JPH0749010Y2 - Fuel injection valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a fuel injection valve, and more particularly to a fuel injection valve effective when applied to a high-power diesel engine.

[Prior art]

Fuel injection valves commonly used in diesel engines are
As shown in the figure, in the holder 1, a cylindrical spring retainer 2
It has a cylindrical spindle guide 3 fitted in the holder 1, a spindle 4 guided by the spindle guide 3, and a coil spring 5 arranged between the spindle 4 and the spring retainer 2. The valve portion 4a provided at the tip of the spindle 4 pressed by the coil spring 5 is configured to be seated on the valve seat formed at the tip of the spindle guide 3, and the upper portion of the holder 1 is closed by the presser metal 6, An atomizer 7 (nozzle) is attached to the bottom.

Fuel oil sent from a fuel injection pump (not shown) is supplied to the lower end of the spindle 4 from a supply port 8 opened in the connecting portion of the presser foot 6 through an oil circulation hole 9 opened in the center of the spring presser 2. The pressure of the fuel oil at this time raises the spindle 4 against the spring force of the coil spring 5 to slightly raise the valve portion 4a from the valve seat, and the atomizer 7 moves a predetermined amount into the cylinder. It is designed to inject fuel oil.

By the way, this fuel oil increases the efficiency of the internal combustion engine,
It is necessary to optimize the pressure and the timing of supply.
That is, recently, it has been attempted to increase the output of the internal combustion engine, and in this case, it is necessary to set the fuel oil at a high pressure corresponding to it, for example, the fuel injection pressure of 2,000 kg / cm ² or higher is adopted. ing.

In the fuel injection valve having the above structure, since a high pressure of fuel oil acts in the spindle 4 to generate a force for separating the spindle 4 from the valve seat, a large coil spring 5 commensurate with this force is required. There is a problem that the injection valve itself becomes large and the manufacturing cost of the fuel injection valve increases.

Further, as the coil spring 5 becomes larger and the weight of the movable part becomes heavier, the responsiveness of the spindle 4 deteriorates. As a result, the characteristics at the time of fuel spraying deteriorate and the seating surface of the valve portion 4a of the spindle 4 wears. There was a problem of increasing the size.

Further, in such a high-power engine, a low-load operation is often performed as necessary, but in this case, as described above, fuel injection using a large spring so as to cope with a high fuel pressure. In the valve, the minimum injection amount that can be injected is large, more fuel oil is supplied than necessary at a low engine load, and as a result, abnormal combustion occurs and the engine speed increases, so optimal operation cannot be performed. was there.

On the other hand, as related techniques, Japanese Patent Laid-Open No. 57-79256 and Japanese Utility Model Publication No.
No. 0-32379 has been proposed.

However, in the former, the control piston is connected to the needle valve, the control piston is pressed by the coil spring, and the fuel pressure is applied to the control piston to adjust the pressing force of the coil spring to adjust the fuel injection timing and injection period. It is configured to do.

However, in this device, since the effective area of the needle valve is extremely small, it is practically impossible to obtain a device that significantly adjusts the fuel injection pressure. Is not adjusted in accordance with the engine load to supply an optimum amount of fuel oil at a high pressure as high as possible to achieve effective operation of the engine.

In particular, since the control piston is pressed with fuel oil, it has extremely low compressibility compared to when it is pressed with air, and since the liquid that is the working fluid has a large mass, large pressure fluctuations occur due to the operation of the needle valve. Is induced in the fuel oil, resulting in unstable fuel injection.

In the latter, a piston is provided below a spring bearing of a primary adjusting pressure spring that presses a spindle, a secondary adjusting pressure spring is interposed between the spring bearing and the piston, and the piston is moved up and down by fluid pressure to make the secondary adjusting pressure spring move. The spring force of the next adjustment pressure spring is changed to change the fuel injection start to a variable pressure.

In the case of this device, when the fluid pressure is not applied to the piston, the force for pressing the spindle utilizes the elastic force of two springs in series. Therefore, the design of this spring must be designed to withstand the maximum fuel valve opening pressure, which makes the spring large, and it is extremely difficult to downsize the fuel injection valve. There's a problem.

