KR20000026444A - High voltage fuel pump for directly injecting gasoline - Google Patents

Abstract

PURPOSE: A high voltage fuel pump is provided to increase the feed rate of fuel by generating high voltage when a plunger does the rectilinear reciprocating motion by reducing the leaked amount of fuel. CONSTITUTION: An eccentric cam(5) is revolved centering upon a camshaft(5a) through the driving force of an engine. The displacement of a position caused by the rotation of the eccentric cam is compensated by the elastic force of a bellows(6). Fuel in a pump housing(1) is compressed with high pressure by inserting a plunger(3) into a barrel(2) as the bellows is contracted if the eccentric cam reaches a resemblance like a full line. Then, the fuel is transferred to a cylinder after pushing a discharge valve plate(8). A part of the fuel introduced into the pump housing flows into each groove through a clearance between the barrel and the plunger. The fuel introduced into the groove is turbulently flowed in the groove through the rectilinear reciprocating motion of the plunger to vanish the kinetic energy leaked along the outer circumference of the plunger.

Description

High Pressure Fuel Pump for Gasoline Direct Injection

The present invention relates to a high-pressure fuel pump for direct injection of gasoline, and more particularly, to prevent the fuel from leaking through the clearance between the plunger and the barrel so that a high pressure is generated during the linear reciprocation of the plunger, thereby increasing the amount of fuel supplied. It relates to a high pressure fuel pump for direct injection of gasoline.

In general, a fuel pump for supplying fuel to a vehicle engine may be classified into a high pressure fuel pump for directly injecting fuel into a combustion cylinder and a low pressure fuel pump for injecting fuel into an injection port of a fuel line to supply fuel to the engine's suction power. The former is mainly used for diesel engines, and the latter has been mainly used for port injection gasoline engines.

However, the recent technical trend of engine development is a time when the technology conversion is being made by direct injection type which shows excellent performance in fuel efficiency, output improvement and emission reduction in not only diesel engine but also gasoline engine. In particular, research and development and commercialization of gasoline direct injection (GDI) engines to replace the MPI (Multi Port Injection) engines currently used in gasoline engines are imminent worldwide.

On the other hand, in the gasoline direct injection engine, when the low pressure fuel pump used for the conventional port injection gasoline engine is used, the fuel flows backward because the pressure in the combustion cylinder (about 8 bar) is higher than the fuel pressure pressure (about 3 bar) of the low pressure fuel pump. Therefore, in order to supply fuel directly to the gasoline direct injection engine, a high pressure fuel pump that can overcome the pressure in the cylinder is used.

An example of the above-described high pressure fuel pump for direct injection of gasoline will be described with reference to the accompanying drawings.

1 is a cross-sectional view showing the structure of a high pressure fuel pump, wherein the high pressure fuel pump includes a pump housing 1, a barrel 2 formed inside the pump housing 1, and a straight reciprocation of the inside of the barrel 2; Plunger 3 for sucking fuel and pumping it at high pressure while moving, a movable plate 4 connected to the plunger 3 while being disposed at one end of the pump housing 1, and spaced apart from the movable plate 4 by a predetermined distance. Eccentric cam 5 and a movable plate which are installed to be rotatable through a cam shaft 5a and linearly move the plunger 3 through the movable plate 4 while being rotated by receiving a driving force of an engine (not shown). 4) and a bellows 6 interposed between the pump housing 1 and the plunger to prevent lubrication film breakage by blocking external leakage of gasoline while linearly reciprocating with the plunger 3 during rotation of the eccentric cam 5. In the suction action of (3), fuel in the fuel tank (not shown) of the pump housing (1) Is achieved by the fuel of the intake valve plate 7 and the pump housing (1) for guiding the flow into the portion including the discharge valve plate (8) for guiding the discharge side of the cylinder.

When the operation of the conventional high pressure fuel pump configured as described above is briefly described, the eccentric cam 5 is rotated about the cam shaft 5a by the driving force of the engine when the engine is driven, and is generated by the rotation of the eccentric cam 5. The position displacement is compensated by the elastic force of the bellows 6. That is, when the eccentric cam 4 reaches the bottom dead center like the imaginary line, the bellows 6 is expanded so that the plunger 3 is drawn out of the barrel 2. In this case, a negative pressure is generated in the pump housing 1 so that fuel pushes the suction valve plate 7 and is sucked into the pump housing 1.

Subsequently, when the eccentric cam 5 continues to rotate and reaches the top dead center as in the solid line, the bellows 6 contracts and the plunger 3 is inserted into the barrel 2 so that the fuel inside the pump housing 1 can be pressurized. And the fuel is pushed to the cylinder side by pushing the discharge valve plate (8). By repeating this operation, the fuel feeding operation is performed.

In this case, low pressure fuel pumps, which are generally used in gasoline engines, are not a big problem for leakage, wear, and durability. However, in the case of high pressure fuel pumps, problems regarding pump durability such as leakage due to high pressure generation and abrasion of relative contacts are generated. have.

In more detail, the high pressure fuel pump has to form the clearance between the plunger 3 and the barrel 2 as narrowly as possible in order to pressurize the fuel to a high pressure during the linear reciprocation of the plunger 3. In order to overcome the deterioration in durability due to the friction loss and the increase in the amount of wear, a wide clearance must be formed, and therefore, there are technical difficulties in satisfying two opposing functions.

In the case of high pressure fuel pumps used in diesel engines, clearance is very narrowly set to generate high pressure, and surface treatment and mirror roughness management of the mating contact part are performed to prevent friction and abrasion caused by this. The lubricating oil supply line is installed in the center of the falling barrel, so that the lubrication is performed as smoothly as possible. However, recently, as regulations on the purification of fuel components are strengthened due to the tightening of the exhaust gas regulations, the lubrication of the fuel itself is significantly lowered, and thus technical solutions are required. In the case of diesel engines, the regulation of sulfur components, which played a major role in the lubricity of the fuel itself, has caused serious friction and wear problems in fuel pumps and injectors in diesel vehicles.

In particular, in the case of gasoline direct injection engines, which are in the spotlight as the next generation engine, the problem is even more serious. The basic fuel lubricity is only about 1/4 of diesel fuel, and unlike diesel engines, no lubricating oil can be supplied, resulting in severe friction and wear.

The gasoline fuel is designed to prevent direct contact between the engine oil and the fuel supply line in the gasoline direct injection engine because the main component is a cleaning component that destroys the lubrication film of the engine oil. Therefore, the high pressure fuel pump for the gasoline direct injection engine should be lubricated only by the gasoline fuel itself without lubricating oil supply, and it is difficult to generate high pressure because it maintains a relatively wide clearance for lubrication. To this end, currently applied technologies are applied with surface treatment and contact surface anti-wear coating to reduce the clearance as much as possible and to reduce friction and wear, but this method solves the problems caused by the low lubricity of gasoline itself. Because of this, there is still a wide clearance.

Therefore, according to the conventional high pressure fuel pump for gasoline direct injection as described above, a very large clearance is formed therebetween in order to reduce frictional resistance between the barrel 2 as the stationary part and the plunger 3 as the moving part. Although the purpose of improving the durability of each component (2) and (3) can be achieved, a large amount of fuel is leaked through the clearance, and in particular, since the viscosity of the gasoline fuel is very low, the barrel (2) The fuel introduced into the clearance between the and plunger 3 leaked out very quickly. Therefore, since the high pressure is not generated inside the barrel 2 due to the leakage of fuel generated during the linear reciprocation of the plunger 3, the amount of fuel supply is inevitably small.

The present invention was created to solve the above problems, and effectively reduces the frictional resistance between the barrel and the plunger, as well as reducing the leakage of the fuel so that a high pressure is generated during the linear reciprocation of the plunger, thereby increasing the amount of fuel supplied. The aim is to provide a high pressure fuel pump for direct injection of gasoline that can be increased.

1 is a cross-sectional view showing the structure of a general high-pressure fuel pump for direct gasoline injection.

2 is a cross-sectional view of an embodiment according to the present invention.

3 is an enlarged cross-sectional view of portion A of FIG. 2 showing an operation state of a groove applied to an embodiment according to the present invention;

Figure 4 is a graph showing the pressure according to the depth of the grooves applied to the present invention compared with the pressure generated during the pumping of the high-pressure fuel pump according to the present invention.

<Description of the symbols used in the main parts of the drawing>

1: pump housing 2: barrel

3: plunger 4: movable plate

5: eccentric cam 6: bellows

10: groove

The present invention for achieving the object as described above, the pump housing, a barrel formed inside the pump housing, a plunger to suck the fuel and pressurized at high pressure while linearly reciprocating the inside of the barrel, and the engine In the high-pressure fuel pump for gasoline direct injection comprising an eccentric cam for linearly reciprocating the plunger via a driving force,

A plurality of grooves are formed in the circumferential direction on the outer circumferential surface of the plunger to prevent the fuel inside the pump housing from leaking between the plunger and the barrel.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 is a cross-sectional view of the embodiment according to the present invention, Figure 3 is an enlarged cross-sectional view of the portion A of Figure 2 for showing the grooves applied to the embodiment according to the present invention, Figure 4 is generated during the pumping action of the embodiment according to the present invention It is a graph comparing the pressure and the pressure generated according to the prior art and the pressure according to the depth of the groove applied to the present invention.

As shown therein, the high pressure fuel pump for direct injection of gasoline according to the present invention includes a pump housing 1, a barrel 2 formed inside the pump housing 1, and a predetermined clearance inside the barrel 2. The plunger 3 is slidably disposed while maintaining the plunger, and plunger 3 sucks fuel at high pressure while linearly reciprocating the inside of the barrel 2, and is connected to the plunger 3 while being disposed at one end of the pump housing 1. The movable plate 4 and the cam plate 5a are rotatably installed at a spaced distance from the movable plate 4 and rotated by the driving force of the engine (not shown), and the plunger (4) moves through the movable plate 4. 3) the eccentric cam (5) for linear reciprocating movement, interposed between the movable plate (4) and the pump housing (1) while the linear reciprocating motion with the plunger (3) during rotation of the eccentric cam (5) Block external leakage to prevent damage to lubricant film A bellows 6, a suction valve plate 7 for guiding the fuel in a fuel tank (not shown) to flow into the pump housing 1 during the suction action of the plunger 3, and the inside of the pump housing 1 And a discharge valve plate 8 for guiding fuel to be discharged to the cylinder side, and a plurality of grooves 10 are formed on the outer circumferential surface of the plunger 3.

The depth of the groove 10 has a close relationship with the pressure generated during the straight reciprocating motion by the plunger 3, and can be used within the range of 0.1 mm ≤ groove depth ≤ 0.9 mm, in particular, the depth of 0.1 mm It is preferable.

Referring to the operational state of the embodiment according to the present invention configured as described above are as follows.

The fuel supply is made by the pressure generated when the plunger 3 linearly reciprocates the inside of the barrel 2 by the rotation of the eccentric cam 5. In more detail, the eccentric cam 5 is rotated about the camshaft 5a by the driving force of the engine when the engine is driven, and the position displacement generated by the rotation of the eccentric cam 5 is bellows. Compensated by the elastic force of (6). That is, when the eccentric cam 5 reaches the bottom dead center like the imaginary line, the bellows 6 is expanded so that the plunger 3 is drawn out of the barrel 2. In this case, a negative pressure is generated in the pump housing 1 so that fuel pushes the suction valve plate 7 and is sucked into the pump housing 1.

Subsequently, when the eccentric cam 4 continues to rotate and reaches the top dead center as in a solid line, the bellows 6 contracts and the plunger 3 is inserted into the barrel 2 so that the fuel inside the pump housing 1 can be pressurized. And the fuel is pushed to the cylinder side by pushing the discharge valve plate (8). By repeating this operation, the fuel feeding operation is performed.

On the other hand, some of the fuel introduced into the pump housing 1 flows into each groove 10 through the clearance between the barrel 2 and the plunger 3.

The fuel introduced into the groove 10 is turbulent in the groove 10 by the linear reciprocating motion of the plunger 3 to dissipate the kinetic energy to leak along the outer circumferential surface of the plunger 3.

That is, since the fuel flowing into the clearance is not leaked and is present between the barrel 2 and the plunger 3 so that a sealing effect is generated between the barrel 2 and the plunger 3, the reciprocating linear movement of the plunger 3 is performed. High pressure is generated. At this time, the lubrication between the barrel 2 and the plunger 3 is made by a clearance as before.

When compared with the conventional with reference to the graph attached to the generated pressure at this time, the graph shown in Figure 4 is divided into 10 segments when the groove 10 is viewed in the axial direction, 1 of the 10 divided segments By showing the pressure generated in the two segments, it can be seen that the pressure difference between the grooveless conventional and the present invention (when the depth of the groove 10 is 0.1mm) is 1.8 bar. On the basis of this, it will be appreciated that the pressure of the 18 bar is increased by the groove 10.

In addition, it can be seen that the generated pressure varies depending on the depth of the groove 10.

Therefore, since the clearance between the barrel 2 and the plunger 3 did not decrease during the linear reciprocation of the plunger 3 for high pressure generation, the sliding portion between the barrel 2 and the plunger 3 can be properly lubricated. In addition, since the fuel to be leaked through the clearance flows into the groove 10 and is turbulent to prevent leakage of the fuel, a sealing effect appears between the barrel 2 and the plunger 3 so that the straight reciprocation of the plunger 3 is performed. Since the generated pressure can be expected to be reduced without reducing the clearance during exercise, the fuel is pushed to a higher pressure than before.

As described above, according to the high pressure fuel pump for direct injection of gasoline according to the present invention, high pressure is generated during linear reciprocation of the plunger, so that the supply amount of fuel is increased, thereby increasing the utility as a fuel supply device.

In addition, the friction between each part and the amount of wear is reduced, as well as can generate a high pressure can be effectively used as a fuel pump for gasoline direct injection engine.

Claims (1)

A pump housing, a barrel formed inside the pump housing, a plunger that sucks fuel and pumps the fuel at a high pressure while linearly reciprocating the inside of the barrel, and an eccentric cam that linearly reciprocates the plunger under the driving force of the engine. In the high-pressure fuel pump for gasoline direct injection comprising a, A plurality of grooves are formed on the outer circumferential surface of the plunger in the circumferential direction so that fuel inside the pump housing does not leak through the plunger and the barrel.