JPH0968072A - Cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a fuel sticking quantity to a cylinder bore by providing a fuel pressure variable means to vary pressure of fuel injected by fuel injection valves, and reducing fuel pressure at engine cold time more than at engine warm time by the fuel pressure variable means. SOLUTION: Respective fuel injection valves 7 arranged in an engine main body 10 are connected to a common delivery pipe 11, and fuel is forcibly sent to the delivery pipe 11 from a fuel pump 12 in which two cylinders 12a and 12b are arranged through a high pressure pipe 13 in which check valves 12c and 12d are interposed. The respective cylinders 12a and 12b of the fuel pump 12 are connected to a fuel passage 14 through respective solenoid valves 12e and 12f, and the respective solenoid valves 12e and 12f are controlled to be opened and closed so that fuel pressure becomes low as a cooling water temperature becomes low when a cooling water temperature detected by a cooling water temperature sensor 23 is not more than a prescribed value, that is, when an engine is cold. Therefore, sticking of fuel to a cylinder bore can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder injection type spark ignition internal combustion engine.

[0002]

2. Description of the Related Art An in-cylinder injection spark ignition internal combustion engine has been proposed in which fuel is directly injected into a cylinder in order to reliably supply a required amount of fuel to the cylinder in accordance with an engine operating state.
In such an internal combustion engine, the injected fuel is more likely to adhere to the cylinder bore, as compared with an engine in which fuel is injected into the intake passage. Even if fuel adheres to the cylinder bore, if the engine temperature is sufficiently high, this adhered fuel will vaporize by ignition using the heat of the cylinder bore and will not cause any particular problems. At times, even at the time of ignition, a part of the fuel is still adhered in a liquid state, and the adhered fuel is discharged without burning, which deteriorates exhaust emission.

To solve this problem, Japanese Patent Laid-Open No. 61-
Japanese Patent No. 250354 has a second injection valve for injecting fuel into an intake passage in addition to a first injection valve for directly injecting fuel into a cylinder. It is disclosed that by injecting fuel, the fuel is supplied as a mixture into the cylinder to reduce the amount of fuel adhering to the cylinder bore at this time.

[0004]

Although the amount of fuel adhering to the cylinder bore is certainly reduced when the engine is cold by the above-mentioned conventional technique, a part of the fuel injected from the second injection valve enters the intake passage. Because of the adhesion, there is a possibility that the required amount of fuel cannot be reliably supplied into the cylinder at this time.

Therefore, an object of the present invention is to provide a cylinder injection type spark ignition internal combustion engine capable of almost certainly supplying the required fuel amount into the cylinder when the engine is cold and reducing the amount of fuel adhering to the cylinder bore. Is to provide.

[0006]

To achieve this object, a cylinder injection type spark ignition internal combustion engine according to the present invention as set forth in claim 1 is a fuel injection system for directly injecting fuel into a cylinder. Valve and fuel pressure varying means for varying the pressure of the fuel injected by the fuel injection valve, and the fuel pressure varying means reduces the fuel pressure when the engine is cold compared to when the engine is warm. Is characterized by. In this in-cylinder injection spark ignition internal combustion engine, the pressure of the fuel injected from the fuel injection valve when the engine is cold is lower than that when the engine is warm, so the fuel injected from the fuel injection valve is
The driving force is weakened.

Further, in the cylinder injection type spark ignition internal combustion engine according to the present invention as defined in claim 2, the first fuel injection valve for directly injecting fuel at a high pressure into the cylinder, and directly into the cylinder. A second fuel injection valve for injecting fuel at a low pressure, the fuel is injected by the first fuel injection valve when the engine is warm, and the fuel is injected by the second fuel injection valve when the engine is cold. It is characterized by In this in-cylinder injection spark ignition internal combustion engine, the fuel is injected at a low pressure by the second fuel injection valve when the engine is cold, so that the fuel injected at this time has its propulsive force weakened.