[Purpose of device]

The present invention was made in order to solve the problems of the conventional device described above. The purpose of the present invention is to significantly reduce the weight of the movable part of the fuel injection valve and to use it as a working fluid. In particular, the use of air pressure is to improve the response operation of the spindle to improve the fuel injection characteristics and the durability of the valve seating surface.

Also, to provide a device that adjusts the valve opening pressure of the fuel injection valve according to the engine load to supply an optimum amount of fuel oil at a high pressure as high as possible, thereby enabling effective operation of the engine. is there. Another object is to provide a fuel injection valve suitable for a large engine.

[Outline of device]

The fuel injection valve 21a according to the present invention for achieving the above object
Is a cylindrical holder 1 having a hole 1a at the tip,
An atomizer 7 having a tip protruding from 1a, a spindle guide 3 that is fitted into the holder 1 and presses the back of the atomizer 7 with the tip, and an opening portion of the holder 1 is closed so that the spindle guide 3 A spring retainer 2 for pressing and fixing an end portion, and an end portion of this spring retainer 2 and a holder 1.
The presser foot 6 fitted and fixed to the end of the spring and the spring presser 2
A spindle 4 engaged with the small-diameter portion of the spindle 4 and a coil spring 5 for applying an elastic force to the spindle 4, and the spindle guide 3 has a thick portion having a guide hole 3a provided at a tip end thereof with a valve seat 3c, The spindle 4 has a cylinder portion 3a extended from the thick portion, and the spindle 4 has a cylindrical portion 4b guided by the guide hole 3a, a valve portion 4a provided at a tip of the cylindrical portion 4b, and the cylinder portion 4a. The spring retainer 2 has a piston portion 4c fitted in an inner surface of 3a in a sealed state, and the spring retainer 2 has a small diameter portion 2a for guiding the spindle 4 at a tip portion thereof, a portion for guiding the coil spring 5, and the cylinder portion 3a. An oil passage hole 9 which is formed of a portion that closes the opening and communicates with the center portion, and an end portion which is parallel to the oil passage hole 9 and whose end portion is opened in the air chamber 10 in which the coil spring 5 is housed. And an air communication hole 13 6, the supply port communicates with the oil through holes 9 8
And an air supply port 11 communicating with the air communication hole 13, and further, a spring force of the coil spring 5 with respect to the spindle 4, and an air pressure which is adjusted and supplied according to the load of the engine. Is added so that the fuel injection amount can be adjusted.

[Action]

The fuel injection valve 21a according to the present invention is provided with a piston portion 4c on a spindle 4 having a valve portion 4a at its tip, and the piston portion 4c is slidably contacted with the inside of the cylinder portion 3a to provide a small cylinder inside the fuel injection valve 21a. A device is formed so that air pressure acts on the piston portion 4c.

By adopting this air pressure, unlike liquids such as fuel oil, due to the extremely large compressibility and extremely small mass of gas,
Air pressure fluctuations due to the operation of the spindle 4 hardly occur, and stable fuel injection can be performed.

In this way, both the elastic force of the coil spring 5 and the air pressure act on the spindle 4 in addition, and since this air pressure is adjusted according to the load of the engine, the valve portion 4a is seated on the valve seat 3c. The pressure applied will be precisely controlled to the required value.

As a result, even in an engine that requires high-pressure injection, the smallest coil spring 5 can be adopted to prevent the increase in size.
Since the movable part is made lighter in weight and the responsiveness is good, the impact pressure on the valve part 4a at the time of sitting can be minimized, so that the durability of the seating surface of the valve part 4a can be improved.

In addition, the minimum fuel injection amount can be reduced by lowering the pressure of the air in the air chamber 10 during low-load operation of the engine, resulting in abnormal combustion and an increase in engine speed. There is no need for efficient driving.

[Embodiment] A fuel injection valve according to the present invention will be described with reference to FIGS. 1 to 4 below.
An example of 21a will be described. 1 to 3, the same reference numerals as those in FIG. 5 showing the conventional fuel injection valve indicate the same names.

In the figure, an atomizer 7 (nozzle) having a flange is inserted into a hole 1a opened at the tip of the tip of a cylindrical holder 1, and a spindle guide 3 is provided so as to press the atomizer 7. The spindle guide 3 has a thick front portion to form a guide hole 3b, and the other portion (rear portion).
Is thinly formed on the cylinder portion 3a, and a valve seat 3c is formed on the bottom portion of the guide hole 3b.

The spindle 4 has a thin cylindrical portion 4b having a valve portion 4a in the front portion, a piston portion 4c in the middle portion, and a thin cylindrical portion into which the coil spring 5 is fitted in the rear portion, and is formed in an annular groove formed on the outer periphery of the piston portion 4c. Sealing material 14 (O-ring) is fitted in.

A spring retainer 2 is fitted in the holder 1. The spring retainer 2 has an oil passage hole 9 in the center and a plurality of fluid communication holes 13 opened in parallel with the oil passage hole 9. The lower part has a reduced tubular part for guiding the coil spring 5, and the upper part has an enlarged part which presses the upper end part against the cylinder part 3a and fits with the inner surface of the upper part of the holder 1 via a sealing material. There is.

The spindle 4 is inserted in the guide hole 3b of the spindle guide 3.
The thin cylinder portion 4b at the tip of is inserted and the piston portion 4c is slidably and closely fitted in the cylinder portion 3a. The coil spring 5 is inserted between the rear surface of the piston portion 4c and the enlarged portion of the spring retainer 2 while the spring retainer 2 is inserted into the cylinder portion.
Close the openings between 3a and holder 1.

Then, the presser foot 6 is fitted on the upper part of the holder 1. The presser foot 6 is fitted on the upper part of the spring presser 2 at the central portion of the lower surface and communicates with the oil circulation hole 9 provided at the center of the spring presser 2. It has a screw portion that opens the supply port 8 and a flange portion that engages with the flange portion on the upper surface of the holder 1 and is fastened with a bolt 12. In addition, a drain hole 15 is provided on the top of the holder 1.
Is provided to discharge fluid such as air accumulated in the air chamber 10.

In addition, an air supply port 11 for air or the like is opened in this flange part, and the inside of the cylinder part 3c in which the coil spring 5 is housed through the air communication port 13 provided in the spring retainer 2 through this air supply port 11. The air is supplied to the air chamber 10 formed in the air chamber 10 so that the air pressure acts on the piston portion 4c forming the lower surface of the air chamber 10.

As described above, since one end of the coil spring 5 is supported by the piston portion 4c of the spindle 4 located in the air pressure 10,
The spindle 4 is configured so that the elastic force of the coil spring 5 and the total force of the air pressure acting on the piston portion 4c act to bring the valve portion 4a into contact with the valve seat 3c.

In the fuel injection valve 21a having the above-described structure, when compressed air is supplied from the air supply port 11 to the air chamber 10, this air pressure acts on the back surface of the piston portion 4c of the spindle 4 to press it, and the auxiliary coil spring 5 The piston part 4c
The air pressure acting on is added to press the spindle 4.

As shown in FIG. 4, the air supply port 11 of the fuel injection valve 21 (21a in FIG. 1 according to the present invention) is connected to a compressed air supply source via a line 23 having an air pressure control valve 22, for example. The air pressure control valve 22 is controlled by a load signal of an engine such as a governor.

Then, this load signal causes the pneumatic control valve 22
The pressure in the air chamber 10 is adjusted by controlling the air pressure, and this air pressure acts on the piston portion 4c of the spindle 4.

Therefore, the predetermined spring force of the coil spring 5 and the air pressure controlled according to the load of the engine acting on the piston portion 4c are added to the spindle 4, and the valve portion 4a is attached to the valve seat 3c provided on the spindle guide 3. The force for pressing is corrected according to the load of the engine.

As a result, the valve opening pressure of the fuel injection valve 21a of the present invention is controlled according to the load of the engine, and the optimum amount of fuel oil can be supplied to the load.

[Effect of device]

Since the fuel injection valve 21a of the present invention is configured as described above, the following effects can be obtained.

A piston portion 4c is provided on a spindle 4 having a valve portion 4a at its tip, and the piston portion 4a is slidably contacted with the inside of the cylinder portion 3a to form a small cylinder device inside the fuel injection valve 21a. Air pressure is applied.

By adopting this air pressure, unlike liquids such as fuel oil, the extremely great compressibility of gas can be achieved from an extremely small mass,
Air pressure fluctuations due to the operation of the spindle 4 hardly occur, and stable fuel injection can be performed.

In this way, both the elastic force of the coil spring 5 and the air pressure act on the spindle 4 in addition, and since this air pressure is adjusted according to the load of the engine, the valve portion 4a is seated on the valve seat 3c. The pressure applied will be precisely controlled to the required value.

As a result, even in an engine that requires high-pressure injection, the minimum coil spring 5 can be adopted to prevent an increase in size. Therefore, the weight of the moving part is reduced and the responsiveness is good.
Since the impact pressure at the time of seating that acts on 4a can be minimized, the durability of the seating surface of the valve portion 4a can be improved.

During low load operation of the engine, the minimum fuel injection amount can be reduced by lowering the air pressure within the air pressure 10.As a result, abnormal combustion does not occur and the engine speed does not rise You can measure your driving.

[Brief description of drawings]

1 to 4 show an embodiment of a fuel injection valve according to the present invention. FIG. 1 is a side sectional view of the fuel injection valve, and FIG.
The figure is a view taken along the line II-II in FIG. 1, and FIG. 3 is the line III-III in FIG.
FIG. 4 is an air control view, and FIG. 5 is a side sectional view of a conventional fuel injection valve. 1 ... Holder, 2 ... Spring retainer, 3 ... Spindle guide,
4 ... Spindle, 4a ... Valve part, 4b ... Valve seat, 4c ... Piston part, 5 ... Coil spring, 6 ... Presser metal object, 7 ... Atomizer (base), 8 ... Supply port, 9 ... Oil flow hole, 10 ... Air chamber , 11
... Air supply port, 12 ... Bolt, 13 ... Air communication hole, 14 ... Seal material, 15 ... Drain hole, 21, 21a ... Fuel injection valve, 22 ... Fluid pressure control valve (air pressure control valve), 23 ... Line.

Claims (1)

[Scope of utility model registration request] 1. A cylindrical holder (1) having a hole (1a) at a tip thereof, an atomizer (7) having a tip protruding from the hole (1a), and being fitted into the holder (1). A spindle guide (3) that presses the back of the atomizer (7) at its tip and a spring retainer (2) that closes the opening of the holder (1) and presses and fixes the end of the spindle guide (3). And a retainer (6) fitted and fixed to the end of the spring retainer (2) and the end of the holder (1), and a spindle (4) engaged with the small diameter portion of the spring retainer (2). And a coil spring (5) for applying an elastic force to the spindle (4), the spindle guide (3) has a thick portion having a guide hole (3a) provided with a valve seat (3c) at a tip end thereof, And a cylinder portion (3a) extended from this thick portion, (4), a cylindrical portion (4 guided by the guide hole (3a)
b) and a valve portion (4a) provided at the tip of this cylindrical portion (4b),
The spring retainer (2) has an inner surface of the cylinder portion (3a) and a piston portion (4c) fitted in a sealed state, and the spring retainer (2) has a small diameter portion (2a) for guiding the spindle (4) to a tip portion. An oil circulation hole (9) which is composed of a portion for guiding the coil spring (5) and a portion for closing the opening of the cylinder portion (3a), and further communicates with the central portion, and is parallel to the oil circulation hole (9). And an end portion thereof has an air communication hole (13) opening into an air chamber (10) accommodating the coil spring (5), and the presser foot (6) is the oil circulation hole. It has a supply port (8) communicating with (9) and an air supply port (11) communicating with the air communication hole (13), and further has a coil spring (5) for the spindle (4). The spring force and the air pressure supplied by adjusting the pressure according to the engine load are added to adjust the fuel injection pressure. Adjustable fuel injection valve.