JPH0454240A - Fuel supply system for internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance an exhaust air properties and responsiveness in transition and promote atomization by detecting a wall flow quantity so as to control a fuel injection valve at an injection timing where the wall flow quantity becomes minimum, and operating an air supply device under an operation condition where the wall flow quantity is increased. CONSTITUTION:In a fuel supply device for an internal combustion engine provided with a fuel injection valve (a) in an engine suction system, there are provided a wall flow quantity detecting means (b) for detecting a wall flow quantity on the basis of a signal output from a reflection type optical sensor disposed on a suction passage wall, and an operation condition detecting means (c) for detecting an engine operation condition. Output signals from the detecting means (b) and (c) are input into an injection control means (d). An injection timing of the fuel injection valve (a) is controlled for each every engine operation condition in such a manner that the wall flow quantity becomes minimum on the basis of the detected wall flow quantity. An air supply signal is output from an air supply control means (e) under the operation condition of a large wall flow quantity. i.e., when the wall flow quantity exceeds a predetermined value at the time of a cold operation and high load operation of a large wall flow quantity, or by direct watching of the wall flow quantity. An air supply device supplies air for promoting atomization of the injected fuel to the fuel injection valve (a).

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel supply system for an internal combustion engine that includes a fuel injection valve in the engine intake system.

<Prior Art> As a conventional fuel supply system for an internal combustion engine, an electrode-type wall flow rate sensor is installed at a location on the inner wall of the engine's intake passage in order to detect the wall flow rate of fuel flowing in liquid form along the inner wall of the intake passage. ,
There is a device in which the amount of fuel injected and supplied by a fuel injection valve is corrected depending on the wall flow rate (Japanese Patent Laid-Open No. 63
(Refer to Publication No.-170538).

Specifically, the optimal wall flow rate is stored in advance for each engine operating state in a steady operating state, and the correction is performed according to the difference between the wall flow rate and the actual wall flow rate detected by the sensor at that time. I do.

As a result, a fuel lag occurs during acceleration (deceleration), and the actual wall flow rate decreases (
Even if the air-fuel ratio increases (increases), the fuel injection amount is corrected to increase (decrease) in accordance with the difference, so that the actual air-fuel ratio approaches the appropriate air-fuel ratio.

<Problems to be Solved by the Invention> However, such conventional fuel supply devices for internal combustion engines do not reduce the wall flow rate itself, and therefore have a problem in that fuel efficiency and emissions cannot be improved.

In addition, when the engine temperature is low or the engine load is high and the amount of fuel injected is large, the atomization of the injected fuel deteriorates, which increases the wall flow rate, further exacerbating the above problems. there were.

SUMMARY OF THE INVENTION In view of these conventional problems, it is an object of the present invention to provide a fuel supply system for an internal combustion engine that can reduce the wall flow rate.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a fuel supply system for an internal combustion engine including a fuel injection valve (a) in the engine intake system, as shown in FIG. (b) to (gl) are provided.

(b) Wall flow rate detection means for detecting the wall flow rate based on a signal from a reflective optical sensor placed on the wall of the intake passage (C) Operating state detection means for detecting the engine operating state (
d) Injection control means for controlling the injection timing of the fuel injector for each engine operating state so that the wall flow rate is minimized based on the detected wall flow rate (e) In an operating state where the wall flow rate is large (wall flow rate Kata(
an air supply control means that outputs an air supply signal when the wall flow rate is at a predetermined value or higher (when the wall flow rate is directly measured and the wall flow rate is above a predetermined value); According to the above configuration, the wall flow rate detection means detects the wall flow rate based on the signal from the reflective optical sensor and detects the operating state. The means detects the operating state of the engine, and the injection control means controls the injection timing of the fuel injection valve for each engine operating state so that the wall flow rate is minimized to perform fuel injection.

Then, when the wall flow rate is high, the air supply control means outputs an air supply signal to operate the air supply device to supplementally supply air to the fuel injection valve, thereby increasing the amount of injected fuel. Promotes atomization. Thereby, the wall flow rate decreases.

<Example> Embodiments of the present invention will be described below based on the drawings.

A system according to an embodiment will be described with reference to FIG.

An intake port 3 and an exhaust boat 4 are formed in the cylinder head 2 at the upper end of the combustion chamber l.

The intake port side opening of the combustion chamber 1 is opened and closed by raising and lowering the intake valve 6, and the exhaust boat side opening of the combustion chamber 1 is opened and closed by raising and lowering the exhaust valve 8. There is.

