JPH10281038A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set injection characteristics of fuel to be injected actually to predetermined boot type characteristics without reducing a displacement speed and an injection pressure of a needle valve element. SOLUTION: A displacement of a needle valve 86 in opening injection holes 84, 85 is stepwise changed with time (i.e., boot type characteristics), and the plurality of injection holes 84, 85 are opened in sequence. Consequently, an initial injection state is determined by the area of the first injection holes 84 and is hardly influenced by the displacement of the needle valve element 86, so that it is unnecessary to reduce a displacement speed of the needle valve element 86 and it is possible to increase an initial lift quantity. Furthermore, since the displacement of the needle valve element 86 is stepwise changed with time, like boot type characteristics, it is possible to secure a long holding time (a time when an initial injection ratio can be kept) without reducing the displacement speed of the needle valve element 86.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve, and is effective when applied to a fuel injection valve for a diesel internal combustion engine (engine) which requires a high injection pressure.

[0002]

2. Description of the Related Art A general structure of a fuel injection valve comprises a fuel reservoir chamber into which high-pressure fuel is introduced, and a bag portion (sack portion) communicating with the fuel reservoir chamber and having a plurality of injection holes formed therein. The communication portion between the sack portion and the fuel storage chamber is opened and closed by a needle-shaped valve element (needle valve).

As a fuel injection characteristic of a diesel engine, as is conventionally known, an initial injection rate is reduced and the injection rate is held for a predetermined time (hereinafter, this time is referred to as a holding time). Call)), then
What is called a boot-type characteristic for increasing the injection rate is desired. Note that the injection rate refers to the injection amount (injection volume, injection mass) of the fuel actually injected per unit time.

As means for realizing the boot-type characteristics, for example, in the invention described in Japanese Patent Application Laid-Open No. 3-47459, attention is paid to the fact that the fuel injection amount is affected by the flow rate of the fuel flowing through the communication section. Thus, the characteristic of the displacement amount (lift amount) of the valve element is set to the boot type characteristic. In the invention described in JP-A-7-332199,
Paying attention to the fact that the fuel injection amount is affected by the opening area of the actually opened injection hole, the change characteristic of the opening area of the actually opened injection hole becomes the boot type characteristic. I have.

[0005]

By the way, the inventors examined the inventions described in the above two publications on a trial basis. However, any of the inventions has an appropriate injection characteristic of the actually injected fuel. Boot-type characteristics could not be obtained. Then, the inventors continued the investigation and found the following causes.

In other words, the opening and closing of the fuel injection valve requires opening and closing the injection hole by appropriately displacing (lifting) the valve body in accordance with the crank angle of the crankshaft. Speed) must be as large as possible. For this reason, in the invention described in JP-A-3-47459, the initial lift amount for determining the initial injection rate becomes large, and the initial injection rate becomes excessively large. Further, in the invention described in JP-A-7-332199, a predetermined holding time cannot be secured. Therefore, it is difficult for any of the inventions to obtain appropriate boot-type characteristics.

That is, in any of the inventions described in the above publications, it is necessary to reduce the displacement speed of the valve body in order to obtain appropriate boot-type characteristics, so that the response of the fuel injector deteriorates. . SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a fuel injection valve in which the injection characteristic of the actually injected fuel has a predetermined boot-type characteristic without reducing the displacement speed of the valve element.

[0008]

The present invention uses the following technical means to achieve the above object. According to the first aspect of the present invention, the amount of displacement of the valve element (86) when opening the injection holes (84, 85) is changed stepwise with time, and the plurality of injection holes (84, 85) are sequentially formed. Open.

Thus, the initial injection state is determined by the area of the injection hole (84) opened first, and the valve element (8)
The valve element (86) is hardly affected by the displacement amount of (6).
It is not necessary to reduce the displacement speed (operating speed) of the motor. Therefore, it is possible to prevent the initial injection rate from becoming excessively large without deteriorating the responsiveness of the fuel injection valve.

Further, since the displacement amount of the valve element (86) is changed stepwise with the passage of time, as in the boot-type characteristic, the displacement speed (operating speed) of the valve element (86) can be reduced without reducing the displacement rate. A longer holding time can be secured than the invention described in JP-A-332199. As described above, according to the present invention, the injection characteristics of the actually injected fuel can be made appropriate boot-type characteristics without lowering the displacement speed of the valve element (86).

According to the second aspect of the present invention, the first passage (9) through which the high-pressure fuel pumped from the fuel pump (5) flows.
3), a fuel reservoir chamber (82) into which high-pressure fuel is introduced via the first passage (93), and a fuel pump via a second passage (94) having a smaller passage area than the first passage (93). The first pressure chamber (9) into which the fuel pumped from (5) is introduced.
0), a first piston (88) which forms a part of the first pressure chamber (90), slides in conjunction with a pressure change in the first pressure chamber (90), and a second passage (94). ) Via the third passage (97) having a smaller passage area.
0) and the first pressure chamber (9).
0) A fourth passageway (92) for communicating the inside with the low pressure side (4).
A solenoid valve (91) for opening and closing the fourth passage (92), and a part of both pressure chambers (90, 96) slidably disposed in the same direction as the first piston (88). After the solenoid valve (91) is opened, the first piston (8
8) communicates with the second piston (98) that collides with the fuel storage chamber (82), and in conjunction with the plurality of injection holes (84, 85) that inject high-pressure fuel and the first piston (88). One valve element (86) that slides and sequentially opens and closes the plurality of injection holes (84, 85) according to the amount of sliding is provided.

As a result, the amount of displacement of the first piston (88) can be changed stepwise with time, as will be described later, so that an effect equivalent to that of the first aspect can be obtained. . In addition, the code | symbol in the parenthesis of each said means shows the correspondence with the concrete means of embodiment mentioned later.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) This embodiment is an example in which a fuel injection valve according to the present invention is applied to a pressure accumulating fuel injection device 1 for a diesel engine (hereinafter, abbreviated as engine). FIG. FIG. 2 is a schematic diagram of the injection device 1.

In FIG. 1, reference numeral 2 denotes an engine, 3 denotes a low-pressure fuel pump (feed pump) for sucking fuel in a fuel tank 4, and 5 denotes a low-pressure fuel pump 3 disposed near the engine 2. Is a high-pressure fuel pump that pressurizes the fuel sent by the above to a predetermined pressure. Reference numeral 6 denotes a common rail (accumulator) in which fuel pressurized by the high-pressure fuel pump 5 is stored. A fuel injection valve (injector) 8 is disposed on the common rail 6 via a pipe 7 for each cylinder. Have been. The opening and closing of these fuel injection valves 8 is controlled by an electronic control unit 10 to be described later via a drive unit (hereinafter referred to as an EDU) 9 including a drive circuit for driving an electromagnetic valve 91 of the fuel injection valves 8. Controlled. The fuel injection valve 8
Will be described later.

The common rail 6 has a pressure sensor (pressure detecting means) 1 for detecting the pressure in the common rail 6.
An output signal (detection value) of the pressure sensor 11 is provided to a central processing unit (CPU), a read-only storage device (ROM) serving as storage means, and a storage device (RAM) that can be read and written at any time. The electronic control unit (hereinafter, abbreviated as ECU) 10 is input to the electronic control unit 10.

The ECU 10 stores a crank angle (rotation angle) of a crank shaft (not shown) of the engine 2.
And an output signal from an accelerator opening sensor 14 for detecting the opening of accelerator means (not shown) operated by the occupant. Then, the ECU 10 controls the crank angle sensor 1
3 controls the opening and closing operation of the fuel injection valve 8 based on the output signal from the engine 3, calculates the rotation speed of the engine 2 from the output signal of the crank angle sensor 18, and calculates the common rail 6 from the calculated engine rotation speed and accelerator opening. The high pressure pump 5 is controlled so that the internal pressure becomes a predetermined value (see FIG. 2).

Next, the structure of the fuel injection valve 8 will be described. FIG. 3 is a schematic diagram showing the structure of the fuel injection valve 8.
Reference numeral 81 denotes a nozzle body in which a fuel storage chamber 82 into which high-pressure fuel from the common rail 6 is guided is formed. Also, 8
Reference numeral 3 denotes a bag portion (sack portion) communicating with the fuel storage chamber 82 and having a plurality of injection holes 84 and 85 formed therein, as shown in FIG. The communication portion 83a is provided with a needle-shaped needle valve body (hereinafter, referred to as a needle valve body).
Abbreviated as needle. ) 86.

The injection holes 84 and 85 are formed so as to be displaced from each other in the longitudinal direction (sliding direction) of the needle 86 with respect to the nozzle body 81 (suck portion 83). (The injection hole is referred to as a second injection hole 85.)
Is located on the tip side of the needle 86 with respect to the injection hole 84 (hereinafter, this injection hole is referred to as a first injection hole 84). By the way, on the tip (one end) side of the needle 86, when the fuel injection valve 8 is closed, a frustoconical tapered portion 86 a that comes into contact with a seat portion 81 a formed on the nozzle body 81, A cylindrical column portion 86b extending toward the two injection holes 85 is formed.

The circumferential surface 86c of the cylindrical portion 86b is
Is slidably in contact with the inner wall 83b of the sack portion 83,
The contact of the circumferential surface 86c with the inner wall 83b prevents the fuel from flowing from the fuel reservoir chamber 82 to the second injection hole 85. The first injection hole 84 is open toward the fuel storage chamber 82, and is closed when the tapered portion 86a contacts the seat portion 81a.

As shown in FIG. 1, the other end of the needle 86 is connected to a first piston 88 slidably disposed in the injector body 87. The first integrated with the first piston 88
It slides in the longitudinal direction of the piston 88. Reference numeral 89 denotes a spring (elastic member) that constantly presses the needle 86 through the first piston 88 in a direction to close the communication portion 83a (both the injection holes 84 and 85).

The first piston 88 constitutes a part of a first pressure chamber 90 into which high-pressure fuel from the common rail 6 is guided. It is configured to slide in the longitudinal direction. Reference numeral 91 denotes the first pressure chamber 90 and the fuel tank 4
The solenoid valve opens and closes a return passage (fourth passage) 92 that communicates with the ECU.
10.

The common rail 6 is connected to the fuel storage chamber 8.
The pressure loss in the fuel passage (first passage) 93 that supplies high-pressure fuel to the second 2 is smaller than the pressure loss in the control pressure passage (second passage) 94 that supplies high-pressure fuel from the common rail 6 to the first pressure chamber 90. In FIG. 1, 95 is
The throttle resistance schematically indicates that the pressure loss in the control pressure passage 94 is larger than the pressure loss in the fuel passage 93 (the passage area is reduced). The pressure loss in the return passage 92 is set to be smaller than the pressure loss in the orifice 97 described later.

The orifice 96 has a larger pressure loss (small passage area) than the control pressure passage 94 (third passage).
The second pressure chamber 96 communicates with the first pressure chamber 90 through a passage 97, and the second pressure chamber 96 is formed by a second piston 98 sliding in the same direction as the first piston 88 and an injector body 87. Is formed. Reference numeral 99 denotes a spring (elastic member) that presses the second piston 98 toward the first piston 88.

The first piston 88 and the second piston 9
8, a predetermined gap 100 is formed in a state where the electromagnetic valve 91 is closed (a state where the communication portion 83a is closed) as shown in FIG. , distance) [delta] ₁ between 98 is smaller than the axial dimension of the cylindrical portion 86b of the needle 86 [delta] ₂ (see FIG. 4).

Incidentally, the area S _S (= πd ₁ ² /) of the portion of the first piston 88 that receives the pressure in the first pressure chamber 90.
4) is adapted to be larger than the area of the site that is being subjected to pressure in the fuel reservoir chamber 82 of the needle ^{_{86 S O (= πd 2 2}} /4). Reference numeral 101 denotes a check packing made of metal. The check packing 101 joins the injector body 87 and the nozzle body 81 in an oil-tight manner, and the maximum displacement δ ₃ (>) of the first piston 88.
δ ₂ ).

Next, the operation of the fuel injection valve 8 will be described. 1. When the ECU 10 issues a valve opening signal, the EDU 9 opens the solenoid valve 91. Thereby, the fuel in the first pressure chamber 90 flows out toward the fuel tank 4 and the first
Since the pressure in the pressure chamber 90 decreases, both pistons 88,
Reference numeral 98 denotes a displacement (lift) in a direction in which the volume of the first pressure chamber 90 is reduced (upper side in FIG. 3).

However, since the pressure loss of the orifice 97 is larger than the return passage 92, the fuel in the first pressure chamber 90 mainly flows out toward the fuel tank 4, so that the first piston 88 is actually mainly It is displaced (lifted) until it collides with the second piston 98 (see FIG. 5). Therefore, in this state, only the first injection hole 84 is opened, and fuel is injected only from the first injection hole 84 (the initial injection state of the boot type characteristic).

Further, when the time advances while the solenoid valve 91 is open, the second pressure chamber 96 passes through the orifice 97.
Since the fuel inside the fuel tank 4 starts to flow toward the fuel tank 4, both pistons 88 and 98 are displaced (lift) in a direction in which the volume of the first pressure chamber 90 is reduced while the first piston 88 is in contact with the second piston 98. ) (See FIG. 6). And
Needle 86 from the time when first piston 88 starts to be displaced
When the total displacement amount (total lift amount) becomes equal to or greater than δ ₂ , the second injection hole 85 is opened, and fuel is injected from both the injection holes 84 and 85.

Incidentally, the time from when the first piston 88 starts to be displaced until the total displacement reaches δ ₂ is the above-mentioned holding time. 2. When the ECU 10 issues a valve closing signal, the EDU 9 closes the solenoid valve 91. Thereby, the first pressure chamber 9 is supplied with the fuel supplied from the control pressure passage 94 to the first pressure chamber 90.
When the pressure within 0 increases, the difference between the area S _S and the area S _O (S
By the elastic force of _S> S _O) and the spring 89, the first
The piston 88 is connected to the communication portion 83a (both injection holes 84 and 85).
, The first pressure chamber 90 is displaced in a direction in which the volume of the first pressure chamber 90 increases, and the two injection holes 84 and 85 are closed.

Next, the features of this embodiment will be described. According to the present embodiment, the initial injection state is mainly the first injection hole 84.
And is hardly affected by the amount of displacement of the needle 86, so there is no need to reduce the displacement speed (operating speed) of the needle 86. Therefore, it is possible to prevent the initial injection rate from becoming excessively large without deteriorating the responsiveness of the fuel injection valve.

Further, since the first piston 88 is displaced by sequentially reducing the volumes of the first and second pressure chambers 90 and 96, the displacement amount of the needle 86 changes with time in a stepwise manner as in a boot-type characteristic. Can be done. Therefore, a longer holding time than the invention described in JP-A-7-332199 can be secured without lowering the displacement speed (operating speed) of the needle 86. In addition,
Needle 86 such as both pressure chambers 90 and 96 and solenoid valve 92
The mechanism for displacing the steps in a stepwise manner with time is collectively called a lift mechanism.

FIG. 7 is a graph showing the relationship between the injection rate and the time. The solid line indicates this embodiment, the broken line indicates the invention described in Japanese Patent Application Laid-Open No. 3-47459, and the dashed line indicates the characteristic. This shows the invention described in Japanese Unexamined Patent Publication No. Hei 7-332199. And, as is clear from this graph, according to the fuel injection valve 8 according to the present embodiment, more ideal injection characteristics can be obtained, so that harmful substances (emission) in exhaust gas can be reduced. Thus, the performance of the engine 2 can be further improved.

By the way, in order to prevent the initial injection rate from becoming excessively large in the invention described in Japanese Patent Application Laid-Open No. 3-47459, it is necessary to reduce the diameter of the sheet portion 81a of this embodiment to a value corresponding to the diameter of the sheet portion 81a. or the sheet size is smaller that or the equivalent to the gap 100 of the present embodiment by, for example to reduce the initial displacement amount (initial lift) [delta] ₁ of the needle 86, by the displacement amount and the sheet size of the valve body It is necessary to reduce the area of the part where the fuel flows, which is determined.

[0034] However, in this way, reduce the sheet size (the area of the portion where the fuel flows), or, since it is necessary to reduce the initial lift amount [delta] _1, the pressure of fuel at the time of flowing the site The loss is increased, and the injection pressure is reduced. In contrast, according to the present embodiment, the initial injection rate, as described above, since it is determined in the area of the first injection hole 84, to reduce the diameter and the initial lift amount [delta] ₁ of the seat portion 81a No need. Therefore, the pressure loss of the fuel in the communication portion 83a can be suppressed, so that a decrease in the injection pressure can be suppressed.

As described above, the initial injection rate in the invention described in Japanese Patent Application Laid-Open No. 3-47459 is determined by the displacement of the valve body and the seat size. in the invention described, variations in the size of the portion corresponding to the dimension [delta] ₁ of the gap 100, thereby directly leading to variations in the initial injection rate. Therefore, the variation in the initial injection rate according to the invention described in Japanese Patent Application Laid-Open No. 3-47459 is determined by the integration tolerance of a plurality of components constituting the gap size.

On the other hand, according to the present embodiment, the variation in the initial injection rate is affected only by the variation in the diameter of the first injection hole 84, and therefore, as in the invention described in JP-A-3-47459. Variations in the initial injection rate can be reduced compared to those affected by the integration tolerance of a plurality of components. Accordingly, the dimensional tolerance of each component constituting the dimension δ _{1 of the} gap 100 can be reduced.
The manufacturing cost of the fuel injection valve 8 can be reduced.

(Second Embodiment) In the above embodiment, the fuel injection valve 8 is opened by displacing the needle 86 upward in FIG. 3, but in the present embodiment, as shown in FIG. The fuel injection valve 8 is opened by displacing the needle 86 downward in the drawing.

Further, in this embodiment, the sack portion 83 is omitted, and both the injection holes 84 and 85 are formed on the tip side of the needle 86. In addition, both injection holes 84 and 85 are
The nozzle body 81 is open toward the radially outer side, and is closed by a wall surface 81b of the nozzle body 81 that slidably contacts the distal end side of the needle 86.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a pressure accumulating fuel injection device.

FIG. 2 is a map showing a relationship between an accelerator opening, an engine speed, and a common rail pressure.

FIG. 3 is a cross-sectional view of the fuel injection valve according to the first embodiment.

FIG. 4 is an enlarged view of a sack portion.

FIG. 5 is a sectional view of the fuel injection valve showing an initial injection state.

FIG. 6 is a cross-sectional view of the fuel injection valve showing a final injection state.

FIG. 7 is a graph showing a relationship between an injection rate and time.

FIG. 8 is a cross-sectional view of a fuel injection valve according to a second embodiment.

[Explanation of symbols]

82: fuel storage chamber, 83: sack part, 84, 85 ...
Injection holes, 86: needle valve element (valve element), 90: first pressure chamber, 91: solenoid valve, 96: second pressure chamber, 97: orifice (third passage).

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 45/08 F02M 45/08 B 47/00 47/00 F 51/00 51/00 F 61/04 61/04 F 61/18 320 61 / 18 320D 350 350B

Claims (2)

[Claims] A fuel injection valve for injecting high-pressure fuel pumped from a fuel pump (5) into an internal combustion engine (2), wherein a plurality of high-pressure fuels pumped from the fuel pump (5) are injected. Of the plurality of injection holes (84, 85), one valve element (86) for opening and closing the plurality of injection holes (84, 85), and displacing the valve element (86). 8
4, 85) to open the lift mechanism (88, 90, 91, 9)
6), the valve body (86) when opening the injection holes (84, 85).
The amount of displacement changes stepwise with time,
A fuel injection valve, wherein the plurality of injection holes (84, 85) are sequentially opened. 2. A fuel injection valve for injecting high-pressure fuel pumped from a fuel pump (5) into an internal combustion engine (2), wherein a first passage through which the high-pressure fuel pumped from the fuel pump (5) flows. (93), a fuel reservoir (82) into which high-pressure fuel is introduced via the first passage (93), and a second passage (94) having a passage area smaller than that of the first passage (93). A first pressure chamber (90) into which fuel pumped from the fuel pump (5) is introduced, and a part of the first pressure chamber (90). A first piston (88) that slides in conjunction with pressure fluctuations, and a first piston (90) that communicates with the first pressure chamber (90) via a third passage (97) having a smaller passage area than the second passage (94). 2 pressure chamber (96), the first pressure chamber (90) and the low pressure side (4) are connected. A fourth passageway (92) for passing therethrough; an electromagnetic valve (91) for opening and closing the fourth passageway (92); and the two pressure chambers slidably disposed in the same direction as the first piston (88). (90, 96), a second piston (98) against which the first piston (88) collides after the solenoid valve (91) is opened, and a fuel reservoir (82). The plurality of injection holes (84, 85) communicating with each other and injecting high-pressure fuel slide in conjunction with the first piston (88), and sequentially slide in accordance with the sliding amount. 84, 85) for opening and closing one valve element (86).