JPH11101146A - Cylinder injection type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce fuel consumption and improve output by injecting fuel dividedly in a range from a first period to a middle period of an intake stroke at the time of an engine being in a uniform combustion range and in a low- rotation operating range in a device for injecting fuel in the intake stroke of a high-load operating area to uniform a mixture. SOLUTION: In an ECU 16 inputting detection signals of sensors such as a crank angle sensor 12, an accelerator sensor 13, an airflow meter 14 and a water temperature sensor 15, an operating state judging means 17 judges which range an engine belongs to among a low-load low-rotation operating range, a medium-load medium-rotation operating range, a high-load operating range, and the like. In a maximum-load low-rotation operating range within a high-load operating range, it is so controlled that fuel is injected being divided to a period within a specified range from a first period to a middle period of an intake stroke and a period within a specified range the first period to the middle period of the intake stroke. Engine output is therefore effectively increased without worsening fuel consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection engine having an injector for directly injecting fuel into a combustion chamber.

[0002]

2. Description of the Related Art Conventionally, as shown in, for example, Japanese Patent Application Laid-Open No. 7-119507, stratified combustion is executed by starting fuel injection from the latter half of the compression stroke when the engine is under low load, and when the engine is under a high load. In the in-cylinder injection engine configured to start fuel injection from the first half of the intake stroke and execute uniform combustion, at the time of low rotation in the operating region of the engine that executes the uniform combustion, that is, at high load and low rotation, By dividing the fuel into multiple injections during the intake stroke, the amount of fuel injected per injection is reduced, this fuel is effectively atomized and diffused, and the fuel is uniformly and well-combusted to achieve good smoke generation. Prevention has occurred.

[0003]

The engine described in the above publication injects half of the required fuel amount from the first half of the intake stroke in the high-load low-speed operation region, and injects the other half at the end of the intake stroke. By doing so, it is possible to prevent the generation of smoke in the exhaust gas by satisfactorily and uniformly burning the fuel, but it has been taken into consideration that the output of the engine is increased in the high-load low-speed operation region. However, there is room for improvement in improving fuel economy and obtaining high output.

[0004] That is, it is known that the output of the engine changes under the influence of the charge amount of the intake air, the uniformity of the air-fuel mixture, and the combustion speed. Then, the filling amount of the intake air in the high-load low-speed operation region changes according to the flow rate of the intake air and the amount of fuel adhering to the combustion chamber wall surface such as the piston, and as shown in FIG. Increases or decreases according to the injection timing. This is because the amount of fuel adhering to the piston varies according to the fuel injection timing, and the temperature of the intake air in the combustion chamber changes according to the heat of vaporization of the fuel injected into the combustion chamber. Because it changes.

[0005] The uniformity of the air-fuel mixture is optimized in a region where the vaporization time of the fuel injected into the combustion chamber is sufficiently ensured and the amount of fuel adhering to the wall of the combustion chamber, such as a piston, is small. It can be measured based on a comparison between the air-fuel ratio of the air-fuel mixture formed around and the average air-fuel ratio of the entire combustion chamber. As shown in FIG. 8 (II), this air-fuel ratio changes variously in accordance with the fuel injection timing, and becomes the best at points α and β where the area around the ignition plug becomes the average air-fuel ratio. further,
The combustion speed increases because the fuel turbulence tends to remain as the injection timing decreases. That is, FIG.
As shown in I), as the fuel injection timing is delayed, the combustion time is shortened, and the output can be increased.

[0006] As described above, since each element that determines the engine output in the high-load low-speed operation region is affected by the fuel injection timing, the fuel injection pressure is high.
Control is performed to increase the engine output while reducing fuel consumption by injecting fuel at the appropriate injection timing required based on each of the above-described elements in the entire rotation range of the direct injection engine in which the injection time is short. It was difficult.

The present invention has been made in view of the above circumstances, and provides a direct injection engine capable of increasing engine output while reducing fuel consumption in a high-load, low-speed operation region.

[0008]

The invention according to claim 1 is
An injector for directly injecting fuel into the combustion chamber is provided, and when the engine is at least in a high-load operation region, the fuel is injected from the injector during an intake stroke to perform uniform combustion in which the mixture is homogenized and burned. In the in-cylinder injection engine configured as described above, when the engine is in the low-speed operation region within the region in which the uniform combustion is performed, the fuel is supplied a plurality of times within the range from the first half to the middle period of the intake stroke. It is provided with fuel control means for controlling the injection state of the fuel so that the fuel is split and injected.

According to the above configuration, in the high load range of the engine that performs uniform combustion, when the engine speed is in the low drive range, the fuel is supplied a plurality of times within the range from the first half to the middle of the intake stroke. By being divided and injected, the filling amount of the intake air is sufficiently ensured, and the air-fuel mixture is properly burned in an effectively uniformed state.

According to a second aspect of the present invention, in the cylinder injection type engine according to the first aspect, when the fuel is injected in the intake stroke to perform uniform combustion, the timing at which the charging efficiency of the intake air is maximized. The fuel is injected separately at a time when the uniformity of the air-fuel mixture becomes optimal.

