JPH031509B2 - - Google Patents

Description

A unit used in a diesel engine including a communication passage 49 formed in the pressure-feeding plunger 36.
Injector.

[Detailed description of the invention]

The present invention relates to a unit injector used in a diesel engine, particularly a unit that injects fuel in a diesel engine in stages through initial stage injection, so-called pilot injection, and main injection to improve fuel combustion.・Regarding the injector.

Generally speaking, unit injectors, unlike in-line fuel injection pumps or distribution-type fuel injection pumps, are installed directly on the cylinder head of a diesel engine without using a high-pressure injection pipe, and are installed directly on the diesel engine's cam. They have been configured to be driven by a shaft and inject fuel.

Such unit injectors have the ability to improve fuel combustion by preventing a sudden pressure rise in the combustion chamber and reducing hydrocarbons (HC) and nitrogen oxides (NOx) contained in exhaust gas. are required, and in order to satisfy these conditions, it is desirable to perform fuel injection in stages as initial stage injection and main injection.

However, in conventional unit injectors, the interval between the first stage injection and the main injection is set in advance to a predetermined interval, and furthermore, the opening area of the first stage injection cut-off port that ends the first stage injection is determined in advance. Because of this, it is difficult to obtain sharp fuel injection characteristics in the first stage injection, and the effect of performing fuel injection in stages tends not to be fully demonstrated.

Furthermore, in Japanese Patent Laid-Open No. 57-83658, fuel is metered by a solenoid valve that is opened for a predetermined time depending on the pilot injection amount, and a check valve is pushed open through a balance orifice to open a fuel passage. A fuel injection device is disclosed in which the fuel is pumped into the pilot pump chamber, and the pilot plunger is pushed up by a stroke corresponding to the pilot injection amount and then stopped. The structure is such that the high-pressure fuel in the pilot pump chamber is released into the supply passage via the communication passage, so the spill pressure of the high-pressure fuel released in this way is The nozzle/needle closure is insufficient, causing unstable fuel shortage during pilot injection.

Furthermore, Japanese Patent Application Laid-Open No. 57-76258 discloses that the fuel injection amount is controlled by a solenoid valve, and the fuel pressure in at least one of the pressure pump chamber and the injection pump chamber is transferred to the pressure transfer plunger and the injection plunger. Although a fuel injection device is disclosed that includes a pressure reduction chamber that temporarily lowers the pressure during stroke,
Since the pressure reduction chamber has a constant volume structure, the pressure that is reduced is extremely small, and as a result, fuel depletion during pilot injection is insufficient.

The purpose and problem of this invention is to perform fuel injection in stages as an initial stage injection and a main injection, and to improve fuel exhaustion in the first stage injection, to prevent a sudden pressure rise in the combustion chamber, and to prevent a sudden pressure increase in the exhaust gas. The present invention provides a unit injector for use in diesel engines that improves fuel combustion by reducing hydrocarbons and nitrogen oxides contained in diesel engines.

In connection with the above-mentioned objects and problems, the unit injector used in the diesel engine of the present invention has a needle spindle bore having a valve seat and a nozzle, and has one end open and the other end connected to the needle spindle bore. a valve body having a plunger bore communicating with the fuel reservoir of the spindle bore; a nozzle needle fitted into the needle spindle bore and seated in its valve seat by a needle spring; and the plunger. - A pressure-feeding plunger that is fitted in a reciprocating manner to the open side of the bore, and a pressure-feeding plunger that is fitted in a reciprocating-slidable manner to the plunger bore that is closed by the pressure-feeding plunger, and the fuel is injected to the fuel reservoir side of the plunger bore. a metering plunger forming a pump chamber on the pressure-feeding plunger side of the plunger bore; a slider bore formed in the valve body by enlarging the opening side of the plunger bore; A pressure pump chamber is connected to the slider bore and the spill port, and an initial injection cut-off port is formed in the valve body at a position to be opened and closed by the pressure plunger, and a reciprocating valve is formed in the valve body at a position to be opened and closed by the pressure plunger. slidably mated and reciprocally slidably fitted into the slider bore, and is slid into the slider bore by pressure within the pressure pump chamber to open the first stage injection cut-off port. a slider that increases the area, a return spring disposed within the slider bore that pushes the slider in a direction that narrows the opening area of the initial injection cut-off port, and connects the pressure pump chamber to the spill port. and a main injection cut-off port formed in the valve body at a position separated from the first-stage injection cut-off port by a predetermined distance and at a position opened and closed by the pressure-feeding plunger; an injection cut formed on the outer circumferential surface of the pumping plunger at a predetermined location and communicating with the first stage and main injection cut-off port when the pumping plunger is slid back and forth within the plunger bore; - It includes an off-groove and a communication passage formed in the pressure-feeding plunger with one end opening into the pressure-feeding pump chamber and the other end opening into the injection cut-off groove.

