JPH07208300A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To provide a fuel injection pump by which the control range of the force-feed stroke can be widely secured without deteriorating the sharp cut in completing of fuel force feeding by a simple structure. CONSTITUTION:In a fuel injection pump wherein a pair of fuel intake and discharging ports 8 on side walls of a plunger barrel into which a plunger 6 is inserted so as to be reciprocated, a pair of inclined leads 20a, 20b facing the intake and discharging ports are formed on the plunger, and a means for changing the rotational position of the plunger according to the operating state is provided, one lead longitudinal groove 21 is formed on the plunger 6, and a pair of leads 20a, 20b are commonly communicated with the lead longitudinal groove. Since a pair of leads 20a, 20b are commonly communicated with one lead longitudinal groove, the number of longitudinal grooves 35 can be decreased without decreasing sharp cut in completing of fuel force feeding, and the structure is simplified, and the processing is facilitated.

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 to a structure of a twin lead for injection amount control formed in a plunger.

[0002]

2. Description of the Related Art Generally, in a vertical type (Bosch type) fuel injection pump, a plunger is reciprocally fitted in a plunger barrel and a pump chamber is provided between a tip end surface of the plunger and an inner surface of the plunger barrel. The fuel sucked into the pump chamber is pressurized by reciprocally driving the plunger with a cam, and when the fuel pressure exceeds a predetermined pressure, the discharge valve is pushed open to pump the fuel to the engine. It is like this. Then, a lead is provided on the outer peripheral surface of the tip of the plunger, and when the lead opens the fuel intake / exhaust port opened on the side wall of the plunger barrel during the fuel pressure feeding process by the plunger, the fuel in the pump chamber passes through the lead and the fuel intake / exhaust port. The fuel is released to the low pressure side, which stops the fuel pumping. The leads are formed to be inclined along the circumferential direction, and when the governor provided outside the pump rotates the plunger via the rack and the pinion, the timing at which the leads close the fuel intake / exhaust port is adjusted. It is like this. Therefore, the fuel injection amount is controlled by rotating the plunger according to the load state of the engine.

By the way, recent diesel engines and gasoline engines are strongly demanded to take measures against exhaust gas.
As one of the means, it is desired to increase the oil feeding pressure of the fuel sent from the fuel injection pump and to make the injection cut off at the end of injection, that is, to make a sharp cut.

For this reason, as described in Japanese Utility Model Publication No. 5-13982, a pair of fuel intake / exhaust ports are formed on the side wall of the plunger barrel, and a pair of leads corresponding to these intake / exhaust ports are formed on the side surface of the plunger. The formed one is being developed (twin lead type). According to such a twin lead type fuel injection pump,
At the end of the fuel injection, the fuel is released from the pair of fuel intake / exhaust ports at the same time, so the fuel injection becomes sharp and effective for white smoke countermeasures.

The technique described in the above publication is
The inclination angles of the pair of leads are made to be different from each other in the high load region, whereby the single lead type injection characteristic is obtained in the high load region.

[0006]

However, the conventional twin-lead type fuel injection pump described in the above publication has the respective leads 20a,
Each lead vertical groove 2 formed on the side surface of the plunger 6 by 20b
They are formed so as to communicate with 1a and 21b, and thus form a pair of fuel escape paths independent of each other. However, in such a structure, a pair of fuel escape paths must be formed on the side surfaces of the plunger 6 independently of each other, the number of lead longitudinal grooves is increased, and the shape of the plunger 6 is complicated. Processing is troublesome.

On the other hand, in this type of fuel injection pump, a fuel leak passage is provided on the inner surface of the plunger barrel 5 for releasing the leaked fuel to the low pressure side when the high pressure fuel leaks. This fuel leak path is connected to the fuel leak hole 37.
And a leak circumferential groove 35 and a leak circumferential groove 35. The leak vertical groove 36 is formed so as to be located between the pair of fuel escape paths independent of each other. Further, for the purpose of improving the starting characteristic, a lead 30 for advancing at the time of starting is formed on the upper end surface of the plunger 6, and the lead 30 for advancing at the time of starting makes the plunger 6 rotate at a predetermined large angle at the time of starting. When it is moved, the lead angle for advancing 30 at the time of starting advances the timing to close the fuel intake / exhaust ports 8, 8.