[0011] According to the above configuration, when the engine speed is low in the high load range of the engine that executes uniform combustion, the charging efficiency of the intake air is within the range from the first half to the middle of the intake stroke. Is divided into a time when the maximum value is maximized and a time when the uniformity of the air-fuel mixture is optimal, so that a sufficient amount of intake air is ensured and the air-fuel mixture is effectively homogenized. It will burn properly in the state of being.

According to a third aspect of the present invention, in the in-cylinder injection engine according to the first or second aspect, when the fuel is divided and injected in a plurality of times in the intake stroke, the fuel injected first. Is set in the range of 40 to 60% of the total injection amount.

According to the above configuration, the amount of fuel injected by dividing the fuel in the intake stroke is appropriately set, and the air-fuel mixture is burned in an appropriately uniformed state.

According to a fourth aspect of the present invention, in the in-cylinder injection engine according to the third aspect, when fuel is divided into a plurality of times during the intake stroke and injected, the amount of fuel injected first is reduced. , Is set to be larger than the injection amount of the fuel to be injected later.

According to the above configuration, when fuel is divided and injected in a plurality of times in the intake stroke, a large amount of fuel is injected first, and the time for vaporization and atomization of this fuel is sufficiently ensured. Become.

According to a fifth aspect of the present invention, the injector is installed so that the fuel is injected obliquely downward from the peripheral edge of the combustion chamber, and a cavity for spraying the fuel is provided at the top of the piston. The direct injection engine according to any one of claims 1 to 4,
When the fuel is divided into a plurality of injections during the intake stroke, the injection timing of the fuel to be injected first is set to 60
It is set at a time after ° CA.

According to the above configuration, when the fuel is divided and injected in the intake stroke when the engine is under a high load, when the piston drops to a predetermined position after the intake top, the fuel is obliquely lowered from the periphery of the combustion chamber. , The fuel is effectively prevented from adhering to the peripheral wall of the cylinder.

According to a sixth aspect of the present invention, in the direct injection engine according to the fifth aspect, the fuel injection angle is inclined by 30 ° or more with respect to the horizontal direction.

According to the above construction, when the fuel is divided and injected in the intake stroke, the fuel is injected obliquely downward from the peripheral portion of the combustion chamber at an injection angle of 30 ° or more, and the fuel adheres to the peripheral wall of the cylinder. Is effectively suppressed.

According to a seventh aspect of the present invention, in the cylinder injection engine according to any one of the first to fourth aspects,
An injector is installed such that fuel is injected from a peripheral portion of the combustion chamber toward an ignition plug installed so as to face the combustion chamber.

According to the above configuration, since the fuel is injected substantially horizontally from the upper part of the combustion chamber, when the fuel is divided and injected in the intake stroke, the fuel is reflected at the top of the piston. Adhesion of fuel to the peripheral wall is suppressed.

According to an eighth aspect of the present invention, in the cylinder injection engine according to any one of the first to fourth aspects,
A spark plug and an injector are installed so as to face the upper center of the combustion chamber, and a cavity into which fuel injected from the injector is blown is formed at the center of the top of the piston.

According to the above configuration, when the fuel is divided and injected in the intake stroke, the fuel is injected downward from above the combustion chamber.

[0024]

1 and 2 show an embodiment of a direct injection engine according to the present invention. This engine has a plurality of cylinders constituted by a cylinder head 1 and a cylinder block 2. A piston 3 is inserted into each cylinder, and a combustion chamber 4 is formed above the piston. The cylinder head 1 has an intake port 5 and an exhaust port 6 communicating with the combustion chamber 4, an intake valve 7 and an exhaust valve 8 for opening and closing these ports 5, 6, and an ignition for generating a spark and burning fuel. A plug 9 and an injector 10 for directly injecting fuel into the combustion chamber 4 are provided.

On the lower surface of the cylinder head 1, there is provided a pent roof type recess forming the combustion chamber 4, and the intake port 5 and the exhaust port 6 are respectively opened on the inclined surface of the pent roof type recess. The intake and exhaust valves 7 and 8 are driven by a valve mechanism (not shown) so that the intake and exhaust ports 5 and 6 are opened and closed at a predetermined timing.

FIG. 1 shows the intake port 5 and the exhaust port 6 one by one, and the intake port 5 and the exhaust port 6 are arranged in parallel in a direction perpendicular to the plane of FIG. It is arranged in. One of the two intake ports 5 is provided with a control valve for controlling the flow of intake air. The control valve is driven by an actuator such as a stepping motor to be fully closed or partially opened. In a state where the flow of intake air at one of the intake ports 5 is restricted, the intake air that flows through the other of the intake ports 5 as shown by the broken line in FIG.
A swirl (horizontal eddy current) is generated along the inner peripheral surface of the.

The intake port 5 is formed so that its downstream side extends obliquely downward.
A tumble (vertical eddy current) is formed by the intake air flowing into the combustion chamber 4 from the inside. Therefore, when the control valve is fully closed or partially opened,
By combining the swirl and the tumble, an oblique swirl is generated in the combustion chamber 4.

