JP2003166451A - Fuel injection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device not applying high fuel pressure to peripheral of a needle valve except for the time of fuel injection, in a common rail type high pressure fuel injection device. <P>SOLUTION: In the common rail type fuel injection device for controlling injection timing and injection quantity by controlling hydraulic pressure of a rear end side of a nozzle needle valve, an open-close valve for opening and closing almost synchronously with start and end of fuel injection is provided at a high pressure fuel passage for supplying high pressure fuel from a common rail to an oil sump at a tip end side of the nozzle needle valve of the fuel injection valve. <P>COPYRIGHT: (C)2003,JPO

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, particularly a diesel engine, and in a pressure-accumulation type high-pressure fuel injection device, the pressure of fuel around a needle valve of an injection valve which becomes relatively high during operation. Is maintained at a low pressure except during fuel injection to suppress the progress of corrosion etc. due to exposure to high temperature and high pressure fuel around the needle valve, improving the reliability of the fuel injection valve and detecting abnormal injection. The present invention relates to a fuel injection device that shuts off fuel injection when abnormal injection occurs to prevent engine damage due to abnormal injection.

[0002]

2. Description of the Related Art It is effective to increase the fuel injection pressure and to reduce the spray atomized particle size in order to reduce the fuel consumption rate of a diesel engine and the exhaust emission, and the injection pressure tends to increase year by year. I followed. However, in conventional row pumps and jerk type unit injectors, the injection pressure depends on the number of revolutions, and the injection pressure must be low at low revolutions. And the injection pressure cannot be controlled independently.

On the other hand, a common rail type fuel injection device in which high pressure fuel is stored in a common rail (accumulation chamber), the high pressure fuel is sent to a fuel injection valve of each cylinder, and injection is controlled by a solenoid valve is becoming popular. In such a pressure-accumulation type high-pressure fuel injection device, the injection timing and the injection amount can be controlled independently, and a high injection pressure can be achieved even at low speed. However, in such an accumulator type high-pressure fuel injection device, the high-pressure fuel of the common rail always reaches the nozzle needle valve of the fuel injection valve, and the tip of the nozzle tip accommodating the nozzle needle valve has the tip of the combustion chamber of the engine. The temperature of the high-pressure fuel existing around the needle valve also rises because the temperature around the nozzle needle valve, in particular, the temperature of the needle valve seat portion becomes considerably high due to the exposure.

Japanese Unexamined Patent Publication (Kokai) No. 5-18333 discloses a pressure-accumulation type high-pressure fuel injection device that slows the rise of the injection rate immediately after fuel injection to reduce exhaust emission and combustion noise. In the fuel injection device, fuel pressure from the common rail is applied to the oil reservoir of the needle valve portion and the pressure control chamber provided above the needle valve via the rod member, and when there is no injection, the pressure control above the needle valve is performed. The needle valve is closed by the pressure of the chamber and the spring force that urges the needle valve downward, and at the time of fuel injection, by controlling the timing when the fuel in the pressure control chamber is discharged through the one-way orifice by the solenoid valve. Although the injection rate immediately after fuel injection is slowed down, the area around the needle valve is always filled with high-pressure fuel introduced from the common rail.

[0005]

As described above, since the tip portion of the nozzle tip accommodating the needle valve is exposed to the combustion chamber, the temperature around the needle valve, especially the seat portion, becomes higher than 300 ° C. . Medium- and large-sized diesel engines often use poor fuel, which contains a large amount of sulfur, etc., and if the bad fuel exists near the needle valve at high pressure and temperature, corrosion of the needle valve progresses, especially spraying due to seat surface corrosion. This causes defects and shortens the life of the injection nozzle. Further, in the pressure-accumulation type high-pressure fuel injection device, when the injection nozzle such as the seat surface is damaged, a large amount of fuel accumulated in the common rail is injected into the combustion chamber, which may damage the engine.

The present invention has been made in view of the above problems, and provides a fuel injection system in which a high pressure fuel is not applied to the vicinity of a needle valve of an injection valve except when fuel is injected. With the goal.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the fuel injection device of the present invention has an injection timing by controlling the position of the needle valve, for example, by controlling the hydraulic pressure at the nozzle needle valve rear end side. In a pressure-accumulation fuel injection device that controls the injection amount and the injection amount, the fuel injection valve opens and closes in a high-pressure fuel passage that supplies high-pressure fuel from the common rail to the oil reservoir on the tip side of the nozzle needle valve of the fuel injection valve. It is characterized in that an on-off valve is provided.

According to this invention, an opening / closing valve that can be electrically opened / closed is provided in a passage for sending the high pressure fuel from the common rail storing the high pressure fuel to the needle valve oil sump of the fuel injection valve,
By opening and closing the on-off valve substantially in synchronism with the start and end of fuel injection, the fuel pressure around the nozzle needle valve can be reduced except when fuel injection is in progress.

In the case of a four-cycle engine, fuel injection is performed once every two revolutions of the engine, but since the fuel injection period is about 25 ° in crank angle, the injection period is two.
It is about 3.5% for 720 ° of rotation, and the remaining 96.
The period of about% is a period without injection. According to the fuel injection device of the present invention, the high-pressure fuel passage from the common rail to the needle valve oil reservoir is opened near the start of injection by the on-off valve, closed near the end of injection, and communication with the common rail is shut off after the valve is closed. Therefore, after closing the on-off valve, the fuel pressure of the needle valve oil sump decreases due to leakage from the nozzle needle valve to the back side of the needle valve. Therefore, the fuel pressure of the needle valve oil sump is low during the period from the end of fuel injection to the start of the next injection, and the nozzle needle is used during the non-injection period, which accounts for approximately 96% of the rest except the injection period during engine operation. The fuel pressure around the valve is kept low. Therefore, even if the fuel around the needle valve becomes hot to some extent, its pressure is much lower than that of the conventional accumulator type high-pressure fuel injection device. Is significantly mitigated and the nozzle life is extended.

According to a second aspect of the present invention, in a pressure-accumulation type high-pressure fuel injection device in which the injection timing and the injection amount are controlled by controlling the position of the nozzle needle valve, the nozzle side of the nozzle needle valve of the fuel injection valve is located from the common rail. The fuel injection is started and ended by switching the communication between the common rail to the oil reservoir of the nozzle needle valve and the communication from the oil reservoir to the return passage to the fuel tank in the high-pressure fuel passage for supplying high-pressure fuel to the oil reservoir. It is characterized in that a three-way valve is provided which operates substantially in synchronism with.

According to this invention, the three-way valve closes the passage from the common rail to the nozzle needle valve oil sump, and at the same time, the needle valve oil sump is communicated with the return passage and the pressure of the needle valve oil sump sharply drops. Therefore, if the three-way valve is switched substantially in synchronism with the end of injection, the fuel pressure in the needle valve oil sump will drop to the pressure in the return passage at approximately the same time as switching. Therefore, the fuel pressure of the needle valve oil sump is low during the period from the end of fuel injection to the start of the next injection, and the non-injection period, which accounts for approximately 96% excluding the injection period during engine operation, is around the nozzle needle valve. The fuel pressure of is kept low. Therefore, even if the fuel around the needle valve becomes hot to some extent, its pressure is much lower than that of the conventional accumulator type high-pressure fuel injection device. Is significantly mitigated and the nozzle life is extended.

According to a third aspect of the invention, the on-off valve or the three-way valve and a control device for controlling an electromagnetic valve for controlling the injection timing and the injection amount are provided, and the needle valve oil sump and the on-off valve or Is a pressure sensor provided in a passage connecting the three-way valve, and inputs the detected pressure signal to the control device, and the control device determines normal injection or abnormal injection according to the detected pressure. In the case of abnormal injection, the control device To prevent the engine from being damaged due to abnormal injection.

According to the present invention, the secondary injection in which the nozzle needle valve is opened again by the reflected wave after the valve is closed and the pressure of the needle valve oil sump after the needle valve is closed are different for each cycle, and as a result, for each injection amount. Abnormal injection such as irregular injection in different cycles or injection due to damage to the injection nozzle is judged by the control device based on the pressure waveform detected by the pressure sensor provided in the passage connecting the needle valve oil reservoir and the on-off valve or the three-way valve. If the occurrence of abnormal injection is recognized, the fuel injection is stopped by the control device, or the injection is temporarily stopped and then the injection is performed again to check whether the abnormal injection continues. Then, if necessary, it is possible to prevent the damage to the engine due to the continuation of the abnormal injection by inspecting the fuel injection device and its peripheral portion. Since the reflected wave to the nozzle needle valve oil sump is very small by the provision of the three-way valve, the three-way valve has an effect of preventing abnormal injection.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. FIG. 1 is a schematic diagram showing a schematic configuration of a first example according to an embodiment of the present invention, and FIG. 2 is a diagram showing an opening / closing state of an opening / closing valve and a fuel pressure time of a nozzle needle valve oil sump in the case of the first example. FIG. 3 is a schematic view showing changes, FIG. 3 is a schematic view showing a schematic configuration of a second embodiment according to the embodiment of the present invention, and FIG. 4 is an opening / closing state of the opening / closing valve and a nozzle needle valve in the case of the second embodiment. It is a figure which simplifies and shows the change over time of the fuel pressure of an oil puddle.

In FIG. 1, 10 is a fuel injection valve,
It includes a nozzle needle valve 1, a nozzle tip 2, and an actuator 3. An on-off valve 4 that is electrically opened and closed is provided in a high-pressure fuel passage 7 that connects a common rail (accumulation chamber) 9 and a needle valve oil sump 5 of the fuel injection valve 10. The fuel injection valve 10 itself is not the main constituent of this patent, and the fuel injection valve 10 in the figure is merely an example, but in brief description, at the time of fuel injection, the fuel injection valve 10 from the common rail via the on-off valve 4 is used. High-pressure fuel is supplied to the needle valve oil sump 5, and the needle valve oil sump has the same pressure as the common rail. The needle valve 1 is a seat surface 2 of a nozzle tip 2 at the tip.
The fuel pressure acting on the conical surface between the outer periphery of the seating surface at b and the outer diameter D of the needle valve is urged upward, that is, in the valve opening direction. on the other hand,
A hydraulic oil chamber 6 is provided on the rear end side of the needle valve, and hydraulic oil is supplied from a hydraulic oil passage 8.

The opening / closing valve 3a at the end of the working shaft of the actuator 3 opens and closes the opening 6a of the working oil chamber 6 by the operation of the actuator 3. The hydraulic oil whose pressure is adjusted is supplied to the hydraulic oil chamber 6, and the nozzle needle valve 1 is urged downward by the pressure of the hydraulic oil chamber 6, that is, in the direction of closing the needle valve. When the opening 6a is opened by the operation of the actuator 3, the pressure in the working chamber 6 decreases and the needle valve 1 rises to open and fuel is injected from the injection hole 2a. The hydraulic oil flowing out of the opening 6a is relieved via a relief passage (not shown). Since the pressure of the working chamber 6 is determined by the opening degree of the opening / closing valve 3a opening the opening 6a, if the valve opening speed of the opening / closing valve 3a by the actuator 3 is controlled, the injection rate control such as reducing the initial injection rate can be performed. You can also do it.

There are various injection valves whose injection rate can be controlled in addition to the injection valve shown in FIG.
Some injection valves, such as -18333, cannot control the injection rate, and the present invention can be applied to all of these injection valves.

A pressure sensor 12 is arranged between the nozzle needle valve oil sump 5 and the on-off valve 4 in the high-pressure fuel passage 7, and the pressure sensor 12, the on-off valve 4 and the actuator 3 are provided with electric wires, respectively. It is connected to the control device 11 by 15, 14, and 13. The control device 11 determines whether or not abnormal injection has occurred based on the pressure detected by the pressure sensor 12, and controls the on-off valve 4 and the actuator 3 according to the determination result. That is, if the abnormal injection occurs, stop the fuel injection,
Alternatively, after the injection is temporarily stopped, the injection is performed again to check whether the abnormal injection continues. By detecting the abnormal injection in this way, it is possible to prevent damage to the engine due to continuation of the abnormal injection.

FIG. 2 is a simplified view showing the open / closed state of the open / close valve and the change in fuel pressure of the nozzle needle valve oil pool with time in the case of the first embodiment shown in FIG. 1. FIG. The open / closed state of the valve 4 is shown, and (B) shows the fuel pressure of the needle valve oil sump 5 against time. In the figure, broken lines S and E respectively indicate the injection start timing and the injection end timing due to the operation of the actuator 3 of the fuel injection valve 10, and the injection period is between S and E. Since it takes some time for the fuel pressure of the needle valve oil pool to reach the fuel pressure of the common rail after opening the on-off valve,
As shown by the solid line in FIG. 2 (A), the opening / closing valve 4 is opened slightly before the injection start S. That is, as shown in FIG. 2 (B), the on-off valve 4 is opened so that the timing at which the fuel pressure of the needle valve oil sump reaches the fuel pressure of the common rail in synchronization with or slightly before the injection start timing.

The closing timing of the on-off valve is shown in FIG.
The valve may be closed slightly before the injection end timing E as indicated by the chain line (opening / closing pattern), or may be closed after a slight delay as indicated by the solid line (opening / closing pattern). That is, after the opening / closing valve 4 is closed, the pressure of the needle valve oil sump 5 decreases with time due to leakage to the drain provided between the hydraulic oil chambers 6, and therefore the chain line (opening / closing) in FIG. The injection may be terminated in the middle of the pressure drop as shown in (in the case of the pattern), or the fuel pressure in the needle valve oil pool may be reduced after the end of injection as shown in the solid line (in the case of the open / close pattern). You may Even at the beginning of injection, the on-off valve 4 may be opened at a timing such that the injection is started while the fuel pressure of the needle valve oil sump 5 is rising. In that case, the injection rate at the initial stage of injection can be reduced.

FIG. 3 is a schematic diagram showing a schematic configuration of a second example according to the embodiment of the present invention. The difference from FIG. 1 is that a three-way valve 16 is provided in place of the on-off valve 4 and a return passage 17 is provided, and the other configurations are the same as in FIG. The three-way valve 16 is arranged in the high-pressure fuel passage 7 that connects the common rail 9 and the needle valve oil sump 5,
This is a solenoid valve that switches between the case where the common rail 9 and the needle valve oil sump 5 are communicated with each other and the case where the communication is cut off and the needle valve oil sump 5 is communicated with the return passage 17.

In this embodiment, when the communication between the common rail and the needle valve oil sump 5 is shut off by the three-way valve 16, the needle valve oil sump 5 is connected to the return passage 17 to the fuel tank.
The fuel pressure in the needle valve oil sump 5 rapidly decreases, and the decreased pressure becomes lower than that in the embodiment of FIG. Therefore, the condition that the periphery of the needle valve, especially the seat surface, is corroded by the particularly bad fuel around the needle valve is relaxed as compared with the case of the embodiment of FIG. 1, and
The occurrence of abnormal injection such as secondary injection due to the reflected wave to the needle valve oil sump is also prevented.

FIG. 4 is a simplified view showing the open / closed state of the open / close valve and the change in fuel pressure of the nozzle needle valve oil pool with time in the case of the second embodiment shown in FIG. 3, and FIG. The open / closed state of the valve 4 is shown, and (B) shows the fuel pressure of the needle valve oil sump 5 against time. 2 is different from FIG. 2 in that the chain line in FIG. 2 is not drawn and the pressure of the needle valve oil sump 5 when the communication between the common rail 9 and the needle valve oil sump 5 in FIG. 4B is cut off. The descent is steeper than in FIG. 2 (B). As described above, when the communication between the common rail 9 and the needle valve oil sump 5 is cut off, the needle valve oil sump 5 is communicated with the return passage 17, so that the pressure drop in the needle valve oil sump 5 becomes sharp, and FIG. It is impossible to control the injection to be terminated in the middle of the pressure drop as shown in FIG. Therefore, in the case of the present embodiment, the communication between the common rail 9 and the needle valve oil sump 5 by the three-way valve needs to be completely synchronized with the end of injection or after the end of injection.

[0024]

The present invention is carried out in the form as described above and has the following effects. That is, the common rail (accumulation chamber) of the accumulator high-pressure fuel injection device
An electrically operated on-off valve or a three-way valve is installed in the connection passage between the needle valve oil sump and the needle valve, and the injection timing is controlled by a solenoid valve or the like for communication between the common rail and the needle valve oil sump. By performing the fuel injection valve substantially in synchronism with the injection start and end timings, the fuel existing in the vicinity of the nozzle needle valve, which has a relatively high temperature, around 96% of the engine operating time during non-injection, communicates with the common rail. Since it is not high pressure fuel, but fuel at a pressure much lower than the high pressure,
The progress of corrosion of the needle valve, especially the seat portion is alleviated, and the life of the injection valve is extended.

Further, a pressure sensor is provided between the on-off valve or the three-way valve and the nozzle needle valve oil sump, and the control device determines whether or not an abnormal injection has occurred and stops the injection. Therefore, it is possible to prevent the engine from being damaged due to the continuation of the abnormal injection.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a first example according to an embodiment of the present invention.

FIG. 2 is a diagram showing a simplified view of the open / closed state of an on-off valve and the change in fuel pressure of a nozzle needle valve oil pool with time in the case of the first embodiment.

FIG. 3 is a schematic diagram showing a schematic configuration of a second example according to the embodiment of the present invention.

FIG. 4 is a diagram showing a simplified view of the open / closed state of an on-off valve and the change in fuel pressure of a nozzle needle valve oil pool with respect to time in the case of a second embodiment.

[Explanation of symbols]

1 nozzle needle valve 2 nozzle tip 3 actuators 4 on-off valve 5 needle valve oil sump 6 hydraulic oil chamber 7 High pressure fuel passage 8 hydraulic oil passage 9 common rail 10 Fuel injection valve 11 Control device 12 Pressure sensor 13 electric wire 14 electric wires 15 electric wires 16 three-way valve 17 Return passage

Continued front page    F-term (reference) 3G066 AC09 BA10 BA32 BA50 CC08U                       CC61 CE12 DA12                 3G301 JA21 LB11 PB08B

Claims (3)

[Claims] 1. In a pressure-accumulation type high-pressure fuel injection device for controlling an injection timing and an injection amount by controlling a position of a nozzle needle valve, a common rail (accumulation chamber) is used to collect oil in a tip end side of a nozzle needle valve of the fuel injection valve. A fuel injection device for an internal combustion engine, comprising: an on-off valve that opens and closes in a high-pressure fuel passage for supplying high-pressure fuel, in synchronization with start and end of fuel injection. 2. In a pressure-accumulation type high-pressure fuel injection device for controlling injection timing and injection amount by controlling the position of a nozzle needle valve, high-pressure fuel is supplied from a common rail to an oil reservoir on the tip side of the nozzle needle valve of the fuel injection valve. In the high pressure fuel passage to
A three-way valve is provided to perform switching between communication from the common rail to the oil reservoir of the nozzle needle valve and communication from the oil reservoir to the return passage to the fuel tank substantially in synchronization with the start and end of fuel injection. A fuel injection device for an internal combustion engine. 3. The on-off valve or a three-way valve, and a control device for controlling an electromagnetic valve for controlling an injection timing and an injection amount are provided, and the needle valve oil sump is connected to the on-off valve or the three-way valve. A pressure sensor is provided in the passage to input the detected pressure signal to the control device, and the control device determines whether the injection is normal injection or abnormal injection based on the detected pressure. In the case of abnormal injection, the control device stops injection. The fuel injection system for an internal combustion engine according to claim 1 or 2, wherein the engine is prevented from being damaged by the abnormal injection.