JP3235286B2 - Fuel injection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an internal combustion engine which accumulates high-pressure fuel in a common rail and injects the accumulated high-pressure fuel into an internal combustion engine. The present invention relates to a fuel injection device for a diesel engine in which a stable main injection is obtained by delaying a return to an initial position.

[0002]

2. Description of the Related Art Conventionally, a high-pressure fuel is stored in a kind of surge tank called a common rail, and the stored high-pressure fuel is injected into a diesel engine. Etc.) have been proposed. This pressure-accumulation type fuel injection device drives the three-way solenoid valve twice for the purpose of performing stable combustion from the start of the main injection and suppressing the vibration of the diesel engine, so that the three-way solenoid valve is driven before the main injection (main injection). A small amount of high-pressure fuel is injected beforehand (so-called pilot injection). The accumulator type fuel injection device includes a nozzle having a needle for opening and closing an injection hole for injecting high-pressure fuel, and a three-way solenoid valve for controlling the injection timing and injection amount of the nozzle.

As shown in FIGS. 15 to 17, a nozzle has a hydraulic piston 101 for driving a needle (not shown), and a nozzle holder 103 having a back pressure chamber 102 for supplying and discharging high-pressure fuel. It has. Further, inside the back pressure chamber 102 of the nozzle, a nozzle holder 103 is provided.
Movable valve element (so-called one-way orifice) loosely fitted inside
104, a coil spring 105 for pressing the movable valve body 104 against a valve seat 111 formed on a valve body 110 of a three-way solenoid valve, and a seat 106 for holding the coil spring 105 are provided. Then, the movable valve element 104
Is formed with a throttle portion 107 for delaying the discharge speed of the high-pressure fuel from the back pressure chamber 102 to the communication passage 112 formed in the valve body 110.

[0004] Next, the operation of the pressure accumulating type fuel injection system during non-pilot injection will be briefly described with reference to a time chart of FIG. At the start of fuel injection, the valve of the three-way solenoid valve rises, so that the back pressure chamber 1
The discharge of the high pressure fuel in 02 is started. Therefore, FIG.
As shown in FIG. 5, the high-pressure fuel is slowly discharged through the restricting portion 107 of the movable valve body 104 seated on the valve seat 111. Accordingly, the needle slowly rises, and the injection of the high-pressure fuel from the injection hole is started.

At the end of the fuel injection, the three-way solenoid valve is lowered so that the back pressure chamber 10
The introduction of the high-pressure fuel into the inside of the movable valve body 10 starts.
4 is separated from the valve seat 111. At this time, as shown in FIGS. 16 and 17, high-pressure fuel is instantaneously introduced into the back pressure chamber 102 through a gap between the outer peripheral surface of the movable valve body 104 and the inner peripheral surface of the nozzle holder 103, Piston 101
Falls at once. As a result, the needle descends at once and closes the injection hole, and the fuel injection ends, so that the delta-type injection rate is obtained. After the fuel injection is completed, the movable valve element 1
When the back pressure chamber 102 is filled with high-pressure fuel and the inner pressure of the back pressure chamber 102 and the inner pressure of the communication passage 112 are equal, the valve seat 1 is energized by the coil spring 105.
Sit at 11.

Next, the operation of the pressure-accumulation type fuel injection device when the injection interval from the pilot injection to the main injection is large will be briefly described with reference to the time chart of FIG.
When the pilot required injection interval is large, the main injection starts after the movable valve element 104 is seated on the valve seat 111 (returns to the initial position) after the pilot injection ends.
The delta injection rate is the same as in the non-pilot injection.

Next, the operation of this pressure-accumulation type fuel injection device when the injection interval from the pilot injection to the main injection is small will be briefly described with reference to a time chart of FIG.
When the interval from the pilot injection to the main injection is small, the main injection starts before the movable valve body 104 is seated on the valve seat 111 (returns to the initial position), so that the convex type having a larger injection rate than the non-pilot injection. Injection rate.

[0008]

However, in the conventional pressure-accumulation type fuel injection system, the injection interval from the pilot injection to the main injection is large and the injection interval is small even when the diesel engine is in the normal operation state. Exists. In such a case, the movable valve element 104 is
By sitting on (returning to the initial position) or not at 11, as shown in FIG. 21, asymmetry between the delta-type injection rate and the convex-type injection rate is caused during the main injection. In such an asymmetric region, since the injection amount of the high-pressure fuel into the combustion chamber of the diesel engine varies, there has been a problem that the vibration of the diesel engine increases.

