JPH0219648A - Fuel injection device - Google Patents

Abstract

PURPOSE:To prevent a control valve from doing its unstable operation as well as to make its leak also so as to be lessened by installing a decompressing mechanism which decompresses high pressure fuel out of a pressure accumulating pipeline and feeds the control valve with this fuel. CONSTITUTION:Fuel decompressed by a pressure reducing valve 55 is fed to a control valve 61. With this, the control valve 61 feeds a working chamber 31 with low pressure fuel whereby this working chamber 31 produces its working force in the valve closing direction of a nozzle needle valve 9 by this low pressure fuel, thus a fuel injection valve 1 is closed. Accordingly, the fuel being fed to the control valve 61 is of low pressure and there is little in a pressure variation, so that a solenoid 111 performs its stable operation despite a small type. In addition, an amount of leakage in the control valve 61 is also reduced owing to the low pressure fuel and, what is more, any loss of energy for driving a fuel pump 45 is also abatable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection device for injecting and supplying fuel to an internal combustion engine such as a diesel engine.

[Prior Art] Conventionally, as a fuel injection device for injecting high-pressure fuel used in diesel engines etc., for example, Japanese Patent Laid-Open No. 59
- Pressure accumulator piping (as disclosed in Publication No. 165858)
A fuel injection device with a common rail (common rail) has been proposed.

In this fuel injection device, high-pressure fuel is accumulated in the common rail by a pressure generation source, and this fuel pressure is used to control the opening and closing of the fuel injection valve and as injection pressure. That is,
The supply direction of this high-pressure fuel is switched by a control valve, and the opening and closing of the fuel injection valve is controlled. The structure of this control valve is, for example, as shown in FIG. This control valve is provided with a first valve body 105 that is slidably fitted into a sliding hole 103 in a control valve main body 101. The first valve body 105 is seated on the first valve seat 109 by the urging force of a spring 107. Also, by energizing the solenoid 111, the first valve body 105 slides and becomes the first valve! 109. Further, a supply hole 113 through which high-pressure fuel is supplied and communicated with the sliding hole 103 is bored, and a discharge hole 117 through which the sliding hole 103 and the fuel tank 115 are communicated, and the first valve seat 1
A first connection hole 119 is formed which communicates with the working chamber of the fuel injection valve via 09. On the other hand, a second valve body 123 is slidably fitted into a sliding hole 121 formed in the first valve body 105, and a second valve seat 125 on which the second valve body 123 is seated is pressed against pressure. It is formed in chamber 127. Further, a communication hole 129 that communicates the pressure chamber 127 and the supply hole 113 is bored in the second valve body 123, and a second connection hole 131 that communicates with the pressure chamber 127 via the second valve seat 125 is formed. has been done.

In this control valve, when the solenoid 111 is not excited, the first valve body 10 is moved by the biasing force of the spring 107.
5 is seated on the first valve seat 109 and blocks the first connection hole 119 and the discharge hole 117. In addition, the supply hole 113,
Due to the force exerted by the pressure of high-pressure fuel supplied to the pressure chamber 127 through the communication hole 129, the second valve body 123
It is separated from the valve seat 125 and moved until it hits the restriction part 133. As a result, the supply hole 113 is connected to the first
It is communicated with the 11 connection holes, high pressure fuel is supplied to the working chamber of the fuel injection valve, and fuel injection is stopped.

Also, when the solenoid 111 is energized, the spring 1
The first valve body 105 is pulled up against the biasing force of 07 and the acting force due to the pressure of high-pressure fuel according to the difference between the area of the large diameter portion 123a of the second valve body 123 and the area of the first valve seat 109. ,
The first valve body 105 is separated from the first valve seat 109. The first valve body 105 moves and the second valve body 123 moves to the second valve body 125.
sit down. When seated, the urging force of the spring 107 and the large diameter portion 123a and small diameter portion 12 of the second valve body 123
The first valve body 10 is moved by the suction force of the solenoid 111 against the acting force due to the pressure of high-pressure fuel according to the area difference between the first valve body 10 and 3b.
5 is held in the raised position. As a result, the supply hole 113 is blocked, the connection hole 119 and the discharge hole 117 are communicated with each other, and fuel is discharged from the working chamber of the fuel injection valve.
The nozzle needle is moved in the valve opening direction by the high pressure fuel supplied to the fuel injection valve, and fuel injection is performed.

[Problems to be Solved by the Invention] However, in such conventional systems, the common rail pressure corresponding to the injection pressure to a diesel engine or the like is extremely high, for example, 800 to 1500 atmospheres. Therefore, the acting force due to the pressure of high-pressure fuel according to the difference in the area of the large diameter portion 123a of the second valve body 123 and the area of the first valve 11m1090 described above, and the large diameter portion 123a of the second valve body 123.
The acting force due to the pressure of the high-pressure fuel according to the area difference between the small diameter portion 123b and the small diameter portion 123b is
It is a very powerful force. Moreover, this fuel pressure fluctuates greatly due to fuel injection, etc., and for example, 200 to 3
00 atm fluctuates. Therefore, in order to slide the first valve body 105 quickly and accurately, the solenoid 111 had to be made very large. Further, if the suction force of the solenoid 111 is not sufficient, the operation of the control valve tends to become unstable, and there is a problem in that appropriate control # of fuel injection may not be executed.

Further, since the first valve body 105 is expanded by the high pressure fuel supplied to the pressure chamber 127 due to the high pressure, a sufficient clearance between the first valve body 105 and the sliding hole 103 is provided in advance. Since such a clearance is provided and the pressure is high, there is a large amount of leakage from this clearance, and furthermore, due to leakage from the first valve seat 109, second valve seat 125, etc., the fuel pump is driven. There was also the problem of increased energy loss.

Therefore, the present invention aims to solve the above problems,
An object of the present invention is to provide a fuel injection device that achieves stable operation and reduces energy loss.

Moxibustion pulse two precepts [Means for solving the problem] In order to achieve the above object, the present invention has the following configuration as a means for solving the problem. That is, in a fuel injection device that generates an acting force in a valve opening direction on a nozzle needle by high pressure fuel supplied to a fuel injection valve from a pressure accumulation pipe that accumulates high pressure fuel, the fuel injection valve is opened and fuel is injected. A pressure reducing mechanism is provided to reduce the pressure of the high-pressure fuel supplied from the pressure accumulation pipe, and an operating chamber is formed in which the pressure of the reduced fuel generates an acting force in the valve closing direction on the nozzle needle that is greater than the acting force in the valve opening direction. , disposing a control valve that selectively communicates the working chamber with the pressure reducing mechanism or the low pressure side, and closing the fuel injection valve by communicating the pressure reducing mechanism and the working chamber with the control valve; This is the configuration of the fuel injection device that is used as a special effect.

[Operation] In the fuel injection device having the above configuration, the pressure reducing mechanism reduces the pressure of the high pressure fuel supplied from the pressure accumulation pipe, and the control valve communicates the working chamber and the pressure reducing mechanism to supply the reduced pressure fuel to the working chamber. Then, the reduced pressure of the fuel in the working chamber generates an acting force in the direction of closing the nozzle needle, thereby closing the fuel injection valve.

Therefore, the control valve is supplied with reduced pressure fuel.
The control valve does not operate unstable due to high-pressure hydraulic oil and has little leakage.

[Example code] Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a schematic diagram of a fuel injection device according to an embodiment of the present invention. In the figure, a valve body sliding hole 3 and a fuel reservoir chamber 5 are formed in a valve casing 2 of a fuel injection valve 1, and a nozzle hole 7 communicating with the fuel reservoir chamber 5 is formed at the tip. . A large diameter portion 11 of a nozzle needle 9 is slidably fitted into the valve body sliding hole 3 . This nozzle needle 9 is integrally formed with a connecting part 13 at the upper part of the large diameter part 11, and a small diameter part 15 and a valve body part 17 at the lower part, and the nozzle hole 7 is opened and closed by this valve body part 17.

A flange 19, a piston pin 21, and a piston 23 are integrally connected to the tip of the connecting portion 13 of the nozzle needle 9. The flange 19 and the housing 25
A spring 27 is interposed in the opening of the valve, and the biasing force of the spring 27 biases the nozzle 9 in the valve closing direction.

The piston 23 is slidably fitted into the cylinder 29, and forms a working chamber 31 surrounded by the piston 23 and the cylinder 29. The piston 23 is configured to be able to slide by supplying and discharging hydraulic oil to the working chamber 31. The piston 23 is moved so that the sum of the acting force generated on the piston 23 and the biasing force of the spring 27 due to the pressure of the hydraulic oil supplied to the working chamber 31 exceeds the acting force in the valve opening direction of the nozzle needle 9, which will be described later.
It is formed with a diameter of A plate valve 37 is provided in the upper part of the working chamber 31 and is biased by the biasing force of a spring 33 supported by the upper end surface of the piston 23 and has an orifice 35 .

On the other hand, as a fuel supply mechanism that supplies fuel to the fuel injection valve 1, there is a fuel pump 45 that pumps up fuel from a fuel tank 41 through a passage 43, and a fuel pump 45 that pumps up fuel from a fuel tank 41 through a passage 47. A pressure accumulation pipe (common rail) 49 that supplies the valve 1 is provided. A passage 51 is provided as a route for supplying fuel from the pressure accumulation pipe 49 to the fuel reservoir chamber 5. Further, a passage 53 is branched from the passage 51, and a pressure reducing valve 55 as a pressure reducing mechanism is interposed in the passage 53 and connected to a control valve 61. This control valve 61 has the same structure as the one shown in FIG. It is also possible to implement the method using the following methods. The passage 53 is connected to the supply hole 113 of the control valve 61.

Further, the first connection hole 119 of the control valve 61 is connected to the fuel injection valve 1
It is connected to a connection hole 57 that communicates with the working chamber 31 of the
The discharge hole 117 is connected to a fuel tank 59 as a low pressure side.

The pressure reducing valve 55 reduces the pressure of the high pressure fuel supplied through the passage 53 and supplies the same, for example, as shown in FIG. 2. The pressure reducing valve 55 has an inflow hole 65 connected to the passage 53 formed in the valve body 63, and the flow hole 65 and the small diameter hole 69 communicate with each other via the valve seat 67. Further, a large diameter hole 71 is formed adjacent to the small diameter hole 69, and the small diameter portion 75 of the piston 73 is inserted into the small diameter hole 69.
Large diameter portions 77 of pistons 73 are slidably fitted into the large diameter holes 71, respectively. Further, an outflow hole 79 is formed to be continuous with the large diameter hole 71.

Further, a spring 81 is provided in the large diameter hole 71 between the large diameter portion 77 of the piston 73 and the valve body 63.
The piston 73 is urged by the urging force of the spring 73 so that the valve body portion 83 at the tip of the small diameter portion 75 is seated on the valve seat 67.

A communication hole 85 connecting the outer periphery of the valve body portion 83 and the rear end of the large diameter portion 77 is bored in the piston 73 . Furthermore,
A chamber 87 surrounded by the valve body 63, the large diameter portion 77, and the small diameter portion 75 is communicated with the fuel tank 91 through a passage 89.

On the other hand, the solenoid 111 of the control valve 61 is connected to an electronic control device 93, which is composed of a well-known microcomputer and outputs a control signal to the control valve 61 according to a predetermined program. .

Next, the operation of the fuel injection device 11 of this embodiment will be explained.

The high-pressure fuel pressurized by the fuel pump 45 is accumulated in the pressure accumulation pipe 49 . The pressure of this accumulated high-pressure fuel is very high, for example, about 800 to 1500 atmospheres. This high pressure fuel is delivered to the fuel injection valve 1 via the passage 51.
The fuel is supplied to the fuel storage chamber 5. The pressure of the high-pressure fuel supplied to the fuel reservoir chamber 5 causes the nozzle needle 9 to move in the valve opening direction (first direction) according to the area difference between the large diameter section 11 and the small diameter section 15
Acting force (in the upper direction of the figure) is applied.

On the other hand, when the solenoid 111 of the control valve 61 is not energized, the high pressure fuel in the pressure accumulation pipe 49 is transferred to the pressure reducing valve 55.
The pressure is reduced by the pressure and supplied to the control valve 61 via the passage 53.

The pressure reduction by the pressure reducing valve 55 is caused by the pressure of the high pressure fuel.
The valve body portion 83 receives an acting force in the direction of separating from the valve seat 67, and the piston 73 slides against the biasing force of the spring 81. When the valve body part 83 separates from the valve seat 67, the flow hole 6
5 is communicated with the outflow hole 79 via the small diameter hole 69, the communication hole 85, and the large diameter hole 71. When high-pressure fuel is supplied to the outflow hole 79 and the pressure in the outflow hole 79 increases, this pressure acts on the large diameter portion 77 in the direction of seating the valve body portion 83 on the valve seat 67 . Therefore, the force acting according to the area of the small diameter portion 75 due to the pressure of the high pressure fuel in the flow hole 65, and the large diameter portion 77 due to the biasing force of the spring 81 and the pressure of the outflow hole 79.
The piston 77 stops at a position where the sum of the acting forces corresponding to the area of is balanced. When the pressure in the outflow hole 79 increases and the force acting on the large diameter portion 77 increases, the spring 81
When the sum of the urging force of
7 , the valve body 83 seats on the valve seat 67 and blocks the inflow hole 65 and the outflow hole 79 . Therefore, the pressure of the outflow hole 79 is determined by balancing the pressure of the high-pressure fuel from the inflow hole 65 with the biasing force of the spring 81 and the sum of the force acting on the large diameter portion 77 and the force acting on the small diameter portion 75. The pressure will be reduced. Moreover, even if the pressure within the pressure accumulation pipe 49 pulsates greatly, the pulsation width is also reduced by the pressure reduction, so the pulsation width of the reduced pressure is small.

The low-pressure fuel thus reduced in pressure is transferred to the outlet hole 79 and the passage 53.
, is supplied to the reading hole 57 of the fuel injection valve 1 via the supply hole 113, the communication hole 129, the second connection hole 131, and the first connection hole 119 of the control valve 61. When low pressure fuel is supplied to the connection hole 57, the plate valve 37 is pushed down and the low pressure fuel is supplied to the working chamber 31. Due to the pressure of this low-pressure fuel, a force corresponding to the area of the piston 23 acts on the piston 23.

Therefore, an acting force acts on the nozzle needle 9 in the valve closing direction via the piston pin 21 and the flange 19.

Therefore, the sum of the biasing force of the spring 27 and the acting force in the valve closing direction exceeds the acting force in the valve opening direction due to the high-pressure fuel supplied to the fuel reservoir chamber 5, and the fuel injection valve 1
Close the valve.

On the other hand, when the solenoid 111 of the control valve 61 is energized, the area of the large diameter portion 123a of the second valve body 123 and the first valve head 109 are
The acting force due to the pressure of the reduced low-pressure fuel according to the area difference between the large diameter portion 123a and the small diameter portion 12 of the ninth valve body 123
The first valve body 105 is pulled up and held against the force exerted by the reduced pressure of the low-pressure fuel according to the area difference between the first valve body 105 and the first valve body 105. When the first valve body 105 is pulled up, the supply hole 113
is blocked, and the first connection hole 119 and the discharge hole 117 are communicated with each other. Therefore, the working chamber 31 is connected to the fuel tank 59 via the orifice 35, the connection hole 57, and the control valve 61. Therefore, the force acting on the nozzle needle 9 in the valve opening direction due to the pressure of the high-pressure fuel supplied to the fuel reservoir chamber 5 resists the biasing force of the spring 27 and raises the nozzle needle 9 to open the valve. When the fuel injection valve 1 is opened, high-pressure fuel is injected and supplied from the nozzle hole 7. When the nozzle needle 9 rises, the fuel in the working chamber 31 is blocked by the orifice 35 and flows out into the fuel tank 59, so the piston 2
3 rises slowly. The nozzle needle 9 also rises via the piston pin 21 as the piston 23 slowly rises.

As mentioned above, the fuel injection device of this embodiment has a pressure reducing valve 55.
The fuel reduced in pressure by the control valve 61 is supplied to the control valve 61.
1 supplies low-pressure fuel to the working chamber 31, and the working chamber 31 uses the low-pressure fuel to generate an acting force in the direction of closing the nozzle needle 9, thereby closing the fuel injection valve 1.

Therefore, the control valve 61 does not operate unstablely due to the pressure of the fuel as hydraulic oil or its fluctuations. That is, low-pressure fuel is supplied to the control valve 61, and the pressure fluctuation of this low-pressure fuel is small, and the solenoid 1 of the control valve 61 generates an acting force that counteracts the acting force due to the pressure of this low-pressure fuel.
The control valve 6 may be small in size and can generate a sufficient force to counteract the force caused by this pressure.
1 has stable operation. In addition, since the pressure of the fuel supplied to the control valve 61 is low, the control valve 61
The amount of leakage within the fuel pump 41 is also reduced, and energy loss for driving the fuel pump 41 can also be reduced.

[Effects of the Invention] As detailed above, the fuel injection device of the present invention supplies fuel whose pressure has been reduced by the pressure reduction mechanism to the control valve, so that the control valve resists the acting force due to the pressure of this reduced fuel. Since a sufficient acting force can be generated, the switching operation can be performed reliably and the control valve can operate stably. In addition, the amount of leakage within the control valve is also reduced accordingly, resulting in the effect that energy loss for driving the fuel pump can also be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a fuel injection device as an embodiment of the present invention, FIG. 2 is a schematic sectional view of a pressure reducing valve of this embodiment, and FIG.
The figure is a schematic cross-sectional view of the control valve. 9... Nozzle needle 31... Working chamber 49...
・Pressure accumulation pipe 55...Pressure reducing valve 61...Control valve

Claims (1)

[Claims] In the fuel injection device, the fuel injection device generates an acting force in a valve opening direction on a nozzle needle by high pressure fuel supplied to the fuel injection valve from a pressure accumulation pipe that accumulates high pressure fuel, opens the fuel injection valve, and injects fuel. A pressure reducing mechanism is provided to reduce the pressure of high-pressure fuel supplied from the pressure accumulation pipe, and an operating chamber is formed in which the pressure of the reduced fuel generates a force in the valve closing direction on the nozzle needle that is greater than the force in the valve opening direction; A control valve that selectively communicates between the working chamber and the pressure reducing mechanism or the low pressure side is provided, and the control valve communicates the pressure reducing mechanism and the working chamber to close the fuel injection valve. Characteristic fuel injection device.