JPH0526949B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection device for a diesel engine.

[Conventional technology]

FIG. 6 shows a conventional fuel injection system for a diesel engine. In the figure, 01 is the fuel pump body, 0
2 is plunger barrel, 03 is plunger, 04
is the plunger lead, 05 is the oil supply and drain hole, 06 is the oil supply chamber, 07' is the discharge valve seat, 08' is the discharge valve, 0
9' is the discharge valve suction back collar, 10' is the discharge valve spring,
11' is a discharge valve presser, and 12' is a control rack. In addition, 101 is a fuel valve body, 102
1 is a nozzle tip, and 103 is a cap nut that fastens the nozzle tip 102 to the fuel valve body 101. 104 is an oil passage in the fuel valve, 105 is an oil passage in the nozzle tip, and 106 is an oil reservoir. 107 is a needle valve, 108 is a nozzle hole, 109 is a needle valve push rod, 110 is a spring receiver, 111 is a spring, and 112 is a needle valve opening pressure adjustment screw. 201 is a high pressure injection pipe that connects the fuel pump and the fuel valve.

A fuel chamber 06 in the fuel pump 01 is filled with fuel by a fuel supply pump (not shown), and the fuel also enters the upper part of the plunger 03 through a fuel supply/drain hole 05 . Next, to explain the operation of the pump, the plunger 03 is raised by a cam that rotates in synchronization with the crankshaft of the engine (not shown), and when the oil supply and discharge hole 05 is closed, the fuel starts to be compressed, and the high-pressure fuel is discharged from the discharge valve. 08' and is guided to the oil reservoir 106 through the injection pipe 201, the oil passage 104 in the fuel valve, and the oil passage 105 in the nozzle tip. Here, oil pressure acts on the needle valve 107, and when the oil pressure becomes greater than the force held down by the spring 111, the needle valve 107 opens.
Fuel is injected from the injection hole 108 into a cylinder of an engine (not shown). When the plunger 03 further rises, the plunger lead 04 enters the oil supply/discharge hole 05, and the high pressure upper part of the plunger communicates with the low pressure oil supply chamber 06, so that the pressure decreases and discharge ends. From this, the pressure in the system gradually decreases, oil sump part 1
The pressure in 06 also decreases, the spring force overcomes the oil pressure, and the needle valve closes, ending the injection. Normally, the pressure at the end of injection is about 40% lower than the pressure at the beginning of injection. Furthermore, when the pressure decreases at the end of discharge, the discharge valve 08' closes immediately, and at this time, a long closed pipeline is formed between the fuel valve and the pump via the injection pipe 201, so that the pressure waves flow back and forth between the fuel valve and the pump. remains, and this pressure wave may cause the needle valve 107 to restart, causing re-injection from the nozzle hole, or creating a cavity in the pipe or oil reservoir. This re-injection phenomenon is usually referred to as 2-injection. Figure 7 shows the injection pressure and movement of the needle valve.

[Problem that the invention seeks to solve]

The above has the following drawbacks.

As mentioned above, the pressure at the end of injection is lower than the pressure at the start of injection. This results in a coarse spray being injected into the cylinder where combustion has already started and air has been consumed, which leads to poor combustion and the generation of smoke, which is undesirable for the engine. Further, since the secondary injection is also an iron-pressure injection and is also an injection at a late timing, the phenomenon is even worse than the above-mentioned one. If the occurrence of cavities becomes large enough, cavitation erosion may occur, which may lead to damage to injection pipes, needle valves, etc. Furthermore, it may lead to deterioration of the sealing part or seizure of the needle valve sliding part. Furthermore, in the low load and low rotation range, the injection pressure decreases due to the decrease in cam speed, so the nozzle hole area becomes relatively large, resulting in a spray with large particles, which deteriorates combustion.

