JPH10159682A - Fuel injection device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the fuel injection device of an engine which maintains the fuel injection adequately, by preventing the infiltration of the fuel from a fuel chamber and a booster chamber into a spring chamber as low as possible, so as to reduce the fuel discharging work by a booster piston. SOLUTION: An O-ring 90 provided between the abutting surfaces 88 and 89 where an injector main body 4 and a fuel feeding main body 5 are abutted, prevents the leak of the fuel from a fuel chamber 20 to a spring chamber 30 through a clearance 48. An O-ring 91 provided between the small diameter part 24 of a booster piston 9 and the hollow hole 42 of the fuel feeding main body 5 prevents the leak of the fuel from a booster chamber 7 to the spring camber 30 through the clearance 28. Work to push and open a ball valve 84 in which the booster piston 9 is provided in a discharge passage 83, and to push out the fuel in the spring chamber 30, is reduced extensively, and the injection of the fuel is maintained adequately.

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 engine, which boosts fuel in a booster chamber supplied from a common rail by a booster piston.

[0002]

2. Description of the Related Art Conventionally, as a hydraulically operated electronically controlled fuel injection device for an engine, there have been disclosed, for example, JP-A-6-294362 and JP-A-6-511524. These fuel injection devices variably control the fuel flow rate characteristics of the hydraulically operated injectors during the fuel injection stroke of the engine, and enable quick start-up. For example, as shown in FIG. It has a structure.

[0003] As shown in FIG. 3, a fuel injection device 1 includes a main body having a hollow hole and an injection hole 13, and a case 6 having a gap formed so as to form a fuel chamber 20 outside the main body. It is configured. The main body of the fuel injection device 1 includes a nozzle main body 2 having a hollow hole 46 and having an injection port 13 formed therein, a fuel supply main body (plunger barrel) 5 forming a pressure intensifying chamber 7, and a nozzle main body 2 and a fuel supply main body 5. The hollow spacer body 21 having the spacer body 81 and the hollow hole 29 located therebetween, the injector body 4 having the pressure chamber 8 to which the high-pressure hydraulic oil is supplied, and the drain groove 39 and the drain passage 38 serving as leak passages It comprises a solenoid body 3 provided with a solenoid valve 16.
The case 6 surrounds the nozzle main body 2, the spacer main body 81, the hollow spacer main body 21, and the fuel supply main body 5 to form the fuel chamber 20. In order to form the fuel chamber 20 formed between the case 6 and the main body, one end of the case 6 is sealed by being locked on the contact surface 14 of the step portion of the nozzle main body 2 and the other end is connected to the injector main body 4. Is sealed by a fitting surface 80 screwed into the connector. A fuel supply port 11 and a fuel discharge port 12 formed in the case 6 are opened in the common rail 51, and fuel is constantly supplied from the common rail 51 to the fuel chamber 20.

[0004] The fuel injection device 1 is for increasing the pressure of the fuel supplied from the fuel chamber 20, a pressure increasing chamber 7 formed in a fuel supply main body 5, and for supplying fuel from the pressure increasing chamber 7 to the injection port 13. , Spacer body 81, hollow spacer body 21
And a fuel passage 22 formed in the nozzle body 2, a needle valve 23 slidably held in a hollow hole 46 of the nozzle body 2 to open the injection port 13 by fuel pressure, and a pressure increasing chamber for increasing the pressure of the fuel in the pressure increasing chamber 7. A pressure piston 8, a pressure chamber 8 to which high-pressure hydraulic oil for applying a high pressure to an end of the pressure-intensifying piston 9 is supplied;
And a solenoid valve (control valve) 16 for controlling the supply of high-pressure operating oil to the pressure chamber 8.

The return spring 18 is disposed in a hollow hole 29 formed in the hollow spacer body 21 and
A spring force is applied to the needle valve 23 in the direction to close the needle valve 3. One end of the return spring 18 contacts the upper end of the needle valve 23, and the other end contacts the spacer body 81. The hollow spring chamber 30 formed by the hollow hole 26 formed in the injector main body 4 is formed between the end face of the large-diameter portion 25 of the pressure-intensifying piston 9 and the end face of the fuel supply main body 5. The spring chamber 30 has a pressure-increasing piston 9
A return spring 17 for urging the pressure toward the pressure chamber 8 is disposed. Hollow hole 8 formed in injector body 4
5 has a solenoid valve 16 on the side where the hydraulic oil is cut.
Is provided.
The spring chamber 30 in which the pressure-intensifying piston 9 is disposed communicates with the fuel chamber 20 through a discharge path 83 formed in the fuel supply main body 5 and a ball valve 84 disposed in the discharge path 83. Normally, the leaked fuel enters the spring chamber 30 and is in a state equivalent to the fuel pressure in the fuel chamber 20. Are formed.

The pressure-intensifying piston 9 has a small-diameter portion 24 which is a plunger that forms a part of the pressure-increasing chamber 7 at the lower end surface, a part of the pressure chamber 8 that is formed at the upper end surface, and a hollow hole 26 of the injector body 4. , And a guide ring portion 41 that hangs down from the entire periphery of the outer peripheral portion of the large diameter portion 25 and forms a sliding surface that slides on the inner surface of the hollow hole 26. The guide ring portion 41 has a function of stabilizing the vertical movement of the pressure-intensifying piston 9. Small-diameter portion 2 of booster piston 9
4 reciprocates in a hollow hole 42 formed in the fuel supply main body 5, and the large diameter portion 25 reciprocates in a hollow hole 26 formed in the injector main body 4. A seal member 44 is disposed in the hollow hole 26 formed in the injector body 4, and seals a gap between the pressure-intensifying piston 9 and the hollow hole 26 with the seal member 44. The spring chamber 30 and the pressure chamber 8 are shut off so that the working oil does not leak into the spring chamber 30.

[0007] At the end of the hollow hole 42 formed in the fuel supply main body 5, a pressure increasing chamber 7 is formed. The fuel is supplied to the pressure intensifying chamber 7 from the fuel chamber 20 through the hollow spacer body 2.
1 through the fuel passage 37 formed in the spacer body 81. In the fuel passage 35,
A check valve 36 is incorporated to prevent the high pressure fuel in the pressure intensifying chamber 7 from flowing back into the fuel chamber 20. Also,
The fuel whose pressure has been increased in the pressure increasing chamber 7 is supplied to the injection port 13 through the fuel passage 22 formed in the spacer main body 81, the hollow spacer main body 21, and the nozzle main body 2. A fuel passage is formed between the nozzle body 2 and the needle valve 23,
The needle valve 23 is lifted by applying high-pressure fuel pressure to the tapered surface 45 at the tip of the needle valve 23. The needle valve 23 is slidably held in the hollow hole 46 of the nozzle body 2, lifted by fuel pressure, and opens the injection port 13.

The pressure-increasing piston 9 has a flat surface 73 in which an outer peripheral portion of a top surface 65 of the large-diameter portion 25 facing the pressure chamber 8 is cut off.
Is formed. The wall surface of the injector body 4 forming the pressure chamber 8 is formed as a flat surface 72 parallel to the top surface 65 of the pressure increasing piston 9. Therefore, in the pressure chamber 8, a narrow annular gap 74 is formed between the flat surface 73 of the pressure-intensifying piston 9 and the flat surface 72 of the injector body 4. The pressure-increasing piston 9 has a top surface 6.
The central projection of 5 is in contact with the flat surface 72 of the injector body 4 by the spring force of the return spring 17.

In the fuel injection device 1, a spring chamber 30 accommodating the return spring 17 is formed in a hollow hole 26 formed in the injector body 4 in which the large-diameter portion 25 of the pressure-intensifying piston 9 and the guide ring portion 41 slide. Have been. Intensifier piston 9 and hollow hole 26 in injector body 4
Is sealed by a seal member 44 disposed between the large diameter portion 25 and the hollow hole 26, so that leakage of fuel from the spring chamber 30 to the pressure chamber 8 is prevented. The fuel that has entered the spring chamber 30 is configured to be discharged to the fuel chamber 20 through a discharge path 83 formed in the fuel supply main body 5. Booster piston 9
In the spring chamber 30 in which the return spring 17 is disposed, the clearance 28 around the plunger of the small diameter portion 24, that is, the sliding surface between the hollow hole 42 of the fuel supply body 5 and the outer peripheral surface of the small diameter portion 24, and the injector body 4 and fuel supply body 5
The fuel from the fuel chamber 20 leaks and penetrates through the gap 48 between the contact surfaces. The fuel that has entered the spring chamber 30 is discharged to the fuel chamber 20 through the discharge path 83. Since the ball valve 84 is provided in the discharge path 83, the fuel is prevented from flowing backward from the fuel chamber 20 to the spring chamber 30 through the discharge path 83. Normally, a space corresponding to the stroke of the pressure-intensifying piston 9 is formed in the spring chamber 30, and fuel enters. Then, when the fuel enters to such an extent that the empty space in the spring chamber 30 becomes equal to or less than the stroke of the booster piston 9, the spring chamber 30 in the hollow hole 26 is reciprocated with the booster piston 9.
Existing in the fuel chamber 20 through the discharge passage 83
, But the backflow is prevented by the operation of the ball valve 84.

FIG. 2 shows a known fuel supply system for an engine in which the fuel injection device 1 is incorporated. In the fuel supply system, a fuel injection device 1 is provided for each cylinder of the engine. The fuel injection device 1 is provided with a common rail 51 which is a common passage for supplying fuel. The fuel in the fuel tank 52 is supplied to the common rail 51 through the fuel filter 54 by the driving of the fuel pump 53. The common rail 51 communicates with each fuel injection device 1 and has a fuel recovery passage 55
Through the fuel tank 52. That is, the fuel injection device 1 is disposed on the common rail 51 in which fuel at a predetermined pressure is constantly supplied to the fuel supply port 11 and the fuel discharge port 12 thereof.

The fuel injection device 1 is configured to supply a high-pressure working fluid, that is, working oil, to the pressure chamber 8 to increase the fuel pressure. The fuel injection device 1 is connected to the high-pressure oil manifold 56, respectively. Oil from an oil reservoir 57 is supplied to the high-pressure oil manifold 56 through an oil supply path 61 by operation of an oil pump 58, and an oil cooler 59 and an oil filter 60 are provided in the oil supply path 61. The oil supply passage 61 branches into a lubrication system passage 67 leading to the oil gallery 62 and a working oil system passage 66 supplied to the pressure chamber of the fuel injection device 1. A high-pressure oil pump 63 is provided in the working oil system passage 66, and the supply of oil from the high-pressure oil pump 63 to the high-pressure oil manifold 56 is controlled via a flow control valve 64. The controller 50 is configured to control the flow control valve 64 and control the solenoid 10 of the fuel injection device 1. The controller 50 receives, as the operating state of the engine, the engine speed detected by the rotation sensor 68, the accelerator opening detected by the load sensor 69, and the crank angle detected by the position sensor 70.
The controller 50 includes a high-pressure oil manifold 5.
The working oil pressure of the high-pressure oil manifold 56 detected by the pressure sensor 71 installed at 6 is input.

In the fuel injection device 1, the opening and closing operation of the nozzle 13 by the needle valve 23 is performed by controlling the solenoid 10. When the solenoid 10 is energized by a command from the controller 50, the armature 32 is attracted. , The solenoid valve 16 fixed to the armature 32
Lifts against the spring force of the return spring 19. When the solenoid valve 16 is lifted, the solenoid valve 1
6, a passage 33 formed between the tapered surface 86 of the injector body 4 and the valve seat 87 of the injector body 4 is opened, and the high-pressure hydraulic oil is supplied from the high-pressure oil manifold 56 through the supply path 31 and the passage 34 formed in the injector body 4 through pressure. Room 8
Supplied to When high-pressure hydraulic oil is supplied to the pressure chamber 8, high-pressure hydraulic oil is supplied to an annular gap 74 formed between the top surface 65 of the large-diameter portion 25 of the pressure-intensifying piston 9 and the wall surface (flat surface) 72 of the injector body 4. The working oil is supplied, and the working pressure is urged to the pressure increasing piston 9. On the other hand, the fuel of the common rail 51 is supplied from the supply port 11 formed in the case 6 to the fuel chamber 20, and then the fuel passage 37 formed in the hollow spacer body 21 and the fuel formed in the spacer body 81 from the fuel chamber 20. The pressure is supplied to the pressure increasing chamber 7 through the passage 35.

