JPH08135541A - Fuel injection pump for internal combustion engine - Google Patents

Abstract

PURPOSE: To prevent generation of negative pressure due to a back flow at the end of force-feeding fuel with less number of parts and assembling manhours in a simple structure. CONSTITUTION: A damping valve chamber 31 is formed between a cylinder 4 and a delivery valve seat 21, and the damping valve chamber 31 is provided with a damping valve 30 having an orifice. A fuel passage 35 which opens when the damping valve is lifted is formed between the damping valve and the inner surface of the damping valve chamber. In the case where the damping valve is pressed to be lifted by fuel pressurized in a pump chamber 6, the fuel is sent to the delivery valve 25 side through the fuel passage, and when force- feed is ended, the damping valve is seated on the seat surface to close the fuel passage and permit backflow of fuel through the orifice 33. Accordingly, backflow can be regulated to moderate a sudden pressure lowering, so that generation of air bubbles due to negative pressure can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection pump for a diesel engine or a gasoline engine, and more particularly to a backflow prevention structure at the end of pressure feeding of fuel.

[0002]

2. Description of the Related Art Generally, in a Bosch type fuel injection pump for supplying fuel to a diesel engine or a gasoline engine, a plunger is reciprocally fitted in a cylinder and
A pump chamber is formed between the tip surface of the plunger and the inner surface of the cylinder, and the plunger is reciprocally driven by a cam so that the fuel introduced into the pump chamber is pressurized and pressure-fed to the fuel injection nozzle on the engine side. It has become.

At the downstream side of the pump chamber, a delivery valve,
And a delivery valve holder accommodating a valve spring for urging the delivery valve is provided, and when the fuel pressure in the pump chamber becomes equal to or higher than a predetermined pressure, the delivery valve is pushed open to remove the fuel in the pump chamber, It is adapted to be sent to the fuel injection nozzle through a fuel supply pipe.

In the fuel injection nozzle, when the fuel pressure in the fuel chamber becomes equal to or higher than the valve opening pressure of the needle valve, the needle valve opens an injection hole, so that the fuel in the fuel chamber is injected from the injection hole toward the engine.

In such a fuel injection pump, when the pressure feeding of the fuel is completed, the fuel in the injection nozzle and the fuel supply pipe starts a reverse flow (spill), and a pressure reflected wave is generated due to the closing of the fuel injection nozzle. Such a backflow of fuel and pressure reflected waves are blocked by the delivery valve.However, if the backflow speed is too fast, the closing operation of the delivery valve will not be in time, and the injection nozzle, fuel supply pipe, and delivery valve holder The pressure drops sharply. Such a sudden pressure drop causes a negative pressure in the injection nozzle, the fuel supply pipe, and the delivery valve holder, and bubbles are generated inside these. Such bubbles may collapse during the next injection, causing cavitation erosion, or causing abnormal injection such as asymmetric injection or secondary injection.

In order to solve such a backflow problem, conventionally, it has been proposed to install a damping valve as disclosed in Japanese Utility Model Laid-Open No. 61-186764.
This damping valve has an orifice in the center and is pressed against the valve seat by a spring, and when fuel is pumped, it is lifted from the valve seat against the spring and allows fuel to pass from the surroundings. When a backflow occurs after the completion of the pumping, the backflow of the fuel is allowed through the orifice seated on the valve seat.

Therefore, when such a damping valve is used, when a backflow occurs, the backflow is allowed through the orifice, so that the backflow is regulated and a sudden pressure drop is alleviated. Occurrence can be suppressed.

[0008]

However, the conventional damping valve described in the above publication requires a special damping valve chamber in the middle of the fuel discharge passage, and requires a valve body, a special spring and a special valve seat. However, the number of parts is increased, the number of assembling steps is increased, and a special space is required on the discharge side of the pump.

