JP2831150B2 - Fuel injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for a diesel engine.

[0002]

2. Description of the Related Art Referring to FIG. In the figure, reference numeral 01 denotes a pressurizing portion which is cylindrical. A pressure plunger 02 reciprocates in the pressure unit 01. Reference numeral 03 denotes a space partitioned by a pressurizing chamber and the pressurizing plunger 02 of the pressurizing section 01. Reference numeral 05 denotes an oil supply chamber provided outside the wall of the pressurizing section 01. Reference numeral 04 denotes an oil supply hole.
And the oil supply chamber 05 and the pressurized chamber 03 communicate with each other. Reference numeral 06 denotes a cutout groove provided on a side surface of the pressure plunger 02, communicates with an upper end surface of the pressure plunger 02 by an axial groove, and includes a groove inclined with respect to the axis of the pressure plunger 02. It is provided at a position where it meets the oil supply hole 04 at a position advanced by a predetermined length. Reference numeral 07 denotes a nozzle which is provided in front of the injector. Reference numeral 072 denotes a hole formed at the tip of the nozzle at the nozzle. Reference numeral 070 denotes a needle valve which fits inside the nozzle 07, and is always seated by a needle valve type valve to close the injection port 072. Reference numeral 08 denotes an injection valve spring which presses the needle valve 070 against a valve seat with a pressing spring. 071
A fuel reservoir is provided near the tip of the nozzle 07 and inside the valve seat of the fuel injection valve. A fuel oil passage 09 connects the pressurizing chamber 03 to the fuel reservoir 071. 01
Reference numeral 0 denotes a check valve which is located in the middle of the fuel oil passage 09 and stops the flow from the fuel reservoir 071 to the pressurizing chamber 03.

The operation of the conventional technique will be described. The refueling hole 04 is opened at a position where the pressure plunger 02 is sufficiently lowered, and fuel flows from the refueling chamber 05 to fill the pressure chamber 03. When the pressurizing plunger 02 advances, the fuel supply hole 04 is closed at a certain position on the side surface of the pressurizing plunger 02, and the fuel in the pressurizing chamber 03 is pushed by the pressurizing plunger 02 to flow into the fuel oil passage 09, and the check valve is provided. 010 is opened and flows into the fuel reservoir 071. Further, as the pressurizing plunger advances, the fuel is pushed and the fuel reservoir
This pressure acts on the conical surface at the tip of the needle valve 070 and pushes it in the axial direction. When this force exceeds the force of the injection valve spring 08, the needle valve 070 is pushed up and the fuel reservoir 071
The fuel flows through the injection port 072 and the fuel is injected from the injection port 072 to start fuel injection. When the pressurizing plunger 02 moves forward to a certain position, the notch groove 06 communicates with the oil supply hole 04. Therefore, the pressurizing chamber 03 communicates with the oil supply chamber 05 through the notch groove 06 and the oil supply hole 04, and the fuel in the pressurizing chamber 03 is discharged. The fuel flows into the fuel supply chamber 05, the pressure in the fuel reservoir 071 drops, and the force of the injection valve spring 08 wins, and the needle valve 070
Is closed, the space between the fuel reservoir 071 and the injection port 072 is cut off, and the injection ends. Since the notch groove 06 is provided to be inclined with respect to the axis of the pressure plunger 02, when the pressure plunger 02 is turned around the axis, the pressure plunger 02 reaches the oil supply hole 04.
And the amount of injected fuel is adjusted.

[0004]

The combustion of a diesel engine is spray combustion in which a mixture of fuel and air is formed by the kinetic energy of the spray of the injected fuel and burned. The larger the kinetic energy of the spray, that is, the injection pressure The higher the value, the higher the mixture formation speed and the higher the combustion performance. In particular, during the post-combustion period after the end of the injection at the end of the combustion, the mixture formation is governed only by the movement of the fuel spray injected at the latter stage of the injection.
It is known that the higher the injection pressure in the latter period, the more the combustion in the afterburning period is promoted, and the lower the fuel consumption is. In order to greatly increase the injection pressure in the latter period of the injection, it is effective to increase the speed of the latter stage of the pressurizing plunger, that is, to increase the cam lift speed in the latter period. At present, there is a limit in the rise of the market and it is not easy to realize.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the fuel consumption of a diesel engine by increasing the injection pressure particularly at the latter stage of the injection without significantly increasing the cam surface pressure due to the increase in the pressure in the pressurizing chamber, and promoting the afterburning at the latter stage of the combustion. It is to provide a fuel injection device that can be realized.

[0006]

According to the fuel injection device of the present invention, a fuel pressurizing section comprising a pressurizing chamber 3 and a pressurizing plunger 2 for pressurizing fuel oil in the pressurizing chamber is provided on a side wall of the pressurizing chamber. An oil supply hole 4 provided, a cutout groove 6 provided on a side surface of the pressure plunger and arranged to shut off and communicate the oil supply hole and the pressure chamber when the pressure plunger is moved in pressure; A fuel injection valve 70 that is in communication with the fuel oil passage 9 and that opens when the pressure in the fuel oil passage exceeds a certain value to inject fuel in the fuel oil passage into the cylinder; A fuel injection device for a diesel engine having a check valve 10 provided on the way to prevent fuel from flowing from the fuel injection valve to the pressurizing chamber; large-diameter and small-diameter pistons are formed integrally and are reciprocally movable. The pistons 22 and 23 and the large-diameter A pressure-increasing piston device 21 having a spring 24 biasing toward the tongue 22 side; a hydraulic oil notch groove 28 provided in the pressure plunger 2; and a hydraulic oil hole 25 provided in a side wall of the pressure chamber. A hydraulic oil passage 26 communicating the oil hole with the top of the large-diameter piston,
Particularly in the latter stage of fuel injection, the fuel pressurizing chamber 3 and the large-diameter piston 22
And a pressurized fuel outflow path composed of a small-diameter piston top and a pressurized fuel oil passage 27 communicating with the fuel oil passage 9 downstream of the check valve 10. It is characterized by becoming.

[0007]

When the pressurized plunger is retracted, the fuel oil is filled and the pressurized plunger moves forward, and when the injection starts, the hydraulic oil hole is closed on the side of the pressurized plunger, and the fuel pressurized in the pressurized chamber is All fuel is injected by pushing up the fuel injection valve through the fuel oil passage and the check valve. When the injection is nearing the end, the hydraulic oil notch groove on the side of the pressurizing plunger communicates with the hydraulic oil hole, and the pressurizing chamber communicates with the hydraulic oil hole. , Through the hydraulic oil hole and the hydraulic oil passage, is fed over the large-diameter piston of the pressure-intensifying piston device, and the pressure causes the pressure-intensifying piston device to move from the large-diameter piston side to the small-diameter piston side against the spring force. Can be At this time, on the small-diameter piston side, a pressure increasing action corresponding to the area ratio of the large-diameter piston and the small-diameter piston is performed, and high hydraulic pressure is generated. Also, the hydraulic pressure generated by the small-diameter piston due to the action of the check valve is not transmitted to the pressurizing chamber, so that the injection pressure in the latter period can be increased. At the end of the injection, the pressure in the pressurizing chamber is reduced by the communication of the oil supply hole by the notch groove as in the prior art, the movement of the piston is stopped, and the pressure-intensifying piston device is pushed back to the initial position by the spring force.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of an embodiment according to the present invention, FIG. 2 is a developed view of a side surface of a pressurizing plunger according to the present invention, and FIG. 3 is a characteristic diagram of a fuel injection device according to the present invention. 1 in the figure
Is a fuel pressurizing section, and 2 is a pressurizing plunger.
It fits inside. Reference numeral 3 denotes a pressurizing chamber, which is a space above the pressurizing plunger 2 of the fuel pressurizing section 1. Reference numeral 4 denotes an oil supply hole which penetrates the wall of the fuel pressurizing section 1. Reference numeral 5 denotes a fuel supply chamber, which is provided outside the fuel pressurizing section 1 and has the fuel supply hole 4 open. Reference numeral 6 denotes a cutout groove, which is formed on the side surface of the pressure plunger 2 and is provided at an angle to the axis of the plunger. The groove in the axial direction communicates with the end face of the pressure plunger 2. A nozzle 70 is provided at the tip of the fuel pressurizing section 1. Reference numeral 7 denotes a needle valve which is fitted in the nozzle by a small clearance fit. A fuel reservoir 71 is provided at the tip of the nozzle. Numeral 72 denotes a hole formed at the tip of the nozzle 70, which communicates with the fuel reservoir 71 through the valve seat of the fuel injection valve 7, and is always closed by the needle valve 7. A spring 8 presses the fuel injection valve 7 against a valve seat. Reference numeral 9 denotes a fuel oil passage which communicates the pressurizing chamber 3 with the fuel reservoir 71. A check valve 10 is provided in the fuel oil passage 9 in the middle of the fuel oil passage 9 and stops a flow from the fuel reservoir 71 to the pressurizing chamber 3. Reference numeral 21 denotes a pressure increasing piston device provided between the fuel pressurizing section 1 and the nozzle 70.

