JP2503653Y2 - Fuel injector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel injection device, and more particularly, to a structure of a fuel injection nozzle in the fuel injection device.

(Prior Art) As is well known, in a diesel engine which is one of internal combustion engines, fuel from a fuel supply system is injected into high pressure air in a combustion chamber using an injection pump and an injection nozzle to burn the fuel. The output corresponding to the thermal energy generated with this is obtained.

(Problems to be solved by the invention) By the way, in the above-described fuel injection device including the fuel injection pump and the fuel injection nozzle, fuel is injected in a concentrated manner at one time, so that ignition delay occurs and noise is generated. May cause.

That is, if the metered fuel is injected into the compressed air, it is difficult to uniformly propagate the flame, and rapid combustion is performed at a certain time, resulting in large explosion and vibration noise.

Separately from this, if the fuel injection is concentrated for a period of time, the temperature in the cylinder after combustion is significantly increased, so that NOx may be generated more often. Therefore, in view of the above-mentioned problems in the fuel injection device, an object of the present invention is to obtain a fuel injection device which can prevent noise at the time of combustion and generation of harmful components in exhaust gas with a simple structure. is there.

(Means for Solving the Problem) In order to achieve this object, the present invention provides a needle valve slidably disposed in a body of a nozzle and capable of opening and closing a nozzle hole, and a pressure receiving force of the needle valve in the nozzle body. A valve opening pressure chamber which is formed around the portion and guides the fuel pressure from the fuel injection pump to the pressure receiving portion, and a fuel supply path which introduces the fuel pressure from the fuel injection pump is connected to one end side. The first pressurizing chamber, which has a cross-sectional area larger than the pressure-receiving area of the pressure-receiving portion and is formed in a tubular shape, and the first pressurization via a communication path having a cross-sectional area smaller than the pressure-receiving area of the pressure-receiving portion. A second pressure chamber communicating with the other end of the chamber, a large end slidably arranged in the first pressure chamber, and a slidable member arranged in the communication passage. A first piston having a small end portion and biased toward the one end side of the first pressure chamber. And a second piston slidably arranged in the second pressurizing chamber, and interposed between the second piston and the needle valve, and the second piston is connected to the communication passage side. A spring for urging the needle valve in the closing direction, one end connected to the sliding surface of the first pressurizing chamber and opened and closed by the peripheral surface of the large end portion, and the other end opened by the valve. A first port connected to the pressure chamber, and a second port branched from the first port and having a tip end connected to a sliding surface of the communication passage and opened and closed by a peripheral surface of the small end portion. The first piston is slid along with the supply of fuel pressure from the fuel injection pump to the first pressurizing chamber, and the large end of the first piston moves to the first end. By closing the one end of the port, the pressure increase in the fuel pressure passage due to the movement of the small end Illot injection is started, and further, the large end opens the one end of the first port to cause pilot injection by pressure drop due to communication between the fuel pressure feed path and the first pressurizing chamber. When the small end closes the tip of the second port and then moves further, the second piston is lowered against the biasing force of the spring to compress the spring. A fuel injection nozzle is provided, which enables main injection with an increased set valve opening pressure of the needle valve.

(Operation) According to the present invention, the first piston is moved to the communication passage side by the pressure-feeding pressure of the fuel from the fuel injection pump, and one end of the first port is closed by the large end to the small end. When it is pushed into the part-gas communication passage, the pressure in the fuel pressure feed passage is increased, and the fuel pressure acts on the second piston and the pressure receiving portion via the second port, the first port and the valve opening pressure chamber. In this case, the fuel pressure receiving area of the second piston, that is, the cross-sectional area of the communication passage is set smaller than the pressure receiving portion of the needle valve when the valve is closed, so only the needle valve is lifted upward,
Low-pressure pilot injection is performed.

Then, when the first piston is further moved and one end of the first port is opened in accordance with the increase in the pumping pressure of the fuel, the fuel pressure in the increased second port, the first port and the valve opening pressure chamber decreases. Therefore, the needle valve is lowered by the urging force of the spring to close the injection hole.

The first piston is moved further so that the small end
When the port of is closed, the second piston is pushed down against the biasing force of the spring, and the valve opening pressure of the needle valve rises,
Higher main injection is performed by the further increase in the pumping pressure from the fuel injection pump.

(Embodiment) An embodiment of the present invention will be described in detail below with reference to FIGS.

