JPH0415394B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in unit injectors used in diesel engines.

In general, unit injectors are different from in-line fuel injection pumps, distribution fuel injection pumps, etc.
They have been constructed to be directly attached to the cylinder head of a diesel engine and driven by the cam shaft of the diesel engine to inject fuel without using a high-pressure injection pipe. Such a unit injector is used to prevent a sudden pressure rise in the combustion chamber and to reduce the amount of hydrocarbons (HC) and nitrogen oxides (NOx) contained in the exhaust gas.
In order to satisfy these conditions, it is desirable to lower the injection rate at the beginning of fuel injection and then gradually increase the injection rate. .

However, conventional unit injectors, i.e., units configured to rotate the plunger, change the relative position of the plunger lead and feed port, and adjust the effective stroke of the plunger.・In the injector, when the pressure in the injection pump chamber reaches a predetermined pressure by pushing the plunger, the nozzle closes the injection port with a needle spring.
Since the needle is lifted and a predetermined amount of fuel is injected at one time, and the fuel injection rate is predetermined, it has been difficult to adjust the injection rate as described above.

The purpose and problem of this invention is to lower the injection rate at the beginning of fuel injection, then gradually increase the injection rate to prevent a sudden pressure rise in the fuel chamber, and to prevent carbonization contained in exhaust gas. It improves fuel combustion by reducing hydrogen and nitrogen oxides, and also allows such injection rate adjustment to be performed using extremely simple means.
The purpose of the present invention is to provide a unit injector used in diesel engines that reduces production costs.

In connection with the above-mentioned objects and problems, the unit injector used in the diesel engine of the present invention includes a needle spindle bore having a valve seat and a jet port, the needle spindle bore being connected to a fuel sump. A plunger bore, a valve body equipped with an injection cut-off port opened in a ring groove on the inner peripheral surface of the plunger bore, and a needle spring fitted into the needle spindle bore. a nozzle needle seated in the valve seat; an injection cut-off groove reciprocally slidably fitted in the plunger bore and in communication with the injection cut-off port; a pressure-feeding plunger having a spill communication passage communicating with the injection cut-off groove; and a pressure-feeding plunger that is fitted into the plunger bore so as to be able to reciprocate and slide, and in the plunger bore, an injection pump chamber is provided on the fuel reservoir side, and the pressure-feeding plunger a metering plunger, each forming a pressure pump chamber on its side; and a vertical groove formed in the outer peripheral surface of the lower end of the pressure plunger, and after the injection cut-off port is closed by the pressure plunger, the pressure plunger and a spill lead communicating the pressure pump chamber with the injection cut-off port, the injection cut-off port being closed by the pressure plunger when the plunger is slid within a predetermined stroke range. Immediately after
The spill reed communicates the pressure pump chamber with the injection cut-off port, with the spill reed acting as a throttle and increasing the throttling effect in response to the depression of the pressure plunger, causing the fuel injection Initially, the injection rate is low, and then the injection rate is gradually increased.

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

1 to 3 show a specific example 10 of a unit injector used in a diesel engine according to the present invention.

