JPH01237339A - Fuel injector of internal combustion engine - Google Patents

Abstract

PURPOSE:To aim at expansion of critical lean combustion range so as to improve fuel consumption by increasing an amount of fuel injection in the cylinders showing a larger amount of torque fluctuation, in an internal combustion engine in which fuel injection is applied simultaneously to both cylinders synchronously with each of two cylinders' intake strokes taking place alternately. CONSTITUTION:In a 4-cylinder engine in which fuel injection is applied simultaneously to two cylinders by simultaneously opening respective fuel injection valves 28 of the first and fourth cylinders and those of the second and third cylinders by means of a first drive circuit 44 and a second drive circuit 46 respectively, a controller 40 for controlling respective drive circuits 44, 46 is provided with a means 1 which applies fuel injection simultaneously to two cylinders synchronously with each of two cylinders' intake strokes taking place alternately. In addition, a means 2 for detecting the amount of torque fluctuation of each cylinder is provided. Further, a means 3 is also provided for increasing an amount of fue injection to a pair of cylinders showing a larger amount of torque fluctuation detected by this detecting means 2 and decreasing amount of fuel injection to the other pair of cylinders.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection device for an internal combustion engine that injects fuel into two cylinders simultaneously.

[Conventional technology]

JP-A No. 57-28834 has a crank angle of 36
A fuel injection method is disclosed in which fuel is simultaneously injected into two cylinders in synchronization with each intake stroke of two cylinders having a stroke difference of 0 degrees, that is, two cylinders whose intake strokes alternate. In this case, in each cylinder, fuel is injected twice per combustion cycle, during the intake stroke of the negative cylinder and during the intake stroke of the other cylinder (in the explosion stroke when the intake valve is closed in the one cylinder). It will be done.

This fuel injection method promotes atomization of the fuel injected during the explosion stroke when the intake valve is closed, and the fuel injected during the intake stroke is stratified in the upper layer of the combustion chamber, resulting in good combustion. can be achieved. Note that if the intake air is swirled in the combustion chamber, there will be a layer of air-fuel mixture with a thin air-fuel ratio in the middle part of the combustion chamber, and a layer of air-fuel mixture with a rich air-fuel ratio will be created in the lower and upper parts on both sides. , by reliably achieving sandwich-like stratification, expanding the flammability limit at a lean air-fuel ratio, and with a layer of air-fuel mixture at a lean air-fuel ratio in the middle, the combustion temperature can be lowered, and the exhaust gas Purification performance (NOx) can be improved.

In addition, Japanese Patent Application Laid-open No. 150446/1983 discloses that a pressure sensor is attached to the combustion chamber of an engine, the pressure in the combustion chamber is sampled at every predetermined crank angle, and the cumulative value of the sampled values of the pressure in the combustion chamber for one cycle is calculated. The average effective pressure (corresponding to torque) is obtained by dividing by the number of samples, and the average effective pressure for each cycle obtained in this way is sampled for multiple cycles, and the torque fluctuation amount is calculated by calculating the mathematical variance (S2). It discloses that it calculates.

In addition, Japanese Patent Application No. 62-35877, which is an earlier application of the present application, calculates the engine load, the fluctuation of the engine rotational speed within a predetermined period of the explosion stroke, and the ratio of the engine load and the fluctuation of the engine rotational speed. , proposes to detect the amount of torque fluctuation from this ratio.

[Problem to be solved by the invention]

As described in Japanese Patent Application Laid-Open No. 57-28834 mentioned above, in a fuel injection device that simultaneously injects fuel into two cylinders in synchronization with the intake strokes of two cylinders whose intake strokes alternate, one cylinder Two fuel injections are performed, one during the intake stroke of one cylinder and the other during the intake stroke of the other cylinder, but the amount of fuel injected during each injection is the same. Therefore, if there are variations in the characteristics of the fuel injection valves or differences in intake air amount between cylinders, variations in air-fuel ratio will occur between the cylinders. Therefore, when setting the air-fuel ratio, it is necessary to set the air-fuel ratio setting value with reference to the thinnest value within the variation,
There is a strong tendency to set the actual air-fuel ratio to a value richer than the lean burn limit. Furthermore, when variations in the air-fuel ratio occur, the amount of torque fluctuation also increases.