Reference numeral 30 denotes a pressure-intensifying piston device main body, in which large-diameter and small-diameter stepped cylindrical holes are provided, and the small-diameter hole has a bottom. A large-diameter piston 22 is fitted in a large-diameter cylindrical hole of the pressure-intensifying piston device 21. Reference numeral 23 denotes a small-diameter piston which fits in a small-diameter cylindrical hole of
And one body. Reference numeral 24 denotes a spring, which is provided between the small-diameter piston 23 and the bottom of the fitting hole. Reference numeral 25 denotes a hydraulic oil hole provided on the wall of the pressurizing chamber 3. Reference numeral 26 denotes a hydraulic oil passage.
Is communicated with the space above the large-diameter piston 22 of the pressure-intensifying piston device 21. Reference numeral 27 denotes a pressure-intensified fuel oil passage which divides a space below the small-diameter piston 23 of the pressure-intensification piston device 21 into the check valve 10 and the fuel reservoir 71 in the fuel oil passage 9.
It is connected to between. Reference numeral 28 denotes a hydraulic oil notch groove, which is provided on a side surface of the pressurizing plunger 2 which meets the hydraulic oil hole 25 at an inclination with respect to the axis at the same inclination as the notch groove 6, and an axial groove is provided on an end face of the pressurizing plunger 3. It is a communicating groove.

FIG. 2 shows the relationship between the notch groove and the hole by stopping the pressurizing plunger 2 and moving the fuel pressurizing section 1 relatively in the opposite direction. 4-A is the position of the oil supply hole 4 at which the oil supply hole 4 is closed, and particularly the compression is about to start, and 25A is the hydraulic oil hole 2 at that time.
5 position. Reference numeral 25B denotes a position of the hydraulic oil hole 25 when the hydraulic oil hole 25 is particularly trying to communicate with the hydraulic oil notch groove 28, and reference numeral 4B denotes a position of the oil supply hole 4 at that time. Reference numeral 4C denotes the position of the oil supply hole 4 when the oil supply hole 4 particularly communicates with the notch groove 6 to terminate the injection, and 25C denotes the hydraulic oil hole 2 at that time.
5 position.

The operation of the embodiment will be described. When the pressurizing plunger 2 is sufficiently retracted, the fuel supply hole 4 communicates with the notch groove 6 and the fuel fills the pressurizing chamber 3 through the notch groove 6. When the pressurizing plunger 2 advances and closes the oil supply hole 4, 4A in FIG.
, The extrusion of the fuel in the pressurized chamber 3 starts. The fuel passes through the fuel oil passage 9, opens the check valve 10 and passes through the fuel reservoir 71.
Flows into. The pressurizing plunger 2 moves further forward and the fuel reservoir 7
When the pressure in 1 rises, the needle valve 7 is pushed up against the force of the spring 8 to open the passage and squirt out of the spout 72. When the pressurizing plunger 2 further advances and reaches the position shown at 25B in FIG. 2, a part of the fuel extruded through the hydraulic oil notch groove 28 through the hydraulic oil hole 25 passes through the hydraulic oil passage 26 and the large-diameter piston 22
And moves the large-diameter piston 22 toward the small-diameter piston 23 against the force of the spring 8. At this time, on the small-diameter piston side, the pressure increasing action is performed according to the large-diameter piston and the small-diameter piston area ratio, and high-pressure oil is generated. The hydraulic pressure generated by the small-diameter piston 23 by the action of the check valve 10 is not transmitted to the pressurizing chamber 3.

As a result, the late injection pressure can be increased. At the end of the injection, the pressure in the pressurizing chamber 3 is reduced by the communication of the oil supply hole 4 by the notch groove 6 as shown in FIG.
When the side pressure drops, the piston stops moving and the spring 2
By the force of 4, the pressure-intensifying piston device 21 is pushed back to the initial position. Since the inclination of the notch groove 6 and that of the hydraulic oil notch groove 28 are equal, even if the effective injection process length is changed, the opening 2 of the hydraulic oil hole 25 is changed.
The process length of the pressurizing plunger 2 between 5B and the opening 4C of the oil supply hole 4 does not change. In FIG. 3, the vertical axis represents the injection pressure on the upper side, the fuel injection valve lift on the lower side, and the horizontal axis represents time. The solid line is the characteristic line of the prior art, and the broken line is the characteristic line of the embodiment.
A, B, and C are A, 4A, 4B, and 4C in FIG.
This is the time corresponding to B and C. In the embodiment, as shown by the broken line, a large increase in the injection pressure is obtained in the latter half of the injection. This embodiment is a unit type fuel injection device in which a fuel pressurizing unit and a fuel injection unit are integrated into one unit. However, the same configuration and operation can be obtained for a unit in which both are separated and fuel is pumped through an injection pipe. be able to.

[0013]

According to the present invention, communication between the pressurizing chamber and the booster piston device is performed by the working oil notch groove and the working oil hole at the latter stage of the injection, and the pressure of the pressurizing chamber is increased by the action of the booster piston device. It is possible to increase the injection pressure in the latter half of the injection without accompanying. As a result, the kinetic energy of the fuel spray at the latter stage of the injection is increased, the formation of the air-fuel mixture is promoted, and the afterburning is promoted. Therefore, the present invention can provide a fuel injection device that realizes a reduction in the fuel efficiency of a diesel engine by promoting post-burning of the latter half of the fuel without a large rise in the cam surface pressure due to a rise in the pressure in the pressurizing chamber.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment according to the present invention.

FIG. 2 is a development view of a side surface of the plunger according to the embodiment of the present invention.

FIG. 3 is a characteristic diagram of an embodiment according to the present invention.

FIG. 4 is a sectional view of a conventional injection device.

[Explanation of symbols]

 21 Pressure Boost Piston Device 22 Large Diameter Piston 23 Small Diameter Piston 24 Spring 25 Hydraulic Oil Hole 26 Hydraulic Oil Passage 27 Booster Fuel Oil Passage 28 Hydraulic Oil Notch Groove

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02M 45/00 F02M 45/12 F02M 57/02 310 F02M 57/02 330

Claims (1)

(57) [Claims] A fuel pressurizing section comprising a pressurizing chamber (3) and a pressurizing plunger (2) for pressurizing fuel oil in the pressurizing chamber;
An oil supply hole (4) provided on the side wall of the pressurizing chamber, and a notch groove (4) provided on the side surface of the pressurizing plunger and arranged to shut off and communicate the oiling hole and the pressurizing chamber when the pressurizing plunger moves. 6), and is communicated with the pressurizing chamber via a fuel oil passage (9). When the pressure in the fuel oil passage exceeds a certain value, the valve is opened to inject fuel in the fuel oil passage into the cylinder. In a fuel injection device for a diesel engine, comprising: a fuel injection valve (70); and a check valve (10) provided in the middle of the fuel oil passage to prevent fuel from flowing from the fuel injection valve to the pressurizing chamber; Large and small diameter pistons are integrally formed and have reciprocally movable pistons (22), (23) and a spring (24) for urging the small diameter piston (23) side toward the large diameter piston (22) side. Booster piston device (21)
A hydraulic oil notch groove (28) provided in the pressure plunger (2) and a hydraulic oil hole (2) provided in a side wall of the pressure chamber.
5) and a hydraulic oil passage (26) communicating the hydraulic oil hole with the top of the large-diameter piston. In particular, at the later stage of fuel injection, the fuel pressurizing chamber (3) and the top of the large-diameter piston (22). And a pressurized fuel outflow path constituted by a pressure-increasing fuel oil passage (27) communicating with the top of the small-diameter piston and a fuel oil passage (9) downstream of the check valve (10). A fuel injection device comprising: