity of the injection port of the injector provided in the intake passage based on the intake pipe pressure of the engine are set. The fuel injection of the internal combustion engine which corrects the target fuel injection amount based on the third estimating means for estimating and the estimated pressure near the injection hole of the injector estimated by the third estimating means, and performs the fuel injection control with the corrected value. A fuel injection amount of an internal combustion engine, which is a fuel amount control device and is provided with a third correction means for correcting a target fuel injection amount based on the estimated pressure so as to be larger than a pressure correction within a predetermined period from engine start. The main point is the control device.

(Operation) According to the invention of claim 1, the pressure regulator adjusts the fuel pressure of the internal combustion engine to be higher than the atmospheric pressure by a constant pressure. The first estimating means estimates the pressure in the vicinity of the injection port of the injector provided in the intake passage based on the operating parameter of the engine. In the fuel injection amount control device, the target fuel injection amount is corrected based on the estimated pressure near the injection port of the injector estimated by the first estimating means, and the fuel injection control is performed with the corrected value. Then, within a predetermined period from the start of the engine, instead of correcting the target fuel injection amount based on the estimated pressure, the fuel is corrected based on a preset pressure behavior characteristic near the injection port of the injector by the correction means within the predetermined period. The pressure of the injection quantity is corrected.

According to the second aspect of the present invention, the pressure regulator adjusts the fuel pressure of the internal combustion engine higher than the atmospheric pressure by a constant pressure. The estimating means estimates the pressure near the injection port of the injector provided in the intake passage based on the intake air amount of the engine. Then, the fuel injection amount control device corrects the target fuel injection amount based on the estimated pressure near the injection port of the injector estimated by the estimation means, and performs the fuel injection control with the corrected value. Then, within a predetermined period from the start of the engine, the second correction means corrects the target fuel injection amount based on the estimated pressure so as to be smaller than the pressure correction.

According to the third aspect of the present invention, the pressure regulator adjusts the fuel pressure of the internal combustion engine higher than the atmospheric pressure by a constant pressure. The estimating means estimates the pressure in the vicinity of the injection port of the injector provided in the intake passage based on the intake pipe pressure of the engine. Then, the fuel injection amount control device corrects the target fuel injection amount based on the estimated pressure near the injection port of the injector estimated by the estimation means, and the fuel injection control is performed with the corrected value. Further, within a predetermined period from the engine start, the third correction means corrects the target fuel injection amount based on the estimated pressure so as to be larger than the pressure correction.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic configuration of a multi-cylinder gasoline engine (hereinafter, simply referred to as an engine) 1 as an internal combustion engine mounted on a vehicle and its peripheral devices. The cylinder block 1a and the cylinder head 1b of the engine 1 form an engine body. In the cylinder block 1a, the same number of cylinder bores 2 as the number of cylinders are arranged side by side in a direction orthogonal to the paper surface, and a piston 3 is housed in each cylinder bore 2 so as to be vertically reciprocable. The piston 3 is connected to the crankshaft 5 by a connecting rod 4. And
The reciprocating motion of the piston 3 is converted into a rotary motion by the connecting rod 4, and the crankshaft 5 is rotationally driven.

A combustion chamber 6 is formed above the piston 3, and an intake passage 7 and an exhaust passage 8 communicate therewith.
A communication portion between the combustion chamber 6 and the intake passage 7 is an intake port 9, and the intake port 9 is opened and closed by an intake valve 11 attached to the cylinder head 1b so as to be vertically movable. Further, a communication portion between the combustion chamber 6 and the exhaust passage 8 is an exhaust port 10, and the exhaust port 10 is opened and closed by an exhaust valve 12 mounted on the cylinder head 1b so as to be vertically movable.

In the intake passage 7, an air cleaner 13, a throttle body 14, a surge tank 15, and an intake manifold 16 are arranged in this order from the upstream side toward the cylinder head 1b, and the outside air is passed through the combustion chamber 6 through these components. Is taken into. A throttle valve 17 is supported by a shaft 18 in the throttle body 14 so as to be integrally rotatable. The shaft 18 is connected to an accelerator pedal (not shown) by a cable or the like. Then, when the driver depresses the accelerator pedal, the depressing operation is transmitted to the shaft 18 via a cable or the like, and the throttle valve 17 causes the shaft 1 to move.
It rotates together with 8. The rotation of the throttle valve 17 opens and closes the intake passage 7 to adjust the amount of intake air to the combustion chamber 6. The surge tank 15 is for smoothing the pulsation of intake air and preventing intake interference of each cylinder. Note that in FIG. 1, the intake manifold 16 is shown to be larger than other portions for convenience of description.

The intake manifold 16 is equipped with the same number of injectors 19 as the number of cylinders. A tip portion 19a of each injector 19 faces the intake passage 7, and fuel can be injected from the tip portion 19a toward the intake port 9 of the corresponding cylinder.

The injector 19 is connected to one delivery pipe 21. The delivery pipe 21 is connected to the fuel tank 23 by a fuel pipe 22.
The inside of both paps 21, 22 constitutes a fuel passage. A fuel pump 24 and a fuel filter 25 are interposed in the middle of the fuel pipe 22, and the fuel in the fuel tank 23 is sucked and discharged by the operation of the fuel pump 24. The fuel discharged from the fuel pump 24 is pressure-fed to the delivery pipe 21 via the fuel filter 25 and the fuel pipe 22. The pressure-fed fuel is distributed to each injector 19 by the delivery pipe 21, and is injected when the injector 19 opens.

A pressure regulator 26 is attached to the delivery pipe 21. The pressure regulator 26 holds the fuel pressure Pf that is pressure-fed to each injector 19 at a value higher than the atmospheric pressure PA by a constant pressure C.
Further, the pressure regulator 26 returns the surplus fuel (return fuel) generated by the adjustment of the fuel pressure to the fuel tank 23 through the return pipe 34.

In order to adjust the fuel pressure, a diaphragm 29 having a valve body 28 is stretched in the case 27 of the pressure regulator 26 as shown in FIG. The valve body 28 and the diaphragm 29 partition the interior of the case 27 into a back pressure chamber 31 and a fuel chamber 32. The fuel chamber 32 is connected to the delivery pipe 21, from which fuel can flow into the fuel chamber 32. In addition, the case 27 has a conduit 33 for communicating the fuel chamber 32 with the outside of the case 27.
Is provided, and this conduit 33 is connected to the fuel tank 23 by a return pipe. Then, the fuel in the fuel chamber 32 can be led out to the fuel tank 23 through the conduit 33 and the return pipe 34.

On the other hand, a coil spring 35 is disposed in a compressed state in the back pressure chamber 31, and the coil spring 35 constantly urges the valve body 28 in the direction of closing the conduit 33. The back pressure chamber 31 is open to the atmosphere, and the inside of the back pressure chamber 31 is always at atmospheric pressure.

A mixture of fuel injected from each injector 19 and outside air introduced into the intake passage 7 is introduced into the combustion chamber 6 through the intake port 9 when the intake valve 11 is opened. In order to ignite the air-fuel mixture introduced into the combustion chamber 6, a semiconductor ignition type ignition device is provided. This ignition device includes an ignition coil 38 and an igniter 39 that generate a high voltage by utilizing a transient phenomenon of an electric circuit, a distributor 41 that distributes the high voltage to each cylinder, and a spark plug 42 that is a discharge unit. ing.

Then, the air-fuel mixture introduced into the combustion chamber 6 is burned by the ignition of the spark plug 42, and the piston 3,
The driving force of the engine 1 can be obtained via the connecting rod 4, the crankshaft 5, and the like. The burned gas (exhaust gas) burned in the combustion chamber 6 is led out from the exhaust port 10 to the exhaust passage 8 when the exhaust valve 12 is opened.

An exhaust manifold 43 and a catalytic converter 44 are provided in the exhaust passage 8 from the cylinder head 1b toward the downstream side, through which exhaust gas is exhausted to the outside.

In order to detect the operating state of the engine 1, an air flow meter 46, an intake air temperature sensor 47, a throttle sensor 48, a water temperature sensor 49, an oxygen sensor 50,
A rotation speed sensor 51, a cylinder discrimination sensor 52, etc. are provided. The air flow meter 46 is an intake air amount detecting means for measuring the amount of intake air taken by the engine 1. In this embodiment, the measuring plate (vane) is pushed open by the pressure difference generated when the intake air passes. Type is used. The intake air temperature sensor 47 is installed in the air flow meter, and detects a temperature change (intake air temperature THA) of the intake air flowing through the intake passage 7 by a change in the resistance value of the built-in thermistor. The intake air temperature THA corresponds to the ambient temperature around the tip portion 19a of the injector 19.

The throttle sensor 48 is attached to the throttle body 14 and detects the opening of the throttle valve 17 (throttle opening). The water temperature sensor 49 is attached to the water outlet and detects the temperature of the cooling water of the engine 1 (cooling water temperature THW). More specifically, like the intake air temperature sensor 47, the water temperature sensor 49 is composed of a thermistor whose resistance value greatly changes with temperature, and detects a change in the cooling water temperature THW by a change in resistance value. Cooling water temperature TH
W corresponds to the temperature of the cylinder block 1a and the cylinder head 1b.

The oxygen sensor 50 is attached to the exhaust manifold 43 and detects the oxygen concentration in the exhaust gas. Both the rotation speed sensor 51 and the cylinder discrimination sensor 52 are built in the distributor 41. Rotation speed sensor 51
Is composed of one timing rotor having a large number (for example, 24) of protrusions on the outer circumference and one pickup coil. In this rotation speed sensor 51, when the timing rotor makes one rotation, the pickup coil outputs the same number of pulse signals as the projections at an equal crank angle (for example, 30 rpm).
°) every time. The cylinder discrimination sensor 52 is composed of one timing rotor having one protrusion on the outer periphery and two pickup coils. In this cylinder discrimination sensor 52, when the timing rotor makes one revolution,
Each pickup coil alternately generates one pulse signal at every crank angle of 360 °.

The air flow meter 46 and various sensors 4
7 to 52 are electrically connected to the input side of an electronic control unit (hereinafter referred to as ECU) 53. The injectors 19 and the igniter 39 are electrically connected to the output side of the ECU 53.

As shown in FIG. 5, the ECU 53 includes a central processing unit (hereinafter, CPU) 54, a read-only memory (hereinafter, ROM) 55, a random access memory (hereinafter, RAM) 56, and a backup RAM 5.
7, an external input circuit 58, and an external output circuit 59, which are connected to each other by a bus 60. CPU5
Reference numeral 4 executes various arithmetic processes according to a preset control program. The CPU 54 constitutes an estimation unit, a first correction unit and a fuel injection amount control unit. Also, R
The OM 55 stores in advance a control program and initial data necessary for the CPU 54 to execute arithmetic processing. The ROM 55 constitutes intake air amount storage means.
The RAM 56 temporarily stores the calculation result of the CPU 54, and the backup RAM 57 is backed up by a battery so as to retain various data even after the power is turned off. The external input circuit 58 has an A / D converter (analog / digital converter) and converts analog signals such as an intake air temperature signal from the intake air temperature sensor 47 and a cooling water temperature signal from the water temperature sensor 49 into a digital signal.

Various signals from the air flow meter 46, the intake air temperature sensor 47, the throttle sensor 48, the water temperature sensor 49, the oxygen sensor 50, the rotation speed sensor 51 and the cylinder discrimination sensor 52 are input to an external input circuit 58. CPU
Reference numeral 54 represents the intake air amount GA, intake air temperature THA, throttle opening, cooling water temperature THW, oxygen concentration, based on these signals.
The engine speed NE, the cylinder discrimination signal, etc. are detected.

On the other hand, the CPU 54 controls the air-fuel ratio (engine 1
The weight ratio of air / fuel in the air-fuel mixture sucked into the air) A / F is detected by the output signal of the oxygen sensor 50, and the air-fuel ratio A / F
The fuel injection amount from the injector 19 is adjusted so that becomes the stoichiometric air-fuel ratio. In order to adjust the fuel injection amount, the CPU 54 described later calculates the target fuel injection time TAU which is the valve opening time of the injector 19 based on the following equation (1).

TAU = K × (GA / NE) × FAF (1) where K is a constant, GA is the intake air amount, NE is the engine speed, and K · (GA / NE) is the theoretical air-fuel ratio. Is the basic injection time set so as to obtain FAF is a feedback correction coefficient that changes with a change in the output signal of the oxygen sensor 50, and the basic fuel injection time K · (GA / N is set so that the air-fuel ratio A / F becomes the stoichiometric air-fuel ratio.
Correct E). Since the method of obtaining the feedback correction coefficient FAF is known, a description thereof will be omitted.

The CPU 54 further calculates the final fuel injection time by multiplying the target fuel injection time TAU by a correction coefficient KFPC, which will be described later, and outputs a drive signal corresponding to the final fuel injection time as shown in FIG. To the injector 19 via the external circuit 59. The output of this signal controls the valve opening time of the injector 19 to inject a predetermined amount of fuel. In this way, feedback control is performed so that the air-fuel ratio A / F becomes the stoichiometric air-fuel ratio. That is, when the fuel injection is performed according to the target fuel injection time TAU, the injection amount at this time becomes the target fuel injection amount, and when the target fuel injection time TAU is corrected, the target fuel injection amount is It will be changed by correction.

The CPU 54 also controls the igniter 39 via the external output circuit 59. That is, the optimal ignition timing corresponding to the operating state of the engine 1 is stored in the ROM 55 in advance, and the CPU 54 detects the operating state of the engine 1 by the signals from the various sensors including the rotation speed sensor 51, and the optimal ignition is performed. Calculate the time. And CPU5
Reference numeral 4 outputs an ignition instruction signal to the igniter 39 via the external output circuit 59 to control the ignition timing.

Next, the operation and effect of the embodiment configured as described above will be described. The flowchart of FIG. 5 shows a routine for calculating the correction coefficient KFPC among the processes executed by the CPU 54. or,
FIG. 6 shows an injection time calculation routine. All of these routines are executed at a predetermined timing.

When the correction coefficient calculation routine of FIG. 5 is started, the CPU 54 first, at step 100, the intake air amount GA detected by the air flow meter 46 and converted into a digital signal by the A / D converter. Read. or,
In the same step, the engine speed NE detected by the speed sensor 51 is read, and then GN = GA / N
Ask for E. Next, at step 110, a time period T from the start of the engine 1 (hereinafter, elapsed time after start) T
Is less than the predetermined time t1. For the elapsed time T after the start, the starter signal from a starter (not shown)
From the time when U54 is input, the time is measured based on the internal clock of the CPU 54. Further, the predetermined time t1 is a time until the estimated intake pipe pressure P1 to be described later does not become different from the actual pressure P when the engine 1 is in a steady state, that is, at the tip pressure of the injector 19, and an experimental value, etc. It was obtained by. In other words, engine 1
Since the pressure near the tip end portion 19a of the injector 19 is initially atmospheric pressure at the time of starting, the time t1 is the time required for the pressure to become constant.

The reason for providing the step 110 is as follows. That is, although the intake air amount GA is detected by the air flow meter 46 provided in the intake passage 7,
The air flow meter 46 is provided far upstream of the injector 19 in the intake passage 7. Therefore, immediately after the engine 1 is started, the intake air amount GA detected by the air flow meter 46 becomes faster than the generation of negative pressure at the tip of the injector, and the estimated intake pipe pressure P1 as the estimated pressure described below is higher than the actual pressure. growing. In consideration of this, within the predetermined time t1, the estimated intake pipe pressure P1 described later is not used because the processing of steps 120 to 140 is not performed in the calculation of the correction coefficient KFPC.

If the elapsed time T after starting is less than the predetermined time t1 in step 110, step 11
Move to 1. In step 111, it is determined whether the engine speed NE is less than the predetermined speed NE1.
If the engine speed NE is less than the predetermined speed NE1, the process proceeds to step 112, and if not, step 11
Move to 3. In step 112 and step 113, the correction coefficient KFPC is calculated from the first KFPC characteristic map and the second KFPC characteristic map, respectively.

In this KFPC characteristic map, the injector tip pressure behavior characteristic at the time of starting is experimentally obtained as a time parameter in advance, and an appropriate correction coefficient KFPC corresponding to the injector tip pressure at each time T is plotted on the ordinate and the time is plotted. It is created as a two-dimensional map with T as the horizontal axis. The first KFPC characteristic map is the time t from the engine start when the engine speed is less than NE1.
The correction coefficient KFPC up to 1 is included. Also, the second K
The FPC characteristic map includes the correction coefficient KFPC from the time when the engine is started to the time t1 when the engine speed NE1 is exceeded. This first and second KFPC
The characteristic map is necessary in order to obtain a more appropriate correction coefficient KFPC according to the engine speed, because the injector tip pressure behavior characteristic at the time of start-up also differs depending on the engine speed, as shown in FIG. . Since the correction coefficient KFPC calculated from these first and second KFPC characteristic maps is based on the injector tip pressure behavior characteristics at the time of starting, which are obtained from experimental values, etc., both are calculated from the estimated intake pipe pressure P1 described below. It is smaller than the calculated correction coefficient KFPC.

In this embodiment, in step 111 of FIG. 5, the engine speed NE is the predetermined speed N.
Although the correction coefficient KFPC is switched depending on whether it is less than E1, the correction coefficient KFPC may be calculated by interpolating the characteristics of FIG. 8 with the engine speed NE. Further, the correction coefficient may be obtained using the intake air amount GA as a parameter instead of the engine speed NE.

When the correction coefficient KFPC is calculated in step 112 or step 113, the correction coefficient KFPC is temporarily stored in the RAM 56 and the processing routine is exited.

In step 110, if the elapsed time T after starting is not less than the predetermined time t1, step 1
Move to 20. In step 120, the air amount GNMAX per unit rotation is calculated. The air amount GNMAX per unit rotation is a standard intake air amount per unit rotation when the throttle valve is fully opened at any engine speed NE, and is obtained in advance by tests, etc. under standard atmospheric pressure and standard intake air temperature. The map data is RO
It is stored in M55. Therefore, the air amount GNMAX per unit rotation is the engine speed N obtained in step 100.
It is obtained by referring to this map data based on E.

Next, in step 130, the CPU 54 calculates the estimated intake pipe pressure P1 by the following equation. P1 = GN / GNMAX (2) By the way, the ratio of GN and GNMAX has a strong correlation with the pressure near the nozzle of the injector 19 (the nozzle pressure), and when GN / GNMAX = 0, it is a vacuum. , GN /
When GNMAX = 1, it can be considered as atmospheric pressure.

Therefore, the pressure in the vicinity of the injection port of the injector 19 is estimated by GN / GNMAX. Next, CP
In step 140, the U54 calculates the correction coefficient KFPC with reference to the map data shown in FIG. Explaining this map data, the map data is a two-dimensional map of the correction coefficient KFPC and the estimated intake pipe pressure P1, and the following relationship is established between them.

KFPC = (C / (C + PA-P1)) ^1/2 (3) where C is the set fuel pressure. PA is atmospheric pressure. Then, a map of the correction coefficient KFPC with respect to the estimated intake pipe pressure P1 is created in advance based on the equation (3), and the ROM 5
Stored in 5. The above formula (3) will be described.

FIG. 7 is a schematic diagram showing the relationship between the intake port pressure and the delivery fuel pressure Pf. PM indicates the intake port pressure (= surge tank pressure). Straight line Pf = PM +
C indicates the case of controlling the conventional fuel pressure, and the straight line Pf = PA
+ C indicates the case where the fuel pressure is controlled to be constant in the present embodiment. A is Pf = PA + C in the present embodiment
And PM, and B is the difference (= C) between Pf = PM + C and PM.

Since it is known that the injection amount of the injector 16 is proportional to the square root of these differential pressures,
Fuel injection amount is basic injection amount TAU x correction coefficient (B / A)
^{Calculated as 1/2} . Further, from FIG. 7, A = (PA + C) −PM B = C. Then, when the estimated intake pipe pressure P1 is substituted for the intake port pressure PM, the correction coefficient (B / A) ^1/2 becomes the equation (3).

As described above, the CPU 54 executes the step 140.
At, the correction coefficient KFPC is calculated, the calculation result is temporarily stored in a predetermined address of the RAM 56, and then this routine is exited.

Next, when the CPU 54 enters the execution processing of the injection time calculation routine in FIG. 6, in step 201, the target fuel injection time TAU is calculated. This target fuel injection time is a process that is calculated in the same manner as in the conventional case, and is calculated based on the equation (1). Next, step 202
In the CPU 54, the correction coefficient K stored in the RAM 56
The FPC is read, and this correction coefficient KFPC is set in step 20.
The final fuel injection time is calculated by multiplying the target fuel injection time TAU calculated in 1, and the final fuel injection time is temporarily stored in the RAM 56.

Thereafter, the CPU 54 outputs a drive signal corresponding to the final fuel injection time to the injector 19 via the external circuit 59. Then, by the output of this signal, the injector 19 controls the valve opening time and injects a predetermined amount of fuel.

As described above, in the present embodiment, the back pressure chamber 31 of the pressure regulator 26 is always kept at the atmospheric pressure, so that the switching valve for correcting the atmospheric pressure is unnecessary,
The system is simplified. Further, by releasing the back pressure of the pressure regulator 26 to the atmospheric pressure, even if the relationship between the conventional injection time and the injection amount is changed, the pressure correction can be easily handled by the control program software, thereby controlling the pressure. Of deterioration is prevented.

Further, in this embodiment, at the time of starting, the first KFPC characteristic map and the second KFPC characteristic map are selectively used within the predetermined time t1 with the predetermined rotational speed NE1 of the engine 1 as a boundary. Then, from the correction coefficient KFPC calculated based on the estimated intake pipe pressure P1,
The correction coefficient KFPC is reduced. Therefore, the fuel injection amount does not become larger than the required value within the post-start elapsed time T at the time of starting, and can be set to an appropriate value. (Second Embodiment) Next, a second embodiment will be described with reference to FIGS. It should be noted that the same or corresponding configurations as those of the first embodiment will be designated by the same reference numerals and the description thereof will be omitted, and different points will be mainly described.

In this embodiment, instead of the first correction means in the first embodiment, the CPU 54
The difference is that it is the second correction means. The operation of the second embodiment will be described.

Now, in the KFPC calculation routine,
The difference from the KFPC calculation routine of the first embodiment is that steps 110 to 113 are omitted, and the process proceeds to step 120 after step 100.

Therefore, in this KFPC calculation routine, the correction coefficient KFPC is calculated only in step 140. Next, when the CPU 54 enters the execution process of the injection time calculation routine in FIG. 11, in step 300, the target fuel injection time TAU is calculated. This target fuel injection time is a process that is calculated in the same manner as in the conventional case, and is calculated based on the equation (1). Next, in step 310, the CP
The U54 reads the correction coefficient KFPC stored in the RAM 56 and multiplies the correction coefficient KFPC by the target fuel injection time TAU calculated in step 201 to calculate the fuel injection time TAUJ _i .

Next, at step 320, it is judged if the elapsed time after starting T is less than the predetermined time t1. When it is determined in step 320 that the post-start elapsed time T is less than the predetermined time t1, the process proceeds to step 350.
In step 350, the "moderation rate N" is calculated. The operation of the moderation rate is performed with reference to the moderation rate map stored in the ROM 55 in advance. That is, the smoothing rate map is composed of a two-dimensional map of the intake air amount GN per unit rotation and the smoothing rate N as shown in FIG. The "annealing rate N" (0 <N≤ so that the injection amount corresponds to the pressure behavior near the tip portion 19a of the injector 19 after the elapse of time.
1) is predetermined. Then, a value corresponding to the intake air amount GN at that time is calculated as the "moderation rate N".

After this, the process proceeds to step 350. or,
When it is determined in step 320 that the elapsed time T after start-up is equal to or longer than the predetermined time t1, the process proceeds to step 330, the "annealing rate N" is set to "1", and the step 3
Move to 40.

Then, in step 340, the final fuel injection time TAU _i is calculated. This final fuel injection time TAU _i is calculated by the following equation. TAU _i = TAU _i-1 + (TAUJ _i −TA
U _i-1 ) / N where i is the current value and i-1 is the previous value.

Therefore, when the "smoothing rate N" is "1",
Final fuel injection time TAU_iIs TAUJ_iBecomes or,
When the "Rating rate N" is a value other than "1", the correction coefficient
Fuel injection amount TAUJ corrected based on KFPC_iGana
The final burned value of the previous
Charge injection time TAU_i-1Is added at the time of final fuel injection
Between TAU_iIt is said. And as a result of this smoothing process,
Final fuel injection time TAU _iIs based on the correction coefficient KFPC
Corrected fuel injection time TAUJ_iSmaller than
Have been.

When the final fuel injection time TAU _i is calculated in this step 340, the final fuel injection time TAU _i is temporarily stored in the RAM 56. After this, the CPU
54 outputs a drive signal corresponding to the final fuel injection time TAUi to the injector 19 via the external circuit 59.
Then, by the output of this signal, the injector 19 controls the valve opening time and injects a predetermined amount of fuel.

As described above, in this embodiment, when the post-start elapsed time T is less than the predetermined time t1, the fuel injection amount TAU corrected based on the correction coefficient KFPC is annealed. Therefore, the elapsed time T after starting is the predetermined time t
When it is less than 1, the final fuel injection time TAUi can be made shorter than the fuel injection time calculated based on the estimated intake pipe pressure P1, and the fuel injection amount corresponding to the actual pressure behavior can be obtained. (Third Embodiment) Next, a third embodiment will be described with reference to FIGS. In addition, also in this embodiment, description will be made focusing on the points different from the first embodiment, and the same configurations or corresponding configurations will be denoted by the same reference numerals.

In this embodiment, instead of the air flow meter 46 of the first embodiment, the surge tank 15 has a pressure (intake pipe pressure (= surge) in the surge tank 15 based on vacuum). For convenience of description, a semiconductor-type intake pressure sensor 69 for detecting PM) is attached for convenience of description. The intake pressure sensor 69 constitutes intake pressure detecting means.

The intake pressure signal from the sensor 69 is input to the external input circuit 58. The CPU 54 of the ECU 53 detects the intake pressure PM based on this signal. And CP
U54 constitutes a third correction means.

In this embodiment, the pressure near the tip portion 19a of the injector 19 is estimated to be equivalent to the surge tank pressure. Also in this embodiment,
The injector 19 is provided for each cylinder.

The correction coefficient KFPC calculation routine of this embodiment is different from that of the first embodiment. Hereinafter, the correction coefficient KFPC calculation routine of this embodiment will be described.

FIG. 13 shows the correction coefficient KFP of this embodiment.
The C calculation routine is shown. This correction coefficient calculation KFP
When the C routine is started, the CPU 54 first detects the intake pressure sensor 69 in step 400,
The intake pressure PM converted into a digital signal by the D converter is read. Further, in the same step, the engine speed NE detected by the speed sensor 51 is read. Next, at step 410, the elapsed time T after starting is the predetermined time t
It is determined whether it is less than 1.

The reason why step 410 is provided is as follows. That is, the intake pressure PM is the surge tank 15
Although it is detected by the intake pressure sensor 69 provided in the, the passage sectional area (volume) of the intake passage (intake pipe) 7 is smaller than that of the surge tank 15. Therefore, particularly at the time of starting the engine 1, the pressure decrease speed (rise of negative pressure) in the vicinity of the tip end portion 19a of the injector 19 becomes considerably fast even in the surge tank 15. As a result, when the correction coefficient KFPC, which will be described later, is calculated based on the pressure in the surge tank 15 (surge tank pressure), the correction coefficient KFPC is calculated based on the pressure larger than the actual pressure in the vicinity of the tip portion 19a of the injector 19. This is because the calculation makes the fuel injection amount smaller than the required value, contrary to the first embodiment.

In consideration of this, if the time is less than the predetermined time t1, the process of step 420 is not performed in the calculation of the correction coefficient KFPC. Then, in step 410, if the elapsed time after startup T is less than the predetermined time t1, the process proceeds to step 430. In step 430, it is determined whether the engine speed NE is less than the predetermined speed NE1. The engine speed NE is the predetermined speed NE
If it is less than 1, the process proceeds to step 440, and if not, the process proceeds to step 450. In steps 440 and 450, the third KFPC characteristic map and the fourth KFPC characteristic map
The correction coefficient KFPC is calculated from each of the KFPC characteristic maps. In each of steps 440 and 450, the intake pressure PM is multiplied by the correction coefficient so that the intake pressure PM becomes smaller than the intake pressure PM in the surge tank 15 at the time of starting PM1 and PM2 depending on the engine speed NE, respectively.
It is corrected to (> PM1). This correction coefficient is obtained in advance from an experimental value or the like, and the surge tank pressure P
This is for making M close to the actual pressure in the vicinity of the tip portion 19a of the injector 19.

Further, the KFPC characteristic map in this embodiment is that the behavior of the injector tip pressure at the time of starting is experimentally obtained in advance as a time parameter, and an appropriate correction coefficient KFPC corresponding to the injector tip pressure at each time T is set. It is created as a two-dimensional map in which the vertical axis represents time T on the vertical axis. Further, the third KFPC characteristic map is composed of a plurality of maps, and each characteristic map includes the correction coefficient KFPC from the engine start time to time t1 when the engine speed NE is less than the predetermined speed NE1. The fourth characteristic map is composed of a plurality of characteristics maps, and each characteristic map includes the correction coefficient KFPC from the time when the engine is started to the time t1 when the engine speed NE exceeds the predetermined speed NE1. This third and fourth KFP
The C characteristic map is necessary in order to obtain a more appropriate correction coefficient KFPC according to the engine speed, because the injector tip pressure behavior at the time of start-up also differs depending on the engine speed NE. is there.

Then, at step 440, the third KFPC characteristic map shows the corrected intake pressure PM1 (<P
M) is selected, and the correction coefficient KFPC is calculated based on the selected characteristic map.

On the other hand, in step 450, the fourth K
The FPC characteristic map shows the corrected intake pressure PM2 (<P
M) is selected, and the correction coefficient KFPC is calculated based on the selected characteristic map.

When the correction coefficient KFPC is calculated in step 440 or step 450, the correction coefficient KFPC is temporarily stored in the RAM 56 and the processing routine is exited.

If it is determined in step 410 that the elapsed time T after starting is not less than the predetermined time t1, step 4 is executed.
Move to 20. In step 420, the correction coefficient K
FPC is calculated with reference to map data. Explaining this map data, the map data has a correction coefficient K.
It is a two-dimensional map of FPC and intake pressure PM, and the following relationships are established between them.

KFPC = (C / (C + PA-PM)) ^1/2 (4) where C is the set fuel pressure. PA is atmospheric pressure. Then, a map of the correction coefficient KFPC with respect to the intake pressure PM is created in advance based on the equation (4) and stored in the ROM 55.

Formula (4) will be described. FIG. 7 is a schematic diagram showing the relationship between the intake port pressure and the delivery fuel pressure Pf. PM indicates the intake port pressure (= surge tank pressure). The straight line Pf = PM + C shows the case where the conventional fuel pressure is controlled, and the straight line Pf = PA + C shows the case where the fuel pressure is constantly controlled in the present embodiment. A indicates the difference between Pf = PA + C and PM in the present embodiment, and B indicates the difference (= C) between Pf = PM + C and PM.

Since it is known that the injection amount of the injector 16 is proportional to the square root of these differential pressures,
Fuel injection amount is basic injection amount TAU x correction coefficient (B / A)
^{Calculated as 1/2} . Further, from FIG. 7, A = (PA + C) −PM B = C. From this, the correction coefficient (B / A) ^1/2 becomes the expression (4).

As described above, the CPU 54 executes the step 420.
At, the correction coefficient KFPC is calculated, the calculation result is temporarily stored in a predetermined address of the RAM 56, and then this routine is exited.

Since the subsequent injection time calculation routine is the same as that of the first embodiment, its explanation is omitted. Then, fuel injection is performed at the final fuel injection time calculated in the injection time calculation routine.

As described above, in this embodiment,
The correction coefficient KFPC is set so that the intake pressure PM detected in the surge tank 15 becomes smaller at the time of starting PM1, PM2.
Then, the correction coefficient KFPC is calculated, and then the correction coefficient KFPC is calculated. As a result, although the negative pressure rise in the vicinity of the tip end portion 19a of the injector 19 is faster than the negative pressure generation measured in the surge tank 15, the fuel injection amount remains unchanged even after the elapsed time after start T is within the predetermined time t1. The fuel injection amount does not decrease below the optimum value, and the fuel injection amount can correspond to the actual pressure behavior.

The present invention may be embodied as follows. (A) In each of the above embodiments, the pressure regulator 26 is embodied as a type that returns excess fuel.
A pressure regulator may be arranged in the fuel tank and the return may be made in the tank.

(B) In the second embodiment, the "meaning coefficient N" uses the intake air amount GN per unit rotation as a parameter, but instead of this, the engine speed, the elapsed time after starting, etc. Is used as a parameter, and the "annealing coefficient N" is calculated based on these parameters.
The fuel injection amount may correspond to the actual pressure behavior in the vicinity of the tip portion 19a of No. 9. Further, the "meaning coefficient N" may be a constant value.

(C) In the second embodiment, the fuel injection amount TAUj corrected on the basis of the correction coefficient KFPC is smoothed, but instead, the estimated intake pipe pressure P1 at start-up = GN / GNMAX may be smoothed (eg, weighted average) to approximate the actual pressure behavior of the tip of the injector 19.

(D) In the third embodiment, when the elapsed time T after starting is within the predetermined time t1, the surge tank 1
The correction coefficient KFPC was calculated after correcting the intake pressure PM detected in Fig. 5 so as to be small at the time of starting, but instead of this, in the injection time calculation routine, according to the pressure behavior near the tip portion 19a of the actual injector. The final fuel injection time may be corrected to be longer than the final fuel injection time calculated based on the intake pipe pressure (surge tank pressure).

From the matters described in this specification, the technical idea grasped other than the claims described in the scope of claims will be described together with their effects. (A) In claim 2, the second correction means, in accordance with the engine parameter within a predetermined period at the time of engine start, during the predetermined period from the engine start, the second correction means corrects the target fuel injection amount based on the estimated pressure. A fuel injection amount control device for an internal combustion engine, which corrects so as to be smaller than the above. The engine parameter can be increased, for example, and the engine speed can be increased, and the pressure of the target fuel injection amount can be corrected more appropriately depending on the magnitude of the engine parameter.

[0085]

As described in detail above, according to the first aspect of the invention, the back pressure chamber of the pressure regulator is always open to the atmosphere, and the injection time and the injection amount are not in a proportional relationship. However, the fuel injection amount can be easily managed. Therefore, a switching valve for performing atmospheric pressure correction is unnecessary, and the system can be simplified.

Further, the pressure in the vicinity of the injector nozzle gradually decreases from atmospheric pressure and a predetermined time is required for the pressure to stabilize. Since the pressure of the fuel injection amount is corrected on the basis of the characteristic, the optimum fuel injection amount can be supplied even within the predetermined period from the time of engine start, whereby the startability and emission can be improved.

According to the second aspect of the present invention, when the engine is started, the intake air amount of the engine becomes faster than the negative pressure generation at the injector tip, but becomes smaller than the target fuel injection amount based on the estimated pressure. Thus, the fuel injection amount can be prevented from becoming larger than the optimum value.

According to the third aspect of the invention, the position where the intake pipe pressure is measured is generally a surge tank, and is measured by the surge tank rather than the negative pressure rise at the tip of the injector provided on the intake port side. Negative pressure is delayed. However, according to the third aspect of the present invention, the fuel injection amount is increased within a predetermined period after the engine is started. Therefore, it is possible to prevent the fuel injection amount from being less than the optimum value.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an engine and its peripheral devices according to a first embodiment.

FIG. 2 is a sectional view of the pressure regulator of the same embodiment.

FIG. 3 is an explanatory diagram of a map of a correction coefficient KFPC and an estimated intake pipe pressure P1.

FIG. 4 is a block diagram showing an electrical configuration of an ECU.

FIG. 5 is a flowchart of a correction coefficient KFPC calculation routine.

FIG. 6 is a flowchart of an injection time calculation routine.

FIG. 7 is a schematic diagram showing a relationship between an intake pressure (= surge tank pressure) and a delivery fuel pressure Pf.

FIG. 8 is a characteristic diagram of injector tip pressure depending on the engine speed.

FIG. 9 is an explanatory diagram of a moderating rate map according to the second embodiment.

FIG. 10 is a flow chart of a KFPC calculation routine.

FIG. 11 is a flowchart of an injection time calculation routine.

FIG. 12 is a schematic configuration diagram of an engine and its peripheral devices according to a third embodiment.

FIG. 13 is a flowchart of a KFPC calculation routine.

[Explanation of symbols]

1 ... Engine, 8 ... Intake passage, 15 ... Surge tank, 1
9 ... Injector, 19a ... Tip, 26 ... Pressure regulator, 46 ... Air flow meter, 53 ... Electronic control unit (ECU), 54 ... Estimation means, 1st, 2nd and 3rd correction means, Fuel injection amount control Central processing unit (CPU), which constitutes the means, 55 ... ROM which constitutes the intake air amount storage means.

Claims (3)

[Claims] 1. A pressure regulator for adjusting a fuel pressure of an internal combustion engine to be higher than an atmospheric pressure by a constant pressure, and an estimating means for estimating a pressure near an injection port of an injector provided in an intake passage based on an operating parameter of the engine. A fuel injection amount control device for an internal combustion engine, which corrects a target fuel injection amount based on an estimated pressure near an injection port of an injector estimated by the estimation means, and performs fuel injection control with the corrected value. During the period, instead of correcting the target fuel injection amount based on the estimated pressure, the first correction for performing the pressure correction of the fuel injection amount based on a preset pressure behavior characteristic near the injection port of the injector within the predetermined period. And a fuel injection amount control device for an internal combustion engine. 2. A pressure regulator for adjusting the fuel pressure of an internal combustion engine to be higher than atmospheric pressure by a constant pressure, and an estimating means for estimating the pressure in the vicinity of an injection port of an injector provided in an intake passage based on the intake air amount of the engine. A fuel injection amount control device for an internal combustion engine, which corrects a target fuel injection amount based on an estimated pressure near an injector nozzle estimated by the estimation means, and performs fuel injection control with the corrected value. A fuel injection amount control device for an internal combustion engine, comprising a second correction means for performing correction so as to be smaller than the pressure correction of the target fuel injection amount based on the estimated pressure within a predetermined period. 3. A pressure regulator for adjusting the fuel pressure of an internal combustion engine to be higher than atmospheric pressure by a constant pressure, and an estimating means for estimating a pressure near an injection port of an injector provided in an intake passage based on the intake pipe pressure of the engine. A fuel injection amount control device for an internal combustion engine, which corrects a target fuel injection amount based on an estimated pressure near an injector nozzle estimated by the estimation means, and performs fuel injection control with the corrected value. A fuel injection amount control device for an internal combustion engine, comprising a third correction means for correcting the target fuel injection amount based on the estimated pressure so as to be larger than the pressure correction within a predetermined period.