JP2007263042A - Variable compression ratio internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology enabling stable formation of stratified condition in a combustion chamber and stable stratified combustion irrespective of high or low compression ratio in a variable compression ratio internal combustion engine. <P>SOLUTION: In the variable compression ratio internal combustion engine provided with a direct injection type fuel injection valve injecting fuel directly to a combustion chamber, injection width during fuel injection is changed in two stages (S106) according to compression ratio to nicely introduce fuel injected from the fuel injection valve to a cavity on a piston top surface in a vicinity of compression top dead center when compression ratio is changed (S105). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a variable compression ratio internal combustion engine having a function of changing the compression ratio of an internal combustion engine.

  In recent years, a technique for changing the compression ratio of an internal combustion engine for the purpose of improving the fuel consumption performance and output performance of the internal combustion engine has been proposed. As this type of technology, the cylinder block and the crankcase are connected so as to be relatively movable, and a camshaft is provided at the connecting portion, and the camshaft is rotated to connect the cylinder block and the crankcase in the axial direction of the cylinder. A technique has been proposed in which the volume of the combustion chamber is changed by relative movement to the internal combustion engine, thereby changing the compression ratio of the internal combustion engine (see, for example, Patent Document 1).

  Further, the connecting rod is divided into two, a connecting member connected to the crankshaft is connected to a swinging member capable of swinging around a predetermined swinging center, and the swinging center is moved by rotating the camshaft. Thus, a technique has also been proposed in which the volume of the combustion chamber and the stroke of the piston are changed, thereby changing the compression ratio of the internal combustion engine (see, for example, Patent Document 2).

  When the compression ratio is changed in the above variable compression ratio mechanism, the positional relationship between the fuel injection valve provided on the top plate of the combustion chamber and the piston at the compression top dead center, or the in-cylinder pressure at the compression top dead center changes. There is a case. As a result, particularly when stratified combustion is to be performed, it may be difficult to inject fuel in the optimum direction and strength for stratified combustion into the cavity on the top surface of the piston.

  On the other hand, a technique has been proposed in which fuel injection is performed by determining the fuel injection pressure and the fuel injection timing using the compression ratio of the variable compression ratio internal combustion engine as a parameter (see, for example, Patent Document 3).

However, in the in-cylinder injection type variable compression ratio internal combustion engine, only by changing the fuel injection pressure and the fuel injection timing when the compression ratio is changed, the change in the positional relationship between the fuel injection valve and the cavity due to the change in the compression ratio, the compression In some cases, it is difficult to cope with the change in the in-cylinder pressure accompanying the change in the ratio, and it is difficult to optimally introduce the injected fuel into the cavity. As a result, it may be difficult to form a stable stratified state in the combustion chamber.
JP 2003-206871 A JP 2001-317383 A JP 2004-218433 A Japanese Patent Laying-Open No. 2005-147067 Japanese Utility Model Publication No. 5-30461

  The present invention has been made in view of the above circumstances, and an object of the present invention is to form a stable stratified state in the combustion chamber regardless of the compression ratio, in a variable compression ratio internal combustion engine. It is to provide a technology that enables stratified combustion.

In order to achieve the above object, the present invention provides a variable compression ratio internal combustion engine having a direct injection type fuel injection valve that directly injects fuel into a combustion chamber, and is injected from the fuel injection valve when the compression ratio is changed. In order for the fuel to be successfully introduced into the cavity on the top surface of the piston near the compression top dead center,
The greatest feature is to change the injection width at the time of fuel injection.

More specifically, a cavity that is provided on the top surface of the piston of the internal combustion engine and that forms a stratified state in the combustion chamber of the internal combustion engine by introducing fuel near the compression top dead center;
A variable compression ratio mechanism for changing the compression ratio of the internal combustion engine;
An injection width variable fuel injection valve that injects fuel into the combustion chamber and can change the injection width of fuel injected from the injection port at the time of fuel injection;
Injection width changing means for changing the injection width according to the compression ratio changed by the variable compression ratio mechanism;
It is characterized by providing.

  Here, when the compression ratio is changed in a variable compression ratio internal combustion engine having a variable compression ratio mechanism, the volume and pressure of the combustion chamber at the compression top dead center often change. In such a case, when the fuel is injected from the fuel injection valve with the same injection width regardless of the compression ratio, the fuel injected from the fuel injection valve is satisfactorily introduced into the cavity near the compression top dead center. As a result, it may be difficult to form an optimum stratified state.