Hereinafter, specific examples of the unit injector used in the diesel engine of the present invention will be explained with reference to the drawings.

Figures 1 and 2 show a specific example 1 of a unit injector used in a diesel engine of the present invention.
It shows 0.

The unit injector 10 is a valve
A needle spindle bore 20 having a seat 21 and nozzles 22 and 23 formed therein, and a plunger having one end open and the other end communicating with a fuel reservoir 24 of the needle spindle bore 20.
A valve body 11 with a bore 30 and a valve seat 2 fitted in the needle spindle bore 20 with a needle spring 34.
1, a pressure-feeding plunger 36 fitted to the opening side of its plunger bore 30 so as to be reciprocatingly slidable, and a nozzle needle 31 seated on the plunger bore 30, which is closed by the pressure-feeding plunger 36; and an injection pump chamber 40 on the fuel reservoir 24 side of the plunger bore 30 .
A pressure pump chamber 41 is located on the side of the pressure plunger 36.
A metering plunger 39 is formed, respectively, a slider bore 43 is formed in the valve body 11 by expanding the opening side of the plunger bore 30 in a circular manner, and a pressure pump chamber 41 is formed in the slider bore 43. - An initial injection cut-off port 45 formed in the valve body 11 at a position that communicates with the bore 43 and the spill port 42 and is opened and closed by the pressure plunger 36, and reciprocates around the pressure plunger 36. The first stage injection cut-off is slidably fitted into the slider bore 43 and slidably inserted into the slider bore 43 by the pressure within the pressure pump chamber 41. - A slider 44 that widens the opening area of the port 45, and a return that is placed in the slider bore 43 on the slider 44 and pushes down the slider 44 in a direction that narrows the opening area of the first stage injection cut-off port 45. - A spring 46 and its pressure pump chamber 41 are connected to its spill port 42, and the pressure pump chamber 41 is connected to its spill port 42 at a predetermined distance downwardly from its initial injection cut-off port 45 and its pressure plunger. A main injection cut formed in the valve body 11 at the position where it is opened and closed at 36.
An off port 47 is formed on the outer circumferential surface of the pumping plunger 36 at a predetermined position, and when the pumping plunger 36 is slid back and forth within the plunger bore 30, the initial stage and main injection cut-off An injection cut-off groove 48 connected to the ports 45 and 47, one end of which is connected to the pressure pump chamber 41, and the other end of which is connected to the injection cut-off groove 4.
The pressure feeding plungers 36 are opened at 8 and 8 respectively.
A communication passage 49 is formed in the outer peripheral surface of the metering plunger 39 at a predetermined position, and the metering plunger 39 is slid back and forth into the plunger bore 30 to a predetermined position. a spill groove 51 which, when placed, communicates with the spill port formed in the valve body 11;
A communication passage 52 is formed in the metering plunger 39 with one end opening into the injection pump chamber 40 and the other end opening into the spill groove 51, and a communication passage 52 opening into the injection pump chamber 40 and the valve body 11. and includes a fuel passageway 52 that conducts fuel from a feed pump (not shown) to the injection pump chamber 40, and in this case, the plunger bore 30 is a pumping plunger bore. 57 and a metering plunger bore 58, the pressure-feeding plunger 36 is fitted into the open side of the pressure-feeding plunger bore 57 so as to be able to reciprocate, and the metering plunger bore 58 is fitted with a The metering plunger 39 was fitted so as to be able to slide back and forth.

