JPS63150462A - Fuel injector - Google Patents

Abstract

PURPOSE:To achieve positive closing of a solenoid valve under a high injection pressure by providing a pressure chamber for holding pressure in the direction of closing a valve body, introducing fuel of an outlet passage into the pressure chamber and forming the bearing surface area of the valve body facing the pressure chamber larger than that facing the outlet passage. CONSTITUTION:If no electric signal is transmitted from a control circuit to an electromagnetic coil 27 of a solenoid valve 23, a valve body 25 is urged by a spring 26 to rest on a valve seat 24d and thereby to close an outlet passage 35. Therefore, fuel in a force feed pump chamber of a unit injector is pressurized, so that fuel is injected through a nozzle. Fuel fed under pressure through the outlet passage 35 is introduced through an inlet port 32 into a pressure chamber 31 and acts on the extreme end rear surface 25d of the valve body 25 to press the valve body 25 in the direction of closing the valve. The bearing surface area of the extreme end rear surface 25d is formed larger than that of the extreme end surface 25c so as to conform the fuel pressure in the outlet passage 35 with that in the pressure chamber 31.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection device for supplying fuel to a diesel engine or the like, and particularly to a unit injector.

[Conventional technology]

Conventionally, unit injectors pressurize fuel sent from a fuel supply pump in a pressure pump chamber using a pressure plunger that moves reciprocally in synchronization with engine operation, and then spray and supply this high-pressure fuel from an injection nozzle to a combustion chamber. do.

In addition, such a unit injector uses a solenoid valve to open and close a discharge passage whose one end opens into the pressure pump chamber, and controls the injection timing by the closing timing of the solenoid valve.
A configuration in which the injection amount is controlled by the valve opening timing is disclosed in US Pat. No. 4,129.253.

[Problem that the invention seeks to solve]

However, in this configuration, the valve body of the solenoid valve is structured to directly receive the injection pressure of high-pressure fuel as pressure in the valve opening direction, so the maximum pressure is 1500 kg/ctfl.
It is extremely difficult to maintain a solenoid valve closed while withstanding fuel pressures that reach up to 1,500 Hz, and to open the solenoid valve with a maximum response of 1500 Hz.

The present invention has been made in view of the above problems.
It is an object of the present invention to provide a highly reliable fuel injection device equipped with a compact electromagnetic valve that can maintain the valve closed even under high injection pressure.

[Means for solving problems]

In order to solve the above problems, the present invention takes the following technical measures.

That is, the fuel in the pressure pump chamber is pressurized to a high pressure by a pressure plunger driven by the engine, and this high-pressure fuel is injected from an injection nozzle, and a discharge passage whose one end opens into the pressure pump chamber is opened and closed by a solenoid valve for injection. In a fuel injection device that controls timing and injection amount, the electromagnetic valve includes a valve body whose one end side is attached to and leaves a valve seat provided in the middle of a discharge passage, and an elastic member that urges the valve body in a seating direction. , a pressure chamber that is formed on the other end of the valve body to maintain pressure in the direction of seating the valve body, an introduction passage that introduces fuel in the discharge passage into the pressure chamber, and a valve that generates magnetic force when energized. When the valve body is seated, the pressure receiving area on the two pressure chamber side is greater than the pressure receiving area on the discharge passage side.

〔Example〕

Next, one embodiment of the present invention will be described using FIGS. 1 and 2. FIG. 1 is a sectional view showing the configuration of this embodiment.
FIG. 2 is a partially enlarged sectional view showing the solenoid valve 23 of FIG. 1.

In FIG. 1, a unit injector 1 is inserted into an engine head 12, and a fuel gear rally 10 is set on the outer circumferential side of the unit injector 1 by O-rings lla and llb.

Then, fuel is taken out from the low-pressure fuel side by, for example, a feed pump driven by the engine, and fuel is supplied to the fuel gear gallery 10 by regulating the maximum pressure with a safety valve or the like.

The unit injector 1 includes a pressure cylinder 2, a nozzle holder 3, and a holder nut 4. A nozzle holder 3 is pressed against the lower surface of the pressure cylinder 2, and the pressure cylinder 2 and the nozzle holder 3 are integrally connected by a holder nut 4. Further, due to this connection, a fuel gear gallery 17 is set within the unit injector 1, and this fuel gear gallery 17 communicates with the fuel gear gallery 10 via the communication hole 16.