However, if the plunger is largely rotated at the time of starting (position C), the fuel leak hole 37 and one of the lead vertical grooves 21a of the fuel escape path may interfere with each other. In such a case, Since fuel pressurized in the pump chamber leaks from the lead vertical groove 21a through the fuel leak hole 37, there is a problem that advance injection at the time of starting becomes impossible.

In order to prevent this, the fuel escape route and the fuel leak route must be provided separately in the axial direction,
This requires a large space in the axial direction. When the fuel escape route and the fuel leak route are to be provided close to each other in the axial direction, the inclination angles of the leads 21a and 21b must be made small, and in this case, the control range of the pressure feeding stroke becomes small. The drawbacks of

The present invention has been made in view of the above circumstances. The object of the present invention is to have a simple structure and ensure a wide control range of the pressure feeding stroke without impairing the sharp cut at the end of fuel pressure feeding. The present invention is intended to provide a fuel injection pump that can be used.

[0011]

According to a first aspect of the present invention, a plunger is reciprocally fitted in a plunger barrel, and a pair of fuel intake / exhaust ports is provided on a side wall of the plunger barrel. In a fuel injection pump having a pair of inclined leads corresponding to intake and exhaust ports and having means for changing the rotational position of the plunger according to operating conditions, one lead vertical groove is formed in the plunger, The pair of leads are commonly communicated with the lead vertical groove.

According to a second aspect of the present invention, a fuel leak hole is formed on the side wall of the plunger barrel between the pair of leads, and the fuel leak hole is provided through the leak vertical groove. It is characterized in that it communicates with a leak circumferential groove formed on the inner surface of the. The invention of claim 3 is the same as claim 1
Alternatively, an advance lead at the time of starting is formed at the tip of the plunger of claim 2.

[0013]

According to the invention of claim 1, since the pair of leads are commonly communicated with one lead vertical groove, the number of vertical grooves can be reduced without impairing the sharp cut at the end of fuel pressure feeding. The structure is simple and the processing is easy.

According to the invention of claim 2, the lead vertical groove is 1
Since it becomes a book, a space can be provided in the circumferential direction, so that a fuel leak hole can be opened in the side wall of the plunger barrel located between the pair of leads, and as a result, the axial space can be increased. The lead can be tilted at a large angle, and a wide control range of the pumping stroke can be secured.

According to the third aspect of the present invention, since the fuel leak hole and the lead can be separated from each other, the lead for advancing at the time of starting, which is formed at the tip of the plunger by rotating the plunger largely at the time of starting, is used. Even in this case, the fuel leak hole and the lead do not interfere with each other.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in FIGS. FIG. 2 shows a vertical (Bosch type) fuel injection pump in a sectional view, and in FIG. 2, reference numeral 1 denotes a pump housing. A cam chamber 2 is formed at the lower end of the pump housing 1, a cam shaft 3 interlocking with the crank shaft of the engine is inserted through the cam chamber 2, and a cam 4 is formed on the cam shaft 3. There is.

A plunger barrel 5 is mounted in the pump housing 1, and a plunger 6 is reciprocally fitted in the plunger barrel 5. A pump chamber 7 is formed between the upper end of the plunger 6 and the inner surface of the plunger barrel 5, and the pump chamber 7 has a pair of fuel intake / exhaust ports formed on the side walls of the plunger barrel 5 when the plunger 6 descends. It is designed to communicate with 8 and 8. The pair of fuel intake / exhaust ports 8 and 8 are formed on the side wall of the plunger barrel 5 and separated from each other by 180 degrees. The fuel intake / exhaust ports 8 and 8 are formed in the fuel pool formed between the plunger barrel 5 and the pump housing 1. It communicates with 9.

A discharge valve 10 is provided at the upper end of the pump housing 1.
Is attached, and the discharge valve 10 communicates with the pump chamber 7. The fuel pressurized in the pump chamber 7 opens the valve body 11 of the discharge valve 10 against the urging force of the return spring 12, whereby the fuel is supplied to the engine (not shown) through the discharge body 13. .

