JP4386081B2 - In-cylinder injection spark ignition internal combustion engine - Google Patents

Description

  The present invention relates to a direct injection spark ignition internal combustion engine.

  By injecting fuel directly into the cylinder in the second half of the compression stroke, a flammable mixture with good ignitability is formed only in the vicinity of the spark plug, and stratified combustion is achieved that can burn a lean mixture as a whole in the cylinder. In-cylinder injection spark ignition internal combustion engines are known. In such an in-cylinder spark-ignition internal combustion engine, the fuel injection valve of each cylinder injects high-pressure fuel in the pressure accumulating chamber, thereby injecting fuel into the cylinder that has become high pressure in the latter half of the compression stroke. It becomes possible to do.

  The fuel in the pressure accumulating chamber is boosted by an engine-driven high pressure pump. As a result, when the engine is started, the high-pressure pump does not operate well, and the fuel in the pressure accumulating chamber is not sufficiently boosted. In a general in-cylinder injection spark ignition internal combustion engine, at the time of engine start, fuel is injected not in stratified combustion but in an intake stroke to perform homogeneous combustion. Accordingly, the cylinder pressure at this time is lower than that in the latter half of the compression stroke, which is advantageous for fuel injection. However, in order to continuously inject the increased amount of fuel at the start of the engine into each cylinder, the fuel pressure in the accumulator chamber Is too low. In this way, a necessary amount of fuel cannot be injected into each cylinder and misfire occurs, and a good engine start cannot be realized.

  It has been proposed that at the time of engine start, fuel injection is performed only to some cylinders, and engine start is completed with only some of these cylinders (see, for example, Patent Document 1). In this way, a necessary amount of fuel is injected into these some cylinders, and reliable combustion is brought about, so that favorable engine start is realized.

JP-A-11-229926

  Generally, when starting the engine, it is necessary to warm up the catalyst device arranged in the engine exhaust system and activate the catalyst device at an early stage. Therefore, the exhaust gas temperature is increased by retarding the ignition timing. However, since such warm-up control is accompanied by deterioration of combustion, as described above, when operating only with some cylinders, in addition to the small number of operating cylinders, the engine generated output in each operating cylinder Therefore, the engine speed increases only slowly, and the engine startability may deteriorate.

  Accordingly, an object of the present invention is to provide an in-cylinder injection spark ignition internal combustion engine capable of ensuring good engine startability and warming up an engine exhaust system catalyst device relatively quickly. .

The in-cylinder spark-ignition internal combustion engine according to claim 1 according to the present invention injects fuel into all cylinders after injecting fuel into only some cylinders at the time of starting the engine. In the in-cylinder injection spark ignition internal combustion engine that performs all-cylinder operation, the partial cylinders start warm-up control for warming up the catalyst device disposed in the engine exhaust system from the partial cylinder operation. The cylinders excluding the partial cylinders start the warm-up control from the time of the full cylinder operation, and in the warm-up control of the partial cylinders and the warm-up control of the cylinders excluding the partial cylinders, the control amount is The exhaust gas temperature increases as the control amount is increased gradually until the set value is increased, but the combustion is worsened, and the increase rate of the control amount in the warm-up control of the partial cylinder is Compared to cylinder operation, it is larger when all cylinders are operating. Is the control amount in the warm-up control of the cylinders except for the partial-cylinder, between which increases to the set value, and characterized in that it is smaller than the control amount in the warm-up control of the partial-cylinder To do.

As described above, according to the in-cylinder spark ignition internal combustion engine according to the present invention, at the time of engine start, fuel is injected into only some cylinders, and after partial cylinder operation is performed, fuel is injected into all cylinders. in direct injection spark ignition internal combustion engine implementing the all-cylinder operation Te, partial-cylinder starts the warm-up control for warming up the catalyst device disposed in the engine exhaust system from the time of partial-cylinder operation, one Cylinders other than some cylinders start warm-up control when all cylinders are in operation, and in the warm-up control of some cylinders and the warm-up control of cylinders excluding some cylinders, the control amount is gradually increased to the set value. As the amount increases, the temperature of the exhaust gas increases, but the combustion worsens, and the rate of increase in the control amount in the warm-up control of some cylinders is increased during all cylinder operation compared to during partial cylinder operation. The control amount in the warm-up control of the cylinders excluding the part cylinder is the set value. During in increasing, and it is smaller than the control amount in the warm-up control of the partial-cylinder. As a result, the engine exhaust system catalyst device can be warmed up relatively early by the warm-up control at the time of starting the engine, and at the same time by reducing the control amount of the warm-up control during the operation of some cylinders. A decrease in engine generated output is suppressed, and good engine startability can be ensured.

