JPH0217177Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention reciprocates a plunger within a barrel by the cam action of a cam engaged with the plunger and the spring force of a plunger spring. The fuel is supplied to the fuel chamber formed on the outside of the barrel by an appropriate feed pump through an oil passage formed on the top surface of the plunger and the side circumferential surface of the plunger. The present invention relates to a fuel injection pump for an internal combustion engine that is capable of sucking fuel into a pressurizing chamber and feeding the fuel under pressure.

(Prior Art) In this type of plunger-type fuel injection pump, when the plunger pressurizes the fuel in the fuel pressurizing chamber formed on the top surface side of the plunger, the plunger is slidably fitted into the fuel pressurizing chamber. A portion of the fuel oil leaks to the cam for driving the plunger through the fitting gap between the side peripheral surface of the plunger and the inner peripheral surface of the barrel. However, in the case where the cam chamber is lubricated by the engine's system oil (this type of structure has been particularly popular in recent years), as mentioned above, the leaked fuel leaking from the fitting gap is absorbed into the cam chamber. If the lubricating oil flows into the cam chamber, the lubricating oil in the cam chamber will be diluted by the leaked fuel, which will adversely affect the lubricating characteristics of various parts of the engine. Therefore, it is necessary to extract this leaked oil by some means before it flows into the cam chamber. Conventional techniques developed for this purpose include, for example, U.S. Pat. There is a device that extracts water using a circumferential groove formed to surround it and discharges it to the outside. However, in this known example, the circumferential groove for extracting leaked fuel is opened to the atmosphere as it is, so the atmospheric pressure inside the circumferential groove is applied and the leaking fuel extraction effect is insufficient. However, there is still a risk that the engine system oil may be diluted by the leaked fuel.

(Purpose of the invention) The present invention makes it possible to more efficiently extract leaked fuel that leaks into the cam chamber through the fitting gap between the barrel and the plunger, and to dilute the lubricating oil in the cam chamber with the leaked fuel. The purpose of this invention is to provide a fuel injection pump for an internal combustion engine that can suppress the

(Structure of the invention) The fuel injection pump for an internal combustion engine of the invention has a circumferential groove for extracting leaked fuel formed on the inner circumferential surface of the barrel so as to surround the outer circumferential surface of the plunger, and the circumferential groove is used for fuel supply. The leakage fuel in the circumferential groove is forcibly sucked and discharged by the suction port pressure of the feed pump, thereby allowing the leakage fuel to dilute the lubricating oil in the cam chamber. It is characterized by suppressing the

(Embodiment) FIG. 1 shows the main parts of a row-type fuel injection pump Z for an internal combustion engine according to an embodiment of the present invention. 3 is a sleeve fitted on the outside of the barrel 2; 4 is a plunger fitted in the barrel 2 so as to be slidable and relatively rotatable; 5 is formed on the outside of the sleeve 3; The fuel chamber 5 has a fuel inlet 6 and a fuel outlet 7 opened therein. Further, reference numeral 8 is a cam for driving the plunger 4 disposed in a cam chamber 32 formed at the lower part of the pump body 1, 9 is a plunger spring, and 10 is a metering rack for rotating the plunger 4.

Further, reference numeral 20 is a feed pump, and a discharge port 22 of the feed pump 20 is connected to the fuel inlet 6 of the fuel injection pump Z via a fuel supply pipe 14.
In addition, the suction port 23 is connected to the fuel return pipe 15.
are respectively communicated with the fuel outlet 7 via. In addition, the code|symbol 21 is a fuel tank.

The fuel injection pump Z configured in this manner causes the plunger 4 to reciprocate within the barrel 2 by the cam action of the cam 8 and the spring force of the plunger spring 9, so that the fuel chamber 5 is injected into the fuel chamber 5 by the feed pump 20. An oil escape port 24 formed in the side wall of the barrel 2 and the plunger 4
The fuel is sucked into a pressurizing chamber 17 formed on the top surface 4a of the plunger 4 through an oil passage 18 formed across the top surface 4a and side peripheral surface 4b of the plunger 4, and pressurized.
The fuel is force-fed through the delivery valve 19 to a fuel injection valve (not shown). The amount of fuel to be injected is determined by appropriately rotating the plunger 4 relative to the barrel 2 by means of the metering rack 10, which is moved forward and backward depending on the operating state of the engine.
4 and the oil passage 18 of the plunger 4 to adjust the amount of escaped oil discharged from the oil escape port 24 to the fuel outlet 7 side via the fuel chamber 5.

By the way, in the fuel injection pump Z configured as described above, when feeding fuel under pressure, the plunger 4 passes through the fitting gap between the plunger 4 and the barrel 2.
from the oil passage 18 side to the barrel lower end 2b side (i.e.
A portion of the fuel oil may leak into the cam chamber 32 side), and the lubricating oil within the cam chamber 32 may be diluted by the leaked fuel. Therefore, in the fuel injection pump Z of this embodiment, there are two circumferential grooves on the inner circumferential surface 2a of the barrel 2, that is, the lower end of the barrel further than the lowest position of the oil passage 18 of the barrel 2 and the plunger 4. A first circumferential groove 30 is formed at a position on the 2b side so as to surround the side circumferential surface 4b of the plunger 4.
and the barrel lower end 2b further from the first circumferential groove 30.
A second circumferential groove 25, which is the main body of the present invention, is formed at a offset position, and the first circumferential groove 30 and the second circumferential groove 2
5, the leaked fuel is extracted in two stages. That is, the first circumferential groove 30 is connected to the first diagonal hole 2
9 is connected to the fuel chamber 5, and the first It acts to cause the fuel to flow back into the fuel chamber 5 through the oblique hole 29. Note that since the first circumferential groove 30 is loaded with the feed pressure of the feed pump 20, leaked fuel cannot be completely extracted. The leaked fuel that cannot be extracted by the first circumferential groove 30 is extracted by the second circumferential groove 25, which will be described later.

The second circumferential groove 25 communicates with a leak fuel outlet 27 formed in the pump body 1 via an oblique hole 26 formed across the barrel 2 and sleeve 3. Furthermore, this leak fuel outlet 27 is
The leak fuel return pipe 16 communicates with the suction port 23 of the feed pump 20. Therefore, almost all of the leaked fuel leaking from the first circumferential groove 30 toward the second circumferential groove 25 is suctioned and extracted by the suction pressure of the feed pump 20 that is applied to the second circumferential groove 25. The water is then refluxed to the feed pump 20 side.
Therefore, there is almost no possibility that fuel oil will get mixed into the lubricating oil (engine system oil is used in this embodiment) in the cam chamber 32 and the lubricating oil will be diluted by the fuel oil. It becomes possible to maintain good oiliness of the lubricating oil over a long period of time.

(Effect of the invention) The fuel injection pump for an internal combustion engine of the invention prevents leaked fuel leaking into the cam chamber through the fitting gap between the barrel and the plunger by surrounding the outer peripheral surface of the plunger onto the inner peripheral surface of the barrel. The fuel oil collected in the circumferential groove is collected by the circumferential groove formed in this way, and the fuel oil collected in the circumferential groove is sucked and extracted by the feed pressure of the feed pump. Compared to the case where the circumferential groove for extracting leaked fuel is opened to the atmosphere, leaked fuel can be extracted more efficiently and more completely, and the lubricating oil in the cam chamber can be diluted by the leaked fuel. This has the practical effect of being able to effectively suppress this.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a main part of a fuel injection pump according to an embodiment of the present invention. 2...Barrel, 4...Plunger, 5...Fuel chamber, 8
...Cam, 9...Plunger spring, 17...Fuel pressurization chamber, 18...Oil passage, 20...Feed pump,
23...Suction port, 25...Peripheral groove.

Claims (1)

[Scope of utility model registration request] By reciprocating the plunger 4 within the barrel 2 by the cam action of the cam 8 engaged with the plunger 4 and the spring force of the plunger spring 9, the barrel 2 is moved by an appropriate feed pump 20. An oil passageway 18 is formed on the top surface 4a of the plunger 4 through which fuel is supplied into the fuel chamber 5 formed on the outside through an oil passage 18 formed across the top surface 4a and side peripheral surface 4b of the plunger 4. A fuel injection pump for an internal combustion engine capable of sucking fuel into a pressurizing chamber 17 and feeding the fuel under pressure, the barrel 2
Moreover, the lower end portion 2b of the barrel is located closer to the cam 8 than the position corresponding to the oil passage 18 of the plunger 4.
A circumferential groove 25 is formed on the inner circumferential surface 2a of the side so as to surround the side circumferential surface 4b of the plunger 4, and furthermore, the circumferential groove 25 is communicated with the suction port 23 of the feed pump 20. Features of this fuel injection pump for internal combustion engines.