JPS5835261A - Fuel injection valve - Google Patents

Abstract

PURPOSE:To reduce combustion noise and smoke and improve fuel efficiency, by providing a ramified oil passage which communicates to an oil reservoir of an injection valve and has a piston and a check valve and is located in parallel with a needle valve and by keeping the ratio of injection low in its initial stage and by preventing injection at low pressure and a low ratio in the rear stage after main injection. CONSTITUTION:High-pressure fuel flows to an oil reservoir 101 through an oil passage 2 and to another oil reservoir 111 through an annular oil passage 112. When the pressure of the reservoir 101 is at a valve opening level Po, that of the other reservoir 111 is at the same level and a piston 13 is moved up nearly simultaneously with a needle valve 3. For that reason, the increase in volume at the time of the ascent of the needle valve 3 is the sum of the increases in the volumes of the reservoirs 101, 111, so that the increase in volume at the time of the ascent of the needle valve is large. Fuel is injected by the ascent of the needle valve 3 and ignited and burned. After the discharge of the fuel, the needle valve 3 is seated, a check valve 10 is closed at the side of the piston 13 and the flow rate of fuel is reduced by an orifice 12 so that the fall in the pressure of the oil reservoir 111 becomes slow. The pressure of the reservoir 111 is made lower than the valve opening level Po so that the piston 13 is moved down after the needle valve 3 is seated. For that reason, fuel corresponding to the change in volume at the time of the descent of the piston 13 is not injected from an injection port 8, so that injection stoppage after main injection is made sharp.

Description

[Detailed description of the invention] The present invention relates to improvements in fuel injection valves for internal combustion engines.

A conventional fuel injection valve of this type is shown in FIG. In the figure,
01 is the fuel injection valve body, 02 is the oil path inside the fuel injection valve, 0
A needle valve 3 is slidably inserted into the fuel injection valve main body 01. 04 is the needle valve push rod.

05 is a needle valve spring, and the spring force presses the needle valve 03 toward the valve seat 01b via the push rod 04. 06 is the valve opening pressure adjustment screw, 0
7 is a spring chamber, 08 is a spout, 09 is a discharge port, and 01a is an oil reservoir.

The fuel oil is compressed by a fuel injection pump (not shown) and sent into an injection pipe (not shown) while becoming high pressure.
The oil reaches the oil reservoir Ola through the oil passage 02 inside the fuel injection valve. The needle valve 03 is pressed against the valve seat 01b by the spring 05, and the fuel oil pressure in the oil reservoir O1a is kept at a constant pressure, that is, the valve opening pressure PG.
An initial spring force is set by the valve opening pressure adjustment screw 06 so that the valve opening pressure does not rise unless it exceeds the above value. Therefore,
When the high pressure wave sent from the fuel injection pump reaches a pressure equal to or higher than the valve opening pressure Po at the oil reservoir Ova.

The needle valve 03 rises, the volume of the oil sump Ola increases, and part of the fuel sent from the fuel injection pump is used for this purpose.
The rest is the combustion chamber in the cylinder from the nozzle 08 (not shown)
Fuel is injected into the engine, ignited and combusted, and the output is compared. When the discharge of the fuel injection engine is completed, the pressure in the oil reservoir O1a decreases, and when this pressure falls below the closing jf pressure, the needle valve (]3 is pressed down by the spring 05 and lowers, and the volume of the oil reservoir becomes Some of it is injected through the nozzle 08, and when the needle valve 03 is seated on the valve seat ( ) 1b, the injection ends. During this time, leakage from the sliding part of the needle valve 03 is caused by the spring chamber 07. and is discharged through the discharge port 09.

However, the above method has the following drawbacks.

In order to reduce the combustion noise of a diesel engine, it is necessary to slightly reduce the amount of fuel during the second ignition delay period, and one method to achieve this from the fuel injection side is to It is considered effective to keep the rate low. In conventional systems, the volume of the oil reservoir increases as the needle valve rises, so part of the fuel delivered from the fuel injection pump is used for this, and the rest is injected from the nozzle.

The injection rate at the initial stage of injection is suppressed, but on the other hand, when the needle valve descends due to a decrease in pressure, the volume of the oil reservoir decreases, and some of it is injected from the nozzle, so even in the latter stage of injection after the end of main injection. As shown in FIG. 2, the low-pressure, low-injection-rate injection continues sluggishly, which has the disadvantage of worsening smoke exhaust.

The purpose of the present invention is to focus on the above points and to suppress the injection rate at the initial stage of injection, that is, to ensure a long period of low injection rate.

Moreover, it is an object of the present invention to provide a fuel injection valve that can prevent low-pressure, low-injection-rate injection in the latter period after the end of main injection and improve the sharpness of injection. , one end of the piston faces a branch oil passage formed by branching off from the oil passage to the oil sump of the needle valve, and the other end is provided with a spring, and the piston is the same as the restrictor provided in the branch oil passage. A check valve is provided in parallel with the calibrator to prevent the flow of fuel from the piston side.

In this case, the movement of the piston can be controlled so that the piston rises in synchronization with the needle valve at the beginning of injection, and when it descends due to pressure drop, the piston descends after the needle valve is seated.There is one problem. can be solved.

If a needle valve and a piston are provided separately and in parallel as in the present invention, each operates in the same way as a conventional needle valve.
It is also good in terms of reliability and durability.

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 3 is a sectional view showing one embodiment of a fuel injection valve according to the present invention.

In the figure, 1 is the fuel injection valve body, and 2 is the oil passage.

A needle valve 3 is slidably inserted into the fuel injection valve main body 1. 4 is the needle valve push rod, and 5 is the needle valve spring.

The needle valve 3 is pressed. 6 is a needle valve opening pressure adjustment screw, 7
is the needle valve spring chamber, 8 is the spout, and 9 is the discharge port.

101 is an oil reservoir of the needle valve, and 102 is a valve seat of the needle valve. 1
0 is a check valve, 1 is a check valve line, 12 is a throttle, 13 is a piston, and 14 is a push rod for the piston.

15 is a spring for the piston, 16 is a piston valve opening pressure adjustment screw and a stone stop, F, 17 is a spring chamber for a bald stone,
19 is the exhaust NO. 111 is the piston oil sump.

112 is an annular oil passage.

One end side of the piston faces a branch oil passage 7 formed by branching out from the oil passage 2 . That is, the two-branch oil passage opens at one end of the piston 13 via an annular oil passage 112 branched from the oil passage 2, a throttle 12 and a check valve 10 provided in parallel, and an oil reservoir 111. There is. Therefore, the piston 13 is provided in parallel with the needle ff3.

The operation in the case of the above configuration will be described.

Fuel oil is compressed by a fuel injection pump (not shown) and sent to an injection pipe (not shown) while being under high pressure.
The oil reaches the oil sump 101 via the oil passage 2 in the fuel injection valve, and the oil sump 111 via the annular oil passage 112. The needle valve 3 is pressed by the spring 5, and the piston 13 is pressed by the spring 15, and will not rise unless the pressure exceeds a certain pressure, that is, the valve opening pressure PG.

Therefore, when the high pressure wave sent from the fuel injection pump becomes equal to or higher than the valve opening pressure Po at the oil sump 101, the needle valve 3 rises, and at this time the check valve 10 opens, so the throttle 12 opens. When the pressure of oil sump) 101 reaches the valve opening pressure PG,
The pressure in the oil reservoir 111 is also the valve opening pressure P'0, and the piston 13 also rises almost simultaneously with the needle valve 3. Therefore, the increase in volume when the needle valve 3 rises is equal to the sum of the increases in the oil reservoirs 101 and 111. As the needle valve 3 rises, 9 fuel is injected [
-18 is injected into the combustion chamber (not shown) in the ring and ignites and burns once to produce output.

When the fuel injection pump finishes discharging, the pressure in the oil reservoir 101 on the needle valve side decreases, and when this pressure falls below the valve closing II force, the needle valve 3 is pressed by the spring 5.
Descend and sit down. On the other hand, on the piston side, when the fuel injection pump finishes discharging and the pressure in the oil passage decreases, the check valve I
O is closed by the check valve spring 11 and the fuel flows through the throttle 12
It receives a throttling action. For this reason, the pressure drop in the oil sump 111 becomes gradual, and the speed of the pressure drop is controlled by appropriate selection of the size and shape of the restrictor. If the pressure in IIl is lower than the valve closing pressure,
After the needle valve is seated, the piston 13 descends. Therefore, the fuel corresponding to the change in volume when the piston 13 descends is not injected from the injection port 8. In addition, the needle valve 3 and piston 13 during this time
Leakages from the sliding parts of the spring chambers 7 and 17 are discharged through the discharge ports 9 and 19, respectively. Furthermore, by making the lower part of the piston 13 conical and seating the piston 13 at the cone, the valve-closing pressure of the piston 13 can be made smaller than the valve-opening pressure, and the start of descent of the piston can be delayed. Therefore, it is even more effective.

The above effects can be summarized with a focus on the injection rate as follows.

(1) At the beginning of injection, the needle valve and piston rise almost simultaneously, resulting in a large increase in volume, and more of the fuel sent from the pump is spent on this. injection rate is suppressed to a low level.

(2) In the latter half of injection, the piston descends after the needle valve is seated, so the change in volume of the piston 13 has no bearing on fuel injection. Therefore, it is possible to prevent the low-pressure, low-injection-rate injection from continuing sluggishly after the end of the main injection, and the sharpness of the injection is improved. Therefore, the injection rate mode is as shown in FIG.

Note that the above points can also be applied to a Hall type injection valve.

The above case has the following effects.

(1) The amount of fuel during the ignition delay period can be reduced, and combustion noise can be reduced.

(2) It is possible to prevent low-pressure, low-injection-rate injection from continuing sluggishly, reducing smoke emissions, fuel consumption, etc.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional fuel injection valve, and Figure 2 is a cross-sectional view of a conventional fuel injection valve.
FIG. 3 is a diagram showing the fuel injection rate of the fuel injection valve shown in the figure. FIG. 3 is a sectional view showing a fuel injection valve according to an embodiment of the present invention, and FIG. 4 is a diagram showing a fuel injection rate of the fuel injection valve of FIG. 3. DESCRIPTION OF SYMBOLS 1... Fuel injection valve body, 2... Oil path, 3... Needle valve, 8... Nozzle port, 10... Check valve, 12... Throttle,
13...Piston, 15...Piston spring, 10
1... Oil reservoir of needle valve, ] 11... Oil reservoir of piston, 112... Annular part oil passage. Fang 1 (21

Claims (1)

[Claims] l In a fuel injection valve for an internal combustion engine, a male stone facing a branch oil passage formed by branching off from the oil passage to the oil reservoir of the needle valve on one end side and provided with a spring on the other end side, is installed in the branch oil passage. A fuel injection valve characterized in that it is provided with a check valve that is provided in parallel with the provided throttle valve and the same valve valve, and that inhibits the flow of fuel from the piston side.