  FIG. 1 is a schematic longitudinal cross-sectional view of a cylinder injection type spark ignition internal combustion engine according to the present invention, and FIG. 2 is a plan view of the piston of FIG. In these drawings, reference numeral 1 denotes an ignition plug disposed substantially at the center of the upper part of the cylinder, and 2 denotes a fuel injection valve for injecting fuel directly from the periphery of the upper part of the cylinder into the cylinder. Reference numeral 3 denotes a piston, and a concave cavity 4 is formed on the top surface thereof. The fuel injection valve 2 is disposed on the intake port side where the temperature becomes relatively low due to the intake air flow in the cylinder in order to prevent fuel vapor.

  The fuel injection valve 2 has a slit-shaped injection hole, and injects the fuel into a thin fan shape. In order to perform stratified combustion, as shown in FIG. 1, fuel is injected into a cavity 4 formed on the top surface of the piston 3 in the latter half of the compression stroke. The fuel immediately after the injection is in a liquid state, but when it travels along the bottom wall 4a of the cavity 4 and expands in the width direction, it is easily vaporized because it absorbs heat from a wide area of the bottom wall 4a. The fuel being vaporized in this way is deflected upward by the opposing side wall 4b.

  As shown in FIG. 2, the opposing side wall 4b has an arc shape in plan view. As a result, the fuel that has been vaporized by traveling on the bottom wall 4a of the cavity 4 is completely vaporized by traveling on the opposing side wall 4b and further absorbing heat, and the central portion is formed by the arc shape of the opposing side wall 4b. And becomes a lump of combustible air-fuel mixture in the vicinity of the spark plug 1. Thus, stratified combustion can be realized by igniting and burning this combustible mixture.

  This in-cylinder injection type spark ignition internal combustion engine forms not only such stratified combustion but also fuel in the intake stroke to form a homogeneous mixture in the cylinder at the time of ignition, and this homogeneous mixture is ignited and combusted. Homogeneous combustion is also possible. Unlike the stratified combustion in which the fuel injection period is limited to the latter half of the compression stroke, the homogeneous combustion is performed at high rotation and high load because a large amount of fuel can be injected.

  By the way, the fuel injection valve 1 of each cylinder is connected to a pressure accumulating chamber for storing high-pressure fuel in order to enable fuel injection into the cylinder that has become high pressure in the latter half of the compression stroke during stratified combustion. In general, an engine-driven high-pressure pump is used for boosting the fuel in the pressure accumulating chamber. As a result, when the engine is started, the high-pressure pump does not operate well, and the fuel in the pressure accumulating chamber is not sufficiently boosted.

  In the in-cylinder injection spark ignition internal combustion engine, at the time of starting the engine, homogeneous combustion capable of fuel injection at a relatively low fuel pressure is performed. However, the fuel pressure in the pressure accumulating chamber at the time of starting the engine is very low, and it is difficult to inject a necessary amount of fuel continuously into each cylinder even during homogeneous combustion. If this is done, not only does some cylinders misfire due to fuel shortage and a large amount of unburned fuel is discharged, but also combustion cylinders do not generate sufficient engine output due to fuel shortage, which is good. The engine cannot be started.

  In this in-cylinder spark-ignition internal combustion engine, at the time of starting the engine, some cylinders (for example, half of the cylinders whose ignition order is not continuous) are injected with fuel and only some of these cylinders are operated. Driving is to be carried out. Thus, by restricting fuel injection to only some cylinders, a required amount of fuel can be reliably injected into some cylinders, and good combustion can be achieved without causing misfiring in some cylinders.

  Generally, when starting the engine, it is necessary to warm up the catalyst device arranged in the engine exhaust system and activate the catalyst device at an early stage in order to purify harmful substances in the exhaust gas. Therefore, in the in-cylinder injection spark ignition internal combustion engine, warm-up control is performed when the engine is started. As this warm-up control, the ignition timing is retarded to raise the exhaust temperature, or the combustion air-fuel ratio is made somewhat leaner than the stoichiometric air-fuel ratio to suppress the temperature drop in the cylinder due to the fuel and to ensure all the fuel The exhaust gas temperature is increased by burning.

