JPH034781Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a fuel injection pump for an internal combustion engine.

[Conventional technology]

Diesel engines use in-line or distributed fuel injection pumps, and their structure, as is widely known, is that a pump chamber and cylinder are formed within the pump body, and the pump chamber and cylinder are connected by a fuel passage. The plunger is connected to the cylinder and is slidably fitted into the cylinder to forcefully feed fuel toward the fuel injection nozzle.

[Problem that the invention attempts to solve]

Light oil is generally known as the fuel for diesel engines. Today, the use of alternative fuels to petroleum fuel is being considered, and alcohol is said to be one of the promising alternatives. However, the boiling point of alcohol is lower than that of light oil, so there is a problem in that vapor is likely to be generated within the pump body. When the amount of fuel vapor increases, a problem arises in that proper fuel injection cannot be performed.

[Means for solving problems]

The present invention is a fuel injection pump as described above, which is characterized in that a fuel passage connecting the pump chamber and the cylinder and a bypass passage connecting the outside of the pump are provided. A small amount of fuel is always discharged from this bypass passage, and vapor in the fuel passage is released together with this fuel.

〔Example〕

FIG. 1 shows a first embodiment of the present invention, most of the detailed structure of which is known as a distribution type fuel injection pump. A pump chamber 12 and a cylinder 14 are formed within the pump body 10. The inside of the pump chamber 12 is filled with fuel from a fuel tank 16 via a feed pump 18 and a pressure regulating valve 20 at a predetermined pressure. In FIG. 1, the feed pump 18 expanded 90 degrees is schematically shown by 18'. The feed pump 18 is driven by a drive shaft 22 connected to the output shaft of the engine, and a gear 24 is further attached to the drive shaft 22, and the gear 24 engages with a known governor mechanism 26.

A plunger 28 is slidably fitted into the cylinder 14 . At the tip of the plunger 28 is a known suction group 28a, with a port extending through its center. A distribution port opens radially from this center port on the outer circumferential surface of the plunger 28, and when it meets one of the distribution passages 30 provided in the cylinder corresponding to the cylinder, fuel is pumped to the fuel injection nozzle 32 of that cylinder. do. The central port is further connected to a spill port 32, and fuel pumping is completed when a spill ring 34 releases this spill port 32. The position of the spill ring 34 is controlled by operating an adjuster steering lever 36, so that fuel is injected in an amount corresponding to the load.

The plunger 28 is connected to a cam plate 38, and the cam plate 38 is connected to the drive shaft 2.
2 via a coupling ring, and is relatively movable in the axial direction while transmitting rotation. The cam plate 38 further includes a timer roller 4.
0 and moves in the axial direction. Thus, plunger 28 is rotatably movable axially to pump and distribute fuel between the cylinders.

A fuel passage 42 is provided to connect the pump chamber 12 and the cylinder 14 in order to introduce fuel into the cylinder 14 at the plunger tip end side. In the embodiment shown in FIG. 1, this fuel passage 42 extends in a dogleg shape, and a valve body of a fuel cut solenoid valve 44 is engaged with one end of the dogleg-shaped fuel passage 42 facing perpendicularly to the cylinder 14. It is becoming more and more common. According to the present invention, a bypass passage 46 is provided to connect the fuel passage 42 to the outside of the pump body 10. That is, the bypass passage 46 extends from the curved portion of the dogleg-shaped fuel passage 42, facing the pump chamber 12 and parallel to the cylinder 14, and
0 is connected to an overflow pipe 48 on the outside. This overflow pipe 48 is connected to the fuel tank 16. This overflow pipe 4
8, the overflow fuel from the fuel injection nozzle 32 and the passage 50 are directly connected to the pump chamber 12.
It is designed so that overflow fuel discharged from the two can join together. An appropriate throttle 52 is provided in the middle of the bypass passage 46, so that the amount of fuel flowing through the bypass passage 46 is relatively small.

The basic operation of the fuel injection pump configured as described above is well known, so detailed explanation will be omitted. Along with the pressure-feeding action of the fuel injection pump, the fuel bubbles due to the stirring action of the feed pump 18, for example. Furthermore, the inside of the pump becomes high temperature due to frictional heat from each sliding part of the fuel injection pump and radiant heat from the engine body. When alcohol or the like having a lower boiling point than light oil is used as a fuel, a large amount of fuel vapor is generated due to such a temperature. Therefore, vapor is mixed into the pump chamber 12. Some of this vapor is in the passage 50.
However, vapor is still contained in the fuel introduced into the fuel passage 42. Most of the fuel introduced into the fuel passage 42 is supplied to the cylinder 14, while the remaining small amount is discharged from the bypass passage 46 via the throttle 52.

If there is vapor within the fuel passageway 42, the vapor will generally lie along the top surface of the wall forming the passageway. The bypass passage 44 according to the present invention is located at a higher position than the portion of the fuel passage 42 that communicates perpendicularly to the cylinder 14 and forms the above-mentioned upper wall surface, and a portion of the fuel is continuous from the fuel passage 42 to the bypass passage 46. Therefore, most of the vapor in the fuel is discharged from the bypass passage 46. However, some of the vapor may flow into the cylinder 14, but it will not be a major problem. This is because the biggest problem with vapor is that it grows and blocks the inlet to the cylinder 14, interrupting the substantial supply of fuel. If the bypass passage 46 were not present, the vapor on the upper wall surface of the fuel passage 42 would gradually collect and its volume would increase, displacing the liquid fuel and being sucked into the cylinder 14 at once, resulting in substantial fuel Supply is interrupted. According to the invention, the vapor does not stay in one place and therefore does not grow as such.

FIG. 2 shows a second embodiment of the present invention, and most of the configuration is similar to the first embodiment. In FIG. 2, the fuel passage 2 extends horizontally from the pump chamber 12;
Subsequently, it is bent at a right angle and communicates with the cylinder 14. The fuel cut solenoid valve 44 engages the horizontal inlet side of the fuel passage 42, and the bypass passage 46 is connected to the fuel passage 42 above the vertical outlet side of the fuel passage 42. It is clear that with this configuration, the vapor in the fuel passage 42 is more easily discharged.

[Effect of idea]

As explained above, according to the present invention, it is possible to prevent fuel vapor from being sucked into the cylinder, so that it is possible to use alcohol with a low boiling point in the same way as general light oil.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention, and FIG. 2 is a sectional view of essential parts of a second embodiment. 10...Pump body, 12...Pump chamber, 14
... cylinder, 28 ... plunger, 42 ... fuel passage, 46 ... bypass passage.

Claims (1)

[Scope of utility model registration request] A fuel injection pump in which a pump chamber and a cylinder are formed in a pump body, a fuel passage is provided to connect the pump chamber and the cylinder, and fuel is pumped by a plunger slidably fitted to the cylinder. A fuel injection pump characterized in that a bypass passage is provided for connecting the fuel passage and the outside of the pump.