JPH04301177A - Fuel injection device - Google Patents

Abstract

PURPOSE:To improve the injection pressure of the later stage of injection without pressure rise of a pressurization chamber to be caused by the work of an intensifying piston device to accelerate later combustion, and reduce the cost by communicating a pressurization chamber and an intensifying piston device through a notch channel and an oil hole in the later stage of fuel injection. CONSTITUTION:Under the condition that a pressure plunger 2 is treated sufficiently, an oil supply hole 4 is communicated with a notch channel 6 to supply the fuel to a pressurized chamber 3. Next, when the pressure plunger 2 is made to progress to close the oil supply hole 4, the fuel of the pressurized chamber 3 is pushed out to be flown into a fuel reservoir 71 through a fuel oil passage 9 and a check valve 10. When the pressure plunger 2 is made to progress furthermore to raise the pressure inside of the fuel reservoir 71, a needle valve 7 is pushed up to inject the fuel from an injection hole 72. Next, an operating oil notch channel 28 is communicated with an operating oil hole 25, and a part of the fuel arrives a chamber above a large diameter piston 22 through an operating oil passage 26, and this piston 22 is moved to a small diameter piston 23 side to increase the pressure of the fuel, and high pressure oil is generated to improve later injection pressure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a fuel injection system for a diesel engine.

0002

2. Description of the Related Art A conventional technique will be explained with reference to FIG. In the figure, 01 is a pressurizing part which is cylindrical. 02 is a pressurizing plunger that reciprocates within the pressurizing section 01. 03 is a space partitioned off by a pressurizing chamber and the pressurizing plunger 02 of the pressurizing section 01. Reference numeral 05 denotes an oil supply chamber, which is provided outside the wall of the pressurizing section 01. 04 is the oil supply hole and the pressurizing part 01
The oil supply chamber 05 and the pressurization chamber 03 are communicated through the wall thereof. Reference numeral 06 denotes a notched groove provided on the side surface of the pressure plunger 02, which communicates with the upper end surface of the pressure plunger 02 through an axial groove, and is inclined to the axis of the pressure plunger 02 so that the pressure plunger 02 It is provided at a position where it meets the oil supply hole 04 at a position advanced by a length. 07 is a nozzle provided at the tip of the injector. 072 is a hole made at the tip of the nozzle. A needle valve 070 is fitted into the nozzle 07 and is always seated to close the nozzle 072. 08 is an injection valve spring that presses the needle valve 070 against the valve seat. 071
is a fuel reservoir provided near the tip of the nozzle 07 and inside the valve seat of the fuel injection valve. A fuel oil passage 09 communicates the pressurized chamber 03 with 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.

[0003] The operation of the conventional technology will be explained. When the pressurizing plunger 02 is sufficiently lowered, the fuel hole 04 opens, and fuel flows from the fuel chamber 05 to fill the pressurizing chamber 03. When the pressurizing plunger 02 moves forward, the oil supply hole 04 is closed on the side of the pressurizing plunger 02 at a certain position, and the fuel in the pressurizing chamber 03 is pushed by the pressurizing plunger 02 and flows into the fuel oil passage 09, and the check valve 010 and flows into the fuel reservoir 071. Further, as the pressurizing plunger moves forward, the fuel is pushed to the fuel reservoir 071.
The pressure increases and 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 overcomes the force of the injection valve spring 08, the needle valve 070 is pushed up and the fuel reservoir 071
The fuel is ejected from the nozzle 072 and fuel injection begins. When the pressurizing plunger 02 advances to a certain point, the notch groove 06 communicates with the oil supply hole 04, so the pressurizing chamber 03 communicates with the oil supply chamber 05 via the notch groove 06 and the oil supply hole 04, and the fuel in the pressurizing chamber 03 is The fuel flows to the fuel supply chamber 05, the pressure in the fuel reservoir 071 decreases, the force of the injection valve spring 08 overcomes, and the needle valve 070
is closed, the gap between the fuel reservoir 071 and the nozzle 072 is cut off, and the injection ends. The notch groove 06 is provided at an angle to the axis of the pressurizing plunger 02, so when the pressurizing plunger 02 is rotated around the axis, the pressurizing plunger 02 will move until it reaches the oil supply hole 04.
The amount of fuel injected is adjusted by changing the length of advance.

