JPH10274130A - Accumulator fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an accumulator fuel injection device to generate high pressure fuel during the starting of an engine through simple constitution. SOLUTION: An accumulator fuel injection device is provided with a volume varying mechanism 10 having a volume chamber 29 communicated with a common rail 9 having an accumulation chamber 39. During the starting of an engine, fuel is fed to an accumulation chamber 39 from a pump and simultaneously, a plunger 23 is energized by working a coil spring 25 by a control means 27 to decrease the volume of the volume chamber 29. This constitution increases a fuel pressure in a pressure storage chamber 39. Thus, a high pressure in the accumulation chamber is generated during the starting of an engine. Besides, a fuel circuit is prevented from complication and constitution is simplified.

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 having an accumulator for accumulating fuel injected from a fuel injection nozzle into a combustion engine. The present invention relates to an accumulator type fuel injection device such as an injection device.

[0002]

2. Description of the Related Art In general, a direct injection internal combustion engine for directly injecting fuel into a combustion chamber of a gasoline engine is known. In a fuel injection device used for this type of internal combustion engine, a high injection pressure is required to increase the fuel injection pressure and make the fuel spray fine. However, since the high-pressure pump is driven by the engine when the engine is started, there is a disadvantage that a sufficiently high discharge pressure cannot be obtained. That is, in the high-pressure pump, since the driving shaft of the engine is driven via a belt or a gear, sufficient pump efficiency and flow rate cannot be obtained at the cranking rotation speed at the time of starting. For this reason, some engines are started at a low pressure that can be obtained with a low-pressure fuel pump when the engine is started, and after a complete explosion of the engine, a high-pressure switching operation is performed, but in this case, the fuel piping becomes complicated and However, in operation with low-pressure fuel, the spray state injected from the injector (fuel injection nozzle) is not sufficiently miniaturized, so that there is a disadvantage that the combustion characteristics at the time of startup are not good.

On the other hand, JP-A-5-321787 discloses a starting auxiliary pump connected in parallel with a high-pressure pump in addition to a high-pressure pump. There has been proposed a configuration in which a low-pressure fuel is supplied from a low-pressure pump to pressurize a reservoir (common rail) to increase the pressure of fuel in the common rail at the time of starting.

[0004]

However, according to the technique disclosed in the above-mentioned publication, it is necessary to connect a low-pressure pump to the starting auxiliary pump and to release the pressure of the starting auxiliary pump when the engine is stopped. There is a problem that it becomes complicated.

Accordingly, an object of the present invention is to provide a simple configuration,
An object of the present invention is to provide a pressure-accumulation type fuel injection device that can obtain high-pressure fuel when the engine is started.

[0006]

According to one aspect of the present invention, there is provided an accumulator for accumulating fuel injected from a fuel injection nozzle into a combustion engine, and supplying fuel to the accumulator. In a pressure accumulating fuel injection device provided with a pump, a housing having a volume chamber communicated with the pressure accumulating chamber, a movable member moving in the housing to change the volume of the volume chamber, and The present invention is characterized in that a variable volume mechanism is provided which includes an urging member for urging the volume to be reduced, and control means for operating the urging member when the engine is started.

According to the first aspect of the present invention, when the engine is started, fuel is supplied from the pump to the accumulator, but at the same time, the control means operates the urging member. Accordingly, the urging member urges the movable member, so that the movable member moves the housing in accordance with the urging force, and reduces the volume of the volume chamber. In this case, the sum of the pressure accumulating chamber and the volume chamber is substantially the volume of the pressure accumulating chamber, but the volume of the volume chamber is reduced, and the substantial volume of the pressure accumulating chamber when the engine is started is reduced. Fuel pressure can be increased. Therefore, even when the engine is started, a high pressure in the accumulator can be obtained,
Moreover, the fuel circuit does not become complicated, and has a simple configuration.

Further, by realizing high-pressure starting,
The spray characteristics of the fuel injected from the fuel injection nozzle are improved, the startability and the combustion characteristics are improved, and in particular, the HC and CO concentrations can be reduced as compared with the conventional low-pressure start.

According to a second aspect of the present invention, in the first aspect of the invention, the control means includes a stopper means for limiting an operating range of the urging member, and a release mechanism for releasing the stopper means when the engine is started. And characterized in that:

According to the second aspect of the present invention, the stopper limits the operating range of the movable member and allows the operating range of the movable member to be within a certain range. Accordingly, the movable member is movable against the urging force of the urging member. Therefore, the volume variable mechanism performs a damper function, and pulsation of the accumulator can be reduced. Further, since the stopper releasing means is provided, when the engine is started, the stopper releasing means releases the stopper so that the urging force of the urging member acts on the movable member with a simple configuration.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the accumulator is a common rail having a plurality of fuel injection nozzles, and the variable volume mechanism is provided on the common rail. It is characterized by having.

According to the third aspect of the present invention, since the variable volume mechanism is provided on the common rail on which the fuel injection nozzle is mounted, it is possible to directly increase the pressure in the common rail when the engine is started, and Good responsiveness at startup.

The invention described in claim 4 is the first to third aspects of the present invention.
In the invention described in the above, the volume variable mechanism includes a position detection mechanism that detects the position of the movable member when the urging member is operated, and the pressure of the pressure accumulating chamber is determined by the position detected by the position detection mechanism. Is detected.

According to the fourth aspect of the present invention, the pressure in the accumulator can be detected by the position detecting mechanism detecting the position of the movable member. Therefore, the volume variable mechanism can be used as a pressure sensor, and there is no need to provide a separate pressure sensor.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG.
An embodiment of the present invention will be described in detail with reference to FIG. A fuel injection device (accumulation type fuel injection device) 3 according to an embodiment of the present invention injects gasoline directly into a combustion chamber (cylinder) of a gasoline engine, and is used for a so-called direct injection gasoline engine. .

As shown in FIG. 1, the fuel injection device 3 is generally fed from a fuel tank 5 and a low-pressure pump 7, a low-pressure regulator 13, a high-pressure pump 8, and a high-pressure pump 8 disposed in the fuel tank 5. A circuit is configured by connecting a common rail 9 as a pressure accumulator for accumulating fuel and a high-pressure regulator 11. And the common rail 9
The variable volume mechanism 10 according to the present invention is disposed at the first position.

The low-pressure pump 7 pumps fuel (gasoline) in the fuel tank 5 to the high-pressure pump 8, and a filter 15 is interposed between the low-pressure pump 7 and the high-pressure pump 8.
The low-pressure pump 7 is driven by a battery.

The high-pressure pump 8 pressurizes the fuel supplied from the low-pressure pump 7 to a high pressure. The high-pressure pump 8 is driven by an engine, pressurizes the fuel to a high pressure, and feeds the fuel to the common rail 9. A check valve 16 is provided between the high-pressure pump 8 and the common rail 9 to prevent the fuel from flowing back from the common rail 9 to the high-pressure pump 8. However, the seat oil tightness of the check valve 16 is not sufficient to maintain a high pressure, and after the engine stops, the pressure in the common rail 9 decreases with time.

A plurality of injectors 17 are connected to the common rail 9, and the fuel stored at a high pressure by the common rail 9 is injected from each injector 17 into a cylinder of the engine.

The common rail 9 is integrally provided with a variable volume mechanism 10 according to the present invention.
To achieve high-pressure injection of fuel when the engine is started.

As shown in FIG. 2, the variable displacement mechanism 10 includes a cylinder (housing) 21 formed integrally with the casing of the common rail 9, a plunger (movable member) 23 moving in the cylinder 21, and a coil spring. (Biasing member) 25 and a control mechanism 27 for controlling the operation of the coil spring 25.

The volume chamber 29 of the cylinder 21 has a communication hole 37
And communicates with the pressure accumulating chamber 39 of the common rail 9 via the second rail, and substantially forms a part of the capacity of the pressure accumulating chamber 39.
The cylinder 21 is provided with a plunger 23 via an O-ring 31 so as to move in a volume chamber 29 of the cylinder 21. A lid member 35 having a closed cylinder hole 33 is fixed to the rear end of the plunger 23. Have been. The cover member 35 is provided with a control mechanism 27.

The coil spring 25 includes a plunger 23
At the rear end side (opposite to the volume chamber) of the plunger 23
And the lid member 35, the plunger 23
Is constantly urged toward the volume chamber 29, in other words,
It is urged to reduce the volume of the volume chamber 29. The biasing force of the coil spring 25 is set to a predetermined value corresponding to the injection pressure in the pressure accumulating chamber 39.
Is balanced when the injection pressure is equal to the set injection pressure.

