WO2006018439A1

WO2006018439A1 - Hydraulic-controlled injector nozzle with variable cross-section

Info

Publication number: WO2006018439A1
Application number: PCT/EP2005/054059
Authority: WO
Inventors: Axel Hockenberger
Original assignee: Robert Bosch Gmbh
Priority date: 2004-08-18
Filing date: 2005-08-17
Publication date: 2006-02-23
Also published as: TR200402048A1

Abstract

In order to ensure injection of high quantity of fuel from injector in internal combustion engines, there are systems containing two rows of holes provided in the nozzle on top of each other relative to injector axis and consisting of one outer needle and one inner needle which separately control opening and closing of such holes. The purpose of the invention explained herein is to convert a coaxial dual-needle (5, 6) system into an incomplicated, simplified structure. In the system explained in this invention, out of such coaxial needles, the outer needle (5) is controlled by a spring (12), while the inner needle (6) is controlled through capillary channels (9) creating throttling effect, which interconnect the volume (8) provided over the needle with the fuel channel (10) in the main injector. If desired, to control the inner needle (6), a small spring (1 1 ) can also be added to the volume (8) provided at the upper side of inner needle. It will be possible that an injector-nozzle system to be thus obtained be used extensively without any major modification since it is similar to usual standard single-needle systems.

Description

HYDRAULIC-CONTROLLED INJECTOR NOZZLE WITH VARIABLE CROSS- SECTION

This invention is concerned with the injectors in a high pressure injection system used in internal combustion engines, and the purpose is to convert a coaxial dual-nccdlc system composed of one hollow outer needle and one inner needle contained in the hollow outer needle, which separately control opening and closing of each row of holes in the nozzles having two rows of holes located on top of each other relative to injector axis into an incomplicated, simplified structure.

The basic function of high pressure injection systems used in internal combustion engines is to inject fuel through an injection nozzle to create a proper air/fuel mixture in a manner to provide full combustion in the combustion chamber within the operating range of the engine. Here, by the operating range of the engine; the engine speed, in other words, the number of revolutions per unit time, and the engine load, in other words, the rotating moment (torque), or the power which is the multiplication of torque by engine speed arc identified. Depending on the rotation speed and the load conditions of the engine, the required quantity of fuel is injected into the cylinder by high pressure fuel injection so as to achieve the required performance in each operating condition. In order to obtain a higher performance, or in other words, a higher torque and power, from the cylinder volume formed by a piston, cylinder head and cylinder itself which limit the combustion chamber of the engine, as much heat energy as possible should be put into the cylinder volume in a very short time interval at each work cycle. The only way of increasing the heat energy put into the cylinder volume is to ensure putting a high quantity of fuel in a very short time interval into the air taken in the cylinder volume during intake or sweeping. The most important criteria that restrict putting a high quantity of fuel into the cylinder at each work cycle, or in other words, injecting thereof through the injector are the creation of a proper air/ fuel mixture to provide full combustion and the realization thereof in a very short time interval, as mentioned at the beginning. Injecting the fuel into the cylinder, or in other words, into the combustion chamber, through the injector in a very short time interval requires a high rate of fuel flow, which, in turn, can be achieved by enlargement of the total cross-sectional area of the injector nozzle holes and by high injection pressure. The creation of a good air/fuel mixture in a manner to ensure full combustion can only be achieved by breaking the injected fuel cluster into as much smaller droplets as possible and by having such droplets meet with air extensively and quickly in the combustion chamber without striking on the combustion chamber walls. Increasing the cross-sectional area of the injector nozzle holes to increase fuel flowrate is possible by increasing the number of holes and/or by enlarging their diameter. However, the very small size of the injector nozzle restricts the number of holes, while enlargement of the diameter of holes causes the injected fuel droplets to get bigger in size, which, in turn, causes the conditions of air/fuel mixture to get worse. While increasing the injection pressure of the fuel injected through an injector nozzle increases the speed of fuel cluster and thus the flowrate, hence causing the injected fuel to be broken inlo small droplets, it also increases the possibility of striking on the combustion chamber walls. As it will be understood from these explanations, the measures to be taken to increase the flowrate of fuel injected into the combustion chamber, or in other words, into the cylinder, through the holes in the injector nozzle arc geometrically limited, and on the other hand, they show partially conflicting effects for formation of a good mixture. In order to overcome the aforesaid problems, it has been proposed to make two rows of holes located in the nozzle, being on top of each other relative to injector axis, as proposed in the patents "DE 27 1 1 390 Al ", "DB 27 1 1 393 Al ", "DE 38 24467 Al " and "DE 41 15 477 C2". Thus, the cross-sectional area is increased without enlarging the diameter of holes and it is ensured that a high quantity of fuel be injected into the combustion chamber in a short time interval by maintaining the conditions to form a proper mixture. Furthermore, in the aforesaid patents, beside the two rows of holes located on top of one another in the injector nozzle relative to injector axis, a system composed of two coaxial needles, namely the outer needle being a hollow one and the inner needle located in the hollow part of outer needle, which separately control the opening and closing of each row of holes has been proposed. Thus each row of holes located on top of each other in the nozzle relative to injector axis are separately controlled, and the process of injecting fuel and creating a proper air/fuel mixture can be performed step by step. The step-by-step control as mentioned here covers the total cross-sectional area of the opening injector nozzle holes and the fuel injection pressure, which, in turn, beside ensuring the injection of high quantity of fuel into the combustion chamber, or in other words, into the cylinder in a short time interval during a work cycle, as mentioned earlier, also ensures prevention of delay in ignition of fuel entering into the combustion chamber at the beginning of injection, particularly in diesel engines, and of the subsequent instant burning thereof causing increase in pressure growth rate and creating detonation, by first opening of the first row of injector holes thus limiting the fuel flowratc and then opening of the second row of injector nozzle holes, despite higher injection flow rates. In the injection systems proposed by the aforesaid patents, a mechanism composed of one hollow outer needle and one coaxial inner needle contained in the hollow outer needle, which provides opening and closing of the two rows of holes provided in the nozzle on top of each other relative to injector axis is controlled by at least one spring provided on each needle and by hydraulic systems connected with the fuel injection system. This situation makes the structure of the injector contained in the fuel injection system more complicated, having more parts and bigger in size as compared to usual injectors.

