JPH02115564A - Delivey type fuel injection pump - Google Patents

Abstract

PURPOSE:To keep the characteristic of pilot injection up stably by providing a fuel release chamber communicated with a pump chamber, storing a piston in the fuel release chamber and opening a spill port by means of the piston so as to let the fuel escape. CONSTITUTION:A fuel release chamber 26 is communicated with a pump chamber 18 through a feed oil passage 8. In the fuel release chamber 26, a piston 30 is stored slidably in the axial direction. The piston 30 receives the force of a return spring 31 and is pressed to the lead-in port side 28. When the moving quantity of the piston 30 becomes the fixed quantity, a spill port 33 is opened and the fuel in the fuel release chamber 26 is released to the low pressure value through the spill port so as to stop the pilot injection. The characteristic of the pilot injection can be thus kept up stably without being affected by the settling of the spring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distributed fuel injection pump that supplies fuel to each cylinder of a diesel engine.

[Conventional technology]

In diesel engines, it is known that pilot injection prior to main fuel injection reduces noise and exhaust gas.

In order to perform such a pilot injection, conventionally,
As described in Japanese Patent No. 1-86539, a means for providing a pilot injection device to a fuel injection pump has been developed. This device is equipped with a valve that operates in response to the fuel pressure pressurized in the pump chamber in a dodge body equipped with a fuel relief chamber connected to the pump chamber. I'm starting to miss out.

[Problem to be solved by the invention]

However, in the conventional pilot injection device, the valve has a conical shape, and the pressure receiving area is different before and after the valve is opened, and the valve is pressed by a spring. As a result, the valve opening area is set by spring force, and as a result, there is a concern that the valve opening characteristics, that is, the pilot injection characteristics, may fluctuate due to fatigue of the spring or the like.

The present invention aims to provide a distribution type fuel injection pump that is capable of stably maintaining pilot injection characteristics without being affected by spring fatigue, etc., and has a simple structure.

[Means to solve the problem]

The first aspect of the present invention is to modify the structure of a pilot injection device to include a fuel relief chamber connected to a pump chamber, and to slide into this fuel relief chamber in response to the fuel pressure pressurized in the pump chamber. The piston accommodates a piston with a small gap between it and the piston, which is moved against the force of the return spring in response to the fuel pressure during the pilot injection of fuel pressurized in the pump chamber. When this amount of movement reaches a predetermined amount, the pilot injection is stopped by opening the spill port and releasing the fuel in the fuel relief chamber to the low pressure side through this spill port, and furthermore, this piston moves the predetermined amount of movement. When the pump moves beyond the limit, it comes into contact with a stopper and is stopped, thereby increasing the pressure of the fuel in the pump chamber again to perform main injection.

A second aspect of the present invention is that the pilot injection device described above is applied to an inner cam type distribution fuel injection pump.

A third aspect of the present invention is characterized in that the pilot injection device is provided within the rotor of the inner cam type distribution fuel injection pump.

[Effect]

According to the present invention, when the fuel is pressurized to a predetermined pressure in the pump chamber, pilot injection is started, and the piston slides under the pressure of the pressurized fuel at this time, and the amount of movement of the piston is adjusted to a predetermined amount. When this happens, the spill port is opened to allow the fuel in the fuel relief chamber to escape to the low pressure side through this spill port.
This completes the pilot injection, and when the piston is moved beyond the predetermined amount, it comes into contact with the stopper and prevents further movement, thereby increasing the fuel pressure in the pump chamber again and starting the main injection. It is possible to do so. With this kind of configuration, there is no difference in the pressure receiving area before and after the valve is opened, and therefore the valve opening area is not affected by spring force, but is affected by spring fatigue, etc. do not have.

Furthermore, if the above pilot injection device is installed inside the rotor of an inner cam type distribution fuel injection pump, a fuel relief chamber can be formed inside the rotor, eliminating the need for a special housing and implementing the implementation with a simple structure. can.

