JPH08210221A - Unit injector - Google Patents

Abstract

PURPOSE: To dispense with a high cost driver and reduce cost by controlling the timing of blocking and unblocking fuel fed from a feed pump to a pump plunger chamber in accordance with the feeding timing and feeding time of the fuel pressure fed from a control pump. CONSTITUTION: A control valve, which actuates fuel from the control pump 26 of a fuel injection pump as pilot pressure oil, is arranged between the fuel passage communicating with a feed pump 15 and the interior of a pump plunger chamber 7 inside a fuel injection nozzle body 2. Fuel feeding to the pump plunger chamber 7 is blocked in accordance with the fuel feeding timing and feeding time of the control pump 26 and fuel infection timing and injection quantity from the injection nozzle is controlled. Thus a small size injection pump may sufficiently serve the purpose causing a high cost drive to be dispensed with and responsiveness equal to the conventional electric method by means of a high speed solenoid valve can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-cost fuel injection pump adopted in a diesel engine of a general vehicle from an electric control system using a high-speed high-speed solenoid valve for controlling fuel injection timing and injection amount. The present invention relates to a unit injector for an internal combustion engine, which is changed to a hydraulic control system that uses the engine as a control pump.

[0002]

2. Description of the Related Art In a conventional unit injector, for example, as disclosed in Japanese Patent Laid-Open No. 61-72867, a high-speed fuel injection pump main body for each cylinder is capable of quickly and quickly switching the fuel injection timing and injection amount without variation. An electromagnetic valve is provided to cut off the communication between the fuel supply passage in the fuel injection pump body and the pump plunger chamber, thereby increasing the pressure of the fuel in the pump plunger chamber and injecting the fuel into the combustion chamber.

[0003]

In the prior art, since the fuel injection timing and the injection amount of each cylinder are electrically controlled by using the high speed solenoid valve, the response is good and the variation is small. The system cost is increased because a driver for supplying a high-voltage current to the solenoid valve is required. Therefore, by controlling the fuel injection timing and the injection amount hydraulically using a fuel injection pump used for a diesel engine of a general vehicle, a costly driver is not required and the cost can be reduced.

[0004]

A fuel injection nozzle main body provided for each cylinder of a multi-cylinder engine, a pressure-feeding unit main body that is a part of the main body, a cylinder formed in the pressure-feeding unit main body, and the cylinder. A cam-driven plunger that is slidably inserted into the pump plunger chamber to constitute a pump plunger chamber, a fuel injection nozzle that is another part of the main body, a fuel passage communicating with the pump plunger chamber, and the pump plunger chamber. A fuel supply path to the oil reservoir of the fuel injection nozzle,
A method of controlling an injection timing and an injection amount of a unit injector including a fuel discharge hole that causes a part of the fuel to overflow by being pumped from the pump plunger chamber to the fuel injection nozzle,
The fuel passage is blocked and the fuel injection timing and injection amount are controlled according to the fuel supply timing and supply time of the control pump.

Further, a fuel injection nozzle main body provided for each cylinder of a multi-cylinder engine, a fuel pressure feed unit main body which is a part of the main body, a cylinder formed in the pressure feed unit main body, and a slide on the cylinder. A cam driven plunger that is movably inserted to form a pump plunger chamber, a fuel injection nozzle that is another part of the main body, a fuel passage that communicates with the pump plunger chamber, and the fuel injection from the pump plunger chamber. A unit injector having a fuel supply passage communicating with an oil reservoir of a nozzle and a fuel discharge hole for overflowing a part of fuel pumped from the pump plunger chamber to the fuel injection nozzle, A control valve assembly that shuts off the fuel supply from the feed pump is connected to the Controlling the the injection amount of fuel injection timing by a blocking communication of the fuel supply to the pump piston chamber in response to the feed timing and time.

[0006]

The control valve operates according to the timing and supply time of the fuel delivered from the engine-driven control pump as a pilot, shuts off the fuel passage communicating with the feed pump and the pump plunger chamber, and from the fuel injection nozzle. The fuel injection timing and the fuel injection amount are controlled.

