JPS6237224B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for a diesel engine, and more particularly to a small-diameter piston that operates in conjunction with a piston that receives fuel pressure and compresses previously supplied fuel when the piston receives fuel pressure. A fuel compression device, a fuel injection nozzle that injects compressed fuel compressed by the fuel compression device, and a nozzle needle holder consisting of two pistons that receive pressure oil that applies pressure in a direction to close the nozzle needle of the fuel injection nozzle. The fuel injection control means consists of two switching valves for controlling the pressure applied to the two pistons of the nozzle needle holder, and controls the injection timing and injection period by controlling the pressure applied to the two pistons of the nozzle needle holder. The present invention relates to a fuel injection device that controls.

JP-A No. 50-45124 can be mentioned as a conventional example. In this example, the opening and closing of the nozzle needle is an automatic valve type that opens when the pressure exceeds the biasing force of the spring, and appropriate opening and closing valve characteristics are used. can't get it. Therefore, the present invention provides a fuel injection device that can appropriately control opening and closing of a nozzle needle.

The present invention will be described below with reference to embodiments shown in the drawings.

In FIG. 1, a fuel tank 1 communicates with the suction side of an oil feed pump 3 via a filter 2, and an electronic pressure reducing valve 4 and an accumulator 5 are provided at the discharge part of the oil feed pump 3, and a first switching It is connected to valve 8.

The oil pump 3 is rotated by the driving force of the driving engine 6, and an electronic pressure reducing valve 4 controls the pressure in the circuit 7 in proportion to the load, that is, full load, partial load, and no load. The control is performed by the output from the control unit 39.

The fuel compression device 10 has a large-diameter bore 11a and a small-diameter bore 11b that are formed vertically in communication with each other, and a servo piston 1 that includes a large-diameter piston 12a and a small-diameter piston 12b is installed in the bores 11a and 11b.
3 are arranged corresponding to the diameter, and the servo piston 13
A piston chamber 14 is provided above the large-diameter piston 12a, and the piston chamber 14 is connected to a pressure oil source via a first switching valve 8. Furthermore, a compression chamber 15 is provided below the small-diameter piston 12b of the servo piston 13 with a fitting bore 11b, and the compression chamber 15 is connected to a fuel injection nozzle 17 described below. Therefore, piston chamber 1
When pressure oil is supplied to 4, the servo piston 13 is moved downward, compressing the fuel in the compression chamber 15,
The fuel is fed under pressure to the fuel injection nozzle 17.

The first switching valve 8 is a 2-position, 4-port electromagnetically operated valve that is switched by an output signal from the control unit 39. When the first switching valve 8 is in the position side, the discharge side of the pump 3 is It communicates with the piston chamber 14 of the fuel compression device 10 . In that position, the compression chamber 15 communicates with the tank via the throttle 9 and the check valve 16. Therefore, pressure oil is supplied into the piston chamber 14, presses the piston 12, and presses the servo piston 13.
moves downward and pumps the fuel in the compression chamber 15. When this first switching valve is switched to the position side, the discharge side of the pump 3 communicates with the compression chamber 15, and the piston chamber 14 communicates with the tank 1. Therefore,
The pressure oil is throttled by the throttle 9 and gradually supplied into the compression chamber 15, and the pressure oil in the piston chamber 14 is transferred to the tank 1.
be returned to.

The fuel injection nozzle 17 is composed of a main body 18 and a nozzle needle 19 disposed inside the main body 18, and is seated on a valve seat by a pressing force transmitted from a pressure pin 22 to close an injection hole 20. The fuel compressed by the fuel compression device 10 is sent from the pipe 23 to the oil sump 21 through the passage 24 . The fuel is injected by the pressure of the fuel oil sent into the oil reservoir 21 applied to the pressure stage of the nozzle needle 19 due to the pressing force from the nozzle needle presser 25 applied via the pressure pin 22 as described below. If this is the case, that is, when the pressing force of the nozzle needle presser 25 is reduced to meet the above conditions, the nozzle needle 19 lifts, the nozzle hole 20 opens, and fuel is injected. The injection ends when the pressing force from the nozzle needle presser 25 is increased to a level greater than the valve opening pressure, and the nozzle needle 19 is lowered and seated on the valve seat.

The nozzle needle holder 25 has a first piston 27a stacked upwardly and a second piston 27b stacked downwardly inside the bore 26, and the side of the first piston 27a in contact with the second piston 27b is tapered. is formed. A rod 27b' is formed on the side of the second piston 27b opposite to the first piston 27a, and the rod 27b' abuts against the pressure pin 22 of the fuel injection nozzle 17 described above. 1st
A first pressure oil chamber 29a is formed by the piston 27a and the bore 26, a second pressure oil chamber 29b is formed by the second piston 27b and the bore 26, and the first pressure oil chamber 29a is formed by the A discharge port or tank 3 of a hydraulic pump 30 as a pressure oil source consisting of a pump 30, a motor 31, a tank 32, a filter 33, and a relief valve 34.
2 is connected via a second circuit 35 having a second switching valve 37 described below.

The second switching valve 37 is an electromagnetically operated two-position, three-port directional switching valve, and the switching operation of the second switching valve 37 switches the connection of the second circuit 35 to the pump side or the tank side. .

The second pressure oil chamber 29b is connected to the discharge port of the hydraulic pump 30 or the tank 32 via a third circuit 36 having a third switching valve 38 described below.
This third switching valve 38 is similar to the second switching valve 37.
This is a 2-position, 3-port switching valve having a configuration similar to that of the third switching valve 38, and the connection of the third circuit 36 to the pump side or the tank side can be switched by the switching operation of the third switching valve 38.

The concrete unit 39 has a rotation speed detector 4
The first switching valve 8 and the second and third switching valves 37 and 38 process signals such as the engine rotational speed obtained from 0 and the displacement amount from the throttle lever 41.
This is a control circuit that outputs control signals to the

In the above configuration, the hydraulic motor 3 is rotated by the engine 6, and the pressure oil is brought to a desired pressure by the electronic pressure reducing valve 4, that is, a pressure that matches the engine load, and is stored in the accumulator 5.

When the first switching valve 8 is in the illustrated position, the pressure oil in the circuit 7 is guided into the piston chamber 14 of the fuel compression device 10, and the servo piston 13 is lowered to enter the compression chamber 15. The fuel supplied when the first switching valve 8 is switched to the position is compressed,
Compressed fuel is passed through the pipe 23 to the fuel injection nozzle 17
to be pumped to. The pressure within the passage 24 of the fuel injection nozzle 17 and the oil reservoir 21 is determined by the volume of the fuel (liquid) flowing into the piston chamber 14.
In addition, the pressure characteristics in the piston chamber 14 and the compression chamber 15
The pressure characteristics within are shown in and in FIG. The solid line is the characteristic at full load, and the dotted line is the characteristic at no load.

Fuel injection from the fuel injection nozzle 17 is performed by switching the second switching valve 37 to the position side while the oil reservoir 21 of the fuel injection nozzle 17 is filled with compressed fuel supplied from the fuel compression device 10.
The pressure in the first pressure oil chamber 29a of the nozzle needle holder 25 suddenly decreases to 0, and the fuel injection nozzle 1
The nozzle needle 19 of No. 7 rises (both the first piston 27a and the second piston 27b are displaced upward).
Then, fuel is injected from the injection hole 20. At that time, the third switching valve 38 is in the position, and the second pressure oil chamber 2
9b is in a low pressure state.

The end of the injection is achieved by switching the third switching valve 38 from position to position, so that the pressure in the second pressure oil chamber 29b increases rapidly, that is, the pressure in the second pressure oil chamber 29b
Since the internal pressure becomes a pressure that overcomes the force applied from low pressure to the pressure stage of the nozzle needle 19 and lifts the nozzle needle 19 upward,
The second piston 27b is pressed downward, the nozzle needle 19 is seated on the valve seat, the nozzle hole 20 is closed, and the injection ends. The first pressure oil chamber 29a and the second pressure oil chamber 2 of the nozzle holder 25 are used to control this injection.
The pressure fluctuation characteristics within 9b are shown in FIG. 2, and the injection characteristics are as shown in FIG. 2, where l is the injection period.

In this invention, the pressure of the compressed fuel from the fuel compression device 10 varies depending on the load as shown by the solid line in FIG.
Because it changes as shown by the dotted line, it has the characteristic that the injection rate changes even during the same injection period,
This allows for extremely severe injection control.

As described above, the present invention provides a fuel injection device in which the injection period is determined by controlling the displacement of the nozzle needle by controlling the pressure supplied to the two pressure oil chambers of the nozzle needle holder. Since the pressure of the two pressure oil chambers is controlled by two switching valves, it is possible to provide a fuel injection device with good fuel injection characteristics. Furthermore, this switching valve has the advantage that a commercially available inexpensive directional switching valve can be used.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of the present invention, and Fig. 2 is a diagram showing the pressure waveforms of the piston chamber and compression chamber of the fuel compression device of the present invention, the second and third pressure oil chambers of the nozzle needle holder, and injection characteristics. FIG. 1...Tank, 3...Hydraulic pump, 8...First
switching valve, 10... fuel compression device, 14... piston chamber, 15... compression chamber, 17... fuel injection nozzle, 19... nozzle needle, 25... nozzle needle holder, 27a... first piston, 27
b...Second piston, 29a...First pressure oil chamber, 29b...Second pressure oil chamber, 35...Second circuit, 36...Third circuit, 37...Second pressure oil chamber Switching valve, 38...Third switching valve.

Claims (1)

[Claims] 1. A piston that receives high fuel pressure supplied from an oil pump, and a small-diameter piston that works in conjunction with this piston to compress the previously supplied fuel when the piston receives fuel pressure. A fuel compression device consisting of a fuel compression device, a fuel injection nozzle that injects the compressed fuel compressed by the fuel compression device, and two pistons that receive pressure oil in the bore to apply pressure in the direction of closing the nozzle needle of the fuel injection nozzle. a nozzle needle holder provided in two stages to form a first pressure oil chamber and a second pressure oil chamber, and a second pressure oil chamber that communicates the first pressure oil chamber of the nozzle needle holder with a pressure oil source. The fuel injection control means comprises a second switching valve provided in the circuit and a third switching valve provided in a third circuit communicating the second pressure oil chamber and the pressure oil source. fuel injection device. 2. The fuel injection device according to claim 1, wherein the high pressure fuel pressure supplied from the oil feed pump is changed in proportion to the load.