JPS59200058A - Unit injector used in diesel-engine - Google Patents

Abstract

PURPOSE:To make it possible to simply adjust the rate of injection, by providing such an arrangement that a spill lead communicates between a pumping chamber and an injection cut-off port when a pumping plunger slides in a predetermined range after the injection cut-off port is closed. CONSTITUTION:When a pumping plunger 36 is pushed in, associated with the rotation of a cam shaft, the fuel pressure in a pumping chamber 41 is raised due to the restricting effect of a spill lead 47 in the plunger 36. When the plunger 35 is further pushed in so that the communication between an injection cut- off port 43 and the spill lead 37 is cut off, the fuel pressure is further increased. Thereby, a metering plunger 39 is pushed downward to lift a nozzle needle 31 overcoming a spring 34, and therefore, fuel is injected from jet ports 22, 23. At this time the pressure in the pumping chamber 41 is gradually increased by the spill lead 47 in association with the depression of the pumping plunger 36 so that the rate of injection which is low in the initial stage of the injection, is gradually increased, resulting in preventing the abrupt rise of pressure in a combustion chamber, thereby the contents of hydrocarbon and NOX in exhaust gas are reduced, and the condition of combustion may be improved.

Description

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

Generally speaking, unit injectors differ from size-type fuel injection pumps and distribution-type fuel injection pumps in that they are directly attached to the diesel engine's cylinder head 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 rapid pressure increases in the combustion chamber and reducing hydrocarbons (HC) and nitrogen oxides (NOx) 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., unit injectors configured to rotate the plunger, change the relative position of the plunger lead and the feed port, and adjust the effective stroke of the plunger. Now, when the pressure inside the injection pump chamber reaches a predetermined pressure by pushing the granger,
The nozzle is closed by 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 of this invention is to lower the injection rate at the beginning of fuel injection, and then gradually increase the injection rate to prevent a sudden pressure rise in the combustion chamber, thereby reducing the amount of hydrocarbons and nitrogen contained in exhaust gas. Reduces oxides, improves fuel combustion, and
Adjustment of such injection rate is carried out by extremely simple means,
Our objective is to provide a real unit injector for use in diesel engines that keeps production costs low.

In view of these problems, the unit injector used in the diesel engine of the present invention includes a needle spindle bore having a pulp nozzle and a nozzle, and a nozzle bore connected to a fuel reservoir of the needle spindle bore. , and a pulp body with an injection cut-off port opening into its plant bore;
The valve (by the needle ring)
A nozzle needle fitted into the needle spindle bore, and a nozzle needle arranged to be reciprocatingly slidable in the planter bore and connected to the injection cut-off hoard so as to be connected to the needle spindle bore. injection cut-off groove,
and a pressure-feeding plunger equipped with a spill communication passage for the reservoir of the injection cut-off groove, and an injection bong 70 chamber in a position on the side of the fuel reservoir in the plunger bore, and a pressure-feeding plunger between the pressure-feeding plunger and the pressure-feeding plunger. A metering plunger and its injection cut-off valve are arranged so as to be reciprocally slidable in their bores so as to form pump zero chambers, respectively.
After the port is closed by its pumping plunger,
a spill lead formed at the end of the pumping plunger to communicate the pumping pump chamber with the injection cut-off port when the pumping plunger is slid within a predetermined stroke range; I have to.

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

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

This unit injector 10 is fitted into a pulp body 11 disposed in a cylinder head (not shown) of a diesel engine, and a needle spindle bore 20 formed in the pulp body 11. .2
A pressure pump chamber 41 is provided between a nozzle needle 31 that opens and closes the pulp body 11, a pressure plunger 36 which is arranged to be able to reciprocate and slide in a planter bore 30 formed in the pulp body 11, and a pressure pump chamber 41 between the pressure feeder plunger 36, A metering plunger 39 is arranged to be reciprocally slidable in the plunger bore 30, and a metering plunger 39 is formed at the lower end of the pressure plunger 36 so as to form an injection pump chamber 40 at a position opposite the pressure plunger 36. The pumping plunger 36 slides within a predetermined stroke range after the pumping plunger 36 is pushed in and closes the injection cut-off port 43 opening in the plantar bore 30. When activated, the spill lead 47 is configured to communicate the pressure pump chamber 41 with the injection cut-off port 43.

The pulp body 11 consists of nuts 1 and 12 that are screw-bonded to each other.
and the nozzle 13 integrated by the metering plunger guide 16, the needle spring guide 14, the partition shiplets 1-15, and the pressure plunger guide 17 screwed to the metering plunger guide 16, the pressure plunger guide 17. It consists of a nut 18 that is threaded together.

That is, the pulp body 11 is fitted into a nut 12 formed in a cylindrical shape with a nozzle fitting hole 19 at the lower end, and the pulp body 11 is fitted into the nut 12 so that the lower end side protrudes from the nozzle fitting hole 19. and a nozzle 13 equipped with a needle spindle bore 20 having a pulp sheet 21 and a plurality of nozzles 22 and 23;
A needle spring chamber 26 is fitted into the nut 12 so as to rest on the upper end surface thereof, and is open at the top and disposed approximately coaxially with the needle spindle bore 20. A needle spring guide 14 provided with the needle spring guide 14, a partition ship 1, 15 fitted into the nut 12 so as to close the open end of the needle spring chamber 26, and the nozzle 1.
3. The needle spring guide 14 and the partition jig rate 15 are screwed into the upper end of the oak 12 so as to be fixed to the oak 12, and biased to one side. metering plunger guide 16 with a metering plunger bore 58 open at the upper end;
and is screwed into the upper end of the metering plan gloss guide 16,
A pressure pumping plunger guide 17 with a pumping plunger bore 57 connected to its metering bore 58 and a nut 18 screwed into the upper end of the pumping plunger guide 17 with a plunger guide bore 60. It is composed of.

Of course, the nozzle 13, needle spring guide 14
, plate 15, and the metering plunger east 16 are provided with mutually connected fuel passages 25, 27, 28, and 59, respectively, and their plunger bore 30, i.e., the metering plunger bore 58, and the metering plunger bore 58, respectively. The plunger bore 57 is connected to the fuel reservoir I) 24 of its needle spindle bore 20.

The pressure-feeding plunger eastward 17 has an injection cut opening at a predetermined position in the pressure-feeding plunger bore 57.
It is equipped with an off port 43.

The injection cut-off port 43 is a spill port 42 that opens on the outer surface of the pump plunger guide 17.
is communicated with.

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, the fuel passage 53 within the partition υ plane 15
A check valve 55 is disposed downstream of the injection pump chamber 40 to prevent fuel from flowing backward from the injection pump chamber 40 to the fuel port 54 side.

Also, at a location opposite the fuel passage 53, the metering plunger guide 16 includes a spill port 50 opening into the metering plunger bore 58; The needle spring chamber 26 of the needle spring guide 14 of the plant is connected via interconnected communication passages 56 and 29 of the planter guide 16 and the partition plate 15.

The nozzle needle 31 is reciprocatably arranged in the needle spindle bore 20 so as to be seated on the pulp sheet 21 in the nozzle 13.

The nozzle needle 31 is integrally provided with an upper end 3z, the pin 32 is passed through a pin hole 33 formed at the lower end of the needle spring guide 14, and the nozzle needle 31 is disposed within the needle spring chamber 26. The needle tip is in contact with the spring seat 35 and is always located within its needle spring chamber 26.
It is pressed against the pulp sea (21) by a spring 34.

The pumping plunger 36 is arranged in the pumping plunger bore 57 of the pumping plunger guide 17 so as to be extended outwardly from the nut 18, and has a follower 37 at its extended end and a flange of the follower 37. A pulp spring 38 restrained between the nut 18 and the pumping plunger bore 5 is disposed coaxially about the extended end thereof and
7 so that it can be slid back and forth.

When the pumping plunger 36 is pushed into position within the pumping plunger bore 57, the pumping plunger 36
An injection cut-off groove 45 connected to an injection cut-off port 43 opened in the plunger bore 57 is provided on the outer periphery of the lower end.
is connected to the metering plunger 39 side, in other words, between the metering plunger 39 and the pressure-feeding plunger 36, which will be described next, via a spill communication passage 46 opened at the lower end face of the pressure-feeding plunger 36. Formed pressure pump chamber 4
1 has been contacted.

The metering plunger 39 has an injection pump chamber 40 in its plunger bore 30 at a position on the fuel reservoir I) 24 side.
A pressure pump chamber 41 is connected between the pressure pump chamber 36 and the pressure pump chamber 36.
'C(D) are reciprocally slidably disposed in the metering plunger bore 58 so as to form, respectively.

When the metering plunger 39 is pushed 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 3.
The injection pump chamber 9 is connected to the injection pump chamber 40 through a spill communication passage 52 opened at the lower end face of the fuel injection pump 9 .

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

A spill lead 47 is formed at the lower end of the pumping plunger 36. That is, the spill lead 47
after the injection cut-off port 43 is closed by the pump plunger 36.
The lower end of the pump plunger 36 is configured to communicate the pump chamber 41 with the injection cut-off port 43 when the pump 6 is slid within a predetermined stroke range.

Of course, immediately after the injection cut-off port 43 is closed by the pressure plunger 36, the pressure pump i41 is communicated with the injection cut-off port 43 by the spill lead 47. At this time, the spill lead 47 acts as a throttle, and the spill lead 47 is configured to increase its throttle effect in response to the pushing of the pressure-feeding plunger 36.

In other words, the spill lead 47 allows the fuel in the pressure pump chamber 41 to escape to the injection cut-off port 43 immediately after the injection cut-off port 43 is closed by the pressure sylanger 36. , to prevent a sudden pressure rise in the pressure pump chamber 41, to lower the initial fuel injection rate, and to create a strangulation effect by the spill lead 47 in response to the push of the pressure plunger 36. It is configured to gradually increase the thickness of the pressure pump chamber 41 to smoothly increase the pressure inside the pressure pump chamber 41 and gradually increase the fuel injection rate.

When the spill lead 47 communicates the pressure pump chamber 41 with the injection cut-off port 43, the pressure plunger bore 57 has a ring groove connected to the injection cut-off port 43. 44, and even if the pressure plunger 36 is rotated, the spill lead 47 prevents the pressure pump chamber 41 from reaching its injection cut-off point within a predetermined sliding stroke range.
It is desirable that the configuration be such that it is reliably communicated with the port 43.

The unit injector IO configured as described above has its nozzle 22, 23 located within the combustion chamber in the cylinder head of a diesel engine (not shown), and
A follower 37 of the pumping planter 36 is mounted to the cylinder head in contact with the end of a rocker arm driven by the camshaft of the diesel engine.

In the unit injector 10 that has been installed in the cylinder head in this way, the fuel port 54 of the fuel passage 53 is fed via a solenoid valve (not shown) by a fuel pipe (not shown). - Spill ports 50, 42 connected to the feed port of the pump and formed in its metering plant gear guide 16 and pumping plant gear guide 17, respectively, are connected to the fuel tank ( (not shown).

Of course, the solenoid valve is controlled by a controller that sends an output signal according to the amount of depression of the accelerator pedal of the vehicle equipped with the diesel engine, the rotation speed of the diesel engine, etc.
(not shown).

Next, to explain the operation of the above-mentioned unit injector 10, first, fuel from the feed pump is metered by a solenoid valve, and the metered fuel is injected into the unit.
is sent to the fuel hoard 54 of the injector 10, and
The fuel is sent to the injection pump chamber 40 through the check valve 55, and the metering plunger 39 is lifted upward by the fuel.

In such a state, the cam shaft rotates, the pressure feeding plant gear 36 is pushed in, and when it reaches a predetermined position, the injection cut-off...t? -) 43 is placed in a substantially closed state by its pressure flange 36, while the pressure pump chamber 41 is forced into its injection cut-off position by means of a spill lead 47. Because of the communication, the pressure of the fuel in the pressure pump chamber 41 does not rise rapidly.

'l When the pressure-feeding plunger 36 is pushed further, the squeezing effect by the spill lead 47 is increased, and the pressure of the fuel in the pressure-feeding pong chamber 41 gradually increases.

Furthermore, when the pressure feeding plant gear 36 is pushed in from such a state, the communication between the spill lead 47 and the injection cut-off port 43 is cut off, in other words, the injection cut-off port 43 is completely closed, and the pressure of the fuel in the pressure pump chamber 41 becomes even higher.

Therefore, as described above, when the pressure of the fuel in the pressure pump chamber 41 rises and the metering planter 39 is pushed downward, and furthermore, the pressure of the fuel in the injection pump chamber 40 reaches a predetermined pressure or more. , the pressure force acts on the fuel reservoir 24 of the spindle bore 20, the nozzle needle 31 is lifted against the needle spring 34, and fuel is injected in the form of a mist from the injection D22, 23. However, due to the spill lead 47, the pressure inside the pressure pump chamber 41 is gradually increased in accordance with the push of the pressure plunger 36, so that the injection rate is low at the beginning of fuel injection. After that, the injection rate gradually increases, preventing a sudden pressure rise in the combustion chamber of the diesel engine.
The lower content of hydrocarbons and nitrogen oxides in the exhaust gas improves fuel combustion.

Also, when the pressure plunger 36 is pushed further, the injection cut-off groove 45 of the pressure plunger 36 is connected to the injection cut-off $-1-43, and at about the same time, the metering plunger 39 is further pushed in. When pushed in, the spill port 50 is opened.

When the spill port 50 of Sunawachi 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 passage. 29°56 through the needle
Sent to Springa Chan/426. Of course, if the injection cut-off groove 45 of the pressure-feeding syringe 36 is connected to the injection cut-off port 43, the fuel in the pressure-feeding pump chamber 41 will flow through the spill communication passage 46. It passes through the injection cut-off groove 45 and its injection cut-off port 43 and returns to the fuel tank side.

Therefore, when the fuel injection ends, the nozzle 2 to 3
The pressure acting on the side that lifts the fuel 1 decreases in an extremely short period of time, and the pressure in the pressure pump chamber 41, which had been compressed until just before the end of the injection, is guided into the needle spring chatuba 26, and the nozzle is・Since the force for seating the needle 31 on the P, +1/F seat 21 is increased, fuel injection is improved.

According to the above invention, a valve body, a nozzle needle fitted into a needle spindle bore of the valve body, a pressure feeding plunger disposed in a plunger bore of the valve body, and a pressure feeding plunger. It includes a metering plunger disposed on the flanger 70 and a spill lead formed in the flanger so as to form a chamber between the flanges and the flanger, and the flanger is pushed into the metering plunger. After closing the injection cut-off port opened in the plunger bore, when the pump plunger is slid within a predetermined stroke range, the spill lead causes the injection pump chamber to close the injection cut-off port.・Since it is configured to communicate with the hoard, the injection rate is low at the beginning of fuel injection, and after that,
The injection rate is gradually increased, the sudden pressure rise 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 The injection rate can be adjusted by extremely simple means, production costs can be kept low, and the system can be extremely practical.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a specific example of a unit injector used in a 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. 3 is a bottom view of the pumping planter shown in FIG. 2.
12. . DESCRIPTION OF SYMBOLS 10... Unit injector used in a diesel engine, 11... Valve body, 20... Needle spindle bore, 21... Noggle seat, 2
2.23...Nozzle port, 24...Fuel reservoir, 30...Plant bore, 31...Nozzle needle, 34...Needle spring, 36...Pressure plunger, 39
... Metering plunger, 40... Injection pump chamber, 41.
・Pressure pump chamber, 43... Injection cut off..., Ie-
), 45... Injection cut-off groove, 46... Spill communication path, 47... Spill lead. Question/(2) 10 2 holes 1t! l. 361-

Claims (1)

[Claims] A needle spindle bore having a valve seat and an injection port, a plunger bore communicating with a fuel reservoir in the needle spindle bore, and an injection cut opening in the plunger bore. a valve body with an off port, a nozzle needle fitted in its needle spindle bore such that it is seated in its valve seat by a needle spring, and reciprocating sliding in its plunger bore; a pumping plunger with an injection cut-off groove arranged so as to be able to communicate with the injection cut-off hoard, and a spill communication passage for the injection cut-off groove; , a metering plunger disposed so as to be able to reciprocate and slide in the plunger bore so as to form an injection pump chamber at a position on the fuel reservoir side and a pressure pump chamber between the pressure plunger and the pressure plunger; After the cut-off port is closed by the pump plunger, the pump chamber is configured to communicate the pump chamber with the injection cut-off port when the pump plunger is slid within a predetermined stroke range. A unit injector used in diesel engines that includes a spill lead formed at the end of a pressure feed blanker.