A pressure-feed plunger 5 is slidably inserted into the pressure-feed cylinder 2, and a pressure-feed pump chamber 6 is formed at one end of the pressure-feed plunger 5. In addition, the pressure-feeding plunger 5
The other end side is connected to a cam follower 7, and this cam follower 7 is moved downward in the figure, either directly or indirectly via a rocker arm or the like, by a cam that rotates in synchronization with an engine (not shown). A follower spring 8 is mounted between the pressure cylinder 2 and the cam follower 7, and the spring 8 causes the cam follower 7 and the pressure plunger 5 to return upward in the figure. Note that 9 is an open hole formed in the pressure-feeding cylinder 2, and serves to supply lubricating oil to the cam follower 7 and vent air.

An annular groove 5a is formed on the outer peripheral surface of the pressure-feeding plunger 5, and this annular groove 5a has a horizontal hole 5b drilled through the pressure-feeding plunger 5 in the radial direction and a vertical hole 5c drilled in the axial direction. It communicates with the pressure pump chamber 6 via.

The sliding surface of the pressure-feeding cylinder 2 with the pressure-feeding plunger 5 has a first
An annular groove 13 and a second annular groove 14 are formed, and the first annular groove 13 and the second annular groove 14 communicate with the fuel gear gallery 17 via a passage 15 . Furthermore, due to the communication between the annular groove 5a and the second annular groove 14, the fuel in the fuel gear gallery 17 is introduced into the pressure pump chamber 6 through the passage 15, the horizontal hole 5a, and the vertical hole 5b in this order.

The pressure pump chamber 6 is connected to the nozzle holder 3 through a passage 18,
It is connected to a needle valve (not shown) inside the nozzle 19. This needle valve is always biased in the closing direction by a spring 21 in a nozzle spring chamber 20 in the nozzle holder 3, and when the pressure in the pressure pump chamber 6 overcomes the set pressure of the spring 21, the needle valve opens. , fuel injection is performed from the nozzle 19.

One end 22 a of a cylinder-side discharge passage 22 , which constitutes a part of a discharge passage 40 , is open to the pressure pump chamber 6 , and the discharge passage 40 is opened and closed by a solenoid valve 23 .

The solenoid valve 23 is fixedly connected to the pressure-feeding cylinder 2, and a solenoid-valve-side fuel gear gallery 30 is set within the pressure-feeding cylinder 2 by this connection. This fuel gear 30 is connected to the passage 5.
0 to the first annular groove 13. That is, the electromagnetic valve-side fuel gear gallery 30 communicates with the fuel gear gallery 17, which is the low-pressure fuel side, via the passage 50, the first annular groove 13, and the passage 15 in this order.

Next, the solenoid valve 23 will be explained using FIG. 2. As shown in FIG. 2, the solenoid valve 23 includes a body 424a, a valve seat body 24b, a valve body 25, a spring 26,
It is equipped with an electromagnetic coil 27.

The body 24a is fixedly connected to the pressure feeding cylinder 2 integrally with the valve seat body 24b, and the pulp housing 24 is connected to the pulp housing 24 by the body 24a and the valve seat body 24b.
is configured.

Inside the housing 24, there is a communication passage 35 communicating with the other end 22b of the cylinder side discharge passage 22;
An annular groove 33 is formed continuously in the annular groove 33, and a communication hole 34 is formed to communicate the annular groove 33 with the electromagnetic valve side fuel gear gallery 30. The cylinder-side discharge passage 22, the communication passage 35, the annular groove 33, and the communication hole 34 constitute the discharge passage 40 of this embodiment. In addition, the communication passage 35 and the annular groove 3
A valve seat 24d is set at the connection portion with 3.

A valve body 25 is movably disposed within the housing 24 . The valve body 25 has a cylindrical shape with a bottom portion 25e on one end side, and a flap portion 25b is integrally provided on the other end side. Further, the valve body 25 is formed of a magnetic material. Then, the valve body 25 opens and closes the discharge passage 40 by coming into contact with and separating from the valve seat 24.

The inner circumferential surface 25f of the valve body 25 is slidable in a cylindrical protrusion 24c integrally provided on the housing 24 while maintaining oil tightness.
4b is kept oil-tight and can slide freely. The fuel leaking from this sliding surface to the other end of the valve body 25 is allowed to escape to the electromagnetic valve-side fuel gear gallery 30 through a passage (not shown), and the leaked fuel is removed from the flange 25b. A plurality of through holes 25g are formed so as not to cause sliding resistance.

A spring 26 is disposed at the other end of the valve body 25, and the spring 26 urges the valve body 25 in the seating direction (downward in the figure).

A pressure chamber 31 is formed between the inner circumferential surface 25b of the valve body 25 and the protrusion 24c, and the valve body 2 is disposed in the pressure chamber 31.
The fuel in the discharge passage 22 is introduced through the introduction hole 32 that is bored through the bottom 25e of the exhaust passage 22. The oil pressure of the fuel introduced into the pressure chamber 31 acts on the back surface 25d of the distal end surface 25c of the valve body 25, urging the valve body 25 in the valve closing direction.

Here, if the diameter of the introduction hole 18 is do, the seat diameter of the other end side opening 22b of the discharge passage 22 is dl, and the guide diameter inside the valve body 25 is d2, then the tip surface 2 of the valve body 25 when the valve is closed is
The fuel pressure receiving area 5c and the fuel pressure receiving area A1 on the rear surface 25d of the tip are shown as follows.

A0=□ Also, in this example, the guide diameter d2 is the seat diameter d
, and the guide diameter d2
and the seat diameter d, which is larger than the diameter d0 of the introduction hole 18 (
It is set. Therefore, the pressure receiving area A of the tip of the valve body 25 @ the back surface 25d is larger than the pressure receiving area A0 of the tip surface 25c.

The electromagnetic coil 27 generates magnetic force when energized,
The valve body 25 is moved against the spring 26 in the unseating direction (upward in the figure). This electromagnetic coil 27 is activated by a command signal from a control circuit (not shown) depending on the operating condition of the engine.

This control circuit receives signals from sensors that detect engine speed, accelerator pedal depression, engine temperature, and other engine operating conditions, calculates the opening/closing timing of the solenoid valve 23 based on these signals, and operates the solenoid valve 23. A command signal is given to the valve 23.

Next, the operation of this embodiment will be explained.

In the unit injector I configured as described above, fuel whose pressure is regulated to about 10 kg/d is supplied to the fuel gear gallery 10. Through communication between the annular groove 5b of the pressure-feeding plunger 5 and the second annular groove 14 of the pressure-feeding cylinder 2, the fuel in the fuel gear gallery 10 is transferred to the communication hole 16, the fuel gear gear 17, the passage 15, the second annular groove 14, and the horizontal hole. 5b,
[It is sent into the pressure pump chamber 6 through the holes 5c in order and is filled.

In this state, the cam follower 7 is pushed down by a cam (not shown) in response to the rotation of the engine against the push-up force of the follower spring 8, and the pressure-feeding plunger 5 is driven downward in the drawing.

When the plunger 5 is driven, the fuel in the pressure pump chamber 6 is pressurized to a high pressure, and this pressurized fuel is pumped into the cylinder side discharge passage 22 and the passage 18.

In this state, the solenoid valve 23 is
When an electric signal is sent to the electromagnetic coil 27,
The generated magnetic force moves the valve body 25 upward in the figure and separates it from the valve seat 24d, so that the pressure pump chamber 6
The pressurized fuel inside is discharged through the discharge passage 40 and the solenoid valve side fuel gear 3.
0, the fuel passes through the passage 50, the first annular groove 13, and the passage 15 in this order, and is released to the fuel gear assembly 17 on the low pressure side. Therefore, fuel injection is not performed.

On the other hand, when no electric signal is sent from the control circuit (not shown) to the electromagnetic coil 27 of the electromagnetic valve 23, the valve body 25 is seated on the valve seat 24d by the urging force of the spring 26, and the discharge passage 40 is closed. Therefore, the fuel in the pressure pump chamber 6 is further pressurized, and when the pressure in the pressure pump chamber 6 overcomes the set pressure of the spring 21, the nozzle 19
A needle valve (not shown) inside is opened, and fuel is injected from the nozzle 19. That is, the fuel injection timing is controlled by closing the electromagnetic valve 23.

In the compression stroke of the pressure-feeding plunger 5, the high fuel pressure in the pressure-feeding pump chamber 6 (maximum approximately 1500 kg/cffl
) acts on the valve body 25 of the solenoid valve 23 via the cylinder side discharge passage 22. That is, the fuel pumped through the cylinder-side discharge passage 22 acts on the distal end surface 25c of the valve body 25 in the seated state, and presses the valve body 25 in the valve opening direction. On the other hand, the fuel pumped through the discharge passage 22 is introduced into the pressure chamber 31 through the introduction hole 32. The fuel pressure in the pressure chamber 31 acts on the rear surface 25d of the tip of the valve body 25, and
Press in the valve closing direction.

Here, the pressure receiving area A of the rear surface 25d of the tip end of the valve body 25 is larger than the pressure receiving area A0 of the tip surface 25c, and the fuel pressure on the discharge passage 40 side and the fuel pressure in the pressure chamber 31 are equal. Therefore, the valve body 25 is pressed in the seating direction by the fuel pressure caused by this difference in pressure receiving area and the biasing force of the spring 26. Therefore, even if the fuel pressure in the pressure pump chamber 6 becomes high, the valve body 25 does not open (maintains its seat).In addition, in this embodiment, the pressure receiving area A1 of the rear end surface 25d
was set to be larger than the pressure receiving area A0 of the tip surface 25c, but the pressure receiving area A1 of the tip back surface 25d and the tip surface 25
Even if the pressure receiving area A0 of c is made equal, the valve body 2
7 is urged in the seating direction (downward in the figure) by the urging force of the spring 26, so that a predetermined effect can be obtained.

When the control circuit (not shown) sends a command signal to the electromagnetic coil 27 of the electromagnetic valve 23 after the injection amount necessary for the engine is obtained, the electromagnetic coil 27 generates a magnetic force, causing the valve body 25 to be attached to the spring 26. In order to move in the unseating direction (upward in the figure) against the force, the communication passage 35 is connected to the annular groove 3.
3, the pressurized fuel in the pressure pump chamber 6 is discharged through a discharge passage 40.
, solenoid valve side fuel gear rally 30, passage 50, first annular groove 1
3. The passages 15 are sequentially valved to allow the fuel to escape to the low-pressure side fuel gear gallery 17, and the fuel injection is completed and the injection amount is controlled.

Note that the solenoid valve 23 of this embodiment has a diameter of approximately 1,500 mm, similar to the conventional one.
Of course, it is possible to operate with high responsiveness on the order of Hz.

As described above, in this embodiment, the solenoid valve 23 has a pressure chamber 31 that holds pressure in the direction of closing the valve body 25, and the introduction hole 32 allows the fuel oil in the discharge passage 22 to flow into the pressure chamber. 31, and the pressure receiving area A of the valve body 25 on the pressure chamber 31 side when the valve is closed is larger than the pressure receiving area A0 on the discharge passage 22 side.

With such a simple configuration, the valve body 25 is connected to the discharge passage 22.
Even if high-pressure fuel acts through the solenoid valve 23, the valve closing pressure of the pressure chamber 31 and the biasing force of the spring 26 press the valve body in the seating direction, without reducing the high responsiveness of the solenoid valve 23. 25 valves can be maintained in a closed state.

Although the electromagnetic valve 23 of this embodiment has a protrusion 24c that slidably holds the valve body 25, the protrusion 24c is integrally formed with the body 24a.
As shown in FIG. 3, the protrusion 24C may be made into a separate body and fixed by a fixing member 34.

〔Effect of the invention〕

As explained above, according to the present invention, with a simple configuration,
It is possible to ensure that the solenoid valve remains closed in response to high injection pressure without reducing the high responsiveness of the solenoid valve, and the reliability of the fuel injection device is greatly improved.

[Brief explanation of the drawing]

1 and 2 relate to an embodiment of the present invention,
1 is a sectional view showing the configuration of this embodiment, FIG. 2 is a partially enlarged sectional view showing the solenoid valve 23 shown in FIG. 1, and FIG. 3 is a sectional view showing a modification of the solenoid valve 23 shown in FIG. 2. It is a diagram.

Claims (3)

[Claims] (1) Fuel in the pressure pump chamber is pressurized to high pressure by a pressure plunger driven by the engine, and the high-pressure fuel is injected from an injection nozzle, and a discharge passage whose one end opens into the pressure pump chamber is opened and closed by a solenoid valve. In a fuel injection device that controls injection timing and injection amount, the electromagnetic valve includes a valve body whose one end side is attached to and leaves a valve seat provided in the middle of the discharge passage, and an elastic member that biases the valve body in a seating direction. a pressure chamber formed on the other end side of the valve body to maintain pressure in a direction to seat the valve body, and an introduction passage for introducing fuel in the discharge passage into the pressure chamber;
an electromagnetic coil that generates a magnetic force when energized to cause the valve body to unseat, and a pressure-receiving area on the pressure chamber side when the valve body is seated is greater than or equal to the pressure-receiving area on the discharge passage side. Fuel injection device. (2) The fuel according to claim 1, wherein the valve body has a cylindrical shape with a bottom at one end, and the pressure chamber is formed on the inner peripheral side of the valve body. Injection device. (3) The fuel injection device according to claim 2, wherein the introduction passage is an introduction hole formed through the bottom of the valve body.