JPH01134065A - Fuel injection system for internal combustion engine - Google Patents

Abstract

PURPOSE:To make improvements in combustion by installing a hydraulic booster valve with a plunger, being driven by fuel pressure acting on a primary chamber, and feeding an injection nozzle with fuel taking in a secondary chamber, and thereby making fuel injection performable at yet higher pressure. CONSTITUTION:In an unit injector 1 consisting of a pump part 2 and a nozzle part 3, a solenoid valve 5 in an upper part of the pump part 2 is excited and a spool 22 is moved to the right whereby fuel is led into a delivery chamber 66 as a second servo chamber in a servo valve 7 from a fuel pump, and pistons 61, 63 at both primary and secondary sides are pushed up by this fuel, whereby fuel required for one time fuel injection is made so as to be filled up in the chamber 55. Next, the solenoid valve 5 is demagnetized, and the spool 22 is moved to the left whereby these pistons 61, 63 are pushed up successively by leading pressure oil into a first servo chamber 64 via a directional selector valve 6, pressurizing the fuel inside the chamber 66, and thus it is made so as to be fed to the nozzle part 3 under pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to a so-called unit injector that integrates a fuel pump and a fuel injection nozzle for use in a diesel engine.

<Prior Art> In a conventional diesel engine, fuel sucked up from a fuel tank is pressurized by a morning type pump, a distribution type pump, etc., and is sent to an injection nozzle via a high pressure pipe and injected into a combustion chamber. However, since the fuel injection amount and injection timing are mechanically determined by a timer, governor, etc. in accordance with the rotation of the engine, precise control according to the operating conditions of the engine cannot be performed. In addition, in the case of a direct injection type, it is necessary to inject fuel at high pressure in order to inject fuel evenly throughout the combustion chamber and achieve complete combustion, but since a high-pressure pipe is used, the injection pressure cannot be made too high. figure,
Moreover, there is a problem that the injection characteristics become unstable.

Therefore, a unit injector has been put into practical use that integrates a fuel pump and an injection nozzle, eliminates a high-pressure pipe, and improves injection characteristics. However, unit injectors have a complicated structure, are difficult to adjust, and are expensive, and like conventional fuel injection devices, they mechanically inject fuel by driving a plunger using a cam that synchronizes with engine rotation. do. For this reason, it is difficult to always properly and precisely adjust fuel injection according to the operating conditions of the engine.

<Problems to be Solved by the Invention> In view of the above-mentioned problems, an object of the present invention is to appropriately and precisely control fuel injection according to the operating conditions of an engine, and to increase the injection pressure to increase fuel injection pressure. An object of the present invention is to provide a high-performance fuel injection device for an internal combustion engine, which can promote the atomization of the fuel and further improve the n-power, thereby improving the combustion of the engine.

According to the present invention, the above object is to provide a fuel injection device for an internal combustion engine that pressurizes and injects fuel delivered at a predetermined fuel pressure from a fuel pump means. , a hydraulic amplification valve having a plunger that is driven by fuel pressure acting on the primary chamber and forces fuel introduced into the secondary chamber to the injection nozzle; and selectively connecting the fuel pump means and the primary chamber. This is achieved by providing a fuel injection device for an internal combustion engine, characterized in that it is equipped with a directional control valve.

<Operation> In this way, the fuel pressure sent from the fuel pump means is selectively applied to the primary chamber of the hydraulic amplification valve by the directional control valve, and by driving the plunger, the fuel pressure is introduced into the secondary chamber. Fuel can be forced into the injection nozzle and injected.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, a diesel engine unit injector 1 according to the present invention includes a pump section 2 and a nozzle section 3 integrally connected thereto. The pump part 2 is
The pump housing 4 includes an electromagnetic valve 5 provided at the top, a hydraulic directional control valve 6 placed immediately below the electromagnetic valve 5, and a servo valve 7 placed further below the electromagnetic valve 5.

The solenoid valve 5 is composed of a solenoid 10 and a four-point/two-position switching valve 11 arranged coaxially therewith. The solenoid 10 consists of a coil wound around a bobbin 12 made of a non-magnetic resin material. A fixed iron core 13 is disposed at the center, and a plunger 14 is disposed so as to be freely slidable along the guide hole 15 in the axial direction. The plunger 14 has a return spring 16 made of a constantly compressed coil spring.
The biasing force is adjusted by the adjustment screw 17.

The switching valve 11 includes a sleeve 20 fixed inside the housing 4 and a spool 22 slidably disposed in the bore 21 of the sleeve 20 along the axial direction. As clearly shown in FIGS. 2 and 3, a pressure port 23 is provided at the center of the sleeve 20 and communicates with a fuel intake port 25 connected to an external fuel pump means via an oil passage 24. are doing. Cylinder ports 26 and 27 connected to the directional control valve 6 are provided on both sides of the pressure port 23. The left and right end openings 28, 29 of the bore 20 are used as return ports connected to the respective nearby cylinder ports 25, 26.

The plunger 14 is screwed onto the right end of the spool 22, and moves in the bore 21 together with the plunger 14 by energizing or demagnetizing the solenoid 10. Boa 2
The right end of the spool 22 is expanded in diameter to form a stepped portion 30.
A radially outwardly projecting flange 31 is disposed between the step 30 and the ring member 32 . Therefore, the spool 22 has seven flange 31 and a stepped portion 30 or ring member 3.
It can only move left and right along the axial direction within a small distance range where it comes into contact with 2. By this distance, spool 2
2 strokes are determined.

Further, the spool 22 is formed hollow with a bore 33 passing through it in the axial direction. By making the spool 22 hollow and lightweight, responsiveness to on/off of the solenoid 10 is improved. Furthermore, the spool 22 has a small hole 34 on the flange 2.
8 and the threaded portion of the plunger 15,
Through this, the bore 33 connects to the return port 29 at the right end of the bore 21.
communicate with. On the other hand, on the left side of the switching valve 11, a pipe joint 35 is screwed onto the housing 4, and a return port 28 passes through the inside of the housing 4 to a return passage 36 passing through the inside, and a return port 29 is connected to a small hole 34. and are in communication via bores 33, respectively.

As described above, since the stroke of the spool 22 is small, not only the opening of the pressure port 24 connected to the cylinder port 26 or 27 is small, but also the wrap 1 is small. For this reason, the pressure oil sent from the fuel pump means has a high pressure of about 100 to 150 Kgf/cn, and especially light oil has low viscosity, so the pressure oil is not connected to the guide clearance between the spool 22 and the bore 21. Leakage to the cylinder port side. However, since the return port on the leaking side is open, it does not affect the operation of the directional control valve 6, which will be described later.

In this case, leakage of pressure oil can be prevented by increasing the lap distance or decreasing the guide clearance, but the operability and responsiveness of the switching valve 11 are reduced. There is also a method of reducing the leakage by reducing the diameter of the spool, but this is not preferred because the effective opening area of the pressure port becomes insufficient and the operation of the directional control valve 6 may be affected.

The directional control valve 6 has a sleeve 4 fixed to the housing 4.
0 and a spool 42 which is movably disposed within its bore 41, and its valve shaft is arranged substantially parallel to the valve shaft of the electromagnetic valve 5. Boa 4
The outer open end of 1 is sealed with a plug 43 press-fitted from the outside.

The sleeve 40 is provided with a pressure port 45 communicating with the fuel intake port 25 via an oil passage 44, a cylinder port 46 communicating with the servo valve 7, and a return port 48 connected with a return passage 47. .

A port 50 opens in a first pressure chamber 49 defined on the left side of the spool 42 by the sleeve 40 and the plug 43, and is connected to the cylinder boat 26 of the switching valve 11 via a passage 51. A second pressure chamber 52 defined on the right side of the spool 42 by the housing 4 and the sleeve 40 is
The other cylinder port 27 of the switching valve 11 via the passage 53
It is connected to the. In this manner, hydraulic pressure from the fuel pump means acts on the spool 42 in both directions. Furthermore, since the pressure on the non-pressurized side is always connected to the return passage 36, the operational response of the directional control valve 6 is improved, and more appropriate injection timing can be obtained.

The servo valve 7 includes a primary piston 61 that is slidably disposed within a sleeve 60, and a secondary piston 63 that is movably disposed within a block 62 concentrically connected to the lower end of the housing 4. Equipped with. A first servo chamber 64 is defined above the primary piston 61 by the housing 4 and the sleeve 60, and is connected to the directional control valve 6 via an oil passage 65.
are connected to ports 1-46 of. Secondary piston 63
A second servo chamber 66 is defined below as a delivery chamber for pumping fuel to the nozzle section 3 .

This delivery chamber 66 is connected to the fuel intake port 25 via a fuel passage 67 and is supplied with fuel from the fuel pump means. The fuel passage 67 has a fuel intake port 25 in the middle.
A check valve 68, known in the art, is provided to prevent backflow. Further, if the opening position of the fuel passage 67 is provided near the upper end of the delivery chamber 66 instead of the check valve 68, the fuel passage 67 is closed when the secondary piston 63 descends, thereby preventing backflow of fuel.

The servo valve 7 is arranged such that its valve shaft is orthogonal to the valve shafts of the electromagnetic valve 5 and the directional control valve 6.

Therefore, the oil passage from the fuel pump means to the first servo chamber 64 via the directional control valve 6 can be provided in the shortest possible length and as straight as possible. This minimizes pressure loss in the oil passage and allows a large flow of fuel to flow between the 1st servo and the 6th servo.
Since the fuel can be introduced into the second servo chamber 66, the fuel in the second servo chamber 66 can be sufficiently pressurized and a high injection pressure can be ensured.

As clearly shown in FIG. 2, the primary piston 61 has a spherical recess 69 in the center of its lower surface, and the upper end 70 of the secondary piston 63 is hemispherical.
1.63 are in spherical contact with each other. For this reason, pistons 61 and 63 during operation due to machining or assembly errors, etc.
It is possible to effectively prevent the collapse of the equipment. Therefore, the first
The pressure inside the servo chamber 64 and the second servo chamber 66 is high, and the guide clearance between the piston 61 and the cylinder inner wall surface is extremely small, for example, 1 to 2 μm, and the sliding surface thereof is sealed under high pressure. These functions are not impaired. Further, with such a structure, manufacturing and assembly of the servo valve 7 are easy.

A recess 71 is provided in the center of the upper surface of the block 62, and a fourth
As shown in the figure, it communicates with the outside via a leak passage 72. As a result, fuel leaking from the guide clearance is smoothly discharged to the outside when the piston 61 descends, so that smooth operation of the servo valve 7 is ensured. but,
If fuel is sucked in from the leak passage 72 when the piston 61 is lifted, it becomes operational resistance when the piston is lowered. Therefore, it is more convenient to provide a check valve in the middle of the leak passage 72 because it prevents the backflow of fuel and improves the operability of the servo valve 7 by -M.

Further, in another embodiment, a return passageway opening on the inner surface of the sleeve 60 can be provided. This return passage is opened during the downward movement of the primary piston 61, causing the hydraulic pressure within the first servo to 53 to leak, stopping the downward movement of the pistons 61 and 63, and ending fuel injection. Therefore, the primary piston 61 collides with the upper surface of the block 62 as a stopper at a descending speed of about 3 to 3.5 m/s and stops, but by alleviating this collision, the durability of the servo valve 7 is improved. .

As shown in FIG. 1, the nozzle portion 3 includes a nozzle holder body 81 integrally connected to the pump housing 4 and the block 62 by a nut 80, and a nozzle holder body 81 integrally connected to the nozzle holder body 81 by a retaining nut 82. It includes a stance piece 83 and a nozzle body 84. An injection chamber 85 is provided inside the nozzle body 84, and a needle valve 86 is accommodated so as to be slidable in the axial direction. A nozzle hole 88 is provided in a circular top portion 87 at the tip of the nozzle body 84 .

An oil reservoir 89 is formed in the upper part of the injection chamber 85 by expanding in the radial direction, and communicates with the delivery chamber 66 via a high-pressure fuel passage 90. An exhaust pressure chamber 91 is formed inside the nozzle holder body 81, and a pressure spring 92 disposed therein biases the needle valve 86 in the valve closing direction via a retainer 93.

The exhaust pressure chamber 91 communicates with the fuel pump means through a return passage 94, and hydraulic pressure is applied from the fuel pump means to the upper end of the needle valve 86. By urging the needle valve 86 in the valve closing direction by the urging force of the pressure spring 92 and the hydraulic pressure acting on the exhaust pressure chamber 91 in this way, the load on the pressure spring 92 can be reduced, so that the pressure spring 92 and the exhaust pressure Room 9
1 can be downsized, and the entire nozzle section 3 can be downsized. If the nozzle part 3 is made smaller, the delivery chamber 6
Since the high-pressure fuel passage 90 leading from 6 to the injection chamber 85 can be shortened, the influence of pressure loss and compressibility in the passage 90 can be reduced, and more stable high-pressure fuel injection can be realized.

In this case, a check valve is provided between the return passage 94 and the fuel pump means to prevent backflow of fuel, and a drain passage is branched and provided before the check valve so as to act on the needle valve 86. Exhaust pressure chamber 91
It is possible to maintain the oil pressure within the pump at a substantially constant level at all times. Also,
It is convenient to provide a check valve in the middle of the drain passage to prevent backflow from the drain side.

Next, the operation of the unit injector 1 according to the present invention will be explained with reference to FIGS. 5 and 6.

The fuel discharged from the external fuel pump 100 is pressure-accumulated and pulsation absorbed by the Akicomulator 101, and then introduced into the fuel intake port 25 of the unit injector 1 at a substantially constant pressure. The fuel passage is branched into two directions from the fuel intake port 25, and the force is transmitted through the passage 24 to the switching valve 11.
, and the other is connected to the pressure port 23 of the passage 4.
4 is further branched into two directions midway, and one side is connected to the pressure port 45 of the directional control valve 6, and the other side is connected to the delivery chamber 66 via a passage 67.

When the solenoid 10 of the solenoid valve 5 is energized (time TO),
The plunger 14 is attracted and the spool 22 moves to the right in FIGS. 1 and 3 (time TI). As a result, the pressure port 23 is connected to the cylinder boat 26, the oil passage 24 and the passage 51 are communicated with each other, and the fuel pump 100 is connected to the pressure port 23.
Pressure oil flows into the first pressure chamber 49 of the directional control valve 6 from there.

On the other hand, the cylinder port 27 is connected to the right side opening of the bore 21 , that is, the return port 29 , and the passage 53 and the return passage 36 communicate with each other through the small hole 34 and the bore 33 , so that the drained oil flows from the second pressure port 52 to the sink 102 . is discharged to. Therefore, the directional control valve 6 moves the spool 42 to the right, the pressure port 45 closes, and the cylinder boat 46 and the return port 4
8 is connected.

In this way, from the fuel pump 100 to the primary piston 6
1 is cut off, and drained oil from the first servo chamber 64 of the servo valve 7 passes through the return passage 47 to the sink 102.
is discharged to. Therefore, the fuel introduced from the fuel pump 100 into the delivery chamber 66 through the fuel passage 67 at a constant pressure pushes the primary piston 61 and the secondary piston 63 upward. As a result, the delivery chamber 66 is filled with fuel necessary for one fuel injection.

Next, the solenoid 10 is energized and then demagnetized after a time Ti (time T4), and the spool 22 is moved to the left by the biasing force of the spring 16 (time T5).

The pressure port 23 is switched and connected to the cylinder boat 27, the passage 24 and the passage 53 communicate with each other, and pressure oil is supplied from the fuel pump 100 to the second pressure chamber 52 of the directional control valve 6.
is supplied to On the other hand, the cylinder boat 26 is connected to the left opening of the bore 21, that is, the return port 2B, and the passage 51 and the return passage 35 communicate with each other, so that waste oil is discharged from the first pressure chamber 49 to the sink 1Q2. In this way, the fuel pump 10
By switching the direction of fuel sent from zero, the direction control valve 6 prevents the spool 42 from moving to the left at time T.
6), the return port 48 is closed and the pressure port 45 is opened. Therefore, pressure oil flows from the fuel pump 100 into the passage 4.
4 into the first servo chamber 64 of the servo valve 7,
Push down the primary piston 61 (time T8)
.

When the secondary piston 63 is pushed down by the primary piston 61, the fuel in the delivery chamber 66 is pressurized and sent to the nozzle portion 3.

Since a check valve 68 is provided in the fuel passage 67, pressurized fuel will not flow back to the fuel pump 100 side. Delivery chamber 6 via high pressure fuel passage 90
When the pressure of the fuel sent from 6 to the injection chamber 85 of the nozzle part 3 exceeds a certain level, it pushes up the needle valve 86 against the pressure spring 92 and the hydraulic pressure in the exhaust pressure chamber 91 (time T9). . As a result, fuel is injected at high pressure from the nozzle hole 88 at the tip of the nozzle body 84, and when the pressure inside the injection chamber 85 decreases, the needle valve 86 is returned to its original closed position, completing one fuel injection ( Time Tl0).

In this way, the on/off timing ToS of the solenoid valve 5
By adjusting T4, excitation time Ti, etc., combustion can be optimally controlled according to engine operation. Further, the amount of fuel to be filled into the delivery chamber 66, that is, the amount of fuel to be injected at one time, is determined by the time from time T3 when the lift of the servo valve 7 starts to time T7 when the lift is completed.

The time from time T3 to time T7 is the time when the direction control valve 6
It is adjusted by the operation timing T6 of the Nfn valve 5, that is, the demagnetization timing T4 of the Nfn valve 5.

<Effects of the Invention> As described above, according to the present invention, fuel can be injected at a higher pressure by pressurizing the fuel using hydraulic pressure supplied from an external fuel pump means and forcefully feeding the fuel to the nozzle part. This will improve the combustion of diesel engines. Moreover, the servo valve that pressurizes the fuel is driven by the oil pressure supplied from the fuel pump means, and its operation is controlled by switching the oil path from the fuel pump means using a solenoid valve, so that the servo valve pressurizes the fuel according to the engine operating condition. Accordingly, fuel injection can be appropriately and precisely controlled.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a unit injector according to the invention. FIG. 2 is a sectional view taken along the line ■--■ in FIG. FIG. 3 is a partially enlarged view of FIG. 1. FIG. 4 is a partial longitudinal sectional view of the unit injector of FIG. 1 viewed from another position. FIG. 5 is a system diagram schematically showing a unit injector according to the present invention. FIG. 6 is a timing chart showing the operation of each element. 1... Unit injector 2... Pump section 3... Nozzle section 4... Pump housing 5... Solenoid valve 6... Directional control valve
7... Servo valve 10... Solenoid 11...
・Switching valve 12...Bobbin 13...Fixed core 14...Plunger 15...Guide hole 16...
・Return spring 17... Adjustment screw 20... Sleeve 21...
- Bore 22... Spool 23... Pressure boat 24... Passage 25... Fuel intake port 26.
27...Cylinder boat 28.29...Return boat 30...Step part 31...Flange 32...
・Ring member 33...Bore 34...Small hole
35...Pipe fitting 36...Return passage 40.
... Sleeve 41 ... Bore 42 ... Spool 43 ... Plug 44 ... Passage 45 ...
・Pressure boat 46...Cylinder boat 47...Return passage 48
...Return boat 49...First pressure chamber 50...
Boat 51... Passage 52... Second pressure chamber
53... Passage 60... Sleeve 61...
Primary side piston 62...Block 63...2
Next piston 64...first servo chamber 65...passage 66...to second servo, delivery chamber 67...
Fuel passage 68...Check valve 69...Recess
70...Top end 71...Concavity 72
...Leak passage 80...Natsuto 81...
Nozzle holder body 82... Retaining nut 83... Distance piece 84... Nozzle body 85... Injection chamber 86... Needle valve 87... Round top 88...
Nozzle hole 89... Oil reservoir 90... High pressure fuel passage 91... Exhaust pressure chamber 92... Pressure spring 93... Retainer 94... Return passage 10
0...Fuel pump 101...Accumulator 10
2... Sink patent applicant: Honda Motor Co., Ltd. representative
Attorney Patent Attorney Yo Oshima - Figure 5 Figure 6

Claims (4)

[Claims] (1) A fuel injection device for an internal combustion engine that pressurizes and injects fuel supplied at a predetermined fuel pressure from a fuel pump means, which is driven by the fuel pressure acting on a primary chamber and introduced into a secondary chamber. A fuel injection device for an internal combustion engine, comprising: a hydraulic amplification valve having a plunger for force-feeding fuel to an injection nozzle; and a directional control valve for selectively connecting the fuel pump means and the primary chamber. . (2) The internal combustion engine fuel injection system according to claim 1, wherein the directional control valve is operated by fuel pressure acting bidirectionally from the fuel pump means by a solenoid-controlled pilot valve. (3) The fuel injection device for an internal combustion engine according to claim 1, wherein the valve shaft of the directional control valve and the valve shaft of the hydraulic pressure amplification valve are arranged in directions perpendicular to each other. . (4) The hydraulic amplification valve has a piston that contacts the plunger through a spherical surface, and the fuel pressure in the primary chamber acts on the piston to drive the plunger. A fuel injection device for an internal combustion engine according to scope 1. (5) The injection nozzle has a needle valve that opens and closes the fuel injection port and a spring that biases the needle valve in the valve closing direction, and fuel pressure from the fuel pump means acts on a back pressure chamber that accommodates the spring. A fuel injection device for an internal combustion engine according to any one of claims 1 to 4, characterized in that: