JPH10238432A - Fuel injector for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress injector noises caused by the collision of a booster piston with seat faces therefor in a fuel injector for an engine, by braking the piston in its return stroke by means of fluid. SOLUTION: The working fluid that a booster piston 9 in its return stroke forces out of a pressure chamber 8 is prevented by check valves 102 from flowing into passages 34a and 34c obtained through division of a working fluid passage, and is allowed to flow into a passage 34b also obtained through the division while being restricted by a restriction 100 as a flow restriction means arranged therein. That arrangement brakes the piston 9 in the return stroke or lower the speed at which the top surface 73 of the piston 9 butts against seat faces 72 in an injector body 4, to thus suppress noises caused by the seated piston 9.

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 in which fuel in a pressure boosting chamber supplied from a common rail is boosted by a pressure boosting 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. This fuel injection device variably controls the fuel flow characteristics of a hydraulically operated injector during a fuel injection stroke of an engine and enables quick start. For example, a structure as shown in FIG. have.

[0003] As shown in FIG.
It comprises a main body in which a hollow hole and an injection hole 13 are formed, and a case 6 arranged with a gap formed so as to form a fuel chamber 20 outside the main body. The main body of the fuel injection device 1 includes a nozzle main body 2 having a hollow hole 46 and the injection hole 13 formed therein, a fuel supply main body (plunger barrel) 5 forming the pressure intensifying chamber 7, the nozzle main body 2 and the fuel supply main body 5. A hollow main body 21 having a spacer main body 81 and a hollow hole 29 located therebetween, an injector main body 4 having a pressure chamber 8 to which a high-pressure working oil as a working fluid is supplied,
And a solenoid body 3 having a drain groove 39 as a leak passage and a discharge passage (drain passage) 38 and a control valve (solenoid valve) 16 disposed therein. Case 6
Are used to form the fuel chamber 20, the nozzle body 2,
It surrounds the spacer body 81, the hollow spacer body 21 and the fuel supply body 5. 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.

The fuel injection device 1 is configured to increase the pressure of the fuel supplied from the fuel chamber 20 and to increase the pressure of the fuel. Therefore, the spacer body 81, the hollow spacer body 21
The fuel passage 22 formed in the nozzle body 2, the needle valve 23 slidably held in the hollow hole 46 of the nozzle body 2 and opening the injection hole 13 by the fuel pressure, and increasing the pressure of the fuel in the pressure increasing chamber 7. The pressure increasing piston 9 includes a pressure chamber 8 to which an end of the pressure increasing piston 9 is supplied with a working oil for applying a high pressure, and a control valve 16 for controlling the supply of the working 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 a direction to close the needle valve 3. One end of the return spring 18 contacts the upper end of the needle valve 23,
The other end is in contact with 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. A return spring 17 for urging the pressure-intensifying piston 9 toward the pressure chamber 8 is disposed in the spring chamber 30. In a hollow hole 85 formed in the injector body 4, a return spring 19 for urging the control valve 16 on the side that cuts the working oil is disposed. The spring chamber 30 in which the pressure-intensifying piston 9 is disposed communicates with the fuel chamber 20 through a discharge passage 83 formed in the fuel supply main body 5.
The discharge passage 83 is provided between the spring chamber 30 and the fuel chamber 2.
A ball valve 84 that allows only the fuel flow toward zero is arranged. 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 the inside of the hollow hole 26 of the injector body 4. , And a guide ring portion 41 that hangs down from the entire periphery of an outer peripheral portion 47 of the large diameter portion 25 and slides on the inner surface of the hollow hole 26 to form a sliding surface 49. . The guide ring portion 41 is provided with the pressure increasing piston 9.
Has the function of stabilizing the vertical movement of The small-diameter portion 24 of the pressure-intensifying piston 9 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. In addition, the injector body 4
A seal member 44 is disposed in the hollow hole 26 formed in the pressure chamber 8 and seals a gap between the pressure-intensifying piston 9 and the hollow hole 26 with the seal member 44, whereby the working oil in the pressure chamber 8 flows to the spring chamber 30. The spring chamber 30 and the pressure chamber 8 are shut off so as not to leak. Booster piston 9
Is returned between the fuel supply main body 5 and the pressure-intensifying piston 9 in a compressed state. In FIG. 12, the small-diameter portion 24 and the large-diameter portion 25 are depicted as an integral structure, but may be configured separately.

[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 hole 13 through a fuel passage 22 formed in the spacer body 81, the hollow spacer body 21, and the nozzle body 2. A fuel passage is formed between the nozzle body 2 and the needle valve 23, and the needle valve 2
The needle valve 23 receives a lifting force by applying high-pressure fuel pressure to the tapered surface 45 at the tip of the needle 3. The needle valve 23 is slidably held in the hollow hole 46 of the nozzle body 2 and opens the injection hole 13 when lifted by a force based on fuel pressure.

In the large diameter portion 25 of the pressure increasing piston 9, a flat top surface 73 forms a part of the wall surface of the pressure chamber 8. The wall surface of the injector body 4 which faces the top surface 73 of the pressure-intensifying piston 9 and forms a part of the wall surface of the pressure chamber 8 is applied by the spring force of the return spring 17 when the pressure-increasing piston 9 is at its return position. The seating surface 72 is urged and seated. When the working oil is supplied into the pressure chamber 8, the working oil enters between the top surface 73 and the seating surface 72. When the pressure-intensifying piston 9 moves from the return position to the pressure-increasing chamber 7 side, a space 74 connected to the pressure chamber 8 is formed between the top surface 73 of the pressure-intensifying piston 9 and the seating surface 72 of the injector body 4. .

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, a very small gap 28 in the sliding surface 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 a very small gap 48 between the contact surfaces of the injector body 4 and the fuel supply body 5.
The fuel from the fuel chamber 20 leaks through and enters. The fuel that has entered the spring chamber 30 is discharged to the discharge path 83.
Through the fuel chamber 20. 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, fuel enters the spring chamber 30 so as to form a space corresponding to the stroke of the pressure-intensifying piston 9. The fuel is supplied to the spring chamber 30 until the space becomes smaller than the stroke of the pressure increasing piston 9.
The fuel existing in the spring chamber 30 in the hollow hole 26 with the reciprocation of the pressure-intensifying piston 9
Through the fuel chamber 20. The discharged fuel does not flow backward due to the operation of the ball valve 84.

A common rail fuel injection system shown in FIG. 11 is known as a fuel supply system for an engine in which the fuel injection device 1 is incorporated. In this fuel injection system, the fuel contained in the fuel tank 52 is removed by the fuel pump 53 by the fuel filter 54.
Through the common rail 51. The fuel injection device 1 is provided for each cylinder of the engine, and each fuel injection device 1 is connected to a common rail 51 that is a common passage between the fuel supply port 11 and the fuel discharge port 12. Each fuel injection device 1 receives supply of fuel from the common rail 51, and surplus fuel not used for injection into the combustion chamber in each fuel injection device 1 is supplied to the fuel recovery passage 5.
5 and is collected in the fuel tank 52.

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 communicating with the oil gallery 62 and a working oil system passage 66 supplied to the pressure chamber 8 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 speed sensor 68, the accelerator opening detected by the load sensor 69, and the crank angle detected by the position sensor 70. The operating oil pressure of the high-pressure oil manifold 56 detected by the pressure sensor 71 installed in the high-pressure oil manifold 56 is input to the controller 50.

In the fuel injection device 1, the opening and closing operation of the injection hole 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. Then, the control valve 16 fixed to the armature 32 is lifted against the spring force of the return spring 19. When the control valve 16 is lifted, the passage 3 formed between the tapered surface 86 of the control valve 16 and the valve seat 87 of the injector body 4
3 is opened, and the working oil is supplied from the high-pressure oil manifold 56 to the pressure chamber 8 through the introduction passage 31 and the passage 34 formed in the injector body 4. When the operating oil is supplied to the pressure chamber 8, the operating oil enters between the top surface 73 of the large-diameter portion 25 of the pressure-intensifying piston 9 and the seating surface 72 of the injector body 4, and the operating pressure is applied to the pressure-increasing piston 9. Is energized. At the same time, the control valve 16 closes the drain groove 39 formed in the solenoid body 3, so that the working oil in the pressure chamber 8 is not discharged to the drain passage 38 which is a discharge passage. 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 fuel pressure is increased, the fuel pressure in the pressure increasing chamber 7 is increased by the needle valve 23.
, The needle valve 23 lifts against the spring force of the return spring 18, and fuel is injected from the injection hole 13. When the urging force of the solenoid 10 is released, the control valve 16 is lowered by the spring force of the return spring 19,
The passage 33 is opened to cut off the supply of the working oil from the introduction passage 31 to the pressure chamber 8, and the drain groove 39 provided in the control valve 16 is opened to allow the working oil in the pressure chamber 8 to flow into the drain groove 39 and the drain passage 38. Is discharged through. When the pressure in the pressure chamber 8 decreases, the pressure increasing piston 9
Return to the return position by the spring force of
The pressure becomes equal to 0, the fuel pressure applied to the needle valve 23 decreases, the taper surface 45 of the needle valve 23 is seated on the valve seat of the nozzle body 2 by the spring force of the return spring 18, and the injection hole 13 is closed. .

