JPH0447416Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a fuel injection device for an engine.

Prior Art As shown in Fig. 1, a rod a is pushed down against a spring b to feed high-pressure fuel into a pressure accumulating chamber c, and when the feeding is completed, a needle d biased by a spring b moves the high-pressure fuel A fuel injection device is known in which high-pressure fuel in a pressure accumulation chamber c is injected into a combustion chamber of an engine through a nozzle hole e by being moved by fuel against a spring b.

However, this device has the following problems because the volume of the pressure accumulation chamber c is constant.

In other words, a jerk-type fuel injection pump or the like supplies high-pressure fuel at a constant pressure to the pressure accumulation chamber in an amount proportional to the engine load, so when the load is high, a large amount of high-pressure fuel is supplied to the pressure accumulation chamber. The amount is small at low loads.

For this reason, the volume inside the pressure accumulator must be increased to ensure the required maximum injection amount; if the required injection amount is small at low load, the volume inside the pressure accumulator will be too large and the movement of the needle will be slow, causing the nozzle hole to move slowly. Therefore, stable injection of high-pressure fuel into the combustion chamber cannot be performed, resulting in problems such as hunting.

Therefore, as shown in Japanese Utility Model Application Publication No. 59-1867, the chamber and the volume control chamber are connected through an orifice to form a pressure accumulating chamber.
When the load is high, that is, when the injection amount is large, the injection period will naturally become longer, so the fuel stored in both the chamber and the volume control chamber is used for injection, and when the load is low, that is, when the injection amount is small, the injection period will naturally be longer. Therefore, a fuel injection device for an engine has been proposed in which the fuel stored in the volume control chamber is not used and only the chamber is used to inject the fuel. In such an engine fuel injection device, the injection behavior is such that the volume of the pressure accumulation chamber is large when the load is high, and the volume of the pressure accumulation chamber is small when the load is low.

However, the above-mentioned engine fuel injection device may be able to perform good fuel injection when the engine is rotating at high speed and under high load, and when the engine is rotating at low speed and under low load.

In other words, since the flow rate of the fuel supplied to the chamber is proportional to the engine rotation speed, when the engine rotates at high speed, the flow rate of the fuel supplied to the chamber is high and the throttling effect is large when it passes through the orifice and flows into the volume control chamber. The pressure of the fuel in the volume control chamber is low and the fuel cannot be injected, resulting in a shortage of injected fuel when the engine is rotating at high speeds and under high load, and when the engine is rotating at low speeds, the flow rate of the fuel supplied to the chamber is slow and the fuel cannot be injected. The throttling effect when flowing into the volume control chamber is small, and the pressure of the fuel inside the volume control chamber becomes equal to the pressure inside the chamber, so the fuel inside the volume control chamber and the volume control chamber are injected, so the engine is injected at low speed and under low load. There will be too much fuel.

Purpose of the invention The purpose of the invention is to increase or decrease the volume within the pressure accumulating chamber in accordance with the amount of fuel fed regardless of the engine rotational speed so that good fuel injection can be obtained.

Structure of the device: The first chamber, where fuel is supplied, and the second chamber, whose volume increases or decreases by sliding the plunger, are connected through a hole, and the first and second chambers form a pressure accumulation chamber, and the amount of fuel that is supplied is The volume of the pressure accumulation chamber can be increased or decreased by sliding a plunger according to the pressure.

Embodiment FIG. 2 is an overall explanatory view, in which a nozzle body 2 is fixed to a nozzle holder 1 with a cap nut 3, and a nozzle hole 5 that is opened and closed by a needle 4 is bored in the nozzle body 2. The nozzle hole 5 has a small diameter hole 6 and a large diameter hole 7.
The first chamber 8 formed in the nozzle holder 1
The needle 4 is in open communication with the step part 6a of the small diameter hole 6.
The pointed end portion 4a is crimped to the step portion 7a of the large diameter hole 7.
The upper part is the first chamber 8.
A flange 4c facing inward is integrally formed.

Reference numeral 9 denotes a rod serving as a check valve, the upper part of which has a large diameter and has a recess 9a, and the lower part has a small diameter and fits into the blind hole 10 of the needle 4.
A hole 11 opening into a recess 9a is formed in the axis, and the rod 9 is connected to a block 1 fitted into the upper wall of the first chamber 8, that is, the upper part of the nozzle holder 1, by a spring 12.
The block 13 and blind plug 14 are provided with high-pressure fuel supply holes 15 and 16 perforated so as to face the recess 9a. , the supply hole 1
6 is a jerk-type fuel injection pump (not shown), etc.
It communicates with means for supplying high pressure fuel at a constant pressure depending on the engine load and engine speed.

A cylinder hole 17 is formed in the block 13, and a plunger 18 is fitted into the cylinder hole 17 to form a second chamber 19.
The plunger 18 is urged downward by a spring 20 and communicates with the inside of the first chamber 8 through a hole 21 .

22 is an air vent hole.

Next, the operation will be explained.

When high-pressure fuel is supplied from a fuel injection pump (not shown) to the supply holes 16 and 15 through pipes (not shown), flows into the recess 9a of the rod 9, overcomes the spring force of the spring 12, and pushes down the rod 9, the high-pressure fuel is It is supplied into the second chamber 19 through the first chamber 8 and the hole 21.

Then, when the high-pressure fuel supply stops, the rod 9
is pushed up by the spring 12 and the supply hole 15 and the first chamber 8
At the same time, the spring force of the spring 12 weakens, and the needle 4 is pushed up by the pressure of the high-pressure fuel in the first chamber 8, and the high-pressure fuel in the first chamber 8 flows through the nozzle hole 5 into combustion (not shown). sprayed into the room.

At this time, if the amount of high-pressure fuel fed is large (when the engine is under high load), the pressure in the first chamber 8 will become sufficiently high and the hole will open, regardless of the flow rate of the supplied fuel due to the engine rotational speed. 21 to 2nd room 19
The liquid flows into the interior of the second chamber 19, pushes the plunger 18 against the spring 20, and increases the volume inside the second chamber 19.
The volume of the first and second chambers 8 and 19, that is, the volume of the pressure accumulation chamber, is increased, and a large amount of fuel can be injected under high load regardless of the engine rotation speed.

Furthermore, when the amount of high-pressure fuel is small (when the engine is under low load), there is little fuel flowing into the second chamber 19 regardless of the flow rate of the supplied fuel depending on the engine rotation speed, and the volume of the second chamber 19 is small. Since the volume of the first and second chambers 8, 19 and the pressure accumulation chamber does not become large, a small amount of fuel can be injected at low load regardless of the engine rotation speed.

In other words, the volume of the pressure accumulation chamber is large enough to match the amount of fuel fed regardless of the engine rotational speed.

Specifically, as shown in FIG. 3, when the injection amount is small (0 to q ₂ ), the plunger 18 is lowered to a position where the setting force of the spring 20 and the fuel pressure are balanced, and the volume of the second chamber 19 is reduced. The injection pressure increases only in the shaded area, resulting in stable injection, and when the injection amount is large (q ₂ - q ₃ -), the fuel pressure overcomes the setting force of the spring 20 and increases the pressure in the second chamber 19. The volume is increased, and the required maximum injection amount can be stably secured as before.

In FIG. 3, A shows a conventional example, B shows an embodiment of the present invention, and C shows only the first chamber 8.

Effects of the invention A pressure accumulating chamber is configured by communicating the first chamber 8 and the second chamber 19 through the hole 21, and the plunger 18 constituting the second chamber 19 is connected to the hole 21 by the spring 20, that is, the second chamber 19
is pushed in the direction of decreasing the volume of the fuel, so when high-pressure fuel is supplied from the supply hole 15, pushes down the rod 9, and is supplied into the first chamber 8, regardless of the flow rate of the supplied high-pressure fuel. When the amount of fuel is large, the plunger 18 of the second chamber 19 is pushed and the volume increases, and the volume of the pressure accumulation chamber made up of the first chamber 8 and the second chamber 19 is equal to the volume of the fuel to be fed regardless of the engine rotation speed. Since the size is commensurate with the amount, the supply hole 15
When the amount of high-pressure fuel sent from the supply hole 15 is small and the injection amount is small, fuel can be injected stably regardless of the engine speed, and even when the amount of high-pressure fuel sent from the supply hole 15 is large and the injection amount is large. Fuel can be injected stably regardless of engine speed.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional example, FIG. 2 is a sectional view of an embodiment of the present invention, and FIG. 3 is a table showing the relationship between injection pressure and injection amount depending on the volume of the pressure accumulation chamber. 1... Nozzle holder, 2... Nozzle body, 4...
...needle, 5...nozzle hole, 8...first chamber, 9...
Rod, 12...Spring, 13...Block, 15...
... Supply hole, 17 ... Cylinder hole, 18 ... Plunger, 19 ... Second chamber, 20 ... Spring, 21 ...
Hole.

Claims (1)

[Scope of utility model registration request] A nozzle body 2 having a nozzle hole 5 is provided at the bottom of the nozzle holder 1, and a block 13 is provided at the top of the nozzle holder 1 to form a first chamber 8 between the nozzle holder 1, the nozzle body 2, and the block 13. The nozzle body 2 is provided with a needle 4 for communicating and blocking the nozzle hole 5 and the first chamber 8, and the supply hole 15 of the block 13 and the first chamber 8 are communicated and isolated in the first chamber 8.
A blocking rod 9 is provided, a spring 12 is provided between the rod 9 and the needle 4 to hold the needle 4 and the rod 9 in the blocking position, and the plunger 18 is inserted into the cylinder hole 17 of the block 13. This second chamber 19 is formed into a hole 21.
The first chamber 8 and the second chamber 19 communicate with the first chamber 8.
constitutes a pressure accumulation chamber, and the plunger 18 is connected to the spring 2.
A fuel injection device for an engine, characterized in that the fuel injection device is biased toward a hole 21 at zero.