According to a third aspect of the present invention, there is provided a cylinder injection type spark ignition internal combustion engine in which a fuel injection valve for injecting fuel toward a piston top surface and a side wall substantially perpendicular to the piston top surface. And a recess formed to have
When the engine is cold, the fuel is injected by the fuel injection valve at the time when the fuel collides with the vicinity of the side wall in the recess. This cylinder injection type spark ignition internal combustion engine,
When the engine is cold, the fuel injected from the fuel injection valve collides with the vicinity of the side wall inside the recess formed on the top surface of the piston, so that the fuel that bounces in the direction of the cylinder bore collides with the side wall of the recess. There is.

A cylinder injection type spark ignition internal combustion engine according to a fourth aspect of the present invention includes a fuel injection valve for injecting fuel toward a piston top surface, and the piston top is provided when the engine is cold. The fuel is injected by the fuel injection valve at the time when the fuel collides only in the vicinity of the center of the surface. In this cylinder injection type spark ignition internal combustion engine, the fuel injected from the fuel injection valve collides only with the vicinity of the central portion of the top surface of the piston when the engine is cold, and therefore the fuel bounces in the direction of the cylinder bore from flying to the cylinder bore. The distance is relatively long.

Further, in the cylinder injection type spark ignition internal combustion engine according to the present invention as defined in claim 5, the first fuel injection valve for injecting fuel toward the top surface of the piston and the fuel injection in the cylinder head direction are provided. And a second fuel injection valve for
When the engine is warm, the first fuel injection valve injects fuel, and when the engine is cold, the second fuel injection valve injects fuel. In this in-cylinder injection spark ignition internal combustion engine, fuel is injected toward the cylinder head by the second fuel injection valve when the engine is cold, so the injected fuel has the highest temperature around the combustion chamber. It collides with the combustion chamber side surface of the head or intake / exhaust valve.

Further, an in-cylinder injection type spark ignition internal combustion engine according to a sixth aspect of the present invention is a fuel injection valve for directly injecting fuel into a cylinder, and when the intake valve is opened, A fuel injection valve is provided so that the fuel collides with the back of the intake valve, and the fuel is injected by the fuel injection valve when the intake valve is open when the engine is cold. In this in-cylinder injection spark ignition internal combustion engine, fuel is injected from the above-mentioned fuel injection valve when the intake valve is opened when the engine is cold, so the injected fuel collides with the back of the intake valve. Bounce back toward the intake passage.

[0012]

1 is a schematic vertical sectional view showing a first embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention. In the figure, 1 is an ignition plug, 2 is an intake passage communicating with the inside of a cylinder via an intake valve 3, and 4 is an exhaust passage communicating with the inside of a cylinder via an exhaust valve 5. Such an intake passage 2
And two exhaust passages 4 are each formed, and one of the two intake passages is the illustrated straight port,
The other is a helical port (not shown) for forming a swirl in the cylinder.

The straight port is provided with a swirl control valve (not shown) (hereinafter referred to as SCV) for changing the amount of intake air passing therethrough. The intake air is supplied only through the helical port to the inside of the cylinder by closing, and a strong swirl is formed in the cylinder. Further, at the time of a high engine load in which the required intake amount is relatively large, the SCV is opened to supply intake air through both ports, and as a result, no swirl is formed in the cylinder. Reference numeral 6 is a piston, and reference numeral 7 is a fuel injection valve for injecting fuel into the top surface of the piston 6 by making the fuel flow in a conical shape. The fuel injection valve 7 injects fuel directly into the cylinder in this way, and makes it possible to reliably supply the required fuel amount according to the engine operating state into the cylinder.

