JPH04358762A - Fuel injection equipment - Google Patents

Abstract

PURPOSE:To quickly close a valve of a valve body. CONSTITUTION:A pilot valve 40 is closed when fuel is pressure-fed to a fuel injection valve 14. This causes the fuel to reach the injection valve 14 from a pressure-feeding chamber 3 via a pressure-feeding passage 13 to be jetted from a nozzle hole 17. On the other hand, opening the pilot valve 40 sends the fuel in the pressure-feeding chamber 3 to a fuel tank 10, closing the injection valve 14. At that time, fuel pressure is applied to a piston 49 by the action of a diaphragm 20 via a back pressure passage 48 and the spring chamber 18 of the injection valve 14. Consequently the nozzle hole 17 is quickly closed with a needle 16 of the injection valve 14 by the fuel pressure. The large pressure-receiving area of the piston 49 amplifies the fuel pressure, causing quicker valve-closing action by synergism with a spring 15.

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.

0002

2. Description of the Related Art A conventional fuel injection device of this type is disclosed in Japanese Patent Application Laid-Open No. 58-51266.

[0003] This is a structure that helps the injector close by using the fuel as back pressure against the injector when the fuel overflows into the fuel tank in order to stop fuel injection. There is.

0004

However, there is a problem to be solved in the past in that the injection valve cannot be closed sufficiently.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention reciprocates a plunger by a cam that rotates in synchronization with the engine, and supplies fuel in a pressure feeding chamber pressurized by the plunger to an injection valve. In a fuel injection device that injects fuel by opening the injection valve and injecting the fuel, the fuel injection device is arranged in a path connecting the pumping chamber and the fuel tank, and when the valve is closed, the fuel in the pumping chamber is transferred to the injection valve. A valve means that operates so that the fuel in the pressure-feeding chamber is discharged into the fuel tank by being force-fed and opened, a pressing means that presses a valve element of the injection valve against a valve seat, and a pressure means that accommodates the pressing means. a throttle means disposed in the passage between the valve means and the fuel tank; one end connected between a downstream side of the valve means and an upstream side of the throttle means, and a back pressure passage whose other end is connected to the chamber; The present invention includes a piston having a diameter and receiving fuel pressure fed through the back pressure passage.

[0006]

[Operation] When the valve means is closed, the fuel in the pressure feeding chamber is fed under pressure to the injection valve, and the nozzle of the injection valve is opened. On the other hand, when the valve means is open, the fuel in the pressure feeding chamber is released into the fuel tank and injection is stopped. At this time, the relief fuel pressure is increased by the throttle means, which acts on the chamber via the back pressure passage. Fuel pressure is then transmitted to the piston within the chamber. Here, since the piston has a size such that its outer wall is in contact with the inner wall of the chamber, the fuel pressure is amplified, and this amplified fuel pressure and pressure are applied to the valve body of the injection valve. The pressing force by the means acts synergistically.

[0007]

[Effect of the invention] Therefore, the valve body of the injector quickly contacts the valve seat and closes, ensuring good fuel depletion.
It is possible to prevent the generation of smoke and also to prevent the combustion gas from flowing back into the injection valve.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on an embodiment shown in the drawings. In FIG. 1, 1 is a cam, which is rotated in synchronization with the crankshaft of the engine. A plunger 2 is actuated by the cam 1, and is reciprocated in a stroke range between top dead center a and bottom dead center d based on the profile of the cam 1. 3 indicates a pressure feeding chamber in which fuel is pressurized by the plunger 2. A feed port 4 , a pressure feed port 5 , a pressure accumulation port 6 , and a pilot port 7 are opened in the pressure feed chamber 3 .

The feed port 4 is opened in the lower part of the pressure feeding chamber 3 below the bottom dead center d of the plunger 2, and is connected to a feed pump 9 through a feed passage 8. The feed pump 9 introduces fuel from the fuel tank 10 and supplies it to the pressure feeding chamber 3. Note that the fuel supplied from the feed pump 9 is regulated to a constant pressure by a relief valve 11 and sent to the pressure feeding chamber 3. 12 is a check valve provided in the feed passage 8.

The pressure port 5 is opened at the bottom of the pressure chamber 3, and is connected to the injection valve 14 through a pressure passage 13. The injection valve 14 is a known type in which a needle valve 16 pressed by a needle spring 15 closes an injection hole 17, and the pressure of the fuel sent from the pressure passage 13 reaches the set load of the needle spring 15 or more. When this happens, the valve opens and the fuel is injected into the engine cylinder.

A piston 49 having a concave shape and having a size that is in contact with the inner wall of the spring chamber 13 is disposed in the spring chamber 18 that accommodates the needle spring 15. in contact with
Further, the shaft portion 16a of the needle valve 16 is in contact with the back surface of the piston 49. The spring chamber 18 is open to the fuel tank 10 through a back pressure passage 48 and a drain passage 19. Further, this drain passage 19 is provided with a throttle 20 as a throttle means.

The pressure accumulation port 6 is opened at a relatively upper position in the drawing of the pressure feeding chamber 3, that is, at a position where the plunger 2 is in a pre-stroke state (range from a to b in FIG. 1). It is connected to a pressure accumulator 22 through a passage 21 . Although the structure of the pressure accumulator 22 is not particularly specified, in this embodiment, one having a piston 24 that is biased by a spring 23 is used.

Further, the pressure accumulation passage 21 is connected to an electromagnetic three-way switching valve 25. The electromagnetic three-way switching valve 25 has a port 26 that communicates with the pressure accumulation passage 21, a communication port 27 that is connected to a pilot valve 40 (described later), and a spill port 2 that is open to the fuel tank 10 through a spill passage 29.
8, and these three ports 26,
27 and 28 are electrically connected. The communication passage 30 is selectively opened and closed by ball valves 31 and 32.
1 and 32 are connected by a rod 33. Due to the biasing force of the spring 34, one ball valve 31 is connected to the communication path 30.
When one end is closed, the communication port 27 and spill port 28
When the other ball valve 32 closes the other end of the communication passage 30 due to the operation of the plunger 36 of the solenoid 35, the communication port 26 and the communication port 27 are brought into communication.

The solenoid 35 is operated by an electronic controller (ECU) 38 that detects the operating condition of the engine and issues a command signal in accordance with the operating condition. The pilot port 7 faces the feed port 4 and opens at the bottom of the pumping chamber 3, and is connected to a pilot valve 40 through a pilot passage 39. The pilot valve 40 is arranged between the path connecting the pressure feeding chamber 3 and the fuel tank 10. The pilot valve 40 is configured to open and close a port 41 connected to the pilot passage 39 using a ball valve 42.
2 is biased in the valve closing direction by a piston 43 and a spring 44. Therefore, the opening pressure P of the pilot valve 40
40 is determined by the set load F44 of the spring 44, and the valve opening pressure P40 of the pilot valve 40 is set to a pressure lower than the valve opening pressure of the injection valve 14.

The chamber containing the ball valve 42 communicates with the drain passage 19 by a drain port 45. Therefore, when the ball valve 42 opens the communication port 41, the communication port 41 and the drain port 45 communicate with each other, and the fuel in the pressure feeding chamber 3 is discharged from the drain passage 19 into the fuel tank 10.

Further, the chamber housing the spring 44 is connected to the communication port 27 of the electromagnetic three-way switching valve 25 through a pressure guiding passage 46. For this reason, the electromagnetic three-way switching valve 2
When the communication port 26 and the communication port 27 of No. 5 are brought into communication, the pressure of the fuel stored in the pressure accumulator 22 acts as back pressure on the pilot valve 40.

The operation of the embodiment related to the above configuration will be explained. While the plunger 2 is raised by the rotation of the cam 1, fuel is introduced from the feed pump 9 into the pressure feeding chamber 3 through the feed passage 8 and the feed port 4. Then, in the process of the plunger 2 descending due to the rotation of the cam 1, the fuel in the pressure feeding chamber 3 is pressurized.

In this pressurizing step, the solenoid 35 of the electromagnetic three-way switching valve 25 is turned off, and therefore, one ball valve 31 of the electromagnetic three-way switching valve 25 is closed to one end of the communication passage 30 by the urging force of the spring 34. is closed to allow communication between the communication port 27 and the spill port 28, and to block communication between the conduction port 26 and the communication port 27.

In this state, during the pressurization stroke, while the plunger 2 reaches the pressure accumulator port 6 from the top dead center a, the fuel in the pressure feeding chamber 3 pressurized by the plunger 2 flows from the pressure accumulator port 6 to the pressure accumulator 22. is pressure-fed and stored in this pressure accumulator 22. At this time, since the pressure feeding chamber 3 also communicates with the pilot valve 40, the fuel pressure in the pressure feeding chamber 3 is transferred to the pilot valve 40.
When the valve opening pressure P40 of 0 is reached or higher, the pilot valve 40 opens and the fuel in the pressure feeding chamber 3 is discharged into the fuel tank 10 through the pilot valve 40 and the drain passage 19. For this reason,
The pressure accumulator 22 stores fuel at a pressure lower than the valve opening pressure P40 of the pilot valve 40.

When the plunger 2 descends beyond the pressure accumulation port 6 (position b), the plunger 2 moves the pressure accumulation port 6
Since the pressure accumulator 22 is closed, the pressure of the fuel stored in the pressure accumulator 22 will not leak.

Further, the plunger 2 is lowered and reaches the bottom dead center d.
The fuel in the pressure-feeding chamber 3 is pressurized until the pressure is reached, but if the solenoid 35 of the electromagnetic three-way switching valve 25 is left off, the opening pressure P40 of the pilot valve 40 increases
Since the fuel in the pressure feeding chamber 3 continues to be discharged into the fuel tank 10 through the pilot valve 40 and the drain passage 19, no injection is performed from the injection valve 14.

However, the plunger 2 moves from point b to point d.
When between points, for example when point c is reached, the electronic controller (
When the ECU) 38 gives a pulse signal to the solenoid 35 to turn on the solenoid 35, the plunger 36 pushes the ball valves 32 and 33 to cut off the communication between the communication port 27 and the spill port 28, and at the same time connect the conduction port 26 and the communication port 27. let Therefore, the pre-pressure fuel stored in the pressure accumulator 22 is transferred to the communication port 26 and the communication port 27.
, the piston 4 of the pilot valve 40 through the pressure guiding passage 46.
Added to the back of 3. Therefore, the opening pressure of the pilot valve 40 is determined by the set load of the spring 44 and the pressure accumulator 22.
Since back pressure is applied from , the ball valve 42 closes the conduction port 41 .

By increasing the opening pressure of the pilot valve 40, the fuel pressure in the pressure feeding chamber 3 is quickly increased to a level higher than the valve opening pressure of the injection valve 4, and as a result, the pressurized fuel in the pressure feeding chamber 3 flows into the pressure feeding passage. 13 to the injection valve 14, the needle 16 is pushed up against the needle spring 15, and the fuel is injected from the injection hole 17.

[0024] Such injection is performed by the electromagnetic three-way switching valve 2.
Therefore, the injection timing is determined by the timing at which this solenoid 35 is turned on, and the injection amount is determined by the time during which the solenoid 35 continues to be turned on.

Since the pulse signal applied to the solenoid 35 can be controlled by an electronic controller (ECU) 38 according to the engine operating condition, the injection timing and injection amount can also be controlled according to the engine operating condition.

To explain further with reference to FIG. 2, the lift curve of the cam 1 has a constant speed range of the plunger 2 between c and c', and within this range, even if the injection timing is changed, the oil delivery rate of the plunger 2 remains constant. In other words, the injection amount is set so that it does not change, that is, the injection amount is uniquely determined by the width of the pulse signal applied to the solenoid 35 regardless of the injection timing.

Pre-stroke of plunger 2 (a-b)
During this period, fuel is stored in the pressure accumulator 22, and the pressure P22 of this accumulated fuel is maintained below the valve opening pressure P14 of the injection valve 14. When plunger 2 exceeds the prestroke (point b),
The pressure accumulation port 6 is closed by the lower surface of the plunger 2 and enters an injection standby state. In other words, cam lift curve b~c'
The area between the two is the injection possible area.

For example, when the solenoid 35 of the electromagnetic three-way switching valve 25 is turned on at point c, the back pressure of the pilot valve 40 rises rapidly, and the opening pressure of this pilot valve 40 also rises rapidly, as described above. Valve opening pressure P14 of the injection valve 14
That's all. Therefore, leakage of fuel from the pilot valve 40 is prevented, the pressure within the pressure feeding chamber 3 rises rapidly, and injection is started when the pressure reaches the opening pressure of the injection valve 14 (point e).

The injection is terminated by turning off the solenoid 35 of the electromagnetic three-way switching valve 25 (point f). This turns off the ports 27 and 28, so the back pressure of the pilot valve 40 is transferred from the spill passage 29 to the fuel tank 10.
Therefore, it is released into the fuel tank 10 through the drain port 45 of the pilot valve 40 and the drain passage 19. Therefore, fuel injection from the injection valve 14 is stopped (point h).

When the fuel in the pressure feeding chamber 3 is released from the drain port 45 of the pilot valve 40 to the fuel tank 10 through the drain passage 19, the drain passage 19 is provided with a restriction 20.
, the fuel pressure in the drain passage 19 temporarily increases (point i). This pressure fuel acts on the spring chamber 18 of the injection valve 14 through a back pressure passage 48 that is open between the downstream side of the pilot valve 40 and the upstream side of the throttle 20, and is amplified by the piston 49 to cause the injection valve 14 to flow. The increased back pressure prompts the needle 16 to close. For this reason,
Good jetting can be achieved.

In the above embodiment, since fuel is stored in the pressure accumulator 22 during the pre-stroke of the plunger 2, a special pressure pump for pre-pressure is not required, and the structure is simplified.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example.

FIG. 2 is a characteristic diagram for explaining FIG. 1;

[Explanation of symbols]

1 Cam 2 Plunger 3 Pressure feeding chamber 9 Feed pump 10 Fuel tank 14 Injection valve 15 Spring 18 Spring chamber 20 Aperture 22 Pressure accumulation chamber 25 Solenoid three-way switching valve 35 Solenoid 40 Pilot valve 48 Back pressure passage 49 Piston

Claims (1)

[Claims] In a fuel injection device in which a plunger is reciprocated by a cam rotated in synchronization with an engine, fuel in a pressure feeding chamber pressurized by the plunger is fed to an injection valve, and the injection valve is opened to inject the fuel. , disposed in a path connecting the pressure-feeding chamber and the fuel tank, and when the valve is closed, the fuel in the pressure-feeding chamber is force-fed to the injection valve, and when the valve is opened, the fuel in the pressure-feeding chamber is released into the fuel tank. a valve means that operates so that the valve body of the injection valve is pressed against a valve seat, a chamber that accommodates the pressing means, and a space between the valve means and the fuel tank in the passageway; a back pressure passage having one end connected between the downstream side of the valve means and the upstream side of the throttling means and the other end connected to the chamber; and a back pressure passage housed in the chamber; The fuel pressure means is interposed between the valve body of the injection valve and the pressing means, and has a size such that an outer wall portion is in contact with an inner wall portion of the chamber, and receives fuel pressure fed through the back pressure passage. A fuel injection device comprising: a receiving piston;