JPS6337259B2 - - 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, a nozzle needle holder consisting of a piston that receives pressure oil that applies pressure in a direction to close the nozzle needle of the fuel injection nozzle, and a nozzle needle. The present invention relates to a fuel injection device comprising a control means for controlling the pressure of pressurized oil applied to a presser foot, and in which injection timing and period are controlled by controlling the pressure applied to the nozzle needle presser.

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

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

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 52.

The fuel compression device 10 has a large diameter bore 11a and a small diameter bore 11b formed vertically in communication with each other, and a servo piston 13 consisting of a large diameter piston 12a and a small diameter piston 12b is installed in the bores 11a and 11b. are arranged corresponding to the diameter, and the servo piston 1
In the upper part of the piston 12a of No. 3, the piston chamber 1
4 is provided, and the piston chamber 14 is connected to a pressure oil source via a 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, when pressure oil is supplied to the piston chamber 14, the servo piston 13 is moved downward, compressing the fuel in the compression chamber 15, and forcing the fuel into the fuel injection nozzle 17.

The switching valve 8 is a 2-position, 4-port electromagnetically operated valve, and is switched by an output signal from the control unit 52. When the switching valve 8 is in the position side,
The discharge side of the pump 3 communicates with the piston chamber 14 of the fuel compression device 10 . In that position, the compression chamber 15 is connected to the throttle 9 and the check valve 1.
It communicates with the tank side via 6. Therefore, pressure oil is supplied into the piston chamber 14 and the piston 12
is pressed, the servo piston 10 descends and the compression chamber 1
The fuel in 5 is pumped. When this switching valve 8 is switched to the position side, the discharge side of the pump 3 is moved to the compression chamber 1.
5, and the piston chamber 14 communicates with the tank 1.
It communicates with 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 returned to the tank 1.

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 presser 25 consists of a bore 26, a piston 27 disposed inside the bore, and a rod 28 connected to the piston 27, and the rod 28 is in contact with the end of the pressure pin 22 of the fuel injection nozzle 17 described above. .

A chamber 29 is formed above the piston 27 by the piston 27 and the bore 26, and in this chamber 29,
A discharge port of the hydraulic pump 30 of a pressure oil source consisting of a hydraulic pump 30, a motor 31, a tank 32, a filter 33, and a relief valve 34 is connected via a circuit 35. Therefore, pressure oil is supplied via this circuit 35. This circuit 35 has one end connected to a tank 32.
A branch circuit 36 is connected to the branch circuit 36, and the branch circuit 36 is provided with a control valve 37 (generally referred to as an electromagnetic proportional control valve) that can control the amount returned to the tank 32 by electromagnetic force. 37 is the second
With the structure shown in the figure, an inlet hole 39 is provided in the main body 38.
and an exit hole 40 are formed, and both holes 39 and 4 are formed.
0 are communicated through an internal chamber 41, and a control valve 42 is disposed within the chamber 41. The valve 42 is held by a rod 46 of a core 45 which is moved by the electromagnetic force of a coil 44 via a spring 43. The valve 42 is seated on a valve seat 49 in the inlet 39 by means of a spring 48 provided at the end of another rod 47 fixed to the core 45 and said spring 43. 50
A stroke sensor detects the position, and the position is detected by the movement of a magnetic material 51 such as iron fixed to the rod 47.

The coil 44 displaces the core 45, and its displacement is controlled by the amount of current supplied to the coil 44, and as the amount of current increases, the valve 42 is moved toward the valve seat 49.
It works as if to force it on. That is, the flow rate can be freely controlled from the cutoff state to the maximum flow rate by changing the amount of current applied. This control valve 37 is used to control the pressure in the circuit 35 (that is, the pressure in the nozzle needle presser 2
5) is controlled in three stages. That is, when the control valve 37 is turned off (blocked state), the amount of oil returned to the tank 32 via the control valve 37 becomes 0, and the pressure from the pressure oil source is reduced to the relief valve 3.
4, the set maximum pressure (for example, 200Kg/cm ² ) is maintained. Next, when the control valve 37 is changed from the cutoff state to the fully open state to allow the maximum flow rate to flow, the circuit 3
The pressure inside 5 is 80Kg/cm ² in the above example. Furthermore, by adding an appropriate restriction to the control valve 37, the amount returned to the tank 32 is reduced and can be increased to 100 kg/cm ² in the above example.

