JP2007321682A - Cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compatibly perform stratified combustion and homogeneous combustion by two point ignition. <P>SOLUTION: A cylinder injection type spark ignition internal combustion engine 10 having a construction for switching between stratified combustion and homogeneous combustion according to engine operation condition, is provided with: a first spark plug 14 having an electrode arranged in fuel spray 23a injected from a fuel injection valve 23 or near a ridge 23b; and a second spark plug 15 having an electrode arranged in a position not near the fuel spray 23a. The first spark plug 14 is ignited in compression stroke and the second spark plug 15 is ignited in expansion stroke or exhaust stroke in stratified combustion and both of ignition plugs 14, 15 are simultaneously ignited in compression stroke in homogeneous combustion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an in-cylinder injection spark ignition internal combustion engine in which fuel is directly injected into a combustion chamber by a fuel injection valve. The present invention relates to a direct injection spark ignition internal combustion engine that can achieve both stratified combustion and homogeneous combustion by ensuring combustion and can suppress smoldering of a spark plug.

  2. Description of the Related Art Conventionally, an in-cylinder spark ignition internal combustion engine (hereinafter abbreviated as “direct injection engine” or “engine”) in which fuel is directly injected into a combustion chamber by a fuel injection valve is known. As a means for fuel injection and ignition in such a direct injection engine, a technique called a so-called spray guide system is known.

  In this spray guide system, the electrode part of the spark plug is arranged so as to be located in the fuel spray injected from the fuel injection valve or in the vicinity of the ridgeline of the fuel spray, and during or immediately after the fuel injection, The fuel spray is directly ignited. According to this spray guide system, effects such as improvement in fuel consumption, reduction in HC, and suppression of smoke can be obtained.

  In the case of the spray guide system, it is sufficient to have a single spark plug in the direction that is directly struck by the fuel spray during stratified combustion. However, during homogeneous lean combustion, the air-fuel mixture is uniformly diffused into the combustion chamber. It is desirable to provide a multipoint ignition with a spark plug.

  Therefore, an engine 100 having a plurality of spark plugs 14 and 35 as shown in FIGS. 9 and 10 has been conventionally provided. Here, FIG. 9 is a sectional view schematically showing a conventional direct injection engine having a plurality of spark plugs, and FIG. 10 is a plan view showing a positional relationship among a fuel injection valve, a spark plug, and intake / exhaust valves. Yes, the cylinder head is seen from the piston side.

  As shown in FIG. 9, the engine 100 is a direct injection type four-cycle gasoline engine in which a fuel spray 23a is directly injected into a combustion chamber 10a by a fuel injection valve 23, and performs stratified combustion and homogeneous combustion according to engine operating conditions. It is configured to be switchable.

  The combustion chamber 10 a includes a cylinder bore 11, a cylinder head 13, and a piston 12 that is reciprocally disposed in the cylinder bore 11. A recess 12 a is formed on the top surface of the piston 12.

  In the combustion chamber 10a, two spark plugs 14 and 35 for igniting the air-fuel mixture are arranged at positions where the fuel spray 23a directly hits. The spark plug 14 is disposed closer to the center of the combustion chamber 10 a so as to be closer to the fuel injection valve 23 than the spark plug 35.

  As shown in FIG. 10, the cylinder head 13 is provided with an intake valve 16 and an exhaust valve 20. The valves 16 and 20 are controlled to be opened and closed by a variable valve timing mechanism that variably controls the opening and closing operation timing.

  Engine components such as the valves 16 and 20, the spark plugs 14 and 35, and the fuel injection valve 23 of the engine 100 are controlled by an electronic control unit (ECU) (not shown).

  As shown in FIG. 11, when the engine operating condition is in a low rotation range and a low torque range, the engine 100 performs control of stratified combustion by a spray guide method, so that the middle rotation range and the middle torque range are controlled. In some cases, control of homogeneous lean combustion is executed, and control of homogeneous stoichiometric combustion is executed in an operating region beyond that. Here, FIG. 11 is an explanatory view showing an example of a combustion pattern.

  Further, as other related prior art, for example, the following is known. That is, in an ignition device for a direct injection engine having a fuel injection valve that directly injects fuel into a combustion chamber, a first ignition plug provided within the injection range of the fuel injection valve and an injection range outside the fuel injection valve are provided. The second ignition plug is provided, and when the engine is warm, ignition by the first ignition plug is executed to perform stratified combustion, and when the engine is cold, only ignition by the second ignition plug is executed to perform homogeneous combustion. Has been proposed (see, for example, Patent Document 1).