The present invention has been made in view of the above circumstances. The object of the present invention is that the structure is simple, the number of parts and the man-hours for assembling are not required, and the negative pressure due to the backflow is generated at the end of the pressure feeding of the fuel. An object of the present invention is to provide a fuel injection pump for an internal combustion engine, which can suppress the occurrence of fuel injection and prevent abnormal injection.

[0010]

According to a first aspect of the present invention, there is provided a cylinder having a pump chamber formed therein, a plunger which is reciprocatably fitted into the cylinder and which pressurizes fuel sucked into the pump chamber. A delivery valve seat having a valve port connected to the cylinder and having a valve port communicating with the pump chamber at one end and a delivery passage formed at the other end, and a delivery valve holder housed in the delivery valve holder. In a fuel injection pump for an internal combustion engine, which is provided with a delivery valve that is pushed open apart from the delivery valve seat by the fuel pressure pressurized in the chamber to send fuel to the discharge passage side, the cylinder and the cylinder connected to the cylinder. A damping valve chamber is formed between the delivery valve seat and the delivery valve seat. A damping valve provided is slidably provided, a fuel passage is formed between the periphery of the damping valve and the inner surface of the damping valve chamber, and a seat surface on which the damping valve comes in contact with and separates from the cylinder side of the damping valve chamber. When the damping valve is pushed by the fuel pressurized in the pump chamber and lifted from the seat surface, the fuel is sent to the delivery valve side through the fuel passage, and when the pressure feeding is completed, the damping valve is formed. Is seated on the seat surface to close the fuel passage and to allow the reverse flow of fuel through the orifice.

According to a second aspect of the present invention, the damping valve has a flat shape having an orifice, and the fuel passage is formed on a side surface and a ceiling surface of the damping valve chamber.

[0012]

According to the invention of claim 1, at the time of fuel pressure feeding, the damping valve is pushed by the fuel pressurized in the pump chamber and lifted from the seat surface, thereby sending the fuel to the delivery valve side through the fuel passage, When the pumping is completed, the damping valve is seated on the seat surface to close the fuel passage and allow the backflow of the fuel through the orifice. Therefore, when the pumping is completed and the backflow occurs, the backflow is allowed through the orifice. Therefore, the backflow is regulated, and the sudden pressure drop is alleviated.
Generation of bubbles due to negative pressure can be suppressed.

Further, according to the first aspect of the present invention, the damping valve chamber is formed between the cylinder and the delivery valve seat connected to the cylinder, and the damping valve is accommodated in the damping valve chamber. It requires no special parts, no damping valve springs, has a small number of parts, is easy to assemble, and requires no special space to form a damping valve chamber. Will be possible.

According to the invention of claim 2, since the damping valve has a flat shape having an orifice and the fuel passage is formed on the side surface and the ceiling surface of the damping valve chamber, the structure of the damping valve is simplified. To do.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the first embodiment shown in FIGS. FIG. 5 is a sectional view showing the whole of the Bosch type fuel injection pump, and in the figure, reference numeral 1 is a pump housing. A cam shaft 2 that interlocks with a crank shaft of an engine (not shown) is provided below the pump housing 1, and a cam 3 is formed on the cam shaft 2.

A cylinder 4 is mounted in the pump housing 1, and a plunger 5 is installed in the cylinder 4.
Is reciprocatingly inserted. A pump chamber 6 is formed between the upper end of the plunger 5 and the inner surface of the upper end of the cylinder 4. The pump chamber 6 communicates with a fuel intake / exhaust port 7 formed on the side wall of the cylinder 4 when the plunger 5 descends. It is supposed to do. The fuel intake / exhaust port 7 communicates with a fuel pool 8 formed between the cylinder 4 and the pump housing 1, and the fuel pool 8 communicates with a fuel introduction passage 9 formed in the pump housing 1.

