JP2003106195A - Control system for spark ignition type direct injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control system for a spark ignition type direct injection engine capable of improving startability under extremely low temperature by increasing ignitability in a cold start when outside temperature is extremely low. SOLUTION: In a spark ignition type direct injection engine having a fuel injection valve 18 arranged at a circumference edge part of a combustion chamber 6 and an electrode of a spark plug 16 arranged in a spray area from the fuel injection valve 18 under an atmospheric pressure condition, a fuel injection control means 51 is provided. The fuel injection control means 51 controls timing of fuel injection from the fuel injection valve 18 to keep the same in a designated period when pressure in the combustion chamber 6 rises above a designated pressure in a compression stroke in start up under a cold condition of outside temperature below 0 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a spark ignition type direct injection engine, which is arranged such that a fuel injection valve is arranged at a peripheral portion of a combustion chamber and an electrode of a spark plug is located in a spray area of the fuel injection valve. In particular, it relates to control of fuel injection at the time of starting.

[0002]

2. Description of the Related Art Conventionally, in a spark ignition type engine, a fuel injection valve is arranged in the peripheral portion of a combustion chamber, and an air-fuel ratio is made lean and a compression stroke is performed from the fuel injection valve in a predetermined operation region on the low speed and low load side. There are various known spark ignition type direct injection engines in which stratified charge combustion is performed by injecting fuel to improve fuel efficiency.

As a technique relating to control of fuel injection at the time of engine start in this type of spark ignition type direct injection engine, for example, a control device disclosed in Japanese Patent Laid-Open No. 9-79066 is known. This control device injects fuel in the compression stroke when the engine coolant temperature is as high as about 80 ° C. at the engine start, and advances the fuel injection timing as the engine coolant temperature becomes lower, for example, When the cooling water temperature is about 20 ° C, fuel injection is performed in the intake stroke. This is done in order to vaporize and atomize the fuel by lengthening the period from the fuel injection timing to the ignition timing when the engine temperature is low at the time of starting the engine.

[0004]

There are various types of spark ignition type direct injection engines, but by injecting fuel from a fuel injection valve so as to oppose a tumble flow generated in a combustion chamber, In the case where the fuel spray collides with the tumble flow and reaches around the spark plug, or the fuel spray from the fuel injection valve reaches directly around the spark plug, the periphery of the combustion chamber near the intake valve is usually used. And a positional relationship between the fuel injection valve and the spark plug so that the electrode of the spark plug is located in the spray area from the fuel injection valve under the atmospheric pressure condition. The fuel injection direction from is set.

According to a research conducted by the present inventor,
In such an engine, at the cold start when the outside air temperature is extremely low, even if the fuel is injected during the intake stroke in order to gain the vaporization and atomization time of the fuel, the ignitability is not necessarily improved and the misfire easily occurs.

Considering the reason for this, as will be described later in detail, when fuel injection is performed during a period in which the intake valve is relatively wide open during the intake stroke, the fuel injection valve intervenes in the spray area. Most of the fuel spray collides with the umbrella portion of the intake valve and tends to adhere to the umbrella portion of the intake valve as it is, or to reflect on this portion to adhere to the wall surface of the combustion chamber ceiling. Then, especially when the outside air temperature is extremely low such as 0 ° C. or less, the fuel adhering to the wall of the roof of the combustion chamber and the umbrella of the intake valve is hardly vaporized by the ignition timing. As a result, fuel droplets flow from the wall surface of the combustion chamber ceiling to the electrode portion of the spark plug and adhere to the electrode, which deteriorates the ignitability.

In view of the above, the present invention provides a control device for a spark ignition type direct injection engine which can improve ignition performance at cold start when the outside air temperature is extremely low and improve startability at extremely low temperature. The purpose is to provide.

[0008]

In order to achieve the above object, the invention according to claim 1 is such that a fuel injection valve is installed in a peripheral portion of a combustion chamber, and a spray area from the fuel injection valve under atmospheric pressure conditions is provided. In a spark ignition type direct injection engine in which the electrode of the spark plug is located inside, the outside air temperature is 0 °.
A fuel injection control means is provided for controlling the fuel injection timing from the fuel injection valve to be within a predetermined period during which the pressure in the combustion chamber rises above a predetermined pressure during the compression stroke at the time of starting in a cold state of C or lower. It is a thing.

