JPH05157019A - Fuel injection device - Google Patents

Abstract

PURPOSE:To reduce all of nitrogen oxides, particle like materials and soot in exhaust gas by forming a cam of a fuel injection pump in a double recess cam, carrying out pilot injection in the initial stage, and also carrying out high pressure injection. CONSTITUTION:A cam 30 of a cam shaft 29 of a fuel injection pump is formed in a double recess cam, and the first recess part 73 and the second recess part 74 are arranged on the outer peripheral surface. Pilot injection is carried out by means of the first recess part 73 prior to main injection, and afterwards, the main injection is carried out by means of the second recess part 74. Since pilot frame is formed in a cylinder by means of the pilot injection and fuel spray of the main injection is burnt successively, combustion can be carried out moderately, so that nitrogen oxides can be reduced. Moreover, since the recess cam thrusts up a plunger 54 at high speed faster than a conventional cam, fuel injection can be carried out under a high pressure. Thereby, since atomization of fuel injected from an injection nozzle becomes possible, more ideal combustion can be carried out, so that the occurrence of soot and so on can be prevented.

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, and more particularly to pressurizing fuel with a fuel injection pump,
The present invention relates to a fuel injection device that supplies pressurized fuel to a fuel injection nozzle through an injection pipe and injects the fuel from the injection port.

[0002]

2. Description of the Related Art In a diesel engine, the intake air is compressed to a high temperature state by moving the piston to the top dead center side, and the fuel is injected from the fuel injection nozzle in synchronization with the piston almost reaching the top dead center. Is injected, and the fuel spray is spontaneously ignited by the heat of intake air to perform combustion. Therefore, the diesel engine is provided with a fuel injection pump, which pressurizes the fuel and supplies it to the fuel injection nozzle through the injection pipe. The fuel is injected from the injection port of the fuel injection nozzle into the cylinder. I am trying to jet it.

[0003]

High-pressure injection is suitable for improving the performance of a diesel engine and exhaust gas, especially for reducing particulate matter, soot and / or smoke contained in exhaust gas. The high pressure injection results in a finer fuel, more complete mixing with air and improved combustion.

On the other hand, in order to reduce the amount of nitrogen oxides in the exhaust gas, it is necessary to lower the combustion temperature. An effective method for lowering the combustion temperature is to delay the timing of injection and to carry out pilot injection prior to the main injection, and to burn the fuel spray of the main injection by the pilot fire obtained by this pilot injection. Is.
However, in the conventional diesel engine, both the high pressure injection and the pilot injection cannot be achieved at the same time.

The present invention has been made in view of the above problems, and the pilot injection is performed at the initial stage of the injection, and the high pressure injection is performed, whereby the nitrogen oxides and the particulate matter in the exhaust gas are made. An object of the present invention is to provide a fuel injection device that reduces both substances and soot.

[0006]

According to the present invention, fuel is pressurized by a fuel injection pump, and the pressurized fuel is supplied to a fuel injection nozzle through an injection pipe, and the fuel is injected from the injection port. In the injector, the cam of the fuel injection pump is composed of a double recessed cam, and a first recess for performing pilot injection and a second recess for performing main injection are provided.

[0007]

The pilot injection is performed prior to the main injection by the first concave portion of the double concave cam of the fuel injection pump. Then, after this, the main injection is performed by the second recess.

[0008]

1 shows a main part of a diesel engine equipped with a fuel injection device according to an embodiment of the present invention, in which a cylinder block 10 is provided with a cylinder 11 consisting of a through hole. A piston 12 is slidably arranged in the cylinder 11. The piston 12 is connected to the connecting rod 14 by a piston pin 13.

The upper opening of the cylinder 11 is closed by a cylinder head 15, and the cylinder head 15 has an intake port 16 and an exhaust port 1.
7 and 7 are formed respectively. These intake ports 1
6 and the exhaust port 17 are opened and closed by an intake valve and an exhaust valve 19, respectively. A fuel injection nozzle 20 is attached to the cylinder head 15 so as to inject fuel toward a combustion chamber 21 formed on the top surface of the piston 12.

The fuel injection nozzle 20, as shown in FIG.
The fuel injection pump 2 is provided by the injection pipe 24 formed of a tapered pipe.
5 corresponding pump units 26. The fuel injection pump 25 includes a mechanical governor 27, and the mechanical governor 27 controls the control rack 28.
Is adjusted to adjust the amount of fuel injected at one time. Further, the fuel injection pump 25 includes a cam shaft 29, and a cam 30 attached to the cam shaft 29 drives each pump unit 26. Further, a timer 31 is provided on the camshaft 29, and the timing of injection is adjusted by the timer 31.

The fuel injection nozzle 20, as shown in FIG.
The tip portion is composed of the nozzle body 34, and 4 to 10 injection holes 35 are formed at the tip portion of the nozzle body 34. The nozzle body 34 is attached to the nozzle holder 37 by the retainer 36. A nozzle needle 38 is slidably held in the nozzle body 34. The upper end of the nozzle needle 38 is connected to the compression coil spring 4 in the nozzle holder 37 via the pressing rod 39.
It is designed to be pressed downward by 0. As a result, the nozzle needle 38 is pressure-bonded to the valve seat 41 formed on the nozzle body 34 to shut off the fuel. Further, the nozzle holder 37 is formed with a fuel passage 42 communicating with the injection pipe 24. The fuel passage 42 communicates with the fuel passage 43 of the nozzle body 34. A fuel sump 51 is formed at the end of the fuel passage 43.

The spring 40 pressing the pressing rod 39 has its upper end received by a spring receiver 44. An adjusting screw 45 is attached to the upper end of the spring receiver 44. The adjusting screw 45 is screwed with a female screw 46 formed on the inner peripheral surface of the nozzle holder 37. Further, a protrusion 48 is formed on the side surface side of the nozzle holder 37, and a male screw 49 is formed on the protrusion 48, and a connecting nut 50 screwed with the male screw 49.
The injection pipe 24 is connected to the nozzle holder 37.

Next, the structure of each pump unit of the fuel injection pump 25 will be described. As shown in FIGS. 3 and 4, a tappet 55 is attached to the lower end of the plunger 54. The tappet 55 is a compression coil spring 56.
Is pressed downward by the cam 30.
Is pressed against the outer peripheral surface of. As shown in FIG. 5, the cam 30 is composed of a recessed cam having a pair of recesses 73 and 74 on its outer peripheral surface. A spill port 58 is formed in the barrel 57 in which the plunger 54 is slidably fitted, and an inclined groove 59 is formed in the outer peripheral surface of the plunger 54 so as to substantially face the spill port 58. ing.

A pinion 60 is rotatably supported on the outer peripheral side of the barrel 57. A control sleeve 61 is fixed to the pinion 60 and a notch 62 formed in the control sleeve 61.
Receives the engagement plate 63. The engagement plate 63 is fixed to the plunger 54.

A delivery valve 64 is provided on the outlet side of each pump unit 26, and is arranged on a valve seat 66 provided at the bottom of the casing 65.
The delivery valve 64 is pressed toward the valve seat 66 by the coil spring 67.

As shown in FIG. 6, a constant residual pressure valve 68 made of a ball is arranged in the delivery valve 64, and is pushed upward by a spring 70 via a spring receiver 69, and a small hole in a valve seat 71. 72 is adapted to be opened and closed.

Next, an outline of the operation of the fuel injection device having the above structure will be described.

A timer 31 is provided depending on a part of the output of the engine.
When the camshaft 29 is driven via the concave shaft, the concave surface of the concave cam 30 having the shape shown in FIG. 5 pushes up the roller of the tappet 55, which causes the plunger 54 to move.
Moves upward in the barrel 57. Then plunger 5
The top surface of No. 4 closes the spill port 58 and starts the fuel pumping. When the plunger 54 moves further upward, the inclined groove 59 eventually aligns with the spill port 58, whereby the pressure in the space above the plunger 54 escapes to the spill port 58 side through the inclined groove 59, and the fuel is pumped. finish.

Mechanical governor 2 of fuel injection pump 25
When the 7 moves the control rack 28, the pinion 60 is rotated, which causes the control sleeve 6 to move.
1 will be rotated. The rotation of the control sleeve 61 is transmitted to the plunger 54 via the notch 62 and the engaging plate 63, and the plunger 54 is rotated in the barrel 57. Therefore spill port 5
8, the effective stroke determined by the position of the inclined groove 59 aligned with 8 changes, the fuel is metered,
The supply amount of fuel injected at one time is controlled. A timer 31 provided on the camshaft 29 of the fuel injection pump 25 controls the phase angle of the camshaft 29 and adjusts the fuel injection timing.

When the plunger 54 pumps the fuel in the barrel 57, the delivery valve 64 is opened and the fuel is pumped to the fuel injection nozzle 20 through the injection pipe 24. The fuel passage 4 of the fuel injection nozzle 20 shown in FIG.
When fuel pressure is applied to the fuel sump 51 through 2 and 43, the nozzle needle 38 moves through the rod 39 into the spring 4
0 is compressed and moves upward, whereby the tip end side portion of the nozzle needle 38 separates from the valve seat 41, and fuel is injected through the injection port 35. When the pressure feeding of the fuel is completed, the elastic restoring force of the spring 40 pushes the nozzle needle 38 downward through the rod 39, and the tip end thereof is pressed against the valve seat 41 to stop the fuel injection.

The fuel is sprayed by the injection port 3 of the fuel injection nozzle 20.
5, the fuel is injected toward the combustion chamber 21 formed on the top surface of the piston 12 shown in FIG. Then, this fuel spray is spontaneously ignited by the heat of the compressed intake air, combustion occurs in the cylinder 11, the piston 12 is pushed downward, and the output of the engine is taken out.
After this, the exhaust valve 19 is opened, and exhaust gas is discharged through the exhaust port 17.

In the fuel injection device for injecting fuel in this way, the camshaft 2 of the fuel injection pump 25
As shown in FIG. 5, the cam 30 attached to the No. 9 is composed of a double recessed cam, and the outer peripheral surface of the cam 30 has a first
The concave portion 73 and the second concave portion 74 are provided. The recesses 73 and 74 are continuous with each other through a smooth curved surface composed of tangent lines. Such a cam 30
The lift diagram and velocity diagram of
The first recess 73 and the second recess 74 change the lift and speed in two steps.

By using such a double recessed cam 30, it becomes possible to perform the pilot injection shown in FIG. 8 in the first recess 73 thereof prior to the main injection. Then, after this, the main injection is performed by the second recess 74. By performing pilot injection,
It becomes possible to form a pilot flame in the cylinder 11, and this pilot flame makes it possible to successively burn the fuel spray of the main injection. Therefore, diesel knock is prevented, and a rapid increase in combustion pressure and combustion temperature is prevented. This means that the combustion in the cylinder 11 is carried out gently, which makes it possible to reduce nitrogen oxides.

Moreover, the cam 30 having the first concave portion 73 and the second concave portion 74 is basically a concave cam, and its velocity diagram is higher than that of the conventional cam, as is apparent from FIG. ing. That is, the plunger 54 is pushed up at high speed. Therefore, it becomes possible to inject fuel at a higher pressure than in the past, and it becomes possible to atomize the fuel injected from the fuel injection nozzle 20. Therefore, the mixing of the fuel spray with the air is promoted, and more ideal combustion is performed. Such combustion makes it possible to prevent the generation of particulate matter, soot, or black smoke contained in the exhaust gas. Therefore, by mounting such a double recessed cam 30 on the camshaft 29 of the fuel injection pump 25, both pilot injection and high pressure injection can be achieved.

A constant residual pressure valve 68 shown in FIG. 6 is incorporated in the delivery valve 64 of the fuel injection pump 25. By incorporating such a constant residual pressure valve 68, it becomes possible to increase the injection pressure in the injection pipe 24 when the injection is finished as shown in FIG. That is, the fuel pressure remaining in the injection pipe 24 is increased to 150 to 220 kg.
The residual pressure is in the range of / cm ² . By superimposing the fuel pressure at the time of the next injection on this residual pressure, higher injection is possible.

The injection pipe 24 is composed of a tapered pipe as shown in FIG. 2, and the inner diameter thereof is the fuel injection nozzle 20.
The value on the side is smaller than that on the side on the fuel injection pump 25. By using such a taper pipe 24, the pressure of the fuel fed under pressure is made higher toward the fuel injection nozzle 20 side. That is, the fuel pressure on the nozzle 20 side is made higher than that on the discharge side of the fuel injection pump 25.

The valve opening pressure of the fuel injection nozzle 20 is set by the compression coil spring 40 incorporated in the nozzle holder 37 shown in FIG. When the compression coil spring 40 is compressed by screwing the adjusting screw 45 through the spring receiver 44, the nozzle needle 38 can be pressed with a larger force, and the valve opening pressure can be set to a high value. In this embodiment, the spring 4 is adjusted by the adjusting screw 45.
By compressing 0 strongly, 300-700 kg / c
The value is set to m ² .

In order to perform high pressure injection, it is necessary to set the valve opening pressure to at least 180 kg / cm ² or more. Incidentally, in the conventional fuel injection nozzle, the valve opening pressure was set to a value of 70 to 200 kg / cm ² .

As described above, in the fuel injection system according to this embodiment, the residual pressure of the fuel in the injection pipe 24 is set to a high residual pressure state by the constant residual pressure valve 68 as shown in FIG. With 30, the plunger 54 is pushed up at high speed and pilot injection is performed prior to the main injection. Moreover, the injection pipe 24 is used as a pressure accumulating chamber, and the cross-sectional area of the injection pipe 24 is a tapered pipe that decreases toward the nozzle 20 side so that the pressure is increased toward the nozzle 20 side. The injection nozzle 20 has a higher fuel pressure.
Further, the compression coil spring 40 in the fuel injection nozzle 20 is set to a high valve opening pressure to achieve ultra-high pressure injection.

Therefore, the fuel injection nozzle 20 shown in FIG. 1 makes it possible to inject fuel into the combustion chamber 21 at high pressure, and the atomized atomized or vaporized spray is directed to the combustion chamber 21 of the piston 12. Will be injected. Therefore, ideal combustion takes place, which suppresses the production of smoke and soot and achieves a significant improvement of the exhaust gas. Further, it is possible to suppress the generation of nitrogen oxides by removing heat from the surroundings by evaporating the fuel and lowering the combustion temperature.

[0031]

As described above, according to the present invention, the cam of the fuel injection pump is composed of the double recessed cam, and the first recess for performing pilot injection and the second recess for performing main injection are provided.
And a concave portion of the.

Therefore, according to this structure, it is possible to perform the pilot injection by the first concave portion of the cam and the main injection subsequently by the second concave portion. By performing the pilot injection prior to the main injection, the fuel spray of the main injection can be ignited by the pilot fire, diesel knock can be prevented, and nitrogen oxides can be reduced. Moreover, the cam is basically composed of a concave cam, and since high-speed pressure feeding is performed, high-pressure injection is possible, and atomization of the fuel is performed to promote mixing of fuel spray with air. Then, it becomes possible to perform ideal combustion.
This makes it possible to prevent the generation of particulate matter, soot, or black smoke in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of a diesel engine including a fuel injection device according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a fuel injection nozzle.

FIG. 3 is a perspective view of a main part of a fuel injection pump.

FIG. 4 is a vertical sectional view of the fuel injection pump.

FIG. 5 is a front view showing the shape of a cam.

FIG. 6 is a vertical sectional view showing a constant residual pressure valve.

FIG. 7 is a graph showing cam lift and speed.

FIG. 8 is a graph showing changes in injection rate.

FIG. 9 is a graph showing a pressure in an injection pipe.

[Explanation of symbols]

 10 Cylinder Block 11 Cylinder 12 Piston 13 Piston Pin 14 Connecting Rod 15 Cylinder Head 16 Intake Port 17 Exhaust Port 18 Intake Valve 19 Exhaust Valve 20 Fuel Injection Nozzle 21 Combustion Chamber 24 Injection Pipe (Tapered Pipe) 25 Fuel Injection Pump 26 Pump Unit 27 Mechanical Governor 28 Control rack 29 Cam shaft 30 Cam 31 Timer 34 Nozzle body 35 Nozzle 36 Retainer 37 Nozzle holder 38 Nozzle needle 39 Push rod 40 Spring 41 Valve seat 42, 43 Fuel passage 44 Spring bearing 45 Adjusting screw 46 Female screw 47 Cap 48 Projection 49 Male screw 50 Connection nut 51 Fuel sump 54 Plunger 55 Tappet 56 Coil spring 57 Barrel 58 Spill port 59 Inclined groove 60 Pin On 61 the control sleeve 62 the notch 63 engagement plate 64 Deriberibarubu 65 casing 66 valve seat 67 coil spring 68 pressure holding valve (ball) 69 spring bearing 70 spring 71 valve seat 72 small holes 73 first recess 74 a second recess

Claims (1)

[Claims] 1. A fuel injection device for pressurizing fuel by a fuel injection pump, supplying the pressurized fuel to a fuel injection nozzle through an injection pipe, and injecting the fuel from the injection port. The fuel injection device is characterized in that the cam is constituted by a double recessed cam, and a first recess for performing pilot injection and a second recess for performing main injection are provided.