JP4739836B2 - Control device for spark ignition type cylinder injection type internal combustion engine - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a control device for a spark ignition type in-cylinder injection internal combustion engine provided with a fuel injection valve that directly injects fuel into the cylinder, and in particular, a spark ignition type in-cylinder injection internal combustion engine suitable for use as an automobile engine. The present invention relates to an engine control device.

  2. Description of the Related Art In recent years, a spark ignition type in-cylinder injection internal combustion engine that includes a fuel injection valve that directly injects fuel into a cylinder has been put into practical use. In such a spark ignition type in-cylinder injection type internal combustion engine, several techniques for promoting combustion and improving fuel consumption have been proposed.

  For example, Patent Document 1 has a tumble control valve that partitions an intake port into an upper port and a lower port, and selectively throttles the upper port and the lower port. Disclosed is a technique that appropriately adjusts the forward tumble flow generated in the above. According to this technique, stable combustion is realized in each combustion mode at the time of stratified combustion corresponding to low load, homogeneous lean combustion corresponding to medium load, and homogeneous stoichiometric air-fuel ratio combustion corresponding to high load.

  Further, in Patent Document 2, a fuel injection valve is attached with an injection port facing a rising gradient surface of a piston having a rising gradient surface that is raised on the top surface, and the first fuel injection is performed in the intake stroke. In the second half of the compression stroke, it is possible to improve the stability of combustion without reducing the compression ratio by executing the second fuel injection in an amount that can cause disturbance in the air-fuel mixture in a small amount. Technology is disclosed.

  Further, Patent Document 3 discloses divided fuel injection by dividing the required fuel injection amount in the compression stroke into a plurality of injection periods in which the injection characteristics of the fuel injection valves are equal in the compression stroke. There is disclosed a technique that can be performed accurately, distribute fuel at an appropriate concentration in an appropriate position in a combustion chamber, and sufficiently ensure an ignition possible period over the entire operation region.

JP 2001-55925 A JP 2003-35188 A JP 2002-115593 A

  However, according to the technique disclosed in Patent Document 1, a certain effect can be expected as long as the forward tumble flow is appropriately generated in the combustion chamber, but the intake air flow rate in the low speed region of the engine is slow. Not much effect is obtained in the region, and it is difficult to promote combustion over the entire operating region.

  Further, in the technique disclosed in Patent Document 2, since fuel is injected toward the upwardly inclined slope surface of the piston top surface, the amount of fuel adhering to the piston top surface increases, resulting in turbulence in the cylinder air. This is also less effective in promoting combustion over the entire operating range.

  Further, in the technique disclosed in Patent Document 3, since the injection is divided into a plurality of injection periods in the compression stroke, the mixture can be ignited in a region where the intake air flow velocity is high, such as a high-speed region of the engine. Formation is limited, which is also difficult to promote combustion over the entire operating range.

  Accordingly, an object of the present invention is to provide a spark ignition type in-cylinder injection internal combustion engine that can promote combustion over the entire operation region and improve fuel efficiency without being restricted by such operation conditions, combustion chamber shape, and the like. It is to provide a control device.

  For this reason, one form of the control apparatus for a spark ignition type in-cylinder injection internal combustion engine according to the present invention is a control apparatus for a spark ignition type in-cylinder injection internal combustion engine that includes a fuel injection valve that directly injects fuel into a combustion chamber. A variable injection characteristic fuel injection valve whose injection characteristic can be changed as a fuel injection valve, an injection characteristic change control means for changing the injection characteristic of the variable injection characteristic fuel injection valve, and fuel from the variable characteristic fuel injection valve Split injection control means for performing injection divided into a plurality of injection periods from the intake stroke to the compression stroke.

  Here, the injection characteristic may be a spray shape, and the injection characteristic change control unit may control to change the spray spread angle in the spray shape to a wide angle during the intake stroke injection and to a narrow angle during the compression stroke injection.

  Moreover, it is preferable that the said injection characteristic change control means carries out change control so that the spray spreading angle in a spray shape may become optimal corresponding to the piston position at the time of fuel injection.

  Further, the injection characteristic may be a spray penetration force, and the injection characteristic change control means may change and control the spray penetration force to be weak during the intake stroke injection and strong during the compression stroke injection.

  Therefore, it is preferable that the injection characteristic change control means performs change control so that the spray penetration force is optimized corresponding to the piston position at the time of fuel injection.

  The injection characteristic may be an injection rate, and the injection characteristic change control means may change and control the injection rate so that it is small during the intake stroke injection and large during the compression stroke injection.

  Here, it is preferable that the injection characteristic change control means performs change control so that the injection rate becomes optimum corresponding to the piston position at the time of fuel injection.

  Further, the injection characteristic change control means may change and control the injection rate according to the engine speed.

  According to one aspect of the control apparatus for a spark ignition type cylinder injection internal combustion engine according to the present invention, in the control apparatus for a spark ignition type cylinder injection internal combustion engine comprising a fuel injection valve that directly injects fuel into the combustion chamber, A variable injection characteristic fuel injection valve whose injection characteristic can be changed is used as the fuel injection valve, and an injection characteristic change control means for changing the injection characteristic of the variable injection characteristic fuel injection valve is provided. Since the fuel injection from the variable characteristic fuel injection valve is performed by the divided injection control means divided into a plurality of injection periods from the intake stroke to the compression stroke, the injection characteristic in the intake stroke and the injection characteristic in the compression stroke Is changed by the injection characteristic change control means, so that it is possible to select an injection characteristic suitable for each injection timing. Combustion can be promoted and fuel consumption can be improved.

  Here, according to the aspect in which the injection characteristic is a spray shape, and the injection characteristic change control means controls the spray spread angle in the spray shape to be changed to a wide angle during the intake stroke injection and to a narrow angle during the compression stroke injection. During the stroke injection, the fuel is injected into the combustion chamber space with a wide spray spread angle, so that the homogeneity of the air-fuel mixture is improved. On the other hand, during the compression stroke injection, the fuel is injected into the combustion chamber space with a narrow spray spread angle. As a result, a strong flow of the air-fuel mixture occurs in the cylinder, and the flame propagation is promoted. Thus, since the combustion speed is increased, the combustion period is shortened and the heat generation amount is increased.

  Further, according to the mode in which the injection characteristic change control means performs the change control so that the spray spread angle in the spray shape is optimized corresponding to the piston position at the time of fuel injection, for example, the fuel injection timing is dead on the intake stroke. When it is on the point side, there is a concern about fuel adhesion to the piston top surface. In such a case, by controlling the spray spread angle to a wide angle, dispersion of the spray is suppressed while suppressing fuel adhesion to the piston top surface. Can be improved.

  The injection characteristic is a spray penetrating force, and the injection characteristic change control means changes and controls the spray penetrating force to be weak during the intake stroke injection and strong during the compression stroke injection. The fuel is injected into the combustion chamber space with a weak spray penetration force, which improves the homogeneity of the mixture. On the other hand, during the compression stroke injection, the fuel is injected into the combustion chamber space with a strong spray penetration force. A strong flow occurs, and flame propagation is promoted. Thus, since the combustion speed is increased, the combustion period is shortened and the heat generation amount is increased.

  Further, according to the mode in which the injection characteristic change control means performs the change control so that the spray penetration force is optimized corresponding to the piston position at the time of fuel injection, for example, the fuel injection timing is on the intake stroke top dead center side. In some cases, fuel adhesion to the piston top surface is a concern, but in such cases, the spray penetration force is weakly changed and controlled to improve spray dispersibility while suppressing fuel adhesion to the piston top surface. be able to.

  Furthermore, according to the mode in which the injection characteristic is an injection rate, and the injection characteristic change control means changes and controls the injection rate so that it is small during the intake stroke injection and large during the compression stroke injection, it is small or not during the intake stroke injection. Since the fuel is injected into the combustion chamber space at a low injection rate, the homogeneity of the air-fuel mixture is improved. On the other hand, during the compression stroke injection, fuel is injected into the combustion chamber space at a large or high injection rate. A strong flow occurs, and flame propagation is promoted. Thus, since the combustion speed is increased, the combustion period is shortened and the heat generation amount is increased.

  Further, according to the mode in which the injection characteristic change control means performs the change control so that the injection rate is optimized corresponding to the piston position at the time of fuel injection, for example, the fuel injection timing is on the intake stroke top dead center side. In some cases, there is concern about the fuel adhering to the piston top surface. In such a case, by controlling the injection rate to be small or low, the dispersibility of the spray is improved while suppressing the fuel adhering to the piston top surface. be able to.

  Further, according to the mode in which the injection characteristic change control means changes and controls the injection rate in accordance with the engine rotation speed, the cooling time of the intake air in the intake stroke becomes shorter as the engine rotation speed becomes higher. Accordingly, since the injection rate is changed and controlled, the intake air can be cooled by the latent heat of vaporization in a short time to increase the filling efficiency.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a system configuration diagram showing an outline of a control device of a spark ignition type cylinder injection internal combustion engine (hereinafter also simply referred to as an engine) to which the present invention is applied. Reference numeral 10 denotes an engine body. The engine body 10 includes a cylinder block 12 and a cylinder head 14 in which cylinders are formed, 16 is a piston that reciprocates in the cylinder, and 18 is a combustion chamber formed in the upper part of the piston 16. 20 is an in-cylinder injector serving as a variable injection characteristic fuel injection valve which is arranged so as to inject fuel directly into the combustion chamber 18 and whose injection characteristic can be changed, and 22 is an ignition plug. Further, although not shown, the combustion chamber 18 is provided with an in-cylinder pressure sensor as torque detecting means. Each in-cylinder injector 20 communicates with a fuel delivery pipe 26 to which high-pressure fuel is supplied from a high-pressure fuel pump 24.

  In the intake system of the engine 10, an intake passage 32 is communicated via an intake manifold to an intake port 30 communicating with the combustion chamber 18 via an intake valve 28. The intake passage 32 communicates with a throttle chamber in which a throttle valve 34 is interposed. The throttle valve 34 is a so-called electronically controlled throttle that is driven by a throttle motor 36 and whose opening is detected by a throttle opening sensor 35. A turbocharger 38 (for example, a turbocharger compressor) is disposed upstream of the throttle chamber. Further, an air flow meter 40 for measuring the intake air flow rate is disposed upstream of the supercharger 38.

  On the other hand, in the exhaust system of the engine 10, an exhaust passage 46 is communicated with an exhaust port 44 communicating with the combustion chamber 18 via an exhaust valve 42 via an exhaust manifold. The exhaust passage 46 is provided with a turbine (not shown) of the supercharger 38 described above, and a three-way catalyst 48 is disposed downstream thereof. The turbocharger as the supercharger 38 of the present embodiment is such that the compressor is rotationally driven by the energy of the exhaust gas introduced into the turbine and sucks and pressurizes air to supercharge. Other mechanical superchargers can be used.

  Further, the engine 10 is provided with a crank angle sensor (hereinafter also referred to as a rotational speed sensor) 50 for detecting the rotational speed of the engine 10 and an accelerator opening sensor 52 for detecting a required load (accelerator opening). It has been. Further, a water temperature sensor 54 for detecting the cooling water temperature of the engine 10 and a pressure sensor (not shown) used for controlling the supercharging pressure are provided. Further, in the present embodiment, the above-described fuel pressure in the fuel delivery pipe 26, that is, the injection pressure sensor 56 for detecting the injection pressure from the in-cylinder injector 20, and the knocking for detecting knocking in the engine 10 are detected. A sensor 58 is provided, and outputs of these various sensors are sent to an electronic control unit 100 constituted by a microcomputer or the like.

  An electronic control unit (hereinafter referred to as ECU) 100 controls a fuel injection amount, a fuel injection timing, an ignition timing, a supercharging pressure, and the like in accordance with output values sent from the above-described sensors. The basic control values used for controlling the fuel injection amount, the fuel injection timing, the ignition timing, the supercharging pressure, etc. An optimum value obtained experimentally in accordance with the required characteristics of the engine 10 is set as a control value in a basic map representing the operating state of the engine 10 taking the load and taking the engine speed (engine speed) on the horizontal axis. These basic maps are stored in the table of the electronic control unit 100.

  Here, a basic configuration of the in-cylinder injector 20 as the variable injection characteristic fuel injection valve that can change the injection characteristic used in the present embodiment will be described with reference to FIG. The in-cylinder injector 20 includes a substantially cylindrical injector main body 200, a needle member 220 slidably fitted to the injector main body 200, and an injection hole forming member 240 fixed to the injector main body 200.

  In the injector body 200, a fuel chamber 202, a first piston accommodating chamber 204, and a needle guide hole 206 that communicates both are formed concentrically. The needle member 220 includes a needle valve portion 222 at the front end portion, a piston portion 224 having an enlarged diameter at the rear end portion, and a sliding guide portion 226 that is slidably fitted into the needle guide hole 206 at an intermediate portion. A fuel passage 228 that extends through the piston portion 224 and branches perpendicularly to the center line above the needle valve portion 222 is formed in the center portion. In the needle member 220, the piston portion 224 is accommodated in the first piston accommodating chamber 204, and the needle valve portion 222 at the distal end thereof is intermediate to open and close a nozzle hole 250 described later formed in the nozzle hole forming member 240. The sliding guide portion 226 is slidably fitted in the needle guide hole 206. Thus, the first piston accommodating chamber 204 is defined by the piston portion 224 into an upper spring accommodating chamber 204U and a lower pressure chamber 204L. Further, in this embodiment, the pressure generator 260 constituting a part of the injection characteristic change control means for changing the injection characteristic of the in-cylinder injector 20 as the variable injection characteristic fuel injection valve capable of changing the injection characteristic is a cylinder in this embodiment. It is incorporated in the inner injector 20. The pressure generator 260 includes a piezoelectric element 262 and a piston 264 driven by the piezoelectric element 262, and the piston 264 is housed in a second piston housing chamber 266 formed in the injector body 200. A pressure chamber 266L is defined on the lower side of the second piston accommodating chamber 266 by a piston 264.

  The pressurizing chamber 266L and the pressure chamber 204L are communicated with each other via a communication passage 268. Further, the pressurizing chamber 266L and the spring accommodating chamber 204U are provided with a check valve 270 in the middle. Communication is established via a one-way communication passage 272. The spring accommodating chamber 204U is provided with a spring 210 that presses the piston portion 224, and the needle valve portion 222 at the tip of the needle member 220 has a nozzle hole 250 formed in the nozzle hole forming member 240. Energizing in the closing direction. Further, a fuel supply passage 212 formed in the injector main body 200 is communicated with the spring accommodating chamber 204U, and the fuel supply passage 212 is communicated with the above-described fuel delivery pipe 26. In the in-cylinder injector 20 of the present embodiment, fuel of a predetermined pressure supplied from the fuel delivery pipe 26 fills the fuel chamber 202 through the fuel supply passage 212, the spring accommodating chamber 204 U and the fuel passage 228 of the needle member 220. Is done. The fuel is also filled in the pressurizing chamber 266L, the communication passage 268, the pressure chamber 204L, and the one-way communication passage 272 so as to be used as a working fluid that transmits the pressure generated by the pressure generator 260.

  In the in-cylinder injector 20 configured by incorporating the pressure generator 260 in this manner, the piston 264 is pressed downward and driven by the piezoelectric element 262 whose expansion coefficient changes according to the applied voltage. When the piston 264 is pressed downward, fuel as a working fluid is introduced from the pressurizing chamber 266L into the pressure chamber 204L through the communication passage 268, and the piston portion 224 and the needle member 220 are urged by the spring 210. Push it up against it. Thus, the needle valve portion 222 at the tip of the needle member 220 opens the nozzle hole 250 formed in the nozzle hole forming member 240. As will be described later, the lift amount of the needle member 220 is made variable by changing the voltage applied to the piezoelectric element 262 and changing the expansion rate to change the moving amount of the piston 264.

  Next, the needle member 220 and the nozzle hole forming member 240 that constitute the variable injection characteristic fuel injection valve that can be used together with the needle member 220 that is configured so that the lift amount is variable and that can change the injection characteristic. This embodiment will be described with reference to FIGS.

First, FIGS. 3A and 3B show different combinations of the needle member 220 and the injection hole forming member 240 of the variable injection characteristic fuel injection valve in which the spray shape can be changed as the injection characteristic. The part is shown enlarged. In the in-cylinder injector 203A in the form shown in FIG. _3A , a spiral groove 222A is formed on the outer periphery of the needle valve portion 222 whose diameter is increased at the tip of the needle member 220. Is formed with a frustoconical recess 240 </ b> A communicating with the nozzle hole 250, and the inclined wall surface of the recess 240 </ b> A and the needle valve portion 222 are in contact with each other. Thus, in the in-cylinder injector 20 _3A, changes the flow rate of the fuel flowing into the groove 222A in accordance with the lift amount of the needle member 220, since the degree of following of the groove 222A is changed, by changing controlling the lift The shape of spray from the nozzle hole 250 is changed. When the lift amount is large, the flow rate of the inflowing fuel is fast and the spray spread angle in the spray shape becomes narrow, whereas when the lift amount is small, the flow rate is slow and the spray spread angle in the spray shape becomes wide.

In addition, in the in-cylinder injector 203 </ b> _{B of the} form shown in FIG. _3B , the needle valve portion 222 at the tip of the needle member 220 has a columnar shape, and the nozzle hole forming member 240 has a wharf communicating with the nozzle hole 250. A conical recess 240 </ b> B is formed, and the fringe surface of the recess 240 </ b> B and the tip surface of the needle valve portion 222 are in contact with each other to close the injection hole 250. And thus, the in-cylinder injector 20 _3B, in the region (FIG. 3 (C) between the tip face and the truncated surface of the concave portion 240B of the needle valve 222 in accordance with the lift amount of the needle member 220 in the "A" Since the fuel pressure in (shown) changes, the shape of the spray from the nozzle hole 250 is changed by changing and controlling the lift amount. When the lift amount is large, the fuel pressure in the region “A” increases, so that the spray spread angle in the spray shape becomes a wide angle (indicated by “I” in FIG. 3C), whereas the lift amount is small. Sometimes the pressure is low and the spray spread angle in the spray shape becomes a narrow angle (indicated by “II” in FIG. 3C).

  Next, FIGS. 4A to 4C show the relationship between the needle member 220 and the injection hole forming member 240 of the variable injection characteristic fuel injection valve in which the spray shape and the spray penetration force can be changed as the injection characteristics. A part of the combination form is shown enlarged. Here, FIG. 4A shows when the lift amount of the needle member 220 is zero, and FIGS. 4B and 4C show when the lift amount is small and large, respectively. Here, in FIGS. 4A to 4C, since the components are the same and only the lift position of the needle member 220 is different, in order to avoid the complexity for facilitating the understanding of the drawings, Duplicate symbols are omitted as appropriate.

4 In-cylinder injector 20 ₄ embodiment shown in (A) through FIG. 4 (C), the needle valve portion 222 of the tip of the needle member 220 is a basic shape cylindrical, upper annular in its different axial positions A groove 222BU and a lower annular groove 222BL are formed. Then, the in-cylinder injector 20 _4, the central portion formed with respect to the aforementioned fuel passage 228 and upward in the perpendicular to branch to the center line which do passage portion of the needle valve portion 222 of the needle member 220 is omitted, A fuel passage 228A that penetrates to the tip of the needle valve portion 222 is formed. Further, the fuel passage 228A communicates with the upper annular groove 222BU and the lower annular groove 222BL.

In the nozzle hole forming member 240, the outer shape is formed in a frustoconical shape, and a concave portion 240C in which the needle valve portion 222 at the tip of the needle member 220 is fitted is formed. Then, while opening the upper nozzle hole 250U and the lower injection hole 250L is axially different "predetermined position" in each recess 240C, different angles (alpha relative to cylinder injector 20 ₄ of the center line, beta, alpha A plurality of radial shapes are formed so as to satisfy> β). The “predetermined position” refers to the upper injection hole 250U when the lift amount of the needle member 220 shown in FIG. 4A is zero in the relationship between the upper annular groove 222BU and the lower annular groove 222BL. When the communication between the lower injection hole 250L and the upper annular groove 222BU and the lower annular groove 222BL is blocked and the lift amount shown in FIG. 4B is small, the upper injection hole 250U and the upper annular groove 222BU When the communication between the lower injection hole 250L and the lower annular groove 222BL is interrupted and the lift amount shown in FIG. 4C is large, the upper injection hole 250U and the upper annular groove 222BU This is a position where the lower nozzle hole 250L and the lower annular groove 222BL communicate with each other. The above relationship may be reversed.

Thus, in the in-cylinder injector 20 _4, the upper annular groove 222BU and lower annular groove 222BL and upper injection hole 250U and the lower injection hole 250L communicates with each of the fuel passage 228A in accordance with the lift amount of the needle member 220 Therefore, the spray shape and the spray penetration force are changed by changing and controlling the lift amount. When the lift amount shown in FIG. 4B is small, the spray spread angle is sprayed from the upper nozzle hole 250U at a wide angle of 2α and the spray penetration force is weak, whereas the lift amount shown in FIG. 4C is large. In this case, the spray spread angle is sprayed from the lower nozzle hole 250L at a narrow angle of 2β, and the spray penetration force becomes strong.

  Further, FIGS. 5A to 5D show a part of the combination of the needle member 220 and the injection hole forming member 240 of the variable injection characteristic fuel injection valve in which the injection rate can be changed as the injection characteristic. Is shown enlarged. Here, FIG. 5A shows when the lift amount of the needle member 220 is zero, and FIGS. 5B to 5D show when the lift amount is small, medium and large, respectively. . Here, in FIGS. 5A to 5D, since the components are the same and only the lift position of the needle member 220 is different, in order to avoid the complexity for facilitating the understanding of the drawings, Duplicate symbols are omitted as appropriate. The “injection rate” refers to the fuel injection amount per unit time.

In FIG. 5 (A) through 5-cylinder injector 20 ₅ embodiment shown in (D), a needle valve portion 222 of the tip of the needle member 220 is formed a small, a medium and large diameter cylindrical stepped ( Hereinafter, these will be referred to as 222S, 222M, and 222L). The fuel passage 228 is the same as that shown in FIG. In the nozzle hole forming member 240, the outer shape of the distal end portion is formed in a frustoconical shape, and the small diameter portion 222S, the intermediate diameter portion 222M, and the large diameter of the needle valve portion 222 at the distal end portion of the needle member 220 are formed inside. Stepped recesses 240D into which the portions 222L are respectively fitted are formed (hereinafter, the corresponding recesses are referred to as 240DS, 240DM, and 240DL). The first injection hole 250 ₁ , the second injection hole 250 _2, and the third injection hole 250 ₃ open to the above-described large-diameter recess 240DL, medium-diameter recess 240DM, and small-diameter recess 240DS in the recess 240D, respectively. It is plural formed radially so as to form the same angle γ with respect to 20 ₅ of the center line.

Thus, in the in-cylinder injector 20 _5, when the lift amount of the needle member 220 shown in FIG. 5 (A) is zero, the small diameter portion 222S of the needle valve portion 222 of the needle member 220, intermediate diameter portion 222M and the large-diameter diameter recess 240DS the part 222L is corresponding, mutually fitted into the middle-diameter portion 240DM and the large diameter recess 240DL, the first injection holes 250 _1, the second injection holes 250, _second and third injection holes 250 ₃ is closed. Then, the lift amount shown in FIG. 5 (B) is at a small, only the first injection holes 250 ₁ part of diameter 222M is positioned in the large diameter recess 240DL within the needle valve 222 is opened. Also, when the lift amount shown in FIG. 5C is intermediate, a part of the small diameter portion 222S of the needle valve portion 222 is fitted in the small diameter concave portion 240DS, and the remaining portion is positioned in the medium diameter concave portion 240DM. injection hole 250 ₁ and second injection holes 250 ₂ are opened. Further, when the lift amount shown in FIG. 5 (D) is large, the small diameter portion 222S of the needle valve portion 222 is not fitted into the small diameter concave portion 240DS, and all of them are positioned in the medium diameter concave portion 240DM and the large diameter concave portion 240DL. All of the first nozzle hole 250 ₁ , the second nozzle hole 250 _2, and the third nozzle hole 250 ₃ are opened.

  Thus, since the number of injection holes communicated with the fuel passage 228 changes according to the lift amount of the needle member 220, the injection rate is changed by changing and controlling the lift amount. When the lift amount shown in FIG. 5 (B) is small, the injection rate is small, when the lift amount shown in FIG. 5 (C) is medium, the injection rate is medium, and when the lift amount shown in FIG. 5 (D) is large. The injection rate is large and each is injected.

  The in-cylinder injector 20 can change the spray spread angle, the spray penetration force, or the injection rate in accordance with the lift amount of the needle member 220, but is not limited to this. The spray spread angle or spray penetration force or spray rate to be sprayed into 18 may be changeable.

  Next, basic control contents executed by the ECU 100 in the engine 10 of the present embodiment will be described with reference to FIG. The engine 10 is set so as to perform so-called split injection in which fuel is injected into the combustion chamber 18 in the compression stroke as well as in the intake stroke. During this split injection operation, the intake stroke injection portion of the total fuel injection amount in a predetermined crank angle interval from a predetermined crank angle position in the intake stroke when the piston 16 descends according to a predetermined split injection rate described later. And the remaining amount is injected at predetermined crank angle intervals from a predetermined crank angle position when the piston 16 ascends after the compression stroke bottom dead center (BDC). In the present invention, the injection characteristic in the intake stroke and the injection characteristic in the compression stroke are changed and controlled in correspondence with the piston position, so that combustion is promoted over the entire operation region and fuel consumption is improved. .

Therefore, one mode of control by the control device according to the first embodiment of the present invention will be described with reference to a flowchart shown in FIG. This control routine is executed, for example, every predetermined crank angle. That is, when control is started, engine information is first read in step S701. Here, as engine information, the engine speed and the position of the piston 16 (hereinafter referred to as piston position) by the crank angle sensor (rotation speed sensor 50), the opening of the throttle valve 34 by the throttle opening sensor 35 (hereinafter referred to as throttle). The cooling water temperature measured by the water temperature sensor 54 is used. next,
Proceeding to step S702, the total fuel injection amount is acquired from the map based on the throttle opening representing the engine load and the engine speed among the engine information. In the next step S703, it is determined whether or not the engine 10 is in the intake stroke based on the piston position read in step S701.

  Here, when in the intake stroke, the routine proceeds to step S704, where the fuel injection amount at the intake stroke is read from the map in correspondence with the divided injection rate based on the engine information, and at the next step S705, the fuel at the intake stroke is read. The injection time is read. Further, in the next step S706, the lift amount of the needle member 220 during the intake stroke is read. On the other hand, if it is determined in step S703 that it is not an intake stroke, the process proceeds to step S707, and it is determined whether or not it is a compression stroke. Here, when it is not the compression stroke, for example, when it is in the exhaust stroke or the expansion stroke, this control routine is ended. When it is in the compression stroke, the process proceeds to step S708, and the fuel injection amount during the compression stroke is read from the map in correspondence with the divided injection rate based on the engine information read in step S701 described above, and in the next step S709. The fuel injection timing during the compression stroke is read at. Further, in the next step S710, the lift amount of the needle member 220 during the compression stroke is read.

  Thus, the fuel injection amount during the intake stroke, the fuel injection timing and the lift amount of the needle member 220 read in steps S704 to S706, the fuel injection amount during the compression stroke read in steps S708 to S710, and the fuel. Based on the injection timing and the lift amount of the needle member 220, the in-cylinder injector 20 in each cylinder is driven at a predetermined timing.

Here, the case where the in-cylinder injector 203B shown in FIG. _{3B in} which the spray shape is changed is used as the variable injection characteristic fuel injection valve in which the injection characteristic can be changed in the first embodiment will be described in more detail. Then, the lift amount of the needle member 220 in step S706 is changed and controlled so that the spray spread angle in the spray shape becomes a wide angle during the intake stroke injection and becomes a narrow angle during the compression stroke injection. That is, the voltage applied to the piezoelectric element 262 of the pressure generating device 260 constituting a part of the injection characteristic change control unit is changed and controlled, and the amount of movement of the piston 264 and the lift of the needle member 220 integrated with the piston portion 224 are controlled. The amount is controlled to change. Thus, since the in-cylinder injector _203B is opened while the lift amount of the needle member 220 is large during the intake stroke injection, the wide spray spread angle (see FIG. 3) as shown in FIG. 8A during the intake stroke injection. (Corresponding to “I” in (C)), the fuel is injected into the space of the combustion chamber 18 and the homogeneity of the air-fuel mixture in the combustion chamber is improved. On the other hand, since the in-cylinder injector _203B is opened while the lift amount of the needle member 220 is small during the compression stroke injection, the narrow spray spread angle (see FIG. 3) as shown in FIG. 8B during the compression stroke injection. (Corresponding to “II” in (C)), fuel is injected into the space of the combustion chamber 18. As a result, a strong flow of the in-cylinder air-fuel mixture occurs and flame propagation is promoted. Thus, since the combustion speed is increased, the combustion period is shortened and the heat generation amount is increased.

In the above description, the case where the in-cylinder injector 203B shown in FIG. _{3B in} which the spray shape is changed is used as the variable injection characteristic fuel injection valve whose injection characteristic can be changed has been described. the cylinder injector _{20 3A} shows, one of the in-cylinder injector 20 ₅ shown in FIG injector 20 ₄ and the cylinder shown in FIG. 4 (a) through FIG. 4 (C) 5 (a) through FIG. 5 (D) Even if it is used, the same effect can be obtained.

  Therefore, the experimental results of the effects obtained by the present invention are shown in FIGS. 9A and 9B in comparison with the prior art in which the injection characteristics are not changed. 9A is a graph showing the crank angle on the horizontal axis and the heat generation rate on the vertical axis, and FIG. 9B is a graph showing the crank angle on the horizontal axis and the heat generation amount on the vertical axis. As is clear from the graph of FIG. 9A, rapid combustion is realized by the promotion of flame propagation, the slope of the heat generation rate becomes steep, and the combustion period is shortened. As a result, as is apparent from the graph of FIG. 9B, the heat generation amount is also greatly increased as compared with the prior art.

  Next, one mode of control by the control device according to the second embodiment of the present invention will be described with reference to the flowchart shown in FIG. This second embodiment is mainly different from the first embodiment described above in that, in addition to the control of the first embodiment, change control is performed so that the injection characteristic is optimized corresponding to the piston position. It is that. Therefore, in the flowchart of FIG. 10, in order to facilitate understanding, the reference numerals of the steps of the flowchart shown in FIG. 7 are used as they are, and additional and changed steps as a part thereof are represented by S1000 units.

  In the second embodiment, after reading the fuel injection amount, the fuel injection timing, and the lift amount of the needle member 220 in the intake stroke in steps S704 to S706 in the first embodiment described above, the process proceeds to step S1001. The piston position at this time is read again. Then, in step S1002 after step S1001, it is determined whether or not this piston position exceeds a predetermined position (distance from the bottom dead center), in other words, whether or not it is on the top dead center side from the predetermined position. Is done. When it is determined that the piston position does not exceed the predetermined position, this control routine is terminated. That is, the in-cylinder injector 20 is driven at a predetermined time based on the lift amount read in step S706 without performing correction in step S1003 described later.

By the way, when the piston position exceeds the predetermined position in the determination in step S1002, that is, on the top dead center side, the process proceeds to step S1003, and the correction amount of the lift amount of the needle member 220 is read. For example, as shown in FIGS. 11A to 11C, the correction amount of the lift amount is set in correspondence with the injection characteristic of the in-cylinder injector 20 used. Example shown in FIG. 11 (A), FIG. 3 (A) and FIG. 3 (B) to indicate within the spray divergence angle can be changed cylinder injector 20 _3A and the in-cylinder variation in the injection characteristics suitable for the injector 20 _3B shows how both, as the piston position at the time of fuel injection is close to the intake top dead center beyond a predetermined position (indicated by d _0), which is to spray divergence angle becomes wider, the lift amount of The correction amount is set to satisfy this. Example shown in FIG. 11 (B) shows a state of change of the injection characteristics suitable for 4 (A) through 4 spray shape and the spray penetration in force as possible changes tubular injector 20 ₄ shown in (C) cage, as the piston position at the time of fuel injection is close to the intake top dead center beyond a predetermined position (indicated by d _0), which is to spray penetration force is weakened, as the correction amount of the lift amount to satisfy this Is set to Furthermore, the example shown in FIG. 11 (C) shows a state of change of the injection characteristics suitable in Fig 5 (A) through FIG. 5 (D) the injection rate shown in modifiable cylinder injector 20 _5, as piston position at the time of fuel injection is close to the intake top dead center beyond a predetermined position (indicated by d _0), it is such that the injection rate decreases, the correction amount of the lift amount is set so as to satisfy this ing.

  In this way, the change control is performed so that the injection characteristics are optimized in accordance with the piston position in order to suppress the fuel adhering to the piston top surface, which causes the occurrence of smoke in the injection on the intake stroke top dead center side, as much as possible. When the fuel injection timing is on the intake stroke top dead center side, the fuel spread on the piston top surface is controlled by optimally changing the spray spread angle, spray penetration force or spray rate according to the piston position. The dispersibility of the spray can be improved while suppressing.

  Next, one mode of control by the control device according to the third embodiment of the present invention will be described with reference to the flowchart shown in FIG. The main difference between the third embodiment and the first embodiment described above is that in the injection rate change control in the first embodiment, the change control is further performed in accordance with the engine speed. . Therefore, in the flowchart of FIG. 12, in order to facilitate understanding, the reference numerals of the steps of the flowchart shown in FIG. Represented by

In the third embodiment, after reading the fuel injection amount and fuel injection timing during the intake stroke in steps S704 and S706 in the first embodiment described above, the process proceeds to step S1201, and the engine speed is again set. Read. In the next step S1202, the lift amount of the needle member 220 is read in accordance with the read engine speed. For example, the lift amount is set to correspond to the change in the injection rate shown in FIG. That is, in the example shown in FIG. 13, the lift amount is set so that the injection characteristics change so that the injection rate increases as the engine speed increases. In FIG. 5 (A) through 5-cylinder injector 20 ₅ shown in (D), the lift amount larger the engine rotational speed is high is large, it is the fuel injection amount per unit time is increased.

  According to the third embodiment, the cooling time of the intake air in the intake stroke is shortened as the engine speed increases, but the change control is performed so that the injection rate increases as the engine speed increases. Thus, the intake air can be cooled in a short time, and the charging efficiency can be increased.

  In the above-described embodiment, the example in which the pressure generator 260 that constitutes a part of the injection characteristic change control unit that changes the injection characteristic is integrally incorporated in the in-cylinder injector 20 has been described. It is good.

It is a system configuration figure showing an outline of a control device of a spark ignition type cylinder injection type internal combustion engine provided with a supercharger to which the present invention is applied. It is sectional drawing which shows the basic composition of the in-cylinder injector as a variable injection characteristic fuel injection valve which can change the injection characteristic used by embodiment of this invention. In the variable injection characteristic fuel injection valve used in the embodiment of the present invention, an enlarged cross-sectional view showing a part of the combination form of the needle member and the injection hole forming member of the in-cylinder injector in which the spray shape can be changed as the injection characteristic (A) shows the case where the needle valve portion is spiral, (B) shows the case where the needle valve portion is cylindrical, and (C) shows the spray shape with respect to the lift amount of the needle member. In the variable injection characteristic fuel injection valve used in the embodiment of the present invention, a part of the combination form of the needle member and the injection hole forming member of the in-cylinder injector in which the spray shape and the spray penetration force can be changed as the injection characteristic is shown. It is an expanded sectional view shown, (A) shows when the lift amount of the needle member is zero, (B) shows the lift amount is small, and (C) shows the lift amount is large. In the variable injection characteristic fuel injection valve used in the embodiment of the present invention, an enlarged cross-sectional view showing a part of a combination form of a needle member and an injection hole forming member of an in-cylinder injector in which an injection rate can be changed as an injection characteristic (A) is when the lift amount of the needle member is zero, (B) is when the lift amount is small, (C) is when the lift amount is medium, and (D) is when the lift amount is large. Yes. It is a timing chart which shows the division | segmentation injection control which injects a fuel in a combustion chamber also in a compression stroke with the intake stroke used for this invention. It is a flowchart which shows one form of control by the control apparatus which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows a spray form, (A) is a wide angle spray spread angle at the time of intake stroke injection, (B) is injection by the narrow spray spread angle at the time of compression stroke injection. It is a graph which shows the experimental result of the effect acquired by the present invention by contrast with the prior art which does not change injection characteristics, (A) shows the heat release rate, and (B) shows the heat generation amount. It is a flowchart which shows one form of control by the control apparatus which concerns on the 2nd Embodiment of this invention. In the 2nd Embodiment of this invention, it is a graph which shows an example of the correction amount of the lift amount of a needle member at the time of carrying out change control of the injection characteristic corresponding to an injection timing or the piston position at the time of injection, (A) is a spray spread. The angle, (B) shows the spray penetration force, and (C) shows the case of the injection rate. It is a flowchart which shows one form of control by the control apparatus which concerns on the 3rd Embodiment of this invention. In the 3rd Embodiment of this invention, it is a graph which shows an example of the correction amount of the lift amount of the needle member at the time of carrying out change control of the injection characteristic corresponding to an engine speed.

Explanation of symbols

10 Engine body 20, 20 _3A , 20 _3B , 20 ₄ , 20 _{5 In-} cylinder injector 34 Throttle valve 50 Crank angle sensor (rotational speed sensor)
DESCRIPTION OF SYMBOLS 100 Electronic control unit 200 Injector main body 204 1st piston accommodation chamber 204U Spring accommodation chamber 204L Pressure chamber 210 Spring 212 Fuel supply passage 220 Needle member 222 Needle valve part 222A Groove 222BU Upper annular groove 222BL Lower annular groove 222S Small diameter part 222M Medium diameter Portion 222L Large diameter portion 224 Piston portion 228, 228A Fuel passage 240 Injection hole forming member 240A, 240B, 240C Recess 240DL Large diameter recess 240DM Medium diameter recess 240DS Small diameter recess 250 Injection hole 250U Upper injection hole 250L Lower injection hole 250 _1st 1 injection hole 250 ₂ 2nd injection hole 250 ₃ 3rd injection hole 260 Pressure generator 262 Piezoelectric element 264 Piston 266 2nd piston accommodation chamber 266L Pressurization chamber 268 Communication passage 270 Check valve 272 One-way communication passage

Claims (3)

In a control device for a spark ignition type in-cylinder injection internal combustion engine comprising a fuel injection valve for directly injecting fuel into a combustion chamber,
While using a variable injection characteristic fuel injection valve whose injection characteristic can be changed as a fuel injection valve,
Injection characteristic change control means for changing the injection characteristic of the variable injection characteristic fuel injection valve;
Split injection control means for dividing the fuel injection from the variable injection characteristic fuel injection valve into a plurality of injection timings from the intake stroke to the compression stroke; and
The injection characteristic is an injection rate, and the injection characteristic change control means controls to change the injection rate to be small during intake stroke injection and large during compression stroke injection. Engine control device. The injection characteristic change control means performs change control so that the injection rate becomes smaller as the piston position during fuel injection exceeds a predetermined position from the bottom dead center and approaches the intake top dead center. 2. A control device for a spark ignition type cylinder injection type internal combustion engine according to 1. 3. The control device for a spark ignition type in-cylinder injection internal combustion engine according to claim 2, wherein the injection characteristic change control means performs change control so that the injection rate increases as the engine speed increases .

Images