According to this structure, at the time of starting in the cold state, the fuel injection is performed while the intake valve is closed, so that the fuel spray does not collide with the umbrella portion of the intake valve.
Moreover, in the compression stroke, the fuel injection is performed within a predetermined period during which the pressure in the combustion chamber rises above the predetermined pressure, so that the high pressure in the combustion chamber at this time is used to suppress overspray of the fuel spray, The fuel is less likely to adhere to the peripheral wall or ceiling of the chamber, and ignition is performed in a state in which most of the fuel spray floats near the spark plug. Therefore, the ignitability is secured, and the startability in the cold state is improved.

In the present invention, it is preferable that the predetermined pressure is a pressure that reduces the spray angle of the fuel injected into the combustion chamber under that pressure (claim 2). By doing so, the arrival distance of the spray is shortened and the spray angle is narrowed as compared with the injection under the atmospheric pressure condition, so that the adhesion to the peripheral wall or the ceiling of the combustion chamber is avoided.

Since it is difficult to inject fuel within a predetermined period of the compression stroke immediately after the start of cranking when the fuel injection pressure of the fuel injection valve is low, the fuel injection control means determines the fuel injection timing. The control is performed within the predetermined period of the compression stroke after the injection pressure of the fuel from the fuel injection valve rises to the predetermined injection pressure at which the fuel can be injected within the predetermined period of the compression stroke during the cranking period at the cold start. It is designed to be carried out (claim 3).

Further, it is preferable that the fuel injection control means controls the fuel injection timing at the time of starting so as to advance the fuel injection timing as the outside air temperature becomes higher (claim 4).
In this way, when the outside air temperature is high, the time from the fuel injection to the ignition becomes longer, so that vaporization and atomization are promoted.

Further, as the control at the time of starting in the cold state by the fuel injection control means, it is also effective to divide the fuel injection into a plurality of times (claim 5). This is advantageous for vaporizing and atomizing the fuel.

In the invention according to claim 6, a fuel injection valve is installed in the peripheral portion of the combustion chamber, and the electrode of the spark plug is located in the spray area from the fuel injection valve under atmospheric pressure conditions. The spark ignition type direct injection engine is provided with fuel injection control means for controlling the fuel injection timing at the time of starting so as to advance the higher the outside air temperature.

According to this structure, when the temperature of the outside air is high, the time from fuel injection to ignition becomes long, so that vaporization and atomization are promoted.

Further, in the invention according to claim 7, the fuel injection valve is installed in the peripheral portion of the combustion chamber, and the electrode of the spark plug is located in the spray area from the fuel injection valve under the atmospheric pressure condition. In the spark ignition type direct injection engine configured,
Fuel injection control for controlling the fuel injection timing from the fuel injection valve to be in the latter half of the intake stroke except at least the period when the lift amount of the intake valve is large at the time of starting in a cold state where the outside air temperature is 0 ° C. or less. It is equipped with means.

According to this structure, at the time of starting in the cold state, it is possible to prevent the fuel spray from colliding with the umbrella portion of the intake valve, and to evaporate and atomize the fuel between the fuel injection and the ignition. Can be earned.

In the present invention, it is preferable that the fuel injection control means controls the fuel injection timing so as to shift to the compression stroke as the fuel injection pressure from the fuel injection valve increases (claim 8).

Further, in the invention according to claim 9, the fuel injection valve is installed in the peripheral portion of the combustion chamber, and the electrode of the spark plug is located in the spray area from the fuel injection valve under the atmospheric pressure condition. In the spark ignition type direct injection engine configured,
The valve lift amount varying means for changing the lift amount of the intake valve and the fuel injection from the fuel injection valve while reducing the lift amount of the intake valve at the time of starting in a cold state where the outside air temperature is 0 ° C. or less. It is provided with a valve lift amount varying means and a control means for controlling the fuel injection valve so that it is performed in the intake stroke.

Also according to this structure, at the time of starting in the cold state, it is possible to prevent the fuel spray from colliding with the umbrella portion of the intake valve, and to evaporate and atomize the fuel between the fuel injection and the ignition. Can be earned.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall structure of a spark ignition type direct injection engine according to an embodiment of the present invention. In this figure, an engine body 1 has a cylinder block 3 in which a plurality of cylinders 2 are arranged, and a cylinder head 4 arranged on the cylinder block 3, and a piston 5 is vertically arranged in each cylinder 2. It is inserted so as to be reciprocally movable in the direction, and a combustion chamber 6 is formed between the piston 5 and the cylinder head 4.

The piston 5 is connected to a crank shaft 7 rotatably supported on the lower portion of the cylinder block 3 via a connecting rod 8. An electromagnetic crank angle sensor 9 that detects a crank angle (a rotation angle of the crank shaft 7) is arranged on one end side of the crank shaft 7.

The combustion chamber 6 of each cylinder 2 is of a so-called pent roof type in which the ceiling portion is composed of two inclined surfaces extending from the central portion to the lower end of the cylinder head. A plurality of intake ports 10 and exhaust ports 11 are opened in the combustion chamber 6, and in the present embodiment, two intake ports 10 and two exhaust ports 11 are opened in each of the two inclined surfaces forming the ceiling portion. . An intake valve 12 and an exhaust valve 13 are provided at the open ends of the ports 10 and 11, and the intake valve 12 and the exhaust valve 13 are composed of two cam shafts 14 and the like that are axially supported on the cylinder head 4. The valve operating mechanism is adapted to open and close each cylinder at a predetermined timing.

Above the center of the combustion chamber 6, the above-mentioned 4
The spark plug 16 is arranged so as to be surrounded by the intake and exhaust valves, and the tip of the spark plug 16 projects into the combustion chamber 6 from the ceiling portion. An ignition circuit 17 is connected to the ignition plug 16, and the ignition plug 16 is energized at a predetermined timing for each cylinder 2. In addition, two intake ports 10 are provided at the peripheral edge of the combustion chamber 6.
The fuel injection valve 18 is disposed so as to be sandwiched between the fuel injection valve 18 and the fuel injection valve 18, and the fuel is directly injected into the combustion chamber 6 from the fuel injection valve 18.

The structure of the engine body 1 is shown in FIGS.
More specifically, referring to FIG. 2, the intake ports 10 extend linearly from the combustion chamber 6 obliquely upward and are open on one side surface (the left side surface in FIG. 2) of the engine body 1. The two intake ports 10 are formed independently of each other. The tumble flow T flows into the combustion chamber 6 by the air flowing into the combustion chamber 6 through the intake ports 10.
Is generated. The combustion chamber 6 as shown in FIG.
In the cross section in which the intake port 10 is located on the left side and the exhaust port 11 is located on the right side, the tumble flow T is generated in the clockwise direction (arrow direction in FIG. 2).

The two inclined surfaces forming the ceiling of the combustion chamber 6 have a relatively large installation angle (sandwich angle) α of the intake valve 12 and the exhaust valve 13 installed so as to be substantially orthogonal to the inclined surfaces. The inclination angle is set to be a value, for example, 35 ° or more. By setting the angle of the inclined surface to a large value in this way, the intake port 10 and the exhaust port 11 are prevented from being greatly bent, and the flow resistance of intake air and exhaust gas is set to a small value. ing.

The fuel injection valve 18 and the spark plug 16
The positional relationship and the injection direction from the fuel injection valve 18 are set so that the electrode of the spark plug 16 is located in the spray area from the fuel injection valve 18 under the atmospheric pressure condition.

In particular, in this embodiment, the fuel injection direction from the fuel injection valve 18 is set to face the tumble flow T in the combustion chamber 6 in order to achieve stratification by utilizing the tumble flow. That is, in the cross section shown in FIG.
By injecting fuel obliquely downward right from the fuel injection valve 18 located on the left side of the, the injected fuel is directed on the crown surface of the piston 5 in the direction opposite to the tumble flow T. .

On the crown surface of the piston 5, a concave portion 5a is formed in a predetermined range across the cylinder axis Z in the cross section on both the left and right sides. Then, as shown in FIG. 3, the flow along the ceiling of the combustion chamber 6 is tumble forward Ts,
When the flow along the bottom of the combustion chamber 6 is defined as the tumble forward flow Tm, the tumble forward flow Tm and the fuel spray Fa are introduced into the recess 5a from opposite directions, so that the inside of the recess 5a is The tumble forward flow Tm and the fuel spray Fa collide head-on.

As shown in FIG. 4, in plan view, the recess 5a is formed in a substantially elliptical shape with the fuel injection direction as the major axis and the direction orthogonal to this as the minor axis. The outer peripheral portion 5b of the crown surface of the piston 5 excluding the installation portion of the recess 5a
Is formed so as to extend substantially along the inclined surface of the ceiling portion of the combustion chamber 6 facing it, and the crown surface of the piston 5 in a predetermined period before the compression top dead center of the cylinder 2, for example, in the period of BTDC 40 ° CA to TDC. The gap between the outer peripheral portion 5b and the ceiling of the combustion chamber 6 is configured to be a squish area. Note that TDC means top dead center, BTDC means before top dead center, and CA means crank angle.

A specific example of the fuel supply system 20 for the fuel injection valve 18 will be described with reference to FIG. 5. A fuel distribution pipe 19 common to all cylinders 2 is connected to the base end of the fuel injection valve 18. The high-pressure fuel supplied from the fuel supply system 20 is distributed to each cylinder, and the fuel supply system 20 is connected to the distribution pipe 19 and the fuel tank 21 from the upstream side of the fuel passage 22. Low pressure pump 23, low pressure regulator 24, fuel filter 25 toward the downstream side
And a high-pressure pump 26 is arranged in order. And
The fuel sucked up from the fuel tank 21 by the low-pressure pump 23 is pressure-controlled by the low-pressure regulator 24, and then pressure-fed to the high-pressure pump 26 while being filtered by the fuel filter 25.

The high-pressure pump 26 is composed of an electromagnetic pump or the like capable of adjusting the discharge amount of fuel over a wide range. By adjusting the discharge amount of fuel to the fuel distribution pipe 19, the fuel pressure (from the fuel injection valve) is adjusted. Fuel injection pressure) is an appropriate value (for example, about 3 MPa to about 13 MPa, preferably 4 MPa to 7 MPa).
The pressure is controlled to about MPa). In addition,
A part of the fuel boosted by the high pressure pump 26 is
A high pressure regulator may be provided to adjust the pressure state of the fuel supplied to the fuel distribution pipe 19 to an appropriate value by returning the fuel from the return passage to the fuel tank 21.

Returning to FIG. 1, the intake passage 3 communicating with the intake port 10 of each cylinder is provided on one side surface of the engine body 1.
On the other hand, the exhaust passage 32 communicating with the exhaust port 11 of each cylinder is connected to the other side surface of the engine body 1.

The intake passage 31 supplies the air filtered by an air cleaner (not shown) to the combustion chamber 6 of each cylinder 2 of the engine body 1, and an air flow sensor for detecting the intake amount in order from the upstream side thereof. 33 and electric motor 3
Electric throttle valve 34 driven by 5 to open and close
And a surge tank 36. The intake passage 31 downstream of the surge tank 36 is an independent intake passage branched for each cylinder 2, and the downstream end of each independent intake passage is further divided into two intake ports. 10 communicate with each.

A tumble adjusting valve 37 for adjusting the strength of the tumble flow in the combustion chamber 6 is arranged on the upstream side of each of the intake ports 10, and the tumble adjusting valve 37 is operated by an actuator 38 which is, for example, a stepping motor. It is designed to be opened and closed. The tumble control valve 37 is formed by cutting out a part of a circular butterfly valve, for example, a part below the valve shaft, and when the tumble control valve 37 is closed, the tumble control valve 37 is inserted through the cutout part. By flowing the intake air to the downstream side, a tumble flow is formed in the combustion chamber 6, and the tumble flow is gradually weakened as the tumble control valve 37 is opened.

The shapes of the intake port 10 and the tumble adjusting valve 37 are not limited to the above-mentioned shapes.
For example, the intake ports 10 may be configured as a so-called common port type that joins together on the upstream side. In this case, the tumble control valve 37 may have a shape corresponding to the cross-sectional shape of the common port as a base, with a part thereof cut out.

On the other hand, the exhaust passage 32 is for exhausting the burnt gas from the combustion chamber 6, and the exhaust manifold 3 communicating with the exhaust port 11 of each cylinder 2 is provided on the upstream end side thereof.
9 is equipped. A linear O ₂ sensor 40 for detecting the oxygen concentration in the exhaust is provided at the collecting portion of the exhaust manifold 39.
Is provided. The linear O ₂ sensor 40 is used to detect the air-fuel ratio based on the oxygen concentration in the exhaust gas, so that a linear output with respect to the oxygen concentration can be obtained in a predetermined air-fuel ratio range including the theoretical air-fuel ratio. Has become.