The ignition plug 9 is disposed substantially at the center of the combustion chamber 4, and is mounted so that the tip of the plug faces the combustion chamber 4. The injector 10 is attached to a peripheral portion of the combustion chamber 4 located on the side of the installation portion of the intake port 5 and is installed at a predetermined angle θ with respect to a horizontal plane, for example, at an angle of 25 to 50 °. Accordingly, the fuel is injected obliquely downward from the injector 10 into the combustion chamber 4.

The injector 10 has a built-in needle valve and a solenoid (not shown). When a pulse signal output from a fuel control unit, which will be described later, is input to the solenoid, the amount of fuel corresponding to the pulse width of the signal is increased. To
For example, it is configured to spray at a pressure of 3 to 15 MPa with a relatively wide spray angle set to 40 ° or more.

A cavity 11 is formed at the top of the piston 3 from a peripheral portion located on the side where the injector 10 is installed to a central portion facing the installation portion where the spark plug 9 is installed. Then, the installation position and the inclination angle of the injector 10 and the position of the cavity 11 are set so that the fuel injected at a predetermined time during the compression stroke in which the piston 3 rises is collected in the cavity 11 and carried around the ignition plug 9. The relationship between the formation range and the installation position of the spark plug 9 is set in advance.

As shown in FIG. 3, the engine includes a crank angle sensor 12 for detecting a crank angle, an accelerator sensor 13 for detecting an amount of depression of an accelerator pedal, an air flow meter 14 for detecting an intake air amount, and cooling of the engine. Various sensors such as a water temperature sensor 15 for detecting the water temperature are provided, and detection signals output from these sensors are input to the ECU 16. The ECU 16 includes an engine operating state determining means 17.
And a fuel control means 18 for controlling the injection state of the fuel injected from the injector 10.

The operating state determining means 17 determines to which of the operating areas shown in FIG. 4 the engine belongs according to the detecting means of each sensor, and sends this determination signal to the fuel control means 18. It is configured to output. The operation region is set based on the engine speed Ne and the engine torque Pe, and the low-load low-speed operation region A in which the fuel injection amount is small and the load and rotation in the low-load low-speed operation region A are set. A relatively high operation region A1 and a middle load medium rotation region operation B in which the fuel injection amount is medium;
Within the medium-load medium-speed operation region B, the operation region B1 in which the load and rotation are relatively high, the high-load operation region C in which the fuel injection amount is large, and the load in the high-load operation region C Operating range C where rotation is low with the accelerator fully open
1, an operation region C2 where the load is maximum and the rotation is medium in the high load operation region C, and an operation region C3 where the load and rotation are the maximum in the high load operation region C, respectively.
It is divided into and.

In the low-rotation low-load operation region A where the fuel injection amount is small and other than the operation region A1 where the load and rotation are relatively high, as shown in FIG. At a predetermined time within the range of BTDC 30 ° to 120 ° CA (the crank angle before compression top dead center 30 ° to 120 °). The fuel control means 18 is configured to execute stratified combustion in which fuel is injected at a time and the mixture is stratified and burned in a lean state. In the stratified combustion in the operation region A, the throttle opening is increased to increase the intake air amount,
This is performed by setting a lean state that is significantly larger than the stoichiometric air-fuel ratio.

In the region A1 where the load and rotation are relatively high in the low load low rotation operation region A, FIG.
As shown in (II) of the compression stroke, the timing within a predetermined range (BTDC 60 ° to 180 ° CA) from the first half to the middle of the compression stroke and the predetermined range (B
TDC of 30 ° to 120 ° CA), the fuel control is performed by injecting the fuels a and b and increasing the throttle opening so as to stratify and burn the air-fuel mixture in a lean state. It is configured to execute in the means 18.

In the middle load medium rotation operation region B where the fuel injection amount is medium, other than the operation region B1 where the load and rotation are relatively high, as shown in FIG. Predetermined range of intake stroke (BTDC 200 ° ~
360 ° CA) and the predetermined range of the compression stroke (BT
By injecting fuel separately at a time within DC 30 ° to 120 ° CA) and increasing the throttle opening, the air-fuel mixture is weakly stratified and burned in a lean state.

Further, in the operation range B1 in which the load and rotation are relatively high in the operation range B of the medium load and medium rotation, as shown in FIG. 5 (IV), a predetermined range of the intake stroke (BTDC2
(00 ° to 360 ° CA), the fuel control means 18 performs uniform combustion in which the fuel mixture is uniformly injected in a lean state by injecting the fuel all at once and increasing the throttle opening. It is configured to be.

Further, in the high-load operation region C where the fuel injection amount is large, the operation regions C1 to C3 where the load is maximum are set.
In regions other than the above, similarly to the operation region B1, fuel is collectively injected at a timing within a predetermined range of the intake stroke, and the fuel is homogenized and burned under a stoichiometric air-fuel ratio where the excess air ratio is 1. The fuel control means 18 is configured to execute uniform combustion.

Further, in the high load operation region C,
In the operation range C1 where the load is maximum and the rotation is low, as shown in FIG. 5 (V), the timing within a predetermined range (BTDC 220 ° to 360 ° CA) from the first half to the middle of the intake stroke, and the intake stroke Predetermined range (BTD
C. The fuel a and b are injected separately at a time within 240 ° C. to 360 ° CA), and the air-fuel mixture is made uniform in an enriched state and burned. When the fuel is divided and injected in the region C1, the fuel b to be injected later is
Is controlled so that the injection amount of the fuel is within the range of 40 to 60% of the total injection amount. Preferably, the injection amount of the fuel a to be injected earlier is the injection amount of the fuel b to be injected later. Is set to a larger value than.

Further, in an operation region C2 where the engine is in a high-load operation region and the engine load is at a maximum and the rotation is moderate, the fuel is collected at a predetermined timing of the intake stroke as in the regions B1 and C. And the mixture is burned in an enriched state in a uniform manner.

Further, in the operation region C3 where the load and the rotation are maximum in the operation region C of the high load, FIG.
(VI), the latter half of the exhaust stroke (BTDC 36
(0 ° to 440 ° CA), the fuel control unit 18 starts the fuel injection at a predetermined time, injects the fuel in a lump, and makes the air-fuel mixture uniform in an enriched state and burns. It is configured as follows.

The control operation performed by the fuel control means 18 will be described with reference to the flowcharts shown in FIGS. When the above control operation is started, first, according to the cooling water temperature of the engine detected by the water temperature sensor 15, the cold operation state in which the exhaust gas purifying catalyst provided in the exhaust passage is likely to be in the inactivated state is high. Is determined (step S1), and if determined to be YES, the combustion control at the time of cold to promote the warm-up of the catalyst is executed (step S2).

That is, when it is confirmed that the catalyst temperature is low in the cold operation state, the fuel is divided and injected into the intake stroke and the compression stroke, and the air-fuel mixture around the ignition plug 9 is converted to the stoichiometric air-fuel ratio or By making the combustion chamber 4 richer than the above and making the entire combustion chamber 4 substantially at the stoichiometric air-fuel ratio, HC and NOx emissions during cold operation of the engine in which the exhaust gas purifying action by the catalyst cannot be sufficiently obtained. The fuel injection state is controlled so as to increase the exhaust gas temperature and promote the warm-up of the catalyst while reducing the amount.

If NO is determined in step S1 and it is confirmed that the engine is not in the cold operation state, the engine is in the predetermined acceleration operation state according to the detection signal of the accelerator sensor 13. It is determined whether or not (step S3). If the determination is YES, combustion control during acceleration for preventing the occurrence of misfire due to an increase in the intake air amount due to a sudden large depression of the accelerator pedal is performed. Is executed (step S4).

That is, in a cylinder injection type engine having a uniform combustion region in which fuel is injected in the intake stroke,
Before and after the start time of the fuel injection, the intake air amount is calculated based on the detected value of the intake air amount, and the fuel injection amount is determined according to the intake air amount calculated at the injection start time. When the intake air charge calculated at the time after the injection is greater than the intake air charge calculated at the time, the amount of fuel corresponding to the increase is additionally injected during the first half of the compression stroke. Further, the combustion state is controlled so as to prevent the air-fuel ratio from becoming excessively large due to the increase in the intake charge, and to prevent the engine from misfiring or the like.

If NO is determined in step S3 and it is confirmed that the engine is in the normal operation state, the output of the engine read from the map using the engine speed and the accelerator opening as parameters. Shaft torque,
That is, by determining whether or not the engine torque Pe is smaller than a first reference value P1 set in advance, it is determined whether or not the engine is in the low-load and low-speed operation region A where the fuel injection amount is small (step). S5).

If YES is determined in the step S5, it is determined whether or not the engine torque Pe is larger than a second reference value P2 set in advance within a range equal to or less than the first reference value P1. Thus, it is determined whether or not the load and rotation of the engine are in the relatively high operation region A1 in the low load and low rotation operation region A (step S6). If it is determined as NO in the above step S6 and it is confirmed that the engine is in the operation region other than the region A1 in the operation region A of low load and low rotation, as shown in (I) of FIG. At a predetermined time within a range from the middle stage to the late stage of the compression stroke, stratified charge combustion is performed in which fuel is collectively injected from the injector 10 into the combustion chamber 4 and a mixture is stratified and burned in a lean state ( Step S7).

If YES is determined in step S6, and it is confirmed that the engine is in the operation range A1 where the load and rotation are relatively high in the operation range A where the load is low and the rotation is low, the process shown in FIG. As shown in (II), fuel a and b are divided into a predetermined time within a range from the first half to the middle of the compression stroke and a predetermined time within a range from the middle to the second half of the compression stroke, and A stratified charge combustion is performed in which the mixture is stratified and burned in a lean state (step S8).

If the determination in step S5 is NO and it is confirmed that the engine torque Pe is greater than the first reference value P1, the engine torque Pe is set to a value greater than the first reference value P1. The set fourth reference value P
By determining whether the fuel injection amount is smaller than 4 or not, it is determined whether or not the fuel injection amount is in the middle load medium rotation operation region B where the fuel injection amount is medium (step S9).

If the result of the determination in step S9 is YES, the engine torque Pe is set to a third reference value preset at a value greater than the first reference value P1 and smaller than the fourth reference value P4. By determining whether or not the engine speed is smaller than P3, it is determined whether or not the engine is in an operation region B1 in which the load and the rotation are relatively high in the operation region B of the medium load and the medium rotation (Step S10). Step S10 above
Is determined to be NO, and when it is confirmed that the engine is in an operation region other than the above-mentioned region B1 in the operation region B of the medium load medium rotation, as shown in (III) of FIG. The fuel injection is divided into a predetermined period and a predetermined period of the intake stroke, and the stratified charge combustion is performed in which the mixture is leanly stratified and burned in a lean state (step S11).

If YES is determined in step S10, and it is confirmed that the engine is in the operation range B1 in which the load and rotation are relatively high within the operation range B of the medium load and medium rotation, FIG. As shown in (IV), fuel is injected at a predetermined time during the intake stroke, and the fuel injection amount and the throttle opening are controlled so that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio. Then, the fuel control means 18 executes uniform combustion in which the air-fuel mixture is made uniform in a lean state and burned (step S12).

If the result of the determination in step S9 is YES, and it is confirmed that the engine torque Pe is in the high-load operating region C larger than the fourth reference value P4, the detection of the accelerator sensor 13 is performed. In accordance with the signal, it is determined whether or not the accelerator is fully open, that is, whether or not the engine load is in the maximum range (step S13). In this step S13, the determination is NO, and the high load operation region C
If it is confirmed that the accelerator opening is not fully open, the fuel injection amount and throttle opening are controlled so that the fuel is injected at a predetermined time during the intake stroke and the stoichiometric air-fuel ratio is achieved. By doing so, uniform combustion control is performed to make the fuel uniform and burn under the stoichiometric air-fuel ratio where the excess air ratio is 1 (step S14).

If the result of the determination in step S13 is YES and it is confirmed that the accelerator pedal is fully opened, the engine speed Ne is less than a preset first reference value N1, for example, 3000 rpm. It is determined whether or not it is (step S15). If it is determined YES in this step S15 and it is confirmed that the engine is in the operating region C1 where the load is maximum and the rotation is low in the high load region C of the engine, as shown in FIG. By controlling the fuel injection amount so that the air-fuel ratio is richer than the stoichiometric air-fuel ratio, the fuel-air mixture is controlled by dividing and injecting the fuel at predetermined times within a range from the first half to the middle half of the intake stroke. The combustion state is controlled so that is burned uniformly in an enriched state (step S16).

If the determination in step S15 is NO, and it is confirmed that the engine speed Ne is equal to or higher than the first reference value N1, the engine speed Ne is higher than the first reference value N1. The second reference value N set to the value
2. It is determined whether or not the vehicle is in a high-speed operation state larger than, for example, 5500 rpm (step S17). If it is determined as NO in step S17 and it is confirmed that the load is in the operation region C2 where the load is maximum and the rotation speed Ne is in the middle in the high load operation region C, the fuel is supplied at a predetermined time during the intake stroke. Are collectively injected, and the fuel injection amount is controlled so that the air-fuel ratio is richer than the stoichiometric air-fuel ratio, so that the air-fuel mixture is controlled to be uniformly enriched and burned (step S18). ).

If YES is determined in the step S17, and it is confirmed that the load and the rotation are in the operation region C3 where the load and the rotation are the maximum, respectively, in the high load operation region C, (VI in FIG. 5) As shown in), the fuel injection is started at a predetermined timing in the latter half of the exhaust stroke, the fuel is injected collectively within the range of the first half of the intake stroke, and the air-fuel ratio is richer than the stoichiometric air-fuel ratio. By controlling the fuel injection amount as described above, the fuel control means 18 executes uniform combustion control for making the air-fuel mixture uniform and burn in an enriched state (step S19).

The injector 10 for directly injecting the fuel into the combustion chamber 4 as described above is provided. When the engine is at least in the high-load operating region C, the fuel is injected from the injector 10 during the intake stroke to mix the fuel. In the cylinder injection type engine configured to perform uniform combustion in which the air is homogenized and burned, when the engine is in the low-speed operation region C1 in the region C in which the uniform combustion is performed, the intake stroke The fuel is divided and injected within the range from the first half to the middle half of the period, so that the filling amount of the intake air is sufficiently secured in the above-mentioned operation region, and the air-fuel mixture is burned in an effectively uniformed state. As a result, the engine output can be increased while reducing fuel consumption.

That is, when the fuel is injected in the intake stroke and the air-fuel mixture is uniformly burned in the high-load low-speed operation region C1 where the fuel injection amount is large, as shown in FIG. The charging amount of the intake air changes according to the fuel injection timing, and the charging efficiency Ce of the intake air changes accordingly as shown in FIG. 9 (I). Further, as shown in (II) of FIG. 8, the uniformity of the mixture changes according to the fuel injection timing, and the fuel injection timing at which the uniformity of the mixture becomes optimal (average air-fuel ratio); The timing at which the amount of intake air is maximized is different from the timing at which the intake efficiency is maximized, and the injection timing at which the uniformity of the air-fuel mixture is optimal is determined during the first half and the middle of the intake stroke, respectively. Occurs within the range.

For this reason, when the engine is in the high-load low-speed operation region C1, the fuel is divided and injected within the range from the first half to the middle of the intake stroke, so that the intake charge amount is reduced. Fuel can be injected corresponding to the maximum timing and the timing at which the uniformity of the air-fuel mixture is optimal, whereby the engine output can be effectively increased without deteriorating fuel efficiency. .

The fuel injection timing at which the uniformity of the air-fuel mixture is optimum is determined by sandwiching the region where the air-fuel mixture is weakly stratified.
However, as shown in FIG. 8 (III), the later the injection timing is, the shorter the combustion time is, so that in order to increase the engine output, By injecting fuel in accordance with the later point β of the points α and β, as shown in FIG. 9 (II), it is possible to maximize the indicated average effective pressure and effectively increase the engine output. it can. In the case of performing the split injection, the number of splits is not limited to two, and may be three or more.

Further, by dividing and injecting fuel in the intake stroke as described above, the amount of fuel injection per injection can be reduced, so that the mixture is not excessively concentrated inside the spray. It is possible to effectively suppress fuel vaporization and atomization. Furthermore, since the time from the first injection time to the ignition time becomes longer, the air-fuel mixture can be sufficiently diffused, and the fuel can be efficiently mixed with the air. The effect of increasing the engine output can be obtained, smoke and CO in the exhaust gas can be reduced, and the exhaust temperature can be effectively reduced.

When performing uniform combustion by injecting fuel in the intake stroke, the fuel injection timing at which the intake charge efficiency Ce becomes maximum (Ce best), and the uniformity and combustion speed of the air-fuel mixture are determined as follows. The fuel injection timing at which the engine torque Pe specified on the basis of the maximum (Pe best) is determined by referring to FIG.
As shown in the figure, the value changes according to the engine speed Ne.
For this reason, when performing uniform combustion by injecting fuel in the intake stroke, the timing at which the intake charging efficiency Ce becomes the maximum,
The time when the uniformity of the air-fuel mixture is optimum and the engine torque Pe is maximized is set in accordance with the engine speed Ne, and the fuel is injected at these times, thereby improving the engine output. Can be more effectively increased.

Further, in the above embodiment, when the fuel is divided and injected in a plurality of times in the intake stroke, the injection amount of the fuel injected first is set within a range of 40 to 60% of the total injection amount. Therefore, it is possible to prevent a large amount of fuel from being injected at one of the injection timings, thereby effectively suppressing excessive concentration of the air-fuel mixture inside the spray, thereby preventing the fuel from being vaporized and atomized. Can be promoted. When the fuel is divided and injected in a plurality of times during the intake stroke, the injection amount a of the fuel injected first is set to be larger than the injection amount b of the fuel injected later. Since the time until the previously injected fuel a is ignited can be sufficiently secured, there is an advantage that the fuel a can be surely dispersed and the air-fuel mixture can be effectively homogenized.

As shown in the above embodiment, the injector 10 is installed so that fuel is injected obliquely downward from the periphery of the combustion chamber 4 and the piston 3
In the cylinder injection type engine provided with the cavity 11 at the top of which the fuel is blown, when the fuel is divided into a plurality of times during the intake stroke and injected, the injection start timing of the fuel a to be injected first is Crank angle after intake top is 60
If it is set at a time after the crank angle (the crank angle before the compression top is 300 °) or later, it is possible to effectively prevent the fuel injected during the intake stroke from adhering to the peripheral wall of the cylinder.

That is, when the fuel is divided and injected in the intake stroke, when the piston 3 drops to a predetermined position after the crank angle after the intake top is 60 ° or more, the fuel is inclined from the peripheral edge of the combustion chamber 4. Since the fuel is injected downward, the amount of fuel that collides with the top of the piston 3 and reflects is suppressed to a small amount, and it is possible to effectively prevent the fuel from adhering to the peripheral wall of the cylinder.

In addition, as described above, the injector 10 is installed so that the fuel is injected obliquely downward from the peripheral edge of the combustion chamber 4, and the cavity 11 into which the fuel is blown is provided at the top of the piston 3. in case of,
When the engine is in the low-load, low-speed operation region A, fuel injected obliquely downward from the injector 10 in the compression stroke is collected by being blown into the cavity 11 of the piston 11, and then around the ignition plug 9. , The surroundings of the ignition plug 9 become enriched, and the air-fuel mixture is effectively stratified. Therefore, the stratified combustion of the air-fuel mixture can be appropriately performed and fuel efficiency can be improved without impairing the ignitability of the fuel.

In particular, in an engine configured to inject fuel obliquely downward from the periphery of the combustion chamber 4, if the fuel injection angle θ with respect to the horizontal direction is set to 30 ° or more, the piston 3 Since the amount of fuel that collides with the top of the cylinder and reflects can be reduced more effectively, the amount of fuel adhering to the peripheral wall of the cylinder can be significantly reduced.

According to the configuration in which the fuel injection angle is set to 30 ° or more as described above, as shown in FIG. 11, when the engine is in the low-speed operation region C1 within the region where uniform combustion is performed. , Ce best injection timing and Pe
The amount of deviation from the best injection timing tends to increase. In the operating region C1, the fuel is divided into a plurality of injections in the range from the first half to the middle half of the intake stroke to inject a sufficient amount of intake air and effectively make the air-fuel mixture uniform. Since the fuel can be burned in the state of being converted into a gas, it is possible to avoid the inconvenience caused by the large difference between the injection timing of the Ce best and the injection timing of the Pe best as described above.

As shown in FIG. 12, the injector 10 is moved from the periphery of the combustion chamber 4 toward the spark plug 9 installed so as to face the upper center of the combustion chamber 4 so that the fuel is injected. In an engine installed at an inclination angle of ２５25 °, when the engine is in the low-speed operation region C1 within the operation region C in which uniform combustion is performed, the fuels a and b are divided into a plurality of times in the intake stroke. You may be comprised so that it may inject. In this case, the injectors 10 to 2
Along with spraying at a relatively narrow spray angle of about 0 ° to 40 °, fuel is sprayed on the peripheral surface of the piston 3 at the top of the piston 3 on the side of the exhaust port installation side, that is, on the side opposite to the installation section of the injector 10. It is desirable to form a cavity 11 for preventing adhesion.

In the engine configured to inject fuel from the peripheral portion of the combustion chamber 4 toward the ignition plug 9 as described above, the fuel is injected substantially horizontally from the upper portion of the combustion chamber 4, so that the intake stroke When the fuel is divided and injected, the fuel injection timing can be set without being affected by the position of the piston 3. Therefore, when fuel is divided and injected during the intake stroke, the crank angle after the intake top is 6 degrees.
It is also possible to start the injection of the fuel before 0 °, and the atomization and vaporization of the fuel can be more effectively promoted by advancing the fuel injection timing.

Further, as shown in FIG. 13, a spark plug 9 and an injector 10 are installed so as to face the upper center of the combustion chamber 4, and a central injection type in which a cavity 11 is formed in the center of the top of the piston 3. The present invention can also be applied to the above-mentioned engine.

Further, in the above embodiment, when the engine is in the low-speed operation region C1 in the region C in which the uniform combustion is performed, the fuel is divided into a plurality of times within the range from the first half to the middle of the intake stroke. While controlling the fuel injection state so as to inject the fuel, the engine is in the low-load low-speed operation region A and in the region where the fuel is injected in the compression stroke,
When the load and rotation of the engine are in the relatively high operating range A1, the fuel is divided into a plurality of injections in the compression stroke and injected, so that the previously injected fuel a is appropriately diffused and vaporized. And by promoting atomization,
Fuel efficiency can be effectively improved, and fuel injected later can be concentrated around the ignition plug 9 to ensure combustion stability. Thus, by injecting fuel in the compression stroke and performing stratified combustion, a region where fuel efficiency can be improved can be expanded as compared with the related art.

That is, in the operation region A1 where the load and rotation of the engine are relatively high in the operation region A in which the fuel is injected in the compression stroke, the fuel injection amount becomes relatively large and the fuel injection amount becomes large. Since the time from the injection time to the ignition timing is shortened, when the fuel is injected in a lump, the fuel is excessively concentrated around the ignition plug 9 and the mixing property with the air is reduced, so that the combustion is reduced. Efficiency tends to deteriorate, and insufficient time for vaporizing and atomizing the fuel tends to cause incomplete combustion and impair combustion stability.

On the other hand, when the fuel is divided and injected in the compression stroke as described above, the previously injected fuel can be appropriately diffused. It is possible to improve the combustion efficiency effectively by keeping time for vaporizing and atomizing the fuel while preventing mixing of the fuel excessively and maintaining the mixing property with the air. it can. Further, the fuel injected later can be concentrated around the spark plug 9 to form an air-fuel mixture having an appropriate air-fuel ratio. Therefore, by maintaining the degree of stratification in the combustion chamber 4 properly, the fuel is There is an advantage that combustion stability can be effectively improved by preventing incomplete combustion.

Further, in the above embodiment, when the engine is in the high-speed operation region C3 in the high-load operation region C for performing uniform combustion, the fuel injection start timing is set in the latter half of the exhaust stroke, Since the fuel injection is started in the latter half of the exhaust stroke, the time from the fuel injection time to the ignition time is sufficiently ensured, and the fuel is reliably burned and atomized to burn the fuel. There is an advantage that the engine output can be effectively increased while improving the engine speed. In addition, in the high-speed operation region C3, since the ascending and descending speed of the piston 3 is extremely high, even when the fuel injection is started in the latter half of the exhaust stroke,
Before the fuel injected from the injector 10 reaches the exhaust port 6, the exhaust port 6 is closed by the exhaust valve 8 to prevent the fuel from flowing through.

Further, as shown in the above embodiment, when the injector 10 is installed so that fuel is injected into the combustion chamber 4 from the intake port 5 side of the periphery of the combustion chamber 4,
In the high-load, high-speed operation region C3 of the engine, it is possible to secure a sufficient time until the injected fuel reaches the exhaust port 8 from the latter half of the exhaust stroke. Can be prevented. In order to reliably prevent the fuel from flowing through, it is desirable to set the inclination angle θ of the injector 10 so that the fuel injection direction is inclined by 30 ° or more with respect to the horizontal direction.

[0075]

As described above, the present invention has an injector for directly injecting fuel into a combustion chamber, and injects fuel from the injector during an intake stroke when the engine is at least in a high-load operating region. When the engine is in a low-speed operation region in the region in which the uniform combustion is performed, the intake air Since the fuel injection state is controlled so as to divide the fuel into a plurality of injections within the range from the first half to the middle of the stroke, the amount of intake air is sufficiently ensured in the above-mentioned operation region, and By burning in a state where the air is effectively homogenized, the engine output can be increased.

[Brief description of the drawings] [Explanation of symbols]

FIG. 1 is an explanatory diagram showing an embodiment of a direct injection engine according to the present invention.

FIG. 2 is a plan view showing a top of a piston of the engine.

FIG. 3 is a block diagram showing a control unit of the engine.

FIG. 4 is a map showing an operation region of the engine.

FIG. 5 is a time chart showing a fuel injection timing.

FIG. 6 is a flowchart showing a first step of a fuel injection control operation.

FIG. 7 is a flowchart showing a second stroke of the fuel injection control operation.

FIG. 8 is a graph showing a change in intake air charge, air-fuel ratio, and combustion time.

FIG. 9 is a graph showing changes in the charging efficiency and the indicated mean effective pressure.

FIG. 10 is a graph showing a change in the injection timing of Ce best and Pe best.

FIG. 11 is a graph showing the correspondence between the injection timings of Ce vest and Pe vest and the injection angle of the fuel.

FIG. 12 is an explanatory diagram showing another embodiment of the direct injection engine according to the present invention.

FIG. 13 is an explanatory view showing still another embodiment of the direct injection engine according to the present invention.

[Explanation of symbols]

 Reference Signs List 3 piston 4 combustion chamber 9 spark plug 10 injector 11 cavity 18 fuel control means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02F 3/28 F02F 3/28 B F02M 61/14 310 F02M 61/14 310A 310S // F02M 45/02 45/02 (72) Inventor Hiroyuki Yamashita 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (8)

[Claims] An injector for injecting fuel directly into a combustion chamber is provided, and when the engine is at least in a high-load operation region, fuel is injected from the injector during an intake stroke to make the mixture uniform and burn. In the in-cylinder injection engine configured to perform uniform combustion, within the range in which the uniform combustion is performed, when the engine is in the low-speed operation range, the engine operates within the range from the first half to the middle of the intake stroke. An in-cylinder injection engine comprising: a fuel control unit that controls a fuel injection state so that fuel is injected in a plurality of times. 2. When performing uniform combustion by injecting fuel in the intake stroke, fuel is divided into a time when the intake air charging efficiency is maximized and a time when the uniformity of the air-fuel mixture is optimal. The in-cylinder injection engine according to claim 1, wherein the engine is configured to perform the following operations. 3. The fuel injection method according to claim 1, wherein when the fuel is divided and injected in a plurality of times in the intake stroke, the injection amount of the fuel injected first is set within a range of 40 to 60% of the total injection amount. Claim 1
A cylinder injection engine according to claim 2. 4. The method according to claim 1, wherein when the fuel is divided and injected in a plurality of times in the intake stroke, the injection amount of the fuel injected first is set to be larger than the injection amount of the fuel injected later. The in-cylinder injection engine according to any one of claims 1 to 3, wherein: 5. An injector is provided such that fuel is injected obliquely downward from a peripheral portion of the combustion chamber, and a cavity is provided at a top of the piston for spraying the fuel. In the in-cylinder injection engine according to any one of the first to fourth aspects, when the fuel is divided and injected in a plurality of times in the intake stroke, the injection start timing of the fuel to be injected first is set to 60 degrees after the top of the intake. The in-cylinder injection engine according to any one of claims 1 to 4, characterized in that the timing is set at a time after?. 6. The fuel injection angle is set to 30 with respect to the horizontal direction.
6. The in-cylinder injection engine according to claim 5, wherein the engine is inclined at an angle of at least. 7. An injector according to claim 1, wherein an injector is installed so that fuel is injected from a peripheral portion of the combustion chamber toward a spark plug installed so as to face the combustion chamber. The in-cylinder injection engine described in the crab. 8. A fuel cell system according to claim 1, wherein a spark plug and an injector are provided so as to face an upper center of the combustion chamber, and a cavity into which fuel injected from the injector is blown is formed at a center of a top of the piston. An in-cylinder injection engine according to any one of claims 1 to 4.