The valve body 11 is screwed to a nozzle 13, a needle spring guide 14, a partition plate 15 and its metering plunger guide 16, which are integrated by a nut 12 and a metering plunger guide 16, which are screwed together. It is comprised of a pressure-feeding plunger guide 17 and a nut 18 screwed to the pressure-feeding plunger guide 17.

That is, the valve body 11 has a nut 1 formed in a cylindrical shape with a nozzle fitting hole 19 at the lower end.
2 and is fitted into the nut 12 so that the lower end side protrudes from the nozzle fitting hole 19,
and a valve seat 21 and a plurality of nozzles 2
Needle spindle bore 2 with 2,23
0, and a nozzle 13 that is placed on the upper end surface of the nozzle 13, is fitted into the nut 12, is open at the top, and is approximately coaxial with the needle spindle bore 20. a needle spring guide 14 having a needle spring chamber 26 disposed in the needle spring chamber 26; a partition plate 15 fitted into the nut 12 so as to close the open end of the needle spring chamber 26; screwed into the upper end of the nut 12 and biased to one side so as to fix the nozzle 13, the needle spring guide 14 and the partition plate 15 to the nut 12; A metering plunger guide 16 with a metering plunger bore 58 open at its upper end, a pumping plunger bore 57 screwed into the upper end of the metering plunger guide 16 and communicating with the metering plunger bore 58, and its pumping. Pumping plunger guides 17 each having a slider bore portion communicating with the pumping plunger bore 57 in such a way that the upper portion of the plunger bore 57 widens concentrically.
By being screwed into the upper end of the pressure-feeding plunger guide 17, the pressure-feeding plunger guide 17
The nut 18 has a slider bore 43 formed astride the nut 18 and a plunger guide bore 60.

Of course, the nozzle 13, needle spring guide 14, plate 15 and metering plunger guide 16 are connected to each other by a fuel passage 25,
27, 28, and 59, respectively, and their plunger bores 30, i.e., metering plungers.
bore 58 and pressure plunger bore 57 to the fuel sump 24 of its needle spindle bore 20.
is in contact with.

The nozzle needle 31 is seated on the valve seat 21 of the nozzle 13 and is slidably disposed in the needle spindle bore 20 thereof.

The nozzle needle 31 has a pin 32 at its upper end.
is integrally provided, and the pin 32 is connected to the needle.
Pin hole 3 formed at the lower end of the spring guide 14
3, the tip of the pin contacts the spring seat 35 disposed within the needle spring chamber 26, and the needle spring 34 disposed within the needle spring chamber 26 always causes the valve seat to It is pressed against 21.

The pumping plunger 36 is arranged in the pumping plunger bore 57 of the pumping plunger guide 17 in such a way that it extends inside the nut 18 thereof;
A follower 37 is mounted on the extended end of the camshaft ( (not shown), the pumping plunger bore 5
7 so that it can be slid back and forth.

The metering plunger 39 is configured such that an injection pump chamber 40 is formed in the plunger bore 30 at a position on the fuel reservoir 24 side, and a pressure pump chamber 41 is formed between the metering plunger 39 and the pressure plunger 36.
It is reciprocally slidably disposed in the metering plunger bore 58.

Of course, the metering plunger bore 58 is in communication with the pumping plunger bore 57, but as shown in FIG. Since it is connected to the pressure plunger bore 57, the upward movement of the metering plunger 39 is restricted by contacting the lower end face of the pressure plunger guide 17.

As mentioned above, the slider bore 43 is formed by concentrically widening the upper portion of its pumping plunger guide 1.
7 and the nut 18, and covers the approximately central portion of the pressure-feeding plunger 36 with a predetermined gap maintained therebetween.

The slider 44 is inserted into the slider bore 43 so as to fit into the pressure-feeding plunger 36.
It is reciprocally slidably disposed in and cooperates with the lower portion of one side of its slider bore 43 to form a first stage injection cut-off port 45 in its pumping plunger guide 17.

That is, when the slider 44 is lowered to the lowest position within the slider bore 43, the first stage injection cut-off port 45
It has a predetermined opening area facing the outer circumferential surface of the plunger 36, and is configured so that as the slider 44 slides upward, the opening area becomes larger sequentially.