  Since all of these warm-up controls involve a slight deterioration in combustion, if they are simply performed during operation of some cylinders, the engine generated output in these some cylinders will decrease, and the engine rotation will only increase slowly. A good engine start is not feasible.

  In order to solve this problem, in the in-cylinder injection spark ignition internal combustion engine, as shown in FIG. 3, the warm-up control amount of some cylinders is compared from zero during the operation of some cylinders at the start of the engine. The engine speed is increased gradually and gradually, and after the engine speed reaches the set speed NE1, it is increased relatively rapidly and changed to the normal value. The set rotational speed NE1 is a rotational speed indicating completion of engine start. From this time, fuel injection into all cylinders is started and all cylinder operation is performed. Here, the warm-up control amount is a retard width in the ignition timing retard. Further, the leaning of the combustion air-fuel ratio is about the leaning, and the combustion air-fuel ratio is leaned from the rich air-fuel ratio at start-up as the warm-up control amount increases.

  Thus, since the warm-up control degree in some cylinders is generally reduced during partial cylinder operation compared to during full cylinder operation, the reduction in engine generated output during partial cylinder operation is suppressed. The engine speed at the time can be raised relatively rapidly, and good engine startability can be ensured.

  The dotted line in FIG. 3 shows the warm-up control amount in cylinders other than some cylinders (resting cylinders). This warm-up control amount is increased to a normal value relatively rapidly after starting all cylinders. To be changed. When operating all cylinders, the number of operating cylinders is larger than when operating some cylinders, and even if the engine warm-up control is relatively large and the engine output in each cylinder is reduced to some extent, engine stoppage etc. There is no. Thus, since the warm-up control is performed at least when some of the cylinders are operated when starting the engine, it is possible to warm up the catalyst device of the engine exhaust system relatively early.

  Of course, compared with the case where significant warm-up control is performed from the time of operation of some cylinders, in the cylinder-injected spark ignition internal combustion engine, the warming power of the catalyst device is somewhat inferior, but at the time of engine start In the partial cylinder operation, the exhaust gas amount is small due to the presence of the idle cylinder, that is, the exhaust harmful substances are also small, so that it does not matter so much. In all cylinder operation, the negative pressure in the intake manifold is increased by the operation of some cylinders, and the fuel pressure in the pressure accumulating chamber is relatively increased, so that the fuel is injected well into the cylinder. Since the fuel vaporizes well due to the negative pressure in the cylinder, the amount of unburned fuel discharged is very small regardless of when the engine is started. This also sufficiently reduces the deterioration of the warming power of the catalytic device. Can be countered.

  FIG. 4 shows another change in the warm-up control amount in the in-cylinder injection spark ignition internal combustion engine. In this example, the warm-up control is stopped when some cylinders are operating, and the warm-up control is started when all cylinders are operating. Increased. As a result, the engine generated output does not decrease during partial cylinder operation, and the rise of the engine rotation is abrupt compared to the change in the warm-up control amount shown in FIG. 3, and the engine startability can be further improved.

  In the warm-up control amount change shown in FIG. 3, when the engine speed reaches the set speed NE1, the operation is switched from the partial cylinder operation to the full cylinder operation. When the amount becomes smaller than the set value, it is possible to switch to all-cylinder operation on the assumption that no further increase in rotation can be expected in some cylinder operation. Further, it is possible to switch from partial cylinder operation to full cylinder operation on the assumption that the engine start has been completed with the elapse of a set time or set cycle number from the start of cranking. As described above, it is preferable that the negative pressure in the intake manifold is increased for good all-cylinder operation, so that when the inside of the intake manifold reaches the set negative pressure, partial cylinder operation is performed. May be switched to the all cylinder operation.

  In the example shown in FIG. 4, when the fuel pressure in the pressure accumulating chamber reaches the set pressure P1, the operation is switched from the partial cylinder operation to the full cylinder operation. As a result, good fuel injection into each cylinder is possible during all-cylinder operation, and emission of harmful substances such as unburned fuel can be reduced. It is possible to sufficiently reduce the amount of harmful substances released into the atmosphere together with the catalyst device warmed up by the control.

  FIG. 5 shows still another warm-up control amount change in the in-cylinder injection spark ignition internal combustion engine. The difference between this example and the change in the warm-up control amount shown in FIG. 3 is that the warm-up control of some cylinders in the partial cylinder operation is started after a predetermined period, for example, a predetermined time or a predetermined number of cycles from the start of cranking. In addition, the warm-up control of the cylinders excluding some cylinders during all cylinder operation is started after a predetermined period, for example, a predetermined time or a predetermined number of cycles from the start of all cylinder operation. is there.

  Thereby, in each cylinder, especially at the first explosion when combustion is unstable, since the warm-up control for reducing the engine output is stopped, the engine startability can be further improved.

  This concept can also be applied to the warm-up control amount change shown in FIG. 4, that is, the warm-up control of all the cylinders is performed for a predetermined period, for example, after elapse of a predetermined time or a predetermined number of cycles from the start of all cylinder operations. It may be started. Thus, if the start of the warm-up control is delayed, the engine startability is improved accordingly, but the warm-up of the catalyst device is deteriorated. In order to solve this, in the three modified examples of the warm-up control amount change shown in the lower side of FIG. 5, after the initial explosion of all the cylinders is completed during the operation of all the cylinders, To be implemented. In this way, the catalyst device can be warmed up early.

  In the warm-up amount control change (1) in the three modified examples, after a lapse of a predetermined period, for example, a predetermined time or a predetermined number of cycles from the start of all cylinder operation, a significant warm-up control is started for all cylinders, and after a while. Therefore, the warm-up control amount is reduced to the normal value. In the warm-up control amount change (2), the large warm-up control is similarly started for all the cylinders, and the warm-up control amount is gradually decreased to the normal value. Further, the warm-up control amount change (3) is the same as the warm-up control amount change (2) for the cylinders excluding some cylinders, but the warm-up control for some cylinders is performed for a predetermined period from the start of cranking. The warm-up control amount is increased relatively slowly during the operation of some cylinders, and increases significantly after a predetermined period from the start of all cylinder operation, as with the cylinders excluding some cylinders. Be made.

  In this in-cylinder spark ignition internal combustion engine, all cylinder operation following partial cylinder operation at the time of engine start is assumed to be homogeneous combustion, but when switching to all cylinder operation, the fuel pressure in the accumulator chamber is sufficiently high. For example, since fuel injection in the latter half of the compression stroke is possible, stratified combustion may be performed. In homogeneous combustion, part of the fuel injected into the cylinder at the end of the intake stroke tends to adhere to the cylinder bore, and the attached fuel is not vaporized from the low-temperature cylinder bore when the engine is started and is discharged as unburned fuel. Will be. In stratified combustion, fuel is injected in the latter half of the compression stroke, so the injected fuel does not adhere to the cylinder bore and the amount of unburned fuel is less than that of homogeneous combustion. It is advantageous in terms of exhaust emission. Of course, stratified combustion is advantageous in terms of fuel consumption because stratified combustion requires less fuel than homogeneous combustion.

1 is a schematic longitudinal sectional view in a cylinder of a cylinder injection type spark ignition internal combustion engine according to the present invention. It is a top view of the piston of FIG. It is a time chart which shows a warm-up control amount change. It is a time chart which shows another warm-up control amount change. It is a time chart which shows another warm-up control amount change.

Explanation of symbols

1 Spark plug 2 Fuel injection valve 3 Piston 4 Cavity

Claims (1)

During engine starting, after performing the partial-cylinder operation by injecting fuel into only some cylinders, in-cylinder injection type spark ignition internal combustion engine implementing the full cylinder operation by injecting the fuel into all the cylinders, the one The partial cylinders start warm-up control for warming up the catalyst device disposed in the engine exhaust system from the time of the partial cylinder operation, and the cylinders other than the partial cylinders start the warm-up control from the time of the full cylinder operation In the warm-up control of the partial cylinders and the warm-up control of the cylinders excluding the partial cylinders, the control amount is gradually increased to a set value, and the exhaust gas is increased as the control amount is increased. The temperature rises but the combustion worsens, and the increase rate of the control amount in the warm-up control of the partial cylinders is increased during the full cylinder operation compared with the partial cylinder operation, The control in the warm-up control of the cylinders except , Between which increases to the set value, the in-cylinder injection spark ignition internal combustion engine, characterized in that it is smaller than the control amount in the warm-up control of the partial-cylinder.

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