A valve seat 15 is connected to the lower end of the plunger 6, and the valve seat 15 is pressed against a tappet 17 by a return spring 16. The tappet 17 has a cam roller 18, and the cam roller 18 has the cam 4
Is in sliding contact with. Therefore, when the cam 4 rotates due to the rotation of the cam shaft 3, the plunger 6 is reciprocally driven through the cam roller 18 and the valve seat 15. In addition, the plunger 6
The reciprocating stroke is determined by the height difference of the cam 4.

A pair of leads 20a and 20b are formed at the upper end of the plunger 6, as shown in FIG. These leads 20a, 20b are formed by grooves cut out at an angle to the outer peripheral surface of the plunger 6,
It has the same inclination angle. These leads 20a, 20b
Are formed 180 degrees apart and are connected to one common lead vertical groove 21. In this case, one of the leads 20a is connected to the common lead 1 via the control lead 22 at the time of starting.
It communicates with the lead vertical groove 21 of the book. The starting control lead 22 is tilted in a direction opposite to the tilt direction of the pair of leads 20a, 20b. Therefore, when the plunger 6 is rotated about the axial center line with respect to the plunger barrel 5, the positions of the leads 20a, 20b corresponding to the fuel intake / exhaust ports 8, 8 formed in the plunger barrel 5 are changed, which causes the fuel Control the injection amount. That is, as the fuel in the pump chamber 7 is pressurized as the plunger 6 moves forward, when the fuel pressure exceeds the valve opening pressure of the discharge valve 10, the discharge valve 10 is pushed open and shown through the discharge port body 13. However, if the leads 20a, 20b communicate with the fuel intake / exhaust ports 8, 8 during the fuel supply, the fuel in the pump chamber 7 will be supplied to the leads 20a, 20b.
It is returned from b to the fuel pool 9 through the fuel intake / exhaust ports 8, 8. This stops the fuel from being pumped to the engine.

The rotation of the plunger 6 changes the timing at which the slanted leads 20a and 20b open the fuel intake / exhaust ports 8 and 8, so that the amount of discharged fuel is controlled according to the rotation angle of the plunger 6.

The lower end of the plunger 6 is engaged with the control sleeve 25. Control sleeve 25
Is rotatably attached to the outer peripheral portion of the plunger barrel 5, and the lower end of the control sleeve 25 and the lower end of the plunger 6 rotate integrally with respect to the rotating direction. When reciprocating, the control sleeve 25 can freely move without restricting the plunger 6.

A pinion 2 is provided on the control sleeve 25.
6 is provided, and this pinion 26 has a rack 27
Are in mesh. The rack 27 is connected to a governor (not shown) installed outside the pump housing 1. This cabana operates according to the operating conditions such as the rotation speed of the engine, thereby moving the rack 27. Therefore,
The movement of the rack 27 rotates the control sleeve 25 through the pinion 26, and this control sleeve 2
5 rotates the plunger 6, so that the leads 20a, 2
0b is displaced relative to the fuel intake / exhaust ports 8 and 8, and the above-described control of the fuel injection amount can be performed.

On the upper end surface of the plunger 6, a start advance lead 30 for advance advance is formed. The lead 30 for advancement at the time of starting is formed at a position corresponding to the pair of fuel intake / exhaust ports 8 and 8 when the plunger 6 is rotated by a predetermined large angle at the time of starting.
From the upper surface 6a of the above by a dimension h. Therefore, when the plunger 6 is rotated up to a predetermined angle at the time of starting and the plunger 6 is pushed up by the cam 4, the timing at which the lead 30 for advancing the start closes the fuel intake / exhaust ports 8, 8 is the upper surface of the plunger 6. 6a becomes earlier than the timing at which the fuel intake / exhaust ports 8 and 8 are closed, that is, advances. For this reason, the timing of pumping the fuel is advanced and the startability is improved.

Further, on the inner surface of the plunger barrel 5, the lead 20 with the plunger 6 lowered to the lowest position is provided.
A fuel leak circumferential groove 35 is formed along the circumferential direction at a position close to a and 20b. The leak circumferential groove 35 is continuously formed on the entire inner surface of the plunger barrel 5 as shown in FIG. Further, a leak vertical groove 36 is formed on the inner surface of the plunger barrel 5 along the axial direction. The leak vertical groove 36 is positioned so as not to communicate with the pair of leads 20a and 20b even if the plunger 6 is rotated for controlling the injection amount.
It is formed at the discontinuous portion of a and 20b, and the lower end communicates with the leak circumferential groove 35. And this Lee
The upper end of the vertical groove 36 communicates with a fuel leak hole 37 formed through the wall of the plunger barrel 5. The fuel leak hole 37 is also formed in the leads 20a, 20b.
Is formed at a non-continuous portion of and is connected to the fuel pool 9.

The operation of the embodiment having such a configuration will be described. The plunger 6, which reciprocates with the rotation of the cam shaft 3, sucks fuel into the pump chamber 7 and ascends when the plunger tip surface 6a or the leads 20a, 20b open the fuel intake / exhaust ports 8, 8 when descending. At this time, when the plunger tip surface 6a closes the fuel suction / discharge ports 8, 8, the fuel in the pump chamber 7 is pressurized. When the fuel pressure in the pump chamber 7 overcomes the force of the spring 12 of the discharge valve 10, the valve body 11
Is pushed open, so that the fuel in the pump chamber 7 is pumped to the engine.

While the fuel in the pump chamber 7 is being pumped, the lead 2
When 0a and 20b open the fuel intake and exhaust ports 8 and 8, the pressurized fuel is released to the fuel pool 9 through the lead vertical groove 21, the leads 20a and 20b and the fuel intake and exhaust ports 8 and 8. As a result, the fuel pressure in the pump chamber 7 drops, and the fuel pressure feed to the engine is stopped. In this case, the fuel intake / exhaust port 8,
Since two lead wires are provided and two lead wires 20a and 20b are provided to form a twin lead wire, fuel can be sucked in and discharged more quickly than a single lead wire, and a sharp cut can be made especially at the end of fuel pressure feeding. become.

Then, a cabana outside the pump is used to control the control sleeve via the rack 27 and the pinion 26.
When the knob 25 is rotated, the plunger 6 also rotates integrally,
As a result, the leads 20a, 20 are formed to be inclined.
b is displaced relative to the fuel intake / exhaust ports 8, 8.
That is, when the position A is set to the idling position in FIG. 1, the full injection position for high load is displaced to the position relatively rotated from the position A as shown in the position B. At the position B, the timing of closing the fuel intake / exhaust ports 8, 8 is delayed, that is, the pressure feeding stroke (shown by the shaded area) is increased, and as a result, the fuel injection amount q can be increased.

Further, when the plunger 6 is rotated to a predetermined starting position, that is, the position C in FIG. 1 through the cab at the time of starting, the starting advance angle formed at the upper end of the plunger 6 while the cam 4 pushes up the plunger 6. The fuel reed 30 closes the fuel intake / exhaust ports 8 and 8, and the closing timing is earlier than the timing at which the upper surface 6a of the plunger 6 closes the fuel intake / exhaust ports 8 and 8, and thus the advance timing is set. Start pumping. Therefore, the fuel injection at the time of starting is advanced, which is effective for white smoke countermeasures.

When the fuel is pressurized, part of the fuel pressurized to a high pressure in the pump chamber 7 may leak through the sliding surface between the inner surface of the plunger barrel 5 and the outer surface of the plunger 6. The leak fuel flows into the leak circumferential groove 35 formed on the inner surface of the plunger barrel 5, and is returned to the fuel pool 9 through the leak vertical groove 36 through the leak hole 37.

According to the above-described embodiment, the pair of leads 20a, 20b are commonly communicated with one lead vertical groove 21, so that the functions of the two leads 20a, 20b are maintained and the fuel pressure feeding is completed. The number of the vertical grooves 21 can be reduced without impairing the sharp cut at the time. For this reason, the structure of the lead is simplified, processing is facilitated, and the shape of the plunger 6 can be simplified.

Since the number of the lead vertical grooves 21 is one, a space can be provided in the circumferential direction of the plunger 6, so that the plunger barrel faces the discontinuous portion of the pair of leads 20a, 20b. Fuel leak on the inside of 5
The hole 37 can be opened. For this reason,
The leak circumferential groove 35, which communicates with the hole 37 through the leak vertical groove 36, can be formed as close as possible to the leads 20a, 20b, and the axial space can be reduced, and the leakage can be reduced. The fuel to be discharged can be recovered at an early stage where it does not spread downward. Further, since the space in the axial direction can be provided, the inclination angles of the leads 20a and 20b can be formed large, and the control range of the pressure feeding stroke can be widened.

Furthermore, the fuel leak hole 37 and the lead 2
Since 0a and 20b can be separated from each other, even if the plunger 6 is largely rotated and controlled to the C position in order to use the lead 30 for advancing at start formed at the tip of the plunger 6 at start, Hole 37 and leads 20a, 20
Since b does not interfere with each other, the advance angle control at the time of starting can be reliably performed, and the pressure feeding stroke at the time of starting can be increased as shown in the injection characteristic diagram of FIG.

In the above embodiment, one lead 20 is used.
The starting control lead 22 connecting a and the lead vertical groove 21 is
Although the case where the lead 20a is tilted in the opposite direction to the tilt direction is shown, the tilt direction of the starting control lead 22 is as follows.
It may be inclined in the same direction as the lead 20a, or may be formed in a horizontal direction parallel to the upper surface of the plunger 6.

[0035]

As described above, according to the first aspect of the present invention, since the pair of leads are commonly communicated with the one lead vertical groove, the function of the sharp cut at the end of the fuel pressure feeding of the twin leads is provided. Since the number of vertical grooves can be reduced without damaging the structure, the structure becomes simple and the processing becomes easy.

According to the second aspect of the present invention, since the lead vertical groove is provided as one, a space can be provided in the circumferential direction, so that the fuel tank is located on the side wall of the plunger barrel between the pair of leads. The hole can be opened, and as a result, the inclination angle of the lead can be increased without increasing the space in the axial direction, and a wide control range of the pressure feeding stroke can be secured.

Further, according to the invention of claim 3, the fuel leak hole and the lead can be separated from each other. Therefore, even when the lead for advancing formed at the tip of the plunger at the time of starting is used, -The hole and lead do not interfere with each other, which is effective for white smoke countermeasures at the time of starting.

[Brief description of drawings]

FIG. 1 is an exploded view showing a lead formed on a plunger according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the entire fuel injection pump of the embodiment.

FIG. 3 is an exploded perspective view showing a plunger barrel and a plunger of the same embodiment.

FIG. 4 is an injection characteristic diagram showing a rack position, an injection amount, and an advance amount.

FIG. 5 is a developed view of a lead formed on a plunger in a conventional case.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pump housing 4 ... Cam 5 ... Plunger barrel 6 ... Plunger 7 ... Pump chamber 8 ... Fuel intake / exhaust port 20a, 20b ... Lead 21 ... Lead vertical groove 22 ... Start control lead 25 ... Control sleeve 26 ... Pinion 27 ... Rack 30 ... Lead for start angle 35 ... Leak circumferential groove 36 ... Leak vertical groove 37 ... Fuel leak hole

Claims (3)

[Claims] 1. A plunger barrel is reciprocally fitted in a plunger barrel, and a pair of fuel intake / exhaust ports is provided on a side wall of the plunger barrel, and a pair of inclined leads corresponding to the intake / exhaust ports are formed on the plunger. In addition, in the fuel injection pump having means for changing the rotational position of the plunger according to the operating condition, one lead vertical groove is formed in the plunger, and the pair of leads are shared by the lead vertical groove. A fuel injection pump that is characterized by communicating with each other. 2. A fuel leak hole is formed in the side wall of the plunger barrel between the pair of leads, and the fuel leak hole is formed on the inner surface of the plunger barrel through a leak vertical groove. The fuel injection pump according to claim 1, wherein the fuel injection pump communicates with the leak circumferential groove. 3. The fuel injection pump according to claim 1, wherein a lead for advancing at the time of starting is formed at the tip of the plunger.