JPH04231646A - Fuel control device for engine - Google Patents

Abstract

PURPOSE:To enhance the startability of the engine by setting a divisional injection amount so that the dividing times may be increased as far as possible in a zone of start, and promoting one atomization of fuel. CONSTITUTION:By determining a total injection time period corresponding to a required amount of injection, dividing a total injection suspension time period obtained by subtracting the total injection time period from a one-stroke time period Tc determined in accordance with a number of engine revolutions Ne, by a pulse OFF time period Toff of an injection pulse for divisional injection to thereby determine a maximum number N of dividing times, and dividing the total injection time period by this number N into equal time period portions to determine the pulse ON time period Ton, the divided amount of injection is set which causes the dividing times per stroke to become as large as possible. In addition, when the engine operation transits to a region where the number Ne of engine revolutions is equal to or greater than a prescribed number of revolutions and the mechanical efficiency of the engine is increased, the divisional injection times are set to divisional injection times less than said maximum number N such that the divisional injection times decrease with an increase in the number Ne of engine revolutions.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control system for an engine, and more particularly to one that injects fuel in parts at least in the starting zone.

0002

[Prior Art] Recently, as an engine fuel control device,
In order to improve starting performance when cold, the engine speed is 500 rpm while the starter motor is being driven.
In the starting zone below m, the required injection amount for each stroke of each cylinder is divided into multiple parts and injected to promote atomization of fuel. 60-159847).

[0003] Usually, in the fuel control device for the above engine,
The pulse ON time Ton and pulse OFF time Toff of the drive pulse to the injector are set to predetermined values (for example, To
n=4 msec, Toff=8 msec), respectively, and drive pulses are output to the injector until the sum of the divided injection amounts becomes approximately equal to the required injection amount.

0004

[Problem to be Solved by the Invention] In the above fuel control device, since the pulse ON time and pulse OFF time are fixedly set, the engine rotational speed is large during a cold start when the required injection amount is large. If this occurs, and the time for one stroke becomes shorter, it may not be possible to inject the fuel split-up the number of times according to the required injection amount within the time of one stroke, and the mixture becomes leaner by the amount that cannot be injected split-up, reducing startability. do. Moreover, although the time for one stroke is longer when the engine speed is low, split injection is completed within a portion of the time for one stroke, so there is still considerable room to increase the number of split injections to promote atomization of the fuel. Remaining. On the other hand, 1 just before the explosion
The pulse ON time and pulse OFF time are set so that the fuel corresponding to the maximum value of the required injection amount can be injected in parts within the stroke time, and the fuel corresponding to the required injection amount is reliably injected throughout the entire starting zone. It is also possible to perform split injection, but in this case, the pulse ON time becomes longer, the number of splits becomes smaller, and the atomization of the fuel is significantly reduced.

[0005] An object of the present invention is to provide an engine fuel control device that can set the split injection amount so that the number of splits per stroke is as large as possible, promote atomization of fuel, and improve engine startability. It is to provide.

[0006]

[Means for Solving the Problem] A fuel control device for an engine according to claim 1, as shown in the functional block diagram of FIG. an injection amount control means, and a divided injection amount calculation means for calculating a divided injection amount for one injection when the required injection amount is divided into a plurality of injections, and at least within a starting zone until the engine is started. In a fuel control device for an engine that divides a requested injection amount into a plurality of times and injects the divided injection amount in units of divided injection amounts, a rotation speed detection means for detecting the engine rotation speed is provided, and the divided injection amount calculation means is configured to be a rotation speed detection means and a rotation speed detection means. In response to the output from the fuel injection amount control means, the divided injection amount is set such that the number of divisions per stroke is as large as possible.

According to a second aspect of the invention, in the engine fuel control device according to the first aspect, the divided injection amount calculating means calculates a total injection time corresponding to the required injection amount, and calculates the total injection time corresponding to the required injection amount. Determine the maximum number of divisions by dividing the total injection pause time, which is obtained by subtracting the total injection time from the one stroke time determined by the rotation speed, by a predetermined lower limit value of the pulse OFF time of the injection pulse of split injection, and calculate the maximum number of divisions for the total injection time. It is configured to determine the divided injection amount by dividing the injection amount into equal parts.

[0008] In the engine fuel control device according to claim 3, in the engine fuel control device according to claim 2, the divided injection amount calculation means is configured to calculate the maximum divided injection amount when the engine rotation speed moves to a predetermined rotation speed or higher. The number of split injections is set with a predetermined characteristic such that the number of split injections is smaller than the number of split injections, and the number of split injections becomes smaller as the engine speed increases.

[0009]

[Operation] In the engine fuel control system according to claim 1, the divided injection amount calculation means for determining the divided injection amount determines the required injection amount for one stroke at least within the starting zone until the engine starts. The divided injection amount is set so that the number of divisions per stroke is as large as possible based on the output from the fuel injection amount control means and the rotation speed detection means that detects the engine rotation speed. Even if the time for one stroke becomes shorter, fuel corresponding to the required injection amount can be reliably injected in parts, and the number of divisions per stroke can be increased as much as possible over the entire starting zone, resulting in atomization of fuel. This can greatly improve starting performance.

In the fuel control system for an engine according to the second aspect of the present invention, basically the same effect as that of the first aspect can be obtained. In addition, the divided injection amount calculation means calculates the total injection time corresponding to the required injection amount, and calculates the total injection pause time, which is obtained by subtracting the total injection time from the one stroke time determined by the engine rotation speed, by turning off the injection pulse of the divided injection. The maximum number of divisions is determined by dividing the time by a predetermined lower limit value, and the divided injection amount is determined by equally dividing the total injection time by the maximum number of divisions, so that the number of divisions per stroke is as large as possible. The injection amount can be determined.

[0011] In the engine fuel control device according to the third aspect, basically the same effect as that in the second aspect can be obtained. In addition, if the engine speed increases to a predetermined number of rotations or higher and the mechanical efficiency of the engine increases, and the actual required injection amount becomes smaller than the calculated required injection amount, the number of divided injections will change to the divided injection amount. The calculation means sets a predetermined characteristic such that the number of split injections is smaller than the maximum number of split injections, and the number of split injections decreases as the engine speed increases, so that fuel that matches the actual required injection amount is set. can be supplied and prevent the mixture from becoming rich.

0012

According to the fuel control device for an engine according to claim 1, as described in detail in the above operation section, fuel corresponding to the required injection amount can be reliably injected in parts, and moreover, The number of divisions per stroke can be increased as much as possible over the entire range, promoting atomization of the fuel and greatly improving startability.

According to the fuel control device for an engine according to the second aspect, the same effects as those in the first aspect can be obtained. In addition, by using the divided injection amount calculation means, it is possible to easily obtain a divided injection amount that maximizes the number of divisions per stroke while ensuring a predetermined lower limit value of the pulse OFF time of the injection pulse.

[0014] In the engine fuel control device according to the third aspect, the same effects as in the second aspect can be obtained. In addition,
When the engine speed reaches a predetermined speed or higher and the mechanical efficiency of the engine increases, fuel can be supplied in accordance with the actual required injection amount, preventing the mixture from becoming richer and improving combustibility. I can do it.

[0015]

Embodiments Hereinafter, embodiments of the present invention will be explained based on FIGS. 1 to 7. This embodiment is a case where the present invention is applied to a fuel control device for an in-line four-cylinder engine for an automobile.

In FIG. 1, an engine E includes a cylinder block 1, cylinder head 2, crankshaft 3, connecting rod 4, piston 5, intake port 6, intake valve 7, and intake passage 8.
, the exhaust port 9, the exhaust valve 10, the exhaust passage 11, the valve operating mechanism 12, etc. are the same as those of existing well-known configurations, so a detailed explanation of their structures will be omitted. The intake passage 8 includes, from the upstream side, an air cleaner 15, an air flow meter 16, a compressor 18 of a turbocharger 17, an intercooler 20, a throttle valve 21, and a surge tank 2.
2, and a duty solenoid type ISC valve (
An idle speed control valve) 28 is interposed, and an injector 23 for injecting fuel toward the intake port 6 is installed at the downstream end of the four branch intake pipes of the intake manifold that constitute the downstream part of the intake passage 8. ing.

A turbo supercharger 1 is installed in the middle of the exhaust passage 11.
7 turbines 19 are provided, and the turbine 19
The wastegate passage 24 is opened and closed by a wastegate valve 25 driven by a diaphragm type actuator 25a, and the intake pressure operating chamber of the actuator 25a is provided with a wastegate passage 24 that bypasses the compressor 18. Air pressure is introduced, and when the intake pressure exceeds a predetermined pressure, the waste gate valve 25 is opened.

The distributor 30 is electrically connected to the ignition unit 31, and the rotating shaft 30a of the distributor 30 is connected to the crankshaft 3 through a mechanism not shown so that it rotates once every two revolutions of the crankshaft 3. A pair of timing rotors are connected to each other and fixed to the rotating shaft 30a, and the distributor 30 includes an electromagnetic pickup type crank angle sensor 32 that detects the rotational speed of the rotating shaft 30a via one of the timing rotors.
An electromagnetic pickup type reference crank angle sensor 33 is provided to detect the timing of the intake TDC of the reference cylinder (for example, the first cylinder) via the other timing rotor.

A control unit 40 is provided for controlling the engine E, and the control unit 40
includes an air flow meter 16 that detects the amount of intake air;
A throttle opening sensor 34 that detects the opening of the throttle valve 21, a water temperature sensor 36 that detects the temperature of the cooling water in the water jacket, a crank angle sensor 32, a reference crank angle sensor 33, a starter switch 35, and others not shown. Signals from various sensors and switches are inputted, and drive signals are outputted from the control unit 40 to the ignition unit 31, injector 23, ISC valve 28, etc.

The control unit 40 is mainly composed of a microcomputer, and also converts various analog signals such as the intake air amount signal from the air flow meter 16 and the throttle opening signal from the throttle opening sensor 34 into an A/D converter. an A/D converter for converting, 4
It is equipped with four drive circuits for each injector 23, a drive circuit for the ignition unit 31, a drive circuit for the ISC valve 28, etc., and the ROM contains a control program for ignition timing control and an accompanying map, A control program for fuel control described below and an accompanying map,
Various other control programs are input and stored in advance. Incidentally, since ignition timing control is already well known, detailed explanation thereof will be omitted.

[0021] Here, the fuel control device of the present application sets the split injection amount so that the number of splits per stroke is as large as possible within the starting zone until the engine starts, and atomizes the fuel by split injection. This is to maximize start-up performance and improve startability.

Next, the above fuel control routine will be explained with reference to FIGS. 2 to 6. In addition, in the figure, Si (i=
1, 2, 3,...) indicate each step.

[0023] When the ignition key is turned on, this control is started, and after the necessary initial settings are executed, the crank angle signal from the crank angle sensor 32 is read, and using this, the engine rotation speed Ne is calculated. At the same time, the water temperature signal from the water temperature sensor 36 and the switch signal from the starter switch 35 are read (S1). Next, it is determined whether the starter switch 35 is ON or not (S2), and if No, it is determined whether the engine rotation speed Ne is Ne=0 (S3), and when the starter switch 35 is OFF, the engine When is stopped, S1 to S3 are repeated.

When the starter switch 35 is turned on, it is determined whether or not the engine speed Ne is Ne≦500rpm (S4).
If it is pm, it is the start zone, so it is determined whether any of the four cylinders is at compression TDC (S5). Then, when S1, S2, S4, and S5 are repeated and any cylinder reaches compression TDC, a subroutine for calculating the number of divisions described below is executed to calculate the maximum number of divisions N and the pulse ON time Ton of the drive pulse of the injector 23. is executed (S6), and then a subroutine for split injection processing, which will be described later, is executed to actually perform split injection (S7).

In this way, S1, S2, S4 to S7 are repeated, and when the engine speed Ne increases to a certain degree and the starter switch 35 is turned off, the starting zone shifts to the normal zone and normal fuel control is executed. (S8
), the fuel injection amount is calculated according to the intake air amount, and fuel is injected at a predetermined timing. Note that this normal fuel control is already well known, so a detailed explanation thereof will be omitted.

Next, the subroutine for calculating the number of divisions will be explained with reference to the flowchart shown in FIG. 2(b). First, the required injection amount Tp is calculated from a map using the cooling water temperature as a parameter (S11), and the total injection time T required to inject the required injection amount Tp is calculated from the characteristic diagram of the injector 23 using the injection amount as a parameter. Calculated (S12), 1 required for the crankshaft 3 to rotate twice
The stroke time Tc (msec) is the current engine speed Ne
is calculated using the formula Tc=2×60×1000/Ne (S13), and the maximum number of divisions N is N=(K×Tc-T)
/Toff is calculated (S14).

Note that Toff is a predetermined lower limit value of the pulse OFF time of the drive pulse of the injector 23, and is set as the minimum preparation time necessary for the next injection while taking into consideration the characteristics of the injector 23. , for example, T
Off is set to 8 msec. K is one stroke time Tc
This is a constant to allow split injection to be performed with some margin within the time period, and is set to, for example, K=0.9. The maximum number of divisions N is set to a natural number with fractions rounded down. Next, the pulse ON time Ton of the drive pulse is Ton=
It is calculated using the formula T/N (S15). Note that when the pulse ON time Ton<2 msec or less, the injector 23
Considering that the characteristics of will become unstable, Ton<2mse
If it becomes c, Ton is set to 2 msec, and the maximum number of divisions N is calculated again using the formula N=T/Ton. Note that when determining the maximum number of divisions N, N may be determined taking into consideration the invalid time of the injection pulse.

Next, the subroutine of the split injection process will be explained with reference to the flowchart shown in FIG. First, it is determined whether the first cylinder is compressed TDC (S21),
If Yes, the maximum number of divisions N and the pulse ON time Ton are output to the injection control subroutine for driving the injector 23 of the first cylinder (S22). If the first cylinder is not at compression TDC, it is determined whether or not the second cylinder is at compression TDC (S23), and if Yes, the injection control subroutine for driving the injector 23 of the second cylinder is Maximum number of divisions N and pulse ON
The time Ton is output (S24). The second cylinder has compression T
If it is not DC, it is determined whether or not the compression TDC is in the third cylinder (S25), and if Yes, the maximum number of divisions N and The pulse ON time Ton is output (S26), and if No, the maximum number of divisions N and the pulse ON time Ton are output to the injection control subroutine for driving the injector 23 of the fourth cylinder (S27). .