  Also, a cylinder injection spark ignition internal combustion engine having a plurality of spark plugs, which can be ignited at the center of the air-fuel mixture in both stratified high load conditions and stratified low load conditions. It is known.

  That is, a stratified low load in which a first spark plug that performs ignition in the vicinity of the bottom surface of the piston cavity and a second spark plug that performs ignition in the center of the combustion chamber are provided, and a small air-fuel mixture is formed near the bottom surface of the piston cavity. In terms of conditions, a technique has been proposed in which ignition is performed by the first spark plug, and ignition is performed by the second spark plug in a stratified high load condition where a large air-fuel mixture is formed above the piston cavity. (For example, see Patent Document 2).

  In addition, a high-pressure fuel injection valve that directly injects fuel into the cylinder obliquely downward with respect to the combustion chamber at the lower portion of the intake port, and three spark plugs along the injection axis direction of the fuel injection valve In-cylinder injection spark ignition internal combustion engine that performs stratified combustion that is arranged apart from each other, and a technique for igniting with a time difference at two or more different positions according to operating conditions has been proposed (for example, (See Patent Document 3).

JP 2004-44434 A JP 2004-190532 A JP 2000-179441 A

  In the prior art shown in FIG. 9 and FIG. 10, since the two spark plugs 14 and 35 are arranged so that the fuel spray 23a hits directly, both of them are ignited during stratified combustion (two points). Fire), a stratified mixture is present around the spark plug 14 near the center of the combustion chamber 10a, so that stable combustion is possible.

  However, there is an air-fuel mixture on the front end side of the fuel spray 23a around the spark plug 35, the air-fuel ratio is very unstable, and fluctuations between cycles are large. As a result, the combustion formed by the ignition of the spark plug 35 becomes unstable, so that the stratified combustion is stabilized and the torque fluctuation is reduced when only the spark plug 14 is combusted.

  Therefore, if a stable air-fuel ratio fuel spray 23a can be injected to both of the spark plugs 14 and 35, combustion improvement by two-point ignition is possible. However, since it is necessary to increase the penetration force of the fuel spray 23a contrary to the concept of combustion in the spray guide system, the spray directly hits the wall surface of the cylinder bore 11 and increases the contradiction such as oil dilution. .

  In the prior art according to Patent Document 1, the second spark plug that does not directly hit the fuel spray is stopped during stratified combustion, so that the electrode of the second spark plug is smoldered and normal during homogeneous lean combustion. There was a possibility that ignition could not be performed.

  Further, during homogeneous combustion when the engine is cold, the two spark plugs are not ignited, but only the second spark plug is ignited. Compared to point ignition means, it was not always desirable.

  Further, in the conventional techniques according to Patent Documents 2 and 3, ignition control is mainly disclosed at the time of stratified combustion, and means for realizing combustion improvement by two-point ignition at the time of homogeneous combustion is disclosed in detail. Not.

  The present invention has been made in view of the above, and enhances the combustion effect by performing multipoint ignition during homogeneous combustion, and ensures good combustion even during stratified combustion, thereby achieving both stratified combustion and homogeneous combustion. An object of the present invention is to provide an in-cylinder injection spark ignition internal combustion engine that can reduce the smoldering of an ignition plug.

  In order to solve the above-described problems and achieve the object, a direct injection spark ignition internal combustion engine according to claim 1 of the present invention includes a fuel injection valve that directly injects fuel into a combustion chamber, and a mixture in the combustion chamber. In a direct injection spark ignition internal combustion engine comprising a plurality of spark plugs for spark ignition to the atmosphere and configured to be able to switch between stratified combustion and homogeneous combustion in accordance with engine operating conditions, the fuel injection valve is injected. A first spark plug in which an electrode is disposed in a fuel spray or in the vicinity of a ridge line of the fuel spray, and a second spark plug in which an electrode is disposed at a position not in the vicinity of the fuel spray. The first spark plug and the second spark plug are ignited at least during the homogeneous combustion of the combustion and the homogeneous combustion.

  Therefore, according to the present invention, at least during the homogeneous combustion of the stratified combustion and the homogeneous combustion, by igniting the first ignition plug and the second ignition plug, the mixture is uniformly diffused in the combustion chamber. It can be ignited quickly and reliably, and stable homogeneous combustion can be performed in the entire combustion chamber.

