JP3301450B2 - Fuel injection device for internal combustion engine - Google Patents

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 internal combustion engine in which high-pressure fuel stored in a pressure storage chamber is injected from a plurality of fuel injection valves.

[0002]

2. Description of the Related Art As means for supplying high-pressure fuel to a plurality of fuel injection valves provided corresponding to a plurality of cylinders of a multi-cylinder internal combustion engine, a so-called high-pressure fuel stored in an accumulator is supplied to each fuel injection valve. A common rail type fuel injection device is known (Japanese Patent Application Laid-Open No. 3-185261).

[0003]

In this conventional common rail type fuel injection system, a single common rail is shared by a plurality of fuel injection valves. For example, in the case of a six-cylinder internal combustion engine, the fuel injection sequence is cylinder-based. # 1, # 5, # 3, #
6, # 2 and # 4 in the first cylinder # 1
The pressure pulsation due to the injection of the fuel injection valve in the above propagates in the fuel passage as a wave, and the pressure pulsation affects the injection amount of the fuel injection valve in the fifth cylinder # 5 which is the next injection cylinder. This pressure pulsation is caused by a water hammer after the end of injection serving as an excitation source, causing pressure oscillation based on a resonance frequency in a path including the fuel injection valve, the common rail, and the fuel pump. The pressure pulsation also has a large effect on a detection signal of a pressure sensor that detects high-pressure fuel in the common rail, and a control unit (ECU) that operates a fuel pump based on the pressure detection signal.

[0004] Such pressure pulsations differ in the manner in which the pressure pulsations propagate to the respective injection valves when the distance between the cylinders of the fuel passage in the common rail is different. There is a problem that the injection amount varies. The present invention has been made to solve such a problem, and even if there is a pressure pulsation in the fuel passage, by making the fuel injection amount between the cylinders uniform,
Stable and smooth operation of the internal combustion engine, reduced vibration,
It is an object of the present invention to provide a fuel injection device for an internal combustion engine that improves fuel efficiency.

[0005]

According to the present invention, there is provided a fuel injection system for an internal combustion engine, comprising:
A plurality of fuel injection valves provided in each cylinder, a common rail for accumulating the pressure of fuel supplied to the plurality of fuel injection valves, and a plurality of fuel passages for independently communicating the common rail and the plurality of fuel injection valves And the plurality of fuels
Each fuel passage between any two fuel injectors of the injector and
The distance through the common rail is constant so that the interference phase of the pressure pulsation generated in the common rail is the same for all cylinders.

[0006]

According to the configuration of the present invention, the effective fuel passage distances from the common point in the common rail to the plurality of fuel injection valves are set to be equal to each other. Since the manner of propagation of the pulsation is uniform, the pulsation has an inherent pressure pulsation and the interference phase of the pressure pulsation becomes equal for all cylinders. In other words, in the present invention, since the pressure pulsation in the common rail is evenly transmitted to each fuel injection valve, the fuel injection amount between each cylinder becomes uniform.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment in which the present invention is applied to a fuel injection device for a six-cylinder diesel engine. FIG.
In the diesel engine (hereinafter, referred to as “engine”) 1, fuel injection valves (hereinafter, referred to as “injectors”) 2 are individually arranged corresponding to a plurality of cylinders, and fuel from the injector 2 to each cylinder is provided. The injection is controlled by turning on / off the injection control solenoid valve 3. The injector 2 is connected to a common high-pressure accumulator pipe, a so-called common rail 4, common to each cylinder. During the period in which the injection control solenoid valve 3 is open, fuel in the common rail 4 is supplied from the injector 2 to the engine 1
Is injected into each cylinder. Since a high predetermined pressure corresponding to the fuel injection pressure needs to be continuously accumulated in the common rail 4, the high pressure supply pump 7 is supplied through the supply pipe 5 and the discharge valve 16.
Is connected. The high-pressure supply pump 7 includes a fuel tank 8
The fuel sucked through a known low-pressure supply pump 9 is pressurized to a high pressure, and the fuel in the common rail 4 is controlled and maintained at a high pressure.

The electronic control unit ECU 40 for controlling this system receives information on the number of revolutions and the load from, for example, the engine revolution number sensor 12 and the load sensor 13, and responds to the engine operating state determined from these signals. The ECU 40 outputs a control signal to each of the injection control solenoid valves 3 so that the determined optimum injection timing and injection amount (injection period) are obtained. At the same time, the ECU 40 outputs a control signal to the high-pressure supply pump 7 so that the injection pressure becomes an optimum value according to the rotation speed, the load, and the like. The common rail 4 is provided with a pressure sensor 14 for detecting the common rail pressure, and controls the discharge amount of the high-pressure supply pump 7 so that the signal of the pressure sensor 14 becomes an optimum value set in advance according to the rotation speed and the load. I do.

As shown in FIGS. 1 and 3, a common rail housing 20 forming the common rail 4 is provided.
Is a common rail 4 having a regular hexagonal cross-sectional shape and having a relatively large diameter in the longitudinal direction.
Are formed. One end 4a of the common rail 4 is closed, and the other end 4b is open to the outside. The above-described pressure sensor 14 is screwed and fixed to this opening. The reason why the common rail 4 is formed to have a large diameter is that each of the injectors 2 (2a, 2b, 2c, 2d,
e, 2f) to supply sufficient fuel. In the vicinity of one end 4 a of the common rail 4, fuel passages 21 and 22 connected from a fuel supply pipe 5 connected to the high-pressure supply pump 7 are connected. In addition, common rail 4
Each injector 2a, 2b, 2 shown in FIG.
Fuel passages 24a, 24b, 24c, 24d, 24e, 24f for supplying fuel to c, 2d, 2e, 2f are formed.

Here, the six fuel passages 24a, 24b,
24c, 24d, 24e and 24f are common rails 4 extending in the longitudinal direction at the center of the common rail housing 20.
Extend radially from a common point X in a direction perpendicular to the common rail axis. These fuel passages 24a, 24b, 24c,
The angle formed by the adjacent passages of 24d, 24e, and 24f is 60 degrees, and the effective distance of the fuel passage is a common point in the common rail 4 so that the phase of the pressure pulsation is the same for all cylinders. X to a plurality of injectors 2a, 2
The values of b, 2c, 2d, 2e, and 2f are set equally for the respective cylinders.

The fuel passages 24a, 24b, 24c, 24 formed on the outer wall of the common rail housing 20
Open ends of d, 24e, and 24f are fuel pipes 26a, 26b, 26c, 26d, 26e,
26f, the injectors 2a, 2b, 2c,
2d, 2e, and 2f. These fuel pipes 26a, 26b, 26c, 26d, 26e, 26f
It is made of flexible piping that is easy to handle.

According to the present embodiment, the fuel passages 24a, 24b, 24 formed in the common rail housing 20 are provided.
Since c, 24d, 24e, and 24f are formed in a radially uniform length, the pressure pulsation in the common rail 4 is equally transmitted to the six injectors 2a, 2b, 2c, 2d, 2e, and 2f. That is, there is no variation in the injection amount among the cylinders due to the pressure fluctuation in the common rail 4, and the fuel injection amount is uniform.

For example, as in this embodiment, in the case of a six-cylinder diesel engine, the compression ignition order of each cylinder, that is, the fuel injection order is, for example, cylinder # 1, # 5, # 3, # 6, #
In the case of 2, # 4, the fuel passage distance in the common rail 4 between the previous injection cylinder and the current injection cylinder becomes equal. On the other hand, a conventional comparative example of a six-cylinder diesel engine will be described with reference to FIG.
Fuel passages 31 and 32 for supplying high-pressure fuel to a common rail 4 formed in the longitudinal direction of the fuel cell 1 are formed,
Fuel passages 41a, 41b, 41c, 41d, 4d for supplying fuel from predetermined positions in the longitudinal direction of the common rail 4 to the injectors 2a, 2b, 2c, 2d, 2e, 2f.
1e and 41f extend. The distance in the common rail between cylinders according to the fuel injection order between these cylinders is shown in Table 1 below.
As shown in FIG.

[0014]

[Table 1] In Table 1, "d" indicates the effective fuel passage distance in the common rail between adjacent cylinders. For example, as shown in Table 1, between injection cylinders # 1 and # 5, between injection cylinders # 5 and # 3, # 6 and # 2
, Between # 2 and # 4, and between # 4 and # 1, the distances in the common rail between the previous injection cylinder and the current injection cylinder are 2 respectively.
d, 3d, 4d (d: constant value). For this reason, since the common rail distance differs for each injection, the manner in which pressure pulsation is transmitted varies between cylinders.

The relationship between the injection waveform after such fuel injection and the associated reflection waveform will be described in detail with reference to FIGS. 4 (A) and 4 (B). In the conventional comparative example, as shown in FIGS. 4A and 9, immediately after the injection control solenoid valve is closed in the injector 2 (for example, 2 a), the wave after the fuel injection is applied to the fuel passage 41 (for example, 41 a). Through the fuel passage 4
The light propagates from 1a into the common rail 4. At this time, the reflected waveform propagating in the common rail 4 from the injector 2a via the internal fuel passage 41a is different from the distance from the injector 2a after injection as, for example, an x point, a y point, and a z point having different distances from the injector 2a. As the distance increases, the amplitude of the reflected waveform decreases and the propagation time of the waveform also delays.
As a result, variations in the fuel injection amount due to pressure fluctuations in the common rail 4 between the previous injection cylinder and the current injection cylinder occur between the cylinders.

On the other hand, in this embodiment of the present invention, the variation in the injection amount between the injection cylinders is eliminated, and the fuel injection amount becomes uniform. That is, in the present embodiment, the fuel injection valves of all the cylinders are arranged at equal positions from the common point X in the common rail so that the interference phases of the pressure pulsations generated in the common rail become equal among the cylinders. Therefore, since the interference of the pressure pulsation becomes the same phase for all cylinders, the fuel injection amount between the cylinders becomes uniform.

Next, a fuel passage in a common rail according to a second embodiment of the present invention is shown in FIGS. The second embodiment shown in FIGS. 5 and 6 is an example in which the common rail housing 50 is formed in a semicircular cross section. The common rail 4 extends linearly in the longitudinal direction of the common rail housing 50, and the fuel passages 24 a, 24 b, 24 c, 24 d, 24 e, 24 are provided at a common point X on the central axis of the common rail 4.
f is connected to one end of the fuel passages 24a, 24b,
The ends of 24c, 24d, 24e and 24f are connected to the injectors of the respective cylinders via flexible piping (not shown) so that they have the same length. Fuel passage 2
4a, 24b, 24c, 24d, 24e, 24f extend radially in the radial direction on the cross section. These fuel passages 24a, 24b, 24c, 24d, 24e,
The effective distance in the common rail housing 50 of 24f is set to be equal because the cross section is circular.

According to the second embodiment, the pressure pulsation in the common rail 4 is transmitted evenly to the injection valves between the cylinders, so that the injection amount between the cylinders is uneven due to the pressure pulsation in the common rail 4. Never be. Next, the third aspect of the present invention
FIG. 7 shows the fuel passage in the housing in the common rail according to the embodiment.
And FIG.

The third embodiment shown in FIGS. 7 and 8 is an example in which the common rail housing 60 is formed in a spherical shape. The center point of the common rail housing 60 is a common point X, and the common rail 4 is formed at the common point X in the radial direction. A fuel passage 24 communicating radially with the injector of each cylinder from a common point X at the center of the common rail 4.
a, 24b, 24c, 24d, 24e, 24f extend in the radial direction. The direction in which these fuel passages 24 extend is arbitrary. This is because the effective distance is uniform in the common rail housing 60 regardless of the extension in any direction.

Also in the third embodiment, since the pressure pulsation in the common rail 4 is evenly transmitted to each injector, the variation in the fuel injection amount between the cylinders is eliminated, and the fuel injection amount between the cylinders is uniform. It becomes something. In the above embodiments, the present invention is applied to a six-cylinder diesel engine, but the number of cylinders of an internal combustion engine to which the present invention can be applied is not limited to six cylinders.

[0021]

As described above, according to the fuel injection system for an internal combustion engine of the present invention, a plurality of fuel injection valves are disposed equidistant from a common point in a common rail for accumulating high-pressure fuel. Even if pressure pulsation occurs in the common rail, the pressure pulsation in the same phase in all cylinders is transmitted to the fuel injection valves, so that the fuel injection amount of the fuel injection valves becomes uniform among the cylinders, so that the internal combustion engine operates. The state becomes smooth, and there is an effect that vibration is reduced and drivability is improved.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of the present invention, and FIG.
It is an I line sectional view.

FIG. 2 is a schematic configuration diagram showing a fuel injection system to which the common rail housing according to the first embodiment of the present invention is applied.

FIG. 3 is a longitudinal sectional view showing a common rail housing according to the first embodiment of the present invention.

FIG. 4A is an explanatory diagram for explaining a wave propagation state after injection of an injector. (B) is a characteristic diagram showing a reflected waveform after injection of the injector.

FIG. 5 is a cross-sectional view of a common rail housing showing a second embodiment of the present invention.

FIG. 6 is a schematic perspective view showing a common rail housing according to a second embodiment of the present invention.

FIG. 7 is a perspective view illustrating a common rail housing according to a third embodiment of the present invention.

FIG. 8 is a sectional view showing a common rail housing according to a third embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing a conventional common rail housing.

[Explanation of symbols]

Reference Signs List 1 engine (internal combustion engine) 2 (2a, 2b, 2c, 2d, 2e, 2f) injector (fuel injection valve) 4 common rail 20 common rail housing 24 (24a, 24b, 24c, 24d, 24e, 24)
f) Fuel passage (fuel branch passage) 26 (26a, 26b, 26c, 26d, 26e, 26)
f) Fuel passage 50 common rail housing 60 common rail housing X common point

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 55/02 310 F02M 55/02 350 F02M 59/44 F02M 47/00 F02M 47/02

Claims (6)

(57) [Claims] 1. A plurality of fuel injection valves provided in each cylinder of an internal combustion engine, a common rail for accumulating pressure of fuel supplied to the plurality of fuel injection valves, and an independent common rail and the plurality of fuel injection valves. And a plurality of fuel passages that communicate with each other.
A fuel injection device for an internal combustion engine, wherein a distance passing through a fuel passage and a common rail is constant so that interference phases of pressure pulsations generated in the common rail are equal in all cylinders. 2. The fuel injection device for an internal combustion engine according to claim 1, further comprising a common rail housing having a plurality of fuel branch passages radially arranged around the common rail and the common rail. 3. The fuel supply system according to claim 2, further comprising a plurality of fuel pipes connecting the fuel branch passage and the fuel injection valve, the fuel pipes having the same passage length, and the plurality of fuel branch passages having the same passage length. The fuel injection device for an internal combustion engine according to claim 2. 4. The fuel injection device for an internal combustion engine according to claim 2, wherein the plurality of fuel branch passages are arranged in a plane radial shape. 5. The fuel injection device for an internal combustion engine according to claim 2, wherein the plurality of fuel branch passages are arranged in a fan radial shape. 6. The fuel injection device for an internal combustion engine according to claim 2, wherein the plurality of fuel branch passages are arranged in a three-dimensional radial manner.