The upstream end of an exhaust pipe 41 is connected to the collecting portion of the exhaust manifold 39, and the exhaust pipe 41 is provided with a catalyst 43 for purifying the exhaust gas.

On the upstream side of the exhaust pipe 41, part of the exhaust gas flowing through the exhaust passage 32 is returned to the intake passage 31.
The upstream end of the GR passage 44 is connected. The downstream end of the EGR passage 44 is provided with the throttle valve 34 of the intake passage 31.
It is connected further downstream, for example, to the surge tank 36.
In the middle of the EGR passage 44, an electric EG whose opening can be adjusted
An R valve 45 is provided so that the amount of exhaust gas recirculated through the EGR passage 44 can be adjusted.

A motor 35 for driving the ignition circuit 17, the fuel injection valve 18, the fuel supply system 20, and the throttle valve 34,
Actuator 38 of tumble control valve 37, electric EG
The R valve 45 and the like are controlled by an engine control unit 50 (hereinafter referred to as ECU). Signals from the crank angle sensor 9, the air flow sensor 33, the linear O ₂ sensor 40, and the like are input to the ECU 50, and further, an accelerator opening degree sensor 46 that detects an accelerator opening degree (an operation amount of an accelerator pedal) outputs a signal. A detection signal, a detection signal from the rotation speed sensor 47 that detects the rotation speed of the engine, a detection signal from the outside air temperature sensor 48 that detects the outside air temperature, a signal from the starter switch 49, and the like are also input.

The ECU 50 has a fuel injection control means 51.
Is included. The fuel injection control means 51 controls the timing of fuel injection from the fuel injection valve 18, the injection amount, and the injection rate.

Specifically, as shown in FIG. 6, the control during the normal operation after the engine is started and warmed up is such that the low load and low rotation operation region (a) of the engine is the stratified combustion region, and the other regions are as follows. The region (B) is set as a uniform combustion region, and in the stratified combustion region (B), a predetermined time (for example, before compression top dead center (BTDC) 40 ° to 140 °) from the fuel injection valve 18 to the compression stroke.
(Range)) so that stratified charge combustion is performed. At this time, the air-fuel ratio is lean (for example, A / F> 25).
The intake air amount and the fuel injection amount are controlled so that On the other hand, in the uniform combustion region (b), the fuel is injected from the fuel injection valve 18 in the intake stroke to perform uniform combustion.
At this time, the air-fuel ratio is approximately the theoretical air-fuel ratio (A / F = 14.7)
The intake air amount and the fuel injection amount are controlled so that It should be noted that the air-fuel ratio may be richer than the stoichiometric air-fuel ratio (for example, about A / F = 13) particularly in the full load operation state.

Further, the control at the time of engine start is based on the signals from the outside air temperature sensor 48 and the starter switch 49 at the time of start in a cold state where the outside air temperature is 0 ° C. or less (hereinafter, at the time of cold start). Or the outside air temperature is 0 ° C
It is determined whether or not the engine is starting in a higher warm state (hereinafter referred to as warm starting). Then, during a cold start, as shown in FIG. 7A, the fuel injection timing is controlled to be within a predetermined period during which the pressure in the combustion chamber rises above a predetermined pressure in the compression stroke.

Here, the predetermined pressure is a pressure which is sufficiently higher than the atmospheric pressure and which makes the arrival distance of the fuel injected into the atmosphere of the pressure shorter than that under the atmospheric pressure condition. More preferably, the pressure is such that the spray angle of the fuel injected into the atmosphere of the pressure becomes smaller than that under the atmospheric pressure condition. The above-mentioned predetermined period is, specifically, the middle stage to the latter stage of the compression stroke. It should be noted that several cycles are required from when the high-pressure pump 26 of the fuel supply system 20 is driven with the start of cranking until the fuel pressure rises to the extent that fuel injection can be performed within a predetermined period of the compression stroke. It takes a degree. Therefore, the control at the time of cold start as described above is performed after the fuel pressure rises to a predetermined fuel pressure (about 1 megapascal) capable of fuel injection within a predetermined period of the compression stroke during the cranking period. .

