JP3844092B2 - Accumulated fuel injection system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure accumulation fuel injection device used for injecting fuel into each cylinder of an internal combustion engine, and more particularly to a configuration of an electromagnetic valve that controls fuel injection.
[0002]
[Prior art]
As one of systems for injecting fuel into an internal combustion engine such as a diesel engine, a pressure accumulation type fuel injection device is used. The accumulator fuel injection device includes an accumulator pipe (common rail) common to the fuel injectors installed in each cylinder of the engine, and the fuel pressure in the accumulator pipe is kept constant by a high-pressure pump, and is predetermined by the fuel injector. At this timing, fuel is injected into each cylinder.
[0003]
An example of this type of pressure accumulator type fuel injection device is disclosed in European Patent No. 0484804B1, which controls the fuel injection by controlling the back pressure of the needle valve that opens and closes the fuel injection hole with an electromagnetic valve. ing. In this device, a control chamber to which high-pressure fuel is supplied is provided on the back of a rod that moves up and down integrally with the needle valve, and the needle valve is urged downward by the pressure of the fuel accumulated in the control chamber. The injection hole is closed. A valve member 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 that is driven by suction by a solenoid. When the solenoid is energized, the control chamber and the drain passage communicate with each other, the pressure in the control chamber becomes low, the needle valve moves upward, the fuel injection hole is opened, and fuel is injected.
[0004]
[Problems to be solved by the invention]
By the way, in the conventional fuel injection device, the drain passage is provided so as to penetrate the central portion of the electromagnetic valve, and the drain fuel flowing out from the control chamber passes through the armature chamber and the spring chamber directly above the control chamber. , Led out from the upper end surface of the solenoid valve. However, this configuration has the advantage that the drain passage opens to the upper end surface of the solenoid valve, and therefore, it is easy to connect to the external drain. On the other hand, the drain fuel is supplied to the armature chamber downstream of the control chamber. There is a problem of directly hitting the armature housed in. Such a flow of drain fuel becomes a large resistance with respect to the moving direction of the armature when energization is stopped, and there is a possibility that the valve closing response of the valve member integrated with the armature is lowered.
[0005]
Furthermore, since the flow of drain fuel increases the internal pressure in the armature chamber which is relatively narrow and causes a large pressure pulsation, the valve member bounces and the valve closing characteristic is deteriorated. For this reason, there has been a problem that the fine adjustment amount accuracy and the controllability at the time of multiple injection are reduced, and the injection performance is reduced.
[0006]
Accordingly, an object of the present invention is to prevent the drain fuel from hitting the armature directly and to open and close between the control chamber and the drain passage in the fuel injection device having the drain passage opened to the upper end surface of the solenoid valve. In addition to improving the valve closing response of the valve member, the bounce of the valve member is reduced to improve the valve closing characteristics and improve the injection performance.
[0007]
[Means for Solving the Problems]
In the configuration of the first aspect of the present invention, the accumulator type fuel injection device includes a needle valve that slides in a hollow housing having a fuel injection hole provided at a tip thereof to open and close the fuel injection hole, and the needle valve integrated with the needle valve. A command piston sliding inside the housing is provided, and the needle valve is urged in the valve closing direction by the pressure of high-pressure fuel filled in a control chamber formed facing the rear end surface of the command piston. In the housing, an introduction path for introducing high-pressure fuel into the control chamber, and a lead-out path communicating with a drain passage for opening the control chamber at the rear end face of the housing and leading the high-pressure fuel to the outside are formed. An armature is disposed facing the control chamber side end surface of the solenoid housed in the rear end portion of the housing. When the solenoid is energized, the armature and the valve member provided integrally therewith are sucked and driven, and when the solenoid is energized, the valve member opens the drain passage and the outlet passage to open the control chamber. Reduce the pressure.
[0008]
The drain passage is disposed on the outer peripheral portion of the armature chamber in which the armature is accommodated, and a communication passage is provided for connecting the lead-out path to the drain passage without passing through the armature chamber. Further, the above-mentioned armature chamber and the drain passage communicates with only one passage, at least a portion of the passage, there as aperture of smaller diameter than the drain passage capable of maintaining the armature chamber oil-tight.
[0009]
In the above configuration, drain fuel from the control chamber bypasses the outer periphery of the armature chamber from the communication path and reaches the rear end surface of the housing. Also, passage to the armature chamber from the drain passage, since the least part was squeezing of smaller diameter than the drain passage, the drain fuel, most of flow through the drain passage of the larger diameter, to hit the armature There is nothing. Therefore, the operation of the armature can be prevented from being influenced by the flow of drain fuel, and the valve closing response of the valve member can be greatly improved.
[0010]
Further, in order to stabilize the operation of the armature, it is preferable that the armature chamber is oil-tight. However, in the above configuration, the armature chamber is made oil-tight through the squeezing which is a small diameter portion of the passage. It is possible to introduce a very small amount of fuel necessary for this. Therefore, the operation of the armature can be stabilized, the bounce of the valve member can be prevented, the valve closing characteristics and the metering accuracy can be greatly improved, and a fuel injection device with excellent injection performance can be realized.
[0011]
In the structure of Claim 2, the said channel | path is comprised by the communicating path | route which connects the said armature chamber and the said drain channel | paths, and the throttle formed in the middle. By appropriately adjusting the squeezing diameter, the flow rate of the fuel introduced into the control chamber can be adjusted, and a desired valve closing characteristic can be obtained.
[0012]
According to a third aspect of the present invention, the flow passage cross-sectional area of the lead-out path is made larger than that of the introduction path. As a result, when the valve member is opened, the drain fuel from the control chamber can be quickly led out to the lead-out passage having a larger flow-path cross-sectional area and discharged through the drain passage.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 3 is a diagram showing an overall configuration of an accumulator fuel injection device for an internal combustion engine. In the figure, the fuel in the fuel tank T is supplied to the high pressure pump P2 by the low pressure pump P1, pressurized to a high pressure, and sent to the common rail (high pressure accumulating piping) R. The common rail R includes a pressure sensor S that detects a common rail pressure, and the engine control computer ECU determines that a signal from the pressure sensor S is determined based on engine operating conditions such as an accelerator opening degree and an engine speed. Thus, the high pressure pump P2 is controlled.
[0014]
A plurality of fuel injection valves I provided corresponding to the cylinders of the engine E are connected to the common rail R, and injection control is performed by the engine control computer ECU. Excess fuel is returned from the fuel injection valve I to the fuel tank T via the drain D.
[0015]
Next, details of the fuel injection valve I will be described with reference to FIG. In the drawing, an injection valve I has a substantially cylindrical housing 1 and a nozzle body 2 fastened and fixed to a lower end of the housing 1 by a retaining nut 12 via a distance piece 11. A valve housing B1 of a later-described electromagnetic valve B for injection control is fixed.
[0016]
The nozzle body 2 is a cylindrical body having a fuel injection hole 21 at the tip, and a needle valve 3 for opening and closing the fuel injection hole 21 is slidably fitted in the cylinder. The upper end of the needle valve 3 is connected to the command piston 4 accommodated in the housing 1 via a spring holder 41, and a nozzle spring 42 is disposed on the outer periphery of the spring holder 41, and the needle valve 3. Is energized downward. A control chamber 5 into which high-pressure fuel is introduced is formed above the command piston 4, and the command piston 4 and the needle valve 3 integrated therewith are moved downward by the pressure of the high-pressure fuel in the control chamber 5. The fuel injection hole 21 at the tip of the nozzle body 2 is closed.
[0017]
In the nozzle body 2, an oil sump 31 is provided on the outer periphery of the needle valve 3, and high-pressure fuel from the common rail R shown in FIG. 3 flows from the inlet 13 provided on the side wall of the upper end of the housing 1 to a bar filter. 14 is always supplied through the fuel passage 15. The opening and closing of the needle valve 3 is controlled by the electromagnetic valve B. When the needle valve 3 moves upward by energizing the electromagnetic valve B, the fuel injection hole 21 is opened and high-pressure fuel is injected.
[0018]
FIG. 1 is an enlarged view of the electromagnetic valve B. The electromagnetic valve B has a cylindrical housing B1 fixed to the upper end opening of the housing 1 and a valve body 6 held in the lower half thereof. The high-pressure fuel introduced from the inlet 13 shown in FIG. 2 is simultaneously introduced into the electromagnetic valve B through the fuel passage 16 and through the in-orifice 51 provided in the valve body 6 as the introduction path. It is introduced into the chamber 5. Above the control chamber 5, an out orifice 52 serving as a lead-out path is provided, and an upper end opening thereof is closed by a valve member 7.
[0019]
The valve member 7 includes a rod 71 projecting from a lower end surface of an armature 9 arranged facing the lower side of the solenoid 8, and a ball 72 held in a hemispherical recess formed in the lower end portion of the rod 71. The ball 72 is seated on an annular seat portion 73 formed to protrude from the upper opening edge of the out orifice 52. The armature 9 is housed in the armature chamber 91 and is urged downward by a valve spring 82 held by a spring holder 81. A spacer 92 is disposed on the outer periphery of the armature 9, and the lift amount of the valve member 7 is adjusted by the height of the spacer 92.
[0020]
A drain chamber 61 is provided on the outer periphery of the lower end portion of the valve member 7, and when the armature 9 is suctioned upward by energizing the solenoid 8, the ball 72 is separated and the out orifice 52. Higher pressure fuel flows into the drain chamber 61. Here, the out-orifice 52 has a channel cross-sectional area larger than that of the in-orifice 51, and the annular drain chamber in which the fuel in the control chamber 5 serves as a communication path from the out-orifice 52 to the drain passage 62. 61 so as to flow quickly.
[0021]
An annular drain passage 62 is formed on the outer periphery of the electromagnetic valve B above the drain chamber 61 so as to extend along the inner peripheral wall of the valve body 6 and the housing B1, and its lower end opens to the upper end surface of the drain chamber 61. is doing. The drain passage 62 communicates with an external drain D (see FIG. 3) via a communication passage 63 provided in a cylindrical member B2 that closes the upper end opening of the housing B1.
[0022]
The armature chamber 91 communicates with the drain passage 62 through the communication passage 64, and a squeezed 65 is formed at the end of the communication passage 64 on the drain passage 62 side. Thus, part of the fuel flowing out from the drain chamber 61 can flow into the armature chamber 91 through the throttle 65 and the communication passage 64. Here, the diameter of the squeezing 65 only needs to be large enough to secure a small flow rate necessary to make the armature chamber 91 oil-tight. For example, when the diameter of the drain passage 62 is 2 to 3 mm, it is 0. About 5mm. As a result, only a small amount of required fuel can be introduced into the armature chamber 91 through the squeezing 65, and the pressure inside the armature chamber 91 can be prevented from being affected by the external pressure.
[0023]
Next, the operation of the fuel injection device having the above configuration will be described. By energizing the solenoid 8, when the armature 9 is suctioned upward against the spring 82, the rod 71 and the ball 72 move upward and are separated from the seat portion 73. Accordingly, the fuel in the control chamber 5 flows out from the out orifice 52 and is led out from the drain chamber 61 to the outside through the drain passage 62 and the communication passage 63.
[0024]
As a result, the pressure in the control chamber 5 is reduced, the force that biases the command piston 4 downward is weakened, and the high-pressure fuel that acts on the pressure receiving portion of the needle valve 3 pushes it upward. When winning, the needle valve 3 moves upward and fuel is injected from the fuel injection hole 21. When the energization to the solenoid 8 is stopped after a desired amount of fuel is injected for a predetermined time, the armature 9 sucked by the solenoid 8 is pushed downward by the valve spring 82, and the valve member 7 The ball 72 is seated on the seat portion 73 to block between the drain chamber 61 and the out orifice 52.
[0025]
Subsequently, when high pressure fuel is introduced from the in-orifice 51 and the pressure in the control chamber 5 rises, the command piston 4 is pushed down again, and the needle valve 3 pushes the fuel injection hole 21. Close and spray stops.
[0026]
As described above, according to the above configuration, the drain passage 62 is disposed on the outer periphery of the armature chamber 91, and the armature chamber 91 and the drain passage 62 are communicated with each other via the communication passage 64 having the squeezing 65. The fuel flowing out from the drain chamber 61 does not directly flow into the armature chamber 91 and hit the armature 9 directly. Therefore, when the energization of the solenoid 8 is stopped, the operation of the armature 9 is not affected by the flow of drain fuel, the operation is stabilized, and the valve closing response of the valve member 7 is improved.
[0027]
If the inside of the armature chamber 91 is not oil-tight, on the contrary, a larger bounce may occur when the valve member 7 is operated. In the present invention, however, the armature chamber 91 and the drain passage are provided. 62 is communicated via the communication passage 64 having the squeezing 65, so that part of the fuel flowing through the drain passage 62 can be introduced into the armature chamber 91. At this time, the air inside the armature chamber 91 is discharged to the upper communication path 63 through a minute gap formed by the spring holder 81 and the solenoid 8 above the armature chamber 91. Here, the gap between the spring holder 81 and the solenoid 8 is used. However, a passage that communicates the upper portion of the armature chamber 91 and the communication passage 63 may be provided, and a discharge may be provided in the middle of the passage.
[0028]
FIG. 4 (a) shows the behavior of the valve lift of the valve member that opens and closes between the outlet passage of the control chamber and the drain passage in the fuel injection device having the conventional structure in which the drain fuel derived from the control chamber directly flows into the armature chamber. FIG. As shown in the figure, in the conventional configuration, when the valve member is closed, the fuel directly hits the armature, resulting in a large resistance in the valve member closing direction, and the valve closing speed (inclination on the lower side of the valve lift) ) Is slow. Furthermore, since the armature vibrates due to a large pressure pulsation generated in the armature chamber, a large bounce occurs after the valve member is seated. This occurs because the amount of drain fuel flowing out of the seat changes due to armature vibration, and the change in common rail pressure causes the injection pulse width to change to change the injection amount. Therefore, the 2-Q characteristic (characteristic of the injection amount with respect to the injection pulse width) is lowered, and the metering accuracy is deteriorated.
[0029]
On the other hand, FIG. 4B is a diagram showing the behavior of the valve lift of the valve member 7 with respect to the same control pulse in the fuel injection device of the present invention shown in FIGS. As can be seen from the drawing, in the structure of the present invention, the drain fuel does not hit the armature 9 directly, so that the valve closing speed of the valve member 7 is increased. Further, the pressure inside the armature chamber 91 is also communicated with the drain passage 62 through the throttle 65, so that it is hardly affected by the outside and pressure pulsation does not occur, so there is almost no bounce. .
[0030]
As described above, according to the present invention, the valve closing response of the electromagnetic valve B for injection control can be improved, the valve closing characteristic can be greatly improved, the metering accuracy can be improved, and the highly accurate injection amount control can be performed. Is possible.
[0031]
In the above embodiment, the armature chamber 91 and the drain passage 62 are communicated with each other by the communication passage 94 and the squeezing 65. However, the passage may be communicated with a passage having a constant diameter smaller than the drain passage 62. Good. Further, the position of the squeezing 65 may be formed in the middle of the communication path 94. Thus, the same effect can be obtained if at least part of the passage to the armature chamber 91 has a smaller diameter than the drain passage 62.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of an electromagnetic valve of a fuel injection device showing a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a main part of the fuel injection device according to the first embodiment.
FIG. 3 is an overall schematic diagram of a fuel injection device according to the first embodiment.
4A is a view showing the behavior of a valve lift in the fuel injection device of the present invention, and FIG. 4B is a view showing the behavior of the valve lift in the conventional fuel injection device.
[Explanation of symbols]
B Solenoid valve B1 Tubular housing (housing)
I Fuel injection valve 1 Tubular housing (housing)
2 Nozzle body (housing)
21 Fuel injection hole 3 Needle valve 31 Fuel reservoir 4 Command piston 5 Control chamber 51 In-orifice (introduction path)
52 Out orifice (leading path)
6 Valve body 61 Drain chamber (communication path)
62 Drain passage 63 Communication passage 64 Communication passage (passage)
65 Squeezing (passage)
7 Valve member 71 Rod 72 Ball 73 Seat portion 8 Solenoid 81 Spring holder 82 Valve spring 9 Armature 91 Armature chamber 92 Spacer

Claims (3)

A needle valve that slides in a hollow housing provided with a fuel injection hole at the tip to open and close the fuel injection hole, a command piston that slides in the housing integrally with the needle valve, and a rear end surface of the command piston A control chamber that urges the needle valve in the valve closing direction by the pressure of the high-pressure fuel that faces and fills the inside, an introduction path for introducing the high-pressure fuel into the control chamber, and the control chamber in the housing A lead-out path that opens at the rear end face and communicates with a drain passage for leading high-pressure fuel to the outside, a solenoid that is housed in the rear end of the housing, and is opposed to the end face on the control chamber side of the solenoid and is sucked by the solenoid The armature to be driven and the pressure in the control chamber by opening the drain passage and the outlet passage when the solenoid is energized and energized to the solenoid. In the accumulator type fuel injection device comprising a valve member for lowering, the drain passage is disposed in an outer peripheral portion of an armature chamber in which the armature is accommodated, and the lead-out path is connected to the drain passage without passing through the armature chamber. The communicating passage is provided, and the armature chamber and the drain passage are communicated with only one passage, and at least a part of the passage is squeezed with a diameter smaller than that of the drain passage capable of maintaining the armature chamber oil-tight. An accumulator fuel injection device characterized by that.   2. The accumulator fuel injection apparatus according to claim 1, wherein the passage is composed of a communication passage communicating the armature chamber and the drain passage and a throttle formed in the middle thereof.   The pressure accumulation type fuel injection device according to claim 1 or 2, wherein a flow path cross-sectional area of the lead-out path is larger than a flow path cross-sectional area of the introduction path.

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