The present invention eliminates asymmetry during the main injection within the injection interval from the pilot injection to the main injection in the normal operation state of the internal combustion engine to eliminate the variation in the injection amount of the high-pressure fuel and to reduce the vibration of the internal combustion engine. It is an object of the present invention to provide a fuel injection device for an internal combustion engine that can suppress the occurrence of a fuel injection.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a fuel injection device for an internal combustion engine, in which pilot injection is performed before main injection for injecting high pressure fuel into an internal combustion engine. A pressure-supplying / discharging back pressure chamber, a valve seat provided on the side opposite to the injection hole side of the back pressure chamber, and a tubular member having a communication passage opened by the valve seat, and movable into the tubular member A needle that closes the injection hole when fuel is introduced into the back pressure chamber and opens the injection hole when fuel is discharged from the back pressure chamber; and a needle that is movable into the back pressure chamber of the tubular member. And when the internal pressure on the communication path side is lower than the internal pressure on the back pressure chamber side, the valve seats on the valve seat to shut off the back pressure chamber and the communication path, and the back pressure From the back pressure chamber to the communication passage by communicating the chamber with the communication passage. A movable valve body having a throttle portion for delaying a fuel discharge speed, and a delay means for delaying the movable valve body from sitting on the valve seat within an injection interval from a pilot injection to a main injection in a normal operation state of the internal combustion engine. And technical means having the following.

The delay means eliminates a gap between the outer peripheral surface of the movable valve body and the inner peripheral surface of the back pressure chamber of the tubular member. Thus, when fuel is introduced into the back pressure chamber, fuel is prevented from flowing from around the movable valve element. Further, a spring for urging the movable valve body toward the valve seat is provided as the delay means, and the set load and the spring constant of the spring are made very weak. This prevents the movable valve body from sitting on the valve seat within the injection interval from the pilot injection to the main injection in the normal operation state of the internal combustion engine. Further, as the delay means, the axial size of the back pressure chamber is increased to increase the moving range of the movable valve element. This prevents the movable valve body from sitting on the valve seat within the injection interval from the pilot injection to the main injection in the normal operation state of the internal combustion engine.

[0012]

According to the present invention, when the fuel is discharged from the back pressure chamber to the communication passage via the throttle of the movable valve body, the needle slowly moves because the fuel discharge speed is limited by the throttle. Pilot injection is started by opening the injection hole. Then, when fuel is introduced into the back pressure chamber from the communication passage, the movable valve element is separated from the valve seat and the needle closes the injection hole, thereby ending the pilot injection.

Then, the fuel is slowly introduced through the throttle portion of the movable valve body, and the internal pressure on the side of the communication passage from the movable valve body is reduced.
When the pressure drops below the internal pressure on the pressure chamber side, the movable valve element is displaced to the side seated on the valve seat. At this time, the movable valve element is not seated within the injection interval from the pilot injection to the main injection in the normal operation state of the internal combustion engine by the delay means. Accordingly, the main injection is started before the movable valve element is seated regardless of the injection interval from the pilot injection to the main injection, so that the main injection can be prevented from entering asymmetrically.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel injection device for an internal combustion engine according to the present invention will be described based on a plurality of embodiments shown in FIGS.

FIGS. 1 to 12 show a first embodiment of the present invention. FIG. 1A shows a main back pressure chamber of a pressure accumulating fuel injection device for a diesel engine. 1 (B) is a diagram showing the vicinity of an injection hole of the pressure accumulating fuel injection device, and FIG. 2 is a diagram showing the entire structure of the pressure accumulating fuel injection device.

The pressure-accumulating fuel injection device 1 is attached to each cylinder of a diesel engine (not shown), and is connected to an introduction pipe (not shown) branched from a common surge tank (not shown). In addition, the accumulator type fuel injection device 1
The high-pressure fuel pumped from a surge tank by a fuel pump (not shown) rotated by a diesel engine is always supplied from an introduction pipe.

Such an accumulator type fuel injection device 1 is shown in FIG.
As shown in the figure, the engine is composed of a needle 2, a nozzle body 3, a hydraulic piston 4, a nozzle holder 5, a three-way solenoid valve 6, etc., and performs pilot injection before the main injection over the entire operation range of the diesel engine. . The nozzle (injection valve) is constituted by the needle 2, the nozzle body 3, the hydraulic piston 4, and the nozzle holder 5.

As shown partially in FIG. 1B, the needle 2 has a nozzle sheet portion 33 of the nozzle body 3 at the tip end side.
There is a seat portion 21 that sits on the seat. This needle 2
The end is connected to the hydraulic piston 4, and the hydraulic piston 4 moves toward the three-way solenoid valve 6 to separate the seat portion 21 from the nozzle seat portion 33, and the hydraulic piston 4 returns to the original position, whereby the seat portion 21 is moved. Nozzle sheet part 33
To sit down.

The needle 2 moves from the start of fuel injection to the end of fuel injection, as shown in FIGS.
As shown in the time chart of No. 1, it moves (lifts) in the reciprocating direction. 5, 10, and 11, the upper end position represents the full lift of the needle 2.

As shown partially in FIG. 1B, the nozzle body 3 slidably holds the needle 2 on its inner periphery, and high-pressure fuel is constantly supplied from a surge tank via an introduction pipe. It has a fuel reservoir 31, an injection hole 32 for injecting high-pressure fuel, a nozzle seat 33 connected to the injection hole 32 and on which the needle 2 is seated, and a suck chamber 34 formed at the tip. The injection of the high-pressure fuel from the injection hole 32 is performed when the needle 2 moves away from the nozzle seat 33 and the fuel pool 31
And when the suck room 34 communicates.

The lower end of the hydraulic piston 4 shown in FIG. 2 is connected to the needle 2 via a pressure pin 41. When the back pressure becomes low, the pressure in the nozzle body 3 causes the urging force of the coil spring 42 to be applied. Overcoming Figure 2
Moves upward in the figure (on the three-way solenoid valve 6 side).

When the back pressure becomes high, the hydraulic piston 4 overcomes the pressure in the nozzle body 3 due to the difference in pressure receiving area and the urging force of the coil spring 42, as shown in FIG.
Moves downward in the figure (toward the nozzle body 3).

The nozzle holder 5 includes a fuel passage 51, a main back pressure chamber 52, a sub back pressure chamber 53, a first valve 7, and a second valve 8.
And a coil spring 9. The fuel passage 51 is
The fuel reservoir 31 in the nozzle body 3 communicates with the introduction pipe, and is a passage that always guides the high-pressure fuel to the fuel reservoir 31.

The main back pressure chamber 52 is open at the end face 54 of the nozzle holder 5 on the side of the three-way solenoid valve 6, and furthermore, has a stepped shoulder 55 formed on the nozzle body 3 side and the end face of the three-way solenoid valve 6. It is surrounded by the step shoulder 56 formed.

The auxiliary back pressure chamber 53 has a smaller diameter than the main back pressure chamber 52 and communicates with the main back pressure chamber 52 via a shoulder 55 having a step. The sub-back pressure chamber 53 slidably holds the hydraulic piston 4.

The main back pressure chamber 52 and the sub back pressure chamber 53 have a high internal pressure when high-pressure fuel is supplied from the three-way solenoid valve 6 and a low internal pressure when high-pressure fuel is discharged from the inside. Become. Further, the main back pressure chamber 52 and the sub back pressure chamber 53
When the pressure becomes high, the hydraulic piston 4 is configured to move to the needle 2 side more than the first valve 7 by a predetermined lift amount L (see FIG. 1) from the stepped shoulder portion 55. The stepped shoulder portion 55 is formed in an annular shape, and the first valve 7
Sits down. The stepped shoulder portion 56 is a valve seat of the present invention, and is formed in an annular shape, and the second valve 8 is seated thereon.

The first valve 7 has a cylindrical shape, and is disposed in the main back pressure chamber 52 so as to be able to reciprocate within the shoulder 55 on the stepped side. The first valve 7 has a first orifice 73 that connects an end surface 71 on the side of the stepped shoulder portion 55 and an end surface 72 on the side of the stepped shoulder portion 56 at the center, and has an outer peripheral surface and an inner peripheral surface of the nozzle holder 5. The outer diameter is smaller than the diameter of the main back pressure chamber 52 so that a gap is formed between the main back pressure chamber 52 and the main back pressure chamber 52.

The first orifice 73 communicates the main back pressure chamber 52 with the sub back pressure chamber 53, and the main back pressure chamber 52 moves the sub back pressure chamber 5 from the main back pressure chamber 52.
The moving speed of the hydraulic piston 4 is reduced by slowing down the introduction speed of the high-pressure fuel into the fuel tank 3.

The first valve 7 is connected to the hydraulic piston 4
Is always projecting into the main back pressure chamber 52,
The side end surface 71 is seated. Also, the first valve 7
When high-pressure fuel is introduced into the main back pressure chamber 52, the end face 71 is stepped over the shoulder 5 while pressing the hydraulic piston 4 toward the needle 2.
5, the communication between the main back pressure chamber 52 and the sub back pressure chamber 53 is interrupted, and when high-pressure fuel is discharged from the main back pressure chamber 52, the end face 71 with the hydraulic piston 4 becomes a stepped shoulder. Move away from 55.

The second valve 8 is a movable valve body according to the present invention, has a cylindrical shape, and is disposed so as to be able to reciprocate within the stepped shoulder portion 56 of the main back pressure chamber 52. This second valve 8 is
At the center, the end surface 81 on the side of the stepped shoulder 55 and the stepped shoulder 56
A second orifice 83 communicating with the side end face 82,
As shown in FIG. 3, the outer peripheral surface is formed as a cylindrical seal portion 84 so as to fill a gap with the inner peripheral surface of the nozzle holder 5. The cylindrical seal portion 84 is a delay unit of the present invention, and prevents the high-pressure fuel from leaking from between the inner peripheral surface of the nozzle holder 5 and the outer peripheral surface of the second valve 8.

The second orifice 83 is a throttle portion of the present invention, and communicates the main back pressure chamber 52 with a communication passage 66 described later, and introduces high-pressure fuel from the communication passage 66 into the main back pressure chamber 52. The moving speed of the needle 2 and the hydraulic piston 4 is reduced by reducing the speed. The second orifice 83 slows the speed of discharging the high-pressure fuel from the main back pressure chamber 52 to the communication passage 66 to slow the moving speed of the needle 2 and the hydraulic piston 4.

When the high-pressure fuel is introduced into the main back pressure chamber 52, the second valve 8 separates the end face 82 from the shoulder 56 and presses the first valve 7 via the coil spring 9, When the high-pressure fuel is discharged from the main back pressure chamber 52, the fuel is moved with the first valve 7 via the coil spring 9 so that the end face 82 is seated on the shoulder 56 with the step, and the communication path 6 with the main back pressure chamber 52 is formed.
The communication state with 6 is cut off.

The end faces 7 of the first and second valves 7 and 8
1, 82, that is, the contact surfaces of the first and second valves 7, 8 with the stepped shoulders 55, 56 are flattened to maintain the sealing performance.

The coil spring 9 is a delay means of the present invention. The coil spring 9 is supported by the end face 72 of the first valve 7 and the end face 81 of the second valve 8, and attaches the first valve 7 to the shoulder 55. And the second valve 8 is urged toward the stepped shoulder 56 side. As shown in the graph of FIG. 4, the second valve 8 of the coil spring 9 is seated on the stepped shoulder 56 within the pilot required injection interval (for example, 0.5 msec to 2 msec) in the normal operation state of the diesel engine. The spring force is set so as not to return to the initial position).

The three-way solenoid valve 6 has a coil 61, an inner valve 62, an outer valve 63, and a valve body 64. The inner valve 62 is slidably disposed in the outer valve 63. The outer valve 63 is slidably disposed in the valve body 64 and has an oil passage 65 inside.

The valve body 64 slidably holds the outer valve 63 on its inner periphery, and has a communication passage 66, fuel passages 67 and 68, and a storage chamber 69 formed therein. Note that the valve body 64, together with the nozzle body 3 and the nozzle holder 5, constitutes the tubular member of the present invention.

The communication passage 66 is opened at the nozzle holder side end surface (stepped shoulder portion 56), and the main back pressure chamber 5 of the nozzle holder 5 is opened.
Face 2. One end of the communication path 66 has the nozzle holder 5.
And the other end thereof communicates with a storage chamber 69 that houses the outer valve 63.

The fuel passage 67 is open at the end face on the nozzle holder 5 side, and high-pressure fuel is always introduced into the inside thereof. One end of the fuel passage 67 is connected to the fuel passage 5 of the nozzle holder 5.
1 and the other end thereof communicates with the storage chamber 69. The fuel passage 68 opens at the end face on the nozzle holder 5 side, and has one end communicating with a low-pressure line (not shown) for returning fuel into the surge tank, and the other end communicating with the storage chamber 69.

When the coil 61 is turned on, the three-way solenoid valve 6 moves with the inner valve 62 and the outer valve 63.
2 is moved upward in FIG. 2 to cut off the communication state between the communication passage 66 and the fuel passage 67, and the communication passage 66 and the fuel passage 68 are communicated via the storage chamber 69, and the main back of the nozzle holder 5 is The high-pressure fuel in the pressure chamber 52 is discharged.

When the coil 61 is turned off, the three-way solenoid valve 6 moves only the outer valve 63 downward in FIG. 2 to cut off the communication between the communication passage 66 and the fuel passage 68, and The high pressure fuel is introduced into the main back pressure chamber 52 of the nozzle holder 5 by making the fuel passage 67 communicate with the fuel passage 67 via the oil passage 65.

[Operation of the First Embodiment] Next, the operation of this embodiment during non-pilot injection will be described with reference to FIGS. This non-pilot injection is performed when the diesel engine is in a high load operation state (for example, at an engine speed of 4000 rpm).
m or more), and the injection interval is, for example, 30 msec.

When the coil 61 of the three-way solenoid valve 6 is off, the outer valve 63 is at the initial position h0 (see the time chart of FIG. 5), and the high-pressure fuel is stored in the main back pressure chamber 52 and the sub back pressure chamber 53. And the internal pressures of the main back pressure chamber 52 and the sub back pressure chamber 53 are high. Therefore, FIG.
As shown in (A), the end face 71 of the first valve 7 is seated on the shoulder 55, and the hydraulic piston 4 is arranged at a position lower than the end face 71 of the first valve 7 by a predetermined lift amount L. You. Therefore, the needle 2 connected to the hydraulic piston 4 via the pressure pin 41 is moved to the initial lift position a.
(Refer to the time chart in FIG. 5).

As a result, the seat 21 of the needle 2
As shown in FIG. 1B, the fuel pool 31 and the suck chamber 34 are shut off by sitting on the nozzle seat portion 33 of the nozzle body 3. Therefore, fuel is not injected from the injection holes 32.

When the coil 61 of the three-way solenoid valve 6 is turned on, the outer valve 63 rises to the full lift position h1 (see the time chart of FIG. 5), and the communication path 66
The high-pressure fuel in the main back-pressure chamber 52 and the sub-back-pressure chamber 53 is also slowly discharged through the second orifice 83 formed in the second valve 8.
And the internal pressure of the auxiliary back pressure chamber 53 becomes low. For this reason, as shown in FIG.
As the high-pressure fuel in the main back pressure chamber 52 is discharged while abutting on the end face 71 of the valve 7, the hydraulic piston 4 and the first valve 7 rise slowly from the shoulder 55.
Therefore, the needle 2 moves up to the full lift position b (see the time chart in FIG. 5).

As a result, the seat 21 of the needle 2
By slowly moving away from the nozzle seat portion 33 of the nozzle body 3, the injection holes 32 are opened, and high-pressure fuel is injected into the combustion chamber of the diesel engine. During the injection period, the internal pressures of the main back pressure chamber 52 and the sub back pressure chamber 53 are low as shown in FIG.
Is located at the full lift position in a state of contacting the end face 71 of the first valve 7, so that the needle 2 is also at the full lift position c.
(Refer to the time chart in FIG. 5).

When the fuel injection is completed, the coil 61 of the three-way solenoid valve 6 is turned off, and the outer valve 63 returns to the initial position h0 (see the time chart of FIG. 5). Introduced communication path 66
The internal pressure becomes high, the second valve 8 is pushed down by this pressure, and the end face 82 of the second valve 8 is lowered away from the stepped shoulder 56 (initial position h0) (see the time chart of FIG. 5).

That is, when the second valve 8 is immediately lowered to the full lift position h1 (see the time chart of FIG. 5), the pressure in the main back pressure chamber 52 becomes high at a stretch. The valve 7 is quickly pushed down, as shown in FIG. 8, the end face 71 of the first valve 7 is instantly seated on the stepped shoulder 55, and the needle 2 is located at the lift position d (see the time chart of FIG. 5). As a result, a good injection cut-off is achieved, and a delta-type injection rate with a reduced initial injection rate is obtained.

After the end surface 71 of the first valve 7 is instantly seated on the shoulder 55, the introduction speed of the high-pressure fuel into the sub-back pressure chamber 53 is limited according to the diameter of the first orifice 73. Therefore, the moving speed of the hydraulic piston 4 becomes slow. Thereafter, as shown in FIG. 9, when the hydraulic piston 4 separates from the end face 71 of the first valve 7 and drops by a predetermined lift amount L, the needle 2 moves to the initial lift position e (see the time chart of FIG. 5). Return to When the main back pressure chamber 52 and the communication passage 66 are filled with the high-pressure fuel, FIG.
As shown in the time chart of FIG. 5 and FIG. 5, the pressure applied to both end faces 81 and 82 of the second valve 8 is balanced.
The end face 82 of the second valve 8 is also seated on the shoulder 56 by the urging force of the coil spring 9.

Therefore, the seat portion 21 of the needle 2 is seated on the nozzle seat portion 33 of the nozzle body 3, and the injection hole 32 is closed. The seating speed of the needle 2 is lower than that of the conventional one because the moving speed of the hydraulic piston 4 is slower, and the impact load of the nozzle seat 33 when the needle 2 is seated on the nozzle seat 33 of the nozzle body 3 is reduced. Is considerably reduced.

Next, the operation of this embodiment when the pilot required injection interval is large will be described with reference to the time chart of FIG. In this embodiment, a pilot that injects a small amount of high-pressure fuel before the main injection in order to suppress the vibration of the diesel engine by performing stable combustion from the start of the main injection when the diesel engine is in a normal operation state Perform injection. Here, when the pilot required injection interval is large, the coil 61 of the three-way solenoid valve 6 is turned on at intervals of, for example, 2 msec, and the outer valve 63 repeats ascending and descending to the full lift position h1 (see the time chart of FIG. 10).

First, when the pilot injection is completed, the coil 61 of the three-way solenoid valve 6 is turned off, and the outer valve 63 returns to the initial position h0 (see the time chart of FIG. 10).
The end face 82 of the second valve 8 separates from the shoulder 56 and descends to the full lift position h1 (see the time chart of FIG. 10). Thereby, the needle 2 is moved to the initial lift position h0.
The seat portion 21 of the needle 2 is returned to the nozzle body 3
Of the injection hole 32 by sitting on the nozzle seat portion 33 of the
Is closed, and the pilot injection ends. And
In a diesel engine injected with a small amount of high-pressure fuel, a mixture of fuel and air self-ignites after a slight ignition delay time.

Next, when the coil 61 of the three-way solenoid valve 6 is turned on after the pilot injection to start the main injection, the outer valve 63 is raised by the full lift position h1 (see the time chart of FIG. 10). At this time, in this embodiment, the flow path is not formed between the cylindrical seal portion 84 of the second valve 8 and the inner peripheral surface of the nozzle holder 5, and the spring force of the coil spring 9 is shown in FIG. Very weak as shown.

As a result, as shown in the time chart of FIG. 10, the main injection is started before the end face 82 of the second valve 8 is seated on the stepped shoulder 56 (returns to the initial position h0). A convex injection rate with an increased initial injection rate than the delta type is obtained. In the case of a diesel engine in which a small amount of a mixture of fuel and air is self-ignited after pilot injection, stable combustion is started in synchronization with main injection, so that vibration of the diesel engine is suppressed.

Next, the operation of this embodiment when the pilot required injection interval is small will be described with reference to the time chart of FIG. When the pilot required injection interval is small, the coil 61 of the three-way solenoid valve 6 is turned on, for example, at intervals of 0.5 msec, and the outer valve 63 is moved to the full lift position h1.
(Refer to the time chart of FIG. 11).

When the pilot required injection interval is small, as shown in the time chart of FIG.
After the pilot injection is completed, the end face 82 of the second valve 8
Since the needle 2 opens the injection hole 32 and the main injection is started before the user sits on the stepped shoulder portion 56 (returns to the initial position h0), the convex injection rate, which is an initial injection rate increased from the delta type, is increased. can get.

[Effects of the First Embodiment] As described above, in the pressure accumulating type fuel injection device 1 of this embodiment, as shown in the graph of FIG. For example, 0.5msec ~ 2mse
Within c), the end face 82 of the second valve 8 does not sit on the stepped shoulder 56 (return to the initial position), and a convex main injection rate can always be obtained. As a result, asymmetry between when a delta-type injection rate is obtained at the time of the main injection and when a convex-type injection rate is obtained does not occur, so that there is no variation in the injection amount of the high-pressure fuel, and the pilot injection is stable. Since the main injection can be performed, vibration of the diesel engine can be suppressed. Also,
At the time of non-pilot injection, since the return of the second valve 8 to the initial position has been completed by the next injection after the end of injection, a delta-type injection rate can be obtained.

Further, at the end of the fuel injection, the seating speed of the needle 2 is suppressed immediately before the needle 2 is seated on the nozzle seat portion 33 of the nozzle body 3, so that the nozzle body 3 is maintained in a good injection cut state. The impact load on the nozzle sheet portion 33 can be significantly reduced. As a result, there is no need to increase the strength of the nozzle sheet portion 33 from the current level, and it is not necessary to increase the thickness around the nozzle sheet portion 33. Therefore, since the volume of the suck chamber 34 does not increase, it is possible to prevent adverse effects such as deterioration of the fuel consumption rate, increase of the exhaust gas temperature and increase of HC.

[Second Embodiment] FIG. 13 shows a second embodiment of the present invention, and is a view showing the vicinity of a back pressure chamber of a pressure accumulating fuel injection device for a diesel engine. In this embodiment, an example is shown in which one valve 8 is slidably disposed in the back pressure chamber 58, and the end face 81 of the valve 8 is seated on the shoulder 55 at the end of the main injection. Also, valve 8
A cylindrical seal portion 84 that slides on the inner peripheral surface of the nozzle holder 5 is formed on the outer peripheral surface of the nozzle holder 5. Further, a coil spring 9 held between the hydraulic piston 4 and the valve 8
Is set to a spring force that gives the valve 8 the same action as in the first embodiment. In the case of this embodiment, the same effect as that of the first embodiment can be obtained while reducing the number of parts.

[Third Embodiment] FIG. 14 shows a third embodiment of the present invention and is a view showing the vicinity of a back pressure chamber of a pressure accumulating fuel injection device for a diesel engine. In this embodiment, a seat 43 for holding the coil spring 9 is provided on the back pressure chamber 58 side of the hydraulic piston 4. On the outer peripheral surface of the valve 8 of this embodiment, a cylindrical seal portion 84 that slides on the inner peripheral surface of the nozzle holder 5 is formed. Further, the coil spring 9 held between the hydraulic piston 4 and the valve 8 is set to a spring force that gives the valve 8 the same action as in the first embodiment.

[Modification] In this embodiment, both the coil spring 9 and the cylindrical seal portion 84 are used as delay means. However, only one of the coil spring 9 and the cylindrical seal portion 84 is used as delay means. Is also good.
Further, the axial size of the back pressure chamber may be increased so as to increase the full lift of the second valve (movable valve element). In this embodiment, the tubular member is composed of the three tubular members of the nozzle body 3, the nozzle holder 5 and the valve body 64. However, the tubular member may be composed of one or two tubular members. It may be composed of two or more tubular members. In the present embodiment, the pressure pin 41 is
The needle 2 is driven via the hydraulic piston 4, but the needle may be driven directly by the hydraulic piston 4.

In this embodiment, the contact surfaces (valve seats) of the stepped shoulders 55 and 56 are flat with respect to the contact surfaces of the first and second valves 7 and 8. The contact surfaces (valve seats) of the shoulder portions 55 and 56 with respect to the contact surfaces of the two valves 7 and 8 may be inclined surfaces or curved surfaces. Further, the contact surfaces of the first and second valves 7 and 8 with respect to the contact surfaces (valve seats) of the stepped shoulder portions 55 and 56 may be inclined surfaces or curved surfaces.

[0062]

According to the present invention, within the injection interval from the pilot injection to the main injection in the normal operation state of the internal combustion engine, a delta injection rate can be obtained during the main injection and a convex injection rate can be obtained during the main injection. Asymmetry with the case does not occur. For this reason, since the stability of the main injection can be improved, the vibration of the internal combustion engine can be suppressed by eliminating the variation in the injection amount to the internal combustion engine.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view showing the vicinity of a main back pressure chamber of a pressure accumulating fuel injection device according to a first embodiment of the present invention,
(B) is a longitudinal sectional view showing the vicinity of the injection hole of the accumulator type fuel injection device.

FIG. 2 is a longitudinal sectional view showing the entire structure of the accumulator type fuel injection device of FIG.

FIG. 3 is a cross-sectional view showing the vicinity of a main back pressure chamber of the accumulator type fuel injection device of FIG.

FIG. 4 is a graph showing a relationship between a return time of a second valve and a spring force.

FIG. 5 is a time chart showing operating states of an outer valve, a second valve, and a needle of the three-way solenoid valve during non-pilot injection.

FIG. 6 is an operation explanatory view of the pressure accumulating fuel injection device of FIG. 1;

FIG. 7 is an operation explanatory diagram of the pressure accumulating fuel injection device of FIG. 1;

FIG. 8 is an operation explanatory view of the pressure accumulating fuel injection device of FIG. 1;

FIG. 9 is a diagram illustrating the operation of the pressure accumulating fuel injection device of FIG. 1;

FIG. 10 is a time chart showing the operating states of the outer valve, the second valve, and the needle of the three-way solenoid valve when the pilot required injection interval is large.

FIG. 11 is a time chart showing the operating states of the outer valve, the second valve, and the needle of the three-way solenoid valve when the pilot required injection interval is small.

FIG. 12 is a time chart showing a pilot request injection interval and a main injection asymmetry region in a normal operation state of the diesel engine of the present invention.

FIG. 13 is a longitudinal sectional view showing the vicinity of a back pressure chamber of a pressure accumulating fuel injection device according to a second embodiment of the present invention.

FIG. 14 is a longitudinal sectional view showing the vicinity of a back pressure chamber of a pressure accumulating fuel injection device according to a third embodiment of the present invention.

FIG. 15 is a longitudinal sectional view showing the vicinity of a back pressure chamber of a conventional pressure accumulating fuel injection device.

FIG. 16 is a longitudinal sectional view showing the vicinity of a back pressure chamber of a conventional pressure accumulating fuel injection device.

FIG. 17 is a cross-sectional view showing the vicinity of a back pressure chamber of a conventional pressure accumulating fuel injection device.

FIG. 18 shows a three-way solenoid valve during non-pilot injection;
It is a time chart which showed the operation state of the 2nd valve and the needle.

FIG. 19 is a time chart showing operating states of the valve, the second valve, and the needle of the three-way solenoid valve when the injection interval from the pilot injection to the main injection is large.

FIG. 20 is a time chart showing the operation states of the valve, the second valve, and the needle of the three-way solenoid valve when the injection interval from the pilot injection to the main injection is small.

FIG. 21 is a time chart showing an injection interval and a main injection asymmetry region in a normal operation state of the diesel engine.

[Explanation of symbols]

 Reference Signs List 1 Accumulation type fuel injection device (fuel injection device for internal combustion engine) 2 Needle 3 Nozzle body (tubular member) 5 Nozzle holder (tubular member) 8 Second valve (movable valve body) 9 Coil spring (delay means) 56 Stepped shoulder Portion (valve seat) 83 Second orifice (throttle portion) 84 Cylindrical seal portion (delay means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 47/00 F02M 45/08 F02M 61/20

Claims (1)

(57) [Claims] 1. A fuel injection device for an internal combustion engine in which pilot injection is performed before main injection for injecting high pressure fuel into an internal combustion engine. (A) An injection hole for injecting high pressure fuel, and fuel is supplied and discharged A tubular member having a back pressure chamber, a valve seat provided on the side opposite to the injection hole side of the back pressure chamber, and a communication passage opened at the valve seat; (b) movably disposed in the tubular member. A needle that closes the injection hole when fuel is introduced into the back pressure chamber and opens the injection hole when fuel is discharged from the back pressure chamber; and (c) moves into the back pressure chamber of the tubular member. When the internal pressure on the communication path side is lower than the internal pressure on the back pressure chamber side, the valve is seated on the valve seat to shut off the back pressure chamber and the communication path. The pressure chamber communicates with the communication passage, and fuel flows from the back pressure chamber to the communication passage. (D) a delay that delays seating of the movable valve body on the valve seat within an injection interval from a pilot injection to a main injection in a normal operation state of the internal combustion engine; And a fuel injection device for an internal combustion engine.