The intake port 3 communicates with the intake manifold 9 on the upstream side, and the fuel injection valve 10 is oriented toward the front side of the intake valve 6 near the intake port 3 of the intake manifold 9.
It's coming.

The fuel injection valve 1o is equipped with an air supply device 12 that is supplied with air (assist air) from an air pump (not shown) via a solenoid valve 11, and surrounds the nozzle 10a of the fuel injection valve 10. Air is supplied into the guide barrel 2a through the air passage 12b, and is injected from the injection port 12c while atomizing the injected fuel.

Here, an optical fiber is used as a reflective optical sensor for wall flow rate detection.

The detection end 13a of the optical fiber 13 is exposed flush with the wall surface on the left side of the intake valve 6 in the drawing of the intake port 3 on the periphery of the intake valve 6.

The optical fiber 13 mainly consists of a core with a high refractive index and a cladding around the core with a lower refractive index, and has a light emitting/receiving part at the detection end 18a.

The base end 13b of the optical fiber is connected to the light emitting element/photoelectric conversion element 14, and the light from the light emitting element (light source) is propagated to the light emitting part, the reflected light is propagated from the light receiving part, and an electrical signal is generated. and input it to a control unit (not shown).

In other words, if there is a wall flow around the detection end 13a (light emitting/receiving part), the difference in refractive index between the optical fiber glass and the fuel (liquid) will become smaller, resulting in higher transmittance and lower reflected light intensity. .

Therefore, the presence or absence of wall flow can be determined based on the strength of reflected light.

Incidentally, as a sensor that utilizes a change in the refractive index of light, there are examples such as Japanese Patent Laid-Open No. 59-44641.

Here, with reference to FIG. 3, a method of determining the amount of wall flow from the presence or absence of wall flow will be explained.

The horizontal axis shows the crank angle.

The vertical axis shows the reflected light intensity, and the reflected light intensity when there is no wall current, that is, when the most light from the light emitter is reflected back to the light receiver, is 1, and a predetermined ratio of this is taken as 1. Set the slice level. This changes as operating conditions change.

Then, while the intensity of the reflected light from the optical fiber 13 is below the slice level (crank angle section CA), it is assumed that there is a wall flow at the detection end 13a of the optical fiber.

Therefore, it is possible to know the wall flow rate depending on the size of the crank angle section CA.

In other words, when the wall flow rate is large, it takes a long time for the wall flow to finish flowing into the combustion chamber 1, and this can be determined by the size of the crank angle section during that time.

Specifically, when the wall flow rate is large, the crank angle section CA becomes longer as shown by the broken line in the figure. On the other hand, when the wall flow rate is small, the crank angle section CA2 becomes short as shown by the solid line in the figure.

A routine for controlling the operation of the air supply device and controlling the injection timing, which is executed in synchronization with the engine rotation, will be described with reference to the flowchart in FIG. 4.

In step 1 (denoted as Sl in the figure, the same applies hereinafter), the engine rotation speed N, which is calculated based on the signal from the crank angle sensor, is detected based on the signal from the air flow meter as parameters indicating the operating state of the engine. Input the intake air flow rate Q and engine cooling water temperature Tw.

In step 2, it is determined whether the engine cooling water temperature Tw is below a predetermined value (when cold) or whether the engine operating state is above a predetermined load (when high load).

In other words, as shown in Fig. 5, when the injected fuel is cold, it is difficult to vaporize, so atomization deteriorates and the wall flow rate increases, and as shown in Fig. 6, when the load is high, As the amount of injected fuel increases, atomization similarly deteriorates and the wall flow rate increases. Therefore, as will be described later, the air supply device 12 is turned off to promote atomization during cold or high load conditions. In order to output the air supply signal for activation, these operating conditions are used as the basis for determining the output of the air supply signal.

If it is determined that it is neither a cold time nor a high load time, proceed to step 3.

In step 3, it is determined whether the air supply signal is being output (outputting) or not (other than that).

If it is determined otherwise, proceed to step 4.

In step 4, step 1
The injection timings T and I corresponding to the current operating state input in step 5 are retrieved, and in step 5, they are substituted for the injection timing T, and fuel is injected via the fuel injection valve 10 at that timing. .

Thereafter, the process proceeds to step 11 and subsequent steps, and the injection timing T is varied by a predetermined amount to select the optimum injection timing, that is, the injection timing at which the wall flow rate is minimized.

If it is determined in step 2 that the condition is cold or under high load, the process proceeds to step 6.