[0007]

1 is a diagram showing an embodiment of a hydraulically controlled fuel injection nozzle body of the present invention, FIG. 2 is a partially enlarged view of the injection nozzle body N of FIG. 1, and FIG. It is a partially enlarged view of a control valve part. 1 of engine crankshaft C
The plunger 5, which is driven in a constant stroke via the rocker arm mechanism R by the rotation of the cam shaft 1 driven at a rotation speed of / 2, is received in the cylinder 6 bored in the fuel injection pump nozzle body case 4. The plunger 5 and the cylinder 6 form a pump plunger chamber 7.

The jet nozzle body N has a known structure,
Retaining nut 8 for fuel injection nozzle body case 4
It is attached to. A nozzle needle valve 11 is received in the nozzle cylinder 10. Nozzle needle valve 11
A needle spring 13 is located on the upper part of the. The pump plunger chamber 7 and the oil reservoir chamber 12 are connected to the fuel supply passage 22,
It communicates via 23. Needle spring chamber 14
Communicate with 24 via fuel discharge passages 21a, 21b, 21c that are formed in the fuel injection nozzle body case 4. The pipe line 25 branches from the fuel discharge line 21c to the tank T.

The large-diameter hole 18a and the small-diameter hole 1 are parallel to and apart from the cylinder 6 opened in the fuel injection nozzle body case 4.
A two-stage hole 18 having an opening 8b is opened. The control valve 16 having a bottomed hole 16a is received in the small-diameter hole 18b of the two-stage hole 18, and is supported by the cover 30. A hole 30a is provided in the central portion of the cover and is connected to a pipe 28 for fuel sent from a control pump 26 of a fuel injection pump described later.

A cover 30 is attached to the fuel injection nozzle body case 4 to form a large diameter hole chamber. A hole 30a is provided in the center of the cover, and is connected to the conduit 30 from the feed pump 15. Control valve 16
Has a spring 17 wound around its outer circumference and faces the cover 30 by its urging force.

The space between the control valve tip portion 16b and the small diameter hole 18b communicates with the pump plunger chamber 7 through the fuel supply passage 20a. Also, the large-diameter hole is used for the fuel passage 2
Needle spring chamber 14 through 1a, 21b, 21c
Is in communication with.

Next, the operation of the fuel injection nozzle body will be described with reference to FIGS. 1, 2, 3 and 4. FIG.
Shows the crank angle on the horizontal axis, the pilot pressure on the vertical axis (a), the control valve lift amount on the vertical axis (b), and the pump plunger chamber pressure (nozzle injection pressure) on the horizontal axis. The control pump 26 of the fuel injection pump has a well-known structure of a distribution type, a row type, etc.
Fuel pressurized to 00kg / cm2 is control valve 1
6 is sent.

FIG. 4 shows the fuel pressure delivered from the control pump 26, that is, the pilot pressure oil for operating the control valve 16, the control valve lift amount and the internal pressure of the pump plunger chamber 7 (injection pressure of the injection nozzle). Shows the relationship with.

The timing at which the high-pressure fuel as pilot pressure oil acts on the control valve 16 is the plunger 5
After the end of the ascending, the fuel passage 20a is shut off by the ascent of the control valve 16 and the fuel introduced into the pump plunger chamber 7 is confined. The pilot pressure oil enters the bottomed hole 16a of the control valve 16 through the pipe 29 and the cover 30. Control valve 1
6 rises against the spring 17, the tip portion 16a is sealed at the S1 portion, and the fuel passage 20a leading to the pump plunger chamber 11 is shut off. Then, the cam 5 is driven to lower the plunger 5 so that the pump plunger chamber 11
The fuel inside rises sharply. This fuel pressure is applied to the fuel passage 2
It enters into the oil reservoir 12 through 2b and 23. Oil sump 12
The fuel pressure acts on the tapered portion 11a of the nozzle needle valve 11 located inside, so that the nozzle needle 11 valve is pushed upward against the needle spring 13 and fuel is injected from the injection port into the combustion chamber.

Further, due to the vertical movement of the nozzle needle valve 11, a part of the fuel sucked up from the oil reservoir chamber 12 into the needle spring chamber 14 is partially discharged into the fuel discharge passages 24, 21c, 2 and 2.
It drains to the tank T through 5.

When the fuel pressure from the control pump 26 drops, the control valve 16 descends due to the spring force of the needle spring 17, and the seal between the tip portion 16a and the S1 portion is released. At this time, since the fuel pressure in the pump plunger chamber 7 is reduced, the nozzle needle valve 11 in the injection nozzle body 8 is closed by the urging force of the needle spring 13, so that the fuel injection into the combustion chamber is stopped. .

[0017]

Since the present invention is configured as described above, in order to hydraulically control the control valve that shuts off the supply of fuel from the feed pump to the pump plunger chamber in the fuel injection nozzle body, By using the fuel injection pump used in the diesel engine of a general vehicle, a costly driver using an electric system using a conventional high-speed solenoid valve is unnecessary. Moreover, since it can be sufficiently used in a small injection pump mounted on a general vehicle, it has a relatively low cost and a response equivalent to that of an electric system using a conventional high-speed solenoid valve.

[Brief description of drawings]

FIG. 1 is a sectional view of an injector unit of the present invention.

FIG. 2 is a partially enlarged view of a jet nozzle body N of FIG.

FIG. 3 is a partially enlarged view of a control valve portion of FIG.

FIG. 4 is a diagram showing a relationship among a pilot pressure, a control valve lift amount, and a fuel pressure (nozzle injection pressure) in a pump plunger chamber.

[Explanation of symbols]

2: Fuel injection nozzle body, 4: Fuel injection nozzle body case, 5: Plunger, 6: Cylinder, 7: Pump plunger chamber, 9: Injection nozzle body case, 1
1: Nozzle needle valve, 13: Needle spring,
15: feed pump, 16: control valve, 18: two-stage hole, 20: fuel passage, 21a, 21
b, 21c, 24: fuel discharge passage, 22, 23: fuel supply passage, 26: control pump.

Claims (2)

[Claims] 1. A fuel injection nozzle main body provided for each cylinder of a multi-cylinder engine, a fuel pumping unit main body that is a part of the main body, a cylinder formed in the pumping unit main body, and a slide on the cylinder. A cam driven plunger that is movably inserted to form a pump plunger chamber, a fuel injection nozzle that is another part of the main body, a fuel passage that communicates with the pump plunger chamber, and the fuel injection from the pump plunger chamber. The fuel injection timing and the injection amount of the unit injector equipped with a fuel supply passage communicating with the oil reservoir chamber of the nozzle and a fuel discharge hole for overflowing a part of the fuel pressure-fed from the pump plunger chamber to the fuel injection nozzle In the control method, the timing at which the fuel supplied from the feed pump to the pump plunger chamber by the pump is cut off from the control pump. A method for controlling a fuel injection timing and an injection amount of a unit injector, which is controlled according to a supply timing and a supply time of supplied fuel pressure. 2. A fuel injection nozzle main body provided for each cylinder of a multi-cylinder engine, a fuel pumping unit main body that is a part of the main body, a cylinder formed in the pumping unit main body, and a slide on the cylinder. A cam driven plunger that is movably inserted to form a pump plunger chamber, a fuel injection nozzle that is another part of the main body, a fuel passage that communicates with the pump plunger chamber, and the fuel injection from the pump plunger chamber. In a unit injector having a fuel supply passage communicating with an oil reservoir of a nozzle and a fuel discharge hole for overflowing a part of fuel pumped from the pump plunger chamber to the nozzle for fuel injection, a fuel is fed to the fuel passage. A control valve and a control pump are provided as means for disconnecting fuel from the pump, and the control valve is controlled. A unit injector characterized in that a fuel passage to the pump plunger chamber is shut off according to a supply timing and a supply time of fuel pressure supplied from a pump.