  Further, at the time of stratified combustion, stratified combustion can be realized by igniting at least the first spark plug. Further, by igniting the second spark plug, the so-called self-cleaning action caused by combustion prevents the smoldering of the electrode of the second spark plug, and normal ignition can be performed during homogeneous lean combustion.

  A cylinder injection type spark ignition internal combustion engine according to claim 2 of the present invention is characterized in that, in the invention according to claim 1, only the first spark plug is ignited during the stratified combustion. It is.

  Therefore, according to the present invention, the second spark plug is not ignited at the time of stratified combustion, so that the combustion by the ignition of the second spark plug can be prevented from disturbing the degree of stratification of the air-fuel mixture.

  According to a third aspect of the present invention, there is provided an in-cylinder injection spark ignition internal combustion engine according to the first aspect, wherein the first spark plug is ignited in a compression stroke during the stratified combustion, and the first The second spark plug is ignited in an expansion stroke or an exhaust stroke, and at the time of the homogeneous combustion, the first spark plug and the second spark plug are ignited in a compression stroke.

  Therefore, according to the present invention, by igniting the second spark plug in the expansion stroke or the exhaust stroke, it is possible to suppress the combustion due to the ignition of the second spark plug from disturbing the degree of stratification of the air-fuel mixture. In addition, the influence on stratified combustion can be reduced.

  In homogeneous combustion, reliable combustion can be performed by ignition with the first spark plug and the second spark plug. Further, by igniting the second spark plug, the spark plug can be self-cleaned and smoldering can be suppressed.

  According to a fourth aspect of the present invention, the in-cylinder injection spark ignition internal combustion engine according to the third aspect is characterized in that the ignition energy of the second spark plug is converted into the first spark plug during the stratified combustion. The ignition energy is set to be smaller than the ignition energy.

  Therefore, according to the present invention, for example, the energization time to the ignition coil of the second spark plug is made shorter than the energization time to the ignition coil of the first spark plug, and the minimum energy that can be ignited is supplied. Thus, it is possible to reduce power consumption necessary for ignition of the second spark plug.

  According to the cylinder injection type spark ignition internal combustion engine according to the present invention (Claim 1), at the time of homogeneous combustion, the homogeneous ignition stable in the entire combustion chamber is achieved by igniting the first ignition plug and the second ignition plug. It can be performed. In addition, stratified combustion can be realized by igniting at least the first spark plug during stratified combustion, and further smoldering of the plug electrode is suppressed by igniting the second spark plug, so that normal ignition is performed during homogeneous lean combustion. be able to.

  According to the in-cylinder spark ignition internal combustion engine of the present invention (Claim 2), the second spark plug is not ignited at the time of stratified combustion, so that the combustion by the ignition of the second spark plug is mixed. Disturbing the degree of stratification can be suppressed, and the influence on stratified combustion can be reduced.

  Further, according to the in-cylinder injection spark ignition internal combustion engine according to the present invention (Claim 3), at the time of stratified combustion, the second ignition plug is ignited at an expansion stroke or an exhaust stroke that hardly affects the stratified combustion. Thus, stable stratified combustion can be realized.

  According to the direct injection spark ignition internal combustion engine of the present invention (claim 4), the minimum energy that can be ignited is supplied to the second spark plug, thereby reducing the power consumption required for ignition. This can reduce the load on the alternator and improve the fuel efficiency.

  Embodiments of a direct injection spark ignition internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  1 is a cross-sectional view schematically showing a direct injection spark ignition internal combustion engine according to Embodiment 1 of the present invention, and FIG. 2 is a plan view showing a positional relationship among a fuel injection valve, a spark plug, and intake and exhaust valves. It shows a state where the cylinder head is viewed from the piston side. In the following description, members that are the same as or correspond to those already described are denoted by the same reference numerals, and redundant description is omitted or simplified.

  The engine (in-cylinder injection spark ignition internal combustion engine) 10 according to the first embodiment is also configured to be able to switch between stratified combustion and homogeneous combustion according to engine operating conditions. Further, the basic configuration of the engine 10 is the same as the configuration of the conventional engine 100 shown in FIGS. 9 to 10 except for a second spark plug 15 described later, and only the characteristic part will be described below. To do.