This unit injector 10 is arranged in a cylinder head (not shown) of a diesel engine, and is connected to a valve seat 21 and a nozzle 2.
Needle spindle bore 2 with 2,23
0, a plunger bore 30 connected to the fuel reservoir 24 of the needle spindle bore 20, and an injection cut-off port 43 opened in a ring groove 44 on the inner peripheral surface of the plunger 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;
An injection cut-off groove 4 is reciprocally slidably fitted into the plunger bore 30 and is connectable to the injection cut-off port 43.
5, and a pressure-feeding plunger 36 equipped with a spill communication passage 52 communicating with the injection cut-off groove 45, and a pressure-feeding plunger 36 that is fitted into the plunger bore 30 so as to be able to reciprocate and slide, and in which the fuel is Injection pump chamber 40 on the reservoir 24 side
A pressure pump chamber 4 is placed on the pressure plunger 36 side.
1, a metering plunger 39 formed respectively;
A vertical groove is formed on the outer peripheral surface of the lower end of the pressure-feeding plunger 36, and after the injection cut-off port 43 is closed by the pressure-feeding plunger 36, the pressure-feeding plunger 36 slides within a predetermined stroke range. and a spill lead 47 that communicates the pressure pump chamber 41 with the injection cut-off port 43 when the pressure pump chamber 41 is pushed into the injection cut-off port 43 , which opens into the plunger bore 30 when the pressure plunger 36 is pushed into the injection cut-off port 43 . After closing the off port 43, the spill lead 47 communicates the pressure pump chamber 41 with the injection cut-off port 43 over a predetermined stroke range of the pressure plunger 36, while the spill・Manufactured in such a way that the reed 47 functions as a throttle and increases the throttle effect in response to the push of the pressure-feeding plunger 36, lowering the injection rate at the beginning of fuel injection and then gradually increasing the injection rate. It was done.

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 chain 26 disposed in the needle spring guide 14; a partition plate 15 fitted into the nut 12 so as to close the open end of the needle spring chain 26; Nozzle 13, needle
Spring guide 14 and partition plate 1
5 is screwed into the upper end of the nut 12 and provided on one side with a metering plunger bore 58 having an open upper end. Metering plunger guide 16 and its metering plunger guide 1
a pressure plunger guide 17 with a pressure plunger bore 57 screwed into the upper end of the pressure plunger guide 6 and communicating with its metering plunger bore 58;
The nut 18 includes a 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 pressure plunger guide 17 is also provided with an injection cut-off port 43 opened at a predetermined position in the pressure plunger bore 57.
The injection cut-off port 43 communicates with a spill port 42 opened on the outer surface of the pump plunger guide 17.

Further, the pressure-feeding plunger guide 17 and the metering plunger guide 16 are provided with a fuel passage 53 connected to each other, and a fuel port 54 opened on the outer surface of the pressure-feeding plunger guide 17 is connected to the fuel passage 28 in the partition plate 15 described above. is in contact with.

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.

Further, at a position opposite to the fuel passage 53, the metering plunger guide 16 is connected to the metering plunger guide 16.
A spill port 50 is provided which opens into the bore 58 and which spill port 50 is further connected to the metering plunger guide 16 and the partition plate 15.
is connected to the needle spring chamber 26 of its needle spring guide 14 via interconnected communication passages 56 and 29 .

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 touches 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 outwardly of the nut 18;
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.

When the pump plunger 36 is pushed into position within the pump plunger bore 57, the pump plunger 36 has an injection cut-off groove 45 that communicates with an injection cut-off port 43 opening in the pump plunger bore 57. The injection cut-off groove 45 is provided on the outer periphery near the lower end, and the injection cut-off groove 45 is connected to the metering plunger 39 side, in other words, to the next Metering plunger 39 as described in
and the pressure pump chamber 41 formed between the pressure plunger 36 and the pressure plunger 36 .

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.

When the metering plunger 39 is pushed up into position within the metering plunger bore 58, the metering plunger 39 opens the spill groove 51, which is connected to the spill port 50 opened in the metering plunger bore 58, into a substantially central position. The spill groove 51 is provided on the outer periphery of the metering plunger 39 and communicates with the injection pump chamber 40 via a spill communication passage 52 opened at the lower end surface of the metering plunger 39 .

Of course, the metering plunger bore 58 is in communication with the pumping plunger bore 57, but as shown in FIG. 1, the metering plunger bore 58 is laterally offset; Since it is connected to the pressure plunger bore 57, the upward sliding movement of the metering plunger 39 is restricted by contacting the lower end face of the pressure plunger guide 17.