〔Example〕

The present invention will be explained below based on an embodiment shown in FIGS. 1 to 4.

In FIG. 1, reference numeral 1 indicates a pump housing, and the pump housing 1 accommodates a rotating rotor 2 that rotates in synchronization with a crankshaft of an engine (not shown).

A dispensing head 3 is attached to the pump housing l, into which the rotor 2 is coaxially and rotatably inserted.

The distribution head 3 has a centrally directed fuel feed passage 4.
is formed, and fuel is supplied to this feed passage 4 from a fuel feed pump 5. Note that the pressure of the fuel sent out from the fuel feed pump 5 is adjusted to a predetermined pressure by a regulator valve B, and then supplied to the feed passage 4.

As shown in FIG. 2, a suction port 7 is formed on the circumferential surface of the rotor 2, and this suction port 7 is connected to an oil feed passage 8 formed on the center line of the rotor 2. The suction boat 7 is intermittently communicated with the feed passage 4 as the rotor 2 rotates.

One discharge boat 9 is formed on the circumferential surface of the rotor 2 at a position spaced apart from the suction port 7 in the axial direction, and this discharge boat 9 is also connected to the oil feed passage 8 .

Opposed to this discharge boat 9, a plurality of distribution passages 10 are formed in the distribution head 3, the number being equal to the number of cylinders and extending in the radial direction. These distribution passages 10・
... are respectively connected to fuel injection nozzles 11 attached to each cylinder of the diesel engine. These distribution passages 10 are intermittently communicated with the discharge boat 9 as the rotor 2 rotates.

Note that when the suction port 7 communicates with the feed passage 4, the distribution passage IO does not communicate with the discharge boat 9, and when the distribution passage IO communicates with the discharge boat 9,
The suction boat 7 is configured not to communicate with the feed passage 4.

One end of the rotor 2 projects from the end of the distribution head 3 and is surrounded by a cam ring 12 around this projection.

The cam ring 12 is attached to the pump housing l so as to be rotatable in the circumferential direction, and a cam surface 13 (see FIG. 2) having a corrugated shape in the circumferential direction is formed on the inner surface of the cam ring 12. The cam ridges on the cam surface 13 are equal to the number of cylinders of the engine, and are formed at equal intervals in the circumferential direction.

A sliding hole 14 is bored in the rotor 2 in the diametrical direction opposite to the cam ring 12.
A pair of plungers 15.15 are accommodated in the radially slidable manner.

The outer end of the plunger 1515 is connected to the cam rollers 1B, 1B
The cam rollers 1B and 16 are in rolling contact with the cam surface 13 of the cam ring 12.

Therefore, due to the rotation of the rotor 2, the plunger 15,
15 is pushed into the rotor 2 by the cam ridge of the cam surface 13, thereby pressurizing the fuel in the sliding hole 14. Therefore, the central portion of the sliding hole 14 constitutes a pump chamber 18, and this pump chamber 18 is communicated with the oil feed passage 8.

Therefore, the fuel in the pump chamber 18 pressurized by the pumping action of the plunger 15, 15 is forced into the oil feed passage 8.

Note that the cam ring 12 is connected to the timer slide pin 19.
It is connected to the timer piston 20 via.

The timer piston 20 is slidably inserted into the timer cylinder 21. Inside this timer cylinder 21,
Fuel pressure controlled according to the operating state of the engine is introduced, thereby moving the timer piston 21 in a direction perpendicular to the paper plane of FIG. 1, and rotating the cam ring 12 in the circumferential direction. Therefore, the cam crest of the cam surface 13 is displaced in the circumferential direction, and the timing of the pump action by pushing the plunger 15.degree. 15 is advanced or retarded, thereby making it possible to control the fuel injection timing.

A pilot injection device 25 is provided at the other end of the rotor 2 . To explain this, a fuel relief chamber 2G is formed at the other end of the rotor 2. This fuel relief chamber 26
is formed by directly drilling a hole in the other end of the rotor 2 and closing this hole with a stopper 27 which also serves as a stopper.

This fuel relief chamber 26 is connected to the oil supply passage 8 through the introduction port 28.
Therefore, this fuel relief chamber 26 communicates with the pump chamber 18.

A piston 30 is accommodated in the fuel relief chamber 26 so as to be slidable in the axial direction. The piston 30 has a small gap (not shown) between it and the inner surface of the fuel relief chamber 26, and is pressed toward the introduction port 28 by the force of the return spring 31.

A spill annular groove 32 is formed on the outer periphery of the piston 30, and this spill annular groove 32 communicates with the inside of the piston 30, that is, into the fuel relief chamber 26 via a spill relief port 33.

A first relief passage 34 is formed in the rotor 2, and this first relief passage 34 communicates with the suction (low pressure) side of the fuel feed pump 5 via an annular groove 35 formed on the outer periphery of the rotor 2. has been done.

Further, a second relief passage 3B is formed in the rotor 2 at a distance in the axial direction from the first relief passage 34, and this second relief passage 36 serves as a feed passage as the rotor 2 rotates. 4 communicates with the suction port 7, it communicates with the suction (low pressure) side of the fuel feed pump 5.

Note that the first relief passage 34 and the second relief passage 3
6 is not limited to being communicated with the suction (low pressure) side of the fuel feed pump 5, but may also be communicated with the fuel tank or the discharge (high pressure) side of the fuel feed pump 5, in other words, it is pressurized in the pump chamber 18. It suffices if it is connected to a pressure part lower than the fuel pressure.

The operation of an embodiment with such a configuration will be explained.

The rotor 2 rotates in response to the rotational force of the drive shaft, and the plunger 15. In the suction process in which the cam ring 15 moves in the outer radial direction opposite to the valley in the cam surface 13 of the cam ring 12, the suction boat 7 communicates with the feed passage 4, and at this time, fuel flows from the feed passage 4 to the suction boat 7 and the oil supply passage. 8 into the pump chamber 18.

The rotor 2 rotates further and the plunger 15. When the plunger 15.15 is moved to a position where it contacts the peak on the cam surface 13 of the cam ring 12, the plunger 15.15 pressurizes the fuel in the pump chamber 18. In this pressurization step, when the discharge port 9 communicates with one of the distribution passages 10, the fuel pressurized in the pump chamber 18 is force-fed to the distribution passage 10 through the oil supply passage 8 and the discharge port 9, and this distribution When the injection pressure exceeds the injection pressure of the fuel injection nozzle 11 connected to the passage 10, the fuel is injected from this injection nozzle 11 into the cylinder.

When such fuel injection is performed, the fuel pressure in the pump chamber 18 is transmitted to the fuel relief chamber 26 through the inlet 28 connected to the oil feed passage 8, and the fuel relief chamber 26 resists the force of the return spring 31. The piston 30 is then slid in the axial direction.

That is, at the initial stage of pressurization when the fuel pressure in the pump chamber 18 increases, pilot injection begins in the injection nozzle 11 as shown by a in FIG. 4 as the fuel pressure in the pump chamber 18 increases. At this time, the state is shown in FIG. 3(A), and the fuel pressure in the pump chamber 18 is transmitted to the fuel relief chamber 26 through the inlet 28, and the piston 30 is pushed to the right in the figure against the force of the return spring 31. It will be done. piston 30
When the fuel tries to move to the right side, the fuel in the fuel relief chamber 26 is pressurized, but this fuel flows through the spill port 33 formed in the piston 30 into the spill annular groove 32 and between the fuel relief chamber 2B and the piston 30. The piston 30 is removed from the first relief passage 34 to the low pressure side through a small gap between the pistons 30 and 30, thereby allowing the piston 30 to move to the right.

However, this movement is restricted by the amount of fuel flowing through the minute gap between the fuel relief chamber 26 and the piston 30, and the piston 3
0 movement speed is regulated.

Due to such slow movement of the piston 30, as shown in FIG. 3(B), when the spill annular groove 32 formed in the piston 30 communicates with the first relief passage 34,
Since the fuel in the fuel relief chamber 2G is released to the outside through the spill port 33, the spill annular groove 32, and the first relief passage 34, the piston 30 is not subjected to the resistance of the fuel pressure in the fuel relief chamber 2B, and the spring 31 quickly move to the right against the force of

Therefore, the fuel pressurized in the pump chamber 18 is transferred to the inlet 28.
Since the pressure of the fuel flowing into the front side of the piston 30 and sent to the injection nozzle 11 decreases, the pilot injection is stopped as shown by b in FIG. 4.

Further, as the fuel continues to be pressurized in the pump chamber 18, the piston 30 comes into contact with the stopper/stopper 27, as shown in FIG. 3(C), and further movement is prevented. Therefore, since fuel is prevented from flowing any further into the front side of the piston 30 through the inlet 28, the pump chamber 18
The fuel pressure rises again, and main injection starts from the injection nozzle 11 as shown by C in FIG.

In this way, pilot injection and main injection are performed,
As the rotor 2 rotates, the suction process begins again.

At this time, the second relief passage 36 formed in the rotor 2 is connected to the fuel relief chamber 26 during the suction process when the pump chamber 18 has a low pressure, that is, when the feed passage 4 is communicating with the suction boat 7. The piston 3o is a return spring 31
It returns to the left side in the figure under the force of .

Thereafter, the above operation is repeated as the rotor 2 rotates to perform pilot injection and main injection.

In such an embodiment, since the pilot injection is controlled only by the movement of the piston 3o, there is no difference in the pressure receiving area before and after opening the valve, unlike when using a conventional conical valve. , Therefore, the valve opening area is not affected by the force of the spring that suppresses the valve.

Therefore, there is no fear that the valve opening characteristics, that is, the pilot injection characteristics will fluctuate due to the influence of spring fatigue or the like.

Further, in the case of the above embodiment, since the pilot injection device 25 is provided inside the rotor 2 of the inner cam type distribution type fuel injection pump, the fuel relief chamber 26 can be constructed by forming a hole directly inside the rotor 2. This eliminates the need for a special housing, simplifying the structure.

Furthermore, according to such a configuration, since the fuel relief chamber 2B is directly communicated with the pump chamber 18 through the inlet 28, it may be influenced by the type of injection amount metering means of the fuel injection pump. do not have.

In other words, in this type of fuel injection pump, in order to adjust the injection amount, a variable throttle device is installed on the feed passage 4 side to adjust the injection amount (inlet throttle type), or the fuel pressurized in the pump chamber 18 is pumped. Although the fuel injection amount is adjusted by overflowing the fuel in the middle of the stroke (overflow adjustment type), the pilot injection device 25 of this embodiment directly injects the fuel pressurized in the pump chamber 18. Since the pressure is controlled at
It is possible to implement.

Note that the present invention is not limited to the above embodiments.

That is, when the fuel in the fuel relief chamber 26 is released to the relief passage 34 side through the minute gap between the fuel relief chamber 26 and the piston 30 during pilot injection, in order to stably perform this leakage, the fifth As in the other embodiment shown in FIG.
It is also possible to form one surface or multiple surfaces, and to secure a minute gap 41 by these cut surfaces 40.

In this case, if the rotation of the piston 30 is not restricted, an annular groove 42 communicating with the cut surface 40 may be provided to communicate with the relief passage 34.

Moreover, the number of escape passages 34 and 36 may be one.

Furthermore, the pilot injection device 25 of the present invention is not limited to being formed on the rotor 2, but may be formed on the distribution head 3 or the pump housing l, for example, as shown in FIG. 7, if space permits. good.

Furthermore, the present invention is not limited to inner cam type distribution type fuel injection pumps, but can also be implemented in face cam type or outer cam type distribution type fuel injection pumps.

〔Effect of the invention〕

As explained above, according to the present invention, when the fuel is pressurized to a predetermined pressure in the pump chamber, pilot injection is started, and the piston is moved inward by the pressure of the pressurized fuel at this time.
When the amount of movement of this piston reaches a predetermined amount, the spill port is opened to allow the fuel in the fuel relief chamber to escape to the low pressure side through this spill port, thereby completing the pilot injection, and furthermore, when the amount of movement of this piston exceeds the predetermined amount of movement. When it is moved, it comes into contact with a stopper and prevents further movement.
As a result, the fuel pressure in the pump chamber can be increased again to perform main injection. Therefore, in such a configuration, there is no difference in the pressure receiving area before and after opening the valve, and the valve opening area is not affected by spring force, so it is not affected by spring fatigue etc. do not have.

Furthermore, if the above pilot injection device is installed in the rotor of an inner cam type distribution fuel injection pump, a fuel relief chamber can be formed in the rotor, and a special housing is not required, making it possible to implement it with a simple structure. There are advantages such as being able to

[Brief explanation of the drawing]

1 to 4 show one embodiment of the present invention, FIG. 1 is a sectional view showing the structure of an inner cam type distribution fuel injection pump, FIG. 2 is an explanatory view showing the relationship between each passage, and FIG. Diagram (A)
, (B) and (C) are sectional views showing different operating states of the pilot injection device, FIG. 4 is a view showing fuel injection characteristics, and FIGS. 5 and 6 are views showing other embodiments of the present invention. , FIG. 5 is a sectional view of a pilot injection device, FIG. 6 is a sectional view taken along the line VT-VT in FIG. FIG. l... Pump housing, 2... Rotating rotor, 3
...Distribution head, 4...Feed passage, 7...Suction port, 8...Oil supply passage, 9...Discharge port, 1
0...Distribution passage, 11...Injection nozzle, 12...
Cam ring, 15... Plunger, 18... Pump chamber, 25... Pilot injection device, 2B... Fuel relief chamber, 27... Stopper 28... Inlet, 30...
Piston, 31... Spring, 32... Spill annular groove, 33... Spill port, 34. 38... Relief passage. Applicant's Representative Patent Attorney Takehiko Suzue Figure 4 Figure 5 Figure 6 Figure 1

Claims (1)

[Scope of Claims] (1) The fuel in the pump chamber is pressurized by reciprocating movement of the plunger, and the pressurized fuel is injected, and the fuel pressurized in the pump chamber is injected into the pilot chamber prior to main injection. In a distribution type fuel injection pump equipped with a pilot injection device for injecting fuel, the pilot injection device has a fuel relief chamber connected to the pump chamber, and the fuel relief chamber receives the fuel pressure pressurized in the pump chamber. It houses a piston that slides and has a small gap between it and this relief chamber, and this piston receives the fuel pressure during the pilot injection of pressurized fuel in the pump chamber and releases the return spring. When the amount of movement reaches a predetermined amount, the spill port is opened and the fuel in the fuel relief chamber is released to the low pressure side through this spill port, thereby stopping the pilot injection. Distributed fuel injection characterized in that when the pump moves beyond the predetermined amount of movement, it comes into contact with a stopper and is stopped, thereby increasing the pressure of the fuel in the pump chamber again to perform main injection. Pump (2) In the pump, the plunger is arranged in the radial direction on a rotor that is driven to rotate, and a cam ring is provided around the rotor, and as the rotor rotates, the plunger slides into contact with the inner surface of the cam ring. 2. The distribution type fuel injection pump according to claim 1, wherein the distribution type fuel injection pump is an inner cam type distribution type fuel injection pump that is reciprocated. (3) The distribution type fuel injection pump according to claim 2, wherein the pilot injection device is provided within a rotor of the inner cam type distribution type fuel injection pump.