JP2004108224A - Direct injection type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure improvement in the fuel consumption in the partial loading and to reduce the load for reducing emission in a direct injection type internal combustion engine. <P>SOLUTION: The volume of a fuel/air mixture forming area 30 is controlled by forming a volume variable fuel/air mixture area 30 in a sub chamber 24 by movable pistons 28-1 and 28-2, and controlling the positions of the movable pistons 28-1 and 28-2 according to the injection quantity of the fuel injected from an injection valve 20 into the fuel/air mixture forming area 30. When the load is adjusted by the fuel injection, the load can be adjusted in a substantially uniform air-fuel ratio without forming the fuel/air mixture concentration distribution in the fuel/air mixture forming area 30 in a stratified manner. Therefore, improvement in the fuel consumption is ensured in the partial loading, and the load in reducing emission can be reduced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a direct injection internal combustion engine that injects fuel directly into a combustion chamber.
[0002]
[Prior art]
An example of a conventional in-cylinder injection type internal combustion engine is disclosed in Japanese Patent Application Laid-Open No. 9-158736 (Patent Document 1). In this conventional direct injection internal combustion engine, fuel is directly injected into a combustion chamber to form an air-fuel mixture. At the time of partial load, the air-fuel ratio is formed stratified so that the air-fuel ratio becomes richer as it is closer to the ignition plug, and the rich air-fuel mixture near the plug is ignited by the ignition plug and flame is propagated from the rich air-fuel mixture to the lean air-fuel mixture ing. This enables lean burn and improves fuel efficiency at partial load.
[0003]
[Patent Document 1]
JP-A-9-158736
[0004]
[Problems to be solved by the invention]
In this conventional in-cylinder injection type internal combustion engine, since the air-fuel mixture is formed stratified at partial load, the air-fuel mixture concentration distribution in the combustion chamber ranges from a rich air-fuel ratio to a lean air-fuel ratio across the stoichiometric air-fuel ratio. Having. A portion of the rich mixture may cause soot generation, and a portion of the lean mixture may generate unburned HC. Therefore, in this conventional in-cylinder injection type internal combustion engine, although fuel efficiency can be improved at a partial load, since the mixture concentration in the combustion chamber has a wide distribution from a rich air-fuel ratio to a lean air-fuel ratio, soot and unburned There is a problem that a burden is imposed on reduction of emissions such as fuel HC.
[0005]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an in-cylinder injection type internal combustion engine that can improve fuel efficiency at a partial load and reduce the burden of reducing emissions.
[0006]
[Means for Solving the Problems]
In order to achieve such an object, the direct injection internal combustion engine according to the first aspect of the present invention draws air into a cylinder, compresses intake air with a piston, and moves fuel into a combustion chamber with an injection valve. An in-cylinder injection internal combustion engine that directly generates an air-fuel mixture by injecting the air-fuel mixture to generate a rotational force by burning the air-fuel mixture, and a region forming unit that forms a variable-volume air-fuel mixture formation region in a combustion chamber. And volume control means for controlling the volume of the mixture formation region formed by the region formation means in accordance with the fuel injection amount injected from the injection valve into the mixture mixture formation region.
[0007]
As described above, the fuel injection is performed by forming the variable-volume mixture forming region in the combustion chamber and controlling the volume of the mixture forming region according to the fuel injection amount injected from the injection valve into the mixture forming region. When the load is adjusted by the amount, the load can be adjusted with a substantially uniform air-fuel ratio without forming a mixture concentration distribution in the mixture formation region in a stratified manner. Therefore, it is possible to secure the improvement of the fuel efficiency at the time of the partial load and to reduce the burden of reducing the emission.
[0008]
A direct injection internal combustion engine according to a second aspect of the present invention is the internal combustion engine according to the first aspect of the present invention, wherein the injection valve has a variable fuel injection divergence angle, The fuel cell system further includes a spread angle control means for changing a fuel injection spread angle.
[0009]
As described above, the injection valve has a variable fuel injection divergence angle, and the fuel injection divergence angle is changed according to the fuel injection amount to adjust the load with the fuel injection amount. The mixture concentration distribution in the inside can be made more uniform. Therefore, the burden of emission reduction can be further reduced.
[0010]
The in-cylinder injection internal combustion engine according to a third aspect of the present invention is the internal combustion engine according to the first or second aspect of the present invention, wherein a plurality of the injection valves are provided, and fuel is injected into the mixture formation region. The fuel cell system further comprises injection valve control means for changing the number of injection valves for injecting fuel according to the injection amount.
[0011]
As described above, when the load is adjusted with the fuel injection amount by changing the number of injection valves that inject fuel according to the fuel injection amount injected into the mixture formation region, Can be made more uniform. Therefore, the burden of emission reduction can be further reduced.
[0012]
According to a fourth aspect of the present invention, there is provided an in-cylinder injection internal combustion engine according to any one of the first to third aspects of the present invention, wherein the volume control means includes: It is characterized in that the volume of the air-fuel mixture formation region is controlled so that the value of (fuel injection amount) is substantially maintained at a desired constant value.