A lower spring seat 10 is connected to the lower end of the plunger 5, and a plunger spring 12 is bridged between the lower spring seat 10 and an upper spring seat 11 attached to the pump housing 1. ing. The plunger spring 12 presses the lower spring seat 10 against the tappet 13. The tappet 13 has a tappet roller 14, and the tappet roller 14 is in sliding contact with the cam 3. Therefore, when the cam 3 rotates, the plunger 5 is reciprocally driven through the tappet roller 14 and the lower spring seat 10. The reciprocating stroke of the plunger 5 is determined by the height difference of the cam 3.

The lead groove 1 is formed on the upper side surface of the plunger 5.
5 is formed. The lead groove 15 is formed by a groove formed on the outer peripheral surface of the plunger 5 so as to be inclined. When the plunger 5 is rotated about the axial center line, the position of the lead groove 15 corresponding to the fuel intake / exhaust port 7 formed in the cylinder 4 is changed, thereby controlling the fuel injection amount. That is, as the plunger 5 moves upward, the fuel in the pump chamber 6 is pressurized, and this pressurized fuel is supplied to the engine side as described later. When 15 communicates with the fuel intake / exhaust port 7, the fuel in the pump chamber 6 is returned from the lead groove 15 to the fuel reservoir 8 through the fuel intake / exhaust port 7. This stops the fuel from being pumped to the engine.

The rotation of the plunger 5 changes the timing at which the inclined lead groove 15 and the fuel intake / exhaust port 7 communicate with each other, so that the amount of fuel discharged is controlled according to the rotation angle of the plunger 5.

The lower end of the plunger 5 is engaged with the control sleeve 17. Control sleeve 17
Is rotatably attached to the outer peripheral portion of the cylinder 4, and the lower end of the control sleeve 17 and the lower end of the plunger 5 rotate integrally with respect to the rotational direction, but the plunger 5 reciprocates. When moving, the control sleeve 17 can move freely without restricting the movement of the plunger 5.

A pinion 1 is provided on the control sleeve 17.
8 is integrally provided, and this pinion 18 meshes with the control rack 19. The control rack 19 is connected to a governor (not shown) installed outside the pump housing 1, and this cab operates according to operating conditions such as the rotational speed of the engine, thereby operating the control rack 19. Therefore, the movement of the control rack 19 rotates the control sleeve 17 through the pinion 18, and the control sleeve 17 is rotated.
Will rotate the plunger 5. Therefore, the lead groove 15 is displaced relative to the fuel intake / exhaust port 7, and the fuel injection amount can be controlled.

A delivery valve holder 20 is connected to the upper end of the pump housing 1. As shown in FIGS. 1 to 4, the delivery valve holder 20 includes a delivery valve seat 21 at the lower end and a discharge passage 22 at the upper end, and the delivery valve seat 21 is provided between the delivery valve seat 21 and the discharge passage 22. A delivery valve chamber 23 is formed.

The delivery valve seat 21 has a lower end surface in close contact with the upper end surface of the cylinder 4 and a valve port 24 at the center thereof. The delivery valve chamber 23 accommodates the delivery valve 25 and the delivery valve spring 26 that presses the delivery valve 25. The delivery valve 25 is pushed by the delivery valve spring 26 to come into close contact with the delivery valve seat 21, thereby closing the valve port 24. Then, when the fuel pressure in the pump chamber 6 reaches or exceeds a predetermined pressure, the delivery valve 25 is pushed by this fuel and lifted from the delivery valve seat 21.
Open the valve port 24. Therefore, the fuel in the pump chamber 6 passes through the valve port 24, is delivered to the discharge passage 22 via the delivery valve chamber 23.

The discharge passage 22 is connected to a fuel injection nozzle 29 on the engine side via a fuel supply pipe 28. Therefore, when the delivery valve 25 is opened, the fuel in the pump chamber 6 is pressure-fed to the fuel injection nozzle 29 on the engine side.