The spill lead 47 is formed in a vertical groove on the outer peripheral surface of the lower end of the pumping plunger 36. That is, the spill lead 47 has its injection cut-off port 43 connected to its pumping plunger 36.
After being closed by the pumping plunger 3
6 is slid within a predetermined stroke range,
The pressure pump chamber 41 is cut off and
A vertical groove is formed in the outer circumferential surface of the lower end of the pressure-feeding plunger 36 and opened in the end surface of the pressure-feeding plunger 36 so as to communicate with the port 43 . Of course,
The length of the longitudinal groove was matched to a predetermined stroke range of the pressure-feeding plunger 36.

Of course, immediately after the injection cut-off port 43 is closed by the injection plunger 36, the spill lead 47 causes the injection pump chamber 41 to close to the injection cut-off port 43.
In this case, the spill lead 47 acts as a throttle, and the spill lead 47 is configured to increase the throttle effect as the pressure-feeding plunger 36 is pressed. ing.

In other words, the spill lead 47 is
Immediately after the injection cut-off port 43 is closed by the pressure plunger 36, the fuel in the pressure pump chamber 41 is removed from the injection cut-off port.
It escapes to the port 43 to prevent a sudden pressure rise in the pressure pump chamber 41 and lower the initial fuel injection rate, and furthermore, the spill lead 47 creates a throttling effect in response to the push of the pressure plunger 36. The fuel injection rate is gradually increased, the pressure within the pressure pump chamber 41 is smoothly increased, and the fuel injection rate is gradually increased.

Further, when the pressure pump chamber 41 is communicated with the injection cut-off port 43 by the spill lead 47, even if the pressure plunger 36 is rotated, the spill will not flow within a predetermined sliding stroke range. - The pressure pump chamber 41 is connected to the injection cut-off port 4 by the lead 47.
3, the injection cut and
The off port 43 opens into a ring groove 44 on the inner peripheral surface of the pumping plunger bore 57.

The unit injector 10 configured as described above has its nozzles 22 and 23 housed in the 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 its cylinder head in contact with the rocker arm end which is driven by the engine's 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 on which the diesel engine is installed, 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 to the injection pump chamber 40, and the metering plunger 39 is lifted upward by the fuel.

When the cam shaft rotates in such a state and the pressure plunger 36 is pushed in and reaches a predetermined position, the injection cut-off port 43 is substantially closed by the pressure plunger 36. However, since the pressure pump chamber 41 is connected to its injection cut-off port 43 by the spill lead 47, the pressure of the fuel in the pressure pump chamber 41 does not rise rapidly.

When the pressure plunger 36 is pushed further, the throttling effect of the spill lead 47 is enhanced, and the pressure of the fuel in the pressure pump chamber 41 gradually increases.

Furthermore, when the pressure-feeding plunger 36 is pushed in from such a state, the spill lead 4
7 and its injection cut-off port 43 is cut off, in other words, its injection cut-off port 43 is completely closed, and the pressure of the fuel in its pressure pump chamber 41 is further increased. .

Therefore, as described above, the pressure pump chamber 4
The pressure of the fuel in the metering plunger 39 increases.
is pushed downward, and further the injection pump chamber 40
When the pressure of the fuel inside reaches a predetermined pressure or more, the pressure acts on the fuel reservoir 24 of the needle spindle bore 20, the nozzle needle 31 is lifted against the needle spring 34, and the nozzle 22, Fuel is injected in a mist form from 23, but the spill lead 47 causes the pressure pump chamber 4
Since the pressure inside 1 is made to gradually increase in accordance with the pushing of the pressure-feeding plunger 36,
The injection rate is low at the beginning of fuel injection, and then the injection rate gradually increases, preventing the rapid pressure rise in the combustion chamber of the diesel engine, and reducing the content of hydrocarbons and nitrogen oxides in the exhaust gas. This improves fuel combustion.

Further, when the pressure-feeding plunger 36 is further pushed in, the injection cut-off groove 45 of the pressure-feeding plunger 36 is communicated with the injection cut-off port 43, and almost at the same time, the metering plunger 39 is further pushed in. Spill port 50 is opened.

That is, when the spill port 50 is opened, the fuel compressed in the pressure pump chamber 41 is returned to the fuel tank side through the spill port 50, and a part of the fuel is also transferred to the communication path. 2
9 and 56 to the needle springer chamber 26. Of course, if the injection cut-off groove 45 of the pressure plunger 36 is connected to the injection cut-off port 43, the fuel in the pressure pump chamber 41 will flow through the spill communication passage 4.
6. It passes through the injection cut-off groove 45 and its injection cut-off port 43 and is returned to the fuel tank side.

Therefore, when fuel injection ends, the pressure acting on the side that lifts the nozzle needle 31 decreases in an extremely short time, and moreover, the pressure in the pressure pump chamber 41, which had been compressed until just before the end of the injection, decreases in a very short time. Since pressure is introduced into the needle spring chamber 26 and the force to seat the nozzle needle 31 on the valve seat 21 is increased, fuel injection is improved.

As can be understood from the above, the unit injector used in the diesel engine of the present invention has a valve body that is connected to a needle spindle bore having a valve seat and a nozzle, and a fuel reservoir in the needle spindle bore. a plunger bore, and an injection cut-off port opening into a ring groove on the inner circumferential surface of the plunger bore, and a spill lead extending vertically on the outer circumferential surface of the lower end of the pump In the unit injector used in the diesel engine of the present invention, after the pressure plunger is pushed in and closes the injection cut-off port opened in the plunger bore, the pressure plunger When the is slid within a predetermined stroke range, its spill lead communicates its pressure pump chamber with its injection cut-off port, causing the injection rate to be low at the beginning of fuel injection; gradually increases, the sudden pressure increase in the combustion chamber is prevented, the content of hydrocarbons and nitrogen oxides in the exhaust gas is reduced, the combustion of fuel is improved, and moreover, such injection rate regulation is extremely It is done by simple means, keeps production costs low, and becomes extremely practical.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a specific example of a unit injector used in the diesel engine of the present invention, FIG. 2 is an enlarged partial vertical cross-sectional view showing the vicinity of the tip of the pressure-feeding plunger shown in FIG. , 3rd
The figure is a bottom view of the pumping plunger shown in FIG. 2. 10...Units used in diesel engines
Injector, 11... Valve body, 20... Needle spindle bore, 21... Valve seat,
22, 23...Nozzle port, 24...Fuel reservoir, 30...Plunger bore, 31...Nozzle needle, 34...
Needle spring, 36...pressure feeding plunger,
39... Metering plunger, 40... Injection pump chamber, 4
DESCRIPTION OF SYMBOLS 1... Pressure pump chamber, 43... Injection cut-off port, 45... Injection cut-off groove, 46... Spill communication path, 47... Spill lead.

Claims (1)

[Scope of Claims] 1. A needle spindle bore having a valve seat and a nozzle, a plunger bore connected to a fuel reservoir of the needle spindle bore, and a ring on the inner peripheral surface of the plunger bore. a valve body having an injection cut-off port opening in a groove; a nozzle needle fitted into the needle spindle bore and seated in the valve seat by a needle spring; and a plunger bore. an injection cut-off groove that is reciprocally slidably fitted into the injection cut-off port and is capable of communicating with the injection cut-off port; , a metering plunger fitted in the plunger bore so as to be reciprocally slidable and forming an injection pump chamber on the fuel reservoir side and a pressure pump chamber on the pressure-feeding plunger side in the plunger bore; and the pressure-feeding plunger. A vertical groove is formed on the outer peripheral surface of the lower end of the injection cut-off.
After the port is closed with its pumping plunger,
A unit used in a diesel engine that includes a spill lead that communicates the pressure pump chamber with the injection cut-off port when the pressure plunger is slid within a predetermined stroke range.
Injector.