FIG. 2 is a schematic diagram showing a fuel supply system for supplying fuel to each fuel injection valve. Each fuel injection valve 7 arranged in the engine body 10 has a common delivery pipe 11
It is connected to the. Reference numeral 12 is a general fuel pump driven by the engine body 10 for pumping fuel to the delivery pipe 11. The fuel pump 12 is provided with two cylinders 12a and 12b, which are respectively connected to the high-pressure pipe 13 connected to the delivery pipe 11 via respective check valves 12c and 12d which allow only the fuel flow in that direction. Has been done. Reference numeral 14 denotes a fuel passage connecting the fuel pump 12 and the fuel tank 15, and a feed pump 14a for providing a fuel flow in each cylinder direction is arranged. Further, a pressure regulator 14c for returning excess fuel to the fuel tank 15 through the return passage 14b when the pressure inside the fuel passage 14 becomes equal to or higher than a predetermined pressure is arranged downstream of the feed pump 14a in the fuel passage 14. ing. Each cylinder 12a, 12b of the fuel pump 12 is connected to such a fuel passage 14 via each solenoid valve 12e, 12f. Reference numeral 16 is a pressure sensor for detecting the fuel pressure in the delivery pipe 11. Reference numeral 20 denotes a control device that controls the fuel pressure in the delivery pipe 11 as well as the fuel injection amount control of the fuel injection valve 7. In addition to the pressure sensor described above, each sensor for detecting the engine operating state,
For example, a rotation sensor 21 for detecting the engine speed,
An air flow meter 22 for detecting the intake air amount, a cooling water temperature sensor 23 for detecting the engine cooling water temperature as the engine temperature, etc. are connected.

The in-cylinder injection spark ignition internal combustion engine in this embodiment executes a homogeneous mixture combustion in each engine operating state, and the fuel injection start timing in each engine operating state is in the cylinder at the time of ignition. It is set in the first half of the intake stroke in order to lengthen the time from the end of fuel injection to ignition with the intention of forming a good homogeneous mixture. The control device 20 usually determines the required fuel amount according to the engine operating state grasped based on the value detected from each sensor, and considers the predetermined fuel pressure so that the required fuel amount is injected. The valve opening period of the fuel injection valve 7 is determined.

The fuel pump 12 alternately feeds fuel to the delivery pipe 11 by two cylinders, and the control device 20 normally controls the fuel pressure in the delivery pipe 11 detected by the pressure sensor 16 as described above. The pressure feed amount of each cylinder is determined so that the predetermined fuel pressure is obtained, and the solenoid valves 12e and 12f that are closed in the discharge stroke of the cylinders 12a and 12b are opened when this pressure feed amount is fed. The excess fuel in the cylinder is returned to the fuel tank 15. In this way, the inside of the delivery pipe 11 is normally maintained at a predetermined fuel pressure. A relatively high pressure is selected as the predetermined fuel pressure in order to shorten the valve opening period of the fuel injection valve 7.

The fuel injected at high pressure from the fuel injection valve 7 has a strong propulsive force and collides with the top surface of the piston 6 to bounce off. When the engine is warm, the piston 6, the cylinder bore, and the cylinder head are sufficiently high in temperature, and even if the rebounding fuel adheres to them, they can be sufficiently vaporized by the time of ignition, and at the time of ignition, they are A homogeneous mixture is formed.

In addition to such normal fuel pressure control and fuel injection amount control, the control device 20 has a cooling water temperature sensor 2
When the cooling water temperature as the engine temperature detected by 3 is equal to or less than a predetermined value, that is, when the engine is cold, as shown in FIG. 3, the lower the cooling water temperature THW, the lower the fuel pressure in the delivery pipe 11. As described above, the electromagnetic valves 12e and 12f of the fuel pump 12 are controlled to open and close based on the fuel pressure corresponding to the current cooling water temperature THW shown in FIG. Further, the valve opening period of the fuel injection valve 7 at this time is determined so that the required fuel amount in the current engine operating state is injected in consideration of the decrease in fuel pressure.

In this way, the fuel pressure is reduced when the engine is cold, and the propulsive force of the injected fuel is weakened. In particular, when the cooling water temperature is considerably low, the fuel pressure is considerably lowered, so that the injected fuel is
As shown in FIG. 5, the phenomenon of floating in the cylinder without colliding with the top surface of the piston 6 and thereby causing the fuel to collide with the top surface of the piston 6 and bounce off does not occur, and the low temperature piston 6, the cylinder bore, and the cylinder It is prevented that fuel adheres to the head and cannot be vaporized by the time of ignition and thus deteriorates exhaust emission. At this time, the fuel injection start timing has a balance with the fuel injection amount, but if possible, it is preferable to be in the latter half of the intake stroke where the distance between the piston 6 and the fuel injection valve 7 becomes longer in the intake stroke. As described above, in order to form a good uniform air-fuel mixture, it is advantageous to shorten the fuel injection period and lengthen the time from the end of fuel injection to ignition, and therefore, gradually increase as the cooling water temperature increases. The fuel pressure is set to rise.
As a result, as the cooling water temperature rises, the injected fuel collides with the piston 6 with a gradually increasing propulsive force. At this time, the temperatures of the piston 6, the cylinder bore, and the cylinder head also gradually rise. However, the fuel that rebounds due to this collision and adheres to these is almost completely vaporized by ignition, and does not deteriorate exhaust emission.

Further, FIG. 3 also shows a map showing opening / closing of the SCV at the time of low engine load in which the required intake air amount can be passed only by the helical port.
The swirl is preferably formed in the cylinder as much as possible because the turbulence can not only form a good uniform air-fuel mixture but also accelerate the combustion speed. However, in the present embodiment, when the cooling water temperature is low and the fuel pressure is relatively greatly reduced, the injected fuel is floating in the cylinder, and if a swirl is formed in the cylinder at this time, this floating fuel is generated. The swirl makes it easier to adhere to the cylinder bore, etc., so at this time,
The SCV is opened so that no swirl is formed.

FIG. 4 is a schematic vertical sectional view showing a second embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention. Only the differences from the first embodiment will be described below. In the present embodiment, for each cylinder, a first fuel injection valve 7a that injects fuel conically at high pressure toward the top surface of the piston 6 and a second fuel injection valve 7b that similarly injects fuel at low pressure are arranged. ing. As shown in FIG. 5, the first and second fuel injection valves 7a and 7b for each cylinder are connected to the high pressure and low pressure first and second delivery pipes 11a and 11b, respectively. A fuel pump (not shown) similar to the one described above is connected to each of the two delivery pipes 11a and 11b so as to maintain the predetermined high and low predetermined fuel pressures in the respective delivery pipes.

The direct injection spark ignition internal combustion engine of this embodiment is shown in FIG. 6 based on the cooling water temperature THW as the engine temperature detected by the cooling water temperature sensor and the intake air amount Q detected by the air flow meter. The map is used to determine which of the first and second fuel injection valves 7a, 7b is to be used. In the map shown in FIG. 6, when the cooling water temperature THW is considerably low, the second fuel injection valve 7b is used regardless of the intake air amount Q, and when the cooling water temperature THW is high, the intake air amount Q is considerably small. The first fuel injection valve 7a is used except when the cooling water temperature between them becomes lower, and the intake air amount Q used by the first fuel injection valve 7a becomes larger as the cooling water temperature becomes lower. There is.

In this way, the first and second fuel injection valves 7
When the engine is cold when the cooling water temperature THW is considerably low, the second fuel injection valve 7b is used to inject fuel at a low pressure, so that the propulsive force of the injected fuel is weakened. In the same manner as when the engine is cold, the injected fuel floats in the cylinder without colliding with the top surface of the piston 6, so that the fuel does not collide with the top surface of the piston 6 and bounce off. It is prevented that fuel adheres to the low-temperature piston 6, the cylinder bore, and the cylinder head, cannot be vaporized by the time of ignition, and deteriorates exhaust emission. Further, as the cooling water temperature THW increases, the in-cylinder temperature rises, and when the cooling water temperature THW is low and the intake air amount Q is large, the fuel injection amount is high and the combustion temperature is high accordingly. The internal temperature is high. At this time, the first fuel injection valve 7a is used, and the injected fuel collides with the piston 6 with a large propulsive force. At this time, the piston 6, the cylinder bore, the cylinder head The temperature of is also sufficiently high,
The fuel that rebounds due to this collision and adheres to these is almost completely vaporized by ignition, and does not deteriorate exhaust emission.

When fuel is injected at a high pressure by the first fuel injection valve 7a, the fuel injection period, which is determined according to the engine operating state, that is, the valve opening period is shortened as a whole, whereby ignition is performed from the end of injection. Can be extended, which is advantageous for forming a homogeneous mixture. In the present embodiment, the second fuel injection valve 7b that injects fuel at low pressure
Since the nozzles are separately provided, the shape and size of the nozzles can be freely designed according to the fuel injection when the engine is cold. For example, by increasing the number of nozzles or the size of the nozzles. If a large amount of fuel can be injected even at a low pressure by increasing the fuel injection period, the fuel injection period is shortened as in the case of injecting fuel at a high pressure by the first fuel injection valve 7a, and the time from the end of injection to ignition is reduced. It can be made longer. In addition, in the present embodiment, when the second fuel injection valve 7b is used, the injected fuel floats in the cylinder, so that it is preferable to open the SCV and not to form a swirl as in the first embodiment. .

FIG. 7A is a schematic vertical sectional view showing a third embodiment of the cylinder injection type spark ignition internal combustion engine according to the present invention. Only the differences from the first embodiment will be described below. The fuel injection valve 7'in the present embodiment is a fuel injection valve that constantly atomizes the fuel into a conical shape toward the top surface of the piston 6'and injects it at a high pressure. On the top of the piston 6 ',
An eccentric recess 8 is formed on the side where the fuel injection valve 7'is located. The recess 8 has a side wall 8b that is substantially perpendicular to the bottom surface 8a.
The bottom surface 8a is at the same height as the top surface of the piston 6'at the edge closest to the fuel injection valve 7 ', and gradually lowers toward the farthest edge. As shown in FIG. 7B which is a plan view of the piston 6 ', the overall shape of the recess 8 is substantially elliptical in accordance with the shape of the fuel colliding with the piston 6'. Further, on the top surface of the piston 6 ', a bulge 6a' which is continuous in the vertical direction with the side wall is formed on the side of the recess 8 far from the fuel injection valve 7 '.

The in-cylinder injection spark ignition internal combustion engine of this embodiment forms a good homogeneous mixture in the cylinder at the time of ignition when it is determined that the engine is warm based on the output of the cooling water temperature sensor. The general fuel injection timing control for executing the engine is executed, but when it is determined that the engine is cold, the routine shown in FIG.
As shown in (A), the fuel injection timing is selected so that the fuel collides with the substantially vertical side wall of the recess 6a 'formed in the top surface of the piston 6'. Although there are an intake stroke and a compression stroke at such a timing, it is advantageous to lengthen the time from the end of fuel injection to ignition for homogeneous mixture combustion, and the intake stroke is preferable.

The fuel injected in this way is recessed 8
Those that collide with the bottom surface 8a of the above and collide with the vicinity of the edge farthest from the fuel injection valve 7 ′ bounce in the cylinder bore direction, and the others bounce in the cylinder head direction. The fuel bounced in the cylinder bore direction is prevented from colliding with the side wall 8b of the recess 8 and the ridge on the top surface of the piston 6'and propagating in the cylinder bore direction. In this way, the injected fuel adheres to the recess 8 and the cylinder head formed on the top surface of the piston 6 ', but does not adhere to the cylinder bore. Since the piston 6'has a small heat capacity and the cylinder head is convected by the combustion heat, these are kept at a relatively high temperature even when the engine is cold compared to the cylinder bore, which has a very large heat capacity and is not related to convection. In addition, the liquid fuel adhering to these is almost completely vaporized at the time of ignition, and is not discharged so much as unburned fuel.

FIG. 8 is a schematic vertical sectional view showing a fourth embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention. Only the differences from the third embodiment will be described below. The piston 6 in this embodiment is a normal piston in which no recesses are formed. The fuel injection timing when the engine is warm is the same as that described above, but the fuel injection timing when the engine is cold is such that the injected fuel is the central portion of the top surface of the piston 6 as shown in FIG. Fuel injection is executed at the time of collision only in the vicinity. At such times,
There is an intake stroke and a compression stroke, but for homogeneous mixture combustion,
It is advantageous to increase the time from the end of fuel injection to ignition, and the intake stroke is preferable.

The fuel thus injected collides with the top surface of the piston 6 and bounces back in the direction of the cylinder head and the cylinder bore. However, since the collision position is near the center of the piston, the center portion having a comparatively high temperature. Flight distance from fuel to the cylinder bore (shown by L in FIG. 8)
Is relatively long, and the propulsive force of the fuel is considerably reduced at the time of collision, and most of this fuel floats in the cylinder without reaching the cylinder bore. In this way, fuel adhesion to the cylinder bore can be reduced.

FIG. 9 is a schematic vertical sectional view showing a fifth embodiment of the cylinder injection type spark ignition internal combustion engine according to the present invention. Only the differences from the fourth embodiment will be described below. The fuel injection valve 7 ″ according to the present embodiment is a fuel injection valve that atomizes the fuel in a conical shape toward the top surface of the piston 6 and injects the fuel at a high pressure. However, when the fuel injection is performed when the intake valve 3 is opened, The injected fuel is arranged so as to collide with the umbrella back portion of the intake valve 3, as shown in FIG.

The fuel injection timing in this embodiment is a normal time when the engine is warm, but is set so that the fuel injection is executed when the intake valve 3 is opened when the engine is cold. . The fuel thus injected collides with the backside of the umbrella of the intake valve 3 and bounces toward the intake passage 2,
It does not proceed in the direction of the cylinder bore through the top surface of the piston 6, so that fuel adhesion to the cylinder bore at this time can be prevented. The fuel bounced in the direction of the intake passage 2 is mixed with the intake air supplied into the cylinder at this time and is supplied into the cylinder without adhering to the intake passage 2 so that the required fuel amount can be almost certainly obtained. Can be supplied in.

FIG. 10 is a schematic vertical sectional view showing a sixth embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention.
Only the differences from the second embodiment will be described below. The in-cylinder injection type spark ignition internal combustion engine in the present embodiment is the second
Similar to the embodiment, each cylinder has first and second fuel injection valves 7a ′ and 7b ′, and the first fuel injection valve 7a ′ is provided.
Is similar to the first fuel injection valve 7a in the second embodiment. On the other hand, the second fuel injection valve 7b 'is connected to the exhaust valve 5
Is a fuel injection valve that injects fuel at a high pressure by making a conical minute flow of fuel toward the surface on the combustion chamber side.

In this embodiment, when the engine is warm, the first
Normal fuel injection amount and fuel injection timing control are performed using the fuel injection valve 7a ', but fuel injection amount and fuel injection timing control are performed using the second fuel injection valve 7b' when the engine is cold. It is like this. Therefore, the fuel injected during engine cold may collide with the combustion chamber side surface of the exhaust valve 5 and bounce back toward the top surface of the piston 6 and adhere to the exhaust valve 5 and the top surface of the piston 6. It does not adhere much to the cylinder bore. Since the exhaust valve 5 has a small heat capacity, is exposed to the exhaust gas for the longest time, and has a considerably high temperature even when the engine is cold, the fuel adhering to the exhaust valve 5 is almost completely vaporized by ignition, Also, the fuel adhering to the top surface of the piston 6 is almost completely vaporized by ignition because the piston 6 has a relatively high temperature, and a good homogeneous air-fuel mixture can be formed. In the present embodiment, it is preferable that the second fuel injection valve 7b ′ injects the fuel toward the exhaust valve that becomes a considerably high temperature even when the engine is cold as described above, but of course, including the intake valve. If the fuel is injected in the cylinder head direction, rebound in the cylinder bore direction can be prevented, and the amount of fuel adhering to the cylinder bore can be considerably reduced.

