JPH05272393A - Fuel feed device for engine - Google Patents

Abstract

PURPOSE:To provide excellent stratified charge combustion without damaging combustion stability and exhaust emmision performance. CONSTITUTION:In an engine 1 in which fuel is directly injected into a combustion chamber 5 from an injector 9 and an ignition plug 8 is arranged facing to the combustion chamber 5, the injection direction of the injector 9 is directed to the ignition plug 8, and a fuel injection pulse is divided into plurality to set ignition timing of the ignition plug 8 at a pulse finishing time of a final injection pulse or within a predetermined period from the pulse finishing time. Accordingly, only fuel due to the final injection pulse is concerned with wetting of the ignition plug 8 and degree of wetting of the ignition plug 8 is reduced so as to secure excellent combustion stability. Stratified charge combustion is realized by ignition of the fuel due to the final injection pulse, existing in the vicinity of the ignition plug 8. Fuel due to an injection pulse preceding the final injection pulse is sufficiently premixed so as to improve exhaust emmission performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine fuel supply device.

[0002]

2. Description of the Related Art A direct injection method (hereinafter abbreviated as DI method) in which fuel is directly injected into a combustion chamber is known as one of engine fuel injection methods. Further, as the arrangement structure of the injector and the ignition plug in this DI type engine, there is disclosed a separation arrangement structure in which the injector and the ignition plug are arranged relatively far apart from each other, for example, Japanese Patent Laid-Open No. 1-273840. As described above, there is a close arrangement structure in which the injector and the spark plug are arranged relatively close to each other.

[0003]

By the way, in an engine, combustion stability and exhaust emission performance are important points in the performance evaluation. However, in the engine of the DI system and the separated arrangement structure, the fuel spray is Since the spark plug is separated from the spark plug, there is little wetting of the spark plug by the fuel, but since there is almost no air-fuel mixture around the spark plug that is the ignition source, combustion stability is especially high in low-load operating conditions with a small amount of fuel injection. Is extremely deteriorated (see the characteristic diagram L _{1 in} FIG. 3).

On the other hand, the engine of the DI type and the closely arranged structure mainly aims to improve the combustibility by the stratified combustion, so that it is necessary to ignite the fuel being injected, and therefore, within the range of the fuel spray or The spark plug is arranged at a position close to this. However, when the spark plug is arranged in the fuel spray or at a position close to the spray as described above, wetting of the spark plug by the fuel occurs, so that the air-fuel mixture around the spark plug is rich in fuel for easy ignition. Ignitability is greatly reduced despite the fact that it is in the state, and as a result, the combustion stability is deteriorated especially in a high load operation state in which the fuel injection amount is large (Fig. 3
(Refer to the characteristic line L _{2 in} Figure ₂ ). Further, since the fuel being injected, that is, the fuel not sufficiently atomized, is ignited, the HC
There is also a problem in that a large amount of unburned gas components such as the above will be generated, leading to deterioration of exhaust emission performance.

In view of the above, the present invention is directed to a direct injection type engine in which an injector and a spark plug are arranged in close proximity to each other, resulting in deterioration of combustion stability due to wetting of the spark plug by fuel and ignition of fuel during injection. The fuel supply device for an engine is designed to realize good stratified combustion without deteriorating the exhaust emission performance and improve the engine performance.

[0006]

According to the invention of claim 1, as a concrete means for solving such a problem in the present invention, the fuel is directly injected from the injector into the combustion chamber and the combustion chamber is encountered. In an engine in which a spark plug is arranged, the injection direction of the injector is directed to the spark plug, while the fuel injection pulse is divided into a plurality of times, and the ignition timing of the spark plug is set at the end of the final injection pulse or at the end of the pulse. The feature is that it is set within a predetermined period from the time.

According to a second aspect of the invention, in the fuel supply system for an engine according to the first aspect, the fuel injection pulse is divided into a first injection pulse having an early injection timing and a second injection pulse having a late injection timing. It is divided, and the second injection pulse is set smaller than the pulse width of the first injection pulse, and the ignition timing is set at the pulse end of the second injection pulse or within a predetermined period from the pulse end. Is characterized by.

According to a third aspect of the invention, in the fuel supply system for an engine according to the first aspect, the fuel injection pulse is divided into a first injection pulse having an earlier injection timing and a second injection pulse having a later injection timing. It is characterized in that it is divided, and that the second injection pulse is set larger than the pulse width of the first injection pulse, and the ignition timing is set within a predetermined period from the end of the pulse of the first injection pulse. ..

[0009]

With each of the inventions of the present application, the following effects can be obtained by adopting such a configuration.

In the first aspect of the invention, the injector is
The fuel spray from is injected toward the spark plug. Therefore, the ignition plug is wetted by the fuel spray.

In this case, since the fuel injection pulse is divided into a plurality of pulses, and the ignition plug is ignited at the end of the final injection pulse or within a predetermined period from the end of the pulse, the injection pulse before the final injection pulse is Since the wetting of the spark plug caused by the fuel spray based on the injection pulse is dried between the injection pulse immediately before the final injection pulse and the final injection pulse, the wetting of the spark plug is actually the fuel at the final injection pulse. Compared to the case where ignition is performed in a state where wetting occurs due to the fuel spray of all injection pulses, the deterioration of ignitability due to wetting is improved, which results in a better operation in a wider operating range. Combustion stability is achieved (see characteristic diagram L in FIG. 3).

Further, since the ignition timing is set at the end of the final injection pulse or within a predetermined period from the end of the pulse, the fuel injected by this final injection pulse becomes a rich mixture near the ignition plug. Since it is present, the ignitability of the air-fuel mixture becomes good, and a high level of stratified combustion is surely achieved.

Further, the fuel injected in the injection pulse prior to the final injection pulse and existing in a position other than the vicinity of the spark plug is sufficiently premixed with the air in the combustion chamber until ignition and becomes a fine particle state. As a result, the utilization rate of air in the combustion chamber is increased, so that the generation of unburned components such as HC is suppressed as much as possible.

According to the second aspect of the invention, as illustrated in FIG. 1B, the injection pulse is divided into a first injection pulse with an early injection timing and a second injection pulse with a late injection timing, and the first injection pulse is divided into two. Since the second injection pulse is set smaller than the pulse width of the injection pulse and the ignition timing is set at the pulse end of the second injection pulse or within a predetermined period from the pulse end, the first injection pulse Since the premixing in S. is sufficiently performed, atomization of the fuel is further promoted, and the wetting of the spark plug is suppressed by a small amount of the injection amount by the second injection pulse to improve the ignitability. Good stratified combustion is achieved with higher combustion stability than that of the invention of claim 1, and good exhaust emission performance is secured. It is.

According to the third aspect of the invention, as illustrated in FIG. 2, the injection pulse is composed of a first injection pulse having an early injection timing and a small pulse width and a second injection pulse having a late injection timing and a large pulse width. And the ignition timing is set within a predetermined period from the end of the pulse of the first injection pulse. Therefore, the rich fuel mixture based on the first injection pulse existing in the vicinity of the ignition plug can be used and the fuel amount can be increased. Since the ignition plug is ignited in a state where the influence of the wetting by the fuel is small due to the small amount of itself, the stratified combustion becomes more reliable, and more fuel based on the second injection pulse is added to the large ignition generated by the stratified combustion. Since it is injected into the fuel cell, the combustion stability is better. Further, in this case, since the ignition timing is set within a predetermined period from the end of the pulse of the first injection pulse, atomization of the fuel is achieved before ignition is executed, and if the ignitability is good. It is something that can be tightened.

[0016]

Therefore, according to the fuel supply system for an engine of the present invention, the following effects can be obtained.

According to the engine fuel supply device of the first aspect, in the engine in which the fuel is directly injected into the combustion chamber and the injection direction is directed to the spark plug, the fuel injection pulse is divided into a plurality of pulses and By setting the ignition timing at the end of the final injection pulse or within a predetermined period from the end of the pulse, deterioration of combustion stability due to wetting of the ignition plug or insufficient atomization of fuel is caused. It is possible to obtain an effect that a higher level of stratified combustion can be realized and the performance of the engine can be improved without deteriorating the exhaust emission.

According to the engine fuel supply device of the second aspect, in addition to the effects described above, the spark plug is set by setting the second injection pulse to be smaller than the pulse width of the first injection pulse. It is possible to further reduce the influence of the wetting of the fuel and promote the premixed combustion of the fuel, and it is possible to obtain the effect of achieving higher combustion stability or exhaust emission performance than the above case. is there.