Next, the injection control subroutine will be explained with reference to the flowchart shown in FIG. still,
Since the injection control for driving the injector 23 of each cylinder has the same configuration, the injection control for driving the injector 23 of the first cylinder will be explained. When this subroutine is started, counter I is reset (S31).
, one divided injection of the injector 23 of the first cylinder is executed based on the pulse ON time Ton and pulse OFF time Toff of the drive pulse (S32), the counter I is incremented (S33), and the counter I becomes I=I= It is determined whether the split injection is N or not, that is, whether the split injection has been executed the maximum number of splits N times (S34), and the split injection is executed until the counter I becomes I=N.

Next, the operation of the fuel control system will be explained with reference to the diagram in FIG. Note that this diagram is for a case where the total injection time T is, for example, T=130 msec. Time required for injection [N×(Ton+Toff)]
is set smaller as the engine speed Ne increases, and split injection is performed within one stroke time Tc, so that fuel corresponding to the required injection amount Tp is applied to the engine E in the region of engine speed Ne = 0 to 500 rpm. can be reliably supplied, and by shortening the one-stroke time Tc, it is possible to reliably prevent the situation where the entire required injection amount cannot be injected and the air-fuel mixture becomes lean and the startability deteriorates. Moreover, since the pulse ON time Ton is set so that the maximum number of divided injections N is as large as possible, atomization of the fuel is promoted and startability is significantly improved.

Note that as the engine speed Ne increases, the mechanical efficiency of the engine E also increases, so the subroutine for calculating the number of divisions is partially changed so that the engine speed Ne becomes a predetermined speed (for example, 300 rpm). In this case, as shown by the broken line A in FIG. 3, the maximum number of divisions may be made smaller than the maximum number of divisions N calculated as described above to prevent the mixture from becoming rich. good. That is, as shown in FIG. 7, the pulse is turned on in S15.
After calculating the time Ton, the engine speed Ne is Ne≧
It is determined whether the engine speed is 300 rpm (S41), and if Yes, the number of divided injections N1 is set smaller than the maximum number of divisions N (S42), and the number of divided injections N1 is set to the maximum number of divisions N (S43). In this embodiment, the present invention is applied to a 4-cylinder in-line engine, but the present invention can be similarly applied to a 6-cylinder in-line engine or a V-type 6-cylinder engine. In this embodiment, the present invention was applied to a fuel injection device that injects fuel in parts during engine startup, but the invention can also be applied to fuel injection devices that inject fuel in parts in other operating regions. The same can be applied.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an engine control system.

FIG. 2 is a flowchart of a fuel control main routine.

FIG. 3 is a flowchart of a subroutine for calculating the number of divisions.

FIG. 4 is a flowchart of a subroutine of split injection processing.

FIG. 5 is a flowchart of an injection control subroutine.

FIG. 6 is a characteristic diagram of split injection.

FIG. 7 is a flowchart of a routine related to a modification of the division count calculation process.

FIG. 8 is a functional block diagram showing the configuration of the invention.

[Explanation of symbols]

E engine 23 Injector 32 Crank angle sensor 36 Water temperature sensor 40 Control unit

Claims (3)

[Claims] 1. Fuel injection amount control means for determining a required injection amount for one stroke for each stroke of each cylinder, and split injection for one injection when the required injection amount is divided into multiple injections. A fuel control device for an engine that divides the required injection amount into multiple injections and injects each divided injection amount at least within a starting zone at least until the engine starts. The divided injection amount calculation means receives the outputs from the rotation speed detection means and the fuel injection amount control means and determines the divided injection amount such that the number of divisions per stroke is as large as possible. A fuel control device for an engine, characterized in that it is configured to set. 2. The divided injection amount calculation means calculates the total injection time corresponding to the required injection amount, and calculates the total injection pause time, which is obtained by subtracting the total injection time from the one stroke time determined by the engine rotation speed, for the divided injection. Pulse OF of injection pulse
Determine the maximum number of divisions by dividing by a predetermined lower limit value of F time,
1. A fuel control device for an engine, characterized in that the total injection time is divided equally into the maximum number of divisions to determine the divided injection amount. 3. The divided injection amount calculation means is configured to perform a divided injection number smaller than the maximum divided number when the engine speed increases to a predetermined number of revolutions or more, and decrease the divided injection number as the engine speed increases. 3. The fuel control device for an engine according to claim 2, wherein the fuel control device for an engine is configured to set the number of divided injections based on a predetermined characteristic such that: