JP2008057479A - Direct injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct injection engine forming a good stratified air-fuel mixture in a wide operational area, and mixing air and fuel in a good manner even if an air flow in a cylinder gets stronger so as to improve an air utilization factor. <P>SOLUTION: A recess is formed to a crown surface part of a piston so as to maintain tumble, a fuel spray jetted from at least one of a plurality of injection holes of a fuel injection valve facing an intake side of a combustion chamber is injected toward the recess. The recess is provided with a spray reflecting face formed of a flat face or a curved face whose inclination angle or curvature is set so that at least one fuel splay jetted toward the recess is collided with the spray reflecting face so as to be reflected to an ignition plug when injection is performed at a compression stroke. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection valve having a plurality of injection ports for directly injecting fuel into a combustion chamber defined above the piston, and a piston provided with a recess for maintaining and maintaining the top surface without breaking the tumble. It is related with the direct-injection gasoline engine for vehicles equipped with.

  Conventionally, a spark ignition direct injection gasoline engine that directly injects fuel into a combustion chamber is widely known. As a characteristic technology of this type of direct injection engine, for example, fuel is injected during the compression stroke at the time of start-up or low load, and the air-fuel mixture is biased in the vicinity of the spark plug. There are known techniques for reducing pumping loss, reducing fuel adhering to the wall surface at the time of start-up, and reducing the air-fuel mixture present in the flame extinguishing layer near the combustion chamber ceiling, and reducing exhaust specific components such as HC, Furthermore, among these, in order to bias the air-fuel mixture in the vicinity of the spark plug, for example, a technique as described in Patent Document 1 below is known.

  According to Patent Document 1, a cylindrical concave bowl (cavity) for maintaining and storing a tumble and a concave portion deeper than this are formed on the top surface portion of the piston. The length of the recess is long when it is assumed that the operation is centered on the stratified low load region, and is short when it is operated mainly on the high load region. By this recess, the fuel spray injected from the fuel injection valve is guided to the vicinity of the spark plug, and a good air-fuel mixture can be formed in the vicinity of the spark plug in a wider operating range than before.

JP 2000-130171 A

However, the conventional direct injection engine configured as described above has the following problems.
That is, as described in the above prior art, even if the air-fuel mixture can be stably supplied in the vicinity of the spark plug at a certain engine speed or load range, if the speed or load fluctuates, the fuel is supplied. There is a problem that it is impossible to guide the concave portion at an optimal timing, and one piston specification cannot cope with a wide range of rotation speeds and loads.

  In addition, when the load is high or when the rotation is high, the amount of intake air increases and the air flow, that is, the tumble (vertical vortex) tends to become strong. When the inventors of the present application conducted an experiment, the fuel injected at a high load cannot overcome this air flow, and a large amount of fuel stays on the intake valve side of the combustion chamber. It became clear that problems such as a decrease in usage rate and a decrease in output occurred. As another method for solving this, a method of injecting fuel from the upper side of the piston in the vicinity of the ignition plug is known. As this is required, space constraints are imposed and the system tends to be expensive. In addition, it is difficult to make the air-fuel mixture stably exist in the vicinity of the ceiling portion of the combustion chamber this time, and there is a problem that the air utilization rate similarly decreases at high loads.

  The present invention has been made in view of the above circumstances, and an object thereof is a direct injection capable of forming a good stratified mixture in a wide range of rotation speeds at a low load under a relatively simple configuration. To provide an engine.

  Another object of the present invention is to provide a direct-injection engine that can mix air and fuel satisfactorily at high loads even when the air flow becomes strong, has a high air utilization rate, and can achieve high output. It is in.

  In order to achieve the above object, a direct injection engine according to the present invention basically injects fuel directly into a piston slidably inserted into a cylinder and a combustion chamber defined above the piston. A fuel injection valve having a plurality of injection ports, a spark plug provided adjacent to the combustion chamber, a tumble generating means provided in an intake system for generating a tumble in the combustion chamber, and a fuel injection mode by the fuel injection valve And control means for controlling.

  The top surface of the piston is provided with a recess for maintaining and storing the tumble without breaking, and the recess is injected from at least one of the plurality of injection ports in the fuel injection valve. When the fuel spray is collided and reflected, and the piston is located in a predetermined angle range when viewed from the crank angle, the fuel spray colliding with the spray reflective surface is applied to the spark plug. It is characterized by being reflected toward.

  In a more preferred specific embodiment of the direct injection engine according to the present invention, basically, a piston is slidably fitted into a cylinder, and fuel is directly fed into a combustion chamber defined above the piston. Based on a fuel injection valve having a plurality of injection ports for injection, a spark plug provided in the combustion chamber, a tumble generating means provided in an intake system for generating a tumble in the combustion chamber, and an engine operating state Control of fuel injection mode such as fuel injection timing, fuel injection amount, number of injections, etc. in one combustion cycle by the fuel injection valve, control of ignition timing by the spark plug, operation control of the tumble generating means, etc. Control means.