Of course, the first stage injection cut-off port 45
is in communication with a spill port 42 formed in its pumping plunger guide 17.

The return spring 46
It is disposed above the bore 43 and presses the slider 44 downward.

The main injection cut-off port 47 is located downwardly at a predetermined distance from the first-stage injection cut-off port 45 and is connected to the pressure plunger bore 57 so as to be connected to the pressure plunger bore 57. It is formed in the guide 17 and communicates with the spill port 42 mentioned above.

Of course, the main injection cut-off port 47
When the pressure-feeding plunger 36 is reciprocated and placed in a predetermined position, the pressure-feeding plunger 36
It is opened and closed by.

The injection cut-off groove 48 is formed in a ring shape around the pumping plunger 36 at a predetermined position.

That is, the injection cut-off groove 48 is communicated with the first-stage injection cut-off port 45 when the pressure-feeding plunger 36 is pushed in and placed in a predetermined position, and the injection cut-off groove 48 is communicated with the first-stage injection cut-off port 45 when the pressure-feeding plunger 36 is further pushed in and placed in a predetermined position. When placed in the position of
It is formed in a ring shape around the lower part of the pumping plunger 36 so as to be connected to the main injection cut-off port 47 .

A communication passage 49 is formed on the lower inner side of the pressure plunger 36 and communicates the pressure pump chamber 41 with the injection cut-off groove 48 .

The spill groove 51 is formed in a ring shape around the metering plunger 39 at a substantially central position.

The spill groove 51 is connected to the metering plunger 39.
When the metering plunger guide 16 is slid back and forth into position within its metering plunger bore 58, it communicates with a spill port 50 formed in its metering plunger guide 16.

Further, a communication passage 52 is formed inside the metering plunger 39 below, and the injection pump chamber 4
0 is connected to the spill groove 51.

Further, the spill port 50 formed in the metering plunger guide 16 is connected to the spill communication passage 56 formed in the metering plunger guide 16 and the spill communication passage 29 formed in the partition plate 15 described above. Then, the needle spring chamber 2 of the needle spring guide 14
6 has been contacted.

The fuel passage 53 has one end, that is, a fuel port 54, opened on the side of the pressure-feeding plunger guide 17, and the other end connected to the fuel passage 28 in the above-mentioned partition plate 15 and the adjustment plunger guide 16 thereof. The pumping plunger guide 17 and the metering plunger guide 16 are formed in communication with the volume plunger bore 58, respectively.

Of course, a check valve 55 is disposed within the partition plate 15 at a position on the downstream side of the fuel passage 53, and a check valve 55 is disposed within the partition plate 15 at a position on the downstream side of the fuel passage 53.
This prevents fuel from flowing backwards to the 4th side.

The unit injector 10 configured as described above has its nozzles 22 and 23 housed in a combustion chamber in the cylinder head of a diesel engine (not shown), and the follower 37 of its pressure-feeding plunger 36 in the cylinder head of a diesel engine (not shown). It is attached to the cylinder head of the engine in such a way that it contacts the cam surface of the camshaft.

In the unit injector 10 attached to the cylinder head in this way, the fuel port 54 of the fuel passage 53 is connected to the feed pump via a solenoid valve (not shown) by a fuel pipe (not shown). Spill ports 50 and 42 connected to the supply port of the metering plunger guide 16 and the pumping plunger guide 17, respectively, are connected to a fuel tank (not shown) via a fuel return pipe (not shown). ) is connected to the return side of

Of course, the solenoid valve is controlled by a controller (not shown) that sends an output signal in accordance with the amount of depression of the accelerator pedal of the vehicle in which the diesel engine is mounted, the rotational speed of the diesel engine, and the like.

Next, to explain the operation of the unit injector 10 described above, first, fuel from the feed pump is metered by a solenoid valve, and the metered fuel is sent to the fuel port 54 of the unit injector 10. Further, the fuel is sent to the check valve 5.
5 and is sent to the injection pump chamber 40.

When fuel is delivered to its injection pump chamber 40, the metering plunger 39 is lifted upwards.

In such a state, the cam shaft rotates and the pressure plunger 36 is pushed in, and as shown in FIG.
When closed, the fuel in the pressure pump chamber 41 is compressed, and its metering plunger 39 is pushed downward.