A damping valve 30 according to the present invention is provided between the pump chamber 6 and the delivery valve 25. Explaining the damping valve 30, a damping valve chamber 31 is formed between the upper end of the cylinder 4 and the lower end of the delivery valve seat 21 connected to the cylinder 4. In this embodiment, the damping valve chamber 31 is formed by forming a recess in the lower end surface of the delivery valve seat 21. The damping valve chamber 31 has a lower end connected to the pump chamber 6, an upper end connected to the valve port 24 of the delivery valve seat 21, and a lower end formed with a seat surface 32 which also serves as an upper end surface of the cylinder 4.

The damping valve 30 is slidably accommodated in the damping valve chamber 31. The damping valve 30 of the present embodiment has a flat disc shape, and an orifice 33 is formed at the center thereof.

A plurality of longitudinally extending grooves 34 are formed in the inner surface of the damping valve chamber 31 accommodating the damping valve 30 in the circumferential direction at intervals. Form a fuel passage.
The inner side surface of the damping valve chamber 31 excluding the grooves 34 serves as a sliding guide surface 36 for moving the damping valve 30 up and down. Further, a plurality of grooves 35 ... Connecting the grooves 34 ... And the valve port 24 are formed in a radial direction on the ceiling surface of the damping valve chamber 31, and these grooves 35 ... Also constitute a fuel passage. The damping valve chamber 31 excluding the grooves 35 ...
The ceiling surface of the stopper surface 37 is stopped when the damping valve 30 is lifted by a predetermined amount (specified lift amount = h).
Has become.

Therefore, between the outer peripheral surface of the damping valve 30 and the inner peripheral surface of the damping valve chamber 31, a fuel passage is formed by the grooves 34 ... And 35.
This fuel passage may be formed on the outer peripheral surface of the damping valve 30, but in the case of the present embodiment, it is formed on the inner peripheral surface of the damping valve chamber 31.

The operation of the embodiment having such a configuration will be described. The plunger 5 reciprocated with the rotation of the cam shaft 3 sucks fuel into the pump chamber 6 when the plunger tip surface or the lead groove 15 opens the fuel intake / exhaust port 7 when descending, and the plunger tip when ascending. When the surface closes the fuel intake / exhaust port 7, the fuel in the pump chamber 6 is pressurized.

When the fuel pressure in the pump chamber 6 overcomes the spring 26 of the delivery valve 25, as shown in FIG.
The delivery valve 25 is lifted from the delivery valve seat 21, so that the fuel in the pump chamber 6 is pumped to the engine side. At this time, the damping valve 30 receives the fuel pressure and is lifted in the damping valve chamber 31.
That is, the damping valve 30 receives fuel pressure, separates from the seat surface 32, and is lifted up along the guide surface 36.
When this reaches a predetermined lift amount h, the damping valve chamber 3
It stops by contacting the stopper surface 37 formed on the ceiling surface of No. 1.

As the damping valve 30 rises, the fuel in the pump chamber 6 passes through the fuel passages 34 and 35 formed between the outer surface of the damping valve 30 and the inner surface of the damping valve chamber 31 to the delivery valve seat 21. It flows out to the valve port 24. Since the delivery valve 25 is lifted, this fuel is pressure-fed to the discharge passage 22 via the delivery valve chamber 23.

This fuel is supplied to the injection nozzle 29 on the engine side through the fuel supply pipe 28. Then, in the injection nozzle 29, when the fuel pressure in the fuel chamber (not shown) becomes equal to or higher than the valve opening pressure of the needle valve, the needle valve opens an injection hole, thereby injecting the fuel in the fuel chamber toward the engine through the injection hole.

When the pumping of the fuel is completed, the pump chamber 6 communicates with the intake / exhaust port 7 through the lead groove 15, so that the fuel in the injection nozzle 29 and the fuel supply pipe 28 starts to flow backward (spill). Further, a pressure reflected wave is generated due to the valve closing of the fuel injection nozzle 29. When such a backflow of fuel and a pressure reflected wave occur, the delivery valve 25 flows back and the pressure of the fuel and the delivery valve spring 26.
Is seated on the delivery valve seat 21, and the valve port 24 is closed to prevent backflow.

However, when the reverse flow speed is fast, the valve closing operation of the delivery valve 25 cannot be completed in time, and the fuel in the injection nozzle 29, the fuel supply pipe 28 and the delivery valve holder 20 is pumped as shown in FIG. Backflow from the chamber 6 through the lead groove 15 to the intake / exhaust port 7 causes the pressure in the injection nozzle 29, the fuel supply pipe 28, and the delivery valve holder 20 to drop sharply. Then, such a sudden pressure drop causes a negative pressure in the injection nozzle 29, the fuel supply pipe 28, and the delivery valve holder 20 to generate bubbles inside them, and such bubbles burst at the time of the next injection. There is a concern that cavitation erosion will occur and that abnormal injection such as asymmetrical injection and secondary injection will occur.

On the other hand, in the above embodiment, the pump chamber 6
With the damping valve 30 provided between the delivery valve 25 and the delivery valve 25, a sudden pressure drop can be prevented.
That is, when the pumping is completed and the backflow is started, the damping valve 30 is pushed down and seated on the seat surface 32.
Since this damping valve 30 has a flat disk shape and has a smaller mass than the delivery valve 25,
The response to the backflow is superior to that of the delivery valve 25, and when the backflow starts, the valve quickly returns and seats on the seat surface 32.

When the damping valve 30 is seated on the seat surface 32, the fuel passages 34 ... Are closed. This prevents backflow. However, since the damping valve 30 has the orifice 33 formed in the center thereof, the fuel flowing back is returned to the pump chamber 6 through the orifice 33. That is, the orifice 33 limits the backflow rate to allow a gentle backflow, whereby the delivery valve 25 returns.

Therefore, when such a damping valve 30 is used, a sudden backflow is alleviated, the generation of negative pressure can be suppressed, and the generation of bubbles due to negative pressure can be prevented. As a result, abnormal injection such as asymmetrical injection or secondary injection can be prevented.

Moreover, the structure of the above-described embodiment has the cylinder 4
Upper end face and delivery valve seat 21 connected to this
Since the damping valve chamber 31 is formed between the lower end and the lower end, it is not necessary to prepare another special chamber, a special member for forming the damping valve chamber 31 is unnecessary, and the number of parts is small. Also, the number of assembly steps is small.
Further, since the damping valve 30 has a flat disk shape, the damping valve chamber 31 can have a flat shape, and the entire pump does not become large.

Further, since the damping valve 30 has a flat shape and the fuel passages 34 ..., 35 ... Are formed by grooves formed in the sidewall of the damping valve chamber 31, the structure of the damping valve 30 is simplified.

The size of the orifice 33 is appropriately selected depending on the degree of pressure drop and the degree of disconnection of injection. If the orifice 33 is too small, the disconnection of injection is exacerbated. The effect of preventing descent cannot be expected.

In the above embodiment, the delivery valve seat 2 is used.
The case where the concave portion is formed on the lower surface of No. 4 and the damping valve chamber 31 is formed in this concave portion has been described, but the present invention is not limited to this, and as in the second embodiment shown in FIG. The recesses may be formed so as to extend over both the lower surface of the cylinder 4 and the upper surface of the cylinder 4, and the damping valve chamber 31 may be formed by these recesses. Alternatively, the recesses may be formed on the upper surface of the cylinder 4 and the damping valve chamber 31 Three
1 may be formed.

Further, the fuel passages 34, 35 are not limited to being formed by grooves formed on the side wall of the damping valve chamber 31, but may be formed by forming grooves on the outer surface of the damping valve 30.

[0043]

As described above, according to the first aspect of the present invention, when the fuel is pumped, the damping valve is pushed by the fuel pressurized in the pump chamber and is separated from the seat surface, thereby delivering the fuel through the fuel passage. When it is sent to the valve side, and when the pressure feeding is completed, the damping valve sits on the seat surface to close the fuel passage and allows the backflow of fuel through the orifice. Therefore, when the pressure feeding is ended and the backflow occurs. Since the backflow is allowed through the orifice, the backflow is regulated and alleviated, abrupt pressure drop can be suppressed, and generation of bubbles due to negative pressure can be prevented. Therefore, it is possible to prevent the occurrence of abnormal injection such as asymmetrical injection or secondary injection.

Moreover, according to the first aspect of the present invention, the damping valve chamber is formed between the cylinder and the delivery valve seat connected to the cylinder, and the damping valve is housed in the damping valve chamber. It does not require any special parts to construct a damping valve spring, has a small number of parts, is easy to assemble, can be manufactured at low cost, and is special in constructing a damping valve chamber. Space is not required, and miniaturization is possible.

According to the second aspect of the invention, the damping valve has a flat shape having an orifice, and the fuel passage is formed on the side surface and the ceiling surface of the damping valve chamber. To simplify.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a first embodiment of the present invention in which a downstream side from a pump chamber of a fuel injection pump is enlarged.

FIG. 2 is a view of the delivery valve seat of the embodiment as seen from the lower surface side.

FIG. 3 is a partial cross-sectional view showing an enlarged downstream side from a pump chamber at the time of fuel pressure feeding of the embodiment.

FIG. 4 is a partial cross-sectional view showing, on an enlarged scale, a downstream side from the pump chamber at the time of reverse fuel flow in the same embodiment.

FIG. 5 is a sectional view showing the entire fuel injection pump of the embodiment.

FIG. 6 is a partial cross-sectional view showing a second embodiment of the present invention and enlarging the downstream side from the pump chamber of the fuel injection pump.

[Explanation of symbols]

1 ... Pump housing 3 ... Cam 4 ... Cylinder 5 ... Plunger 6 ... Pump chamber 7 ... Fuel intake / exhaust port 15 ... Lead groove 17 ... Control sleeve 18 ... Pinion 19 ... Control rack 20 ... Delivery valve holder 21 ... Delivery valve seat 22 ... Discharge passage 23 ... Delivery valve chamber 24 ... Valve port 25 ... Delivery valve 26 ... Delivery valve spring 28 ... Fuel supply pipe 29 ... Fuel injection nozzle 30 ... Damping valve 31 ... Damping valve chamber 32 ... Seat surface 33 ... Orifice 34, 35 ... Fuel passage (groove) 36 ... Guide surface 37 ... Stopper surface

Claims (2)

[Claims] 1. A cylinder in which a pump chamber is formed, a plunger which is reciprocally fitted in the cylinder and pressurizes the fuel sucked into the pump chamber, and a cylinder which is connected to the cylinder and has the pump chamber at one end. A delivery valve seat having a valve port communicating with the delivery valve seat and a delivery passage formed at the other end, and a delivery valve holder that is housed in the delivery valve holder and pressurized by the fuel pressure in the pump chamber. A fuel injection pump for an internal combustion engine, comprising: a delivery valve that pushes apart from a valve seat and sends fuel to the discharge passage side; and a damping valve between the cylinder and the delivery valve seat connected to the cylinder. Form a valve chamber and slide a damping valve equipped with an orifice into this damping valve chamber. The damping valve is freely provided, and a fuel passage is formed between the periphery of the damping valve and the inner surface of the damping valve chamber, and a seat surface is formed on the cylinder side of the damping valve chamber for contacting and separating the damping valve. When pushed by the fuel pressurized in the pump chamber and lifted from the seat surface, the fuel is sent to the delivery valve side through the fuel passage, and when the pressure feeding is completed, the damping valve is seated on the seat surface. A fuel injection pump for an internal combustion engine, characterized in that the fuel passage is closed and a reverse flow of fuel is allowed through an orifice. 2. The internal combustion engine according to claim 1, wherein the damping valve has a flat shape having an orifice, and the fuel passage is formed on a side surface and a ceiling surface of the damping valve chamber. Fuel injection pump for.