JPH11294291A - Accumulator fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a high pressure and a low pressure from being directly communicated with each other and to prevent excess high-pressure fuel other than the fuel required for injection control from flowing out by providing a two-way valve of a first throttle and normally opened(NO) on a guiding-in path, and providing a two-way valve of a second throttle and normally closed(NC) on a guiding-out path. SOLUTION: The high-pressure fuel from a high-pressure pump is communicated with a guiding-in path 16 guided to a control chamber 4 above a needle valve 3 via an IN orifice 1 serving as a first throttle through a two-way valve 2 NO. The high-pressure fuel is guided to the vicinity of nozzle hole 7 from the oil sump 6 of a nozzle via a common rail 103. The needle valve 3 is slid in a hollow housing 100 provided with the nozzle hole 7 to open or close the nozzle hole 7. The control chamber 4 is communicated with a guiding-out path 19 returned to a fuel tank 99 via an OUT orifice 8 serving as a second throttle and a two-way valve 9 NC, thereby the outflow of fuel from a high pressure to a low pressure can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator type fuel injection device used for injecting fuel into each cylinder of an internal combustion engine.

[0002]

2. Description of the Related Art As one of systems for injecting fuel into each cylinder of an internal combustion engine such as a diesel engine, a so-called accumulator type fuel injection device is used. The accumulator type fuel injection device includes a common accumulator pipe (common rail) for the fuel injection valve mounted on each cylinder of the engine. At the timing, the fuel in the accumulator pipe is injected into each cylinder.

[0003] An example of this kind of accumulator type fuel injection device is described in Japanese Patent Publication No. 19938/1992. In this example, the injection of fuel is controlled by controlling the back pressure of a needle valve that opens and closes an injection hole with an electromagnetic valve. A control chamber for supplying high-pressure fuel is provided on the back of a rod that moves up and down integrally with the needle valve, and when injection is stopped, the needle valve is urged downward by the pressure of the fuel stored in the control chamber. The orifice is closed. A valve member of an electromagnetic valve for opening and closing the control chamber and the drain passage is disposed between the control chamber and the drain passage, and the valve member is provided integrally with an armature driven by suction by a solenoid. When the solenoid is energized in the operating state, the armature is sucked and the valve member assumes the valve opening position, so that the control chamber and the drain passage communicate with each other, the pressure in the control chamber becomes low, and the needle valve is pushed upward. The needle valve moves upward due to the oil pressure of the fuel to open an injection hole, and the fuel is injected into each cylinder of the engine.

[0004]

In recent years, exhaust regulations have become strict, and a map of injection pressure has become indispensable, and there has been a demand for an injection system having an injection pressure of 2000 atm or more. However, in the conventional pressure-accumulation type fuel injection device, when the three-way valve performing the injection control switches between the high pressure and the low pressure, the high pressure and the low pressure always communicate once, so that what is called “switching leak” is unnecessary. Fuel spills out. This increases as the injection pressure increases,
This causes an increase in the load on the high-pressure pump and deterioration in fuel efficiency of the engine.

Further, in the conventional pressure-accumulation type fuel injection device, the opening and closing of the needle valve are fixed by the flow rate of the orifice selected in advance. It is impossible to adjust a small injection amount. In order to solve the above-mentioned problem,
Instead of a three-way valve, a two-way valve of normally controllable (hereinafter referred to as NC) and normally open (hereinafter referred to as NO), which can be controlled independently, is always used to directly communicate high pressure and low pressure. Pressure-accumulation type fuel injection that can prevent the flow of excess high-pressure fuel other than the fuel necessary for injection control and control the valve-opening response of the needle valve by controlling two two-way valves as needed It is intended to provide a device.

[0006]

The present invention employs the technical means described in claims 1 to 3 in order to solve the above-mentioned problems. According to the first and second aspects of the present invention, the first throttle and the two-way valve of NO (normally open) are provided in the introduction path, and the second throttle and the NC (normally closed) are provided in the outlet path. Since the two-way valve is provided, it is possible to prevent the high pressure and the low pressure from always communicating directly with each other, and to suppress the flow of excess high-pressure fuel other than the fuel necessary for injection control. According to the third aspect of the present invention, the injection rate is made variable by changing the valve opening timing of the normally open two-way valve. The valve opening response of the needle valve can be controlled by the control.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 3 to 6 relate to a first embodiment of the present invention. FIG. 1 is a main part flow system diagram showing a main part of a flow system around a needle 3. FIG. 3 is an overall configuration diagram of the accumulator type fuel injection device of the internal combustion engine, FIG. 4 is a time chart showing an operation state, and FIG. It is a time chart figure showing the state of operation | movement, (A), (B), (C).
3 is a time chart showing an operation state corresponding to the valve opening timing of the NO 2-way valve 2 indicated by an arrow in the figure. FIG. 6 is a characteristic diagram showing a change in the leak amount with respect to the injection pressure of the present invention shown in comparison with the conventional example.

In FIG. 3, fuel in a fuel tank 99 is supplied to a high-pressure pump 102 by a low-pressure pump 101, pressurized to a high pressure, and sent to a common rail (high-pressure accumulator pipe) 103. Common rail 103
Has a pressure sensor 104 that detects a common rail pressure. The engine control computer ECU 105 determines that a signal from the pressure sensor 104 is a pressure determined based on engine operating conditions such as an accelerator opening and an engine speed. Thus, the high pressure pump 102 is controlled.

A plurality of fuel injection valves 107 provided corresponding to each cylinder of a four-cylinder engine 106 are connected to the common rail 103, and injection is controlled by an engine control computer ECU 105. Excess fuel is returned from the fuel injection valve 107 to the fuel tank 99 via the drain passage 108 and its collecting part. The details of the present invention will be described based on FIG. The high-pressure fuel from the high-pressure pump 102 shown in FIG.
The orifice 1 is connected to an introduction passage 16 which is introduced through the NO 2 way valve 2 into the control chamber 4 above the needle valve 3. Separately, high pressure fuel is introduced from the oil sump 6 of the nozzle to the vicinity of the injection hole 7 via the common rail 103. The needle valve 3 slides inside the hollow housing 100 having the injection hole 7 to open and close the injection hole 7.

[0010] From the control room 4, OU forming the second squeezing is provided.
Fuel tank 9 through T orifice 8 and NC two-way valve 9
It is connected to a lead-out path 19 returning to 9. FIG. 1 shows a state in which the needle valve 3 is closed, and no high-pressure fuel leaks. FIG. 2 relates to the second embodiment of the present invention, and is a main part flow system diagram showing the main part of the flow system around the needle 3.
In the second embodiment shown in FIG. 2, an embodiment in which the command piston 20 is used to reduce the volume of the control chamber 4 is shown. Compared to the first embodiment shown in FIG. 1, since the spring chamber 21 is a low-pressure part, the leak slightly increases due to the leak from the slight clearance of the needle guide part 22 and the body 23. Since the operation is performed using only the necessary amount of working fuel, the amount of leaked fuel can be significantly reduced as compared with the related art.

Since the second embodiment differs from the first embodiment only in the presence or absence of the command piston 20, the operation will be described in detail with reference to the first embodiment. FIG. 4 shows a time chart of the operation state. As shown in FIG.
First, at an arbitrary time before starting the injection, the NO 2-way valve 2 is closed to shut off the introduction of high pressure, and then the NC 2-way valve 9 is opened. Then, when the pressure in the control chamber 4 decreases and the hydraulic force acting on the oil sump 6 increases, the rising force of the needle 3 increases, the needle 3 rises, and high-pressure fuel is injected from the injection hole 7.

At this time, by setting the control chamber 4 as small as possible, it is possible to control the high-pressure fuel leaking at the time of injection to an extremely small amount. Next, when ending the injection,
First, the NC two-way valve 9 is closed, and then the NO two-way valve 2 is opened. Then, a high pressure is introduced into the control chamber 4 through the NC two-way valve 9, the control chamber pressure increases, and the needle 3 is pushed down,
The injection ends.

As described above, by shifting the opening and closing timings of the two two-way valves at the time of injection, it is possible to prevent the high pressure line and the low pressure line from communicating at the same time, and it is possible to greatly reduce unnecessary high pressure fuel leakage. This is one of the features of the present invention. In particular, what is needed for the NC two-way valve 9 is good responsiveness of valve opening. Similarly, what is required for the NO 2 way valve 2 is good responsiveness of valve closing.

While the conventional three-way valve requires responsiveness for both the on-off valve and the responsiveness of only one of the two valves, it is easy to manufacture a two-way valve, which leads to cost reduction. . Another major feature of the present invention will be described with reference to FIG. FIG. 5A is the same as FIG. The difference between FIGS. 5A, 5B, and 5C is the opening timing of the NO 2-way valve 2 indicated by an arrow in each figure.

Depending on the conditions of the engine, there are times when it is better that the initial injection rate is lower than the rectangular injection rate.
Conventionally, only a single injection pattern selected with a fixed orifice can be realized. However, in the present invention, even if the orifice is fixed, the valve opening timing is controlled as shown in FIG. The needle lift can be made variable by controlling the inflow and outflow of the needle.

Of course, under the conditions of high pressure and high load, a high injection rate with a rectangular degree is preferable. Therefore, the opening timing of the NO 2 valve 2 is controlled as shown in FIG. Can be reduced. FIG. 6 shows the effect of the present invention. FIG.
In view of the leakage amount with respect to the injection pressure, by using the present invention, the outflow from a high pressure to a low pressure can be significantly suppressed, so that the leakage amount can be almost halved.

[Brief description of the drawings]

FIG. 1 is a main part flow system diagram showing a main part of a flow system around a needle 3 according to a first embodiment of the present invention.

FIG. 2 is a main part flow system diagram showing a main part of a flow system around a needle 3 according to a second embodiment of the present invention.

FIG. 3 is an overall configuration diagram of a pressure accumulating fuel injection device for an internal combustion engine according to the first embodiment of the present invention.

FIG. 4 is a time chart showing an operation state according to the first embodiment of the present invention.

FIGS. 5A and 5B are time charts showing an operation state when the opening timing of a NO (normally open) two-way valve 2 is changed according to the first embodiment of the present invention, and FIGS. ,
(C) is a time chart showing an operation state corresponding to the valve opening timing of the NO 2-way valve 2 indicated by an arrow in the figure.

FIG. 6 is a characteristic diagram illustrating a change in a leak amount with respect to an injection pressure according to the first embodiment of the present invention, which is shown in comparison with a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first throttle (IN orifice) 2 normally open two-way valve (NO two-way valve) 3 needle valve 4 control room 7 injection hole 8 second throttle (OUT orifice) 9 normally closed two-way valve (NC2) 16) Introducing path 19 Outgoing path 20 Command piston 23 Body 100 Housing

Claims (3)

[Claims] 1. A needle valve that slides in a hollow housing having an injection hole at a tip thereof to open and close the injection hole, and a high-pressure fuel formed facing the rear end surface of the needle valve and filled therein. A control chamber for urging the needle valve in the valve closing direction by the pressure of, and an introduction path for introducing high-pressure fuel into the control chamber,
A discharge path communicating with a drain passage for discharging high-pressure fuel from the control chamber to the outside; a first throttle and a normally open two-way valve in the introduction path; and a second throttle and normally close in the discharge path. And a two-way valve. 2. A needle valve which slides in a hollow housing having an injection hole at its tip to open and close the injection hole, a command piston which slides in the body integrally with the needle valve, A control chamber for urging the needle valve in the valve closing direction by the pressure of the high-pressure fuel formed facing the rear end face of the command piston and filling the inside thereof; an introduction passage for introducing high-pressure fuel into the control chamber; An outlet passage communicating with a drain passage for leading high-pressure fuel to the outside from the control chamber; a first throttle and a normally open two-way valve in the inlet passage; and a second throttle and normally closed valve in the outlet passage. An accumulator type fuel injection device comprising a two-way valve. 3. The accumulator fuel according to claim 1, wherein an injection rate is varied by changing a valve opening timing of the normally open two-way valve. Injection device.