[0013]
As described above, the volume of the air-fuel mixture formation region is controlled so that the value of (volume of the air-fuel mixture formation region) / (fuel injection amount) is substantially maintained at a desired constant value. When the load is adjusted, the air-fuel ratio can be kept substantially at a desired constant value regardless of the level of the load. Therefore, the burden of emission reduction can be further reduced.
[0014]
According to a fifth aspect of the present invention, there is provided an in-cylinder injection type internal combustion engine according to any one of the first to third aspects of the present invention, wherein the volume control means comprises: It is characterized in that the volume of the air-fuel mixture formation region is controlled such that the value of (fuel injection amount) becomes a predetermined value according to the fuel injection amount.
[0015]
As described above, the volume of the air-fuel mixture formation region is controlled such that the value of (volume of the air-fuel mixture formation region) / (fuel injection amount) becomes a predetermined value according to the fuel injection amount. For example, when the load is low, the air-fuel ratio can be made lean, and when the load is high, the air-fuel ratio can be made rich. Therefore, it is possible to further reduce fuel consumption at a low load and achieve high rotational force at a high load.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter, referred to as embodiments) will be described with reference to the drawings.
[0017]
1 and 2 are views schematically showing an internal configuration of a direct injection internal combustion engine according to an embodiment of the present invention. FIG. 1 is a side view, and FIG. 2 is a top view. This embodiment shows a case where the present invention is applied to a spark ignition type internal combustion engine. The in-cylinder injection internal combustion engine of the present embodiment is used, for example, as a motor for driving a vehicle, and includes a cylinder 10, a cylinder head 12, a piston 14, an intake valve 16, an exhaust valve 18, an injection valve 20, and a spark plug 22. I have. A substantially cylindrical sub chamber 24 is formed in the cylinder head 12, and the sub chamber 24 is a combustion chamber. The sub-chamber 24 and the inside of the cylinder 10 are connected via a communication port 26. The injection valve 20 and the spark plug 22 are provided on the peripheral wall 24a of the sub chamber 24. The piston 14 is connected to a not-shown crankshaft via a not-shown connecting rod.
[0018]
In the intake stroke, the intake valve 16 opens and air is sucked into the cylinder 10. In the compression stroke, the intake valve 16 is closed, the intake air is compressed by the piston 14, and the fuel is directly injected into the sub-chamber 24 by the injection valve 20 to form an air-fuel mixture in the sub-chamber 24. Then, the air-fuel mixture in the sub chamber 24 is ignited by the ignition plug 22 and burned. In the expansion stroke, the combustion gas expands to generate a rotational force on a crankshaft (not shown), and in the exhaust stroke, the exhaust valve 18 opens and the combustion gas in the cylinder 10 is discharged from the exhaust valve 18. In the direct injection type internal combustion engine, the load is adjusted by adjusting the fuel injection amount from the injection valve 20, and the fuel injection amount and the injection timing are controlled by an electronic control unit (not shown).
[0019]
In the present embodiment, two movable pistons 28-1 and 28-2 are provided in the sub-chamber 24 as region forming means slidable along the peripheral wall 24a. An air-fuel mixture formation region 30 is formed in the sub chamber 24 by the two movable pistons 28. Gas seal rings 36-1 and 36-2 are provided around the movable pistons 28-1 and 28-2, respectively, and the gas seal rings 36-1 and 36-2 are in contact with the peripheral wall 24a. Each of the movable pistons 28-1 and 28-2 is connected to a rod 32-1 and 32-2, respectively, and the rods 32-1 and 32-2 penetrate the wall surface 24b from inside the sub-chamber 24 and outside the sub-chamber 24. Extending to Gas seal rings 34-1 and 34-2 are provided around the rods 32-1 and 32-2 at the position of the wall surface 24b, respectively, so that the airtightness in the sub chamber 24 is maintained. The rods 32-1 and 32-2 are connected to a linear actuator (not shown), and the linear actuators are driven to move the movable pistons 28-1 and 28-2 in opposite directions along the peripheral wall 24a to mix the rods. The volume of the gas forming region 30 can be changed. Note that the injection valve 20 and the spark plug 22 are provided on the peripheral wall 24a at a position where the mixture formation region 30 is formed. The mixture formation region 30 and the other portion of the sub chamber 24 communicate with each other through the communication port 26. Further, as the material of the movable pistons 28-1 and 28-2 and the rods 32-1 and 32-2, it is preferable to use a material having sufficient heat resistance to the temperature of the combustion gas.
[0020]
In the present embodiment, the position of the movable pistons 28-1 and 28-2 is controlled by the linear actuator in accordance with the amount of fuel injected from the injection valve 20 into the air-fuel mixture formation region 30, so that the air-fuel mixture is controlled. The volume of the formation region 30 is controlled. That is, the electronic control unit (not shown) has a volume control unit that calculates and outputs a control command value to the linear actuator from a control command value indicating the fuel injection amount. Here, since the fuel injection amount from the injection valve 20 is set based on the load of the internal combustion engine, the fuel injection amount and the volume of the mixture formation region 30 are controlled based on the load of the internal combustion engine. More specifically, when the load increases, both the fuel injection amount and the volume of the mixture formation region 30 increase, and when the load decreases, both the fuel injection amount and the volume of the mixture formation region 30 decrease. Let it.
[0021]
In the compression stroke of the present embodiment, as shown in FIG. 3A, the air in the cylinder 10 flows into the sub chamber 24 through the communication port 26, and follows the shape of the peripheral wall 24a in the sub chamber 24. A swirling airflow is generated. Further, during the compression stroke, fuel is injected from the injection valve 20 into the air-fuel mixture formation region 30, and the injected fuel is mixed with air as shown in FIG. At that time, the mixing is promoted by the swirling airflow, so that the air-fuel mixture concentration distribution in the air-fuel mixture forming region 30 is substantially uniform, as shown in FIG. Further, the air-fuel mixture hardly diffuses outside the air-fuel mixture formation region 30 due to the swirling airflow. Then, the air-fuel mixture in the air-fuel mixture forming region 30 having a substantially uniform concentration distribution is ignited by the ignition plug 22 and burned. The formation of the air-fuel mixture having a substantially uniform concentration distribution in the air-fuel mixture formation region 30 is maintained even when the load changes. That is, in the conventional direct injection internal combustion engine, the mixture concentration distribution is formed stratified at the time of partial load, whereas in the direct injection internal combustion engine of the present embodiment, the mixture is also maintained at the partial load. The mixture concentration distribution in the formation region 30 maintains a substantially uniform state. However, the air-fuel ratio in a substantially uniform state may change according to the load as described later.
[0022]
The fuel injection timing from the injection valve 20 during the compression stroke may be changed according to the engine speed. For example, as shown in FIG. 4 (A), by increasing the engine rotation speed and increasing the fuel injection timing, it is possible to ensure the formation of a mixture having a substantially uniform concentration distribution even during high rotation. . Further, the fuel injection timing from the injection valve 20 may be changed in accordance with the load. For example, as shown in FIG. 4B, the fuel injection timing is advanced as the load increases, so that the fuel injection amount is increased. Even under a high load, formation of an air-fuel mixture having a substantially uniform concentration distribution can be ensured.
[0023]
Next, some specific examples of the fuel injection amount-mixture formation region volume characteristics stored in the electronic control unit will be described as to how to control the volume of the mixture formation region 30 according to the fuel injection amount. I will explain it.
[0024]
FIG. 5A shows a case where the fuel injection amount-air-fuel mixture formation region volume characteristic is substantially directly proportional. That is, in FIG. 5A, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is almost kept at a prescribed constant value A0. Here, the prescribed constant value A0 is set to a value such that the air-fuel ratio when the concentration distribution in the air-fuel mixture formation region 30 is formed substantially uniformly becomes the stoichiometric air-fuel ratio. When the volume of the air-fuel mixture formation region 30 is controlled so as to have the characteristics shown in FIG. 5A, the substantially uniform air-fuel ratio in the air-fuel mixture formation region 30 becomes as shown in FIG. The stoichiometric air-fuel ratio is almost maintained regardless of the height.
[0025]
In FIG. 6A, when the fuel injection amount is equal to or less than the predetermined value L1, the fuel injection amount-mixture formation region volume characteristic maintains a substantially directly proportional relationship similar to that of FIG. When the value is larger than the value L1, it indicates a case where the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) becomes smaller than a predetermined constant value A0. Preferably, the predetermined value L1 of the fuel injection amount is substantially equal to the maximum injection amount when the stoichiometric air-fuel ratio is maintained regardless of the level of the load in FIG. When the volume of the air-fuel mixture formation region 30 is controlled so as to have the characteristics shown in FIG. 6A, the substantially uniform air-fuel ratio in the air-fuel mixture formation region 30 becomes low, medium, and low as shown in FIG. At the time of load, the stoichiometric air-fuel ratio is substantially maintained, and at the time of high load, the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio.
[0026]
In FIG. 7A, when the fuel injection amount is within the predetermined range L2 to L3, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is larger than a predetermined constant value A0, Is near the lower limit value L2 of the predetermined range, the value of (volume of the fuel / air mixture formation region 30) / (fuel injection amount) is substantially equal to the prescribed constant value A0, and the fuel injection amount is larger than the upper limit value L3 of the predetermined range. At this time, the case where the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) becomes smaller than a predetermined constant value A0 is shown. When the volume of the air-fuel mixture formation region 30 is controlled so as to have the characteristics shown in FIG. 7A, the substantially uniform air-fuel ratio in the air-fuel mixture formation region 30 becomes extremely low as shown in FIG. At the time of load, the stoichiometric air-fuel ratio becomes almost the same, at low and medium loads, the air-fuel ratio becomes leaner, and at the time of high load, the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio.
[0027]
In FIG. 8A, when the fuel injection amount is within the predetermined range L4 to L5, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is set to a constant value A1 smaller than a predetermined constant value A0. When the fuel injection amount is substantially kept and is larger than the upper limit L5 of the predetermined range, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) becomes smaller than the fixed value A1. When the volume of the air-fuel mixture formation region 30 is controlled so as to have the characteristics shown in FIG. 8A, the substantially uniform air-fuel ratio in the air-fuel mixture formation region 30 becomes as shown in FIG. At the time of load, the air-fuel ratio becomes slightly richer than the stoichiometric air-fuel ratio.
[0028]
In the present embodiment, the movable pistons 28-1 and 28-2 form a variable-volume air-fuel mixture formation region 30 in the sub chamber 24. The volume of the mixture formation region 30 is controlled by controlling the positions of the movable pistons 28-1 and 28-2 according to the amount of fuel injected from the injection valve 20 into the mixture mixture formation region 30. ing. Therefore, when the load is adjusted by the fuel injection amount, the load can be adjusted with a substantially uniform air-fuel ratio without forming a mixture concentration distribution in the mixture formation region 30 in a stratified manner. For example, by setting the volume of the air-fuel mixture formation region 30 at a low load to be smaller than that at a high load, stable combustion can be realized without forming a mixture concentration distribution even if the fuel injection amount is small. Therefore, it is possible to secure the improvement of the fuel efficiency at the time of the partial load and to reduce the burden of reducing the emission.
[0029]
When the volume of the air-fuel mixture formation region 30 is controlled as shown in the fuel injection amount-air-fuel mixture formation region volume characteristic of FIG. 5A, the substantially uniform air-fuel ratio in the air-fuel mixture formation region 30 is reduced by the load. Since the stoichiometric air-fuel ratio is substantially maintained irrespective of the height, the burden of emission reduction can be further reduced over the entire load range.
[0030]
When the volume of the mixture formation region 30 is controlled as shown in the fuel injection amount-mixture formation region volume characteristic of FIG. 6A, the substantially uniform air-fuel ratio in the mixture formation region 30 is low. At a medium load, the stoichiometric air-fuel ratio is substantially maintained, and at a high load, the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio. Therefore, the burden of emission reduction can be further reduced at low and medium loads, and the rotational force can be increased at high loads.
[0031]
When the volume of the mixture formation region 30 is controlled as shown in the fuel injection amount-mixture formation region volume characteristic of FIG. 7A, the substantially uniform air-fuel ratio in the mixture formation region 30 is extremely small. At low load, the stoichiometric air-fuel ratio becomes almost the same, at low-medium load, leaner than the stoichiometric air-fuel ratio, and at high load, richer than the stoichiometric air-fuel ratio. Therefore, combustion can be stabilized at extremely low loads, NOx can be reduced and fuel efficiency can be improved at low and medium loads, and the rotational force can be increased at high loads.
[0032]
Further, when the volume of the mixture formation region 30 is controlled as shown in the fuel injection amount-mixture formation region volume characteristic of FIG. 8A, the substantially uniform air-fuel ratio in the mixture formation region 30 is low. At a medium load, the air-fuel ratio becomes slightly richer than the stoichiometric air-fuel ratio, and at a high load, the air-fuel ratio becomes further richer than at a low air load. Therefore, for example, when the catalyst needs to be warmed up early, such as during a cold start, the exhaust gas temperature can be increased in a short time, and the rotational force can be increased at a high load.
[0033]
Further, the injection valve 20 of the present embodiment can change the fuel injection spread angle, and the electronic control unit has a spread angle control unit that changes the fuel injection spread angle according to the fuel injection amount. Good. Here, the configuration of the injection valve for changing the fuel injection divergence angle can be realized by using the configuration disclosed in Japanese Patent Application Laid-Open No. 11-351103. Hereinafter, this configuration will be described with reference to FIGS. I do.
[0034]
FIG. 9 is a cross-sectional view showing a tip portion near an injection hole in the injection valve, and FIG. 10 is a cross-sectional view showing the sack portion 43 taken out. Two injection holes 48 and 49 are formed through the sack portion 43. As shown in the sectional views of FIGS. 10 (B) and 10 (C), the spray holes 48 and 49 have different spread angles, and the spread angle α1 of the spray hole 48 is smaller than the spread angle α2 of the spray hole 49. The needle valve 44 has an injection hole selector 45 at the tip. The injection hole selection part 45 is slidable along the inner wall of the sack part 43, and a fuel passage 51 communicating with the outside is formed inside the injection hole selection part 45. The position of the injection valve selector 45 is controlled by controlling the position of the needle valve 44 by electric or mechanical driving means. A fuel passage 50 is formed outside the needle valve 44, and fuel flows from the fuel passage 50 into the fuel passage 51 by driving the needle valve 44. As shown in FIG. 9A, if the position of the injection hole selector 45 is controlled so that the fuel passage 51 and the injection hole 48 communicate with each other, the fuel is injected at the spread angle α1, and the fuel is injected as shown in FIG. 9B. As described above, if the position of the injection hole selection unit 45 is controlled so that the fuel passage 51 and the injection hole 49 communicate with each other, the fuel is injected at the spread angle α2. As described above, by controlling the position of the injection hole selection unit 45 and selecting the injection holes that communicate with the fuel passage 51, the injection spread angle can be changed.
