JP2001221127A - Fuel injection system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a structure, especially around a cylinder head, without requiring positioning by a fork and the like when an injector 2 is secured to the cylinder head. SOLUTION: Multiple injectors 2 forming a cylinder bank are substantially directly connected through adopters 2 to a common rail (fuel rail) 6 where high pressure fuel is supplied. Each injector 2 is connected to the common rail 6 by a knock pin (positioning pin) 7 at a position off an axis X to position both parts 6, 2 about the axis X. Each injector 2 is thereby positioned in a circumferential direction of the axis X relative to the cylinder head with each injector 2 fitted into a mounting hole of the cylinder head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection device for an internal combustion engine having a structure in which a plurality of injectors are substantially directly connected to a fuel rail (common rail) to which high-pressure fuel is supplied from a fuel pump.

[0002]

2. Description of the Related Art A direct-injection internal combustion engine, which is a fuel-efficient internal combustion engine, has been in the spotlight due to the recent increase in environmental awareness. Above all, a direct injection diesel engine equipped with a common rail type fuel injection device can achieve both low fuel consumption and low noise / low exhaust due to the low driving torque of the fuel pump and the high degree of freedom of the fuel injection control. It is regarded as a next-generation engine.

[0003] As a conventional common rail type fuel injection device, for example, a fuel injection device described in Japanese Patent Application Laid-Open No. H11-229991 stores a fuel pump driven from the engine side and a high pressure fuel pumped from the fuel pump. And a injector for injecting high-pressure fuel supplied from the common rail into the combustion chamber. The fuel pump and the common rail are connected by a high-pressure pipe, and the common rail and each injector are connected by a high-pressure pipe. In such a fuel injection device, problems related to the high-pressure pipe are often pointed out, such as durability of the high-pressure pipe, reliability at a connection portion, and noise due to resonance of the high-pressure pipe itself.

As one means for solving such a problem, as disclosed in Japanese Patent Application Laid-Open No. 9-88861, a common rail and an injector, and a common rail and a fuel pump are substantially directly connected by a joint, and a high-pressure pipe is provided. Has been proposed.

[0005]

Incidentally, in a direct injection diesel engine or the like, for example, depending on the layout, the shape of the combustion chamber in the piston is offset from the center of the piston, or the injector is inserted obliquely into the combustion chamber. In some cases, particularly for these reasons, in order to achieve good combustion, it is necessary to fix the injector injection hole direction to the combustion chamber in a predetermined direction. That is, it is necessary to position the injector relative to the cylinder head in the direction around the axis. Therefore, when fixing the injector to the cylinder head, it is necessary to attach the injector using a fork or the like so that the injector does not rotate around the axis. As a result, the bolt fixing point,
A lot of space is required on the cylinder head side such as securing a pivot point, so that the layout of the cylinder head becomes difficult, and the fuel injection noise may be deteriorated due to fork resonance.

The present invention has been made in view of such unresolved problems of the prior art, and a plurality of injectors are substantially directly connected to a fuel rail such as a common rail without using a high-pressure pipe or the like. In the fuel injection device,
With a simple structure that does not use parts such as forks,
An object of the present invention is to provide a fuel injection device capable of favorably positioning each injector in a direction around an axis with respect to a cylinder head.

Another object of the present invention is to simplify the structure for positioning and fixing the fuel rail and the injector to the cylinder head, thereby improving the layout of the cylinder head, reducing the number of parts, and the like. And cost reduction.

[0008]

A fuel injection device for an internal combustion engine according to the present invention is fitted in a fuel rail for storing high-pressure fuel and a mounting hole of a cylinder head, and is substantially directly connected to the fuel rail. And a plurality of injectors for injecting high-pressure fuel supplied from the fuel rail into the combustion chamber.

The invention according to claim 1 is characterized in that a positioning mechanism is provided between the fuel rail and each of the injectors for positioning the two in the direction around the axis of the injector.

As described above, since each injector and the fuel rail are directly connected to each other and are positioned in the direction around the axis of the injector, each injector inserted and fitted into the mounting hole of the cylinder head is attached to the cylinder head. It is in a state of being positioned around the axis. Therefore, when fixing the injector (and the common rail) to the cylinder head, it is not necessary to position each injector using a fork or the like as in the conventional example.

The above-mentioned positioning mechanism is provided at a position deviated from the axis of each injector, for example, as in the second aspect of the present invention.
It has a positioning pin fitted or fixed to both each injector and the fuel rail.

The fuel rail and the injector are substantially directly connected via, for example, an adapter.
In other words, they are directly connected by a simple structure without using a high-pressure pipe or the like.

In the case of such a configuration using an adapter,
Preferably, the positioning mechanism is a first auxiliary positioning mechanism for positioning the adapter and the injector in the direction around the axis, and a second auxiliary positioning mechanism for positioning the adapter and the fuel rail in the direction around the axis. And two auxiliary positioning mechanisms. These auxiliary positioning mechanisms are constituted by, for example, a recess provided on one of the injector or the fuel rail and the adapter, and a projection provided on the other and fitted in the recess.

[0014] More preferably, as in the invention of claim 4,
By fixing at least one of the injector and the fuel rail to the cylinder head, both the fuel rail and the injector are fixed to the cylinder head side. In this case, the configuration is further simplified as compared with a case where the injector and the fuel rail are individually fixed to the cylinder head.

More specifically, the fuel injector and the injector are fixed to the cylinder head by fixing each injector to the cylinder head using a screw.

[0016] Alternatively, by fixing the fuel rail to the cylinder head via the bracket in a pressed state as in the invention of claim 6, both the fuel rail and the injector are fixed to the cylinder head side in a pressed state. To be configured.

In the case where the fuel rail and each injector are directly connected via an adapter, the adapter is preferably used selectively from a plurality of adapters having different dimensions. Is done.

[0018]

According to the first aspect of the present invention, the positioning mechanism for positioning the fuel rail and the injector in the direction around the axis of the injector is provided between the fuel rail and the injector. Each injector is forcibly positioned in a direction around a predetermined axis with respect to the cylinder head. Therefore, when fixing the injector and the fuel rail to the cylinder head side, it is not necessary to position each injector using a fork or the like as in the related art, and the mounting work is easy,
The number of parts and the manufacturing cost are sufficiently reduced. In addition, since the configuration around the cylinder head is particularly simplified, the layout is improved. In addition, the generation of noise caused by the conventional fork and the like is eliminated.

In particular, according to the invention of claim 2, the fuel rail and each injector can be positioned in the direction around the axis of the injector with a relatively simple structure using the positioning pin.

According to the third aspect of the present invention, the positioning mechanism is provided at a portion directly connected to the fuel rail and each injector via an adapter, which is more advantageous in terms of layout and uses an adapter or the like. With this structure, the number of parts can be further reduced and the cost can be reduced.

According to the present invention, the structure is further simplified as compared with the case where the fuel rail and the injector are individually fixed to the cylinder head. The number of points can be reduced, the cost can be reduced, and the like.

For example, according to the fifth aspect of the present invention, it is not necessary to fix only the fuel rail to the cylinder head, and the structure corresponding to this can be omitted.

According to the sixth aspect of the present invention, it is not necessary to fix only the injector to the cylinder head, and the structure corresponding thereto can be omitted. Further, since a pressing force to the cylinder head side is also applied to each injector via the fuel rail, sufficient mounting rigidity can be secured.

Further, according to the invention of claim 7, the adapter arranged between each injector and the fuel rail is configured to be used by selecting from a plurality of adapters having different dimensions. This makes it possible to absorb variations in each cylinder due to dimensional errors of the injector and the cylinder head mounting hole, and more specifically, the injector contact surface of the cylinder head mounting hole from the axis of the fuel rail. And the dimension from the axis of the fuel rail to the cylinder head contact surface of the injector can be accurately matched. As a result, in the case where the injector is fixed to the cylinder head as in the invention of claim 5, no extra stress is applied to the fuel rail, and the fuel rail is connected to the cylinder head as in the invention of claim 6. In this case, the pressing force acting on each injector from the fuel rail can be made uniform. Therefore, the fuel injection noise caused by the rattling of the injector can be more reliably suppressed, and the reliability of the fuel injection device can be further improved.

[0025]

Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 3 show a first embodiment in which the fuel injection device according to the present invention is applied to a direct injection diesel engine. Here, components such as a glow plug, a cam shaft, a cam cap, and a head cover are not shown. Although FIG. 2 is a schematic diagram of an in-line four-cylinder or V-type eight-cylinder, an engine having another number of cylinders may be used.

FIG. 1 is a cross-sectional view of a cylinder head, and FIG. 2 is a vertical cross-sectional view of a cylinder head. As shown in FIGS. 1 and 2, an injector mounting hole 4 is formed in the cylinder head 1 for each cylinder.
, The injector 2 is inserted and fitted respectively. The mounting holes 4 and the injectors 2 are arranged in parallel along the cylinder row direction (for each bank in the case of a V-type engine).

Each injector 2 is attached to the cylinder head 1 by screwing a substantially cylindrical screw 3 which is fitted to the outer peripheral portion thereof into a screw hole 4 a having a large diameter in the mounting hole 4. It is fixed in a pressed state. That is, the inner peripheral portion of the screw 3 is in axial contact with the snap ring 5 provided on the outer periphery of the injector body, and a pressing force to the cylinder head 1 is applied to the injector 2 via the snap ring 5. You. Each injector 2 has a tip end facing a combustion chamber (not shown) of each cylinder. In response to a signal from a well-known engine control unit (not shown), a high pressure supplied from a common rail (fuel rail) 6 is provided. It is configured to inject and supply fuel into the combustion chamber.

The common rail 6 has a long and substantially cylindrical shape extending along the cylinder row direction, and is connected via a high-pressure pipe 8 from a fuel pump (not shown) driven by a camshaft or the like of the internal combustion engine. The high-pressure fuel is supplied, and the high-pressure fuel is temporarily stored. In addition,
The fuel pump and the common rail 6 may be substantially directly connected via a joint or the like, and the high-pressure pipe 8 may be omitted.

A plurality of (four in this embodiment) injectors 2 constituting a cylinder row are substantially directly connected to the common rail 6. That is, each injector 2 and the common rail 6 are semi-directly connected via an adapter 12 described later without using a high-pressure pipe or the like.

FIG. 3 is a sectional view showing in detail the structure of a portion directly connected to each injector 2 and the common rail 6 (portion A in FIG. 2). Each injector 2 has a common rail 6.
The substantially cylindrical boss portions 13 are formed at positions where the bosses are joined. Each boss 13 is formed with a screw hole 13 a into which the adapter 12 is screwed, and a communication passage 13 b communicating the screw hole 13 a with the inside of the common rail 6. The communication passage 13 b is connected to the injector 2. It functions as a combustion outlet for sending fuel to

The adapter 12 is in the form of a hollow bolt having a fuel passage 12a formed therein.
Is externally fitted to the screw hole 13a. The nut 14 has an annular engaging portion 14b integrally fitted on the adapter 12 and engaging with the head 12b of the adapter 12 on one axial side of a nut body having a threaded portion 14a formed on the inner periphery. It is a structure formed in.

On the other hand, a joint 15 for fixing the adapter is fixedly provided on the head of each injector 2. The joining portion 15 has a fuel passage 15a formed therein, an engaging portion 15b provided on the top surface thereof for appropriately abutting and engaging with the head portion 12b of the adapter 12, and an outer peripheral surface thereof. Screw part 15 screwed with screw part 14a of nut 14
c is formed.

Therefore, by tightening the nut 14 to the joint 15 of the injector 2, the head 12 b of the adapter 12 is jointly fastened between the engaging part 14 b of the nut 14 and the engaging part 15 b of the joint 15. The adapter 12 is firmly fixed to the injector 2 in a predetermined posture.

Here, when the rigidity of the injector 2 itself and the coupling portion (adapter 12, nut 14, etc.) between the common rail 6 and the injector 2 is sufficiently high, the common rail 6 is sufficiently moved to the cylinder head 1 side via the injector 2. Since the common rail 6 is fixedly supported at a high strength, it is not necessary to separately fix only the common rail 6 to the cylinder head 1 via a bracket or the like.

As described above, since the common rail 6 and each injector 2 are firmly directly connected to each other, a high-pressure pipe for connecting each injector 2 and the common rail 6 is unnecessary, and only the common rail 6 is connected to the cylinder head side. Parts to be fixed to the head can also be omitted. Therefore, the number of parts can be reduced and the cost can be reduced, and the structure around the cylinder head is particularly simplified, and the layout is improved.

In this embodiment, a knock pin 7 is provided between each injector 2 and the common rail 6 as a positioning pin for positioning the common rail 6 and the injector 2 in a direction around the axis X of the injector 2. . More specifically, a recess 11 for driving is formed in the common rail 6 near the boss 13. on the other hand,
A recess 16 for fixing the knock pin 7 is provided on the outer periphery of the head of the injector 2. When fixing each injector 2 to the common rail 6,
1 and the dowel pin 7 fixed to the
, Each injector 2 and the common rail 6 are connected via the knock pin 7 at a position deviated from the axis X of the injector 2.
Are positioned around the axis of the injector 2.

As described above, in this embodiment, since each injector 2 and the common rail 6 are directly connected to each other and are positioned around the axis X, each injector 2 fitted into the mounting hole 4 of the cylinder head 1 is provided. 2 is positioned in the direction around the axis X with respect to the cylinder head 1. Therefore, when the injector 2 is fastened and fixed to the cylinder head 1, there is no need to use a positioning component such as a fork as in the conventional case, and the mounting operation is easy, and the number of components is reduced and the cost is reduced. The layout can be improved because the structure around the cylinder head can be simplified and the structure around the cylinder head is particularly simplified. in addition,
The deterioration of fuel injection noise caused by the conventional fork resonance is also eliminated.

FIGS. 4 to 7 show a second embodiment in which the fuel injection device according to the present invention is applied to a direct injection diesel engine. Components common to the first embodiment are denoted by the same reference numerals, and redundant description is omitted as appropriate. Parts such as a glow plug, a camshaft, and a head cover are not shown.

FIG. 4 is a cross-sectional view of the cylinder head of the engine, and FIG. 5 is a vertical view of the cylinder head. Similarly to the first embodiment, the four injectors 2 constituting the cylinder row are inserted and fitted into the mounting holes 4 of the cylinder head 1 while being substantially directly connected to one common rail 6.

In this embodiment, a plurality of brackets 21 integrally formed on the outer periphery of the common rail 6 are fastened and fixed to the cylinder head 1 together with the cam cap 22 by bolts 23 to directly connect the common rail 6 and the common rail 6. The two injectors 2 are strongly pressed against the cylinder head 1 and are fixedly supported on the cylinder head 1. In other words, the common rail 6 and the bracket 21 for fixing the injector 2 are attached to the cylinder head 1 by using the bolt 23 for fixing the cam cap 22 to the cylinder head 1.
It is fixed to the side to further simplify the configuration.

The brackets 21 extend obliquely downward from both sides of the common rail 6 as viewed in the axial direction shown in FIG. 4, and extend along the axial direction as shown in FIG. It is provided at a total of five places between the section and the cylinder. The cam cap 22 basically rotatably supports a cam shaft (not shown) in cooperation with the cylinder head 1, and a pair of support portions 9a through which the cam shaft is inserted are recessed on the lower surface side. And is arranged at the same axial position as the bracket 21 described above.

FIG. 6 shows the injector 2 and the common rail 6.
FIG. 6 is a cross-sectional view corresponding to FIG. The common rail 6 is integrally provided with a boss 13 for fastening the adapter 12 at a position where the injector 2 of each cylinder is connected. The boss 13 is
A screw hole 13a into which the adapter 12 is screwed, and a communication passage 13 communicating the screw hole 13a with the inside of the common rail 6.
b, and the communication passage 13b is connected to the injector 2
It functions as a fuel outlet to the Adapter 1 above
2 is fastened to the screw hole 13a with the nut 14 inserted in the outer periphery in advance.

An adapter 12 is mounted on the head of the injector 2.
The joint 15 for positioning and fixing is integrally provided. This joint 15 is connected to the fuel passage 1 of the adapter 12.
A fuel passage 15a communicating with 2a is formed inside, and an engaging portion 15b having a shape corresponding to the top surface of the head 12b of the bolt 23 is formed on the upper surface thereof. Then, the screw portion 14a of the nut 14 is screwed into the screw portion 15c formed on the outer peripheral surface of the joint portion 15, and the nut 14 is tightened, so that the bolt 23 is fixedly fixed to the injector 2 side in a predetermined posture. Is done.

In this embodiment, a positioning mechanism for positioning the common rail 6 and the injector 2 in a direction around the axis X of the injector 2 is provided at a portion where the common rail 6 and the injector 2 are directly connected via the adapter 12. Is provided.

More specifically, as shown in FIGS. 6 and 7, a protrusion (piece) 24 is formed on the top surface of the head 12b of the adapter 12 at a predetermined position on the outer peripheral portion deviating from the axis X. I have. On the other hand, a concave portion 25 is formed on the upper surface of the joint portion 15 of the injector 2 at a predetermined position on the outer peripheral portion deviated from the axis X thereof. Then, the adapter 12 and the injector 2
At the time of fastening, the nut 12 is tightened in a state where the projection 24 is fitted in the recess 25 in advance, so that the adapter 12 and the injector 2 are positioned around the axis X (first auxiliary positioning). mechanism).

Further, a projection 26 is formed on the distal end surface of the adapter 12 at a predetermined position on the outer peripheral portion deviating from the axis X thereof. On the other hand, the bottom of the screw hole 13a of the boss 13 is provided with a recess 2 at a predetermined position of the outer peripheral portion deviated from the axis X thereof.
7 are formed. When the adapter 12 is fastened to the common rail 6, the adapter 12 is tightened to a position where the above-mentioned protrusion 24 is appropriately fitted into the concave portion 25, so that the adapter 12 and the common rail 6 can move in the direction around the axis X. They are positioned with respect to each other (second auxiliary positioning mechanism).

As described above, the adapter 12 and the injector 2 are positioned in the direction around the axis X, and
By positioning the adapter 12 and the common rail 6, the injector 2 and the common rail 6 are positioned with respect to each other via the adapter 12.

When the adapters 12 are fastened to the common rail 6, it is necessary to accurately manage the thread positions of the adapters 12 in advance so that the projections of the adapters 12 are aligned in a fixed direction. is there. In addition, it is necessary to take measures such as fitting the projection 26 at the tip of the adapter and the concave portion 27 of the boss portion 13 when the fastening is completed.

In the present embodiment, the common rail 6 is fixed to the cylinder head 1 so that the injector 2 directly connected to the common rail 6 is
Although a certain pressing force is applied to the injector 2 of each cylinder, as shown in FIG. 5, the head contact surface 2a of the injector 2 is moved from the axis X2 of the common rail 6 as shown in FIG. It is necessary to exactly match the dimension h1 of the common rail 6 with the dimension h2 from the axis X2 of the common rail 6 to the injector contact surface 4b of the mounting hole 4 of the cylinder head 1. However, in practice, the values of h1 and h2 often do not match in each cylinder due to the processing tolerance of the mounting hole 4 and the variation in the manufacturing tolerance of the injector. For this reason, several types of adapters having different axial dimensions are prepared in advance, and the adapters are selected and used so that the dimensions h1 and h2 exactly match in each cylinder. Can exert an even pressing force on the injectors,
The reliability of the fuel injection device can be further improved.

According to the fuel injection device of the second embodiment, components such as high-pressure pipes and injector fastening members are not required, so that the layout can be improved and the cost can be reduced by reducing the number of components. Further, in addition to eliminating the deterioration of the fuel injection noise caused by the conventional high-pressure pipe resonance and fork resonance, an equal pressing force acts on each injector 2, so that the cantilever of the injector head is 8 is sufficiently suppressed, resulting in a very high rigidity structure as a whole.
As shown in the graph, the effect of significantly reducing the fuel injection noise can be obtained.

In the case where each injector 2 is directly fixed to the cylinder head 1 as in the first embodiment, preferably, each adapter is selected from a plurality of adapters having different dimensions. I do. In this case, no extra stress is applied to the common rail 6 directly connected to each injector, and the reliability of the fuel injection device can be further improved.

Although the specific embodiments of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments. For example, the present invention can be applied to a direct injection gasoline engine. It is.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a cylinder head of an internal combustion engine to which a fuel injection device according to a first embodiment of the present invention is applied.

FIG. 2 is a longitudinal sectional view of the cylinder head of FIG.

FIG. 3 is a sectional view corresponding to a portion A in FIG. 2;

FIG. 4 is a cross-sectional view corresponding to a cylinder head of an internal combustion engine to which a fuel device according to a second embodiment of the present invention is applied.

FIG. 5 is a cross-sectional view of the cylinder head of FIG. 4;

FIG. 6 is a sectional view corresponding to a portion B in FIG. 5;

FIG. 7 is a perspective view showing an adapter and an injector according to a second embodiment.

FIG. 8 is a graph showing a noise reduction effect according to the present invention (second embodiment).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylinder head 2 ... Injector 4 ... Mounting hole 6 ... Common rail (fuel rail) 7 ... Dowel pin (Positioning mechanism) 12 ... Adapter 14 ... Nut 21 ... Bracket 24 ... Projection (1st auxiliary positioning mechanism) 25 ... Recess (1st) Auxiliary positioning mechanism) 26 ... Projection (second auxiliary positioning mechanism) 27 ... Recess (second auxiliary positioning mechanism)

Claims (7)

[Claims] 1. A fuel rail for storing high-pressure fuel, which is fitted into a mounting hole of a cylinder head, is substantially directly connected to the fuel rail, and injects high-pressure fuel supplied from the fuel rail into a combustion chamber. Multiple injectors,
A fuel injection device for an internal combustion engine, comprising: a positioning mechanism for positioning the fuel rail and each injector in a direction around the axis of the injector. 2. The positioning mechanism according to claim 1, wherein the positioning mechanism has a positioning pin fitted or fixed to both the injector and the fuel rail at a position off the axis of each injector. A fuel injection device for an internal combustion engine. 3. The fuel rail and the injector are substantially directly connected via an adapter, the positioning mechanism comprising: a first auxiliary positioning mechanism for positioning the adapter and the injector in a direction around an axis;
2. The fuel injection device for an internal combustion engine according to claim 1, further comprising a second auxiliary positioning mechanism that positions the adapter and the fuel rail in a direction around an axis. 4. The fuel injection system according to claim 1, wherein at least one of said injector and said fuel rail is fixed to a cylinder head, so that both said fuel rail and said injector are fixed to said cylinder head side. The fuel injection device for an internal combustion engine according to any one of the above. 5. The internal combustion engine according to claim 4, wherein each injector is fixed to the cylinder head by using a screw, so that both the fuel rail and the injector are fixed to the cylinder head side. Engine fuel injector. 6. The fuel rail is fixed to the cylinder head in a pressed state via a bracket, so that both the fuel rail and the injector are fixed to the cylinder head side in a pressed state. The fuel injection device for an internal combustion engine according to claim 4. 7. The fuel rail and each injector,
The fuel injection of an internal combustion engine according to any one of claims 1 to 6, wherein the fuel injection is substantially directly connected via an adapter, and the adapter is selectively used from a plurality of adapters having different dimensions. apparatus.