JP2015230001A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve having improved spray characteristics.SOLUTION: A fuel injection valve comprises: a needle 2 including a valve body portion 17 provided in a tip end portion thereof; and a nozzle body 1 accommodating therein the needle 2 so as to be able to move the needle 2 up and down, and including a seat portion 5, the valve body portion 17 being able to abut on a tip end portion of the seat portion 5, and controls fuel injection in response to lift of the needle 2, a sack chamber 13 being provided in an extreme tip end portion of the nozzle body 1, the sack chamber 13 being constituted by a hemispherical portion 13a including a hemispherical inner surface and a tubular portion 13b whose one end is connected to the seat portion 5 and whose other end is connected to the hemispherical portion 13a, an injection hole 4 communicating with the hemispherical portion 13a being provided in the nozzle body 1, and a portion 17b formed on a tip end of the valve body portion 17 and formed into a truncated conical shape converging toward a tip end direction being provided in the needle 2. A diameter Dof one end of the tubular portion is set equal to or smaller than 0.8 mm, and a distance h between a truncated surface 9 of the portion 17b and an extreme tip end portion 10 of the hemispherical portion 13a at a time of abutment between the valve body portion 17 and the seat portion 5 is set to be equal to or smaller than 0.15 mm.

Description

  The present invention relates to a fuel injection valve applied to a fuel injection device for an internal combustion engine.

  As a conventional fuel injection valve, for example, there is one disclosed in Patent Document 1. A needle is accommodated in the nozzle body of the fuel injection valve so as to be able to move up and down, and is configured to control fuel injection into the combustion chamber in the cylinder in accordance with the contact and separation of the tapered surfaces at the tip thereof. .

Japanese Patent Laid-Open No. 11-093805

  In a conventional fuel injection valve, when a small injection amount is obtained in a low lift state, the fuel injection is low and the spray spreads. On the other hand, when a large injection amount is obtained in a high lift state, a high penetration is performed. Is called. Due to this spray characteristic, during pilot injection with a small injection amount, the spray fuel burns in the vicinity of the outlet of the nozzle hole communicating with the combustion chamber. Then, during the subsequent main injection, the sprayed fuel is ignited at a position near the outlet of the nozzle hole, and smoke is generated, and a large amount of fuel flame injected at high penetration collides with the combustion chamber wall surface to cool it down. As a result, heat loss occurs and fuel consumption decreases.

  Accordingly, an object of the present invention is to provide a fuel injection valve with improved spray characteristics.

For this purpose, the present invention includes a needle having a valve body portion at a tip portion, and a nozzle body having a seat portion that can accommodate the needle body so that the valve body portion can abut on the tip portion. A fuel injection valve for controlling fuel injection according to the lift of the needle,
The nozzle body has a sac chamber provided at the most distal end thereof, and the sac chamber is connected to a hemispherical portion having a hemispherical inner surface, one end connected to the seat portion, and the hemispherical portion. A tubular portion having the other end, and the nozzle body has a nozzle hole communicating with the hemispherical portion,
The needle is formed on the distal end side of the valve body portion, and has a portion having a truncated cone shape that converges toward the distal direction,
The diameter of the tubular portion at the one end is 0.8 mm or less, and the distance between the truncated surface of the portion and the most distal portion of the hemispherical portion when the valve body portion and the seat portion are in contact with each other is 0. It is characterized by being 15 mm or less.

  According to the present invention, a fuel injection valve having favorable spray characteristics, that is, when a needle is in a low lift state for pilot injection and a small injection amount is obtained, a highly penetrating injection is performed, and a needle is in a high lift state for main injection. When obtaining a large injection amount, it is possible to realize a fuel injection valve that performs low penetration injection.

It is sectional drawing which shows the principal part of the fuel injection valve which concerns on a comparative example. It is sectional drawing which shows the principal part of the fuel injection valve which concerns on one Embodiment of this invention. (A) And (b) is sectional drawing for demonstrating operation | movement of the fuel injection valve of FIG. (A) And (b) is sectional drawing for demonstrating the preferable dimension setting of the principal part of a fuel injection valve. It is the graph which showed the change of the penetration force with respect to the time from the injection start of several fuel injection valves. It is a figure which shows the characteristic of the fuel injection valve comprised according to prescription | regulation of this invention. It is sectional drawing for demonstrating the problem which arises when the amount of lifts is excessive. It is a timing chart for explaining the concept of pilot injection and main injection according to one embodiment of the present invention. It is explanatory drawing which shows schematic structure of the diesel engine which can apply this invention, and its control system. It is sectional drawing which shows the whole structure of the fuel injection valve which can apply the principal part shown in FIG. It is a flowchart which shows an example of the control procedure for controlling the fuel injection valve which concerns on this invention. It is sectional drawing for demonstrating the structure which restrict | limits the maximum lift amount. It is sectional drawing which shows the modification of the principal part of the fuel injection valve shown in FIG.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

(Comparative example)
First, the main part of a fuel injection valve according to a comparative example, which is a premise of the present invention, will be described with reference to FIG. At the tip of the nozzle body 1 (the lower side in the figure is the tip side), a sheet portion 5 having a tapered surface that converges toward the tip direction, and a hemispherical sac chamber connected to the tip side of the sheet portion 5 3 and an injection hole 4 forming a fuel injection passage from the sac chamber 3 to the combustion chamber. On the other hand, a tapered portion 7a having a tapered surface having a convergence angle slightly smaller than the taper angle of the seat portion 5 is formed at the distal end portion of the needle 2, and a taper located at the distal end side having a slightly larger convergence angle. A valve body portion 7 having a tapered portion 7b formed with a surface and a relief portion 8 having a conical shape and formed at the most distal portion so as to be able to enter the sack chamber 3 is provided.

  The gap between the inner peripheral surface of the nozzle body 1 and the outer peripheral surface of the needle 2 is connected to, for example, a common rail that stores fuel pumped from a fuel supply pump (not shown) in a high pressure state. When fuel injection is not performed, the needle 2 is at the lowest position. At this time, the connecting portion 7c of the taper portions 7a and 7b abuts against the seat portion 5 to form a sealing line. Inflow of fuel is blocked. When the needle 2 is lifted (lifted) from this state, the connecting portion 7c is detached from the seat portion 5 to release the sealed state, so that the fuel flows into the sac chamber 3 and then into the combustion chamber via the nozzle hole 4. Fuel injection is performed. The fuel injection amount is controlled by adjusting the lift amount of the needle 2 and enlarging / reducing the cross-sectional area of the fuel flow path formed by the gap between the inner peripheral surface of the nozzle body 1 and the outer peripheral surface of the needle 2. For example, when performing pilot injection, the lift amount can be relatively small (low lift state), and when performing main injection, the lift amount can be relatively large (high lift state). .

  However, in the structure as shown in FIG. 1, even when a small injection amount is obtained in the low lift state, the conical escape portion 8 enters the sac chamber 3 and surrounds the entrant portion. 3 space is big. For this reason, a vortex is generated in the vicinity of the entrance of the nozzle hole 4 due to the flow separated from the side surface of the entry portion, and the vortex flows into the nozzle hole 4 communicating with the sac chamber, thereby reducing the fuel flow velocity. Therefore, in the low lift state, the fuel spray into the combustion chamber is low penetrating and the spray spreads. On the other hand, when a large injection amount is obtained as a high lift state (the state shown in FIG. 1), no vortex is generated or it is generated at a position away from the injection hole 4, so that the flow rate of fuel through the injection hole 4 Does not decrease, so that high-intensity injection is performed. Due to this spray characteristic, spray fuel burns in the vicinity of the outlet of the nozzle hole 4 during pilot injection with a small injection amount. Then, during the subsequent main injection, the sprayed fuel is ignited at a position near the outlet of the nozzle hole 4, and smoke is generated, and a large amount of fuel flame injected at high penetration collides with the combustion chamber wall surface. It is cooled and heat loss occurs, resulting in a reduction in fuel consumption.

  The present inventor has obtained the above knowledge and has come to make the present invention.

(Basic configuration)
FIG. 2 is a cross-sectional view showing the main part of the fuel injection valve according to one embodiment of the present invention, and the same reference numerals are assigned to the corresponding parts that perform the same functions as those shown in FIG. .

1 is different from the configuration of FIG. 1 in that the needle 2 is not a conical relief 8 but extends from the tapered portion 7a to the distal end side with a uniform convergence angle θ _ndl. A tapered portion 17b having a conical shape is formed, and the valve body portion 17 whose end face 9 is the terminal end of the needle 2 is employed. In addition, regarding the nozzle body 1 of the present embodiment, a sac chamber 13 is provided at the foremost portion thereof, and the sac chamber 13 is connected to the hemispherical portion 13a having a hemispherical inner surface and the seat portion 5 at one end. The other end is connected to the hemispherical portion 13a and has a tubular portion 13b having a cylindrical inner surface with a constant radius. The “hemispherical shape” here does not necessarily mean only a complete hemispherical shape, but includes a complete hemispherical shape and a similar shape. That is, “hemispherical shape” means a substantially hemispherical shape. Similarly, the “hemisphere portion” does not necessarily have a complete hemisphere shape, and can be rephrased as a substantially hemisphere portion in that sense. Here, the taper portion 7a of the needle 2 has a convergence angle smaller than the convergence angle of the seat portion 5, and the convergence angle θ _{ndl of the} taper portion 17b is the convergence angle θ _nzl of the seat portion 5 of the nozzle body 1. It is set larger (for example, θ _ndl = 60 °, θ _nzl = 59 °). Therefore, as shown by a two-dot chain line in FIG. 2, when the needle 2 is closed at the lowest position, the connecting portion 17 c between the tapered portion 7 a and the tapered portion 17 b of the valve body portion 17 comes into contact with the tapered portion 5. As a result, a sealing line is formed, and the vicinity of the head portion of the tapered portion 17 b enters the sack chamber 13.

  FIG. 3 is a cross-sectional view for explaining the operation of the fuel injection valve according to the present embodiment, in which the main part is shown broken along the needle center axis Cndl. When the needle 2 is lifted from the state when the valve is closed at the lowest position, a flow path is formed between the valve body portion 17 and the seat portion 5, that is, the inner peripheral surface of the nozzle body 1 and the outer peripheral surface of the needle 2. The gap portion is formed, and the fuel flows into the sac chamber 13 from the gap portion, and the fuel is injected into the combustion chamber via the nozzle hole 4. At this time, a flow along the tapered portion 17 b occurs at the entrance of the sack chamber 13, and then peels off and flows into the nozzle hole 4.

  At the time of low lift to obtain a small injection amount, as shown in FIG. 3A, the space of the sack chamber 13 surrounding the tapered portion 7b is narrow as the gap between the truncated surface 9 and the most distal portion 10 of the hemispherical hemispherical portion 13a. Since it is small, vortices are less likely to be formed by the separated flow, so that the fuel flow in the nozzle hole 4 is relatively less disturbed. Accordingly, the penetration force of the spray S is high and the spread of the spray S is small. On the other hand, when the space between the truncated surface 9 and the hemispherical most distal portion 10 expands as the lift increases, the flow separated from the tapered portion 17b of the needle 2 as shown in FIG. Thus, a vortex is generated in the vicinity of the ridgeline between the truncated surface 9 and the tapered portion 17b. When the lift amount reaches a certain amount, the vortex center Ec is generated at a position close to the entrance center Nc of the nozzle hole 4, and this vortex flows into the nozzle hole, whereby a strong swirling flow is generated in the nozzle hole 4. As a result, the spray S exiting the nozzle hole 4 has a radial velocity, so that it spreads greatly, and an increase in penetration force is suppressed.

  As described above, in the present embodiment, it is possible to control the vortex formation in the sac chamber 13 by appropriately determining the structure of the fuel injection valve, particularly the structure of the nozzle body and the tip of the needle. Spray characteristics can be realized. That is, at the time of low lift that realizes a small injection amount for pilot injection, vortices are hardly generated and the flow disturbance in the nozzle hole is small, so that high penetration is performed and the sprayed fuel is discharged from the outlet of the nozzle hole 4. Burns away. On the other hand, at the time of high lift that achieves a large injection amount for main injection, vortices are generated, and this is introduced into the injection hole 4 to suppress an increase in penetration force. It occurs at a position away from the outlet of the hole 4 and the collision of the flame with the combustion chamber wall is mitigated. As a result, the spray characteristics can be improved to suppress the generation of smoke and heat loss, and as a result, the effect of reducing fuel consumption can be obtained.

In order to obtain the above-described spray characteristics, in the present invention, as shown in FIG. 2, a diameter D _sac (hereinafter referred to as a _sac diameter) of one end of the _sac chamber 13 connected to the seat portion 5. The diameter of the inner surface of the tubular portion 13b is equal to or less than 0.8 mm, and the suck chamber 13 extends from the most distal portion of the needle 2 (that is, the truncated surface 9) when the needle 2 is in the lowest lowered position. Distance, that is, the clearance h is defined as 0.15 mm or less. Hereinafter, the reason why the dimensions are determined in accordance with the regulations will be described.

FIGS. 4 (a) and 4 (b) show high lift for structures where the _sac diameter D _sac is preferably defined (ie, 0.8 mm or less) and excessive (ie, greater than 0.8 mm), respectively. It shows the flow of fuel at the time. 4A, the distance between the inner surface of the tapered portion 17b and the inner surface of the sac chamber 13 is relatively small, and is formed by a gap between the inner peripheral surface of the nozzle body 1 and the outer peripheral surface of the needle 2. The change in the cross-sectional area of the flow path at the entrance from the flow path to the sack chamber 13 is small. For this reason, there is no significant reduction in the speed of the fuel flowing into the sac chamber 13. Therefore, the swirling speed of the vortex generated by the flow separated from the taper portion 17b of the needle 2 is increased, and since this vortex is introduced into the nozzle hole 4, an increase in the penetration force can be preferably suppressed. On the other hand, in the state of FIG. 4B, the flow path cross-sectional area is greatly enlarged at the entrance of the sack chamber 13, and the inflow speed is reduced. Accordingly, the swirling speed of the vortex generated by the flow separated from the taper portion 17b of the needle 2 is reduced, and even if this vortex is introduced into the nozzle hole 4, a sufficient swirling flow cannot be obtained, and the penetration force is increased. Cannot be effectively suppressed.

FIG. 5 shows the time when the needle 2 is lifted at a constant speed from a lift amount of zero (closed state) using several fuel injection valves having tip structures with different _sac diameters D _sac and clearances h. It is the graph which showed the change of penetration force with respect to (namely, time from the injection start). In FIG. 5, a fuel injection valve according to the provisions of the present invention, ie (i) a combination of D _sac = 0.70 mm and h = 0.04 mm, (ii) D _sac = 0.75 mm and h = 0.04 mm. And (iii) three fuel injectors each having a combination of D _sac = 0.70 mm and h = 0.11 mm, and a fuel injector outside the scope of the present invention, ie (iv) D _sac = 1. The change curve of the penetration force of one fuel injection valve which has a combination of 0 mm and h = 0.3 mm is illustrated. As is clear from FIG. 5, in a short period (corresponding to the minute injection amount) of the elapsed time from the start of the injection to 0.2 ms (corresponding to the minute injection amount), the penetration force is almost uniform in any of the cases (i) to (iv). Will increase. However, after that period, in all of cases (i) to (iii), the rate of increase of the penetration force is smaller than in the case of (iv), and the penetration force is relatively lower than in the case of (iv). I understand that Therefore, in the time of 0.5 ms or more which becomes a large injection amount, in the case of (i) to (iii), the main injection with a reduced penetration force can be performed compared to the case of (iv).

After verifying various combinations including these cases, the inventor configures the fuel injection valve in accordance with the provisions of the present invention, that is, the sack diameter D _sac is 0.8 mm or less and the clearance h is 0.15 mm or less. It was confirmed that the desired spray characteristics could be realized.

(Lift amount setting)
Now, since the horizontal axis of FIG. 5 shows the time when the needle 2 is lifted at a constant speed from the closed state (time from the start of injection), the horizontal axis substantially represents the lift amount, Therefore, FIG. 5 represents the change of the penetration force with respect to the lift amount. If attention is paid to (i) to (iii) having a combination of a sack diameter and a clearance, generally, spray characteristics as shown in FIG. 6 are obtained when the provisions of the present invention are followed. Here, the upper part of FIG. 6 shows the change of the lift amount with respect to the time from the start of injection, and the lower part shows the change of the penetration force with respect to the time from the start of injection. As can be seen from the upper part of FIG. 6, the needle 2 is lifted at a constant speed. Therefore, based on the characteristics shown in FIG. 6, a preferable lift amount can be set in each of the pilot injection and the main injection.

  Specifically, the required penetrating force can be obtained by setting the lift amount corresponding to the case where the time from the start of injection is 0.2 ms or less with respect to the minute injection amount. For the large injection amount, a lift amount corresponding to the case where the time from the start of injection is 0.5 ms or more can be set.

  However, it has been confirmed that when the lift amount becomes excessive, the penetration force starts to increase greatly again. As shown in FIG. 7, the reason is that as the lift amount increases, the positional deviation in the direction of the needle center axis Cndl between the pier surface 9 and the inlet of the nozzle hole 4 increases, and the vortex center Ec becomes the inlet of the nozzle hole. This is because the vortex is less likely to flow into the nozzle hole by moving away from the center Nc, so that the swirling flow in the nozzle hole 4 is weakened and the speed in the radial direction of the spray is reduced. Therefore, if the lift amount corresponding to the time from the start of injection is 0.5 to 1.1 ms is set for the large injection amount based on the characteristics shown in FIG. The flow can be maintained and an increase in penetration can be suppressed. Note that the lift amount corresponding to the case where the time from the start of injection exceeds 1.1 ms is not set, that is, the lift amount corresponding to the case where the time from the start of injection is 1.1 ms is the maximum lift amount Lmax. It is preferable to do so. This point will be described later.

As shown in FIG. 8, for example, a lift amount Lp corresponding to the point at which 0.1 ms has elapsed from the start of injection is determined, pilot injection P is started (fuel injection valve is turned on) (time tp _on ), and valve closing is instructed The lift amount Lp can be maintained until (when the fuel injection valve is turned off, time point tp _off ). Also, for example, a lift amount Lm corresponding to the time when 0.75 ms has elapsed from the start of injection is determined, main injection M is started (fuel injection valve is turned on) (time tm _on ), and a valve closing instruction is given (fuel injection valve is turned _on ). The lift amount Lm can be maintained until the time point of turning off, the time point tm _off ). Incidentally, (time from _{tm on} until _{tm off)} period of the ON period (from the time _{tp on} to time _{tp off)} and the main injection for turning on the pilot injection are all of the required fuel injection amount and injection It is preferable to set in consideration of the rise / fall time.

(Configuration of internal combustion engine and its control system)
FIG. 9 is an explanatory diagram showing a schematic configuration of a diesel engine as an example of an internal combustion engine to which the present invention can be applied and its control system. However, the present invention is applicable to internal combustion engines and control systems other than those described here. The engine 101 includes a cylinder block 119 having a plurality of cylinders 118 and a cylinder head 103. Each cylinder 118 accommodates a piston 102, and each piston 102 is connected to a crankshaft (not shown), which is an output shaft of the engine, via a connecting rod 130. The engine 101 is provided with a combustion chamber 120 for each cylinder. An intake passage 108 and an exhaust passage 109 are connected to each combustion chamber 120, and an EGR passage 123 into which an EGR valve 122 is inserted connects these passages.

  A fuel injection valve 110 that injects fuel into the combustion chamber 120 of each cylinder 118 is attached to the cylinder head 103. This fuel injection valve 110 includes the main part shown in FIG. 2, and can turn on / off pilot injection and main injection by changing the lift amount of the needle 2 as described above. It is. The fuel injection valve 110 provided for each cylinder 118 is connected to a common rail 111 that is a common pressure accumulating pipe, and the common rail 111 is further connected to a supply pump (not shown) via a supply pipe. It is possible to supply fuel inside. On the other hand, air can be introduced into the cylinder 118 from the intake passage 108 via the throttle valve 121.

  For an electronic control unit (hereinafter referred to as ECU) 106 that constitutes a control unit, a rail pressure sensor 112 that detects the fuel pressure in the common rail 111, an intake air temperature sensor 113 that detects the temperature of the intake air, and the temperature of the cooling water A water temperature sensor 114 for detecting the accelerator, an accelerator opening sensor 115 for detecting the accelerator opening, an intake air amount sensor 116 for detecting the intake air amount, a crank angle sensor 117 for detecting the crank angle, and an internal pressure of the intake manifold. An intake pressure sensor 128 is connected, and the operation of the engine 101 is controlled based on those detection signals.

  FIG. 10 is a cross-sectional view showing the overall configuration of the fuel injection valve 110 to which the main part shown in FIG. 2 can be applied. In addition, the main part which has the structure and dimension according to the prescription | regulation of this invention is applicable to the fuel injection valve which has various well-known structures including the fuel injection valve 110 shown in FIG.

  In the configuration of FIG. 10, the nozzle body 1 is connected to the valve body 201 by a fastening member 202. In the valve body 201, the needle stopper 23 and the balance piston 24 are sequentially connected to the base end side (the upper side in the figure is the base end side) with respect to the needle 2 described above. It can slide in the state. Then, high pressure fuel is supplied from the common rail 111 to the upper end surface of the balance piston 24 via the high pressure passage 28. Further, high pressure fuel is supplied to a gap formed by the inner peripheral surface of the nozzle body 1 and the outer peripheral surface of the needle 2 through a high pressure chamber 204 communicating with the high pressure passage 28. As shown in the figure, the needle 2 has a stepped portion 203 whose diameter is enlarged on the proximal end side, and is accommodated in the nozzle body 1 so that the stepped portion 203 is located in the high pressure chamber 204. Therefore, a push-up force that pushes up the needle 2 acts on the needle 2 by the high pressure acting on the valve body portion 17 (particularly the portion 7 a) on the distal end side and the stepped portion 203 located in the high-pressure chamber 204. On the other hand, the needle stopper lower chamber 31 adjacent to the lower side of the needle stopper 23 is supplied with fuel pressurized by a piezo piston 26 connected to the piezo actuator 25 and slidable in an oil-tight state in the valve body 201. The

  The upper chamber 32 adjacent above the needle stopper 23 communicates with a low pressure chamber 51 in which the piezo actuator 25 is accommodated. A spring 41 that urges the needle stopper 23 in the valve closing direction of the needle 2 together with the balance piston 24 is housed in the upper chamber 32. In the piezo piston 26, there is formed a communication passage that connects the lower chamber 61 and the low pressure chamber 51 adjacent to each other below, and a check that blocks the flow from the lower chamber 61 to the low pressure chamber 51 in the communication passage. A valve 62 is arranged. Further, the piezo piston 26 is biased toward the piezo actuator 25 by a spring 63.

  When the piezo actuator 25 is not energized (when the valve opening is not instructed), the needle 2 is pressed down by the cooperation of the biasing force of the spring 41 and the balance piston 24 in which the high pressure is always applied to the upper end surface. Has been closed. However, when the valve opening is instructed, that is, when the piezo actuator 25 is energized, the piezo actuator 25 expands to move the piezo piston 26 downward in the drawing, and the spring 63 is compressed accordingly. Here, since the flow of fuel from the lower chamber 61 to the low pressure chamber 51 is blocked by the check valve 62 arranged in the piezo piston 26, the lower chamber 61 and a needle stopper communicating with the lower chamber 61 are compressed as the spring 63 is compressed. The internal pressure of the lower chamber 31 increases. As the internal pressure rises, the needle stopper 23 is pushed up, and when the above-mentioned push-up force acting on the needle 2 exceeds the push-down force, the needle 2 starts to be lifted to open the valve hole 4 as described above. From the fuel to the combustion chamber 120.

  In the above configuration, the downward force (which is derived from the pressure of the high-pressure fuel and the biasing force of the spring 41) that pushes down the needle 2 and closes the valve, and the upward force that pushes up the needle 2 and opens the valve. The lift on / off of the needle 2 can be controlled in accordance with the balance relationship, and the lift of the needle 2 can be controlled in accordance with the extension amount of the piezo element.

  FIG. 11 is a flowchart showing an example of a control procedure executed by the ECU 106 in order to control the fuel injection valve according to the present invention using the configuration shown in FIG. In this procedure, for each of the pilot injection and the main injection, appropriate fuel injection is performed based on the detected value of the accelerator opening by the accelerator opening sensor 115 and the engine speed calculated based on the detected value of the crank angle sensor 117. The amount and fuel injection timing (needle 2 lift start timing) are set (steps S1 and S2). Next, the common rail pressure for performing the pilot injection and the main injection is set by the same method (step S3). At this time, feedback control using the detection signal of the rail pressure sensor 112 is performed. Further, the common rail pressure when performing the pilot injection and the main injection may be the same or different. These settings may be performed by function calculation, or may be performed by referring to a predetermined map stored in a ROM included in the ECU 106.

  In step S4, the operation amount of the piezo actuator 25 corresponding to the setting in step S1, that is, the extension amount (corresponding to the lift amount of the needle 2) and the ON period of the piezo actuator 25 are set as the pilot injection and the main injection. Set for each.

After that, when the pilot injection time set in step S2 comes according to the control procedure not shown in the figure, as shown in FIG. By setting the piezo actuator 25 and turning on the piezo actuator 25, the pilot injection P is started (time tp _on ), and the piezo actuator 25 can be turned _off when a predetermined time has elapsed (time tp _off ). Then, when the main injection time set in step S2 comes, as shown in FIG. 8, for example, a lift amount corresponding to the time point at which 0.75 ms has elapsed from the start of injection is set as the lift amount of the needle 2, and the piezoelectric actuator 25 The main injection M is started by turning on (time tm _on ), and the piezoelectric actuator 25 can be turned _off when a predetermined time has elapsed (time tm _off ).

(Other embodiments)
The present invention is not limited to the embodiment described above, and various modifications or changes can be made. For example, in the above-described embodiment, the lift amount fixed for each of the pilot injection and the main injection is used, but may be changed as appropriate. Even if the lift amount is fixed or can be changed, as is clear from FIG. 6, at the time of pilot injection at any time within a period of more than 0 ms and less than 0.2 ms. A corresponding lift amount can be used, and at the time of main injection, a lift amount corresponding to any time within a period of 0.5 ms to 1.1 ms can be used.

  For the main injection, the maximum lift amount that can maintain the swirling flow in the nozzle hole 4 may be set in consideration of the characteristics shown in FIG. In this case, as shown in FIG. 12, the position of the needle tip, that is, the truncated surface 9 when the needle 2 is lifted to the maximum is lifted from the intersection Cp between the central axis Cnzl of the nozzle hole 4 and the central axis Cndl of the needle 2. It is possible to adopt a configuration in which the maximum lift amount is set so that the position is separated by the radius d / 2 of the nozzle hole 4 in the direction. According to this, the center of the vortex generated in the vicinity of the ridge portion between the tapered portion 17b and the pier surface 9 is substantially contained (overlapped) within the height range of the entrance of the nozzle hole 4 in the central axis Cnzl direction. Thus, the vortex can surely flow into the nozzle hole. As shown in FIG. 6, the maximum lift amount Lmax corresponds to the lift amount when the time from the start of injection is 1.1 ms, for example.

Furthermore, in the above-described embodiment, the tubular portion 13b of the sac chamber 13 has a cylindrical inner surface with a constant radius. However, for example, as shown in FIG. 13, the portion may be a tubular portion 13 b ′ having a tapered surface that converges from the portion connected to the seat portion 5 toward the hemispherical portion 13 a. Also in this case, the sack diameter D _sac is an inner diameter at one end of the tubular portion 13b ′ connected to the seat portion 5. Moreover, the convergence angle θsac of the tapered surface of the tubular portion 13b ′ can be less than the convergence angle θ _ndl of the truncated conical tapered portion 17b of the valve body portion 17.

DESCRIPTION OF SYMBOLS 1 Nozzle body 2 Needle 5 Seat part 17 Valve body part 13 Suck chamber 4 Injection hole 9 Wharf surface 10 Hemispherical part most advanced part 13a Hemispherical part 13b, 13b 'Tubular part 110 Fuel injection valve

Claims (1)

A needle body having a valve body portion at a distal end portion, and a nozzle body having a seat portion which can accommodate the valve body portion at the distal end portion and accommodates the needle so as to be movable up and down, and according to the lift of the needle A fuel injection valve for controlling fuel injection,
The nozzle body has a sac chamber provided at the most distal end thereof, and the sac chamber is connected to a hemispherical portion having a hemispherical inner surface, one end connected to the seat portion, and the hemispherical portion. A tubular portion having the other end, and the nozzle body has a nozzle hole communicating with the hemispherical portion,
The needle is formed on the distal end side of the valve body portion, and has a portion having a truncated cone shape that converges toward the distal direction,
The diameter of the tubular portion at the one end is 0.8 mm or less, and the distance between the truncated surface of the portion and the most distal portion of the hemispherical portion when the valve body portion and the seat portion are in contact with each other is 0. A fuel injection valve characterized by being 15 mm or less.