On the other hand, at the time of warm start, as shown in FIG. 7 (b), the fuel injection timing is controlled to be within the intake stroke period. As the control at the time of starting, the fuel injection timing may be switched between the time shown in FIG. 7A and the time shown in FIG. 7B depending on whether it is warm starting or warm starting.
The fuel injection timing may be advanced as the outside air temperature rises in multiple stages or steplessly from the timing shown in FIG. 7A to the timing shown in FIG. 7B.

In addition to the fuel injection control as described above, the ECU 50 closes the tumble control valve 37 at least in the stratified combustion region or strengthens the tumble flow by setting a small opening degree as control according to the operating state. The fuel pressure is controlled by controlling the high pressure pump 26 of the fuel supply system 20 and the like so that the strength of the tumble flow and the penetrating force of the fuel spray are balanced. EGR to make the return flow
The valve 45 is controlled.

According to the apparatus of this embodiment as described above,
During normal operation after engine startup and warm-up, in the stratified charge combustion region, fuel is injected from the fuel injection valve 18 in the compression stroke, and a tumble flow is generated in the combustion chamber 6, and this tumble flow is generated. When the fuel is injected so as to face the fuel cell, the tumble flow and the fuel spray collide with each other in the combustion chamber 6, and the vaporization and atomization of the fuel are promoted, and the flammable mixture near the spark plug 16 is generated at the ignition timing. Air is generated and stratified combustion is performed. Further, when in the uniform combustion region during the normal operation, fuel is injected from the fuel injection valve 18 in the intake stroke, and uniform combustion is performed.

By the way, when the engine is started, especially when the outside air temperature is 0 ° C. or lower in a cold state, the fuel pressure rises to a predetermined fuel pressure in the cranking period, and then the pressure in the combustion chamber becomes a predetermined pressure in the compression stroke. By injecting fuel within a predetermined period in which the pressure rises above the pressure (see FIG. 7A), misfiring is prevented and startability is improved. This action will be specifically described with reference to FIGS. 2 and 8.

As shown in FIG. 2, the fuel injection valve 18 is located in the vicinity of the intake valve 12 (between the two intake valves) at the periphery of the combustion chamber and slightly downward from the horizontal direction toward the center of the combustion chamber. It is arranged to inject fuel. When fuel injection is performed in the middle of the intake stroke during cold start in such a structure as in the prior art in such a structure, the intake valve 12 in the open state is opened in the spray area of the fuel injection valve 18 as shown by the chain double-dashed line in FIG. The umbrella portion of the intake valve 12 intervenes, and most of the fuel spray collides with the umbrella portion of the intake valve 12 and adheres to the umbrella portion of the intake valve 12 as it is, or is reflected at this portion and is reflected on the wall surface of the ceiling portion of the combustion chamber. It is easy to adhere to. In particular, when the outside air temperature is 0 ° C. or lower, the fuel attached to the wall of the umbrella portion of the intake valve 12 or the ceiling of the combustion chamber is hardly vaporized by the ignition timing, so that the fuel is sprayed around the ignition plug. Seldom reaches the point where ignition is impossible, or droplets of fuel flowing from the wall surface of the ceiling of the combustion chamber along the peripheral surface of the spark plug adhere to the electrodes to prevent ignition, resulting in misfire. Becomes

On the other hand, when the fuel injection is performed in the compression stroke as in the present embodiment, the intake valve 12 is closed and does not intervene in the spray area, so the fuel spray may collide with the umbrella portion of the intake valve 12. Absent.

Further, since the engine speed is low at the time of starting and the tumble flow hardly occurs, the action of retaining the fuel spray around the spark plug by the tumble flow and the action of promoting vaporization and atomization cannot be expected, but the compression stroke In FIG. 8, the fuel injection is performed within a predetermined period in which the pressure in the combustion chamber rises above a predetermined pressure, so that the spray reach distance is longer than that under the atmospheric pressure condition (two-dot chain line), as shown in FIG. Becomes shorter and the spray angle becomes narrower. Therefore, the fuel spray is less likely to fly too much and adhere to the peripheral wall and the ceiling of the combustion chamber 6, and ignition can be performed in a state where most of the fuel spray floats near the ignition plug.

Since there is almost no tumble flow and the time from injection timing to ignition is short, it is disadvantageous in terms of vaporization and atomization of the fuel. If is floating around the spark plug 16 in a sprayed state, it is possible to ignite and burn sufficiently, and misfire can be avoided. In particular, if a fuel injection valve 18 having a high atomization performance such as a swirl injector is used, good ignition,
Burning can be performed.

