JP2831137B2 - Diesel engine fuel injection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for a diesel engine.

[0002]

2. Description of the Related Art A conventional fuel injection device is disclosed in, for example, US Pat. No. 3,516,395. This device comprises a fuel tank 01 as shown in FIG.
It comprises a fuel pump 02, an injection unit 03, and a piston stroke control means 04 of the unit.

[0003] The injection unit 03 has a large-diameter cylinder 05.
A servo piston 06 slidably supported in the inside, a pump piston 08 slidably supported in the small-diameter cylinder 07, and a spring 09 for urging the two pistons 06 and 08 to come into contact with each other. Have a large diameter cylinder 05
To the servo pressure chamber 010 via a three-way switching valve 011
Further, fuel at a predetermined pressure is supplied from the fuel pump 02 to the small-diameter cylinder 010 via a three-way switching valve 011 and to the pump working chamber 012 of the small-diameter cylinder 07 via an electromagnetic valve 13 and a check valve 014, respectively. It has become.

The working chamber 012 communicates with an injection nozzle (not shown). Reference numeral 015 denotes a leak chamber of the large-diameter cylinder 05, and fuel leaking into the leak chamber is the fuel tank 0.
Returned to 1. The solenoid valve 013 has a control circuit 01
The three-way switching valve 011 is selectively connected to the servo pressure chamber 010 and the fuel tank 01 or the fuel pump 02. 017 is a pressure regulating valve.
The aforementioned solenoid valve 013, control circuit 016, fuel pump 0
2. The check valve 014 constitutes a piston stroke control means 04 which controls the strokes of the pistons 06 and 08 of the injection unit 03 as a whole.

Therefore, in such a fuel injection device, the fuel pressurized by the fuel pump 02 is pumped via the three-way switching valve 011 to the servo pressure chamber 010 on the one hand and the solenoid valve 013 on the other hand. After the fuel is supplied to the working chamber 012 and the pressure in the pump working chamber 012 is increased in proportion to the pressure accumulation area with the servo piston 06, the fuel is injected from an injection nozzle (not shown).

[0006]

However, in order to realize high pressure injection in a fuel injection device for a diesel engine, it is necessary to instantaneously apply a large amount of high pressure hydraulic oil to a servo pressure chamber. There is no conventional three-way switching valve of this type which operates at a higher speed and flows a large flow rate with good reliability and durability.

An object of the present invention is to solve the above-mentioned problems of the conventional apparatus, to realize high-pressure fuel injection, to operate stably from a small injection amount to a large injection amount, and to obtain a highly reliable injection type diesel engine. To provide a fuel injection device.

[0008]

SUMMARY OF THE INVENTION A fuel injection device for a diesel engine according to the present invention has a pressure accumulator 2 for storing pressurized hydraulic oil.
2 having a different diameter by controlling the hydraulic pressure of the accumulator
When the plunger 8 on the large diameter side of the fuel pump including the large and small diameter plungers 2 and 8 is operated, the pressure oil of the accumulator is loaded or drained into the pressure oil chambers 11b and 16b to open and close the valve. Two logic valves 11,
16, two ports connected to the two logic valves 11 and 16, one port connected to the pressure accumulator 22, two ports connected to the drain oil passage 21,
One spool valve 103 that opens and closes these five ports
The logic valves 11 and 16 are opened and closed by alternately loading or draining the pressure oil of the pressure accumulator driven from the crankshaft into the pressure oil chambers 11b and 16b of the two logic valves at accurate fuel injection timing. A 5-port spool control valve 19 to be controlled; and oil passages 14 and 12 for communicating the pressure accumulator with the large-diameter plunger hydraulic oil chamber 9 via the logic valve 11.
And oil passages 12, 13, and 18 that connect the large-diameter plunger hydraulic oil chamber 9 to the hydraulic oil tank 24 via the logic valve 16. In the fuel discharge stroke, the logic valve 11 is opened and the logic valve is opened. 16 to close the pressure accumulator 22 and the large-diameter plunger hydraulic oil chamber 9, and at the end of fuel discharge, the logic valve 1
1 is closed, the logic valve 16 is opened, and the hydraulic oil in the large-diameter plunger hydraulic oil chamber 9 is drained to the hydraulic oil tank 24.

As a result, the 5-port spool valve type solenoid valve only needs to control a small amount of pilot oil pressure, and can be made compact and operate at high speed. In addition, two logic valves are opened and closed in response to a change in pilot oil pressure that acts at high speed, and a large amount of high-pressure hydraulic oil stored in the pressure accumulator can be instantaneously operated on the large-diameter piston of the fuel pump. Injection can be realized. Furthermore, since the hydraulic pressure acting on the large-diameter piston can be instantaneously released even at the end of injection, a sharp and quick end of injection can be achieved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a system configuration diagram according to a first embodiment, FIG. 2 is an operation diagram of one example of a spool control valve according to the first embodiment, and FIG. 3 is another operation diagram.

In FIG. 1, 1 is a pump body, 2 is a fuel discharge plunger (hereinafter abbreviated as a small diameter plunger), 3 is a plunger return spring, 4 is a fuel supply chamber, 5 is a discharge valve, 6 is an injection pipe, and 7 is a fuel valve. , 8 is a large diameter plunger, 9 is a large diameter plunger hydraulic oil chamber, 10 is a back pressure chamber, 11 is a logic valve at the start of discharge, 12 is a hydraulic oil path, 13 is a communication oil path for both logic valves, and 14 is a pressure accumulation chamber. An oil passage connecting the discharge start logic valve 11, an oil passage 15 connecting the discharge start logic valve and the spool control valve, a discharge end logic valve 16, an oil passage connecting the discharge end logic valve and the spool control valve, 18 Is an oil drain pipe from the discharge end logic valve to the tank.

Reference numeral 19 denotes a spool control valve, which is driven by a controller (not shown) in synchronization with the crank rotation of the engine. The control valve 19 is a five-port control valve, the details of which are shown in FIGS. 20 is an oil passage from the pressure accumulator to the control valve, 21 is an oil drain pipe from the control valve to the tank, 22 is a pressure accumulator, 2
Numeral 3 denotes a hydraulic power supply for supplying high-pressure hydraulic oil to the accumulator. 24
Is a hydraulic oil tank, 25 is a low pressure hydraulic power source device, and 26 is a hydraulic oil pipe to the back pressure chamber 10. 27 is a fuel tank, 28 is a fuel supply device, and 29 is a fuel supply pipe.

Next, the structure of the spool control valve 19 will be described with reference to FIG.
Is a sleeve, and 103 is a spool valve that slides up and down inside the sleeve 102. 104 is a push rod, 105 is a stopper, 1
06 is a coil, 107 is an armature, 108 is a push rod,
109 is a stopper, 110 is a coil, 111 is an armature, and 112 is a spring.

Next, the operation of the spool control valve will be described with reference to FIGS. FIG. 2 shows a state before the next injection starts after the previous injection is completed. The spool valve 103 is pressed against the stopper 105 by the spring 112 via the armature 111 and the push rod 108.
The pressure P is in communication with X ₁ port, X ₂ port is communicated with the drain T ₂ ports. In this state, when the coil (106) is next energized by a controller (not shown), the armature (107) is pulled downward, and the push rod (104) is moved to the spool valve (1).
Move 03 down. During this operation, P port and X ₁
X ₁ port and T ₁ Port Port is closed communicates. At the same time, X ₂ port and T ₂ port are closed, and P port and X port are closed.
_{The two} ports communicate. Further, when the excitation of the coil 106 continues, the spool valve 103 finally hits the stopper 109 and stops. FIG. 3 shows this state.

After a predetermined time has elapsed, the excitation of the coil 106 is released, and when the coil 110 is energized, the armature 111 is pulled up and the spool valve 103 returns upward via the push rod 108. Port switching in the middle is the reverse of the operation described above. That opens P port and X ₁ port, X ₁ port and T ₁ is closed At the closed port P and X ₂ port simultaneously, X ₂ port and T ₂ port leads. Then, after the spool 103 comes into contact with the stopper 105, the excitation of the coil 110 is released. This state is maintained, one cycle of operation is completed, and the state returns to the state shown in FIG.

The operation of the injection device shown in FIG. 1 will be described based on the operation of the spool control valve just described. The upper part of the plunger 2 is filled with fuel from the fuel supply device 28. Now, when the coil 106 of the spool control valve 19 is excited and the spool valve 103 moves downward, the high pressure from the accumulator 20 acting on the large-diameter oil passage 15 of the logic valve 11 at the start of discharge is closed, and at the same time, the drain pipe is closed. In addition, the pressure is reduced to the large-diameter side oil passage 1 of the end-of-discharge logic valve 16 through which the pressure decreases.
7, the pressure from the accumulator 20 acts, and the logic valve 16 receives a large force on the closing side.

As described above, when the oil pressure in the oil passage 15 is released, the high-pressure hydraulic oil from the accumulator 20 in the oil passage 14 pushes up the logic valve 11 at the start of discharging, and the large-diameter plunger operating oil chamber 9 through the oil passage 12. And push up the large diameter plunger 8 upward. This hydraulic pressure also acts on the communication oil passage 13,
Since the logic valve 16 is closed, the hydraulic pressure is not drained to the accumulator. When the small-diameter plunger 2 is pushed up by the large-diameter plunger 8, the fuel flowing above the small-diameter plunger is increased in pressure, the discharge valve 5 is pushed up, and the injection pipe 6 is raised.
And is injected from the fuel valve 7 into the cylinder. When the predetermined injection is performed, the excitation of the coil 106 is released and the coil 110 is excited.

Then, the spool valve 103 is lifted upward, and the high pressure from the pressure accumulator 20 acts on the large-diameter oil passage 15 of the logic valve 11 at the start of discharge. , The pressure is released and the discharge end logic valve 16 is opened. Thereby, the oil passage 12
The high-pressure oil in the large-diameter plunger hydraulic oil chamber 9 escapes, and the small-diameter plunger 2 and the large-diameter plunger 8 are displaced by the plunger return spring 3.
And the fuel is pumped. By maintaining the pressure in the back pressure chamber 10 properly by the low-pressure hydraulic source 25, it is possible to eliminate problems such as occurrence of cavitation.

[0019]

The present invention is constructed as described above, uses a small high-speed spool control valve as a pilot valve, and operates a large-diameter plunger using two logic valves with a large flow of hydraulic oil. In addition, the fuel injection can be realized, and the system can be configured with small devices, stable and sharp operation can be performed from a small injection amount to a large injection amount, and a highly reliable fuel injection device can be provided.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram according to a first embodiment,

FIG.

FIG. 3 is a diagram illustrating the operation of the spool control valve according to the first embodiment,

FIG. 4 is a diagram corresponding to FIG. 1 of a conventional example.

[Explanation of symbols]

2 Small-diameter plunger 8 Large-diameter plunger 11 Discharge start logic valve 16 Discharge end logic valve 19 Spool control valve 22 Accumulator 23 High-pressure hydraulic power source device

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 59/46 F02M 59/46 Y (72) Inventor Tadashi Fukuyoshi 1-1, Akunouramachi, Nagasaki-shi, Nagasaki Pref. Mitsubishi Heavy Industries, Ltd. 72) Inventor Yasutaka Irie 12 Nishiki-cho, Naka-ku, Yokohama City, Kanagawa Prefecture Mitsubishi Heavy Industries, Ltd. Yokohama Works (56) References JP-A-55-12298 (JP, A) Japanese Patent Publication No. 2-23708 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02M 47/00 F02M 51/00 F02M 59/46

Claims (1)

(57) [Claims] An accumulator (2) for storing pressurized hydraulic oil.
And 2) controlling the oil pressure of the accumulator to actuate a large-diameter plunger (8) of a fuel pump comprising two large- and small-diameter plungers (2) and (8) in series having different diameters. The pressure oil of the accumulator is stored in the pressure oil chamber (11b),
(16b) two logic valves (11) and (16) which are respectively loaded or drained to open and close the valves, and two ports connected to the two logic valves (11) and (16); One port connected to the accumulator (22), two ports connected to the drain oil passage (21),
One spool valve (10
And 3) alternately load or drain the hydraulic oil driven from the crankshaft into the hydraulic oil chambers (11b) and (16b) of the two logic valves at accurate fuel injection timing. A five-port spool control valve (19) for controlling the opening and closing of the valves (11) and (16); and an oil passage connecting the accumulator to the large-diameter plunger working oil chamber (9) via a logic valve (11). Oil passages (12), (1) connecting the large-diameter plunger hydraulic oil chamber (9) to the hydraulic oil tank (24) via the logic valve (16).
In the fuel discharge stroke, the logic valve (11) is opened, the logic valve (16) is closed, and the pressure accumulator (22) and the large-diameter plunger hydraulic oil chamber (9) are provided. ), At the end of fuel discharge, close the logic valve (11) and open the logic valve (16) to drain the pressure oil in the large diameter plunger hydraulic oil chamber (9) to the hydraulic oil tank (24). A fuel injection device for a diesel engine, comprising: