JPH10266927A - Fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cavitation erosion from occurring to a lubrication system, by providing a fuel sump between the outer peripheral of a plunger and the inner peripheral of a plunger barrel, and equipping the plunger with a lubricating chamber pressurizing part. SOLUTION: A fuel sump 35 communicating with a lubricating chamber 13 through a communicating hole 36 is placed between the outer peripheral of a plunger 3 and the inner peripheral of a plunger barrel 2. A lubricating chamber pressurizing part 31 which pressurizes fuel in the sump 35 using reciprocating motion of the plunger 3 and sends it to the lubricating chamber 13 is placed in the plunger 3. Due to rising of the plunger 3, the lubricating chamber pressurizing part 31 supplies the fuel in the fuel sump 35 to the lubricating chamber 13 through the communicating hole 36. Therefore, pressure of the lubricating chamber 13 including a supply/exhaust port 6 is kept positive, and negative pressure cavity is prevented from being formed in a lubricating system after closing of the supply/exhaust port 6. In addition, pressure variance of high frequency wave is prevented from occurring after opening of the supply/ exhaust port 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jerk type fuel injection pump used for an internal combustion engine and a fuel injection pump such as a unit injector.

[0002]

2. Description of the Related Art FIG. 2 shows a system diagram of a fuel injection system for a diesel engine. In FIG. 2, 101 is a fuel tank, 103 is a refueling pump, 107 is a fuel injection pump, 1
Reference numeral 09 denotes a fuel injection valve. The fuel pumped from the fuel tank 101 to the fuel supply pipe 102 by the fuel supply pump 103 is filtered by a filter 104, and is supplied to a fuel supply main pipe 105.
Then, the fuel enters the fuel injection pump 107 provided for each cylinder via the fuel supply branch pipe 106 for each cylinder.

In the fuel injection pump 107, fuel is pressurized to a high pressure at a predetermined timing by a fuel cam (not shown) linked to a crankshaft. The fuel gas passes through the fuel injection valve 109 and is injected into the combustion chamber 110.

FIG. 4 is a longitudinal sectional view of a conventional fuel injection pump 107 in the fuel injection system.
In FIG. 4, 1 is a pump body, 2 is a plunger barrel fixed in the pump body 1, 3 is a plunger fitted reciprocally slidably on the inner periphery of the plunger barrel 2, 2.
Reference numeral 2 denotes a tappet for driving the plunger 3, reference numeral 21 denotes a tappet spring, reference numeral 24 denotes a pinion connected to the lower portion of the plunger 3 so as to be rotatable therewith, and reference numeral 25 denotes a fuel metering meshed with the pinion 24. It is a control rack.

Reference numeral 8 denotes a plunger chamber formed with the top surface 4 of the plunger 3 facing, 10 denotes a discharge valve, 23 denotes a discharge port communicating with the injection pipe 108 (see FIG. 2), 11 denotes a constant pressure valve, and 12 denotes Is a constant pressure valve restrictor provided to restrict the passage to the constant pressure valve 11. Reference numeral 106 denotes a refueling branch pipe, and a refueling main pipe 105 (see FIG. 2) from the refueling pump 103 (see FIG. 2).
It is connected to the. Reference numeral 14 denotes a fitting for fastening the joint of the refueling branch pipe 106 to the pump body 1.

Reference numeral 6 denotes an oil supply / discharge hole formed in the plunger barrel 2, and an oil supply chamber 13 is formed around the oil supply / discharge hole 6. Reference numeral 7 denotes a deflector for shock absorption during refueling. Reference numeral 4 denotes a plunger top which controls the start of fuel injection, and reference numeral 5 denotes a plunger lead which controls a fuel injection throttle.

When the engine having the conventional fuel injection pump 107 is operated, fuel of a predetermined fuel pressure is supplied to the fuel supply chamber 13 through the fuel supply main pipe 105 and the fuel supply branch pipe 106 by the fuel supply pump 103 shown in FIG. Supplied. When the fuel cam (not shown) is lifted and the plunger 3 is pushed up against the elasticity of the tappet spring 21 via the tappet 22 and the top surface 4 closes the oil supply / drainage hole 6, the plunger passes through the oil supply chamber 13. The pumping of the fuel filled in the chamber 8 starts.

The fuel in the plunger chamber 8 is pressurized as the plunger 3 rises, pushing the discharge valve 10 open, passing through the injection pipe 108 (see FIG. 2) from the discharge port 23, and the fuel injection valve 109 (see FIG. 2). To the injection valve 10).
From 9 is injected into the combustion chamber.

At the beginning of the discharge, while the plunger 3 is rising, the fuel flows back from the oil supply / discharge hole 6 to the oil supply system, and the oil supply system is slightly pressurized. For a while, as shown in FIG. 5A, the oil supply pressure, that is, the pressure of the oil supply system such as the oil supply chamber 13 decreases to "0" or negative pressure.

When the plunger 3 rises and the plunger lead 5 comes into contact with the lower edge of the oil supply / drainage hole 6, the high pressure plunger chamber 8 communicates with the oil supply / drainage hole 6, and the plunger chamber is connected. 8, the pressure in the fuel oil passage from the fuel injection valve 109 to the fuel injection valve 109 drops sharply, the discharge valve 10 lifted at the time of the discharge closes, the constant pressure valve opens, and the fuel is injected from the discharge port 23 by the restricting action of the constant pressure valve restrictor 12. The pressure of the high-pressure system reaching the valve 109 is adjusted.

Due to the opening of the oil supply / drainage hole 6, the high-pressure oil on the plunger chamber 8 side rapidly flows from the oil supply / drainage hole 6 to the oil supply chamber 1.
Spill to 3 Note that the deflector prevents the wall surface around the oil supply chamber 13 from being damaged due to the rapid oil drainage.

[0012]

In the above-described fuel injection pump, for a while from the moment when the oil supply / drainage hole 6 is closed by the top surface 4 of the plunger 3, the pressure of the oil supply system as shown in FIG. (Refueling pressure) is “0” (zero) or negative pressure.

When the oil supply / drain hole 6 is opened by the plunger lead 5 in this state, the high-pressure oil in the plunger chamber 8 flows backward from the oil supply / drain hole 6 to the oil supply chamber 13, and the oil supply pressure in the oil supply chamber 13 is reduced as shown in FIG. A high-frequency pressure fluctuation as shown in the Z section of FIG. 7A occurs, and as a result, the cavity at the negative pressure level as described above is destroyed, and the occurrence of cavitation erosion is observed.

On the other hand, when the oil supply pressure from the oil supply pump 103 is increased, as shown in FIG. 5B, a negative pressure phenomenon after the oil supply / discharge hole 6 is closed or the oil supply / The occurrence of high-frequency pressure fluctuations when opened is avoided.

However, in such a case, when the plunger 3 descends, the volume of the plunger chamber 8 increases by an amount corresponding to the discharge stroke.
As shown in the figure, the pressure of the oil supply chamber 13 (oil supply pressure) decreases to the negative pressure level between the time the oil supply / drainage hole 6 is closed and the time it is opened,
When the oil supply / drainage hole 6 is opened by the top surface 4 of the plunger 3 in this state, the high-pressure oil in the plunger chamber 8 is drained to the oil supply chamber 13 and a high-frequency pressure fluctuation as shown in FIG. Then, the occurrence of cavitation erosion near the top surface 4 of the plunger 3 is observed due to the depressing action of the negative pressure cavity near the oil supply hole 6 due to the high pressure.

In view of the problems of the prior art according to the present invention, by avoiding the formation of a cavity due to the pressure drop to the negative pressure level in the oil supply system before and after the oil supply / drain hole is closed by the plunger, such a cavity is prevented. It is an object of the present invention to provide a fuel injection pump having improved durability by preventing occurrence of cavitation erosion in an oil supply system due to formation of a tee.

[0017]

According to the present invention, there is provided a fuel supply chamber provided in a pump body, a plunger barrel having a supply / discharge oil hole communicated with the fuel supply chamber, and a plunger barrel. A plunger fitted reciprocally slidably on the inner periphery of the plunger barrel, wherein when the first lead portion of the plunger closes the oil supply / discharge hole, the plunger is supplied to the plunger chamber via the oil supply / discharge hole. Pressurized fuel is sent to the fuel injection valve, and when the second lead portion of the plunger opens the oil supply / drain hole, the fuel in the plunger chamber is returned from the oil supply / drain hole to the oil supply chamber. A fuel injection pump configured as described above, wherein, between the outer periphery of the plunger and the inner periphery of the plunger barrel, a fuel reservoir communicated with the fuel supply chamber through a communication hole is provided, and the plunger is provided in the plunger. Of the plunger Backward by proposing a fuel injection pump, characterized in that a fuel feed to pressurize the feed chamber Kyusuru feed chamber pressurizing in the fuel reservoir.

According to this invention, as the plunger 3 rises, the fuel supply chamber pressurizing portion integrated therewith also rises, the volume of the fuel reservoir is reduced, and the fuel stored in the fuel reservoir is pressurized. The fuel flows into the fueling chamber through the communication hole.

Thus, the pressure of the oil supply chamber including the inside of the oil supply / discharge hole is maintained at a positive pressure, and the formation of the negative pressure cavity of the oil supply system after the oil supply / discharge hole is closed as in the prior art is avoided. At the same time, the occurrence of high-frequency pressure fluctuation after the opening and closing of the oil supply / drain hole is also avoided. This prevents the negative pressure cavity from being destroyed by the high-pressure oil after the opening and closing of the oil supply / drainage holes, and the occurrence of cavitation erosion due to high-frequency pressure fluctuations in the oil supply system.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just

FIG. 1 is a sectional view of a fuel injection pump for a diesel engine according to an embodiment of the present invention. In FIG.
107 is a fuel injection pump, 1 is a pump body thereof, 2 is a plunger barrel fixed in the pump body 1, 3 is a plunger fitted reciprocally slidably on the inner periphery of the plunger barrel 2, and 22 is a plunger. Tappet 21 for driving the plunger 3, 21 is a tappet spring, 24 is a pinion connected to the lower part of the plunger 3 so as to be rotatable therewith, 25 is a control rack for fuel metering meshed with the pinion 24. It is.

Reference numeral 8 denotes a plunger chamber formed so as to face the top surface 4 of the plunger 3; 10, a discharge valve; 23, a discharge port connected to an injection pipe (see FIG. 2);
Reference numeral 2 denotes a constant-pressure valve restrictor provided to restrict the passage to the constant-pressure valve 11. Reference numeral 106 denotes a fuel supply branch pipe,
3 (see FIG. 2) from the refueling main pipe 105 (see FIG. 2). Reference numeral 14 denotes a fitting for fastening the joint of the refueling branch pipe 106 to the pump body 1. 6
Reference numeral denotes an oil supply / discharge hole formed in the plunger barrel 2, and an oil supply chamber 13 is formed around the oil supply / discharge hole 6. Reference numeral 7 denotes a deflector for buffering an impact when the oil is drained.

The above basic configuration is the same as that of the conventional fuel injection pump shown in FIG. 4. In the embodiment of the present invention, the plunger 3 and the plunger barrel 2 are improved. That is, in FIG. 1, a lower portion of the plunger 3 is provided with a refueling chamber pressurizing portion 31 formed to have a larger diameter D2 than an outer diameter D1 of an upper portion 32 where the plunger lead 5 in the upper portion of the plunger 3 is formed. I have.

The plunger barrel 2 has an upper hole 33 into which the upper part 32 of the plunger 3 is fitted, and a large-diameter (D2) lower hole 34 into which the oil supply chamber pressurizing part 31 is fitted.
And two holes are formed. A closed annular fuel reservoir 35 is formed between the outer periphery of the upper portion 32 of the plunger 3 above the oil supply chamber pressurizing portion 31 and the inner periphery of the lower hole 34 of the plunger barrel 2.

When the plunger 3 comes to the lowermost position (position of the plunger lift "0") as shown in FIG. 1, the fuel reservoir 35 has the largest volume, and the plunger 3 becomes a fuel cam (not shown) and a tappet. When pushed up to the uppermost position by 22, the smallest volume having a certain distance between the upper edge of the oil supply chamber pressurizing portion 31 and the stepped portion 39 between the upper hole 33 and the lower hole 34. Is a space in which the volume is changed by the movement of the plunger 3. The plunger barrel 2 is provided with a communication hole 36 for communicating the fuel reservoir 35 with the oil supply / drainage hole 6 for each oil supply / drainage hole 6.

During operation of the engine having the fuel injection pump having the above-described structure, the fuel supply chamber 13 is supplied with a fuel having a predetermined fuel pressure through the fuel supply main pipe 105 and the fuel supply branch pipe 106 by the fuel supply pump 103 shown in FIG. Is supplied. When the fuel cam (not shown) is lifted and the plunger 3 is pushed up against the elasticity of the tappet spring 21 via the tappet 22 and the top surface 4 closes the oil supply / discharge oil resistance 6, the plunger passes through the oil supply chamber 13. The pumping of the fuel filled in the chamber 8 starts.

The fuel in the plunger chamber 8 is pressurized with the rise of the plunger 3 and pushes the discharge valve 10 open.
The fuel is supplied from the discharge port 23 to the fuel injection valve 109 through the injection pipe 108 (see FIG. 2), and the fuel is supplied from the injection valve 109 to the combustion chamber 11.
It is injected within 0.

At the start of discharge, fuel flows backward from the oil supply / discharge hole 6 to the oil supply or the like while the plunger 3 is rising, and the oil supply / discharge system is slightly pressurized. In
As shown in FIG. 5A, the refueling pressure, that is, the pressure of the refueling system such as the refueling chamber 13 tends to decrease to "0" or negative pressure.

Then, when the plunger 3 is raised and the plunger lead 5 is applied to the lower edge of the oil supply / drainage hole 6, the plunger chamber 8 and the oil supply / drainage hole 6, which are under high pressure, are communicated with each other. The pressure in the fuel oil passage from the nozzle to the fuel injection valve 109 drops sharply, the discharge valve 10 lifted at the time of the discharge closes, the constant pressure valve 11 opens, and the constant pressure valve throttle 12
, The pressure of the high-pressure system from the discharge port 23 to the fuel injection valve 109 is adjusted.

With the opening of the oil supply / discharge hole 6, the high-pressure oil on the plunger chamber 8 side is rapidly discharged from the oil supply / discharge hole 6.
Spill to 3 The deflector 7 is for preventing the wall surface around the refueling chamber 13 from being damaged due to the rapid oil drainage. On the other hand, as the plunger 3 rises, the fuel supply chamber pressurizing portion 31 integral therewith also rises, thereby reducing the volume of the fuel reservoir 35. As a result, the fuel in the fuel reservoir 35 flows into the oil supply / drainage hole 6 through the communication hole 36, and the pressure of the oil supply system of the oil supply chamber 13 and the like connected to the oil supply / drainage hole 6 increases as shown in FIG. Part C (fill back)
And the pressure drop to the pressure “0” or the negative pressure as described above is avoided.

In FIG. 3, Y is the pressure of the fuel injection valve 109, that is, the injection pressure. Therefore, in this state, even if the plunger lead 5 opens the oil supply / drainage hole 6 as described above, and the high-pressure oil on the plunger chamber 8 side is discharged from the oil supply / drainage hole 6 to the oil supply chamber 13, the cavities due to the negative pressure are not affected. Since no tee is formed, no cavitation erosion occurs. Further, since no negative pressure is generated in the oil supply system immediately before oil discharge as described above, high-pressure oil is supplied to the oil supply chamber 1 immediately after the oil supply / discharge oil hole 6 is opened.
Even when the fuel is rapidly discharged into the fuel supply chamber 3, no high-frequency pressure fluctuation occurs in the fuel supply chamber 13 as shown in the Z part of FIG. 5, and a smooth pressure fluctuation with the high-frequency component removed as shown in FIG.

By preventing the occurrence of such cavitation erosion and high-frequency pressure fluctuation, damage to the oil supply system is prevented.

【The invention's effect】

As described above, according to the present invention, between the outer periphery of the plunger and the inner periphery of the plunger barrel,
A fuel reservoir communicated with the fuel supply chamber through a communication hole is provided, and the plunger pressurizes the fuel in the fuel reservoir by the reciprocating motion of the plunger by reciprocating the plunger. Since the refueling chamber for feeding the refueling chamber is provided with a pressurizing section, when the plunger is raised, the fuel in the fuel reservoir is supplied to the refueling chamber through the communication hole by the refueling chamber pressurizing section.

Accordingly, the pressure of the oil supply chamber including the inside of the oil supply / discharge hole is maintained at a positive pressure, and the formation of the negative pressure cavity of the oil supply system after the oil supply / discharge hole is closed as in the above-mentioned prior art is avoided. At the same time, the occurrence of high-frequency pressure fluctuation after the opening and closing of the oil supply / drain hole is also avoided. Accordingly, it is possible to prevent the negative pressure cavity from being destroyed by the high-pressure oil after the oil supply / discharge holes are opened, and to prevent the occurrence of cavitation erosion due to high-frequency pressure fluctuation in oil supply or the like.

[Brief description of the drawings]

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

FIG. 2 is a system diagram of a fuel supply injection system of a diesel engine.

FIG. 3 is a pressure fluctuation diagram of the fuel injection pump according to the embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a fuel injection pump according to the related art.

FIG. 5 is a pressure fluctuation diagram of a fuel injection pump according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump body 2 Plunger barrel 3 Plunger 4 Top surface (plunger) 5 Plunger lead 6 Oil supply / discharge hole 8 Plunger chamber 9 Discharge valve pressure 10 Discharge valve 11 Constant pressure valve 12 Constant pressure valve restrictor 13 Oil supply chamber 21 Tappet spring 23 Discharge port 24 Pinion Reference Signs List 25 control rack 31 refueling chamber pressurizing part 32 upper part 33 upper hole 34 lower hole 35 fuel reservoir 36 communication hole 103 refueling pump 105 refueling main pipe 106 refueling branch pipe 107 fuel injection pump 108 injection pipe 109 fuel injection valve

Claims (1)

[Claims] An oil supply chamber provided in a pump body, a plunger barrel provided with an oil supply / discharge hole communicating with the oil supply chamber, and a reciprocally slidably fitted to an inner periphery of the plunger barrel. When the first lead portion of the plunger closes the oil supply / discharge hole, the fuel supplied to the plunger chamber through the oil supply / drain hole is pressurized and sent to a fuel injection valve. A fuel injection pump configured to return fuel in the plunger chamber from the oil supply / drain hole to the oil supply chamber when the second lead portion of the plunger opens the oil / drain hole; A fuel reservoir communicated with the fuel supply chamber through a communication hole is provided between the plunger barrel and the inner periphery of the plunger barrel, and the plunger pressurizes fuel in the fuel reservoir by reciprocating movement of the plunger. The said pay Fuel injection pump, characterized in that provided feed Kyusuru oil chamber pressurizing the chamber.