When the pressure-increasing piston 9 is lowered by the pressure of the working oil in the pressure chamber 8, the fuel passage 35 is closed by the check valve 36, and the pressure in the pressure-increasing chamber 7 is increased. Booster chamber 7
When the pressure of the fuel is increased, the fuel pressure is
The needle valve 23 is lifted against the spring force of No. 8. When the urging force of the solenoid 10 to the solenoid valve 16 is released, the solenoid valve 16 is lowered by the spring force of the return spring 19, the drain groove 39 provided in the solenoid valve 16 is opened, and the high pressure hydraulic oil in the pressure chamber 8 is released. Is discharged through the drain groove 39 and the drain passage 38. Pressure chamber 8
Is discharged, the pressure-intensifying piston 9 returns to its original state by the spring force of the return spring 17, and the pressure-increasing chamber 7
Has a pressure equivalent to that of the fuel chamber 20, and the needle valve 2
3, the fuel pressure applied to the nozzle body 23 decreases, and the taper surface 45 of the needle valve 23
And the nozzle hole 13 is closed.

[0014]

As described above, when the intrusion of the fuel into the spring chamber 30 increases and the vacant space in the spring chamber 30 decreases to a value not more than the stroke of the pressure-intensifying piston 9, the excess fuel The spring chamber 30 in the hollow hole 26 with the reciprocating motion of the pressure increasing piston 9.
Existing in the fuel chamber 20 through the discharge passage 83
The fuel is discharged to the fuel chamber 20.
Work to push and open the ball valve 84 against the internal fuel pressure is required, and this work is provided by the work given to the pressure-intensifying piston 9, so that it is used to increase the pressure of the fuel in the pressure-increasing chamber 7. Work is reduced. For this reason, the degree to which the pressure-intensifying piston 9 increases the pressure of the fuel differs depending on whether the fuel is discharged to the fuel chamber 20 through the discharge path 83 or not, depending on the degree of the decrease in the empty space. A difference occurs in the injection amount. As a result, for example, a variation in the rotation of the engine output shaft at the time of idling of the engine occurs.

In general, the stroke amount of the pressure-intensifying piston 9 corresponds to the fuel injection amount. Therefore, the state in which the fuel injection amount is small, such as when the vehicle suddenly starts or accelerates after idling. If the fuel injection amount suddenly shifts to the maximum state after a long period of time, the spring chamber 30
In a state where the empty space inside is already reduced,
Will increase the stroke. However,
In this state, the amount of fuel discharged to the fuel chamber 20 through the discharge path 83 becomes excessive, so that the fuel discharge work increases rapidly, and as a result, the target fuel injection amount cannot be obtained, and the acceleration performance Becomes extremely worse.

Further, when the fuel is discharged to the fuel chamber 20 through the discharge passage 83, the ball of the ball valve 84 is caused to collide with the upper surface of the spacer body 81, and the ball is deformed while repeating the collision, so that the ball valve 84 is deformed. Function may be impaired. When the ball undergoes such deformation, the fuel flows back from the fuel chamber 20 to the spring chamber 30 through the gap between the deformed portion of the ball and the valve seat, and is filled. As a result, a large amount of fuel is discharged from the spring chamber 30 when the pressure-intensifying piston 9 operates, and the discharge work of the pressure-increasing piston 9 increases, so that the target fuel injection amount can be obtained in the same manner as described above. In the worst case, the booster piston 9
However, the fuel cannot be injected due to the inability to make a stroke.

[0017]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and it is an object of the present invention to provide a fuel injection system for an engine in which fuel in a pressure boosting chamber supplied from a common rail is boosted by a pressure boosting piston to inject fuel. In the apparatus, the fuel intrusion into the spring chamber is prevented as much as possible to reduce the number of times the booster piston discharges the fuel from the discharge passage, thereby causing the booster piston to bear the fuel discharging work. An object of the present invention is to provide a fuel injection device for an engine that solves the above-mentioned disadvantages that occur.

According to the present invention, a pressure increasing chamber formed in a main body to which fuel from a common rail is supplied is driven by a working fluid supplied to a pressure chamber formed in the main body to increase the pressure of the fuel in the pressure increasing chamber. A pressure booster piston, a needle valve housed in the main body, which opens and closes an injection port for injecting fuel from the pressure booster chamber with fuel pressure, and a control for controlling supply of a working fluid for driving the pressure booster piston to the pressure chamber. A valve, and a case disposed on the outer periphery of the main body to form a fuel chamber and having a fuel supply port and a fuel discharge port opened to the common rail, wherein the pressure-intensifying piston is a wall surface of the pressure-increasing chamber. And a large diameter part forming a part of the wall surface of the pressure chamber. The main body has a slide in which the large diameter part of the pressure-intensifying piston slides and a return spring is arranged. The fuel chamber is formed between a first main body having a ring chamber and the case, and a hollow hole in which the small-diameter portion of the pressure-intensifying piston slides is formed and disposed in contact with the first main body. A first seal member is disposed between the contact surfaces of the first body and the second body, the small diameter portion of the pressure-intensifying piston and the second body. A second seal member is disposed between the hollow member and the hollow hole.

In this fuel injection device for an engine, as described above, the first seal member is disposed between the contact surfaces where the first main body and the second main body come into contact, and the small-diameter portion of the pressure-intensifying piston slides. Since the second seal member is disposed between the surface and the hollow hole of the second main body, the first seal member prevents the fuel from leaking from the fuel chamber to the spring chamber, and the second seal member increases the fuel pressure. Prevents fuel from leaking from the pressure chamber to the spring chamber. As a result, the amount of fuel per unit time charged into the spring chamber is greatly reduced, the time until the vacant space in the spring chamber becomes smaller becomes longer, and the number of times of discharging the fuel through the discharge path in a certain period is greatly increased. Decrease.

The second main body has a discharge passage for discharging fuel in the spring chamber to the fuel chamber. In the fuel injection device configured as described above, the fuel leaked to the spring chamber is returned to the fuel chamber through the discharge path, and is again supplied to the pressure increasing chamber. In addition, the exhaust passage is provided with a ball valve that allows the flow of fuel from the spring chamber to the fuel chamber, but blocks the reverse flow of fuel. In the fuel injection device configured as described above, fuel can be discharged from the spring chamber to the fuel chamber, but is prevented from entering the fuel chamber from the fuel chamber.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an engine fuel injection device according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of a fuel injection device for an engine according to the present invention. The fuel injection device for the engine shown in FIG. 1 is different from the fuel injection device for the engine shown in FIG. 3 between the small-diameter portion forming the gap 28 and the hollow hole, and the abutment forming the gap 48. Except for the point that a seal member is arranged between the surfaces, they have the same configuration and the same function, so the same components are denoted by the same reference numerals, and redundant description will be omitted. In addition, since there is no change in the basic fuel injection operation as the fuel injection device of the engine, the overlapping description of the fuel injection operation is omitted.

The fuel injection device of this engine is incorporated in the fuel supply system shown in FIG. 2 and applied, and is arranged in each cylinder of the engine. In this embodiment, one fuel injection device will be described with reference to FIG. The fuel injection device 1 is in a state where the fuel supply port 11 and the fuel discharge port 12 are opened in the common rail 51 in the fuel supply system, and the fuel on the common rail 51 is always supplied. A first seal is provided between a contact surface 88 on the injector body 4 side where the injector body 4 as the first body and the fuel supply body 5 as the second body abut, and a contact surface 89 on the fuel supply body 5 side. An O-ring 90 as a member is arranged.
The O-ring 90 moves fuel between the fuel chamber 20 and the spring chamber 30 through the gap 48 between the contact surfaces 88 and 89, and in particular, transfers fuel from the fuel chamber 20 to the spring chamber 30 through the gap 48. Prevents leaks.
In the illustrated example, the O-ring 90 is disposed in an annular groove formed on the contact surface 88 on the injector body 4 side.
An annular groove may be formed in the contact surface 89 on the fuel supply body 5 side, and the O-ring 90 may be arranged in the annular groove.

The small-diameter portion 24 of the pressure-intensifying piston 9 and the second
An O-ring 91 as a second seal member is arranged between the main body and the hollow hole 42 of the fuel supply body 5. The O-ring 91 is provided between the booster chamber 7 and the spring chamber when the fuel is pressurized in the booster chamber 7, particularly when the fuel passes through the gap 28 formed between the booster chamber 7 and the spring chamber 30. The fuel leakage to the fuel cell 30 is prevented. In the illustrated example, O
The ring 91 is arranged in an annular groove formed on the peripheral surface on the distal end side of the small diameter portion 24 of the pressure-intensifying piston 9, and the annular groove is formed on the hollow hole 42 side of the fuel supply body 5, and the O-ring 91 is formed. May be arranged in the annular groove.

The fuel injection device 1 is configured as described above, and operates as follows. That is, the gap 28 and the gap 48
The amount of fuel per unit time that enters the spring chamber 30 through the air passage is greatly reduced, and the time until the space inside the spring chamber 30 becomes smaller becomes longer. In this case, the number of times the fuel is discharged through the discharge path 83 is greatly reduced. Therefore, the number of times the ball valve 84 is pushed and opened against the fuel pressure in the fuel chamber 20 is greatly reduced, and the pressure-increasing piston 9 is connected to the ball valve 8.
No work is expended to push and open the fuel pressure 4, and the pressure increase width of the fuel by the pressure increasing piston 9 is constant, so that there is no difference in the fuel injection amount under constant operating conditions. Even during idle operation of the engine, there is no variation in the rotation of the engine output shaft.

Further, even when the vehicle suddenly starts or accelerates after idling, the space in the spring chamber 30 is not reduced, and the stroke of the pressure-intensifying piston 9 does not increase. Therefore, the fuel to be discharged to the fuel chamber 20 through the discharge path 83 is not generated unless the idling operation has been performed for a considerably long time, and the acceleration performance does not deteriorate in a normal operation state.

Further, since the number of times of discharging the fuel through the discharge path 83 during a certain period is reduced, the number of times that the ball of the ball valve 84 collides with the upper surface of the spacer body 81 is also reduced. There is no problem, and the life of the ball valve 84 can be extended.

[0027]

According to the fuel injection device for an engine according to the present invention, as described above, in the fuel injection device for an engine in which the fuel in the pressure boosting chamber supplied from the common rail is boosted by a pressure boosting piston to inject fuel, the spring is provided. Since the intrusion of the fuel into the chamber is prevented as much as possible, the number of times the booster piston discharges the fuel from the discharge path is reduced, and the above-mentioned disadvantages caused by the booster piston performing the work of discharging the fuel are reduced. Can be eliminated. That is, since the amount of fuel leaking into the spring chamber can be greatly reduced, the number of times of discharging the fuel through the discharge passage is greatly reduced, and the ball valve provided in the discharge passage is hardly pushed open. In addition, the present invention prevents variations in the rotation of the engine output shaft during idling operation of the engine, prevents the acceleration performance from deteriorating even when the vehicle suddenly starts or accelerates after idling, and is provided in the exhaust passage. The life of the ball valve can be extended.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a fuel injection device for an engine according to the present invention.

FIG. 2 is a schematic explanatory view showing a fuel supply system of an engine fuel injection device.

FIG. 3 is a sectional view showing a conventional fuel injection device for an engine.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fuel injection device 2 nozzle body 3 solenoid body 4 injector body 5 fuel supply body 6 case 7 booster chamber 8 pressure chamber 9 booster piston 11 fuel supply port 12 fuel outlet 13 injection port 16 solenoid valve (control valve) 17 return spring Reference Signs List 20 fuel chamber 23 needle valve 24 small diameter portion 25 large diameter portion 28 gap 30 spring chamber 42 hollow hole 48 gap 51 common rail 81 spacer body 83 discharge path 84 ball valve 88 contact surface 89 contact surface 90 O-ring (first seal member) ) 91 O-ring (second seal member)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 61/10 F02M 61/10 S 61/16 61/16 K

Claims (3)

[Claims] An intensifying chamber formed in a main body to which fuel from a common rail is supplied, and a pressure intensifier driven by a working fluid supplied to a pressure chamber formed in the main body to increase the pressure of the fuel in the intensifying chamber. A piston, a needle valve housed in the main body and opening / closing an injection port for injecting fuel from the pressure boosting chamber with fuel pressure, a control valve for controlling supply of a working fluid for driving the pressure boosting piston to the pressure chamber, And a case disposed on the outer periphery of the main body to form a fuel chamber and having a fuel supply port and a fuel discharge port opened to the common rail. The main body includes a spring chamber in which the large-diameter portion of the pressure-intensifying piston slides and a return spring is disposed. The fuel chamber is formed between the formed first body and the case, and a hollow hole in which the small-diameter portion of the pressure-intensifying piston slides is formed, and a second hole is disposed in contact with the first body. A first seal member disposed between contact surfaces of the first main body and the second main body, the small diameter portion of the pressure-intensifying piston and the hollow of the second main body. The fuel injection device for an engine, comprising a second seal member disposed between the hole and the hole. 2. The fuel injection device for an engine according to claim 1, wherein a discharge passage for discharging fuel in the spring chamber to the fuel chamber is formed in the second main body. 3. The exhaust passage according to claim 2, wherein a ball valve is provided to allow a flow of fuel from the spring chamber to the fuel chamber, but to prevent a flow of fuel in the opposite direction. Engine fuel injection device.