According to the engine fuel supply device of the third aspect, in addition to the effects described above, by setting the second injection pulse to be larger than the pulse width of the first injection pulse, the spark plug is set. It is possible to further reduce the influence of the wetting of the fuel and promote the premixed combustion of the fuel, and it is possible to obtain the effect of achieving higher combustion stability or exhaust emission performance than the above case. is there.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Hereinafter, a fuel supply system for an engine of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1A shows the fuel according to the embodiments of the present invention described in claims 1 and 2 of the present application. A main part of a V-type two-cycle engine 1 for a vehicle equipped with a supply device is shown. In the figure, reference numeral 2 is an intake passage, 3 is an exhaust passage, 4 is an intake port, 5 is a combustion chamber, and 6 is A piston, 7 is an exhaust valve, 8 is a spark plug, and 9 is an injector.

This engine 1 is intended for stratified combustion, and therefore, the injector 9 is installed in the combustion chamber 5 for this purpose.
The fuel is directly injected into the combustion chamber 5 by arranging the spark plug 8 in the upper part of the fuel injection chamber, and the spark plug 8 is arranged in the vicinity of the injector 9 so that the electrode portion 8a thereof is located in the fuel spray. Then, the fuel supply control from the injector 9 and the ignition control of the ignition plug 8 are performed by the control unit 10 based on the crank angle signal, the engine speed signal, and the intake air amount signal.
In this case, the injector 9 and the ignition plug 8 are brought close to each other in order to more reliably perform the stratified combustion, which is the initial purpose, and at the same time improve the combustion stability and promote the premixed combustion to enhance the exhaust emission performance. In consideration of problems peculiar to the engine 1 having the arranged structure, the fuel injection mode and the ignition timing are set as described later.

That is, as a peculiar problem, which has already been described in the section "Problems to be solved by the invention", the electrode portion 8a of the spark plug 8 is in the fuel spray in order to realize the stratified combustion. Since the ignition is performed immediately after the end of fuel injection (that is, when the rich air-fuel mixture layer is maintained), the fuel first wets the electrode portion 8a of the spark plug 8 and Combustion stability deteriorates due to impaired ignitability (see Fig. 3). Secondly, since ignition is performed in a state where fuel atomization is insufficient, its ignitability deteriorates and exhaust emission performance deteriorates. It is a point to do.

In order to suppress such problems as much as possible and to perform the stratified combustion more reliably, in this embodiment, as shown in FIG. 1B, calculation is performed based on the engine speed and the intake air amount. The injection pulse of the fuel per cycle is divided into two pulses before and after the first injection pulse 21 having an early injection timing and the second injection pulse 22 having a late injection timing, and has a pulse width of the first injection pulse 21. On the other hand, the pulse width is relatively set so that the second injection pulse 22 becomes smaller, and the ignition timing is set when the pulse of the second injection pulse 22 ends.

When the fuel injection mode and the ignition timing are set in association with each other in this manner, the following unique effects can be obtained. That is, first, with respect to the wetting of the electrode portion 8a of the spark plug 8, if the ignition timing is set at the end of the second injection pulse 22 as in this embodiment, for example, the first injection pulse 21 Even if wetting occurs due to fuel injection based on
From the end of the injection pulse 21 to the second injection pulse 22
Since it is removed as dry as possible during the period up to the start of the fuel injection, the only wetting at the time of ignition is substantially only the fuel injection based on the second injection pulse 22, and the fuel based on the second injection pulse 22 is substantially used. Since the injection amount is originally small, the degree of wetting of the electrode portion 8a is higher than the degree of wetting generated by the fuel injection based on, for example, all the injection pulses (the sum of the first injection pulse 21 and the second injection pulse 22). Therefore, the deterioration of the ignitability due to the wetting is eliminated as much as possible, the ignition and combustion are performed under the good ignitability, and as a result, a high level of combustion stability is achieved. In this case, the rich mixture existing in the vicinity of the spark plug 8 is ignited and the combustion proceeds with the rich mixture as the ignition source. Therefore, the stratified combustion state is reliably realized, and the engine 1 It achieves low fuel consumption and high output.

Secondly, a large amount of fuel is injected by the first injection pulse 21, and this large amount of fuel is burned in the combustion chamber 5 between the end of the pulse of the first injection pulse 21 and the actual ignition. Well premixed with the air inside. This premixing promotes atomization of the fuel, and the air utilization rate in the combustion chamber 5 is increased accordingly, so that the HC
Premixed combustion with less generation of unburned components such as is realized, and as a result, exhaust emission performance is improved.

As described above, in this embodiment, the fuel injection pulse is divided into the first injection pulse 21 having a large pulse width and the second injection pulse 22 having a small pulse width, and is output. With a simple configuration in which the ignition timing is set at the end of the injection pulse 22, the deterioration of combustion stability due to the wetting of the spark plug 8 and the deterioration of exhaust emission performance due to ignition immediately after the end of injection are both suppressed, and the spark plug 8 A layered combustion is realized in the vicinity of, and a premixed combustion is realized in the other portions, and a high engine performance can be secured as a synergistic effect of these.

In this embodiment, the ignition timing is set at the end of the pulse of the second injection pulse 22, but the gist of the present invention is to set the ignition timing to the pulse of the second injection pulse 22. It is not limited to the end time, but is set at the end of the pulse or within a predetermined period from the end of the pulse, and when the ignition timing is set within the predetermined period from the end of the pulse of the second injection pulse 22, Also, the same effect as above can be obtained.

Second Embodiment FIG. 2 shows the relative relationship between the fuel injection mode and the ignition timing in the fuel supply system according to the second embodiment to which the invention of claim 3 of the present application is applied. The second embodiment is similar to the first embodiment in that the injection pulse per cycle of the engine 1 is divided into a first injection pulse 21 and a second injection pulse 22. 1
In the embodiment, the pulse width of the first injection pulse 21 is set to be larger than the pulse width of the second injection pulse 22, and the ignition timing is set at the end of the pulse of the second injection pulse 22. The difference is that the pulse width of the first injection pulse 21 is set smaller than the pulse width of the second injection pulse 22 and the ignition timing is set after a lapse of a predetermined period from the end of the pulse of the first injection pulse 21. There is.

When the setting of the injection mode and the ignition timing as in the second embodiment is adopted, the following peculiar operational effects can be obtained. That is, the fuel injection based on the first injection pulse 21 is reduced and the first injection pulse 2 is reduced.
Since the ignition timing is set after a lapse of a predetermined period from the end of the pulse of No. 1, the stratified state of the rich air-fuel mixture existing in the vicinity of the spark plug 8 is maintained without being broken and the fuel is sufficiently finely divided. Ignition is executed by the spark plug 8 under the reduced condition and in the condition that the influence of the wetting is small. As a result, the ignitability of the fuel is favorably maintained and the combustion stability is ensured, and a large amount of fuel based on the subsequent second injection pulse 22 smoothly burns due to the large ignition source generated by this first combustion. The high level of stratified combustion is realized by this.

In the second embodiment, the ignition timing is set after the lapse of a predetermined period from the end of the first injection pulse 21, but the gist of the invention of claim 3 is not limited to this. Instead, the ignition timing is set within a predetermined period from the end of the first injection pulse 21. For example, the ignition timing can be set immediately after the end of the first injection pulse 21. Of course, even when the setting is made, the same effect as the above can be obtained.

[Brief description of drawings]

FIG. 1A is a longitudinal sectional view of an essential part of an engine equipped with a fuel supply device according to a first embodiment of the present invention.

FIG. 1B is a correlation diagram between fuel supply characteristics and ignition timing in the fuel supply device for the engine of FIG. 1A.

FIG. 2 is a correlation diagram between fuel supply characteristics and ignition timing in the second embodiment of the present invention.

FIG. 3 is a correlation diagram between engine load and combustion stability.

[Explanation of symbols]

1 is an engine, 2 is an intake passage, 3 is an exhaust passage, 4 is an intake port, 5 is a combustion chamber, 6 is a piston, 7 is an exhaust valve, 8 is an ignition plug, 9 is an injector, and 10 is a control unit. is there.

Claims (3)

[Claims] 1. In an engine in which fuel is directly injected from an injector into a combustion chamber and an ignition plug is arranged so as to face the combustion chamber, the injection direction of the injector is directed to the ignition plug while the fuel is injected. A fuel supply system for an engine, characterized in that a pulse is divided into a plurality of parts, and an ignition timing of the spark plug is set at the end of the final injection pulse or within a predetermined period from the end of the pulse. 2. The fuel injection pulse according to claim 1, wherein the fuel injection pulse is divided into two parts, a first injection pulse having an early injection timing and a second injection pulse having a late injection timing, and having a pulse width of the first injection pulse. On the other hand, the engine fuel supply device is characterized in that the second injection pulse is set to be small and the ignition timing is set at the pulse end of the second injection pulse or within a predetermined period from the pulse end. 3. The fuel injection pulse according to claim 1, wherein the fuel injection pulse is divided into two parts, that is, a first injection pulse having an early injection timing and a second injection pulse having an late injection timing, and a pulse width of the first injection pulse. On the other hand, the engine fuel supply device is characterized in that the second injection pulse is set to a large value and the ignition timing is set within a predetermined period from the end of the pulse of the first injection pulse.