When the metering plunger 39 is pushed in in this way, the fuel in the injection pump chamber 40 is sent to the fuel reservoir 24 of the needle spindle bore 20 via the fuel passages 59, 28, 27, 25, and the fuel When the pressure within the reservoir 24 reaches a predetermined pressure, the nozzle needle 31 is lifted against the needle spring 34, and a predetermined amount of fuel is injected from the nozzles 22, 23, thereby performing the initial injection.

The pressure feeding plunger 36 is pushed further,
Injection cut-off groove 4 of the pressure-feeding plunger 36
8 is communicated to its first stage injection cut-off port 45, the pressure in its pressure pump chamber 41 is increased at its first stage injection cut-off port 45.
It acts on the lower end face of the slider 44, and the slider 44 is lifted upward against the return spring 46 (see FIG. 2).

That is, the opening area of the first-stage injection cut-off port 45 is rapidly expanded, and the fuel in the pressure pump chamber 41 is spilled in an extremely short period of time.
It is returned to the fuel tank side via port 42.

When the fuel in the pressure pump chamber 41 is returned to the fuel tank side in this way, the pressure pump chamber 41
As the pressure within the metering plunger 3 decreases, its metering plunger 3
9 slides upwards and the pressure in its injection pump chamber 40 decreases.

Therefore, the pressure within the fuel reservoir 24 also decreases,
The nozzle needle 31 is pressed against the valve seat 21 by the needle spring 34, the injection ports 22 and 23 are closed, and the first stage injection is completed.

Of course, in the above-described operation, when the slider 44 is lifted upward and the opening area of the first stage injection cut-off port 45 is rapidly expanded, the fuel in the pressure pump chamber 41 is drained in an extremely short period of time. Since the fuel is returned to the fuel tank side, the fuel is better drained during the first stage injection.

In addition, since the slider 44 is disposed so as to be able to slide back and forth within the slider bore 43 via a return spring 46, the pressure waves generated when the fuel is cut off as described above are removed from the slider 44. Attenuated by the slider 44, cavitation corrosion of the fuel supply system caused by the pressure waves is prevented.

The pressure-feeding plunger 36 is removed from the above-mentioned state.
When pushed in further, its injection cut-off groove 48 is located between its first stage and main injection cut-off ports 45 and 47, and these ports 4
5, 47 is closed by its pumping plunger 36.

When the pressure-feeding plunger 36 is pushed in in this way, the pressure within the pressure-feeding pump chamber 41 increases, and the metering plunger 39 is pushed down, so that the injection pump chamber 40 and The pressure inside the fuel reservoir 24 increases,
The nozzle needle 31 is lifted up against the needle spring 34, and a predetermined amount of fuel is injected from the injection ports 22, 23 to perform main injection.

Furthermore, when the pressure-feeding plunger 36 is pushed in, the injection cut-off groove 48 of the pressure-feeding plunger 36 opens into its main injection cut-off port 47.
will be contacted.

That is, almost in the same way as in the case of the end of the first-stage injection described above, the fuel in the pressure pump chamber 41 is returned to the fuel tank side, the pressure in the pressure pump chamber 41 decreases, and the metering plunger 39 slides upward and its injection pump chamber 40 and fuel reservoir 2
The pressure inside 4 decreases.

Therefore, the nozzle needle 31 is pressed against the valve seat 21 by the needle spring 34, the injection ports 22, 23 are closed, and the main injection is completed.

As understood from the above, in the unit injector used in the diesel engine of the present invention, the slider bore is formed in the valve body by widening the opening side of the plunger bore, and the first stage injection cut-off port is formed in the valve body at a position opened and closed by the pressure plunger so as to communicate a pressure pump chamber formed in the plunger bore with the slider bore and the spill port;
A slider is reciprocally slidably fitted around the pumping plunger and reciprocally slidably fitted in the slider bore, and a return spring is disposed within the slider bore to close the first stage injection cut-off. Push the slider in the direction to narrow the opening area of the port to cut off the main injection.
A port connects the pressure pump chamber to the spill port, and is located in the valve body at a predetermined distance from the initial injection cut-off port and at a position opened and closed by the pressure plunger. and an injection cut-off groove is formed in the outer circumferential surface of the pumping plunger at a predetermined location so that when the pumping plunger is slid back and forth into the plunger bore, the first stage and main injection cut-off groove In the diesel engine of the present invention, a communication passage is formed in the pressure plunger with one end opening into the pressure pump chamber and the other end opening into the injection cut-off groove. The unit injector used in the engine injects fuel in stages into the initial stage injection and main injection, which prevents a sudden pressure rise in the combustion chamber and reduces hydrocarbons and nitrogen oxides contained in the exhaust gas. This improves the combustion of the fuel, especially at the end of the first stage injection.
The pressure in the pressure pump chamber acts on the lower end of the slider at the first cut-off port, lifting the slider against the return spring and lifting the slider at the first cut-off port. The opening area is rapidly expanded, and the fuel is cut off from the pressure pump chamber through the spill port to the fuel tank in an extremely short period of time, and as the pressure in the pressure pump chamber decreases, the adjustment is performed. quantity plunger is pushed back,
The pressure in the injection pump chamber is reduced and the first stage injection is terminated, and as a result, in this first stage injection,
The fuel runs out faster, and the fuel is cut and reduced.
The pressure wave generated when it is turned off is effectively damped by the slider and return spring, and cavitation corrosion of the fuel supply system caused by the pressure wave is prevented, making it extremely practical.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing a specific example of a unit injector used in a diesel engine of the present invention, and FIG. 2 is an enlarged section showing the unit injector shown in FIG. 1 in a state where the first stage injection is completed. FIG. 10...Unit injector used in diesel engines, 11...Valve body, 20...
... Needle spindle bore, 21 ... Valve seat, 22, 23 ... Nozzle, 24 ... Fuel reservoir, 30 ... Plunger bore, 31 ... Nozzle needle, 34 ... Needle spring,
36... pressure plunger, 39... metering plunger, 40... injection pump chamber, 41... pressure pump chamber, 42... spill port, 43... slider bore, 44... slider, 45... first stage Injection cut-off port, 46...Return spring, 47...Main injection cut-off port,
48...Injection cut-off groove, 49...Communication path,
53...Fuel passage.

Claims (1)

[Claims] 1. A needle spindle bore 20 having a valve seat 21 and nozzles 22, 23, and a plunger having one end open and the other end communicating with a fuel reservoir 24 of the needle spindle bore 20. - a valve body 11 with a bore 30; a nozzle needle 31 fitted into its needle spindle bore 20 and seated on its valve seat 21 with a needle spring 34; a pressure-feeding plunger 36 fitted to the opening side so as to be reciprocatingly slidable; a pressure-feeding plunger 36 fitted to the plunger bore 30 closed by the pressure-feeding plunger 36 so as to be reciprocally slidable;
and a metering plunger 39 forming an injection pump chamber 40 on the fuel reservoir 24 side of the plunger bore 30 and a pressure pump chamber 41 on the pressure plunger 36 side of the plunger bore 30; A slider bore 43 is formed in the valve body 11 by enlarging the opening side of the valve 30, and a pressure pump chamber 41 is formed in the slider bore 4.
3 and the spill port 42, and is formed in the valve body 11 at a position opened and closed by the pressure plunger 36, and reciprocatingly slides around the pressure plunger 36. are reciprocally slidably fitted into the slider bore 43 and are slid into the slider bore 43 by the pressure within the pressure pump chamber 41 to open the first stage injection cut-off port. a return spring 46 disposed within the slider bore 43 to push the slider 44 in a direction that narrows the opening area of the initial injection cut-off port 45; and a pressure pump. Chamber 41 and its spill port 4
2, and a main injection cut formed in the valve body 11 at a position separated from the first stage injection cut-off port 45 by a predetermined interval and at a position opened and closed by the pressure-feeding plunger 36.・off port 47 and its pumping plunger 36 in a predetermined position
injection cut-off ports 45 and 47 formed on the outer peripheral surface of the injection cut-off ports 45 and 47 when the pump plunger 36 is slid back and forth within the plunger bore 30;
The off groove 48 has one end opened into the pressure pump chamber 41 and the other end opened into the injection cut off groove 48.