  That is, as shown in FIG. 1, the first spark plug 14 has an electrode (not shown) arranged in the fuel spray 23a injected from the fuel injection valve 23 or in the vicinity of the ridge line 23b of the fuel spray 23a. And projecting from the ceiling surface of the cylinder head 13.

  The “ridge line 23b of the fuel spray 23a” referred to here is a portion corresponding to the outer edge of the fuel spray 23a injected in a substantially conical shape, and means a portion having a predetermined air-fuel mixture concentration.

  The second spark plug 15 has an electrode disposed at a position not near the fuel spray 23 a, that is, at a position away from the ridge line 23 b, and protrudes from the ceiling surface of the cylinder head 13.

  As shown in FIG. 2, the spark plugs 14 and 15 and the fuel injection valve 23 are disposed between the intake valve 16 and the exhaust valve 20 and on the diameter of the cylinder head 13 at a predetermined interval.

  Next, ignition control will be described with reference to FIGS. 1, 2, 4, and 5 based on FIG. 3 is a flowchart showing ignition control, FIG. 4 is a time chart showing an example of an injection / ignition pattern during stratified combustion, and FIG. 5 is a time chart showing an example of an injection / ignition pattern during homogeneous combustion. It is.

  As shown in FIG. 3, first, it is determined whether the current combustion mode is stratified combustion or homogeneous combustion (step S10). This is determined using, for example, a combustion mode characteristic map (not shown) created in advance based on the rotational speed and required torque of the engine 10.

  If it is determined that the current combustion mode is stratified combustion (Yes in step S10), as shown in FIG. 4, the first spark plug 14 is ignited in the compression stroke after fuel injection by a predetermined injection signal, The second spark plug 15 is ignited in the exhaust stroke or the expansion stroke (step S20), and the control is terminated.

  In this way, by igniting the second spark plug 15 in the expansion stroke or the exhaust stroke, it is possible to suppress the combustion due to the ignition of the second spark plug 15 from disturbing the degree of stratification of the air-fuel mixture. Therefore, stable stratified combustion can be realized.

  Further, since not only the first spark plug 14 but also the second spark plug 15 is ignited, the so-called self-cleaning action due to combustion suppresses the smoldering of the electrode of the second spark plug 15 and is normal during homogeneous lean combustion. Can be ignited.

  On the other hand, if it is determined that the current combustion mode is homogeneous combustion (No in step S10), as shown in FIG. 5, the first spark plug 14 and the second spark plug after fuel injection by a predetermined injection signal are performed. 15 are simultaneously ignited in the compression stroke (step S30), and the control is terminated.

  Thus, by performing ignition at two points during homogeneous combustion, it is possible to quickly and surely ignite the air-fuel mixture uniformly diffused in the combustion chamber 10a, and stable homogeneous combustion can be performed in the entire combustion chamber 10a.

  Since other basic control methods for operating the engine 10 can be implemented based on known means, detailed description thereof will be omitted.

  As described above, according to the in-cylinder injection spark ignition internal combustion engine according to the first embodiment, stratification is achieved by ensuring good combustion during stratified combustion by two-point ignition and enhancing the combustion effect even during homogeneous combustion. Both combustion and homogeneous combustion can be achieved. Further, smoldering of the second spark plug 15 can be effectively suppressed.

  In the first embodiment, the description has been given assuming that one second spark plug 15 in which an electrode is disposed at a position that is not in the vicinity of the fuel spray 23a is provided. However, the present invention is not limited to this. For example, as shown in FIG. 6, two second spark plugs 15 and 15a may be provided. Further, as shown in FIG. 7, three second spark plugs 15, 15a, 15b may be provided.

  In these cases, the same effect as in the first embodiment can be expected. Here, FIG. 6 is a plan view showing the positional relationship between the two second ignition plugs, the fuel injection valve, and the intake / exhaust valve, and FIG. 7 is the three second ignition plugs, the fuel injection valve, and the intake valve. -It is a top view which shows the positional relationship of an exhaust valve.

  In the first embodiment, the two-point ignition is described at the time of stratified combustion. However, the present invention is not limited to this, and only the first spark plug 14 may be ignited at the time of stratified combustion.

  Thus, by not igniting the second spark plug 15 at the time of stratified combustion, it is possible to suppress the combustion due to the ignition of the second spark plug 15 from disturbing the degree of stratification of the air-fuel mixture. The influence can be reduced.

  FIG. 8 is a time chart showing an example of an injection / ignition pattern during stratified combustion according to Embodiment 2 of the present invention.

  In the second embodiment, the basic configuration and basic control of the engine 10 shown in the first embodiment are the same. The difference is that the ignition energy of the second spark plug 15 is set smaller than the ignition energy of the first spark plug 14 during stratified combustion.

  That is, as shown in FIG. 8, for example, the energization time t2 to the ignition coil (not shown) of the second spark plug 15 is changed to the energization time to the ignition coil (not shown) of the first spark plug 14. It is shorter than t1 and supplies the minimum energy that can be ignited.

  As described above, according to the in-cylinder injection spark ignition internal combustion engine according to the second embodiment, by supplying the minimum energy that can be ignited to the second spark plug 15, the second spark plug 15 Power consumption required for ignition can be reduced, and the load on an alternator (not shown) can be reduced to improve fuel efficiency.

  In the second embodiment, it has been described that the energization time to the ignition coil (not shown) of the second spark plug 15 is shortened. However, the present invention is not limited to this. For example, the ignition coil is supplied to the ignition coil. The current value and the voltage value may be reduced, or these current values and the like may be reduced with the energization time. In these cases, the same effect as in the second embodiment can be expected.

  As described above, the in-cylinder injection spark ignition internal combustion engine according to the present invention is useful for the in-cylinder injection spark ignition internal combustion engine that performs multipoint ignition, and in particular, performs multipoint ignition at the time of homogeneous combustion to produce a combustion effect. This is suitable for an in-cylinder spark ignition internal combustion engine that aims to achieve both stratified combustion and homogeneous combustion by suppressing good smoldering by ensuring good combustion even during stratified combustion.

1 is a cross-sectional view schematically showing a direct injection spark ignition internal combustion engine according to Embodiment 1 of the present invention. It is a top view which shows the positional relationship of a fuel injection valve, a spark plug, and an intake / exhaust valve. It is a flowchart which shows ignition control. It is a time chart which shows an example of the injection and ignition pattern at the time of stratified combustion. It is a time chart which shows an example of the injection and ignition pattern at the time of homogeneous combustion. It is a top view which shows the positional relationship of two 2nd spark plugs, a fuel injection valve, and an intake / exhaust valve. It is a top view which shows the positional relationship of three 2nd spark plugs, a fuel injection valve, and an intake / exhaust valve. It is a time chart which shows an example of the injection and ignition pattern at the time of stratified combustion which concerns on Example 2 of this invention. It is sectional drawing which shows typically the direct injection engine provided with the conventional several spark plug. It is a top view which shows the positional relationship of a fuel injection valve, a spark plug, and an intake / exhaust valve. It is explanatory drawing which shows an example of a combustion pattern.

Explanation of symbols

10 Engine (In-cylinder injection spark ignition internal combustion engine)
10a Combustion chamber 14 First spark plug 15, 15a, 15b Second spark plug 16 Intake valve 20 Exhaust valve 23 Fuel injection valve 23a Fuel spray 23b Ridge line

Claims (4)

A fuel injection valve that injects fuel directly into the combustion chamber;
A plurality of spark plugs that spark ignite the air-fuel mixture in the combustion chamber;
With
In a cylinder injection spark ignition internal combustion engine configured to be able to switch between stratified combustion and homogeneous combustion according to engine operating conditions,
A first spark plug in which an electrode is disposed in a fuel spray injected from the fuel injection valve or in the vicinity of a ridge line of the fuel spray;
A second spark plug in which an electrode is disposed at a position not in the vicinity of the fuel spray;
With
A direct injection spark ignition internal combustion engine that ignites the first spark plug and the second spark plug during at least the homogeneous combustion of the stratified combustion and the homogeneous combustion.   2. The direct injection spark ignition internal combustion engine according to claim 1, wherein only the first spark plug is ignited during the stratified combustion. 3. During the stratified combustion, the first spark plug is ignited in a compression stroke, and the second spark plug is ignited in an expansion stroke or an exhaust stroke.
2. The direct injection spark ignition internal combustion engine according to claim 1, wherein at the time of the homogeneous combustion, the first spark plug and the second spark plug are ignited in a compression stroke.   The direct injection spark ignition internal combustion engine according to claim 3, wherein the ignition energy of the second spark plug is set smaller than the ignition energy of the first spark plug during the stratified combustion.

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