[Means to solve the problem]

In order to solve the above problems, the fuel injection device for an internal combustion engine according to the present invention, for example, referring to FIG. 1, injects fuel into two cylinders simultaneously in synchronization with each intake stroke of the two cylinders whose intake strokes alternate. means 1, means 2 for detecting the torque fluctuation amount of each cylinder, and a fuel injection amount at the time of fuel injection synchronized with the intake stroke of the cylinder having a larger torque fluctuation amount according to the output of the torque fluctuation amount detection means. The present invention is characterized in that it is provided with means 3 for increasing the amount of fuel and decreasing the amount of fuel injected when fuel is injected in synchronization with the intake stroke of the other cylinder.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

Referring to FIG. 1, an internal combustion engine main body 10 has a four-cylinder combustion chamber 12. An intake port 14 and an exhaust port 16 are formed in each cylinder.

An intake valve 18 and an exhaust valve 20, which are driven in synchronization with the engine crankshaft, are arranged at the intake port 14 and the exhaust port 16, respectively. Further, an ignition plug 22 is attached to the combustion chamber 12. Furthermore, a pressure sensor 24 is attached to the combustion chamber 12. Note that the intake port 14 is formed in a helical shape so that intake air generates a swirl within the combustion chamber 12.

The intake port 14 is connected to each branch pipe of an intake manifold 26, and a fuel injection valve 28 is disposed in each branch pipe. A throttle valve 30 and an air flow meter 32 are arranged in the intake pipe upstream of the intake manifold 26. Exhaust port 16 is connected to exhaust manifold 34. Also shown in FIG. 1 is a rotational speed sensor 34 that detects the rotational speed of the engine. As the rotation speed sensor 34, a sensor known in the field of internal combustion engines can be used, and other sensors such as an engine cooling water temperature sensor, an oxygen concentration sensor, etc. can also be used.

The fuel injection valve 28 is controlled by a control device 40. The control device 40 is a central processing unit (CPU) 42 that is configured as a microcomputer and has calculation and control functions.
has. The control device 40 further includes a read-only memory (ROM) in which programs are stored, and a random access memory (ROM) in which data is stored. J (RAM), and an input/output interface. In the present invention, two drive circuits 44, 46 are provided, and the control device 40 receives detection signals from the pressure sensor 24, air flow meter 32, rotation speed sensor 34, etc., and sends them via the two drive circuits 44, 46. A control signal is sent to the fuel injection valve 28.

The first drive circuit 44 is connected to the fuel injection valve 28 of the first cylinder and the fuel injection valve 28 of the fourth cylinder, and can open these two fuel injection valves 28 at the same time for the same amount of time. The second drive circuit 46 is similarly connected to the fuel injection valve 28 of the second cylinder and the fuel injection valve 28 of the third cylinder. Here, the ignition order is the 1st, 3rd, 4th, and 2nd cylinders, and the intake strokes of the 1st and 4th cylinders alternate every 360 degrees in crank angle. Similarly, the intake strokes of the second and third cylinders alternate every 360 degrees in crank angle. Although this embodiment is an example of a four-cylinder internal combustion engine, the present invention can also be practiced in the case of a six-cylinder internal combustion engine, etc., using pairs of two cylinders each having alternating intake strokes.

FIG. 2 shows the intake stroke and fuel injection timing for a four-cylinder engine. The intake stroke is indicated by hatching, and the fuel injection timing is indicated by dots. During the intake stroke of the first cylinder, fuel is injected into the first cylinder and the fourth cylinder simultaneously, and further, during the intake stroke of the fourth cylinder, fuel is injected into the first cylinder and the fourth cylinder simultaneously. Since the fuel injection valves 28 of the first and fourth cylinders are commonly controlled by the first drive circuit 44, the fuel injection time, that is, the fuel injection amount is the same.