  The top surface of the piston is provided with a recess having a substantially cylindrical bottom that extends in the intake-exhaust direction along the turning direction of the tumble so as to maintain and preserve the tumble without breaking it. The fuel injection valve is provided adjacent to the intake side of the combustion chamber so that fuel spray injected from at least one of the plurality of injection ports is directed to the recess of the piston. When fuel injection is performed within a predetermined angle before compression top dead center by the control means, at least one fuel spray toward the recess collides and is reflected toward the spark plug. A spray reflecting surface extending in the intake-exhaust direction, which is a flat surface or a curved surface in which the inclination angle, curvature, etc. are set, is provided.

  In another preferred embodiment of the direct injection engine according to the present invention, basically, a piston slidably fitted in a cylinder and a combustion chamber defined above the piston directly. A fuel injection valve having a plurality of injection ports for injecting fuel; a spark plug provided in the combustion chamber; a tumble generating means provided in an intake system for generating tumble in the combustion chamber; and an engine operating state Based on the fuel injection timing, the fuel injection amount, the number of injections, etc. in one combustion cycle by the fuel injection valve, the control of the ignition timing by the spark plug, the operation control of the tumble generating means, etc. And a control means for performing.

  The top surface of the piston is provided with a recess having a substantially cylindrical bottom that extends in the intake-exhaust direction along the turning direction of the tumble so as to maintain and preserve the tumble without breaking it. The fuel injection valve is provided adjacent to the intake side of the combustion chamber so that fuel spray injected from at least one of the plurality of injection ports is directed to the recess of the piston. When fuel is injected into the recess at a predetermined angle after exhaust top dead center by the control means, at least one fuel spray toward the recess collides with the spark plug at the ceiling of the combustion chamber. A spray reflecting surface extending in the intake-exhaust direction, which is a flat surface or a curved surface with a tilt angle, a curvature, etc., is provided so as to reflect toward the exhaust side.

  In a preferred aspect of the present invention, the combustion chamber is a pent roof type or a hemispherical type, and the spark plug is provided in the center of the ceiling portion of the combustion chamber.

  Preferably, the control means is configured to change the fuel injection mode so that the reflection direction of the fuel spray colliding with the spray reflection surface is different between a low load and a high load.

  In another preferred aspect, the control means is configured to perform fuel injection divided into a plurality of times during one combustion cycle when the engine is in a predetermined operating state, and at least one of the divided injections. At times, the fuel spray reflected and reflected by the spray reflecting surface is directed to the spark plug, and at the time of another injection, the fuel spray reflected by the spray reflecting surface is reflected by the It is made to point to parts other than a spark plug.

  In another preferred embodiment, the fuel spray toward the recess, the normal to the collision point of the fuel spray, and the spark plug are in the same plane.

  In another preferred aspect, a bottom groove for mainly maintaining and storing the tumble and a spray reflecting surface for mainly reflecting the fuel spray are juxtaposed in the recess.

  In another preferred embodiment, a surface for mainly maintaining and storing the tumble and a spray reflecting surface for mainly reflecting the fuel spray are separately provided in the recess.

  In another preferred aspect, the fuel spray injected from at least one of the plurality of injection ports of the fuel injection valve is directed directly to the spark plug, and the directly directed fuel spray and the spray reflection The time required to reach the vicinity of the spark plug differs from the fuel spray reflected from the surface and directed to the spark plug mainly due to the length of the path.

  In another preferred aspect, the fuel spray reflected by the spray reflecting surface and directed to the spark plug changes in timing when it reaches the vicinity of the spark plug by changing the collision point according to the lift position of the piston. Thus, the time during which the air-fuel mixture stays around the spark plug is extended.

  In another preferred embodiment, at least two fuel sprays injected from the fuel injection valve are reflected by the spray reflecting surface and directed toward the spark plug, and the control means is configured to bring the engine into a predetermined operating state. At one time, during one combustion cycle, fuel injection is divided into a plurality of times, and at least two fuel sprays reflected by the spray reflecting surface and directed to the spark plug mainly have injection timing and the length of the path. Accordingly, the timing of reaching the vicinity of the spark plug is made different so that the time during which the air-fuel mixture stays around the spark plug is extended.

The effects of the present invention are listed as follows.
First, at the time of start-up or at a low load, by performing compression stroke injection, a combustible air-fuel mixture can be formed only in the vicinity of the spark plug, and a stratified combustion operation becomes possible. This makes it possible to stably perform ignition combustion while reducing the pumping loss by inhaling a large amount of air even at low load, enabling efficient combustion while suppressing misfire and combustion fluctuation become. In addition, since it is difficult for the fuel to adhere to the piston or the combustion chamber wall, it is possible to suppress the discharge of unburned hydrocarbons (HC).

  In addition, when the load is high, by performing the intake stroke injection, the fuel spray diffuses along the flow of the tumble, so that a homogeneous mixture is formed in the combustion chamber, thereby improving the combustion efficiency and the air utilization rate. As a result, high torque can be obtained while improving fuel efficiency.

  Furthermore, by performing split injection, even if the fuel spray has the same direction, the first injection and the second injection can be led to different parts, while controlling the reach of the fuel spray A good air-fuel mixture can be formed at an appropriate air-fuel ratio while reducing wall surface adhesion, and ignition combustibility can be improved, HC can be reduced, and air utilization can be improved simultaneously.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a cylinder injection engine of the present invention will be described with reference to the drawings.
FIG. 1 and FIG. 2 are a schematic configuration diagram and a schematic plan view, respectively, showing an embodiment (common to each example) of a direct injection engine according to the present invention.
The illustrated direct injection engine 90 is an in-vehicle in-line four-cylinder engine, for example, and includes a cylinder 92 and a piston 107 slidably fitted into each cylinder 92 (only one cylinder is shown). A pent roof type combustion chamber 95 is defined above the piston 107. In the combustion chamber 95, a spark plug 113 to which a high voltage is applied via the ignition coil 114 is erected in the center of the ceiling (on the cylinder center line), and combustion is performed on the intake passage (intake port) 101 side. A fuel injection valve 122 for directly injecting fuel into the chamber 95 is provided sideways.

  The fuel injection valve 122 is a multi-hole type having a plurality of (for example, four) injection ports (nozzle holes), and is directed to at least one of the plurality of injection ports, that is, a fuel spray injected therefrom. 125 a, 125 b 1, 125 b 2 are directed to the piston 107 (the top surface portion thereof), and at least one of the remaining injection ports, that is, the fuel spray 124 injected therefrom is directed to the spark plug 113. (Each embodiment will be described in detail later).

  Air to be used for combustion of fuel is taken in from an air cleaner 106 provided at the start end of the intake passage 101, passes through an air flow sensor 105, passes through an electric throttle valve 108, and enters a collector 116. The air is distributed to the downstream passage portion (intake pipe, intake port) 101A of the intake passage 101 connected to the cylinder and sucked into the combustion chamber 95 through the intake valve 111 disposed at the downstream end thereof.

  The air-fuel mixture of the air sucked into the combustion chamber 95 and the fuel injected from the fuel injection valve 122 is ignited by the spark plug 113 and explosively burned, and the combustion waste gas (exhaust gas) passes through the exhaust valve 112. The exhaust gas is discharged to the exhaust passage 110, purified by the three-way catalyst 115 disposed in the exhaust passage 110, and then discharged to the outside through the silencer 117.

  A downstream passage portion (intake pipe, intake port) 101A of the intake passage 101 is divided into an upper passage portion 101a and a lower passage portion 101b by a partition plate 102 so as to generate a tumble (vertical vortex) 120 in the combustion chamber 95. An intake control valve 103 is disposed at the upstream end portion of the lower passage portion 101b, and the lower passage portion 101b is selectively opened and closed by the intake control valve 103. It is designed to adjust the intensity.

  The in-cylinder injection engine 90 of the present embodiment incorporates a microcomputer to control each part of the engine 90 including the fuel injection valve 122, the spark plug 113, the intake control valve 103, and the electric throttle valve 108. A control unit 200 is provided.

  The control unit 200 is well known per se, and is composed of MPU, EP-ROM, RAM, I / OLSI including an A / D converter, etc., and measured by a fuel pressure sensor 133 as an input signal. The signal corresponding to the fuel pressure in the fuel gallery 132, the signal corresponding to the intake air amount detected by the air flow sensor 105, the signal corresponding to the opening of the throttle valve 108 detected by the throttle sensor 104, the crank angle In addition to a signal indicating the rotational speed of the crankshaft from the sensor 97, that is, the engine speed, not shown, but depending on, for example, the oxygen concentration in the exhaust gas detected by the air-fuel ratio sensor disposed in the exhaust passage 110 A signal corresponding to the engine coolant temperature detected by the water temperature sensor disposed in the cylinder 92, Signal indicating the beginning of startup from Knitting Deployment switch (cranking start), a signal indicating a depression amount of an accelerator pedal obtained from an accelerator sensor, a signal or the like corresponding to the running speed of the vehicle obtained from the vehicle speed sensor is also provided.

  The control unit 200 fetches each signal with a predetermined period, grasps the operating state of the engine based on the signal, executes a predetermined calculation process based on the operating state, and calculates a control signal calculated as a result of the calculation. Is supplied to the fuel injection valve 122, the ignition plug 113, the intake control valve 103, the electric throttle valve 108, etc., and fuel injection mode (fuel injection amount = injection pulse width, injection timing, number of injections) control, ignition timing control Then, the opening control of the intake control valve 103, the opening control of the throttle valve 108, and the like are executed.

  Here, the control unit 200 basically requires air flow when the load is low, so the intake control valve 103 is controlled in the closing direction to control the tumble strength to be optimum, and the stratification is performed. In order to perform the combustion operation, fuel injection is performed in the compression stroke. On the other hand, at the time of high load, in order to perform homogeneous combustion operation, the intake control valve 103 is opened, and fuel injection is performed in the intake stroke.

  As for fuel injection, when an injection pulse signal is given from the control unit 200 to the fuel injection valve 122, each injection port of the fuel injection valve 122 is opened in a valve opening time corresponding to the pulse width (duty ratio), and each injection is performed. Fuel is injected from the mouth. In this case, since the actual fuel injection amount varies depending on the valve opening time and the pressure in the fuel gallery 132 measured by the fuel pressure sensor 133, the control unit 200 determines the pulse width in consideration of the fuel pressure. It has become.

Next, each embodiment (mainly the specifications of the piston 107 and the fuel injection valve 122) will be described.
<Example 1>
In the first embodiment, as shown in FIGS. 3, 4A, and 4B, the top surface of the piston 107 is tumbled so as to maintain and store the tumble 120 (see FIG. 1) without breaking it. A central bottom surface 107a curved in a cylindrical shape extending in the intake-exhaust direction (Y-Y direction) along the turning direction of 120, and a side inclined surface 107b1 formed between the central bottom surface 107a and the side surfaces 107c1, 107c2. , 107b2 is provided with a recess 107A. In this embodiment, the center bottom surface 107a and the side inclined surfaces 107b1 and 107b2 are spray reflecting surfaces (described later).

  Further, in this example, the fuel injection valve 122 is provided with four injection ports, and one direction thereof, that is, the fuel spray (axis line) 124 injected therefrom is arranged on the cylinder center line O. The spark plug 113 is directed to one of the remaining three injection ports, that is, the fuel spray (axis) 125a injected from the direction of the center in the width direction of the central bottom surface 107a. The other two directions, that is, the fuel sprays (axis lines) 125b1 and 125b2 injected therefrom are directed to the center in the width direction of the inclined surfaces 107b1 and 107b.

  Here, assuming that the collision points of the fuel sprays 125a, 125b1, 125b2 with the central bottom surface 107a and the side inclined surfaces 107b1, 107b2 are A, B1, B2, respectively, the fuel sprays 125a at these collision points A, B1, B2 The specifications of the piston 107 and the fuel injection valve 122 are set so that the incident angle and the reflection angle of 125b1, 125b2 are substantially equal.

  Further, the fuel spray 125b1 (injection port of the fuel injection valve 122), the normal extending from the collision point B1 of the fuel spray 125b1, and the spark plug 113 are in the same plane. Similarly, the fuel spray 125b2 (fuel injection valve) 122), the normal extending from the collision point B2 of the fuel spray 125b2, and the spark plug 113 are also in the same plane. In this embodiment, the angle between these planes and the horizontal plane is about 30 °. ing. Further, the plane including the collision point A of the fuel spray 125a, the spark plug 113, and the fuel injection valve 122 is substantially orthogonal to the horizontal plane.

  With this configuration, the fuel sprays 125b1 and 125b2 directed toward the piston 107 are reflected and guided in the direction of the spark plug 113, so that the fuel spray 124 that directly reaches the vicinity of the spark plug 113 is combined with the vicinity of the spark plug 113. Thus, the combustible air-fuel mixture 121 can be formed only in the stratified combustion operation. As a result, fuel can be distributed only in the vicinity of the spark plug 113 when the load is low, and the stratification degree of the air-fuel mixture can be increased. Therefore, ignition can be performed while reducing the pumping loss by inhaling a large amount of air even when the load is low. Combustion can be stably performed, and efficient combustion can be performed while suppressing misfire and combustion fluctuation. In addition, since it is difficult for the fuel to adhere to the piston 107 and the combustion chamber wall, the discharge of unburned hydrocarbon (HC) can be suppressed.

<Example 2>
FIG. 5 schematically shows the shape of the top surface of the piston 107 in the second embodiment. In the following, the specification (top surface shape) of the piston 107 of the second embodiment and its setting method will be described with reference to FIGS. 6, 7, and 8. For the sake of simplicity, the inside of the recess 107B in FIGS. 6 to 8 will be described by dividing it into several planes 1 to 20 as shown in FIG. Note that this description is for one side of the fuel spray 125b, that is, the spray 125b1, and the spray 125b2 has a symmetrical relationship with respect to the center line in the width direction of the recess 107A, and thus the description is omitted. Further, the configuration of the fuel injection valve 122 and the spray 124 directly directed to the ignition plug 113 are basically the same as those in the first embodiment, and thus the description thereof is omitted.

  In the same manner as in the first embodiment, the top surface portion of the piston 107 of the present embodiment is arranged in the intake-exhaust direction so as to follow the turning direction of the tumble 120 in order to maintain and preserve the tumble 120 (see FIG. 1) without breaking it. A recess 107B having an elongated central bottom groove 107i, 107i curved in a cylindrical shape is provided. The recess 107B is provided with a central protrusion 107g having a constant width between the central bottom grooves 107i-107i, and a constant width between the central bottom grooves 107i, 107i and the side faces 107c1, 107c2. Side inclined protrusions 107h1 and 107h2 are provided. Small recesses 107m, 107j, 107m are provided on the intake side of the central projecting surface 107g and the side inclined projecting surfaces 107h1, 107h2, and large recesses 107n are provided from the ends of the small recesses 107j, 107m, 107m to the exhaust side. 107k and 107n are provided.

  The central projecting surface 107g and the side inclined projecting surfaces 107h1 and 107h2 correspond to the central bottom surface 107a and the side inclined surfaces 107b1 and 107b2 in the first embodiment, respectively, and the fuel spray 125a collides with the central projecting surface 107g. The fuel sprays 125b1 and 125b2 collide with the side inclined protrusions 107h1 and 107h2, respectively, and are reflected.

  Here, as shown in FIGS. 6 and 8, the fuel spray 125 a (and 125 b 1 and 125 b 2) always flows in the same direction from the individual injection ports of the fuel injection valve 122 regardless of the position of the piston 107. Head.

  Next, the fuel injection mode will be described separately for the case of the compression stroke injection and the case of the intake stroke injection. At the time of the compression stroke injection, that is, when the piston 107 is in the compression stroke, for example, 20 degrees before the compression top dead center in the crank angle, the piston 107 is at the position shown by p in FIG. At this time, the spray 125a directed to the central projecting surface 107g of the piston 107 collides with the surface S1 in FIG. 7, and the spray 125b1 directed outward from this impinges on the surface S5 in FIG. At this time, the inclination angle, curvature, etc. of the surface S1 are set so that the incident angle on the fuel injection valve 122 side and the reflection angle on the spark plug 113 side are substantially equal with respect to the normal line of the surface S1. The same applies to the surface S5, but since the spray is directed outward from the cylinder center line, the surface S5 is an inclined surface that falls toward the central bottom groove 107i.

  Prior to the above, when the crank angle is 30 degrees before compression top dead center, the position of the piston 107 is lower than that at 20 degrees before compression top dead center, and is at the position q in FIG. At this time, the fuel spray 125a collides with the surface S2. As shown in FIG. 8, the spray 125b1 collides with the surface S10 outside the surface S6 because the reaching point spreads outward when the distance from the piston 107 increases. At this time, as in the case of 20 degrees before compression top dead center, the inclination angles and curvatures of the surfaces S2 and S10 are set so that the incident angle and the reflection angle are substantially equal with respect to the normal line of each surface. Is set.

  On the other hand, at the time of intake stroke injection, that is, when the piston 107 is at the intake stroke, for example, at 40 degrees after exhaust top dead center at the crank angle, the piston 107 is at a position r lower than the above state. The fuel spray 125a and the fuel spray 125b1 collide with the surface S3 and the surface S15, respectively. Since the air-fuel mixture is diffused in the intake stroke to increase the air utilization rate, the position where the air-fuel mixture is reflected differs from the case of p or q described above, and is closer to the exhaust side than the spark plug 113 in the ceiling portion of the combustion chamber 95. For example, the point T is directed. Here, in the same procedure as described above, when the normal line of the surfaces S3 and S15 is used as a reference, the incident angle on the fuel injection valve 122 side and the reflection angle toward the point T are equal to each other. Set the tilt angle and curvature.

  When the piston 107 injects fuel at a position s 50 degrees after exhaust top dead center, the fuel sprays 125a and 125b1 are closer to the exhaust side than the spark plug 113 and the point T at the ceiling of the combustion chamber 95. For example, the inclination angles and curvatures of the surfaces S4 and S20 are set so as to be directed to the point U.

  It should be noted that the surface on which the spray does not collide, for example, the inclination angle and curvature of the surface S6, keeps continuity with the surfaces S5 and S10, and effectively uses the tumble 120 generated in the combustion chamber 95. It is formed with a smooth surface so that it can be maintained and preserved. The same applies to other aspects.

  Further, since the movement of the piston 107 is continuous, all of the fuel spray 125a and the fuel spray 125b1 hold the spark plug 113 between 20 and 30 degrees before compression top dead center, preferably around 35 degrees before compression top dead center. In this embodiment, it is divided into two stages. However, if the piston position is multistage, even if the surface is divided finely, the inclination angle and Curvature etc. can be set. If this idea is developed, each surface may be constituted by a smooth curved surface instead of a continuous mesh-shaped plane. The lateral width of each surface may be determined according to the spread when the sprays 125a and 125b1 collide with the piston 107 and the spread to the outside of the spray arrival point when the piston 107 moves downward. At this time, if the width of the reflecting surface is too wide, the effect of the piston 107 maintaining and preserving the tumble 120 is diminished, so the total width of the central projecting surface 107g and the side inclined projecting surfaces 07h1 and 107h2 as the reflecting surface is a recess. It is desirable that the ratio is about 30 to 70%, preferably about 50% with respect to the entire width of 107B. By performing these examinations in order, a curved surface as shown in FIG. 5 can be formed.

  FIG. 9 shows an air-fuel mixture formation state at the time of compression stroke injection in Example 2 (at the time of stratified combustion operation = low load). In this example, it is assumed that the fuel sprays 125a and 125b (1,2) are reflected by the piston 107 between 20 degrees and 30 degrees before compression top dead center, that is, between q and p in the figure. The fuel injection timing is injected several degrees earlier at the crank angle in consideration of the time until the spray 125 exits the fuel injection valve 122 and reaches the piston 107. On the other hand, a plurality of (four in this case) fuel sprays are injected from the fuel injection valve 122 (injection ports thereof), and the fuel spray 124 is a spray directed directly to the spark plug 113. Although spraying is performed at the same time, the spray 124 reaches the plug 113 first because of the difference in the reach distance, and then the spray 125a reflected by the central projecting surface 107g and then 125b reflected by the outer side. In this way, by allowing the sprays 124, 125a, and 125b to reach the vicinity of the spark plug 113 with a time difference, the air-fuel mixture 126 can exist for a long time in the vicinity of the spark plug 113, and stable stratified combustion can be performed.

  FIG. 10 shows an air-fuel mixture formation state during intake stroke injection (during homogeneous combustion operation = high load) in the second embodiment. Since the load is high, the fuel injection amount, that is, the injection pulse width is large, and the injection is started from around 40 degrees after the top dead center of the exhaust stroke. The end of injection is near the bottom dead center of the intake stroke. The sprays 125a and 125b (1,2) toward the piston 107 are the central projecting surface 107g and the side inclined projecting surfaces until 40 to 50 degrees after the top dead center shown in the figure, that is, until the piston 107 reaches r to s. Reflected by 107h1 and 107h2 and diffused to the exhaust side. On the other hand, the spray 124 directly directed to the spark plug 113 mainly reaches the intake valve 111 side, and forms an air-fuel mixture 126 therearound. Since it is the intake stroke injection, the intake flow flows along the central bottom grooves 107i and 107i of the recess 107B to form the tumble 120. The sprays 125a and 125b (1, 2) diffuse along this flow, thereby forming a homogeneous air-fuel mixture in the combustion chamber 95, thereby improving combustion efficiency and air utilization rate, and improving fuel efficiency. It is possible to obtain a high torque while aiming.

  11 and 12 show changes in the air-fuel mixture formation state in the intake stroke and the compression stroke, respectively, when two injections of the intake stroke (first time) and the compression stroke (second time) are performed. The injection (first time) in the intake stroke shown in FIG. 11 is sprayed 125a onto the piston 107 (the central projecting surface 107g and the side inclined projecting surfaces 107h1, 107h2) between 40 degrees and 50 degrees after exhaust top dead center. And 125b (1,2) are reached. As a result, as in the case shown in FIG. 10, the fuel spray 124, 125 a, 125 b causes the spray 125 to diffuse widely from the intake valve 111, the spark plug 113 to the exhaust valve 112, and is mixed with the tumble 120 to achieve homogeneous mixing. A gas 126 is formed.

  The injection (second time) in the compression stroke shown in FIG. 12 is performed so as to be reflected by the piston 107 at 20 to 30 degrees before the compression top dead center, as in the case shown in FIG. The stratified fuel spray 125 reaches the vicinity of 113. In this way, a homogeneous air-fuel mixture 126 exists in the entire combustion chamber 95, and a rich air-fuel mixture 125 is formed only in the vicinity of the spark plug 113, resulting in a weakly stratified state and increasing the air utilization rate while stabilizing the combustion. For example, the exhaust temperature can be raised to reduce HC during fast idling immediately after startup.

<Example 3>
FIG. 13 shows the configuration of the piston 107 and the fuel injection valve 122 of the third embodiment. The basic configuration of the piston 107 and the fuel injection valve 122 of the present embodiment is the same as that of the second embodiment, but the fuel spray from the fuel injection valve 122 toward the piston 107 is increased by one from the left and right from the second embodiment to make a total of five. Yes. That is, two fuel sprays (fuel sprays 125b1 and 125b3 and fuel sprays 125b2 and 125b4) collide and be reflected on the side inclined protrusions 107h1 and 107h2, respectively. In this case, the shapes of the side inclined protrusions 107h1 and 107h2 are slightly changed, and the widths of the fuel sprays 125b3 and 125b4 near the outside of the piston are wider than the fuel sprays 125b1 and 125b2 of the second embodiment.

  Hereinafter, the fuel sprays 125b1 and 125b3 on one side will be described. When the piston 107 is at a crank angle of 20 degrees before compression top dead center, the spray 125b1 collides with the surface S5 and the spray 125b3 collides with the surface S9. The inclination angle and curvature of the surface are set so as to reach the vicinity. When the piston 107 descends, the collision positions of the fuel sprays 125b1 and 125b3 on the side inclined protrusions 107h1 are such that the spray 125b1 is the surface S6, the surface S11, the surface S16, and the spray 125b3 is the surface S14, the surface S19, In this case, the sprays 125b1 and 125b are located in the vicinity of the spark plug 113 or in a portion closer to the exhaust side than the spark plug 113 in the ceiling portion of the combustion chamber 95, as described above. What is necessary is just to set the inclination angle, curvature, etc. of each surface so that it may face. Of the surfaces S1 to S24, the surfaces on which the sprays do not collide are arranged as smoothly as possible so that the tumble 120 can be maintained and stored in consideration of the angle with the other surfaces.

<Example 4>
FIG. 14 shows the configuration of the piston 107 and the fuel injection valve 122 of the fourth embodiment. The basic configuration of the piston 107 and the fuel injection valve 122 of this embodiment is the same as that of the second embodiment, but the shapes of the side inclined protrusions 107h1 and 107h2 are slightly changed. More specifically, in this embodiment, when the piston 107 is at 40 to 50 degrees after exhaust top dead center, that is, when the fuel spray 125b1 and 125b2 are mainly reflected in the intake stroke, the fuel spray 125b1 and 125b2 is The direction of collision and reflection on the side inclined protrusions 107h1 and 107h2 is toward the outer peripheral side of the ignition plug 113 at the ceiling of the combustion chamber 95 and toward the opposing wall side of the combustion chamber 95 when viewed from the fuel injection valve 122. As described above, the inclination angle, curvature, and the like of the side inclined protrusion surfaces 107h1 and 107h2 are set.

  With this configuration, the air-fuel mixture 126 at the time of intake stroke injection can be widely distributed in the combustion chamber 95 to obtain a higher torque, or the exhaust gas temperature can be increased at the start.

  15A, 15B, 15C, and 15D show a comparison between the direct injection engine (product of the present invention) 90 of the present embodiment and a conventional example. As can be seen from FIG. 15, the product of the present invention can perform stratified combustion more stably than the conventional example, so the pumping loss is reduced by reducing the air-fuel ratio or increasing the EGR amount, and the fuel consumption amount. Can be reduced. Furthermore, since the fuel adhesion to the piston 107 and the wall surface of the cylinder 92 can be suppressed, the amount of HC emission can be reduced. Immediately after the engine is started, a weak stratified mixture is formed by two injections of the intake stroke and the compression stroke, etc., and the ignition timing is delayed to promote afterburning and the exhaust temperature can be raised. At this time, as shown in FIG. 16, warming-up (activation) of the exhaust purification catalyst is completed at an early stage while reducing the HC emission amount due to the exhaust gas temperature rise, and the accumulated HC emission amount after starting can be suppressed. it can.

  In addition, this invention is not necessarily limited to the said embodiment (Example), Of course, a various change may be added to a piston and a fuel injection valve. For example, in the above-described embodiment, the fuel injection valve 122 whose fuel spray injection direction is unchanged (fixed) is used. Instead, a fuel injection valve that can change the number and direction of the spray according to the operating state is used. In this case as well, a good stratified combustion operation and homogeneous combustion operation can be realized by setting the inclination angle and curvature of the reflecting surface in the same manner as in the above embodiment.

  Further, for example, when the piston 107 is in the vicinity of the top dead center, the reflected spray is directed toward the outer peripheral side of the spark plug 113 in the ceiling portion of the combustion chamber 95, and when the piston is lowered further than this. The spark plug may be directed, or the spray may be directed to the vicinity of the spark plug in a wider crank angle range.

  Further, in the above embodiment, the angle of inclination of the reflecting surface is set so that the incident angle and the reflection angle are substantially equal to the normal at the collision point of the fuel spray, but when the air flow is strong such as tumble. In consideration of the influence, the inclination angle of the reflecting surface may be determined, and when the incident angle reaches a large angle of, for example, 45 degrees or more, a so-called wall guide is formed in which the spray flows along the piston surface. In some cases, the present invention may be combined with these known methods for inducing spray or air-fuel mixture.

1 is a schematic configuration diagram showing an embodiment of a direct injection engine according to the present invention. 1 is a schematic plan view showing an embodiment of a direct injection engine according to the present invention. FIG. 3 is a plan view of a piston top surface portion used for explanation of fuel spray behavior and the like in the first embodiment. It is a figure with which it uses for description of the behavior of fuel spray, etc. in Example 1, (A) is XX arrow sectional drawing of FIG. 3, (B) is YY arrow sectional drawing of FIG. FIG. 5 is a bird's-eye view of a piston used in Example 2. FIG. 6 is a cutaway side view for explaining fuel spray behavior and the like in the second embodiment. The conceptual diagram with which it uses for description of examples, such as the behavior of the fuel spray in Example 2. FIG. FIG. 6 is a cutaway side view for explaining another example such as the behavior of fuel spray in the second embodiment. FIG. 6 is a cutaway side view for explaining the air-fuel mixture formation during stratified combustion in the second embodiment. FIG. 6 is a cutaway side view for explaining the air-fuel mixture formation at the time of high load in Example 2. FIG. 9 is a cutaway side view for explaining the formation of the air-fuel mixture in the first injection when the injection is performed twice in the intake stroke and the compression stroke in the second embodiment. FIG. 6 is a cutaway side view used for explaining the formation of the air-fuel mixture in the second injection when the injection is performed twice in the intake stroke and the compression stroke in the second embodiment. The conceptual diagram with which it uses for description of the behavior etc. of the fuel spray in Example 3. FIG. FIG. 9 is a cutaway side view for explaining the fuel spray behavior and the like in the fourth embodiment. The figure which is provided for the comparative explanation of (A) fuel consumption, (B) torque, (C) exhaust temperature, and (D) HC emission amount in the product of the present invention and the conventional example. The figure which is provided for the comparison explanation of the time change of HC discharge amount at the time of starting in the present invention and a conventional example.

Explanation of symbols

90 ... direct injection engine 92 ... cylinder 95 ... combustion chamber 101 ... intake passage 102 ... partition plate 103 ... intake control valve 107 ... piston 107A ... recess 107a ... center bottom surface (spray reflection surface)
107b1, 107b2 ... side inclined surfaces (spray reflection surfaces)
110 ... Exhaust passage 111 ... Intake valve 112 ... Exhaust valve 113 ... Ignition plug 114 ... Ignition coil 115 ... Catalyst 116 ... Collector 120 ... Tumble 121 ... Mixture 122 ... Fuel injection valve 124 ... Fuel spray 125a directly directed to the ignition plug ... Fuel sprays 125b1, 125b2 reflected by collision with the central bottom surface of the recess ... Fuel sprays 200 reflected by collision with the inclined side surfaces of the recess ... Control unit

Claims (12)

A piston slidably inserted into the cylinder, a fuel injection valve having a plurality of injection ports for directly injecting fuel into the combustion chamber defined above the piston, and an ignition plug provided adjacent to the combustion chamber; A direct injection engine comprising: tumble generating means provided in an intake system for generating tumble in the combustion chamber; and control means for controlling a fuel injection mode by the fuel injection valve,
The top surface portion of the piston is provided with a recess for maintaining and storing the tumble without breaking, and the fuel injected from at least one of the plurality of injection ports in the fuel injection valve into the recess When a spray reflecting surface is provided to reflect and collide with the spray, and when the piston is located within a predetermined angle range when viewed from the crank angle, the fuel spray that has collided with the spray reflecting surface is directed toward the spark plug. A direct injection engine characterized by being reflected. A piston slidably inserted into the cylinder, a fuel injection valve having a plurality of injection ports for directly injecting fuel into the combustion chamber defined above the piston, and an ignition plug provided adjacent to the combustion chamber; , Tumble generating means provided in the intake system to generate tumble in the combustion chamber, and fuel injection timing, fuel injection amount, number of injections, etc. in one combustion cycle by the fuel injection valve based on the engine operating state A direct-injection engine comprising: a fuel injection mode control; an ignition timing control by the spark plug; and a control means for controlling the operation of the tumble generating means,
The top surface of the piston is provided with a recess having a substantially cylindrical bottom that extends in the intake-exhaust direction along the swivel direction of the tumble so as to maintain and preserve the tumble without breaking, The fuel injection valve is provided on the intake side of the combustion chamber so that fuel spray injected from at least one of the plurality of injection ports is directed to the recess of the piston. When the fuel injection is performed within the predetermined angle before the compression top dead center by the control means, the inclination is such that at least one fuel spray toward the recess collides and is reflected toward the spark plug. A direct-injection engine having a spray reflecting surface extending in an intake-exhaust direction, which is a flat surface or curved surface, in which an angle, a curvature, and the like are set. A piston slidably inserted into the cylinder, a fuel injection valve having a plurality of injection ports for directly injecting fuel into the combustion chamber defined above the piston, and an ignition plug provided adjacent to the combustion chamber; , Tumble generating means provided in the intake system to generate tumble in the combustion chamber, and fuel injection timing, fuel injection amount, number of injections, etc. in one combustion cycle by the fuel injection valve based on the engine operating state A direct-injection engine comprising: a fuel injection mode control; an ignition timing control by the spark plug; and a control means for controlling the operation of the tumble generating means,
The top surface of the piston is provided with a recess having a substantially cylindrical bottom that extends in the intake-exhaust direction along the swivel direction of the tumble so as to maintain and preserve the tumble without breaking, The fuel injection valve is provided on the intake side of the combustion chamber so that fuel spray injected from at least one of the plurality of injection ports is directed to the recess of the piston. When the fuel injection is performed at a predetermined angle after the exhaust top dead center by the control means, at least one fuel spray directed toward the recess collides with the spark plug at the exhaust chamber on the ceiling side of the combustion chamber. A direct-injection engine having a spray reflecting surface extending in the intake-exhaust direction, which is a flat surface or curved surface with a tilt angle, a curvature, etc. set so as to be reflected toward the Down.   4. The direct injection engine according to claim 1, wherein the combustion chamber is a pent roof type or a hemispherical type, and the ignition plug is provided in the center of a ceiling portion of the combustion chamber. 5. .   2. The fuel injection mode according to claim 1, wherein the control means is configured to change a fuel injection mode so that a reflection direction of the fuel spray colliding with the spray reflection surface is different between a low load and a high load. The direct injection engine according to any one of 1 to 4.   The control means is configured to perform fuel injection in one combustion cycle divided into a plurality of times when the engine is in a predetermined operation state, and at least at the time of one of the divided injections, The fuel spray reflected and collided with the spray reflecting surface is directed to the spark plug, and at the time of another injection, the fuel spray reflected and collided with the spray reflecting surface is a part other than the spark plug. The direct-injection engine according to any one of claims 1 to 5, wherein the direct-injection engine is directed toward the engine.   The direct injection engine according to any one of claims 1 to 6, wherein the fuel spray toward the recess, the normal to the collision point of the fuel spray, and the spark plug are in the same plane. .   The bottom surface groove for mainly maintaining and preserving the tumble and the spray reflecting surface for mainly reflecting the fuel spray are arranged in parallel in the recess. The direct injection engine according to one item.   9. The surface according to claim 1, wherein a surface for mainly maintaining and storing the tumble and a spray reflecting surface for mainly reflecting the fuel spray are separately provided in the recess. The direct injection engine according to one item.   The fuel spray injected from at least one of the plurality of injection ports of the fuel injection valve is directed directly to the spark plug, and is reflected by the spray reflection surface by the direct fuel spray and the spray reflection surface. 10. The fuel spray directed to the spark plug is different in time required to reach the vicinity of the spark plug mainly due to the length of the path. 10. Direct injection engine.   The fuel spray reflected from the spray reflecting surface and directed to the spark plug changes its timing of arrival near the spark plug by changing its collision point according to the lift position of the piston. The direct-injection engine according to any one of claims 1 to 10, wherein a period of time during which the air-fuel mixture stays around the spark plug is extended by the above.   At least two fuel sprays injected from the fuel injection valve are reflected by the spray reflecting surface so as to be directed to the spark plug, and the control means has one combustion cycle when the engine is in a predetermined operating state. The fuel injection is divided into a plurality of times, and at least two fuel sprays reflected by the spray reflecting surface and directed to the spark plug are near the spark plug mainly due to the injection timing and the length of the path. 12. The timing at which the air-fuel mixture reaches the valve is made different so that the time during which the air-fuel mixture stays around the spark plug is extended. 12. Direct injection engine.

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