In step 6, similarly to step 3, it is determined whether the air supply signal is being output (outputting) or not (other than that).

If it is determined otherwise, in step 7, the output of the air supply signal is started in order to operate the air supply device 12, and the process proceeds to step 8. However, if it is determined that the air supply signal is being output, the process proceeds to step 8. Proceed to.

Note that while the air supply device 12 is in operation, air is supplied in synchronization with fuel injection from the fuel injection valve IO.

In step 8, the operating state input in step 1 is selected from the map ■ in the RAM that stores the injection timing according to the engine speed N and the intake air flow rate Q when the air supply device 12 is operating. Search for the injection timing TM■ corresponding to , and substitute it for the injection timing T in step 9.
The fuel is injected via the

Thereafter, the process similarly proceeds to step 11 and subsequent steps, and the injection timing T is varied by a predetermined amount to select the optimum injection timing, that is, the injection timing at which the wall flow rate is minimized.

If it is determined in step 3 that the air supply signal is being outputted, the process proceeds to step 10, in which the output of the air supply signal is stopped in order to deactivate the air supply device 11, and in step 4,
Proceed to step 5.

Then, in step 11, it is determined whether the learning conditions are satisfied. That is, if the engine operating state is steady, it is assumed that the learning condition is met and the process proceeds to step 12; otherwise, it is assumed that the learning condition is not met and this routine is ended.

In step 12, the calculated wall flow rate or wall flow rate (wall flow rate/fuel injection amount) is input, but in this embodiment, as described above, the crank angle section C is used as an indicator of the wall flow rate.
Enter A+.

In step 13, the injection timing T is advanced by a predetermined amount ΔT to become a new injection timing T, and fuel is injected via the fuel injection valve 10 at that timing.

In step 14, the crank angle section CA t is used as the wall flow rate in the injection at the injection timing T.
Enter.

In step I5, CA + and CA 2 are compared, and if CAI > CA * (wall flow rate decrease), this indicates that the direction of changing the injection timing T is correct (to advance). , crank angle section CA
The operation of advancing the injection timing T is repeated as long as 2 decreases.

That is, in step 16, the crank angle section CA2 is assigned to the crank angle section CA, and in step 17, flag F is set, and the process returns to step 13.

Further, if the determination in step 15 is that CA + ≦CA2 (wall flow rate increase), the process proceeds to step 18 .

In step 18, it is determined whether flag F is set. When standing, crank angle section CA2 (
This indicates that the injection timing T at which the wall flow rate) becomes the minimum value has been found, so the process proceeds to step 23.

On the other hand, when the user is not standing, this indicates that the wall flow rate has increased as a result of advancing the injection timing T in step 13, which means that it was a mistake to advance the injection timing T in the first place. Therefore, this time, the injection timing T is delayed and the process proceeds to step 19 in order to observe the change in the wall flow rate.

In step 19, the crank angle interval CA2 is substituted into the crank angle interval CAr.

In step 20, the injection timing T is delayed by a predetermined amount ΔT, this is set as a new injection timing T, and fuel is injected via the fuel injection valve 10 at that timing.

In step 21, the crank angle section CA is input as an indicator of the wall flow rate in the injection at the injection timing T.

In addition, in step 22, CA and CA2 are compared, and when CAI > CA2 (wall flow rate decrease), it is indicated that the direction of changing the injection timing T or this direction (slowing direction) was correct. Therefore, crank angle section CA
2 decreases, the process returns to step 19 to repeat the operation of delaying the injection timing T.

In the judgment of step 22, CA, ≦CA2 (wall flow rate increase)
When , this indicates that the injection timing T at which the crank angle section CA2 (wall flow rate) becomes the minimum value has been found, so this operation is completed and the flag F is cleared in step 23.

In step 24, the injection timing T advanced in step 13 or the injection timing T delayed in step 20 is determined to be within the range that allows injection during the intake stroke (the most advanced injection timing TA and the most retarded injection timing T). between)
If it is within the range, step 2
Proceeding to step 6, the map searched in step 4 or step 8 is rewritten to the injection timing T advanced in step 13 or the injection timing delayed in step 20, and this routine ends.

If the determination in step 24 is that it is not within the range, then in step 25, if the injection timing T exceeds the most advanced injection timing TA, it is fixed at TA, and if the injection timing T exceeds the most retarded injection timing T, If so, it is fixed to TI, and in step 26 the map searched in step 4 or step 8 is rewritten to this value, and this routine ends.