  Therefore, in the present invention, the fuel injection valve is an injection width variable fuel injection valve capable of changing the injection width of the fuel injected from the injection port, and the injection width is changed according to the compression ratio of the variable compression ratio internal combustion engine. It was decided. According to this, by changing the injection width, the penetration force can be changed if the fuel pressure is the same. Then, the injected fuel can be satisfactorily introduced into the cavity regardless of the change in the in-cylinder pressure at the compression top dead center accompanying the change in the compression ratio or the change in the distance between the fuel injection valve and the cavity. Here, the injection width is the width or spread angle of the fuel spray mass injected from the nozzle of the fuel injection valve.

In the present invention, the higher the compression ratio of the internal combustion engine, the higher the pressure in the combustion chamber at the compression top dead center,
The injection width changing means may reduce the injection width as the compression ratio of the internal combustion engine is higher.

  That is, depending on the configuration of the variable compression ratio mechanism, the cylinder pressure at the compression top dead center often increases as the compression ratio increases. In that case, if the fuel is injected from the fuel injection valve with the same injection width as when the compression ratio is low, the penetrating force is insufficient, and the injected fuel may not reach the cavity as planned. If it does so, a fuel cannot be favorably introduce | transduced in a cavity and it will become difficult as a result to form a favorable stratification state.

  Therefore, in the present invention, the injection width changing means reduces the injection width as the compression ratio is higher and the pressure in the combustion chamber at the compression top dead center is higher. By doing so, the injected fuel can be satisfactorily introduced into the cavity regardless of the compression ratio, and a good stratified state can be formed. As a result, it is possible to operate the internal combustion engine that achieves both stable combustion and low fuel consumption.

In the present invention, the lower the compression ratio of the internal combustion engine, the longer the distance between the variable injection fuel injection means and the piston at the compression top dead center,
The injection width changing means may reduce the injection width as the compression ratio of the internal combustion engine is lower.

That is, although depending on the configuration of the variable compression ratio mechanism, when the compression ratio is low, the position of the piston at the compression top dead center is often far from the fuel injection valve. In that case, when fuel is injected from the fuel injection valve with the same injection width as when the compression ratio is high, the penetrating force is insufficient, and thus the injected fuel may not reach the cavity as planned. If it does so, injected fuel cannot be satisfactorily introduced into the cavity, and as a result, it becomes difficult to form a good stratified state.

  Accordingly, in the present invention, in contrast to such a case, the injection width changing means is configured such that the injection width changes as the compression ratio is low and the position of the piston at the compression top dead center is farther from the injection width variable fuel injection valve. Was made smaller. By doing so, the injected fuel can be satisfactorily introduced into the cavity regardless of the compression ratio, and a good stratified state can be formed. As a result, it is possible to operate the internal combustion engine that achieves both stable combustion and low fuel consumption.

Further, the variable compression ratio internal combustion engine in the present invention,
A cavity that is provided on the top surface of the piston of the internal combustion engine and that forms a stratified state in the combustion chamber of the internal combustion engine by introducing fuel near the compression top dead center;
A variable compression ratio mechanism that changes the compression ratio of the internal combustion engine by changing the volume of the combustion chamber of the internal combustion engine;
An injection direction variable fuel injection valve that injects fuel into the combustion chamber and can change the injection direction of fuel injected from the injection port at the time of fuel injection;
Injection direction changing means for changing the injection direction according to the compression ratio of the internal combustion engine changed by the variable compression ratio mechanism;
With
The lower the compression ratio of the internal combustion engine, the longer the distance between the injection direction variable fuel injection means at the compression top dead center and the piston,
The injection direction changing means may change the injection direction from the top dead center side to the bottom dead center side as the compression ratio is lower.

  As described above, when the compression ratio is changed in the variable compression ratio internal combustion engine having the variable compression ratio mechanism, the volume of the combustion chamber at the compression top dead center is often increased. That is, as described above, when the compression ratio is low, the position of the piston at the compression top dead center is often far from the fuel injection valve. In such a case, if fuel is injected from the fuel injection valve in the same injection direction regardless of the compression ratio, it becomes difficult to satisfactorily introduce the fuel injected from the fuel injection valve into the cavity near the compression top dead center. As a result, it may be difficult to form a good stratified state.

  Therefore, in the present invention, the injection direction control means sets the injection direction to the top dead center of the piston as the compression ratio is low and the position of the piston at the compression top dead center is farther from the injection direction variable fuel injection valve. Changed from the side to the bottom dead center side.

  As a result, regardless of the compression ratio of the internal combustion engine, the fuel injected from the fuel injection valve can be satisfactorily introduced into the cavity, and a good stratified state can be formed. As a result, it is possible to operate the internal combustion engine that achieves both stable combustion and low fuel consumption.

  The means for solving the above-described problems of the present invention can be used in combination as much as possible.

  In the present invention, in a variable compression ratio internal combustion engine, a stable stratified state can be formed in the combustion chamber regardless of the compression ratio, and stable stratified combustion is possible.

The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  The internal combustion engine 1 described below is a variable compression ratio internal combustion engine, and a compression ratio is obtained by moving a cylinder block 3 having a cylinder 2 in the direction of the central axis of the cylinder 2 with respect to a crankcase 4 to which a piston is connected. Is to change.

First, the configuration of the variable compression ratio mechanism according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, a plurality of raised portions are formed at the lower portions on both sides of the cylinder block 3, and bearing housing holes 5 are formed in the raised portions. The bearing housing hole 5 has a circular shape, and is formed so as to be perpendicular to the axial direction of the cylinder 2 and parallel to the arrangement direction of the plurality of cylinders 2. The bearing housing holes 5 are all located on the same axis. The pair of axes of the bearing housing holes 5 on both sides of the cylinder block 3 are parallel.

  The crankcase 4 is formed with a standing wall portion so as to be positioned between the plurality of raised portions in which the bearing housing holes 5 described above are formed. A semicircular recess is formed on the surface of each standing wall portion facing the outside of the crankcase 4. Moreover, the cap 7 attached with the volt | bolt 6 is prepared for each standing wall part, and the cap 7 also has a semicircle recessed part. Further, when the cap 7 is attached to each standing wall portion, a circular cam housing hole 8 is formed. The shape of the cam storage hole 8 is the same as that of the bearing storage hole 5 described above.

  Similar to the bearing housing hole 5, the plurality of cam housing holes 8 are perpendicular to the axial direction of the cylinder 2 when the cylinder block 3 is attached to the crankcase 4 and parallel to the arrangement direction of the plurality of cylinders 2. Each is formed to be. The plurality of cam storage holes 8 are also formed on both sides of the cylinder block 3, and the plurality of cam storage holes 8 on one side are all located on the same axis. The pair of axes of the cam storage holes 8 on both sides of the cylinder block 3 are parallel. Further, the distance between the bearing housing holes 5 on both sides and the distance between the cam housing holes 8 on both sides are the same.

Cam shafts 9 are inserted through the two rows of bearing housing holes 5 and cam housing holes 8 arranged alternately. As shown in FIG. 1, the cam shaft 9 includes a shaft portion 9a and a cam portion 9b having a right circular cam profile fixed to the shaft portion 9a in a state of being eccentric with respect to the central axis of the shaft portion 9a. The movable portion 9c has the same outer shape as the cam portion 9b and is rotatably attached to the shaft portion 9a. The cam portions 9b and the movable bearing portions 9c are alternately arranged. The pair of cam shafts 9 have a mirror image relationship. Further, a mounting portion 9d of a gear 10 described later is formed at the end portion of the cam shaft 9. The center axis of the shaft portion 9a and the center of the attachment portion 9d are eccentric, and the center of the cam portion 9b and the center of the attachment portion 9d coincide.

  The movable bearing portion 9c is also eccentric with respect to the shaft portion 9a, and the amount of eccentricity is the same as that of the cam portion 9b. In each camshaft 9, the eccentric directions of the plurality of cam portions 9b are the same. Since the outer shape of the movable bearing portion 9c is a perfect circle having the same diameter as the cam portion 9b, the outer surface of the plurality of cam portions 9b and the outer surfaces of the plurality of movable bearing portions 9c are rotated by rotating the movable bearing portion 9c. Can be matched with the side.

A gear 10 is attached to one end of each camshaft 9. Worm gears 11a and 11b are engaged with the pair of gears 10 fixed to the ends of the pair of cam shafts 9, respectively. The worm gears 11 a and 11 b are attached to one output shaft of the single motor 12. The worm gears 11a and 11b have spiral grooves that rotate in opposite directions. For this reason, when the motor 12 is rotated, the pair of cam shafts 9 rotate in opposite directions via the gear 10. The motor 12 is fixed to the cylinder block 3 and moves integrally with the cylinder block 3.

  Next, a method for controlling the compression ratio in the internal combustion engine 1 having the above-described configuration will be described in detail. 2 (a) to 2 (c) are cross-sectional views showing the relationship between the cylinder block 3, the crankcase 4, and the cam shaft 9 constructed between them. 2A to 2C, the central axis of the shaft portion 9a is indicated by a, the center of the cam portion 9b is indicated by b, and the center of the movable bearing portion 9c is indicated by c. FIG. 2A shows a state in which the outer peripheries of all the cam portions 9b and the movable bearing portion 9c coincide with each other when viewed from the extension line of the shaft portion 9a. At this time, here, the pair of shaft portions 9 a are located outside the bearing housing hole 5 and the cam housing hole 8.

  When the motor 12 is driven from the state of FIG. 2A to rotate the shaft portion 9a in the direction of the arrow, the state of FIG. 2B is obtained. At this time, since the cam portion 9b and the movable bearing portion 9c are displaced in the eccentric direction with respect to the shaft portion 9a, the cylinder block 3 can be slid to the top dead center side with respect to the crankcase 4. The sliding amount is maximized when the cam shaft 9 is rotated until the state shown in FIG. 2C is reached, and is twice the eccentric amount of the cam portion 9b and the movable bearing portion 9c. The cam portion 9b and the movable bearing portion 9c rotate inside the cam storage hole 8 and the bearing storage hole 5, respectively, and allow the position of the shaft portion 9a to move inside the cam storage hole 8 and the bearing storage hole 5, respectively. is doing.

  By using the mechanism as described above, the cylinder block 3 can be moved relative to the crankcase 4 in the axial direction of the cylinder 2, and the compression ratio can be variably controlled. The above-described mechanism constitutes a variable compression ratio mechanism in the present embodiment.

  Next, the combustion mode of the internal combustion engine will be described. Here, the combustion forms of the internal combustion engine include homogeneous mixed combustion and stratified combustion, and either combustion form is selected according to the operating state. That is, in a high-load high-rotation operation region or a stoichiometric region of an internal combustion engine such as during normal traveling operation, uniform mixed combustion is performed in which a homogeneous air-fuel mixture is formed and ignited.

  On the other hand, in a lean combustion region where the air-fuel ratio is very large (lean burn region), that is, in a low-load low-speed operation region of an internal combustion engine such as when idling, stratification that enables reliable ignition by stratification of the air-fuel mixture Combustion takes place. In this case, the fuel injected from the fuel injection valve is introduced into a cavity formed on the top surface of the piston and flows to the discharge electrode of the spark plug. For this reason, an ignitable air-fuel mixture is formed in a layer around the discharge electrode. Then, this is ignited at an appropriate timing to burn the air-fuel mixture.

  As described above, in stratified combustion of an internal combustion engine, the amount of fuel injected from the fuel injection valve is reliably introduced into the cavity formed on the top surface of the piston, so that the spark plug discharges at low load and low speed. It is possible to locally increase the fuel concentration around the electrode, thereby preventing misfire and improving combustion stability.

  Next, the case where the stratified combustion is performed in the variable compression ratio internal combustion engine 1 as described above will be described. In FIG. 3, the schematic of the combustion chamber vicinity of the internal combustion engine 1 which concerns on a present Example is shown. When stratified combustion is performed in the internal combustion engine 1, the fuel injected from the fuel injection valve 17 is introduced into a cavity 13 a provided on the top surface of the piston 13.

However, regardless of the compression ratio, when the injection width of the fuel injection from the fuel injection valve 17 is a constant value, the cylinder pressure is high in the high compression ratio state, so the fuel injected from the combustion injection valve 17 Difficult to diffuse as compared with the low compression ratio state, and may not be sufficiently introduced into the cavity 13a. In FIG. 3, the solid line indicates the state of the piston 13 and the injected fuel F when the compression ratio is high, and the broken line indicates the state of the piston 13 and the injected fuel F when the compression ratio is low. . In addition, when the injection width is set such that the fuel F injected in the high compression ratio reaches the cavity, the fuel injected in the low compression ratio may collide with the cavity excessively strongly. It was.

  Then, depending on the change in the compression ratio, stable stratified combustion becomes difficult to execute, and the combustion state may become unstable.

  Therefore, in this embodiment, the injection width related to the fuel injection from the fuel injection valve 17 is changed according to the compression ratio of the internal combustion engine 1. More specifically, the higher the compression ratio of the internal combustion engine 1, the smaller the injection width related to fuel injection. Then, as shown in FIG. 4, when the compression ratio of the internal combustion engine 1 is high and the in-cylinder pressure is high, the penetration force of the injected fuel can be increased, and the injected fuel is more reliably supplied by the cavity 13 a of the piston 13. Can be introduced. Specific control is performed based on a control signal from the ECU 40.

  FIG. 5 shows a flowchart of a compression ratio and fuel injection width determination routine according to the above control. This routine is a flow executed by the ECU 40 every predetermined period while the internal combustion engine 1 is in operation. In this routine, the injection width of the fuel injection from the fuel injection valve 17 is switched in two steps according to the compression ratio of the internal combustion engine 1.

  When this routine is executed, first, in S101, the operating state of the internal combustion engine 1 is acquired. Specifically, the engine load and engine speed of the internal combustion engine 1 are acquired from outputs of an accelerator position sensor and a crank position sensor (not shown).

  Next, in S102, the compression ratio value ε optimum for the operation state is derived from the operation state acquired in S101. Specifically, a map storing the relationship between the operation state and the optimum compression ratio is created in advance, and the value of the compression ratio ε corresponding to the operation state acquired in S101 is derived from the map. The optimum compression ratio value for each operating state may be the highest compression ratio within a range where knocking does not occur in each operating state.

  In S103, the fuel injection width corresponding to the value of the compression ratio ε derived in S102 is selected. Specifically, the compression ratio and the fuel injection width to be selected for introducing fuel from the fuel injection valve 17 to the cavity 13a against the pressure of the combustion chamber at the compression top dead center at each compression ratio. A map storing the relationship is prepared in advance based on experiments, and the value of the fuel injection width corresponding to the compression ratio ε is read out from the map. In brief, the switching compression ratio ε0 as a threshold value at the time of selection of the injection width may be obtained in advance, and the injection width of the fuel injection may be selected depending on whether the compression ratio ε is greater than or equal to the switching compression ratio ε0.

  Next, in S104, it is determined whether or not the current compression ratio of the internal combustion engine 1 is equal to the compression ratio ε derived in S102. If it is determined that the current compression ratio is equal to ε, this routine is terminated as it is. In this case, it is considered that an injection width at which the fuel can be introduced from the fuel injection valve 17 into the cavity 13a at the current compression ratio has already been selected at the previous execution of this routine. On the other hand, if it is determined that the current compression ratio is not ε, the process proceeds to S105.

  In S105, the compression ratio of the internal combustion engine 1 is changed to ε. Specifically, the motor 12 is energized and the camshaft 9 is rotated to change the relative position between the cylinder block 3 and the crankcase 4.

  In S106, the injection width of the fuel injected by the fuel injection valve 17 is set as the fuel injection width derived in S103. When the process of S106 ends, this routine is temporarily ended. Here, the ECU 40 that executes this routine constitutes the injection width changing means in the present embodiment.

  Here, a method of switching the injection width of the fuel injection by the fuel injection valve 17 will be described with reference to FIG. FIG. 5A is a cross-sectional view showing a schematic configuration of the fuel addition valve 17 having a plurality of injection ports. The fuel addition valve 17 includes a first needle 18, a second needle 19, and a nozzle holder 17a. The first needle 18 has a cylindrical shape and a tip that is pointed in a conical shape, and is provided on the central axis of the nozzle holder 17a.

  The conical surface at the tip of the first needle 18 is in contact with the inner wall of the nozzle holder 17a. The second needle 19 is cylindrical and has a diameter larger than that of the first needle 18, and the first needle 18 is slidably stored therein. The tip of the second needle 19 has a conical shape, but a hole for accommodating the first needle 18 is formed around the central axis. The conical surface at the tip of the second needle 19 is in contact with the inner wall of the nozzle holder 17a. The first needle 18 and the second needle 19 can be operated separately. Further, pressurized fuel is supplied between the first needle 18 and the second needle 19 and between the second needle 19 and the nozzle holder 17a.

  Further, two first injection ports 17b are provided at a portion where the conical surface of the first needle 18 of the nozzle holder 17a contacts. Similarly, two second injection ports 17c are provided at a portion where the conical surface of the second needle 19 contacts. As shown in FIG. 5A, the first injection port 17b and the second injection port 17c have the same opening angle with respect to the central axis of the nozzle holder 17a. On the other hand, as shown in FIG. 5B, the first injection port 17b and the second injection port 17c have an arc shape with respect to the circumferential direction of the nozzle holder 17a, and the second injection port 17c It is formed longer in the circumferential direction than the first injection port 17b.

  In the fuel addition valve 17 configured as described above, by operating the first needle 18, fuel can be injected with a small injection width with respect to the circumferential direction of the nozzle holder 17a. Further, by operating the second needle 19, fuel can be injected with a large injection width in the circumferential direction of the nozzle holder 17a. The fuel injection valve 17 corresponds to a variable injection width fuel injection valve in this embodiment.

  As described above, in this embodiment, when the compression ratio of the internal combustion engine 1 is high and the in-cylinder pressure at the compression top dead center is high, the fuel injected by reducing the injection width of the fuel injection It was decided to strengthen the penetrating power. Further, when the compression ratio of the internal combustion engine 1 is low and the pressure of the combustion chamber at the compression top dead center is low, the penetration force of the injected fuel is reduced by increasing the injection width of the fuel injection. . By doing so, the injected fuel can be satisfactorily introduced into the cavity 13a of the piston 13 regardless of the compression ratio of the internal combustion engine 1, and a stable stratified state can be formed.

  Next, a second embodiment of the present invention will be described. In the present embodiment, when the compression ratio of the internal combustion engine 1 becomes low and the distance between the fuel injection valve at the compression top dead center and the cavity provided on the piston top surface becomes long, the fuel is injected from the fuel injection valve. An example of increasing fuel penetration will be described. The configuration of the internal combustion engine 1 in the present embodiment is the same as that described in the first embodiment, and a description thereof will be omitted.

  In the first embodiment, attention has been paid to the fact that the cylinder pressure at the compression top dead center increases as the compression ratio of the internal combustion engine 1 increases, and an example in which the injected fuel is satisfactorily introduced into the cavity has been described. . However, depending on conditions such as the compression ratio value and operating conditions, the change in the distance between the fuel injection valve and the cavity at the compression top dead center caused by the change in the compression ratio rather than the change in the pressure in the combustion chamber. May be a problem.

  In this case, when the compression ratio of the internal combustion engine 1 is low, the distance between the fuel injection valve 17 and the cavity 13a at the compression top dead center is long, so that the fuel injected from the fuel injection valve 17 sufficiently enters the cavity 13a. May not reach. Therefore, in this embodiment, when the compression ratio of the internal combustion engine 1 is equal to or less than the switching compression ratio ε1, the fuel is injected by reducing the injection width of the fuel injected from the fuel injection valve 17 and increasing the penetration force. The fuel was introduced well into the cavity 13a provided on the top surface of the piston 13. An outline of the vicinity of the combustion chamber at that time is shown in FIG.

  In FIG. 7, the piston 13 and the injected fuel F in the high compression ratio state are indicated by broken lines. The piston 13 and the injected fuel F in the low compression ratio state are indicated by solid lines. As shown in FIG. 7, in the state of the low compression ratio, the distance between the fuel injection valve 17 and the piston 13 is increased by reducing the injection width of the fuel injected from the fuel injection valve 17 and increasing the penetration force. Even in this case, the injected fuel can be satisfactorily introduced into the cavity 13a.

  In the first and second embodiments, the control for switching the injection width of the fuel injected from the fuel injection valve 17 in two stages according to the compression ratio of the internal combustion engine 1 has been described. However, instead of this control, the control is made such that the injection width of the fuel injection optimal for the compression ratio is derived one by one for the compression ratio value of the internal combustion engine 1, and the injection width is always set to the optimal value. Good.

  Specifically, a map storing the relationship between the compression ratio and the injection width at which fuel can be introduced from the fuel injection valve 17 into the cavity 13a against the cylinder pressure at the compression top dead center at each compression ratio, Alternatively, the relationship between the compression ratio and the injection width at which fuel can be introduced from the fuel injection valve 17 into the cavity 13a with respect to the distance between the fuel injection valve 17 and the cavity 13a at the compression top dead center at each compression ratio is A stored map may be created in advance based on experiments, and an injection width value corresponding to the compression ratio ε may be read from the map.

  In that case, for example, as shown in FIG. 8, the injection width related to the injected fuel from the fuel injection valve 17 is provided with a third injection port 27 c provided relatively long in the circumferential direction at the tip of the fuel injection valve 27. Alternatively, the spray width may be continuously changed by appropriately rotating the shielding plate 20.

  Next, Example 3 in the present example will be described. In this embodiment, the fuel injected from the fuel injection valve when the compression ratio of the internal combustion engine 1 becomes low and the distance between the fuel injection valve at the compression top dead center and the cavity provided on the top surface of the piston becomes longer. An example in which the injection direction of the fuel injected from the fuel injection valve is changed instead of increasing the penetration force will be described. The configuration of the internal combustion engine 1 in the present embodiment is the same as that described in the first embodiment, and a description thereof will be omitted.

  In the present embodiment, as shown in FIG. 9, the fuel injection valve 37 is used when the compression ratio of the internal combustion engine 1 is higher than the switching compression ratio ε2 and when the compression ratio of the internal combustion engine 1 is equal to or less than the switching compression ratio ε2. The injection direction of the fuel F injected from is changed in two stages.

  In this way, it is possible to prevent the injected fuel from being satisfactorily introduced into the cavity 13a due to the change in the distance at the compression top dead center between the fuel injection valve 37 and the cavity 13a depending on the compression ratio of the internal combustion engine 1. . Also in this case, since specific control is performed based on a control signal from the ECU 40, the ECU 40 constitutes the injection direction changing means in the present embodiment.

FIG. 10 is a cross-sectional view showing a schematic configuration of the fuel injection valve 37 in this case. FIG. 10 is a schematic configuration diagram of a fuel addition valve 37 having a plurality of injection ports according to the present embodiment. Fuel addition valve 37
Is configured to include a third needle 35, a fourth needle 36, and a nozzle holder 37a. The third needle 35 has a semi-cylindrical shape and has a tip sharpened in a semi-conical shape, and is provided on the left side of the central axis of the nozzle holder 37a in FIG. The semiconical surface at the tip of the third needle 35 is in contact with the inner wall of the nozzle holder 37a. The fourth needle 36 has a semi-cylindrical shape like the third needle 35, and is provided on the right side of the central axis of the nozzle holder 37a in FIG. The tip of the fourth needle 36 also has a semi-conical shape, and its semi-conical surface is in contact with the inner wall of the nozzle holder 37a. The third needle 35 and the fourth needle 36 can be operated separately.

  Furthermore, the 4th injection port 37b is provided in the part which the semi-conical surface of the 3rd needle 35 of the nozzle holder 37a touches. Similarly, a fifth injection port 37c is provided at a portion where the semiconical surface of the fourth needle 36 contacts. The fourth injection port 37b and the fifth injection port 37c have opening angles that are symmetric with respect to the central axis of the nozzle holder 37a.

  In the fuel addition valve 37 configured as described above, by operating the third needle 35, it is possible to inject fuel in the left direction in FIG. 10 with respect to the central axis of the nozzle holder 37a. Further, by operating the fourth needle 36, fuel can be injected in the right direction in FIG. 10 with respect to the central axis of the nozzle holder 37a. When the fuel addition valve 37 is attached to the combustion chamber, for example, the fourth injection port 37b is directed to the crankcase 4 side in the cylinder 2 and the fifth injection port 37c is directed to the spark plug 15 side in the cylinder 2. To. When the compression ratio of the internal combustion engine 1 is higher than the switching compression ratio ε2, the fourth needle 36 is operated during fuel injection to inject fuel from the fifth injection port 37c. On the other hand, when the compression ratio of the internal combustion engine 1 is equal to or less than the switching compression ratio ε2, the third needle 35 is operated during fuel injection to inject fuel from the fourth injection port 37b.

  By doing so, the injection direction of the fuel injection can be changed according to the compression ratio of the internal combustion engine 1. The fuel injection valve 37 corresponds to the injection direction variable fuel injection valve in this embodiment. The control for changing the fuel injection direction by switching from the state in which fuel is injected from the fifth injection port 37c of the fuel injection valve 37 to the state in which fuel is injected from the fourth injection port 37b is the top dead center of the piston 13. This corresponds to the control of changing the fuel injection direction from the side to the bottom dead center side.

  In the present embodiment, as described above, the injection direction of the fuel injection from the fuel addition valve 37 is changed in two stages according to the compression ratio of the internal combustion engine 1. The fuel injection direction may be continuously changed so that the optimum fuel injection direction according to the compression ratio is obtained. In this case, for example, the fuel injection direction may be changed by mechanically changing the mounting angle of the fuel injection valve 37 itself.

1 is an exploded perspective view showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. It is sectional drawing which shows progress which the cylinder block in the internal combustion engine which concerns on the Example of this invention moves relatively with respect to a crankcase. It is a figure for demonstrating the relationship between the injection fuel state and compression ratio in the conventional internal combustion engine. It is a figure for demonstrating the relationship between the injection fuel state and compression ratio of the internal combustion engine which concerns on Example 1 of this invention. It is a flowchart which shows the compression ratio and fuel injection width determination routine in Example 1 of this invention. It is a figure which shows schematic structure of the fuel injection valve which concerns on Example 1 of this invention. It is a figure for demonstrating the relationship between the injection fuel state and compression ratio of the internal combustion engine which concerns on Example 2 of this invention. It is a figure which shows another example of schematic structure of the fuel injection valve which concerns on Example 1 and 2 of this invention. It is a figure for demonstrating the relationship between the injection fuel state and compression ratio of the internal combustion engine which concerns on Example 3 of this invention. It is a figure which shows schematic structure of the fuel injection valve which concerns on Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Cylinder block 4 ... Crankcase 9 ... Cam shaft 10 ... Gear 11a, 11b ... Worm gear 12 ... Motor 13 ... Piston 13a ... cavity 15 ... spark plugs 17, 27, 37 ... fuel injection valve 40 ... ECU
F ... Injected fuel

Claims (4)

A cavity that is provided on the top surface of the piston of the internal combustion engine and that forms a stratified state in the combustion chamber of the internal combustion engine by introducing fuel near the compression top dead center;
A variable compression ratio mechanism for changing the compression ratio of the internal combustion engine;
An injection width variable fuel injection valve that injects fuel into the combustion chamber and can change the injection width of fuel injected from the injection port at the time of fuel injection;
Injection width changing means for changing the injection width according to the compression ratio changed by the variable compression ratio mechanism;
A variable compression ratio internal combustion engine comprising: The higher the compression ratio of the internal combustion engine, the higher the pressure in the combustion chamber at the compression top dead center,
2. The variable compression ratio internal combustion engine according to claim 1, wherein the injection width changing means reduces the injection width as the compression ratio of the internal combustion engine increases. The lower the compression ratio of the internal combustion engine, the longer the distance between the injection width variable fuel injection valve and the piston at the compression top dead center,
2. The variable compression ratio internal combustion engine according to claim 1, wherein the injection width changing means reduces the injection width as the compression ratio of the internal combustion engine is lower. A cavity that is provided on the top surface of the piston of the internal combustion engine and that forms a stratified state in the combustion chamber of the internal combustion engine by introducing fuel near the compression top dead center;
A variable compression ratio mechanism that changes the compression ratio of the internal combustion engine by changing the volume of the combustion chamber of the internal combustion engine;
An injection direction variable fuel injection valve that injects fuel into the combustion chamber and can change the injection direction of fuel injected from the injection port at the time of fuel injection;
Injection direction changing means for changing the injection direction according to the compression ratio of the internal combustion engine changed by the variable compression ratio mechanism;
With
The lower the compression ratio of the internal combustion engine, the longer the distance between the injection direction variable fuel injection valve and the piston at the compression top dead center,
The variable compression ratio internal combustion engine, wherein the injection direction changing means changes the injection direction from the top dead center side to the bottom dead center side as the compression ratio is lower.

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