JPH0643263U - Fuel injection pump - Google Patents

Abstract

(57) [Summary] (Correction) [Objective] By increasing the fuel injection pressure, the spill pressure of the plunger after pumping the fuel increased, and cavitation occurred in the fuel in the oil reservoir. Even in the case, to provide a fuel injection pump capable of preventing erosion of the fuel injection pump housing and improving its durability. [Structure] An oil reservoir chamber 10 is provided between the housing 2 of the fuel injection pump 1 and a plunger barrel 12 mounted in a fitting hole 11 formed in the housing 2. In order to prevent cavitation erosion of the housing 2, a protective member 13 having a hardness higher than that of the housing 2 is provided at a portion where the fuel is likely to settle.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection pump for a diesel engine, and more particularly to a variable prestrooke fuel injection pump capable of preventing cavitation erosion of a fuel injection pump housing.

[0002]

[Prior art]

 A conventional prestroke variable fuel injection pump used in a diesel engine is shown in FIG. Normally, the housing 2 of the fuel injection pump 1 is formed of an aluminum alloy, and by rotating the operating shaft 3 in the housing 2 in the circumferential direction, the lever 4 attached to the operating shaft 3 is rotated. The pre-stroke of the plunger 6 is adjusted by changing the angle and moving up and down the position of the control sleeve 5 with which the tip of the lever 4 is engaged. As a result, the effective stroke of the plunger 6 is made variable, and the fuel injection amount is adjusted to an appropriate amount according to the engine load.

Further, when the pressure feeding of the fuel by the effective stroke of the plunger 6 is completed, the lead 7 formed in the plunger 6 and the vertical groove 8 communicate with each other, and the overflow amount from the spill port 9 of the control sleeve 5 during the pressure feeding of the fuel is reached. The pressurized fuel, that is, is jetted into the oil reservoir 10.

[0004]

[Problems to be solved by the device]

 By the way, in recent years, high-pressure fuel injection has been performed as a measure to reduce fuel consumption, exhaust emissions, and improve output. However, when the fuel injection pressure is increased, the fuel is pumped by the rise of the plunger 6. When the above is finished, the spill pressure of the pressurized fuel ejected from the spill port 9 of the control sleeve 5 also becomes high, and cavitation easily occurs in the fuel in the oil reservoir 10.

Then, there is a problem that the cavitation is collapsed by the spill pressure, and an impact pressure is applied to the housing 2 facing the oil reservoir 10 to cause erosion in the housing 2. Normally, the housing 2 of the fuel injection pump 1 is formed of an aluminum alloy having a relatively low hardness for the purpose of weight reduction. Therefore, the cavitation erosion is as shown by A in the housing 2 shown in FIG. The fuel in the oil storage chamber 10 is likely to settle, that is, the portion where cavitation is likely to be concentrated is likely to occur.

In view of the above problems, the present invention increases the fuel injection pressure to increase the spill pressure of the plunger after the fuel is pumped, which causes cavitation in the fuel in the oil sump chamber. An object of the present invention is to provide a fuel injection pump capable of preventing erosion of the fuel injection pump housing and improving its durability even if it occurs.

[0007]

[Means for Solving the Problems]

 The fuel injection pump of the present invention for achieving the above object has an oil reservoir between a housing of the fuel injection pump and a plunger barrel mounted in a fitting hole formed in the housing. A protective member having a hardness higher than that of the housing is provided in a portion of the oil reservoir where fuel is likely to settle so as to prevent cavitation erosion of the housing.

The portion where the protective member is provided is such that when fuel is injected from the pressurizing chamber between the plunger and the delivery valve through the spill port of the control sleeve into the oil reservoir chamber after the fuel injection is completed. It is preferable to install the cavitation generated in a region where the cavitation is likely to concentrate, that is, in a region where the fuel is likely to settle and the cross-sectional area is small and narrow in the oil reservoir. It is preferable to use a metal material or a ceramic material having a higher hardness than the housing of the injection pump.

[0009]

[Operation] The fuel injection pump of the present invention has the above-described structure, and is used when the fuel injected from the spill port of the control sleeve causes cavitation in the fuel in the oil reservoir after the fuel injection is completed. However, since a high-hardness protective member is provided at the site that is easily subject to erosion due to the collapse of cavitation, it is possible to prevent erosion from occurring in the housing of the fuel injection pump.

[0010]

【Example】

 An embodiment in which the present invention is applied to the conventional fuel injection pump 1 shown in FIG. 4 will be described with reference to the drawings. First, as shown in FIG. 4, a fitting hole 11 is formed in the housing 2 of the fuel injection pump 1, and a plunger barrel 12 is mounted in the fitting hole 11. An oil sump chamber 10 is formed between the plunger barrel 12 and the aluminum alloy housing 2, and a narrow space B in the oil sump chamber 10 has a height as shown in FIG. A protective member (protective cup) 13 made of hard steel (stainless steel) is provided.

The protective cup 13 is formed in a dish shape having a bead 13 b formed on the bottom 13 a for preventing rattling, and when the protective cup 13 is mounted on the housing 2, the diameter of the oil storage chamber 10 is reduced. Even if the diameter of the fitting hole 11 is smaller than that of the fitting hole 11, the fitting hole 11 is preliminarily divided into two parts as shown in FIG. 2 so that the fitting hole 11 can be mounted in close contact with the inner peripheral wall 10a. Further, the edge portion 13c of the protective cup 13 projects higher than the height of the flange portion 12a of the plunger barrel 12, and the height of the entire edge portion 13c is usually about 5 mm.

In the fuel injection pump 1 provided with such a protection cup 13, pressurized fuel is jetted from the spill port 9 of the control sleeve 5, causing cavitation in the fuel in the oil sump chamber 10 Even if the cavitation collapses due to the pressure and impact pressure acts on the surroundings, the protection cup 13 is provided in the narrow space B in the oil reservoir 10 where the cavitation easily concentrates. The housing 2 is protected from impact pressure and cavitation erosion is prevented.

In the present embodiment, as shown in FIG. 3, the joint portion 13 d of the protective cup 13 divided into two parts causes cavitation particularly due to the influence of the opening direction of the spill port 9 of the control sleeve 5. It is pre-positioned so that it will not be placed at the position indicated by C, which is easy. In this case, although not shown, a publicly known positioning pin or the like may be used to prevent the position of the protection cup 13 from shifting.

In the present embodiment, the protective cup 13 is provided in the oil reservoir 10 where the cavitation generated in the fuel tends to settle, that is, between the flange 12 a of the plunger barrel 12 and the housing 2. However, it may be provided in another narrow portion in the oil reservoir 10 similar to this portion. Further, although steel (stainless steel) is used as the material of the protective cup 13 in this embodiment, other materials such as high hardness metal or ceramic may be used.

[0015]

[Effect of device]

 The fuel injection pump of the present invention has an oil reservoir between the housing of the fuel injection pump and the plunger barrel mounted in the fitting hole formed in the housing, and the fuel in the oil reservoir is likely to settle. Since a protective member having a hardness higher than that of the housing is provided in the portion so as to prevent the cavitation erosion of the housing, the following effects can be obtained.

Since the protection member is arranged in a portion where cavitation is easily concentrated, cavitation occurs in the fuel in the oil storage chamber, and the impact pressure when the cavitation collapses due to spill pressure Even when acting on the pump housing, the housing is protected from the impact pressure by the protective member, so that the cavitation erosion is prevented from occurring in the housing of the fuel injection pump and its durability is improved. You can

Further, since the fuel injection pressure can be increased as much as possible while sufficiently ensuring the durability of the fuel injection pump, fuel consumption is improved and harmful components in exhaust gas are reduced. The output can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a fuel injection pump according to an embodiment of the present invention.

FIG. 2 is a perspective view of a protection member used in the fuel injection pump of FIG.

FIG. 3 is a plan view showing an installed state of the protection member of FIG.

FIG. 4 is a vertical sectional view of a conventional fuel injection pump.

[Explanation of symbols]

1 Fuel injection pump 2 Housing 10 Oil reservoir 11 Fitting hole 12 Plunger barrel 13 Protective member (protective cup)

Claims (1)

[Scope of utility model registration request] 1. An oil sump chamber is provided between a housing of a fuel injection pump and a plunger barrel mounted in a fitting hole formed in the housing, and a portion of the oil sump chamber where fuel is likely to settle, A fuel injection pump comprising a protective member having a hardness higher than that of the housing so as to prevent cavitation erosion of the housing.