KR101999908B1

KR101999908B1 - A fuel injection unit for an internal combustion engine

Info

Publication number: KR101999908B1
Application number: KR1020177021910A
Authority: KR
Inventors: 얀네 엔룬드; 안띠 부오히요끼
Original assignee: 바르실라 핀랜드 오이
Priority date: 2015-03-06
Filing date: 2015-03-06
Publication date: 2019-07-12
Also published as: EP3265668B1; CN107110102B; WO2016142570A1; EP3265668A1; KR20170102534A; CN107110102A

Abstract

The present invention discusses a new fuel injection unit for a large internal combustion engine having a common rail system. The fuel injection unit 10 of the present invention is connected to a common rail fuel system and the fuel injection unit 10 includes a first nozzle 22 and a second nozzle 24, And a first needle control volume 34 connected to the first valve 16 by a passage 48. The first nozzle 22 and the second nozzle 24 have a common needle cavity 30, The flow fuse 50 is arranged in relation to the flow passage 48 connecting the first needle control volume 34 to the first control valve 16.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a fuel injection unit for an internal combustion engine,

The present invention relates to a fuel injection unit for an internal combustion engine having a plurality of cylinders and using a common rail fuel system according to the premise of claim 1. The present invention also relates to an internal combustion engine having a plurality of cylinders having cylinder heads and utilizing a common rail fuel system, wherein each cylinder head is provided with a fuel injection unit according to any one of claims 1 to 11 .

In modern internal combustion engines, fuel is injected directly into the cylinder of the engine by a fuel injection valve or injector. Since injection occurs relatively late in the last part of the compression stroke, a pressure high enough for injection is required. In a conventional fuel supply system, each cylinder has its own injection pump for pumping fuel into the combustion chamber of the cylinder through the injector. However, the use and control of conventional systems has significant limitations. The configuration of the system can not be easily adjusted. In addition, the pressure in the injection pump can be varied, so that injection into different cylinders may be done under different pressures, thus providing a different amount of fuel, respectively. In addition, since the prior art injection nozzles are mainly hydraulic mechanics, i.e. they are closed at a certain predetermined fuel pressure and also when the pressure is reduced below a predetermined value, the control of the injection timing and duration can be controlled during use of the system , That is, wear of system components should be taken into account when operating the engine.

A more recent solution is the so-called "common rail injection" or "common pressure injection" in which the provision of pressure and the injection of fuel are functionally separated from one another. The fuel is supplied by at least one high-pressure fuel pump into a common pressure supply, i. E. Rail, from which fuel flows into separate cylinders through separate pipes. In practice, the operation of the injector is electronically controlled, for example by means of a solenoid or a piezo-electric control valve, in order to obtain a sufficiently short and accurate injection.

Many of the most obvious problem areas of conventional fueling systems are the use of common fuel supplies at high pressures (up to about 2200 bars) and electronically controlled fuel injectors capable of injecting fuel into the engine cylinders multiple times, e.g. during the same compression stroke . In other words, the timing of injection, the duration of injection, and the amount of fuel injected are clearly better controlled than prior art fuel injection pumps, so that the emission levels in normal operating conditions of the internal combustion engine are also rapidly .

The operation of the fuel injector is controlled by an electronic control valve which is in fluid communication with the nozzle today. The control valve and the nozzle are operated such that the total fuel rail pressure is provided within the cavity around the needle, i. E. In the needle cavity, and the pressure tends to open the needle of the nozzle. However, the needle has a spring that pushes the needle against its seat surfaces upstream of the spray nozzle opening. Also, with respect to the end of the needle opposite the nozzle opening, the so-called needle control volume is arranged such that the pressure in the needle control volume pushes the needle in the same direction as the spring. The needle control volume and the needle cavity may include one or more properly dimensioned openings or flow channels that limit the flow between the two cavities, i. E. The rate at which the pressure can rise in the needle control volume Are arranged in flow communication with one another. The actual control of the needle is done by electronically opening the control valve so that the pressurized fuel in the needle control volume can escape through the control valve to the low pressure fuel drain so that the total fuel pressure affects the injector needle, The sheet surface for opening the injection nozzle is lifted and the injection is started. After a desired period for which fuel injection is to be taken, the control valve is closed and the pressure in the needle control volume is raised, whereby the needle control volume pressure closes the nozzle with the spring, i. E. Push it out.

So far, diesel engines have been optimized at full load in terms of emissions. However, future emission regulations require that emission levels should be minimized under all operating conditions. In other words, all load spectrum tuning must be performed. For example, the use of electronic control of modern common rail fuel systems and fuel injectors does not result in the desired outcome being related to engine operation at low loads, or more generally at loads far from the design load. The ultimate goal is to improve the injection of fuel so that the emissions of the engine can be kept to a minimum level throughout the operating conditions of the engine, from the minimum load to the maximum load.

This effort leads to the use of injection valves or injectors with two injection nozzles. For example, US-B2-7,556, 017 describes an injector body that defines a hollow interior configured to receive pressurized fuel, a first nozzle configured to provide a first fuel spray pattern, and a second nozzle configured to provide a second fuel spray pattern A fuel injector having a second nozzle configured to provide a fuel spray pattern is discussed. The first nozzle and the second nozzle may be configured to inject the fuel supplied from the common source into the combustion space. The nozzle can be used in separate steps during the compression stroke of the piston, such that the first nozzle injects a predetermined amount of fuel at an early stage of the compression stroke and the second nozzle at a later stage or end of the compression stroke. The first nozzle is often referred to as a pilot nozzle, and the second nozzle is referred to as a main nozzle.

The prior art discloses a device called a flow restriction valve or flow fuse arranged in communication with a fuel injector to handle situations where the injector nozzle is launched at a position where the fuel can bleed in the cylinder. Flow fuses function by sensing the change in fuel pressure, which affects flow in the case of abnormal pressure drop conditions. For example, if the injector needle leaks pressure after the flow fuse has dropped, the flow fuse will stop feeding fuel to the injector. The flow fuse is designed and dimensioned to allow injection quantities corresponding to the requirements set for the fuel quantity by the cylinder at maximum load with a slight margin naturally before the injector is stopped.

However, using a flow fuse with respect to the two nozzles, i.e., the injector having the pilot nozzle and the main nozzle, it is difficult to share the same fuel volume. If a single flow fuse is arranged in the fuel line that introduces the pressurized fuel into the injector, it must naturally be dimensioned for the main nozzle or needle. In other words, if the main needle fails or is opened, the flow fuse interrupts the oil introduction into the fuel volume shared by both nozzles. However, failure of the pilot needle does not affect the operation of the flow fuse for any reason, since the injection amount of the main needle to which the flow fuse is dimensioned is typically several tens of times greater than the pilot needle injection amount. In other words, since the injection amount of the pilot needle is very small, the flow fuse can not detect small changes caused by the pilot needle leaking from the fuel pressure. As a result, the fuel may flow in the fuel volume and may also be injected from the nozzle openings into the engine cylinders without interruption.

Pilot needles may leak for two distinct reasons. First, the needle of the pilot nozzle may be opened, or second, the control valve may fail. Since the prior art does not mention that the control valve may be a component that may fail, the latter problem is now considered more closely. In other words, the control valve may remain open while the pin of the control valve may not return to its seat after a period in which fuel injection through the pilot needle is supposed to be taken for some reason, Drain the fuel to the fuel line. In practice, this fuel drain means that when the control valve is closed, the pressure to be generally raised in the needle control volume is not raised, so that the pilot needle remains open and the fuel is continuously injected into the cylinder.

An object of the present invention is to solve the above-mentioned problems.

Another object of the present invention is to increase safety in a common rail fuel-injection system.

It is a further object of the present invention to prevent excessive fuel injection to the engine cylinders.

It is a further object of the present invention to reduce emissions formed by internal combustion engines.

At least the object of the present invention is achieved by a fuel injection unit suitable for injecting fuel into and injecting fuel into a cylinder of an internal combustion engine having a common rail fuel system having at least one high pressure fuel pump, The unit is connected to a common rail fuel system, and the fuel injection unit includes a first nozzle and a second nozzle, the first nozzle having a first needle control volume connected by a flow path with the first control valve, The first nozzle and the second nozzle having a common needle cavity and the flow fuse being arranged in relation to the flow passage connecting the first needle control volume to the first control valve.

At least one object of the invention is met by a large internal combustion engine having a plurality of cylinders having cylinder heads and also utilizing a common rail fuel system, wherein each cylinder head is equipped with a fuel injection system according to any one of claims 1 to 10, Unit is provided.

Other specific features of the fuel injection unit of the present invention will become apparent from the appended dependent claims.

The present invention, in solving at least one of the above problems, results in a number of advantages in the case of control pin failures, some of which are listed as follows:

- Eliminates the risk of excessive cylinder pressures from excessive fuel injection,

- reduce emissions,

- reduces the amount of circulating fluid,

- reduce the energy required to pressurize the fuel,

Hereinafter, the fuel injection unit of the present invention will be described in more detail with reference to the accompanying drawings.

1 schematically shows a cross-sectional view of a fuel injection unit according to a preferred embodiment of the present invention.
Figure 2 schematically shows in enlarged detail the details of the fuel supply arrangement of Figure 1;

Fig. 1 schematically shows a cross-sectional view of the fuel injection unit of the present invention. The fuel injection unit 10 includes a fuel accumulator 12 that receives fuel at a desired pressure from a common rail (not shown), a main flow fuse 14, a first control valve 16, a second control valve 18 And a fuel injector 20. The fuel injector 20 includes a first or pilot nozzle 22 having a first needle 24 and a second or main nozzle 26 having a second needle 28. The first and second nozzles (22, 26) are provided with a common needle cavity (30). The nozzles of both have nozzle openings and seat surfaces at the end of the injection unit 10 facing the engine cylinder. The end of the needle facing the engine cylinder, i.e., its first end, rests on the seat surface that closes the flow communication from the needle cavity 30 to the nozzle opening 32. At an opposite end or a second end of the first needle 24 that is facing away from the engine cylinder there is a first needle control volume 34 and an upper end of the second needle 28, The second needle control volume 36 is located at the end or second end that is directed toward the second needle. Needle control volumes 34 and 36 are arranged in flow communication with common needle cavity 30 through first restrictive flow passages 38 and 40, respectively. The first needle and second needle 26 and 28 are maintained in their closed position, i.e., by the fuel pressure acting on the needle control volumes 34 and 36, and by the springs 42 and 44, And presses their seat surfaces at the first end of the needles. What has been described so far is the fuel injection unit of the prior art.

To illustrate how the prior art fuel injection unit operates, a first nozzle 22 is taken as an example. The starting point is such that when exposed to fuel pressure, the total fuel rail pressure acting on the entire surfaces of the first needle 26, including the surfaces that tend to lift the first needle 28 at its seat surface, (12) and the needle cavity (30). However, since the first control valve 16 is closed, the same rail pressure also affects the first needle control volume 34, so that the fuel pressure in the needle control volume 34 and the force of the compression spring 42 1 needle 26 relative to its seat surface, whereby the first nozzle 22 is closed. The direct flow path for the pressurized fuel from the first needle control volume 34 to the low pressure fuel outlet drain 46 is controlled by the first needle control < RTI ID = 0.0 > Is formed through the flow passage (48) between the volume (34) and the first control valve (16). At the same time the pressure in the first needle control volume 34 drops and the spring 42 alone can not hold the first needle 26 against its seat surface, And the high-pressure fuel jet is sprayed into the cylinder through the first nozzle 22. The high- The engine's electronic control unit then directs the first control valve 16 to be closed, thereby directing the direct flow passage from the needle control volume 34 to the low pressure fuel outlet drain 46 to be closed. At the same time, the pressure in the first needle control volume 34 begins to rise, so that the pressure together with the spring 42 can push the first needle 26 against its seat surface to stop the spring action. The function of the second nozzle 24 is exactly the same.

However, the above-described injector unit, and in particular its first nozzle 22, has a weak point, which is the first control valve 16. If the control valve 16 fails, that is, it can not close the direct flow path of the pressurized fuel from the needle control volume 34 to the low pressure fuel outlet drain 46, the pressure in the needle control volume 34 will not rise And the first needle 26 is maintained in its lifted state such that the fuel is continuously sprayed into the cylinder of the engine. At the same time there is a continuous flow from the needle control volume 34 through the flow passage 48 and the first control valve 16 to the low pressure fuel outlet drain 46. In order to solve the self-evident problem of the injector unit, the present invention proposes an improvement of the injection unit.

The improvement introduced by the prior art injector unit of the present invention described above can also be seen in Figure 1 wherein the injector unit 10 includes a first control valve 16 and a first needle 26 at a second end (50) arranged in the flow passage (48) between the first needle control volume (34).

The flow fuse 50 discussed in more detail in FIG. 2 is formed with a cylindrical cavity 52 having an inner wall 54 and a bottom surface 56 and the flow passage 48 has an opening 48 'therein. . A cup shaped piston 58 formed from a bottom 60 facing the first needle control volume 34 and a skirt 62 extending away from the bottom 60 facing away from the first needle control volume 34, A spring 64 is arranged in the cylindrical cavity 52 such that it is arranged within the piston skirt 62 between the bottom 60 of the piston 58 and the bottom surface 56 of the cylindrical cavity 52. The bottom portion 60 of the piston 58 and the skirt 62 place at least one limited flow passage 66 between itself and the inner wall 54 of the cylindrical cavity 52. The flow fuse 50 is opened in a normal operating state, i.e. in a manner that is intended to be activated, such that the first control valve 16 allows oil flow from the needle control volume 34 to the first control valve 16 The piston 58 of the flow fuse 50 moves away from the first needle control volume 34 and the pressure in the first needle control volume 34 compresses the spring 64 to the piston 58, As shown in FIG. The prerequisite for this kind of operation is that the flow resistance of the first control valve 16 is less than the flow resistance of the at least one restricted flow passage 66 such that the volume flow through the control valve 16 is at least one limited Is greater than the volume flow through the flow passage (66). As a result, the results are that the pressure in the first needle control volume 34 is relieved such that the first needle 26 is lifted from its seat surface, and fuel injection may occur. After the first control valve 16 is closed, the needle control volume 34 is quickly filled with the pressurized fuel through the at least one first restricted flow passageway 38, so that the first needle 26 returns to its seat And is pushed against the surface. Now, when the first control valve 16 is closed, some of the fuel in the needle control volume 34 reaches at least one second restricted flow passage 66 so that the fuel pressures on both sides of the piston 58 are equalized. Thus, as it passes through the piston 58, the spring 64 pushes the piston 58 towards the needle control volume 34. At least one second restricted flow passage 66 as well as the piston 58, its skirt 65 and the cylindrical cavity 52 are configured such that when the piston 58 is moved in a direction away from the needle control volume 34, The mitigated space is dimensioned to be sufficient to reduce the pressure in the space below the pressure required to hold the first needle 28 against its seat surface. In other words, the flow resistance of the first limited flow passage 38 is greater than the flow resistance of the second limited flow passage 66.

When the first control valve 16 is left unopened and remains open after a predetermined period of time that is equal to a certain volume of oil flowing into the low pressure fuel drain 46 under abnormal operating conditions, The piston 58 is configured such that the skirt 62 of the piston 58 meets the bottom surface 56 of the cylindrical cavity 52 and extends from the first needle control volume 34 through the flow passage 48 to the low pressure fuel outlet drain 46 until the flow connection to the needle control volume 34 is blocked. In other words, the needle control volume 34 through the at least one second restricted flow passage 66, as the flow passage 48 opens within the skirt 62 toward the bottom surface 56 of the cylindrical cavity 52, Lt; / RTI > is blocked. Thereafter, when the first control valve 16 is closed so that the first needle 26 can be pushed back against its seat surface, the pressure in the first needle control volume 34 may be raised as it is normally performed . However, since the fuel pressure in the first needle control volume 34 can not enter the interior of the piston 58, the pressure in the piston 58 that helps return the piston 58 back toward the needle control volume 34 There is no pressure, so that the first needle 28 remains closed until the first control valve 16 is closed.

It is to be understood that the foregoing is merely illustrative of the novel and novel fuel injection unit of the internal combustion engine. It is to be understood that while the foregoing description discusses the specific location of the flow fuse, the location thereof does not limit the present invention to the position discussed. This applies to the type of flow fuse, i.e. the detailed configuration of the flow fuse, for example, is limited to the functions just described. Thus, the floating fuse may be a ball-type, a piston-type or any other type of floating valve. Similarly, the flow fuse may be located anywhere along the length of the flow path between the first needle control volume at the second end of the first needle and the first control valve. Thus, the flow fuse not only communicates directly with the first needle control volume, but may also be arranged completely upstream of the control valve. The foregoing description is not to be construed as limiting the invention by any means, and the full scope of the invention is defined only by the appended claims. From the foregoing description, it is to be understood that separate features of the invention may be used in connection with other distinct features, even if such combinations are not disclosed or shown in the detailed description or illustrated in the drawings.

Claims

A fuel injection unit suitable for injecting fuel into and injecting fuel into a cylinder of an internal combustion engine having a common rail fuel system having at least one high-pressure fuel pump,
The fuel injection unit (10) is connected to the common rail fuel system,
The fuel injection unit 10 includes a first nozzle 22 and a second nozzle 24,
The first nozzle 22 has a first needle control volume 34 and a first needle 26 connected to the first control valve 16 by a flow passage 48,
The first nozzle (22) and the second nozzle (24) have a common needle cavity (30)
Wherein a flow fuse (50) is arranged on the flow passage (48) connecting the first needle control volume (34) to the first control valve (16).

The method according to claim 1,
Characterized in that the flow fuse (50) comprises means for closing the flow connection from the first needle control volume (34) to the first control valve (16).

The method according to claim 1,
Characterized in that the flow fuse (50) is a ball-type or piston-type floating valve.

3. The method of claim 2,
Characterized in that the means for closing the flow connection is a piston (58) arranged in a cylindrical cavity (52) between the needle control volume (34) and the first control valve (16).

5. The method of claim 4,
The piston 58 has a bottom 60 and a skirt 62 and the bottom 60 faces the needle control volume 34 and the skirt 62 moves away from the needle control volume 34 (60) in a direction away from the bottom (60).

6. The method of claim 5,
The cylindrical cavity 52 includes a bottom surface 56 and a bottom surface 56 of the cylindrical cavity 52 and a bottom portion 60 of the piston 58, , And a spring (64) which is provided on the outer circumferential surface of the fuel tank.

The method according to claim 6,
The opening 48 'for the flow passage 48 in the bottom surface 56 of the cylindrical cavity 52 is such that the skirt 62 of the piston 58 is pressed against the bottom surface 56 Is positioned and dimensioned to surround the opening (48 ') to block flow connection from the piston (58) to the flow passage (48).

The method according to claim 1,
Characterized in that at least one first restricted flow passage (38) has a first flow resistance between the common needle cavity (30) and the needle control volume (34).

6. The method of claim 5,
Characterized in that at least one second restricted flow passage (66) has a second flow resistance between the side wall (54) of the cylindrical cavity (52) and the piston (58).

6. The method of claim 5,
At least one first restricted flow passage (38) has a first flow resistance between the common needle cavity (30) and the needle control volume (34)
At least one second restricted flow passage (66) has a second flow resistance between the side wall (54) of the cylindrical cavity (52) and the piston (58)
Wherein the first flow resistance is greater than the second flow resistance.

10. The method of claim 9,
Characterized in that the control valve (16) has a flow resistance and the flow resistance of the control valve (16) is less than the second flow resistance.

An internal combustion engine having a plurality of cylinders having cylinder heads and utilizing a common rail fuel system,
Each cylinder head including the fuel injection unit (10) according to any one of claims 1 to 11.