FIG. 1 is a schematic configuration diagram of an injection nozzle used in a fuel injection device according to an embodiment of the present invention.

The fuel injection nozzle 1 according to the present embodiment has a pilot injection pressure setting structure and a main injection pressure setting structure that are performed before the main injection.

That is, the pilot injection pressure setting structure has the first pressurizing chamber 2 as a main part, and the first pressurizing chamber 2 has a fuel supply passage 3 from a fuel injection pump (not shown) at one end side thereof. A first piston 5 having a slidable large end portion 5a which is always biased by a spring 4 against the pressure of fuel from the injection pump side and is slidable therein. There is. The first piston 5 is biased by the spring 4 against the pressure-feeding pressure of the fuel from the injection pump, and this biasing causes the fuel pressure-feeding passage to be described later.
It is designed to close the first 12 ports 12A.

Further, the first pressurizing chamber 2 is provided with a second pressurizing chamber 7 via a communication passage 6 in a space opposite to a space into which fuel from the injection pump enters, and the second pressurizing chamber 7 is provided. Inside the pressure chamber 7, a second piston 8 having a larger cross-sectional area than the communication passage 6 is arranged.

The second piston 8 is a main part of the valve opening pressure setting structure of the needle valve 9, and holds one end of a valve opening pressure setting spring 10 arranged between the needle valve 9 and the top thereof. The initial position is set to a position to be seated on the upper surface of the second pressurizing chamber 7, and the valve opening pressure of the needle valve 9 is increased by displacing from this position to the needle valve 9 side. ing. The cross-sectional area of the communication passage 6 is set smaller than that of the pressure receiving portion 9a of the needle valve 9.

On the other hand, the first pressure chamber 2 and the valve opening pressure chamber 11 of the needle valve 9 described above.
A fuel pressure feed path 12 is provided between
Is a first port connected to the peripheral surface side of the first pressurizing chamber 2.
The above-mentioned communication passage 6 having 12 A and reaching the valve opening pressure chamber 11
The second port 12B is connected to the peripheral surface of the communication passage 6 by branching to the. Inside the communication passage 6, the first piston 5
The small end 5b of the is inserted slidably.

Since the present embodiment has the structure as described above, as the initial position, as shown in FIG. 1, the first piston 5 is in a position to close the first port 12A of the fuel pressure feeding passage 12, and The second piston 8 is seated on the upper surface of the second pressurizing chamber 7.

Then, from this state, when fuel is supplied to the first pressurizing chamber 2 by the rotation of the plunger drive cam (not shown) on the injection pump side, the first piston 5 resists the bias of the spring 4. Then, the piston 5 is pushed down, and the piston 5
By increasing the pressure in the communication passage 6 until the first port 12A of 12 is opened, the pressure rises due to the difference in cross-sectional area between the communication passage 6 and the valve opening pressure chamber 11. When the pressure in the valve opening pressure chamber 11 becomes equal to or higher than the valve opening pressure of the needle valve 9 due to the effect obtained, the pressure receiving area of the second piston 8 is equal to the pressure receiving portion 9a of the needle valve 9.
Since it corresponds to the cross-sectional area of the communication passage 6 having a smaller pressure receiving area, the valve closing force exerted on the needle valve 9 by the second piston 8 via the valve opening pressure setting spring 10 is larger than the valve opening pressure chamber 11 Since the second piston 8 does not move, the needle valve 9 is lifted to open the injection hole and start the fuel injection, as shown in FIG. 2 (A).

Then, as shown in FIG. 2 (B), this injection is performed by the large end portion 5a of the first piston 5 opening the first port 12A of the fuel pressure feeding passage 12, and the fuel pressure feeding passage 12 boosted in pressure. It ends when the needle valve 9 is closed due to the pressure drop that occurs when the fuel inside communicates with the space on the fuel supply side in the first pressurizing chamber 2.

On the other hand, the rotation of the plunger drive cam on the injection pump side continues, and as the cam stroke approaches the maximum amount,
The pressure in the first pressurizing chamber 2 rises, and the descending amount of the first piston 5 increases.

Therefore, when the first piston 5 descends, the small end
Since the communication passage 6 is closed by 5b, the fuel in the communication passage 6 is used as it is for pressure transmission to the second piston 8, and as shown in FIG. 8 is lowered to increase the pressure of the valve opening pressure setting spring 10.

In this state, when the above-mentioned plunger drive cam reaches the maximum stroke, the pressure in the fuel pressure feeding path 12 is further increased, and at the time when the pressure reaches or exceeds the valve opening pressure increased by the lowering of the second piston 8, The needle valve 9 is opened and high-pressure fuel injection is performed as shown in FIG.

When the stroke of the plunger drive cam on the injection pump side is reduced, the pressure in the first pressurizing chamber 2 is reduced and a so-called fuel return phenomenon occurs, so that the pressure in the fuel pressure feeding passage 12 is also reduced. As a result, the needle valve 9 is closed by the urging of the valve opening pressure setting spring 10, as shown in FIG.

The two-stage fuel injection described above, as shown in FIG.
The injection in the former stage is a pilot injection for executing a temporary small amount injection to improve the flame propagating property, and the latter stage injection is a main injection for executing a large amount and high pressure injection.

According to the present embodiment, when the needle valve 9 is closed after the main injection, the first piston 5 is rapidly brought to the initial position by the biasing of the spring 4 in response to the pressure drop in the first pressurizing chamber. Since the return is made, the initial state of the second piston 8 is quickly returned through the negative pressure in the communication passage 6, whereby the dripping of the fuel is prevented in advance and the so-called "fuel exhaustion" is performed. Can be improved to improve abnormal combustion such as afterfire.

(Effect of the Invention) As described above, according to the present invention, the fuel injection is performed by dividing the small amount injection and the large amount injection, so that the concentrated combustion is prevented in advance and the flame is continuously propagated. It is possible to suppress the generation of noise and vibration.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of a main part of a fuel injection device according to an embodiment of the present invention, and FIG. 2 is a configuration corresponding to FIG. 1 for explaining an operation of the main part shown in FIG. 3 and 4 are diagrams for explaining the operation of the main part shown in FIG. 1 ... Fuel injection device, 2 ... First pressurizing chamber, 3 ... Fuel supply passage from injection pump side, 5 ... First piston, 5a
...... Large end of the first piston, 5b ...... Small end of the first piston, 6 ...... Communication passage, 7 ...... Second pressurizing chamber, 8 ...... Second piston, 9 ...... Needle valve, 9a ... Pressure receiving part of needle valve, 11 ...
… Valve opening chamber, 12 …… Fuel pressure feed line, 12A …… First port, 12B …… Second port.

Claims (1)

(57) [Scope of utility model registration request] 1. A needle valve slidably arranged in a body of a nozzle and capable of opening and closing an injection hole; and a fuel injection pump formed in the nozzle body around a pressure receiving portion of the needle valve and in the pressure receiving portion. A valve opening pressure chamber for introducing the fuel pressure from the fuel injection pump and a fuel supply passage for introducing the fuel pressure from the fuel injection pump are connected to one end side, and the cross-sectional area is larger than the pressure receiving area of the pressure receiving portion and is cylindrical. And a second pressurizing chamber that is connected to the other end side of the first pressurizing chamber via a communication path having a cross-sectional area smaller than the pressure receiving area of the pressure receiving section. A chamber, a large end slidably arranged in the first pressure chamber, and a small end slidably arranged in the communication passage, and the one end of the first pressure chamber The first piston biased toward the side, and the first piston slidably arranged in the second pressure chamber. And a spring that is interposed between the second piston and the needle valve, and urges the second piston toward the communication passage and the needle valve in the closing direction, and has one end From the first port, which is connected to the sliding surface of the first pressurizing chamber and is opened and closed by the peripheral surface of the large end portion, and the other end of which is connected to the valve opening pressure chamber, and from the first port A fuel pressure feed passage having a second port branched and having a tip connected to the sliding surface of the communication passage and opened and closed by the peripheral surface of the small end portion, wherein the first piston is the fuel When slid along with the supply of fuel pressure from the injection pump to the first pressurizing chamber, the fuel is generated by the movement of the small end while the large end closes the one end of the first port. Pilot injection is started by the pressure increase in the pressure feed path, The large end opens the one end of the first port to end the pilot injection due to the pressure drop due to the communication of the fuel pressure feed passage and the first pressurizing chamber, and then the small end is connected to the first end. When the tip of the second port is closed and further moved, the second piston is lowered against the biasing force of the spring, and the spring is compressed to increase the set valve opening pressure of the needle valve. 2. A fuel injection device comprising a fuel injection nozzle that enables main injection.