[0014]

The above-described fuel injection device 1
In, the control valve 16, the pressure-intensifying piston 9, and the needle valve 23, which operate in accordance with the supply and discharge of the working oil to and from the pressure chamber 8, are seated so as to collide with a valve seat or a seating surface. In particular, the pressure-intensifying piston 9 has a very large valve stroke compared to other valves (for example, even if the strokes of the control valve 16 and the needle valve 23 are within 1 mm, Reaches several mm), the piston speed when the pressure-intensifying piston 9 is seated on the seating surface 72 by receiving the spring force of the return spring 17 is, as shown by a broken line V in FIG. Increases, that is, increases as the fuel injection amount per injection increases. When the booster piston 9 collides with the seating surface 72,
As seen in the graph of displacement of the pressure increasing piston 9 shown in FIG. 8, the pressure increasing piston 9 is bound seated on the seating surface 72 at time t _{1 0,} to generate a shock noise. Booster piston 9
The seating noise increases as the piston speed of the booster piston 9 when seated increases, that is, as the fuel injection amount increases. In FIG. 8, time t ₀ is a time when the introduction passage 31 is opened by the control valve 16 for introducing the working fluid, and actual fuel injection is started at time t ₁ . The time t ₆ is the time when the drain groove 39 is opened by the control valve 16, and the time when the fuel injection actually ends is the time t ₇ .
A curve Dmax shows the state of displacement of the pressure-intensifying piston 9 when the fuel injection amount is maximized, and the curves D _{1 to} D
₃ shows the state of displacement of the pressure-intensifying piston 9 during the partial injection when the fuel injection amount is gradually increased. As shown in _{B (B 1 ~B 3, Bmax} ) in FIG. 8, when the pressure increasing piston 9 collides with the seating surface 72,
The pressure boosting piston 9 bounces on the seating surface 72.

Further, since the valve stroke of the pressure-intensifying piston 9 is very large, the seating surface is quickly worn by the impact at the time of sitting. When the seating surface is worn, the return amount of the pressure-intensifying piston 9 by the return spring 17 increases, and the return position of the pressure-intensifying piston 9 moves upward, so that the stroke amount when the pressure-intensifying piston 9 is pushed down by the working oil is reduced. Therefore, there is a problem that the pilot injection amount increases.

Here, an injection mechanism for pilot injection will be described. Diesel engines tend to produce combustion noise when operating in low speed and low load conditions, such as idling. Such combustion noise is generated due to fuel ignition delay. Therefore, it is known that it is effective to perform pilot injection (preliminary injection) in which a part of the total fuel injection amount in the combustion cycle is injected prior to the main injection as a means for dealing with combustion noise. Have been. The temperature of the combustion chamber is sufficiently increased by burning the fuel injected by the pilot injection prior to the main injection,
After that, the main fuel amount is injected (main injection),
The ignition delay of the main injection can be prevented.

Means for controlling the pilot injection include those shown in FIGS. That is, the distal end portion 90 of the small-diameter portion 24 of the pressure-intensifying piston 9 is formed with a peripheral groove 91 and a plurality of communication holes 92 that communicate the peripheral groove 91 and the pressure-increasing chamber 7. The fuel supply main body 5 is formed with a pilot port 93 that opens to the hollow hole 42 and communicates with the fuel chamber 20. When the pressure-intensifying piston 9 is at the return position, the pilot port 93 is closed by the distal end portion 90 of the small diameter portion 24 as shown in FIG. When the operating oil acts on the pressure chamber 8 and the pressure-intensifying piston 9 starts to descend, the fuel in the pressure-increasing chamber 7 is pushed out and the fuel injection is started.
When the pilot port reaches the position shown in FIG. 14, the pilot port 93 communicates with the circumferential groove 91 of the small-diameter portion 24, so that the fuel in the pressure-intensifying chamber 7 flows through the communication hole 92 as shown by the flow in FIG. Drain from the groove 91 through the pilot port 93. Therefore, the fuel pressure in the pressure increasing chamber 7 decreases, and the injection of fuel from the injection holes 13 is temporarily stopped.

Therefore, as shown by the solid line in FIG. 15, the fuel injection rate starts increasing from time t ₁ with time, but increases when pilot port 93 opens into circumferential groove 91 at time t _2. Since the fuel in the pressure chamber 7 starts to drain through the communication hole 92, the fuel injection rate decreases. When the fuel pressure in the intensifying chamber 7 is reduced under the opening pressure of the needle valve 23, needle valve 23 reached the time t ₃ the injection of fuel is interrupted by closing. Further intensifying piston 9 continues to downward stroke, will be closed pilot port 93 again at time t _4, the fuel pressure in the pressure increasing chamber 7 exceeds the valve opening pressure of the needle valve 23 rises again, Fuel injection is resumed at time t
₅ after becoming a maximum, the injection is carried out until the time t _7. Thus, the initial injection of the fuel injection cycle becomes the pilot injection P, and the subsequent injection becomes the main injection M.

When the seating surface 72 is worn, the fuel injection rate is increased as shown by a broken line in FIG.
Is shifted upward, so that the pilot port 93 cannot be opened unless a large stroke is made when the pressure-intensifying piston 9 is pushed down by the pressure of the working oil.
Therefore, stop time t ₈ for the pilot injection, will be delayed in comparison to the stop time t ₃ in the normal stroke of the intensifying piston 9, after all, so that the injection amount of the pilot injection P1 is increased. In addition, pilot port 9
The time t ₉ until the closing of the pressure-increasing piston 3 again is also later than the time t ₄ at the time of the normal stroke of the pressure-intensifying piston 9. If the total injection quantity during the fuel injection cycle does not change, the main injection M
The injection amount at 1 becomes smaller. As described above, when the pilot injection amount becomes abnormal, relatively large combustion is performed at the beginning of the combustion cycle, the combustion state such as combustion noise and vibration deteriorates, and the idling operation becomes unstable, Exhaust gas cleanliness decreases.

[0020]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problem, and the flow of the working fluid flows through a passage through which the working fluid discharged from the pressure chamber by a pressure-intensifying piston in a return stroke passes. Means for reducing the seating noise caused by a strong collision of the pressure-intensifying piston against the seating surface by applying a fluid brake to the pressure-intensifying piston in the return stroke and providing a seating surface. It is an object of the present invention to provide a fuel injection device for an engine which makes it possible to reduce wear of the engine.

In order to solve the above-mentioned object, the present invention is configured as follows. That is, the present invention provides a main body in which a booster chamber into which fuel from a common rail is fed and an injection hole for injecting fuel from the booster chamber are formed, and the main body is housed in the main body, and the injection hole is opened and closed by fuel pressure. A pressure chamber formed in the main body and supplied with a working fluid for driving a pressure boosting piston for boosting fuel in the pressure boosting chamber; and a pressure chamber formed in the body and connected to the pressure chamber. A control valve for selectively connecting a working fluid passage to an introduction passage or a discharge passage of the working fluid to control supply and discharge of the working fluid to and from the pressure chamber, wherein the working fluid passage and the discharge passage are provided. At least one of the two is provided with a flow restricting means for restricting the flow of the working fluid discharged from the pressure chamber as the pressure-intensifying piston returns to the return position. It relates to a fuel injection system of the engine.

The fuel injection device for an engine according to the present invention is configured as described above and operates as follows. That is, as the pressure-intensifying piston returns to the return position, the working fluid is discharged from the pressure chamber. Since at least one of the working fluid passage connecting the pressure chamber and the control valve and the discharge passage discharging the working fluid from the control valve is provided with a flow restricting means for restricting the flow of the working fluid. The flow rate through the flow restricting means, i.e., the flow rate of the working fluid pushed out of the pressure chamber by the pressure intensifying piston is limited, and the pressure intensifying piston acts as a brake while trying to return. I do.

In the fuel injection device for an engine according to the present invention, a part or all of the working fluid passage is constituted by a plurality of divided passages formed in parallel, and at least one of the divided passages is provided with the flow restricting means. The split passage is provided with a check valve which allows the flow of the working fluid from the control valve to the pressure chamber but prevents the flow from the pressure chamber to the control valve. When the booster piston is in the booster stroke, the check valve allows the working fluid to flow toward the pressure chamber without interrupting or limiting the working fluid from the control. However, when the pressure-intensifying piston is in the return stroke, the working fluid discharged from the pressure chamber is not discharged through the split passage provided with the check valve, but is provided with the flow restricting means. Exhausted through passage only. Therefore, the flow of the working fluid discharged from the pressure chamber is restricted, and the return of the pressure-intensifying piston is braked.

Further, in the fuel injection device for an engine according to the present invention, the flow restricting means is for restricting an opening area through which the flow of the working fluid passes, or for alternately passing and blocking the flow of the working fluid. Open / close valve that repeats opening and closing. By repeating the opening and closing of the on-off valve, the opening degree of the on-off valve becomes a certain opening degree between the full opening and the complete closing on average over time.

In the fuel injection device for an engine according to the present invention, the effective opening of the throttle can be changed according to the operating state of the engine. Further, the effective opening degree of the on-off valve can be changed by distributing a time during which the on-off valve is open and a time during which the on-off valve is closed, that is, by changing a duty ratio, according to an operating state of the engine. be able to. In the case of a throttle, the effective opening is defined as an opening based on the ratio of the opening area to the cross-sectional area of the passage, and is defined as an effective opening for actually passing the working fluid. Is relative to the cross-sectional area of the passage,
It can be defined as the ratio of the effective open area that is open as an average over time.

Further, the effective opening of the throttle or the on-off valve is reduced in accordance with the fact that the engine load is a partial load. When the engine load is a partial load such as in an idling operation state, the specific sound occupying the noise of the booster piston is large relative to the engine noise. Contributes to the reduction of Therefore, when the engine load is a partial load, the effective opening of the throttle or the on-off valve is reduced,
Reduce the seating speed of the booster piston.

Further, in the above fuel injection device for an engine, the pressure-intensifying piston may be constituted by a small-diameter portion having an end face forming a part of a wall surface of the pressure-increasing chamber and a large-diameter portion having the top surface. . Further, a case is provided in which a fuel supply port and a fuel discharge port that are open to the common rail are formed, and are arranged on the outer periphery of the main body to form a fuel chamber.

[0028]

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. 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 sectional view taken along a plane indicated by line XX in FIG. 1, and FIG. 3 is a fuel injection device according to the present invention. FIG. 4 is an explanatory view schematically depicting a working fluid passage of FIG.
Is a sectional view of an orifice provided in the passage, FIG. 5 is a longitudinal sectional view of a check valve provided in the passage, and FIG. 6 is a bottom view of the check valve shown in FIG. In the fuel injection device of the engine shown in FIGS. 1 to 3, compared to the fuel injection device of the engine shown in FIG. 12, components denoted by the same reference numerals have the same functions, Is 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.

This engine fuel injection device is applied to each cylinder in the engine fuel supply system shown in FIG. Referring to FIGS. 1, 2 and 3, 1
A first embodiment according to the present invention will be described for two fuel injection devices. The fuel injection device 1 includes a fuel supply port 11 and a fuel discharge port 12 on a common rail 51 in the fuel supply system.
Are opened, and the fuel of the common rail 51 is always supplied. In the fuel injection device 1 shown in FIG.
Although only one working fluid passage 34 that connects the control valve 16 and the pressure chamber 8 is drawn, as shown in FIGS. 2 and 3, the working fluid passages 34 are arranged in parallel in the circumferential direction. Are divided into three divided passages 34a, 34b, 34c in the illustrated example.

In the three passages 34a, 34b, 34c, at least one passage (34b in the illustrated example) is provided with an orifice 100 as a throttle. As shown in FIG. 4, the orifice 100 has a passage 1 with a narrow opening area through which the working fluid can pass to restrict the flow of the working fluid.
It is an aperture having 01. Check valves 1 that allow the working fluid to flow from the control valve 16 to the pressure chamber 8 but prevent the working fluid from flowing in the opposite direction are provided in the remaining passages 34a and 34c.
02 is provided. An example of the check valve 102 is shown in a cross-sectional view shown in FIG. 5 and a bottom view shown in FIG. The check valve 102 includes a ball 103 and a holding plate 104 having a small hole 105 that prevents the ball 103 from dropping but allows the working fluid to pass. Accordingly, when injecting fuel, the working fluid supplied through the inflow valve 16A of the control valve 16 is sufficient through the orifice 100 for the passage 34b and through the open check valve 102 for the passages 34a and 34c. A quantity of working fluid is supplied to the pressure chamber 8.

After the fuel injection by the injector is completed,
To prepare for the next fuel injection, the outflow valve 1 of the control valve 16
6B, the working fluid in the pressure chamber 8 is discharged to the drain passage 38, and the pressure of the working fluid in the pressure chamber 8 is released.
The pressure-intensifying piston 9 enters the return stroke by the return force of the return spring 17. At this time, the passages 34a, 34c
Is closed by the pressure of the working fluid on the pressure chamber 8 side, so that the working fluid passes through the passage 3.
It does not flow through 4a and 34c. The flow of the working fluid is concentrated in the passage 34b, and since the orifice 100 is provided in the passage 34b, the flow rate of the working fluid flowing through the orifice 100 decreases, and the working fluid is discharged from the pressure chamber 8 per unit time. The working fluid flow rate is reduced. As a result, the return speed of the pressure increasing piston 9 becomes slow,
The collision speed at which the vehicle collides with the seating surface 72 is reduced, and the impact at the time of sitting is reduced. Note that the degree of the pressure drop in the pressure chamber 8 becomes gentler compared to the case where the orifice 100 is not provided, and the state is in opposition to the return force of the return spring 17.

As shown by a solid line U in FIG. 7, the moving speed of the pressure-intensifying piston 9 when seated is lower than the moving speed V of the conventional pressure-increasing piston regardless of the piston stroke. Piston speed is suppressed. In addition, the piston displacement amount of the pressure-intensifying piston 9 is, for example, as shown in FIG.
As shown by the solid line in x), from when the pressure increasing piston 9 is returned into the process at time t ₇ the end injection, as compared to the rapid decrease of the piston displacement in the conventional return stroke indicated by the dotted line, gently It can be seen that it has decreased.

Next, another embodiment of the fuel injection device for an engine according to the present invention will be described. FIG. 9 is an enlarged sectional view of a main part of a second embodiment of the fuel injection system for an engine according to the present invention. The second embodiment shown in FIG. 9 is substantially the same as the embodiment shown in FIGS. 1 to 3 except that the position at which a throttle for restricting the flow of the working fluid discharged from the pressure chamber 8 is provided is different. Since they have the same structure, by assigning the same reference numerals to corresponding components in the same structure,
The description will not be repeated.

In the second embodiment, the orifice 110 as a restrictor for restricting the flow of the working fluid discharged from the pressure chamber 8 serves as a discharge passage disposed downstream of the discharge valve 16B of the control valve 16. The drain passage 38 is provided. When the operation of the control valve 16 is switched to close the inflow valve 16A and open the outflow valve 16B, the return spring 17
The working fluid in the pressure chamber 8 is passed through the passage 34 and the outflow valve 16 by the pressure-intensifying piston 9 pushed to the return position by the spring force of
The orifice 110 restricts the flow of the working fluid flowing through the drain passage 38 through the drain B and the drain passage 38. As a result, the return speed of the pressure-intensifying piston 9 is reduced, and the impact when the pressure-increasing piston 9 is seated on the seating surface 72 is reduced. In this embodiment, as in the embodiment shown in FIGS. 1 to 3, a restrictor 100 is provided in the working fluid passage 34 and cooperates with the restrictor 110 so that the pressure-intensifying piston 9 is seated on the seating surface 72. The shock at the time of performing may be further reduced.

The orifice 100 provided in the passage 34b in the first embodiment and the orifice 110 provided in the drain passage 38 in the second embodiment are orifices as fixed throttles having a fixed opening area. 3
4b or a variable aperture which can change the opening area of the drain passage 38. The variable throttle can be constituted, for example, by a solenoid valve whose displacement of the armature is controlled by an analog signal. By making the throttle a variable throttle, the return speed of the pressure-intensifying piston is adjusted. The opening area of the variable throttle is controlled according to the operation state of the engine by a control signal from the controller 50 of the fuel injection control system of the engine. That is, when the engine is in a high rotation and high load operation state,
The fuel injection cycle is short and the engine fuel noise is loud.
Since the effect of the seating noise of the booster piston 9 is relatively small, the opening area of the variable throttle is widened to make it easier for the working fluid to flow out, thereby increasing the return speed of the booster piston 9 and shortening the fuel injection cycle. Can respond. On the other hand, when the engine is in a low-rotation, low-load operation state such as the mind ring operation, the fuel injection cycle is long and the fuel noise of the engine is small. Since the influence of the seating noise of the pressure-intensifying piston 9 becomes relatively large, the opening area of the variable throttle is reduced by utilizing the long fuel injection cycle to reduce the flow amount of the working fluid through the variable throttle. The return speed of the booster piston 9 can be reduced.

The orifice 100 of the first embodiment or the orifice 110 of the second embodiment as a flow restricting means.
Can be replaced by an on-off valve that repeats applied opening and closing at a high speed. Such an on-off valve can be a solenoid valve that opens and closes with a digital signal, that is, a pulse signal that repeats on and off. FIG. 10 shows a control signal (a) applied to the solenoid when the control valve 16 is a solenoid valve, a displacement (b) of the control valve 16 operated based on the control signal, and an application to an on-off valve as a flow restricting means. 6 is a graph showing a change over time of a control signal (c) and a displacement (d) of a pressure-intensifying piston 9 with time.

[0037] Based on FIG. 10, when explaining the operation of the opening and closing valve as a flow restrictor means, the pulse signal applied to the control valve 16 shown in (a), ON becomes at time t _{2 0,} in response thereto ( As shown in b), the control valve 16 starts displacing. The working fluid is introduced into the pressure chamber 8 through the working fluid passage 34 through the inflow valve 16A, and the outflow valve 16B is closed. At this time, the on-off valve is maintained in the open state. After a time lag, the pressure increasing piston 9 is time t _{2 1}
In starts displacement pressure increase direction, the fuel injection is started at time t _{2 2.} Control valve at time t _{2 3} 1
6, the control valve 16 starts to return, the inflow valve 16A closes to shut off the inflow of the working fluid, and the outflow valve 16B opens to reduce the pressure as shown in FIG. The working fluid in the chamber 8 starts to be discharged. In the pressure increasing piston 9 is a time t _{2 4,} the return spring 1 on the basis of the decrease in the pressure of the working fluid in the pressure chamber 8
The return stroke is entered by the spring force of 7. At time t _{2 4,} injection of fuel is stopped.

During the return stroke of the pressure-increasing piston 9, a control signal shown in (c) is applied to an on-off valve provided in the working fluid passage 34 or the drain passage 38. That is, the time t
In _{2 5,} ON / OFF signal pulse period as compared to the time required to return the pressure increasing piston 9 is shorter successive starts to be applied to the solenoid on-off valve, at least the pressure increasing piston 9 is at time t _{2 6} is continued until the seating (continues until time t _{2 7).} The working fluid on the pressure chamber 8 side of the on-off valve is discharged only when the on-off valve is open.
Since the opening and closing operation of the on-off valve is an operation that repeats opening and closing in a short cycle, the opening degree becomes a certain degree between the full opening and the complete closing on a time average, and the on-off valve eventually has the same action as the throttle. . As a result, the return operation of the pressure-intensifying piston 9 is braked, and the return speed becomes slower than the return speed of the conventional pressure-intensifying piston 9 (see the graph shown by the broken line in FIG. 8).

Further, the on-off valve can apparently perform the same function as a variable throttle by changing the cycle and duty ratio of the pulse signal. The change of the cycle and the duty ratio of the pulse signal to the on-off valve can be performed according to the operating condition of the engine as described for the variable throttle. That is, when the engine is in a high-rotation, high-load operating state, the time during which the control signal to the on-off valve is turned on is increased, so that the working fluid easily flows out through the on-off valve, and the return speed of the pressure-intensifying piston is increased. . On the other hand, when the engine is in the low rotation and low load operating state, the fuel injection cycle is long, the fuel noise of the engine is small, and the influence of the seating noise of the pressure boosting piston 9 becomes relatively large. The return speed of the pressure-intensifying piston 9 can be reduced by reducing the flow rate of the working fluid.

As described above, the pressure-intensifying piston 9 is
2 can be effectively suppressed by the throttle provided in the working fluid passage or the discharge passage, and the occurrence of injector noise due to the collision of the pressure-intensifying piston with the seating surface can be greatly reduced. Further, since the energy of the collision is suppressed, the progress of wear of the seating surface 72 is effectively suppressed. Therefore, even in the injector to which the mechanism for performing the pilot injection according to the stroke of the pressure-intensifying piston 9 shown in FIGS. 7 and 8 is applied, the stroke of the pressure-increasing piston 9 is shifted from the pilot port. The occurrence can be suppressed, and the pilot injection can be maintained in an appropriate state.

[0041]

According to the fuel injection system for an engine according to the present invention, as described above, when the pressure-intensifying piston is in the return stroke and the working fluid is discharged from the pressure chamber, the working fluid is discharged to the path through which the working fluid is discharged. Since the provided flow restricting means restricts the flow of the working fluid and applies the fluid brake to the return of the pressure intensifier piston, the speed at which the pressure intensifier piston is seated on the seating surface, i.e., the collision speed decreases. As a result, the injector noise caused by the collision of the pressure-intensifying piston is reduced. Further, even in a fuel injection device including a pilot injection mechanism that operates in accordance with the stroke of the pressure-intensifying piston, wear of the seating surface is reduced, and the pilot injection amount can be appropriately maintained.

[Brief description of the drawings]

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

2 is a cross-sectional view of a main part of the fuel injection device of the engine, taken along a plane indicated by line XX in FIG. 1;

FIG. 3 is an explanatory diagram of a fuel injection device according to the present invention, schematically illustrating a working fluid passage connected to a pressure chamber.

FIG. 4 is a sectional view of an orifice provided in a working fluid passage of the fuel injection device for the engine shown in FIG. 1;

FIG. 5 is a cross-sectional view of a check valve provided in a working fluid passage of the fuel injection device for the engine shown in FIG. 1;

FIG. 6 is a bottom view of the check valve shown in FIG. 5;

FIG. 7 is a graph showing a relationship between a stroke of a pressure-intensifying piston and a piston speed at the time of seating in a fuel injection device of an engine according to the present invention and a fuel injection device of a conventional engine.

FIG. 8 is a graph showing a time change of a displacement amount of a booster piston in an engine fuel injection device according to the present invention and a conventional engine fuel injection device.

FIG. 9 is a sectional view of a main part of another embodiment of the fuel injection device for an engine according to the present invention.

FIG. 10 shows a control signal (a) applied to the control valve when the discharge control valve is provided in the discharge passage, a displacement (b) of the control valve operated based on the control signal, and a control applied to the discharge control valve. 5 is a graph showing a change in a signal (c) and a displacement (d) of a pressure-intensifying piston over time.

FIG. 11 is a schematic explanatory view showing a fuel supply system of a fuel injection device for an engine.

FIG. 12 is a sectional view showing a conventional fuel injection device for an engine.

FIG. 13 is a cross-sectional view of a main part showing a mechanism for performing pilot injection in a conventional fuel injection device for an engine.

14 is a cross-sectional view showing another operation state of a main part showing the mechanism for performing the pilot injection shown in FIG.

FIG. 15 is a graph illustrating a time change of a fuel injection rate for performing pilot injection in a fuel injection device of 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 hole 16 solenoid valve (control valve) 17 return Spring 20 Fuel chamber 23 Needle valve 24 Small diameter portion 25 Large diameter portion 31 Introductory passage 34 Working fluid passage 34a, 34b, 34c Dividing passage 38 Discharge passage 51 Common rail 72 Seating surface 73 Top surface 100 Restrictor 102 Check valve 110 Restrictor

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 57/02 320 F02M 57/02 320Z 61/16 61/16 A Y

Claims (7)

[Claims] 1. A main body having a booster chamber into which fuel from a common rail is fed, and an injection hole for injecting fuel from the booster chamber. The main body is housed in the main body and opens and closes the injection hole by fuel pressure. A needle valve, a pressure chamber formed in the main body and supplied with a working fluid for driving a pressure-intensifying piston for pressure-increasing fuel in the pressure-increasing chamber, and formed in the main body and connected to the pressure chamber. A control valve for selectively connecting a working fluid passage to an introduction passage or a discharge passage of the working fluid to control supply and discharge of the working fluid to and from the pressure chamber; At least one of them is provided with a flow restricting means for restricting the flow of the working fluid discharged from the pressure chamber as the pressure-intensifying piston returns to the return position. Gin's fuel injector. 2. A part or the whole of the working fluid passage is composed of a plurality of divided passages formed in parallel, at least one of the divided passages is provided with the flow restricting means, and the remaining divided passages are provided with at least one of the divided passages. The fuel injection device for an engine according to claim 1, further comprising a check valve that allows the working fluid to flow from the control valve to the pressure chamber, but prevents the flow from the pressure chamber to the control valve. . 3. The flow restricting means is a throttle that narrows an opening area through which the working fluid flows, or an on-off valve that repeats opening and closing to alternately pass and block the flow of the working fluid. Or a fuel injection device for an engine according to 2. 4. The effective opening of the throttle or the on-off valve is:
The fuel injection device for an engine according to claim 3, wherein the fuel injection device can be changed according to an operation state of the engine. 5. The fuel injection device for an engine according to claim 4, wherein the effective opening degree is reduced according to a partial load of the engine load. 6. The pressure-intensifying piston includes a small-diameter portion having an end face forming a part of a wall surface of the pressure-increasing chamber and a large-diameter portion forming a part of a wall surface of the pressure chamber. The fuel injection device for an engine according to any one of the preceding claims. 7. A case in which a fuel supply port and a fuel discharge port opened to the common rail are formed in the main body, and a space between an outer periphery of the main body and the case communicates with the pressure increasing chamber. A fuel chamber is formed.
The fuel injection device for an engine according to any one of claims 6 to 13.