JPH078843Y2 - Fuel injector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a fuel injection device.

(Prior Art) Conventionally, there has been known a fuel injection device that injects fuel into a fuel chamber to form an air-fuel mixture.

FIG. 3 shows this fuel injection device.

As shown in the figure, this fuel injection device is an electronic fuel injection device applied to a diesel engine, and is equipped with a solenoid 1 for controlling opening and closing of an exhaust passage 2 by a signal from a controller (not shown). There is. Fuel from a fuel pump (not shown) flows into the cylinder 4 from the fuel supply passage 3 shown by the dotted line. In the cylinder 4, there is slidably arranged a plunger 6 which is biased upward in the drawing by a compression spring 5, and the plunger 6 is formed with a through hole 6a penetrating a bottom surface and a side surface. There is. On the bottom surface of the cylinder 4, there is formed a flow passage 7 connected to a fuel injection port (not shown), and a flow passage 7 is formed in the middle thereof.
The discharge passage 2 is formed in a direction substantially opposite to the above and has a relatively long distance connected to the solenoid 1. A concave ring portion 11a is formed on the wall surface of the cylinder 4 including the connecting portion between the fuel supply passage 3 and the cylinder 4 so that the fuel can be sent to the other second passage 11.

Next, the operation of the conventional fuel injection device thus configured will be described.

First, before fuel injection, the fuel from the fuel supply passage 3 flows into the chamber 4a formed by the bottom surface of the plunger 6 and the cylinder 4 through the through hole 6a formed in the plunger 6, and the flow passage 7 Has reached the fuel injection port. Here, in the injection stage, when the holder 9 supporting the plunger 6 is pushed downward in the figure against the spring force of the compression spring 5, the chamber 4a is compressed, and the compressed fuel opens the injection port. , Fuel is injected from the injection port. When the fuel injection is completed, the solenoid 1 which has been on until now is turned off and the valve closing the discharge passage 2 is opened, so that the injection port side from the branch point with the discharge passage 2 is opened. The compressed residual fuel in the flow path 7a of
It is returned to the fuel supply path 3 via the discharge path 2 and the connection path 10, and at the same time, the plunger 6 is returned to the position before fuel injection by the spring force of the compression spring 5.

(Problems to be Solved by the Invention) As described above, the discharge passage 2 connecting the injection port and the solenoid valve has a relatively long distance, and due to the connection, the discharge passage 2 is bent, and the flow passage for fuel pressure feeding is further provided. Since it is a branch path of 7, the return resistance in the discharge path 2 is extremely large. Therefore, even if the solenoid 1 is turned off and the discharge path 2 is opened, the fuel does not return easily and the fuel is injected from the injection port even though the injection timing has passed, that is, the residual injection is performed. There was a problem such as.

An object of the present invention is to provide a fuel injection device which eliminates residual injection and has excellent responsiveness.

(Means for Solving the Problems) In order to achieve the above object, a fuel injection device of the present invention has a cylinder connected to a fuel supply passage, a plunger slidable in the cylinder, the cylinder and the fuel. A flow path that connects the injection port and sends the fuel compressed by the plunger to the fuel injection port and sends back the residual fuel into the cylinder at the end of injection, and is connected to the cylinder at the end of injection. A discharge path for returning the sent-back fuel to the fuel supply side, the plunger sends fuel from the fuel supply path to the flow path side before fuel injection, and immediately after the fuel injection end timing. From the time until the plunger returns to the position before fuel injection, a through hole for letting the fuel from the flow path side escape to the discharge passage is provided.

(Operation) According to the present invention, the through-hole allows the fuel from the flow passage side to be always discharged satisfactorily to the discharge passage immediately after the fuel injection end time and before the plunger slides back to the position before the fuel injection. Comes to escape, eliminating the residual injection at the end of fuel injection,
It works to improve the responsiveness of the injector.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.
1 is a side sectional view of a fuel injection device showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA in FIG. 1, and FIG.
Those having the same functions and functions as those of the conventional technique described in the figure are designated by the same reference numerals, and the description thereof will be omitted to avoid duplication.

The difference between the fuel injection device of the present embodiment and that of the prior art is that
This is that a notch 6b that is continuous with the through hole 6a is newly formed in the plunger 6 so that the other end of the discharge path whose one end is connected to the solenoid 1 is connected to the side surface of the cylinder 4. The notch 6b is continuously provided in the lower portion of the opening on the side surface side of the through hole 6a, and the position of the newly formed connection portion of the discharge passage 12 with the cylinder 4 is located in the fuel supply passage 3. It is below that of the connecting portion with the cylinder 4.

Before fuel injection, the opening 6c on the cylinder 4 side of the through hole 6A formed by the through hole 6a and the notch 6b.
Is located at a position facing the concave ring portion 11a connected to the fuel supply passage 3, and the opening 6c is always connected to the discharge passage 12 immediately after the fuel injection end timing and before the plunger returns to the position before the fuel injection. It is in the opposite position.

That is, the notch 6b, the discharge path 12 and the like are formed so as to have the above-mentioned positional relationship.

It should be noted that FIG. 1 shows a state before fuel injection. Therefore, before fuel injection, the fuel from the fuel supply passage 3 passes through the through hole 6a formed in the plunger 6 and the bottom surface of the plunger 6. It flows into the chamber 4a formed by the cylinder 4 and reaches the fuel injection port through the flow path 7. Here, in the injection stage, when the holder 9 that supports the plunger 6 is pushed downward in the figure against the spring force of the compression spring 5, the plunger 6 slides downward, and the fuel supply path 3 moves to the plunger. It will be blocked by the side surface of 6. Then, when the plunger 6 is pushed in by a predetermined amount, the discharge path 12 now faces the cylinder side opening of the through hole 6a. Here, since the solenoid 1 is still in the ON state and the discharge path 2 is closed, the flow path 7
The fuel on the side does not flow back, ie it does not return. Then, at the fuel injection end timing, the solenoid 1 is turned off,
The discharge path 2 is opened. Then, the flow path 7, the through hole 6a, the cylinder side opening of the through hole 6a, and the discharge path 12 are directly connected, so that the fuel remaining in the flow path 7 is It passes through the cylinder side opening of 6a and the discharge passage 12 in that order, and is quickly returned to the fuel supply side.

Then, due to the spring force of the compression spring 5 and the pressure acting on the bottom surface of the plunger 6, the plunger 6 is returned in the opposite direction and returns to the position before the fuel injection. Since the notch 6b continuously provided to the cylinder side opening of the hole 6a is located at a position facing the discharge path 12 from beginning to end,
The fuel remaining in the flow path 7 still has a
It passes through 6a, the notch 6b, and the discharge path 12 in that order, and is quickly returned to the fuel supply side.

Thus, immediately after the fuel injection end timing, the plunger 6
Until it returns to the position before fuel injection,
Since 12 is always in communication with each other through the through hole 6A, the fuel on the flow path 7 side satisfactorily escapes to the discharge path 12 side, and the occurrence of residual injection at the fuel injection end timing is prevented. As a result, the responsiveness of the device is improved.

Then, the plunger 6 returns to the original position before the fuel injection,
That is, when the discharge path 12 and the cylinder side opening of the through hole 6a face each other, the solenoid 1 is turned on,
The discharge passage 2 is closed and put in a standby state for the next injection.

The present invention is not limited to the above embodiment,
Various modifications can be made without departing from the spirit of the invention. For example, in the above embodiment, the application example to the electronic fuel injection device is described, but the fuel injection device of the present invention is a mechanical fuel injection device. The same can be applied to the injection device.

Further, although the fuel injection device of the above embodiment is applied to a diesel engine, it goes without saying that the fuel injection device of the present invention can also be applied to a gasoline engine.

(Effects of the Invention) As described above, according to the fuel injection device of the present invention, the fuel injection device includes a cylinder connected to the fuel supply passage, a plunger slidable in the cylinder, the cylinder and the fuel. A flow path that connects the injection port and sends the fuel compressed by the plunger to the fuel injection port and sends back the residual fuel into the cylinder at the end of injection, and is connected to the cylinder at the end of injection. A discharge path for returning the sent-back fuel to the fuel supply side, the plunger sends fuel from the fuel supply path to the flow path side before fuel injection, and immediately after the fuel injection end timing. Since the plunger is returned to the position before the fuel injection, the through hole for letting the fuel from the flow path side escape to the discharge passage is provided, so that the plunger does not start immediately after the fuel injection end timing. The fuel from the flow path side can always escape quickly to the discharge path through the through hole before the engine slides back to the position before fuel injection, and residual injection occurs at the fuel injection end timing. Is prevented, and the fuel injection device has excellent responsiveness.

[Brief description of drawings]

FIG. 1 is a side sectional view of a fuel injection device showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA in FIG. 1, and FIG. 3 is a side sectional view of a fuel injection device showing a prior art. . 2, 12 ... Discharge path, 3 ... Fuel supply path, 4 ... Cylinder,
4a ... Chamber, 6 ... Plunger, 6A, 6a ... Through hole, 6b ... Notch, 7 ... Flow path, 10 ... Connection path.

Claims (1)

[Scope of utility model registration request] 1. A cylinder connected to a fuel supply passage, a plunger slidable in the cylinder, the cylinder and a fuel injection port are connected to each other, and the fuel compressed by the plunger is supplied to the fuel injection port. Along with the sending, at the end of injection, a flow path for returning the residual fuel into the cylinder, and a discharge path that is connected to the cylinder and returns the sent fuel at the end of injection to the fuel supply side, Before the fuel injection, the fuel is sent to the flow path side from the fuel supply path, and the flow path side is provided immediately after the fuel injection end timing until the plunger returns to the position before the fuel injection. A fuel injection device, characterized in that a through hole for letting the fuel from the inside escape to the discharge passage is provided.