JP2011247172A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily reduce spray particle size.SOLUTION: A fuel injection device includes a fuel injection valve connected to an ECU, a crank angle sensor, a cylinder pressure sensor and a knocking sensor. The fuel injection valve includes an air introduction passage for introducing air together with swirling fuel into a swirl stabilization chamber provided at an end portion. The air introduction passage is connected to a surge tank through an air pipe on which an air pump and a control valve are arranged. The ECU reduces the supply pressure of air to be introduced into the swirl stabilization chamber by controlling the air pump and the control valve when a crank angle at which the cylinder pressure reaches a peak is observed later than the crank angle forming a threshold on the basis of data acquired from the crank angle sensor and the cylinder pressure sensor. When knocking is observed by the knocking sensor, the ECU increases the supply pressure of air to be introduced into the swirl stabilization chamber by controlling the air pump and the control valve. Air bubbles of the amount corresponding to a fuel amount are generated to atomize the fuel.

Description

  The present invention relates to a fuel injection device.

  Conventionally, proposals aimed at promoting the mixing of fuel and air in the combustion chamber have been made. For example, a fuel injection nozzle in which a spiral passage is formed between a wall surface of a hollow hole of a nozzle body and a sliding surface of a needle valve has been proposed (for example, Patent Document 1). In this proposal, the fuel that has passed through the spiral passage is accelerated as a rotating flow in a fuel reservoir provided at the tip of the nozzle body. The fuel has a tangential velocity of the single injection hole and is diffused into the combustion chamber to be mixed with air.

Japanese Patent Laid-Open No. 10-141183

  By the way, it is known that refinement of the spray particle diameter of the injected fuel is effective for improving the fuel consumption and exhaust emission of the internal combustion engine. Although the said patent document 1 can accelerate | stimulate mixing with fuel and air, since the mixing is performed in a combustion chamber, sufficient atomization of fuel and atomization are not performed by ignition, There was a risk of fuel adhering to the wall.

  Then, this invention makes it a subject to promote refinement | miniaturization of the spray particle size.

  In order to solve the above-described problems, a fuel injection device disclosed in the present specification includes a nozzle body having a nozzle hole provided at a tip portion thereof, and is slidably disposed in the nozzle body, and a fuel is provided between the nozzle body and the nozzle body. A needle having a seat portion that is seated at a seating position in the nozzle body while forming an introduction path, and a swirl component formed in the fuel introduced from the fuel introduction path, formed upstream of the seat portion of the needle A swirl flow generating portion in which a spiral groove is formed, a swirl stabilizing chamber formed at the tip of the nozzle body, into which fuel that has passed through the swirl flow generating portion is introduced, and air in the swirl stabilizing chamber A fuel injection valve comprising: an air introducing means for introducing; a bubble concentration recognizing means for recognizing a bubble concentration with respect to the fuel introduced into the swirl stabilizing chamber; and a bubble recognized by the bubble concentration recognizing means. A pneumatic adjusting means for adjusting the air supply pressure to be introduced into the cornering stability chamber based on the time, and is characterized by comprising.

  The fuel introduced into the spiral groove from the fuel introduction path forms a swirl flow in the swirl stabilizing chamber. The pressure drops near the center of the swirling flow created by the fuel. Air is introduced into the region where the pressure is reduced through the air introduction means. The introduced air creates fine bubbles in the fuel. Since air is introduced into the area where the pressure has decreased, it can be easily introduced into the swirl stabilizing chamber to which high-pressure fuel is supplied. The air can be introduced from the outside of the internal combustion engine body, for example, from a surge tank, or the burned gas remaining in the combustion chamber can be introduced as air.

  The swirl flow velocity of the fuel is faster on the center side in the swirl stabilizing chamber and becomes slower as it approaches the wall surface. Further, in the turning stable chamber, the internal pressure is low on the center side and becomes high as it approaches the wall surface. Under such circumstances, the fine bubbles are more concentrated on the wall surface side as the particle size is smaller. By providing the injection holes in the region where the fine bubbles having a small particle diameter are concentrated, the fine bubbles can be ejected. The injected fine bubbles are ruptured and become atomized fuel after being injected.

  As described above, when the fine bubbles generated in the fuel are injected from the injection hole, a fuel bubble having a shell-like film is formed by the fuel at the gas-liquid interface of the bubbles. At this time, the film thickness of the fuel bubble is constant and uniform due to the surface tension of the fuel. For this reason, excess fuel remains in the original fuel in a state where fine bubbles are mixed, and is used for the formation of fuel bubbles from the next time. Thus, the amount of fuel required for one fine bubble to form one fuel bubble is substantially constant. For this reason, it is calculated | required that the quantity of the bubble mixed with a fuel is an appropriate quantity with respect to the amount of fuel. Therefore, when the amount of fuel is large, a large amount of bubbles is required, whereas when the amount of fuel is small, a small amount of bubbles is sufficient. If the amount of air bubbles is too large, the air bubbles become dense and the liquid film between the air bubbles becomes thin, and it is considered that the air bubbles are coupled. On the other hand, if the amount of bubbles is too small, there is a fuel that is ejected as mere droplets, which may result in a spray with a large particle size. The number of bubbles increases as the amount of supplied air increases. Further, the amount of supplied air changes according to the air pressure. Therefore, the internal combustion engine injection control device disclosed in the present specification adjusts the air supply pressure so as to obtain an appropriate amount of bubbles relative to the amount of fuel.

  The bubble concentration recognizing means observed the in-cylinder pressure together with the crank angle, and the air pressure adjusting means was observed by the bubble concentration recognizing means later than the crank angle at which the crank angle at which the peak in-cylinder pressure was reached became a threshold value. Sometimes the air supply pressure can be reduced. For example, a crank angle and an in-cylinder pressure sensor are used to observe the crank angle and the in-cylinder pressure. When the crank angle at which the peak in-cylinder pressure is reached is delayed from a predetermined crank angle, it can be considered that the number of bubbles is excessive with respect to the fuel amount. Therefore, in this case, an operation for reducing the air supply pressure is performed. Thereby, the amount of bubbles can be reduced, and the fuel amount and the amount of bubbles can be matched.

  The bubble concentration recognition means can observe knocking occurring in the internal combustion engine, and the air pressure adjusting means can increase the air supply pressure when knocking is observed by the bubble concentration recognition means. For example, the occurrence of knocking is observed with a knocking sensor. When the occurrence of knocking is observed, it can be considered that the number of bubbles is too small relative to the amount of fuel. Therefore, in this case, an operation for increasing the air supply pressure is performed. Thereby, the amount of bubbles can be increased, and the fuel amount and the amount of bubbles can be matched.

  The air introducing means is an air introducing path formed inside the needle, and the air pressure adjusting means can adjust the pressure of air introduced into the air introducing path. For example, the air pressure can be adjusted by connecting an air introduction path and a surge tank and installing an air pump in the connection path. Along with the air pump, a control valve and an air pressure sensor can be provided in the connection path, and these can be cooperated to adjust the air pressure.

  The air introducing means is a communication hole that connects the swirl stabilizing chamber and the combustion chamber, and the air pressure adjusting means advances the start timing of fuel injection that is started in the initial stage of the intake stroke as the amount of injected fuel increases. Can be horned. When burnt gas is used as air for generating bubbles, in order to increase the amount of air introduced, fuel injection may be performed at a timing when the in-cylinder pressure is high. If the start timing of the fuel injection that is started at the beginning of the intake stroke is advanced, the fuel injection is started at a timing when the in-cylinder pressure is high. Therefore, the fuel quantity and the bubble quantity can be matched by increasing the advance amount as the fuel quantity increases.

  According to the fuel injection valve disclosed in the present specification, fine bubbles can be mixed into the injected fuel, and the atomization of the spray particle size can be promoted.

FIG. 1 is a diagram illustrating a configuration example of an engine system including the fuel injection device according to the first embodiment. FIG. 2 is an explanatory view showing a state where the nozzle body and needle of the fuel injection valve of the first embodiment are separated, and FIG. 2B shows a state where the needle is combined with the nozzle body of the fuel injection valve of the first embodiment. It is explanatory drawing. FIG. 3 is a cross-sectional view of a needle included in the fuel injection valve according to the first embodiment. FIG. 4 is a flowchart illustrating an example of control performed by the fuel injection device according to the first embodiment. FIG. 5 is an explanatory diagram showing the relationship between the crank angle and the peak in-cylinder pressure. FIG. 6 is a flowchart illustrating an example of control performed by the fuel injection device according to the first embodiment. FIG. 7 is an explanatory diagram of a fuel injection valve according to the second embodiment. FIG. 8 is a PV diagram of the engine. FIG. 9 is an explanatory diagram showing an example of a map used for control of the fuel injection device.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, in the drawings, the dimensions, ratios, and the like of each part may not be shown so as to completely match the actual ones. Further, details may be omitted depending on the drawings.

  Embodiment 1 of the present disclosure will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration example of an engine system 1 in which a fuel injection device 2 including a fuel injection control valve 30 is mounted. FIG. 1 shows only a part of the configuration of the engine 100.

  An engine system 1 shown in FIG. 1 includes an engine 100 that is a power source, and includes an engine ECU (Electronic Control Unit) 10 that comprehensively controls the operation of the engine 100. The engine system 1 includes a fuel injection valve 30 that injects fuel into the combustion chamber 11 of the engine 100. The engine ECU 10 has a function of a control unit. The engine ECU 10 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read Only Memory) that stores programs, a RAM (Random Access Memory) and NVRAM (Non Volatile RAM) that store data and the like. Computer.

  The engine 100 is an engine mounted on a vehicle and includes a piston 12 that constitutes a combustion chamber 11. Piston 12 is slidably fitted to a cylinder of engine 100. And the piston 12 is connected with the crankshaft which is an output shaft member via the connecting rod.

  The intake air flowing into the combustion chamber 11 from the intake port 13 is compressed in the combustion chamber 11 by the upward movement of the piston 12. The engine ECU 10 determines the fuel injection timing based on the position of the piston 12 from the crank angle sensor and the information of the cam shaft rotation phase from the intake cam angle sensor, and sends a signal to the fuel injection valve 30. The fuel injection valve 30 injects fuel at an instructed injection timing in accordance with a signal from the engine ECU 10. The fuel injected from the fuel injection valve 30 is mixed with the atomized and compressed intake air. Then, the fuel mixed with the intake air is burned by being ignited by the spark plug 18, expands in the combustion chamber 11, and lowers the piston 12. The descending motion is changed to the shaft rotation of the crankshaft through the connecting rod, whereby the engine 100 obtains power.

  Connected to the combustion chamber 11 are an intake port 13 that communicates with the combustion chamber 11 and an intake passage 14 that is connected to the intake port 13 and guides intake air from the intake port 13 to the combustion chamber 11. Further, an exhaust port 15 communicating with the combustion chamber 11 and an exhaust passage 16 for guiding exhaust gas generated in the combustion chamber to the outside of the engine 100 are connected to the combustion chamber 11 of each cylinder. A surge tank 22 is disposed in the intake passage 14.

  An air flow meter, a throttle valve 17 and a throttle position sensor are installed in the intake passage 14. The air flow meter and the throttle position sensor detect the amount of intake air passing through the intake passage 14 and the opening of the throttle valve 17, respectively, and transmit the detection results to the engine ECU 10. The engine ECU 10 recognizes the intake air amount introduced into the intake port 13 and the combustion chamber 11 based on the transmitted detection result, and adjusts the intake air amount by adjusting the opening of the throttle valve 17.

  The throttle valve 17 preferably employs a throttle-by-wire system using a step motor. For example, the opening of the throttle valve 17 is changed in conjunction with an accelerator pedal (not shown) via a wire instead of a step motor. A mechanical throttle mechanism as described above can also be applied.

  A turbocharger 19 is installed in the exhaust passage 16. The turbocharger 19 uses the kinetic energy of the exhaust gas flowing through the exhaust passage 16 to rotate the turbine, compresses the intake air that has passed through the air cleaner, and sends it to the intercooler. The compressed intake air is cooled by the intercooler, temporarily stored in the surge tank 22, and then introduced into the intake passage 14. In this case, the engine 100 is not limited to a supercharged engine including the turbocharger 19 and may be a natural aspiration engine.

  The piston 12 has a cavity on its top surface. A wall surface of the cavity is formed by a gentle curved surface continuous from the direction of the fuel injection valve 30 to the direction of the ignition plug 18, and the fuel injected from the fuel injection valve 30 is adjacent to the ignition plug 18 along the wall shape. Lead to. In this case, the piston 12 can form a cavity at an arbitrary position and shape according to the specifications of the engine 100, such as a reentrant combustion chamber in which a cavity is formed in an annular shape in the central portion of the top surface.

  The fuel injection valve 30 is attached to the combustion chamber 11 below the intake port 13 in an oblique direction. The fuel injection valve 30 is based on an instruction from the engine ECU 10, and the fuel supplied from the fuel pump through the fuel flow path through the fuel flow path is injected into the combustion chamber 11 from the nozzle holes 32 provided at equal intervals in the circumferential direction of the tip of the nozzle body 31. Inject directly into. The injected fuel is atomized in the combustion chamber 11 and mixed with the intake air, and is guided to the vicinity of the spark plug 18 along the shape of the cavity. The leaked fuel from the fuel injection valve 30 is returned from the relief valve to the fuel tank through the relief pipe.

  In this case, the fuel injection valve 30 is not limited to the lower portion of the intake port 13 and can be installed at an arbitrary position in the combustion chamber 11. Further, the fuel injection valve 30 is not limited to the combustion chamber 11 and may be provided in the intake port 13, or may be provided in both the combustion chamber 11 and the intake port 13.

  Engine 100 is not limited to a gasoline engine using gasoline as a fuel, and may be any of a diesel engine using light oil as a fuel and a flexible fuel engine using a fuel in which gasoline and alcohol are mixed at an arbitrary ratio. The engine system 1 may be a hybrid system that combines the engine 100 and a plurality of electric motors.

  Next, the internal configuration of the fuel injection valve 30 according to an embodiment of the present invention will be described in detail. FIG. 2A is an explanatory view showing a state where the nozzle body 31 and the needle 33 of the fuel injection valve 30 of the embodiment are separated. FIG. 2B is an explanatory view showing a state in which the needle 33 is combined with the nozzle body 31 of the fuel injection valve 30 of the embodiment. 2A and 2B show only the configuration of the tip portion of the fuel injection valve 30. FIG.

  The fuel injection valve 30 includes a nozzle body 31 having a nozzle hole 32 provided at the tip. The inlet of the nozzle hole 32 is opened at a corner where a bottom surface and a side surface of a swirl stabilizing chamber 45 described later intersect. The nozzle body 31 includes a sheet position 31a inside. The fuel injection valve 30 includes a needle 33 that is slidably disposed in the nozzle body 31. The needle 33 forms a fuel introduction path 34 between the nozzle body 31 and the needle 33 as shown in FIG. The needle 33 includes a first eccentricity suppressing portion 35 on the distal end side, and includes a seat portion 33 a that sits on the seat position 31 a inside the nozzle body 31 on the distal end side. The first eccentricity suppressing unit 35 suppresses the eccentricity of the needle 33 by being fitted into the nozzle body 31 while maintaining a slight gap with the inner peripheral wall of the nozzle body 31. The needle 33 is driven by a piezo actuator.

  The needle 33 includes a swirl flow generating unit 36 in the first eccentricity suppressing unit 35. The swirl flow generator 36 is formed on the upstream side of the seat portion 33a. The swirl flow generator 36 includes a spiral groove 36 a that imparts a swirl component to the fuel introduced from the fuel introduction path 34. The spiral grooves 36a may be in one or more rows, and in this embodiment, two rows of spiral grooves 36a are provided.

  Inside the needle 33, as shown in FIG. 3, an air introduction path 37 is formed as air introduction means for introducing air into a swirl stabilizing chamber 45 described later. The outlet 38 on the outlet side of the air introduction path 37 is located at the tip of the needle 33. The air introduction path 37 introduces air from the base end side of the fuel injection valve 30 toward the front end side, similarly to the fuel. A spherical check valve 39 urged by a spring 40 is provided in the vicinity of the mouth portion 38 of the air introduction path 37. The check valve 39 is opened when the inside of a turning stable chamber 45 described later is in a negative pressure state.

  The needle 33 includes a second eccentricity suppressing portion 41 on the proximal end side with respect to the first eccentricity suppressing portion 35. A circumferential groove 42 is provided on the outer peripheral wall of the second eccentricity suppressing portion 41. In the groove 42, the mouth portion 43 on the inlet side of the air introduction path 37 is exposed. The nozzle body 31 is provided with an air introduction hole 44. The air introduction hole 44 is connected to the surge tank 22 by the air pipe 21 as shown in FIG. When the air introduction hole 44 faces the groove 42, the air introduction path 37 and the surge tank 22 communicate with each other. The air introduction hole 44 only needs to be able to introduce air into the air introduction path 37, and the connection destination is not limited to the surge tank 22.

  As shown in FIGS. 2 (A) and 2 (B), the nozzle body 31 includes a turning stabilization chamber 45 at the tip. The swirl stabilization chamber 45 is introduced with the fuel that has passed through the swirl flow generator 36 and the air that has passed through the air introduction path 37. In the swirl stabilization chamber 45, the swirl flow velocity of the fuel generated in the swirl flow generator 36 is increased, and the swirl flow becomes stable along the inner peripheral wall of the swirl stabilization chamber 45. When the swirl flow is stabilized, a negative pressure portion is generated at the center of the swirl stabilizing chamber 45. The mouth portion 38 of the air introduction path 37 faces the central portion of the swirl stabilizing chamber 45 so as to be exposed to the negative pressure portion. Thereby, air is introduced into the negative pressure part. Since the negative pressure portion has a low pressure, air can be easily introduced. Further, by introducing the air by exposing the mouth portion 38 of the air introduction path 37 to the negative pressure portion, the disturbance of the swirling flow is also suppressed.

  The fuel introduced into the swirl stabilizing chamber 45 takes in air and generates fine bubbles. The fine bubbles are ejected from the nozzle hole 32. After the injection, the fuel film forming the injected fine bubbles is split, and the fuel is in an ultrafine state. By making the fuel into an ultra-fine state, it is possible to achieve a high level balance with a reduction in ignition delay period, an increase in combustion speed, suppression of oil dilution by fuel, suppression of deposit accumulation, and suppression of knocking.

  As shown in FIGS. 1 and 2, an air pump 23, an air pressure sensor 24, and a control valve 25 are arranged in the air pipe 21 connecting the combustion injection valve 30 and the surge tank 22 as described above. The air pump 23, the air pressure sensor 24, and the control valve 25 are all electrically connected to the ECU 10. The ECU 10, the air pump 23, and the control valve 25 function as air pressure adjusting means for adjusting the pressure of the air introduced into the air introduction path 37 in cooperation. It should be noted that the function of the air pressure adjusting means can be given only by the combination of the ECU 10 and the air pump 23, or the function of the air pressure adjusting means can be given only by the combination of the ECU 10 and the control valve 25. In the case of the present embodiment, the turbocharger 19 which is an example of a supercharger and the surge tank 22 provided on the downstream side of the intercooler and the air introduction path 37 are connected. In this case, since the pressure of the turbocharger 19 can be used, the air pump 23 may be eliminated and the air pressure may be adjusted by adjusting the opening of the control valve 25. If the air pump 23 can be eliminated, the cost is reduced. Further, since the driving loss that occurs when the air pump 23 is driven is eliminated, fuel efficiency is expected to be improved.

  When adjusting the air pressure, the ECU 10 can control the rotational speed of the air pump 23 and the opening of the control valve 25 singly or in combination according to the fuel injection amount obtained from the engine load. That is, as the fuel injection amount increases, the supply gas pressure is increased and the supply air amount is increased. Thereby, the air quantity with respect to the fuel quantity can be adjusted, and the bubble concentration with respect to the fuel quantity can be adjusted. Thereby, atomization of fuel can be promoted appropriately.

  As described above, when adjusting the air pressure, the rotational speed of the air pump 23 and the opening degree of the control valve 25 can be controlled while monitoring the air pressure sensor 24. That is, the ECU 10 can control the air pump 23 and the control valve 25 so that the value indicated by the air pressure sensor 24 becomes a value that is associated with the fuel amount in advance. As described above, the fuel amount and the air pressure can be associated with each other. The air pressure and the supply air amount, and thus the air pressure and the bubble amount can be associated with each other. For this reason, the air pressure sensor 24 can function as a bubble concentration recognition means. By using the air pressure sensor 24, precise control is possible, and efficient operation of the air pump 23 can be achieved. For this reason, reduction of power consumption and improvement of fuel consumption are expected.

  Further, other bubble concentration recognition means can be employed without using the air pressure sensor 24. The fuel injection device 2 includes an in-cylinder pressure sensor 26 and a crank angle sensor 28. The in-cylinder pressure sensor 26 and the crank angle sensor 28 are each electrically connected to the ECU 10. The in-cylinder pressure sensor 26 and the crank angle sensor 28 together with the ECU 10 function as a bubble concentration recognition unit. Specifically, the ECU 10 observes the in-cylinder pressure together with the crank angle, and determines that the bubble concentration is excessive when the crank angle that has reached the peak in-cylinder pressure is observed later than a predetermined crank angle. Then, the air supply pressure is decreased by controlling the air pump 23 and the control valve 25.

  The fuel injection device 2 includes a knocking sensor 27. Knocking sensor 28 is electrically connected to ECU 10. The knocking sensor 27 functions as a bubble concentration recognition unit together with the ECU 10. Specifically, ECU 10 observes knocking that occurs in engine 100, and determines that the bubble concentration is too low when knocking is observed. Then, the air supply pressure is increased by controlling the air pump 23 and the control valve 25.

  When the cylinder pressure sensor 26, the knocking sensor 27, and the crank angle sensor 28 are used to recognize the amount of bubbles relative to the amount of fuel, the air sensor 24 may be eliminated. When the amount of bubbles relative to the amount of fuel is recognized using the in-cylinder pressure sensor 26, the knocking sensor 27, and the crank angle sensor 28, it is possible to accurately cope with changes in the structure of the fuel, changes in temperature and pressure, and highly robust injection. Control can be performed. That is, when the air supply pressure is directly controlled based on the amount of fuel, the amount of data on the map becomes enormous if appropriate control is performed according to the surrounding environment such as the change in the structure of the fuel, temperature, and pressure. Although there is a possibility, highly accurate control can be performed by performing control based on a phenomenon actually observed when the amount of bubbles is excessive or insufficient with respect to the amount of fuel.

  First, referring to FIGS. 4 and 5, an example of control when the ECU 10, the in-cylinder pressure sensor 26, and the crank angle sensor 28 function as bubble concentration recognition means for recognizing the bubble concentration with respect to the fuel introduced into the turning stable chamber 45. However, it will be explained. FIG. 4 is a flowchart showing an example of control performed by the fuel injection device 2. FIG. 5 is an explanatory diagram showing the relationship between the crank angle and the peak in-cylinder pressure.

The ECU 10 continuously collects data related to in-cylinder pressure from the in-cylinder pressure sensor 26 and continuously collects data related to the crank angle from the crank angle sensor 28. Then, the crank angle X ° at the time when the peak in-cylinder pressure is observed is observed (step S1). In FIG. 5, X ₀ ° is a crank angle serving as a threshold value. The crank angle X ₀ ° is defined as a value that should be observed when the amount of bubbles is not excessive or insufficient with respect to the amount of fuel.

At step S2 subsequently performed step S1, the observed X ° is determines whether or not a retard side of X ₀ °. As shown in FIG. 5, when X ° is on the more retarded side than X ₀ °, it is determined YES in step S2 and the process proceeds to step S3, where the bubble concentration is excessive. This is because the phenomenon in which X ° is retarded from X ₀ ° is considered to be caused by the bubbles being combined and the fine particle size of the fuel being deteriorated due to the excessive number of bubbles. On the other hand, when it is determined NO in step S2, the process ends.

  If it is determined in step S3 that the bubble concentration is excessive, an air supply pressure lowering measure is taken in the subsequent step S4. Specifically, the rotational speed of the air pump 23 is reduced, or the opening degree of the control valve 25 is reduced. Moreover, an injection retarding measure can be taken.

  Next, an example of control in a case where the ECU 10 and the knocking sensor 27 are caused to function as a bubble concentration recognition means for recognizing the bubble concentration with respect to the fuel introduced into the turning stable chamber 45 will be described with reference to FIG. FIG. 6 is a flowchart showing an example of control performed by the fuel injection device 2.

  The ECU 10 continuously collects data related to knocking from the knocking sensor 27. Then, it is determined whether knocking has been observed (step S11). If knocking is observed and YES is determined in step S11, the process proceeds to step S12, and it is assumed that the bubble concentration is too low. This is because the occurrence of knocking is considered to be caused by the fact that the liquid fuel induces knocking around the combustion chamber 11 due to the excessive number of bubbles. On the other hand, when it is determined NO in step S11, the process ends.

  If it is determined in step S12 that the bubble concentration is too low, an air supply pressure increase measure is taken in the subsequent step S13. Specifically, the rotational speed of the air pump 23 is increased or the opening degree of the control valve 25 is increased. Also, it is possible to take injection advance measures.

  As described above, highly robust fuel injection can be performed by performing control based on an actually occurring event.

  Next, Example 2 will be described with reference to FIGS. FIG. 7 is an explanatory diagram of the fuel injection valve 50 of the second embodiment. FIG. 8 is a PV diagram of engine 100. FIG. 9 is an explanatory diagram showing an example of a map used for controlling the fuel injection device 2. The second embodiment is different from the first embodiment in that the second embodiment includes a fuel injection valve 50 instead of the fuel injection valve 30. The fuel injection valve 50 includes a communication hole 51 instead of the air introduction path 37 in the fuel injection valve 30. The communication hole 51 is an example of intake air introduction means, and introduces burned gas into the swirl stabilization chamber 45 as air by communicating the swirl stabilization chamber 45 and the combustion chamber 11. In the second embodiment, the air pump 23, the air pressure sensor 24, and the control valve 25 disposed in the shape of the air pipe 21 are abolished with the abolition of the air introduction path 37. Since the other configurations of the second embodiment are not different from those of the first embodiment, common components are denoted by the same reference numerals in the drawings, and detailed description thereof is omitted.

  In the second embodiment, the ECU 10 functions as an air pressure adjusting unit, and as shown in FIG. 8, the start timing of the fuel injection that is started at the beginning of the intake stroke is advanced as the amount of injected fuel increases. The advance amount is determined by referring to the map shown in FIG. That is, the advance amount increases as the fuel injection amount increases.

  The pressure in the combustion chamber 11 is increased by the residual pressure of the burned gas remaining in the combustion chamber 11 due to the delay in pushing out the burned gas by the piston in the late stage of the exhaust stroke. This residual pressure increases as the load increases when the fuel amount increases. Therefore, the amount of burnt gas introduced into the swirl stabilizing chamber 45 is increased by advancing the injection start timing performed in the initial stage of the intake stroke in accordance with the increase of the injected fuel. That is, by starting fuel injection at a timing when the in-cylinder pressure is high, a large amount of burned gas is taken into the swirl stabilizing chamber 45 and the amount of bubbles corresponding to the fuel amount is set. Thereby, atomization of suitable fuel can be performed. The map may set injection conditions for each operating condition.

  In the second embodiment, since the air pump 23, the air pressure sensor 24, the control valve 25, and other equipment associated therewith are unnecessary, an inexpensive system can be constructed.

  The above embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to these, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

DESCRIPTION OF SYMBOLS 1 Engine system 2 Fuel injection apparatus 22 Surge tank 30, 50 Fuel injection valve 31 Nozzle body 31a Seat position 31b Inner peripheral wall 32 Injection hole 33 Needle 33a Seat part 33b Inner peripheral wall 34 Fuel flow path 35 1st eccentricity suppression part 36 Swirling flow Generation part 36a, 36b Spiral groove 37 Air introduction path 38 Port part 39 Check valve 40 Spring 41 Second eccentricity suppression part 42 Groove 45 Turning stabilization chamber 51 Communication hole 100 Engine

Claims (5)

A nozzle body having a nozzle hole provided at a tip end thereof is slidably disposed in the nozzle body, and a fuel introduction path is formed between the nozzle body and a seating position in the nozzle body. A needle provided with a seat portion, a swirl flow generating portion formed on the upstream side of the seat portion of the needle and formed with a spiral groove for imparting a swirl component to the fuel introduced from the fuel introduction path; and the nozzle A fuel injection valve comprising: a swirl stabilization chamber formed at the tip of the body and into which fuel that has passed through the swirl flow generator is introduced; and air introduction means for introducing air into the swirl stabilization chamber;
Bubble concentration recognition means for recognizing bubble concentration with respect to fuel introduced into the swirl stabilizing chamber;
Air pressure adjusting means for adjusting the air supply pressure introduced into the swirl stabilizing chamber based on the bubble concentration recognized by the bubble concentration recognizing means;
A fuel injection device comprising: The bubble concentration recognizing means observes the in-cylinder pressure together with the crank angle,
The air pressure adjusting means reduces the air supply pressure when the bubble concentration recognizing means observes the crank angle at which the peak in-cylinder pressure is reached later than the threshold crank angle. Item 2. The fuel injection device according to Item 1. The bubble concentration recognition means observes knocking occurring in the internal combustion engine,
3. The fuel injection device according to claim 1, wherein the air pressure adjusting means increases the air supply pressure when knocking is observed by the bubble concentration recognizing means.   The air introduction means is an air introduction path formed inside the needle, and the air pressure adjustment means adjusts the pressure of air introduced into the air introduction path. The fuel injection device according to any one of claims.   The air introducing means is a communication hole that connects the swirl stabilizing chamber and the combustion chamber, and the air pressure adjusting means advances the start timing of fuel injection that is started in the initial stage of the intake stroke as the amount of injected fuel increases. The fuel injection device according to claim 1, wherein the fuel injection device is angled.

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