The purpose of the invention explained here is to convert a coaxial dual-needle system composed of one hollow outer needle and one inner needle contained in the hollow outer needle, which separately control the opening and closing of the two rows of holes located in the nozzle on lop of each other relative to injector axis, into an incomplicatcd, simplified structure. It will be possible that an injector-nozzle system to be thus obtained be used extensively without any major modification since it is similar to usual standard single- needle systems with single row of holes in terms of its main structure. In the system explained in this invention; while, out of the coaxial needles, the hollow outer needle is controlled by means of a spring and a electromagnetic valve or a piezoelectric valve, the inner needle is controlled through, capillary channels which connect the volume provided on the aforesaid needle to the main fuel channel in the injector and create throttling effect. Depending on the operating conditions of injector, beside such capillary channels having throttling effect, a small spring can also be added to the aforesaid volume provided at the upper side of inner needle between the hollow outer needle and the inner needle for controlling the inner needle. Thus the coaxial dual-needle system composed of one hollow outer needle and one inner needle contained in the hollow outer needle, which separately controls opening and closing of each row of holes can be converted into an incomplicatcd, simplified structure. Drawings explaining the invention are as follows :

Figure 1. Sectional view of an hydraulic-controlled injector nozzle with variable cross- section.

Figure 2 A. Volume provided at the upper side of inner needle between outer needle and inner needle as shown in the sectional view of an hydraulic-controlled injector nozzle with variable cross-section.

Figure 2 B. A spring installed as a controlling component in addition to the volume provided at the upper side of inner needle between the outer needle and the inner needle as shown in the sectional view of an hydraulic-controlled injector nozzle with variable cross- section.

Detailed explanation of the invention :

The sectional view of an hydraulic-controlled injector nozzle with variable cross-section is shown in Figure 1. There are two rows of holes ( 3, 4) on top of each other on the nozzle (2) located at the tip of the injector body (1) contained in the fuel injection system. The holes in the upper row (4) are controlled by the hollow outer needle (5), while the holes in the lower row (3) are controlled by the inner coaxial needle (6) contained in the hollow outer needle. The hollow portion inside the outer needle (5) is not in form of an open- ended channel running throughout the full length of needle, but it is in such length as to leave a volume between the upper side (7) of inner needle (6) and the outer needle (5). The aforesaid volume (8) is made in such size as to allow the needles to perform their back and forth movement and the inner needle (6) to perform its control function. The volume (8) remained between the upper side (7) of inner needle and the hollow outer needle is interconnected with the capillary channels (9) having throttling effect as well as with the pressurized fuel channel (10) provided outside the outer needle in the injector body ( 1). The diameter and/or the number of holes (9) which create throttling effect is so sized as to allow the inner needle (6) to perform its control function. In Figure 2 A, the detail of the volume (8) provided at the upper side of inner needle between the outer needle (5) and the inner needle (6) in the sectional view of an hydraulic-controlled injector nozzle with variable cross-section is shown. Depending on the working conditions of the injector, beside such capillary channels (9) having throttling effect, a small spring (1 1 ) can also be added to the aforesaid volume (8) provided at the upper side of inner needle between the hollow outer needle (5) and the inner needle (6) for controlling the inner needle. In Figure 2 B, the case where a spring (1 1) has been installed as a controlling component in addition to the volume (8) provided at the upper side of inner needle between outer needle (5) and inner needle (6) in the sectional view of an hydraulic-controlled injector nozzle with variable cross-section is shown. When no fuel is injected from the injector, the hollow outer needle (5) closes the upper row of holes (4) provided in the nozzle (2) with the force exerted by the spring (12). In such case, the pressure in the volume (8) over the inner needle (6) contained in the hollow outer needle (5) will be the same as the pressure in the pressurized fuel channel (10) provided outside the outer needle (5) in the injector body ( 1 ) with which it is connected through capillary channels (9) having throttling effect. This pressure exerted on the inner needle (6) causes the inner needle (6) to close the lower row of holes (3) provided in the injector nozzle (2). When the process of fuel injection from the injector is to start, the pressure in the fuel channel (10) provided between the outer needle (5) and the injector body rises and when the force exerted by this pressure on the bottom surface (13) of the outer needle and on the chamfer (14), if any, reaches a level to overcome the spring force (12), the outer needle (5) moves upward and thus the upper row of holes (4) provided in the injector nozzle (2) are made open. Since initially the fuel pressure in the volume (8) provided over the inner needle (7) between outer needle and inner needle is maintained when the outer needle (5) opens the upper row of holes (4) in the injector body, the inner needle (6) keeps the lower row of holes (3) in the injector body in closed position. However, with the effect of rising pressure in the fuel channel (10) provided between the outer needle (5) and the inside of injector body with the outer needle being in open position, the magnitude of the force pushing the inner needle (6), with a certain time delay, upward from the bottom surface (15) of inner needle exceeds the force of pressure in the volume (8) remained between the outer needle (5) and the top surface (7) of inner needle and thus the inner needle (6) moves upward, causing the lower row of holes (3) provided in the injector nozzle (2) to open. The reason why the inner needle (6) opens with a certain time delay is that the rising pressure in the fuel channel ( 10) effects on the bottom surface (15) of the inner needle through a relatively wide opening between the outer needle (5) and the injector nozzle (2) with no pressure loss and that during this time, the effective pressure in the volume (8) between the outer needle and the top surface (7) of inner needle remains at a lower level. The fact that the effective pressure in the volume (8) between the outer needle and the top surface (7) of inner needle remains at a lower level is due to a pressure loss created by the capillary channels (9) having throttling effect, which interconnect the aforesaid volume with the fuel channel located between the inside surface of injector body and the outer needle. The required time delay between opening of the upper row of holes (4) provided in the injector nozzle (2) by the outer needle (5) and opening of the lower row of holes (3) by the inner needle (6) is achieved by properly dimensioning the volume (8) remained between the outer needle and the top surface (7) of inner needle as well as the capillary channels (9) with throttling effect, which interconnect the aforesaid volume with the fuel channel (10) located between the inside surface of injector body and the outer needle. When required, an additional control function can be added by mounting a small spring (1 1) of a proper feature in the volume (8) remained between the outer needle and the top surface (7) of inner needle.

Claims

1. The hydraulic-controlled injector nozzle with variable cross-section as described above covers an injector (1) used as a fuel injecting component in internal combustion engines and two rows of holes (3, 4) provided in the injector nozzle (2) on top of each other relative to injector axis and additonally a system composed of two coaxial needles, one being a spring-controlled (12) hollow outer needle (5) and the other one being a hydraulic- controlled inner needle (6) contained in the hollow outer needle, each separately controlling the opening and closing of one row of holes.

2. It is a system as in Claim 1, in which the hollow portion inside the outer needle (5) is not in form of an open-ended channel running throughout the full length of needle, but is of such depth as to form a volume (8) between the upper side of inner needle (7) and the outer needle (5) to provide the required time delay between opening of the upper row of holes (4) in the injector nozzle (2) by the outer needle and opening of the lower row of holes (3) by the inner needle (6).

3. It is a system as in Claims 1 and 2, in which the volume (8) remained between the upper side of inner needle (7) and the hollow outer needle is interconnected with the pressurized fuel channel (10) provided outside of the outer channel in the injector body through capillary holes (9) having throttling effect.

4. It is a system as in Claims 2 and 3, in which the diameter and/or the number of holes creating throttling effect (9) is so sized as to allow the inner needle (6) to perform its control function.

5. It is a system as in Claims 1 and 2, in which a small spring (11) of a proper quality can be mounted in the volume (8) remained between the upper surface of inner needle (7) and the outer needle when required in order to provide an additional control component.

6. It is a system covering the aforesaid 5 claims, in which the hydraulic-controlled injector nozzle with variable cross-section as described above can be applied in usual standard row type injection systems operated by distributor type of pumps, and it can also be applied in the injection systems containing more recent types of high pressure common rail or unit pumps.