The same applies to the second and third cylinders.

Figure 3 shows how a layer of air-fuel mixture with a rich air-fuel ratio and a layer of air-fuel mixture with a lean air-fuel ratio are stratified in a sandwich-like manner. It is a figure which shows the 1st cylinder at the time of fuel injection. At this time, the fourth cylinder is in the explosion stroke and fuel injection is performed at the same time, but its intake valve is closed. In the first cylinder, before the intake stroke, for example, at the time of fuel injection synchronized with the intake stroke of the fourth cylinder shown as B in FIG. 2, fuel injection is also performed in the first cylinder, and this fuel is It vaporizes in the port 14 and mixes with the air there, forming a relatively rich mixture. When the intake valve 18 of the first cylinder opens, this air-fuel mixture first enters the combustion chamber 12. The intake port 14 is formed in a helical shape that generates a swirl, and the air-fuel mixture flows into the combustion chamber 12 while swirling around the axis, forming a layer of rich air-fuel mixture on the piston 36 side. Then, after the air-fuel mixture accumulated in the intake port 14 flows out and until the fuel injection valve 28 opens, the air-fuel mixture becomes very lean and enters the middle part of the combustion chamber 12. Next, when the fuel injection valve 28 opens, a rich mixture layer is formed in the upper part of the combustion chamber 12. Thus, achieving sandwich-like stratification expands the flammability limit at lean air-fuel ratios,
In addition, since there is a layer of air-fuel mixture with a low air-fuel ratio in the middle part, the combustion temperature can be lowered, and the generation of NOx can be prevented.

In the present invention, such stratification is achieved, and the amount of torque fluctuation is detected to correct the fuel injection amount.

FIG. 7 is a flowchart of a routine executed by the control device 40 of FIG. 1 to calculate a fuel correction coefficient for correcting the fuel injection amount. First, in step 50, the torque fluctuation amount ΔTri for each cylinder is calculated. For this purpose, the detected value of the pressure sensor 24 attached to each cylinder is used. The torque fluctuation amount ΔTri can be calculated, for example, according to the procedure described in the above-mentioned Japanese Patent Laid-Open No. 6O-(q) 150446. In other words, the pressure in the combustion chamber is sampled at every predetermined crank angle, and the cumulative value of the sampled values of the pressure in the combustion chamber for one cycle is divided by the number of samples to find the average effective pressure (corresponding to torque). The amount of torque fluctuation is calculated by sampling the average effective pressure for each cycle for a plurality of cycles and calculating the mathematical variance (S2). Alternatively, the amount of torque fluctuation can be calculated by sampling the maximum pressure during combustion and calculating the variance of this maximum pressure. Alternatively, as described in Japanese Patent Application No. 62-35877, which is an earlier application of the present application, engine load and engine rotational speed fluctuations within a predetermined period of the explosion stroke, and engine load and engine rotational speed fluctuations. The torque fluctuation amount can be detected from this ratio.

When the torque fluctuation amount ΔTri for each cylinder is obtained in this way, in step 51, it is determined whether the torque fluctuation amount ΔTr of the first cylinder and the torque fluctuation amount ΔTr4 of the fourth cylinder are equal. If no, the process proceeds to step 52, where it is determined whether the torque fluctuation amount ΔTr of the first cylinder is larger than the torque fluctuation amount ΔTr4 of the fourth cylinder. If yes, the process proceeds to step 53, where the increment Δα is added to the fuel correction coefficient α1 synchronized with the intake stroke of the first cylinder, and the increment Δα is added to the fuel correction coefficient α4 synchronized with the intake stroke of the fourth cylinder. Subtract.

This process will be explained using FIGS. 4 and 5.

In FIG. 5, the white dots indicate the individual torque fluctuation amount of the first cylinder, and the black dots represent the individual torque fluctuation amount of the fourth cylinder. For example, at time T. In , if the torque fluctuation amount of the first cylinder indicated by the white dot is larger than the torque fluctuation amount of the fourth cylinder indicated by the black dot, then according to this relationship, the amount increase and the increase shown in FIG. Weight reduction is being carried out.

Figure 4 shows the changes in the correction coefficient for correcting the fuel injection amount, where the white dots are for fuel injection synchronized with the intake stroke of the 1st cylinder, and the black dots are for the intake stroke of the 4th cylinder. This represents fuel injection synchronized with The fuel injection synchronized with the intake stroke of the first cylinder corresponds to the one shown by A in FIG. 2, and the fuel injection synchronized with the intake stroke of the fourth cylinder corresponds to the one shown by A in FIG. corresponds to In either case, fuel injection is performed in both the first cylinder and the fourth cylinder.

In step 52 of FIG. 7, in the fuel injection indicated by the white dot, the correction coefficient is larger than 1.0, so the fuel injection amount obtained by multiplying the basic injection amount by the correction coefficient is increased. It turns out.

On the other hand, in the fuel injection indicated by the black dot, the correction coefficient is smaller than 1.0, so the fuel injection amount obtained by multiplying the basic injection amount by the correction coefficient is reduced. Since the intake stroke of the first cylinder and the intake stroke of the fourth cylinder are alternate, the white dots and the black dots appear alternately in time, and therefore, fuel increases and decreases alternately. Overall, do not increase the amount of fuel.

Thus, the overall amount of fuel does not increase or decrease with respect to the basic amount, but when fuel is injected in synchronization with the intake stroke of the first cylinder, the amount of fuel is increased, and when fuel is injected in synchronization with the intake stroke of the fourth cylinder, the amount of fuel is decreased. That will happen. Here, referring to FIG. 3, the fuel injected in synchronization with the intake stroke of the first cylinder is located in the upper part of the combustion chamber 12, and can be said to mainly control the ignitability and combustion speed. The increase in the amount of fuel in the portion contributes to stabilizing combustion in the overall lean air/fuel mixture. Therefore, the amount of torque fluctuation in the first cylinder decreases as shown by the white dots in FIG. Correspondingly, in the fourth cylinder, the amount of fuel in the intake stroke is reduced, and the amount of torque fluctuation increases. Therefore, at time T1, the torque fluctuation amounts of the first cylinder and the fourth cylinder become equal.

If NO in step 52 of FIG. 7, the magnitude relationship of the torque fluctuation amount is opposite to that explained with reference to FIG. Increment Δα from fuel correction coefficient α1 synchronized with stroke
is subtracted, and an increment Δα is added to the fuel correction coefficient α4 synchronized with the intake stroke of the fourth cylinder. Thereby, even when the torque fluctuation amount of the fourth cylinder is larger, it is possible to eliminate variations in the torque fluctuation amount.

If YES in step 51 of FIG. 7, the process proceeds to step 55. Whereas the previous steps were related to the processing of the first and fourth cylinders, steps 55 to 58 are related to the processing of the second and third cylinders. Steps 55 to 58 correspond to steps 51 to 58, respectively, so their explanation will be omitted.

FIG. 8 corresponds to the processing after time T1 in FIGS. 4 and 5. In step 6o, the torque fluctuation amount ΔTr of the first cylinder and the torque fluctuation amount ΔTr4 of the fourth cylinder are determined.
It is determined whether the difference between the two values is smaller than the allowable value kTr. If YES, as shown in FIG. 5, it is determined whether the average value of the torque fluctuation amount of the first cylinder and the fourth cylinder is larger than the limit value of the torque fluctuation amount. If yes, at snap 63, an increment Δα is added to the fuel correction coefficient α1°α4 in order to reduce torque fluctuations in both the first and fourth cylinders. If no, it is determined that the torque fluctuation is small and fuel reduction can be prioritized.
In step 62, fuel correction coefficient α1. Subtract the increment Δα from α4. If the answer in step 60 is NO, the process proceeds to step 64. Step 64 to Step 67
As in the case of FIG. 7, steps 60 to 63 are performed.
This relates to the second and third cylinders correspondingly.

As a result, according to FIG. 7 (as shown at time T1 in FIG. 5), the torque fluctuation amounts of the first cylinder and the fourth cylinder become equal, and the torque fluctuation amounts of the second cylinder and the third cylinder become equal. Then, the torque fluctuations of these two cylinder groups are compared and the torque fluctuations of the gold cylinders are averaged.

This will be explained using FIG. 4, FIG. 5, and FIG. 6.

At time T1, the amount of torque fluctuation in the first cylinder and the amount of torque fluctuation in the fourth cylinder are equal.

Further, after time T1, the torque fluctuation amounts shown in FIG. 5 remain the same, and the correction coefficients shown in FIG. 4 are both reduced in step 62 in FIG. 8. As a result, as shown in FIG. 6, the air-fuel ratio reaches a point T when the amount is alternately increased and decreased. It remains constant between and time T1, but becomes thinner thereafter.

〔Effect of the invention〕

As explained above, according to the present invention, there are provided means for simultaneously injecting fuel into two cylinders in synchronization with the respective intake strokes of the two cylinders whose intake strokes alternate, means for detecting the amount of torque fluctuation in each cylinder, and In response to the output of the torque fluctuation amount detection means, the fuel injection amount is increased during fuel injection synchronized with the intake stroke of the cylinder with the larger amount of torque fluctuation, and the fuel injection amount is increased during fuel injection synchronized with the intake stroke of the other cylinder. Since a means for reducing the injection amount is provided, it is possible to perform stable combustion at a lean air-fuel ratio. In particular, when driving two fuel injectors with one drive circuit, it is not possible to change the air-fuel ratio of each cylinder independently, but it is possible to synchronize with the intake stroke in relation to the detected torque fluctuation amount. By changing the fuel injection amount, it is possible to equalize the torque fluctuation level.In contrast to the conventional method where the lean burn limit was restricted when the variation was large, the present invention allows the lean burn limit to be restricted. This can be expanded to improve fuel efficiency and exhaust purification performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an internal combustion engine according to the present invention, and FIG.
Figure 3 is a diagram explaining the characteristics of simultaneous fuel injection in two cylinders in synchronization with the intake stroke in the internal combustion engine shown in Figure 3. Figure 3 is a diagram explaining how stratification of the air-fuel mixture is achieved in the combustion chamber by the fuel injection shown in Figure 2. , FIG. 4 is a diagram showing changes in the correction coefficient for increasing and decreasing fuel amount, FIG. 5 is a diagram showing changes in torque fluctuation amount, FIG. 6 is a diagram showing changes in air-fuel ratio, and FIG. 7 is a diagram showing changes in the amount of torque fluctuation. FIG. 8 is a flowchart of control for calculating a correction coefficient according to the amount of torque fluctuation. FIG. 8 is a flowchart of control for calculating a correction coefficient further from that shown in FIG. 12... Combustion chamber, 14... Intake port,
24...Pressure sensor, 26...Intake manifold, 28...Fuel injection valve.

Claims (1)

[Claims] 2 in synchronization with each intake stroke of the 2 cylinders whose intake strokes alternate.
means for simultaneously injecting fuel into the cylinders; means for detecting the amount of torque fluctuation in each cylinder; and fuel injection time synchronized with the intake stroke of the cylinder with the larger amount of torque fluctuation according to the output of the torque fluctuation amount detection means. A fuel injection device for an internal combustion engine, comprising means for increasing the amount of fuel injected in one cylinder and decreasing the amount of fuel injected during fuel injection synchronized with the intake stroke of the other cylinder.