In all the embodiments, the combustion during engine warming is a stratification in which fuel is injected in the compression stroke to form a mixture having good ignitability only around the spark plug even in the case of homogeneous mixture combustion as described above. Combustion may be used, or stratified charge combustion may be performed only in a specific engine operating state, for example, when the engine load is low. On the other hand, when the engine is cold,
Except for the fifth embodiment in which the fuel injection timing is limited to the intake stroke, either homogeneous mixture combustion or stratified charge combustion is possible. Further, in all the embodiments, the fuel injection valve may be one that injects fuel in a column shape instead of injecting the fuel in a conical shape.

[0035]

As described above, according to the cylinder injection type spark ignition internal combustion engine of the present invention as set forth in claim 1, the fuel pressure varying means compares the fuel pressures when the engine is cold when the engine is warm. In this case, the fuel injected directly from the fuel injection valve into the cylinder at this time has its propulsion force weakened, and it becomes difficult for it to adhere to the piston, cylinder head, cylinder bore, etc. around the combustion chamber. In addition to reliably supplying the fuel into the cylinder, the amount of adhered fuel discharged as unburned fuel from the low temperature cylinder bore can be considerably reduced, and the oil dilution on the wall surface of the cylinder bore is also reduced.

According to the cylinder injection type spark ignition internal combustion engine of the present invention as defined in claim 2, when the engine is cold, the fuel is directly injected into the cylinder at a low pressure by the second fuel injection valve. Therefore, the fuel injected at this time has its propulsive force weakened, and becomes difficult to adhere to the piston, the cylinder head, the cylinder bore, etc. around the combustion chamber, and the cylinder injection type spark ignition internal combustion engine according to claim 1. In addition to obtaining the same effect as above, the size and shape of the injection port of the second fuel injection valve can be freely set because the first fuel injection valve for the engine warm time is additionally provided. It is also possible to shorten the fuel injection time.

According to the cylinder injection type spark ignition internal combustion engine of the present invention as defined in claim 3, when the fuel collides with the vicinity of the side wall in the recess formed in the piston top surface when the engine is cold. Since the fuel is directly injected into the cylinder by the fuel injection valve, when the fuel injected from the fuel injection valve at this time bounces from the recess in the cylinder bore direction, it collides with the side wall of the recess and advances in the cylinder bore direction. Therefore, the same effect as that of the cylinder injection type spark ignition internal combustion engine according to the first aspect can be obtained without the need for the fuel pressure varying means.

According to the cylinder injection type spark ignition internal combustion engine of the present invention as set forth in claim 4, the cylinder is driven by the fuel injection valve when the fuel collides only near the center of the top surface of the piston when the engine is cold. Since the fuel is directly injected into the cylinder, the fuel injected from the fuel injection valve at this time has a relatively long flight distance from the piston to the cylinder bore of the fuel bouncing back in the cylinder bore direction. It becomes difficult to reach the cylinder bore, and the same effect as that of the in-cylinder injection spark ignition internal combustion engine according to the third aspect can be obtained without requiring the recessed portion on the top surface of the piston.

According to the cylinder injection type spark ignition internal combustion engine of the present invention as defined in claim 5, when the engine is cold, the fuel is directly injected into the cylinder in the cylinder head direction by the second fuel injection valve. Since the fuel is injected, the injected fuel collides with the surface of the cylinder head or the intake / exhaust valve, which has the highest temperature around the combustion chamber, on the combustion chamber side, and is unlikely to bounce in the cylinder bore direction. The same effect as that of the internal injection type spark ignition internal combustion engine can be obtained.

According to the cylinder injection type spark ignition internal combustion engine of the present invention as defined in claim 6, it is a fuel injection valve for directly injecting fuel into the cylinder, and the intake valve is opened. Sometimes the fuel injection valve is arranged so that the fuel collides against the back of the intake valve. When the engine is cold, the fuel is injected by the fuel injection valve when the intake valve is opened. Collides with the back of the intake valve and bounces back in the direction of the intake passage. At this time, it mixes with the intake air supplied into the cylinder and is supplied into the cylinder, ensuring that almost the required amount of fuel is supplied into the cylinder. Moreover, this fuel does not go toward the cylinder bore, and the amount of adhesion to the cylinder bore can be considerably reduced.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing a first embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention.

FIG. 2 is a schematic diagram showing a fuel supply system of the first embodiment.

FIG. 3 is a map showing a relationship between cooling water temperature and fuel pressure in the first embodiment.

FIG. 4 is a schematic vertical sectional view showing a second embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention.

FIG. 5 is a plan view showing a fuel supply system of a second embodiment.

FIG. 6 is a map showing which of the two fuel injection valves is used in the second embodiment.

FIG. 7 is a diagram showing a third embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention, in which (A) is a schematic vertical sectional view,
(B) is a schematic plan view of the piston top surface.

FIG. 8 is a schematic vertical sectional view showing a fourth embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention.

FIG. 9 is a schematic vertical sectional view showing a fifth embodiment of the cylinder injection type spark ignition internal combustion engine according to the present invention.

FIG. 10 is a schematic vertical sectional view showing a sixth embodiment of a cylinder injection type spark ignition internal combustion engine according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Spark plug 2 ... Intake passage 3 ... Intake valve 4 ... Exhaust passage 5 ... Exhaust valve 6,6 '... Piston 7, 7', 7 "... Fuel injection valve 7a, 7a '... First fuel injection valve 7b, 7b '... Second fuel injection valve 8 ... Concave

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F02M 69/04 F02M 69/04 P Z

Claims (6)

[Claims] 1. A fuel injection valve for directly injecting fuel into a cylinder, and fuel pressure varying means for varying the pressure of fuel injected by the fuel injection valve. An in-cylinder injection spark ignition internal combustion engine, characterized in that the fuel pressure is reduced by the fuel pressure varying means as compared to when the engine is warm. 2. A first fuel injection valve for injecting fuel directly into a cylinder at a high pressure, and a second fuel injection valve for directly injecting fuel at a low pressure into the cylinder, An in-cylinder injection spark ignition internal combustion engine characterized in that fuel is injected by the first fuel injection valve when the engine is warm and fuel is injected by the second fuel injection valve when the engine is cold. 3. A fuel injection valve for injecting fuel toward a top surface of a piston, and a recess formed so as to have a side wall substantially vertical to the top surface of the piston. The recess when the engine is cold. An in-cylinder injection spark ignition internal combustion engine characterized in that fuel is injected by the fuel injection valve at the time when fuel collides with the vicinity of the side wall inside. 4. A fuel injection valve for injecting fuel toward the top surface of the piston is provided, and when the engine is cold, fuel is injected by the fuel injection valve only when the fuel collides only near the center of the top surface of the piston. A cylinder injection type spark ignition internal combustion engine characterized by being injected. 5. A first fuel injection valve for injecting fuel toward the top surface of the piston, and a second fuel injection valve for injecting fuel in the cylinder head direction are provided, and the first fuel injection valve is provided when the engine is warm. 1. A cylinder injection type spark ignition internal combustion engine, characterized in that fuel is injected by one fuel injection valve and fuel is injected by the second fuel injection valve when the engine is cold. 6. A fuel injection valve for directly injecting fuel into a cylinder, wherein the fuel injection valve is arranged so that the fuel collides with a backside of the intake valve when the intake valve is opened. An in-cylinder injection spark ignition internal combustion engine, characterized in that, when the engine is cold, fuel is injected by the fuel injection valve when the intake valve is opened.