The control unit 52 includes a rotation speed detector 5
This is a control circuit that processes signals such as the engine rotational speed obtained from 3 and the displacement amount from the control lever 54 and outputs control signals to the switching valve 8 and the control valve 37.

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

When the 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, the servo piston 13 is lowered, and the switching valve is placed in the compression chamber 15. The fuel supplied when 8 is switched to the position is compressed and the compressed fuel is pumped through the line 23 to the fuel injection nozzle 17. The pressure in the passage 24 and oil reservoir 21 of the fuel injection valve 17 is determined by the volume of fuel (liquid) flowing into the piston chamber 14 when the switching valve 8 is in the position. Incidentally, the pressure characteristics within the piston chamber 14 and the pressure characteristics within the compression chamber 15 are shown in FIG. The solid line is the characteristic at full load, and the dotted line is the characteristic at no load.

In order to inject fuel from the fuel injection nozzle 17, when the control valve 37 is fully opened from the throttled state while the compressed fuel is supplied from the fuel compression device 10 to the oil reservoir 21 of the fuel injection nozzle 17, the nozzle needle presser opens. The pressure in the chamber 29 of the fuel injection nozzle 17 suddenly decreases (in the example mentioned above, the pressure in the chamber decreases from 100 kg/cm ² to 80 kg/cm ² ), and the force applied from the oil reservoir 21 of the fuel injection nozzle 17 increases. The nozzle needle 19 rises and fuel flows into the nozzle hole 20.
More sprayed.

The end of injection occurs when the control valve 32 is switched to the fully closed state, and the pressure inside the chamber 29 rises rapidly (in the above example, it rises from 80 Kg/cm ² to 200 Kg/cm ² ). 19 descends to close the nozzle hole 20 and the injection ends abruptly.

That is, fuel injection is performed by the nozzle needle presser 25.
The opening and closing of the nozzle hole 20 is controlled by the pressure change. The pressure fluctuation characteristics of the chamber 29 of the nozzle needle holder 25 for controlling this injection are determined by the third
In the figure, 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 extremely severe injection control.

As described above, in this invention, the injection period is determined by controlling the displacement of the nozzle needle by controlling the pressure supplied to the nozzle needle holder. This can be considerably improved compared to the conventional example, and the injection waveform can be approximated to a square wave.

When injecting fuel, especially at the end, a large pressing force that is more than twice the valve opening pressure can be applied to the nozzle needle, reducing the falling time and ensuring that the nozzle needle is firmly seated on the valve seat of the main body. This can improve the sharpness of the jet.

Furthermore, since the pressure of the compressed fuel from the fuel compression device can be adjusted according to the load, it is possible to control the fuel injection rate in addition to the injection period.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the present invention, FIG. 2 is a sectional view of a control valve, and FIG. 3 is a diagram showing pressure waveforms in the piston chamber, compression chamber, and nozzle needle presser chamber of the fuel compression device of the present invention. . 1...Tank, 3...Hydraulic pump, 8...Switching valve, 10...Fuel compression device, 14...Piston chamber, 15...Compression chamber, 17...Fuel injection nozzle,
19... Nozzle needle, 25... Nozzle needle holder, 29... Chamber, 35... Circuit, 36... Branch circuit, 37... Control valve.

Claims (1)

[Claims] 1. A large-diameter piston 12a that receives high fuel pressure supplied from the oil pump 3, and when the large-diameter piston 12a receives fuel pressure in conjunction with the large-diameter piston 12a. Servo piston 1 consisting of a small diameter piston 12b that compresses fuel supplied in advance
3, a fuel injection nozzle 17 that injects the compressed fuel compressed by the fuel compression device 10, and a piston 27 that receives pressure oil that applies pressure in the direction of closing the nozzle needle 19 of the fuel injection nozzle 17. Nozzle needle presser 25 consisting of
and an electromagnetically operated control means 37 for controlling the pressure of the pressure oil supplied to the nozzle needle holder 25, and the injection timing and injection period are controlled by controlling the pressure applied to the nozzle needle holder 25. A fuel injection device featuring: 2 A control means 37 for controlling the pressure of the pressure oil supplied to the nozzle needle holder 25 connects a tank 32 to a circuit 35 for supplying pressure to the nozzle needle holder 25.
Connect a branch circuit 36 communicating with the branch circuit 36 .
2. The fuel injection device according to claim 1, further comprising an electromagnetically operated control valve 37 which can control the amount returned to the tank. 3. 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.