A guide member 41 extends from the plunger 23 to the rear end thereof. The guide member 41 extends through the cover member 35 and has a guide passage formed in the cover member 35. 43 is slidable.

The guide member 41 has a stopper 45 to be described later.
(Notch) 47 is formed in which the plunger 23 is allowed to move by a predetermined range L when the stopper 45 is located in the groove 45. As described above, the movement within the predetermined range L is permitted, so that the volume variable mechanism 1
0 can have a damper function of reducing the pulsation in the pressure accumulating chamber 39.

The control mechanism 27 is provided on the lid member 35 and has a stopper 45 projecting from the guide passage 43 and an exciting portion 4 for pulling the stopper 45 from the guide passage 43.
9 and when the excitation unit 49 is energized,
The stopper 45 is retracted from the guide passage 43 by the electromagnetic force, and releases the engagement with the guide member 41.
The excitation of the control mechanism 27 is controlled by the control device 51 so that the excitation unit 49 is energized when, for example, the ignition key is started, and is energized during normal operation (at steady operation) or when the engine is stopped. Stop and degauss.
The stopper 45 is always urged by the return spring 52 so as to protrude into the guide passage 43. When the exciting portion 49 is energized, the stopper 45 is opposed to the urging force of the return spring 52. Is raised.

Further, in this embodiment, a position detecting mechanism 53 for detecting the position of the end 41a is provided on the end 41a side of the guide member 41.
3 detects the position of the end 41a, thereby detecting the position of the plunger 23, and thereby detecting the pressure in the common rail 9. That is, the position detection mechanism 53
Has a function as a pressure sensor. In the present embodiment, the position detection mechanism 53 is an operation transformer, and detects a current generated in the operation transformer in accordance with an amount by which the end of the guide member 41 enters the inside of the operation transformer. It is configured to detect the position of a part.

Next, the operation of the present embodiment will be described. During normal operation when the pressure in the common rail 9 is sufficiently high and at the moment when the engine is stopped, as shown in FIG. 3, the excitation unit 49 is not energized, and the stopper 45 applies the urging force of the return spring 52. As a result, it is in a state of protruding into the guide passage 43. Therefore, the stopper 45 is connected to the guide member 45.
In the groove 47. In this case, the groove 47 has a predetermined dimension L
And the plunger 23 is movable within the range of the dimension L. Further, since the coil spring 25 is set to the pressure in the common rail during normal operation, the stopper 45 is located substantially at the center of the groove 47 in balance with the pressure in the accumulator.

In the state shown in FIG. 3, if pulsation occurs in the fuel pressure in the common rail, the plunger 23 can move against the urging force of the coil spring 25, so that the volume variable mechanism 10 reduces the pulsation. Acts as a damper.

Further, the plunger 23 moves according to the pressure in the common rail 9 within the range of the dimension L. For example, if the pressure in the common rail 9 is smaller than the set pressure of the coil spring 25, the plunger 23 Room 2
9, and if the pressure in the common rail 9 is larger than the set pressure of the coil spring 25,
The plunger 23 moves downward so as to expand the volume chamber 29. Therefore, the guide member 4 extending from the plunger 23
By detecting the position of the first end 41a by the position detection mechanism 53, the pressure in the common rail 9 can be detected, and functions as a pressure sensor. Thus, by detecting the pressure in the common rail 9, the opening and closing of the valve of the injector 17 is controlled accordingly,
By controlling the injection pulse width and the like of the injector 17, the injection amount can be appropriately controlled. Alternatively, the discharge amount of the high-pressure pump 8 may be controlled by detecting the pressure in the common rail 9. As described above, by utilizing the pressure sensor function, feedback control is performed, and the discharge amount from the injector 17 can be easily controlled. Further, since it is not necessary to separately provide a pressure sensor on the common rail 9, the structure is simple and the manufacturing can be performed at low cost.

On the other hand, when the engine is stopped, the pressure in the common rail 9 decreases. Then, as shown in FIG. 4, the plunger 23 moves upward by being urged by the coil spring 23 and moves so as to reduce the inside of the volume chamber 29, but the stopper engages with the guide member 41 and holds it. The plunger 23 is prevented from further moving to the volume chamber 29 side.

At the start of the start of the engine, for example, when the control device 51 detects the start of the ignition key, the excitation unit 49 is energized, and the stopper 45 is pulled up against the return spring 52, and the stopper 45 is pulled out of the groove 47 of the guide member 41. The stopper 45 is pulled up. As a result, at the time of starting the engine, the pressure in the common rail 9 is sufficiently lower than the set pressure of the spring 25, so that the plunger 23 moves the volume chamber 29 in accordance with the urging force of the coil spring 25 as shown in FIG. Move in a decreasing direction. That is, the sum of the pressure accumulating chamber 39 and the volume chamber 29 in the common rail substantially becomes the volume of the pressure accumulating chamber, but the volume of the volume chamber 29 is reduced, and the substantial volume of the pressure accumulating chamber 39 at the time of engine start is reduced. Therefore, the fuel pressure in the accumulator 39 can be increased. Therefore, a high pressure in the accumulator 39 can be obtained when the engine is started. Moreover, the fuel circuit does not become complicated, and has a simple configuration.

Further, since the fuel pressure can be increased by directly acting on the pressure accumulating chamber 39 in the common rail at the time of starting the engine, the responsiveness at the time of starting the engine is good.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the invention. For example, in the above-described embodiment, a piston has been described as an example of a movable member. However, the present invention is not limited to this, and a similar effect can be obtained as long as the volume of a diaphragm, a bellows, or the like can be changed.

The same effect can be obtained by using a piezo (piezoelectric element) or a hydraulic pressure as the control means for operating the biasing member.

Furthermore, the position detecting device has been described using an operation transformer as an example. However, the present invention is not limited to this, and a Hall element,
The position may be detected by eddy current, laser, or the like.

[0037]

According to the first aspect of the present invention, when the engine is started, the movable member is urged to reduce the volume of the volume chamber, so that the fuel pressure of the accumulator can be increased. it can. Therefore, a high pressure in the accumulator can be obtained when the engine is started. In addition, the fuel circuit does not become complicated, and can have a simple configuration.

According to the second aspect of the present invention, by allowing the operating range of the movable member to be within a certain range, the volume variable mechanism performs a damper function, thereby reducing the pulsation of the accumulator. Further, since the stopper releasing means is provided, when the engine is started, the urging member can act on the movable member with a simple configuration by releasing the stopper.

According to the third aspect of the present invention, since the variable volume mechanism is provided on the common rail on which the fuel injection nozzle is mounted, the pressure in the common rail at the time of starting the engine can be directly increased, and the engine can be started. Good responsiveness at the time.

According to the fourth aspect of the present invention, the pressure in the accumulator can be detected by the position detecting mechanism detecting the position of the movable member. Therefore, the volume variable mechanism can be used as a pressure sensor.

[0041]

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a fuel injection device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a variable volume mechanism in a common rail.

FIG. 3 is a cross-sectional view showing the operation of the variable volume mechanism during normal operation or at the moment when the engine stops.

FIG. 4 is a cross-sectional view showing the operation of the volume variable mechanism when the engine stops.

FIG. 5 is a cross-sectional view showing the operation of the variable volume mechanism when the engine is started.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 fuel injection device 9 common rail (accumulation chamber) 10 variable capacity mechanism 21 cylinder (housing) 23 plunger (movable member) 25 coil spring (biasing member) 27 control means 29 volume chamber 45 stopper (stopper means) 49 exciting section (release) Mechanism) 53 Position detection mechanism

Claims (4)

[Claims] 1. A pressure accumulating type fuel injection device comprising a pressure accumulating chamber for accumulating fuel injected from a fuel injection nozzle to a combustion engine and a pump for supplying fuel to the accumulating chamber, wherein a volume chamber communicated with the accumulating chamber. A movable member that moves in the housing to change the volume of the volume chamber, an urging member that urges the movable member to reduce the volume of the volume chamber, and a urging member that moves the urging member when the engine is started. A pressure-accumulation type fuel injection device comprising a volume variable mechanism constituted by control means for operating. 2. The accumulator according to claim 1, wherein said control means includes a stopper means for limiting an operation range of the urging member, and a release mechanism for releasing the stopper means when the engine is started. Fuel injection device. 3. The accumulator fuel according to claim 1, wherein the accumulator is a common rail having a plurality of fuel injection nozzles, and the variable volume mechanism is provided on the common rail. Injection device. 4. The volume variable mechanism includes a position detection mechanism that detects a position of a movable member when an urging member is actuated.
The accumulator type fuel injection device according to claim 1, wherein the pressure of the accumulator is detected.