[Means for solving problems]

The purpose of the present invention is to focus on the above-mentioned points, to eliminate secondary injection and cavity formation, to complete injection at high pressure at the same time, to improve the so-called "cutting of injection", and to further improve the low load (low rotation) region. To provide a combustion injection device that can increase injection pressure and maintain good combustion by closing a part of the fuel valve.The main feature of this device is that it is possible to increase the injection pressure and maintain good combustion by closing a part of the fuel valve. In a fuel injection system for a diesel engine in which a cylinder is provided with a plurality of fuel valves, a check valve is provided in the fuel pump and opens when fuel is discharged, and a check valve is opened by pressure on the discharge side when discharge ends. , a piston that receives hydraulic pressure separate from the injection system provided in each of the fuel valves and presses the needle valve of the same fuel valve, a solenoid valve that opens and closes the hydraulic pipes leading to the piston, and an engine speed, a microcomputer that controls the opening and closing of the solenoid valve based on the crank rotation angle, engine load, etc., and the microcomputer supplies hydraulic pressure to the piston of each fuel valve at the end of injection of each fuel valve, The valves are closed, and when the engine is under partial load, hydraulic pressure is supplied to the pistons of some fuel valves, and injection of each fuel valve is intermittently stopped depending on the engine load, and the fuel valves that stop injection are cycled. It is controlled so that they are alternated sequentially.

[Effect]

(1) By completing the injection at high pressure, the engine will have good combustion with less afterburn.

(2) Furthermore, by closing some fuel valves in the low speed range, injection pressure increases and combustion is improved.

(3) By changing the idle fuel valve every cycle without having to fix it, problems such as carbon clogging of the fuel valve can be avoided.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing one embodiment of a fuel injection device according to the present invention.

In the figure, 01 is the fuel pump body, 02 is the plunger barrel, 03 is the plunger, 04 is the plunger lead, 05 is the oil supply/drain hole, 06 is the oil supply chamber,
07 is a valve seat, 08 is a ball valve or check valve, 09 is a spring, and 10 is a spring receiver, and an oil passage is provided therein.

11 is a ball valve or check valve, 12 is a spring, 13
It has an oil path with a spring holder. 14 is an orifice, 15 is a presser foot, and 16 is a control rack.

101 is a fuel valve body, 102 is a nozzle tip,
A cap nut 103 fastens the nozzle tip 102 to the fuel valve body 101. 104 is an oil passage in the fuel valve, 105 is an oil passage in the nozzle tip, and 106 is an oil reservoir. 107 is a needle valve, 108 is a nozzle hole,
109 is a needle valve push rod, 110 is a spring holder, 111 is a spring, 112 is a needle valve opening pressure adjusting screw, and 113 is a lock nut. 114 is a piston guide,
115 is a piston. 116 is a piston push rod, 117 is a spring, and 118 is a piston upper metal fitting.

201 is a high pressure injection pipe that connects the fuel pump and the fuel valve.

301 is a hydraulic pipe, 302 is a solenoid valve mounting hardware, 3
03 is a solenoid valve (Normal Close), 304 is a solenoid valve (Normal Open), 305 is a relief pipe, 306,
307 is a hydraulic pipe, 308 is a pressure reservoir, 309 is a pump, and 310 is an oil tank.

401 is a rack position detector (for example, a potentiometer), 402 is a trigger signal generator, and 403 is a rotational pulse generator.

As shown in FIG. 1, oil pressurized by a hydraulic pump 309 is guided to the electromagnetic valve fitting via oil passages 307 and 306. The pressure accumulator 308 is for suppressing pressure fluctuations.

For the solenoid valve, 303 is Normal close, and 304 is Normal close.
Normally open, the oil passage 301 to the piston opens to the secondary side of the electromagnetic valve 303 and the primary side of the solenoid valve 304. The drain oil passage 305 is connected to the secondary side of the solenoid valve 304, and when applying hydraulic pressure to the piston, the solenoid valve 303 is opened and the solenoid valve 304 is closed. When ending hydraulic action, use solenoid valve 3.
03 is closed and 304 is closed.

The operation in the case of the above configuration will be described.

First, I will explain how a microcomputer works.

The computer has a memory section that stores information about the engine rotational speed.
The crank rotation angle at which the trigger signal should be issued is pre-inputted for N _E and pump rack R _C.

When the engine rotation speed pulse, rack position signal, and trigger signal are input, the engine rotation speed is calculated, the rack position is determined, the input trigger signal and the required trigger timing are calculated, and a trigger signal is issued. .

Next is the newly installed hydraulic system, tank 310
The oil is brought to high pressure by the pump 309, and the pressure is increased to the pressure accumulator 3.
The pressure is kept constant by the action of 08. The solenoid valve mounting hardware 302 has an oil passage formed therein, and the solenoid valve 303
and 304 are installed. The solenoid valve 303
The solenoid valve 304 is a Normal close type and is normally closed, the solenoid valve 304 is a Normal open type and is normally open, and the hydraulic pipe 301 and relief pipe 305 are open to the tank.

The operating times of the solenoid valves 303 and 304 are set by a solenoid valve controller, and are driven by a trigger signal from a microcomputer.

First, we will discuss the operation of the injection system under high loads.

A fuel chamber 06 in the fuel pump 01 is filled with fuel by a fuel supply pump (not shown), and the fuel also enters the upper part of the plunger 03 through a fuel supply/drain hole 05 . The plunger 03 is raised by a cam that rotates in synchronization with the crankshaft of the engine (not shown), and when the oil supply and discharge hole 05 is closed, fuel compression begins, and the high-pressure fuel pushes open the ball valve 08, and the injection pipe 20
1. Fuel valve oil passage 104, nozzle tip oil passage 1
05 and is led to the oil sump section 106. Here, oil pressure acts on the needle valve 107, and when the oil pressure becomes larger than the force held down by the spring 111, the needle valve 107
07 opens and fuel is injected from the injection hole 108 into a cylinder of an engine (not shown).

When the plunger 03 further rises and the plunger lead 04 hits the oil supply/discharge hole 05, the high pressure upper part of the plunger communicates with the low pressure oil supply chamber 06, so the pressure decreases and discharge ends. This also reduces the pressure within the sequential system. At this time, the aforementioned hydraulic system and electromagnetic valve are already in operation, and hydraulic pressure acts on the upper part of the piston 115 through the hydraulic pipe 301. Piston 11
Since the needle valve 5 has a diameter several times larger than the needle valve 107, the pressure is balanced at one-tenth or less of the pressure in the oil reservoir 106. When the oil pressure at the top of the piston exceeds this level, the piston descends and the piston push rod 116,
The needle valve 107 also moves down via the spring receiver 110 and the push rod 109, completing the injection. At this time, the oil reservoir 106
Even though the pressure is high, the needle valve is lowered and the nozzle hole is closed, so the pressure increases further and propagates to the pump side. However, on the pump side, the ball valve 11 is pushed through the orifice and the pressure is appropriately decelerated. Therefore, pressure propagation at high pressure to the nozzle side is eliminated. When high pressure no longer acts on the oil reservoir 106, the solenoid valve is deactivated and the pressure above the piston 115 is reduced. The piston is returned by spring 117. At this time, the oil reservoir 10
The pressure at 6 has dropped sufficiently and the needle valve 107 is closed by the spring 111.

In this way, the injection can be completed at a high pressure in the latter half of the injection.

FIG. 2 shows the injection phenomenon according to the present invention. You can see that oil pressure acts on the piston in the latter half of injection, and injection is complete even though the pressure on the nozzle side is still quite high. It can be seen that even though the pressure on the nozzle side is high due to the valve closing, the pressure is absorbed on the pump side.

Although the explanation has been made for one fuel valve here, the same applies to other fuel valves where a plurality of fuel valves are installed.

Next, we will discuss the effects of medium load and low load on an injection system having three fuel valves as shown in FIG. 3 as a plurality of fuel valves.

Figure 4 shows the operation of nozzle pressure, needle valve lift, and hydraulic pressure over several cycles in a medium load range. This applies hydraulic pressure to completely close one of the three fuel valves in each cycle; in the first cycle in the figure, fuel valve c, then b, then a, Next, the timing at which the hydraulic pressure is applied is set so that the fuel valve that becomes non-injected changes in each cycle, as shown in c... (The activation timing is memorized and the device operates accordingly.)

At this time, the area of the nozzle hole is reduced to two-thirds of the conventional one, so the injection is performed at high pressure. As for the other two fuel valves, as described above, hydraulic pressure is applied in the latter half of the injection to complete the injection at high pressure.

Next, a case where the load or rotational speed is further reduced and the injection pressure is considerably low in the conventional system will be explained with reference to FIG.

Here, hydraulic pressure is applied to completely close two of the three fuel valves in each cycle. That is, in the first cycle in the figure, only one of the three fuel valves injects fuel, followed by fuel valve a, then c, b, a, and so on. However, the active fuel valves alternate. At this time, the area of the nozzle hole is reduced to 1/3 of that of the conventional one, making it possible to achieve high-pressure injection even when the load and rotational speed are considerably low.

〔Effect of the invention〕

The above case has the following effects.

As mentioned above, injection can be completed with high pressure in the latter half of injection, and there is no problem with secondary injection or cavitation because the pressure is absorbed on the pump side. (1) Sloppy injection at low pressure in the latter half of injection This eliminates mist, which is poorly atomized, and completes injection quickly, ensuring good combustion in the engine and leading to improved performance.

(2) Since the occurrence of secondary injection that adversely affects engine performance or cavitation that causes a decrease in durability can be eliminated, a highly reliable engine injection system can be provided.

In addition, in the partial load range, by closing some of the fuel valves, the nozzle hole area is narrowed and high-pressure injection can be achieved, and the fuel valves that are stopped are not the same every cycle, but are alternated. , (3) Improved combustion performance under partial load can be achieved.

(4) In addition, problems such as fuel valve deterioration or carbon clogging that may occur due to suspension of operation can be eliminated by alternating suspension of operation, and high reliability can be maintained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a device according to an embodiment of the present invention, and FIG. 2 is a diagram showing piston oil pressure, needle valve lift, nozzle pressure, and pump pressure of the device in FIG. 1.
Fig. 3 is an explanatory diagram showing an injection device having three fuel valves, and Fig. 4 shows a state in which one fuel valve out of the three fuel valves is alternately set to no injection in each cycle. 5 is a diagram showing the state when two fuel valves are alternately set to non-injection, FIG. 6 is an explanatory diagram showing a conventional fuel injection device, and FIG. 7 is a diagram similar to that of FIG. 6. It is a diagram showing the performance of the device. 01... Fuel pump body, 08, 11... Check valve, 101... Fuel valve body, 107... Needle valve, 1
15... Piston, 201... Injection pipe, 303,
304... Solenoid valve.

Claims (1)

[Claims] 1. In a fuel injection system for a diesel engine in which a plurality of fuel valves are provided in one cylinder branched from a jerk-type fuel pump, a check valve that is provided in the fuel pump and is opened when fuel is discharged, and a discharge termination valve. a check valve that is opened by pressure on the discharge side; a piston that is installed in each of the fuel valves and receives hydraulic pressure separate from the injection system to press the needle valve of the fuel valve; and a hydraulic pipe that leads to the piston. and a microcomputer that controls the opening and closing of the solenoid valves based on the engine speed, crank rotation angle, engine load, etc., and the microcomputer controls the timing at the end of injection of each fuel valve. Hydraulic pressure is supplied to the piston of the fuel valve to close the fuel valve, and when the engine is under partial load, hydraulic pressure is supplied to the piston of the temporary fuel valve, and injection of each fuel valve is intermittently stopped depending on the engine load. A multi-fuel valve injection device characterized in that the fuel valves that stop injection are controlled to be periodically and sequentially replaced.