JP2002115629A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the direction of actual fuel injection during actual injection from a nozzle hole, depending on driving conditions. SOLUTION: This fuel injection control device for an internal combustion engine comprises a fuel injection nozzle for injecting a fuel from the nozzle hole directly into a combustion chamber formed in a cylinder and deviation angle control means for variable control of a deviation angle to the center axis of the nozzle hole along the vertical direction of the cylinder at the center in the direction of actual fuel injection of the fuel actually injected from the nozzle hole. Thus, a fuel mixture can be formed in an optimum area in the combustion chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly, to a fuel injection control device for an internal combustion engine that variably controls a direction of fuel injection from an injection hole.

[0002]

2. Description of the Related Art In a fuel injection nozzle for directly injecting fuel into a combustion chamber from an injection hole, the center of the actual fuel injection direction with respect to the injection hole center axis is required unless the fuel flow velocity distribution in the injection hole is uniform. Deviate. That is, the center of the actual fuel injection direction is shifted toward the side where the flow velocity of the fuel in the injection hole is lower than the center axis of the injection hole.

When the fuel injection nozzle has a plurality of injection holes at the tip of the nozzle body, and the flow velocity distribution of the fuel in the injection holes differs for each injection hole, the actual fuel injection direction is determined for each injection hole. The angle at which the center of the nozzle deviates from the central axis of the injection hole (deflection angle) is different, and the process in which the fuel injected from each injection hole forms a fuel-air mixture in the combustion chamber is also different. Becomes For this reason, the air-fuel ratio of each fuel mixture becomes different, and there is a possibility that the combustion efficiency in the entire combustion chamber deteriorates.

Therefore, the actual fuel injection direction of each injection hole becomes a predetermined direction, and the actual fuel injection direction of each injection hole has the same angle with respect to the axis of the combustion chamber along the vertical direction of the cylinder. Conventionally, a fuel injection nozzle in which an injection hole piercing angle is set for each injection hole is known (for example,
See JP-A-9-60566).

[0005]

SUMMARY OF THE INVENTION Here, JP-A-9-6
In the configuration disclosed in Japanese Patent No. 0566, the predetermined direction is set from the injection hole toward the cavity such that the fuel mixture in the cylinder is concentrated in the cavity formed in the piston crown.

However, in such a configuration, considering that the piston moves up and down in the cylinder during operation of the engine, the relative positional relationship between each injection hole and the piston is not constant. Therefore, there is a problem that the fuel cannot always be injected in the optimum direction for concentrating the fuel mixture in the cavity.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to a fuel injection nozzle for directly injecting fuel from an injection hole into a combustion chamber defined in a cylinder, and a fuel injection nozzle with respect to a center axis of the injection hole. And a deviation angle control means for variably controlling a deviation angle of the fuel actually injected from the injection hole along the vertical direction of the cylinder at the center of the actual fuel injection direction. The center of the actual fuel injection direction is displaced in the vertical direction of the cylinder with respect to the central axis of the injection hole according to the flow velocity distribution of the fuel flowing in the injection hole. Thus, the deflection angle is controlled according to the operating conditions of the engine.

According to a second aspect of the present invention, in the first aspect of the invention, the fuel injection nozzle injects fuel when the needle valve is lifted, and the deflection angle control means includes:
The deviation angle is variably controlled by controlling the lift amount of the needle valve. Thus, by controlling the lift amount of the needle valve according to the engine operating condition, the flow velocity distribution of the fuel in the injection hole is controlled.

According to a third aspect of the present invention, in the second aspect of the invention, the deviation angle control means increases the lift amount of the needle valve when increasing the deviation angle. It is characterized by.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the deviation angle control means variably controls the deviation angle in accordance with the position of the piston during fuel injection. Features.

According to a fifth aspect of the present invention, in the invention according to the fourth aspect, the deviation angle control means is arranged such that when the piston is near the top dead center, compared to when the piston is near the bottom dead center. In this case, the deviation angle is relatively increased.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the deviation angle control means increases the deviation angle as the piston approaches the top dead center. .

According to a seventh aspect of the present invention, in the invention of the sixth aspect, the deviation angle control means reduces the deviation angle at an early stage of a fuel injection period, and at a later stage of the fuel injection period. It is characterized in that the deflection angle is increased.

According to an eighth aspect of the present invention, in the invention of the fourth aspect, the fuel injection nozzle performs pilot injection for injecting a fixed amount of fuel before main injection, and the deviation angle control means. Is characterized in that the deviation angle is made larger during the main injection than during the pilot injection.

According to a ninth aspect of the present invention, in the invention according to the eighth aspect, the deviation angle control means at the time of pilot injection adjusts the deviation angle as compared with when the internal combustion engine is under a high load. It is characterized in that it is increased when the load of the engine is low.

The invention described in claim 10 is the invention according to claims 1 to 9
In the invention described in any one of the above, a control range of the deviation angle is based on an inclination angle formed between a central axis of the injection hole and an inner wall surface of a tip end of the nozzle body at a position where the injection hole is formed through. Is set. The flow velocity distribution of the fuel in the injection hole changes depending on the magnitude of the inclination angle. Thereby, the control range of the deviation angle is set based on the magnitude of the inclination angle.

According to an eleventh aspect of the present invention, in the invention of the tenth aspect, the control range of the deviation angle is set wide by reducing the inclination angle.

The invention according to claim 12 is the invention according to claims 1 to 9
In the invention described in any one of the above, the control range of the deviation angle is set based on the length of the injection hole. The flow velocity distribution of the fuel in the injection hole changes depending on the length of the injection hole. Thereby, the control range of the deflection angle is set based on the length of the injection hole.

According to a thirteenth aspect of the present invention, in the twelfth aspect of the invention, the control range of the deflection angle is set wide by shortening the length of the injection hole. .

The invention according to claim 14 is the invention according to claims 1-1.
3. The invention according to any one of 3), wherein the fuel injection nozzle lifts the needle valve in accordance with the magnitude of a voltage applied to the piezoelectric element.

The invention according to claim 15 is the invention according to claims 1 to 1.
In the invention according to any one of the fourth to ninth aspects, the axial direction of the fuel injection nozzle is disposed in substantially the same direction as the axial direction of a cylinder constituting the combustion chamber.

[0022]

According to the present invention, the deflection angle of the center of the actual fuel injection direction along the vertical direction of the cylinder with respect to the center axis of the injection hole can be controlled according to the operating conditions of the engine. Depending on the operating conditions of the engine, a fuel mixture is always formed in an optimal region in the combustion chamber, so that the combustion efficiency is improved and the exhaust performance is improved.

According to the fourth aspect of the present invention, fuel can be injected into a predetermined region in the combustion chamber according to the position of the piston.

According to the fifth and sixth aspects of the present invention, the deviation angle can be controlled continuously during the fuel injection period.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the overall configuration of a fuel injection device for an internal combustion engine according to the present invention.

The fuel is introduced into the fuel supply pump 6 from the fuel tank 2 via the suction passage 4, and is stored in the common rail 10 through the discharge passage 8 in a state of being pressurized.

The high-pressure fuel of the common rail 10 is supplied to the injection nozzle 14 of each cylinder via the supply passage 12, and a plurality of injection holes 1 provided at the tip of the fuel injection nozzle 14.
6 (see FIG. 2 for details), the fuel is injected into a combustion chamber composed of a cylinder 20 and a capacity 20 formed on the top surface of the piston 18. The fuel pressure in the common rail 10 is controlled by the control unit 24.

The fuel injection nozzle 14 is disposed such that the axial direction of the fuel injection nozzle 14 is the same as the axial direction of the cylinder 22.

The control unit 24 includes a crank angle sensor 26 for detecting an engine speed and a crank angle, and an accelerator opening sensor 2 for detecting an accelerator opening.
8, the detection signal is input.

Then, the control unit 24 retrieves the target values of the injection pressure, the injection amount, and the injection timing based on the accelerator opening and the engine speed, and sets the target values of the injection amount and the injection timing so as to be the target values. The opening and closing timing of a control valve 30 described later in the fuel injection nozzle 14 is set, and control is performed such that the fuel pressure in the common rail 10 becomes a target value.

Next, the specific configuration of the fuel injection nozzle will be described with reference to FIG. 2. The fuel injection nozzle 14 includes a needle valve 34 for opening and closing the injection hole 16 in a nozzle body 32, and the common rail described above. The high pressure fuel in 10
Nozzle chamber 3 through fuel passage 36 in nozzle body 32
8 and the fuel passage 36
A part of the fuel diverged from the nozzle orifice is introduced into the pressure chamber 44 above the nozzle piston 42 through the charging orifice 40.

A return spring 46 is interposed between the nozzle piston 42 and the needle valve 34 to prevent fuel from leaking from the injection hole 16 when the engine is stopped.
The needle valve 34 is constantly biased in the seating direction.

The control valve 30 in the fuel injection nozzle 14 comprises a valve 50 for opening and closing the discharge orifice 48, and an actuator 52 having a piezoelectric element (piezo element) laminated in parallel with the opening and closing direction of the needle valve 34. .

Nozzle piston 42 in pressure chamber 44
The pressure receiving area of the needle valve 34 in the nozzle chamber 38
Is set to be larger than the pressure receiving area. Accordingly, in a state where the actuator 52 is extended by energizing the actuator 52 and the valve 50 is seated and the discharge orifice 48 is closed, the force in the valve closing direction acting on the nozzle piston 42 acts on the needle valve 34. Therefore, the needle valve 34 is seated and no fuel is injected. When the energization to the actuator 52 is stopped or the energization voltage is lowered from this state, the actuator 52 contracts, the valve 50 is lifted, and the discharge orifice 48 is opened. That is, the lift amount of the valve 50 changes according to the magnitude of the energization voltage. When the discharge orifice 48 opens, the pressure in the pressure chamber 44 decreases, the needle valve 34 lifts, and fuel is injected from the injection hole 16. Then, when the valve 50 closes the discharge orifice 48 by the actuator 52, the needle valve 34 is seated, and the fuel injection ends.

On the other hand, an actuator 54 facing one end of the nozzle piston 42 is provided in the pressure chamber 44. The actuator 54 has piezoelectric elements (piezo elements) stacked in the vertical direction in FIG. 2, and when energized by the control unit 24, extends in the direction of pushing down the stop rod 56 (downward in FIG. 2). That is, the fuel injection nozzle 14 is configured so that the lift amount of the needle valve 34 can be variably controlled by regulating the amount of upward movement of the nozzle piston 42 in FIG. 2 by the stop rod 56. Further, since the piezoelectric element is used for the actuator 54, the lift amount of the needle valve 34 can be arbitrarily set according to the magnitude of the voltage applied to the actuator 54. That is, the higher the energizing voltage to the actuator 54, the lower the stop rod 56 moves in FIG. 2, and the smaller the maximum lift of the needle valve 34 becomes.

FIG. 3 is a sectional view of the tip of the fuel injection nozzle 14 described above, and also shows the actual fuel injection direction of the fuel actually injected from the injection hole 16. The center of the actual fuel injection direction of the fuel injected from the injection hole 16 with respect to the injection hole central axis angle α which is the center axis of the fuel injection nozzle 14 is the upper side in FIG. Displaced upward in the vertical direction. In the figure, β indicates a deviation angle of the center of the actual fuel injection direction with respect to the injection hole center axis.

The process in which the center in the actual fuel injection direction deviates from the injection hole center axis will be described with reference to FIG. As shown by the arrow in FIG. 4, the fuel flow path is sharply bent at the inlet of the injection hole 16, thereby causing entrainment. for that reason,
The flow velocity distribution of the fuel inside the injection hole 16 is biased, and the injection hole 16
In the flow velocity distribution of the fuel inside, the flow velocity in the lower part in FIG. 4 is relatively larger than the flow velocity in the upper part in FIG. In other words, in the injection hole 16, the flow velocity on the nozzle chamber 38 side, which is on the upstream side of the fuel flow path, becomes relatively small.

As a result, when the fuel injection nozzle 14 is disposed so that the axial direction of the fuel injection nozzle 14 is the same as the axial direction of the cylinder 22, as in the present embodiment, the center of the actual fuel injection direction is the injection hole center axis. , The upper side of the cylinder 22 in the vertical direction,
In other words, the fuel is displaced toward the nozzle chamber 38 on the upstream side of the fuel flow path with respect to the injection hole 16.

As shown in FIG. 5, as the central axis angle α of the injection hole increases, the change in the flow path at the inlet of the injection hole 16 becomes more abrupt, and the deviation of the center of the actual fuel injection direction with respect to the central axis of the injection hole. The position angle β tends to be large.

The reason why the center of the actual fuel injection direction shifts with respect to the central axis of the injection hole 16 is due to a sudden change in the flow path at the inlet of the injection hole 16, and the flow velocity of the fuel inside the injection hole 16. By controlling the distribution, the actual fuel injection direction can be variably controlled.

In the present invention, the flow velocity distribution of the fuel in the injection hole 16 is controlled by the lift amount of the needle valve 34, and the actual fuel injection direction is controlled so as to be optimal according to the operating condition. Next, the control will be described in detail.

FIGS. 6 and 7 show differences in the flow velocity distribution of the fuel in the injection hole 16 depending on the lift amount of the needle valve 34. FIG.

As shown in FIG. 6, when the lift amount of the needle valve 34 is large, the flow rate of the fuel flowing into the injection hole 16 increases, and the fuel whose flow path is sharply bent at the inlet of the injection hole 16 is injected. In the hole 16, a high flow velocity is distributed on the lower side in FIG. In this case, the center of the actual fuel injection direction is shifted upward in FIG. 6 with respect to the injection hole center axis.

As shown in FIG. 7, when the lift amount of the needle valve 34 is small, the flow rate of the fuel flowing into the injection hole 16 decreases, and the dispersion of the velocity distribution of the fuel in the injection hole 16 decreases. The center in the fuel injection direction is along the injection hole center axis.

FIGS. 8 and 9 show an example of control of the actual fuel injection direction of the fuel injection nozzle 14 according to the position of the piston 18.

As shown in FIG. 8, when the fuel is injected at a time when the piston 18 is located below the top dead center, the lift amount of the needle valve 34 is reduced to reduce the fuel flow rate flowing into the injection hole 16. The fuel injection nozzle 14 is controlled such that the center of the actual fuel injection direction is along the injection hole center axis, that is, the deviation angle β is reduced.

As shown in FIG. 9, the fuel injection at the time when the piston 18 is located near the top dead center increases the lift amount of the needle valve 34 to increase the fuel flow rate flowing into the injection hole 16. Is controlled so that the center of the actual fuel injection direction is displaced upward with respect to the central axis of the injection hole in FIG. In other words, the fuel injection nozzle 14 is set so that the deviation angle β becomes large.
Control.

FIGS. 10 to 12 show the lift amount of the needle valve 34 during the fuel injection period. FIG. 10 shows the case where the fuel injection is performed only by the main injection and FIGS.
2 shows the case where pilot injection is performed prior to main injection.

As shown in FIG. 10, when the fuel injection is performed only by the main injection, at the beginning of the fuel injection period, the lift amount of the needle valve 34 is kept small and the center of the actual fuel injection direction is the injection hole center axis. Is controlled so as to overlap. In the latter part of the fuel injection period, the lift amount of the needle valve 34 is increased with the rise of the piston 18 so that the center of the actual fuel injection direction is shifted upward with respect to the injection hole center axis in the vertical direction of the cylinder 22. To control the position.

That is, the lift amount La ₂ of the needle valve 34 in the latter part of the fuel injection period is made larger than the lift amount La ₁ of the needle valve 34 in the early part of the fuel injection period, and the deviation angle in the latter part of the fuel injection period is increased. Increase β.

As shown in FIG. 11, when the pilot injection is performed prior to the main injection at a high load, the piston 18 is below the top dead center at the pilot injection timing, and the piston 18 is at the top injection center at the main injection timing. Nearby. That is, when the pilot injection is offset angle β is smaller the lift amount Lb ₁ of the needle valve 34 to be smaller, at the time of main injection, the lift amount of the needle valve 34 as Lb ₁ is greater than Lb _2, the offset angle β Enlarge.

As shown in FIG. 12, when pilot injection is performed prior to main injection at low load, the piston 18
Is located near the top dead center, the pilot injection timing and the main injection timing are reached. At the time of pilot injection, offset angle β is smaller lift amount Lc ₁ of the needle valve 34 to be smaller, at the time of main injection, the lift amount of the needle valve 34 as Lc ₁ is greater than Lc _2, the offset angle β Enlarge.

[0054] Further, as apparent from FIGS. 11 and 12. The lift amount Lc ₁ of the pilot injection at the time of low load is greater than the lift amount Lb ₁ of the pilot injection at high loads.

The control of the actual fuel injection direction based on the lift amount of the needle valve 34 has been described above.
The control range of the center in the actual fuel injection direction by the shape of No. 6 will be described.

As shown in FIGS. 13 and 14, the control range in the actual fuel injection direction changes depending on the difference in the inclination angle γ between the inner wall 58 of the fuel injection nozzle tip and the central axis of the injection hole.

That is, when the inclination angle γ is reduced, the injection hole 1
Since the fuel flow path is sharply bent at the inlet 6, the control range of the center of the actual fuel injection direction in the case of the inclination angle γ ₁ , that is, the maximum deviation angle β ′ ₁ (see FIG. 13) , the maximum offset angle beta _'2 becomes actual fuel injection direction of the center of the control range when the inclination angle gamma ₂ which is a gamma _2> gamma ₁ (Fig. 1
4). By decreasing the inclination angle γ, it is possible to increase the maximum deviation angle β ′ which is the control range of the center in the actual fuel injection direction.

As shown in FIG. 15, when the injection hole length L is increased, the fuel flow velocity distribution in the injection hole 16 becomes uniform.
Therefore, by increasing the injection hole length L, the maximum deviation angle β ′, which is the control range of the center in the actual fuel injection direction, decreases.

By performing the above-described variable control of the center of the fuel injection direction, the fuel mixture is formed in a predetermined optimum region in accordance with the relative position of the fuel injection nozzle 14 and the piston 18 which changes according to the engine operating conditions. It is possible to
Exhaust can be improved.

The above-described embodiment is a so-called Valv
e Covered Oriental Type Nozz
Although the above description has been made using the fuel injection nozzle of “le”, the same tendency occurs in the relationship between the injection hole center axis and the deviation angle in other tip-shaped fuel injection nozzles. The present invention can also be applied to the fuel injection nozzle.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of the entire fuel injection device according to the present invention.

FIG. 2 is a sectional view showing one embodiment of a fuel injection nozzle.

FIG. 3 is a sectional view of a tip of a fuel injection nozzle.

FIG. 4 is an explanatory diagram showing a cross-sectional view of a tip of a fuel injection nozzle and showing a flow velocity distribution of fuel in an injection hole.

FIG. 5 is a correlation diagram between an injection hole central axis angle α and a deviation angle β.

FIG. 6 is an explanatory diagram showing a fuel flow velocity distribution in an injection hole when a needle valve lift is large.

FIG. 7 is an explanatory diagram showing a fuel flow velocity distribution in an injection hole when a needle valve lift is small.

FIG. 8 is an explanatory diagram showing an example of actual fuel injection direction control when the piston is located below the top dead center.

FIG. 9 is an explanatory diagram showing an example of actual fuel injection direction control when the piston is located near top dead center.

FIG. 10 is an explanatory diagram illustrating an example of needle valve lift control during a fuel injection period.

FIG. 11 is an explanatory diagram showing an example of lift control of a needle valve during a fuel injection period.

FIG. 12 is an explanatory diagram showing an example of needle valve lift control during a fuel injection period.

FIG. 13 is an explanatory diagram showing a correlation between an inclination angle γ and an actual fuel injection direction.

FIG. 14 is an explanatory diagram showing a correlation between an inclination angle γ and an actual fuel injection direction.

FIG. 15 is an explanatory diagram showing a correlation between the injection hole length and the actual fuel injection direction.

[Explanation of symbols]

 14 ... fuel injection nozzle 16 ... injection hole 30 ... control valve 44 ... pressure chamber 50 ... valve 52 ... actuator 54 ... actuator 56 ... stop rod

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) F02M 45/08 F02M 45/08 Z 61/10 61/10 DF Term (Reference) 3G066 AA07 AB02 AC09 BA23 CC06U CC14 CC26 CC34 CC48 CE27 DA09 DB08 DB09 DC04 DC05 DC09 3G301 HA02 KA08 KA09 LB11 MA14 MA18 MA23 PE01Z PE03Z PF03Z

Claims (15)

[Claims] 1. A fuel injection nozzle for directly injecting fuel from an injection hole into a combustion chamber defined in a cylinder, and actual fuel injection of fuel actually injected from the injection hole with respect to an injection hole central axis. A deviation angle control means for variably controlling a deviation angle along a vertical direction of a cylinder at a center of the direction, and a fuel injection control device for an internal combustion engine. 2. The fuel injection nozzle injects fuel when a needle valve lifts, and the deflection angle control means variably controls the deflection angle by controlling a lift amount of the needle valve. The fuel injection control device for an internal combustion engine according to claim 1, wherein 3. The fuel injection control of an internal combustion engine according to claim 2, wherein the deviation angle control means increases the lift amount of the needle valve when increasing the deviation angle. apparatus. 4. The fuel injection control device for an internal combustion engine according to claim 1, wherein the deviation angle control means variably controls the deviation angle in accordance with a position of a piston during fuel injection. . 5. The deviation angle control means increases the deviation angle when the piston is near the top dead center as compared to when the piston is near the bottom dead center. The fuel injection control device for an internal combustion engine according to claim 4. 6. The fuel injection control apparatus for an internal combustion engine according to claim 5, wherein the deviation angle control means increases the deviation angle as the piston approaches a top dead center. 7. The deviation angle control means decreases the deviation angle at the beginning of a fuel injection period, and increases the deviation angle at a later stage of the fuel injection period.
3. The fuel injection control device for an internal combustion engine according to claim 1. 8. The fuel injection nozzle performs a pilot injection for injecting a fixed amount of fuel before the main injection, and the deviation angle control means sets the deviation angle larger during the main injection than during the pilot injection. The fuel injection control device for an internal combustion engine according to claim 4, wherein: 9. The system according to claim 1, wherein the deviation angle control means at the time of pilot injection increases the deviation angle when the internal combustion engine has a low load as compared to when the internal combustion engine has a high load. 9. A fuel injection control device for an internal combustion engine according to claim 8. 10. A central axis of the injection hole, an inner wall surface at a tip end of the nozzle body at a position where the injection hole is formed through,
The fuel injection control device for an internal combustion engine according to any one of claims 1 to 9, wherein a control range of the deviation angle is set based on an inclination angle formed by the control unit. 11. The fuel injection control device for an internal combustion engine according to claim 10, wherein the control range of the deviation angle is set wide by reducing the inclination angle. 12. The fuel injection control device for an internal combustion engine according to claim 1, wherein a control range of the deviation angle is set based on a length of the injection hole. . 13. The fuel injection control device for an internal combustion engine according to claim 12, wherein the control range of the deviation angle is set wide by shortening the length of the injection hole. 14. The fuel injection control for an internal combustion engine according to claim 1, wherein the fuel injection nozzle lifts a needle valve according to a magnitude of an energization voltage to a piezoelectric element. apparatus. 15. The fuel injection nozzle according to claim 1, wherein an axial direction of the fuel injection nozzle is substantially the same as an axial direction of a cylinder constituting the combustion chamber. A fuel injection control device for an internal combustion engine.