0004

[Problem to be Solved by the Invention] Combustion in a diesel engine is a spray combustion in which a mixture of fuel and air is formed and combusted by the kinetic energy of the spray of injected fuel, and the greater the kinetic energy of the spray, the higher the injection pressure. The higher the value, the faster the mixture formation rate and the better the combustion performance. Especially during the afterburning period after the end of injection in the latter half of combustion, the mixture formation is controlled only by the movement of the fuel spray injected in the latter half of injection.
It is known that the higher the injection pressure in the latter stage, the more the combustion during the afterburning period is promoted, and the more fuel efficiency is reduced. In order to greatly increase the injection pressure in the latter half of injection, it is effective to increase the speed of the pressurizing plunger in the latter half, that is, to increase the cam lift speed in the latter half. At present, it is not easy to realize this because there is a limit to how much it can increase.

An object of the present invention is to increase the injection pressure especially in the late stage of injection without causing a large increase in the cam surface pressure due to the pressure increase in the pressurizing chamber, and to reduce the fuel consumption of a diesel engine by promoting afterburning in the late stage of combustion. The object of the present invention is to provide a fuel injection device that achieves this goal.

[0006]

[Means for Solving the Problems] The fuel injection device of the present invention includes a fuel pressurizing section consisting of a pressurizing plunger that pressurizes fuel oil and a pressurizing chamber, an oil supply hole provided in the wall of the pressurizing chamber, and a pressurizing chamber. There is a cutout groove on the side of the plunger that is arranged to block and communicate the refueling hole and the pressurizing chamber when the pressurizing plunger moves under pressure. A diesel engine having a fuel injection valve configured to have a fuel injection valve, a fuel passage communicating between a pressurizing chamber and the fuel injection valve, and a check valve provided in the middle of the fuel passage to stop the flow from the fuel injection valve to the pressurizing chamber. In the fuel injection system of the engine;
A pressure booster piston device that has a reciprocating piston that is made up of large and small diameter pistons, and a spring that biases from the small diameter piston side to the large diameter piston side; A hydraulic oil hole provided in the side wall of the pressurizing chamber. and; A pressure increasing fuel oil passage that opens between the check valve and the fuel injection valve in the middle of the fuel oil passage and communicates with the small diameter piston; and; A pressure increasing fuel oil passage that is provided in the pressurizing plunger and that opens between the check valve and the fuel injection valve in the middle of the fuel oil passage; After blocking the oil supply hole,
It is characterized by having a hydraulic oil notch groove formed so that the hydraulic oil hole and the pressurizing chamber are communicated with each other immediately before the oil supply hole and the pressurizing chamber are communicated with the notch groove again.

[0007]

[Operation] When the pressurizing plunger retreats, it is filled with fuel oil, and when the pressurizing plunger moves forward and starts injection, the hydraulic oil hole is closed by the side of the pressurizing plunger, and the fuel pressurized in the pressurizing chamber is All the fuel passes through the fuel oil passage and check valve, and is injected by pushing up the fuel injection valve. When the injection approaches 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, and as a result, a part of the fuel in the pressurizing chamber flows into the hydraulic oil notch groove 28. , the hydraulic oil hole, and the hydraulic oil passage onto the large-diameter piston of the pressure booster piston device, and the pressure causes the pressure booster piston device to move from the large-diameter piston side to the small-diameter piston side against the spring force. It will be done. 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 oil pressure is generated. Further, due to the action of the check valve, the hydraulic pressure generated in the small diameter piston is not transmitted to the pressurizing chamber, and as a result, the injection pressure in the latter stage can be increased. At the end of injection, the pressure in the pressurizing chamber is reduced due to the communication of the oil supply hole by the notched groove as in the conventional system, the movement of the piston is stopped, and the pressure booster piston device is pushed back to the initial position by the spring force.

[0008]

[Embodiment] An embodiment of the present invention will be explained with reference to FIGS. 1 to 3. FIG. 1 is a cross-sectional view of an embodiment of 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 the fuel injection device according to the present invention. In the figure 1
is a fuel pressurizing part, 2 is a pressurizing plunger, and 2 is a pressurizing plunger.
It is fitted 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 a fuel 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 therein. Reference numeral 6 denotes a notched groove, which is provided on the side surface of the pressure plunger 2 at an angle to the axis of the plunger, and communicates with the end surface of the pressure plunger 2 through an axial groove. A nozzle 70 is provided at the tip of the fuel pressurizing section 1. Reference numeral 7 denotes a needle valve which is fitted into the nozzle with a narrow clearance fit. A fuel reservoir 71 is provided at the tip of the nozzle. Reference numeral 72 denotes an injection port, which is a hole drilled 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 the valve seat. A fuel oil passage 9 communicates the pressurized chamber 3 with the fuel reservoir 71. A check valve 10 is provided in the middle of the fuel oil passage 9, and is a valve that stops the flow from the fuel reservoir 71 side to the pressurization chamber 3 side. Reference numeral 21 denotes a pressure boosting piston device, which is provided between the fuel pressurizing section 1 and the nozzle 70.

Reference numeral 30 denotes the main body of the pressure booster piston device, which is provided with stepped cylindrical holes of large diameter and small diameter, and the small diameter hole has a bottom. A large diameter piston 22 is fitted into a large diameter cylindrical hole of the pressure increasing piston device 21. 23 is a small-diameter piston that fits into a small-diameter cylindrical hole of the pressure booster piston device 21, and is connected to the large-diameter piston 22.
It has become one body. 24 is a spring and is provided between the small diameter piston 23 and the bottom of the hole into which it fits. Reference numeral 25 denotes a hydraulic oil hole, which is a hole provided in the wall of the pressurizing chamber 3. 26 is a hydraulic oil passage and the hydraulic oil hole 25
is communicated with the space above the large diameter piston 22 of the pressure increasing piston device 21. Reference numeral 27 denotes a pressure boosting fuel oil passage which connects the space under the small diameter piston 23 of the pressure boosting piston device 21 to the check valve 10 in the middle of the fuel oil passage 9 and the fuel reservoir 71.
It communicates between. Reference numeral 28 denotes a hydraulic oil notched groove, which is provided on the side surface of the pressurizing plunger 2 that meets the hydraulic oil hole 25 at an angle equal to the notch groove 6 with respect to the axis, and is an axial groove provided on the end face of the pressurizing plunger 3. It is a groove that leads.

FIG. 2 shows the relationship between the notch groove and the hole when the pressurizing plunger 2 is stopped and the fuel pressurizing part 1 is relatively moved in the opposite direction. 4-A is the position of the oil supply hole 4 where the oil supply hole 4 is closed and compression is about to start, and 25A is the hydraulic oil hole 2 at that time.
This is position 5. 25B is the position of the hydraulic oil hole 25 when the hydraulic oil hole 25 is about to communicate with the hydraulic oil notch 28, and 4B is the position of the oil supply hole 4 at that time. 4C is the position of the oil supply hole 4 when the oil supply hole 4 particularly passes through the notch groove 6 and the injection is about to end, and 25C is the position of the hydraulic oil hole 2 at that time.
This is position 5.

[0011] The operation of the embodiment will be explained. When the pressurizing plunger 2 is sufficiently retreated, the fuel supply hole 4 communicates with the notched groove 6, and the pressurizing chamber 3 is filled with fuel through the notched groove 6. When the pressurizing plunger 2 moves forward and closes the oil supply hole 4, 4A in FIG.
The fuel in the pressurizing chamber 3 begins to be pushed out. 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 inside 1 rises, the needle valve 7 is pushed up against the force of the spring 8, opening the passage and ejecting water from the nozzle 72. When the pressurizing plunger 2 advances further and reaches the position shown at 25B in FIG.
The large diameter piston 22 is moved toward the small diameter piston 23 against the force of the spring 8. At this time, on the small-diameter piston side, a pressure increasing action is not performed in accordance with the area ratio of the large-diameter piston and the small-diameter piston, and high-pressure oil is generated. Further, due to the action of the check valve 10, the hydraulic pressure generated in the small diameter piston 23 is not transmitted to the pressurizing chamber 3.

As a result, the latter injection pressure can be increased. At the end of injection, the pressure in the pressurizing chamber 3 decreases due to the communication of the oil supply hole 4 by the notch groove 6, as shown in 4C in FIG.
The side pressure decreases, the piston stops moving, and spring 2
The force of 4 pushes the pressure booster piston device 21 back to its initial position. Since the inclinations of the notch groove 6 and the hydraulic oil notch groove 28 are equal, even if the effective injection stroke length is changed, the opening 2 of the hydraulic oil hole 25
The stroke length of the pressurizing plunger 2 between 5B and the opening 4C of the oil supply hole 4 remains unchanged. In FIG. 3, the vertical axis shows injection pressure on the upper side, fuel injection valve lift on the lower side, and time on the horizontal axis. The solid line is the characteristic line of the conventional technique, and the broken line is the characteristic line of the embodiment. A, B, and C are A, B of 4A, 4B, and 4C in Figure 2, respectively.
, C. In the example, as shown by the broken line, a large increase in injection pressure was obtained in the latter half of injection. Although this embodiment is a unit type fuel injection device in which the fuel pressurizing section and the fuel injection section are integrated into one unit, a similar structure and effect can be obtained in a device in which both are separate units and fuel is pumped through an injection pipe. be able to.

[0013]

[Effects of the Invention] According to the present invention, communication between the pressurizing chamber and the pressure boosting piston device is established by the working oil notch groove and the working oil hole in the latter stage of injection, and the pressure increase in the pressurizing chamber is prevented by the action of the pressure boosting piston device. Injection pressure in the latter half of injection can be increased without any interference. As a result, the kinetic energy of the fuel spray in the latter stage of injection is increased, the formation of an air-fuel mixture is promoted, and afterburning is promoted. Therefore, the present invention can provide a fuel injection device that realizes a reduction in fuel consumption of a diesel engine by promoting afterburning of fuel in the latter stage without causing a large increase in cam surface pressure due to an increase in pressure in a pressurizing chamber.

[Brief explanation of drawings]

[Fig. 1] Cross-sectional view of an embodiment according to the present invention

[Fig. 2] Developed side view of a plunger according to an embodiment of the present invention.

[Fig. 3] Characteristic diagram of the embodiment according to the present invention

[Fig. 4] Cross-sectional view of a conventional injection device

[Explanation of symbols]

21 Pressure boosting piston device 22 Large diameter piston 23 Small diameter piston 24 Spring 25 Hydraulic oil hole 26 Hydraulic oil passage 27 Pressurized fuel oil passage 28 Hydraulic oil notch groove

Claims (1)

[Claims] [Claim 1] A pressurizing plunger (2) that pressurizes fuel oil.
) and a pressurizing chamber (3), a refueling hole (4) provided on the side wall of the pressurizing chamber, and a refueling hole (4) provided on the side of the pressurizing plunger that is connected to the refueling hole when the pressurizing plunger moves under pressure. a notch groove (6) arranged to block and communicate the pressurized chamber;
A fuel injection valve (70) configured to open when fuel pressure increases and close when fuel pressure decreases, a fuel oil passage (9) that communicates the pressurized chamber and the fuel injection valve, and a fuel oil passage midway through the fuel oil passage. In a fuel injection device for a diesel engine having a check valve (10) installed in the fuel injection valve to stop the flow from the fuel injection valve to the pressurizing chamber; A pressure booster piston device (21) having a spring (24) that biases from the (23) side to the large diameter piston (22) side; a hydraulic oil hole (25) provided in the side wall of the pressurizing chamber; and a fuel oil A pressurized fuel oil passage (27) opens between the check valve and the fuel injection valve in the middle of the passage and communicates with the small diameter piston; is provided in the pressurizing plunger so that the side surface of the plunger is supplied with oil when the pressurizing plunger moves under pressure. After the hole is closed, a hydraulic oil notch groove (28) is formed so that the hydraulic oil hole and the pressurizing chamber are communicated with each other immediately before the oil supply hole and the pressurizing chamber are communicated again by the notch groove (6). A fuel injection device made of