[0035]
When the fuel injection amount is equal to or less than a predetermined value L6, that is, when the value of the volume of the air-fuel mixture formation region 30 is equal to or less than a predetermined value V6, the divergence angle control means connects the fuel passage 51 and the injection hole 48 to each other as shown in FIG. The position of the injection hole selector 45 is controlled so that fuel is injected at a narrow injection spread angle α1 as shown in the top view of FIG. On the other hand, when the fuel injection amount is larger than the predetermined value L6, that is, when the value of the volume of the mixture formation region 30 is larger than the predetermined value V6, the fuel passage 51 and the injection holes 49 are communicated with each other, and the top view of FIG. The position of the injection hole selector 45 is controlled so that the fuel is injected at a wide injection spread angle α2 as shown in FIG. As described above, when the fuel injection amount is small, that is, when the volume of the air-fuel mixture formation region 30 is small, the fuel is injected at a narrow injection spread angle, and when the fuel injection amount is large, that is, when the volume of the air-fuel mixture formation region 30 is large, a wide injection is performed. By injecting the fuel at the spread angle, the fuel can be more uniformly injected into the mixture forming region 30, and the mixture concentration distribution in the mixture forming region 30 becomes more uniform with respect to a wide range of load fluctuation. can do. Therefore, the burden of emission reduction can be further reduced.
[0036]
9 to 11 illustrate the case where the fuel injection spread angle is changed in two steps, but the fuel injection spread angle may be changed in three or more steps using the same principle.
[0037]
Further, a plurality of injection valves 20 are provided at different positions on the peripheral wall 24a of the sub-chamber 24, and the electronic control unit determines the number of the injection valves 20 for injecting fuel in accordance with the fuel injection amount injected into the mixture formation region 30. You may have the injection valve control means to change. At this time, a plurality of ignition plugs 22 are provided on the peripheral wall 24a of the sub chamber 24 corresponding to each of the injection valves 20, and the number of plugs used for ignition is changed according to the number of injection valves 20 for injecting fuel. Is preferred. As shown in the top view of FIG. 12, the injection valve control means increases the number of injection valves 20 for injecting fuel in accordance with an increase in the fuel injection amount, that is, an increase in the volume of the mixture formation region 30. As described above, since the number of the injection valves 20 that inject fuel is increased in accordance with the increase in the volume of the mixture forming region 30, the fuel can be more uniformly injected in the mixture forming region 30, and a wide range of load can be obtained. In this case, the mixture concentration distribution in the mixture formation region 30 can be made more uniform with respect to the variation of the mixture. Therefore, the burden of emission reduction can be further reduced.
[0038]
FIG. 12 illustrates a case where three injection valves 20 are provided, but the number of injection valves 20 can be arbitrarily set.
[0039]
Further, as shown in the side view of FIG. 13A, the piston 14 has a projection 38 at the top thereof, and the projection 38 fits in the communication port 26 communicating the inside of the cylinder 10 and the sub chamber 24 near the top dead center. You may do so. As a result, the volume of the air-fuel mixture forming region 30 in the combustion chamber can be increased by reducing the volume of the communication port 26 where the air-fuel mixture hardly diffuses, so that a higher rotational force can be realized at a high load.
[0040]
Further, as shown in the side view of FIG. 13B, the communication port 26 has a tapered shape in which the opening area decreases toward the sub-chamber 24 side, and the projection 38 of the piston 14 is also connected to the communication port 26 near the top dead center. It may have a tapered shape to fit. Thereby, the efficiency when the air in the cylinder 10 flows into the sub chamber 24 can be enhanced, and the overheating of the projection 38 can be avoided.
[0041]
The configuration for changing the volume of the air-fuel mixture formation region 30 is not limited to the configuration shown in FIG. 2. For example, the volume of the air-fuel mixture formation region 30 is also changed in the configurations shown in the top views of FIGS. be able to. However, in FIGS. 14 to 16, only the configuration of the sub-chamber 24 and its surroundings are shown, and illustration of other configurations is omitted.
[0042]
In FIG. 14, sliders 61-1 and 61-2 are respectively connected to side surfaces of movable pistons 28-1 and 28-2, and sliders 61-1 and 61-2 are provided with openings 24c provided in peripheral wall 24a. And extends outside the sub chamber 24. The movable pistons 28-1 and 28-2 are driven in opposite directions along the peripheral wall 24a by the translational driving of the sliders 61-1 and 61-2 in the opposite direction in the shaft axis direction by the rotation of the shaft 62. You. The mechanism for translationally driving the sliders 61-1 and 61-2 in the shaft axis direction can be realized by using, for example, a ball screw. By cutting the screws in opposite directions, the sliders 61-1 and 61-2 can be moved in opposite directions. Translational drive can be realized. The shaft 62 is driven to rotate by an actuator (not shown). The sub chamber 24 communicates with a blow-by gas recovery device (not shown) through an opening 24c, and a small amount of combustion gas leaking through the opening 24c is recovered by the blow-by gas recovery device. The other configuration is the same as the configuration shown in FIG. Further, it is preferable to use a material having sufficient heat resistance to the temperature of the combustion gas as the material of the sliders 61-1 and 61-2 and the shaft 62.
[0043]
In FIG. 15, racks 71-1 and 71-2 are connected to the insides of the movable pistons 28-1 and 28-2, respectively, and the racks 71-1 and 71-2 are substantially equivalent to shafts 72-1 and 72-2. They are in mesh with the pinions 73-1 and 73-2 provided at the center, respectively. When the shafts 72-1 and 72-2 are driven to rotate in the same direction, the racks 71-1 and 71-2 are driven to translate in opposite directions, and the movable pistons 28-1 and 28-2 move along the peripheral wall 24a. Are driven in opposite directions. The shafts 72-1 and 72-2 pass through the side surfaces of the movable pistons 28-1 and 28-2, respectively, and further extend through the peripheral wall 24a and out of the sub chamber 24. The shafts 72-1 and 72-2 are driven to rotate by an actuator (not shown). Gas seal rings 74-1 and 74-2 are provided around the shafts 72-1 and 72-2 at the position of the peripheral wall 24a, respectively, so that the airtightness in the sub chamber 24 is maintained. The other configuration is the same as the configuration shown in FIG. Further, as the material of the racks 71-1, 71-2 and the shafts 72-1, 72-2, it is preferable to use a material having sufficient heat resistance to the temperature of the combustion gas.
[0044]
In FIG. 16, the sub chamber 24 is formed by the movable piece 81 and the fixed pieces 82-1 and 82-2. The movable piece 81 includes a partition wall 83 for forming the mixture formation region 30 in the sub chamber 24. The movable piece 81 is driven to translate along the side surfaces of the fixed pieces 82-1 and 82-2 by an actuator such as a hydraulic cylinder 84, so that the volume of the mixture formation region 30 can be changed. Gas seal rings 85-1 and 85-2 are provided between the side of the movable piece 81 and the side of the fixed piece 82-1 and between the side of the movable piece 81 and the side of the fixed piece 82-2, respectively. Thereby, the airtightness in the sub chamber 24 is maintained. The injection valve 20 and a spark plug (not shown) are provided on the side of the movable piece 81 on the side of the mixture formation region 30. The other configuration is the same as the configuration shown in FIG.
[0045]
In FIG. 17, the movable pistons 28-1 and 28-2 and the sliders 61-1 and 61-2 are provided with magnets for attracting the movable piston and the slider to each other. The relative positional relationship between the movable piston 28-2 and the slider 61-2 is defined by the magnetic force. The sliders 61-1 and 61-2 are translationally driven in the direction opposite to each other in the shaft axis direction by the rotation of the shaft 62. The movable piston 28-1 is interlocked with the translational drive of the sliders 61-1 and 61-2 in the opposite direction. , 28-2 are driven in opposite directions along the peripheral wall 24a. The mechanism for translationally driving the sliders 61-1 and 61-2 in the shaft axis direction can be realized by using, for example, a ball screw. By cutting the screws in opposite directions, the sliders 61-1 and 61-2 can be moved in opposite directions. Translational drive can be realized. The shaft 62 is driven to rotate by an actuator (not shown). The other configuration is the same as the configuration shown in FIG.
[0046]
In the above description, the case of a spark ignition type internal combustion engine in which an air-fuel mixture is ignited by a spark plug has been described, but the in-cylinder injection type internal combustion engine to which the present invention can be applied is not limited to the spark ignition type internal combustion engine. The present invention is also applicable to a compression ignition type internal combustion engine that compresses and ignites an air-fuel mixture. In the compression ignition type internal combustion engine, by changing the volume of the air-fuel mixture formation region 30 according to the fuel injection amount, the change in the self-ignition timing due to the increase or decrease in the fuel injection amount can be reduced, and the self-ignition operation range can be greatly increased. Can be spread out.
[0047]
The fuel injection amount-mixture formation region volume characteristics shown in FIGS. 18 and 19 show characteristics in the case where the air-fuel mixture is compressed and ignited without being ignited by the spark plug and burned at the partial load.
[0048]
In FIG. 18A, when the fuel injection amount is smaller than the lower limit value L7 of the predetermined range, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is sufficiently larger than the predetermined constant value A0, When the injection amount is within the predetermined range L7 to L8, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is substantially equal to the prescribed constant value A0, and the fuel injection amount is larger than the upper limit L8 of the predetermined range. At this time, the case where the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) becomes smaller than a predetermined constant value A0 is shown. When the fuel injection amount is smaller than the lower limit L7 of the predetermined range, the compression ignition operation is performed, and otherwise, the spark ignition operation is performed. When the volume of the air-fuel mixture formation region 30 is controlled so as to have the characteristics shown in FIG. 18A, the substantially uniform air-fuel ratio in the air-fuel mixture formation region 30 becomes low, medium, and low as shown in FIG. At the time of load, the air-fuel ratio becomes extremely leaner than the stoichiometric air-fuel ratio. At the time of medium load, the air-fuel ratio becomes substantially the stoichiometric air-fuel ratio. As a result, it is possible to further reduce NOx and improve fuel efficiency at low and medium loads, and to increase the rotational force at high loads.
[0049]
In FIG. 19 (A), when the fuel injection amount is smaller than the lower limit value L9 of the predetermined range, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is substantially equal to or slightly equal to the prescribed constant value A0. When the fuel injection amount is large and is within the predetermined range L9 to L10, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is sufficiently larger than the prescribed constant value A0, and the fuel injection amount is within the predetermined range L10 to L10. When the fuel injection amount is within L11, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is substantially equal to the prescribed constant value A0, and when the fuel injection amount is larger than the upper limit L11 of the predetermined range, the value of (air-fuel mixture formation) The case where the value of (volume of the region 30) / (fuel injection amount) becomes smaller than a predetermined constant value A0 is shown. The compression ignition operation is performed when the fuel injection amount is within the predetermined range L9 to L10, and the spark ignition operation is performed otherwise. When the volume of the air-fuel mixture formation region 30 is controlled so as to have the characteristics shown in FIG. 19A, the substantially uniform air-fuel ratio in the air-fuel mixture formation region 30 becomes extremely low as shown in FIG. At the time of load, the stoichiometric air-fuel ratio becomes slightly leaner than the stoichiometric air-fuel ratio, at low and medium loads, becomes extremely lean than the stoichiometric air-fuel ratio, becomes almost stoichiometric at the medium load, and becomes richer than the stoichiometric air-fuel ratio at the time of high load. As a result, combustion can be stabilized at extremely low loads, NOx reduction and fuel efficiency can be further improved at low and medium loads, and the rotational force can be increased at high loads.
[0050]
In the fuel injection amount-fuel mixture formation region volume characteristic shown in FIG. 20, fuel is injected during the compression stroke during partial load to burn the air-fuel mixture by compression ignition, and during high load, fuel is injected at the end of the compression stroke. The example of the characteristic at the time of carrying out diesel combustion is shown. In FIG. 20 (A), when the fuel injection amount is equal to or less than the predetermined value L12, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is sufficiently larger than a prescribed constant value A0, and the fuel injection amount is reduced. When the value is larger than the predetermined value L12, the value of (volume of the air-fuel mixture formation region 30) / (fuel injection amount) is larger than the predetermined constant value A0 and smaller than the value when the fuel injection amount is equal to or smaller than the predetermined value L12. Shows the case. When the fuel injection amount is equal to or less than the predetermined value L12, fuel is injected during the compression stroke to burn the air-fuel mixture by compression ignition, and otherwise, fuel is injected at the end of the compression stroke to perform diesel combustion. When controlling the volume of the air-fuel mixture formation region 30 so as to have the characteristics shown in FIG. 20A, the substantially uniform air-fuel ratio in the air-fuel mixture formation region 30 becomes as shown in FIG. At the time of load, the air-fuel ratio becomes extremely leaner than the stoichiometric air-fuel ratio, and at the time of high load, the air-fuel ratio becomes richer than at the time of low-medium load and becomes leaner than the stoichiometric air-fuel ratio. This makes it possible to further reduce NOx and improve fuel efficiency at low and medium loads.
[0051]
Also in the compression ignition type internal combustion engine, the fuel injection timing from the injection valve 20 in the compression stroke may be changed according to the engine speed. For example, as shown in FIG. 21A, in the range of the engine speed at which the fuel is injected during the compression stroke to perform the compression ignition operation, the engine speed is increased and the fuel injection timing is advanced to thereby increase the concentration distribution. A substantially uniform mixture can be formed. If the engine speed exceeds the range of the engine speed at which the compression ignition operation is performed, the fuel injection timing is delayed until the end of the compression stroke, and the operation is switched to diesel combustion.
[0052]
Further, the fuel injection timing from the injection valve 20 may be changed according to the load. For example, as shown in FIG. 21B, the range of the load in which the fuel is injected during the compression stroke to perform the compression ignition operation In this case, the fuel injection timing is advanced along with the increase in the load, so that the formation of an air-fuel mixture having a substantially uniform concentration distribution can be ensured. When the load exceeds the range for performing the compression ignition operation, the fuel injection timing is delayed until the end of the compression stroke to switch the operation to diesel combustion.
[0053]
【The invention's effect】
As described above, according to the present invention, a variable-volume air-fuel mixture formation region is formed in the combustion chamber, and the volume of the air-fuel mixture formation region is changed according to the fuel injection amount injected from the injection valve into the air-fuel mixture formation region. , It is possible to secure the improvement of fuel efficiency at the time of partial load and at the same time to reduce the burden of emission reduction.
[Brief description of the drawings]
FIG. 1 is a side view schematically showing an internal configuration of a direct injection internal combustion engine according to an embodiment of the present invention.
FIG. 2 is a top view schematically showing an internal configuration of the direct injection internal combustion engine according to the embodiment of the present invention.
FIG. 3 is a diagram illustrating a compression stroke of the direct injection internal combustion engine according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating an example of fuel injection timing control according to the embodiment of the present invention.
FIG. 5 is a diagram showing an example of a fuel injection amount-air-fuel mixture formation region volume characteristic in the embodiment of the present invention.
FIG. 6 is a diagram showing an example of a fuel injection amount-air-fuel mixture formation region volume characteristic in the embodiment of the present invention.
FIG. 7 is a diagram illustrating an example of a fuel injection amount-air-fuel mixture formation region volume characteristic in the embodiment of the present invention.
FIG. 8 is a diagram illustrating an example of a fuel injection amount-air-fuel mixture formation region volume characteristic in the embodiment of the present invention.
FIG. 9 is a cross-sectional view illustrating a configuration of an injection valve used in another embodiment of the present invention.
FIG. 10 is a sectional view showing a configuration of an injection valve used in another embodiment of the present invention.
FIG. 11 is a cross-sectional view illustrating a configuration of an injection valve used in another embodiment of the present invention.
FIG. 12 is a top view illustrating the operation of a direct injection internal combustion engine according to another embodiment of the present invention.
FIG. 13 is a top view illustrating the operation of a direct injection internal combustion engine according to another embodiment of the present invention.
FIG. 14 is a top view schematically showing another configuration for changing the volume of the mixture formation region in the embodiment of the present invention.
FIG. 15 is a top view schematically showing another configuration for changing the volume of the air-fuel mixture formation region in the embodiment of the present invention.
FIG. 16 is a top view schematically showing another configuration for changing the volume of the air-fuel mixture formation region in the embodiment of the present invention.
FIG. 17 is a top view schematically showing another configuration for changing the volume of the air-fuel mixture formation region in the embodiment of the present invention.
FIG. 18 is a diagram showing an example of a fuel injection amount-mixture formation region volume characteristic in another embodiment of the present invention.
FIG. 19 is a diagram showing an example of a fuel injection amount-air-fuel mixture formation region volume characteristic in another embodiment of the present invention.
FIG. 20 is a view showing an example of a fuel injection amount-mixture formation region volume characteristic in another embodiment of the present invention.
FIG. 21 is a diagram illustrating an example of fuel injection timing control according to another embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 20 injection valve, 22 spark plug, 24 sub-chamber, 28-1, 28-2 movable piston, 30 mixture formation region.

Claims (5)

In-cylinder, in which air is sucked into a cylinder, compressed air is sucked by a piston, and fuel is directly injected into a combustion chamber by an injection valve to form an air-fuel mixture, and the air-fuel mixture is burned to generate a rotational force. An injection-type internal combustion engine,
Region forming means for forming a variable volume mixture forming region in the combustion chamber;
Volume control means for controlling the volume of the mixture formation region formed by the region formation means in accordance with the fuel injection amount injected from the injection valve into the mixture formation region;
A direct injection internal combustion engine, comprising: The direct injection internal combustion engine according to claim 1,
The injection valve has a variable fuel injection spread angle,
An in-cylinder injection type internal combustion engine further comprising a spread angle control means for changing a fuel injection spread angle according to a fuel injection amount. The direct injection internal combustion engine according to claim 1 or 2,
A plurality of the injection valves are provided,
An in-cylinder injection type internal combustion engine, further comprising: an injection valve control means for changing the number of injection valves for injecting fuel in accordance with a fuel injection amount injected into the mixture mixture region. An in-cylinder injection internal combustion engine according to any one of claims 1 to 3,
The volume control means controls the volume of the mixture formation region such that the value of (volume of mixture formation region) / (fuel injection amount) is substantially maintained at a desired constant value. Internal injection type internal combustion engine. An in-cylinder injection internal combustion engine according to any one of claims 1 to 3,
The volume control means controls the volume of the air-fuel mixture region such that the value of (volume of the air-fuel mixture region) / (fuel injection amount) becomes a predetermined value according to the fuel injection amount. In-cylinder injection internal combustion engine.

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