In other words, regarding the injection timing T, it is assumed that the injection is performed during the intake stroke from the viewpoint of responsiveness. The condition is that the retarded injection timing T is within the range.

The reason why the air supply device 12 is not operated all the time is to prevent the efficiency of the engine from decreasing.

Furthermore, the reason why two types of maps (map I and map ■) were used for injection timing is as follows.

That is, the direction of the injected fuel is bent by the intake air, but since the spray diameter of the injected fuel is different when the air supply device 12 is operating and when it is not operating, the degree to which the direction is bent by the intake air is large. different.

Therefore, if the same map is used to search for the injection timing and then the optimal injection timing is selected by varying the amount by T in increments of a predetermined amount, it will take time to complete the selection.

Therefore, by using appropriate maps for when the air supply device 12 is in operation and when it is not in operation, the optimal injection timing can be quickly selected.

More specifically, it is as follows.

That is, normally, the injected fuel is injected in front of the intake valve 6, but when the air supply device 12 is in operation, the diameter of the spray of the injected fuel becomes smaller, making it easier for the injected fuel to get onto the intake air. Therefore, if the intake air is injected immediately after the intake valve 6 is opened, the intake air will bend too much above the intake valve 6, and a wall flow will easily occur. Therefore, in this case, the injection timing is preferably selected so that the intake valve 6 opens just before the injected fuel arrives at the intake valve 6.

Furthermore, when the air supply device 12 is inactive, the diameter of the spray is large and the spray is heavy, so the extent to which it is bent by the intake air is small. Therefore, in this case, if the injection timing is set immediately after the intake valve opens, the intake air can efficiently flow into the fuel chamber l.

Here, step 1 corresponds to the driving state detection means, step 5. 9.13.20 corresponds to the injection control means together with the fuel injection valve IO, step 12.14.21 corresponds to the wall flow rate detection means together with the optical fiber 13, and step 7
, IO corresponds to the air supply control means.

As explained above, it is possible to perform one injection by the fuel injection valve 10 at the injection timing when the wall flow rate is minimized, which improves emissions, improves responsiveness during transients, and improves fuel efficiency. can also be improved.

Incidentally, at this time, since a map of injection timing is used according to the state at that time, it is possible to quickly select the more optimal injection timing (minimum wall flow rate).

Furthermore, when the atomization of the injected fuel deteriorates and the wall flow rate increases during cold or high load operating conditions, the air supply device 12 is activated to promote atomization.
The above effects can be further enhanced.

Further, as operating conditions for operating the air supply device 12,
In addition to the above-mentioned cold conditions and high load conditions, as shown in Figure 7,
The air supply device 12 may be operated by directly checking the wall flow rate and when the wall flow rate reaches a predetermined value or more.

The same effect can be obtained by doing the second method.

<Effects of the Invention> As explained above, according to the present invention, the fuel injection valve can perform injection at the injection timing that minimizes the wall flow rate, maintains an appropriate air-fuel ratio, and improves exhaust properties. At the same time, it is possible to improve the responsiveness during transients and improve fuel efficiency.

Furthermore, during operating conditions where the wall flow rate increases, the air supply device is activated to promote atomization.
It is also possible to obtain the effect that the above effects can be further enhanced.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a sectional view of an internal combustion engine near an intake valve showing an embodiment of the present invention, and FIG. 3 is a diagram showing reflected light intensity with respect to crank angle. Fig. 4 is a flowchart showing the control details, Fig. 5 is a diagram showing the relationship between engine cooling water temperature and wall flow rate, Fig. 6 is a line diagram showing the relationship between engine load and wall flow rate, and Fig. 7 is a diagram showing the relationship between engine cooling water temperature and wall flow rate. It is a timing chart showing the relationship between activation/non-activation of the air supply device and wall flow rate. 3... Intake port 6... Intake valve 10.
...Fuel injection valve 12...Air supply device 13.
・・Optical fiber

Claims (1)

[Scope of Claims] A fuel supply system for an internal combustion engine including a fuel injection valve in an engine intake system, comprising: wall flow rate detection means for detecting a wall flow rate based on a signal from a reflective optical sensor disposed on an intake passage wall; an operating state detection means for detecting the engine operating state; an injection control means for controlling the injection timing of the fuel injector for each engine operating state so that the wall flow rate is minimized based on the detected wall flow rate; an air supply control means that outputs an air supply signal during an operating state where there is a large amount of air, and an air supply device that receives the air supply signal and supplies air for promoting atomization of the injected fuel to the fuel injection valve. A fuel supply device for an internal combustion engine, characterized in that: