WITH FUEL INJECTION NOZZLE

BACKGROUND OF THE INVENTION

1 . Field of the Invention

[0001] The present invention relates to a fuel injection nozzle that injects fuel, and an internal combustion engine that is equipped with the fuel injection nozzle. 2. Description of Related Art

[0002] In general, an internal combustion engine is configured to adjust various parameters that relate to combustion of fuel so that operating conditions which are determined by various requirements can be achieved. For example, in a diesel engine, fuel in an amount that meets the requirements regarding the output (for example, operating conditions such as the load of the internal combustion engine) is injected from a fuel injection nozzle that is provided in each combustion chamber at a time that meets the requirements.

[0003] A fuel injection nozzle of this type usually has a fuel injection hole through which fuel is injected through the tip thereof, and is configured to be able to inject fuel that is supplied from outside (from what is called a common rail, for example) to the fuel injection nozzle through the fuel injection hole. In addition, as a fuel injection nozzle of this type, a fuel injection nozzle that has, in addition to the fuel injection hole, an air introduction hole that is used to introduce air into the fuel to be injected from the fuel injection hole in order to adjust the conditions of the fuel that is injected (for example, the degree of atomization of fuel) (what is called an air-assist fuel injection nozzle) has been also proposed.

[0004] For example, one of conventional fuel injection nozzles (which may be hereinafter occasionally referred to as "conventional nozzle") has, through the tip thereof, a fuel injection hole and an air introduction hole that is located in the vicinity of the fuel injection hole. The air introduction hole is configured to have a first end that is open toward the combustion chamber and a second end that is open toward the fuel injection hole. When fuel is injected from the fuel injection hole, the conventional nozzle uses a suction force that is created by the stream of fuel through the fuel injection hole to direct the air in the combustion chamber into the fuel injection hole through the air introduction hole and mix the air into the fuel. Thus, the conventional nozzle can increase the degree of atomization of fuel (refer to Japanese Patent Application Publication No. 2004-225549 (JP 2004-225549 A), for example).

[0005] In the above-mentioned conventional nozzle, air is mixed into the fuel to be injected to increase the degree of atomization of the fuel that is injected from the fuel injection nozzle. On the other hand, as is well-known, in order to burn the fuel that has been injected from the fuel injection nozzle properly, it is effective to adjust the degree of mixing of fuel and air (for example, equivalent ratio in the fuel spray) to a degree suitable for combustion in addition to increasing the degree of atomization of fuel.

[0006] In general, however, when fuel is injected from a fuel injection nozzle, the air in a combustion chamber of an internal combustion engine (which may contain additional gasses other than air depending on the operating conditions of the internal combustion engine) flows by the effect of a stream of air that is created when air is sucked into the combustion chamber during an intake stroke, a stream of air that is created by the motion of the piston during a compression stroke and so on. For example, when the piston of the internal combustion engine has a cavity (recess), a stream of air that flows from the outer periphery of the combustion chamber toward the center thereof (what is called a squish stream) is created as air flows into the cavity during a

compression stroke. It is believed that because the fuel that has been injected from the fuel injection nozzle is merged into the air stream and dispersed within the combustion chamber, the degree of mixing of the fuel and air varies depending on the degrees of the merger and dispersion.

[0007] Thus, in order to increase the degree of atomization of fuel and adjust the degree of mixing of fuel and air simultaneously, it is considered desirable that the fuel injection nozzle is configured to be able not only to mix air into fuel to be injected but also to inject fuel based on the movement of air in the combustion chamber. It is considered that when a fuel injection nozzle that is configured that way is applied to an internal combustion engine, fuel can be burned properly based on the operating conditions of the internal combustion engine.

SUMMARY OF THE INVENTION

[0008] The present invention provides a fuel injection nozzle that can inject fuel based on the movement of air in the combustion chamber, and an internal combustion engine that is equipped with the fuel injection nozzle.

[0009] A fuel injection nozzle according to a first aspect of the present invention comprises a valve element and a tubular valve housing that accommodates the valve element so as to define a flow path between an inner peripheral face of the tubular valve housing and an outer peripheral face of the valve element, and a tip of the tubular valve housing having a fuel injection hole into which fuel is introduced from the flow path and through which the fuel is injected and an air introduction hole that introduces air into the fuel injection hole.

[0010] The fuel injection hole has a fuel inlet which is provided at one end of the fuel injection hole, and through which fuel is introduced into the fuel injection hole, and has a fuel outlet which is provided at the other end of the fuel injection hole, and through which fuel is injected in a direction away from the central axis of the fuel injection nozzle. The air introduction hole has an air inlet which is provided at one end of the air introduction hole, and through which air is introduced into the air introduction hole, and has an air outlet which is provided at the other end of the air introduction hole, and through which air is introduced into the fuel injection hole between the fuel inlet and the fuel outlet in a direction away from a nozzle center where the central axis of the fuel injection nozzle crosses a surface of the tip of the fuel injection nozzle. [001 1] In the fuel injection nozzle according to the first aspect of the present invention, the air inlet may be configured to be located closer to the nozzle center than the fuel outlet is.

[0012] In the fuel injection nozzle according to the first aspect of the present invention, the fuel outlet of the fuel injection hole and the air inlet of the air introduction hole may be configured to have respective aperture planes on different planes.

[0013] An internal combustion engine according to a second aspect of the present invention comprises a cylinder defining a combustion chamber of the internal combustion engine, and a fuel injection nozzle that injects fuel into the combustion chamber.

[0014] The combustion chamber is configured to create a stream of gas that flows from the outer periphery of the combustion chamber toward the center thereof when fuel is injected from the fuel injection nozzle into the combustion chamber.

[0015] The fuel injection nozzle has a valve element and a tubular valve housing that accommodates the valve element so as to define a flow path between an inner peripheral face of the tubular valve housing and an outer peripheral face of the valve element, and a tip of the tubular valve housing having a fuel injection hole into which fuel is introduced from the flow path and through which the fuel is injected and an air introduction hole that introduces air into the fuel injection hole. The fuel injection hole has a fuel inlet which is provided at one end of the fuel injection hole, and through which fuel is introduced into the fuel injection hole, and has a fuel outlet which is provided at the other end of the fuel injection hole, and through which fuel is injected in a direction away from the central axis of the fuel injection nozzle toward an inner peripheral face of the combustion chamber. The air introduction hole has an air inlet which is provided at one end of the air introduction hole, and through which air is introduced into the air introduction hole, and has an air outlet which is provided at the other end of the air introduction hole, and through which air is introduced into the fuel injection hole between the fuel inlet and the fuel outlet in a direction away from a nozzle center where the central axis of the fuel injection nozzle crosses a surface of the tip of the fuel injection nozzle. [0016] In the internal combustion engine according to the second aspect of the present invention, the combustion chamber may be defined by a piston that has a cavity, and the fuel injection nozzle may be configured such that the air inlet is located closer to the nozzle center than the fuel outlet is and the air inlet is open toward the cavity.

[0017] In the internal combustion engine according to the second aspect of the present invention, the fuel outlet and the air inlet are configured to have respective aperture planes on different planes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic view of a fuel injection nozzle according to an embodiment of the present invention and an internal combustion engine that is equipped with the fuel injection nozzle;

FIG. 2 is a schematic view of the fuel injection nozzle in FIG. 1 ;

FIG. 3 is a schematic diagram that illustrates the flow of fuel that is infected from the fuel injection nozzle in FIG. 1 and the flow of air that is introduced into the fuel;

FIG. 4 is a schematic diagram that illustrates the relationship between the fuel injection amount from the fuel injection nozzle in FIG. 1 and the fuel injection direction;

FIG. 5 is a schematic diagram that illustrates the relationship between the fuel that is injected from the fuel injection nozzle in FIG. 1 and the squish stream that is created in the vicinity of the top face of the piston;

FIG. 6 is a schematic view of a fuel injection nozzle according to another aspect of the present invention;

FIG. 7 is a schematic view of a fuel injection nozzle according to yet another aspect of the present invention; and

FIG. 8 is a schematic view of a fuel injection nozzle according to still yet another aspect of the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

[0019] Description is hereinafter made of an illustrative embodiment of a fuel injection nozzle and an internal combustion engine according to the present invention with reference to the drawings.

[0020] FIG. 1 illustrates the general configuration of a fuel injection system 10 that has a fuel injection nozzle 1 1 according to an embodiment of the present invention, an internal combustion engine 20 to which the fuel injection system 10 is applied, various sensors 31 to 33, and an electronic control device 40. While the internal combustion engine 20 is a four-cycle multi-cylinder diesel engine, only one of the cylinders is shown in cross-section in FIG. 1 for convenience sake.

[0021] The fuel injection system 10 includes a fuel injection nozzle 1 1 that injects fuel, a common rail 12, a supply pump 13 and a fuel tank 14. The common rail 12 feeds high-pressure fuel into the fuel injection nozzle 1 1. The supply pump 13 delivers high-pressure fuel to the common rail 12. The fuel tank 14 supplies fuel to the supply pump 13. The supply pump 13 pressurizes the fuel that is supplied from the fuel tank 14 and supplies the pressurized fuel to the common rail 12. The common rail 12 temporarily stores the fuel that is supplied from the supply pump 13 with its pressure (fuel pressure) maintained. When the pressure of fuel in the common rail 12 exceeds a predetermined maximum value, a portion of the fuel is discharged through a pressure limit valve 12a and returned to the supply pump 13 or the fuel tank 14.

[0022] The fuel injection nozzle 1 1 is described in more detail below. FIG. 2 is a schematic diagram that illustrates the outline of the fuel injection nozzle 1 1. As shown in FIG. 2, the fuel injection nozzle 1 1 has a valve element (needle) 1 Id, and a tubular valve housing that accommodates the valve element. A tip of the tubular valve has a fuel injection hole 1 la through which the fuel to be injected passes, and an air introduction hole 1 lb that introduces air to the fuel injection hole. The fuel injection nozzle 1 1 also has a flow path 1 lc that introduces fuel to the fuel injection hole 1 la. [0023] The fuel injection hole 1 la and the air introduction hole 1 lb are provided through the tip of the fuel injection nozzle 1 1 (specifically, an end of the fuel injection nozzle 1 1 which faces a combustion chamber 27 when the fuel injection nozzle 1 1 is attached to the internal combustion engine 20; the lower end as seen in FIG. 2). The flow path 1 lc is a void that is formed in the fuel injection nozzle 1 1 and allows passage of fuel therethrough. The valve element 1 Id is a columnar member that has a tip 1 Ida (a lower end as seen in the drawing) which has a generally conical shape. The valve element 1 Id is supported in the fuel injection nozzle 1 1 for movement along the axis of the valve element 1 Id (in directions parallel to the long axis of the valve element 1 Id; up-and-down movement as seen in the drawing). The valve element 1 Id is moved according to an external force (elastic force) that is exerted downward as seen in FIG. 2 by a spring 1 1 e in contact with the other end (the upper end as seen in the drawing) 1 1 db of the valve element l id and an external force (electromagnetic force) that is exerted upward as seen in FIG. 2 when a solenoid coil 1 If is activated in response to a command from the electronic control device 40.

[0024] The fuel that is fed from outside the fuel injection nozzle 1 1 (the common rail 12 in FIG. 1) into the fuel injection nozzle 1 1 passes through a passage that is formed in the valve element 1 Id as indicated by black arrows in the drawing and flows along the valve element 1 Id to the tip of the fuel injection nozzle 1 1. In the tip of the fuel injection nozzle 1 1, when the valve element 1 Id is moved upward as seen in the drawing upon activation of the solenoid coil 1 1 f as shown in the partial enlarged view in FIG. 2, the tip 1 Ida of the valve element is separated from an inner wall surface 11 ca of the flow path 1 lc and the flow path 1 lc is opened to allow passage of fuel. When the solenoid coil 1 If is not activated, the tip 1 Ida of the valve element 1 Id is pressed against the inner wall surface 1 lea by the spring 1 le to close the flow path 1 1c. The fuel injection amount is controlled by adjusting the period of time for which the flow path 1 1c is held open and closed.

[0025] When the flow path 1 lc is opened as described above, fuel flows into the tip of the fuel injection nozzle 1 1 as shown in the partial enlarged view in FIG. 2. Then, the fuel is injected out of the fuel injection nozzle 1 1 through the fuel injection hole 1 la. In addition, the air outside the fuel injection nozzle 1 1 is sucked through the air introduction hole 1 1 b as indicated by white arrows in the drawing by a suction force that is created by the stream of fuel through the fuel injection hole 1 1 a. As can be understood from the partial enlarged view in FIG. 2, the fuel injection hole 1 la is a passage through which fuel passes, and the air introduction hole 1 1 b is a passage through which air passes.

[0026] The flows of fuel and air are described in more detail below. FIG. 3 is a schematic diagram that illustrates the tip of the fuel injection hole 1 la in a further enlarged fashion. As shown in FIG. 3, the fuel injection hole 1 1a has a fuel inlet 1 lain at one end of the fuel injection hole 1 la, and through which fuel is introduced into the fuel injection hole. The fuel injection hole 1 1 a also has a fuel outlet 1 laout at the other end of the fuel injection hole 1 1, and through which fuel is injected in a direction away from the central axis AX of the fuel injection nozzle 1 1. The air introduction hole 1 lb hole has an air inlet 1 lbin at one end of the air introduction hole, and through which air is introduced into the air introduction hole, and has an air outlet 1 1 bout which is provided at the other end of the air introduction hole, and through which air is introduced into the fuel injection hole between the fuel inlet 1 lain and the fuel outlet 1 laout in a direction away from a nozzle center CP, the intersection between the central axis AX of the fuel injection nozzle and the surface of the tip of the fuel injection nozzle.

[0027] The air inlet 1 lbin is provided at a location that is closer to the nozzle center CP than the fuel outlet 1 laout is. In addition, the fuel outlet 1 laout and the air inlet 1 lbin are configured such that the fuel outlet 1 laout and the air inlet 1 lbin have respective aperture planes on different planes.

[0028] The air outlet 1 1 bout of the air introduction hole 1 lb is connected to the fuel injection hole 1 la between the fuel inlet 1 lain and the fuel outlet 1 laout of the fuel injection hole 1 1a. Thus, when the pressure (static pressure) that the fuel in the fuel injection hole 1 la applies to the surrounding area is decreased as the fuel flows through the fuel injection hole 1 1a, air is introduced (mixed) through the air introduction hole 1 lb into the fuel that is passing through the fuel injection hole 1 la because of the difference in pressure between the fuel and air. As a result, the fuel and air are mixed as they are injected from the fuel injection hole 1 1a.

[0029] In the following, the direction of the vector that starts at the center P of the aperture plane of the fuel outlet 1 laout and ends at an outer edge Q of the fuel spray as shown in the drawing is referred to as "fuel injection direction Fid," and the direction in which air flows through the center R of the aperture plane of the air outlet 1 lbout is referred to as "air introducing direction Agd."

[0030] The fuel injection direction is described in more detail below. FIG. 4 is a schematic diagram that illustrates the relationship between the fuel injection amount and the fuel injection direction. As described above, when fuel flows through the fuel injection hole 1 l a, the pressure (static pressure) of the fuel decreases. When fuel is injected, the pressure of the fuel in the fuel injection hole 1 1a decreases to a very low level because the flow velocity of the fuel that is flowing through the fuel injection hole 1 la is usually very high. On the other hand, the air introduction hole 1 lb is open to the outside of the fuel injection nozzle 1 1 via the air inlet 1 lbin, and the pressure of the air at the air outlet 1 lbout is usually higher than the pressure of the fuel in the fuel injection hole. Thus, the fuel that is flowing through the fuel injection hole 1 la receives an external force that results from the difference in pressure between the fuel and air from the air that is introduced through the air introduction hole 1 lb at the location where the fuel injection hole 1 1a and the air introduction hole 1 lb are connected (connecting location). The direction of the external force substantially coincides with the air introducing direction Agd.

[0031] Thus, as shown in FIG. 4(a), the fuel injection direction Fid is shifted in the air introducing direction Agd (in other words, in a direction away from the nozzle center CP) from the fuel injection direction that is determined by the structure (for example, shape, position and orientation of the aperture) of the fuel injection hole 1 1a (the axis direction Fax of the fuel injection hole 1 la in FIG. 4). In FIG. 4(a), the fuel injection direction Fid is shifted in the air introducing direction Agd (in a direction away from the nozzle center CP; upward as seen in the drawing) from the axis direction Fax by an angle Θ1.

[0032] In addition, as the fuel injection amount is greater, a larger amount of air is usually introduced into the fuel at the connecting location and the external force is applied from the air to the fuel for a longer period of time. Thus, when the fuel injection amount is larger than that in the case of FIG. 4(a), the fuel injection direction Fid is shifted more significantly in the air introducing direction Agd (in a direction away from the nozzle center CP) as shown in FIG. 4(b). In FIG. 4(b), the fuel injection direction Fid is shifted in the air introducing direction Agd from the axis direction Fax by an angle Θ2 (Θ2 > Θ 1 ). As can be understood from the above description, the amount of change in the fuel injection direction Fid (Θ2 - Θ1) increases as the fuel injection amount increases.

[0033] As described above, the fuel injection nozzle 1 1 can change the fuel injection direction Fid according to the fuel injection amount. Specifically, the greater the fuel injection amount, the more significantly the fuel injection direction Fid is shifted in a direction away from the nozzle center CP (in other words, in a direction away from the direction Fax that is determined by the structure of the fuel injection hole 1 la).

[0034] Referring again to FIG. 1 , the internal combustion engine 20 has an intake passage 21 , a cylinder 22, a piston 23, a crankshaft 24, a connecting rod 25, and an exhaust passage 26. A top face of the piston 23, an inner peripheral surface of the cylinder 22 and a lower surface of a cylinder head define a combustion chamber 27. Air is introduced into the cylinder 22 through the intake passage 21. The piston 23 reciprocates in the cylinder 22. The connecting rod 25 transmits the reciprocating motion of the piston 23 to the crankshaft 24. The exhaust gas that results from combustion is discharged through the exhaust passage 26.

[0035] A cavity (recess) is provided in the top face of the piston 23 to regulate the flow of gas in the combustion chamber 27 (refer to FIG. 5, for example). The cavity creates a stream of gas that flows from the outer periphery of the combustion chamber 27 toward the center thereof (what is called a squish stream) when the piston 23 compress the air in the combustion chamber 27 during a compression stroke (in other words, when the piston 23 approaches the fuel injection nozzle 1 1).

[0036] The above-mentioned fuel injection nozzle 1 1 is attached to the cylinder head (not shown), which is mounted on the cylinder 22, and injects fuel toward the squish stream (in other words, toward the outer periphery of the combustion chamber 27) (refer to FIG. 5, for example).

[0037] The fuel injection system 10 and the internal combustion engine 20 are provided with a common rail pressure sensor 31 , a crank position sensor 32 and an accelerator pedal operation amount sensor 33 as the various sensors 31 to 33.

[0038] The common rail pressure sensor 31 is located on the common rail 12 and is configured to output a signal according to the pressure of the fuel in the common rail 12. When the fuel pressure that is acquired based on the signal exceeds a predetermined maximum value, a portion of the fuel is discharged through the pressure limit valve 12a.

[0039] The crank position sensor 32 is located in the vanity of the crankshaft 24 and is configured to output a signal according to the rotation of the crankshaft. Based on this signal, the rotational speed of the crankshaft 24 per unit time (engine rotation speed) is acquired.

[0040] The accelerator pedal operation amount sensor 33 is located on an accelerator pedal 28 and is configured to output a signal according to the operation amount of the accelerator pedal 28. Based on this signal, the accelerator pedal operation amount is acquired.

[0041] The amount of fuel that is injected from the fuel injection nozzle 11 (fuel injection amount) is determined based on the operating conditions of the internal combustion engine 20 (the engine rotation speed and the accelerator pedal operation amount, for example).

[0042] The electronic control device 40 has a CPU 41 , a ROM 42, a RAM 43, a backup RAM 44, and an interface 45. Programs, tables (maps), constants and so on that the CPU 41 uses are stored in the ROM 42 in advance. The RAM 43 temporarily stores data upon request from the CPU 41. The backup RAM 44 stores data when the power is on and retains the stored data even when the power is off. The CPU 41, the ROM 42, the RAM 43, the RAM 44 and the interface 45 are connected to one another by a bus.

[0043] The interface 45 is connected to the sensors and is configured to transmit signals that are output from the sensors to the CPU 41. In addition, the interface 45 is connected to the fuel injection nozzle 1 1 , the supply pump 13 and so on and is configured to send command signals thereto in response to a command from the CPU 41.

[0044] Specifically, the CPU 41 is configured to send a command signal that controls the fuel injection amount, the amount of fuel to be injected from the fuel injection nozzle 1 1 , and a command signal that controls the fuel injection timing, the timing of fuel being injected from the fuel injection nozzle 1 1 , to the fuel injection nozzle 1 1 (or a control device that controls the operation of the fuel injection nozzle 1 1) via the interface 45. The CPU 41 is also configured, for the purpose of controlling the pressure of fuel to be fed into the fuel injection nozzle 1 1 , to send a command signal that controls the fuel feeding pressure to the supply pump 13 (or a control device that controls the operation of the supply pump 13), for example.

[0045] The above is the outline of the fuel injection system 10 which has the fuel injection nozzle 1 1 according to an embodiment of the present invention and the internal combustion engine 20 to which the fuel injection system 10 is applied.

[0046] The operation of the fuel injection nozzle 1 1 is described below with reference to FIG. 5. FIG. 5 is a schematic diagram that illustrates how the fuel that is injected from the fuel injection nozzle 1 1 and a squish stream that is created in the vicinity of the top face of the piston 23 are merged. As shown in FIGs. 5(a) and 5(b), a cavity 23a is formed in the top face of the piston 23. When the piston 23 approaches the fuel injection nozzle 1 1 (when the piston 23 is moved upward as seen in the drawing) during a compression stroke, a stream of air that is forced out of the space between the piston 23 and the top face of the combustion chamber 27 into the cavity 23a (squish stream) is created. Thus, the squish stream flows in a direction from the outer periphery of the piston 23 (the outer periphery of the combustion chamber 27) toward the center thereof.

[0047] As shown in FIG. 5(a), when the amount of fuel that is injected from the fuel injection nozzle 1 1 is small (during low-load operation, for example), the fuel is injected in a direction not away from the nozzle center CP (into the cavity 23a, for example) and merged into the squish stream in a region close to the center of the piston 23 (a downstream part of the squish stream). After that, the fuel flows within the combustion chamber 27 while being mixed into the squish stream.

[0048] In this case, it takes a relatively short period of time until the piston reaches the top dead center (until the creation of the squish stream is completed) after the fuel is merged into the squish stream. Thus, in this case, the degree of dispersion of fuel is kept so low that improper combustion possibly caused by the fuel being mixed with an excessively large amount of air can be prevented.

[0049] On the other hand, as shown in FIG. 5(b), when the amount of fuel that is injected from the fuel injection nozzle 1 1 is large (during high-load operation, for example), the fuel is injected in a direction away from the nozzle center CP (to the outside of the cavity 23a, for example) and merged into the squish stream in a region close to the outer periphery of the combustion chamber 27 (an upstream part of the squish stream). After that, the fuel flows into the cavity 23a while being mixed into the squish stream, and flows within the combustion chamber 27.

[0050] In this case, the period of time that it takes until the piston reaches the top dead center (until the creation of the squish stream is completed) after the fuel is merged into the squish stream is longer than that in the case of FIG. 5(a). Thus, even if the fuel injection amount is large, the fuel can be mixed with air in an amount that matches the fuel injection amount. As a result, the fuel can be burned properly.

[0051] The above is the description of an illustrative embodiment of a fuel injection nozzle and an internal combustion engine according to the present invention.

[0052] As described above, the fuel injection nozzle 1 1 according to an embodiment of the present invention has a fuel injection hole 1 la which allows passage of fuel to be injected therethrough and an air introduction hole 1 lb which introduces air into the fuel injection hole 1 la through the tip thereof.

[0053] In the fuel injection nozzle 1 1 , the fuel injection hole 1 la has a fuel inlet

1 lain at one end of the fuel injection hole 1 la, and through which fuel is introduced into the fuel injection hole. The fuel injection hole 1 la also has a fuel outlet 1 laout at the other end of the fuel injection hole 1 la, and through which fuel is injected in a direction

Fid away from the central axis AX of the fuel injection nozzle 1 1. The air introduction hole 1 lb has an air inlet 1 lbin at one end of the air introduction hole 1 lb and through which air is introduced into the air introduction hole. The air introduction hole l ib also has an air outlet 1 lbout which is provided at the other end of the air introduction hole 1 lb, and through which air is introduced into the fuel injection hole 1 la between the fuel inlet

1 lain and the fuel outlet 1 laout in a direction away from a nozzle center CP, the intersection between the central axis AX of the fuel injection nozzle 1 1 and the surface of the tip of the fuel injection nozzle 1 1.

[0054] In the fuel injection nozzle 1 1 , the air inlet 1 lbin is provided at a location that is closer to the nozzle center CP than the fuel outlet 1 laout is.

[0055] In the fuel injection nozzle 1 1 , the fuel outlet 1 laout and the air inlet

1 lbin are configured such that the fuel outlet 1 laout and the air inlet 1 lbin have respective aperture planes on different planes.

[0056] In addition, the internal combustion engine 20 according to an

embodiment of the present invention is equipped with the fuel injection nozzle 1 1, which injects fuel into the combustion chamber 27 of the internal combustion engine.

[0057] In the internal combustion engine 20, the combustion chamber 27 is configured to be able to create a stream of gas that flows from the outer periphery of the combustion chamber 27 toward the center thereof (squish stream) when fuel is injected from the fuel injection nozzle 1 1 into the combustion chamber 27.

[0058] In the internal combustion engine 20, the fuel injection nozzle 1 1 has a fuel injection hole 1 la which allows passage of fuel to be injected therethrough and an air introduction hole l ib which introduces air in the combustion chamber 27 into the fuel injection hole 1 la through the tip thereof.

[0059] In addition, in the fuel injection nozzle 1 1 , the fuel injection hole 1 la is configured to inject the fuel flowing thereinto through a fuel inlet 1 lain at one end of the fuel injection hole 1 la to the outside of the fuel injection nozzle 1 1 through a fuel outlet 1 laout at the other end of the fuel injection hole 1 la in a direction away from the central axis AX of the fuel injection nozzle 1 1 toward the inner periphery of the combustion chamber 27, and the air introduction hole 1 lb is configured to introduce the air that flows thereinto through an air inlet 1 1 bin at one end of the air introduction hole l ib into the fuel injection hole 1 1a between the fuel inlet l lain and the fuel outlet 1 laout in a direction away from a nozzle center CP, the intersection between the central axis AX of the fuel injection nozzle 1 1 and the surface of the tip of the fuel injection nozzle 1 1.

[0060] In the internal combustion engine 20, the combustion chamber 27 is defined by a piston that has a cavity, and the fuel injection nozzle 1 1 is configured such that the air inlet 1 lbin is located closer to the nozzle center CP than the fuel outlet 1 1 aout is and is open toward the cavity.

[0061] In the internal combustion engine 20, the air inlet 1 lbin and the fuel outlet 1 laout are configured such that the fuel outlet 1 laout and the air inlet 1 lbin have respective aperture planes on different planes.

[0062] The present invention is not limited to the above embodiment and various modification can be made within the scope of the present invention.

[0063] For example, in the above embodiment, there is no specific limitation to the shape of the fuel injection hole 11a except that it has a shape that allows passage of fuel. However, as shown in FIG. 6, the fuel injection nozzle 1 1 of the present invention may be configured such that the fuel outlet 1 laout has an aperture area (a diameter of the fuel injection hole 1 la) that is greater than that of the fuel inlet 1 lain, for example. In other words, the fuel injection hole 1 la of the fuel injection nozzle 1 1 may be configured to have a portion with an enlarged aperture area (large-diameter portion) 1 laexp in the vicinity of the fuel outlet 1 laout. [0064] When the fuel injection hole 1 la has the above-mentioned structure (large-diameter portion 1 laexp), air is introduced from the air introduction hole 1 lb into the fuel injection hole 1 la more efficiently and the air is mixed with the fuel to be injected from the fuel injection hole 1 la more appropriately. One of the reasons for this is that a portion of the fuel is separated from the inner wall surface of the fuel injection hole 1 1 a (the inner wall surface of the large-diameter portion 1 1 aexp) when the fuel flows into the large-diameter portion 1 1 aexp and the area in which the fuel can contact the air from the air introduction hole 1 1 b increases, for example.

[0065] In addition, when the fuel injection hole 1 1a has the above-mentioned structure (large-diameter portion 1 laexp), the fuel injection hole 1 l a and the air introduction hole 1 lb may be configured such that the axis of the fuel injection hole 1 la does not cross the axis of the air introduction hole 1 lb (in brief, such that the fuel injection hole 1 la and the air introduction hole 1 lb are eccentric relative to each other). With this configuration, because the fuel and air are spirally rotated as they are mixed, the fuel and air can be mixed more efficiently. In addition, even when the axis of the fuel injection hole 1 la crosses the axis of the air introduction hole 1 lb, the fuel injection hole 1 la and the air introduction hole 1 lb may be configured to have their respective axes on different planes.

[0066] In addition, the large-diameter portion 1 laexp may be configured such that the axis of the passage between the air inlet 1 lbin and the large-diameter portion

1 laexp is not coincident with the axis of the large-diameter portion 1 laexp (in brief, such that the passage between the air inlet 1 lbin and the large-diameter portion 1 laexp is eccentric relative to the large-diameter portion 1 laexp).

[0067] In addition, as shown in FIG. 7, the fuel injection nozzle 1 1 of the present invention may be configured such that the air inlet 1 lbin of the air introduction hole 1 lb has an aperture area that is greater than that of the air outlet 1 lbout. With this configuration, air is sucked from the air inlet 1 lbin more efficiently. In particular, when the air that has been compressed by the piston 23 is moved toward the fuel injection nozzle 1 1, the air can be introduced into the air introduction hole 1 lb more efficiently. [0068] In addition, as shown in FIG. 8(a), the fuel injection nozzle 1 1 of the present invention may be configured such that the tip of the air introduction hole 1 lb is recessed in a direction along the central axis AX. With this configuration, the air that is flowing from the piston 23 toward the fuel injection nozzle 1 1 can be introduced into the air introduction hole 1 1 b more efficiently. In contrast to the above case, the internal combustion engine 20 of the present invention may be configured such that the top face of the piston 23 is recessed in a direction along the central axis AX as shown in FIG. 8(b). With this configuration, a large amount of air can be introduced from the piston 23 toward the fuel injection nozzle 1 1. As a result, air can be introduced into the air introduction hole 1 lb more efficiently.

[0069] In addition, the fuel injection nozzle 1 1 of the present invention may have a coating that prevents adhesion of deposit on the inner wall surfaces of the fuel injection hole 1 1a and the air introduction hole l ib. The coating, however, may be applied only to the inner wall surface of the air introduction hole l ib because fuel passes through the fuel injection hole 1 la at such a high speed that deposit is unlikely to adhere to the inner wall surfaces of the fuel injection hole 1 1a.

[0070] In addition, the fuel injection nozzle 1 1 of the present invention may be configured to have a plurality of fuel injection holes 1 1 a through the tip thereof. In addition, the fuel injection nozzle 1 1 of the present invention may be configured such that all of the plurality of fuel injection holes 1 la are connected to respective air introduction holes 1 lb, or may be configured such that some of the plurality of the fuel injection holes 1 la are connected to respective air introduction holes l ib.

[0071] The above is the description of different aspects of the present invention.

[0072] The present invention can be used as a fuel injection nozzle that can inject fuel based on the movement of air in the combustion chamber, and as an internal combustion engine that is equipped with such a fuel injection nozzle.

[0073] With the above configuration, because the other end of the air introduction hole (air outlet) is connected to the fuel injection hole at a location between the fuel inlet and the fuel outlet of the fuel injection hole, air is introduced (mixed) into the fuel according to the relationship between the pressure of air at the air outlet and the pressure of fuel in the fuel injection hole.

[0074] Specifically, because the flow velocity of the fuel that flows through the fuel injection hole is usually very high, the pressure (what is called a static pressure) that the fuel in the fuel injection hole applies to the surrounding area significantly decreases when the fuel is injected. On the other hand, the pressure of air at the air outlet is usually higher than the pressure of fuel in the fuel injection hole although it varies depending on the flow velocity of the air that flows through the air introduction hole. Thus, when fuel is injected from the fuel injection nozzle, air is introduced (mixed) into the fuel that is passing through the fuel injection hole because of the difference between the pressures.

[0075] When the mixing of fuel and air is discussed from a different perspective, it is considered that the fuel that flows through the fuel injection hole receives an external force that results from the difference in pressure between the fuel and air from the air that is introduced through the air introduction hole at the location where the fuel injection hole and the air introduction hole are connected (which may be hereinafter occasionally referred to as "connecting location"). Based on this concept, it is believed that the direction in which fuel is injected from the fuel injection hole (which may be hereinafter occasionally referred to as "fuel injection direction") is shifted from the fuel injection direction that is determined by the structure (for example, shape, position and orientation of the aperture) of the fuel injection hole by an extent proportional to the external force.

[0076] In the above-mentioned configuration according to the present invention, air is introduced into the fuel injection hole in a direction away from the nozzle center. Thus, in the fuel injection nozzle of the present invention, it is believed that the fuel injection direction is shifted in a direction away from the nozzle center by an extent proportional to the magnitude of the external force (in other words, the difference in pressure between the fuel and air). More specifically, it is believed that a larger amount of air is usually introduced into the fuel at the connecting location and the external force is applied from the air to the fuel for a longer period of time as the amount of fuel that passes through the fuel injection hole (which may be hereinafter occasionally referred to as "fuel injection amount") is larger. As a result, as the amount of fuel that passes through the fuel injection hole is larger, the fuel injection direction is shifted to a larger extent in a direction away from the nozzle center.

[0077] When a fuel injection nozzle that has the above feature is applied to an internal combustion engine, fuel can be injected based on the movement of air in the combustion chamber. Specifically, in an internal combustion engine that is provided with a piston which has a cavity with a shape that can create a squish stream that flows from the outer periphery (radially outside) of the combustion chamber toward the center (radially inside) thereof, for example, a case is assumed where the fuel injection nozzle is placed in the top face of the combustion chamber (for example, at the center in the top face of the combustion chamber) and fuel is injected from the fuel injection nozzle in a direction from the center of the combustion chamber toward the outer periphery thereof (refer to FIG. 4, for example).

[0078] According to the above assumption, when the fuel injection amount is large (for example, when the internal combustion engine is being operated at high load), the fuel is injected in a direction away from the nozzle center (in other words, in a direction away from the top face of the piston) and is merged into the squish stream in a region close to the outer periphery of the combustion chamber (an upstream part of the squish stream). After being merged into the squish stream, the fuel flows into the cavity together with the squish stream.

[0079] As described above, when the fuel injection amount is large, the fuel is dispersed into the squish stream over a relatively long period of time because the fuel is merged into the squish stream at an upstream part of the squish stream. Thus, in this case, because the fuel is dispersed to a large extent, the fuel can be mixed with air in an amount that matches the fuel injection amount even when the fuel injection amount is large. As a result, the fuel is burned properly and problems, such as the generation of smoke that results from incomplete combustion of fuel, can be prevented. [0080] On the other hand, when the fuel injection amount is small (for example, when the internal combustion engine is being operated at low load), the fuel is injected in a direction not away from the nozzle center (in other words, in a direction toward the top face of the piston) and merged into the squish stream in a region close to the center of the combustion chamber (a downstream part of the squish stream). After being merged into the squish stream, the fuel flows into the cavity together with the squish stream. In this case, as can be understood from the above description, the degree of movement (in other words, the degree of dispersion) of the fuel is lower than that in the case where the fuel injection amount is large.

[0081] As described above, when the fuel injection amount is small, because the fuel is merged into the squish stream at a downstream part of the squish stream, the period of time for which the fuel is dispersed into the squish stream is relatively short. Thus, in this case, the degree of dispersion of fuel is kept so low that improper combustion possibly caused by the fuel being mixed with an excessively large amount of air can be prevented. As a result, the fuel is burned properly, and problems, such as an increase in unburned fuel, can be prevented.

[0082] As described above, when used to inject fuel directly into a combustion chamber of an internal combustion engine, the fuel injection nozzle of the present invention can inject fuel based on the movement of air in the combustion chamber.

Specifically, because the fuel injection nozzle of the present invention adjusts the degree of mixing of fuel and air based on the operating conditions of the internal combustion engine (fuel injection amount), it enables the fuel to be burned properly based on the operating conditions of the internal combustion engine (regardless of whether the fuel injection amount is large or small).

[0083] Incidentally, the direction in which fuel is injected from the

above-mentioned "fuel injection hole" is not specifically limited as long as the fuel is injected in a direction away from the central axis of the fuel injection nozzle. The phrase "in a direction away from the central axis of the fuel injection nozzle" can be also expressed as "in such a direction that the angle between the fuel injection direction and the central axis is greater than 0 degree (parallel to each other) and equal to or smaller than 90 degrees (perpendicular to each other), for example. In other words, the fuel injection hole may be configured such that the fuel is injected from the fuel injection hole in a direction between a direction perpendicular to the central axis and away from the central axis and a direction parallel to the central axis and away from the fuel injection nozzle through the nozzle center.

[0084] The above-mentioned "fuel injection direction" is not specifically limited as long as it is a direction that is determined based on criteria according to which the direction in which fuel is injected from the fuel injection hole is determined uniquely. For example, the direction of a "vector that starts at the center of the aperture plane of the fuel outlet and ends at a front edge of the mixed gas of fuel and air (fuel spray) that is injected from the fuel injection hole" may be employed as the fuel injection direction.

[0085] On the other hand, the direction in which air is introduced into the fuel injection hole through the "air introduction hole" (which may be hereinafter occasionally referred to as "air introducing direction") is not specifically limited as long as it is a direction away from the nozzle center. The phrase "in a direction away from the nozzle center" can be also expressed as "in such a direction that the angle between the straight line that connects the nozzle center and the connecting location between the fuel injection hole and the air introduction hole (which may be hereinafter occasionally referred to as "reference straight line") and the air introducing direction is equal to or greater than 0 degree (parallel to each other) and equal to smaller than 90 degrees (perpendicular to each other), for example. In other words, the air introduction hole may be configured such that the direction in which air is introduced into the fuel injection hole from the air introduction hole is between a direction parallel to the reference straight line and away from the connecting location and a direction perpendicular to the reference straight line and away from the reference straight line.

[0086] In addition, the "air introducing direction" is preferably forward with respect to the direction of flow of fuel through the fuel injection hole. In this case, air can be mixed into the fuel more efficiently and fuel can be prevented from flowing (in reverse) into the air introduction hole compared to the case where the air introducing direction is opposite to the direction of flow of fuel. The term "forward" can be also expressed as "in such a direction that the angle between the air introducing direction and the direction of the flow of fuel through the fuel injection hole is equal to or greater than 0 degree (parallel to each other) and smaller than 90 degrees (perpendicular to each other), for example.

[0087] The above-mentioned "air introducing direction" is not specifically limited as long as it is a direction that is determined based on criteria according to which the direction in which air is introduced into the fuel injection hole through the air introduction hole is determined uniquely. For example, the direction air as it flows through the center of the aperture plane of the air outlet may be employed as the air introducing direction.

[0088] The "air introduction hole" only has to be a flow path that introduces a gas which contains at least air into the fuel injection hole, and may not necessarily be a flow path that introduces "only air." In other words, the gas that passes through the air introduction hole only has to contain air and may not be necessarily composed of "only air." For example, the gas that passes through the air introduction hole may contain air, exhaust gas from internal EGR and external EGR, and unburned components that remain in the combustion chamber.

[0089] The structure of the "fuel injection hole" and the "air introduction hole" is not specifically limited as long as they are configured to be able to fulfil the

above-mentioned functions (injection of fuel and mixing of fuel and air).

[0090] Thus, the phrase "the fuel injection hole has a fuel inlet at one end of the fuel injection hole, and through which fuel is introduced into the fuel injection hole, and has a fuel outlet at the other end of the fuel injection hole, and through which fuel is injected in a direction away from the central axis of the fuel injection nozzle" can be rephrased as "the fuel injection hole has a first end that is open in a surface of the fuel injection nozzle in the vicinity of the nozzle center and a second end that is open toward the fuel flow path in the fuel injection nozzle, and is configured to inject the fuel that flows thereinto through the second end through the first end in a direction away from the central axis of the fuel injection nozzle," for example.

[0091] In addition, the phrase "the air introduction hole has an air inlet at one end of the air introduction hole, and through which air is introduced into the air introduction hole, and has an air outlet at the other end of the air introduction hole, and through which air is introduced into the fuel injection hole between the fuel inlet and the fuel outlet in a direction away from a nozzle center where the central axis of the fuel injection nozzle crosses a surface of the tip of the fuel injection nozzle" can be rephrased as "the air introduction hole has a third end that is open in a surface of the fuel inj ection nozzle and a fourth end that is open toward the air introduction hole between the first end and the second end, and is configured to introduce the air that flows thereinto through the third end into the fuel injection hole through the fourth end," for example.

[0092] As can be understood from the above description, the "fuel injection nozzle" of the present invention is applied to an internal combustion engine of the type in which fuel is directly injected into a combustion chamber. Examples of the internal combustion engines to which the fuel injection nozzle of the present invention is applied include direct injection gasoline and diesel engines.

[0093] The configuration and effect of the fuel injection nozzle of the present invention are described in the foregoing. In the following, some of the aspects (aspects 1-1 and 1-2) of the fuel injection nozzle of the present invention are described.

[0094] In aspect 1-1, the fuel injection nozzle according to the present invention can inject fuel based on the fuel injection amount and the movement of air in the combustion chamber when applied to an internal combustion engine as described above. To adjust the fuel injection direction more properly, it is considered preferred that air is introduced from the air inlet of the air introduction hole as efficiently as possible.

[0095] According to the fuel injection nozzle of this aspect, when the fuel injection nozzle is located at the center of a combustion chamber of an internal combustion engine as described above, for example, the air around the center of the combustion chamber (in general, air that is less affected by the fuel that has been injected from the fuel outlet) is introduced into the air inlet as the piston is moved. In other words, air that has a relatively low content of combustion products and unburned matter is compressed and moved toward the air inlet by the piston.

[0096] Thus, compared to the case where air is simply sucked through the air inlet, air can be introduced into the air inlet more efficiently because the air itself is moved toward the air inlet. In addition, the formation of adherent matter (so-called deposit), which is composed of combustion products, unburned matter and so on, in the air introduction hole can be prevented.

[0097] In general, the moving speed of the piston (the engine rotation speed of the internal combustion engine) tends to be higher as the load of the internal combustion engine is higher. Thus, according to the fuel injection nozzle of this aspect, when the load of the internal combustion engine is high and the fuel injection amount is large, air is introduced into the air introduction hole efficiently because the moving speed of the piston is high and the moving speed of the air that is compressed toward the air introduction hole is also high. As a result, fuel is injected toward an upstream part of the squish stream more reliably.

[0098] As described above, according to the fuel injection nozzle of this aspect, the effect that the fuel injection direction is adjusted by an increase in the moving speed of the air that is compressed toward the air inlet can be achieved in addition to the effect that the fuel injection direction is adjusted by an increase in the fuel injection amount (in other words, a decrease in the pressure of the fuel in the fuel injection hole as described above). As a result, the fuel injection direction can be adjusted more efficiently.

[0099] The position of the "air inlet" is not specifically limited as long as it is located closer to the nozzle center than the fuel outlet is. For example, the air inlet may be open in the vicinity of the nozzle center or open at a location coincident with the nozzle center.

[0100] In aspect 1 -2, when combustion products and unburned matter that are sucked into the air introduction hole may adhere to the inner wall surface of the air introduction hole and form deposit as described above. It is considered that when an excessively large amount of deposit is formed in the air introduction hole, it may prevent a sufficient amount of air from passing through the air introduction hole.

[0101] According to the fuel injection nozzle of this aspect, the fuel that has been injected from the fuel outlet is less likely to be sucked directly into the air inlet compared to the case where the aperture plane of the fuel outlet and the aperture plane of the air inlet are located on the same plane. Thus, the possibility of deposit being formed in the air introduction hole is lower compared to the case where the aperture planes are located on the same plane.

[0102] According to the above configuration, fuel is injected from the fuel injection nozzle in a direction that is determined by the fuel injection amount as described above. In other words, fuel is injected toward an upstream part of the squish stream when the fuel injection amount is large, and fuel is injected toward a downstream part of the squish stream when the fuel injection amount is small.

[0103] Thus, the internal combustion engine of the present invention can adjust the degree of mixing of fuel and air in the combustion chamber based on the operating conditions of the internal combustion engine (fuel injection amount) and burn the fuel properly based on the operating conditions of the internal combustion engine (regardless of whether the fuel injection amount is large or small).

[0104] The configuration of the "combustion chamber" by which a gas stream that flows from the outer periphery of the combustion chamber toward the center thereof is created is not specifically limited. For example, the combustion chamber may be configured such that a cavity that can create the gas stream is formed in the top face (the surface that faces the inside of the combustion chamber) of the piston that defines the combustion chamber.

[0105] The configuration and effect of the internal combustion engine of the present invention are described in the foregoing. In the following, some of the aspects (aspects 2-1 and 1-2) of the internal combustion engine of the present invention are described. [0106] In aspect 2-1 , to enable the fuel injection nozzle to adjust the fuel injection direction more properly, it is considered preferred that air is introduced from the air inlet of the air introduction hole as efficiently as possible as described above.

[0107] According to the internal combustion engine of this aspect, air can be introduced into the air inlet more efficiently compared to the case where air is simply sucked through the air inlet of the air introduction hole because the air itself is pressed to move by the piston as described above. In addition, deposit is prevented from being formed in the air introduction hole. In addition, because the effect that the fuel injection direction is adjusted by an increase in the fuel injection amount and the effect that the fuel injection direction is adjusted by an increase in the moving speed of the air that is compressed toward the fuel injection nozzle are achieved, the fuel injection direction can be adjusted more efficiently.

[0108] In aspect 2-2, the formation of deposit is preferably minimized as described above.

[0109] According to the internal combustion engine of this aspect, the possibility of deposit being formed in air introduction hole can be smaller compared to the case where the aperture plane of the fuel outlet and the aperture plane of the air inlet are located, on the same plane as described above.

[01 10] As described with reference to some aspects in the foregoing, the fuel injection nozzle and the internal combustion engine of the present invention provide the effect that fuel can be injected based on the movement of gas in the combustion chamber.

[011 1] While the disclosure has been explained in conjunction with specific exemplary embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, exemplary embodiments of the disclosure as set forth herein are intended to be illustrative, not limiting. There are changes that may be made without departing from the scope of the disclosure.