In this way, the startability during cold starting is improved, and good starting can be performed even at an extremely low temperature of minus several tens of degrees, which is lower than 0 ° C. it can.

On the other hand, at the time of warm start, the injection timing is advanced to prolong the mixing time with air, and fuel injection is performed, for example, during the intake stroke period (see FIG. 7B).
In this case, even if the fuel spray collides with the umbrella portion of the intake valve 12 in the open state and adheres to the umbrella portion or the ceiling surface, it can be vaporized by the ignition timing because it is warm, and ignition occurs. The goodness is maintained.

The specific structure of the apparatus of the present invention is not limited to the above embodiment, but various modifications can be made. Some examples will be described below.

In the above embodiment, the batch injection is performed within the predetermined period of the compression stroke at the cold start, but it is also possible to perform the divided injection a plurality of times, for example, as shown in FIG. It is also possible to perform the late injection within the predetermined period of the stroke and the early injection at an earlier timing (for example, the first half of the compression stroke). In this way, the fuel for early injection has time for vaporization and atomization before ignition.

The fuel injection control at the cold start is as follows.
As shown in FIG. 10, fuel injection may be performed in the latter part of the intake stroke except at least the period when the lift amount of the intake valve is large. Even in this case, since the intake valve 12 does not intervene in the spray area at the fuel injection timing, the fuel spray does not collide with the umbrella portion of the intake valve 12. Further, vaporization and atomization are achieved between the fuel injection timing and the ignition timing.

The fuel may be injected in the latter stage of the intake stroke when the fuel pressure is low immediately after the start of the engine, and the injection timing may be shifted to the compression stroke when the fuel pressure becomes high.

Further, the valve mechanism for the intake valve 12 is provided with a valve lift amount varying means for changing the lift amount of the intake valve, and the control means included in the ECU causes the intake valve 12 to be operated at the time of normal operation or warm start. 11 is controlled so that the valve lift amount varying means is brought into a high lift state shown by a broken line in FIG. 11, and the valve lift amount varying means is brought so as to bring the intake valve 12 into a low lift state shown by a solid line in FIG. 11 at the time of cold start. In addition to the control, the fuel injection may be performed in the intake stroke. Even in this case, the intake valve 12 is prevented from intervening in the spray area, the fuel spray does not collide with the umbrella portion of the intake valve 12, and the fuel is vaporized between the fuel injection timing and the ignition timing. Atomization is achieved.

In the above embodiment, when the stratified charge combustion operation is performed after the engine is started and warmed up, the spray from the fuel injection valve collides with the tumble flow to stratify the air-fuel mixture around the spark plug. However, the present invention can be applied to a fuel injection valve which directly injects fuel around the ignition plug.

[0062]

As described above, according to the present invention, in the spark ignition type direct injection engine, when the engine is started in the cold state, the fuel injection timing from the fuel injection valve is set to a predetermined value in the combustion chamber during the compression stroke. Since the control is performed so that the pressure rises above a predetermined period, it is possible to prevent the fuel spray from colliding with the umbrella portion of the intake valve, and moreover, by utilizing the high pressure in the combustion chamber during the compression stroke, It is possible to prevent the spray from flying too much and adhering to the peripheral wall or the ceiling of the combustion chamber, and to ignite the fuel in a state where most of the fuel spray floats near the ignition plug. Therefore, even when the outside air temperature is extremely low, the ignitability can be secured and the startability can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of the entire structure of a spark ignition type direct injection engine to which a control device of the present invention is applied.

FIG. 2 is a sectional view of an engine body.

FIG. 3 is a sectional view showing a specific shape of a piston.

FIG. 4 is a plan view showing the arrangement of pistons, intake ports, fuel injection valves, etc., and the fuel injection state.

FIG. 5 is a block diagram showing a fuel supply system.

FIG. 6 is a diagram showing an example of a control map in which a stratified combustion region and a uniform combustion region are set.

FIG. 7 is a diagram showing fuel injection timings at cold start and warm start.

FIG. 8 is an explanatory diagram showing a distribution state of fuel spray from the fuel injection valve at the time of cold start.

FIG. 9 is a diagram showing another example of fuel injection at cold start.

FIG. 10 is a diagram showing a valve lift amount and a fuel injection timing at a cold start according to another embodiment.

FIG. 11 is a diagram showing a valve lift amount and a fuel injection timing at a cold start according to still another embodiment.

[Explanation of symbols]

1 engine body 6 Combustion chamber 10 intake ports 16 spark plugs 18 Fuel injection valve 48 Outside temperature sensor 49 Starter switch 50 ECU 51 Fuel injection control means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 43/00 301 F02D 43/00 301J 301Z 45/00 360 45/00 360F 364 364K (72) Inventor Araki Keiji 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture F-term in Mazda Corporation (reference) 3G084 AA04 BA15 BA20 BA21 BA23 CA01 CA02 DA09 EC01 FA01 FA02 FA10 FA36 3G092 AA01 AA06 AA09 AA10 AA11 AA17 AB02 BB06 DA01 DA03 DC06 EA04 EA02 EA02 FA31 GA01 HA13X HB02X HB03X HD07X HF05Z HG07Z HG08Z 3G301 HA04 HA13 HA16 HA17 HA19 KA01 KA02 LA05 LA07 LB04 MA19 MA26 NE06 NE11 NE12 PA09Z PA10Z PD15 PF03Z PF16Z

Claims (9)

[Claims] 1. A fuel injection valve is installed at a peripheral portion of a combustion chamber,
In a spark ignition type direct injection engine configured such that the electrode of the spark plug is located in the spray area from the fuel injection valve under atmospheric pressure conditions, when starting in a cold state where the outside air temperature is 0 ° C or less. A spark ignition system characterized by comprising fuel injection control means for controlling the fuel injection timing from the fuel injection valve to be within a predetermined period during which the pressure in the combustion chamber rises above a predetermined pressure in the compression stroke. Control device for direct injection engine. 2. The spark ignition according to claim 1, wherein the predetermined pressure is a pressure such that a spray angle of fuel injected into an atmosphere of the pressure becomes smaller than that under an atmospheric pressure condition. Direct injection engine control device. 3. The fuel injection control means controls the fuel injection timing within a predetermined period of the compression stroke so that the injection pressure of the fuel from the fuel injection valve in the cranking period at the time of cold start is the predetermined compression stroke. The control device for a spark ignition type direct injection engine according to claim 1 or 2, wherein the control is performed after the fuel injection is increased to a predetermined injection pressure within a period. 4. The spark ignition system according to claim 1, wherein the fuel injection control means controls the fuel injection timing at the time of start so as to advance the fuel injection timing as the outside air temperature increases. Control device for direct injection engine. 5. The spark ignition system according to claim 1, wherein the fuel injection control means causes the fuel injection to be divided into a plurality of times when starting in the cold state. Control device for direct injection engine. 6. A fuel injection valve is installed at a peripheral portion of the combustion chamber,
In a spark ignition type direct injection engine configured such that the electrode of the spark plug is located in the spray area from the fuel injection valve under atmospheric pressure conditions, the fuel injection timing at the start is advanced as the outside air temperature becomes higher. A control device for a spark-ignition direct-injection engine, characterized in that it comprises a fuel injection control means for controlling so as to control. 7. A fuel injection valve is installed at the periphery of the combustion chamber,
In a spark ignition type direct injection engine configured such that the electrode of the spark plug is located in the spray area from the fuel injection valve under atmospheric pressure conditions, when starting in a cold state where the outside air temperature is 0 ° C or less. A spark ignition direct injection characterized by including fuel injection control means for controlling the fuel injection timing from the fuel injection valve to be in the latter half of the intake stroke excluding at least the period when the lift amount of the intake valve is large. Engine control unit. 8. The spark ignition system according to claim 7, wherein the fuel injection control means controls the fuel injection timing to shift to a compression stroke as the fuel injection pressure from the fuel injection valve increases. Control device for direct injection engine. 9. A fuel injection valve is installed at a peripheral portion of the combustion chamber,
A variable valve lift amount that makes it possible to change the lift amount of an intake valve in a spark ignition type direct injection engine configured so that an electrode of a spark plug is located in a spray area from the fuel injection valve under atmospheric pressure conditions. And a valve lift amount varying means and a fuel so that fuel is injected from the fuel injection valve in the intake stroke while the lift amount of the intake valve is reduced at the time of starting in a cold state where the outside air temperature is 0 ° C. or less. A control device for a spark ignition type direct injection engine, comprising a control means for controlling an injection valve.